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Purpose TransitQA is an innovative method for Tomotherapy transit dosimetry using the on-board detector (OBD). Our previously published model for Tomotherapy treatment plan verification (AirQA) has been enhanced to take into account patient and couch transmission. AirQA estimates the OBD signal during irradiation with nothing in the beam path from the leaf control sinogram, allowing us to check whether the planned treatment is correctly delivered by the machine. TransitQA allows us to check the treatment delivery with the patient on the couch, potentially showing the effects of changes in the patient anatomy and delivery errors. Methods Patient and couch transmission have been added to the model using the OBD projections of pre-treatment megavoltage computed tomography (MVCT). The difference in the energy spectra between the imaging and treatment beams has been corrected by an exponent from the MVCT projections consisting of the ratio of the mass attenuation coefficients. This exponent has been found to not vary significantly with the atomic number Z, allowing us to apply this procedure to heterogeneous media, such as patients. The attenuated OBD projections acquired during the treatment are compared to the model via a signed global Υ-index analysis. The dose criterion was 5% of the 95th percentile of the dose distribution, and the distance to agreement (DTA) was 4 mm. Results Our method has been applied to a heterogeneous phantom with 98.1% of the points passing the Υ-evaluation test, showing that the model can predict the attenuated OBD projection. The method has been applied to two representative patients throughout the whole treatment, highlighting variations in the signal transmission and Υ-index. Conclusion This paper establishes the proof-of-concept of transit dosimetry for all patients treated by Tomotherapy. Moreover, this method can be used as a surrogate for in vivo dosimetry This article is protected by copyright. All rights reserved.

Background Non-resected locally advanced and microscopic positive-margin resected (R1) pancreatic adenocarcinoma are associated with a dismal prognosis. The combination of high dose radiotherapy and concomitant chemotherapy is among the strategies that are used to improve the outcome. The aims of this study were to evaluate the acute and late toxicities and patients' outcome in a retrospective study from a single center. Material and methods From 2009 to 2015, 24 patients, with non-resected locally advanced or R1 resected pancreatic adenocarcinoma, have been treated with concomitant radiochemotherapy, with a median dose of 60 Gy and gemcitabine (50 mg/m2 administered bi-weekly). The acute and late toxicities were evaluated during and after the treatment. Results The actuarial overall survival rates were 39% at 24 months and 8.6% at 36 months. The disease-free survival rates were 32.5% at 24 months and 12.2% at 36 months. Acute toxicities were mainly grade 1 (G1) to grade 2 (G2) except for one patient who presented with severe digestive bleeding potentially linked to the treatment. Late toxicities consisted mainly of G1 digestive toxicities. Conclusion This study confirms the feasibility of high dose radiotherapy combined with gemcitabine-based chemotherapy in patients with locally advanced pancreatic adenocarcinoma. While the outcome remains unsatisfactory, some patients seem to have benefited from this aggressive therapy, which merits to be investigated further.

In this work, a fast and simple procedure for tomotherapy treatment plan verification using the on-board detector (OBD) has been developed. This procedure allows verification of plans with static and dynamic jaws (TomoEDGE). A convolution-based calculation model has been derived in order to link the leaf control sinogram from the treatment planning system to the data acquired by the OBD during a static couch procedure. The convolution kernel has been optimized using simple plans calculated in the Tomotherapy Cheese phantom. The optimal kernel has been found to be a lorentzian function, whose parameter Γ is 0.186 for the 1 cm jaw opening, 0.232 for the 2.5 cm jaw opening and 0.373 for the 5 cm jaw opening. The evaluation has been performed with a γ-index analysis. The dose criterion was 3% of the 95th percentile of the dose distribution and the distance-to-agreement criterion is 2 mm. In order to validate the procedure, it has been applied to around 50 clinical treatment plans, which had already been validated by the Delta4 phantom (Scandidos, Sweden). 96% of the tested plans have passed the criteria. Concerning the other 4%, significant discrepancies between the leaf pattern in the leaf control sinogram and the OBD data have been shown, which might be due to differences in the leaf open time. This corresponds also to a higher sensitivity of this method over the Delta4, adding the possibility of better monitoring the treatment delivery.

