414 Book Reviews

P H Y S I C A L M E C H A N I S M S FOR B I O L O G I C A L E F F E C T S O F U L T R A S O U N D

By W. L. NYBORG. DHEW Publication (FDA) 78-8062, 59 pp., available without charge from BRH Technical Information Staff (HFX-25), 5600 Fishers Lane, Rockville, MD 20857

(Limited distribution).

This valuable publication comprises the text of four lectures delivered by Prof. Nyborg at the Bureau of Radiological Health, FDA, Rockville, MD during the spring 1976. The accurate abstract reads:

"In this report, available information is re- viewed on the principles or mechanisms, as they are often called, by which ultrasound produces changes in living systems. In the science of biolo- gical ultrasound, as in any other science, a know- ledge of principles is valuable in that it enhances our ability to make predictions. It is natural to stress physical mechanisms because ultrasound is a physical agent. The mechanism best understood is that of sonically generated heat. Temperature elevations can lead to sipiflcaat alterations in rates of biochemical reactions, to structural breakdown of macromolecules and membranes, and to abnormalities in developing orlunisms,

Many experiments have been done in which ultrasound is applied to aqueous suspensions of macromolncules or cells; in these, enzymes m y be inactivated or cells modified in structure and/or function. Here (when temperature elevation is avoided) the mechanism is usually sonic cavita- tion, an activity of small bodies comprised of gas or vapor.

When ultrasound produces bineffects under. cond/tions where temperature elevation is ruled out the mechanism can sometimes be identified as one associated with t ime-avemj~ souicaliy generated stresses. Among mechanisms in this class are the phenomena of radiation force (time- averaged force on a particle or structure), radia-

tion torque (time-averaged torque on a small body, which may cause it to twist or spin) and acoustic microstreaming (time-averaged circulations set up in fluid-filled spaces). Viscous stresses associated with acoustic microstreaming are especially im- portant near microscopic gaseous bodies; it is im- portant to know whether these exist in mammalian systems.

The report also contains a brief summary of available data for effects of ultrasound on mare- marian tissues. In particular the lowest intensity levels at which significant effects have been reported are compared w/th levels generated by equipment presently being used in diagnostic medical practice. Attempts to explain these b/oe~ects data in terms of principles reveal the inadequacy of our understanding at this time. Continued and inteus/fled research on mechanisms is obviously needed, especially for viscoelastic and inlmmogeueous media sim/lar to tissues. Until these mechanisms are known we cannot confidently extrapolate to cfinical situations the results obtained from laboratory experiments."

The publication of these lectures by one of the most eminent, cautious and trustworthy scientists engnged in biophysical research on the effects of ultrasound is a timely and essential service to the scientific community and the public in general.

This report can be unequivocably recommended to all readers of tbiq journal

5R/Internat/ona/ Menlo Park, California 94025, U.S.A.

P~TF~ 13. EDMONDS

E C H O C A R D I O G R A P H I C DIAGNOSIS O F C O N G E N I T A L H E A R T • D I S E A S E

By RonERTA G. WILLIAMS and CHARL~ R. TUCKER. Little Brown and Company, Boston, 1978. 352 pp. 115 t ip . U.S. $19.95.

This book has recently joined the ranks of other fine texts on Pediatric Echocard/ngraphy. It draws upon at least five years of experience by the authors. The major goal of this book is not to provide a comprehensive text on the subject of pediatric echocardingraphy and thus omits chap- ters on the physical princ/ples of diagnostic ultrasound, suprasternal notch, and contrast

echecardiosmphy. Rather, the goals of the book are to provide: fam/lian'ty with the diagnostic alp- plications, an understanding of the role and reli- abil/ty of echocardiosraphy in the clinical situn- fion, and finally, assessment of the pitfalls of the technique.

Hence, the authors have attempted to provide a quick reference atlas which can be used to sup-

Book Reviews 415

plement more complete texts on pediatric echo- cardiography. To this end, I think the authors have achieved their goals.

The book has been divided into four parts: a very brief Introduction, Normal Echocardio- graphic Anatomy, Echocardiographic Diagnosis in Acyanotic Heart Disease, and finally, Echocar- diographic Diagnosis in Cyanotic Heart Disease. Each chapter has conveniently been presented in an outline form under the following headings: anatomy, examination technique, diagnostic fea- tures, pitfalls, and differential diagnosis. This will enable readers to find very quickly specific in- formation about particular defects or lesions. In addition, the authors provide pertinent references for each of the points they. wish to make. Numerous tables of normal values likewise are referenced. This approach has provided a ready reference book on a complex subject matter. The somewhat arbitrary separation of subjects that normally inter-relate has, as the authors stated, not interfered with the design of the book or its use- fulness.

At times, the anatomic descriptions are quite detailed and may be difficult for individuals without a substantial background in congenital heart disease to follow the descriptive text. This problem could have been avoided by including more appropriate illustrations regarding the ana-

tomy. In many instances, the echoes though ac- curate and representative of the disease discussed, are very small and difficult to see. It would cer- tainly have helped if the echoes could have been expanded into much of the unused portions of the pages. Often, there was little referral of the illus- trations and echocardiograms in the text to the figures used to illustrate material. This made read- ing of the text more difficult. There were many instances in which additional illustrations and echoes would have enhanced the echographic and anatomic points that the authors wished to emphasize. This is particularly true for the pitfalls. Finally, it was somewhat disappointing that the authors failed to emphasize the clinical utility of echocardiographic systolic time intervals in assessing pulmonary vascular resistance.

All in all, I think this text provides a useful adjunct to current literature on Pediatric Echo- cardiography and would certainly be a welcome addition to the library of most pediatricians and other physicians interested in pediatric echocar- diography.

Childrens' Hospital Medical Center Cincinnati Ohio U.S.A.

R. A. MEYER