Collimator and energy window optimization for practical imaging protocol and quantification of Yttrium-90 bremsstrahlung spect/ct: A phantom study

Yttrium-90 (90Y) bremsstrahlung imaging is very complex which increases the demands on the imaging protocol and reconstruction. We evaluate the choice of collimator and energy windows (EWs) settings. All images were acquired using low-energy high-resolution (LEHR) collimator, medium-energy general-purpose (MEGP) and high-energy general-purpose (HEGP) in different energy windows (EWs) settings, ranging from 60 keV to 300 keV. The EW based scatter-correction technique was adopted by the authors. The planar images of a customised cylindrical acrylic phantom with a90Y chloride solution vial positioned in the center of phantom were assessed based on image quality, signal-to-background ratio (SBR) and coefficient of variation (CV). HEGP has the highest SBR followed by MEGP and LEHR whereas LEHR has the lowest CV followed by MEGP and HEGP. EW with two energy windows always has highest SBR followed by three energy windows and one energy windows. In term of image quality, MEGP with 2 or 3 energy windows have the images with best spatial resolution compared to septa effect in HEGP images and grainy images with poor resolution in LEHR images. MEGP collimator with 2 energy windows gave good results in term of good spatial resolution and moderate SBR and CV. The proposed imaging protocol in planar imaging is readily to be used to tailor 90Y SPECT/CT acquisition, attenuation correction (AC), scatter correction (SC) and reconstruction protocols for improved 90Y imaging in our hospital. •Yttrium-90 Bremsstrahlung imaging is essential in PRRT.•MEGP with Dual energy window is suitable to use in Yttrium-90 Bremsstrahlung SPECT/CT.•HEGP will have septa effect.