Elisabet O. Orville
As stated previously it has been estimated by several writers that ultrasonic imaging is now used in 20% of pregnancies in the United States. Some doctors feel that in the future it nay well be used routinely in all pregnancies to check for abnormalities. A few people would even go so far as to say that universal imaging would be desirable because it would help the mother bond to her child when she sees it moving on the screen. I feel that this would be going much too far, both because of the expense and also because of the worrisome issue of the biological safety of ultrasound.
In 1979 the American Institute of Ultrasound in Medicine published a booklet titled, “
Who’s Afraid of a Hundred Milliwatts Per
Square Centimeter
?” The conclusion of this publication was that no deleterious biological effects have ever been measured at less than 100 milliwatts per cm
2
of tissue. Present ultrasound machines deliver less than 100 mW cm
2
, and many go as low as 40 mW/cm2.
A conference in 1982 on the safety of ultrasound was co-sponsored by the March of Dimes and the Pediatrics Department of Columbia University’s College of Physicians and Surgeons. Most of the studies presented indicated that there was no increase in birth defects or cancer in children who received ultrasound
in
utero
. However, as reported by the popular press, experiments
in
vitro
were less reassuring.
8
Several of these investigations seemed to indicate that there might be biological damage to cells at diagnostic levels of ultrasound. For instance, one experiment suggested that there was an effect on chromatid exchanges in human white blood cells. However, a basic dictum of science is that a scientist’s work must be reproducible by other scientists before an experiment is valid. The results of this experiment , as well as several others, could not be confirmed by other investigators.
Despite these reassuring negative results, it is still good to be cautious when using a new modality. Many of us can remember when the danger from X-rays was considered to be so minimal that irradiation was a standard treatment for swollen tonsils and acne.
The following quote sums up the current status of the question of safety of ultrasound:
In terms of identifiable hazards, obstetric ultrasound receives a clean bill of health. In addition to the substantial literature relating specifically to the fetus, we find no study in the entire body of biomedical ultrasound which clearly demonstrates that there is any effect on the mammalian fetus from pulse-echo ultrasound.
However, a responsible and vigorous scientific community will continue the search for effects.
9
Lesson Plan I: Two-dimensional sections through three-dimensional objects
Purpose To familiarize students with the appearance of two dimensional slices through a three-dimensional object. This sort of visualizing is necessary in order for them to begin to understand that ultrasound pictures really represent thin slices through the body.
Lesson Plan I will utilize common classroom and household objects and will be presented as a game to flex students’ imaginations.
Procedure
-
1. Look carefully at your pen or pencil.
-
____
a. Draw a transverse section (cross-section).
-
____
b. Draw a longitudinal section. (encourage them to draw the lead or ink cartridge as well.)
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2. Continue the exercise by having them draw both longitudinal and transverse slices through some of the following objects: coffee mug with handle, pack of cigarettes, onion etc.
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3. Now turn it into a guessing game. You draw sections of familiar objects on the board and have your students guess the object. For instance, apple, teapot, book, beaker etc.
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4. Homework. Have your students look around their homes to find other objects that they can draw sections through, then bring the drawings to class and let the other students guess what they represent.
Lesson Plan II: Sections through the human body
Purpose This lesson plan builds on the previous one. It teaches students about planes of the body and then goes on to have them identify the organs in both a transverse and sagittal (longitudinal) section. The final step is to look at slides of sonograms and to identify the organs.
Procedure
-
1. Draw the indicated sections through these two figures.
____
Transverse planes
(figure available in print form)
____
Longitudinal planes (Sagittal)
(figure available in print form)
-
2. Identifying two-dimensional views of the body organs. It is recommended that students have dissected frogs or at least looked at a three dimensional model of the human body first.
-
____
a.
Transverse section
. (This view is seen looking upward from the feet of a supine patient (lying on back). Therefore the
(figure available in print form)
-
____
Labels
:
-
____
____
1. Liver
-
____
____
2. stomach
-
____
____
3. pancreas
-
____
____
4. rgt kidney
-
____
____
5. Left kidney
-
____
____
6. spleen
-
____
____
7. spine
-
____
____
8. inferior vene cava
-
____
____
9. aorta
-
____
b.
Longitudinal
Section. (This view is seen with the patient’s feet at the right and his head at the left).
(figure available in print form)
-
____
Labels:
-
____
____
1. rib
-
____
____
2. Liver
-
____
____
3. gallbladder
-
____
____
4. kidney
-
____
____
5. intestines (small)
Lesson Plan III: Ultrasound videotapes and slides
Purpose To make the whole field of ultrasound come alive for students by showing them both slides and real-time ultrasound videotapes.
Procedure The slides which are at McCabe Center (787-8758) have a written guide accompanying them. They begin with pictures of ultrasound equipment followed by sonograms of the upper abdomen, reproductive organs and various stages of pregnancy.
The videotape (at the Yale New Haven Teachers Institute436-3316) shows several modalities such as nuclear medicine, fluoroscopy. The real-time ultrasound segment shows the organs of the upper abdomen as well as the reproductive organs.
NOTES
-
1. Kenneth J.W. Taylor,
Atlas
of Gray-Scale Ultrasonography;
New York: Churchill Livingstone, 1978, p. 39
-
2. John C. Hobbins, personal communication, July 21, 1983.
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3. John C. Hobbins, et. al., Ultrasonography in Obstetrics and Gynecology; Baltimore: Williams and Wilkins, 1983, p. 211.
-
4. John C. Hobbins, personal communication, July 21, 1983.
-
5. W.S. Van Bergen,
Obstetric Ultrasound: Applications and Principles
; Menlo Park: Addison-Wesley , 1980, p. 7.
-
6. Hobbins, pp. 136-137
-
7. John C. Hobbins, personal communication, July 21, 1983.
-
8. Joan Arehart-Treichel, Fetal Ultrasound:How Safe?,
Science
News
, v. 121, June 12, 1982, p. 396
-
9.
The Effects of Ultrasound on the Fetus
, The University of Rochester, College of Engineering and Applied Science, Rochester, N.Y. May 1983., p. 19.
