Medical physicists' implication in radiological diagnostic procedures: results after 1 y of experience.

Since January 2008-de facto 2012-medical physics experts (MPEs) are, by law, to be involved in the optimisation process of radiological diagnostic procedures in Switzerland. Computed tomography, fluoroscopy and nuclear medicine imaging units have been assessed for patient exposure and image quality. Large spreads in clinical practice have been observed. For example, the number of scans per abdominal CT examination went from 1 to 9. Fluoroscopy units showed, for the same device settings, dose rate variations up to a factor of 3 to 7. Quantitative image quality for positron emission tomography (PET)/CT examinations varied significantly depending on the local image reconstruction algorithms. Future work will be focused on promoting team cooperation between MPEs, radiologists and radiographers and on implementing task-oriented objective image quality indicators

The use of out-of-plane high Z patient shielding for fetal dose reduction in computed tomography: Literature review and comparison with Monte-Carlo calculations of an alternative optimisation technique.

When performing CT examinations on pregnant patients, great effort should be dedicated towards optimising the exposure of the mother and the conceptus. For this purpose, many radiology departments use high-Z garments to be wrapped around the patient's lower abdomen for out-of-plane organ shielding to protect the fetus. To assess their current protection efficiency, we performed a literature review and compared the efficiencies mentioned in the literature to Monte-Carlo calculations of CT protocols for which the overall scan length was reduced. We found 11 relevant articles, all of them reporting uterus exposure due to CT imaging performed for exclusion of pulmonary embolism, one of the leading causes of peripartum deaths in western countries. Uterus doses ranged between 60 and 660 µGy per examination, and relative dose reductions to the uterus due to high-Z garments were between 20 and 56%. Calculations showed that reducing the scan length by one to three centimetres could potentially reduce uterus dose up to 24% for chest imaging, and even 47% for upper abdominal imaging. These dose reductions were in the order of those achieved by high-Z garments. However, using the latter may negatively influence the diagnostic image quality and even interfere with the automatic exposure control system thus increasing patient dose if positioned in the primary beam, for example in the overranging length in helical acquisition. We conclude that efforts should be concentrated on positioning the patient correctly in the gantry and optimising protocol parameters, rather than using high-Z garments for out-of-plane uterus shielding

Task-based quantification of image quality using a model observer in abdominal CT: a multicentre study.

We investigated the variability in diagnostic information inherent in computed tomography (CT) images acquired at 68 different CT units, with the selected acquisition protocols aiming to answer the same clinical question. An anthropomorphic abdominal phantom with two optional rings was scanned on 68 CT systems from 62 centres using the local clinical acquisition parameters of the portal venous phase for the detection of focal liver lesions. Low-contrast detectability (LCD) was assessed objectively with channelised Hotelling observer (CHO) using the receiver operating characteristic (ROC) paradigm. For each lesion size, the area under the ROC curve (AUC) was calculated and considered as a figure of merit. The volume computed tomography dose index (CTDI <sub>vol</sub> ) was used to indicate radiation dose exposure. The median CTDI <sub>vol</sub> used was 5.8 mGy, 10.5 mGy and 16.3 mGy for the small, medium and large phantoms, respectively. The median AUC obtained from clinical CT protocols was 0.96, 0.90 and 0.83 for the small, medium and large phantoms, respectively. Our study used a model observer to highlight the difference in image quality levels when dealing with the same clinical question. This difference was important and increased with growing phantom size, which generated large variations in patient exposure. In the end, a standardisation initiative may be launched to ensure comparable diagnostic information for well-defined clinical questions. The image quality requirements, related to the clinical question to be answered, should be the starting point of patient dose optimisation. • Model observers enable to assess image quality objectively based on clinical tasks. • Objective image quality assessment should always include several patient sizes. • Clinical diagnostic image quality should be the starting point for patient dose optimisation. • Dose optimisation by applying DRLs only is insufficient for ensuring clinical requirements

Contemporary snapshot of tumor regression grade (TRG) distribution in locally advanced rectal cancer: a cross sectional multicentric experience.

