Gonad shielding in pelvic radiography: modern optimised X-ray systems might allow its discontinuation.

OBJECTIVE: As gonad shielding is currently under debate, this study evaluates the practice, from its introduction in about 1905 until today. METHODS: The literature was searched for developments in shielding and insights into the effects of ionising radiation on gonads. Based on own pre-1927 dose reconstructions, reported doses after 1927, a 2015-report from the European Union and recent own measurements, the effects of technological evolution and optimisation on radiation dose and hereditary risk were assessed. RESULTS: In the 1900s, gonad shielding was first applied to prevent male sterility, but was discontinued when instrumental developments led to reduced radiation doses. In the 1950s, concerns about hereditary risks intensified and gonad shielding was recommended again, becoming routine worldwide. Imaging-chain improvements over time were considerable: in 2018, the absorbed dose was 0.5% of its 1905 value for the testes and 2% for the ovaries, our optimised effective dose a factor five lower than the value corresponding to the current EU diagnostic reference level, and the reduction in detriment-adjusted risk by shielding less than 1 × 10-6 for women and 5 × 10-6 for men. CONCLUSIONS: Assessment of pelvic doses revealed a large reduction in radiation risks facilitated by technological developments. Optimisation likewise contributed, but unfortunately, its potential was never adequately exploited. Today, using a modern and optimised X-ray system, gonad shielding can be safely discontinued for women. For men, there might be a marginal benefit, but potential negative side-effects may well dominate. Discontinuation of gonad shielding seems therefore justifiable.

The skin dose of pelvic radiographs since 1896.

OBJECTIVES: To derive conversions of antiquated exposure data into modern equivalents and to apply these in the assessment of the skin dose of pelvic radiographs since 1896. METHODS: The literature 1896-2018 was searched for implicit and explicit dose information. The early implicit dose data contained now obsolete descriptions of radiation quality and quantity for long since disappeared X-ray systems of limited efficiency. Converting the old information into modern specifications was achieved using contemporary data and computer simulations. Final dose calculations were done with modern software. Explicit radiation doses of later date reported in old quantities and units were adapted according to current recommendations. RESULTS: For the period before 1927 conversion algorithms for spark gap data and penetrometer hardnesses to high voltage could be derived. Electrical and X-ray efficiencies of several old röntgen systems were determined. Together they allowed reconstruction of 53 doses. After 1927 doses were generally explicitly specified; 114 were retrieved. Although an enormous spread was observed, the average skin dose was reduced by a factor of about 400. CONCLUSIONS: Antiquated exposure data were successfully used for dose reconstruction. Extreme dose variability was a constant. Efforts to cut down doses were effective as skin doses went down from sub-erythema values to about one milligray.

Impact of prompt gamma coincidence correction on absorbed dose estimation in differentiated thyroid cancer using 124I PET/CT imaging.

INTRODUCTION: Iodine-124 positron emission tomography/computed tomography (I PET/CT) is increasingly being used in the absorbed dose estimation in the radioiodine treatment of differentiated thyroid cancer (DTC). However, the produced prompt gamma coincidences (PGCs) associated with the I decay result in a bias in the absorbed dose estimation. The impact of a sinogram-based PGC correction approach on the absorbed dose estimation in I PET/CT DTC imaging is investigated. METHODS: I phantom and patient measurements were performed on a Siemens Biograph mCT PET/CT system. All images were reconstructed with (PGCon) and without PGC correction (PGCoff). The phantom contained seven spheres (diameters: 6.6-37 mm). The spheres and background compartment were filled with a I solution, resulting in a low (9.4 : 1) and a high sphere-to-background activity concentration ratio (750 : 1). Sphere recovery coefficient (RC) values were determined. In addition, the impact of PGC correction on measured lesion uptake and calculated lesion-absorbed dose was assessed for 66 lesions identified in 24 DTC patients. RESULTS: PGC correction systematically increased sphere RC values up to 71% for the smallest spheres. For the patient data, PGC correction significantly increased both the measured I uptake (P<0.005) and the calculated lesion-absorbed dose (P=0.008) by ∼3%. The percentage difference in the calculated lesion-absorbed dose ranged from -19% to 50%, showing that PGC correction had a variable and large impact for a few lesions. CONCLUSION: PGC correction resulted in significantly higher sphere RC values, I lesion uptake values and estimated lesion-absorbed doses.

