Medical Hypotheses (1992) n, 2zs231
Medical ffyp0porks.r @LmgmGmpUKLid19!32
Some Thoughts about the Importance of X-ray Exposure Histories for Patients L. S. KRAIN University of Illinois at the Medical Center (Chicago), Chicago, Illinois 60640, USA)
(Reprint requests to 5415 North Sheridan Road,
Abstract - The controversy regarding the importance of the definition and standardization of a radiation exposure history is identified. Cancer incidence is increasing partly due to increased diagnostic accuracy but some over utilization of diagnostic X-ray exposure has been linked with increased breast, brain, thyroid and skin cancer, leukemia and multiple myeloma incidence. Since there is a lack of standardization of radiation histories and lack of knowledge by some physicians of radiation exposure dosages, this practitioner has compiled a suggested practical reference list of common radiation exposure dosages and indications for a detailed radiation history with current references.
Introduction About 87% of the total collective dose of ionizing radiation that a typical patient population receives from man-made sources comes from diagnostic Xrays, (l-9) (according to a UK study). It has been estimated that half of this exposure is unnecessary since about 20% of X-rays are clinically redundant (1). Data concerning trends and variability of exposures are available from the Nationwide Evaluation of X-Ray Trends (NEXT) program (9). These data suggest that in spite of technological advances there has been little change in exposure (l-9). The National Council on Radiation Protection and Measurements has quantified the frequency of diagnostic X-ray exams by type and noted an l&50% increase of X-ray exams by type over the last decade (11). Date received 8 August 1991 Date accepted 30 September 1991
However only l-2% of all cancers can be attributed to medical irradiation (2). Because of a long latent period of 20-26 years for leukemia (3,4), some previous studies may underestimate radiation cancer associations and life-time cancer risks by a factor of four because follow-up is too short (4, 5). Results are inconsistent partly because the magnitude of the possible effect from fixed low dosages of radiation is so small compared with the natural occurrence of cancer (3). For this among other reasons, the taking of a radiation exposure history is controversial (Table 1) (3). Diagnostic X-radiation has been shown to be equivocally related to mortality for leukemia (3) and multiple myeloma (3) and breast cancer incidence (6). Thyroid, salivary, brain and central nervous system cancers have been significantly associated with diagnostic radiation procedures (4). Squamous cell carci-
225
226
MEDICAL HYpoTHEsEs
noma of the skin and malignant melanoma have been associated with therapeutic radiation (4). All of the above cancers are increasing in incidence beyond what would be expected by earlier diagnostic accuracy with striking increases noted for malignant melanoma (tripled since 1955) (4) childhood malignancies (4), brain tumors in the elderly (7) and children’s leukemia (4) and multiple myeloma (3). Excessive diagnostic radiation may cause complications from isotopic use in the elderly (8) birth defects (4), and sterility and/or fertility defects in middle aged populations (4). Recent studies have shown ways to assure minimum X-ray exposure such as ‘tuned-up’ state of the art equipment, trained technologists, use of rare earth
filtration, increasing filtration, intensifying screens, optimal compression in mammography, good collimation (only dose is to area within collimation) and use of shielding, etc (11). However, newer isotopic scans such as PET and thallium scans of the heart and brain deliver significant doses to target organs and poorly maintained X-ray units have added to the X-ray burden (3,4, 11) since exposure times for fluoroscopic machines vary widely (11). In addition, any fluoroscopic procedure (barium enema, upper gastrointestinal, coronary angiogram, etc) has a variable amount of fluorotime which constitutes most of the radiation received during the examination (11, 12, 13). The taking of the radiograph contributes
Table 1A Potential reasons to obtain a proper radiation history 1. To protect against radiation-induced exposure for selected populations such as:
cancer, premature
cataracts,
genetic defects and limit incremental
radiation
a. Radiation workers b. Former cancer patients who were treated with radiation and c. Individuals exposed to radiation as children during the 1940s and 1950s 2. To promote
standardization
of radiation
3. To perform public health education 4. To decrease unnecessary results.(ll) 5. Occasionally
histories and decrease medico-legal
and preventitive
liability.
public health service functions.
X-rays that may cause a greater potential for morbidity
to identify specific practitioners
who indiscriminately
use diagnostic
associated
with false positive
radiation.
