Dataset Information

Online dosimetric evaluation of larynx SBRT: A pilot study to assess the necessity of adaptive replanning.

ABSTRACT: We have initiated a multi-institutional phase I trial of 5-fraction stereotactic body radiotherapy (SBRT) for Stage III-IVa laryngeal cancer. We conducted this pilot dosimetric study to confirm potential utility of online adaptive replanning to preserve treatment quality.We evaluated ten cases: five patients enrolled onto the current trial and five patients enrolled onto a separate phase I SBRT trial for early-stage glottic larynx cancer. Baseline SBRT treatment plans were generated per protocol. Daily cone-beam CT (CBCT) or diagnostic CT images were acquired prior to each treatment fraction. Simulation CT images and target volumes were deformably registered to daily volumetric images, the original SBRT plan was copied to the deformed images and contours, delivered dose distributions were re-calculated on the deformed CT images. All of these were performed on a commercial treatment planning system. In-house software was developed to propagate the delivered dose distribution back to reference CT images using the deformation information exported from the treatment planning system. Dosimetric differences were evaluated via dose-volume histograms.We could evaluate dose within 10 minutes in all cases. Prescribed coverage to gross tumor volume (GTV) and clinical target volume (CTV) was uniformly preserved; however, intended prescription dose coverage of planning treatment volume (PTV) was lost in 53% of daily treatments (mean: 93.9%, range: 83.9-97.9%). Maximum bystander point dose limits to arytenoids, parotids, and spinal cord remained respected in all cases, although variances in carotid artery doses were observed in a minority of cases.Although GTV and CTV SBRT dose coverage is preserved with in-room three-dimensional image guidance, PTV coverage can vary significantly from intended plans and dose to critical structures may exceed tolerances. Online adaptive treatment re-planning is potentially necessary and clinically applicable to fully preserve treatment quality. Confirmatory trial accrual and analysis remains ongoing.

SUBMITTER: Mao W

PROVIDER: S-EPMC5689891 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Online dosimetric evaluation of larynx SBRT: A pilot study to assess the necessity of adaptive replanning.

Mao Weihua W Rozario Timothy T Lu Weiguo W Gu Xuejun X Yan Yulong Y Jia Xun X Sumer Baran B Schwartz David L DL

Journal of applied clinical medical physics 20161222 1

<h4>Purpose</h4>We have initiated a multi-institutional phase I trial of 5-fraction stereotactic body radiotherapy (SBRT) for Stage III-IVa laryngeal cancer. We conducted this pilot dosimetric study to confirm potential utility of online adaptive replanning to preserve treatment quality.<h4>Methods</h4>We evaluated ten cases: five patients enrolled onto the current trial and five patients enrolled onto a separate phase I SBRT trial for early-stage glottic larynx cancer. Baseline SBRT treatment p ...[more]

PMID: 28291932

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Project description:Purpose: The purpose of this work was to propose an online replanning algorithm, named intensity field projection (IFP), that directly adjusts intensity distributions for each beam based on the deformation of structures. IFP can be implemented within a reasonably acceptable time frame. Methods and Materials: The online replanning method is based on the gradient-based free form deformation (GFFD) algorithm, which we have previously proposed. The method involves the following steps: The planning computed tomography (CT) and cone-beam CT image are registered to generate a three-dimensional (3-D) deformation field. According to the 3-D deformation field, the registered image and a new delineation are generated. The two-dimensional (2-D) deformation field of ray intensity in each beam direction is determined based on the 3-D deformation field in the region of interest. The 2-D ray intensity distribution in the corresponding beam direction is deformed to generate a new 2-D ray intensity distribution. According to the new 2-D ray intensity distribution, corresponding multi-leaf collimator (MLC), and jaw motion data are generated. The feasibility and advantages of our method have been demonstrated in 20 lung cancer intensity modulated radiation therapy (IMRT) cases. Results: Substantial underdosing in the CTV is seen in the original and the repositioning plans. The average prescription dose coverage (V100%) and D95 for CTV were 100% and 60.3 Gy for the IFP plans compared to 82.6% (P < 0.01) and 44.0 Gy (P < 0.01) for original plans, 86.7% (P < 0.01), and 58.5 Gy (P < 0.01) for repositioning plans. On average, the mean total lung doses were 12.2 Gy for the IFP plan compared to the 12.4 Gy (P < 0.01) and 12.6 Gy (P < 0.01) for the original and the repositioning plans. The entire process of IFP can be completed within 3 min. Conclusions: We proposed an online replanning strategy for automatically correcting interfractional anatomy variations. The preliminary results indicate that the IFP method substantially increased planning speed for online adaptive replanning.

