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The goal of this study was to develop a method to quantitatively assess the structural shielding performance of computed tomography (CT) rooms in Switzerland. The method was based on the comparison between calculated maximum allowed ambient dose rate (DR) and measured ambient DR in adjacent spaces. If the measured DR exceeds the calculated maximum allowed value, additional shielding is required; otherwise the shielding is sufficient. The maximum allowed ambient DR was calculated using two different shielding concepts either based on the tube loading of the scanner or on the accumulated dose length product of the scans. The method was validated for 36 spiral CT head protocols. The average ratio of the maximum allowed ambient DR between both concepts was 1.11 (range 0.57-2.14). Among 36 CT rooms, 7 room boundaries were insufficiently shielded. In conclusion, this method allows the authority to check on-site the compliance of the structural shielding with legal requirements. [ABSTRACT FROM AUTHOR]

Background 13C-Acetate labeled meals are widely used to determine meal emptying by means of analyzing resulting 13CO2 exhalation dynamics. In contrast to the underlying metabolic processes, only few 13C breath test meal emptying studies have focused on intragastric processes that may alter 13CO2 exhalation. This work assessed the effect of enhanced gastric secretion on the reliability of half emptying time ( t50) measurements by 13C-acetate breath test. Methods 13CO2 exhalation data were acquired in a double-blind, randomized, cross-over gastric emptying study in 12 healthy volunteers receiving either pentagastrin or placebo intravenously. The standard method proposed by Ghoos et al. was applied to calculate t50 ( t50_Ghoos) from 13CO2 exhalation data, which were compared and tested for agreement to meal half emptying times ( t50_MV) from concurrent recorded MRI (magnetic resonance imaging) volume data. In addition, the accumulated gastric secretion volumes during infusion as detected by MRI (AUC_SV60) were correlated with the corresponding cumulative percent 13C doses recovered (cPDR60). Key Results t50_Ghoos and t50_MV showed a linear correlation with a slope of 1.1 ± 0.3 ( r2 = 0.67), however, a positive offset of 136 min for t50_Ghoos. No correlation was detected between AUC_SV60 and cPDR60 ( r2 = 0.11). Both, breath test and MRI, revealed a prolonged t50 under pentagastrin infusion with median differences in t50_Ghoos of 45[28-84] min ( P = 0.002) and t50_MV of 39[28-52] min ( P = 0.002). Conclusions & Inferences This study suggests that 13CO2 exhalation after ingestion of a 13C-labeled liquid test meal is not affected by stimulated gastric secretion, but is rather reflecting the dynamics of meal or caloric emptying from the stomach. [ABSTRACT FROM AUTHOR]

A wide variation in patient exposure has been observed in interventional radiology and cardiology. The purpose of this study was to investigate the patient dose from fluoroscopy-guided procedures performed in non-academic centres when compared with academic centres. Four procedures (coronary angiography, percutaneous coronary intervention, angiography of the lower limbs and percutaneous transluminal angioplasty of the lower limbs) were evaluated. Data on the dose–area product, fluoroscopy time and number of images for 1000 procedures were obtained from 23 non-academic centres and compared with data from 5 academic centres. No differences were found for cardiology procedures performed in non-academic centres versus academic ones. However, significantly lower doses were delivered to patients for procedures of the lower limbs when they were performed in non-academic centres. This may be due to more complex procedures performed in the academic centres. Comparison between the centres showed a great variation in the patient dose for these lower limb procedures. [ABSTRACT FROM PUBLISHER]

Objectives: To establish an education and training programme for the reduction of CT radiation doses and to assess this programme's efficacy.Methods: Ten radiological institutes were counselled. The optimisation programme included a small group workshop and a lecture on radiation dose reduction strategies. The radiation dose used for five CT protocols (paranasal sinuses, brain, chest, pulmonary angiography and abdomen) was assessed using the dose-length product (DLP) before and after the optimisation programme. The mean DLP values were compared with national diagnostic reference levels (DRLs).Results: The average reduction of the DLP after optimisation was 37% for the sinuses (180 vs. 113 mGycm, P < 0.001), 9% for the brain (982 vs. 896 mGycm, P < 0.05), 24% for the chest (425 vs. 322 mGycm, P < 0.05) and 42% for the pulmonary arteries (352 vs. 203 mGycm, P < 0.001). No significant change in DLP was found for abdominal CT. The post-optimisation DLP values of the sinuses, brain, chest, pulmonary arteries and abdomen were 68%, 10%, 20%, 55% and 15% below the DRL, respectively.Conclusions: The education and training programme for radiological institutes is effective in achieving a substantial reduction in CT radiation dose. [ABSTRACT FROM AUTHOR]