6. To identify for periodic monitoring for early detection of adverse effects, persons at increased cancer because of prior exposure, e.g. the groups identified in la, b, and c.
risk of radiogenic
Table 1B Potential reams not to obtain a proper radiaticm history 1. There is no such thing as a safe ‘radiation
dosage’ due to variability
in patient:
a. Racial, genetic and ethnic factors (e.g. chromosomal markers) b. Cumulative exposure history to natural background radiation and environmental factors as diet, migration history, occupation, attitude, radon and solar flare exposure c. Undetermined variable exposure to non-background radiation of which the patient is ignorant 2. Because there is a linear dose/effect relationship for radiation, the additional risk for a diagnostic procedure is the same whether the patient has had previous exposure or not and the only relevant risk in determining the benefit/detriment ratio of a diagnostic X-ray examination is the incremental risk of the examination which is impossible to estimate because of: a. The long latent and risk period between X-ray dose and cancer occurrence, 20 years for such cancers as multiple myeloma and leukemia.(3) b. Current inability to genetically map individuals to rule out coincidental and/or familial cancer or genetic association.
221
SOME THOUGHTS ABOUT THE IMPORTANCE OF X-RAY EXPOSURE HISTORIES FOR PATIENTS
Table 2 Medical dental exposure
(millisieverts) Avg dose to bone tmrrow per exam
Type of exami~lion
Mammography (Breast Screening) Upper intestine Thoracic spine Lower intestine (Barium Enema) Lumbosacral spine Lumbar spine Intravenous pyelogram Cervical spine Cholecystography
3.00 3.00 2.00 6.00 2.00 2.00 3.00 0.50 1.00 1.00 0.50 1.00 0.46 0.20 1.00 0.50 0.04 0.10 0.30 0.30
AbdOWZl
Skull Lumbo-pelvic Chest Dental (whole mouth) Hip or upper femur (thigh) Shoulder Dental (bitewing) Extremities Positron emission scan CT scan Original Tables adapted from references Protection (1, 4. 11-14, 21, 22. 23).
Table 3 Other exposures
and data provided
3.00-5.00 1.50-4.00 1SO-I.00 0.90-2.50 0.70-2.50 0.50-1.80 0.50-1.50 0.40-0.80 0.25-0.60 0.10-0.60 0.20-0.50 0.05-0.35 0.05JJ). 10 0.10-0.30 0.20-2.50 0.20-2.50 0.05 0.05 1.&-I-5.00 1.OO-5.00
Av
Average annual dose for aviation crewmembers Residents of Denver, Colorado Frequent flyers (>lOOO flight hrs a year) 10 h polar flight, California to Europe 10 yearly concorde flights without solar flare 10 yearly commercial jet flights Cosmic radiation background average per year Tenestial radiation Radon Source: Original 13. 14
table adapted from references
Avg gona&l dose/ exam Male Female 0.10 0.30 0.10 2.00 10.00 13.00 13.00 0.10 0.05 5.00 0.10 7.00 0.10 0.10 12.00 0.10 0.02 0.10 0.30 0.30
0.10 1.50 0.10 8.00 40.00 8.00 8.00 0.10 1.50 5.00 0.10 2.50 0.10 0.10 5.00 0.10 0.02 0.10 0.15 0.15
to the author from FAA. EPA and the National Council for Radiation
(millisievens)
Activify
Avg equivalenr wholebody dose1exam
equivalent whole-body dose 1.00-17.00 0.50 1.00 0.10 0.50 0.15-2.50 0.28-1.50 0.26-1.00 0.25-0.30 1, 4. 12,
only a small portion to the total radiation dose received in these examinations (12, 13). Both the US Environmental Protection Agency (EPA) and the Food and Drug Administration have developed guidelines (11, 12, 13) for the exposure of the public to medical procedures, but few physicians and patients have them readily available. In addition a recent conference for radiation control program development has modified these (14).
This author has compiled tables of current dosage exposure from the above publications and personal communications to assist the busy practitioner, as a handy reference guide with the understanding that the government exposure references provided themselves vary between agency because they are based on different studies and consultants (11); the original reference cited should be consulted in any medical-legal dispute. Generally, most authors recommend delaying diagnostic ionizing radiation where non-life-threatening conditions are involved e.g. where workup is for academic curiosity, or studies are merely repeated for institutional convenience (rather than send for recent previous films). Institutional convenience is not a justification for repeat studies even if the dose incurred is less than SmSv. (This is especially true if the patient is under 50 years of age (1, 14).) Methods and results A comprehensive review was undertaken of Index Medicus and MEDLINE supplemented with a personal manual survey of the research literature since 1970 and data from Air Force, Navy, and Armed Forces Institute, the National Cancer Institute, National Academy of Sciences (4), SEER program,
228 Table 4 Occupatimal
MEDICAL HYPOTHESES
exposures Average annual
Source Commercial nuclear power plants (effluent releases) population within 10 miles Commercial nuclear power plants Fuel reprocessing and fabrication Industrial radiography Airline crewmembers Health workers
whole-body dose (milliFieverrs)
Medical ffyp0porks.r @LmgmGmpUKLid19!32
Some Thoughts about the Importance of X-ray Exposure Histories for Patients L. S. KRAIN University of Illinois at the Medical Center (Chicago), Chicago, Illinois 60640, USA)
(Reprint requests to 5415 North Sheridan Road,
Abstract - The controversy regarding the importance of the definition and standardization of a radiation exposure history is identified. Cancer incidence is increasing partly due to increased diagnostic accuracy but some over utilization of diagnostic X-ray exposure has been linked with increased breast, brain, thyroid and skin cancer, leukemia and multiple myeloma incidence. Since there is a lack of standardization of radiation histories and lack of knowledge by some physicians of radiation exposure dosages, this practitioner has compiled a suggested practical reference list of common radiation exposure dosages and indications for a detailed radiation history with current references.
