From Diagnosis to Therapy: Progress in SPECT and PET Reconstruction for Theranostics

The theranostic paradigm enables personalization of treatment by selecting patients with a diagnostic radiopharmaceutical and monitoring therapy using a matched therapeutic isotope. This strategy relies on accurate image reconstruction of both pre-therapy and post-therapy images for patient selection and monitoring treatment. However, traditional reconstruction methods are hindered by challenges such as crosstalk in multi-isotope imaging and extremely low-count measurements when imaging of alpha- ({\alpha}-) emitting therapies. Additionally, to fully realize the benefits of new imaging systems being developed for theranostic applications, advanced reconstruction techniques are needed. These needs, alongside the growing clinical adoption of theranostics, have spurred the development of novel PET and SPECT reconstruction algorithms. This review highlights recent progress and addresses critical challenges and unmet needs in theranostic image reconstruction.