ISSN: 2689-8020
Authors: Masoomi M*, Alnafisi N, Alenezi S, Aldousari HA and Alshammari I
Introduction: 90Y bremsstrahlung scintigraphy suffers from a low spatial resolution due to indirect imaging of a continuous scatter radiation spectrum without a pronounced photo-peak resulting in a coarse representation of the microsphere biodistribution. The authors are investigating the feasibility of 90Y PET/CT TOF imaging as a technique to improve detection accuracy of 90Y distribution and leakage post radiation synovectomy in relation to conclusive information of activity presence in the target area. Procedures: A knee phantom with the compartments that is mimicking the bone and soft tissue scattering – attenuation was developed using saline solution and Dipotassium Hydrogen Phosphate (K2HPO4). A dose of 185 MBq of 90Y confined to a small container was embedded in the knee phantom. A LYSO PET with a 64 slice CT, as well as a 16 slice SPECT/CT camera was used. PET scans were acquired using positron fraction 3.186 × 10−5, half-life 64.1 h, 15 min per bed position. For bremsstrahlung SPECT imaging the energy windows were set to 55-285 keV. Results: An algorithm which incorporates TOF+PSF, non-TOF and 3D-OSEM were used for image acquisition and reconstruction. The images were assessed for spatial resolution, technical success and detection of non-target activity. The PET images appeared to be suffering from low true coincident rate. Qualitative evaluation showed superior spatial resolution of PET/CT over bremsstrahlung SPECT with a clear edge definition of the phantom. We are planning to apply the procedure on patient imaging, and it appears the 90Y PET scans of patients for microsphere bio-distribution in radiosynovectomy is the first time to be done in Kuwait. The preliminary study suggests, although 90Y PET imaging is suffering from low true counts, but it has qualitative superiority and results are indicating that it can serve in two primary clinical roles in radiosynovectomy: (1) evaluating technical success (2) predicting treatment efficacy.
Keywords: Yittrium-90 (90Y); Radiosynovectomy; Time of Flight PET/CT; SPECT