Dose-Response Relationship in Differentiated Thyroid Cancer Patients Undergoing Radioiodine Treatment Assessed by Means of 124I PET/CT.

UNLABELLED: The dose-response relationship in a fixed-activity approach generally applied in the treatment of differentiated thyroid cancer was assessed using (124)I PET/CT. METHODS: Pretherapeutic (124)I PET/CT images of 47 patients scheduled for radioiodine therapy were retrospectively analyzed. (124)I PET/CT images were acquired 24 and 96 h after oral administration of approximately 28 MBq of (124)I-sodium iodide. Lesions were identified as thyroid remnants or metastases (lymph node, lung, bone). After a neoteric segmentation technique allowing accurate volume estimation down to the (124)I PET spatial resolution of 0.15 mL was applied, lesions were divided into a known-volume group and a small-volume group. For the known-volume group, average lesion-absorbed dose (AD) values were calculated, whereas for the small-volume group a minimum lesion AD was estimated. Lesion response was determined on the basis of (124)I PET/CT and (131)I SPECT/CT follow-up images. A lesion not detectable on any of the follow-up images was considered a completely responding lesion. Differences in lesion AD estimations between completely and incompletely responding lesions were evaluated by Mann-Whitney U test. Moreover, receiver-operating-characteristic curves were used to test the performance of pretherapeutic (124)I PET/CT lesion AD for prediction of complete lesion response. RESULTS: In the approach of fixed radioiodine activity (3.0 ± 1.0 GBq), 89% of thyroid remnants and 69% of metastases responded completely. Except for the small-volume groups, the lesion AD of completely responding lesions was significantly higher than that of incompletely responding lesions. Using receiver-operating-characteristic curve analysis, it was shown that for the known-volume group, pretherapeutic (124)I PET/CT lesion dosimetry can be used as a prognostic tool to predict lesion-based (131)I therapy response with an area under the curve of 0.76 for remnants and 0.97 for metastases. The corresponding lesion AD threshold value maximizing correct complete response prediction was 90 Gy for remnants and 40 Gy for metastases. CONCLUSION: In a fixed-activity approach, a statistically significant dose-response relationship for both thyroid remnants and metastases using pretherapeutic (124)I PET/CT lesion dosimetry was found. The findings may be useful in patient management.

Effect of spinal immobilisation devices on radiation exposure in conventional radiography and computed tomography.

Trauma patients at risk for, or suspected of, spinal injury are frequently transported to hospital using full spinal immobilisation. At the emergency department, immobilisation is often maintained until radiological work-up is completed. In this study, we examined how these devices influence radiation exposure and noise, as a proxy for objective image quality. Conventional radiographs (CR) and computer tomography (CT) scans were made using a phantom immobilised on two types of spineboard and a vacuum mattress and using two types of headblocks. Images were compared for radiation transmission and quantitative image noise. In CR, up to 23 % and, in CT, up to 11 % of radiation were blocked by the devices. Without compensation for the decreased transmission, noise increased by up to 16 % in CT, depending on the device used. Removing the headblocks led to a statistically significant improvement in transmission with automatic exposure control (AEC) enabled. Physicians should make an informed decision whether the increased radiation exposure outweighs the risk of missing a clinically significant injury by not making a CR or CT scan. Manufacturers of immobilisation devices should take radiological properties of their devices into account in the development and production process.

Early X-ray workers: an effort to assess their numbers, risk, and most common (skin) affliction.

OBJECTIVE: To assess quantitatively the number of early X-ray workers, their risk of becoming a radiation victim, and their most common radiation-induced (skin) disease. METHODS: Information on professional life and occupational disease was retrieved from the Ehrenbuch, a book of honour containing biographies of 404 radiation victims, as well as member and congress lists of the German and US radiological societies, obituaries, books, articles, and the Internet. RESULTS: The estimated numbers of X-ray users in a medical setting in the US increased from about 300 to 600 in 1900-1903, in Germany from about 700 to 1200 during 1905-1908. The risk for a beginning user eventually to die from radiation was 1-2 % in these years, but up to 10-25 % in 1896. Data on 198 victims of fatal radiation-induced skin disease were collected. The incidence of the various stages of skin afflictions with a fatal outcome was characterized by very wide distributions. CONCLUSIONS: After 1896, the radiation risk decreased very fast at first and more slowly thereafter to nearly zero in 1935. Many victims became quite old, partly because of the slower progress of tissue reactions at lower radiation doses, partly because of the success of often multiple surgical interventions. MAIN MESSAGES: US and German X-ray users amounted to several hundreds to thousand in 1900-1908. The risk eventually to die from radiation was about 1-2 % during 1900-1908. After 1896, this risk decreased from >10 % to nearly zero in 1935. The incidence of subsequent stages of skin harm varied strongly in time. X-ray victims could become quite old, dependent on radiation dose and surgery.

