The use of dose quantities in radiological protection: ICRP publication 147 Ann ICRP 50(1) 2021.

The International Commission on Radiological Protection has recently published a report (ICRP Publication 147;Ann. ICRP50, 2021) on the use of dose quantities in radiological protection, under the same authorship as this Memorandum. Here, we present a brief summary of the main elements of the report. ICRP Publication 147 consolidates and clarifies the explanations provided in the 2007 ICRP Recommendations (Publication 103) but reaches conclusions that go beyond those presented in Publication 103. Further guidance is provided on the scientific basis for the control of radiation risks using dose quantities in occupational, public and medical applications. It is emphasised that best estimates of risk to individuals will use organ/tissue absorbed doses, appropriate relative biological effectiveness factors and dose-risk models for specific health effects. However, bearing in mind uncertainties including those associated with risk projection to low doses or low dose rates, it is concluded that in the context of radiological protection, effective dose may be considered as an approximate indicator of possible risk of stochastic health effects following low-level exposure to ionising radiation. In this respect, it should also be recognised that lifetime cancer risks vary with age at exposure, sex and population group. The ICRP report also concludes that equivalent dose is not needed as a protection quantity. Dose limits for the avoidance of tissue reactions for the skin, hands and feet, and lens of the eye will be more appropriately set in terms of absorbed dose rather than equivalent dose.

Trends in Medical Imaging During Pregnancy in the United States and Ontario, Canada, 1996 to 2016.

Importance: The use of medical imaging has sharply increased over the last 2 decades. Imaging rates during pregnancy have not been quantified in a large, multisite study setting. Objective: To evaluate patterns of medical imaging during pregnancy. Design, Setting, and Participants: A retrospective cohort study was performed at 6 US integrated health care systems and in Ontario, Canada. Participants included pregnant women who gave birth to a live neonate of at least 24 weeks' gestation between January 1, 1996, and December 31, 2016, and who were enrolled in the health care system for the entire pregnancy. Exposures: Computed tomography (CT), magnetic resonance imaging, conventional radiography, angiography and fluoroscopy, and nuclear medicine. Main Outcomes and Measures: Imaging rates per pregnancy stratified by country and year of child's birth. Results: A total of 3 497 603 pregnancies in 2 211 789 women were included. Overall, 26% of pregnancies were from US sites. Most (92%) were in women aged 20 to 39 years, and 85% resulted in full-term births. Computed tomography imaging rates in the United States increased from 2.0 examinations/1000 pregnancies in 1996 to 11.4/1000 pregnancies in 2007, remained stable through 2010, and decreased to 9.3/1000 pregnancies by 2016, for an overall increase of 3.7-fold. Computed tomography rates in Ontario, Canada, increased more gradually by 2.0-fold, from 2.0/1000 pregnancies in 1996 to 6.2/1000 pregnancies in 2016, which was 33% lower than in the United States. Overall, 5.3% of pregnant women in US sites and 3.6% in Ontario underwent imaging with ionizing radiation, and 0.8% of women at US sites and 0.4% in Ontario underwent CT. Magnetic resonance imaging rates increased steadily from 1.0/1000 pregnancies in 1996 to 11.9/1000 pregnancies in 2016 in the United States and from 0.5/1000 pregnancies in 1996 to 9.8/1000 pregnancies in 2016 in Ontario, surpassing CT rates in 2013 in the United States and in 2007 in Ontario. In the United States, radiography rates doubled from 34.5/1000 pregnancies in 1996 to 72.6/1000 pregnancies in 1999 and then decreased to 47.6/1000 pregnancies in 2016; rates in Ontario slowly increased from 36.2/1000 pregnancies in 1996 to 44.7/1000 pregnancies in 2016. Angiography and fluoroscopy and nuclear medicine use rates were low (5.2/1000 pregnancies), but in most years, higher in Ontario than the United States. Imaging rates were highest for women who were younger than 20 years or aged 40 years or older, gave birth preterm, or were black, Native American, or Hispanic (US data only). Considering advanced imaging only, chest imaging of pregnant women was more likely to use CT in the United States and nuclear medicine imaging in Ontario. Conclusions and Relevance: The use of CT during pregnancy substantially increased in the United States and Ontario over the past 2 decades. Imaging rates during pregnancy should be monitored to avoid unnecessary exposure of women and fetuses to ionizing radiation.

