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.

Diagnostic reference levels (DRLs) were established for 21 indication-based CT examinations for adults in Switzerland. One hundred and seventy-nine of 225 computed tomography (CT) scanners operated in hospitals and private radiology institutes were audited on-site and patient doses were collected. For each CT scanner, a correction factor was calculated expressing the deviation of the measured weighted computed tomography dose index (CTDI) to the nominal weighted CTDI as displayed on the workstation. Patient doses were corrected by this factor providing a realistic basis for establishing national DRLs. Results showed large variations in doses between different radiology departments in Switzerland, especially for examinations of the petrous bone, pelvis, lower limbs and heart. This indicates that the concept of DRLs has not yet been correctly applied for CT examinations in clinical routine. A close collaboration of all stakeholders is mandatory to assure an effective radiation protection of patients. On-site audits will be intensified to further establish the concept of DRLs in Switzerland.

Over the past few years the frequency of computed tomography (CT) examinations has dramatically increased. Simultaneously, there has been also a significant increase in CT patient dose due to high-resolution imaging and application of more complex scan techniques. Since no dose limit exists for patients, the International Commission on Radiological Protection introduced the concept of diagnostic reference levels (DRL) as a means of dose optimization. The aim of this project is to collect patient doses for the most frequently applied CT protocols and to provide a realistic basis for establishing DRL in CT in Switzerland. Starting in 2007, patient doses of every Swiss radiological institute operating a CT scanner were going to be collected. Volume computed tomography dose index (CTDIvol) and dose-length product (DLP) for standard patients was collected for selected clinical CT protocols. The 75th percentile of the CTDIvol and DLP distribution was calculated and compared to the proposed DRL which is partly based on the Swiss survey in 1998 and recommendations of the European Union. For standard examination of the skull/brain the 75th percentiles are higher than the proposed DRL (72 mGy vs. 60 mGy; 1180 mGy∙cm vs. 1000 mGy∙cm). For examination of thorax and abdomen/pelvis the 75th percentiles are close to the proposed DRL (thorax: 15 mGy vs. 15 mGy; 511 mGy∙cm vs. 450 mGy∙cm; abdomen/ pelvis: 16 mGy vs. 15 mGy; 701 mGy∙cm vs. 700 mGy∙cm). In conclusion, there is always a trade-off between dose reduction and diagnostic image quality. However, especially for skull/brain examinations, optimization is still feasible. The concept of DRL provides a valuable means for practitioners and manufacturers in optimizing CT protocols.

The purpose of this paper is to present a strategy to define diagnostic reference levels DRL for fluoroscopic, dose-intensive examinations in cardiology and interventional radiology. This work is part of the project of the Federal Office of Public Health of Switzerland to translate the guidelines of the ICRP and the EU into action. After the 2002 survey in all University Hospitals in Switzerland this work will present the results of the 2006-2007 survey performed in small and medium sized hospitals. The data of the small and medium sized hospitals are analyzed to establish DRL. They are corrected to patient size and analyzed in respect to the difficulty of the examination, the experience of the operator and the type of image detection system. The results of the study will be compared to those of the former study in the University Hospitals.

Surveying the frequency of medical x-ray examinations is of prime importance in the assessment of the collective detriment due to diagnostic and interventional radiology. In the past, this was performed using paper questionnaires, but today there is an increasing interest in the automatic collection of the frequency data for reasons related to reducing the work load and increasing the accuracy of the results. This paper present the work performed in Switzerland to explore the use of the Tarmed coding system for this purpose. The preliminary investigation covering a sample of examinations indicates that Tarmed coding can easily be used for the collection of radiography and CT examinations, but presents some difficulties for fluoroscopy, mainly in the case of complex angiography and interventional examinations.

Purpose: Gated treatments using the Varian RPM—gating™ System include in a standard configuration a coaching tool based on voice commands (“breathe‐in”/“breathe‐out”) called audio‐coaching. As this configuration does not include feedback information like amplitude and breathing period, there are limitations concerning respiration depth and breathing pattern. The aim of this study was to evaluate the impact of video‐coaching as biofeedback to achieve more regular breathing and — as a consequence — quality improvements of the 4D‐CT scans as well as duty cycle enhancements. Method and Materials: Varian RPM‐gating system is used for acquisition of the CT‐Scan (4D‐CT) as well as the treatments; for the latter it manages the controlled switching of the radiation beam during a pre‐selected specific phase of the respiratory cycle. 80 patients with gated treatments have been analyzed, whereas 40 were only audio‐coached and 40 audio‐coached with video‐feedback. We evaluated periodicity and amplitude changes as well as compliance with regard to the theoretically calculated duty cycle and determined the dependency of the parameters on the coaching type. Results: For the CT acquisitions several changes has been observed, i.e. fluctuations of the inspiration maxima are significantly smaller (p=0.005) and the breathing curves are smoother. The compliance during the treatment course was significantly increased: almost all video‐coached patients reached in average their theoretical duty cycle, whereas 60% of the patients with audio‐coaching only had more than 25% longer treatment times due to inappropriate amplitudes (p=0.001). Conclusion: Video‐coaching is suitable to significantly improve the quality of 4D scans and allows optimizing the treatment time due to better compliance. We also implemented this feedback technology combined with voluntary end‐inspiration breath hold technique thus allowing the patient to control the treatment themselves in a direct way. These results indicate that this approach could suit the individual patient need in a better way.