Radiation exposure of abdominal cone beam computed tomography.

PURPOSE: To evaluate patients radiation exposure of abdominal C-arm cone beam computed tomography (CBCT). METHODS: This prospective study was approved by the institutional review board; written, informed consent was waived. Radiation exposure of abdominal CBCT was evaluated in 40 patients who underwent CBCT during endovascular interventions. Dose area product (DAP) of CBCT was documented and effective dose (ED) was estimated based on organ doses using dedicated Monte Carlo simulation software with consideration of X-ray field location and patients' individual body weight and height. Weight-dependent ED per DAP conversion factors were calculated. CBCT radiation dose was compared to radiation dose of procedural fluoroscopy. CBCT dose-related risk for cancer was assessed. RESULTS: Mean ED of abdominal CBCT was 4.3 mSv (95 % confidence interval [CI] 3.9; 4.8 mSv, range 1.1-7.4 mSv). ED was significantly higher in the upper than in the lower abdomen (p = 0.003) and increased with patients' weight (r = 0.55, slope = 0.045 mSv/kg, p < 0.001). Radiation exposure of CBCT corresponded to the radiation exposure of on average 7.2 fluoroscopy minutes (95 % CI 5.5; 8.8 min) in the same region of interest. Lifetime risk of exposure related cancer death was 0.033 % or less depending on age and weight. CONCLUSIONS: Mean ED of abdominal CBCT was 4.3 mSv depending on X-ray field location and body weight.

Forgotten electrical accidents and the birth of shockproof X-ray systems.

OBJECTIVES: To commemorate victims of electrical accidents that occurred in the first decades of radiology and relate these accidents to the evolution of the X-ray apparatus. METHODS: Digitised newspapers, scientific journals, books and reports of legal procedures were searched for electrical accidents involving X-ray systems. Information on the historical systems was retrieved from the scientific literature and brochures from manufacturers. RESULTS: We found 51 fatal and 62 non-fatal but serious electrical accidents. Most of them occurred between 1920 and 1940 and involved transformers that provided output currents well above the threshold for the induction of ventricular fibrillation. The accidents led to recommendations and regulations to improve safety for operators and patients, and spurred manufacturers to technical developments that culminated in fully electrically shockproof systems by 1935. CONCLUSIONS: Although largely forgotten, the development of the shockproof X-ray systems we take for granted today lasted about 4 decades and was associated with considerable human suffering. The complete solution of the problem is a success story of engineering realised by contributions from all parties involved. MAIN MESSAGES: • The development of electrically shockproof X-ray systems took about 4 decades (1895-1935). • Between 1896 and 1920 electrical shocks from X-ray systems were common, but their consequences limited. • After 1920, transformers killed by delivering currents above the ventricular fibrillation threshold. • Inductors, static generators and high-frequency coils were generally low-current systems and safe. • We found 51 fatal and 62 serious non-fatal electrical accidents, most occurring from 1920 to 1940.

Gonad shielding in paediatric pelvic radiography: disadvantages prevail over benefit.