Project description:The Radiation Therapy Oncology Group (RTOG) 0813 protocol requires the use of dose calculation algorithms with tissue heterogeneity corrections to compute dose on stereotactic body radiation therapy (SBRT) non-small cell lung cancer (NSCLC) plans. A new photon dose calculation algorithm called Acuros XB (AXB) has recently been implemented in the Eclipse treatment planning system (TPS). The main purpose of this study was to compare the dosimetric results of AXB with that of anisotropic analytical algorithm (AAA) for RTOG 0813 parameters. Additionally, phantom study was done to evaluate the dose prediction accuracy of AXB and AAA beyond low-density medium of different thicknesses by comparing the calculated results with the measurements. For the RTOG dosimetric study, 14 clinically approved SBRT NSCLC cases were included. The planning target volume (PTV) ranged from 3.2-43.0 cc. RapidArc treatment plans were generated in the Eclipse TPS following RTOG 0813 dosimetric criteria, and treatment plans were calculated using AAA with heterogeneity correction (AAA plans). All the AAA plans were then recalculated using AXB with heterogeneity correction (AXB plans) for identical beam parameters and same number of monitor units. The AAA and AXB plans were compared for following RTOG 0813 parameters: ratio of prescription isodose volume to PTV (R100%), ratio of 50% prescription isodose volume to PTV (R50%), maximal dose 2 cm from the PTV in any direction as a percentage of prescription dose (D2cm), and the percentage of ipsilateral lung receiving dose equal to or larger than 20 Gy (V20). The phantom study showed that the results of AXB had better agreement with the measurements, and the difference ranged from -1.7% to 2.8%. The AAA results showed larger disagreement with the measurements, with differences from 4.1% to 12.5% for field size 5 × 5cm2 and from 1.4% to 6.8% for field size 10 × 10 cm2. The results from the RTOG SBRT lung cases showed that, on average, the AXB plans produced lower values for R100%, R50%, and D2cm by 4.96%, 1.15%, and 1.60%, respectively, but higher V20 of ipsilateral lung by 1.09% when compared with AAA plans. In the set of AAA plans, minor deviation was seen for R100% (six cases), R50% (nine cases), D2cm (four cases), and V20 (one case). Similarly, the AXB plans also showed minor deviation for R100% (one case), R50% (eight cases), D2cm (three cases), and V20 (one case). The dosimetric results presented in the current study show that both the AXB and AAA can meet the RTOG 0813 dosimetric criteria.

Project description:Purpose/objectivesRetrospective analysis suggests that dose escalation to a biologically effective dose of more than 70 Gy may improve overall survival in patients with pancreatic ductal adenocarcinoma (PDAC), but such treatments in practice are limited by proximity of organs at risk (OARs). We hypothesized that CT-guided online adaptive radiotherapy (OART) can account for interfraction movement of OARs and allow for safe delivery of ablative doses.Materials/methodsThis is a single institution retrospective analysis of patients with PDAC treated with OART on the Ethos platform (Varian Medical Systems, a Siemens Healthineers Company, Palo Alto). All patients were treated to 40 Gy in 5 fractions. PTV overlapping with a 5 mm planning risk volume expansion on the stomach, duodenum and bowel received 25 Gy. Initial treatment plans were created conventionally. For each fraction, PTV and OAR volumes were recontoured with AI assistance after initial cone beam CT (CBCT). The adapted plan was calculated, underwent QA, and then compared to the scheduled plan. A second CBCT was obtained prior to delivery of the selected plan. Total treatment time (first CBCT to end of radiation delivery) and active physician time (first to second CBCT) were recorded. PTV_4000 V95 %, PTV_2500 V9 5%, and D0.03 cc to stomach, duodenum and bowel were reported for scheduled (S) and adapted (A) plans. CTCAEv5.0 toxicities were recorded. Statistical analysis was performed using a two-sided T test and α of 0.05.Results21 patients with unresectable or locally-recurrent PDAC were analyzed, with a total of 105 fractions. Average total time was 29 min and 16 s (16:36-49:40) and average active physician time was 19:41 min (9:25-39:34). All fractions were treated with adapted plans. 97 % of adapted plans met PTV_4000 V95.0 % >95.0 % coverage goal and 100 % of adapted plans met OAR dose constraints. Median follow up was 6.6 months. Only 1 patient experienced acute grade 3+ toxicity directly attributable to radiation. Only 1 patient experienced late grade 3+ toxicity directly attributable to radiation.ConclusionsDaily CT-based OART was associated with significantly reduced dose OARs while achieving superior PTV coverage. Given the relatively quick total treatment time, radiation delivery was generally well tolerated and easily incorporated into the clinic workflow. Our initial clinical experience demonstrates OART allows for safe dose escalation in the treatment of PDAC.

