Interleaved acquisition for cross scatter avoidance in dual cone-beam CT

Area of Science:

• Medical Physics
• Radiological Imaging
• Radiation Oncology

Background:

• Cone-beam x-ray imaging is crucial for image-guided radiation therapy (IGRT).
• Dual cone-beam systems offer potential benefits like reduced imaging time and improved artifact reduction.
• A significant challenge in dual cone-beam imaging is cross scatter, where photons from one source contaminate the other detector.

Purpose of the Study:

• To characterize cross scatter in dual cone-beam imaging.
• To propose and evaluate a method for mitigating cross scatter.
• To assess the impact of cross scatter on image quality in IGRT applications.

Main Methods:

• A prototype dual-source cone-beam computed tomography (CBCT) system was utilized.
• Cross scatter was quantified using cylindrical phantoms of varying sizes (15, 20, 30 cm) across a range of kilovoltage peak (kVp) settings.
• A novel interleaved data acquisition strategy was developed and implemented to avoid cross scatter.

Main Results:

• Cross scatter ratios reached up to 0.59 in larger phantoms, with scatter-to-primary ratios exceeding 4 in some cases.
• Image contrast was significantly reduced (average 48.7% in a 30 cm phantom) due to cross scatter.
• The proposed interleaved acquisition method effectively eliminated the observed cross-scatter degradations.

Conclusions:

• Cross scatter is a substantial issue in dual cone-beam imaging systems.
• Interleaved data acquisition is a viable and effective strategy to mitigate cross scatter.
• This method can be implemented by adjusting data acquisition rate or rotation speed without compromising angular sampling.