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Background: Although many patients now survive the short-term complications of bone marrow transplantation for life-threatening hematologic disease, information on the health and activity of long-term survivors is sparse.Objective: To evaluate the morbidity and mortality of patients surviving more than 5 years after allogeneic bone marrow transplantation.Design: Retrospective, multicenter study.Patients: 798 recipients of bone marrow transplants (477 adults, 321 children) from 43 European centers. Patients had received transplants before December 1985 and had survived at least 5 years. Patients had received allogeneic or syngeneic bone marrow for leukemia, lymphoma, inborn diseases of the hematopoietic and immune systems, and severe aplastic anemia.Measurements: Survival, clinical performance according to Karnofsky score (in increments of 10%), and social reintegration were assessed as outcomes. Patient age and sex, primary disease and status at transplantation, histocompatibility of the donor, conditioning regimen, type of prophylaxis of graft-versus-host disease, and acute and chronic graft-versus-host disease were evaluated as variables.Results: For the 55 5-year survivors, actuarial mortality was 8% at 10 years and 14% at 15 years. The leading causes of death were disease recurrence (21 patients), chronic graft-versus-host disease with complicating infections and lung disease (11 patients), secondary cancer (8 patients), and the acquired immunodeficiency syndrome (AIDS) (5 patients). When patients with recurrent disease were excluded, late death was associated with chronic graft-versus-host disease (P < 0.001), occurrence of secondary cancer (P < 0.001), male sex of the patient (P = 0.05), and female sex of the donor (P = 0.002). Clinical performance was normal (Karnofsky score, 100%) or minimally reduced (Karnofsky score, 90%) in 93% of patients; 89% of patients resumed full-time work or school. Reduced performance status and incomplete resumption of social activity were associated with chronic graft-versus-host disease, recurrent leukemia, AIDS, secondary cancer, organ dysfunction, and neurologic or psychological problems. Other risk factors for incomplete resumption of social activity were female sex (P = 0.002) and older age at transplantation (P = 0.001).Conclusions: More than 5 years after bone marrow transplantation, most patients were in good health (93%) and had returned to full-time work or school (89%). Recurrence of the primary disease, secondary cancer, and chronic graft-versus-host disease and its sequelae remain problems for some patients. [ABSTRACT FROM AUTHOR]

Background: Patients who receive bone marrow transplants have increased risk for new malignant conditions because of several risk factors, including conditioning with radiation and chemotherapy, immune stimulation, and malignant primary disease. The occurrence of and risk factors for malignant neoplasm in long-term survivors must be assessed.Objective: To determine the risk and define potential risk factors for new malignant conditions in long-term survivors after marrow transplantation.Design: Retrospective multicenter study.Setting: Study of the Late Effects Working Party with 45 transplantation centers cooperating in the European Cooperative Group for Blood and Marrow Transplantation.Patients: 1036 consecutive patients who underwent transplantation for leukemia, lymphoma, inborn diseases of the hematopoietic and immune systems, or severe aplastic anemia. Transplantation was done before December 1985, and patients had survived more than 5 years.Measurements: Reports on malignant neoplasms were evaluated, and the incidence was compared to that in the general population. Patient age and sex, primary disease and status at transplantation, histocompatibility of the donor, conditioning regimen, type of prophylaxis of graft-versus-host disease, development of acute and chronic graft-versus-host disease, and treatment of chronic graft-versus-host disease were evaluated as variables.Results: Median follow-up since transplantation was 10.7 years (range, 5 to 22.1 years). Malignant neoplasms were seen in 53 patients; the actuarial incidence (+/- SE) was 3.5% +/- 0.6% at 10 years and 12.8% +/- 2.6% at 15 years. The rate of new malignant disease was 3.8-fold higher than that in an age-matched control population (P < 0.001). The most frequent malignant diseases were neoplasms of the skin (14 patients), oral cavity (7 patients), uterus (including cervix) (5 patients), thyroid gland (5 patients), breast (4 patients), and glial tissue (3 patients). Median age of patients and their donors was 21 years. Malignant neoplasms were more frequent in older patients and in patients with chronic graft-versus-host disease. Older patient age and treatment of chronic graft-versus-host disease with cyclosporine were significant risk factors for new malignant neoplasms after bone marrow transplantation.Conclusions: The spectrum of neoplasms and immunosuppressive treatment with cyclosporine for chronic graft-versus-host disease as dominant risk factors indicate that immunosuppression is the major cause of malignant neoplasms in patients receiving marrow transplants. [ABSTRACT FROM AUTHOR]

