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Purpose In laparoscopy, the Operating Room Black Box® (ORBB) provides insights into operative performance to improve patient safety. This technology may also enhance endovascular surgical practice; however, the use of a C-arm and X-rays pose important challenges, hindering transferability to an endovascular context. We describe the first implementation of ORBB technology in a hybrid angiosuite and illustrate its value in evaluating surgeons’ radiation safety, technical and non-technical performance. Methods Team members (surgeons, nurses, anaesthesiologists) and stakeholders were informed during several information sessions. Together with teams from Surgical Safety Technologies (Toronto, Canada), an implementation plan was developed, and video-evaluation frameworks were chosen. Radiation safety was assessed using dose measurements and video-evaluation of safety-related behaviours. Technical performance was assessed using ‘global’ (GRS) and ‘procedure-specific’ (PRS) rating scales and the ‘EndoVascular Aortic Repair Assessment of Technical Expertise’ (EVARATE) framework. Surgeons’ non-technical skills were assessed with the NOTSS framework. Results The system captures Audio-visual data from four ceiling-mounted cameras, three ceiling-array microphones, the fluoroscopy screen and anaesthesia monitor. After patient and team consent, an elective endovascular aneurysm repair was successfully analysed. Dose-Area-Product and Air Kerma were 71094 mGy.cm2 and 270 mGy, respectively. Behavioural analysis revealed deficiencies in stepping back and radiation safety communication. Technical skill assessment was feasible: GRS: 29/40; ‘PRS’: 27/35; EVARATE: 29/35. Non-technical analysis highlighted surgeons’ leadership qualities. Conclusion An innovative data capture platform has been successfully installed to evaluate overall performance during endovascular procedures. This technology may facilitate identification of (radiation) safety-related errors and instigate educational interventions based on real-world issues.

Background Personal radiation protective equipment (PRPE) such as lead aprons, vests, skirts and thyroid shields minimize radiation exposure of operators using ionizing radiation. However, PRPE might be prone to cracks and tears in the attenuating layer of the garments which results in inadequate radiation protection and increased operator dose. Currently, there are no uniform guidelines regarding regular inspection and/or rejection criteria of PRPE. Purpose This study aims to investigate the prevalence, qualification and quantification of PRPE integrity during a longitudinal follow-up. Methods All PRPE of a large, general hospital was yearly evaluated in the period 2018–2020. The equipment was inspected on a tele-operated X-ray table and cracks and tears were qualified and quantified using an X-ray opaque ruler. Rejection criteria of Lambert & McKeon were applied to accept or reject further use of the PRPE. In brief, all pieces, except for thyroid shields, with a total defect area larger than 670mm2 are rejected. For tears, specifically at the position of the gonads, an extra rejection criterion of 15mm2 is defined. For thyroid shields, the rejection criterion is set to 11mm2. Results In the 3-year follow-up period, a total of 915 PRPE were evaluated. 43.3% of PRPE showed tears and 29.3% needed to be rejected based on the Lambert & McKeon criteria. More specifically, in 2018, 2019 and 2020, respectively, 17.4%, 16.9% and 21.2% were rejected. In the attached figure, typical examples of visualized defects are represented. The median tear area (interquartile range) was 12 (30) mm2. Remarkably, of 195 newly registered PRPE, 8.7% showed tears in the first year of use of which 88.2% needed to be rejected. In the latter case, the median tear area (interquartile range) was 40 (50) mm2. Information regarding purchase date and size is missing in respectively 45.5% and 50.7% of the cases. Additionally, 13.7% lacked information regarding lead equivalency. Conclusion PRPE are prone to tears and cracks. Up to 40% of PRPE showed tears and cracks resulting in nearly 20% rejections. Newly purchased PRPE are not guaranteed to remain free of cracks and tears in the first year of use. These results urge the importance for regular X-ray based integrity analysis of PRPE. Funding Acknowledgement Type of funding sources: None.

Purpose To assess compliance of lumbar spine imaging referrals with national imaging recommendations and to evaluate the impact of inappropriate imaging on the collective radiation dose and health insurance costs. Method In 2011 and 2015, 633 lumbar spine imaging referrals were evaluated across 9 Belgian hospitals. For each patient, a new clinical anamnesis and physical examination were performed. Together with the referral, this data were confronted with the national imaging recommendations. Collective radiation dose was estimated for the radiography and CT procedures. Cost analysis was based on national reimbursement fees. Statistical analysis was performed using multilevel linear and logistic regression models. Results The fraction of unjustified imaging referrals decreased from 50 % in 2011 to 41 % in 2015 (p = 0.255). The odds of a justified examination are 3.1 times higher when the referral is done by a specialist instead of a general practitioner. The highest percentage of unjustified examinations was found for CT (85 % in 2011, 81 % in 2015; p = 0.044). Seventy-five percent of the collective dose of both the 2011 and the 2015 study population was not justified. Adherence to the recommendations could result in an estimated 16 % and 5 % cost reduction for the 2011 and 2015 study samples, respectively. Conclusions Between 2011 and 2015, no significant improvement was found in requesting justified lumbar spine imaging procedures, although a positive trend was observed for CT. A shift from CT to MRI is necessary to improve the appropriateness of lumbar spine imaging referrals and to reduce the collective radiation dose.

On 5 December 2013 the European Council promulgated Directive 2013/59/EURATOM. This Directive is important for Medical Physicists and Medical Physics Experts as it puts the profession on solid foundations and describes it more comprehensively. Much commentary regarding the role and competences has been developed in the context of the European Commission project “European Guidelines on the Medical Physics Expert” published as Radiation Protection Report RP174. The guidelines elaborate on the role and responsibilities under 2013/59/EURATOM in terms of a mission statement and competence profile in the specialty areas of Medical Physics relating to medical radiological services, namely Diagnostic and Interventional Radiology, Radiation Oncology and Nuclear Medicine. The present policy statement summarises the provisions of Directive 2013/59/EURATOM regarding the role and competences, reiterates the results of the European Guidelines on the Medical Physics Expert document relating to role and competences of the profession and provides additional commentary regarding further issues arising following the publication of the RP174 guidelines.

