Background and Purpose:Volumetric Modulated Arc Therapy (VMAT) has enabled highly conformal Total Body Irradiation (TBI), improving dose homogeneity and sparing of organs-of-interest. However, the increased complexity of VMAT-based TBI requires robust quality assurance strategies. This study evaluated the feasibility, accuracy, and reproducibility of Electronic Portal Imaging Device (EPID)-based in-vivo dosimetry (IVD) for VMAT TBI treatments. Materials and Methods:Forty pediatric patients treated with VMAT-based TBI were retrospectively analyzed with two prescription schemes: 12 Gy/six fractions and 9.99 Gy/three fractions. EPID transmission images were acquired during each VMAT arc and analyzed using a gamma passing rate (Pγ) of 5%/2 mm, 10% threshold. IVD was evaluated across different anatomical regions. The impact of inter-fraction anatomical variations (weight loss, abdominal swelling, gastrointestinal air) was assessed through dose recalculations on modified CT datasets. Phantom measurements were performed to validate the sensitivity of EPID-based IVD to clinically relevant perturbations. Results:IVD measurements showed median Pγ of 97.3 ± 3.2%. Across the forty patients, a mean Pγ of 99.3 ± 0.8% and 99.0 ± 0.4% was observed in the head and thoracic regions respectively, lower values (96.5 ± 3.4% and 94.3 ± 3.6%) were found in the lumbar and pelvic regions respectively. Simulated abdominal swelling ≥1.5 cm reduced target coverage, while weight loss and gastrointestinal air had limited dosimetric impact. Phantom tests confirmed IVD sensitivity to significant anatomical changes. Conclusions:EPID-based IVD was a feasible tool for verifying VMAT-based TBI, enabling detection of clinically relevant inter-fraction anatomical variations and supporting safe treatment delivery.

The application and provision of prehospital care in disasters and mass-casualty incident response in Europe is currently being explored for opportunities to improve practice. The objective of this translational science study was to align common principles of approach and action and to identify how technology can assist and enhance response. To achieve this objective, the application of a modified Delphi methodology study based on statements derived from key findings of a scoping review was undertaken. This resulted in 18 triage, eight life support and damage control interventions, and 23 process consensus statements. These findings will be utilized in the development of evidence-based prehospital mass-casualty incident response tools and guidelines.

PurposeThe European Union Horizon 2020 research and innovation funding program awarded the NIGHTINGALE grant to develop a toolkit to support first responders engaged in prehospital (PH) mass casualty incident (MCI) response. To reach the projects' objectives, the NIGHTINGALE consortium used a Translational Science (TS) process. The present work is the first TS stage (T1) aimed to extract data relevant for the subsequent modified Delphi study (T2) statements.MethodsThe authors were divided into three work groups (WGs) MCI Triage, PH Life Support and Damage Control (PHLSDC), and PH Processes (PHP). Each WG conducted simultaneous literature searches following the PRISMA extension for scoping reviews. Relevant data were extracted from the included articles and indexed using pre-identified PH MCI response themes and subthemes.ResultsThe initial search yielded 925 total references to be considered for title and abstract review (MCI Triage 311, PHLSDC 329, PHP 285), then 483 articles for full reference review (MCI Triage 111, PHLSDC 216, PHP 156), and finally 152 articles for the database extraction process (MCI Triage 27, PHLSDC 37, PHP 88). Most frequent subthemes and novel concepts have been identified as a basis for the elaboration of draft statements for the T2 modified Delphi study.ConclusionThe three simultaneous scoping reviews allowed the extraction of relevant PH MCI subthemes and novel concepts that will enable the NIGHTINGALE consortium to create scientifically anchored statements in the T2 modified Delphi study.

The treatment of victims on the field, in particular during a mass casualty incidents (MCI), requires rapid decisions based on the understanding of the impairment of the patient's vital functions. Rapid evaluation of vital functions is necessary not only for triage but also to start immediate life-saving procedures and decide transportation to definite care. Presently, most of these activities are carried out by first responders on the field through semiologic assessment, while the availability of even very simple diagnostic devices would be useful. These devices should be simple to use, low cost and possibly disposable. Modern technologies are now available, but they must be adapted to the needs of the patient on the field and healthcare operators. An overview of photoplethysmography, the most promising technology for this purpose, and the parameters that it consents to measure seems timely.

