Clinical image quality assessment and mean glandular dose for full field digital mammography.

This study aims to assess the image quality (IQ) of 12 mammographic units and to identify units with potential optimisation needs. Data for 350 mammography examinations meeting inclusion criteria were collected retrospectively from April 2021 to April 2022. They were categorised based on the medical reports into 10 normal cases, 10 cases displaying calcifications and 10 cases presenting lesions. Two radiologists assessed the IQ of 1400 mammograms, evaluating system performance per Boitaet al's study and positioning performance following European guidelines. To measure agreement between the two radiologists, the Cohen's Kappa coefficient (κ) was computed, quantifying the excess of agreement beyond chance. The visual grading analysis score (VGAS) was computed to compare system and positioning performance assessments across different categories and facilities. Median average glandular dose (AGD) values for cranio caudal and medio lateral oblique views were calculated for each category and facility and compared to the national diagnostic reference levels. The health facilities were categorised by considering both IQ VGAS and AGD levels. Inter-rater agreement between radiologists ranged from poor (κ< 0.20) to moderate (0.41 <κ< 0.60), likely influenced by inherent biases and distinct IQ expectations. 50% of the facilities were classified as needing corrective actions for their system performance as they had IQ or high AGD that could increase recall rate and radiation risk and 50% of the health facilities exhibited insufficient positioning performance that could mask tumour masses and microcalcifications. The study's findings emphasise the importance of implementing quality assurance programs to ensure optimal IQ for accurate diagnoses while adhering to radiation exposure guidelines. Additionally, comprehensive training for technologists is essential to address positioning challenges. These initiatives collectively aim to enhance the overall quality of breast imaging services, contributing to improved patient care.

Reproducibility of surface-based deep inspiration breath-hold technique for lung stereotactic body radiotherapy on a closed-bore gantry linac.

Background and purpose: Tumor motion and delivery efficiency are two main challenges of lung stereotactic body radiotherapy (SBRT). The present work implemented the deep inspiration breath hold technique (DIBH) with surface guided radiation therapy (SGRT) on closed-bore linacs and investigated the correlation between SGRT data and internal target position. Materials and methods: Thirteen lung SBRT patients treated in DIBH using a closed-bore gantry linac and a ring-mounted SGRT system were retrospectively analysed. Visual coaching was used to achieve DIBH with a ± 1 mm threshold window in the anterior-posterior direction. Three kV-CBCTs were added to the treatment workflow and examined offline to verify intra-fraction tumor position. Surface-based DIBH was analysed using SGRT treatment reports and an in-house python script. Data from 73 treatment sessions and 175 kV-CBCTs were studied. Correlations between target and surface positions were studied with Linear Mixed Models. Results: Median intra-fraction tumor motion was 0.8 mm (range: 0.7-1.3 mm) in the anterior-posterior direction, 1.2 mm (range: 1-1.7 mm) in the superior-inferior direction, and 1 mm (range: 0.7-1.1 mm) in the left-right direction, with rotations of <1° (range: 0.6°-1.1°) degree in all three directions. Planned target volumes and healthy lung volumes receiving 12.5 Gy and 13.5 Gy were reduced on average by 67% and 54%, respectively. Conclusions: Lung SBRT in DIBH with the ring-mounted SGRT system proved reproducible. The surface monitoring provided by SGRT was found to be a reliable surrogate for internal target motion. Moreover, the implementation of DIBH technique helped reduce target volumes and lung doses.

SurVolT: Surface to Volume conversion Tool. A proof of concept.

