Exposure of the Pregnant Patient to Diagnostic Radiations
Author: Louis Wagner et alISBN: 9780944838723 ISBN10: 0944838723
Published: 1997 | 259 pp |
OUT OF PRINT
MedicalPhysics | August 1998
"One of the most troubling moments in my career was seeing the emotional turmoil of a young lady who had been told by her physician that she should seriously consider terminating her pregnancy solely because she had received a chest x-ray. Unfortunately, many of those who counsel women concerning the risks of a radiological procedure unknowingly performed during pregnancy, or of the risks of a radiological procedure contemplated during a known pregnancy, do not have accurate information for these purposes. I found the first edition of this book, published in 1985, to be an excellent source of such information and had guarded my copy carefully while it was out of print for several years. Now this book is back in print, in a second edition, updated, and with an improved and expanded format.
"The explanations in this edition are quite clear and to the point. Even in the introduction the authors clear up possible misunderstandings by defining the terms 'gestation age,' 'conception age,' and 'menstrual age,' and also the terms 'embryo,' 'fetus,' and 'conceptus.' (My note: what we usually refer to as a 'fetal dose calculation' should more properly be called a 'conceptus dose calculation'--as it is in this book.)
"The book is divided into three parts plus appendices. Part I is titled 'Diagnostic Radiations and Risks to Unborn Children' and is composed of four chapters. Chapter 1 explains some basic concepts about radiation, x-ray examinations, and radionuclide examinations. Some fundamental radiobiology is discussed emphasizing effects on the conceptus, including the classic graphs from Russell and Brent. The nature of nonionizing radiations from ultrasound and MRI are also explained. The mechanisms for possibly harmful effects from ultrasound and from the static magnetic fields, field gradients, and radiofrequency fields of MRI are discussed.
"Chapter 2 summarizes the basic units of radiation and radioactivity. Also, the measures and units of importance in ultrasound and MRI are explained.
"Chapter 3 describes the various types of diagnostic x-ray procedures and the various factors which affect conceptus dose. Several tables provide approximate dose ranges or limits for various types of x-ray examination. A number of important concepts are clearly stated. For example when discussing the calculation of conceptus dose from CT the authors state:
It is essential not to use the CTDI for the abdomen as a reliable model for
dose estimation to the conceptus. CTDI is likely to underestimate the actual
dose for many reasons. [Bold and italics are the authors'] "Five reasons
are then given for this statement. This chapter also discussed the many factors
which affect the conceptus dose from nuclear medicine examinations. To aid
in the calculation of dose from radiopharmaceuticals the authors include
a comprehensive table, extending over six pages, of the estimated conceptus
dose per administered activity for various radio-pharmaceuticals at different
conception ages. "Chapter 4 discusses the prenatal risks from ionizing radiation
in detail and also describes the possible risks from ultrasound, magnetic
fields, and radiofrequency waves. The possible effects of ionizing radiation
include prenatal death, growth retardation, small head size, severe mental
retardation, intellectual deficit, seizures, other malformations, malignancies,
and heritable mutations. The level of risks indicated by numerous scientific
studies (this chapter alone gives 152 references, 78 of them within the last
10 years), along with the sensitive periods, are presented in a comprehensive
but concise manner. Going beyond the simple description of risks the authors
try to give some perspective to these risks. A good example is Table 4-1:
the 'Percent Likelihood of NOT developing Childhood Cancer after Prenatal
Diagnostic Irradiation.' Table 4-2 gives an excellent summary of the effects
of diagnostic levels of radiation on the conceptus and is one of the single
most useful pages of information in the book. "Part II of this book is titled,
'The Clinical Management of the Pregnant Patient Needing Diagnostic Study.'
Here we are faced with decisions concerning the diagnostic imaging of a patient
known to be pregnant. This section starts off with a detailed flow diagram
for decision making in these situations. In Chapters 5, 6, and 7 the authors
proceed through the decision making process: 'Stage I, Preliminary
Considerations, 'Stage II, Assessing the Risks--What are the Data?,' and
'Stage III, To Proceed or Not to Proceed.' Again the authors try to put the
benefits and risks into proper perspective. They state: 'To put risks into
perspective, the physician should be awaae of the normal risks of pregnancy
and the multiple teratogenic factors in modern living..' Thus in Table 7-1
they list agents or conditions (other than radiation) with associated risks
during pergnancy, which I found quite interesting. In stage I they discuss
topics such as emergency versus elective procedures and screening for pregnancy;
in stage II, estimating conceptus doses, determing gestational age, and risks
of delaying a study; in stage III, decisions to delay a study, minimizing
the dose in the study, and counseling the patient. "Part III is titled, 'The
Clinical Evaluation of Pregnant Patients Previously Exposed to Diagnostic
Radiations.' Again this section starts off with a detailed flow diagram for
decision making. In Chapters 8, 9, and 10 the authors proceed through the
decision making process in a manner similar to part II. "Chapter 11 describes
23 case studies, illustrating the concepts discussed in the rest of the book.
For example the first two cases are 'Broadside motor vehicle accident, pelvic
injury' and 'Herniated disk in 34-year-old woman.' I found this chapter a
welcome addition to the new edition. "Some readers may find the appendices
the most useful part of the book. Appendix A, 'Conceptus Dose Calculations
for X-Ray Examinations,' provides extensive guidance in the calculation of
conceptus dose with numerous tables, graphs, and equations. Several examples
are numerically worked out, comparing the results of as many as four different
methods of obtaining the conceptus dose. Doses from CT scans are covered
in depth. Also the sometimes confusing topic of doses when the conceptus
is outside the primary beam is discussed. In a similar fashion, Appendix
B covers the calculation of conceptus dose for radionuclide studies. "Exposure
of the Pregnant Patient to Diagnostic Radiations is clear, comprehensive,
and extraordinarily useful. The discussions in this book are thoughtful and
balanced, drawing from a large store of referenced publications. In short,
it is a 'classic.' It is rare to find a technical book so well done and so
on target in filling an unmet need: I know of no other publication that comes
close to comprehensively describing the concerns of diagnostic radiation
exposures to the pregnant patient. This book should be part of the essential
library of any diagnostic medical physicist. I also highly recomend it to
radiologists and genetic counselors. Anyone involved in the counseling of
pregnant patients exposed to diagnostic radiation or in the decision making
for diagnostic procedures on pregnant patients should definitely have access
to a copy of this book. Its clear, logical explanations, figures, tables,
flow charts, and numerous worked-out examples make it an excellent instructional
book for those that need to learn about this subject. Yet still it remains
a uniquely useful reference for those already familiar with the field, and
I would be surprised if the 'old pros' did not gain substantial valuable
new information and insights from this book."
Reviewed by Frank N. Ranallo
Frank N. Ranallo, Ph.D. is an Assistant Professor (CHS) of Medical Physics at the University of Wisconsin-Madison and the Radiation Consultant
to the Wisconsin Teratogen Project--Clinical Genetics Department.