1,721,254 research outputs found
BELgian dosimetry Audits in RadioTherapy
No full textPurpose: Independent dosimetry audits are crucial for the QA of radiotherapy departments. The Nuclear Technology Centre (NuTeC) is performing dosimetry audits since 2009 in Belgium and occasionally in some neighbouring countries. The BELdART project started when the Belgian Federal Agency for Nuclear Control (FANC/AFCN) requested a national audit program for reference and non-reference conditions with support from the Cancer plan. During 2009-2011, all Belgian clinics participated in the dosimetry audits for standard static fields. Then in 2012, auditing of more sophisticated techniques was introduced such as IMRT, Arc therapy and Tomotherapy. In 2017, an audit program for intracranial SRS was developed and later for lung SBRT early in 2020. Additionally, NuTeC also provides external audits upon request from the clinics. Materials and Methods: A combination of alanine/EPR and film dosimetry is used for the dose measurements, the alanine being used for point dosimetry and the film for evaluating 2D dose distributions. The audits are composed of basic dosimetric checks in water and solid water with alanine pellets and End-To-End (E2E) tests on an anthropomorphic phantom containing film/alanine detectors. The films are analysed with 3-channel dosimetry. All measurements for a beam are performed on the same day to allow identifying the source of possible problems during the E2E test. Since 2012, the audits are entirely mailed. Results: 61/91 machines were audited during 2009-2011 with 60/61 of the machines having acceptable parameters and for the dosimetric evaluation, all the 212 beams were within 5%. During 2012-2016, 33 beams were audited for IMRT/Arc treatment on a prostate case. 87.9% and 78.8% of the beams were within 3% for the alanine pellets placed in the prostate and seminal vesicles regions respectively. For the gamma analysis with the films with 3%/3mm criteria, 97% of the films had a passing rate higher than 95%. For the intracranial SRS audits, 16 beams were audited up to now with 68.8% of the beams being within 3% for the alanine measurement. For the films with 5%1mm criteria for the gamma analysis, 15/16 had a passing rate higher than 90%. 2 lung SBRT audits are performed at the time of writing. Conclusions: The BELdART team continues to provide dosimetry auditing services to the radiotherapy community in Belgium. The results up to now show that in general, the dosimetric accuracy in Belgian clinics is very good for the different audited techniques
Environmental impact assessment for the recycling of phosphogypsum in alternative cementitious binders
No full textEnvironmental impact assessment for the recycling of phosphogypsum in alternative cementitious binders
No full textWith the support of the
Fund Prof. T. Van Autenboer,
managed by the King Baudouin Foundation
BELdART: Belgian dosimetry audits in radiotherapy
No full textPurpose: Contemporary external radiotherapy requires the outmost precision in patient positioning. This can be achieved through 2D/3D image acquisition by the on-board imager (OBI) integrated into the linear accelerator. In this study, OBI 2D image acquisition protocols were assessed and optimized with regard to dose in an effort to reduce overall patient dose without degrading kV image quality. Materials and Methods: A phantom for high/low spatial resolution assessment was placed at the center of appropriately compiled PMMA plates to serve as cephalic (19cmX17cm) and pelvic (24cmX37cm) phantoms. Anterior-posterior and lateral scanning of the phantoms was carried out using the predefined/default acquisition protocols to assess image quality and measure the entrance dose utilizing a low dose rate probe. Anterior-posterior and lateral images were then acquired for all available kV/mAs configurations and corresponding entrance dose were recorded. An experienced user rejected all protocols that produced images with quality inferior to that achieved by the default protocol. The optimized head and pelvis protocols were selected as those corresponding to the lowest doses. A Rando phantom was scanned with both default and dose-optimized protocols, while proposed protocols were used for intra-session imaging in 10 patients. A physician employed a 5-point scale to subjectively assess quality of Rando and patient images. Effective doses were estimated in an average-sized anthropomorphic model for default and optimized acquisitions. Results: Low spatial resolution exhibited a strong dependence on kV/mAs settings, in contradistinction to high spatial resolution. Optimized head protocols for anterior-posterior/lateral scans employed 80/60 kVp and 6.4/5.0 mAs, whilst proposed pelvis protocols for anterior-posterior/lateral acquisitions utilized 80/100 kVp and 6.25/64.0 mAs. In comparison to the default parameters, the implementation of optimized settings resulted in 49% and 29% entrance dose reduction in the cephalic anterior-posterior and lateral scans, respectively, and in 29% and 27% entrance dose reduction in the pelvic anterior-posterior and lateral acquisitions, respectively. Quality of Rando images acquired with proposed protocols was equivalent to that of default protocols. Quality of patient images obtained with optimized settings was graded at least as acceptable, indicating that proposed settings may be routinely used. Optimized protocols were found to decrease effective dose by 27.5% and 49% in pelvic and cephalic acquisitions, respectively. Conclusions: Considering the relatively large number of radiotherapy sessions and consequently of image acquisitions, it is postulated that dose-optimized kV protocols may contribute towards a significant reduction in the overall patient radiation dose without compromising positioning accuracy. P101 Implementation and clinical validation of an atlas based auto segmentation method of head and neck radiotherapy volumes of interest Purpose: To implement and validate an atlas based segmentation