To develop a clinically applicable method to estimate patient-specific organ and blood doses and lifetime attributable risks (LAR) from paediatric torso CT examinations. Individualized voxel models were created from full-body CT data of 10 paediatric patients (2–18 years). Patient-specific dose distributions of chest and abdominopelvic CT scans were simulated using Monte Carlo methods. Blood dose was calculated as a weighted sum of simulated organ doses. LAR of cancer incidence and mortality were estimated, according to BEIR-VII. A second simulation and blood dose calculation was performed using only the thoracic and abdominopelvic region of the original voxel models. For each simulation, the size-specific dose estimate (SSDE) was calculated. SSDE showed a significant strong linear correlation with organ dose (r > 0.8) and blood dose (r > 0.9) and LAR (r > 0.9). No significant differences were found between blood dose calculations with the full-body voxel models and the thoracic or abdominopelvic models. Even though clinical CT images mostly do not cover the whole body of the patient, they can be used as a voxel model for blood dose calculation. In addition, SSDE can estimate patient-specific organ and blood doses and LAR in paediatric torso CT examinations. • Blood dose can be simulated using the patient’s clinical CT images. • SSDE estimates patient-specific organ/blood dose and LAR in paediatric CAP CT-examinations. • SSDE makes on-the-spot dose and LAR estimations possible in routine clinical practice.

Background\ud The European directive on basic safety standards (Council directive 2013/59 Euratom) mandates dosimetry-based treatment planning for radiopharmaceutical therapies. The directive comes into operation February 2018, and the aim of a report produced by the Internal Dosimetry Task Force of the European Association of Nuclear Medicine is to address this aspect of the directive. A summary of the report is presented.\ud \ud Results\ud A brief review of five of the most common therapy procedures is included in the current text, focused on the potential to perform patient-specific dosimetry. In the full report, 11 different therapeutic procedures are included, allowing additional considerations of effectiveness, references to specific literature on quantitative imaging and dosimetry, and existing evidence for absorbed dose-effect correlations for each treatment. Individualized treatment planning with tracer diagnostics and verification of the absorbed doses delivered following therapy is found to be scientifically feasible for almost all procedures investigated, using quantitative imaging and/or external monitoring. Translation of this directive into clinical practice will have significant implications for resource requirements.\ud \ud Conclusions\ud Molecular radiotherapy is undergoing a significant expansion, and the groundwork for dosimetry-based treatment planning is already in place. The mandated individualization is likely to improve the effectiveness of the treatments, although must be adequately resourced.

IntroductionCardiac catheterization procedures result in high radiation doses and often multiple procedures are necessary for congenital heart disease patients. However, diagnostic reference levels (DRL) remain scarce. Our first goal was finding the optimal DRL parameter and determining appropriate DRLs. The second goal was to calculate organ doses (OD), effective doses (ED) and lifetime attributable risks (LAR) per procedure and to provide conversion factors based on dose area product (DAP).Materials and methodsDRLs are calculated for each procedure type, as the 75th percentile of the cumulative value per procedure from the corresponding parameter. All irradiation events in the DICOM Structured Reports were automatically processed and simulated using PCXMC, resulting in OD, ED and LAR. Using a Kruskal Wallis H test and subsequent pairwise comparisons, differences in median values of the DRL parameter between procedure types were assessed.ResultsLinear regression showed a strong correlation and narrow confidence interval between DAP and product of body weight and fluoroscopy time (BWxFT), even when all procedures (diagnostic and interventional) are combined. Only 15% of the pairwise comparisons were statistically significant for DAP normalized to BWxFT (DAPBWxFT). The latter pairs contained less frequent procedure types with significant outliers. For DAP normalized to BW (DAPBW), 38% of the pairwise comparisons showed statistically significant differences. Conversion factors from DAPBW to OD and ED were reported for various weight groups, due to the higher correlation between DAPBW and both OD and ED than between DAP and both OD and ED.ConclusionsThe P75 of DAPBWxFT for all procedures combined serves as an appropriate DRL value. This facilitates local DRL determination in smaller paediatric centres, which often have insufficient data to produce appropriate DRLs for different procedure types. Conversion factors are more reliable starting from DAPBW instead of DAP and should be used according to the appropriate BW group.

International audience; The “intended purpose” in all therapeutic exposures is treatment efficacy against malignant disease. The optimization principle (as low as reasonably achievable, ALARA) of article 56, when applied in a therapy situation, states that absorbed doses to nontarget tissues should be kept reasonably low, but not so low as to lose efficacy. We think that this applies above all to the fight against life-threatening cancer. As a consequence, we believe that to adhere to the optimization principle in oncological patients, nuclear medicine therapy should be based on individualized dosimetry.

Background: Biologicals directed against tumour necrosis factor (TNF) have proven their efficacy in the treatment of spondyloarthritis and rheumatoid arthritis. We present a radiolabelling method for certolizumab pegol (CZP), a commercially available humanized Fab'-fragment directed against TNF. A biodistribution and dosimetry study was conducted. Tc-S-HYNIC CZP was synthesized. The in vitro TNF neutralizing activity was tested by exposing L929s-cells to various concentrations 99mTc-S-HYNIC CZP and measuring TNF-induced cytotoxicity. For biodistribution and dosimetry, WB images and blood and urine sampling were performed up to 24 h pi. Cumulative activities were estimated using mono-exponential fitting, and organ doses were estimated using OLINDA/EXM. The effective dose was calculated using the International Commission on Radiological Protection 103 recommendations. The uptake of the tracer in the peripheral joints was assessed visually and semiquantitatively. Results: In vitro tests showed blocking of TNF cytotoxicity by the Tc-99m-S-HYNIC CZP formulation comparable to the effect obtained with the unlabelled CZP with or without the HYNIC linker. We analysed eight patients with rheumatoid arthritis or spondyloarthritis. The highest mean absorbed organ doses were recorded for kidneys, spleen, and liver: 56 (SD 7), 34 (SD 6), and 33 (SD 7) mu Gy/MBq. The effective dose was 6.1 (SD 0.9) mSv for a mean injected activity of 690 (SD 35) MBq. The urinary excretion was 15.1% (SD 8.1) of the IA at 22.5 h. Blood analysis yielded a distribution half-life of 1.2 h (SD 1.5) and an elimination half-life of 26.9 h (SD 2.7). Visual analysis of the scans revealed marked tracer accumulation in the clinically affected peripheral joints. In addition, there was a statistically significant higher uptake of the tracer in the swollen joints (median uptake ratio compared to background of 3.3 in rheumatoid arthritis and 2.4 in peripheral spondyloarthritis) compared to clinically negative joints (respectively 1.3 and 1.6). Conclusions: We present a radiolabelling technique for CZP, a Fab'-fragment directed against TNF and currently used as a therapeutic agent in rheumatology. An effective dose of 6.1 mSv (SD 0.9) was estimated. We confirmed the uptake of this new radiopharmaceutical in clinically affected peripheral joints.

