SU-E-J-151: Dosimetric Evaluation of DIR Mapped Contours for Image Guided Adaptive Radiotherapy with 4D Cone-Beam CT

S Balik; E Weiss; J Williamson; G Hugo; N Jan; L Zhang; N Roman; G Christensen

doi:10.1118/1.4888204

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SU-E-J-151: Dosimetric Evaluation of DIR Mapped Contours for Image Guided Adaptive Radiotherapy with 4D Cone-Beam CT

Abstract

Peer reviewed

SU-E-J-151: Dosimetric Evaluation of DIR Mapped Contours for Image Guided Adaptive Radiotherapy with 4D Cone-Beam CT

S Balik, E Weiss, J Williamson, G Hugo, N Jan, L Zhang, N Roman and G Christensen

Medical physics (Lancaster), Vol.41(6), pp.191-191

06/01/2014

DOI: 10.1118/1.4888204

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Abstract

Purpose: To estimate dosimetric errors resulting from using contours deformably mapped from planning CT to 4D cone beam CT (CBCT) images for image-guided adaptive radiotherapy of locally advanced non-small cell lung cancer (NSCLC). Methods: Ten locally advanced non-small cell lung cancer (NSCLC) patients underwent one planning 4D fan-beam CT (4DFBCT) and weekly 4DCBCT scans. Multiple physicians delineated the gross tumor volume (GTV) and normal structures in planning CT images and only GTV in CBCT images. Manual contours were mapped from planning CT to CBCTs using small deformation, inverse consistent linear elastic (SICLE) algorithm for two scans in each patient. Two physicians reviewed and rated the DIR-mapped (auto) and manual GTV contours as clinically acceptable (CA), clinically acceptable after minor modification (CAMM) and unacceptable (CU). Mapped normal structures were visually inspected and corrected if necessary, and used to override tissue density for dose calculation. CTV (6mm expansion of GTV) and PTV (5mm expansion of CTV) were created. VMAT plans were generated using the DIR-mapped contours to deliver 66 Gy in 33 fractions with 95% and 100% coverage (V66) to PTV and CTV, respectively. Plan evaluation for V66 was based on manual PTV and CTV contours. Results: Mean PTV V66 was 84% (range 75% – 95%) and mean CTV V66 was 97% (range 93% – 100%) for CAMM scored plans (12 plans); and was 90% (range 80% – 95%) and 99% (range 95% – 100%) for CA scored plans (7 plans). The difference in V66 between CAMM and CA was significant for PTV (p = 0.03) and approached significance for CTV (p = 0.07). Conclusion: The quality of DIR-mapped contours directly impacted the plan quality for 4DCBCT-based adaptation. Larger safety margins may be needed when planning with auto contours for IGART with 4DCBCT images. Reseach was supported by NIH P01CA116602.

60 APPLIED LIFE SCIENCES

ALGORITHMS

ANIMAL TISSUES

BEAMS

CAT SCANNING

CONES

ERRORS

EVALUATION

IMAGES

LUNGS

MANUALS

MODIFICATIONS

NEOPLASMS

PATIENTS

PLANNING

PLANT TISSUES

RADIOLOGY AND NUCLEAR MEDICINE

RADIOTHERAPY

REVIEWS

SAFETY MARGINS

Details

Title: Subtitle: SU-E-J-151: Dosimetric Evaluation of DIR Mapped Contours for Image Guided Adaptive Radiotherapy with 4D Cone-Beam CT
Creators: S Balik - Cleveland Clinic
E Weiss - Virginia Commonwealth University
J Williamson - Virginia Commonwealth University
G Hugo - Virginia Commonwealth University
N Jan - Virginia Commonwealth University
L Zhang - Virginia Commonwealth University
N Roman - San Antonio Precision Center Ctr, San Antonio, TX
G Christensen - University of Iowa
Resource Type: Abstract
Publication Details: Medical physics (Lancaster), Vol.41(6), pp.191-191
DOI: 10.1118/1.4888204
ISSN: 0094-2405
eISSN: 2473-4209
Language: English
Date published: 06/01/2014
Academic Unit: Electrical and Computer Engineering; Iowa Technology Institute; Radiation Oncology; Radiation Research Laboratory; The Iowa Institute for Biomedical Imaging; Advanced Pulmonary Physiomic Imaging Laboratory; Holden Comprehensive Cancer Center
Record Identifier: 9984197923102771

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