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Scatter correction for cone-beam CT in radiation therapy
Lei Zhu1, Yaoqin Xie, Jing Wang
1Department of Radiation Oncology, Stanford University, Stanford, California 94305, USA. leizhu@stanford.edu
Medical Physics
|July 21, 2009
Summary
This study presents a novel method to improve cone-beam CT (CBCT) imaging quality in radiation therapy by correcting scatter. The technique uses a partially blocked scan to estimate scatter and adapt it for subsequent treatments, significantly reducing image artifacts.
Area of Science:
- Medical Physics
- Radiological Imaging
- Radiation Therapy
Background:
- Cone-beam CT (CBCT) is crucial for patient setup and adaptive replanning in radiation therapy.
- Image quality in CBCT is fundamentally limited by scatter, hindering accurate dose calculations.
- Existing scatter correction algorithms lack a standardized, practical solution.
Purpose of the Study:
- To develop a practical scatter removal scheme for CBCT in radiation therapy.
- To enable the use of scatter data from an initial scan for corrections in subsequent treatments.
- To improve CBCT image quality for critical applications like adaptive radiation therapy.
Main Methods:
- A partially blocked CBCT scan with a strip pattern was used to extract scatter distributions.
- Scatter was estimated from shadow regions using interpolation/extrapolation.
- Patient transformation was determined via rigid registration for scatter adaptation in subsequent scans.
Main Results:
- Hounsfield unit (HU) errors on a Catphan 600 phantom reduced from ~350 to <50 HU.
- Image errors on an anthropomorphic phantom decreased from 15.7% to 5.4%.
- The method effectively corrects scatter, enhancing CBCT image quality.
Conclusions:
- A simple and effective method for scatter estimation and correction in CBCT was demonstrated.
- The technique leverages prior scatter data for adaptive corrections in repetitive patient scans.
- This approach significantly improves CBCT image quality, vital for adaptive radiation therapy.