To investigate critical aspects and effectiveness of in vivo dosimetry (IVD) tests obtained by an electronic portal imaging device (EPID) in a multicenter and multisystem context. Eight centers with three commercial systems—SoftDiso (SD, Best Medical Italy, Chianciano, Italy), Dosimetry Check (DC, Math Resolution, LCC), and PerFRACTION (PF, Sun Nuclear Corporation, SNC, Melbourne, FL)—collected IVD results for a total of 2002 patients and 32,276 tests. Data are summarized for IVD software, radiotherapy technique, and anatomical site. Every center reported the number of patients and tests analyzed, and the percentage of tests outside of the tolerance level (OTL%). OTL% was categorized as being due to incorrect patient setup, incorrect use of immobilization devices, incorrect dose computation, anatomical variations, and unknown causes. The three systems use different approaches and customized alert indices, based on local protocols. For Volumetric Modulated Arc Therapy (VMAT) treatments OTL% mean values were up to 8.9% for SD, 18.0% for DC, and 16.0% for PF. Errors due to “anatomical variations” for head and neck were up to 9.0% for SD and DC and 8.0% for PF systems, while for abdomen and pelvis/prostate treatments were up to 9%, 17.0%, and 9.0% for SD, DC, and PF, respectively. The comparison among techniques gave 3% for Stereotactic Body Radiation Therapy, 7.0% (range 4.7–8.9%) for VMAT, 10.4% (range 7.0–12.2%) for Intensity Modulated Radiation Therapy, and 13.2% (range 8.8–21.0%) for 3D Conformal Radiation Therapy. The results obtained with different IVD software and among centers were consistent and showed an acceptable homogeneity. EPID IVD was effective in intercepting important errors.

Poster: EuroSafe Imaging 2020 / ESI-10114 / Craniostenosis imaging: optimization of the CT protocol for the right dose by: M. Gentile1, A. GUIDI2, P. Polidori3, R. Calandrelli4, A. Fidanzio5, L. Bonomo6, C. Colosimo7; 1 Roma/IT, 2 Anguillara Sabazia (RM)/IT, 3 Rome/IT, 4Radiology Rome/IT, 5Fondazione Policlinico Universitario Gemelli IRCCS Rome/IT, 6Policlinico Rome/IT, 7Catholic University and School of Medicine Rome/IT

Purpose Aim of this study is to investigate the MRIdian (ViewRay) TPS accuracy in calculating the dose distribution in presence of magnetic field at tissue-lung interface, where the electron return effect (ERE) plays a primary role. Methods The investigation was realised using Gafchromic EBT3 films. A dose calibration step was planned on MRIdian, exposing thirteen 3 × 3 cm2 film pieces perpendicularly to the beam axis at different Co-60 source exposure times (15–460 s). Films were arranged in a slab water phantom (SAD = 105 cm; SSD = 100 cm) and analysed one day after irradiation. An absolute dose measurement was performed by using a 125 cc ion chamber to estimate correlation between exposure time and absorbed dose. To evaluate dose accuracy at lung-tissue interface, two EBT3 films were inserted at the interfaces of a non-homogeneous sandwich phantom composed by a 5 cm lung-equivalent slab (ρ = 0.39 g/cm3) embedded inside two water-equivalent slabs (see Fig. 1). Three treatment plans were calculated and delivered: •Plan A: one 4.2 × 4.2 cm2 beam delivered at 0 degree •Plan B: three 6.3 × 6.3 cm2 beams delivered at 330,0 and 30 degree •Plan C: an IMRT complex plan constituted by 9 equidistant beams The dose distributions measured by EBT3 films were compared to those calculated by TPS in terms of 1%/1 mm, 3%/1 mm, 3%/3 mm and 25 cGy/1 mm gamma analysis. The dosimetric workflow was also validated by delivering Plan A on a totally homogeneous phantom. Results Table 1 contains the γ < 1 values obtained for the different plans delivered. All plans show a 3%/3 mm gamma-passing rate higher than 90% (tolerance criteria recommended for IMRT by ESTRO Booklet 7). When tighter spatial criteria were considered (delta distance = 1 mm), a decrease of passing rate is observed, whose entity is correlated to the plan complexity. Conclusions MRIdian TPS is able to calculate with high accuracy dose distribution in presence of magnetic field at the tissue-lung interface, correctly modelling the ERE contribution.

