Related Experiment Videos
Low-dose megavoltage cone-beam CT for radiation therapy
Jean Pouliot1, Ali Bani-Hashemi, Josephine Chen
1Department of Radiation Oncology, University of California San Francisco, CA 94143-1708, USA. pouliot@radonc17.ucsf.edu
Summary
This study demonstrates that low-exposure megavoltage cone-beam CT (MV CBCT) can produce high-quality 3D images for patient alignment. These images, acquired rapidly with a standard linear accelerator, are suitable for clinical use in radiotherapy.
Area of Science:
- Medical Physics
- Radiotherapy Technology
- Image Reconstruction
Background:
- Accurate patient alignment is crucial for effective radiotherapy.
- Kilovoltage CT (kV CT) is standard for planning, but megavoltage CT (MV CBCT) offers potential for in-treatment imaging.
- Acquiring high-quality MV CBCT at low doses is essential for clinical feasibility.
Purpose of the Study:
- To demonstrate the feasibility of acquiring low-exposure MV CBCT 3D image data.
- To achieve image quality sufficient for registering MV CBCT to kV CT for patient alignment and dose verification.
Main Methods:
- Utilized a 6-MV linear accelerator in arc therapy mode with an amorphous-silicon flat-panel electronic portal-imaging device (EPID).
- Acquired projection images with low monitor units (0.02-0.08 MU/image) using a triggered acquisition mode.
- Reconstructed 3D MV CBCT images from 90-180 projection images for phantoms and a head-and-neck cancer patient undergoing IMRT.
Main Results:
- Acquired low-noise, artifact-free 3D MV CBCT images with a total dose of 5-15 cGy.
- Image acquisition and reconstruction times were rapid (approx. 90 seconds each).
- Demonstrated millimeter and degree accuracy in registering MV CBCT to kV CT, with visible bony anatomy and soft-tissue details.
Conclusions:
- Low-exposure MV CBCT provides sufficient image quality for clinical application.
- Rapid acquisition and reconstruction times support its use for patient alignment in radiotherapy.
- Standard linear accelerators with flat-panel imagers can perform clinically viable MV CBCT.