Stereotactic Breast BiopsyDesign and Testing

Robert J. Pizzutiello, Jr., F.A.C.M.P.Upstate Medical Physics, Inc.

716-924-0350

Overview

uWhat is a SBB?u Purpose of ACR-SBBAPu Requirements for accreditationu Technologist’s QC Testsu Medical Physicists QC Tests

Detection vs. Diagnosisu Detection

BSEPhysician Physical ExamMammographyUltrasound

u Tissue DiagnosisBiopsyCytologyHistology

333

SBB- Imaging andDose Considerations

u Localization (not detection) ofabnormalities

u Limited numbers of “normals”u Complex backgroundu Microcalcifications, massesu Limited FOV neededu Radiation risk to selected “at risk”

population

SBB X-ray Systemsu Dedicated prone units: similar to

Diagnostic Mammography Unitsu Smaller FOV required, 16o target

angleu Light Field may be replaced by two

illuminating lampsu SID may be longeru AEC may or may not be available

Types of SBB Equipment

uDedicated prone tablesuAdd-on stereo unitsuScreen-film imaginguDigital Image receptors

The CCD ImageReceptor

The CCD ImageReceptor

u Charge-Coupled Deviceu An integrated circuit (chip)

silicon wafer

u About the size of a postage stampu Converts light into electronic

image

detectors

amplifiers

LGE NL 11-22-96 #4

CCD ImageReceptors

CCD ImageReceptorsu5cm x 5cm FOV CCD, typical

uLoRad DSM (below) 5 cm x 5 cmuGE Senovision (right) 8 cm x 8 cm

Display Gradient

1 2 5 10 20 50 1000

0.05

0.1

0.15

0.2

0.25

0.3

Relative Exposure

Gra

dien

t

Characteristic Curve

1 2 5 10 20 50 1000

1

2

3

4

Relative Exposure

Opt

ical

Den

sity

Higher Film Contrast means less tolerance for exposurevariation

Exposure Latitude

Conventional x-rayexposure creates an aerialimage

Readout CCD to computer

Minify light image to CCD size

Intensifying screen convertslatent x-ray image to visiblelight image

Display, manipulate, archivedigital image

Side View

Focal Spot X-rayTube

Small areaCollimator

CompressedBreast

Phosphor

Mirror

CCD

Front View

DMAA/D

Optical coupling/mirror systemLight reflection from phosphor

Lens

CCD

Side View

Focal Spot X-rayTube

Small areaCollimator

CompressedBreast

PhosphorFiber Optic

CCD

Front View

DMAA/D

2:1 fiberoptic taper demagnificationLight transmission through phosphor

Digital Image Quality

u Contrastu Bluru Noiseu Artifactsu Dose

Factors Affecting BreastDoseu kVp, mAs

u exposure time (film only)u breast thicknessu breast composition (dense or fatty)umultiple exposures

u digital image processing does NOT affectdose

u optical density of film (if hardcopy is used)does NOT affect dose

To Minimize Breast Doseu Develop and maintain a good technique chartu Obtain manufacturer’s suggested techniquesu Evaluate image quality at different mAs values

(Technologist and Medical Physicist)u Moderately higher mAs will reduce image

noise, but increase doseu Insufficient mAs will produce a noisy (grainy)

image, but can be made to appear “wellexposed” with window/level control

u Excessive mAs images may also appear “OK”with window/level adjustment

u Minimize retakes

Principle ofStereotacticLocalization

u2-D localization -planar view

u3-D localization -triangulation neededfor depth coordinate

Our first exposure to StereoLocalization Techniques

How many pins are left?

The origin of the 15o stereo shift?

+ 15° - 15°

+ 15° View - 15° View

+ 15° - 15°

+ 15° View - 15° View

Before Lesion After Lesion

Methods of ImagingGuided Breast Biopsy

u Ultrasound guided, hand-held needleu Stereotactically guided core biopsy

Not visible on ultrasoundLocalize with millimeter precision

Core Biopsy

ACR-SBBAPHistory

u Committee convened Fall, 1995Develop professional standardsDevelop SBBAP materials for facilities

u Pilot program 1st quarter, 1996u Announced at ACR Breast Cancer

Meeting (April, 1996)u Reviewers trained

ACR-SBBAPu Modeled after ACR-MAPu 1996 vs. 1987u Personnel qualificationsu Equipment performanceu QCu Procedure verification

(through clinical image evaluation)u Image quality (phantom images)u Dose

Personnel QualificationsMedical Physicist

u Board Certification or alternate requirementsu 15 hours CE in Mammo Physics every 3 yearsu < 6/1/97

3 hands-on SBB MP Surveys, or1 hands on SBB MP Survey under guidance ofQualified SBB MP

u > 6/1/971 hands-on SBB MP Survey under guidance

u At least 1 SBB MP Survey per yearu 3 hrs CE in SBB Physics every 3 years

Physician Qualificationsvs.

