SU-E-J-270: Study of PET Response to HDR Brachytherapy of Rectal Cancer

Journal Article · Sun Jun 01 04:00:00 EDT 2014 · Medical Physics

DOI:https://doi.org/10.1118/1.4888324· OSTI ID:22339949

Hobbs, R; Le, Y; Armour, E; Efron, J; Azad, N; Wahl, R; Gearhart, S; Herman, J ^[1]

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1. Johns Hopkins University, Baltimore, MD (United States)

Purpose: Dose-response studies in radiation therapy are typically using single response values for tumors across ensembles of tumors. Using the high dose rate (HDR) treatment plan dose grid and pre- and post-therapy FDG-PET images, we look for correlations between voxelized dose and FDG uptake response in individual tumors. Methods: Fifteen patients were treated for localized rectal cancer using 192Ir HDR brachytherapy in conjunction with surgery. FDG-PET images were acquired before HDR therapy and 6–8 weeks after treatment (prior to surgery). Treatment planning was done on a commercial workstation and the dose grid was calculated. The two PETs and the treatment dose grid were registered to each other using non-rigid registration. The difference in PET SUV values before and after HDR was plotted versus absorbed radiation dose for each voxel. The voxels were then separated into bins for every 400 cGy of absorbed dose and the bin average values plotted similarly. Results: Individual voxel doses did not correlate with PET response; however, when group into tumor subregions corresponding to dose bins, eighty percent of the patients showed a significant positive correlation (R2 > 0) between PET uptake difference in the targeted region and the absorbed dose. Conclusion: By considering larger ensembles of voxels, such as organ average absorbed dose or the dose bins considered here, valuable information may be obtained. The dose-response correlations as measured by FDG-PET difference potentially underlines the importance of FDG-PET as a measure of response, as well as the value of voxelized information.

• OSTI ID: 22339949
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 6 Vol. 41; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
ABSORBED RADIATION DOSES
BRACHYTHERAPY
DOSE RATES
IMAGES
NEOPLASMS
PATIENTS
PLANNING
POSITRON COMPUTED TOMOGRAPHY
RECTUM
SURGERY
UPTAKE