CMR-based quantitative myocardial perfusion: pixel-wise and pound-wise.

p b c uantitative measurement of myocardial perfusion has been a goal of cardiovascular investigators for a number of years. Positron emission tomography (PET) has allowed assessment of myocardial blood flow in absolute value (milliliters per gram per minute) (1) and is accurate at dentifying both flow-limiting epicardial coronary artery isease (CAD) as well as microvascular abnormalities. ualitative cardiac magnetic resonance (CMR) stress erfusion has also made clinical inroads of late, demnstrating higher sensitivity and negative predictive alue than single-photon emission computed tomograhy (SPECT) in a head-to-head comparison of sympomatic patients against x-ray coronary angiography mployed as the reference standard (2). Although the easibility is established the more important question is f we could do better with absolute quantitation of yocardial blood flow? A recent comparative study of ualitative versus quantitative analysis of myocardial lood flow reserve with CMR did not demonstrate ny incremental value of quantitative assessment for the verall per patient accuracy, and this approach may be easonable if the goal is to identify a patient with ischmia significant for justification of mechanical interention (3). However, the quantitative approach was ore accurate for the assessment of pathophysiology in ore detail such as the delineation of the amount of yocardium at jeopardy. Quantitative measures of myocardial blood flow ave been validated over the years against microspheres n animal models (4), usually on a per segment or per ector level. In this issue of iJACC, Hsu et al. (5) take his validation one step further, demonstrating accurate