PURPOSE: To develop SurVolT, a conversion tool able to apply volumetric changes to DICOM Computed Tomography (CT) data using daily surface (obj) data acquired with AlignRT® (VisionRT Ltd.), primarily designed and validated for breast treatments. MATERIALS AND METHODS: SurVolT proceeds in 4 steps: 1. AlignRT .obj files extraction, 2. Contour deformation where the surface data points are matched to the initial external contour on a Region Of Interest, ROImatch, on which the anatomy is supposed to be unchanged. Then, external contour substitution is performed on the ROIttt covering the treated breast area. This is validated on a female torso phantom with a tissue-equivalent bolus mimicking an edema. The Planning Treatment Volume (PTV) contour from the initial CT is also deformed according to the new external contour in the ROIttt. 3. Volumetric data estimation according to the new external contour, validated on an anthropomorphic pelvis phantom. 4. Import of new DICOM data into the Treatment Planning System (TPS). Finally, the workflow is applied on a first patient presenting an anatomical change during the treatment. RESULTS: The validation of step 2 and 3 shows a bolus thickness estimation of 5.8±1.2mm (expected 5 mm) and the non-rigid deformation of initial CT images follows the new external contour at the ROIttt bolus site while revealing negligible deformation elsewhere. CONCLUSION: This first proof of concept introducing a Surface Guided Radiotherapy (SGRT) tool allowing daily surface data to volume conversion is a fundamental step toward SGRT-based adaptive radiotherapy.

Investigating the robustness of the AlignRT InBore™ co-calibration process and determining the overall tracking errors.

OBJECTIVE: To determine the overall tracking errors inherent to the co-calibration procedure of AlignRT InBore™'s (Vision RT Ltd., London, UK) ceiling-mounted and ring-mounted cameras. METHODS: Extrinsic calibration errors related to the mismatch between ceiling and InBore cameras' isocentres and treatment isocentre were determined using MV images and the SRS package and compared to traditional plate-based error. Next, using a realistic anthropomorphic female phantom, intrinsic calibration errors were determined while varying source-skin distance (80 to 100 cm), breast board inclination (0° to 12.5°), room lighting conditions (0 to 258 lx), skin colour (dark, white and natural skin colour), and pod occlusion. RESULTS: MV images of the cube proved plate-based calibration to suffer from large errors especially in the vertical direction (up to 2 mm). Intrinsic calibration errors were considerably lower. Indeed, RTD values of ceiling and InBore cameras showed little variability with isocentre depth (within 1.0 mm/0.4°), surface orientation and breast board inclination (within 0.7 mm/0.3°), changing lighting conditions (within 0.1 mm/0.2°), skin colour/tone (within 0.3 mm/0.3°) and camera pod occlusion (within 0.3 mm/0.2°). CONCLUSION: The use of MV-images proved critical to maintain co-calibrating errors of ceiling and InBore cameras to Halcyon's treatment isocentre below 1 mm.

Neutron Radiation Dose Measurements in a Scanning Proton Therapy Room: Can Parents Remain Near Their Children During Treatment?

Purpose: This study aims to characterize the neutron radiation field inside a scanning proton therapy treatment room including the impact of different pediatric patient sizes. Materials and Methods: Working Group 9 of the European Radiation Dosimetry Group (EURADOS) has performed a comprehensive measurement campaign to measure neutron ambient dose equivalent, H*(10), at eight different positions around 1-, 5-, and 10-year-old pediatric anthropomorphic phantoms irradiated with a simulated brain tumor treatment. Several active detector systems were used. Results: The neutron dose mapping within the gantry room showed that H*(10) values significantly decreased with distance and angular deviation with respect to the beam axis. A maximum value of about 19.5 µSv/Gy was measured along the beam axis at 1 m from the isocenter for a 10-year-old pediatric phantom at 270° gantry angle. A minimum value of 0.1 µSv/Gy was measured at a distance of 2.25 m perpendicular to the beam axis for a 1-year-old pediatric phantom at 140° gantry angle.The H*(10) dependence on the size of the pediatric patient was observed. At 270° gantry position, the measured neutron H*(10) values for the 10-year-old pediatric phantom were up to 20% higher than those measured for the 5-year-old and up to 410% higher than for the 1-year-old phantom, respectively. Conclusions: Using active neutron detectors, secondary neutron mapping was performed to characterize the neutron field generated during proton therapy of pediatric patients. It is shown that the neutron ambient dose equivalent H*(10) significantly decreases with distance and angle with respect to the beam axis. It is reported that the total neutron exposure of a person staying at a position perpendicular to the beam axis at a distance greater than 2 m from the isocenter remains well below the dose limit of 1 mSv per year for the general public (recommended by the International Commission on Radiological Protection) during the entire treatment course with a target dose of up to 60 Gy. This comprehensive analysis is key for general neutron shielding issues, for example, the safe operation of anesthetic equipment. However, it also enables the evaluation of whether it is safe for parents to remain near their children during treatment to bring them comfort. Currently, radiation protection protocols prohibit the occupancy of the treatment room during beam delivery.

