Citation preview
Edited by
Kendall Preston. Jr. Carnegje-Mellon University Pittsburgh,
Pennsylvania
Kenneth J. W. Taylor Yale University School of Medicine New Haven,
Connecticut
Steven A. Johnson Mayo Foundation Rochester, Minnesota
and
William R. Ayers Georgetown University School of Medicine
Washington, D. C.
Plenum Press· New York and London
Library of Congress Cataloging in Publication Data
Main entry under title:
Medical imaging techniques.
"Based on the proceedings of the Engineering Foundation Conference
held in Henniker, New Hampshire, August 15-20, 1976."
Includes indexes. 1. Diagnosis, Radioscopie - Congresses. 2.
Imaging systems in medicine
Congresses. I. Preston, Kendall, 1927- H. United Engineering
Trustees, inc., New York. [DNLM. 1. Radionuclide imaging - Methods
- Congresses. 2. Tomog raphy, Computerized axial - Congresses.
WN445 M489 1976] RC78.M34 616.07'57 79-4424 ISBN-13:
978-1-4684-3488-0 e-ISBN-13: 978-1-4684-3486-6 DOI:
10.1007/978-1-4684-3486-6
Based on the proceedings of the Engineering Foundation Conference
held in Henniker, New Hampshire, August 15-20, 1976.
This book was prepared with the support of NSF Grant APR 76-24161.
However, any opinions, findings, conclusions and/or recommendations
herein are those of the authors and do not necessarily reflect the
views of NSF.
© 1979 United Engineering Trustees
Plenum Press, New Y ork A Division of Plenum Publishing Corporation
227 West 17th Street, New York, N.Y. 10011
All rights reserved
No part of this book may be reproduced, stored in a retrieval
system, or transmitted, in any form or by any means, e1ectronic,
mechanical, photocopying, microfilming, recording, or otherwise,
without written permission
Preface
The need for a book on medica1 imaging techniques became evi dent
to the editors of this vo1ume at the 1976 Engineering Founda tion
Conference on Non-Invasive Medica1 Diagnosis. This conference
treated imaging of the thorax, abdomen, brain, and extremities
using ultrasound, radiology, computed tomography, and nuc1ear medi
cine. During 1976 and 1977 the editors solicited participants in
the conference for contributions to this vo1ume. Other sources were
also sought in special areas of interest in medical imaging beyond
those individua1s who had been conference participants. Most of the
writing and editing was done in late 1977 and in 1978 resu1ting in
this 25-chapter book which is organized into sections on (1)
Systems Considerations, (2) C1inical Results, (3) Research Topics,
and (4) Tutorials. A short survey of the book is contained in the
Introduction.
The editors wish to acknowledge the United States National Science
Foundation, particularly J. C. Aller, Program Manager, for partial
financia1 support of the conference and of the publication of this
book under Grant APR76-24161. The exce11ent typing services of
Caroline Wadhams's organization (Report Production Associates,
Cambridge, Massachusetts) and her staff, particu1ar1y Susan Dunham,
are acknowledged as weIl as the efforts of Meg Grant and Winnie
Garcia (Tucson, Arizona) who assisted with the subject index. The
splendid cooperation of the staff of Plenum Press, in particular
Stephen Dyer (Assistant Managing Editor) and Derrick Mancini
(Editor), has been inva1uab1e.
K. Preston, Jr. K. J. W. Taylor S. A. Johnson W. R. Ayers
v
Contents
Introduction .......•.........•.....•. xvii
SYSTEMS CONSIDERATIONS
Health Planning for a New Technology: Computerized Tomography
Planning Issues in 1975 and 1976
Patricia A. Gempel
l. 2. 3.
4.
5.
6.
Introduction . Information Needs of Health Planners Effect of CT on
Alternative Diagnostic Neurologie Procedures .• .: .• . Health
Planning Issues . ... 4.1 Equipment Selection Criteria 4.2 Early
Instrument Obsolescence 4.3 Diffusion of CT Scanning Systems 4.4
Geographie Location . . Planning Approach. '" 5.1 Areawide Planning
for CT Scanning Systems 5.2 Assessment of Areawide Need . • 5.3
Guidelines for Procurement of Initial CT Scanner 5.4 Guidelines of
Procurement of Additional Scanners 5.5 Body Scanner Applications
References. .
vii
3 5 5 6 6 6 7 7 7 8
10 10 11
viii CONTENTS
An Overview of Government Regulation of the Use of Computed
Tomography through 1978
Patricia A. Gempel and Jane B. Hetzger
l. 2.
3. The Social Security
Standards - The Food and Drug
5. 6. 7.
Hultiple Endpoints in the Assessment of Non-Invasive
Technology
W. R. Ayers
Diseases . . . . . . 1.2 Assessment of Hedical Technology
2. Levels of Technology . . . . . . 3. Health Services Delivery
Systems 4. Conclusion 5. References. . . . .
The Evaluation of Diagnostic Tests S. N. Rasmussen
l. 2.
3. 4. 5. 6. 7.
Introduction . . . . . . . . . . . . . . . . . . Hethods of
Procedure . . . . . . . . . . . . . . 2.1 The Diagnostic
Information Obtained by the
Investigation .............. . 2.2 The Therapeutic Consequence of
Establishing
Excluding a Diagnosis . . . . . . . 2.3 Discomfort and Risk to the
Patient 2.4 Economic Cost ........ . Evaluation of Diagnostic
Information The Direct Hethod The Indirect Hethod Summary
References .
or
37 38
CONTENTS
The Impact of Technology on Health Care Productivity G. B.
Devey
l. 2. 3.
Introduction . . . . . . . . . . Pitfalls of Inflexible Policies
Impact of Current Technology 3.1 Ultrasound 3.2 Nuclear Medicine
3.3 New Skills
4. 5.
CLINICAL RESULTS
Scintigraphy, Ultrasound, and CT Scanning of the Liver K. J. W.
Taylor, D. Sullivan, J. Simeone, A. T. Rosenfield
1. Introduction . 1.1 Nuclear Medicine Imaging 1.2 Ultrasound
Imaging and Computed Tomography
2. Comparison . . 2.1 Metastases 2.2 Diffuse Abnorrnalities 2.3
Ascites 2.4 Biliary Tree 2.5 Gallstones
3. Discussion 4. References
W. F. SampIe
1. Introduction ..... 2. Materials and Methods 3. Results 4.
Discussion .. . 5. Conclusion .. . 6. Acknowledgements 7.
References.
A Preliminary Report on Computed Tomography of the Thorax and
Abdomen
R. J. Alfidi
47 48 49 50 50 50 51 52
55 55 56 56 61 67 69 69 70 73 76
79 81 82 85 87 87 88
91 91
x
3. Results 3.1 Liver . · 3.2 Effusions 3.3 Pancreas 3.4 Kidneys ·
3.5 Aorta . · 3.6 Ga11bladder and Bile Ducts 3.7 Retroperitoneal
Abnormalities 3.8 Mediastinal Masses 3.9 Bony Abnormalities 3.10
Breast
4. Discussion
1. 2.
3. 4. 5.
Introduction • • • • • • • • • . • • • • Accepted Uses of
Ultrasound in Detection 2.1 Gynecological Tumors 2.2 Abdominal
Lymph Nodes • 2.3 Retroperitoneal Masses 2.4 Tumors of the Pancreas
2.5 Other Gastrointestinal Tumors 2.6 Liver Metastases 2.7
Neoplasms of the Kidney ••• 2.8 The Thyroid Gland ••.••. Analysis
of Ultrasound Patterns of Tumors Diagnostic Ultrasound in the
Management of Refer ences • •• .
Computed Tomography of the Liver and Biliary Tract S. Sagel and R.
J. Stanley
1. Introduction.. •••• • •.•• 2. The Normal Liver and Biliary Tract
• 3. The Abnormal Liver and Biliary Tract
3.1 Space-Occupying Hepatic Lesions 3.2 Jaundice •••.. 3.3
Gallbladder Disease
4. Discussion 5. References. •
3.1 Normal Liver
100 100 101 101 103
105 105 106 107 107 108 110 110 110 111 112 113 114
117 117 118 118 119 120 120 122
123 123 124 124
CONTENTS
3.2 Tumors 3.3 Cysts. 3.4 Cirrhosis 3.5 Abcess 3.6 Obstructive
Jaundice
xi
124 126 126 126 126 131 131 132 132 133
4.1 Contrast Agents .. . 4.2 CT Biopsy ..... . 4.3 Transhepatic
Cho1angiography
5. References ........... .
Echographie Diagnosis of Lesions of the Abdominal Aorta and Lyrnph
Nodes
A. K. Freimanis
2.1 Modern Echographie Procedure 136 2.2 Echographie Measurement
138 2.3 Echographie Measurernents in the Management of
Aneurysms 138 2.4 Method of Examination 138 2.5 Diagnostic
Procedure 141 2.6 A Few Pitfa11s 142 2.7 Differential Diagnosis of
Large Abdominal
Lyrnph Nodes ... 142 2.8 Indications for Procedure 142 2.9
Reliability . ... 143 2.10 Thoraeie Aortic Aneurysms 143 2.11
Inferior Vena Cava 144
3. Retroperitonea1 Lyrnph Node En1argement 144 3.1 Deve10pment of
Examination Procedure 145 3.2 Acoustic Nature of Lyrnph Nodes 145
3.3 Distribution . . . . . . . . 147 3.4 Out1ining of Radiation
Ports 148 3.5 Indications. . . . . 150 3.6 Differential Diagnosis
152
4. Summary . . . . 152 5. Acknow1edgements 152 6. References
153
xii CONTENTS
RESEARCH TOPICS
The Use of Computerized Tomography in the Diagnosis of Pu1monary
Nodu1es
W. R. Ayers and H. K. Huang
1. Introduetion . . . . . • . • . . . . .• 155 2. Standard
Management of the Solitary Pu1monary Nodu1e 156 3. The Use of CT -
Material and Methods . • . . • . • 157
3.1 Read a CT Sean from Magnetie Tape or Disk . •. 159 3.2 Iso1ate
a Patho1ogiea1 Region in the CT Sean 159 3.3 Generate the Frequeney
Distribution and Histogram 159 3.4 Determine Patho1ogiea1
Boundaries 160 3.5 Estimate Vo1ume . . . . • . 160 3.6 Produee
Subtraetion Images 160
4. Resu1ts • . • . . • . . . . . . 160 4.1 An Illustrative Case
Study 161 4.2 Comment 163
5. Summary 163 6. Referenees. 164
Image Proeessing of Computerized Tomographie Seans J. A. Horton, C.