Objectives: The randomized TOmosynthesis plus SYnthesized MAmmography (TOSYMA) screening trial has shown that digital breast tomosynthesis plus synthesized mammography (DBT + SM) is superior to digital mammography (DM) in invasive breast cancer detection varying with breast density. On the other hand, the overall average glandular dose (AGD) of DBT is higher than that of DM. Comparing the DBT + SM and DM trial arm, we analyzed here the mean AGD and their determinants per breast density category and related them to the respective invasive cancer detection rates (iCDR)., Methods: TOSYMA screened 99,689 women aged 50 to 69 years. Compression force, resulting breast thickness, the calculated AGD obtained from each mammography device, and previously published iCDR were used for comparisons across breast density categories in the two trial arms., Results: There were 196,622 exposures of 49,227 women (DBT + SM) and 197,037 exposures of 49,132 women (DM) available for analyses. Mean breast thicknesses declined from breast density category A (fatty) to D (extremely dense) in both trial arms. However, while the mean AGD in the DBT + SM arm declined concomitantly from category A (2.41 mGy) to D (1.89 mGy), it remained almost unchanged in the DM arm (1.46 and 1.51 mGy, respectively). In relative terms, the AGD elevation in the DBT + SM arm (64.4% (A), by 44.5% (B), 27.8% (C), and 26.0% (D)) was lowest in dense breasts where, however, the highest iCDR were observed., Conclusion: Women with dense breasts may specifically benefit from DBT + SM screening as high cancer detection is achieved with only moderate AGD elevations., Clinical Relevance Statement: TOSYMA suggests a favorable constellation for screening with digital breast tomosynthesis plus synthesized mammography (DBT + SM) in dense breasts when weighing average glandular dose elevation against raised invasive breast cancer detection rates. There is potential for density-, i.e., risk-adapted population-wide breast cancer screening with DBT + SM., Key Points: Breast thickness declines with visually increasing density in digital mammography (DM) and digital breast tomosynthesis (DBT). Average glandular doses of DBT decrease with increasing density; digital mammography shows lower and more constant values. With the smallest average glandular dose difference in dense breasts, DBT plus SM had the highest difference in invasive breast cancer detection rates., (© 2024. The Author(s).)

Background: Radiologic imaging technologies like computed tomography (CT) have the potential to screen for various diseases. The potential benefits of screening are always associated with risks, particularly from the application of ionizing radiation., Materials and Methods: The International Basic Safety Standards as well as the Council Directive 2013/59/Euratom have set guidelines for the application of ionizing radiation in early detection which were transposed into the German Radiation Protection Law. Accordingly, the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) approves screening examinations on a generic level, based on a scientific report provided by the German Federal Office for Radiation Protection (BfS), and defines in a federal statutory ordinance which type of screening is permissible for detecting a disease for a particular group of persons and under which conditions., Results: With exception of the mammography screening programme, no radiological examination for the early detection of disease has been approved in Germany to date. However, such screenings are currently being offered in Germany. The BfS is currently conducting a scientific evaluation for lung cancer screening with low-dose CT., Conclusions: Screening examinations with radiological imaging can only be approved when studies with the highest level of evidence have demonstrated that the benefits outweigh the risks. To translate this favourable benefit-risk balance into general health care, strict requirements for the entire screening process including quality assurance must be defined.

