Digital phantoms for the evaluation of a software used for an automatic analysis of the Winston-Lutz test in image guided radiation therapy

11 pagesInternational audienceAccurate isocentre positioning of the treatment machine is essential for the radiation therapy process, especially in stereotactic radio surgery and in image guided radiation therapy. We present in this paper a new method to evaluate a software which is used to perform an automatic analysis of the Winston-Lutz1, 2 test used in order to determine position and size of the isocentre. The method consists of developing digital phantoms that simulate mechanical distortions of the treatment machine as well as misalignments of the positioning laser targeting the isocentre. These Digital Test Objects (DTOs) offer a detailed and profound evaluation of the software and allow determining necessary adjustments which lead to high precision and therefore contributes to a better treatment targeting

Dosimetric comparison between coplanar and non coplanar field radiotherapy for ethmoid sinus cancer

<p>Abstract</p> <p>Background</p> <p>To compare non coplanar field (NCF) with coplanar field (CF) -intensity-modulated radiotherapy (IMRT) planning for ethmoid cancer.</p> <p>Methods</p> <p>Seven patients treated with NCF IMRT for ethmoid cancer were studied. A CF IMRT optimization was prepared with the same constraints as for the NCF treatment. The maximum point doses (D max) obtained for the different optic pathway structures (OPS) should differ no more than 3% from those achieved with the NCF IMRT plan. The distribution of the dose in the target volume and in the critical structures was compared between the two techniques, as well as the Conformity (CI) and the Homogeneity Indexes (HI) in the target volume.</p> <p>Results</p> <p>We noted no difference between the two techniques in the OPS for the D1, D2, and D5%, in the inner ear and controlateral lens for the average Dmax, in the temporo-mandibular joints for the average mean dose, in the cord and brainstem for the average D1%. The dose-volume histograms were slightly better with the NCF treatment plan for the planning target volume (PTV) with a marginally better HI but no impact on CI. We found a great improvement in the PTV coverage with the CF treatment plan for two patients with T4 tumors.</p> <p>Conclusion</p> <p>IMRT is one of the treatment options for ethmoid cancer. The PTV coverage is optimal without compromising the protection of the OPS. The impact of non coplanar versus coplanar set up is very slight.</p

Three Years of Salvage IMRT for Prostate Cancer: Results of the Montpellier Cancer Center

Background. To assess the feasibility of salvage intensity-modulated radiation Therapy (IMRT) and to examine clinical outcome. Patients and Methods. 57 patients were treated with salvage IMRT to the prostate bed in our center from January, 2007, to February, 2010. The mean prescription dose was 68 Gy in 34 fractions. Forty-four patients received concomitant androgen deprivation. Results. Doses to organs at risk were low without altering target volume coverage. Salvage IMRT was feasible without any grade 3 or 4 acute gastrointestinal or urinary toxicity. With a median follow-up of 21 months, one grade 2 urinary and 1 grade ≥2 rectal late toxicities were reported. Biological relapse-free survival was 96.5% (2.3% (1/44) relapsed with androgen suppression and 7.7% (1/13) without). Conclusion. Salvage IMRT is feasible and results in low acute and chronic side-effects. Longer follow-up is warranted to draw conclusions in terms of oncologic control

Etude comparative des sequences d'echos de spins, d'echos stimules et d'echos de gradients en I.R.M. : Optimisation du contraste

Available from INIST (FR), Document Supply Service, under shelf-number : T 86354 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Nouvelle méthode automatique de contrôle de qualité des systèmes de planification géométrique des traitements en radiothérapie externe conformationnelle