To investigate if direct radiography (DR) performs better than screen-film mammography (SF) and computed radiography (CR) in dense breasts in a decentralized organised Breast Cancer Screening Programme. To this end, screen-detected versus interval cancers were studied in different BI-RADS density classes for these imaging modalities. The study cohort consisted of 351,532 women who participated in the Flemish Breast Cancer Screening Programme in 2009 and 2010. Information on screen-detected and interval cancers, breast density scores of radiologist second readers, and imaging modality was obtained by linkage of the databases of the Centre of Cancer Detection and the Belgian Cancer Registry. Overall, 67% of occurring breast cancers are screen detected and 33% are interval cancers, with DR performing better than SF and CR. The interval cancer rate increases gradually with breast density, regardless of modality. In the high-density class, the interval cancer rate exceeds the cancer detection rate for SF and CR, but not for DR. DR is superior to SF and CR with respect to cancer detection rates for high-density breasts. To reduce the high interval cancer rate in dense breasts, use of an additional imaging technique in screening can be taken into consideration. • Interval cancer rate increases gradually with breast density, regardless of modality. • Cancer detection rate in high-density breasts is superior in DR. • IC rate exceeds CDR for SF and CR in high-density breasts. • DR performs better in high-density breasts for third readings and false-positives.

To determine the correlation between the clinical and physical image quality of chest images by using cadavers embalmed with the Thiel technique and a contrast-detail phantom.The use of human cadavers fulfilled the requirements of the institutional ethics committee. Clinical image quality was assessed by using three human cadavers embalmed with the Thiel technique, which results in excellent preservation of the flexibility and plasticity of organs and tissues. As a result, lungs can be inflated during image acquisition to simulate the pulmonary anatomy seen on a chest radiograph. Both contrast-detail phantom images and chest images of the Thiel-embalmed bodies were acquired with an amorphous silicon flat-panel detector. Tube voltage (70, 81, 90, 100, 113, 125 kVp), copper filtration (0.1, 0.2, 0.3 mm Cu), and exposure settings (200, 280, 400, 560, 800 speed class) were altered to simulate different quality levels. Four experienced radiologists assessed the image quality by using a visual grading analysis (VGA) technique based on European Quality Criteria for Chest Radiology. The phantom images were scored manually and automatically with use of dedicated software, both resulting in an inverse image quality figure (IQF). Spearman rank correlations between inverse IQFs and VGA scores were calculated.A statistically significant correlation (r = 0.80, P.01) was observed between the VGA scores and the manually obtained inverse IQFs. Comparison of the VGA scores and the automated evaluated phantom images showed an even better correlation (r = 0.92, P.001).The results support the value of contrast-detail phantom analysis for evaluating clinical image quality in chest radiography.

As dynamic flat-panel detectors (FD) are introduced in interventional cardiology (IC), the relation between patient dose and image quality (IQ) needs to be reconsidered for this type of image receptor. On one hand this study investigates IQ of a FD system by means of a threshold contrast-detail analysis and compares it to an image intensifier (II) system on a similar X-ray setup. On the other hand patient dose for coronary angiography (CA) procedures on both systems is compared by Dose-Area Product (DAP)-registration of a patient population. The comparative IQ study was performed for a range of entrance dose rates (EDR) covering the fluoroscopy and cinegraphy working mode. In addition the IQ investigation was extended to a similar study under automatic brightness control (ABC). As well the systematic study of IQ as a function of EDR as the study performed under ABC point to a better IQ for FD in cinegraphy mode and no difference between both systems in fluoroscopy mode. The patient population study resulted in mean DAP values of 31 Gy cm2 (II system) and 33 Gy cm2 (FD system) (p = 0.68) for CA procedures. As well total DAP as contributions of fluoroscopy and cinegraphy on both systems are not significantly different. To conclude, we could state that profit was taken from the intrinsic better performance of the FD for cinegraphy mode in producing higher quality images in this mode but without any effect on patient dose for CA procedures.

Background: Cone beam computed tomography (CBCT) has become an extremely useful technique for dentomaxillofacial imaging because it provides clear images of highly contrasted structures. Previous studies evaluating the applicability of this technique in otologic imaging were very encouraging but were only performed in vitro on temporal bone specimens. The intracochlear positioning of the individual electrodes after cochlear implantation by means of CBCT has not yet been shown in vivo. Objective: We describe a protocol for in vivo postoperative imaging of cochlear implants by CBCT. Moreover, the effective dose was measured and compared with the effective dose used on 4- and 16-slice multislice computed tomography (MSCT) by using a RANDO-phantom. Main Outcome Measure: Developing a protocol for in vivo postoperative imaging of cochlear implants by CBCT. Results: CBCT provides high-resolution and almost artifact-free multiplanar reconstruction images allowing assessment of the precise intracochlear position of the electrode and visualization of each of the individual contacts. The calculated effective dose of the used CBCT and MSCT acquisitions is 80 mu sv for the CBCT, 3,600 mu sv for the 16-slice computed tomography, and 4,800 mu sv for the 4-slice computed tomography. Conclusion: These preliminary results suggests that, for in vivo postoperative evaluation of cochlear implants, CBCT can provide at least the same information as conventional radiography, digital radiograph, and MSCT but in a more comfortable and a much more safer way.

Absorbed thyroid dose and effective half-life were determined in 46 hyperthyroid cats after treatment with a low dose (mean 111 MBq) of radioiodine intravenously. Thirteen of these cats had received iohexol for glomerular filtration rate (GFR) measurement within 24 h before treatment with radioiodine in view of another ongoing study at our institution. Pre-therapy values were obtained for total thyroxine (TT4) and for the thyroid to salivary gland ratio with sodium pertechnetate γ-camera imaging. All cats underwent post-therapy scans at 24, 48 and 120 h for evaluation of radioactive iodine uptake (RAIU) and the effective half-life of radioiodine. The absorbed dose was calculated from the cumulative activity with Olinda software. Both groups were comparable in age, TT4 and the ratio of thyroid activity to salivary gland activity. Statistical analysis revealed a significant decreased absorbed dose in the thyroid in the iohexol group. This decreased uptake was not accompanied by an decreased effective half-life of the radioiodine. The variation of inter-individual RAIU decreased in this group and more homogenous absorbed doses were obtained. No significant difference in outcome could be demonstrated. However, a tendency towards a higher number of residual hyperthyroidism in the iohexol group was noted (15 versus 6% in control group). This study demonstrates that iohexol interferes with the uptake of radioiodine in the hyperthyroid cat but does not provoke increased turnover. In this study, albeit including a small number of cats, outcome did not seem to be significantly affected.

