Part 1. Sources of Information on Diagnostic Doses for 1920-1960
Gofman and O'Connor (p.11, 1985) tabulated data (originally from Shleien and co-workers, 1977) for medical radiographic examinations (excluding examinations of the extremities). Note carefully that these data are for a period at least a decade after the close of the 1920 to 1960 period. The key point is that whatever doses such examinations were giving in the 1977 period, we expect and shall show that, for the same numbers of examinations, the doses must have been considerably higher during the period of 1920 to 1960. We shall examine the frequency of various examinations in the post-1960 period and then examine the dose which must be considered to have gone with such frequencies or other frequencies in the earlier period.
All entries expressed as number of examinations per 100 persons (Annually) Medical Radiographic Examinations Fluoroscopic Examinations (excluding examinations of extremities) (including spot films and plates) Age Group Number of exams Age Group Number of exams (Years) per 100 persons (Years) per 100 persons Under 15 16 Under 15 1 15-24 42 15-24 3 25-34 56 25-34 5 35-44 65 35-44 9 45-54 72 45-54 12 55-64 73 55-64 13 65-74 73 65-74 15
Since these frequencies are expressed per 100 persons, the size of the total population is not at issue; at issue is the average dose for the various examinations.
How Did Doses During the 1920-1960 Period Compare with Those Beyond 1960?
An absolutely essential introduction which is required to deal realistically with the pre-1960 era consists of several facts and several descriptions of reality concerning x-radiation practice during the pre-1960 period. It will become abundantly clear why this is so.
The Statements of C.B. Braestrup (1969)
C.B. Braestrup was intimately involved in engineering practice in the radiation field in the early period. His report (Braestrup 1969) contains the following statement, according to Shapiro 1990 at page 379:
"Within the first few years of Roentgen's discovery, the application of x-rays in diagnosis required doses of the order of 1000 times that required today [meaning in 1969]. Radiographs of heavy parts of the body took exposures 30-60 minutes long. Maximum allowable exposures were set by the production of skin erythemas (300-400 rad). Thus the skin served as a personal monitor. The Wappler fluoroscope, manufactured around 1930-1935, produced 125-150 R/min at the panel. Skin reactions were produced and in some cases, permanent injury. To minimize hazard, a 100 R per examination limit was set in the New York City hospitals."
This is truly mind-boggling to hear of the earlier doses with x-ray films and plates. Scientists and physicians in practice today have trouble conceiving of a period where there was no agreed-upon physical or chemical dosimeter to ascertain how much radiation was being delivered. One monitor was, as Braestrup states appropriately, the skin of humans. It was noted that with enough radiation one finally achieves a reddening of the skin, known medically as an erythema of the skin. The early roentgenologists tended to make the assumption that if the skin had not reddened, one could not be near any serious radiation source. And as a number of these early radiologists died, their Journal showed photos of "those who pioneered for their profession and gave their lives in doing so." (See early years of American Journal of Roentgenology and Radium Therapy.)
This dosimeter --- skin --- was crude. Response depended on how big an area of skin had been irradiated. It depended on the voltage across the x-ray tube (which determines kVp of the x-rays coming out). It depended on window thickness of the x-ray tube and on the amount and type of filtration between tube and patient.
It was the erythema dose-unit, which led authors to write about delivering "one-tenth, one-fifth, or one-half an erythema." If one studies those early issues of American Journal of Roentgenology, he(she) will see the controversies about the appropriate use of the erythema doses and the controversies about physical dosimeters that would ultimately replace the living dosimeter.
Early fluoroscopy was in many ways even more mind-boggling, with physician over-exposure, patient over-exposure, and numerous technician and nurse over-exposures due to machines inadequately shielded and beams inadequately collimated. We note the introduction of the Wappler fluoroscope with a bountiful X-ray output, 125-150 R/min at the panel. So the roentgenologists who had become accustomed to a dearth of adequate exposure now found themselves not realizing what could happen in two minutes. Incidentally, the Wappler fluoroscope was a high-quality machine. "Westinghouse liked the machine so well, it bought the company." [Victor Kiam, please excuse borrowing your line.]