Introduction Since the acquisition of our Tomotherapy in 2011, we have developed a method of validating the treatment of patients without additional measuring instruments. The idea was to use the onboard detector (OBD). This previously published [1] model for Tomotherapy treatment plan verification (called AirQA) has been enhanced in order to take into account patient and couch transmission (we call it TransitQA). TransitQA is an innovative method for Tomotherapy transit dosimetry using the OBD. AirQA estimates the OBD signal during irradiation without anything in the beam path from the leaf control sinogram, allowing to check whether the planned treatment is correctly delivered by the machine. TransitQA allows to checks the treatment delivery with the patient on the couch, potentially showing the effects of changes in the patient anatomy and delivery errors. Methods AirQA was for us a well-controlled concept in 2015 [1] . Today more than 500 patient treatments have been validated by this method. This great experience has made it possible to go further in the project. Patient and couch transmission have been added to the model, using the OBD projections of the pre-treatment megavoltage computed tomography (MVCT). The difference in the energy spectra between the imaging and treatment beam has been corrected by an exponent on the MVCT projections, consisting in the ratio of the mass attenuation coefficients. This exponent has been found not to vary significantly with the atomic number Z, giving the opportunity to apply this procedure to heterogeneous media like patients. The attenuated OBD projections acquired during the treatment are compared to the model via a signed?-index analysis. The dose criterion was 5% of the 95th percentile of the dose distribution and the distance to agreement was 4 mm. Results Our method has been applied to a heterogeneous phantom with 98.1% of point passing the gamma evaluation test, showing that the model is able to predict attenuated OBD projection. The method has been applied on two representative patients, during the whole treatment, showing a great sensitivity. Conclusions This talk describes the experience of the AirQA and also establishes the proof of concept of transit dosimetry for all patients treated by Tomotherapy. Moreover, this method called TransitQA can be a surrogate for in vivo dosimetry.

Purpose : A dummy run was organized to test the compliance of participating centres with the guidelines of EORTC protocol 22931, which compares high dose radiotherapy with concomitant radiochemotherapy in a postoperative setting for patients presenting with locally advanced head and neck carcinomas. Methods : In a first step the participants (seven centres, six replies) were asked to define the planning target volume (PTV) in a given patient on the basis of clinical, surgical and radiological (CT-images) data-sets and according to the protocol guidelines. In a second phase a series of CT-reconstructed slices with on- and off-axis PTV outlines were sent to 11 centres (10 replies), which were asked to plan a treatment following the recommendations made in the frame of the trial. Results : The first step of this dummy run emphasized wide intercentre variations in PTV extensions. This fact raises the question of the reproducibility when pooling patients in multicentric trials. The second step indicated a large variability in the field arrangements which was left to the discretion of the investigators. Only three out of 10 of the institutions followed the ICRU 50 recommendations for dose reporting. Moreover, protocol requirements were not met for dose distribution homogeneity in any centre. Conclusions : In order to reduce intercentre treatment heterogeneities, several actions have been taken by the EORTC Radiotherapy Group, e.g. amendments have been brought to protocol 22931 regarding a better definition of clinical and planning target volumes. Furthermore, a stricter application of the ICRU 50 recommendations for dose reporting has been sought.

Two stereotactic surgery methods, arc and micro-multi-leave collimator (MMLC) therapy, were compared in the particular case of arteriovenous malformations (AVMs) treatment. Different methods of the treatment optimisation were used. The comparison covered a group of 22 patients suffering from peripheral and central AVMs of different sizes who underwent initially arc therapy. Several parameters were evaluated to compare the two methods: 2D and 3D isodose representations, dose-volume histograms (DVHs) and probability of success. The 3D isodoses were compared for the 22 patients showing a better conformity for the MMLC (three cases are presented). The DVHs of the AVM were also in favour of MMLC. In terms of probability of success, the results showed that are therapy was superior only in the case of small spherical lesions. MMLC therapy proved to be superior to arc therapy in all cases but central spherical small volume AVMs.

One forward-planning method and five inverse-planning methods for optimisation of treatment in radiation therapy were compared in the particular case of radiosurgery with micro-multi-leaves collimator (MMLC) and arc therapy. The “manual” method, two matrix methods (singular value decomposition and non-negative least square fit), two gradient methods (quasi-Newton and conjugate gradient algorithms) and the “simulated annealing” stochastic method were investigated. The performance of these methods was assessed in terms of the speed of convergence to an optimum, the ability to account for the organs at risk, and probability of targeted success. The study employed an adapted version of the GRATIS treatment planning system. A group of 22 patients previously treated by arc therapy for arteriovenous malformations (AVMs) were studied to evaluate the performance of the various optimisation methods for MMLC and arc therapy. The conjugate gradient method proved to be the most appropriate for most cases.