In this paper, a large-scale multicentre patient dose study performed in eight Belgian interventional cardiology departments is presented. Effective dose (E) was calculated based on a detailed dose-area product (DAP)-registration during each procedure and by using conversion coefficients generated by the Monte Carlo-based computer program PCXMC. Conversion coefficients were found to be 0.177 mSv Gycm −2 for systems that do not use any additional copper filtration in cineradiography and 0.207 mSv Gycm −2 for systems that use additional copper filtration in cineradiography. Mean E values of 9.6 and 15.3 mSv for diagnostic and therapeutic procedures, respectively, were obtained. DAP distributions were investigated in order to derive dose reference levels: 71 and 106 Gycm 2 for diagnostic and therapeutic procedures, respectively, are proposed. Significant differences were observed in DAP distributions taking into account whether additional copper filtration was used in the cineradiography mode. Apart from the skin, the organs most at risk are lungs and heart. The probability of fatal cancer for the studied population amounted to 1.1 × 10 −4 and 2.1 × 10 −4 for diagnostic and therapeutic procedures, respectively, for the age distribution of the patients considered in this multicentre study.

Background: The first aim of this study was to evaluate the correlation between clinical and physical-technical image quality applied to different strengths of iterative reconstruction in chest CT images using Thiel cadaver acquisitions and Catphan images. The second aim was to determine the potential dose reduction of iterative reconstruction compared to conventional filtered back projection based on different clinical and physical-technical image quality parameters. Methods: Clinical image quality was assessed using three Thiel embalmed human cadavers. A Catphan phantom was used to assess physical-technical image quality parameters such as noise, contrast-detail and contrast-to-noise ratio (CNR). Both Catphan and chest Thiel CT images were acquired on a multislice CT scanner at 120 kVp and 0.9 pitch. Six different refmAs settings were applied (12, 30, 60, 90, 120 and 150refmAs) and each scan was reconstructed using filtered back projection (FBP) and iterative reconstruction (SAFIRE) algorithms (1,3 and 5 strengths) using a sharp kernel, resulting in 24 image series. Four radiologists assessed the clinical image quality, using a visual grading analysis (VGA) technique based on the European Quality Criteria for Chest CT. Results: Correlation coefficients between clinical and physical-technical image quality varied from 0.88 to 0.92, depending on the selected physical-technical parameter. Depending on the strength of SAFIRE, the potential dose reduction based on noise, CNR and the inverse image quality figure (IQF(inv)) varied from 14.0 to 67.8 %, 16.0 to 71.5 % and 22.7 to 50.6 % respectively. Potential dose reduction based on clinical image quality varied from 27 to 37.4 %, depending on the strength of SAFIRE. Conclusion: Our results demonstrate that noise assessments in a uniform phantom overestimate the potential dose reduction for the SAFIRE IR algorithm. Since the IQF(inv) based dose reduction is quite consistent with the clinical based dose reduction, an optimised contrast-detail phantom could improve the use of contrast-detail analysis for image quality assessment in chest CT imaging. In conclusion, one should be cautious to evaluate the performance of CT equipment taking into account only physical-technical parameters as noise and CNR, as this might give an incomplete representation of the actual clinical image quality performance.

Objective : To compare the organ doses and lifetime-attributable risk of cancer for electrocardiogram-triggered sequential and high-pitch helical scanning in a clinical patient population. Methods : Phantom thermoluminiscence dosimeter measurements were used as a model for the organ dose assessment of 314 individual patients who underwent coronary computed tomographic angiography. Patient-specific lifetime-attributable cancer risks were calculated. Results : Phantom measurements showed that heart rate had a significant influence on the delivered radiation exposure in sequential mode, and calcium scoring and contrast bolus tracking scans make a nonnegligible contribution to patients' dose. Therefore, they should be taken into account for patients' organ dose estimations. Median cancer induction risks are low, with 0.008% (0.0016%) and 0.022% (0.056%) for high-pitch and sequential scanning for men (women), respectively. Conclusions : The use of high-pitch helical scanning leads to 65% and 72% lower lifetime-attributable risk values for men and women, respectively, compared with sequential scanning.

Purpose: To investigate the association between six transforming growth factor β1 gene ( TGFβ1 ) polymorphisms (-1.552delAGG, -800G>A, -509C>T, Leu10Pro, Arg25Pro, Thr263Ile) and the occurrence of late normal tissue reactions after gynecologic radiotherapy (RT). Methods and Materials: Seventy-eight women with cervical or endometrial cancer and 140 control individuals were included in the study. According to the Common Terminology Criteria for Adverse Events version 3.0 (CTCAEv3.0) scale, 25 patients showed late adverse RT reactions (CTC2+), of whom 11 had severe complications (CTC3+). Polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP), single base extension and genotyping assays were performed to examine the polymorphic sites in TGFβ1 . Results: Homozygous variant -1.552delAGG, -509TT, and 10Pro genotypes were associated with the risk of developing late severe RT reactions. Triple (variant) homozygous patients had a 3.6 times increased risk to develop severe RT reactions ( p = 0.26). Neither the -800A allele, nor the 25Pro allele or the 263Ile allele were associated with clinical radiosensitivity. There was perfect linkage disequilibrium (LD) between the -1.552delAGG and the -509C>T polymorphisms, and tight LD between the -1.552/-509 and the Leu10Pro polymorphisms. Haplotype analysis revealed two major haplotypes but could not distinguish radiosensitive from nonradiosensitive patients. Conclusions: The present study shows that homozygous variant TGFβ1 -1.552delAGG, -509TT, and 10Pro genotypes may be associated with severe clinical radiosensitivity after gynecologic RT.