It is alarming to consider what these powerful machines meant in terms of fluoroscopic dosage. The statement that skin reactions were produced and in some cases, permanent injury was produced, is chilling, but not unexpected. And to learn that New York City set a 100 R examination limit on fluoroscopy in the New York hospitals should not be assumed to mean that all was well elsewhere. No doubt this is just a reflection of a little more concern there than elsewhere.
It is very hard to doubt that average fluoroscopic doses for such procedures as Upper G.I. Series, or Thorax Studies, or Gall-Bladder Examinations (cholecystograms), were at least 2, 3, or 5 Roentgens in the early period --- at a time when legislators tried to limit such exposures per exam from exceeding 100 Roentgens. In Part 3 of this chapter, we surely underestimate exposure by using 3 Roentgens as the entrance dose per average fluoroscopy in 1920-1960.
The Special Problems of Fluoroscopy in Pediatric Practice
Some special problems must be noted for newborns, infants, and children in the pediatric years.
Dr. Hanson Blatz (Blatz 1970), the director, Office of Radiation Control, New York City Department of Health, is cited in Shapiro at page 421 discussing the problem of the prescription of excess numbers of x-rays.
What follows stretches the mind so much, we felt impelled to check. We had known of Dr. Blatz, but had never met him. We telephoned Dr. Karl Z. Morgan, widely recognized as the "father" of the health physics profession. Yes, Karl knew his work well, and Karl gave him an excellent recommendation in the health physics field. These are Dr. Blatz's words from 1970 (as reported in Shapiro 1990, p.421):
"The problem of excessive use of unnecessarily repeated examinations is an abuse that could not be regulated under any circumstances. Popular feeling and professional education have been and will probably continue to be the only effective controls." And:
"And I don't think we should overlook popular feeling. Those of you who have been in the field a long time know that it was once the practice of pediatricians to fluoroscope babies and young children every month and when they had the annual checkup [presumably in the 1940s and 1950s]. When we questioned this practice, pediatricians would say, `Well, the parents expect it. They think if I don't fluoroscope the patients, they are not getting a complete examination'."
Non-Recorded Doses May Exceed Anything on Record
We now have confirmatory evidence from two sources that what Dr. Blatz described for New York City was also happening in Rochester, New York, and in Seattle, Washington. The observations of Franz Buschke and Herbert Parker (1942) and of James Pifer (1963) are detailed in Chapter 31. Some pediatricians (but not all) were routinely fluoroscoping all their patients at the monthly "well-baby" examination in the first and second years after birth. Buschke and Parker ascertained that exposures from a skillful examiner could add up --- by the second birthday --- to 200 Roentgens of entrance dose, and much more from a non-skilled examiner.
Such information suggests that fluoroscopy in young children could dominate the diagnostic radiation exposure in the 1920-1960 period. It would all depend on what fraction of pediatricians engaged in this practice --- a practice which many of them may not have recorded at all, and a practice for which they surely did not record how long the x-ray beam was on, at each examination.
Do we know of anyone who had fluoroscopy during every pediatric check-up? Yes, we do. While we were doing this study, we happened to hear by letter from a woman in New York who remembers being fluoroscoped at every pediatric exam from age 4 through age 12. Before age 4, she has no recall one way or the other, and she can not ask her mother who is no longer alive.