Evaluation of perfusion CT and dual-energy CT for predicting microvascular invasion of hepatocellular carcinoma.

PURPOSE: Evaluation of perfusion CT and dual-energy CT (DECT) quantitative parameters for predicting microvascular invasion (MVI) of hepatocellular carcinoma (HCC) prior to surgery. METHODS: This prospective single-center study included fifty-six patients (44 men; median age 67; range 31-84) who provided written informed consent. Inclusion criteria were (1) treatment-naïve patients with a diagnosis of HCC, (2) an indication for hepatic resection, and (3) available arterial DECT phase and perfusion CT (GE revolution HD-GSI). Iodine concentrations (IC), arterial density (AD), and 9 quantitative perfusion parameters for HCC were correlated to pathological results. Radiological parameters based principal component analysis (PCA), corroborated by unsupervised heatmap classification, was meant to deliver a model for predicting MVI in HCC. Survival analysis was performed using univariable log-rank test and multivariable Cox model, both censored at time of relapse. RESULTS: 58 HCC lesions were analyzed (median size 42.3 mm; range of 20-140). PCA showed that the radiological model was predictive of tumor grade (p = 0.01), intratumoral MVI (p = 0.004), peritumoral MVI (p = 0.04), MTM (macrotrabecular-massive) subtype (p = 0.02), and capsular invasion (p = 0.02) in HCC. Heatmap classification of HCC showed tumor heterogeneity, stratified into three main clusters according to the risk of relapse. Survival analysis confirmed that permeability surface-area product (PS) was the only significant independent parameter, among all quantitative tumoral CT parameters, for predicting a risk of relapse (Cox p value = 0.004). CONCLUSION: A perfusion CT and DECT-based quantitative imaging profile can provide a diagnosis of histological MVI in HCC. PS is an independent parameter for relapse. CLINICAL TRIALS: ClinicalTrials.gov: NCT03754192.

Benchmarking the AlignRT surface deformation module for the early detection and quantification of oedema in breast cancer radiotherapy.

PURPOSE: To determine the accuracy of AlignRT surface deformation module in detecting and quantifying oedema in breast cancer radiotherapy. MATERIALS AND METHODS: A female torso phantom and water-equivalent boluses of different thicknesses (0.5-1.5 cm) were used. The variation of surface displacement and the percentage of surface within tolerance, as a function of bolus thickness and Region of Interest (ROI) size, were investigated. Additionally, a dynamic phantom was used to study the impact of patient breathing on the swelling estimation. Lastly, a flowchart was derived to alert physicians in the case of breast swelling. RESULTS: Average displacement value proved to be inversely correlated with ROI size (R2 > 0.9). As such, for a ROI smaller than the bolus size (2.5x2.5 cm2), the average displacement (1.05 cm) provides an accurate estimate of the oedema thickness (within 5%). In opposition, with a clinical ROI, the 1 cm-thick bolus was largely underestimated with an average displacement value of 0.28 cm only. To limit the impact of patient breathing on surface deformation, dynamic surface captures and the use of the corrected patient position should be privileged. Using AlignRT, a clinical workflow for breast swelling follow-up was developed to help in the decision for repeat simulation and dosimetry. CONCLUSION: The surface deformation module provides an accurate, simple, and radiation-free approach to detect and quantify breast oedema during the course of radiotherapy.

Harmonisation of imaging protocols, radiation doses and image quality in gastrointestinal fluoroscopy examinations - multicentre study.