W. Kerber, and J. M. Herron
1. Introduetion . . . . . 1.1 Limitations of CT Seanning 1.2
Lirnitations of Human Visua1
2. Materials and Methods 3. The Sigma Sean Image 4. Speeifie Case
Studies 5. Diseussion . . 6. Aeknow1edgements 7. Referenees .
Determination of Organ Volume S. N. Rasmussen
1. 2. 3.
. .
175 177 179 181 181 182 183
CONTEtl"TS
Three-Dimensiona1 Dynamic Imaging of the Heart, Lungs, and
Circulation by Roentgen-Video Computed Tomography
R. A. Robb
1. Introduction 2. Methods 3. Resu1ts 4. Discussion 5. Summary 6.
Acknow1edgements 7. References ...
A Digital Moving Target Indicator System for Detection of
Intracrania1 Arterial Echoes
R. W. Barnes
1. Introduction 2. System Description 3. Resu1ts 4. Conclusions 5.
References.
Relationship of Images of Acoustic Refractive Index and Attenuation
to Tissue Types within Excised Fema1e Breast
J. F. Green1eaf and S. A. Johnson
1. Introduction 2. Method of Procedure 3. Conclusion. • . 4.
Acknow1edgements. .
Feasibi1ity of NMR Zeugmatographic Imaging of the Heart and
Lungs
P. C. Lauterbur
l. 2. 3.
4. 5. 6.
Introduction Potential App1ications in Medica1 Diagnostic
Preliminary Experiments . . . . . • . . 3.1 NMR Properties of Lung
Tissue ... 3.2 NMR Properties of Myocardia1 Tissue Physica1
Lirnitations Acknowledgements References . . . . .
Imaging
xiii
199 200 201 203 204
205 206 207 207
xiv CONTENTS
Otto H. Schmitt
TUTORIALS
1. 2.
3. 4.
Introduction Basic Princip1es. •• 2.1 Frequencies Emp10yed 2.2
Production of Ultrasound 2.3 Intensity of Ultrasound • 2.4 The
Ref1ection Process 2.5 Resolution of Ultrasound Systems 2.6 Tissue
Attenuation and TGC 2.7 Types of Reflectors •••• 2.8 Gray-sca1e
Systems • . .• . 2.9 Scanning Techniques in Gray-sca1e
U1trasonography 2.10 Recording Systems •••. 2.11 Real-Time
Ultrasound Systems Conc1usion References • •
Nuclear Medicine Imaging L. Kaufman
1. Introduction . . . . . 1.1 lmaging Moda1ities 1.2 Detection
Systems
2. The Imaging Problem 2.1 Resolution . . . . 2.2 Imaging
Performance
219 220 222 223 224 225 226 227 228
231 232 232 232 234 235 238 240 241 244 247 248 251 259 260
263 263 264 267 267 268
CONTENTS xv
3. Imaging Concepts • . . . . . . . . . . . . . . . .. 269 3.1
Sources of Noise in the Nuclear Medicine Image 270
4. The High Purity Germanium (HPGe) Camera 274 4.1 Comparative
Sensitivity 276 4.2 Contrast Resolution 277 4.3 Comparative Imaging
279
5. Tracers 279 6. Discussion 283 7. References 284
Algorithms in Computerized Tomography J. M. S. Prewitt
1. Introduction. . . • . . . . . . 1.1 The Reconstruction Problem
1.2 The Reconstruction Paradigm
2. Reconstruction Algorithms 2.1 Transform Methods - Parallel
Geometry 2.2 Transform Methods - Divergent Geometry 2.3 Series
Expansion Methods
3. Comparison of A1gorithms 4. Impact on Medicine 5. Summary 6.
References.
Scanning Methods and Reconstruction A1gorithms for Computerized
Tomography
H. K. Huang and R. S. Led1ey
1. Introduction 2. Scanning Modes . . .
.
. . 2.1 Translation and Rotation Mode Using a Pencil
Thin Co11imated X-ray Beam . 2.2 Translation and Rotation Mode
Using a Fan-Beam
X-ray Technique . . . . . . . 2.3 Rotation Mode Using a Larger Fan
Beam
3. Picture Reconstruction A1gorithm .. 3.1 Parallel A1gorithm:
A1gebraic, Convo1ution
and Fast Fourier Transformer 3.2 Fan Algorithm
4. Conc1usion 5. References.
K. Preston, Jr.
2.1 Investigations by Mountford and We11s
287 288 289 290 294 296 297 303 306 308 311
313 314
xvi
3. Signal Analysis Theory and Methods 3.1 Signal Regimes 3.2 Tissue
Signatures
4. Experimental Data 4.1 Materials and Methods 4.2 Transducer
Calibration 4.3 In Vivo Recording . 4.4 Case Study (Human) 4.5 Case
Study (Animal)
5. Acknowledgements 6. References
CONTENTS
333 333 334 337 337 339 340 349 351 353 354
355
359
363
Inkoduction
This book presents recent advances in the major medical imaging
modalities: (1) traditional radiography, (2) computed x-ray
tomography, (3) ultrasonography, and (4) nuclear medicine imaging
using radionuclides. Chapters have been written by both practi
tioners and researchers in radiology as weIl as by authors covering
the engineering aspects of medical image generation, processing,
and display. The book also provides five tutorial chapters on the
fundamentals of ultrasound, computed tomography, nuclear medicine
imaging, and electronic signal and image analysis.
Medical imaging is a rapidly evolving field, especially in those
aspects influenced by advances in digital computer technology. Thus
no book on this subject can be entirely up-to-date. The emphasis in
this volume is on classic advances in the field which have taken
place during the decade of the 1970s. This decade has seen the
rapid adoption in the hospital, clinic, and health center of new
imaging instrumentation in ultrasound, x-ray tomography, and
nuclear medicine. The major advance in ultrasound is in gray-scale
display (Figure 1). Display techniques have also rapidly advanced
in computed radiography and x-ray tomography as has resolution and
sensitivity (Figures 2-6). Nuclear medicine imaging has also ad
vanced with the introduction of computerized displays, more sensi
tive detectors, and computed emission tomography (see, for example,
the chapter by L. Kaufman). Finally, we have just seen the intro
duction by industry of the entirely new technique of nuclear mag
netic resonance imaging (Figure 7).
We feel indeed fortunate to have obtained outstanding chapters
illustrating clinical applications of these new imaging techniques
and instruments. These chapters have been provided by K. J.
W.
xvii
Fig. 1. Gray-level displays of sixteen sequentia1 ultrasound
B-scans of the breast taken at approximate1y l-second intervals at
different longitudinal positions. (Courtesy G. Baum, Albert
Einstein College of Medicine, New York.)
INTRODUCTION xix
Fig. 2. Computed radiogram of the head. (Courtesy General Electric
Co., Milwaukee.)
(A) (B)
Fig. 3. Two different displays of the same computed x-ray tomogram
using different level and window settings. (A) Structure of the
spine, ribs, heart, and musculature (level: 0, window: 300). (B)
Structure of the lungs (level: -523, window: 1000). (Courtesy
General Electric Co., Milwaukee.)
xx INTRODUCTION
(A) (B)
Fig. 4. (A) Gomputed radiogram display permitting seleetion of
angulated sean through seleeted vertebra. ( E ) Magnified view of
seleeted angulated sean with level 191 and window 1000 to permit
examination of bone strueture. (Courtesy General Eleetrie Co.,
Milwaukee. )
(A) (B)
Fig. 5. Computer eonstruetion and display of both lateral seetion
(A) and longitudinal seetion (E ) from 21 previously eomputed
trans verse tomographie seetions taken axially at lOrnrn
intervals. (Courtesy General Eleetrie Co., Milwaukee.)
INTRODUCTION xxi
(A) CB)
Fig. 6. Demonstration of spatial and contrast resolution in com
puted x -ray tomography using the General Electric gray-white
phantom (model 3 ). Two different displays of the same tomogram
show (A) contrast resolution to 0.2% for large ( ~ lcm) structures
displayed with level 0 and window 40 and (E) spatial resolution of
1.5mm structures at 3.0% contrast displayed with level -15 and
window 40. The small wedge-shaped struc ture is water density.
(Courtesy General Electric Co., Milwaukee.)
Fig. 7. Nuclear magnetic resonance ima ge of the human head.
(Courtesy EMI Medical, Ltd., Great Britain.)
xxii INTRODUCTION
Taylor, W. F. Sample, R. J. Alfidi, A. K. Freimanis, and S. Sagel.*
These authors have emphasized the comparative aspects of these
imaging modalities. Some have furnished flow-charts of their
multi-modality imaging protocols for both examination and diag
nosis.
Besides these chapters on clinical results there are also chapters
by the biomedical engineering community on current research. It is
hoped that these research chapters will ass ist the reader in
evaluating future trends which are clearly pointing towards further
sophistication in diagnostic sensitivity, specificity, and produc
tivity for the decade of the 1980s. In this section of the book the
chapter by W. R. Ayers and H. K. Huang and the chapter by J. A.
Horton, C. W. Kerber, and J. M. Herron provide some of the first
evidence that computer generated (or displayed) tissue signatures
may be used in the determination of pathology. (Horton has received
the 1978 Cornelius G. Dyke prize of the Arnerican Society of Neuro
radiology for his work.) R. W. Barnes illustrates methods of em
ploying ultrasound for the purpose of determining blood flow in the
cerebral arteries and S. N. Rasmussen discusses its use in cal
culating organ volume. J. F. Greenleaf and S. A. Johnson report on
progress in computed ultrasound tomography particularly as regards
imaging of the breast. o. H. Schrnitt predicts tomographie imaging
using the spatial variations in the electrical impedance of tissue.