OBJECTIVE: To re-evaluate gonad shielding in paediatric pelvic radiography in terms of attainable radiation risk reduction and associated loss of diagnostic information. METHODS: A study on patient dose and the quality of gonad shielding was performed retrospectively using 500 pelvic radiographs of children from 0 to 15 years old. In a subsequent study, 195 radiographs without gonad shielding were included. Patient doses and detriment adjusted risks for heritable disease and cancer were calculated with and without gonad shielding. RESULTS: For girls, gonad shields were placed incorrectly in 91% of the radiographs; for boys, in 66%. Without gonad shielding, the hereditary detriment adjusted risk for girls ranged between 0.1 × 10(-6) and 1.3 × 10(-6) and for boys between 0.3 × 10(-6) and 3.9 × 10(-6), dependent on age. With shielding, the reduction in hereditary risk for girls was on average 6 ± 3% of the total risk of the radiograph, for boys 24 ± 6%. Without gonad shielding, the effective dose ranged from 0.008 to 0.098 mSv. CONCLUSIONS: With modern optimised X-ray systems, the reduction of the detriment adjusted risk by gonad shielding is negligibly small. Given the potential consequences of loss of diagnostic information, of retakes, and of shielding of automatic exposure-control chambers, gonad shielding might better be discontinued.

The application of x-rays in radiology: from difficult and dangerous to simple and safe.

OBJECTIVE: This article will provide an assessment of the application of x-rays in the early days of radiology, which is an excellent way to come to value the convenience and safety of modern x-ray systems. CONCLUSION: The gas tubes that were originally applied for x-ray production were very unstable because of variations in the tube's vacuum. In an effort to understand some of the problems of these tubes and the high occupational exposure that was indirectly caused by the tubes' erratic behavior, we measured x-ray output rates as a function of the gas pressure inside the tube. The pressure range for the optimal production of x-rays, using an original Ruhmkorff inductor as a high-voltage generator, was found to be narrow. With the vacuum changing over time, this might explain the many photographs from the first years of radiology with operators watching their unshielded tube, either with bare eyes or with a fluoroscope, and their own hand as a test object. This practice often led to severe damage of the hands and to many early deaths due to cancer. Today, after a century of technologic development of x-ray tubes and associated equipment, the total average effective dose of workers in radiology can be close to natural background levels.

Dosimetry in molecular nuclear therapy.

Advanced personalized dosimetry for molecular nuclear therapy has been shown to be feasible in clinical practice. At the same time instrumentation and dosimetric software are still evolving at a high pace. Procedures developed so far differ in approach and sophistication, and standard operating procedures necessary for accurate patient specific dosimetry do not yet exist. For this reason we restricted ourselves to reviewing the literature and highlighting relevant developments.

Activity quantification combining conjugate-view planar scintigraphies and SPECT/CT data for patient-specific 3-D dosimetry in radionuclide therapy.

PURPOSE: Three-dimensional dosimetry based on quantitative SPECT/CT has potential advantages over planar approaches, but may be impractical due to acquisition durations. We combine one SPECT/CT with improved quantification of multiple planar scintigraphies to shorten acquisitions. METHODS: A hybrid 2-D/3-D quantification technique is proposed, using SPECT/CT information for robust planar image quantification and creating virtual SPECTs out of conjugate-view planar scintigraphies; these are included in a 3-D absorbed dose calculation. A projection model simulates photon attenuation and scatter as well as camera and collimator effects. Planar and SPECT calibration techniques are described, offering multiple pathways of deriving calibration factors for hybrid quantification. Model, phantom and patient data are used to validate the approach on a per-organ basis, and the similarity of real and virtual SPECTs, and of planar images and virtual SPECT projections, is assessed using linear regression analysis. RESULTS: Organ overlap, background activity and organ geometry are accounted for in the algorithm. Hybrid time-activity curves yield the same information as those derived from a conventional SPECT evaluation. Where correct values are known, hybrid quantification errors are less than 16% for all but two compartments (SPECT/CT 23%). Under partial volume effects, hybrid quantification can provide more robust results than SPECT/CT. The mean correlation coefficient of 3-D data is 0.962 (2-D 0.934). As a consequence of good activity quantification performance, good agreement of absorbed dose estimates and dose-volume histograms with reference results is achieved. CONCLUSION: The proposed activity quantification method for 2-D scintigraphies can speed up SPECT/CT-based 3-D dosimetry without losing accuracy.

Occupational radiation dose during transcatheter aortic valve implantation.