Project description:PurposeMotion often hinders the safe delivery of ablative doses of radiation in the treatment of pancreatic tumors. Real-time tumor-tracking methods are an emerging technique to increase the accuracy of delivery. In this study, we report on a large, retrospective cohort of pancreatic patients treated with real-time, fiducial-based, kV-image guidance of stereotactic body radiation therapy (SBRT). The purpose of our study was to determine the impact of real-time tracking on treatment accuracy, tumor dose, and clinical workflow.Methods and materialsReal-time tracking data from 68 patients treated with pancreatic SBRT were analyzed. The kV images orthogonal to the treatment beam were acquired in real time during treatment to visualize the location of implanted fiducial markers. Positional corrections were made if the fiducial markers were observed >3 mm from the expected reference position. We recorded the frequency and nature of treatment interventions resulting from real-time tracking and derived a neural network-based dosimetric model to calculate the impact of these in-treatment interventions on target dose.ResultsTreatment pauses that required patient realignment because of real-time tumor tracking occurred during 32% of all fractions. The median magnitude of realignment shifts was 5.2 mm (range, 2.1-18.9 mm). Forty-five percent of shifts resulted in dosimetric differences to the tumor; of these, the median point dose difference was 23% ± 22% of prescription dose (maximum, 94%). The number of pauses per fraction was significantly higher in patients treated with respiratory gating (vs abdominal compression) and in patients with greater treatment time.ConclusionFiducial-based, real-time target tracking is clinically feasible for pancreatic SBRT treatment. Our data indicate that real-time tumor tracking leads to patient realignment in 32% of cases and results in significant benefits to target coverage. The increased accuracy of real-time target tracking may potentially enable safe dose escalation in pancreatic SBRT.

Project description:Stereotactic body radiotherapy (SBRT) is currently well-adopted as a curative treatment for primary and metastatic liver tumors. Among SBRT methods, dynamic conformal arc therapy (DCAT) and volumetric-modulated arc therapy (VMAT) are the most preferred methods. In this study, we report a comparison study measuring the dose distribution and delivery efficiency differences between DCAT and VMAT for liver SBRT. All patients who were treated with SBRT for primary or metastatic liver tumors with a curative aim between January 2016 and December 2017 at DIRAMS were enrolled in the study. For all patients, SBRT plans were designed using the Monte Carlo (MC) algorithm in Monaco treatment planning system (version 5.1). The planning goals were set according to the RTOG 0813, RTOG 0915, and RTOG 1112 protocols. A plan comparison was made on the metrics of dose volume histogram, planning and delivery efficiency, monitor unit (MU), and dosimetric indices. PTV coverage was evaluated using the following: Dmean, D95%, D98%, D2%, D50%, Dmax, V95%, heterogeneity index (HI), and conformality index (CI). For DCAT and VMAT, respectively, the Dmean was 5942.8 ± 409.3 cGy and 5890.6 ± 438.8 cGy, D50% was 5968.8 ± 413.1 cGy and 5954.3 ± 405.2 cGy, and CI was 1.05 ± 0.05 and 1.03 ± 0.04. The D98% and V95% were 5580.0 ± 465.3 cGy and 20.4 ± 12.0 mL for DCAT, and 5596.0 ± 478.7 cGy and 20.5 ± 12.0 mL for VMAT, respectively. For normal liver, V40, V30, V20, V17, V5, Dmean, Dmax were evaluated for comparison. The V30, V20, and V10 were significantly higher in DCAT; other parameters of normal livers showed no statistically significant differences. For evaluation of intermediate dose spillage, D2cm(%) and R50% of DCAT and VMAT were 45.8 ± 7.9 and 5.6 ± 0.9 and 45.1 ± 6.7 and 5.5 ± 1.2, respectively. Planning and delivery efficiency were evaluated using MU, Calculation time, and Delivery time. DCAT had shorter Calculation time and Delivery time with smaller MU. MU was smaller in DCAT and the average difference was 300.1 MU. For liver SBRT, DCAT is an effective alternative to VMAT plans that could meet the planning goals proposed by the RTOG SBRT protocol and increases plan and delivery effectiveness, while also ignoring the interplay effect.

Dataset Information

Online dosimetric evaluation of larynx SBRT: A pilot study to assess the necessity of adaptive replanning.

Publications

Online dosimetric evaluation of larynx SBRT: A pilot study to assess the necessity of adaptive replanning.

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