The Immature Technology Available in the 1920 - 1960 Era
In the 1920-1960 period, film-speed was much slower than in the post-1960 period. This had several repercussions. It took a longer exposure to make a roentgenogram. And because it took a longer exposure, the effect of motion was very serious for films, and caused bad blurring of images. So there was a high tendency for the roentgenologist to choose to do fluoroscopy. But more fluoroscopy meant even higher doses. A massive improvement became available in the later period, not available in most of the 1920-1960 era, namely fast film-screens which could enhance images in roentgenograms, and fast film screens which could enhance images in fluoroscopic practice. So on both these counts, the doses in 1920-1960 were necessarily much higher than in the 1970's and beyond, since lesser exposures became required with the faster film screens.Part 2. Radiological Doses in the Pre-1960 and the Post-1960 Eras
The Words of Dr. Francis Curry Concerning Practice as Late as in 1960
We have alluded to some of Dr. Curry's comments concerning x-ray exposure from tuberculosis screening. But we must give some more consideration of what some of his remarks must mean for dose estimates for the 1920-1960 era.
Dr. Francis Curry, deputy director and later director of public health and hospitals in San Francisco from 1960 to 1976, is quoted by Caufield at page 144 as follows:
"What was so horrible about what was happening then is that so many machines had no filters, no coning, no shielding. Many people were getting total body exposures and were getting doses big enough to show clinical symptoms."
If Dr. Curry had this to say about the 1950s, what are we to think about doses in the far more immature era of 1920 to 1950?
We have now covered some of the crucial evidences that indicate we must expect doses for any specific procedure in the 1920-1960 era to be considerably higher than those in the mid-1970s, for which we have some reasonably meaningful estimates of average doses for major diagnostic radiological procedures.
How We Shall Handle the Diagnostic Doses in the 1920-1960 Period
1. We shall assume that the frequency of examinations (diagnostic exams per 100 persons for any age bracket) is the same before 1960 as after 1960. There may be some difference, but we must carefully differentiate between growth in total number of exams which is in part related to population growth (which is large in that period) and the frequency of examinations per 100 persons in each age category after 1960.
2. The issue of "wasted radiation" is extremely important in our handling of the dose estimates. For these considerations we turn to an important publication of David Johnson and Walter Goetz (1986).
Wasted Radiation in Diagnostic Medical Exposures in the Early Period
It is a fundamental principle of diagnostic radiography today that one never permits the beam of radiation to be of larger total area than the area of the film exposed. All radiation in excess of that needed for the film is "wasted radiation" --- exposing the patient needlessly to radiation having nothing to do with diagnosis. Johnson and Goetz point out that enormous progress was made between 1964 and 1983 in reducing the amount of wasted radiation. For 1964, they found the total dose of radiation delivered in diagnostic work was 3.2 times what was needed for the film. So two-thirds of the exposure being experienced by the patient added to injury but added nothing to diagnostic efficiency. By 1982, the wasted radiation was almost all eliminated by proper collimation of the beam.
What this tells us is that before 1960, the situation was even worse --- with at least three times as much area of the body exposed as was necessary. In effect, this means that a diagnostic examination such as Upper G.I. Series undoubtedly exposed the breasts unnecessarily. Examination of the chest exposed several abdominal organs unnecessarily.
In Gofman and O'Connor (1985), for each exam we provided the anatomic limits generally used for each type of examination. Thus (at page 171) we find the following for the Upper Gastro-Intestinal Exam:
"Length of Field: For adults, the field length is 43.2 cm, and extends from 4 cm below the sternal notch to 6 cm below the iliac crests. The field center is 6 cm below the xiphoid process ..."
These dimensions tell us, by reference to anatomical diagrams, which organs are fully in the x-ray beam field, which organs are far away even from the edge of the x-ray field, and which organs are near the border of the x-ray field. When we are calculating the dose in rads to an organ by using conversion factors from entrance dose in Roentgens to absorbed organ dose in rads, we are speaking of the organ dose for those organs fully in the x-ray field. And we know about this from the position limits given above under "Length of Field" and its position with reference to body points.
The implication of the work of Johnson and Goetz is that in the earlier days (before 1964) the exposure field was much greater than is the case for exams taken more recently. This means that organs which would be partially in the field by methods used after 1983 could have been totally in the x-ray field before 1964. Organs outside the field by 1984 standards might be partially or totally within the field before 1964.
