Impact of reconstruction parameters on quantitative bone SPECT imaging: A novel thoracic spine phantom study

The aim of this study was to validate the effect of reconstruction parameters on quantitative accuracy of bone single-photon emission computed tomography (SPECT) images using a novel thoracic spine phantom.

We used a novel thoracic spine phantom for bone SPECT image evaluation. This phantom consisted of a body, a vertebral body, a spinous process, and a tumor part (spheres, diameter: 13, 17, 22, 28mm), which were filled with ^99mTc and bone-equivalent solution. The SPECT/CT images were acquired with a dual-head SPECT/CT camera (Infinia8 Hawkeye 4, GE) equipped with low-energy high resolution collimator. The bone phantom images were reconstructed using the ordered subset expectation maximization (OSEM) algorithm with resolution recovery and CT-based attenuation correction and scatter correction. The number of iterations was varied from 1 to 20 and the number of subsets was fixed at 10. The maximum, peak, and mean standardized uptake values (SUVmax, SUVpeak, SUVmean) were calculated for the body and the tumor part, and the relative measurement error was assessed.

All quantitative values increased as the number of iterations increased and reached plateaus at 50-100 update numbers. The SUVmax of tumor part was 59.2 when the number of iterations was 2 and 55.7 when the number of iterations was 20. The maximum relative measurement error on the tumor part (reference value: 50) was obtained using the number of iteration 1 and over 10.

Our results indicated that the quantitative accuracy of bone SPECT images was affected by reconstruction parameters. It is important to optimize the reconstruction parameters, and improve quantitative accuracy in bone SPECT imaging.