R. A. Robb describes progress in the Mayo Foundation DSSR project
in real-time tomographie imaging of the thorax. Finally, the basics
of nuclear magnetic resonance imaging in determining the properties
of lung and myocardial tissue are reported by P. C. Lauterbur along
with initial results in nuclear magnetic resonance imaging.
The tutorial chapters have been added so as to provide basic
reference material which not only elucidates the basic physical
principles of medical imaging modalities but also surveys funda
mental physical progress in each modality with a broad perspective.
K. J. W. Taylor discusses the generation of ultrasonic pulses,
methods of ultrasound image formation from pulse echoes, ultra
sound image display and interpretation. His chapter also reviews
some of the new real-time scanning mechanisms which use phased
arrays and sec tor scanners. L. Kaufman presents the basic
principles of nuclear medicine imaging, reviews the use and selec
tion of radionuclides, discusses the meaning of both spatial and
spectral resolution, and introduces new results obtained using his
high purity germanium camera. The tutorial chapters on computed
tomography by J. M. S. Prewitt and also by H. K. Huang and R.
S.
*Full addresses are given for all authors in the Appendix.
INTRODUCTION xxiii
Ledley catalog and discuss a multiplicity of reconstruction algo
rithms using illustrations obtained from mathematical phantoms as
weIl as reviewing tomographic scanning modes and beam geometries,
respectively. Finally, K. Preston describes the fundamentals of
electronic signal processing with respect to the generation of
tissue signatures in ultrasound imaging.
As a counterbalance to the enthusiasm generated for the advances in
diagnostic capability provided by modern medical imaging, we cannot
disregard the quest ions of both medical ad ministrators and the
user community concerning the cost-effective ness of the new (and
often very expensive) instrumentation which has proliferated in the
1970s. Thus at the very outset of this book there are five chapters
concerned with the medical systems problems faced in the
procurement and use of medical imaging in strumentation and the
impact of this procurement and use on health care and health
management. The chapters by P. A. Gempel and J. B. Metzger review
the impact of such government regulations as the National Health
Planning and Resources Development Act, the Radia tion Control for
Health and Safety Act of 1968, and the Medical Device Amendments of
1976 especially as regards the development of national guidelines
for the procurement, installation, and use of CT scanners. The
references in these chapters are an invaluable chronicle of the
effect of government regulation on the use of modern imaging
instrumentation. The chapters by W. R. Ayers and G. B. Devey
discuss types of new medical technology and methods of assessing
costs, benefits, and productivity, respectively. Finally, S. N.
Rasmussen presents an analytical treatment, based upon prob
ability theory, of the evaluation of diagnostic tests. He provides
specific illustrations of performance evaluation using both in
direct and direct methods of assessment as regards the detection of
pancreatic cancer using images generated by ultrasound.
In summary, it is our hope that this book is sufficiently catholic
to satisfy the need of the reader who desires a broad treatment of
modern medical imaging and sufficiently comprehensive and
analytical to satisfy the specialist. Assembling the chapters which
are presented in the following pages and participating in the
Engineering Foundation Conference on Non-Invasive Medical Diagnosis
wherein some of this material was originally presented was a most
worthwhile learning experience for all of the editors. It is our
hope that the reader will benefit likewise.
19 February 1979 Kendall Preston, Jr. New Haven, Connecticut Senior
Editor
HEALTH PLANNING FOR A NEW TECHNOLOGY: COMPUTERIZED TOMOGRAPHY
PLANNING ISSUES IN 1975 and 1976
Patricia A. Gempel
Cambridge, Massachusetts
1. INTRODUCTION
Public Law 93-641 divided the United States into just over 200
Health System Agencies (HSA's) with several irnportant and broad
based charges. Arnong these are limiting duplication of services,
preventing unnecessary proliferation of expensive equipment, and
ensuring equal access to necessary health services for the entire
population. The responsibility for health planning resides within
these HSA's and is indeed at the local level. Although they are
unique, their needs for information relating to emerging new tech
nologies are generically similar.
In July 1975, Arthur D. Little, Inc. (ADL) , under contract to the
Health Resources Administration (HRA), began to develop several
health planning documents for the purpose of assisting local plan
ners in planning for emerging medical technologies. One of these
documents dealing with the subject of computerized tomography (CT)
was completed in November 1975. The outline of the CT case study is
surnrnarized in Table 1. Other case studies include multi-phasic
screening, electron radiography, thermography, automated white
blood cell counters, laminar air flow, miniature centrifuge
analyzers, anesthesia gas scavengers, computerized patient
monitoring, and automated hospital information systems. These case
studies have cornrnon elements in that each technology is rela
tively new, controversial, or for some other reason of intense
interest to local planners.
1
2
TECHNICAL CHARACTERISTICS
• Equipment Selection Criteria
• Early Instrument Obsolescence
PLANNING APPROACH
• Areawide Planning
GEMPEL
2. INFORMATION NEEDS OF HEALTH PLANNERS
To ensure focusing on the information needs of local health
planners, the ADL team developed the information for each study
through a combined interview and expert reviewer process. The quest
ions which needed answering were first defined by the local HSA's
themselves. Estimates of need were thus obtained from the clinical
community and documentation on currently available equip ment was
directly from equipment manufacturers. The ADL team also developed
additional insights on likely future developments from researchers
and funding agencies. The team assimilated new data with existing
information in ADL's files and these findings, tempered by the case
team's and reviewers' judgement, were sum marized into a single
"technical assistance and planning document."
One of the mandates of the National Health Planning and Resources
Development Act is that, for all institutional capital equipment
purehases of more than $150,000, a certificate-of-need (CON)
application must be filed by the institution and approved by the
HSA. States have the right to enact separate CON laws dropping this
ceiling to as low as $1,000. For purehases of equipment utilizing
evolving new technologies, analysis of a CON application can
present a problem. For example, a local agency's information needs
on CT scanning are relatively straightforward, but the avail able
data are confusing, usually not designed for their purposes, and
often developed by groups with vested interests in the tech
nology.
The technical and clinical characteristics of CT head and body
scanners are discussed elsewhere in this book and will not be re
peated here, except when there is particular significance to
planning and estimating medical need for CT scanners.
3. EFFECT OF CT ON ALTERNATIVE DIAGNOSTIC NEUROLOGIC*
PROCEDURES
To health planners interested in analyzing the institutional "need"
for various equipment necessary to service a given popula tion
adequately, an estimation of the effect on established neuro logie
practice is vital. Several procedures are used, in various
proportions, in diagnostic neurologie work-ups: clinical examina
tions, skull x-rays, echoencephalography, nuclear medicine brain
scans, pneumoencephalography, and cerebral angiograms. Table
2
*An estimate of the effect of CT on diagnostic medicine in addition
to neurology had not been done at this writing since few
instruments capable of body scanning in less than 20 seconds/slice
were avail able.
4 GEHPEL
eompares the risk and patient hospitalization eharaeteristies of CT
brain seanning vs. other neurologie proeedures.
Table 2 - Proeedures Used in Neurologie Diagnosis*
PROCEDURE RISK HOSPITALIZATION
Pneumoeneephalograph X 4 - 6
Nuelear medieine brain sean X X
- Skull X-ray X X
*Souree: Arthur D. Little, Ine.
Sinee the CT scanner is primarily a soft tissue imaging deviee, its
primary impact is on other soft tissue imaging deviees proeedures.
Partieipants in the National Cancer Institute (NCI) CT neurologie
evaluation projeet (Mayo, Massaehusetts General Hospital, Columbia,
Cornell and George Washington) had examined enough patients to see
emerging ehanges in praetiee. ADL aeeumulated their estimates of
approximate percent reduetions in established neurologie soft
tissue diagnosis proeedures due to replaeement by CT seanning as a
basis for assessing CT impact (see Table 3).
CT PLANNING ISSUES IN 1975 AND 1976
Table 3 - Effect of Use of CT Scanning on Established Neurologic
Diagnostic Soft Tissue Imaging Procedures*
PROCEDURE PERCENT REDUCTION IN 3-5 YEARS
Pneumoencephalograph 65 - 75%
Nuclear medicine "brain scan" 25 - 35%
*Source: Arthur D. Little, Inc. (estimates based on experience of
early users), 1976.
4. HEALTH PLANNING ISSUES
The major issues affecting health planning, as defined by planners
at ADL, were:
• equipment selection criteria,
Each of these is summarized briefly.
4.1 Equipment Selection Criteria
Equipment selection criteria do not differ substantially for head
and whole-body scanners. Radiologists and physicists make a series
of informed judgments relating to instrument capability and cost,
patient population, and manufacturer's reliability, service, and
reputation. There is no strict correlation between the need for
head or body scanning capability and the cost and even the type of
equipment purchased. Everyone prefers faster scanners; the fast
body scanners produce better brain images than do slow brain
scanners; and thus, body scanners are often purchased for brain
scanning applications.
6 GEMPEL
There is adefinite need for more clinical experience with body
scanners in extraneurologic applications. Medical benefits for
brain scanners are established for all practical purposes, but it
will take time to develop similar data for body scanners. Early
reports indicate usefulness in at least liver, kidney, and pancreas
tumor detection; radiation treatment planning; and needle biopsy
guidance. With many CT body scanners now operational, more defini
tive information should be accumulated rapidly and guidelines for
diffusion of body scanners for use in total body applications
should be possible.
4.2 Early Instrument Obsolescence
Early instrument obsolescence is not a serious problem since
retrofit packages are available. Institutions are budgeting about
$25,000 per year for these packages. ADL feels that it will be 3-5
years before equipment with scan times of substantially less than 5
seconds and equivalent improvement in diagnostic detail will be
developed so as to make current models obsolete.
Justification of system purchase for brain scanning is based on the
primary objective of providing better medical care. CT equipment
is, however, a major capital expense for any health care
institution and thus economic considerations are important. Recent
cost/benefit calculations based on in-patient days and
representative patient charges indicate that a reduction in
pneumoencephalograms of about 15 per month can cost-justify a CT
system (amortized over 5 years) on the basis of reduced hospital
charges alone. The pure economics of CT scanning demonstrate that
hospitals with CT systems utilized at a rate of 10 patients per day
do not lose money at patient charge rates of ~$150. The potential
for overutilization of CT scanning is now limited by the small
number of CT units in use.