In Gofman/O'Connor 1985 at page 171, we listed six organs in females which generate most of the cancer risk from an Upper G.I. Exam: Large intestine, kidneys, pancreas, breasts, stomach, and bronchi. But that is according to post-1980 standards of practice. The reason why breast does not head the list of such organs is that the breasts are not fully in the field. So, the estimated cancer risk to breasts is less than it would be if the breasts were fully in the x-ray field.
In the pre-1964 era (and our concern is for 1920-1960), the body parts exposed represented 3 times or more than the area needed to do the examination ---- and that wasted radiation brought the breasts essentially fully in the x-ray field for some exams, partially into the field for other common exams. And for some of the common exams, the position of the beam is sufficiently far enough away, that even with the wasted radiation, we consider that there was essentially no exposure of the breasts in such exams, for example, in the pelvic and hip exams. For such examinations, we shall list the breast dose as zero. This will all come together as we consider precisely how the estimates are actually made, in the text which follows.
As we now prepare to estimate the diagnostic radiology doses for 1920-1960, we shall have to take into account for each of the x-ray procedures just what fraction of the organ is in the x-ray field before we can apply the conversion factor from Roentgens of entrance exposure to rads absorbed by the organ --- in our case, the breast-pair. And we necessarily must take wasted radiation into account. We will let the reader know which organs are regarded as fully in the field and which are only fractionally in the field. Our analysis will give accounting for such differences in developing our final estimates of breast-doses from diagnostic radiology in the 1920-1960 period.Part 3. Estimation of Diagnostic Radiology Doses for (1920-1960)
Step 1. What Were the Major Diagnostic X-Ray Procedures in Use?
NCRP 100 provides a listing of the total number of such procedures in the United States, for the 1964 - 1980 period in Table 3.7 at page 15, based upon Mettler's work (1987). Our interest is in the tabulations for the 1964 period, since this is the closest to our 1920-1960 period. We shall need the frequencies listed here for developing a final weighted average dose per diagnostic procedure.
Examination Number of Examinations (1964) Weighting (thousands) Fraction Skull 3,000 0.0442 Other Head and Neck 1,900 0.0280 Cervical Spine 2,900 0.0428 Chest Radiographic 32,400 0.4779 Abdomen (K-U-B) 2,800 0.0413 Cholecystogram 2,800 0.0413 Thoracic Spine 1,200 0.0177 Lumbar Spine 5,800 0.0855 Upper GI 5,500 0.0811 Barium Enema 3,000 0.0442 Pyelogram (Kidneys) 3,300 0.0487 Pelvis 2,100 0.0310 Hip 1,100 0.0162 ------- ------- Total, all listed exams 67,800 1.0000Excluded are extremities, since those are not tabulated in our frequency
per 100 diagnostic exams.
Excluded is Full-Spine, which is primarily a chiropractic exam, and has
been treated in the chiropractic chapter, 22.
Excluded are mammograms, which are treated in a separate chapter.
Excluded are CT Scans, which were not available in the 1920-1960 period.
The weighting factors derived here will be appplied to the doses per exam to reach our final conclusion of population average dose for 1920-1960. It is not possible to be certain that the relative distribution of exams was the same as in 1964, but any effects of variation of the distribution will not be a major factor in our dose estimation.
Step 2. Determination of the Dose for Each Complete Procedure
The basic data for each exam are provided both in Gofman/O'Connor 1985 and in Table 3.19 at pages 28-29 in NCRP 100. The entries are essentially identical in both sources, except for a minor difference in the estimated average number of films per procedure. We warn the reader that Entrance Exposure in NCRP 100 is given in coulombs per kilogram, whereas in Gofman/O'Connor, entrance exposure is given in Roentgens. NCRP does provide the conversion coefficient to Roentgens, the more familiar unit, by far.