BACKGROUND: Paediatric gastrointestinal fluoroscopy examinations can impart varying amounts of radiation for the same patient size and exam type. OBJECTIVE: To investigate the variability of imaging protocol, radiation dose and image quality in paediatric fluoroscopy examinations in order to provide recommendations for the harmonisation and optimisation of local practices. MATERIALS AND METHODS: Five paediatric radiology departments performing fluoroscopically-guided contrast enema, micturating cystourethrography and upper gastrointestinal tract examinations participated in this study. Information on imaging protocols and radiation doses was retrospectively collected for more than 2,400 examinations. Image quality was analysed on clinical and phantom images. RESULTS: Patient doses showed great variability among centers with up to a factor of 5 for similar fluoroscopy times. The five departments had imaging protocols with major differences in fluoroscopy dose regulation curves and additional filtration. Image quality analysis on phantoms and patients images showed no major improvement in contrast, spatial resolution or noise when increasing the radiation dose. Age-based diagnostic reference levels using both dose area product and fluoroscopy time were proposed per procedure type. CONCLUSION: Disparities between centers and no correlation of radiation dose with image quality criteria create margins for optimisation. These results highlight the need for guidelines on fluoroscopy image quality and dose reference levels in paediatric gastrointestinal examinations to harmonise practices and optimise patient dose.

Percutaneous closure of ventricular septal defects in children: key parameters affecting patient radiation exposure.

BACKGROUND: Ventricular septal defect (VSD) transcatheter closure is gaining worldwide popularity despite its complexity. Reports on key factors affecting radiation exposure in children are scarce. AIMS: This clinical study is the first to comprehensively analyze the impact of all relevant parameters on children's radiation exposure during VSD interventional closures. METHODS: Between March 2016 and August 2019, all pediatric VSD cases percutaneously treated at a reference center for interventional congenital cardiology and equipped with a single-plane Innova 2100 X-ray unit were retrospectively reviewed. Multiple linear regression was performed to investigate the impact of clinical, technical, and procedural parameters on patients' radiation exposure assessed using total air kerma area product (PKA,T). RESULTS: A total of 85 patients were included in this study and 82.4% had perimembranous defects. Device implantation was successful in 96.5% of cases. The procedure lasted for a median of 60 min with a median PKA,T of 19.6 Gy.cm2 (range, 1.1 to 244.8 Gy.cm2). Patients' weight (B = 1.679, P = 0.01), number of operators (B = 1.561, P = 0.02), device positioning complexity (B = 2.381, P = 0.002), and procedural incidents (B = 2.096, P = 0.008) significantly increased PKA,T. Patients' age (B = 1.053, P = 0.784), device design (B = -1.216, P = 0.780) and approach of delivery (B = -1.119, P = 0.511) did not significantly affect PKA,T. CONCLUSIONS: Radiation exposure in children undergoing VSD percutaneous closure was highly variable. A higher patient's weight, numbers of operators, complexity in device positioning, and procedural incidents, were identified as key factors increasing patient dose for this kind of intervention.

A European perspective on dental cone beam computed tomography systems with a focus on optimisation utilising diagnostic reference levels.

Cone beam computed tomography (CBCT) has been available since the late 1990s for use in dentistry. European legislation requires optimisation of protection and the use of diagnostic reference levels (DRLs) as well as regular quality control (QC) of the imaging devices, which is well outlined in existing international recommendations. Nevertheless, the level of application is not known. Earlier studies have indicated that few European countries have established DRLs and that patient doses (exposure parameters) have not been properly optimised. The EURADOS Working Group 12-Dosimetry in Medical Imaging undertook a survey to identify existing practices in Member States. Questionnaires were developed to identify equipment types, clinical procedures performed, and exposure settings used. The surveys were circulated to 22 countries resulting in 28 responses from 13 countries. Variations were identified in the exposure factors and in the doses delivered to patients for similar clinical indicators. Results confirm that patient doses are still not properly optimised and DRLs are largely not established. There is a need to promote the importance of performing QC testing of dental CBCT equipment and to further optimise patient exposure by establishment and use of DRLs as a part of a continuous optimisation process.

Investigating the parameters that affect the radiation exposure and establishing typical values based on procedure complexity for cerebral angiography and brain aneurysm embolization.