4.3 Diffusion of CT Scanning Systems
The diffusion of CT scanning systems has so far been described by a
substantial equipment shortage due to limits on manufacturers'
production capacity. These equipment shortages are not likely to be
eliminated until 1977. By that time, the uses of CT extraneuro
logic scanning will also be more clearly defined. Thus, when and if
national guidelines are developed, the potential for overutiliza
tion should be seriously evaluated.
4.4 Geographic Location
The geographic location of CT scanning systems is also an issue. CT
scanners should be geographically distributed as widely
CT PLANNING ISSUES IN 1975 AND 1976 7
as possible to ensure patient access, but this cannot be done with
out considering the diagnostic and therapeutic neurologie caseloads
and the capabilities of various hospitals. This issue is discussed
further below.
5. PLANNING APPROACH
5.1 Areawide Planning for CT Scanning Systems
Areawide planning for CT scanners is based on the assumption that
all patients who could benefit should have access to scanning
capability but that scanners should be placed where there is suf
ficient patient load for full time clinical use. Thus, planning for
computerized tomography (or any other new technology) involves two
distinct activities:
• assessment of the area's need for the equipment on the basis of
overall regional need based on population; demand for CT scanning
as indicated by utilization of specific diagnostic
procedures;
• selection of those facilities which offer access to appropriate
medical specialists and other related facilities as weIl as
geographie location to facilitate patient access.
Ideally, areawide planning for CT scanning should begin before the
first application for CON approval is submitted. Until more
definitive information about the extraneurologie applications for
CT scanning becomes available, areawide planning will be concerned
with CT brain scanning.
5.2 Assessment of Areawide Need
One proposed measure for approximating the number of systems
required to meet the need for CT in neurology is based on
population. The area population is divided by the estimated
national average need--one CT brain scanner for each
250,000-300,000 population. However, because of the uneven
geographie distribution of neuro logical services in the United
States, one area may serve as a referral center for a large
multi-state region for sophisticated neurological procedures. In
such cases, a need assessment based solelyon local population would
result in an underassessment of the size of the referral area and
overassessment of the need in other areas in the region with
limited local neurological services. Therefore, area population can
be used only to give a general assessment of need.
8 GEMPEL
Another proposed measure of the systems required is based on
existing neurological procedures. The experience of early users of
CT brain scanners has demonstrated a correlation between the level
of a hospital's neurological diagnostic and surgical activity and
the adequate utilization of each CT brain scanner purchased. This
correlation can be used in assessing total areawide need for CT
brain scanners.
On the basis of current usage of existing systems, hospitals with
the neurologie activity characteristics shown in Table 4 have been
found to perform at least 1,500 CT scans per year. Therefore,
division of the areawide neurologie activity totals by these levels
of minimum activity can provide a measure for estimating the area
wide requirements for CT scanners for neurologie use. These
characteristics should be surveyed for all area hospitals. Each
activity total for the whole area should be then divided by the
appropriate minimum level.
These formulas provide a conservative areawide estimate based on
initial experience with CT scanning. As further experience with the
technology is accumulated, methods and bases for areawide planning
will have to be modified accordingly.
5.3 Guidelines for Procurement of Initial CT Scanner
Once areawide need for scanners has been established, a de cis ion
has to be made concerning where scanners should be located and,
hence, which applications for scanners shoulrl be approved.
Obviously those hospitals with the largest neurology services
should be selected as the most suitable location for CT brain
scanners in the area. Othei smaller hospitals, which individually
have less than the minimum activity in the neurological services
required to utilize adequately a CT brain scanner, should be en
couraged to share CT facilities. Insofar as possible, CT brain
scanners should also be geographically distributed throughout the
area.
At the present time, CT scanners are most cost-effective when
located in hospitals with specialized neurological and neuro
surgical services. Therefore, site selection should be based mainly
on availability of appropriate medical specialists and an existing
active specialty service and, to a lesser degree, on geo graphie
distribution in order to provide efficient patient access to the
facilities. (See Table 4 for minimum staffing requirements.)
CT PLANNING ISSUES IN 1975 AND 1976
Table 4 - Minimum Requirements for Approval of Certifieate-of-Need
Applieation for CT Scanners
Justified on the Basis of Neurologie Use Only (for institutions
without a CT scanner)
SERVICES AND SPECIAL1STS
• radiology teeh. *Board Certified (1-2 per shift)
NEUROLOGIC ACTIVITY
• intraeranial proeedures > 50 per year
• eerebral arterio/angiograms > 200 per year
• pneumoeneephalograms > 25 per year
ACCESS CONSIDERATIONS
• geographie distribution
• scanners regionally available (1/300,000 indigenous
population)
Source: Arthur D. Little, Ine. estimates based on review of 1975
planning guidelines, 1976.
9
5.4 Guide1ines of Procurement of Additional Scanners
A1though in the mid 1970's on1y three hospitals in the United
States (Mayo C1inic, l1a11inckrodt Institute, and C1eve1and C1inic)
had more than one scanner, other 1arge hospitals and hea1th center
comp1exes now have multiple systems. The primary consideration in
reviewing such requests for additional scanners is, of course, the
experience with the first CT system, specifica11y the uti1ization
rate and patient backlog. However, before approving a second
scanner with on1y neuro1ogica1 capabi1ity, the c1inica1 potential
for extraneuro1ogic app1ications shou1d be eva1uated and the
advisabi1ity of adding who1e-body scanning capabi1ity shou1d be
considered. There is concern among hea1th p1anners that more CT
scanners than necessary to service a given patient population will
be purchased and that, in order to cost-justify this equipment,
patients will be scanned unnecessari1y.
One way of monitoring need is to gather positive and negative
diagnostic data. The current rate of positive diagnosis with
traditiona1 radiographs is approximate1y 20% as compared with posi
tive diagnosis with CT scans of 70%.
5.5 Body Scanner App1ications
The evaluation of CT scanning of other regions of the body than the
brain is moving rapid1y ahead as is reported in other chapters of
this book. However, estimates of c1inica1 uti1ity are difficu1t,
a1though there is c1ear1y considerab1e promise for use of the
technique in the diagnosis of tumors, aneurysms, and simi1ar soft
tissue patho1ogy. Purchase of equipment for body scanning shou1d
present1y be 1imited to those institut ions which have de ve10ped
adequate research and c1inica1 trial protoco1s and in which medica1
discip1ines appropriate to the proposed c1inica1 app1ica tion are
represented. Thus, installation of such CT systems shou1d probab1y
be restricted to major research centers and teaching hos
pitals.
Specific requests for purchase approva1 for extraneuro1ogic
app1ications shou1d be eva1uated for consistency with areawide
plans and in accordance with the fo11owing criteria.
• experience and reputation of princip1e investigators, • adequacy
of supporting faci1ities, • pertinence and imp1ications of research
protocol, • sufficient patient load in proposed discip1ine
for
satisfactory clinica1 trials, and • coordination of research in
severa1 c1inical areas.
CT PLANNING ISSUES IN 1975 AND 1976
6. REFERENCES
Ambrose, J., "Computerized Traverse Axial Scanning (Tomography):
Part 2 C1inica1 App1ication," Brit. J. Radiol. 46:1023-1047
(1974).
11
A1fidi, R. J., et al. , "Computer Tomography of the Thorax and
Abdomen: A Pre1iminary Report," Radio1ogy 11.:257-264 (1975).
Baker, L., et al., "Computer Assisted Tomography of the Head. An
Ear1y Evaluation," Mayo C1inic Proceedings 49:24-27 (1974).
Baker, H. L., "The Impact of Computed Tomography on Neuroradio
logic Practice," Radio1ogy 116:637-645 (1975).
Bu11, "Editorial. The Changing Face of Neuroradio1ogy Over Near1y
Forty Years," Neuroradio1ogy 2.:111-115 (1975).
Comprehensive Hea1th P1anning Counci1, Inc., "Interim P1anning
Guide1ines for Computerized Transaxial Tomography (CTT),"
Philadelphia, Pa., September 25, 1974.
Davis, D. 0., et al., "Computerized Tomography of the Brain, "
Radio1. C1in. N. Amer. 12:297-313 (1974).
"Editorial: Computer-assisted Tomography of the Brain," Lancet 2:
1052-1054 (1974).
"Editorial: Image Reconstruction: Computerized X-ray Scanners,"
Science 190:542 (1975).
Genessee Regional Hea1th P1anning Counci1, Rochester, N.Y., "A
Methodo1ogy Out1ine for Deve10pment of a Computer Tomography (CT)
Plan."
Gunn, W. V., et al. , "Image Generation and Display Techniques for
CT Scan Data," Invest. Radiol. 10:403-416 (1975).
Hea1th Resources Administration, Bureau of Hea1th Resources
Deve1opment, "Technica1 Assistance Memorandum #16. Compu terized
Axial Tomograph Scanners," Rockvi11e, MD (June 6, 1974).
Hea1th Resources Administration, Bureau of Hea1th Resources
Deve1opment, "Technica1 Assistance Memorandum 1133. Additional
Information on Computerized Axial Tomography (Now ca11ed "Computed
Tomography or CT")," Rockvi11e, MD (December 3, 1974).
12 GEMPEL
"Hospitals Race to Buy Scanners as P1anning Groups Try to Hold
Line," Medica1 Wor1d News, September ~:28-29 (1975).
Hounsfie1d, G. N., "Computerized Transverse Axial Scanning
(Tomography). Part 1. Description of System," Brit. J. Radio1.
46:1016-1022 (1973).
Led1ey, R. S., et al. , "Computerized Transaxial X-ray Tomography
of the Human Body," Science 186:207-212 (1974).
Led1ey, R. S., et al. , "The ACTA-Scanner: The Who1e Body Com
puterized Transaxial Tomography," Computers Bio1. Med. 4: 133-136
(1974).
Levins, H. L., "How Many Scanners are Anough?" Modern Hea1th Care
~: 62-64 (1975).
Litt1e, Arthur D., Inc., A Hea1th P1anning Document: Computerized
Tomographie Scanning Systems, contract HRA 230-75-0063, Hea1th
Resources Administration, Hyattsvi11e, MD (November, 1975).