Purpose: Aim of this study is to experimental evaluate the impact of a 0.35 T transverse magnetic field on dose distribution in presence of tissue-air and tissue-lung interfaces. Methods: The investigation was carried out using MRIdian (ViewRay, Cleveland, Ohio) and it consisted of comparing experimental measurements performed by Gafchromic EBT3 film dosimetry, to Montecarlo simulations, carried out in the presence and, as well as, the absence of the magnetic field. A preliminary dose calibration was planned on MRIdian, arranging 3 x 3 cm(2) film pieces in a water slab phantom and exposing them at different beam-on times, in a dose range equal to 0.1-12.1 Gy. All experimental measurements were then carried out using the calibrated films and delivering one single beam orthogonally to three different phantoms: without inhomogeneity, with an air gap and with a lung inhomogeneity. The dose distributions measured by EBT3 films in presence of magnetic field were compared to those calculated in the presence and, as well as, the absence of the magnetic field, in terms of gamma analysis. A quantification of electron return effect (ERE) was also performed. Results: All the tested plans considering the magnetic field show a gamma-passing rate higher than 98% for 3%/3 mm gamma analysis. In presence of tissue-air interface, the electron return effect causes an over-dosage of + 31.9% at the first interface and an under-dosage of -33% at the second interface. The dosimetric variations in presence of tissuelung interface results to be smaller ( + 0.8% first interface, - 1.3% second interface). Conclusion: The impact of 0.35 T magnetic field is not negligible and it can be effectively modelled by the Montecarlo dose calculation platform available in the MRIdian TPS.

Purpose The aim of this work was to compare two approaches of cone-beam computed tomography (CBCT) image intensity-correction for dose recalculation of volumetric arc radiotherapy (VMAT) plans. Methods and materials CBCT-based dose calculation accuracy was assessed for pelvic, lung, and head and neck (H&N) treatment sites. The dose distributions of 10 patients for each body regions were re-calculated by RayStation (RS) and Eclipse treatment planning systems (TPS). In particular CBCT RS were calibrated by patient specific density assignment method supplied by RS TPS, while CBCT ROI , obtained applying ROI-based lookup tables for each body region were used in Eclipse TPS. Dose Volume Histogram (DVH) statistics and 3D γ -analysis (3%, 3 mm) of the dose maps and dose-volume statistics were determined to compare the CBCT dose distributions with those of the planning CTs in absence of morphological changes. Results The results indicate a comparable performance of both intensity correction techniques in the scope of VMAT. The differences in the investigated DVH parameters with respect to the pCT were mostly below 2% for both methods, however the γ -index analysis, being more sensitive to local dose changes, pointed out slight inaccuracies in the CBCT ROI dose distributions with respect to CBCTRS. In particular γ -index pass-rates were found increased for CBCTRS with respect to CBCTROI in pelvic (98% against 95%) in lung (97% against 93%) and in H&N (99% against 95%). Conclusion Both the CBCT intensity correction approaches are attractive options for CBCT dose recalculation and in vivo dose reconstructions [ 1 Fidanzio A. et al. Med Phys. 2014; 41: 062103 Crossref Scopus (19) Google Scholar , 2 Consorti R. et al. Phys Med. 2017; 42: 157-161 Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar ]. No added value was found by using a patient-specific HU table, showing similar results as the group based HU tables in terms of DVH indices while the γ -analysis showed better results for CBCTRS. The aim of this work was to compare two approaches of cone-beam computed tomography (CBCT) image intensity-correction for dose recalculation of volumetric arc radiotherapy (VMAT) plans. CBCT-based dose calculation accuracy was assessed for pelvic, lung, and head and neck (H&N) treatment sites. The dose distributions of 10 patients for each body regions were re-calculated by RayStation (RS) and Eclipse treatment planning systems (TPS). In particular CBCT RS were calibrated by patient specific density assignment method supplied by RS TPS, while CBCT ROI , obtained applying ROI-based lookup tables for each body region were used in Eclipse TPS. Dose Volume Histogram (DVH) statistics and 3D γ -analysis (3%, 3 mm) of the dose maps and dose-volume statistics were determined to compare the CBCT dose distributions with those of the planning CTs in absence of morphological changes. The results indicate a comparable performance of both intensity correction techniques in the scope of VMAT. The differences in the investigated DVH parameters with respect to the pCT were mostly below 2% for both methods, however the γ -index analysis, being more sensitive to local dose changes, pointed out slight inaccuracies in the CBCT ROI dose distributions with respect to CBCTRS. In particular γ -index pass-rates were found increased for CBCTRS with respect to CBCTROI in pelvic (98% against 95%) in lung (97% against 93%) and in H&N (99% against 95%). Both the CBCT intensity correction approaches are attractive options for CBCT dose recalculation and in vivo dose reconstructions [ 1 Fidanzio A. et al. Med Phys. 2014; 41: 062103 Crossref Scopus (19) Google Scholar , 2 Consorti R. et al. Phys Med. 2017; 42: 157-161 Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar ]. No added value was found by using a patient-specific HU table, showing similar results as the group based HU tables in terms of DVH indices while the γ -analysis showed better results for CBCTRS.

