First performance measurements of a new multi-detector CZT-Based SPECT/CT system: GE StarGuide

Purpose: StarGuide (General Electric, Israel) is a new multi-detector CZT-Based SPECT/CT system. The NM system, associated to a conventional CT, is composed of 12 detectors each of which comprising 7 modules of 16x16 2.46mm-collimated pixels and a registered Tungsten collimator. The aim of this study is to evaluate physical performance of the system.

Methods: In planar mode, sensitivity, spatial resolution and energy resolution were measured for ^99mTc, ¹²³I, ²⁰¹Tl and ¹¹¹In (only 171keV peak) following NEMA NU1-2018[1]. Due to the system geometric configuration, spatial resolution and sensitivity were performed with a source-collimator distance of 15 cm and not 10 cm as recommended. Spatial resolution was derived for 10 cm from the collimator face[2]. Average ± Standard deviation (over the twelve detectors simultaneous measurements) is reported. In tomographic mode, system volume sensitivity (SVS) and SPECT resolution with scatter were also evaluated following NEMA NU1-2018[1] for ^99mTc. SVS measurements included data recording and camera motion times. The evaluation of image quality was made imaging Jaszczak phantom filled with 800 MBq of ^99mTc. We demonstrated 3 configurations: 1) phantom on the system table , 2) on a specific holder so that rotation radius is the smallest possible (as recommended in AAPM Task group 177 report[3]), and 3) using the CT data of the on-table phantom acquired to correct partial volume effects.

Results: Detector Planar Sensitivity, is 96.9 ± 1.9, 77.5 ± 2.3, 128.5 ± 2.8 and 137.1 ± 2.5 [counts/(s.MBq)] for ^99mTc, ¹²³I, ²⁰¹Tl and ¹¹¹In, respectively. Detector spatial resolution at 10 cm, is 7.0 ± 0.2, 7.0 ± 0.2, 7.2 ± 0.2 and 7.8 ± 0.2 [mm] respectively for ^99mTc, ¹²³I, ²⁰¹Tl and ¹¹¹In. Energy resolution is 5.5 ± 0.4, 5.5 ± 0.5 and 5.8 ± 0.6 [%] respectively for ^99mTc, ¹²³I and ¹¹¹In. For ²⁰¹Tl, energy resolution is 10.1 ± 0.9 and 9.9 ± 0.6 [%] respectively at 71 keV and 167 keV.System volume sensitivity is 542.4 kcount.s^-1/(MBq.ml^-1) and system volume sensitivity per axial centimetre is 29.16 kcount.s^-1/(MBq.ml^-2). Central, radial and tangential resolution are 4.27 mm, 3.96 mm and 2.96 mm, respectively. Depending on the configuration, at least 15.9 mm sphere can be visualized and 9.5 mm rod can be resolved.

Conclusions: StarGuide shows good and consistent detection performance for a wide range of low and medium energy radionuclides used in nuclear medicine, without the need for collimator exchange. Further image quality measurements are required to fully characterized the system, such as Tomographic Contrast described by NEMA NU1-2018[1]. References [1] « NEMA NU 1-2018 Standard for Performance Measurements of Gamma Cameras ». [2] S. Cherry, J. Sorenson, et M. Phelps, Physics in Nuclear Medicine 4th Edition.[3] AAPM Task Group 177, « Acceptance Testing and Annual Physics Survey Recommendations for Gamma Camera, SPECT, and SPECT/CT Systems (2019) ».

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