Performance evaluation of two quantitative gamma cameras using NEMA NU-01 2018 standards

Purpose: To evaluate and compare the performance characteristics of two quantitative gamma cameras using the newly proposed NEMA NU-01 2018 standards. Materials and Methods: Two SPECT/CT gamma cameras Intevo-6 and Intevo-excel (Siemens Healthcare) capable of absolute quantitation were evaluated. Spatial resolution (FWHM/FWTM) and spatial linearity were measured using slit phantom and ^99mTc source housed in a 3-sided shielded source with copper plates. Intrinsic energy resolution was measured using collimated source of ^99mTc. Intrinsic flood field uniformity was measured for both central and useful field-of-views. Multiple window spatial registration was measured using Ga-67 source by calculating the centroid of counts. Count rate was evaluated with copper attenuators. System spatial resolution was measured using the point spread function. System sensitivity was measured using flat plastic dish. The effectiveness of shielding was assessed for each detector. System alignment was measured using spherical symmetric 3-point sources images reconstructed using FBP. Whole-body system resolution without scatter was measured using two capillary tubes, parallel and perpendicular to the motion. ACR phantom with point sources was used to access overall image quality. Spatial co-registration was calculated using the centroid of each point source in both the CT and SPECT images.

Results: Intrinsic spatial resolution and linearity results are summarized in Table 1. The energy resolution for intevo-6 detector-1 and detector-2 was 9.4 and 8.8, whereas it was 10.27 and 9.41 for intevo-excel respectively. The maximum count rate (in kcps) for intevo-6 detector-1 and detector-2 was 411 and 421; whereas it was 422 and 410 for intevo-excel respectively. Multiple energy window spatial registration ranged from minimum of 0.14 to maximum of 0.71. The measured sensitivity detector-1 and detector-2 was 191cpm/uci and 192 cpm/uci for intevo-6; and 193 cpm/uci and 188 cpm/uci for intevo-6 respectively. Whole-body system resolution ranged from 7.2 to 4.4 FWHM for vertical and horizontal directions. Co-registration between SPECT and CT gantries and image quality were acceptable. SPECT mage contrast and reconstructed resolution using ACR phantom are shown in figure 1. Clinical cardiac images using two gamma cameras are shown in figure 2.

Conclusions: The performance evaluation of two gamma cameras has been characterized using the newly proposed NEMA NU01-2018 standards. The overall performance shows that the two gamma cameras are suitable for qualitative and quantitative clinical studies. NEMA NU01-2018 standards are reproducible for acceptance testing of gamma cameras. Table 1.Comparison of intrinsic spatial resolution and linearity in X- and Y -direction for Intevo-6 and Intevo-excel gamma camera

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