PURPOSE: The purpose of this study is to investigate the parameters that affect the radiation exposure and to establish typical values (TV) based on procedure complexity for cerebral angiography (CA) and brain aneurysm embolization (BAE). METHODS: Clinical parameters and exposure data were retrospectively reviewed for 348 examinations performed between March 2016 and December 2019 at a single specialized neuroradiology center. TV were derived as the median value of the distribution of exposure parameters such as total air kerma area product (PKA,T), air kerma at the patient entrance reference point, fluoroscopy time, and number of frames. A statistical analysis was conducted to investigate the exposure variability with patient's gender, number of treated vessels during CA and patient gender, aneurysm location and dimension, and treatment strategies during BAE. RESULTS: Patient gender was associated with a significant increase in the exposure level for both CA and BAE. For CA, TV were in term of PKA,T of 52 Gycm2 for male vs. 28 Gycm2 for female patients. For BAE, these were 113 Gycm2 for male vs. 75 Gycm2 for female patients. Exposure levels increased significantly with the number of treated vessels in CA. TV were 20 Gycm2 for one vessel vs. 77 Gycm2 for 5-6 vessels CA. For BAE, aneurysm location was also a key factor that affects the patient exposure. TV were 55 Gycm2 for aneurysms grouped in location 1 vs. 105 Gycm2 for those grouped in location 2. CONCLUSION: Male gender, number of treated vessels, and aneurysm location are key parameters affecting patient exposure during CA and BAE procedures.

Commissioning and performance testing of the first prototype of AlignRT InBore™ a Halcyon™ and Ethos™-dedicated surface guided radiation therapy platform.

PURPOSE: To commission and assess the performance of AlignRT InBore™, a Halcyon™ and Ethos™-dedicated Surface Guided Radiation Therapy (SGRT) platform which combines ceiling-mounted cameras for patient setup and bore-mounted cameras for in-bore tracking. METHODS: To check the potential impact of InBore™ cameras on dose delivery, 16 SRS, H&N, breast and pelvis patients' quality assurance (QA) treatment plans were measured with/without AlignRT InBore™ and using ArcCHECK® and SRS MapCHECK®. Impact on image quality was determined using Catphan® 540 phantom and considering all available MV and CBCT protocols (head, breast, chest and pelvis). The stability, accuracy and overall performance of AlignRT InBore™ was assessed using an MV Cube and anthropomorphic phantoms. RESULTS: Comparison of 2D dose distributions with/without AlignRT InBore™ showed no impact on treatment delivery for all 16 QA checks (p-value > 0.25). 2D and CBCT images showed no artefacts or change in the contrast-to-noise ratio, resolution and noise values measured with Catphan® 540. Anti-collision sensors were unaffected by the bore-mounted cameras. Additionally, AlignRT InBore™ cameras allowed for motion detection with sub-0.5 mm accuracy and sub-0.4 mm stability with surface coverage of >50 × 60 × 35 cc. Accurate transition (sub-0.3 mm) from virtual to treatment isocentres was achieved. Finally, Halcyon™ rotations during CBCT and beam delivery resulted in limited camera vibrations with translation uncertainty <0.5 mm in left-right and anterior-posterior directions and <0.1 mm in head-feet direction. CONCLUSION: AlignRT InBore™ provides SGRT setup and intrafraction monitoring capabilities with a performance comparable to standard SGRT solutions while having no adverse effect on Halcyon™.

BENCHMARKING THE DOSE MAP SOFTWARE FOR CLINICAL IMPLEMENTATION AND ESTABLISHMENT OF A LOCAL FOLLOW-UP PROTOCOL FOR THE MANAGEMENT OF SKIN INJURES FOLLOWING COMPLEX INTERVENTIONAL CARDIOLOGY PROCEDURES.

This paper aims to validate the accuracy of the peak skin dose (Dskin,max) computed by the Dose Map software (DMS)-general electric and establish a local follow-up protocol for the management of patient skin injuries following complex interventional cardiology procedures (ICPs). Dskin,max was computed by the DMS and was simultaneously measured by a dense mesh of 72 thermoluminescent dosemeters for 20 ICP. Measured and computed Dskin,max were compared using Lin's concordance coefficient (${\rho}_c$). The implementation of a local follow-up strategy was based on a computed Dskin,max of 2 Gy. After eliminating 2 outliers, the average deviation between the two methods was 6% (range: -36 to +40%). Concordance between the two methods was moderate with ${\rho}_c$ (confidence interval) of 0.9128 (0.8541-0.9486). DMS computes Dskin,max with an acceptable accuracy and can be used to setup an individual follow-up process for patients with high skin exposure and risks.

