Towards Enhancing Auxiliary Lymph Node Detection Using a Breast Insert with a Whole-Body PET/MRI Scanner

In general, breast PET inserts are designed to improve the detection capability for small lesions and early metastases. Expanding on prior research, the insert our group is developing aims to enhance the spatial resolution of axillary lymph nodes beyond the insert’s field-of-view (FOV) via the combination with a clinical whole-body (WB) PET scanner. To explore this potential, Monte Carlo simulations were conducted using Na-22 point sources positioned outside of the insert’s FOV to mimic real lymph node locations. A dedicated reconstruction was developed to accommodate different types of coincidences in this hybrid setup, and the system model was partially validated using a phantom of uniformly distributed activity. Results indicate that, while the WB-PET’s spatial resolution may degrade due to insert attenuation, the combination of conventional WB-PET coincidences and mixed coincidences from both systems enhances spatial resolution in terms of full-width at half-maximum in x-direction, and also helps to mitigate the negative effects of the insert in y-direction. Future steps include a comprehensive assessment of image quality, refinement of the reconstruction algorithm to include the solid angle effect, and evaluation of image performance with realistic phantoms.