The aim of this study was to investigate the feasibility of administering increasing activities of (188)Re-4-hexadecyl-1-2,9,9-tetramethyl-4,7-diaza-1,10-decanethiol/lipiodol ((188)Re-HDD/lipiodol) for the treatment of hepatocellular carcinoma (HCC) in patients with well-compensated cirrhosis.The activity levels were increased by 1.1 GBq/step after a 6-week interval without unacceptable adverse events in at least five consecutive patients. Absorbed doses to the various organs were calculated according to the MIRD formalism, based on three gamma-scintigraphic studies. Response was assessed by means of MRI and alpha-fetoprotein (AFP) monitoring.Thirty-five treatments were carried out in 28 patients. Activities from 4.8 to 7.0 GBq (188)Re-HDD/lipiodol were administered via a transfemoral catheter. The mean absorbed dose to the liver (including tumour) was 7.6+/-2.2, 9.8+/-4.9 and 15.2+/-4.9 Gy for the 4.8-, 5.9- and 7.0-GBq groups, respectively. Treatment was well tolerated at all activity levels. Further escalation of the administered activity was not feasible owing to limitations related to the radiolabelling procedure. Response assessment on MRI showed partial response, stable disease and disease progression in 1, 28 and 2 assessable treatments, respectively. In 8 of 17 treatment sessions with an initially elevated AFP, a reduction ranging from 19% to 97% was observed 6 weeks later.Following the intra-arterial administration of 4.8-7.0 GBq (188)Re-HDD/lipiodol in patients with HCC and well-compensated liver cirrhosis, no severe adverse events occurred. Further escalation was not feasible owing to limitations in the radiolabelling procedure.

The aim of this study was twofold: firstly, to determine whether the European Association of Nuclear Medicine (EANM) dosage card results in weight-independent effective doses or weight-independent count rates; secondly, to determine whether one dosage card is sufficient for 95 different radiopharmaceuticals, and, if not, how many cards we reasonably need to take into account inter-tracer variability.Normalisation factors for count rate and effective dose were calculated as a function of body weight, with 70 kg as standard. Calculations were performed, using whole-body absorption fractions and MIRDOSE 3 software, for seven anthropomorphic phantoms and ten radionuclides. An analytic function for both relations was proposed. Normalisation factors for effective dose for 95 radiopharmaceuticals were investigated using cluster analysis.Normalisation factors for count rate and effective dose can be estimated accurately as a function of body weight W by (W/70)a holding only one parameter, called the a value. The a values for 95 radiopharmaceuticals were classified into three clusters (nA=7, nB=76, nC=12). Cluster A contains tracers for renal studies. Cluster B contains all remaining tracers, except iodine-labelled tracers for thyroid studies and 89Sr for therapy, which belong to cluster C.Correction factors proposed by the EANM task group mainly correct for effective dose. They are very similar to the factors obtained for cluster A. Using the EANM factors for tracers belonging to clusters B and C results in significantly higher effective doses to children. We suggest using three tracer-dependent dosage cards for which the correction factors have been calculated to obtain weight-independent effective doses.

Background External beam radiotherapy and beta radioimmunotherapy (RIT) are effective treatments for lymphoid malignancies. The development of RIT with alpha emitters is attractive because of the high linear energy transfer (LET) and short path length, allowing higher tumour cell kill and lower toxicity to healthy tissues. Aim To assess the binding of rituximab to samples of B cell chronic lymphocytic leukaemia (B-CLL) and splenic lymphoma with villous lymphocytes (SLVL), and to evaluate the induction of apoptosis by conventional therapies as well as with 2 1 3 Bi conjugated to rituximab. Method 2 1 3 Bi was eluted from a 2 2 5 Ac generator and conjugated to CD20 antibody (rituximab) with CHX-A"-DTPA as chelator. Binding assays with 2 1 3 Bi-rituximab were correlated to antibody binding capacity obtained by flow cytometry. Apoptosis was scored by flow cytometric analyses of the cells stained with annexin V-FITC and 7-amino-actinomycin D. Results Binding of 2 1 3 Bi-rituximab was significantly lower for B-CLL compared to SLVL samples (12 ′ 3 and 42 ′ 10 2 1 3 Bi atoms per cell, respectively, at 370 kBq.ml - 1 ). The induction of apoptosis did not differ significantly between the two groups (B-CLL and SLVL) after external gamma irradiation or treatment with methylprednisolone and fludarabine (17 ′ 12% and 18 ′ 11%; 23 ′ 14% and 21 ′ 12%; 9 ′ 9% and 11 ′ 8%, respectively; all results expressed as percentages of all cells). Rituximab conjugated or not to 2 1 3 Bi induced significantly more apoptosis in SLVL (42 ′ 19% and 42 ′ 17%) compared to B-CLL samples (27 ′ 12% and 6 ′ 8%). Conclusion Binding assays confirm that SLVL samples present more CD20 antigens compared to B-CLL samples. Conventional therapies such as fludarabine, methylprednisolone or external gamma irradiation induce similar responses in the two populations but SLVL samples present higher sensitivity towards 2 1 3 Bi-rituximab. These data are in favour of alpha-RIT in SLVL patients.

Purpose To determine accurately the radiation burden of both patients and staff from intracoronary radiotherapy (IRT) with 192 Ir and to investigate the importance of IRT in the patient dose compared with interventional X-rays. Methods and materials The Radiation Burden Assessment Study (RABAS) population consisted of 9 patients undergoing γ-IRT after percutaneous transluminal coronary angioplasty and 14 patients undergoing percutaneous transluminal coronary angioplasty only as the control group. For each patient, the dose to the organs and tissues from the internal and external exposure was determined in detail by Monte Carlo N-particle simulations. Patient skin dose measurements with thermoluminescence dosimeters served as verification. Staff dosimetry was performed with electronic dosimeters, thermoluminescence dosimeters, and double film badge dosimetry. Results With respect to the patient dose from IRT, the critical organs are the thymus (58 mGy), lungs (31 mGy), and esophagus (27 mGy). The mean effective dose from IRT was 8 mSv. The effective dose values from interventional X-rays showed a broad range (2–28 mSv), with mean values of 8 mSv for the IRT patients and 13 mSv for the control group. The mean dose received by the radiotherapist from IRT was 4 μSv/treatment. The doses to the other staff members were completely negligible. Conclusion Our results have shown that the patient and personnel doses in γ-IRT remain at an acceptable level. The patient dose from IRT was within the variations in dose from the accompanying interventional X-rays.