McCu11ough, E. C., et al. , "An Evaluation of the Quantitative and
Radiation Features of a Scanning X-ray Transverse Axial Tomography:
The EMI Scanner," Radio1ogy 111:709-715 (1974).
New, P. F. J., Scott., W. R., Schnur, J. A., Davis, K. R., and
Taveras, J. M., "Computerized Axial Tomography with the EMI
Scanner," Radio1ogy 110:109-123 (1974).
Paxton, R. and Ambrose, J., "The EMI-Scanner: A Brief Review of the
First 650 Patients," Brit. J. Radiol. Q: 330-365 (1974).
Perry, B. J. and Bridges, C., "Computerized Transverse Axial
Scanning (Tomography, Part 3. Radiation Dose Considerations),"
Brit. J. Radio1. 46:1048-1051 (1974).
Report of the Joint Committee for Stroke Faci1ities XII, "Computed
Tomography in the Management of Cerebrovascu1ar Disease," Stroke
~:103-107 (1975).
Sche11inger, D., et a1., "Ear1y C1inica1 Experience with the ACTA
Scanner," Radio1ogy 114:257-261 (1975).
Scott, W. R., New, P. F. J., Davis, K. R., and Schnur, J. A., "New
Computerized Axial Tomography of Intracerebra1 and Intraventricu1ar
Hemorrhage," Radio1ogy 112:73-80 (1974).
Shapiro, S. H. and Wymore, S. M., "CAT Fever," New England Journal
of Medicine 294:954-956 (1976).
CT PLANNING ISSUES IN 1975 AND 1976
Smith, P. R., Peters, T. M., Muller, H. R., and E1ke, M., "Towards
the Assessment of the Limitations on Computerized Axial
Tomography," Neuroradio1ogy 2.:1-8 (1975).
13
Wortzman, G., Holgate, R. C., and Morgan, P. P., "Crania1 Computed
Tomography: An Evaluation of Cost Effectiveness," Radio1ogy
117:75-77 (1975).
Ze1ch, J. V" Ducheneau, P. M., Meaney, T. F., LaIli, A. F., A1fidi,
R. J., and Ze1ch, M. G., "The EMI Scanner and Its App1ication to
C1inica1 Diagnosis," C1eve1and C1inic Quarter1y 41:79-91
(1974).
AN OVERVIEW OF GOVERNMENT REGULATION OF THE USE OF COMPUTED
TOMOGRAPHY THROUGH 1978
Arthur D. Litt1e, Inc.
1. INTRODUCTION
Since its introduction to the hea1th care system of the United
States about five years ago, computed tomography (CT) has become
wide1y adopted. The rapidity with which c1inica1 experience has
accumu1ated and the diagnostic usefu1ness recognized at major
research centers is ana1ogous to the experience with x-ray
fo11owing Roentgen's discovery in the 19th century. However,
because of the high initial capita1 cost of CT and its introduction
at a time when hea1th care costs are under c10se scrutiny,
government agencies have worked to ensure appropriate uti1ization
and distribution of the techno1ogy. Figure 1 summarizes the factors
that have inf1uenced this process.
This chapter summarizes the status of three areas of government
po1icy that has inf1uenced the uti1ization and diffusion of CT:
hea1th p1anning, reimbursement, and performance and safety.
Fina11y, major groups are described that have no exp1icit
po1icy-making authority but have inf1uenced decision makers in
other government agencies.
2. HEALTH PLANNING - THE HEALTH RESOURCES ADMINISTRATION
The National Hea1th P1anning and Resources Deve10pment Act (P.L.
93-641) is a comp1ex 1aw with far-reaching imp1ications. Of all the
pertinent statutes in force today, it is the one most 1ike1y to
have a significant long-term effect on the uti1ization of CT in the
United States.
15
16
COST / BENEFIT ANALYSIS
ACTUAL MARKET DEMAND FOR CT
SSA
GOVERNMENT REGULATION OF CT THROUGH 1978
Very generally, the goals of the law are to improve the delivery of
health care in its broadest sense, to maintain some restraints on
the cost of health care, and to improve the health status of
previously under-served groups in the population.
17
To accomplish these tasks, a multilevel health planning net work
is being developed, which has more II c l out ,1I is subject to
more explicit performance standards, and is better financed than
its forerunners.
The Health Resources Administration (HRA) of the Department of
Health, Education and Welfare (DHEW) has been charged with
developing lI a national health planning capability geared to
promoting equal access to quality health care at a reasonable cost.
1I The HRA Bureau of Health Planning and Resource Development
(BHPRD) oversees the designation and funding of Health Systems
Agencies (HSA's) and State Health Planning and Development Agencies
(SHPDA's) and provides policy direction and technical assistance to
the designated agencies. According to the recently proposed
reorganization of the Administra tion these functions will
continue to be performed by the BHPRD.
2.1 The Certificate-of-Need Process (CON)
One of the requirements of the National Health Planning and
Resources Development Act with the most immediate implications for
CT is the provision that every state require CON application and
approval for the addition of new services and for capital expendi
tures that exceed $150,000. (This process has been described in the
previous chapter.)
During 1975 and 1976, local health planning agencies (IIBII
agencies that were in many cases reorganized into HSA's under P.L.
93-641) were beseiged with applications by hospitals for approval
of CT purchases. Because of the high cost of CT and the fact that
CT's unprecedented rapid diffusion coincided with the per iod of
implementation of more stringent health planning controls, CT
became a focal point for cost-containment efforts and a paradigm
for medical technology planning as a whole.
Local planners sought to decide where CT services should be offered
and how many CT units were needed in the absence of either
generally accepted methods for determining need or conclusive
information concerning the efficacy of the technology. Most
resorted to one or more of five general methods of determining need
or allocating CT resources:
18 GEMPEL AND METZGER
• Size of population to be served (see Health Services Management,
Inc., 1976; Alabama Department of Public Health, 1976),
• Distribution of installed units within area to be served (see
Ohio Department of Health, 1975).
• Number of diagnostic procedures to be performed or patients with
CT-detectable disorders being admitted to hospitals (see Health
Planning Council, Inc., 1976),
• Incidence of CT-detectable disorders (cancer and neurologic
disease) in the population (see Compre hensive Health Planning
Council of Kentucky, 1975),
• Characteristics of provider institutions, such as availability of
specialized medical staff and diag nostic and therapeutic services
offered (see New York Department of Public Health, 1977).
Needs as measured by the methods developed varied widely. As part
of a policy study on CT, the Hassachusetts Department of Public
Health (1976) applied eleven different need formulae to Massachu
setts; the resulting estimates of need for CT in the State ranged
from 5 to 52.
By 1976, the influence of the health planning process on dif
fusion of CT in the United States was apparent in terms of both the
numbers of units acquired and the distribution nationwide. By mid-
1976, 18 states and many local planning agencies had developed CT
guidelines as reported by the Arnerican Hospital Association
(1977). Moratoriums on additional CT units had been declared by
five state planning agencies to allow more time for the development
of stan dards and criteria or to await the development of more
definitive information concerning the clinical benefits of CT.
According to the Arnerican Hospital Association survey in July of
1976, 34 CT applications had been denied.
One aspect of CT diffusion that has concerned health planners and
third-party reimbursers alike was the installation of CT systems in
physicians' offices and private clinics (not under health plan
ning jurisdiction in most states). By mid-1976, 45 (of about 300
operational) units were located in neurology practices. These units
were dedicated head scanners. In response to this concern, planning
authority has been extended to cover CT purchases for private
physician offices in two states, and similar legislation is under
consideration in several others.
GOVERNMENT REGULATION OF CT THROUGH 1978 19
Paradoxically, the early trend for physicians in private prac tice
to purchase CT units was in some part the result of the attempts by
health planners to contain the proliferation of CT as pointed out
by Shapiro and Wyman (1976). Welling (1976) notes that the planning
process may also have intensified the purchases of CT by hospitals
and doctors fearful of more restrictive requirements in the future.
Lack of uniform guidelines and differing health planning mechanisms
contributed to an uneven distribution of CT units nationwide in
1974-1975. By mid-1976 (placements reflecting 1974-1975 sales), one
CT scanner was in use for every 800,000 Uni ted States inhabitants.
The scanner-to-population ratio for in dividual states, however,
ranged from 1:665,000 (New Jersey) to 1:300,000 (Florida) according
to the American Hospital Association survey of 1976. By mid-1977,
however, an analysis of state-by state placements of CT* indicated
a relatively uniform distribution of CT scanners with one scanner
per 400,000 population operational and one scanner per 180,000
population sold (including those units ordered but not
installed).
According to the survey of Fineberg et al. (1977), every state but
Missouri had some regulatory control over purchases of CT scan
ners and four-fifths had CT guidelines in effect or under develop
ment. More than 80 applications for CT had been denied, not in
cluding the important and often not counted group of applications
withdrawn before the final action of the planning authority (e.g.,
five such cases in Massachusetts alone). The ratio of denied appli
cations had risen from 1:16 in 1976 to approximately 1:10.
2.2 National Guidelines for CT
Section 1501 of the Public Health Service Act, as amended by P.L.
93-641, required that the Secretary of DHEW develop and promul
gate National Guidelines for Health Planning, including:
• Standards respecting the appropriate supply, dis tribution, and
organization of health resources,
• A statement of national health planning goals developed under
consideration of the national he health priorities set forth in
Section 1502 of the Act.
*Arthur D. Little, Inc. survey of all state and local planning
agencies (unpublished).
20 GEMPEL AND METZGER
The complete set of Guidelines will include a wide range of issues
including cost containment, access to care, availability and
distribution of health care resources, quality of care, and health
status.
In its first set of guidelines, the Health Resources Adminis
tration chose to "focus on a limited number of issues relating to
hospital resources that present important short-term opportunities
for the containment of costs and the enhancement of the quality of
care" (see Federal Register, 1978A). Significantly, CT was in
cluded as the only device among the eleven issues, which were pre
dominantly services (such as obstetrical services or supply/occu
pancy of general hospital beds).
