Towards quantitative in vivo dosimetry using x-ray acoustic computed tomography

Area of Science:

• Medical Physics
• Radiotherapy Imaging
• Dosimetry

Background:

• Accurate radiation dosimetry is critical for effective radiation therapy (RT).
• Current RT dose verification relies on simulations, lacking in-line clinical verification.
• X-ray-induced acoustic computed tomography (XACT) is a promising tool for in vivo dosimetry.

Purpose of the Study:

• To evaluate the feasibility of XACT for quantitative in vivo dose reconstruction in RT.
• To move beyond XACT's primary use in radiation beam localization.

Main Methods:

• Developed a model-based image reconstruction algorithm for XACT quantitative dosimetry.
• Deconvoluted X-ray pulse shape and ultrasound detector frequency response.
• Compared model-based reconstruction with universal back-projection (UBP) using simulated and experimental data.

Main Results:

• Model-based XACT accurately reconstructed 3D radiation dose in simulations.
• Reconstructed doses showed good agreement with percent depth dose (PDD) profiles post-calibration.
• Model-based XACT achieved over 85% SSIM and 8x lower RMSE compared to UBP.

Conclusions:

• XACT with model-based reconstruction offers superior accuracy for in vivo dosimetry compared to UBP.
• XACT is potentially applicable for clinical quantitative dosimetry across various RT modalities.
• XACT's real-time, volumetric imaging suits emerging techniques like FLASH radiotherapy.