As stated by the Fleischner Society, an additional computed tomography (CT) scan in expiration is beneficial in patients with chronic obstructive pulmonary disease (COPD). It was thus the aim of this study to evaluate the radiation risk of a state-of-the-art paired inspiratory-expiratory chest scan compared to inspiration-only examinations. Radiation doses to 28 organs were determined for 824 COPD patients undergoing routine chest examinations at three different CT systems-a conventional multi-slice CT (MSCT), a 2nd generation (2nd-DSCT), and 3rd generation dual-source CT (3rd-DSCT). Patients examined at the 3rd-DSCT received a paired inspiratory-expiratory scan. Organ doses, effective doses, and lifetime attributable cancer risks (LAR) were calculated. All organ and effective doses were significantly lower for the paired inspiratory-expiratory protocol (effective doses: 4.3 ± 1.5 mSv (MSCT), 3.0 ± 1.2 mSv (2nd-DSCT), and 2.0 ± 0.8 mSv (3rd-DSCT)). Accordingly, LAR was lowest for the paired protocol with an estimate of 0.025 % and 0.013% for female and male patients (50 years) respectively. Image quality was not compromised. Paired inspiratory-expiratory scans can be acquired on 3rd-DSCT systems at substantially lower dose and risk levels when compared to inspiration-only scans at conventional CT systems, offering promising prospects for improved COPD diagnosis.

Background: In Germany, approximately 95% of man-made radiation exposure of the population results from diagnostic and interventional X‑ray procedures. Thus, radiation protection of patients in this field of application is of great importance., Objective: Quantification and evaluation of current data on the frequency and doses of X‑ray procedures as well as temporal trends for the years 2007-2014., Material and Methods: For outpatients the frequency of X‑ray procedures was estimated using reimbursement data from health insurances and for inpatients by means of hospital statistics. For the years under review, representative values for the effective dose per X‑ray application were determined mainly from data reported by X‑ray departments to the competent authorities., Results: In 2014 approximately 140 million X‑ray procedures were performed in Germany with some 40% from dental examinations. On average 1.7 procedures per inhabitant and year were almost constantly carried out between 2007 and 2014. Besides dental diagnostics, X‑ray examinations of the skeleton and thorax were performed most frequently. The number of computed tomography (CT) examinations increased by approximately 40%. The increase in magnetic resonance imaging (MRI) was even more pronounced with approximately 55% but overall CT examinations were still performed more often than MRI. The doses per X‑ray procedure were only slightly reduced, despite the various dose reduction approaches established in recent years; therefore, the mean effective dose per inhabitant increased from approximately 1.4 mSv in 2007 to 1.6 mSv in 2014, mainly due to the increasing frequency of CT examinations., Conclusion: The principles of justification and optimization of radiological procedures are to be consistently applied in each individual instance, especially in the case of CT examinations.

The aim of this study was to systematically evaluate the cumulative radiation exposure and the associated lifetime-cancer-risk from diagnostic imaging in patients with Hodgkin-lymphoma-(HL) or diffuse-large-B-cell-lymphoma (DLBCL). 99 consecutive patients (53-males) diagnosed with HL or DLBCL were included in the study and followed. Based on the imaging reports, organ and effective-doses-(ED) were calculated individually for each patient and the excess lifetime risks were estimated. The average ED in the first year after diagnosis was significantly different for men (59 ± 33 mSv) and women (74 ± 33 mSv)-(p < 0.05). The mean cumulative ED in each of the following 5 years was 16 ± 16 mSv without significant differences between men and women-(p > 0.05). Over all years, more than 90% of the ED resulted from CT. The average cumulative radiation risk estimated for the first year was significantly lower for men (0.76 ± 0.41%) as compared to women (1.28 ± 0.54%)-(p < 0.05). The same was found for each of the subsequent 5-years (men-0.18 ± 0.17%; women-0.28 ± 0.25%)-(p < 0.05). In conclusion, for HL and DLBCL patients investigated in this study, a cumulative radiation risk of about 1 excess cancer per 100 patients is estimated for diagnostic imaging procedures performed during both the first year after diagnosis and a follow-up period of 5 years.