Use of effective dose.

International Commission on Radiological Protection (ICRP) Publication 103 provided a detailed explanation of the purpose and use of effective dose and equivalent dose to individual organs and tissues. Effective dose has proven to be a valuable and robust quantity for use in the implementation of protection principles. However, questions have arisen regarding practical applications, and a Task Group has been set up to consider issues of concern. This paper focusses on two key proposals developed by the Task Group that are under consideration by ICRP: (1) confusion will be avoided if equivalent dose is no longer used as a protection quantity, but regarded as an intermediate step in the calculation of effective dose. It would be more appropriate for limits for the avoidance of deterministic effects to the hands and feet, lens of the eye, and skin, to be set in terms of the quantity, absorbed dose (Gy) rather than equivalent dose (Sv). (2) Effective dose is in widespread use in medical practice as a measure of risk, thereby going beyond its intended purpose. While doses incurred at low levels of exposure may be measured or assessed with reasonable reliability, health effects have not been demonstrated reliably at such levels but are inferred. However, bearing in mind the uncertainties associated with risk projection to low doses or low dose rates, it may be considered reasonable to use effective dose as a rough indicator of possible risk, with the additional consideration of variation in risk with age, sex and population group.

A comparison of morphometric definitions of vertebral fracture.

To compare the accuracy of several approaches for defining prevalent vertebral fractures from measurements of vertebral dimensions (morphometry), we measured the lateral dimensions of vertebral bodies of 115 normal premenopausal and 100 postmenopausal women. Of the postmenopausal women two observers agreed that 49 had definite vertebral fractures and 38 were definitely normal. Using these classifications as an independent reference, women were then classified as fractured or normal by several definitions based on vertebral morphometry. No morphometric definition of vertebral fracture agreed perfectly with the consensus classifications. In general, definitions that involved combinations of measurements of anterior (Ha), middle (Hm), and posterior (Hp) vertebral height classified women more accurately than did definitions based on a single measurement or ratio. The Ha/Hp ratio produced many false positives unless it was adjusted for normal variations in the shapes of different vertebral bodies. Definitions of fracture based on a greater than 15% reduction in heights or ratios had higher sensitivity but more false positives than definitions that used a more stringent (greater than 20%) criterion. All morphometric definitions of vertebral fracture separated the post-menopausal women into two groups (fractured and normal) that had significantly (P less than 0.001) different mean spine bone density by quantitative computed tomography. Definitions that had the lowest rates of false positives also produced the largest differences in bone density between those defined as fractured and those defined as normal.

Is screening mammography effective in elderly women?

PURPOSE: Screening mammography is effective in reducing breast cancer mortality in women between the ages of 50 and 69 years. We sought to determine whether older women who undergo screening mammography have a decreased risk of metastatic breast cancer. SUBJECTS AND METHODS: We studied 690,993 women aged 66 to 79 years who were California Medicare beneficiaries from January 1992 to December 1993, and who chose the fee-for-service plan. Health Care Financing Administration part B billing records were used to determine the use of screening mammography. The extent of breast cancer (in situ, local, regional, or metastatic) was ascertained for the 6,767 women who were diagnosed with the disease in 1993, using data from the California State Cancer Registry. For each type (extent) of breast cancer, the relative risk (RR) and 95% confidence (CI) of developing breast cancer was estimated by dividing the risk of its development in screened women by the risk in women who were not screened. RESULTS: A total of 46% of women had mammography during the 2-year study period. In situ, local, and regional breast cancer were more likely to be detected among women who underwent screening mammography. For example, the relative risk of detecting local breast cancer in screened women was 3.3 (95% CI: 3.1 to 3.5). The risk of detecting metastatic breast cancer, on the other hand, was significantly reduced among women aged 66 to 79 years who underwent screening mammography (RR = 0.57, 95% CI: 0.45 to 0.72). CONCLUSION: Screening mammography is associated with a decreased risk of detecting metastatic breast cancer among elderly women. Public health recommendations need to weigh the benefit of screening elderly women against the cost and potential harm from screening and treating early lesions that may have no effect on mortality.