Practice Model

Where a radiologist or surgeon (or otherphysician) are practicing independently, the

expertise in the diagnosis and management ofbreast disease of an individual physician mayprovide the patient with an equivalent benefit.

In a collaborative practice, the patient derives thebenefit of consultation and collaboration from the

radiologist and surgeon (or other physician)working together.

Collaborative Independent

Physician Credentialsu Mammogramsu SBBu Training, Experienceu Category I SBB coursesu QAu Radiation Physics Trainingu Supervision of RT and MPu Post biopsy recommendationsu Lesion identification at time of biopsy

Approximate StatusSeptember, 1998

u 377 facilities appliedu 278 facilities accreditedu 382 units applied - activeu 105 units applied - pendingu 182 units accredited on initial attempt

147 units with deficiencies oninitial evaluation

Clinical onlyClinical in combinationPhantom onlyPhantom in combinationDose

62 (42%)34 (23%)31 (21%) 4 ( 3%)16 (11%)

96 units passed after re-application

The latest word...u No longer accepting optical disk or

diskette. Hard copy images only.u FDA will implement regulations

mandating accreditation of facilitiesif they do not comply voluntarily

u Check TLD technique (10% failurerate for dose)

u QC Manual available early 1998

Darkroom CleanlinessProcessor Quality ControlScreen CleanlinessViewboxes & Viewing Conditions

Phantom ImagesVisual ChecklistRepeat AnalysisAnalysis of Fixer RetentionDarkroom FogScreen-Film ContactCompression

DailyDaily

WeeklyWeeklyWeeklyMonthly

QuarterlyQuarterly

Semi-annuallySemi-annuallySemi-annually

D (SF only)D (SF only)W (SF only)W (SF only)

WeeklyMonthly

QuarterlyQ-(SF only)S - (SF only)S - (SF only)

Semi-annually

Mammo SBB

QC Tests Common to Mammographyand SBB Minimum Testing Frequencies

Zero Alignment Test(only on some units)

Localization Accuracy Test (in Air)

Phantom Image Quality TestHardcopy Output Quality(if hard copy is produced from digital data)

Visual Equipment CheckRepeat AnalysisCompression Force Test

Before each patient

Daily

WeeklyMonthly

Monthly

Semi-annuallySemi-annually

QC Tests Unique to SBBMinimum Testing Frequencies

Zero Alignment Test(only on some units)

Localization Accuracy Test (in Air)

Phantom Image Quality TestHardcopy Output Quality(if hard copy is produced from digital data)

Visual Equipment CheckRepeat AnalysisCompression Force Test

An overview of the QC Tests Unique to SBB(Radiologic Technologist)

RT

Zero Alignment Test

u Perform before each patientu Verify that zero coordinate is

accurateu Assures that stereotactic unit is not

improperly installed

B

RT

Localization Accuracyu Closed loop system testu Position needle to a known

coordinateu Digitize position of needle tipu Targeting software calculates

position of needle tipu Coordinates should be identicalu ± 1.0 mm sphere

D

RT

Phantom ImageQuality Evaluation

FiberDiameters

(mm)1.561.120.890.750.540.40

SpeckDiameters

(mm)0.540.400.320.240.16

Mass Diameters (mm) 2.00, 1.00, 0.75, 0.50, 0.25

D-102

Phantom ImageQuality Evaluation

NuclearAssociates Digital

Mini Phantom

MammographyAccreditation

Phantom

W

RT

Fibers

Specks

Masses

1.561.120.80.750.540.540.40.320.240.16

21

0.750.50.25

xx

0.930.740.540.54

x0.320.240.2x1

0.750.50.25

ACRAccreditation NA Digital

Minimum PassingPhantom Image Scores

FibersSpecksMasses

ACR-MAP

Screen/film

4.03.03.0

AccreditationPhantom

Digital

5.04.03.5

Mini-Phantom

Digital

3.03.02.5

Phantom Imaging: a common avoidablefailureu NAD Digital Mini Phantom

1st image (image quality)2nd image (TLD)

u Mammo Accreditation Phantom4 images for image quality5th image for TLD

u OK to window/level digital imagesu Use grid (or not) per clinical technique

HardcopyOutput Qualityu Laser or multiformat camerau Evaluate SMPTE Test Pattern, if

availableu Record window width, levelu Produce hardcopyu Measure OD at 4 consistent

locationsu Record and monitor for consistency

M

RT

Visual Checklist

u Use ACR checklist or equivalentu Lights, switches, motion, accessoriesu Customize for your

machine/roomu Documentation

(date, initials)