Introduction About 87% of the total collective dose of ionizing radiation that a typical patient population receives from man-made sources comes from diagnostic Xrays, (l-9) (according to a UK study). It has been estimated that half of this exposure is unnecessary since about 20% of X-rays are clinically redundant (1). Data concerning trends and variability of exposures are available from the Nationwide Evaluation of X-Ray Trends (NEXT) program (9). These data suggest that in spite of technological advances there has been little change in exposure (l-9). The National Council on Radiation Protection and Measurements has quantified the frequency of diagnostic X-ray exams by type and noted an l&50% increase of X-ray exams by type over the last decade (11). Date received 8 August 1991 Date accepted 30 September 1991
However only l-2% of all cancers can be attributed to medical irradiation (2). Because of a long latent period of 20-26 years for leukemia (3,4), some previous studies may underestimate radiation cancer associations and life-time cancer risks by a factor of four because follow-up is too short (4, 5). Results are inconsistent partly because the magnitude of the possible effect from fixed low dosages of radiation is so small compared with the natural occurrence of cancer (3). For this among other reasons, the taking of a radiation exposure history is controversial (Table 1) (3). Diagnostic X-radiation has been shown to be equivocally related to mortality for leukemia (3) and multiple myeloma (3) and breast cancer incidence (6). Thyroid, salivary, brain and central nervous system cancers have been significantly associated with diagnostic radiation procedures (4). Squamous cell carci-
225
226
MEDICAL HYpoTHEsEs
noma of the skin and malignant melanoma have been associated with therapeutic radiation (4). All of the above cancers are increasing in incidence beyond what would be expected by earlier diagnostic accuracy with striking increases noted for malignant melanoma (tripled since 1955) (4) childhood malignancies (4), brain tumors in the elderly (7) and children’s leukemia (4) and multiple myeloma (3). Excessive diagnostic radiation may cause complications from isotopic use in the elderly (8) birth defects (4), and sterility and/or fertility defects in middle aged populations (4). Recent studies have shown ways to assure minimum X-ray exposure such as ‘tuned-up’ state of the art equipment, trained technologists, use of rare earth
filtration, increasing filtration, intensifying screens, optimal compression in mammography, good collimation (only dose is to area within collimation) and use of shielding, etc (11). However, newer isotopic scans such as PET and thallium scans of the heart and brain deliver significant doses to target organs and poorly maintained X-ray units have added to the X-ray burden (3,4, 11) since exposure times for fluoroscopic machines vary widely (11). In addition, any fluoroscopic procedure (barium enema, upper gastrointestinal, coronary angiogram, etc) has a variable amount of fluorotime which constitutes most of the radiation received during the examination (11, 12, 13). The taking of the radiograph contributes
Table 1A Potential reasons to obtain a proper radiation history 1. To protect against radiation-induced exposure for selected populations such as:
cancer, premature
cataracts,
genetic defects and limit incremental
radiation
a. Radiation workers b. Former cancer patients who were treated with radiation and c. Individuals exposed to radiation as children during the 1940s and 1950s 2. To promote
standardization
of radiation
3. To perform public health education 4. To decrease unnecessary results.(ll) 5. Occasionally
histories and decrease medico-legal
and preventitive
liability.
public health service functions.
X-rays that may cause a greater potential for morbidity
to identify specific practitioners
who indiscriminately
use diagnostic
associated
with false positive
radiation.
