Computed Quantitative Planar Imaging for Targeted Alpha Therapy: Model-Based Sparse Reconstruction Validated With a...

Area of Science:

• Nuclear medicine
• Medical imaging
• Radiotherapy

Background:

• Targeted Alpha Therapy (TAT) utilizes alpha-emitting radionuclides (AER) for treating advanced cancers.
• Current TAT dosimetry relies on activity, neglecting individual biodistribution and kinetics.
• Accurate patient-specific dosimetry requires in-vivo imaging of AER, which is challenging due to limited imageable photons.

Purpose of the Study:

• To develop and evaluate a novel computed quantitative planar (CQP) imaging method for reconstructing the 3D AER distribution.
• To enable patient-specific dosimetry for TAT based on absorbed dose criteria.
• To overcome imaging challenges associated with scarce photons from AER.

Main Methods:

• Developed a CQP imaging method to reconstruct coronal projection of 3D AER distribution from anterior/posterior scintigraphy coregistered with CT.
• Employed maximum a posteriori estimation with sparse ℓ1 tight-framelet transforms for model regularization.
• Utilized a convergence-guaranteed fixed-point proximity algorithm for solving the model.
• Experimentally validated the method using a phantom with a known distribution of ²²⁵Ac.

Main Results:

• CQP reconstruction demonstrated significantly reduced bias and noise compared to geometric mean methods.
• Improved spatial resolution and signal-to-noise ratios were achieved with CQP.
• The phantom study confirmed the accuracy of the reconstructed AER distribution.

Conclusions:

• The CQP imaging method is a clinically implementable solution for AER biodistribution imaging using conventional SPECT/CT systems.
• This approach can significantly improve dosimetry workflows in TAT, particularly when 3D SPECT/PET is not feasible.
• CQP imaging facilitates patient-specific treatment delivery in Targeted Alpha Therapy.