M

RT

Repeat Analysisu Count repeated and rejected film by

category and tabulateu Include a log of images repeated, but

not discardedu Overall repeat rate should be < 5%u Document analysis and corrective

action - even if your repeat rate islow

Q

RT

Compression Forceu Bathroom scale or

compression gaugeu Measure maximum

compression in manualand power modes

u The scale should read25-40 pounds inautomatic mode

u Documentation

S

RT

Additional Technologist’sQC Tests (Screen-Film

only)TEST

Darkroom Cleanlinessprocessor QC

Screen CleanlinessViewboxes & Viewing

ConditionsFixer Retention Analysis

Screen-Film ContactDarkroom Fog

FREQUENCYDailyDaily

Weekly

WeeklyQuarterly

Semi-AnnuallySemi-Annually

SBB Annual Medical Physics Surveyu SBB Unit Assembly Evaluationu Collimation Assessmentu Focal Spot Performance and System Limiting

Resolutionu kVp Accuracy and Reproducibilityu Beam Quality Assessment (HVL)u Automatic Exposure Control System

Performanceu Uniformity of Screen Speed or Digital Fieldu Breast ESE, AGD, AEC Reproducibilityu Image Quality Evaluation (phantom)u Artifact Evaluationu Localization AccuracyMP

Assembly Evaluationu Free-standing unit is mechanically stable

u All moving parts move smoothly, withoutobstructions to motion

u All locks and detents work properly

u Image receptor holder is free from vibrations

u Image receptor is held securely by assembly inany orientation

MP

Assembly Evaluationu Image receptor slides smoothly into holder

assembly

u Compressed breast thickness scale is accurateto ± 0.5 cm, reproducible to ± 2 mm

u Patient or operator is not exposed to sharp orrough edges or other hazards

u Operator technique charts are posted

u Operator protected by adequate radiationshielding

MP

CollimationuDoes the x-ray beam exceed the image

receptor?

Note: X-rays beyond the digital imagereceptor will not be seen on the monitor

uDoes the biopsy window align with the imagefield of view?

MP

Performance - SystemLimitingResolutionu Line Pair Test Patternu Use film to test x-ray

machineu Use CRT image to test

“system”u Technique, clinical kVpu Scoring the image

Lines distinct over 1/2 length

kVp Accuracy -Reproducibility

u Verify that actual kVp’s are the same as the

indicated kVp’s

u Range of clinical kVp values

u Accuracy within 5%

u Reproducible CV < 0.02

MP

Beam Quality (HVL)u Thickness of aluminum

to reduce radiationexposure by one-half

u Affects contrast anddose

u Used in dosecalculation

u minimum = kVp/100

MP

AEC System Performanceu AEC available on some digital SBB unitsu Performance Capability

Record signal level asfunction of thicknessand technique

u Monitor exposure timeu Performance Capability

(4,6,8 cm)u Provide suggested

technique chart

MP

Varying thicknesses ofbreast equivalent material

Uniformity of ScreenSpeed or Digital Field

u Image a uniform phantomu Screen Film systems

Each cassette produces the sameoptical density under the sameconditions

u Digital SystemsDigital detector produces uniform signalvalues across the field of view

MP

Phantom Image Qualityu Same procedure as

for technologistsu Medical Physicist

reviews scoringprocedure andchecks forconsistency

u Uses techniquefactors for dosedeterminationMP

Breast Entrance Exposure,AGD

u Data per technique chartu Measure ESEu HVL determines DgNu AGD = ESE * DgNu AGD < 300 mradu Dose and Optical Density

MP

Artifact EvaluationUnwanted irregularity not caused

by structures of interestCauses (Digital)

Digital Image ReceptorCauses (Screen-Film)

Lint, dust, static, filter,compression device, grid,BSD, screen, film,cassette, phantom

Common CausesUnwanted objects in x-ray beamMP

Source of Artifacts (Film)

Direction of Film Feed

Source of ArtifactsChange of orientation

Processor related

Either parallel orperpendicular todirection of travel

Plus or minus density

Rollers

Guide shoes

Replenishment stream

No change of orientation

X-ray tube

Filter

Compression device

BSD

Grid (stop motion)

Cassette

Targeting Accuracyu Performed annually by technologist

under supervision of medical physicistu Position gel-type phantomu Image, target and sampleu Result: was the lesion collected?

MP

QC Program Review

u Review procedures(ACR SBB-QC Manual)

u Review documentationu Answer questionsu Written recommendations

MP

For all Technologist QC Tests

Role of the Surgeon inQuality Control

u Understand the importance of QC in SBBu Assures that personnel remain qualifiedu Support QC activities

Allow enough time for QCProvide for QC trainingPeriodically check that QC is done as required

u Confer with medical physicist annuallyu Assure that follow-up is done if the QC

program indicates corrective action is requiredu Accreditation

Summary

uWhat is a SBB?u Purpose of ACR-SBBAPu Requirements for accreditationu Technologist’s QC Testsu Medical Physicists QC Tests