Dynamic contrast-enhanced (DCE) CT studies are increasingly used in both medical care and clinical trials to improve diagnosis and therapy management of the most common life-threatening diseases: stroke, coronary artery disease and cancer. It is thus the aim of this review to briefly summarize the current knowledge on deterministic and stochastic radiation effects relevant for patient protection, to present the essential concepts for determining radiation doses and risks associated with DCE-CT studies as well as representative results, and to discuss relevant aspects to be considered in the process of justification and optimization of these studies. For three default DCE-CT protocols implemented at a latest-generation CT system for cerebral, myocardial and cancer perfusion imaging, absorbed doses were measured by thermoluminescent dosimeters at an anthropomorphic body phantom and compared with thresholds for harmful (deterministic) tissue reactions. To characterize stochastic radiation risks of patients from these studies, life-time attributable cancer risks (LAR) were estimated using sex-, age-, and organ-specific risk models based on the hypothesis of a linear non-threshold dose-response relationship. For the brain, heart and pelvic cancer studies considered, local absorbed doses in the imaging field were about 100-190 mGy (total CTDI(vol), 200 mGy), 15-30 mGy (16 mGy) and 80-270 mGy (140 mGy), respectively. According to a recent publication of the International Commission on Radiological Protection (ICRP Publication 118, 2012), harmful tissue reactions of the cerebro- and cardiovascular systems as well as of the lenses of the eye become increasingly important at radiation doses of more than 0.5 Gy. The LARs estimated for the investigated cerebral and myocardial DCE-CT scenarios are less than 0.07% for males and 0.1% for females at an age of exposure of 40 years. For the considered tumor location and protocol, the corresponding LARs are more than 6 times as high. Stochastic radiation risks decrease substantially with age and are markedly higher for females than for males. To balance the diagnostic needs and patient protection, DCE-CT studies have to be strictly justified and carefully optimized in due consideration of the various aspects discussed in some detail in this review., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Objectives: To present a detailed analysis of the cumulative radiation exposure and cancer risk of patients with ischemic heart diseases (IHD) from diagnostic and therapeutic imaging., Methods: For 1219 IHD patients, personal and examination data were retrieved from the information systems of a university hospital. For each patient, cumulative organ doses and the corresponding effective dose (E) resulting from all imaging procedures performed within 3 months before and 12 months after the date of the diagnosis were calculated. The cumulative lifetime attributable risk (LAR) of the patients to be diseased by radiation-related cancer was estimated using sex-, age-, and organ-specific risk models., Results: Among the 3870 procedures performed in the IHD patients, the most frequent were radiographic examinations (52.4%) followed by coronary catheter angiographies and percutaneous cardiac interventions (41.3%), CT scans (3.9%), and perfusion SPECT (2.3%). 87% of patient exposure resulted from heart catheter procedures. E and LAR were significantly higher in males than females (average, 13.3 vs. 10.3 mSv and 0.09 vs. 0.07%, respectively). Contrary to the effective dose, the cancer risk decreased markedly for both sexes with increasing age., Conclusions: Although IHD patients were partially exposed to considerable amounts of radiation, estimated LARs were small as compared to their baseline risk to develop cancer in the remaining life., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Purpose: Assessment of radiologist's hand dose in CT-guided interventions and determination of influencing factors., Materials and Methods: The following CT-guided interventions were included: Core biopsy, drainage, periradicular therapy, and celiac plexus neurolysis. The hand dose was measured with an immediately readable dosimeter, the EDD-30 (Unfors, Sweden). The default parameters for CT fluoroscopy were 120 kV, 90 mA and a 4 mm slice thickness. All interventions were performed on a 16-slice CT unit (Aquilion 16 Toshiba, Japan). The tumor size, degree of difficulty (1 - 3), level of experience and device parameters (mAs, dose-length product, scan time) were documented., Results: 138 CT-guided interventions (biopsy n = 99, drainage n = 23, pain therapy n = 16) at different locations (lung n = 41, retroperitoneum n = 53, liver n = 25, spine n = 19) were included. The lesion size was 4 - 240 mm (median: 23 mm). The fluoroscopy time per intervention was 4.6 - 140.2 s (median: 24.2 s). The measured hand dose ranged from 0.001 - 3.02 mSv (median: 0.22 mSv). The median hand dose for lung puncture (n = 41) was slightly higher (median: 0.32 mSv, p = 0.01) compared to that for the liver, retroperitoneum and other. Besides physical influencing factors, the degree of difficulty (p = 0.001) and summed puncture depth (p = 0.004) correlated significantly with the hand dose., Conclusion: The median hand dose for different CT-guided interventions was 0.22 mSv. Therefore, the annual hand dose limit would normally only be reached with about 2000 interventions., (© Georg Thieme Verlag KG Stuttgart · New York.)

