Image Quality Assessment Using NEMA Standards for Lu-177 Radionuclide

A lutetium 177 (¹⁷⁷Lu) radiopharmaceutical has been used as a theragnostic agent in molecular radiotherapies. This study aimed to produce images simulating those obtained in a total body imaging study with hot lesions to assess and investigate the image quality of the Hawkeye SPECT/CT images from Lu-177. The NEMA image quality phantom (PTW) with spheres (inner diameters of 10, 13, 17, 22, 28 and 37 mm) and lung insert was used. The measured volume in the background of the current phantom setting was 9482 mL. The five smaller spheres were filled with an activity concentration of 0.461 MBq/mL and the biggest sphere was filled with water. The phantom was placed on the couch and scanned at four hot sphere-to-background concentrations, which are no background, 16:1, 8:1 and 4:1. The images obtained from the scans were imported onto the OXIRIS image analysis tool. Regions of interest (ROIs) were drawn on each sphere of the reconstructed SPECT image. Image contrast and background variability ratios for hot spheres were used as measures of image quality. In addition, the accuracy of corrections were determined from the uniform background and cold lung insert regions. The 37 mm cold sphere had the highest percent contrast, whiles the 10 mm hot sphere had the least for the various hot sphere to background ratios. The background variability for each hot sphere was also determined. The average lung residual error was calculated to be 23.13% for the 16:1 and 22.57% for both the 8:1 and 4:1 hot sphere to background ratio. The results show that the scanner has very good overall performance.