In vivo dosimetry (IVD) is the last step of a radiotherapy quality control program aimed to ensure that the dose delivered is in agreement with that prescribed. IVD procedures based on single detectors are time-consuming and impossible to use for the modern radiotherapy techniques, based on static or kinetic beams (modulated in intensity fluence); this means that more efficient and practical methods are highly recommended. The practical method SOFTDISO, based on the use of electronic portal image device (EPID), provides two tests (i) the R ratio between the reconstructed and the planned isocenter doses to verify an agreement within 5% and (ii) the γ-analysis of the EPID images, to verify γ% ≥ 90% and γmean ≤ 0.4. This paper reports the results of 11,357 IVD tests carried out for 823 patients treated by three-dimensional conformal radiation therapy and volumetric modulated arc therapy techniques. In particular, the dose disagreements are reported distinguishing two kinds of causes, those of (i) class 1 that includes the errors due to inadequate quality controls and (ii) the class 2, due to patient morphological changes. About the tests out of tolerance, 6% were by VMAT and 21% by 3DCRT, but taking into account the only class 1 of errors, i.e., removing the causes of class 2, only 7% of patients examined presented at least one of the three mean indexes out of tolerance. The workload for IVD on 9 patients/day per linac is about 52 min/day but recently, a new automated SOFTDISO version has been implemented to reduce the time to about 34 min/day.

Purpose: EPID-based in vivo dosimetry (IVD) has been implemented for stereotactic body radiotherapy treatments of non-small cell lung cancer to check both isocenter dose and the treatment reproducibility comparing EPID portal images. Methods: 15 patients with lung tumors of small dimensions and treated with volumetric modulated arc therapy were enrolled for this initial experience. IVD tests supplied ratios R between in vivo reconstructed and planned isocenter doses. Moreover a gamma-like analysis between daily EPID portal images and a reference one, in terms of percentage of points with.-value smaller than 1, P.< 1, and mean gamma-values, gamma(mean), using a local 3%-3 mm criteria, was adopted to check the treatment reproducibility. Tolerance levels of 5% for R ratio, P-gamma< 1 higher than 90% and gamma(mean) lower than 0.67 were adopted. Results: A total of 160 EPID images, two images for each therapy session, were acquired during the treatment of the 15 patients. The overall mean of the R ratios was equal to 1.005 +/- 0.014 (1 SD), with 96.9% of tests within +/- 5%. The 2 D image gamma-like analysis showed an overall.mean of 0.39 +/- 0.12 with 96.1% of tests within the tolerance level, and an average P-gamma< 1 value equal to 96.4 +/- 3.6% with 95.4% of tests with P-gamma< 1 > 90%. Paradigmatic discrepancies were observed in three patients: a set-up error and a patient morphological change were identified thanks to CBCT image analysis whereas the third discrepancy was not fully justified. Conclusions: This procedure can provide improved patient safety as well as a first step to integrate IVD and CBCT dose recalculation.