Keywords: LTS5 ; Atlas-based segmentation ; IMRT ; Radiotherapy ; Lymph nodes ; Label Fusion ; MRF Reference EPFL-CONF-183871 Record created on 2013-02-18, modified on 2017-05-10

Purpose: To describe the implementation and use of an electronic patient-referral system as an aid to the efficient referral of patients to a remote and specialized treatment center. Methods and Materials: A system for the exchange of radiotherapy data between different commercial planning systems and a specially developed planning system for proton therapy has been developed through the use of the PAPYRUS diagnostic image standard as an intermediate format. To ensure the cooperation of the different TPS manufacturers, the number of data sets defined for transfer has been restricted to the three core data sets of CT, VOIs, and three-dimensional dose distributions. As a complement to the exchange of data, network-wide application-sharing (video-conferencing) technologies have been adopted to provide methods for the interactive discussion and assessment of treatments plans with one or more partner clinics. Results: Through the use of evaluation plans based on the exchanged data, referring clinics can accurately assess the advantages offered by proton therapy on a patient-by-patient basis, while the practicality or otherwise of the proposed treatments can simultaneously be assessed by the proton therapy center. Such a system, along with the interactive capabilities provided by video-conferencing methods, has been found to be an efficient solution to the problem of patient assessment and selection at a specialized treatment center, and is a necessary first step toward the full electronic integration of such centers with their remotely situated referral centers.

Purpose : A comparative treatment planning study has been undertaken between standard photon delivery techniques,b intensity modulated photon methods and spot scanned protons in order to investigate the merits and limitations of each of these treatment approaches. Methods : Plans for each modality were performed using CT scans and planning information for nine patients with varying indications and lesion sites and the results have been analysed using a variety of dose and volume based parameters. Results : Over all cases, it is predicted that the use of protons could lead to a reduction of the total integral dose by a factor three compared to standard photon techniques and a factor two compared to IM photon plans. In addition, in all but one Organ at Risk (OAR) for one case, protons are predicted to reduce both mean OAR dose and the irradiated volume at the 50% mean target dose level compared to both photon methods. However, when considering the volume of an OAR irradiated to 70% or more of the target dose, little difference could be shown between proton and intensity modulated photon plans. On comparing the magnitude of dose hot spots in OARs resulting from the proton and IM photon plans, more variation was observed, and the ranking of the plans was then found to be case and OAR dependent. Conclusions : The use of protons has been found to reduce the medium to low dose load (below about 70% of the target dose) to OARs and all non-target tissues compared to both standard and inversely planned photons, but that the use of intensity modulated photons can result in similar levels of high dose conformation to that afforded by protons. However, the introduction of inverse planning methods for protons is necessary before general conclusions on the relative efficacy of photons and protons can be drawn.

Background and purpose : This work was undertaken to improve the definition of target volumes for radiosurgery using the angiographic and CT data. Materials and methods : The basis of this new method is to combine both imaging modalities and to compare them in each representation, i.e. to plot the volume obtained by angiography on CT images and also the contours defined by the CT on angiographic films. To obtain the angiographic volume, the radiographs are taken at several incidence angles. The X-ray sources position and the position of the films are determined using rectangular markers, then the intersection of all the loci of the target volume are calculated. Results : Verifications with a phantom show the accuracy of the procedure and the benefit obtained by increasing the number of angles of incidence in the angiographic imaging. The centre of gravity of the experimental target could be localized to an accuracy of better than 0.4 mm. The method was used in 11 clinical cases with excellent clinical results. Conclusions : The method can be easily applied and improves the delineation of target volumes in radiosurgery. CT data counterbalances the relative weakness of angiography concerning the three-dimensional geometry. Angiography adds useful information on the blood flow that is not shown in CT. Almost all the presented clinical cases benefit from the technique described here.

This paper presents automated segmentation of structures in the Head and Neck (H&N) region, using an active contour-based joint registration and segmentation model. A new atlas selection strategy is also used. Segmentation is performed based on the dense deformation field computed from the registration of selected structures in the atlas image that have distinct boundaries, onto the patient’s image. This approach results in robust segmentation of the structures of interest, even in the presence of tumors, or anatomical differences between the atlas and the patient image. For each patient, an atlas image is selected from the available atlas-database, based on the similarity metric value, computed after performing an affine registration between each image in the atlas-database and the patient’s image. Unlike many of the previous approaches in the literature, the similarity metric is not computed over the entire image region; rather, it is computed only in the regions of soft tissue structures to be segmented. Qualitative and quantitative evaluation of the results is presented.

In medical imaging, merging automated segmentations obtained from multiple atlases has become a standard practice for improving the accuracy. In this letter, we propose two new fusion methods: "Global Weighted Shape-Based Averaging" (GWSBA) and "Local Weighted Shape-Based Averaging" (LWSBA). These methods extend the well known Shape-Based Averaging (SBA) by additionally incorporating the similarity information between the reference (i.e., atlas) images and the target image to be segmented. We also propose a new spatially-varying similarity-weighted neighborhood prior model, and an edge-preserving smoothness term that can be used with many of the existing fusion methods. We first present our new Markov Random Field (MRF) based fusion framework that models the above mentioned information. The proposed methods are evaluated in the context of segmentation of lymph nodes in the head and neck 3D CT images, and they resulted in more accurate segmentations compared to the existing SBA.