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Extended localization and adaptive dose calculation using HU corrected cone beam CT: Phantom study. | LitMetric

Extended localization and adaptive dose calculation using HU corrected cone beam CT: Phantom study.

Rep Pract Oncol Radiother

Department of Radiotherapy, Christian Medical College, Vellore 632004, Tamil Nadu, India.

Published: February 2018

AI Article Synopsis

  • The study investigates improved dose calculation methods using cone beam CT (CBCT) and Hounsfield unit (HU) corrections to address limitations in the scanning length for localization in clinical settings.
  • Two stitching strategies for extending CBCT scanning were implemented, leading to a significant increase in localizing length by up to 16 cm while maintaining accuracy in treatment plans and dosimetric analyses.
  • Results indicated high agreement in dosimetric evaluations, with pass rates over 98.5% in gamma evaluations, suggesting the adapted strategies provide reliable localization and dose calculation for patient treatment planning.

Article Abstract

Background And Aim: The practicability of computing dose calculation on cone beam CT (CBCT) has been widely investigated. In most clinical scenarios, the craniocaudal scanning length of CBCT is found to be inadequate for localization. This study aims to explore extended tomographic localization and adaptive dose calculation strategies using Hounsfield unit (HU) corrected CBCT image sets.

Materials And Methods: Planning CT (pCT) images of the Rando phantom (T-to-midthigh) were acquired with pelvic-protocol using Biograph CT-scanner. Similarly, half-fan CBCT were acquired with fixed parameters using Clinac2100C/D linear accelerator integrated with an on-board imager with 2-longitudinal positions of the table. For extended localization and dose calculation, two stitching strategies viz., one with "penumbral-overlap" (S) and the other with "no-overlap" (S) and a local HU-correction technique were performed using custom-developed MATLAB scripts. Fluence modulated treatment plans computed on pCT were mapped with stitched CBCT and the dosimetric analyses such as dose-profile comparison, 3D-gamma (γ) evaluation and dose-volume histogram (DVH) comparison were performed.

Results: Localizing scanning length of CBCT was extended by up to 15 cm and 16 cm in S and S strategies, respectively. Treatment plan mapping resulted in minor variations in the volumes of delineated structures and the beam centre co-ordinates. While the former showed maximum variations of -1.4% and -1.6%, the latter showed maximum of 1.4 mm and 2.7 mm differences in anteroposterior direction in S and S protocols, respectively. Dosimetric evaluations viz., dose profile and DVH comparisons were found to be in agreement with one another. In addition, γ-evaluation results showed superior pass-rates (≥98.5%) for both 3%/3 mm dose-difference (DD) and distance-to-agreement (DTA) and 2%/2 mm DD/DTA criteria with desirable dosimetric accuracy.

Conclusion: Cone beam tomographic stitching and local HU-correction strategies developed to facilitate extended localization and dose calculation enables routine adaptive re-planning while circumventing the need for repeated pCT.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5856675PMC
http://dx.doi.org/10.1016/j.rpor.2018.01.005DOI Listing

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