Abstract
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Objectives: To expedite testing of dedicated cardiac cameras with multi-pinhole collimators interfaced with solid state detectors (SSD), a new SPECT spatial resolution with scatter (SRC) phantom has been developed. The NEMA Nu-1 SRC measurement requires a 20x20 cm phantom and line source inserts and a water filled cylinder. Dedicated cardiac cameras have undergone SRC testing with modified phantom configurations. The resulting version is considered an ‘express’ version of a SPECT SRC NEMA compliant phantom. This new phantom will be evaluated on a multi-pinhole SSD camera and a conventional fixed angle cardiac camera with the objective to reduce the complexity of required phantom components and phantom preparation and enhance its utility for routine system performance testing.
Methods: The NEMA compliant phantom for SPECT SRC with scatter is scanned using three points source inserts to yield Point Source Functions (PSF) located in the same locations defined by NEMA [Fig. 1]. The point source holders a 2.4x2.4 mm volume for isotope storage. This point source phantom is scanned on a GE Ventri and a GE Discovery NM530c first with 99mTc, then a 57Co sealed source insert. These scans are repeated with a 5 cm thick annulus centered on the phantom [Fig. 2]. The third phantom configuration is using the same 5 cm thick annulus with a solid 5 cm thick disc insert with 3 machined holes for the source holders [Fig. 3]. This phantom configuration is with both 99mTc and57Co point sources.
Results: FWHM and FWTM values are measured using horizontal and vertical line spread functions derived from resulting PSF, using a central composite slice [Fig. 4] from each set of acquisitions for three phantom configurations; 20 cm cylinder, 20 cm cylinder with 5 cm elliptical annulus and 5 cm annulus with solid insert as a substitute for the 20 cm cylinder. Center, tangential and radial spatial resolution values are calculated (according to NEMA Nu-1 2012) and compared to GE published NEMA specifications.[See Table 1]
Conclusion: The Express SRC phantom for dedicated cardiac cameras can enhance its utility in system performance testing specifically for specialized cameras that are multi-pinhole or focusing collimation with an additional feature of simulating patient scatter. This is particularly true when substituting liquid sources with solid point sources. Research Support: None Table
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