Several authors have demonstrated the good tolerance of hepatic intra-arterial 131 I-Lipiodol therapy and report survival rates of 21-25% after 1 year in inoperable patients. This study explored the possibility that more selective hepatic arterial instillation could be a strategy for increasing tumoural uptake and response of 131 I-Lipiodol. Between June 1999 and September 2001 we selected 24 patients: 14 received a selective instillation of 131 I-Lipiodol to the proper hepatic artery (SEL group); and 10 received a hyperselective instillation in the right or left hepatic artery (HYP-SEL group). The individual 131 I-Lipiodol activity as a per cent of the injected activity per millilitre of tumour (%IA/ml tumour) was correlated with the selectivity of instillation in 28 tumours and with tumour response in 24 tumours. Differences in tumour response or tumour uptake between the SEL and HYP-SEL groups were not significant. In general, we observed a %IA/ml tumour of 0.05-2.6% for the uptake of 131 I-Lipiodol. The uptake was significantly higher in responsive disease than in stable or progressive disease (P = 0.002). A large tumour volume was invariably related to low uptake of 131 I-Lipiodol and progressive disease (P = 0.008). In conclusion, our study does not support the general use of hyper-selective or super-selective intra-arterial administration of 131 I-Lipiodol. This result may be extrapolated to similar types of intra-arterial, loco-regional hepatic radionuclide therapy.

Objectives The purpose of this study was to quantify the reduction in patient radiation dose during coronary angiography (CA) by a new X-ray technology, and to assess its impact on diagnostic image quality. Background Recently, a novel X-ray imaging technology has become available for interventional cardiology, using advanced image processing and an optimized acquisition chain for radiation dose reduction. Methods 70 adult patients were randomly assigned to a reference X-ray system or the novel X-ray system. Patient demographics were registered and exposure parameters were recorded for each radiation event. Clinical image quality was assessed for both patient groups. Results With the same angiographic technique and a comparable patient population, the new imaging technology was associated with a 75% reduction in total kerma-area product (KAP) value (decrease from 47 Gycm2 to 12 Gycm2, P

During interventional cardiology procedures patient and staff are exposed to X-ray radiation. Minimizing radiation dose is a crucial part of quality care. This study quantifies the radiation dose reduction for patient and staff enabled by a novel X-ray imaging technology using advanced real-time

To investigate the impact of digitalisation on performance parameters and breast dose of the Flemish Breast Cancer Screening Programme. Both computed (CR) and direct radiography (DR) are compared with screen-film mammography (SFM).Data from 975,673 mammographic examinations were collected from units which underwent digitalisation from SFM to CR (41 units) or DR (72 units) in the period 2005-2011. Performance indicators were obtained by consulting the Screening Programme database. Phantom and patient dosimetry data were acquired from the physical technical quality assurance of the programme.Digitalisation induced no significant change in cancer detection rate (CDR), percentage of ductal carcinomas in situ and percentage of breast cancers smaller than 1 cm. A decrease in false-positive results and third readings was observed, which was a time-related observation. After digitalisation, positive predictive value (PPV) increased and recall rates decreased. Compared with SFM, an increase of 30% in mean glandular dose (MGD) was found for CR, while a similar change in the opposite direction was found for DR.No major differences in performance parameters after digitalisation were found. Transition of SFM to CR resulted in a higher MGD and associated lower detection-over-induction ratio (DIR), while the change to DR induced an improvement of DIR.• Performance parameters showed no major differences after digitalisation to CR or DR. • Transition from SFM to CR results in a higher mean glandular dose. • Transition from SFM to DR results in a lower mean glandular dose.

Objectives The purpose of this study was to assess patient-specific organ doses and cancer risk with 3D-rotational acquisitions versus the current standard of multiple single-plane coronary angiography (CA). Background Catheter-based CA remains one of the most commonly performed diagnostic invasive procedures delivering a relatively high radiation dose to the patient. With the introduction of flat-panel technology, three-dimensional rotational angiography became an alternative for the conventional two-dimensional angiography. However, limited information is available on the difference in patient radiation exposure with both acquisition techniques. Methods Eighty adult patients (45 males, age 38–93 years) were randomly assigned to the rotational or standard angiography group. Exposure parameters were registered and skin dose distribution was measured during the procedure. Patient-specific organ doses and related cancer risks were assessed with dedicated software. Results Rotational angiograms were associated with 33% lower KAP-values (decrease from 49.99 Gycm2 to 33.37 Gycm2, P

Purpose The impact on patients’ health of radiopharmaceuticals in nuclear medicine diagnostics has not until now been evaluated systematically in a European context. Therefore, as part of the EU-funded Project PEDDOSE.NET (www.peddose.net), we review and summarize the current knowledge on biokinetics and dosimetry of commonly used diagnostic radiopharmaceuticals. Methods A detailed literature search on published biokinetic and dosimetric data was performed mostly via PubMed (www.ncbi.nlm.nih.gov/pubmed). In principle the criteria for inclusion of data followed the EANM Dosimetry Committee guidance document on good clinical reporting. Results Data on dosimetry and biokinetics can be difficult to find, are scattered in various journals and, especially in paediatric nuclear medicine, are very scarce. The data collection and calculation methods vary with respect to the time-points, bladder voiding, dose assessment after the last data point and the way the effective dose was calculated. In many studies the number of subjects included for obtaining biokinetic and dosimetry data was fewer than ten, and some of the biokinetic data were acquired more than 20 years ago. Conclusion It would be of interest to generate new data on biokinetics and dosimetry in diagnostic nuclear medicine using state-of-the-art equipment and more uniform dosimetry protocols. For easier public access to dosimetry data for diagnostic radiopharmaceuticals, a database containing these data should be created and maintained. Electronic supplementary material The online version of this article (doi:10.1007/s00259-011-1904-z) contains supplementary material, which is available to authorized users.

The purpose of this study was to evaluate the diagnostic performance of digital tomosynthesis in comparison with digital radiography in the detection of urinary stones with MDCT as the reference standard.Fifty consecutively enrolled patients (32 men, 18 women; mean age, 51.5 years; range, 19-83 years) referred for unenhanced MDCT of the abdomen with suspicion of urinary stones also underwent digital tomosynthesis and digital radiography (anteroposterior and bladder inlet views). Images from all examinations were randomly read by three blinded radiologists. The mean effective doses for digital tomosynthesis, digital radiography, and low- and high-dose MDCT were measured on a male phantom. Free-response receiver operating characteristics and receiver operating characteristics analyses were used to compare the diagnostic performance of digital radiography with that of digital tomosynthesis.Both types of analysis showed significantly better performance of tomosynthesis over digital radiography for all urinary stones (p0.05). No such improvement was found for ureteral stones. The gain in sensitivity with tomosynthesis was largest for stones between 2 and 5 mm in diameter. The mean effective dose was 0.5 mSv for digital radiography, 0.85 mSv for tomosynthesis, 2.5 mSv for low-dose MDCT, and 12.6 mSv for high-dose MDCT.Use of digital tomosynthesis of the abdomen results in improved detection of urinary stones in general over digital radiography with only a slight increase in effective dose. Use of tomosynthesis, however, was not associated with major improvement in the diagnosis of ureteral stones. The technique has potential as an alternative imaging technique in the detection and follow-up of urinary stones.