Purpose: For image‐guided radiotherapy (IGRT) the different vendors of linear accelerators offer new kV imaging tools. These systems include — besides a radiographic and fluoroscopic mode — CT functionality. The aim of this study was to evaluate the future potential of such a cone beam CT option for therapy planning purposes allowing dynamic adaptation for target volume changes. Method and Materials: The Varian On‐Board Imager™ (OBI) Cone Beam CT (CBCT) option consists of a kV‐source and kV‐Imager mounted on robotic arms perpendicular to the MV therapy beam. In a single 360° rotation a volumetric CT data set can be acquired with a 25 or 45 cm field‐of‐view. In order to calibrate the system with regard to HU a special phantom has been designed to include the whole imager area. Removable inserts allow the measurement of central axis doses. A planning study has been carried out to determine the usability of CBCT data and compare these to with diagnostic CT date. Results: Comparisons of data between a diagnostic CT scanner and the 3D‐calibrated Cone Beam CT with regard to image quality and hounsfield units representation for an humanoid phantom (RSD Alderson) indicate good accordance. Central axis doses applied during the acquisition of one volumetric data set are between 1 and 3 cGy depending on the geometry. Results with real patient data show appropriate image quality. Relative dose distributions in CBCT‐based plans show minor differences to plans calculated using a diagnostic CT image dataset (p=0.002) and absolute dosage deviations are within 1% (p=0.001). Conclusion: This work illustrates that a properly calibrated Cone Beam CT option allows off‐line treatment planning. Furthermore the image quality is sufficient for contouring of target outlines. CBCT can serve as control CT in order to adapt the target volume and resize the treatment fields and/or optimize the treatment plan.

Gated treatments using the Varian RPM-gating TM System include in a standard configuration a coaching tool based on voice commands ("breathe-in"/"breathe-out") called audio-coaching. As this configuration does not include feedback information like amplitude and breathing period, there are limitations concerning respiration depth and breathing pattern. The aim of this study was to evaluate the impact of video-coaching as biofeedback to achieve more regular breathing and–as a consequence–quality improvements of the 4D CT scans as well as duty cycle reductions. Varian RPM-gating system is used for acquisition of the CT-Scan (4D-CT) as well as the treatments; for the latter it manages the controlled switching of the radiation beam during a pre-selected specific phase of the respiratory cycle. 40 patients with gated treatments have been analyzed, whereas 20 were only audio-coached and 20 audio-coached with video-feedback. We evaluated periodicity and amplitude changes as well as compliance with regard to the theoretically calculated duty cycle and determined the dependency of the parameters on the coaching type. For the CT acquisitions several changes has been observed, i.e., fluctuations of the inspiration maxima are significantly smaller (p = 0.005) and the breathing curves are smoother. The compliance during the treatment course was significantly increased: almost all video-coached patients reached in average their theoretical duty cycle, whereas 60% of the patients with audio-coaching only had more than 25% longer treatment times due to inappropriate amplitudes. Periodicity is not dependent on the kind of coaching (p = 0.01). Video-coaching is suitable to significantly improve the quality of 4D scans and allows optimizing the treatment time due to better compliance. In the meantime we also implemented this feedback technology combined with deep inspiration breath hold technique thus allowing the patient to control the treatment themselves in a direct way. These results indicate that this approach could suit the individual patient need in a better way.

Purpose: Gated treatments using the Varian RPM—gating™ System include in a standard configuration a coaching tool based on voice commands (“breathe‐in”/“breathe‐out”) called audio‐coaching. As this configuration does not include feedback information like amplitude and breathing period, there are limitations concerning respiration depth and breathing pattern. The aim of this study was to evaluate the impact of video‐coaching as biofeedback to improve gated treatments of breast cancer.Method and Materials: Varian RPM‐gating system is used for acquisition of the CT‐Scan (4D‐CT) as well as the treatments; for the latter it manages the controlled switching of the radiation beam during a pre‐selected specific phase of the respiratory cycle. 100 patients with gated treatments have been analyzed, whereas 50 were only audio‐coached and 50 audio‐coached with video‐feedback. We evaluated periodicity and amplitude changes as well as compliance with regard to the theoretically calculated duty cycle and determined the dependency of the parameters on the coaching type. Results: For the CT acquisition several changes has been observed, i.e. amplitude fluctuations are significantly smaller (p=0.005) and the breathing curves are smoother. This leads to an increased compliance during the treatment course: almost all video‐coached patients reached in average their theoretical duty cycle, whereas 60% of the patients with audio‐coaching only had more than 25% longer treatment times due to inappropriate amplitudes. Periodicity is not dependent on the kind of coaching (p=0.01). Conclusion: Video‐coaching is suitable to significantly improve the quality of 4D scans and allows optimizing the treatment time due to better compliance. In a next step we are currently implementing this feedback technology combined with deep inspiration breath hold technique thus allowing the patient to control the treatment themselves in a direct way. Preliminary results indicate that this approach could suit the individual patient need in a better way.