National audienceEn radiothérapie externe conformationnelle, les systèmes de planification des traitements (TPS : Treatment Planning System) sont au cœur du processus décisionnel. Ils assistent le radiothérapeute, le physicien et le dosimétriste dans la définition de chacun des paramètres du traitement. La qualité des outils logiciels développés sur le TPS va donc directement influencer la précision des traitements préparés sur cette console. Il est alors impératif de contrôler les performances des systèmes de planification des traitements par radiothérapie. Pour se faire nous proposons une solution innovante de contrôle de qualité des outils de planification géométrique des TPS (simulation virtuelle) basée sur l'utilisation d'Objets-Tests-Numériques (OTN). Ces OTN viennent se substituer avantageusement aux fantômes physiques traditionnellement utilisés pour ce type de contrôles de qualité. En effet les contrôles qui découlent de l'utilisation de fantômes physiques sont longs, incomplets et imprécis. Par ailleurs, ils nécessitent une acquisition tomographique préalable à leur chargement sur les consoles informatiques à tester. Enfin, l'évaluation des résultats des tests effectués avec ces fantômes repose principalement sur l'utilisation des outils graphiques du TPS testé. Nous présentons ici le concept global de l'utilisation d'OTN pour le contrôle de qualité des plateformes de traitement d'image, et en particulier des solutions de contrôle de qualité pour quatre opérations effectuées par les TPS : la délinéation automatique des structures, l'application automatique de marges d'expansion ou d'érosion, le réglage automatique de la position de l'isocentre et la conformation automatique du collimateur classique ou multi-lames. La méthode « OTN » que nous avons mise au point permet d'assurer un contrôle de qualité automatique, rapide, précis et complet des outils géométriques des TPS. Les avantages de notre méthode sont nombreux : 1. Les OTN directement conçus et générés en voxels au format DICOM présentent une géométrie « parfaite », non détériorée par une acquisition préalable par le scanner. Ainsi, les tests produits sont plus précis car ils reflètent la qualité intrinsèque du TPS et non pas celle du couple scanner-TPS. 2. Les OTN peuvent être produits beaucoup plus facilement que les fantômes physiques grâce au logiciel OTN-Creator que nous avons développé (logiciel de conception 3D vs. machine outils). Cela nous permet de tester beaucoup plus en profondeur les outils logiciels développés par les TPS en ayant recours à de nombreux OTN. 3.Les résultats des tests sont comparés à des étalons conçus et produits sur la forme d'OTN (OTN de sortie de référence) grâce à l'utilisation d'algorithmes analytiques de référence. Ainsi toutes les données manipulées pour le contrôle de qualité sont numériques (OTN d'entrée, OTN de sortie de référence, résultat du traitement de l'OTN d'entrée par le TPS) ce qui nous permet de déployer de nombreux outils logiciels d'analyse automatique des résultats des contrôles de qualité. Ce procédé permet de réduire de manière importante la durée des opérations de contrôle tout en améliorant leur précision grâce à l'utilisation de méthodes objectives. Deux TPS (Eclipse de Varian et Advantage Sim de GEMS) ont été contrôlés avec la méthode que nous proposons. L'évaluation de leurs performances a révélé quelques erreurs dans le fonctionnement des outils logiciels, et a mis en avant certaines de leurs particularités. Cette mise en œuvre a également été l'occasion de comparer notre méthode de contrôle de qualité basée sur des OTN avec la méthode classique basée sur les objets-tests physiques

Comparison of volumetric-modulated arc therapy and dynamic conformal arc treatment planning for cranial stereotactic radiosurgery

International audienceThe aim was to analyze arc therapy techniques according to the number and position of the brain lesions reported by comparing dynamic noncoplanar conformal arcs (DCA), two coplanar full arcs (RAC) with volumetric-modulated arc therapy (VMAT), multiple noncoplanar partial arcs with VMAT (RANC), and two full arcs with VMAT and 10° table rotation (RAT). Patients with a single lesion (n= 10), multiple lesions (n = 10) or a single lesion close to organs at risk (n = 5) and previously treated with DCA were selected. For each patient, the DCA treatment was replanned with all VMAT techniques. All DCA plans were compared with VMAT plans and evaluated in regard to the different quality indices and dosimetric parameters. For single lesion, homogeneity index (HI) better results were found for the RANC technique (0.17 ± 0.05) compared with DCA procedure (0.27± 0.05). Concerning conformity index (CI), the RAT technique gave higher and better values (0.85 ± 0.04) compared with those obtained with the DCA technique (0.77 ± 0.05). DCA improved healthy brain protection (8.35 ± 5.61 cc vs. 10.52 ± 6.40 cc for RANC) and reduced monitor unit numbers (3046 ± 374 MU vs. 4651 ± 736 for RANC), even if global room occupation was higher. For multiple lesions, VMAT techniques provided better HI (0.16) than DCA (0.24 ± 0.07). The CI was improved with RAT (0.8 ± 0.08 for RAT vs. 0.71 ± 0.08 for DCA). The V10Gy healthy brain was better protected with DCA (9.27 ± 4.57 cc). Regarding the MU numbers: RANC < RAT< RAC < DCA. For a single lesion close to OAR, RAT achieved high degrees of homogeneity (0.27 ± 0.03 vs. 0.53 ± 0.2 for DCA) and conformity (0.72± 0.06vs. 0.56 ± 0.13 for DCA) while sparing organs at risk (Dmax = 12.36 ± 1.05Gyvs. 14.12 ± 0.59 Gy for DCA, and Dmean = 3.96 ± 3.57Gyvs. 4.72 ± 3.28Gy for DCA). On the other hand, MU numbers were lower with DCA (2254 ± 190 MUvs. 3438 ± 457 MU for RANC) even if overall time was inferior with RAC. For a single lesion, DCA provide better plan considering low doses to healthy brain even if quality indexes are better for the others techniques. For multiple lesions, RANC seems to be the best compromise, due to the ability to deliver a good conformity and homogeneity plan while sparing healthy brain tissue. For a single lesion close to organs at risk, RAT is the most appropriate technique

Evaluation of reproducibility of tumor repositioning during multiple breathing cycles for liver stereotactic body radiotherapy treatment