We illustrate the procedure for determining breast-dose using the Upper Gastro-Intestinal Series data. And we shall comment for this and every other examination whether we regard the organ to be fully in the x-ray field (in 1920-1960 practices) or not. If the organ is fully in the field, the breast-dose will be as calculated. If not fully in the field, we shall provide an estimate of the fraction of the calculated dose to be used.
Upper Gastro-Intestinal Examination
Col.A Col.B Col.C Col. D Col.E Col.F Col. G Beam Entrance Rads to No. of Beam Beam HVL Final Rads Direction Dose Breasts Films HVL Adjust. per Breast-Pair Roentgens Rads AP 0.640 0.443 0.73 2.80 1.27 0.411 PA 0.547 0.020 1.15 2.86 1.55 0.036 LAT 1.147 0.210 0.05 3.01 1.61 0.017 OBL-PA 0.775 0.085 1.93 2.94 1.59 0.262 Total Average Dose ------> 0.726 rads
o - Col. A provides the kinds of directions of the x-ray beam going into the body.
AP (anterior-posterior) means the x-ray beam enters the front of the body and exits through the back of the body.
PA (posterior-anterior) means the beam enters the back, and exits through the front of the body.
LAT (lateral) means the beam enters one side of the body and exits the other side.
Detailed specification gives the information as to whether the beam enters the left side of the body or the right side. So we have LAT-LR and LAT-RL.
OBL-PA (Oblique posterior-anterior) means the beam enters half-way between the back and the side of the body. Had it been OBL-AP, it would have meant a beam entering half-way between the front and the side of the body.
o - Col. B provides the entrance dose in Roentgens. NCRP 100 gives this dose in coulombs per kilogram, which is convertible to Roentgens. We have used the NCRP 100 values, after conversion. They agree essentially perfectly with the Roentgen values for the various exams in Gofman/O'Connor 1985.
o - Col. C provides the dose in rads received by a specific organ for the entrance exposure and for the particular direction, if the organ is fully in the field. The values for dose per unit Entrance Exposure are in Table C, p. 404 of Gofman/O'Connor 1985. The entries for Female Breast are as follows (in rads per Entrance Roentgen):Organ Beam Beam Beam Beam Beam AP PA LAT-LR OBL-AP OBL-PA Breast-Pair Female 0.693 0.037 0.183 0.438 0.110All of these values are for a beam quality ("hardness"), expressed as a Half-Value Layer of 2.3 millimeters (mm) of Aluminum (Al.). This corresponds to 30 keV x-rays.
Thus, for the first line (AP) direction of beam, Col. C is obtained by multiplying 0.693 by Col.B entry in Roentgens.
(0.693 rads / Roentgen) x 0.640 Roentgens = 0.443 rads
But this is for one film and a beam quality of 2.3 mm Al. HVL.
o - Col. D provides the average number of films per examination (from NCRP 100). Of course, there are no fractional films. The fractional values reflect the taking of 0 films in some institutions, 1 film in others, 2 films in still others.
o - Col. E provides the Half-Value Layer in mm Al.
o - Col. F provides the adjustment factor for each HVL value.
Since these values are mostly not 2.3 mm Al., it is necessary to use an adjustment factor for all values other than 2.3 mm Al. Such adjustment factors are presented in Table D of Gofman/O'Connor 1985. For the AP direction and an HVL of 2.80 mm Al., the adjustment factor is 1.27, which is the value entered in Col. F.
o - Col.G. This is the final value in rads for organs fully in the x-ray field.
Col. G entry = (Col. C entry) x (Column D entry) x (Col. F entry)
= 0.443 rads/film x 0.73 films x 1.27
= 0.411 rads.
Since we consider that the breasts are essentially fully in the field with the wasted- radiation factor of the period 1920-1960, there will be no adjustment for this value of 0.411 rads for the AP view of Upper Gastro-Intestinal Exam.
