Hybrid single-photon emission computed tomography and computed tomography (SPECT–CT) and positron emission tomography computed tomography (PET–CT) imaging have grown tremendously over the last two decades.
Depending upon the equipment, the CT component of SPECT/CT and PET/CT images is useful for attenuation correction, identification of coronary artery calcification, CT coronary angiography, or localization of radiotracer uptake in radiopharmaceutically avid images.
Coronary artery calcium score when combined with a myocardial perfusion imaging is valuable for the management of patients with suspected ischemic heart disease.
Cardiac PET/MR provides simultaneous PET and MR acquisitions and is currently used primarily for research applications.
There has been significant growth in hybrid single-photon emission computed tomography and computed tomography (SPECT–CT) and positron emission tomography computed tomography (PET–CT) systems over the past decade, driven in large part by oncologic imaging. A fortuitous byproduct of this has been the development, application, and validation of myocardial perfusion imaging (MPI) using these hybrid systems. Cardiac hybrid SPECT–CT and PET–CT systems offer distinct advantages compared with traditional SPECT or PET MPI. The CT provides for excellent attenuation correction and improves the specificity of MPI, CT-derived coronary artery calcium (CAC) score adds substantial incremental diagnostic and prognostic information to MPI, and hybrid scanners offer the ability to combine a physiologic assessment of perfusion, function, or metabolism with an anatomic assessment of atherosclerosis and structural heart disease. Hybrid SPECT–CT and PET–CT imaging also offers unprecedented opportunities for molecular cardiology research. The primary focus of this chapter is to discuss the clinical applications of hybrid radionuclide MPI with calcium scoring and coronary CTA.
The hardware of SPECT–CT and PET–CT scanners comprises a conventional SPECT scanner or a PET scanner coupled with a CT scanner of various configurations. While all SPECT–CT and PET–CT scanners offer CT-based attenuation correction, calcium scoring (≥4 slice MDCT) and coronary CTA (≥64 slice MDCT) may be performed only on certain hybrid SPECT–CT and PET–CT scanners. Sample hybrid PET–CT and SPECT–CT protocols are shown in Figure 27-1A and B, respectively. The CAC score and/or coronary CTA study can be performed sequentially right before or after the SPECT or PET scan or at a separate setting.
Sample protocols for (A) PET/CT and (B) SPECT/CT myocardial perfusion imaging. CTAC, CT for AC (10 mA, 120 keV, nongated free breathing); CAC, calcium score CT scan (300 mA, 140 keV, ECG-gated CT scan with breath hold); *, optional.
ATTENUATION CORRECTON WITH CT FOR BOTH SPECT AND PET
Attenuation correction using transmission scanning employing external radioactive sources or cardiac CT improves the count uniformity of the image and helps distinguish attenuation artifacts from real defects. It also offers the possibility of stress-only imaging, with potential savings of time, cost, and radiation dose. ...