Biological Image-Guided Radiotherapy in Rectal Cancer: Challenges and Pitfalls
- Department of Radiation Oncology, Leuven Cancer Institute, University Hospital Leuven, Leuven (Belgium)
- Medical Image Computing, ESAT/Radiology, Medical Imaging Center, Catholic University Leuven, Leuven (Belgium)
- Department of Nuclear Medicine, University Hospital Leuven, Leuven (Belgium)
- Center for Molecular Imaging and Experimental Radiotherapy, Universite Catholique de Louvain, Brussels (Belgium)
- Department of Radiology, University Hospital Leuven, Leuven (Belgium)
- Department of Pathology, University Hospital Leuven, Leuven (Belgium)
- Department of Abdominal Surgery, University Hospital Leuven, Leuven (Belgium)
Purpose: To investigate the feasibility of integrating multiple imaging modalities for image-guided radiotherapy in rectal cancer. Patients and Methods: Magnetic resonance imaging (MRI) and fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) were performed before, during, and after preoperative chemoradiotherapy (CRT) in patients with resectable rectal cancer. The FDG-PET signals were segmented with an adaptive threshold-based and a gradient-based method. Magnetic resonance tumor volumes (TVs) were manually delineated. A nonrigid registration algorithm was applied to register the images, and mismatch analyses were carried out between MR and FDG-PET TVs and between TVs over time. Tumor volumes delineated on the images after CRT were compared with the pathologic TV. Results: Forty-five FDG-PET/CT and 45 MR images were analyzed from 15 patients. The mean MRI and FDG-PET TVs showed a tendency to shrink during and after CRT. In general, MRI showed larger TVs than FDG-PET. There was an approximately 50% mismatch between the FDG-PET TV and the MRI TV at baseline and during CRT. Sixty-one percent of the FDG-PET TV and 76% of the MRI TV obtained after 10 fractions of CRT remained inside the corresponding baseline TV. On MRI, residual tumor was still suspected in all 6 patients with a pathologic complete response, whereas FDG-PET showed a metabolic complete response in 3 of them. The FDG-PET TVs delineated with the gradient-based method matched closest with pathologic findings. Conclusions: Integration of MRI and FDG-PET into radiotherapy seems feasible. Gradient-based segmentation is recommended for FDG-PET. Spatial variance between MRI and FDG-PET TVs should be taken into account for target definition.
- OSTI ID:
- 21362215
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 75, Issue 3; Other Information: DOI: 10.1016/j.ijrobp.2008.11.031; PII: S0360-3016(08)03869-8; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
Similar Records
Optimal Timing for Assessment of Tumor Response to Neoadjuvant Chemoradiation in Patients With Rectal Cancer: Do All Patients Benefit From Waiting Longer Than 6 Weeks?
A multimodality segmentation framework for automatic target delineation in head and neck radiotherapy
Related Subjects
COMBINED THERAPY
FLUORODEOXYGLUCOSE
NEOPLASMS
NMR IMAGING
POSITRON COMPUTED TOMOGRAPHY
RADIOTHERAPY
RECTUM
ANTIMETABOLITES
BODY
COMPUTERIZED TOMOGRAPHY
DIAGNOSTIC TECHNIQUES
DIGESTIVE SYSTEM
DISEASES
DRUGS
EMISSION COMPUTED TOMOGRAPHY
GASTROINTESTINAL TRACT
INTESTINES
LARGE INTESTINE
MEDICINE
NUCLEAR MEDICINE
ORGANS
RADIOLOGY
THERAPY
TOMOGRAPHY