Patient exposure and diagnostic reference levels in operating rooms: a multi-centric retrospective study in over 150 private and public French clinics.

To investigate patient exposure in operating rooms and establish Diagnostic Reference Levels (DRLs), fifteen different procedures and nearly 4500 surgeries performed between January 2017 and December 2019 at over 150 different private (79% of data) and public (21% of data) French clinics were recorded. Collected information include the used C-arm equipment, exposure parameters (kVp, mAs, Fluoroscopy Time - FT and Air Kerma-Area Product - PKA) and patient Body Mass Index (BMI) whenever available. Multi-centric DRLs were derived as the 75th percentile of the median exposure data collected in more than 10 different hospitals. For the less frequent procedures, DRLs were determined as the 75th percentile of pooled exposure data with a minimum of 4 centres and 100 patients. Patient exposure proved to be significantly different among the centres. Highest DRLs were found for Abdominal Aortic Aneurysm Endoprosthesis (18 min, 81 Gy cm2), Iliac Angioplasty (6 min, 24 Gy cm2) and Flutter Ablation surgeries (17 min, 14 Gy cm2). In opposition, lowest DRLs were obtained for Hallux Valgus (0.4 min, 0.04 Gy cm2), Hand/Wrist Fracture (0.6 min, 0.16 Gy cm2), and Venous Access Device Implantation surgeries (0.3 min, 0.36 Gy cm2). Similar exposure levels are registered in private clinics and public hospitals. Multi-centric DRLs for fifteen surgical procedures including six new reference values were established to help optimise patients' radiation protection.

Establishing local diagnostic reference levels for pediatric percutaneous transhepatic cholangiography interventions and optimizing the routine practice.

BACKGROUND: Liver-transplanted, immunosuppressed pediatric patients undergoing repeated percutaneous transhepatic cholangiography (PTC) require optimized exposure to ionizing radiation. OBJECTIVE: To establish local diagnostic reference levels (DRL) for pediatric PTC and investigate the routine use of X-ray equipment. MATERIALS AND METHODS: The study retrospectively analyzed data collected between October 2016 and June 2018 from a single center performing PTC. We collected exposure parameters including kerma area product (PKA), air kerma at patient entrance reference point (Ka,r) and fluoroscopy time via a dose archiving and communication system. Local diagnostic reference levels were derived as the 50th percentile of the distributions while considering published recommended weight groups. We investigated exposure variability with procedure complexity and with technical parameters recovered from the radiation dose structured report. RESULTS: The analysis included 162 PTC procedures performed in 64 children: 58% male, average age 6 years (range 39 days to 16 years) and weight 24 kg (range 3-60 kg). Local DRLs for weight groups 0-5 kg, 5-15 kg, 15-30 kg, 30-50 kg and 50-80 kg were, respectively, 6 cGy.cm2, 22 cGy.cm2, 68 cGy.cm2, 107 cGy.cm2 and 179 cGy.cm2 in PKA. Local DRLs per weight group were also established for intermediate and complex procedures. Radiation dose structured report analysis highlighted good local practice with efficient collimation, low fluoroscopy pulse rate, no magnification and limited use of radiographic acquisitions. Meanwhile, table and detector positioning and tube projection could still be optimized. PKA correlated significantly with the number of acquisitions and tube-to-table distance. CONCLUSION: We established local DRLs for children undergoing PTC.

Diagnostic Reference Levels, Deterministic and Stochastic Risks in Pediatric Interventional Cardiology Procedures.

