MR Perfusion Imaging for the Detection of Myocardial Ischemia C. H. C. Janssen, D. Kuijpers, M. Oudkerk Department of Radiology, State University and Academic Hospital Groningen, Groningen, The Netherlands Correspondence to: C. H. C. Janssen Department of Radiology, State University and Academic Hospital Groningen Hanzeplein 1, 9713GZ Groningen, The Netherlands Tel: +31 503 611451; Fax: +31 503 617008; E-mail: c.h.c.janssen@rad.azg.nl Key words: Myocardial perfusion, magnetic resonance imaging, post-processing, semiquantitative analysis, signal intensity, myocardial perfusion reserve. Abstract A wide variety of imaging modalities is available for the diagnosis of ischemic coronary artery disease (CAD). Myocardial hypo-perfusion is one of the first steps in the ischemic cascade and can be detected before clinical symptoms, ECG alterations or wall motion abnormalities occur. Currently, nuclear medicine techniques (scintigra- phy) such as single-photon emission computed tomography using Thalium-201 or TC-99 m sestamibi are most fre- quently used for the imaging of myocardial perfusion. Positron emission tomography (PET) is the reference standard for myocardial perfusion imaging. These tech- niques attain a sensitivity and specificity for the detection of myocardial ischemia of, respectively, 83–95 and 53–95%. However, PET is not widely available, which makes it relatively inaccessible. Other disadvantages of myocardial perfusion imaging scintigraphy are: high costs, long-time commitment, radiation exposure, specificity depending on quality control of laboratory and trained readers and low specificity in presence of left bundle branch block. As a result of the fast hardware and software development magnetic resonance imaging (MRI) has become a prom- ising new technique for perfusion imaging. This paper will give an introduction to myocardial perfusion MRI for the detection of ischemic heart disease followed by an overview of the post-processing procedures. Introduction A wide variety of imaging modalities is available for the diagnosis of ischemic coronary artery disease (CAD). Myocardial hypo-perfusion is one of the first steps in the ischemic cascade and can be detected before clinical symptoms, ECG alterations or wall motion abnormalities occur (Fig. 1). Currently, nuclear medicine techniques (scintigraphy) such as single-photon emission computed tomography (SPECT) using Thalium-201 or TC-99m sestamibi are most frequently used for the imaging of myocardial perfusion. Positron emission tomography (PET) is the reference standard for myocardial perfusion imaging (1). These techniques attain a sensitivity and spe- cificity for the detection of myocardial ischemia of, respectively, 83–95 and 53–95% (2–4). However, PET is not widely available, which makes it relatively inaccessible. For example, in the Netherlands only four PET centers are available on a population of over 16 million people. Other disadvantages of myocardial perfusion imaging scintigra- phy are; high costs, long-time commitment, radiation exposure, specificity depending on quality control of laboratory and trained readers and low specificity in presence of left bundle branch block (LBBB) (5). As a result of the fast hardware and software development magnetic resonance imaging (MRI) has become a promising new technique for perfusion imaging, and is increasingly being applied as an alternative to nuclear imaging for assessing myocardial perfusion. Although nuclear medicine and MRI are both suitable for myocardial perfusion imaging, some considerable differences between the two techniques can be distinguished (Table 1). This paper will give an introduction to myocardial perfusion MRI for the detec- tion of ischemic heart disease followed by an overview of the post-processing procedures. Myocardial perfusion Myocardial perfusion is defined as the volume of blood flowing in a given portion of myocardium per unit of time (ml/g/min). The amount of perfusion alters with the level of metabolism of the myocardium, i.e. the metabolism, and thus the demand for oxygen during exercise will increase, resulting in an increased myocardial perfusion. On the other hand, the perfusion is limited by the supply of plas- ma, i.e. if a significant stenosis or occlusion of a coronary artery exists, the maximum blood supply is not sufficient to answer the increased demand, resulting in ischemia. In some cases though, the balance between metabolism and stenosis is maintained during rest despite of a stenosis, and 2/2004 n IMAGING DECISIONS