Cardiac Imaging

Two examples of CT myocardial perfusion (CTP) imaging assessment software. Canon is on the left and GE Healthcare is on the right. Both of these technologies have been around for a few years, but there have been an increasing amount of clinical data from studies showing the accuracy of the technology compared to nuclear imaging, the current stand of care for myocardial perfusion imaging, and cardiac MRI.

Figure 1: Depiction of the fully automated CT biomarkers tools used in this study. (A) Schematic depiction of the automated process for assessing fat, muscle, liver, aortic calcification, and bone from original abdominal CT scan data. (B) Case example in an asymptomatic 52-year-old man undergoing CT for colorectal cancer screening. At the time of CT screening, he had a body-mass index of 27·3 and Framingham risk score of 5% (low risk). However, several CT-based metabolic markers were indicative of underlying disease. Multivariate Cox model prediction based on these three CT-based results put the risk of cardiovascular event at 19% within 2 years, at 40% within 5 years, and at 67% within 10 years, and the risk of death at 4% within 2 years, 11% within 5 years, and 27% within 10 years. At longitudinal clinical follow-up, the patient suffered an acute myocardial infarction 3 years after this initial CT and died 12 years after CT at the age of 64 years. (C) Contrast-enhanced CT performed 7 months before death for minor trauma was interpreted as negative but does show significant progression of vascular calcification, visceral fat, and hepatic steatosis. HU=Hounsfield units.

With the advent and optimization of nuclear scintigraphy protocols using bone-avid radiotracers, cardiac amyloidosis caused by transthyretin protein (ATTR) can now be diagnosed noninvasively without a tissue biopsy. The radiotracer 99mTc-pyrophosphate (99mTc-PYP) binds to deposited ATTR amyloid fibrils in the myocardium and can be visualized using planar and SPECT imaging. This is Figure 2, showing how SPECT imaging allows the reader to distinguish between blood pool activity (ventricular cavity, etc) and myocardial activity and identify regional myocardial differences in radiotracer uptake.