Cone-beam CT (CBCT) and digital tomosynthesis are becoming interesting tools for paranasal sinus imaging. In present study, the effective dose of these new techniques was compared with the effective dose of multi slice CT (MSCT) acquisitions.

Uterine artery embolization (UAE) is an efficient option for the treatment of uterine fibroids. Recently, conebeam CT (CBCT) acquisitions are being introduced during these procedures. The purpose of current study was to evaluate the radiation dose contribution of these cone-beam CT runs. Therefore an anthropomorphic Rando phantom study was set up. The phantom was filled with 156 thermoluminescent dosemeters. Organ and effective dose conversion factors were determined for three different set-ups: cone-beam CT acquisitions, digital subtraction angiography (DSA) PA and DSA oblique. Using these factors, the ovarian and effective doses for the first two subsequent patient procedures were calculated. The contribution of the CBCT runs was determined.

In this paper is explained how systematic tables are calculated for the determination of organ doses and effective dose from DAP values for interventional radiology and cardiology. This information is useful as an additional tool for dose optimization of patients for complex high-dose procedures. In the Monte Carlo calculation, 2 voxel based phantoms Golem and Laura are used.

Alemtuzumab (Campath, Berlex) is a humanized IgG1 rat monoclonal antibody directed against the cell surface CD52 antigen, found on lymphocytes and monocytes. It is being developed for the treatment of chronic lymphocytic leukemia (CLL), autoinumme disease and for the prevention of transplant rejection. This study focused on synthesis, quality control, in vitro evaluation and biodistrubution of Re-188-labeled alemtuzumab for radioimmunotherapy of B-cell CLL.Re-188-alemtuzumab was synthesized using a direct radiolabeling method. Reduction of the intramolecular disulfide bonds of the antibody was performed with tris-(carboxyethyl)-phosphine (Pierce), using a 1:60 molar excess. Reaction took place at room temperature for 20 min. A PD-10 desalting column was used to purify the reduced antibody from excess phospine.Complexation and transchelation of (ReO4-)-Re-188 was achieved using sodium gluconate as weak chelator and SnCl2 as reducing agent. Quality control was done using instant thin-layer chromatography. Binding assays were performed on a CD52-positive cell line (HuT-78). Female NMRI mice were injected intravenously with 20 mu g radiolabeled alemtuzumab and killed at preset time intervals for biodistribution studies. Tissues were dissected, weighed and counted for determination of radioactivity. Data were expressed as percentage injected activity per gram of tissue (% IA/g tissue) or as percentage injected activity (%IA).Re-188-alemtuzumab was prepared achieving high radiochemical yields. Labeling efficiency of more than 95% can be obtained using optimal reaction conditions. Re-188-alemtuzumab showed good in vitro stability, remaining intact at 24 h after radiolabeling. In mice, Re-188-alemtuzumab showed high uptake in the blood (25.10 +/- 1.36% IA at 1 h p.i.), followed by a biexponential clearance (t(1/2 alpha) =4.790 h and t(1/2 beta)=55.45 h). Increased uptake was observed in kidneys and heart (9.29 +/- 0.46% IA/g in kidneys and 6.10 +/- 1.82% IA/g in heart at I p.i.). The highest absorbed radiation dose was received by the kidneys (0.159-3.26 mGy/MBq) and heart wall (0.0705-0.132 mGy/MBq). The predicted radiation dose for the total body was in the range of 0.0459-0.0529 mGy/MBq. The effective dose for the human reference adult was estimated to be approximately 0.0486-0.195 mSv/mBq.Re-188-alemtuzumab can be prepared with high radiochemical yield and purity and showed good in vitro behavior and favorable biodistribution. Therefore, Re-188-alemtuzumab would be an ideal candidate for radioimmunotherapy of chronic lymphocytic leukemia. (C) 2008 Elsevier Inc. All rights reserved.

Effective dose ( E), representing the risk of late radiation-induced effects, can be estimated by the use of conversion factors (CF), converting direct measurable quantities such as dose-area-product into E. Eight Belgian hospitals participated in the study with a total number of 318 procedures. E-values, calculated with PCXMC, were compared for the different hospitals for diagnostic and therapeutic procedures separately. E-values varied significantly depending on the hospital where the procedure was performed (P < 0.001), on filtration insertion (P < 0.001), on whether a centre is a training centre or not, the dose conscious action of the cardiologists and the complexity of the procedure ( P < 0.001). Hospital-specific CF were calculated. An average CF of 0.185 mSv Gycm(-2) was obtained with a satisfactory correlation (r = 0.966, P < 0.001). The differences in CF between hospitals were due to, a large extent, the availability of additional filtration in cinegraphy mode (P < 0.001) and not to the differences in irradiation geometries in the clinical protocol of the interventional procedures.

To investigate compliance with the acceptance criteria of the European guidelines for quality assurance in breast cancer screening, a typetesting programme of the physical characteristics of digital mammography systems based on direct readout (DR) technology or computed radiography (CR) was organised and executed within the Flemish breast cancer screening programme. While in general image quality/dose characteristics of flat panel DR systems passed the acceptance criteria more easily than CR systems, the slit-scanning direct photon counting system included in present study was outstanding in combining a very low dose with a good image quality. The data obtained up to now indicate the necessity of retuning the AEC for DR systems according to constant contrast to noise ratio (CNR) over the whole range of PMMA thicknesses (20–70 mm) to improve image quality in imaging breasts of large thickness at the cost of higher doses. For the two CR systems which passed the typetesting procedure dose levels do not allow a similar improvement of CNR for thick objects for these systems. The obtained results highlight the importance of the use of high Z target/filter combinations in X-ray generating systems for imaging thick objects to meet the image quality/dose criteria. With respect to image display aspects high-quality 3-megapixel LCD monitors succeeded also in the typetesting procedure in addition to 5-megapixel monitors. However, as zooming and scrolling are necessary for 3-megapixel monitors to get the full resolution capabilities of the image capture system, 5-megapixel monitors are preferred in a busy screening environment.

