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Four-dimensional planning for motion synchronized dose delivery in lung stereotactic body radiation therapy.

ABSTRACT: To investigate a weighted four-dimensional (W-4D) treatment planning strategy based on the greater clinical advantage of the conformal over the intensity-modulated technique in lung stereotactic body radiotherapy (SBRT).Two planning strategies (individual-phase 4D [IP-4D] and W-4D) were evaluated in eighteen lung SBRT patients. The IP-4D plan can deliver a constant fluence during whole respiratory phases. The W-4D plan's key concept was to escalate (or reduce) fluence using a 4D optimization algorithm when the tumour target was out-of-line (or in-line) with an organ-at-risk. The fluence was converted to a dynamic multi-leaf collimator leaf sequence for deliverable 4D irradiation.In all patients, the W-4D plan enabled planning tumour volume conformity comparable to the IP-4D plan. The W-4D plan yielded a significantly lower maximum dose than the IP-4D plan for the spinal cord (-11%; p<0.01), oesophagus (-14%; p<0.01), heart (-22%; p=0.01) and stomach (-23%; p=0.07), and a lower mean dose to liver (-19%; p=0.18) while maintaining the mean dose to lung (-1%; p=0.23).W-4D is a robust, practical planning approach that achieves significant dose sparing relative to non-time-resolved tracking; it may be of greater clinical benefit in radiotherapy than the spatially intensity-modulated 4D approach.

SUBMITTER: Tachibana H

PROVIDER: S-EPMC5201122 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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Four-dimensional planning for motion synchronized dose delivery in lung stereotactic body radiation therapy.

Tachibana Hidenobu H Sawant Amit A

Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology 20160430 3

<h4>Background and purpose</h4>To investigate a weighted four-dimensional (W-4D) treatment planning strategy based on the greater clinical advantage of the conformal over the intensity-modulated technique in lung stereotactic body radiotherapy (SBRT).<h4>Material and methods</h4>Two planning strategies (individual-phase 4D [IP-4D] and W-4D) were evaluated in eighteen lung SBRT patients. The IP-4D plan can deliver a constant fluence during whole respiratory phases. The W-4D plan's key concept was ...[more]

PMID: 27143560

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Project description:PurposeWe present a rapid computational method for quantifying interfraction motion of the esophagus in patients undergoing stereotactic body radiation therapy on a magnetic resonance (MR) guided radiation therapy system.Methods and materialsPatients who underwent stereotactic body radiation therapy had simulation computed tomography (CT) and on-treatment MR scans performed. The esophagus was contoured on each scan. CT contours were transferred to MR volumes via rigid registration. Digital Imaging and Communications in Medicine files containing contour points were exported to MATLAB. In-plane CT and MR contour points were spline interpolated, yielding boundaries with centroid positions, CCT and CMR. MR contour points lying outside of the CT contour were extracted. For each such point, BMR(j), a segment from CCT intersecting BMR(j), was produced; its intersection with the CT contour, BCT(i), was calculated. The length of the segment Sij, between BCT(i) and BMR(j), was found. The orientation ? was calculated from Sij vector components:??=?arctan[(Sij)y / (Sij)x]A set of segments {Sij} was produced for each slice and binned by quadrant with 0°?<?????90°, 90°?<?????180°, 180°?<?????270°, and 270°?<?????360° for the left anterior, right anterior, right posterior, and left posterior quadrants, respectively. Slices were binned into upper, middle, and lower esophageal (LE) segments.ResultsSeven patients, each having 3 MR scans, were evaluated, yielding 1629 axial slices and 84,716 measurements. The LE segment exhibited the greatest magnitude of motion. The mean LE measurements in the left anterior, left posterior, right anterior, and right posterior were 5.2?±?0.07?mm, 6.0?±?0.09?mm, 4.8?±?0.08?mm, and 5.1?±?0.08?mm, respectively. There was considerable interpatient variability.ConclusionsThe LE segment exhibited the greatest magnitude of mobility compared with the middle and upper esophageal segments. A novel computational method enables personalized, nonuniform esophageal margins to be tailored to individual patients.

Project description:PurposeSelective internal radiation therapy (SIRT) is administered to treat tumors of the liver and is generally well tolerated. Although widely adopted for its therapeutic benefits, SIRT is rarely combined with external beam radiation therapy (EBRT) owing to the complexity of the dosimetry resulting from the combination of treatments with distinct radiobiological effects. The purpose of this study was to establish a dosimetric framework for combining SIRT and EBRT using clinical experience derived from representative patients with hepatocellular carcinoma (HCC) who received both therapies.Methods and materialsTreatments from 10 patients with HCC given EBRT either before or after SIRT were analyzed. The dosimetry framework used here considered differences in the radiobiological effects and fractionation schemes of SIRT versus EBRT, making use of the concepts of biological effective dose (BED) and equivalent dose (EQD). Absorbed dose from SIRT was calculated, converted to BED, and summed with BED from EBRT dose plans. Two of these patients were used in a virtual planning exercise to investigate the feasibility of combining stereotactic body radiation therapy and SIRT.ResultsThe combination of EBRT and SIRT in 10 patients with HCC showed no major toxicity. No Child-Pugh scores went above 8 and albumin-bilirubin scores from only 1 patient worsened to grade 3 (> -1.39) from treatment through 3-months follow-up. A framework with radiobiological modeling was developed to manage the combined treatments in terms of their sum BED. The exploratory SIRT plus SABR inverse dose plans for 2 patients, incorporating radiobiologically informed 90Y SIRT dosimetry, achieved dose distributions comparable to SBRT alone.ConclusionsTreatment with both EBRT and SIRT can be given safely to patients with HCC. The BED and EQD concepts should be used in combined dosimetry to account for the differing radiobiological effects of EBRT and SIRT. Inverse dose planning of EBRT after SIRT could provide improved dose distributions and flexibility to the clinical workflow. Further research into combination therapy is needed through prospective trials.

Dataset Information

Four-dimensional planning for motion synchronized dose delivery in lung stereotactic body radiation therapy.

Publications

Four-dimensional planning for motion synchronized dose delivery in lung stereotactic body radiation therapy.

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