OBJECTIVES: To examine the occupational radiation dose during transcatheter aortic valve implantation (TAVI) in both transfemoral and transapical approach. BACKGROUND: Interventional fluoroscopic guided cardiac procedures lead inevitably to radiation exposure of workers, which over time may be associated with an increased incidence of cancer and cataract. METHODS: Using thermoluminescence dosimeters, the radiation dose of the cardiothoracic surgeon, cardiologist, and two assistants was measured on the apron at chest height and on both feet. In addition, dose measurements were performed on the hands of the two operators and on the eyes of the cardiothoracic surgeon. This study involved 11 transapical and 11 transfemoral TAVIs. The effective dose was estimated from the dose measured on the apron. RESULTS: In the transapical TAVI the cardiothoracic surgeon received a significantly higher equivalent hand dose (average ± SD), 1.9 ± 0.6 mSv, equivalent foot dose, 0.57 ± 0.31 mSv, equivalent eye dose, 0.11 ± 0.06 mSv, and effective dose, 0.03 ± 0.02 mSv, than any staff member in the transfemoral TAVI, with highest average doses of 0.03 ± 0.02 mSv, 0.22 ± 0.19 mSv, 0.03 ± 0.01 mSv, and 0.003 ± 0.005 mSv, respectively. CONCLUSIONS: This study provides hitherto unavailable data on the radiation exposure of staff during transfemoral and transapical TAVIs. Relatively high doses were observed in the transapical approach. The dose of the right hand of the cardiothoracic surgeon will reach the annual limit within about 250 procedures per year, implying that hand dose measurements should become standard and that the number of procedures performed by the cardiothoracic surgeon involving X-rays may have to be limited.

Characteristics of a first-generation x-ray system.

PURPOSE: To compare the antiquated x-ray system of Hoffmans and van Kleef (circa 1896) with modern x-ray equipment in terms of radiation dose, x-ray beam properties, image quality, and electrical parameters. MATERIALS AND METHODS: The antiquated x-ray system consisted of a Ruhmkorff inductor, battery, and Crookes tube. The radiation dose rate, x-ray beam properties, and electrical characteristics of this system were determined. A modern computed radiography plate was used to compare images of a hand specimen obtained by using the antiquated system with images obtained by using the modern system. RESULTS: A peak voltage of 73 kV was obtained with an 8-V battery. With Crookes tube number 9, the half-value layer of the generated x-rays was 0.56 mm Al. Pinhole images showed that the x-rays originated from an extended area of the glass wall, causing image blurring. When measured on the skin of a hand specimen, the radiation dose of the antiquated system was about 10 times greater than that of the modern system for the same detector signal. The estimated skin dose was about 74 mGy for the antiquated system and 0.05 mGy for the modern system. The corresponding exposure times were 90 minutes and 21 msec. CONCLUSION: Radiation dose and exposure time of the antiquated system were greater than those of the modern system by about three and five orders of magnitude, respectively. Images of the hand specimen obtained with the antiquated system were severely blurred but were still awe inspiring, considering the simplicity of the system. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101899/-/DC1.

Effect of the positron range of 18F, 68Ga and 124I on PET/CT in lung-equivalent materials.

PURPOSE: The aim of this study was to investigate the effect of positron range on visualization and quantification in (18)F, (68)Ga and (124)I positron emission tomography (PET)/CT of lung-like tissue. METHODS: Different sources were measured in air, in lung-equivalent foams and in water, using a clinical PET/CT and a microPET system. Intensity profiles and curves with the cumulative number of annihilations were derived and numerically characterized. RESULTS: (68)Ga and (124)I gave similar results. Their intensity profiles in lung-like foam had a peak similar to that for (18)F, and tails of very low intensity, but extending over distances of centimetres and containing a large fraction of all annihilations. For 90% recovery, volumes of interest with diameters up to 50 mm were required, and recovery within the 10% intensity isocontour was as low as 30%. In contrast, tailing was minor for (18)F. CONCLUSION: Lung lesions containing (18)F, (68)Ga or (124)I will be visualized similarly, and at least as sharp as in soft tissue. Nevertheless, for quantification of (68)Ga and (124)I large volumes of interest are needed for complete activity recovery. For clinical studies containing noise and background, new quantification approaches may have to be developed.

Less radiation in a radiology department than at home.

