TY - JOUR T1 - Monte Carlo simulation of the acquisition conditions for <sup>177</sup>Lu molecular imaging of hepatic tumors JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 3034 LP - 3034 VL - 60 IS - supplement 1 AU - Yuya Sekikawa Y1 - 2019/05/01 UR - http://jnm.snmjournals.org/content/60/supplement_1/3034.abstract N2 - 3034Objectives: 177Lu is used for peptide receptor radionuclide therapy of neuroendocrine tumors. This study aimed to examine the influence of acquisition time on 177Lu single-photon emission computed tomography (SPECT) images using Monte Carlo simulation. Methods: Gamma camera simulation of SPECT was performed based on Monte Carlo electron and photon simulation equipped with a medium-energy, general-purpose collimator; 96 projections were generated across 360°1. The phantom background was modeled on a NEMA IEC BODY phantom; spheres were installed in the phantom with diameters of 10, 13, 17, 22, 28, and 37 mm. The phantom background was assumed to be a healthy liver tissue, whereas the spheres were assumed to be tumors. Radioactivity concentrations of the background and hot sphere were set at 155 kBq/mL and 2.12 MBq/mL, respectively, 24 h after administration according to a previously reported time-activity curve2. Concentrations after 6 and 72 h were also set, and 177Lu SPECT images were simulated for each. Acquisition times were set as 12, 6, 3, 2, 1.5, and 1.2 min in each case. Projection images were pre-filtered using a Butterworth filter (cut-off frequency: 0.50 cycle/cm, order: 8), and filtered images were reconstructed using ordered subset expectation maximization (iteration: 8, subset: 6). Reconstructed images were then corrected using attenuation correction and collimator response correction. To evaluate image quality, contrast-to-noise ratios (CNRs) were calculated for each image. In this study, the threshold of CNR for detectability was assumed to be 5.0. Results: In images obtained after 6 h, 17-37-mm spheres were detectable across all acquisition times. The 13-mm sphere required an acquisition time of at least 2.0 min, whereas the 10-mm sphere was not detectable under any condition. In images obtained following 24 and 72 h, the 13-37-mm spheres were detectable across all acquisition times; however, the 10-mm sphere required an acquisition time of at least 6.0 and 3.0 min, respectively. Conclusion: 177Lu SPECT images were successfully generated using Monte Carlo simulation. In images obtained 24 h after administration, an acquisition time of 6 min was required to detect 10-mm spheres. ER -