The proposed guidelines were published (Federal Register, September
1977) for review and comment. The means for preventing duplication
of CT services and containing cost was to ensure full and
appropriate utilization of existing units. Minimum utilization was
defined as 2,500 procedures per year. It was also proposed that:
"There should be no CT scanners approved unless every ex isting or
approved CT scanner in the service area is performing at a rate
greater than 4,000 patient procedures." If actually promul gated,
this requirement would certainly have slowed the rate of CT
acquisitions in the Uni ted States. Although the American Hos
pital Association survey (1977) did indicate that some CT units
were examining as many as 25 patients per day, the mean was 13 per
day. A survey by Evens and Jost (1976) of 98 installations showed
that weekly patient volume averaged 50-55 or 10-12 patients per
day. These data suggest that a significant number of CT units
already in use would not have met the proposed guideline for maxi
mum utilization.
Hearings were held in Washington, D.C. on November 16, 1977.
Numerous issues were raised concerning the validity and
appropriate ness of establishing guidelines at all. A great deal
of concern was expressed regarding the apparent inflexibility of
the guide lines applied to differing local conditions. Finally a
number of respondents feIt that the proposed "maximum level" of
4,000 CT procedures was virtually unattainable.
The revised proposed standards published in the Federal Regis ter
(1978A) had been changed substantially. Perhaps most signifi cant
for the future utilization of CT was the lowering of the "maximum
utilization" figure from 4,000 to 2,500. Final guide lines were
issued on March 28, 1978 (see Federal Register, 1978B).
The presently constituted guidelines are reasonably consistent with
utilization requirements and other priorities being used by many
state and local planning agencies. A national standard
GOVERNMENT REGULATION OF CT TRROUGR 1978
obviously will facilitate more uniform distribution of CT units
nationwide.
21
The guidelines are to be reviewed periodically, at least every 2
years. Significant new information establishing more clearly the
efficacy of CT (including patient outcome measures) or its cost
effectiveness will probably be required before the present CT
guidelines are significantly revised or refined.
3. REIMBURSEMENT POLICY - TRE SOCIAL SECURITY ADMINISTRATION
Through the Social Security Administration (SSA) , which ad
ministers Medicare and Medicaid, the federal government exerts a
strong influence on use patterns of medical technology by its re
imbursement mechanisms and policies. The Social Security Act (which
was amended by the Social Security Amendments of 1972, P.L. 92-603)
required Federal health programs to withhold reimbursement to
hospitals for depreciation, interest, and return on equity capi
tal relating to unwarranted capital expenditures. Operationally
stated, this means that reimbursement for procedures performed on
Medicare or Medicaid patients will not be reimbursed unless CON
approval has been received. Additionally, other third-party payors,
such as Blue Cross/Blue Shield are influenced by current positions
of the SSA.
As reported by the National Academy of Sciences (1977), since
October of 1976, the SSA policy concerning Medicare coverage for CT
diagnostic services has specifically excluded body scans (i.e.,
scans other than the head). The policies of private reimbursers
with regard to CT services vary on a state-to-state basis. As a
result of the National Academy of Sciences, most states are now re
imbursing for those body procedures listed as efficacious in that
study.
4. PERFORMANCE AND SAFETY STANDARDS - TRE FOOD AND DRUG ADMINIS
TRATION
The authority of the federal government over the performance and
safety of medical equipment is derived from two statutes. One, the
Medical Device Amendments of 1976 (P.L. 94-295), which greatly
expanded the provisions of the Food, Drug, and Cosmetic Act of
1938. Under the amendments, all medical equipment and devices are
grouped into one of three classes. General controls over good
manufacturing practices are to be developed for all medical de
vices (Class 1), performance standards are to be developed for many
product classes (Class 2), and pre-market review and approval will
be required for new life-sustaining products (Class 3).
22 GEHPEL AND HETZ GER
The other statute, the Radiation Control for Health and Safety Act
of 1968 (P.L. 90-602) calls for the development and enforcement of
standards for x-ray equipment performance. The Bureau of Radio
logical Health (BRH) of the FDA does not concern itself with equip
ment design per se; however, the performance criteria have a direct
impact on design and fabrication methods.
In addition, the BRH has direct authority over the maintenance and
assembly of x-ray equipment and, in cooperation with state and
local agencies, inspects and tests products being manufactured and
in the field. Finally, the BRH concerns itself with evaluation of
x-ray techniques and practices. In this respect, compliance with
Bureau Guidelines is not compulsory but these recommendations carry
heavy de facto weight in court under circumstances of a malpractice
suit.
The BRH has allowed for aperiod from August 1, 1974 to August 1,
1979 in which x-ray components which do not meet the federal
standard may still be used, allowing for depletion of in
ventories. No specific regulations for CT units are contained in
the law or its amendments; however, performance standards for CT
equipment are currently being drafted and are expected to be
adopted by 1979. Performance standards can be expected to be modi
fied as device technology evolves.
5. LEGISLATIVE ASSISTANCE GROUPS
Legislative assistance groups advise policymakers on compli cated
issues, such as the degree and type of regulation of the health
care system needed. The implicit power of these groups is
extensive. Information gathering groups such as these ultimately
influence the formulating of such legislation as the Medical De
vices Law and the National Health Planning and Resources Develop
ment Act and the establishment of new agencies such as the Office
of Health Technology (legislation pending). Several such groups
have been actively studying CT.
In June of 1976, the Congressional Office of Technology Assess
ment published a draft memorandum concerning CT and the health
planning problems posed by its introduction and use (see Banta and
Sanes, 1976). This report pointed out the high costs of CT,
emphasizing the inconclusiveness of available evidence concerning
the benefits to be derived.
In August of 1976, the Health Research Group, a Nader-affili ated
consumer organization, urged public and private thirty-party payors
not to reimburse health care providers for CT examinations and
health planners not to approve further purchases of CT "until there
is objective evidence that the cost of buying and maintaining
GOVERNMENT REGULATION OF CT THROUGH 1978
such machines is off set by cost savings or medical benefits to
patients." (See Bogue and Wolfe, 1976.) Largely based on the
23
draft memorandum by the Congressional Office of Technology Assess
ment the study warned that CT was in danger of becoming "yet
another case of medical technology which increases health care
costs with out providing commensurate benefits to consumers of
health care." These sentiments were also presented by the group at
the CT National Guidelines Hearings in November and December of
1977.
Under the sponsorship of the Blue Cross Association, the National
Institute of Medicine of the National Academy of Sciences convened
a special committee to review what was known about CT efficacy,
cost and level of reimbursement, placement, and policy
implementation and to develop recommendations for both third-party
reimbursers and health planners (see National Academy of Sciences,
1977). The recommendations with the greatest significance for the
future diffusion of CT concerned reimbursement and control of CT in
non-institutional settings. Efficacious clinical applications
(including body examinations) were identified, and third-party
reimbursers were urged to cover CT diagnostic services for these
specified uses. In order to close the loophole in the health
planning regulations that had resulted in installation of CT units
in physicians' offices, or in clinics, the report recommended three
actions:
• "Congress should amend the National Health Planning and Resources
Development Act of 1974 to include the review of proposals for
large capital equipment expenditures in free standing ambulatory
care settings,"
• "Third-party payors should reimburse only for services provided
by CT installations approved under a Certificate-of-Need
program,"
• "Certificate-of-Need laws in each state should require the review
and approval of the acquisition of major capital equipment whether
by an indi vidual, group, or institution."
Although no specific estimates of the need for CT were given, the
report recommended that no new units be approved until, "there is
full and appropriate use of existing scanners."
At the request of the Chairman, House Committee on Appropria
tions, the General Accounting Office reviewed the plans for the
Department of Defense, the Veterans Administration, and the Depart
ment of Health, Education, and Welfare for planning and using CT
units in federal institut ions. The report (see General Accounting
Office, 1978) released in January of 1978, concluded that a
24 GEMPEL AND METZGER
coordinated Federal approach was required, coordinated with the
civilian sector.
All of these major legislative assistance groups have urged
increasing controls on the acquisition and use of CT, through con
trol of purchases and of distribution. This control has been
exerted through the reimbursement mechanisms.
Although it is difficult to isolate the specific influence of such
groups on health policy decision makers, their combined in fluence
is visible. For example, the Office of Technology Assess ment
study was influential in the setting of reimbursement policies by
the Social Security Administration. Further, in several states the
private third-party reimbursers now only reimburse for CT services
in approved installations, and in some states the CON process has
jurisdiction over all health-care providing institu tions (and
hence clinics and physician offices).
6. CONCLUSION
The use of Computed Tomography, though widely hailed by the medical
community as representing an advance in the capability of
clinicians to diagnose disease, remains a controversial issue in
the medical community in 1978. Several groups are involved in the
regulation of CT (summarized in Table 1). The efforts of those
groups over the past five years signal the beginning of a new era
of governmental influence on the United States health care system:
more rigorous clinical trials and cost justification of new
modalities will probably replace the previous process of limited
use in a few research hospitals, random trials, and eventual dif
fusion of efficacious techniques.
GOVERNMENT REGULATION OF CT THROUGH 1978 25
Table 1 - Government Regulation of CT
Health Resources Administration (HRA)
Health Systems Agency (HSA)
Social Security Administration (SSA)
Health Research Group (Nader)
General Accounting Office (GAO)
26 GEMPEL AND HETZGER
Alabama Department of Pub1ic Hea1th, Guide1ines for Acquiring Com
puterized Axial Units, Hontgomery, AL (1976).
American Hospital Association, CT Scanners: A Technica1 Report,
Chicago, IL 91977.
Banta, H. D. and Sanes, J. R., A Hemorandum on Computed Tomography
(CT) Scanners, U.S. Congress, Office of Techno1ogy Assessment (June
23, 1976).
Bogue, T. and Wolfe, S. H., CAT Scanners: Is Faneier Techno1ogy
Worth a Billion Dollars of Hea1th Consumers' Honey?, Hea1th
Research Group, Washington, D.C. (August 1976).
Comprehensive Hea1th P1anning Counci1 of Kentucky, Guide1ines and
Criteria for Special Technica1 Apparatus, Frankfurt, KY
(1975).
Evens, R. G. and Jost, R. G., "Economic Analysis of Computed
Tomography Units," Amer. J. Roentgenol. 127:191-198 (1975).
Federa1 Register 42(185):48502-48505 (September 23, 1977).