In vivo dosimetry (IVD), a direct method of measuring radiation doses to cancer patients during treatment, has shown unique features to trace deviations between planned and actually delivered dose distributions. Lung stereotactic ablative radiotherapy (SBRT) involves the delivery of high doses in a few fractions for ablative purposes. Then SBRT treatments strongly benefit from IVD procedures, as any uncertainties in dose delivery is more detrimental for treatment goals. We assessed the feasibility of EPID-based IVD for clinical lung SBRT treatments using VMAT technique. 8 patients with lung metastases treated with Elekta VMAT were enrolled. Dose prescription was 50Gy in 5 fractions. Patients were simulated and treated using the Active Breath Coordinator (Elekta), a spirometer enabling a temporary controlled interruption of patient breathing at the end of inspiration phase. VMAT plans were generated with Ergo++ TPS with a single 360° arc; the VMAT delivery sequence was divided into multiple subarcs according to the patient predefined breath-hold periods. IVD was performed using SOFTDISO software (Best Medical Italy). IVD tests were evaluate by means of (i) R ratio between isocenter daily in-vivo dose and planned dose and (ii) g-analysis between EPID integral images in terms of percentage of points with g-value smaller than one (g%) and mean g-values (gmean), using a global 3%-3 mm criteria. Alert criteria of ±5% for R ratio, g% <90% and gmean > 0.67 were chosen., the last two in order to accept only 10% of the values to exceed 3%/3mm and an average discrepancy of the order of 2%/2mm, respectively. A total of 40 transit EPID images were acquired. Two images (5%) were removed from analysis for image deterioration and/or electronic acquisition failures. The overall mean R ratio was equal to 0.999 ± 0.021 (1 SD) for all patients, with more than 98% of tests within 5% alert criteria. The 2D portal images g-analysis show an overall gmean of 0.29±0.13 with 100% of tests within alert criteria, and a mean g% equal to 97.9±3.2% with 100.0% of tests within alert criteria. The results are supplied in quasi real-time, with IVD tests performed and displayed after only 1 minute from the end of arc delivery. Our results showed that the integration of ABC multi-segmented breath-hold control into the VMAT-SBRT delivery strategy translated in high reproducibility treatments.

ESTRO 36 _______________________________________________________________________________________________ 10 FFF for a 40x40 cmxcm field.Differences between recombination corrected and uncorrected PDDs, and among PDDs measured with different detectors, increase with field size.Differences between recombinationcorrected and uncorrected PDDs were found ranging from 1.2% for PTW Semiflex ion chamber to 2.5% for PTW Roos ion chamber, both measured for a 40x40 cmxcm at 350 mm deep. ConclusionResults show that plane parallel ion chambers can be used for photon PDD measurements, with minimal polarity effects, if recombination effects are corrected for as needed.Medical physicists should use their own clinical judgement to decide about whether or not PDDs must be corrected for saturation effects.

Introduction: Several factors such as patient setup and the anatomical changes can affect the dose delivery in radiotherapy. The cone beam CT (CBCT) allows a timely assessment of the treatment and its calibration, in terms of relative electron densities (RED), allows hybrid plan calculation useful to adopt an adaptive strategy. However the CBCT calibration suffers from some problems such as time stability and patient variability. This work reports the dosimetric assessment of an original patient-specific CBCT calibration method.