Effect of previous benign breast biopsy on the interpretive performance of subsequent screening mammography.

BACKGROUND: Most breast biopsies will be negative for cancer. Benign breast biopsy can cause changes in the breast tissue, but whether such changes affect the interpretive performance of future screening mammography is not known. METHODS: We prospectively evaluated whether self-reported benign breast biopsy was associated with reduced subsequent screening mammography performance using examination data from the mammography registries of the Breast Cancer Surveillance Consortium from January 2, 1996, through December 31, 2005. A positive interpretation was defined as a recommendation for any additional evaluation. Cancer was defined as any invasive breast cancer or ductal carcinoma in situ diagnosed within 1 year of mammography screening. Measures of mammography performance (sensitivity, specificity, and positive predictive value 1 [PPV1]) were compared both at woman level and breast level in the presence and absence of self-reported benign biopsy history. Referral to biopsy was considered a positive interpretation to calculate positive predictive value 2 (PPV2). Multivariable analysis of a correct interpretation on each performance measure was conducted after adjusting for registry, year of examination, patient characteristics, months since last mammogram, and availability of comparison film. Accuracy of the mammogram interpretation was measured using area under the receiver operating characteristic curve (AUC). All statistical tests were two-sided. RESULTS: A total of 2,007,381 screening mammograms were identified among 799,613 women, of which 14.6% mammograms were associated with self-reported previous breast biopsy. Multivariable adjusted models for mammography performance showed reduced specificity (odds ratio [OR] = 0.74, 95% confidence interval [CI] = 0.73 to 0.75, P < .001), PPV2 (OR = 0.85, 95% CI = 0.79 to 0.92, P < .001), and AUC (AUC 0.892 vs 0.925, P < .001) among women with self-reported benign biopsy. There was no difference in sensitivity or PPV1 in the same adjusted models, although unadjusted differences in both were found. Specificity was lowest among women with documented fine needle aspiration-the least invasive biopsy technique (OR = 0.58, 95% CI = 0.55 to 0.61, P < .001). Repeating the analysis among women with documented biopsy history, unilateral biopsy history, or restricted to invasive cancers did not change the results. CONCLUSIONS: Self-reported benign breast biopsy history was associated with statistically significantly reduced mammography performance. The difference in performance was likely because of tissue characteristics rather than the biopsy itself.

How thick is too thick? When endometrial thickness should prompt biopsy in postmenopausal women without vaginal bleeding.

OBJECTIVE: Transvaginal sonography (TVS) is routinely performed as part of a pelvic sonogram in postmenopausal women, and images of the endometrium are frequently obtained. In women without vaginal bleeding, the threshold separating normal from abnormally thickened endometrium is not known. The aim of this study was to determine an endometrial thickness threshold that should prompt biopsy in a postmenopausal woman without vaginal bleeding. METHODS: This was a theoretical cohort of postmenopausal women aged 50 years and older who were not receiving hormone therapy. We determined the risk of cancer for a postmenopausal woman with vaginal bleeding when the endometrial thickness measures > 5 mm, and then determined the endometrial thickness in a woman without vaginal bleeding that would be associated with the same risk of cancer. We used published and unpublished data to determine the sensitivity and specificity of TVS, the incidence of endometrial cancer, the percentage of women symptomatic with vaginal bleeding, and the percentage of cancer that occurs in women without vaginal bleeding. Ranges for each estimate were included in a sensitivity analysis to determine the impact of each estimate on the overall results. RESULTS: In a postmenopausal woman with vaginal bleeding, the risk of cancer is approximately 7.3% if her endometrium is thick (> 5 mm) and < 0.07% if her endometrium is thin (< or = 5 mm). An 11-mm threshold yields a similar separation between those who are at high risk and those who are at low risk for endometrial cancer. In postmenopausal women without vaginal bleeding, the risk of cancer is approximately 6.7% if the endometrium is thick (> 11 mm) and 0.002% if the endometrium is thin (< or = 11 mm). The estimated risk of cancer was sensitive to the percentage of cancer cases that were estimated to occur in women without vaginal bleeding. For the base case we estimated that 15% of cancers occur in women without vaginal bleeding. When we changed the estimate to project that only 5% of cancers occur in women without vaginal bleeding, the projected risk of cancer with a thick measurement was only 2.2%, whereas when we estimated that 20% of endometrial cancers occur in women without bleeding, the projected risk of cancer with a thick measurement was 8.9%. As a woman's age increases, her risk of cancer increases at each endometrial thickness measurement. For example, using the 11 mm threshold, the risk of cancer associated with a thick endometrium increases from 4.1% at age 50 years to 9.3% at age 79 years. Varying the other estimates used in the decision analysis within plausible ranges had no substantial effect on the results. CONCLUSIONS: In a postmenopausal woman without vaginal bleeding, if the endometrium measures > 11 mm a biopsy should be considered as the risk of cancer is 6.7%, whereas if the endometrium measures < or = 11 mm a biopsy is not needed as the risk of cancer is extremely low.

