Kromek has developed an advanced CZT detector technology that achieves strongly enhanced spatial and depth-of-interaction (DOI) resolution through high-level sub-pixelisation enabled by a machine learning (ML) framework. The approach combines state-of-the-art CZT modules with an ML model trained on high-fidelity simulated datasets, providing scalable and adaptable performance for detector arrays of any size. The model also performs DOI-dependent energy correction and compensates for charge-sharing losses, reducing low-energy tailing while preserving excellent energy resolution.

The technology was demonstrated using a large-area CZT camera comprised of 5-mm thick detectors with an 11×11 grid of 2-mm pixels. Characterisation studies show that the latest generation of the ML model enables up to 10×10 subpixelisation using anode-only signals, achieving lateral position resolution of ~250 µm and DOI resolutions of ~1 mm near the cathode and ~500 µm at mid-depth. This performance provides a favourable combination of energy resolution typical of gamma detectors with mm-scale pixels and spatial resolution approaching that of mid-range x-ray imaging.

The new technology was integrated into a prototype next-generation Ultra-Fast Molecular Breast Imaging (UFMBI) camera developed by Kromek and University College London. The system incorporates dual opposing stationary CZT detector arrays and high-density multi-pinhole collimators with hundreds of pinholes for wide-range angular sampling, together with novel de-multiplexing algorithms that mitigate the resulting multiplexing artefacts in tomographic image reconstruction. Phantom studies with 99mTc demonstrate that UFMBI addresses key limitations of the current MBI, including relatively high patient dose and long scan times. Results indicate feasibility of UFMBI as a low-dose screening modality as per criteria set by regulatory bodies, with scan time reduced by a factor of 3–4.

The demonstrated UFMBI performance indicates promising applicability of the underlying technologies to a broad range of nuclear imaging applications beyond breast imaging.