This general procedure is followed for all other projections, PA, LAT, OBL-PA. The sum of all the rad doses in Col. G represents the total dose to breasts for this particular roentgen examination, for organs fully in the x-ray field.
All other examinations are handled similarly.
We can now calculate what the dose is for all the major diagnostic radiological exams to use for 1920-1960 estimates of combined dose.
o - Note: The unseen "trailing digits" in the calculations
sometimes cause results to look "off" in very small ways.
CERVICAL SPINE Col.A Col.B Col.C Col.D Col.E Col. F Col. G Beam Entrance Rads to No. of Beam Beam HVL Final Rads Direction Dose,R Breasts Films HVL Adjust. per Breast-Pair AP 0.26 0.180 1.45 2.23 0.96 0.251 PA 0.15 0.006 0.04 2.43 1.07 0.000 LAT 0.17 0.031 1.27 2.35 1.02 0.040 OBL-PA 0.20 0.022 0.89 2.35 1.05 0.020 Total Average Dose 0.311 rads Adjustment for breasts not fully in field = 0.5. Final Average Dose 0.156 rads RIBS Col.A Col.B Col.C Col.D Col.E Col. F Col. G Beam Entrance Rads to No. of Beam Beam HVL Final Rads Direction Dose,R Breasts Films HVL Adjust. per Breast-Pair AP 0.357 0.247 0.87 2.24 0.97 0.209 PA 0.289 0.011 0.80 2.44 1.07 0.009 LAT 0.186 0.034 0.08 2.98 1.34 0.004 OBL-PA 0.627 0.069 1.20 2.38 1.05 0.087 Total Average Dose 0.308 rads No adjustments for organ not fully in field. Final Average Dose 0.308 rads SHOULDER (We cut Column C in half, since exam is of one shoulder.) Col.A Col.B Col.C Col.D Col.E Col. F Col. G Beam Entrance Rads to No. of Beam Beam HVL Final Rads Direction Dose,R Breasts Films HVL Adjust. per Breast-Pair AP 0.194 0.067 1.45 2.15 0.92 0.089 PA 0.147 0.003 0.04 2.10 0.83 0.000 LAT 0.973 0.089 0.15 2.53 1.22 0.016 OBL-PA 0.306 0.017 0.13 2.30 1.00 0.002 Total Average Dose 0.108 rads No adjustments at all for breasts not fully in x-ray field. Final Average Dose 0.108 rads THORACIC SPINE (WIDE) Col.A Col.B Col.C Col.D Col.E Col. F Col. G Beam Entrance Rads to No. of Beam Beam HVL Final Rads Direction Dose,R Breasts Films HVL Adjust. per Breast-Pair AP 0.663 0.459 1.07 2.37 1.04 0.511 PA 0.516 0.019 0.00 2.50 1.19 0.000 LAT 1.457 0.267 0.93 2.42 1.12 0.278 OBL-PA 0.756 0.083 0.12 2.42 1.12 0.011 Total Average Dose 0.800 rads No adjustments at all for breasts not fully in x-ray field. Final Average Dose 0.800 rads CHOLECYSTOGRAM (Gall-Bladder) Col.A Col.B Col.C Col.D Col.E Col. F Col. G Beam Entrance Rads to No. of Beam Beam HVL Final Rads Direction Dose,R Breasts Films HVL Adjust. per Breast-Pair AP 0.543 0.376 0.48 2.46 1.08 0.195 PA 0.547 0.020 1.41 2.41 1.11 0.032 LAT 0.752 0.138 0.13 2.51 1.20 0.021 OBL-PA 0.744 0.082 1.21 2.52 1.21 0.120 Total Average Dose 0.368 rads No adjustments at all for breasts not fully in x-ray field. Final Average Dose 0.368 rads LUMBAR SPINE Col.A Col.B Col.C Col.D Col.E Col. F Col. G Beam Entrance Rads to No. of Beam Beam HVL Final Rads Direction Dose,R Breasts Films HVL Adjust. per Breast-Pair AP 0.884 0.612 1.03 2.37 1.03 0.650 PA 0.543 0.020 0.03 2.48 1.09 0.001 LAT 3.198 0.585 1.33 2.58 1.26 0.981 OBL-PA 1.109 0.122 0.46 2.51 1.20 0.067 Total Average