To establish diagnostic reference levels (DRLs) and investigate deterministic and stochastic risks in pediatric interventional cardiology (IC) procedures. Exposure parameters were retrospectively reviewed for 373 patients treated between May 2016 and November 2018 at a single specialized hospital. Weight specific DRLs were derived for pediatric IC procedures. Additionally, peak skin dose (Dskin,max) was measured using thermoluminescent dosimeters for a sample of 7 diagnostic and 43 therapeutic procedures. Finally, using PCXMC software, organ doses were computed and the risk of exposure-induced cancer death (REID) was estimated using the risk models of the Biological Effects of Ionizing Radiation VII committee. DRLs for ventricular septal defect (VSD) occlusions, lacking in the literature, in terms of air kerma at patient entrance reference point (388 and 629 mGy) and total air kerma-area product (28 and 61 Gycm) were proposed for patients weight-groups 5 - < 15 kg and 15 - < 30 kg, respectively. The mean (range) Dskin,max was 15 (1-30) mGy and 94 (1-491) mGy for diagnostic and therapeutic procedures, respectively. Meanwhile, VSD occlusion involved the highest organ doses where the lungs, liver, stomach, and breasts mean doses were 57, 37, 6, and 10 mGy, respectively, and the associated REID were 0.5% and 0.3% in female and male patients, respectively. DRLs were proposed for pediatric IC procedures; these will help optimize patient exposure. Dskin,max values were lower than the 2 Gy threshold for skin injuries. Pediatric organ doses and the REID were the highest during VSD occlusion and may be critical for repetitive procedures.

Dose reference levels and clinical determinants in stroke neuroradiology interventions.

OBJECTIVES: To establish dose reference levels (RLs) for stroke interventions while carefully analysing the impact of clinical and technical parameters on patient exposure. METHODS: The study retrospectively analysed data from 377 stroke patients prospectively collected between 15 October 2015 and 30 March 2017 at a single, level-3 stroke centre equipped with Philips Allura Clarity systems. Local dose RLs were first derived as the 75th percentile of the dose area product (DAP), cumulative air kerma (Ka,r), fluoroscopy time (FT) and the number of images (NI). Univariate and multivariate negative binomial regressions were considered for the statistical analysis to investigate the dose variability with clinical and technical parameters such as patient's age and sex, occlusion removal technique, number of passages, single-plane or biplane equipment, etc. RESULTS: Local stroke dose RLs were derived in terms of total DAP (162 Gy cm2), Ka,r (854 mGy), FT (42 min) and NI (559). Gender (relative dose multiplier (RDM) 1.31; 95% CI 1.12-1.45), number of passages (RDM 1.22 per passage; 95% CI 1.10-1.22) and procedure success (RDM 0.52, 95% CI 0.55-0.80) proved to be key parameters affecting patient dose. Meanwhile the statistical analysis did not find any difference in relative dose received by patients owing to age, baseline NIHSS score, occlusion removal technique, posterior circulation, support of an anaesthesiologist or use of biplane equipment. CONCLUSIONS: Stroke dose RLs introduced in this work promote the optimisation of patient doses. Male gender, number of passages and success of recanalisation are independent key parameters affecting patient dose. KEY POINTS: • Stroke dose RLs derived in terms of total DAP (162 Gy cm 2 ), K a,r (854 mGy), FT (42 min) and NI (559) will help optimise the radiation safety of patients treated with mechanical thrombectomy. • Male gender (relative dose multiplier 1.31; 95% CI 1.12-1.45), number of passages (RDM 1.22 per passage; 95% CI 1.10-1.22) and success of recanalisation TICI score > 2b (RDM 0.52, 95% CI 0.55-0.80) are independent key parameters affecting patient dose. • Stent retriever or aspiration technique showed no significant difference in terms of the dose delivered to the patient; neither technique should be favoured for dosimetric reasons provided that there is no difference regarding clinical outcomes.

Benchmarking the DACS-integrated Radiation Dose Monitor® skin dose mapping software using XR-RV3 Gafchromic® films.