International audienceAIM:To evaluate the tumor repositioning during gated volumetric modulated arc therapy (VMAT) for liver stereotactic body radiotherapy(SBRT) treatment using implanted fiducial markers and intrafraction kilovoltage (kV) images acquired during dose delivery.MATERIALS AND METHODS:Since 2012, 47 liver cancer patients with implanted fiducial markers were treated using the gated VMAT technique with a Varian Truebeam STx linear accelerator. The fiducial markers were implanted inside or close to the tumor target before treatment simulation. They were defined at the maximum inhalation and exhalation phases on a 4-dimensionnal computed tomography (4DCT) acquisition. During the treatment, kV images were acquired just before the beam-on at each breathing cycle at maximum exhalation and inhalation phases to verify the fiducial markers positions. For the five first fractions of treatment in the first ten consecutive patients, a total of 2705 intrafraction kV images were retrospectively analyzed to assess the differences between expected and actual positions of the fiducial markers along the cranio-caudal (CC) direction during the exhalation phase.RESULTS:The mean absolute intrafractional fiducial marker deviation along the CC direction was 1.0 mm at the maximum exhalation phase. In 99%, 95% and 90% cases, the fiducial marker deviations were ≤4.5 mm, 2.8 mm and 2.2 mm, respectively.CONCLUSION:Intrafraction kV images allowed us to ensure the consistency of tumor repositioning during treatment. In 99% cases, the fiducial marker deviations were ≤4.5 mm corresponding to our 5 mm treatment margin. This margin seems to be well-adapted to the gated VMAT SBRT treatment in liver disease

Imaged-guided liver stereotactic body radiotherapy using VMAT and real-time adaptive tumor gating. Concerns about technique and preliminary clinical results

BackgroundMotion management is a major challenge in abdominal SBRT. We present our study of SBRT for liver tumors using intrafraction motion review (IMR) allowing simultaneous KV information and MV delivery to synchronize the beam during gated RapidArc treatment.Materials and methodsBetween May 2012 and March 2015, 41 patients were treated by liver SBRT using gated RapidArc technique in a Varian Novalis Truebeam STx linear accelerator. PTV was created by expanding 5[[ce:hsp sp="0.25"/]]mm from the ITV. Dose prescription ranged from 40 to 50[[ce:hsp sp="0.25"/]]Gy in 5–10 fractions. The prescribed dose and fractionation were chosen depending on hepatic function and dosimetric results. Thirty-four patients with a minimal follow-up of six months were analyzed for local control and toxicity. Accuracy for tumor repositioning was evaluated for the first ten patients.ResultsWith a median follow-up of 13 months, the treatment was well tolerated and no patient presented RILD, perforation or gastrointestinal bleeding. Acute toxicity was found in 3 patients with G1 abdominal pain, 2 with G1 nausea, 10 with G1 asthenia and 1 with G2 asthenia. 6 patients presented asymptomatic transitory perturbation of liver enzymes.In-field local control was 90.3% with 7 complete responses, 14 partial responses and 7 stabilisations. 3 patients evolved “in field”. 12 patients had an intrahepatic progression “out of field”.Mean intrafraction deviation of fiducials in the craneo-caudal direction was 0.91[[ce:hsp sp="0.25"/]]mm (0–6[[ce:hsp sp="0.25"/]]mm).ConclusionThe clinical tolerance and oncological outcomes were favorable when using image-guided liver SBRT with real-time adaptive tumor gating

Imaged-guided liver stereotactic body radiotherapy using VMAT and real-time adaptive tumor gating. Concerns about technique and preliminary clinical results

International audienceBACKGROUND:Motion management is a major challenge in abdominal SBRT. We present our study of SBRT for liver tumors using intrafraction motion review (IMR) allowing simultaneous KV information and MV delivery to synchronize the beam during gated RapidArc treatment.MATERIALS AND METHODS:Between May 2012 and March 2015, 41 patients were treated by liver SBRT using gated RapidArc technique in a Varian Novalis Truebeam STx linear accelerator. PTV was created by expanding 5 mm from the ITV. Dose prescription ranged from 40 to 50 Gy in 5-10 fractions. The prescribed dose and fractionation were chosen depending on hepatic function and dosimetric results. Thirty-four patients with a minimal follow-up of six months were analyzed for local control and toxicity. Accuracy for tumor repositioning was evaluated for the first ten patients.RESULTS:With a median follow-up of 13 months, the treatment was well tolerated and no patient presented RILD, perforation or gastrointestinal bleeding. Acute toxicity was found in 3 patients with G1 abdominal pain, 2 with G1 nausea, 10 with G1 asthenia and 1 with G2 asthenia. 6 patients presented asymptomatic transitory perturbation of liver enzymes. In-field local control was 90.3% with 7 complete responses, 14 partial responses and 7 stabilisations. 3 patients evolved "in field". 12 patients had an intrahepatic progression "out of field". Mean intrafraction deviation of fiducials in the craneo-caudal direction was 0.91 mm (0-6 mm).CONCLUSION:The clinical tolerance and oncological outcomes were favorable when using image-guided liver SBRT with real-time adaptive tumor gating