method for the automatic contouring of organ at risks (OARs) in the frame of head and neck radiotherapy planning. In this context, an accurate and standardized delineation of OARs is required to face the challenge posed by the location of many critical organs in close proximity to target volumes and the high focalized dose distributions. The atlas can help to speed up the planning workflow, partially replacing manual segmentation, and reduce the intra-and inter-operator dependence improving the standardization process. Materials and Method: In this study, an auto-segmentation method with a "Medium-Atlas" approach was implemented. The atlas consisted of twenty datasets of head and neck radiotherapy patients. The optimization and validation of the method were carried out by comparing the results of the automatic segmentation with those of the manual one. The comparison was carried out on a group of ten datasets belonging to the same institution from which the atlas was built and on a group of ten patients provided by another center. The comparison was made using the following quantitative metrics: Dice similarity index (DSC), average distance to agreement (MDC), sensitivity and positive predictive value (PPV). Results: The number of the ATLAS datasets used to build the medium atlas significantly affects the quality of the segmented contours on the test images (ANOVA: F = 2,96, p <0,05): the optimal number for the accuracy of delineation is N=5. The results of the analysis showed that the automatic segmentation method was accurate for OAR volumes higher than 10 cc: DSC=0,82±0,01, sensitivity=0,74±0,01, PPV=0,92±0,01 and MDC=2,77±0,06 mm. For volumes less than 10 cc the agreement between automatic and manual segmentation worsened and were deemed unsatisfactory. Time consuming was reduced by 50% compared to the manual segmentation. The atlas also showed good performances in its multi-institutional application: for volumes greater than 10 cc: DSC=0,77±0,04, sensitivity=0,83±0,04, PPV=0,75±0,05 and MDC=2,62±0,06 mm; the method does not show statistically significant differences with its mono center application (p=0.43, =0,05). Conclusions: The implemented atlas-based auto-segmentation, in both tested applications, was found to be an efficient and accurate method in the delineation of OARs with volumes greater than 10 cc
Effect of NaOH content on hydration, mineralogy, porosity and strength in alkali/sulfate-activated binders from ground granulated blast furnace slag and phosphogypsum
No full textsponsorship: This work was supported by the Fund for Scientific Research Flanders (FWO). The authors would like to thank the networking support of the COST Action TU1301, www.norm4building.org.Marcin Selent (University of Oulu, Finland) and Kristof Van Hecke (University of Ghent, Belgium) are gratefully acknowledged for their valuable feedback with respect to XRD. (Fund for Scientific Research Flanders (FWO), COST Action|TU1301)status: Publishe
Environmental impact assessment for the recycling of phosphogypsum in alternative cementitious binders
No full textWith the support of the
Fund Prof. T. Van Autenboer,
managed by the King Baudouin Foundation
BELgian dosimetry Audits in RadioTherapy
No full textPurpose: Independent dosimetry audits are crucial for the QA of radiotherapy departments. The Nuclear Technology Centre (NuTeC) is performing dosimetry audits since 2009 in Belgium and occasionally in some neighbouring countries. The BELdART project started when the Belgian Federal Agency for Nuclear Control (FANC/AFCN) requested a national audit program for reference and non-reference conditions with support from the Cancer plan. During 2009-2011, all Belgian clinics participated in the dosimetry audits for standard static fields. Then in 2012, auditing of more sophisticated techniques was introduced such as IMRT, Arc therapy and Tomotherapy. In 2017, an audit program for intracranial SRS was developed and later for lung SBRT early in 2020. Additionally, NuTeC also provides external audits upon request from the clinics. Materials and Methods: A combination of alanine/EPR and film dosimetry is used for the dose measurements, the alanine being used for point dosimetry and the film for evaluating 2D dose distributions. The audits are composed of basic dosimetric checks in water and solid water with alanine pellets and End-To-End (E2E) tests on an anthropomorphic phantom containing film/alanine detectors. The films are analysed with 3-channel dosimetry. All measurements for a beam are performed on the same day to allow identifying the source of possible problems during the E2E test. Since 2012, the audits are entirely mailed. Results: 61/91 machines were audited during 2009-2011 with 60/61 of the machines having acceptable parameters and for the dosimetric evaluation, all the 212 beams were within 5%. During 2012-2016, 33 beams were audited for IMRT/Arc treatment on a prostate case. 87.9% and 78.8% of the beams were within 3% for the alanine pellets placed in the prostate and seminal vesicles regions respectively. For the gamma analysis with the films with 3%/3mm criteria, 97% of the films had a passing rate higher than 95%. For the intracranial SRS audits, 16 beams were audited up to now with 68.8% of the beams being within 3% for the alanine measurement. For the films with 5%1mm criteria for the gamma analysis, 15/16 had a passing rate higher than 90%. 2 lung SBRT audits are performed at the time of writing. Conclusions: The BELdART team continues to provide dosimetry auditing services to the radiotherapy community in Belgium. The results up to now show that in general, the dosimetric accuracy in Belgian clinics is very good for the different audited techniques
Environmental impact assessment for the recycling of phosphogypsum in alternative cementitious binders
No full text
Towards bio-based PLA/TPS composites as a host matrix for embedding and release of particulate biochar fillers: exploring phase compatibility and microstructural variations
No full text- …