Uniform postgastric processing of the gastric emptying (GE) marker 13C-acetate (Ac) is an unverified assumption behind its widespread application to measure GE. This study assessed the postgastric processing of Ac administered by intraduodenal (i.d.) infusion simulating different physiological conditions. 13CO2 in breath was assessed in three groups of six volunteers after i.d. administration of A: Different caloric densities (0.75/1.5/3 kcal min−1) in a 200 mL meal at constant 1 mg Ac min−1 simulating a physiological range of nutrient delivery rates; B: different tracer delivery rates (0.5/1.0/2.5 mg Ac min−1) simulating delayed, normal and increased GE; C1: a 500 mL meal resulting in same marker and caloric delivery compared to protocol A; C2: 50 mL water bolus injections of 12.5/25/50/100 mg Ac and C3 bolus injections of 50 mg Ac in 50/100/200 mL water in randomized order. A: 13CO2 excretion was independent of caloric load ( P = 0.59). B: The dynamic of 13CO2 excretion was modulated by tracer elimination which was in turn dependent on the speed of tracer delivery, i.e. with faster deliveries resulting in lower 13CO2 recovery during infusion ( P < 0.001). C: Increasing Ac doses resulted in decreased 13CO2 recovery ( P < 0.001) over the first hour. 13CO2 recovery kinetics was independent of the volume delivered. This study shows 13C-acetate absorption and metabolism is independent of the volume and caloric delivery of test meals. The ‘lag’ in estimates of GE derived from 13CO2 breath tests is due to a postgastric, dose-dependent delay to 13CO2 elimination. This can be corrected for in analytical derivations of GE parameters based on 13C-acetate breath test measurements. [ABSTRACT FROM AUTHOR]

Objectives: To assess task-based image quality for two abdominal protocols on various CT scanners. To establish a relationship between diagnostic reference levels (DRLs) and task-based image quality., Methods: A protocol for the detection of focal liver lesions was used to scan an anthropomorphic abdominal phantom containing 8- and 5-mm low-contrast (20 HU) spheres at five CTDI vol levels (4, 8, 12, 16, and 20 mGy) on 12 CTs. Another phantom with high-contrast calcium targets (200 HU) was scanned at 2, 4, 6, 10, and 15 mGy using a renal stones protocol on the same CTs. To assess the detectability, a channelized Hotelling observer was used for low-contrast targets and a non-prewhitening observer with an eye filter was used for high contrast targets. The area under the ROC curve and signal to noise ratio were used as figures of merit., Results: For the detection of 8-mm spheres, the image quality reached a high level (mean AUC over all CTs higher than 0.95) at 11 mGy. For the detection of 5-mm spheres, the AUC never reached a high level of image quality. Variability between CTs was found, especially at low dose levels. For the search of renal stones, the AUC was nearly maximal even for the lowest dose level., Conclusions: Comparable task-based image quality cannot be reached at the same dose level on all CT scanners. This variability implies the need for scanner-specific dose optimization., Key Points: • There is an image quality variability for subtle low-contrast lesion detection in the clinically used dose range. • Diagnostic reference levels were linked with task-based image quality metrics. • There is a need for specific dose optimization for each CT scanner and clinical protocol., (© 2021. The Author(s).)

Objectives: 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., Methods: 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 vol ) and dose-length product (DLP) values per CT scanner., Results: 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 vol 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%)., Conclusions: 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., Key Points: • 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.

The original version of this article, published on 28 May 2018, unfortunately contained a mistake.