6. To identify for periodic monitoring for early detection of adverse effects, persons at increased cancer because of prior exposure, e.g. the groups identified in la, b, and c.
risk of radiogenic
Table 1B Potential reams not to obtain a proper radiaticm history 1. There is no such thing as a safe ‘radiation
dosage’ due to variability
in patient:
a. Racial, genetic and ethnic factors (e.g. chromosomal markers) b. Cumulative exposure history to natural background radiation and environmental factors as diet, migration history, occupation, attitude, radon and solar flare exposure c. Undetermined variable exposure to non-background radiation of which the patient is ignorant 2. Because there is a linear dose/effect relationship for radiation, the additional risk for a diagnostic procedure is the same whether the patient has had previous exposure or not and the only relevant risk in determining the benefit/detriment ratio of a diagnostic X-ray examination is the incremental risk of the examination which is impossible to estimate because of: a. The long latent and risk period between X-ray dose and cancer occurrence, 20 years for such cancers as multiple myeloma and leukemia.(3) b. Current inability to genetically map individuals to rule out coincidental and/or familial cancer or genetic association.
221
SOME THOUGHTS ABOUT THE IMPORTANCE OF X-RAY EXPOSURE HISTORIES FOR PATIENTS
Table 2 Medical dental exposure
(millisieverts) Avg dose to bone tmrrow per exam
Type of exami~lion
Mammography (Breast Screening) Upper intestine Thoracic spine Lower intestine (Barium Enema) Lumbosacral spine Lumbar spine Intravenous pyelogram Cervical spine Cholecystography
3.00 3.00 2.00 6.00 2.00 2.00 3.00 0.50 1.00 1.00 0.50 1.00 0.46 0.20 1.00 0.50 0.04 0.10 0.30 0.30
AbdOWZl
Skull Lumbo-pelvic Chest Dental (whole mouth) Hip or upper femur (thigh) Shoulder Dental (bitewing) Extremities Positron emission scan CT scan Original Tables adapted from references Protection (1, 4. 11-14, 21, 22. 23).
Table 3 Other exposures
and data provided
3.00-5.00 1.50-4.00 1SO-I.00 0.90-2.50 0.70-2.50 0.50-1.80 0.50-1.50 0.40-0.80 0.25-0.60 0.10-0.60 0.20-0.50 0.05-0.35 0.05JJ). 10 0.10-0.30 0.20-2.50 0.20-2.50 0.05 0.05 1.&-I-5.00 1.OO-5.00
Av
Average annual dose for aviation crewmembers Residents of Denver, Colorado Frequent flyers (>lOOO flight hrs a year) 10 h polar flight, California to Europe 10 yearly concorde flights without solar flare 10 yearly commercial jet flights Cosmic radiation background average per year Tenestial radiation Radon Source: Original 13. 14
table adapted from references
Avg gona&l dose/ exam Male Female 0.10 0.30 0.10 2.00 10.00 13.00 13.00 0.10 0.05 5.00 0.10 7.00 0.10 0.10 12.00 0.10 0.02 0.10 0.30 0.30
0.10 1.50 0.10 8.00 40.00 8.00 8.00 0.10 1.50 5.00 0.10 2.50 0.10 0.10 5.00 0.10 0.02 0.10 0.15 0.15
to the author from FAA. EPA and the National Council for Radiation
(millisievens)
Activify
Avg equivalenr wholebody dose1exam
equivalent whole-body dose 1.00-17.00 0.50 1.00 0.10 0.50 0.15-2.50 0.28-1.50 0.26-1.00 0.25-0.30 1, 4. 12,
only a small portion to the total radiation dose received in these examinations (12, 13). Both the US Environmental Protection Agency (EPA) and the Food and Drug Administration have developed guidelines (11, 12, 13) for the exposure of the public to medical procedures, but few physicians and patients have them readily available. In addition a recent conference for radiation control program development has modified these (14).
This author has compiled tables of current dosage exposure from the above publications and personal communications to assist the busy practitioner, as a handy reference guide with the understanding that the government exposure references provided themselves vary between agency because they are based on different studies and consultants (11); the original reference cited should be consulted in any medical-legal dispute. Generally, most authors recommend delaying diagnostic ionizing radiation where non-life-threatening conditions are involved e.g. where workup is for academic curiosity, or studies are merely repeated for institutional convenience (rather than send for recent previous films). Institutional convenience is not a justification for repeat studies even if the dose incurred is less than SmSv. (This is especially true if the patient is under 50 years of age (1, 14).) Methods and results A comprehensive review was undertaken of Index Medicus and MEDLINE supplemented with a personal manual survey of the research literature since 1970 and data from Air Force, Navy, and Armed Forces Institute, the National Cancer Institute, National Academy of Sciences (4), SEER program,
228 Table 4 Occupatimal
MEDICAL HYPOTHESES
exposures Average annual
Source Commercial nuclear power plants (effluent releases) population within 10 miles Commercial nuclear power plants Fuel reprocessing and fabrication Industrial radiography Airline crewmembers Health workers
whole-body dose (milliFieverrs)
