Limited-angle x-ray luminescence tomography: methodology and feasibility study.

Area of Science:

• Biomedical Imaging
• Medical Physics

Background:

• X-ray luminescence tomography (XLT) combines nanoparticle sensitivity with X-ray spatial localization.
• Current XLT methods face limitations in geometric constraints, temporal resolution, and radiation dose.
• New approaches are needed for applications like image-guided surgery.

Purpose of the Study:

• To extend XLT utility by incorporating a photon propagation model into a limited-angle (LA) geometry reconstruction algorithm.
• To enable XLT for applications with geometric limitations, higher temporal resolution needs, or lower dose requirements.
• To demonstrate the feasibility of LA-XLT for detecting deep lesions in image-guided surgery.

Main Methods:

• Formulated a hybrid X-ray/diffuse optical model for limited-angle X-ray luminescence tomography (LA-XLT).
• Validated the model using numerical and experimental breast-sized phantoms with simulated lesions of varying sizes and depths.
• Incorporated a photon propagation model into the reconstruction algorithm for improved accuracy.

Main Results:

• Achieved high localization accuracy with a median error of 2.2 mm (4% of object depth) for lesions 2-14 mm in diameter, from 1 to 4.5 cm deep.
• Demonstrated robustness in recovered lesion size, with standard deviation < 2.5 mm irrespective of depth.
• Showed sensitivity sufficient for µg ml⁻¹ concentrations at radiological doses and ng ml⁻¹ at therapy dosages.
• Experimental results closely matched numerical predictions, with positional errors within 8.6% and 5.2% for 5 mm and 10 mm objects, respectively.

Conclusions:

• Limited-angle X-ray luminescence tomography (LA-XLT) is a viable technique for biological imaging, particularly in intra-operative settings.
• LA-XLT offers superior depth resolution compared to fluorescence optical imaging for small lesions.
• The developed hybrid X-ray/diffuse optical model enhances lesion detection in challenging, limited-angle geometries.