Nonstop gated CBCT for respiratory gating lung SBRT: A feasibility study

Area of Science:

• Medical Imaging
• Radiation Oncology
• Computed Tomography

Background:

• Current gated cone-beam CT (gCBCT) for lung SBRT setup verification is time-consuming (2-8 min) and increases radiation dose due to repeated gantry stops/starts.
• Longer scan times in gCBCT can cause patient discomfort and increase the risk of movement, compromising image quality.
• Extra kV projections acquired during gantry acceleration in gCBCT contribute to a higher imaging dose compared to standard 3D CBCT.

Purpose of the Study:

• To introduce and assess the feasibility of a novel nonstop gated CBCT (ngCBCT) imaging technique.
• To substantially reduce scan time and imaging dose in lung SBRT pretreatment setup verification.
• To maintain or improve image quality compared to conventional gCBCT.

Main Methods:

• Developed ngCBCT by enabling continuous gantry rotation with kV x-ray activation only during the gating window.
• Emulated ngCBCT acquisitions using retrospective gCBCT projection data from two lung SBRT patients (half-fan and full-fan).
• Evaluated three reconstruction algorithms (FDK, PL, PIBR) for their performance on non-uniform, under-sampled ngCBCT data.

Main Results:

• Feldkamp-Davis-Kress (FDK) reconstructions showed significant streak artifacts, rendering them clinically unsuitable.
• Penalized Likelihood (PL) reconstruction offered improvements over FDK but was surpassed by Prior-Image-Based Iterative Reconstruction (PIBR).
• PIBR consistently produced the best visual and quantitative results, leveraging patient-specific prior images.

Conclusions:

• The proposed ngCBCT technique effectively addresses the limitations of current gCBCT by reducing acquisition time and radiation dose.
• ngCBCT combined with PIBR achieves diagnostically adequate image quality for clinical application.
• This ngCBCT-PIBR approach presents a promising advancement for pretreatment setup verification in lung SBRT.