Clinical implementation of kVCT-guided tomotherapy with ClearRT

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Diagnostic Imaging

Background:

• Tomotherapy units have integrated a helical fan-beam kilovoltage computed tomography (kVCT) system.
• This innovation aims to enhance clinical workflow and adaptive planning capabilities.
• Comparison with existing megavoltage computed tomography (MVCT) is crucial for understanding its clinical utility.

Purpose of the Study:

• To evaluate the initial clinical workflow experience with kVCT.
• To compare kVCT performance against MVCT in terms of efficiency and image quality.
• To assess the potential of kVCT for adaptive radiotherapy planning.

Main Methods:

• Retrospective analysis of 23 patients who received both MVCT and kVCT scans.
• Comparison of image acquisition time, dose length product (DLP), and registration parameters.
• Image quality assessment via expert scoring and phantom measurements.
• Dosimetric evaluation of CT number stability and adaptive radiotherapy implementation.

Main Results:

• kVCT demonstrated significantly reduced DLP (except highest kVp), acquisition, and registration times compared to MVCT.
• kVCT received higher image quality scores, with exceptions in artifacts and uniformity.
• Phantom studies showed superior kVCT image performance, excluding uniformity.
• CT number variations could cause minor dose differences (0.5%) for target and organs-at-risk.
• Dose differences exceeding 1% in PTV metrics were noted in areas with significant density discontinuities.

Conclusions:

• kVCT offers enhanced soft-tissue visualization and improved treatment efficiency, potentially increasing daily patient throughput.
• Dose calculation accuracy with kVCT is generally acceptable, but careful consideration is needed for regions with severe artifacts or density variations.
• kVCT represents a valuable advancement for radiotherapy workflows, particularly in adaptive planning scenarios.