# Development of a novel phantom for evaluating jawbone SPECT targeting medication-related osteonecrosis of the jaw

## TL;DR

A new phantom was developed to improve the evaluation of jawbone SPECT for diagnosing medication-related osteonecrosis of the jaw.

## Contribution

A novel phantom was created and validated for optimizing jawbone SPECT image reconstruction parameters.

## Key findings

- The phantom study showed that increasing update numbers improved contrast and recovery coefficients.
- OSEMjaw parameters (120 updates, no filter) provided better SUVmean correlation with clinical stages than current methods.
- OSEMjaw-reconstructed images were visually superior to those from the current standard method.

## Abstract

We developed a new phantom for technical evaluation of jawbone single-photon emission computed tomography (SPECT) examinations for medication-related osteonecrosis of the jaw (MRONJ). In this study, we verified the utility of the phantom by determining optimal image reconstruction parameters.

We evaluated the image quality and quantification in jawbone SPECT images obtained by different reconstruction parameters using the phantom. The phantom images were acquired using a SPECT/computed tomography (CT) system and then reconstructed using ordered-subset expectation maximization (OSEM) iterative reconstruction with resolution recovery as well as scatter and attenuation correction with various update numbers and Gaussian filter full width at half maximums (FWHMs). The percent contrast (%contrast) and absolute recovery coefficient were calculated to determine the optimal reconstruction parameters (OSEMjaw). Nineteen patients with a clinical diagnosis of MRONJ who underwent bone SPECT/CT were enrolled for the clinical study. The performance of OSEMjaw was verified by comparison with OSEMcurrent determined by a spherical phantom, using the correlation between the mean standardized uptake value (SUVmean) and clinical staging and visual assessment as endpoints.

In the phantom study, %contrast and absolute recovery coefficient increased with increasing update numbers. As the Gaussian filter FWHM increased, the quantitative accuracy and image sharpness decreased. The parameter determined by the phantom study (OSEMjaw) recommended 120 updates and no filter.

In the clinical study, the mean and standard deviation of SUVmean obtained from OSEMjaw were 8.9 ± 1.4 for stage 1 lesions, 12.9 ± 4.1 for stage 2 lesions, and 13.8 ± 1.4 for stage 3 lesions. For OSEMcurrent, they were 5.4 ± 2.3 for stage 1 lesions, 8.3 ± 2.5 for stage 2 lesions, and 8.0 ± 0.9 for stage 3 lesions. The SUVmean obtained from OSEMjaw had a stronger correlation with clinical stage. Based on visual assessment, the quality of the SPECT images reconstructed by OSEMjaw (3.7 ± 0.9) was superior to that reconstructed by OSEMcurrent (2.9 ± 1.1).

We developed a novel phantom and adapted it for technical evaluation. This study demonstrated the utility of the developed phantom.