Federa1 Register 43(14):3056-3069 (January 20, 1978A).
Federa1 Register 43(60):13040-13050 (Hareh 28, 1978B).
Fineberg, H. V., Parker, G. S., and Pear1man, L. S., "CT Scanners:
Distribution and P1anning Status in the United States," New Eng. J.
Hed. 297:216-218 (1977).
General Accounting Office, Computed Tomography Scanners: Oppor
tunity for Coordinated Federa1 P1anning Before Substantia1
Acquisitions, Report to Congress (January 30, 1978).
Hea1th P1anning Counci1, Inc., Acquisition and Use of Computer
Assisted Tomography in Rhode Is1and, Providence, RI (January 1976)
.
Hea1th Services Hanagement, Inc. and The Seven Area-wide Compre
hensive Hea1th P1anning Agencies of Indiana, Computerized
Tomography: How Hany Scanners are Enough?, Indianapo1is, IN
Hassachusetts Department of Pub1ic Hea1th, CT Scanning, Boston, HA
(1976) .
GOVERNMENT REGULATION OF CT THROUGH 1978
National Academy of Sciences, Institute of Medicine, A Po1icy
Statement: Computed Tomographie Scanning, Washington, D.C. (April
1977).
New York Department of Pub1ic Hea1th, Pre1iminary Interim Guide-
1ines for Computerized Transaxial Tomography, Albany, NY (1977)
.
Ohio Department of Hea1th, Review Criteria on Computed Tomography
(CT), Co1umbus OH (1975).
Shapiro, S. H. and Wyman, S. H., "CAT Fever," New Eng. J. Med.
294:954-956 (1976).
Socia1 Security Administration, Hedicare Coverage of Computerized
Tomography Diagnostic Services (October 1976).
27
We11ing, K. M., "CAT Lovers. The Medica1 Profession Embraces the
Computerized Scanner," Barron's (August 16, 1976), p. 11.
MULTIPLE ENDPOINTS IN THE ASSESSMENT OF NON-INVASIVE
TECHNOLOGY
W. R. Ayers
1. INTRODUCTION
In 1966, $42.1 billion or 5.9 percent of the Gross National Produet
(GNP) was spent on health eare. By fiseal year 1976, health eare
spending had more than tripled - growing to $139.9 billion - and
eonsumed about 8.6 percent of the GNP. (See Washing ton Post, May
8, 1977, p. Al et seq.) Between 1965 and 1974, aeeording to a
eongressional estimate, half of the 27.7 billion inerease in
hospital eare eosts eould be aeeounted for direetly or indireetly
by the introduetion of new medieal teehnology as eited by Culliton
(1977). Despite these large dollar inereases, data showing that
more spending has resulted in improved health are un available.
The biomedieal eommunity and elinieal medieine espeeially ean no
longer afford the luxury of eostly development, wasted initial
expenditure, and ultimate attrition by disrepute - a sequenee
eharaeterized in gastrie freezing teehniques for the eontrol of
upper gastrointestinal hemorrhage and in hyperbarie oxygen
ehambers, to name two fairly reeent medieal fiaseos.
1.1 Non-Invasive Teehnology for Clinieal Chest Diseases
For example, like all elinieians, ehest physieians (pulmonary and
eardiae) depend primarily on the elinieal history, the physieal
examination, and routine laboratory studies, ineluding x-rays and
the eleetroeardiogram. Most diagnoses are made or at least strongly
suggested during that "standard elinieal workup." To be sure, the
ehest physieian mayaiso use some speeialized studies such as sputum
examination in the ease of the pulmonologist or speeialized
29
30 AYERS
maneuvers to enhance heart sounds and murmurs in the case of the
cardiologist, but these are "tricks of the trade."
The chest physician, like other specialists, has in the past been
forced to use invasive techniques (e.g., biopsies, surgical
explorations, cardiac catheterizations, etc.) in the diagnosis and
management of a sizeable portion of conditions encountered in clin
cal practice. And chest physicians, like other physicians, are in
trigued and enthused by the newer non-invasive techniques discussed
in this book.
Nuclear imaging and the measurement of radio-labeled gases for the
determination of ventilation/perfusion abnormalities in lung
disorders gained widespread clinical use in the early 1960's as
reported by Taplin (1964) and Wagner (1964). These techniques are
routinely used in the diagnosis and monitoring of pulmonary vascu
lar syndromes and more recently in the delineation of areas of myo
cardial necrosis in cardiology.
Ultrasonic imaging has been in wide clinical use since the late
1960's. (See Newell, 1963, and Grossman, 1966.) It is a rou tinely
performed diagnostic study applied primarily to cardio vascular
conditions of the chest.
Computerized tomography, a new imaging technique introduced in the
last five years, has had an unprecedented growth rate. There are
already more than 700 of these instruments in the United States,
each costing from $85,000 to $800,000. The initial instruments,
designed to scan only the head, were technically successful, but as
pointed out by Peterson (1976) at Harvard depicted very few lesions
that were treatable. Whole body scanners, now in wide clinical use,
must compete with other imaging devices, e.g., ultrasonography,
nuclear scanning, angiography and other conventional x-ray studies,
for the proper place in the diagnostician/monitor's
armamentarium.
1.2 Assessment of Medical Technology
What is needed, of course, are controlled studies using agreed-upon
criteria for measurement. Medicine must assiduously guard against
the development of such measures by economists alone. It is
characteristic of econometric analyses to quantify benefits in
terms of successful ultimate outcomes. In medical systems this
usually translates into reduced death rates or improved state of
health in a defined community.
Burger (1974) reports that, with a few notable exceptions (e.g.,
near irradication of polio by development of vaccines), most
breakthroughs in total community health have come from
technologies
ASSESSMENT OF NON-INVASIVE TECHNOLOGY
outside medicine such as nutrition, sanitation and education. (See
also the New York Times, June 26, 1977, p. E19 et seq.)
31
No one expected the development of the electrocardiograph and the
subdiscipline of electrocardiography to irradicate heart disease.
The determinants of heart health and heart disease include
variables unrelated to a device useful in the diagnosis and
monitoring of some cardiac conditions. It is likewise illogical to
expect an imaging device, such as computerized tomography, to alter
materially the incidence or outcome of community disease
rates.
Meaningful assessment of medical technology requires the
development of two conceptual frameworks. One should be used to
categorize the levels of technology being applied; the other, to
categorize the characteristics of health services to be delivered.
Then rationaloutcomes are nearly self-evident and are setting
specific.
2. LEVELS OF TECHNOLOGY
Fortunately, Thomas (1971) has categorized medical technology for
uso His concepts have been applied by Ayers (1977) to tech nology
for handicapping conditions. In Thomas' view there are three levels
of technology. The first is termed "non-technology," which is
impossible to measure in terms of its capacity to alter either the
natural course of illnesses or their outcome. It is what is meant
by the phrases "caring for" and "standing by." It is indispensable.
It is valued highly by the humanitarians in medicine and their
patients. It is sometimes called "supportive therapy." The measures
of effectiveness for this level of tech nology do not easily fit
cost-effectiveness studies.
The next level of medical technology is termed "halfway tech
nology." This relates to the kinds of things that must be done
after the fact of illness. It includes detection of or inter
vention in a process whose course quite often one is unable to do
very much about, most likely because of astate of ignorance re
garding the fundamental aspects of the disease. This level of
technology is inherently both highly sophisticated and profoundly
primitive. Some outstanding recent examples are organ transplants
and the fabrication of artificial organs and limbs. It is the
wonderfully technical world of sensors and transducers that
measure, stimulate, or simulate the body structure and function. It
is the kind of technology that in the public mind and in the media
is viewed as a breakthrough rather than as a stopgap. This is the
kind of technology, technique, or instrumentation that one must use
until there is a genuine understanding of the basic mechanisms
involved in a given disease. It is the characteristic of this kind
of technology that it costs an enormous amount of money and
requires a continuing expansion of specialized personnel
32 AYERS
and faci1ities. Computerized tomography is in this c1ass. But, most
important1y, the measures of effectiveness for ha1fway tech no10gy
are intermediate rather than ultimate. Because members of this
techno10gic c1ass are imperfect, comparative studies are especia11y
important.
The third type of techno10gy is the kind that is so effective that
it is taken for granted and attracts 1itt1e pub1ic notice. This is
the genuine1y "decisive techno10gy" of Thomas. This is the rea11y
high techno10gy that is based on the resu1ts of funda mental
understanding of disease mechanisms. When it becomes avai1ab1e, it
is re1ative1y inexpensive and easy to deliver. The Sa1k/Sabin
vaccine for polio is an examp1e. It is characteristic of most
decisive techno10gy that it is usua11y based on severa1 generations
of ha1fway techno10gy. Outcomes for ha1fway techno10gy ought not be
measured in terms app1icab1e to decisive techno10gy.
3. HEALTH SERVICES DELIVERY SYSTEMS
Many conceptua1 frameworks for the description of hea1th services
de1ivery in this country have been proposed and discussed by such
authors as F1ag1e (1969), Kissick (1970), and Garfie1d (1970).
Common to all is the deve10pment of a concept for the rational
a110cation of scarce resources to specific outcomes. These
theoretica1 descriptions must hav~ counterparts in actua1ity so
that the impact of imp1emented techno10gy can be measured. The
conceptua1ized system must be characterized according to its
inputs, the medium to be transformed, and its outcomes. One
conceptua1 system is charted in Tab1e 1.