Pre-operative chemoradiotherapy (CRT) followed by surgical resection is still the standard treatment for locally advanced low rectal cancer. Nowadays new strategies are emerging to treat patients with a complete response to pre-operative treatment, rendering the optimal management still controversial and under debate. The primary aim of this study was to obtain a snapshot of tumor regression grade (TRG) distribution after standard CRT. Second, we aimed to identify a correlation between clinical tumor stage (cT) and TRG, and to define the accuracy of magnetic resonance imaging (MRI) in the restaging setting. Between January 2017 and June 2019, a cross sectional multicentric study was performed in 22 referral centers of colon-rectal surgery including all patients with cT3-4Nx/cTxN1-2 rectal cancer who underwent pre-operative CRT. Shapiro-Wilk test was used for continuous data. Categorical variables were compared with Chi-squared test or Fisher's exact test, where appropriate. Accuracy of restaging MRI in the identification of pathologic complete response (pCR) was determined evaluating the correspondence with the histopathological examination of surgical specimens.In the present study, 689 patients were enrolled. Complete tumor regression rate was 16.9%. The "watch and wait" strategy was applied in 4.3% of TRG4 patients. A clinical correlation between more advanced tumors and moderate to absent tumor regression was found (p = 0.03). Post-neoadjuvant MRI had low sensibility (55%) and high specificity (83%) with accuracy of 82.8% in identifying TRG4 and pCR.Our data provided a contemporary description of the effects of pre-operative CRT on a large pool of locally advanced low rectal cancer patients treated in different colon-rectal surgical centers

Update of national diagnostic reference levels for adult CT in Switzerland and assessment of radiation dose reduction since 2010.

To update the national diagnostic reference levels (DRLs) for adult CT in Switzerland using dose management software and to compare them to the previous Swiss DRLs from 2010. CT dose data from 14 radiological institutes with a total of 50 CT scanners were collected with locally installed dose management software between 2014 and 2017. Data were assigned to 15 defined master protocols. Data cleaning steps were developed and adjusted individually for each participating institute and protocol. The DRLs for each master protocol were calculated as the 75th percentile of the distribution of the median volume computed tomography dose index (CTDI <sub>vol</sub> ) and dose-length product (DLP) values per CT scanner. In total, 220,269 CT exams were available after data cleaning. Updated DRLs showed a clear trend towards lower doses compared with previous DRLs. The average relative change in the DRLs for CTDI <sub>vol</sub> was - 30% (0 to - 47%) and - 22% for DLP (+ 20 to - 40%). The largest relative decrease in the DRL for DLP was observed for the cervical spine protocol (- 40%), the two chest protocols (chest, - 37%; and exclusion of pulmonary embolism, - 33%), and the two neck protocols (neck, - 32%; and carotid angiography, - 28%). The DRLs for other protocols, for example the head and the abdomen-pelvis protocol, showed smaller relative changes (- 11% and - 17%). The updated national DRLs are substantially lower than the previous values from 2010, demonstrating technological progress and the efforts of the radiological community to lower CT radiation exposure. • Dose management software allows the establishment of DRLs based on big data. • Updated Swiss DRLs for adult CT are substantially lower compared with those from 2010. • Swiss DRLs are low compared with other national DRLs

Efficacy of the SEPARPROCATH® radiation drape to reduce radiation exposure during cardiac catheterization: A pilot comparative study.

