Next | ToC | Prev

Major Diagnostic Radiological Contributions to Breast Tissue Dose

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.

          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
Female          0.693   0.037   0.183   0.438   0.110
All 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.

   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

   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

   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

   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

   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

   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

   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

   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

   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

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
   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                0.250
          Now 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:

Fluoroscopic Examinations (including spot films and plates)

   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                        0.006
Final 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.

# # # # #

Next | ToC | Prev
back to PBC | CNR | radiation | rat haus | Index | Search