Journal: Physics in Medicine and Biology

Abbreviation

Phys. Med. & Biol.

Publisher

IOP Publishing

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ISSN

1361-6560
0031-9155

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Publications1 - 10 of 159
  • Experimental validation of daily adaptive proton therapy
    Item type: Journal Article
    Nenoff, Lena; Matter, Michael; Charmillot, Marjolaine; et al. (2021)
    Physics in Medicine and Biology
    Anatomical changes during proton therapy require rapid treatment plan adaption to mitigate the associated dosimetric impact. This in turn requires a highly efficient workflow that minimizes the time between imaging and delivery. At the Paul Scherrer Institute, we have developed an online adaptive workflow, which is specifically designed for treatments in the skull-base/cranium, with the focus set on simplicity and minimizing changes to the conventional workflow. The dosimetric and timing performance of this daily adaptive proton therapy (DAPT) workflow has been experimentally investigated using an in-house developed DAPT software and specifically developed anthropomorphic phantom. After a standard treatment preparation, which includes the generation of a template plan, the treatment can then be adapted each day, based on daily imaging acquired on an in-room CT. The template structures are then rigidly propagated to this CT and the daily plan is fully re-optimized using the same field arrangement, DVH constraints and optimization settings of the template plan. After a dedicated plan QA, the daily plan is delivered. To minimize the time between imaging and delivery, clinically integrated software for efficient execution of all online adaption steps, as well as tools for comprehensive and automated QA checks, have been developed. Film measurements of an end-to-end validation of a multi-fraction DAPT treatment showed high agreement to the calculated doses. Gamma pass rates with a 3%/3 mm criteria were >92% when comparing the measured dose to the template plan. Additionally, a gamma pass rate >99% was found comparing measurements to the Monte Carlo dose of the daily plans reconstructed from the logfile, accumulated over the delivered fractions. With this, we experimentally demonstrate that the described adaptive workflow can be delivered accurately in a timescale similar to a standard delivery.
  • Log file based Monte Carlo calculations for proton pencil beam scanning therapy
    Item type: Journal Article
    Winterhalter, Carla; Meier, Gabriel; Oxley, David; et al. (2019)
    Physics in Medicine and Biology
  • Improving DIBH-PBS treatment for NSCLC: reducing delivery time with advanced spot reduction techniques
    Item type: Journal Article
    Bonomi, Martina; Toschini, Mathilde; Colizzi, Isabella; et al. (2025)
    Physics in Medicine and Biology
    Objective. Breath-hold (BH) is a promising approach for proton therapy of moving targets, but multiple BHs per field are needed to compensate for long irradiation time. In pencil beam scanning therapy, two factors define the treatment delivery time: the beam-on time and the dead time, which is the time required for energy-layer and spot-position adjustments. This study examines the interplay of various spot-reduction techniques to decrease delivery time without sacrificing robustness or plan quality. Approach. We created treatment plans for a cohort of 12 non-small cell lung cancer patients, combining a range modulator (RM) that broadens the Bragg peak into a Gaussian shape with three different spot placement algorithms (SPA):a fixed grid-based spot placement technique, an energy-dependent grid-based on the beam's size in air and water, and two types of optimization: a conventional and a spot suppression (SS.) optimization. These configurations were compared in terms of plan quality and clinical acceptability. Main results. RM combined with a fixed grid, leads to the best performance regarding plan quality and robustness. All SPAs reduce treatment time similarly. The SS. optimization reduces the number of spots but does not impact the treatment time. Given the time efficiency of the non-SS. algorithm, the reference optimization algorithms seem to be a better choice. Significance. By combining RM with a spot placement algorithm based on a fixed grid, we can obtain treatment plans with good clinical quality and low irradiation time, thus potentially improving BH treatment efficiency.
  • Dosimetric comparison of autocontouring techniques for online adaptive proton therapy
    Item type: Journal Article
    Smolders, Andreas; Choulilitsa, Evangelia; Czerska, Katarzyna; et al. (2023)
    Physics in Medicine and Biology