Objectives: A nationwide survey was performed assessing current practice of dose data analysis in computed tomography (CT)., Material and Methods: All radiological departments in Switzerland were asked to participate in the on-line survey composed of 19 questions (16 multiple choice, 3 free text). It consisted of four sections: (1) general information on the department, (2) dose data analysis, (3) use of a dose management software (DMS) and (4) radiation protection activities., Results: In total, 152 out of 241 Swiss radiological departments filled in the whole questionnaire (return rate, 63%). Seventy-nine per cent of the departments (n = 120/152) analyse dose data on a regular basis with considerable heterogeneity in the frequency (1-2 times per year, 45%, n = 54/120; every month, 35%, n = 42/120) and method of analysis. Manual analysis is carried out by 58% (n = 70/120) compared with 42% (n = 50/120) of departments using a DMS. Purchase of a DMS is planned by 43% (n = 30/70) of the departments with manual analysis. Real-time analysis of dose data is performed by 42% (n = 21/50) of the departments with a DMS; however, residents can access the DMS in clinical routine only in 20% (n = 10/50) of the departments. An interdisciplinary dose team, which among other things communicates dose data internally (63%, n = 76/120) and externally, is already implemented in 57% (n = 68/120) departments., Conclusion: Swiss radiological departments are committed to radiation safety. However, there is high heterogeneity among them regarding the frequency and method of dose data analysis as well as the use of DMS and radiation protection activities., Key Points: • Swiss radiological departments are committed to and interest in radiation safety as proven by a 63% return rate of the survey. • Seventy-nine per cent of departments analyse dose data on a regular basis with differences in the frequency and method of analysis: 42% use a dose management software, while 58% currently perform manual dose data analysis. Of the latter, 43% plan to buy a dose management software. • Currently, only 25% of the departments add radiation exposure data to the final CT report.

Purpose: Definition of new national diagnostic reference levels (DRLs) for volume computed tomography dose index (CTDI vol ) and dose length product (DLP) for neuro-paediatric CT examinations depending on the medical indication., Methods: Paediatric cranial CT data sets acquired between January 2013 and December 2016 were retrospectively collected between July 2016 and March 2017 from eight of the largest university and cantonal hospitals that perform most of the neuro-paediatric CTs in Switzerland. A consensus review of CTDI vol and DLP was undertaken for three defined anatomical regions: brain, facial bone, and petrous bone, each with and without contrast medium application. All indications for cranial CT imaging in paediatrics were assigned to one of these three regions. Descriptive statistical analysis of the distribution of the median values for CTDI vol and DLP yielded values in the minimum, maximum, 25th percentile (1st quartile), median (2nd quartile), and 75th percentile (3rd quartile). New DRLs for neuro-paediatric CT examinations in Switzerland were based on the 75th percentiles of the distributions of the median values of all eight centres. Where appropriate, values were rounded such that the DRLs increase or at least remain constant as the age of the patient increases., Results: Our results revealed DRLs for CTDI vol and DLP up to 20% lower than the DRLs used so far in Switzerland and elsewhere in Europe., Conclusions: This study provides Swiss neuro-paediatric CT DRL values to establish optimum conditions for paediatric cranial CT examinations. Periodic national updates of DRLs, following international comparisons, are essential.

Objectives: This study applies concurrent magnetic resonance imaging (MRI) and high-resolution manometry (HRM) to test the hypothesis that structural factors involved in reflux protection, in particular, the acute insertion angle of the esophagus into the stomach, are impaired in gastroesophageal reflux disease (GERD) patients., Methods: A total of 24 healthy volunteers and 24 patients with mild-moderate GERD ingested a test meal. Three-dimensional models of the esophagogastric junction (EGJ) were reconstructed from MRI images. Measurements of the esophagogastric insertion angle, gastric orientation, and volume change were obtained. Esophageal function was assessed by HRM. Number of reflux events and EGJ opening during reflux events were assessed by HRM and cine-MRI. Statistical analysis applied mixed-effects modeling., Results: The esophagogastric insertion angle was wider in GERD patients than in healthy subjects (+7° ± 3°; P=0.03). EGJ opening during reflux events was greater in GERD patients than in healthy subjects (19.3 mm vs. 16.8 mm; P=0.04). The position of insertion and gastric orientation within the abdomen were also altered (both P<0.05). Median number of reflux events was 3 (95% CI: 2.5-4.6) in GERD and 2 (95% CI: 1.8-3.3) in healthy subjects (P=0.09). Lower esophageal sphincter (LES) pressure was lower (-11 ± 2 mm Hg; P<0.0001) and intra-abdominal LES length was shorter (-1.0 ± 0.3 cm, P<0.0006) in GERD patients., Conclusions: GERD patients have a wider esophagogastric insertion angle and have altered gastric morphology; structural changes that could compromise reflux protection by the "flap valve" mechanism. In addition, the EGJ opens wider during reflux in GERD patients than in healthy volunteers: an effect that facilitates volume reflux of gastric contents.