Interventional cardiologists are exposed to radiation-induced diseases, partly due to patient's scatter radiation. We sought to compare the radiation exposure (RE) of the cardiac catheterization room staff using SEPARPROCATH®, a novel radio-protective drape versus standard shielding equipment. This was a two-step prospective, randomized pilot trial: first, in experimental conditions using a phantom model, and second, during cardiac catheterization. Primary end-point was operator RE corresponding to the ratio between operator cumulative dose (CD) and dose area product (DAP). Secondary end-points were nurse RE, operator and nurse CD, DAP, and fluoroscopy time. A total of 51 patients were included. SEPARPROCATH® was associated with a lower operator RE (0.07 [0-0.19] vs. 0.37 [0.23-0.81] μSv/Gy.cm <sup>2</sup> without SEPARPROCATH®, p value <0.0001) and lower nurse RE (0 [0-0.05] vs. 0.13 [0.03-0.28] μSv/Gy.cm <sup>2</sup> , p value <0.0001) corresponding to an RE relative risk reduction of 81% and 99%, respectively. Similar reductions were observed for operator and nurse CDs. No difference was found in DAP (19 [11-29] vs. 14 [10-32] Gy.cm <sup>2</sup> without SEPARPROCATH®, p value 0.81). SEPARPROCATH® offers significant additional radioprotection to the operator and nurse during cardiac catheterization without affecting patient safety

Swiss survey on hybrid imaging CTs doses in Nuclear Medicine and proposed national dose reference levels.

A multidisciplinary working group led by the Swiss Federal Office of Public Health was formed to plan and perform a nationwide survey of patient radiation exposure from computed tomography (CT) in hybrid devices across Nuclear Medicine departments. The survey included 16 departments (of which 5 were university hospitals) and the submitted responses included 10,673 entries for the 33 different protocols proposed (11 in PET and 22 in SPECT). The working group determined the selection and exclusion criteria applied to the analysis. This work presents the survey preparation and data analysis including the exclusion criteria used. The results are used to inform recommendations for National Diagnostic Reference Levels (DRL) for CT procedures in Nuclear Medicine in Switzerland. Of the 33 protocols initially proposed, 10 protocols for both PET and SPECT modalities were retained after exclusion criteria and thresholds were applied. The results obtained in terms of volume-weighted computed tomography dose index (CTDI <sub>vol</sub> ) and dose length product (DLP) have been put forward as recommendations for national Diagnostic Reference Levels for protocols in hybrid imaging devices in Nuclear Medicine in Switzerland and will be published by the Federal Office of Public Health

Radiation Exposure of the Operator During Coronary Interventions (from the RADIO Study).

We sought to compare operator radiation exposure during procedures using right femoral access (RFA), right radial access (RRA), and left radial access (LRA) during coronary angiography (CA) and percutaneous coronary intervention (PCI). Because of an increased incidence of long-term malignancy in interventional cardiologists, operator radiation exposure is of rising concern. This prospective study included all consecutive patients who underwent elective or emergency CA ± PCI from September 2014 to March 2015. The primary end point was operator radiation exposure, quantified as the ratio of operator cumulative dose (CD) and patient radiation reported as dose-area product (DAP) (CD/DAP). Secondary end points included CD, DAP, and fluoroscopy time (FT). Overall 830 procedures (457 CA [55%] and 373 PCI [45%]) were performed, 455 (55%) through RFA, 272 (33%) through RRA, and 103 (12%) through LRA. The CD/DAP was lower in RFA (0.09 μSv/Gycm(2) [0.02 to 0.20]) compared with RRA (0.47 μSv/Gycm(2) [0.25 to 0.75], p <0.001). The LRA showed lower CD/DAP compared with RRA (p <0.001). CD was significantly lower in RFA (3 μSv [1 to 7]) compared with RRA (12 μSv [6 to 29], p <0.001). The LRA showed lower CD compared with RRA (p <0.001). There were no significant differences in DAP among the 3 access sites. FT was similar for the 3 groups (RFA 7 ± 7, RRA 5 ± 5, LRA 6 ± 5 minutes, RFA vs RRA: p = 1, RFA vs LRA: p = 0.16, RRA vs LRA: p = 0.52). In conclusion, the use of RFA during CA ± PCI is associated with significantly lower operator radiation exposure compared with RRA. LRA is associated with significantly lower operator radiation exposure compared with RRA