Tab1e 1 - Conceptua1 System for Categorization of Elements in
Hea1th Services De1ivery System (after Kissick, 1970)
INPUTS MEDIUM OUTPUTS
Personne1 Organizationa1 Services (Le., structure of medi- their
kind, qua1ity,
Know1edge and ca1 care quantity, avai1- skills ability, nature
and
Financing mecha- cost) Facilities and nisms equipment
Educationa1 Dollars avai1ab1e networks
ASSESSMENT OF NON-INVASIVE TECHNOLOGY 33
Critica1 to the characterization and assessment of techno1ogy in
c1inica1 medicine is the rea1ization that diagnostic techno1ogies
can be used to support two different kinds of decisions that
doctors make with regard to their patients: (1) Nominative
decisions derived from patho-physio1ogic 1aws resu1ting in the
naming of a disease process, i.e., diagnostic decisions and (2)
Managerial decisions based on management techniques cu1minating in
the se1ection of a course of action. For examp1e, in c1inica1 chest
medicine one may be interested in not on1y naming and monitoring
the disease (i.e., diagnosis and prognosis) but also in choosing an
action (i.e., patient management). In c1inica1 situations it is not
a1ways necessary to arrive at an absolute diagnosis in order to
choose an appropriate course of action. Thus, in the case of 1ung
nodu1es, it may on1y be required to differentiate benign 1esions
from ma1ignant 1esions without attaching a specific patho1ogic
diagnosis to the nodu1e. Likewise, in cardiovascu1ar diseases, it
may be sufficient to de1ineate the anatomic character istics of an
intracardiac abnorma1ity and the order of magnitude of the
pressure/f1ow deficits, both of which can be done by non-invasive
techniques, rather than measure the precise physio1ogic deficits
that usua11y require invasive methodo1ogy.
In some of the chapters that fo11ow, se1ected case studies in the
app1ication of non-invasive techniques to c1inica1 situations in
chest medicine are discussed. No attempt has been made to be
exhaustive1y comp1ete; the cases cited are to be viewed as examp1es
of app1ication on1y.
4. CONCLUSION
Newer techno1ogies a10ne or in combination (e.g., radio1abe1ed
injections at the time of computerized tomography, angiographic
studies performed simu1taneousiy with tomography, etc.) hold
immense prospects for quicker, 1ess traumatic resu1ts that the
c1inician can use in the managerial and nominative decisions that
he makes about his patients. On1y when the benefits of these tech
niques are identified and compared can the required cost-benefit
and cost-effectiveness studies be performed.
Organized medicine has had thorny quest ions about ha1fway
techno1ogy put to it before but never when dollar cost was the
immediate concern. Esca1ating hea1th care costs and severe compe
tition for federa1 dollars have brought today's perspectives to the
assessment of ha1fway techno1ogy. The biomedica1 sciences ought to
conduct the appropriate studies of cost-benefit and cost-effective
ness with the rea1ization that criteria for measurement are
specific for the settings in which the techno1ogy is used and
shou1d be based on an appreciation of outcomes for specific levels
of techno1ogy.
34 AYERS
In the setting of increased costs and uncertain or unclear
benefits, Federal response is predictable - regulatory
legislation.
ASSESSMENT OF NON-INVASIVE TECHNOLOGY
5. REFERENCES
Ayers, W. R., "The App1ication of Techno1ogy to Handicapping Con
ditions and for Handicapped Individua1s," The White House
Conference on Handicapped Individua1s, Vo1. 1 (1977), p. 15.
Burger, E. J., "Hea1th and Hea1th Services in the United States,"
Ann. Int. Med. 80:645 (1974).
Cu11iton, B., "Science, Society and the Press," N. Eng. J. Med.
296:1450 (1977).
35
F1ag1e, C. D., "Communications and Contro1 in Comprehensive Patient
Care and Hea1th P1anning," Ann. N. Y. Acad. Sci. 161:714
(1969).
Garfie1d, S. R., "The De1ivery of Medica1 Care," Sci. Am. 222:15
(1970).
Grossmann, C. C. et a1. (eds.), Ultrasound in Medica1 Diagnosis,
New York, Plenum Press (1966).
Kissick, W. L., "Hea1th Po1icy Directions for the 1970's," N. Eng.
J. Med. 282:1343 (1970).
Newe11, J. A., "U1trasonics in Medicine," Phys. Med. Biol. 8: 241
(1963).
Peterson, o. L., "Eva1uating Medica1 Techno1ogy (Editorial) ," Ann.
Int. Med., 85:819 (1976).
Tap1in, G. V. et al. , "Suspension of Radioalbumin Aggregates for
Photoscanning of the Liver, Spleen, Lung and Other organs," J.
Nuc1. Med. 2:259 (1964).
Thomas, L., "The techno1ogy of Medicine," N. Eng. J. Med. 285: 1366
(1971).
Wagner, H. N. et a1., "Diagnosis of Massive Pu1monary Embo1ism in
Man by Radioisotope Scanning," N. Engl. J. Med. 271:377
(1964).
THE EVALUATION OF DIAGNOSTIC TESTS*
S. N. Rasmussen
Herlev Hospital
Herlev, Denmark
1. INTRODUCTION
A number of factors must be considered in the evaluation of new
methods of investigation including (a) diagnostic value, (b)
therapeutic consequence, (c) discomfort and risk to the patient,
and (d) economic cost. This chapter deals with the evalu ation of
a diagnostic test in connection with the detection or exclusion of
anatomically defined diseases with an accessible diagnostic
criterion (e.g., malignant tumors). In such cases the diagnostic
specificity may be calculated (i.e., the probability that a patient
has the disease provided the test is positive p(dlt» and the
diagnostic sensitivity may also be calculated (i.e., the
probability that a patient does not have the disease provided the
test is negative p(dlr».
Unfortunately p(dlt) and p(dlt) are rarely calculated. Instead the
clinically irrelevant inverse probabilities are determined, i.e.,
the probability that the test is positive in a patient known to
have the disease P(tld) and the probability that the test is
negative in a person who does not have the disease p(rld). Fixed
standards have been laid down for the testing of new treatments in
controlled clinical trials, whereas new methods of diagnostic
investigation are rarely subjected to a probabalistic cost/benefit
evaluation in a controlled study. Such studies are greatly
needed.
*From Rational Diagnosis and Treatment (1976) with permission of
the author, S. N. Rasmussen, and the publisher, L. B. Lippincott
Co., Philadelphia.
37
2. METHODS OF PROCEDURE
Diagnosticians, i.e., doctors working in departments of radiology,
ultrasonics, nuclear medicine, etc., carry out diagnostic
examinations and develop new diagnostic methods in order to help
their clinical colleagues. Consider the whole sequence of the
decision process: (1) The clinician defines his patient's problems
and collects the data base, i.e., routine history taking and
physical examination; (2) He decides which investigations are to be
done; (3) He assesses the results of these investigations and makes
a diagnosis; (4) He decides on the best treatment, and (5) He
assesses the treatment result. Thus, the decision process comprises
two types of decisions: (a) decisions about investiga tions and
(b) decisions about treatment.
Many clinicians have realised that it is no longer permissible to
base therapeutic decisions on tradition and uncontrolled
experience, but that the effect of both old and new therapeutic
treatment must be tested on controlled therapeutic trials. This
viewpoint is also supported by health authorities in several
countries which do not permit the introduction of new drugs unless
such trials are carried out. However, in the case of methods of
investigation most clinicians do not make the same demand. The
number of diagnostic tests at our disposal is steadily increasing,
but, in contrast to new therapeutic treatments, the benefit of
these new diagnostic tests to patients is very rarely evaluated in
controlled studies.
Books on clinical research methods effectively deal with the
principles of controlled therapeutic trials (i.e., selection of
patients, randomization, prevention of bias, statistical
evaluation, etc.) but no fixed standards have been laid down for
the evaluation of new diagnostic methods. This chapter discusses
this problem taking the approach of the clinician, because it is
the clinician who defines the clinical problem, decides which
diagnostic tests are to be done, and assesses the results of these
tests. This means that the diagnostician must provide the clinician
with infor mation which is formulated in such a way that it is
relevant to the clinician's decision on his patient's diagnosis. In
that situa tion the clinician knows the result of the diagnostic
test and he wants to decide whether or not the patient has the
disease in question.
When a new diagnostic procedure is evaluated a complex cost
benefit analysis should be carried out. Four factors have to be
considered as defined in the paragraphs below.
EVALUATION OF DIAGNOSTIC TESTS
2.1 The Diagnostic Information Obtained by the Investigation
One must take into account that clinicians use diagnostic tests (a)
to establish and (b) to exclude different diagnostic possibilities.
A test need not be equally valuable for both (a) and (b).
2.2 The Therapeutic Consequence of Establishing or Excluding a
Diagnosis
It must be considered unethical to perform an investigation
39
if it can be predicted in advance that the result will not benefit
the patient. Usually the benefit must consist of effective therapy,
although it may in some cases be important to prove that a patient
suffers from an incurable malignant disease or that he suffers from
a benign disease which needs no treatment.
2.3 Discomfort and Risk to the Patient
We must always bear in mind that some diagnostic examinations are
unpleasant and that others expose the patient to a risk of serious
complications.
2.4 Economic Cost
This includes wages to medical personnel, cost of instruments, cost
of prolonged admission to the hospital and patient's loss of
income. Such costs have to some extent been ignored by the medical
profession, but they need serious attention at a time when we are
being forced to realize that expenditure within the health care
system cannot continue its uninhibited growth.
3. EVALUATION OF DIAGNOSTIC INFORMATION
An analysis of the value of diagnostic tests is inherently linked
to the problem of different types of diseases. Consider very
briefly the three types of diseases: (1) Anatomically defined
diseases with an accessible defining criterion, e.g., most
malignant tumors; (2) Diseases with a concealed anatomical defining
criterion, e.g., myocardial infarction, where the true diagnosis is
never ascertained in the majority of patients suspected of this
disease, since they survive; (3) Clinical syndromes, e.g.,
rheumatoid arthritis where there is a continuum from patients with
completely typical pictures to patients with such atypical pictures
that some clinicians will diagnose rheumatoid arthritis and others
will not. (The American Rheumatism Association has established
a
40 RASMUSSEN
definition of rheumatoid arthritis using arbitrary criteria, but
further changes in the delimitation of the syndrome are
foreseen.)
It is extremely difficult to establish standards for the evaluation
of new tests for the diagnosis of diseases with a con cealed
defining criterion and for the diagnosis of syndromes. Therefore,
we shall concentrate on the first type of diseases, i.e., those
diseases which are anatomically defined with an accessible defining
criterion. The diagnosis of such diseases has been well analyzed in
the literature, especially by Lusted (1968).
If a new diagnostic test is suggested for the diagnosis of, for
instance, a malignant tumor, it is necessary to determine p(dlt)
and p(cllt) where P means probability, d is the presence of the
disease in question and t is the positive outcome of the test. The
symbol cl s