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The failure mode and effect analysis (FMEA) approach was used to assess the potential risks for patients during the delivery of tomotherapy treatments. This study, which completed a previous investigation recently performed on the tomotherapy pretreatment phases, enabled the delineation of the delivery process tree and the identification of 30 failure modes, 9 of which were judged to be of particular concern. Novel solutions and strategies for dealing with these failures are accordingly proposed, and addressed both to the clinical staff directly involved in the delivery process, and to the machine vendor.

Purpose An increase of skin dose during RT for head-neck (HN) cancer due to anatomy deformation may potentially translate into an increased risk of skin toxicity, suggesting a potential benefit from planning adaptation (ART) to counteract this effect. Current study applied an original method for dose-of-the-day calculation in quantifying changes of skin dose during Tomotherapy for head and neck (HN) cancer in order to identify those patients that could benefit of ART. Methods Planning CTs of 32 patients (SIB: 54/66 Gy, 30 fractions) were deformable registered to MVCT images taken at fraction 15 and 30 using a constrained-intensity-based algorithm. Dose-of-the-day were calculated on the deformed images; this approach was previously validated by comparing dose distributions of deformed CT and diagnostic kVCT of the same day. Superficial body layers (SL) were considered as a surrogate of skin, considering a 2 mm thickness. Skin dose variation during therapy ( Δ SL) in terms of fraction of SL receiving at least 95%–105% of the prescribed PTV dose (66 Gy) were considered. Based on the previous validation, a change ≥ + 1 cc was assessed to define patients that may benefit of ART. Results Δ SL occurred during treatment with individually variable patterns, depending on several factors like the PTV location/dimension/shape/shrinkage. Only 3 patients experienced >1 cc change of SL95%-105% during treatment (maximum variation: 6 cc) while negative Δ SL95%-105% > 1 cc, up to 17 cc, were seen in 15/33 patients. A negative change was correlated with the presence of some overlap between PTV and SL at planning (p = 0.03). Δ SL 95% are shown for all patients in Fig. 1. Download : Download high-res image (301KB) Download : Download full-size image Conclusions Most patients treated with a SIB approach with Tomotherapy for HN cancer showed negative or irrelevant changes to the dose delivered to the skin. Less than 10% of patients seem to be candidate to ART to counteract any significant skin dose increase during therapy.

Purpose To assess the robustness of PET radiomic features (RF) against tumour/PET positive nodes (T/N) delineation uncertainty in two clinically relevant situations, namely head-and-neck (HNC) and pancreatic cancer. Methods Twenty-five HNC (T and N) and 25 pancreatic cancer (only T) patients previously treated with IMRT and 18FDG-PET/CT based planning optimization were included in the study. Seven contours were delineated for each lesion following manual (2 independent observers), semi-automatic (based on SUV_max gradient: PET_edge) and automatic (40%,50%,60%,70% SUV_max thresholds) methods using MIM software(MimVista). For each contour, 71 RF (12 of first and 59 of higher order) were extracted by using the CGITA (v1.4) software. The impact of delineation on volume agreement (DICE-index) and RF was assessed by Intra-class Correlation Coefficients (ICC), considering a threshold of 0.80. Semi-automatic contouring repeatability was also tested. Results A large disagreement between manual and automatic SUV_max method was found for threshold values ⩾50%. Inter-observer variability was moderately high with median DICE values between 0.81 (HN-T) and 0.73 (pancreas). Volumes defined by PET_Edge were in better agreement with the manual ones compared to SUV40%; the repeatability of PET_Edge was excellent (median DICE = 0.95). Regarding RF, 14/14/35 features showed an ICC Conclusions About 80%/50% of 72 RF extracted with the CGITA software were consistent with respect to manual delineation for HN/pancreas patients. PET_edge was sufficiently robust with about 60%/40% of RF consistent with manual delineation while a worse performance was found for SUV40%. This result suggests the possibility to replace manual delineation of HN and pancreas tumours in studies including PET radiomic analyses.

Purpose The aim of this study was to test the feasibility and dosimetric accuracy of a method that employs planning CT-to-MVCT deformable image registration (DIR) for calculation of the daily dose for head and neck (HN) patients treated with Helical Tomotherapy (HT). Methods For each patient, the planning kVCT (CTplan) was deformably registered to the MVCT acquired at the 15th therapy session (MV15) with a B-Spline Free Form algorithm using Mattes mutual information (open-source software 3D Slicer), resulting in a deformed CT (CTdef). On the same day as MVCT15, a kVCT was acquired with the patient in the same treatment position (CT15). The original HT plans were recalculated both on CTdef and CT15, and the corresponding dose distributions were compared; local dose differences