The frequency of X-ray examinations in Germany and the resulting radiation exposure is amongst the highest in comparison with other European countries. To reduce medical radiation exposure and to safeguard radiation protection regulations, the X-ray ordinance stipulates a justification of each individual X-ray application. The justification principle means that the X-ray application should produce sufficient health benefit to offset the radiation risk. Such a benefit-risk assessment needs an adequate estimation of radiation risk. The aim of this paper is to explain the principles of benefit-risk assessment for different situations (e.g. healthcare and screening). The basics and concepts of radiation effects and radiation epidemiology as well as examples of risk estimation and benefit-risk assessments are given.

Unlabelled: AIM To estimate and evaluate the risks for the offspring due to the administration of radiopharmaceuticals to women during the first pregnancy weeks after conception (weeks p.c.)., Methods: The in-utero exposition of the embryo due to diagnostic nuclear medicine procedures, for which diagnostic reference levels (DRL) are specified, as well as due to radio iodine therapy (RIT) was determined. To this end, it is assumed that the activity of the diagnostic radiopharmaceuticals administered to the mother corresponds with the DRL and amounts to 600 MBq or 4 GBq 131I for RIT of benign or malignant thyroid disease, respectively. Based on these data, the radiation risk for the offspring was assessed and compared with the spontaneous risks (R0)., Results: The dose for the offspring does not exceed 7.8 mSv for the diagnostic procedures considered, resulting in an excess risk for the offspring of less than 0.12% (R0 approximately 25%) to die from cancer during life, of less than 0.07% (R0 approximately 0.2%) to develop cancer up to the age of 15 years, and of less than 0.16% (R0 approximately 2%) for hereditary effects. RIT during the first 8 weeks p.c. results in doses for the offspring of about 100-460 mSv, resulting in an excess risk for malformations of the child of 3.4%-22% (R0 approximately 6%)., Conclusions: The risk of stochastic radiation effects for the offspring due to a diagnostic nuclear medicine procedure of the mother during the first 8 weeks p.c. is--compared with the spontaneous risks--very small; deterministic effects are unlikely. In contrast, deterministic effects for the offspring may occur following RIT. In order to decide on a possibly indicated abortion after RIT, an individual risk assessment is mandatory.

Man-made radiation exposure to the German population predominantly results from the medical use of ionizing radiation. According to the most recent evaluation, the mean effective dose per inhabitant and year from X-ray procedures increased from 1.6 to 1.8 mSv between 1996 and 2001. This rise is mainly caused by the expanding use of CT and reflects the growing importance of this imaging modality. Besides actual data on the frequency and dose of various types of X-ray examinations, patient-specific factors will be highlighted which have to be considered in the assessment of the associated individual and collective radiation risk. Moreover, different concepts to reduce radiation exposure of patients will be discussed as well as some current trends in health service that may affect radiation hygiene -- such as diagnosis-related groups for inpatients and CT screening.

For women between 50 and 70 years of age, X-ray mammography presently represents the most effective method for early breast cancer detection. It is commonly accepted that quality assured mammography examinations conducted at regular intervals can reduce mortality from breast cancer. In the year 2002, the German Bundestag agreed to the implementation of a mammography screening program for Germany based on the European guidelines. The effectiveness of a mammography screening program is controversially discussed and two of the most commonly cited hazards are the occurrence of false-positive results and the so-called overdiagnosis. Another issue of criticism is the radiation risk due to the mammography examinations. However, in women aged 50-70 years the radiation risk has no substantial importance. In contrast to the present situation in Germany in which opportunistic screening is widespread, standardized quality assured screening will guarantee that false-positive rates are kept as low as possible and that further assessment diagnostics are effective and minimally invasive.

