Shift detection discrepancy between ExacTrac Dynamic system and cone-beam computed tomography.

Area of Science:

• Medical Physics
• Radiation Oncology
• Image Guidance

Background:

• Accurate patient positioning is crucial in radiation therapy to maximize tumor dose and minimize normal tissue exposure.
• Existing image guidance systems require validation for precise shift detection.
• The ExacTrac Dynamic (EXTD) system integrates optical surface and thermal tracking for real-time patient monitoring.

Purpose of the Study:

• To evaluate the shift detection accuracy of the ExacTrac Dynamic (EXTD) system.
• To compare the performance of EXTD (optical surface and thermal tracking) with cone-beam computed tomography (CBCT) for 6-degrees-of-freedom (6DoF) patient alignment.
• To assess the accuracy of thermal tracking for detecting positional shifts in cranial and pelvic phantoms.

Main Methods:

• Utilized anthropomorphic cranial and pelvis phantoms with simulated bone structures and a heat pad.
• Applied controlled translational (±2 cm) and rotational (±2°) displacements to the phantoms.
• Compared positional shifts detected by EXTD (thermal and X-ray modalities) against CBCT measurements in 6DoF.

Main Results:

• The translational difference between EXTD_Thml and CBCT was approximately 0.57-0.66 mm for cranial and pelvis phantoms.
• The translational difference between EXTD_Xray and CBCT was approximately 0.60-0.76 mm.
• Rotational differences between EXTD_Thml and CBCT were around 0.19° for both phantoms.
• Rotational differences between EXTD_Xray and CBCT ranged from 0.13° to 0.65°.

Conclusions:

• The ExacTrac Dynamic (EXTD) system, particularly with its thermal mapping capability, demonstrates high accuracy in detecting patient shifts.
• EXTD offers comparable accuracy to CBCT for 6DoF shift detection in both cranial and pelvic sites.
• This validates the potential of EXTD as a reliable tool for image-guided radiation therapy, enhancing treatment precision.