PURPOSE: To perform a benchmark of a new DACS-integrated patient skin dose mapping solution using on-phantom measurements with Gafchromic® films. MATERIALS AND METHODS: To calculate cumulative patient skin dose distribution with 1-cm2 resolution, a Radiation Dose Monitor (RDM, Medsquare), using the Radiation Dose Structured Report (RDSR), tabulated backscatter and mass energy absorption coefficients together with site-specific corrections for table, mattress attenuation, and air kerma calibration factor. Peak skin dose (PSD) and two-dimensional (2D) skin dose distributions calculated with RDM were compared against on-phantom measurements with XR-RV3 Gafchromic® films considering two widely used x-ray equipment. Seventeen different settings which include simple and multiple beam projections with extreme angulations (up to 75°), all available fields-of-view (FOVs 48-11 cm), additional collimation, variable table height and lateral positions, and variable phantom thickness (12, 20, and 30 cm) were involved. RESULTS: Due to a careful calibration of films using clinical beam qualities, 22.8% (k = 2) overall measurement uncertainty was achieved. Calculated and measured PSD values agreed with an average difference of 10% ± 7% and 9% ± 7% for 34 test conditions performed on Siemens Artis Zee and GEMS Innova IGS interventional systems, respectively. Finally, RDM's 2D skin dose maps closely matched those registered on XR-RV3 films considering the 1-cm2 resolution. While RDM correctly reproduced beam overlapping due to variable tube projections, FOV, table positions, etc., few challenges were identified related to conversion of rectangular fields to square areas in the RDSR and a stair-step effect visible for large tube projections (>45°). CONCLUSION: The accuracy of RDM's DACS-integrated skin dose mapping software was acceptable considering measurement uncertainties associated with Gafchromic® films.

Past and present work practices of European interventional cardiologists in the context of radiation protection of the eye lens-results of the EURALOC study.

This paper investigates over five decades of work practices in interventional cardiology, with an emphasis on radiation protection. The analysis is based on data from more than 400 cardiologists from various European countries recruited for a EURALOC study and collected in the period from 2014 to 2016. Information on the types of procedures performed and their annual mean number, fluoroscopy time, access site choice, x-ray units and radiation protection means used was collected using an occupational questionnaire. Based on the specific European data, changes in each parameter have been analysed over decades, while country-specific data analysis has allowed us to determine the differences in local practices. In particular, based on the collected data, the typical workload of a European cardiologist working in a haemodynamic room and an electrophysiology room was specified for various types of procedures. The results showed that when working in a haemodynamic room, a transparent ceiling-suspended lead shield or lead glasses are necessary in order to remain below the recommended eye lens dose limit of 20 mSv. Moreover, the analysis revealed that new, more complex cardiac procedures such as chronic total occlusion, valvuloplasty and pulmonary vein isolation for atrial fibrillation ablation might contribute substantially to annual doses, although they are relatively rarely performed. The results revealed that considerable progress has been made in the use of radiation protection tools. While their use in electrophysiology procedures is not generic, the situation in haemodynamic procedures is rather encouraging, as ceiling-suspended shields are used in 90% of cases, while the combination of ceiling shield and lead glasses is noted in more than 40% of the procedures. However, we find that still 7% of haemodynamic procedures are performed without any radiation protection tools.

Feasibility of setting up generic alert levels for maximum skin dose in fluoroscopically guided procedures.

PURPOSE: The feasibility of setting-up generic, hospital-independent dose alert levels to initiate vigilance on possible skin injuries in interventional procedures was studied for three high-dose procedures (chemoembolization (TACE) of the liver, neuro-embolization (NE) and percutaneous coronary intervention (PCI)) in 9 European countries. METHODS: Gafchromic® films and thermoluminescent dosimeters (TLD) were used to determine the Maximum Skin Dose (MSD). Correlation of the online dose indicators (fluoroscopy time, kerma- or dose-area product (KAP or DAP) and cumulative air kerma at interventional reference point (Ka,r)) with MSD was evaluated and used to establish the alert levels corresponding to a MSD of 2 Gy and 5 Gy. The uncertainties of alert levels in terms of DAP and Ka,r, and uncertainty of MSD were calculated. RESULTS: About 20-30% of all MSD values exceeded 2 Gy while only 2-6% exceeded 5 Gy. The correlations suggest that both DAP and Ka,r can be used as a dose indicator for alert levels (Pearson correlation coefficient p mostly >0.8), while fluoroscopy time is not suitable (p mostly <0.6). Generic alert levels based on DAP (Gy cm2) were suggested for MSD of both 2 Gy and 5 Gy (for 5 Gy: TACE 750, PCI 250 and NE 400). The suggested levels are close to the lowest values published in several other studies. The uncertainty of the MSD was estimated to be around 10-15% and of hospital-specific skin dose alert levels about 20-30% (with coverage factor k = 1). CONCLUSIONS: The generic alert levels are feasible for some cases but should be used with caution, only as the first approximation, while hospital-specific alert levels are preferred as the final approach.