A kV-MV approach to CBCT metal artifact reduction using multi-layer MV-CBCT
Matthew W Jacobson1, Tom Harris1, Marios Myronakis1
1Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, MA, 02115, United States of America.
Physics in Medicine and Biology
|January 10, 2024
Summary
This study shows combining low-dose megavoltage (MV) and kilovoltage (kV) cone-beam CT (CBCT) effectively reduces metal artifacts in radiotherapy. This approach improves image quality and target visualization without increasing radiation dose.
Area of Science:
- Medical Physics
- Radiotherapy Technology
- Image Processing
Background:
- Metal artifacts in radiotherapy imaging degrade image quality and can obscure critical structures.
- Current methods for metal artifact reduction (MAR) often involve trade-offs in dose or image quality.
Purpose of the Study:
- To demonstrate that combined MV-energy and kV-energy cone-beam CT (CBCT) scans can reduce metal artifacts in radiotherapy guidance.
- To maintain standard-of-care X-ray dose levels during artifact reduction.
Main Methods:
- Acquired MV-CBCT and kV-CBCT scans at half normal dose.
- Utilized a 4-layer MV-imager prototype and reduced LINAC energy (2.5 MV) to mitigate dose impact on MV-CBCT quality.
- Employed model-based poly-energetic correction and interleaving of kV-CBCT and MV-CBCT data, guided by MV-CBCT implant localization.
- Incorporated edge-preserving regularization for noise reduction in MV data.
Main Results:
- Tested in digital and pelvis phantoms with large spherical inserts simulating hip replacements.
- Achieved a compromise between kV-CBCT contrast and MV-CBCT low artifact content.
- Demonstrated a 3-fold improvement in contrast-to-noise ratio (CNR) compared to standard MV-CBCT at matched dose.
- Significantly improved visual delineation of the bladder and prostate over standalone kV- or MV-CBCT.
Conclusions:
- A full MV-CBCT scan can be combined with kV-CBCT to reduce metal artifacts without complex beam collimation.
- Significant improvements in CNR are achievable compared to current clinical MV-CBCT metal artifact reduction practices.