OBJECTIVE: To compare the total work-related radiation dose in our department of radiology with the dose in Dutch residences, taking x-ray radiation, external natural radiation and radon into account. METHODS: Annual doses due to exposure to x-rays and external natural radiation were derived from the measured personal dose equivalent [H(p)(10)] of 144 workers. Additionally, departmental (222)Rn concentrations were assessed over 1 year. RESULTS: The departmental radon concentration was 5 ± 1 Bq/m(3), the personal dose equivalent due to external natural radiation 0.32 ± 0.10 mSv/year, considerably lower than the average Dutch residential values of 13.5 Bq/m(3) and 0.88 mSv/year. As a consequence, working results in a lower dose than being at home as long as the x-ray-induced personal dose equivalent is lower than 1.25 mSv/year, which was the case for 131 of the 144 radiological workers, as well as for the whole group on average. CONCLUSIONS: Working in our x-ray department results in a reduction in the collective effective dose, not an increase. The worldwide average radon concentration of 40 Bq/m(3), much higher than in the Netherlands, and the large decrease potentially achieved by the high ventilation rates common in hospitals, suggest that even considerably higher reductions are possible in other countries.

Bone metabolic activity in hyperostosis cranialis interna measured with 18F-fluoride PET.

PURPOSE: (18)F-Fluoride PET/CT is a relatively undervalued diagnostic test to measure bone metabolism in bone diseases. Hyperostosis cranialis interna (HCI) is a (hereditary) bone disease characterised by endosteal hyperostosis and osteosclerosis of the skull and the skull base. Bone overgrowth causes entrapment and dysfunction of several cranial nerves. The aim of this study is to compare standardised uptake values (SUVs) at different sites in order to quantify bone metabolism in the affected anatomical regions in HCI patients. METHODS: Nine affected family members, seven non-affected family members and nine non-HCI non-family members underwent (18)F-fluoride PET/CT scans. SUVs were systematically measured in the different regions of interest: frontal bone, sphenoid bone, petrous bone and clivus. Moreover, the average (18)F-fluoride uptake in the entire skull was measured by assessing the uptake in axial slides. Visual assessment of the PET scans of affected individuals was performed to discover the process of disturbed bone metabolism in HCI. RESULTS: (18)F-Fluoride uptake is statistically significantly higher in the sphenoid bone and clivus regions of affected family members. Visual assessment of the scans of HCI patients is relevant in detecting disease severity and the pattern of disturbed bone metabolism throughout life. CONCLUSION: (18)F-Fluoride PET/CT is useful in quantifying the metabolic activity in HCI and provides information about the process of disturbed bone metabolism in this specific disorder. Limitations are a narrow window between normal and pathological activity and the influence of age. This study emphasises that (18)F-fluoride PET/CT may also be a promising diagnostic tool for other metabolic bone disorders, even those with an indolent course.

Calcium scores and matrix Gla protein levels: association with vitamin K status.

BACKGROUND: Vascular calcification in humans is associated with an increased cardiovascular risk. Carboxylated matrix Gla protein (cMGP) inhibits vascular calcification. Vitamin K is an essential cofactor for the activation of uncarboxylated matrix Gla protein (ucMGP). It has been suggested that patients on long-term treatment with vitamin K antagonists develop aortic valve calcifications because of lower levels of circulating MGP. We therefore hypothesized that arterial calcification and a low vitamin K status are associated with ucMGP. To that aim, we measured arterial calcium scores, the osteocalcin ratio (OCR), as a proxy for vitamin K status, and ucMGP. MATERIALS AND METHODS: In 36 hypertensive patients, we determined the Agatston score with computer tomography scans of the abdominal aorta, carotid and coronary arteries. The total calcium score was calculated as the sum of the separate Z-scores. RESULTS: The total calcium Z-score was significantly correlated to age (r = 0.683, P < 0.001), smoking (r = 0.372, P = 0.026), total cholesterol (r = 0.353, P = 0.034), LDL cholesterol (r = 0.490, P = 0.003), triglycerides (r = 0.506, P = 0.002), fasting glucose (r = 0.454, P = 0.005), systolic blood pressure (r = 0.363, P = 0.029) and pulse pressure (r = 0.685, P < 0.001). In multivariate regression analyses, OCR and total calcium score were significantly associated with ucMGP. CONCLUSIONS: We found a positive association of total arterial calcium score and a high OCR (reflecting low vitamin K status) with ucMGP serum levels. This warrants further studies to explore the pathophysiological background of this phenomenon.