We developed an efficient technique to auto-propagate parotid gland contours from planning kVCT to daily MVCT images of head-and-neck cancer patients treated with helical tomotherapy. The method deformed a 3D surface mesh constructed from manual kVCT contours by B-spline free-form deformation to generate optimal and smooth contours. Deformation was calculated by elastic image registration between kVCT and MVCT images. Data from ten head-and-neck cancer patients were considered and manual contours by three observers were included in both kVCT and MVCT images. A preliminary inter-observer variability analysis demonstrated the importance of contour propagation in tomotherapy application: a high variability was reported in MVCT parotid volume estimation (p = 0.0176, ANOVA test) and a larger uncertainty of MVCT contouring compared with kVCT was demonstrated by DICE and volume variability indices (Wilcoxon signed rank test, p < 10-4 for both indices). The performance analysis of our method showed no significant differences between automatic and manual contours in terms of volumes (p > 0.05, in a multiple comparison Tukey test), center-of-mass distances (p = 0.3043, ANOVA test), DICE values (p = 0.1672, Wilcoxon signed rank test) and average and maximum symmetric distances (p = 0.2043, p = 0.8228 Wilcoxon signed rank tests). Results suggested that our contour propagation method could successfully substitute human contouring on MVCT images. © 2011 Institute of Physics and Engineering in Medicine.

Purpose To develop and apply a stepping validation approach for Knowledge-based (KB) models for planning optimization, starting from the complex and clinically relevant case of the treatment of pelvic nodes and prostate + seminal-vesicles bed in post-prostatectomy patients (pts). Methods Fifty-two VMAT (Varian, RapidArc) plans optimized by two planners (reference of the protocol) were selected to generate KB-model using the RapidPlan tool implemented in the Eclipse system (v.13.5). The DVH prediction model was set on the lower DVH population quartile for each OARs (rectum, bowel, bladder, femurs and penile bulb). A stepping-validation was performed: 20 randomly chosen pts used to generate the model (Closed-loop); 10 new pts, planned by the same two operators (Open-loop); 20 new pts, planned by 4 additional planners (Wide-loop). KB-plans were generated following two modalities: RP + planner intervention (RP) and fully-automatic RP (only-RP). All plans were compared against clinical plans (RA), in terms of dose-volume parameters and generalized equivalent uniform dose (gEUD). Two tails paired t-test was used to assess statistically significant differences. Results KB-based plans were generally better than or equivalent to clinical plans; similar trends could be appreciated without major differences between the three steps. PTVs coverage and homogeneity were comparable (Fig. 1). Concerning OARs, RP was always better with most of the improvements statistically significant; for only-RP, a better average OARs sparing was obtained (few significant differences). Concerning gEUD, RP was significantly better than RA: >1 Gy gEUD reduction was found in 80% of pts for rectum, bladder and bowel. For only-RP vs RA, the average differences were significant for few parameters: however, >1 Gy gEUD reduction was found in 50% of pts for rectum/bladder and in 70% for bowel. Conclusions A comprehensive validation of KB-model showed the possibility of automatically generating high-quality plans; planner interaction further improved performances. The model is going to be introduced in the clinical routine.

Purpose Radiotherapy in brain tumors is associated with several detrimental effects. White-matter (WM) regions are associated with higher radiosensitivity respect to grey-matter but no dose constraints are used [1] . Magnetic Resonance(MR)-Tractography is the only technique that allows to in-vivo visualize WM eloquent tracts adjacent/inside brain tumors [2] . In this work feasibility of MR-Tractography integration in treatment planning is investigated aiming to spare eloquent regions from dose delivered during RT-treatment. Methods 19 patients with high-grade-gliomas underwent MR acquisitions before RT (1.5 T scanner), including structural images and DTI sequence (32 or 15 directions, b-value = 1000 s/mm2) and structural imaging for Target and OAR definition. RT-treatment was delivered with helical tomotherapy. Bilateral tracts considered are: corticospinal tracts (CST), superior-longitudinal fascicle (SLF), inferior fronto-occipital fascicle (IFOF) and uncinate fascicle (UNC). Tracts were then converted in binary masks and then imported in TPS for automatic contouring. The original plans were compared with optimized plans including WM-tracts. Results No significant differences were found for PTV coverage between plans (p = 0.29). Comparing mean-dose and Dmax significant dose reduction for all tracts was found (results for mean-dose are reported in table for contralateral and omolateral-tracts). DVH analyses showed that low doses are reduced for contralateral-tracts and V30 for all tracts except for CST (p = 0.28). For omolateral-tracts significantly reduction was achieved for SLF and IFOF (p Conclusions Integration of MR-Tractography into RT-planning is feasible and beneficial to spare important WM structures without reducing clinical goal of RT-treatment.

Purpose To propose new Quality Indicators (QIs) for the Intensity Modulated(IMRT)/Image-Guided(IGRT) Radiotherapy techniques. Materials and methods Two structure, 10 process and 2 outcome QIs were elaborated. A working group including Radiation Oncologist, Medical Physicist and Radiation Technologists was made up. A preliminary set of indicators was selected on the basis of evidenced critical issues; the criteria to identify more relevant and specific QIs for IMRT/IGRT were defined; structure, process and outcome QIs were defined. The elaborated indicators were tested in four Italian Radiotherapy Centers. Results Fourteen indicators were proposed. Seven indicators were completely new while a new standard is proposed for four indicators based on Validation Centers (VC) data. No change was reported for 3 indicators. The indicators were applied in the four VC. The VC considered were able to respect all indicators except indicator 2 for one Center. Discussion and conclusion QIs may provide useful measures of workload and service performances.