Nationwide surveys on radiation dose to the population from medical radiology are recommended in order to follow the trends in population exposure and ensure radiation protection.The last survey in Switzerland was conducted in 1998,and the annual effective dose from medical radiology was estimated to be 1 mSv y j(-1) per capita. The purpose of this work was to follow the trends in diagnostic radiology between 1998 and 2008 in Switzerland and determine the contribution of different modalities and types of examinations to the collective effective dose from medical x-rays. For this reason, an online database(www.raddose.ch) was developed. All healthcare providers who hold a license to run an x-ray unit in the country were invited to participate in the survey. More than 225 examinations, covering eight radiological modalities, were included in the survey. The average effective dose for each examination was reassessed. Data from about 3,500 users were collected (42% response rate). The survey showed that the annual effective dose was 1.2 mSv/capita in 2008. The most frequent examinations are conventional and dental radiographies (88%). The contribution of computed tomography was only 6% in terms of examination frequency but 68% in terms of effective dose. The comparison with other countries showed that the effective dose per capita in Switzerland was in the same range as in other countries with similar healthcare systems, although the annual number of examinations performed in Switzerland was higher.

Purpose: To develop and validate magnetic resonance (MR) imaging protocols for quantitative assessment of the structural and functional properties of the gastroesophageal junction (GEJ) and to compare MR imaging detection of reflux events against concurrent manometry as a reference method., Materials and Methods: The local ethics committee approved this study, and written informed consent was obtained. Twelve healthy volunteers were examined. Three-dimensional models of the GEJ and proximal portion of the stomach were reconstructed from high-spatial-resolution anatomic MR images to assess the insertion angle of the esophagus into the stomach and proximal stomach distention before and after ingestion of a large test meal. A linear mixed-effects model was used to detect differences in the insertion angle and proximal stomach distention with respect to the respiratory cycle and gastric filling. Additionally, dynamic MR imaging at high temporal resolution was used to detect reflux events., Results: The esophageal insertion angle, given in units of plane angle (radians), was more acute in expiration than in inspiration (0.57 vs 0.73 radian, P = .004) but was not affected by feeding. Progressive distention of the proximal stomach was observed from baseline compared with the postprandial period (0.95 vs 0.65 radian(-1), P < .05). Eighteen reflux events detected by using MR imaging were also detected by using manometry., Conclusion: MR imaging methods were developed and validated for the assessment of GEJ structure and function (a) to describe the effects of respiration and feeding on the reflux barrier and (b) to detect reflux events in real time. Anatomic and dynamic MR imaging may be useful techniques in the assessment of GEJ physiology and reflux.

Purpose: To evaluate the noninvasive quantification of gastric secretion volume after administration of a labeled viscous glucose solution by fast T(1) mapping., Materials and Methods: T(1) values of a series of labeled and diluted glucose solutions were measured in vitro to characterize the interrelationship between T(1) and contrast agent concentration (C(Gd)) as well as the dependency of relaxivity and reference T(1) (T(10)) on the macromolecular concentration. Abdominal T(1) mapping in five healthy volunteers of different body mass index was performed after filling an intragastric balloon with a labeled and diluted glucose solution. In additional ex vivo experiments, T(1) values of gastric (GJ) and duodenal juice (DJ) and 0.1 N HCl solution were determined., Results: A linear relationship between relaxivity and macromolecular concentration and between T(10) and macromolecular concentration was found. The in vitro T(1)-C(Gd) calibration curve was successfully validated in all volunteers. T(1) values of GJ, DJ, and HCl (2939 msec vs. 2858 msec vs. 2760 msec) were close to the T(1) of water ( approximately 3000 msec)., Conclusion: The presented method allows one to noninvasively quantify the spatial distribution of gastric secretory products in the human stomach and provides a valuable tool for evaluating the efficacy of drugs to stimulate/inhibit gastric secretion., ((c) 2008 Wiley-Liss, Inc.)

