System Matrix Generation For Angular Domain Tomographic Reconstruction

The ADEPT system is an angular domain optical projection tomography imaging system being developed to address the problem of undetected micrometastases in lymph node biopsy tissues. The relatively weak scattering nature of lymph nodes combined with a very low numerical aperture enables the approximation of straight-line projections that can be reconstructed into images simply with filtered back-projection (FBP). This was demonstrated in previous work where 0.2 mm diameter inclusions were detected in similar to 1 cm diameter lymph nodes; and while FBP was sufficient, the Radon transform is not a true representation of the imaging system. To investigate the degree of improvement that a more complex reconstruction algorithm could provide, a Monte Carlo based system matrix was generated and used to solve the inverse problem. Simulated phantoms were used to test this, and results revealed greater detection sensitivity at the periphery of samples. Such findings lend guidance in the ongoing design of the ADEPT system and so more robust evaluation of the reliability of the system matrix will be implemented in future work.