Dose 1.698 rads No adjustments at all for breasts not fully in x-ray field. Final Average Dose 1.698 rads ABDOMEN (KIDNEY-URETER-BLADDER) Col.A Col.B Col.C Col.D Col.E Col. F Col. G Beam Entrance Rads to No. of Beam Beam HVL Final Rads Direction Dose,R Breasts Films HVL Adjust. per Breast-Pair AP 0.663 0.459 1.28 2.54 1.12 0.658 PA 0.419 0.015 0.23 2.45 1.15 0.004 LAT 2.097 0.384 0.07 2.51 1.20 0.032 OBL-PA 1.221 0.134 0.11 2.44 1.14 0.017 Total Average Dose 0.712 rads No adjustments at all for breasts not fully in x-ray field. Final Average Dose 0.712 rads BARIUM ENEMA Col.A Col.B Col.C Col.D Col.E Col. F Col. G Beam Entrance Rads to No. of Beam Beam HVL Final Rads Direction Dose,R Breasts Films HVL Adjust. per Breast-Pair Barium Enema AP 0.760 0.526 1.52 2.95 1.33 1.064 PA 0.771 0.029 0.93 2.92 1.58 0.042 LAT 4.012 0.734 0.49 3.12 1.67 0.601 OBL-PA 1.349 0.148 1.02 3.05 1.66 0.251 Total Average Dose 1.958 rads Adjustment for breasts not being fully in field = 0.33 Final Average Dose 0.646 rads INTRAVENOUS PYELOGRAM (Kidney Exam) Col.A Col.B Col.C Col.D Col.E Col. F Col. G Beam Entrance Rads to No. of Beam Beam HVL Final Rads Direction Dose,R Breasts Films HVL Adjust. per Breast-Pair AP 0.597 0.414 4.51 2.47 1.08 2.015 PA 0.442 0.016 0.20 2.53 1.22 0.004 LAT 0.527 0.096 0.04 2.59 1.27 0.005 OBL-PA 0.915 0.101 0.70 2.59 1.26 0.089 Total Average Dose 2.112 rads Adjustment for breasts not being fully in field = 0.33 Final Average Dose 0.697 rads CHEST Col.A Col.B Col.C Col.D Col.E Col. F Col. G Beam Entrance Rads to No. of Beam Beam HVL Final Rads Direction Dose,R Breasts Films HVL Adjust. per Breast-Pair AP 0.050 0.035 0.10 2.44 1.07 0.004 PA 0.027 0.001 0.92 2.51 1.20 0.001 LAT 0.081 0.015 0.50 2.80 1.47 0.011 OBL-PA 0.120 0.013 0.02 2.49 1.19 0.000 Total Average Dose 0.016 rads No adjustments at all for breasts not fully in x-ray field. Final Average Dose 0.016 rads PELVIS exam gives just about 0 rads to breast --- too low in position Final Average Dose 0.00 rads HIP exam gives just about 0 rads to breast---- too low in position. Final Average Dose 0.00 rads SKULL seems too high to affect the breasts Final Average Dose 0.00 rads OTHER HEAD AND NECK It is reasonable to take the average of skull and cervical spine doses. (0.156+0.00)/2 = 0.078 rads Final Average Dose 0.078 rads
Now we list the estimated total number of diagnostic x-ray procedures and their dose in order to obtain an overall average dose.Breast Rads Times Exam Rads Access Frequency Frequency Skull 0.000 3,000 0.0 Other Head and Neck 0.078 1,900 148.2 Cervical Spine 0.156 (0.5) 2,900 451.0 Chest Radiographic 0.016 32,400 518.4 Ribs 0.308 NA Not calculated Shoulder (One) 0.108 NA Not calculated Abdomen (KUB) 0.712 2,800 1993.6 Biliary 0.368 2,800 1030.4 Thoracic Spine 0.800 1,200 960.0 Lumbar Spine 1.698 5,800 9848.4 Upper GI 0.726 5,500 3993.0 Barium Enema 0.646 (0.33) 3,000 1938.4 Pyelogram 0.697 (0.33) 3,300 2300.0 Pelvis 0.000 2,100 0.0 Hip 0.000 1,100 0.0 Sum 67,800 23181.34 Dose for Average Exam ----> 0.342 rads
Dose to breasts per person = (0.342 rads per exam) x (exams per person).