In nuclear medicine, an increasing number of radiolabelled agents are under investigation for future use in diagnostic imaging and for applications in radionuclide therapy. All these studies require large amounts of human data to allow for statistical comparisons with existing and well established diagnostic or therapeutic methodologies. In the framework of a good clinical practice environment, clinical trials should be carried out according to international guidelines and regulations as described in the Declaration of Helsinki. Studies involving ionizing radiation, as is the case in nuclear medicine, require special consideration to comply with the ALARA (as low as reasonably achievable) principle. Special publications of the International Commission of Radiological Protection and the World Health Organization deal with this topic in medical research. From the legislation point of view, the 97/43/EURATOM Directive represents the reference to clinical research using ionizing radiation within the European Union. In order to keep the radiation dose of (healthy) volunteers as low as possible, predictive dosimetry studies based on in-vivo animal biokinetics are essential. On the other hand, patients included in dose-escalation radionuclide therapy trials should be monitored individually with respect to dosimetry of the tumour and the critical organs. In this paper the importance and methodology of contemporary patient dosimetry in diagnostic and therapeutic nuclear medicine research are reviewed. It is concluded that reliable dosimetry is essential in performing scientific clinical studies according to the principle of good clinical practice.

This paper reports on the biodistribution and dosimetry of (99m)Tc-depreotide in patients.Whole body planar images were acquired 30 minutes, 1, 2, 4, 9, and 24 hours after intravenous injection of 555-740MBq (99m)Tc-depreotide in 5 breast cancer patients. Urine was collected up to 24 hours after injection, allowing for a calculation of renal clearance and an interpretation of whole body clearance. Time activity curves were generated for the thyroid, lungs, liver, spleen, kidneys, colon, thoracic vertebrae/sternum, and whole body by fitting the organ-specific geometric mean counts, obtained from regions of interest (ROIs). The Medical Internal Radiation Dose (MIRD) formulation was applied to calculate the absorbed radiation dose for various organs.The whole body images show most of the activity distributed in the liver, spleen, and kidneys. Nearly all excretion of activity occurred by the renal system, and hepatobiliary excretion was negligible. Elimination of administered activity occurred predominantly through physical decay. The mean cumulative measured urinary excretion at 24 hours postinjection was 14.0% (standard deviation; 11.8%) of the administered activity. The highest absorbed dose was received by the kidneys, thyroid, and spleen. The average effective dose was estimated to be 1.15E-02mSv/MBq (standard deviation; 1.41E-03mSv/MBq).The biodistribution of (99m)Tc-depreotide demonstrated low lung and myocardial uptake allowing early imaging of the supradiaphragmatic region and this with a dosimetry favorable for clinical whole body and single photon emission computed tomography (SPECT) imaging.

External source radiotherapy and beta radioimmunotherapy (RIT) are effective treatments for lymphoid malignancies. The development of RIT with alpha emitters is attractive because of the high linear energy transfer (LET) and short path length, allowing higher tumour cell kill and lower toxicity to healthy tissues. We assessed the relative biological efficacy (RBE) of alpha RIT (in vitro) compared to external gamma irradiation with respect to induction of apoptosis in B chronic lymphocytic leukaemia (B-CLL) and induction of chromosomal damage in healthy donor B and T lymphocytes. The latter was measured by a micronucleus assay. 213Bi was eluted from a 225Ac generator and conjugated to CD20 antibody (rituximab) with CHX-A''-DTPA as a chelator. B-CLL cells from five patients were cultured for 24 h in RPMI/10% FCS while exposed to 213Bi conjugated to CD20 antibody or after external 60Co gamma irradiation. Binding assays were performed in samples of all patients to calculate the total absorbed dose. Apoptosis was scored by flow cytometric analyses of the cells stained with annexin V-FITC and 7-AAD. Apoptosis was expressed as % excess over spontaneous apoptosis in control. Full dose range experiments demonstrated 213Bi-conjugated CD20 antibody to be more effective than equivalent doses of external gamma irradiation, but showed that similar plateau values were reached at 10 Gy. The RBE for induction of apoptosis in B-CLL was 2 between 1.5 and 7 Gy. The micronucleus yield in lymphocytes of healthy volunteers was measured to assess the late toxicity caused by induction of chromosomal instability. While gamma radiation induced a steady increase in micronucleus yields in B and T cells, the damage induced by 213Bi was more dramatic, with RBE ranging from 5 to 2 between 0.1 Gy and 2 Gy respectively. In contrast to gamma irradiation, 213Bi inhibited mitogen-stimulated mitosis almost completely at 2 Gy. In conclusion, high-LET targeted alpha particle exposure killed B-CLL cells more effectively than did external gamma irradiation at a low dose (RBE=2), while a plateau was reached at a high dose. Long-term toxicity on healthy B and T lymphocytes was systematically higher for the alpha emitter (RBE=5 to 2).

Objectives Investigation of DNA damage induced by CT x-rays in paediatric patients versus patient dose in a multicentre setting. Methods From 51 paediatric patients (median age, 3.8 years) who underwent an abdomen or chest CT examination in one of the five participating radiology departments, blood samples were taken before and shortly after the examination. DNA damage was estimated by scoring γ-H2AX foci in peripheral blood T lymphocytes. Patient-specific organ and tissue doses were calculated with a validated Monte Carlo program. Individual lifetime attributable risks (LAR) for cancer incidence and mortality were estimated according to the BEIR VII risk models. Results Despite the low CT doses, a median increase of 0.13 γ-H2AX foci/cell was observed. Plotting the induced γ-H2AX foci versus blood dose indicated a low-dose hypersensitivity, supported also by an in vitro dose–response study. Differences in dose levels between radiology centres were reflected in differences in DNA damage. LAR of cancer mortality for the paediatric chest CT and abdomen CT cohort was 0.08 and 0.13 ‰ respectively. Conclusion CT x-rays induce DNA damage in paediatric patients even at low doses and the level of DNA damage is reduced by application of more effective CT dose reduction techniques and paediatric protocols. Key Points • CT induces a small, significant number of double-strand DNA breaks in children. • More effective CT dose reduction results in less DNA damage. • Risk estimates based on the LNT hypothesis may represent underestimates.