Validation of virtual water phantom software for pre-treatment verification of single-isocenter multiple-target stereotactic radiosurgery

Objectiu múltiple; SRS; Fantasma virtualObjetivo múltiple; SRS; Fantasma virtualMultiple‐target; SRS; Virtual phantomThe aim of this study was to benchmark the accuracy of the VIrtual Phantom Epid dose Reconstruction (VIPER) software for pre-treatment dosimetric verification of multiple-target stereotactic radiosurgery (SRS). VIPER is an EPID-based method to reconstruct a 3D dose distribution in a virtual phantom from in-air portal images. Validation of the VIPER dose calculation was assessed using several MLC-defined fields for a 6 MV photon beam. Central axis percent depth doses (PDDs) and output factors were measured with an ionization chamber in a water tank, while dose planes at a depth of 10 cm in a solid flat phantom were acquired with radiochromic films. The accuracy of VIPER for multiple-target SRS plan verification was benchmarked against Monte Carlo simulations. Eighteen multiple-target SRS plans designed with the Eclipse treatment planning system were mapped to a cylindrical water phantom. For each plan, the 3D dose distribution reconstructed by VIPER within the phantom was compared with the Monte Carlo simulation, using a 3D gamma analysis. Dose differences (VIPER vs. measurements) generally within 2% were found for the MLC-defined fields, while film dosimetry revealed gamma passing rates (GPRs) ≥95% for a 3%/1 mm criteria. For the 18 multiple-target SRS plans, average 3D GPRs greater than 93% and 98% for the 3%/2 mm and 5%/2 mm criteria, respectively. Our results validate the use of VIPER as a dosimetric verification tool for pre-treatment QA of single-isocenter multiple-target SRS plans. The method requires no setup time on the linac and results in an accurate 3D characterization of the delivered dose

Verification of stereotactic radiosurgery plans for multiple brain metastases using a virtual phantom-based procedure

Background: The purpose of this study was to describe the use of the VIPER software for patient-specific quality assurance (PSQA) of single-isocenter multitarget (SIMT) stereotactic radiosurgery (SRS) plans. Materials and methods: Twenty clinical of intensity-modulated (IMRT) SIMT SRS plans were reviewed. A total of 88 brain metastases were included. Number of lesions per plan and their individual volumes ranged from 2 to 35 and from 0.03 to 32.8 cm3, respectively. Plans were designed with the Eclipse system, and delivered using a Varian CLINAC linac. SRS technique consisted of non-coplanar static-field sliding-window IMRT. Each plan was mapped onto a virtual cylindrical water phantom (VCP) in the Eclipse to calculate a 3D dose distribution (verification plan). The VIPER software reconstructed the 3D dose distribution inside the VCP from the acquired in-air electronic portal image device (EPID) images of the treatment fields. A 3D gamma analysis was used to compare the reconstructed doses to the Eclipse planned doses on the VCP. Gamma passing rates (GPRs) were calculated using 3% global/2 mm criteria and dose thresholds ranged from 10% to 90% of the maximum dose. Results: The averages (± 1 SD) of the 3D GPRs over the 20 SRS plans were: 99.9 ± 0.2%, 99.7 ± 0.3%, 99.6 ± 0.5%, 99.3 ± 0.9%,99.1 ± 1.6%, 99.0 ± 1.6%, and 98.5 ± 3.3%, for dose thresholds of 10%, 20%, 30%, 50%, 70%, 80% and 90% respectively. Conclusions: This work shows the feasibility of the VIPER software for PSQA of SIMT SRS plans, being a reliable alternative to commercially available 2D detector arrays

Tractament de manteniment amb metadona: manual de pràctica clínica

Tractament de manteniment amb metadona; Pràctica clínica; DrogodependènciesTratamiento de mantenimiento con metadona; Práctica clínica; DrogodependenciasMethadone maintenance treatment; Clinical practice; Drug addictionsEl Manual pretén ser una eina útil per disminuir la variabilitat de la pràctica clínica i garantir un nivell òptim de qualitat i millora de l'atenció sanitària en el tractament de manteniment amb metadona (TMM). Aplica les normes bàsiques utilitzades per a la preparació de guies de pràctica clínica; en primer lloc, incloent-hi la millor evidència possible sobre la base de revisions sistemàtiques de la literatura, en segon lloc, amb recomanacions clares i curtes, i en tercer lloc, en absència d’una evidència fiable en la literatura, incorporant-hi la opinió d’experts per mitjà de tècniques de consens com el mètode Delphi

A closer look at the conventional Winston-Lutz test: Analysis in terms of dose

AimTo investigate whether the target-isocenter deviations reported by a conventional Winston-Lutz (WL) test actually reflect the shifts of the measured prescription isodose line with respect to the target.BackgroundA conventional WL test uses a metallic ball as a target that aims at several fields. But this test does not report information on the accuracy of the delivery in terms of dose.Materials and methodsA conventional WL test using a metallic pointer as a target (Pointer-WL test) has been recreated in the Eclipse treatment planning system over an acrylic phantom containing a radiochromic film (Dose-WL test). After Dose-WL test delivery, the shift of the 80% prescription isodose line with respect to the target center (d80%-center) was measured using film dosimetry. The Pointer-WL and Dose-WL tests were performed in 10 different sessions. The isocenter deviation reported by the Pointer-WL test was compared to the d80%-center vector, according to the three patient's directions (Left–Right or LR; Anterior–Posterior or AP; and Superior–Inferior or SI).ResultsThe deviations (mean±SD) found for the Dose-WL tests (LR: 0.5±0.4mm; AP: 0.5±0.4mm; SI: 0.6±0.2mm) were in most cases less than 1mm, and they were significantly smaller (all