Quantitative capabilities of four state-of-the-art SPECT-CT cameras

Abstract

BackgroundFour state-of-the-art single-photon emission computed tomography-computed tomography (SPECT-CT) systems, namely Philips Brightview, General Electric Discovery NM/CT 670 and Infinia Hawkeye 4, and Siemens Symbia T6, were investigated in terms of accuracy of attenuation and scatter correction, contrast recovery for small hot and cold structures, and quantitative capabilities when using their dedicated three-dimensional iterative reconstruction with attenuation and scatter corrections and resolution recovery.MethodsThe National Electrical Manufacturers Association (NEMA) NU-2 1994 phantom with cold air, water, and Teflon inserts, and a homemade contrast phantom with hot and cold rods were filled with 99mTc and scanned. The acquisition parameters were chosen to provide adequate linear and angular sampling and high count statistics. The data were reconstructed using Philips Astonish, General Electric Evolution for Bone, or Siemens Flash3D, eight subsets, and a varying number of iterations. A procedure similar to the one used in positron emission tomography (PET) allowed us to obtain the factor to convert counts per pixel into activity per unit volume.ResultsEdge and oscillation artifacts were observed with all phantoms and all systems. At 30 iterations, the residual fraction in the inserts of the NEMA phantom fell below 3.5%. Contrast recovery increased with the number of iterations but became almost saturated at 24 iterations onwards. In the uniform part of the NEMA and contrast phantoms, a quantification error below 10% was achieved.ConclusionsIn objects whose dimensions exceeded the SPECT spatial resolution by several times, quantification seemed to be feasible within 10% error limits. A partial volume effect correction strategy remains necessary for the smallest structures. The reconstruction artifacts nevertheless remain a handicap on the road towards accurate quantification in SPECT and should be the focus of further works in reconstruction tomography.

Hybrid Imaging: Instrumentation and Data Processing

“…Two facets of the design of the integrated CT components can be identified: first, SPECT/CT systems include fullydiagnostic CT systems with fast-rotation detectors that permit the simultaneous acquisition of 16 or 64 detector rows, while the X-ray tubes provide sufficient tube voltages together with high tube current and automatic exposure control (General Electric Discovery NM/CT 670 and the Siemens Symbia [32]). These systems also support advanced CT capabilities such as cardiac gating, calcium scoring and iterative reconstruction [18,33].…”

“…On the other hand, SPECT/CT systems include rotating SPECT components that come with adapted rotation times and dose-optimized acquisition modes, while employing CTtype components with limited acquisition flexibility, such as lower tube voltages and currents (General Electric Hawkeye, Philips Brightview-XCT [32]). The Hungarian company Mediso, for example, offers a triple-modality SPECT/CT/PET system (Mediso AnyScan), which combines all three modalities within a single device (Figure 1).…”

Quantification of 99mTc-DPD concentration in the lumbar spine with SPECT/CT

“…In our experience, the system behaviour is stable over time. The sensitivity can vary between SPECT systems from different vendors and for differently sized phantoms as Seret et al [19] have shown. They report relatively small error bars (−3.83%, 4.15% and 0.76%) for a NEMA standard phantom with a SPECT/CT Symbia system similar to those used in this study.…”

99mTc-Annexin A5 quantification of apoptotic tumor response: a systematic review and meta-analysis of clinical imaging trials

“…SPECT/CT hardware image fusion may allow precise three-dimensional anatomic localization of 99m Tcannexin A5 uptake and CT-based attenuation correction, and may significantly improve SPECT image quality with OSEM reconstruction and corrections for all imagedegrading factors [14,18,[78][79][80][81][82].…”