Abstract
Background Two novel methods of image reconstruction, xSPECT Quant (xQ) and xSPECT Bone (xB) that use an ordered subset conjugate gradient minimizer (OSCGM) for bone SPECT/CT have been proposed. The present study compares the performance characteristics of xQ, xB and conventional Flash3D (F3D) reconstruction using images derived from phantoms and patients. Methods A custom-designed body phantom for bone SPECT was scanned using a Symbia Intevo (Siemens Healthineers) and reconstructed xSPECT images were evaluated. The phantom experiments proceeded twice in different activity concentrations and sphere sizes. A phantom with 28-mm spheres containing a 99mTc background and having tumor-to-normal bone ratios (TBR) of 1, 2, 4 and 10, were generated and its convergence property was evaluated across 96 iterations. A phantom with four spheres (13-, 17-, 22-, and 28-mm diameters), containing a 99mTc-background at TBR4, was also generated. The full width at half maximum of an imaged spinous process (10 mm), coefficients of variance (CV), contrast-to-noise ratio (CNR) and recovery coefficients (RC) of an imaged spine were evaluated with F3D, xQ and xB.Images from 20 patients with suspected bone metastases (male, n = 13) were acquired using 99mTc-(H)MDP SPECT/CT, then the CV and standardized uptake value (SUV) at the 4th vertebral body (L4) were compared with xQ and xB in a clinical setup. Results Mean activity concentrations with various TBR converged accordance to increasing numbers of iterations. Spatial resolution was improved in the order of xB, xQ and F3D regardless of the number of iterations during reconstruction. The CV and RC were better for xQ and xB than for F3D. The CNR peaked at 24 iterations for xQ and 48 iterations for F3D and xB, respectively. The RC significantly differed between xQ and xB at lower numbers of iterations, whereas those of xQ and xB became almost equivalent at higher numbers of iterations. Significant differences in the clinical patients’ SUVmax and SUVpeak were observed in the reconstructed xQ and xB images. Conclusions The reconstructed xQ and xB images were more accurate than those conventionally reconstructed using F3D. Bone SPECT xB imaging offered essentially unchanged spatial resolution even when the numbers of iterations did not converge. The xB further enhanced SPECT image quality using CT data. Our findings provide important evidence for understanding the performance characteristics of the novel xQ and xB algorithms.
Determination of Bone SPECT Image Reconstruction Conditions in the Head and Neck Region