This follows since we have calculated the mean dose from all exams, excluding exams of extremities.
Medical Radiographic Examinations 1920-1960: Each yielding 0.342 rads to breast.Age Group Number of Exams Breast Dose (Rads) per Person per Person Under 15 years 0.16 0.055 15-24 years 0.42 0.144 25-34 years 0.56 0.192 35-44 years 0.65 0.222 45-54 years 0.72 0.246 55-64 years 0.73 0.250 65-74 years 0.73 0.250Now we shall consider the additional dose from fluoroscopic exams.
We shall very conservatively estimate the fluoroscopic exposure at 3 Roentgens per exposure, at a beam half-value layer of 2.3 mm Al. In view of the discussions above concerning limiting fluoroscopic exams to 100 Roentgens per exam in New York, it would be hard to consider 3 Roentgens of entrance dose per average fluoroscopy in 1920-1960 as any sort of overestimate. By contrast, the entrance dose from each pediatric fluoroscopy was estimated by Buschke and Parker (1942, p.527) to be 8 Roentgens if the examiner was skilled, or considerably higher if the examiner was inexperienced. Below, however, readers will see that we use zero as the annual average breast-dose from fluoroscopy for children below age 15.
For all the other ages, we will pretend that the fluoroscopic beam was never used from front to back (the AP view) --- an unrealistic approximation which clearly results in an underestimate of breast-dose for all the age-groups below. Additionally, we will assume that only one-third of the fluoroscopies exposed breast tissue. So we calculate as follows:
- For breast in PA view, 0.037 rads per Roentgen for 2.3 mm Al as half-value layer.
- For 3 Roentgens exposure, total dose = 3 x 0.037 = 0.111 rads.
- And assume only 1/3 of the fluoroscopies affected the breast tissue.
- Breast Dose from fluoroscopic examinations, = (1 /3) x 0.111 = 0.037 rads.
- No adjustment for beam hardness is needed at 2.3 mm Al half-value layer.
Fluoroscopic Examinations (including spot films and plates)
Average Age Group Number of Exams Breast-Dose in Rads per Person per Person, per Year Under 15 years 0.01 0.000 15-24 years 0.03 0.001 25-34 years 0.05 0.002 35-44 years 0.09 0.003 45-54 years 0.12 0.004 55-64 years 0.13 0.005 65-74 years 0.15 0.006Final Total Doses to Breasts at Various Ages, Roentgenograms + Fluoroscopic Exams
Average Rads, Total Age Group Breast Dose per Breast-Dose per Breast-Dose Person (films) Person (fluoroscopic) per Person Under 15 years 0.055 + 0.000 0.055 15-24 years 0.144 + 0.001 0.145 25-34 years 0.192 + 0.002 0.194 35-44 years 0.222 + 0.003 0.225 45-54 years 0.246 + 0.004 0.250 55-64 years 0.250 + 0.005 0.255 65-74 years 0.250 + 0.006 0.256
Transfer of Source Data to the Master Table (Col.P)
This final tabulation, taking into account roentgenographic and fluoroscopic exams, exceedingly conservatively stated, will provide entries for every single age-year in the Master Table, Column P.
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