The index of radiographic area (IRA): a new approach to estimating the severity of vertebral deformity.

To assess the overall severity of vertebral deformity for an individual, we developed the index of radiographic area (IRA), a computerized method for analyzing vertebral dimensions from lateral radiographs of the spine. Six coordinates for each vertebral body are recorded in a computer by means of a digitizer. A computer program identifies all abnormal vertebrae, computes the radiographic area of the remaining normal vertebrae, and then estimates the expected normal radiographic area for the abnormal vertebrae in that individual. Differences between the expected and observed radiographic area of all abnormal vertebrae are summed to produce the IRA score. The score correlated well with the quantitative score of vertebral deformity of an experienced radiologist (r = 0.85), and with the vertebral bone density by quantitative computed tomography (QCT) (r = 0.66). The IRA is a practical, standardized method for quantitating the overall severity of vertebral deformity in individuals who have vertebral fractures. Its reproducibility for longitudinal studies and clinical trials needs further study.

Effect of ultrasound transducer frequency on the appearance of the fetal bowel.

We evaluated how ultrasound transducer frequency affected the appearance of the fetal bowel. One hundred women with singleton pregnancies, who were undergoing routine ultrasonographic examination, were assessed at a single institution. Patients with known fetal anomalies, abnormal biochemical screening results, or a history of cystic fibrosis were excluded. Images of the fetal abdomen were obtained in all patients using a single multi-Hertz transducer, with transducer frequencies set at 5 MHz and 8 MHz. Images were read separately by two radiologists, blinded to patient name and transducer frequency. Observers rated the presence or absence of echogenic bowel, defined as bowel with echogenicity greater than or equal to that of adjacent bone. Using the 8 MHz frequency, the radiologists interpreted 31% of the cases as having echogenic bowel, whereas using the 5 MHz frequency, the radiologists interpreted only 3% of the cases as having echogenic bowel (P<0.0001). A fetus was 10 times as likely to be given a diagnosis of echogenic bowel by both observers when the 8 MHz transducer was used than when the 5 MHz transducer was used by one observer (relative risk 10, 95% CI 3-11). Furthermore, using the 8 MHz frequency transducer, at least one of the radiologists interpreted echogenic bowel in 62% of the cases. We concluded that echogenic fetal bowel is a very common observation when imaging is performed with an 8 MHz transducer, and thus echogenic bowel diagnosed with an 8 MHz transducer is unlikely to reflect underlying abnormality. Identification of echogenic bowel with an 8 MHz transducer should not prompt further testing.

The variability in the interpretation of prenatal diagnostic ultrasound.

