Purpose To describe in detail a dataset consisting of longitudinal fan‐beam computed tomography (CT) imaging to visualize anatomical changes in head‐and‐neck squamous cell carcinoma (HNSCC) patients throughout radiotherapy (RT) treatment course. Acquisition and validation methods This dataset consists of CT images from 31 HNSCC patients who underwent volumetric modulated arc therapy (VMAT). Patients had three CT scans acquired throughout the duration of the radiation treatment course. Pretreatment planning CT scans with a median of 13 days before treatment (range: 2–27), mid‐treatment CT at 22 days after start of treatment (range: 13–38), and post‐treatment CT 65 days after start of treatment (range: 35–192). Patients received RT treatment to a total dose of 58–70 Gy, using daily 2.0–2.20 Gy, fractions for 30–35 fractions. The fan‐beam CT images were acquired using a Siemens 16‐slice CT scanner head protocol with 120 kV and current of 400 mAs. A helical scan with 1 rotation per second was used with a slice thickness of 2 mm and table increment of 1.2 mm. In addition to the imaging data, contours of anatomical structures for RT, demographic, and outcome measurements are provided. Data format and usage notes The dataset with DICOM files including images, RTSTRUCT files, and RTDOSE files can be found and publicly accessed in the Cancer Imaging Archive (TCIA, http://www.cancerimagingarchive.net/) as collection Head‐and‐neck squamous cell carcinoma patients with CT taken during pretreatment, mid‐treatment, and post‐treatment (HNSCC‐3DCT‐RT). Discussion This is the first dataset to date in TCIA which provides a collection of multiple CT imaging studies (pretreatment, mid‐treatment, and post‐treatment) throughout the treatment course. The dataset can serve a wide array of research projects including (but not limited to): quantitative imaging assessment, investigation on anatomical changes with treatment progress, dosimetry of target volumes and/or normal structures due to anatomical changes occurring during treatment, investigation of RT toxicity, and concurrent chemotherapy and RT effects on head‐and‐neck patients.
Purpose:The aim of this study is to compare the effects of dose rate on volumetric-modulated arc therapy plans to determine optimal dose rates for prostate and head and neck (HN) cases.Materials and Methods:Ten prostate and ten HN cases were retrospectively studied. For each case, seven plans were generated: one variable dose rate (VDR) and six constant dose rate (CDR) (100–600 monitor units [MUs]/min) plans. Prescription doses were: 80 Gy to planning target volume (PTV) for the prostate cases, and 70, 60, and 54 Gy to PTV1, PTV2, and PTV3, respectively, for HN cases. Plans were normalized to 95% of the PTV and PTV1, respectively, with the prescription dose. Plans were assessed using Dose-Volume-Histogram metrics, homogeneity index, conformity index, MUs, and delivery time.Results:For the prostate cases, significant differences were found for rectum D35 between VDR and all CDR plans, except CDR500. Furthermore, VDR was significantly different than CDR100 and 200 for bladder D50. Delivery time for all CDR plans and MUs for CDR400–600 were significantly higher when compared to VDR. HN cases showed significant differences between VDR and CDR100, 500 and 600 for D2 to the cord and brainstem. Significant differences were found for delivery time and MUs for all CDR plans, except CDR100 for number of MUs.Conclusion:The most significant differences were observed in delivery time and number of MUs. All-in-all, the best CDR for prostate cases was found to be 300 MUs/min and 200 or 300 MUs/min for HN cases. However, VDR plans are still the choice in terms of MU efficiency and plan quality.
Purpose: Stereotactic body radiotherapy (SBRT) is used for spine treatments as it precisely delivers high radiation dose to tumors in close proximity to organs-at-risk (OARs). The goal of this work is to evaluate dosimetric properties of SBRT for spinal treatments with linear accelerators and CyberKnife (CK). Materials and methods: Plans of 27 patients, treated with CK for spine tumors, were also retrospectively optimized for linac-based (LB) intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). One nine-field IMRT plan and five VMAT plans were generated for each patient. The LB target volumes were uniformly expanded by 0.1 cm to accommodate for the uncertainty in patient positioning. All plans were optimized to cover 90% of the target volumes with a prescription dose of 27 Gy in three fractions. If dose constraints to OARs were not met, the prescription dose was decreased to 24 Gy. Target dose conformity and falloff were evaluated with Paddick's conformity (CI) and gradient (GI) indices. Results: PTV expansion resulted in a 31.5% volume increase in the LB plans. The three full-arcs VMAT (VMAT_3full) plans resulted in the best average CI(0.820) compared to CK(0.758) with worst average from one half-arcs VMAT (VMAT_1half) plans (0.747). Dose falloff was also superior with the VMAT_3full plans with an average GI value of 3.596, in comparison to CK(3.786) and IMRT(4.447). In 6 cases CK plans were unable to meet OAR constraints and the prescription dose was decreased to 24 Gy, compared to only 2 for VMAT_3full. Conclusion: Regardless of the larger target volumes, LB plans were comparable to CK plans. Conformity of target doses of the VMAT_3full plans were better than CK in all cases and dose fall-off was better 23 of 27 plans. Dose to OARs were lower for CK, but constraints met for all plans. The use of VMAT would reduce the treatment time.
Purpose: To explore the effects of dose‐volume (Dvh) and dose‐mass (Dmh) inverse optimization approaches on the lung ventilation for SBRT in NSCLC. Methods: Six cases were studied. For each case ventilation was computed on voxel‐by‐voxel basis, derived from the time‐resolved (4D) CT scans. Ventilation is defined as voxel volume change between full inspiration and full expiration, divided by voxel volume. The ventilation volume was mapped to full expiration phase. For each patient case two IMRT plans were created ‐ one with Dvh and one with Dmh quadratic objective function, applied to the OARs. The OARs used as dose limiting structures were lung, spinal cord, esophagus, and heart. After obtaining the IMRT solutions average doses as well as 2000 cGy isovolumes and isomases were extracted for ventilation volumes of 0.5, 0.9, 1.1, 1.2, and 1.5. Ventilation volume of 0.5 incorporates all CT voxels having a voxel volume change (exhale‐to‐inhale) 50% and more. Similarly, ventilation volume of 1.5 encompasses all CT voxels with volume change of 150% and more. Thereby, ventilation volume of 0.5 encompasses almost the entire lung, while ventilation volume of 1.5 represents ∼1% of ventilation 0.5 volume. The doses, the isovolumes, and the isomasses derived from the Dvh optimization were used as references. Results: The results indicate that with decreasing ventilation (from 1.5 to 0.5) the differences between Dvh and Dmh derived tallied quantities decrease. For some cases the differences between the average doses for the different ventilation volumes are up to 20%. The changes in the isovolumes and the isomasses for the different ventilations are much more dramatic and can differ by a factor of 3.5. Conclusion: This is the first investigation on the effects of different optimization schemes on lung ventilation. The presented results indicate that the larger the ventilation the more dramatic the effects. Supported in part by NIH R01 CA163360
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