Fast T(1) mapping techniques are a valuable means of quantitatively assessing the distribution and dynamics of intravenously or orally applied paramagnetic contrast agents (CAs) by noninvasive imaging. In this study a fast T(1) mapping technique based on the variable flip angle (VFA) approach was optimized for accurate T(1) quantification in abdominal contrast-enhanced (CE) MRI. Optimization methods were developed to maximize the signal-to-noise ratio (SNR) and ensure effective RF and gradient spoiling, as well as a steady state, for a defined T(1) range of 100-800 ms and a limited acquisition time. We corrected B(1) field inhomogeneities by performing an additional measurement using an optimized fast B(1) mapping technique. High-precision in vitro and abdominal in vivo T(1) maps were successfully generated at a voxel size of 2.8 x 2.8 x 15 mm(3) and a temporal resolution of 2.3 s per T(1) map on 1.5T and 3T MRI systems. The application of the proposed fast T(1) mapping technique in abdominal CE-MRI enables noninvasive quantification of abdominal tissue perfusion and vascular permeability, and offers the possibility of quantitatively assessing dilution, distribution, and mixing processes of labeled solutions or drugs in the gastrointestinal tract.

Objective: Gastric contents empty from the stomach despite frequent changes in body position. The mechanism that maintains gastric emptying independent of position is poorly understood. The aim of this study was to determine the effects of body position on gastric emptying and motor function., Material and Methods: Twelve volunteers were investigated in seated position (SP) and upside-down position (UDP) after ingestion of 300 ml water. Magnetic resonance imaging provided a non-invasive assessment of gastric emptying and volumes, intragastric distribution and peristaltic function., Results: A marked difference in distal/proximal intragastric distribution between UDP and SP was present (7% versus 40%; p < 0.01). Gastric-emptying time was similar but emptying pattern was linear in UDP and exponential in SP. Peristalsis was slower in UDP than SP (2.75 versus 2.96 min-1; p < 0.01), but no correlation was found between peristaltic frequency and the rate of gastric emptying in either position. Postprandial volume response (gastric relaxation) was greater in UDP than SP (280 versus 250 ml; p < 0.05). A correlation was found between gastric relaxation and gastric-emptying time in SP (r2=0.46) but not in UDP., Conclusions: The stomach maintains the rate of gastric emptying despite radical changes in body position and intragastric distribution of gastric contents. In SP, hydrostatic pressure (modulated by gastric tone) dictates the gastric emptying. In UDP, gastric emptying also appears to be mediated by continuous adaptation of gastric tone. These findings provide support for the hypothesis that the mechanism of gastric emptying resembles a "pressure pump" rather than a "peristaltic pump".

Purpose: To determine the effect of the right decubitus lying body position (RP) on relevant parameters of human gastric motor function in healthy volunteers., Materials and Methods: Postprandial gastric function after ingestion of a solid/liquid meal (150 g/150 mL) was assessed over 90 minutes in volunteers in the RP and seated position (SP). Ten healthy volunteers were imaged using two MRI systems that differed in architecture and field strength. Stomach and intragastric air volume, intragastric meal distribution, gastric emptying, and gastric peristalsis were compared between the RP and SP., Results: Body position did not affect gastric relaxation (RP, 372 mL vs. SP, 384 mL) and initial gastric volumes (stomach: RP, 458 mL vs. SP, 462 mL; meal: RP, 377 mL vs. SP, 399 mL; intragastric air: RP, 110 mL vs. SP, 98 mL). Postprandial stomach volume and gastric activity (RP and SP, 3.1 minute(-1)) were also similar. Meal emptying showed different characteristics, resulting in a significant but small difference in meal volume of -43 mL at t = 90 minutes (P < 0.05)., Conclusion: Gastric MRI in RP is feasible for clinical research assessing gastric motor function. The subtle difference in meal emptying may be induced by posture-dependent vagal activity. This study confirms that MRI is a highly sensitive imaging technique for assessing gastrointestinal function in humans., ((c) 2006 Wiley-Liss, Inc.)