OBJECTIVES: Although prenatal ultrasound is broadly used to detect abnormal fetuses, the variability in the interpretation of second-trimester prenatal ultrasound examinations is unknown. We sought to evaluate the consistency of the interpretation of prenatal ultrasound examinations. DESIGN: Physicians who perform prenatal ultrasound and who participate in the California Maternal Serum Expanded AFP program were asked to interpret a series of test ultrasound examinations. The series of cases was selected to include a random sample of fetal structural abnormalities, ultrasound markers that have been associated with chromosomal abnormalities, and normal cases. Interobserver agreement was evaluated using a kappa statistic for each organ system. The sensitivity and false-positive rate were calculated for detecting specific anatomic abnormalities within each organ system. RESULTS: Of the 210 sonologists eligible for inclusion in the study, completed responses were received from 148 (70%). There was moderate to substantial agreement between physicians in reporting the presence of fetal abnormalities for all organ systems (kappa range 0.40-0.88, P < 0.001). The consistency was highest for the central nervous system (CNS), neck, and face. Within each organ system, the consistency was similar for major structural abnormalities and ultrasound markers of chromosomal abnormalities. The sensitivity ranged from 62% (95% confidence interval (CI) 58-66%) for major renal abnormalities to 91% (95% CI 88-94%) for CNS abnormalities, with corresponding false-positive rates of 7% (95% CI 6-9%) for renal abnormalities and 9% (95% CI 7-11%) for CNS abnormalities. For most organ systems, the sensitivity for detecting ultrasound markers of chromosomal abnormalities was similar to the sensitivity for detecting structural abnormalities. CONCLUSION: There is moderate to substantial agreement in the interpretation of second-trimester prenatal ultrasound examinations. Whether the identification of specific ultrasound abnormalities and markers is overall beneficial to patients remains to be determined.

Second-trimester ultrasound to detect fetuses with Down syndrome: a meta-analysis.

CONTEXT: Second-trimester prenatal ultrasound is widely used in an attempt to detect Down syndrome in fetuses, but the accuracy of this method is unknown. OBJECTIVE: To determine the accuracy of second-trimester ultrasound in detecting Down syndrome in fetuses. DATA SOURCES: English-language articles published between 1980 and February 1999 identified through MEDLINE and manual searches. STUDY SELECTION: Studies were included if they recorded second-trimester findings of ultrasonographic markers, chromosomal abnormalities, and clinical outcomes for a well-described sample of women. A total of 56 articles describing 1930 fetuses with Down syndrome and 130 365 unaffected fetuses were included. DATA EXTRACTION: Articles were independently reviewed, selected, and abstracted by 2 reviewers. Discrepancies in data abstraction were resolved by consensus with a third reviewer. Overall estimates of sensitivity, specificity, and positive and negative likelihood ratios were calculated for the following markers: choroid plexus cyst, thickened nuchal fold, echogenic intracardiac focus, echogenic bowel, renal pyelectasis, and humeral and femoral shortening. Results were stratified by whether markers were identified in isolation or in conjunction with fetal structural malformations. DATA SYNTHESIS: When ultrasonographic markers were observed without associated fetal structural malformations, sensitivity for each was low (range, 1%-16%), and most fetuses with such markers had normal outcomes. A thickened nuchal fold was the most accurate marker for discriminating between unaffected and affected fetuses and was associated with an approximately 17-fold increased risk of Down syndrome. If a thickened nuchal fold is used to screen for Down syndrome, 15 893 average-risk women or 6818 high-risk women would need to be screened for each case of Down syndrome identified. For each of the other 6 markers, when observed without associated structural malformations, the marker had marginal impact on the risk of Down syndrome. Because the markers were detected in only a small number of affected fetuses, the likelihood of Down syndrome did not decrease substantially after normal examination findings (none of the negative likelihood ratios were significant). CONCLUSIONS: A thickened nuchal fold in the second trimester may be useful in distinguishing unaffected fetuses from those with Down syndrome, but the overall sensitivity of this finding is too low for it to be a practical screening test for Down syndrome. When observed without associated structural malformations, the remaining ultrasonographic markers could not discriminate well between unaffected fetuses and those with Down syndrome. Using these markers as a basis for deciding to offer amniocentesis will result in more fetal losses than cases of Down syndrome detected, and will lead to a decrease in the prenatal detection of fetuses with Down syndrome.

Endovaginal ultrasound to exclude endometrial cancer and other endometrial abnormalities.