Risk coefficients representing the lifetime radiation-induced cancer mortality (or incidence) attributable to an exposure to ionizing radiation, have been published by major international scientific committees. The calculations involve observations in an exposed population and choices of a standard population (for risk transportation), of suitable numerical models, and of computational techniques. The present lack of a firm convention for these choices makes it difficult to inter-compare risk estimates presented by different scientific bodies. Some issues that relate to a necessary harmonization and standardization of risk estimates are explored here. Computational methods are discussed and, in line with the approach utilized by ICRP, conversion factors from excess relative risk (ERR) to lifetime attributable risk (LAR) are exemplified for exposures at all ages and for occupational exposures. A standard population is specified to illustrate the possibility of a simplified standard for risk transportation computations. It is suggested that a more realistic perception of lifetime risk could be gained by the use of coefficients scaled to the lifetime spontaneous cancer rates in the standard population. The resulting quantity lifetime fractional risk (LFR) is advantageous also because it depends much less on the choice of the reference population than the lifetime attributable risk (LAR).

There is no firm scientific information on the potential health effects, such as increased cancer rates, due to low doses of ionizing radiation. In view of this uncertainty ICRP has adopted as a prudent default option the linear no-threshold (LNT) assumption and has used it to derive nominal risk coefficients. Subsequent steps, such as the comparison of putative fatality rates in radiation workers with observed accident rates in other professions, have given the risk estimates a false appearance of scientific fact. This has encouraged meaningless computations of radiation-induced fatalities in large populations and has caused a trend to measure dose limits for the public not against the magnitude of the natural radiation exposure and its geographic variations, but against the numerical risk estimates. In reaction to this development, opposing claims are being made of a threshold in dose for deleterious health effects in humans. In view of the growing polarization, ICRP is now exploring a new concept "controllable dose" that aims to abandon the quantity collective dose, emphasizing, instead, individual dose and, in particular, the control of the maximum individual dose from single sources. Essential features of the new proposal are here examined, and it is concluded that the control of individual dose will still have to be accompanied by the avoidance of unnecessary exposures of large populations, even if their magnitude lies below that acceptable to the individual. If a reasonable cut-off at trivial doses is made, the collective dose can remain useful. Misapplications of collective dose are not the deeper cause of the current controversy; the actual root is the misrepresentation of the LNT-assumption as a scientific fact and the amplification of this confusion by loose terminology. If over-interpretation and distortion are avoided, the current system of radiation protection is workable and essentially sound, and there is no need for a fruitless LNT-controversy. The new concept of controllable dose promises simplifications and improvements, but any major change of principles needs to be carefully considered in a broad discussion that ICRP is presently seeking.

This study is comprised of 1577 ankylosing spondylitis patients from 9 German hospitals who have been treated with multiple injections of (224)Ra. The majority of the patients, most of them treated in the years 1948-1975, received one series of 10 weekly intravenous injections of about 1 MBq of (224)Ra each. This dose leads to a mean absorbed dose due to alpha-particle radiation of 0.56 Gy to the marrow-free skeleton of a 70- kg man (mean bone surface dose of about 5 Gy). To provide comparative information on causes of death and on health effects possibly related to the basic disease itself, a control group of 1462 ankylosing spondylitis patients with roughly the same age distribution has been established. By the end of 1998, 649 patients in the exposed group and 762 control patients had died. Among other observations, it is of particular interest that 13 cases of leukemia in the exposed group have been observed. This is a highly significant excess (P < 0.001) compared to a standard population, but only a marginally significant excess in comparison to the seven cases observed in the control group. Subclassification of the leukemias shows a clear preponderance of the myeloid leukemias in the exposed group (8 cases observed compared to 1.7 cases expected, P < 0.001), whereas in the control group the observed cases are within the expected range for myeloid leukemia (3 cases observed compared to 2.2 cases expected, P = 0.3). The (224)Ra cohort of the earlier study (higher-dose group) has provided a risk coefficient that predicts about 8 excess malignant bone tumors for the irradiated cohort in this study. In actuality, 4 cases of malignant tumors in the skeleton have been observed so far. However, excess of breast cancer has not been observed in either the irradiated or the control group, which is in contrast to the findings in the earlier (224)Ra cohort of Study I.