    Objective. Anatomical and daily set-up uncertainties impede high precision delivery of proton therapy. With online adaptation, the daily plan is reoptimized on an image taken shortly before the treatment, reducing these uncertainties and, hence, allowing a more accurate delivery. This reoptimization requires target and organs-at-risk (OAR) contours on the daily image, which need to be delineated automatically since manual contouring is too slow. Whereas multiple methods for autocontouring exist, none of them are fully accurate, which affects the daily dose. This work aims to quantify the magnitude of this dosimetric effect for four contouring techniques. Approach. Plans reoptimized on automatic contours are compared with plans reoptimized on manual contours. The methods include rigid and deformable registration (DIR), deep-learning based segmentation and patient-specific segmentation. Main results. It was found that independently of the contouring method, the dosimetric influence of using automatic OAR contours is small (<5% prescribed dose in most cases), with DIR yielding the best results. Contrarily, the dosimetric effect of using the automatic target contour was larger (>5% prescribed dose in most cases), indicating that manual verification of that contour remains necessary. However, when compared to non-adaptive therapy, the dose differences caused by automatically contouring the target were small and target coverage was improved, especially for DIR. Significance. The results show that manual adjustment of OARs is rarely necessary and that several autocontouring techniques are directly usable. Contrarily, manual adjustment of the target is important. This allows prioritizing tasks during time-critical online adaptive proton therapy and therefore supports its further clinical implementation.
  • 4D MR imaging of respiratory organ motion and its variability
    Item type: Journal Article
    Siebenthal, M. von; Székely, Gábor; Gamper, U.; et al. (2007)
    Physics in Medicine and Biology
  • Radiotherapy planning for glioblastoma based on a tumor growth model
    Item type: Journal Article
    Unkelbach, J.; Menze, B.H.; Konukoglu, E.; et al. (2014)
    Physics in Medicine and Biology
  • Detection of range shifts in proton beam therapy using the J-PET scanner: a patient simulation study
    Item type: Journal Article
    Brzeziński, Karol; Baran, Jakub; Borys, Damian; et al. (2023)
    Physics in Medicine and Biology
    Objective. The Jagiellonian positron emission tomography (J-PET) technology, based on plastic scintillators, has been proposed as a cost effective tool for detecting range deviations during proton therapy. This study investigates the feasibility of using J-PET for range monitoring by means of a detailed Monte Carlo simulation study of 95 patients who underwent proton therapy at the Cyclotron Centre Bronowice (CCB) in Krakow, Poland. Approach. Discrepancies between prescribed and delivered treatments were artificially introduced in the simulations by means of shifts in patient positioning and in the Hounsfield unit to the relative proton stopping power calibration curve. A dual-layer, cylindrical J-PET geometry was simulated in an in-room monitoring scenario and a triple-layer, dual-head geometry in an in-beam protocol. The distribution of range shifts in reconstructed PET activity was visualized in the beam’s eye view. Linear prediction models were constructed from all patients in the cohort, using the mean shift in reconstructed PET activity as a predictor of the mean proton range deviation. Main results. Maps of deviations in the range of reconstructed PET distributions showed agreement with those of deviations in dose range in most patients. The linear prediction model showed a good fit, with coefficient of determination r 2 = 0.84 (in-room) and 0.75 (in-beam). Residual standard error was below 1 mm: 0.33 mm (in-room) and 0.23 mm (in-beam). Significance. The precision of the proposed prediction models shows the sensitivity of the proposed J-PET scanners to shifts in proton range for a wide range of clinical treatment plans. Furthermore, it motivates the use of such models as a tool for predicting proton range deviations and opens up new prospects for investigations into the use of intra-treatment PET images for predicting clinical metrics that aid in the assessment of the quality of delivered treatment.
  • Experimental validation of beam quality correction factors for proton beams
    Item type: Journal Article
    Gomà, Carles; Hofstetter-Boillat, Bénédicte; Safai, Sairos; et al. (2015)
    Physics in Medicine and Biology
  • Dielectric properties of human placenta, umbilical cord and amniotic fluid
    Item type: Journal Article
    Peyman, A.; Gabriel, C.; Benedickter, Hans-Rudolf; et al. (2011)
    Physics in Medicine and Biology
  • Wobbled splatting—a fast perspective volume rendering method for simulation of x-ray images from CT
    Item type: Journal Article
    Birkfellner, Wolfgang; Seemann, Rudolf; Figl, Michael; et al. (2005)
    Physics in Medicine and Biology
Publications1 - 10 of 159