CONTEXT: Postmenopausal vaginal bleeding is a common clinical problem. Endovaginal ultrasound (EVUS) is a noninvasive diagnostic test that may help determine which women should undergo endometrial biopsy. OBJECTIVE: To determine the accuracy of EVUS in detecting endometrial disease in postmenopausal women with vaginal bleeding according to hormone replacement use. DATA SOURCES: Literature search of English-language and non-English-language articles published from 1966 through November 1996 using MEDLINE and by a manual search of bibliographies of published articles. STUDY SELECTION: Studies were included if they prospectively collected EVUS measurements of endometrial thickness prior to obtaining endometrial tissue for histologic evaluation in postmenopausal women with vaginal bleeding. Of 85 studies that included data on EVUS and endometrial histology, 35 were included in the meta-analysis and included 5892 women. DATA EXTRACTION: Articles were reviewed and independently selected and abstracted by 2 reviewers. Disagreement was resolved by consensus. DATA SYNTHESIS: The overall summary mean weighted estimates of sensitivity and specificity were calculated for thresholds of endometrial thickness from 3 to 10 mm. Using a 5-mm threshold to define abnormal endometrial thickening, 96% (95% confidence interval [CI], 94%-98%) of women with cancer had an abnormal EVUS result, whereas 92% (95% CI, 90%-93%) of women with endometrial disease (cancer, polyp, or atypical hyperplasia) had an abnormal result. This did not vary by hormone replacement use. However, the number of women with normal histology who had an abnormal EVUS result did vary by hormone replacement use. In women who were not using hormone replacement therapy, 593 (8%) with normal histological findings had an abnormal EVUS result (specificity, 92%; 95% CI, 90%-94%), whereas 1544 (23%) using hormone replacement therapy had an abnormal EVUS result (specificity, 77%; 95% CI, 75%-79%). For a postmenopausal woman with vaginal bleeding with a 10% pretest probability of endometrial cancer, her probability of cancer is 1% following a normal EVUS result. CONCLUSION: Endovaginal ultrasound has a high sensitivity for detecting endometrial cancer and other endometrial disease and can reliably identify postmenopausal women with vaginal bleeding who are highly unlikely to have significant endometrial disease so that endometrial sampling may be unnecessary.

Evaluation of the woman with postmenopausal bleeding: Society of Radiologists in Ultrasound-Sponsored Consensus Conference statement.

OBJECTIVES: A panel of 14 physicians practicing medicine in the United States with expertise in radiology, obstetrics and gynecology, gynecologic oncology, hysteroscopy, epidemiology, and pathology was convened by the Society of Radiologists in Ultrasound to discuss the role of sonography in women with postmenopausal bleeding. Broad objectives of this conference were (1) to advance understanding of the utility of different diagnostic techniques for evaluating the endometrium in women with postmenopausal bleeding; (2) to formulate useful and practical guidelines for evaluation of women with postmenopausal bleeding, specifically as it relates to the use of sonography; and (3) to offer suggestions for future research projects. SETTING: October 24 and 25, 2000, Washington, DC, preceding the annual Society of Radiologists in Ultrasound Advances in Sonography conference. PROCEDURE: Specific questions to the panel included the following: (1) What are the relative effectiveness and cost-effectiveness of using transvaginal sonography versus office (nondirected) endometrial biopsy as the initial examination for a woman with postmenopausal bleeding? (2) What are the sonographic standards for evaluating a woman with postmenopausal bleeding? (3) What are the abnormal sonographic findings in a woman with postmenopausal bleeding? (4) When should saline infusion sonohysterography or hysteroscopy be used in the evaluation of postmenopausal bleeding? (5) Should the diagnostic approach be modified for patients taking hormone replacement medications, tamoxifen, or other selective estrogen receptor modulators? CONCLUSIONS: Consensus recommendations were used to create an algorithm for evaluating women with postmenopausal bleeding. All panelists agreed that because postmenopausal bleeding is the most common presenting symptom of endometrial cancer, when postmenopausal bleeding occurs, clinical evaluation is indicated. The panelists also agreed that either transvaginal sonography or endometrial biopsy could be used safely and effectively as the first diagnostic step. Whether sonography or endometrial biopsy is used initially depends on the physician's assessment of patient risk, the nature of the physician's practice, the availability of high-quality sonography, and patient preference. Similar sensitivities for detecting endometrial carcinoma are reported for transvaginal sonography when an endometrial thickness of greater than 5 mm is considered abnormal and for endometrial biopsy when "sufficient" tissue is obtained. Currently, with respect to mortality, morbidity, and quality-of-life end points, there are insufficient data to comment as to which approach is more effective. The conference concluded by identifying several important unanswered questions and suggestions that could be addressed by future research projects.