Predominantly from 1945 to 1955, a group of patients in Germany was treated with multiple injections of the short-lived alpha-particle emitter (224)Ra. The patients suffered from ankylosing spondylitis, tuberculosis and in a few cases from other diseases. The "Spiess study" (study I) follows up the health of 899 of these patients; it includes most of the patients who were treated with high doses (mean bone surface dose: 30 Gy, mean specific activity: 0.66 MBq/kg), and nearly all of those treated under the age of 21 years. The most striking consequence of the (224)Ra injections was the occurrence of 56 malignant bone tumors. They appeared in a temporal wave that peaked around 8 years after exposure. A new analysis was recently performed, because a reassessment of the dosimetry resulted in changed bone surface doses, especially for the patients treated at younger ages. Averaged over all ages at exposure, the estimated risk coefficient is in general agreement with earlier analyses. However, there is now an increase in bone tumor risk that is significantly greater for younger ages at exposure. The earlier finding of an inverse protraction factor is confirmed. During the most recent years of follow-up, a significant excess of nonskeletal solid malignancies has become manifest. In 1998, a significant increase of breast cancer incidence, of soft tissue malignancies, of thyroid carcinomas, and of liver, kidney and bladder cancer was found. An eightfold increased risk of mammary cancers in those treated at a young age is particularly striking. Equally notable are two cases of breast cancer in male patients. To identify potential confounders, a control group of tuberculosis patients not treated with (224)Ra was established. The comparison confirms that the (224)Ra treatment is responsible for most of the excess of mammary cancer.

While it is recognized that neutrons contributed to the excess cancer incidence and mortality among the atomic bomb survivors in Hiroshima, there is no possibility to deduce the magnitude of this contribution from the data. This remains true even if the neutron doses in the dosimetry system DS86 are corrected upwards in line with recent neutron activation measurements. In spite of this fact, important information can be obtained in the form of an inverse relation of the risk coefficients for gamma-rays and neutrons. Such an interrelation must apply because the observed excess incidence or mortality is made up of a gamma-ray and a neutron component; increased attribution to neutrons decreases the attribution to photons. Computations with the uncorrected and the corrected DS86 are performed for the mortality and the incidence of solid tumors combined. They refer to doses up to 2 Gy and employ the constant relative risk model and a linear-quadratic dose dependence with variable ratio-the neutron relative biological effectiveness (RBE) at low doses-of the linear component for neutrons and gamma-rays. In line with past analyses, no quadratic component is obtained with the uncorrected DS86. but it is seen, even in these calculations, that the assumption of increased neutron RBEs does not translate into proportional increases of the risk coefficients of neutrons, because it leads to substantially reduced risk estimates for gamma-rays. Calculations with the corrected dosimetry bring out this reciprocity even more clearly. High values of the neutron RBE reduce-in line with recent suggestions by Rossi and Zaider-the risk estimates for gamma-rays substantially. Even a purely quadratic dose relation for gamma-rays is consistent with the data; it requires no major increase of the nominal risk coefficients for neutrons over the currently assumed values. The cancer data from Hiroshima can still provide 'prudent' risk estimates for photons, but with the corrected DS86, they do not prove that there is a linear component in the dose dependence for photons.

The objective of this study was the computation of microdosimetric functions and quantities for sparsely ionizing radiations. The calculations are performed on simulated electron tracks generated by Monte-Carlo techniques. Ten different radiations of biomedical interest are considered. The comparison of radiation qualities shows marked differences between these sparsely ionizing radiations. The microdosimetric date are represented graphically for use in radiation biology and in clinical applications.