Filters Effect on Image Quality of 177Lu-DOTATATE SPECT Images for Neuro-Endocrine Tumors Scanning

Abstract

Purpose: The quality of the image in SPECT scans depends on the imaging parameters which are determined experimentally in the field of nuclear medicine. Designing a dedicated scanning parameter for ¹⁷⁷Lu-DOTATATE SPECT images is required to optimize reconstruction. Therefore, this study aims to evaluate the effect of different filters on image quality for bone SPECT scanning using ¹⁷⁷Lu-DOTATATE.

Materials and Methods: The filtered back-projection reconstruction method was used in neuro-endocrine tumor scanning using ¹⁷⁷Lu-DOTATATE. Three hours after injection of ¹⁷⁷Lu-DOTATATE, SPECT scans from ¹⁷⁷Lu-DOTATATE for 30 patients were acquired using a dual-head EvoExel detector system. Seven parameters were considered, including the contrast/noise ratio, injection activity, uptake duration, acquisition time per injection, frame time, measuring time, and type of filters.

Results: In all cases, the application of different filters increased Contrast to Noise Ratio (CNR) (9.1%, 1.8%, 10.9%, 61.8%, 23.6%, 29.1%, and 58.2% for Wiener, Butterworth, Parzen, Metz, Ramp, Shepp-Logan, and Hamming filters, respectively). The percentage of increase in Signal-to-Noise Ratio (SNR) was 3.3%, 1.7%, -24%, 21.7%, 9.8%, 11.9%, and 20.6%.

Conclusion: Based on the quantitative analysis of the results, the application of the Metz filter (power 2) and Hamming filter (with 0.27, 0.47, and 0.67 cut-off frequencies) on SPECT scans of neuro-endocrine tumors is recommended because of their capacity to provide high-quality images.