How I do CMR Myocardial Perfusion imaging This presentation is posted for members of scmr as an educational guide – it represents the views and practices of the author, and not necessarily those of SCMR. SCMR Website 2006 Christopher Klassen MD, PHD University of Florida Health Science Center Dr. Norbert Wilke

Two phases of myocardial enhancement after contrast injection 1st Dynamic First Pass Perfusion Imaging Occurs within the first minute following injection Wash in and Wash out of contrast agent Transient differences in signal intensity indicate potential ischemia 2nd Delayed Enhancement Imaging 5-30 minutes after injection Hyperenhancement indicates potential infarction

Sequences There are a number of different sequences that can be applied to myocardial perfusion imaging TurboFLASH EPI FISP, BFFE

Acquisition Protocol Localizer views of 2chamber, 3ch, 4ch Long Axis Short Axis stack of localizer views Cine of 4ch Long Axis to examine base motion Infuse stress agent (Adenosine 140 mcg/kg/min, peripheral IV) Gadolinium Contrast + Dynamic Perfusion imaging (hyperemia) Acquire complete cine exam (short axis + long axis views) Gadolinium Contrast + Dynamic Perfusion imaging (rest) Perform Delayed Enhancement Myocardial Viability imaging

Image Interpretation Perfusion Defects Criteria Defect is present in at least 3-4 frames during peak signal intensity Defect size is constant from frame to frame Defect localizes to a physiologic consistent distribution according to coronary artery territories Scenario 1: Defect is present at stress and rest and on delayed enhancement (DCE) Scenario 2: Defect is present during pharmacologic stress but not DCE Signal intensity of the defect doesn’t fluctuate from frame to frame Quantitative parameters are reduced as derived from the myocardial signal intensity curves.

Perfusion Artifacts Relative Converse of Previous slide Defect fluctuates in signal intensity and or size Defect is only present transiently in only 1-2 frames Defect is not consistent with physiology of coronary territories defect is present only at rest and not stress Quantitative parameters demonstrate noisy signal curves

Differential Diagnosis 1. Subendocardial Area of reduced signal intensity on stress perfusion imaging Ischemia with significant or intermediate signal intensity Advanced microvascular disease 2. Circumferential subendocardial defect 3 vessel disease Microvascular disease 3. Defect at rest and stress Myocardial infarction

Reporting Recommend AHA 17 segment model of myocardium 3 slices (base, mid, apex) Base and mid slice divided into 6 radial sectors (anterior septal, anterior, anteriolateral, inferolateral, inferior, inferiorseptal) Apex divided into 4 radial sectors (septal, anterior, inferior, lateral) One segment at tip of apex seen only on long axis, if available

Myocardial Perfusion (Various Clinical Scenarios) Cine Function Rest Perfusion Stress Perfusion Delayed Enhancement Imaging Normal normal no defects Infarction scar with wall thinning Severe defect hyper enhancement Hibernating mild hypokinesia mild defect mild perfusion defect Stunning Ischemia normal or mildly reduced perfusion defect

Myocardial Perfusion Case 1 Three short axis and one 2 chamber LA using Turboflash sequence. Adenosine images top row, and resting bottom row. Arrow points to Subendocardial Defect at the septal wall.

Delayed Enhancement Case 1 Arrow points to hyperenhancement in the septal wall.

Myocardial Perfusion Case 2 Adenosine images top row, and resting bottom row. Arrow points to Defect at the posterior wall.

Delayed Enhancement Case 2 Negative delayed enhancement scan

Perfusion Analysis Qualitative interpretation as above For quantitative and semi-quantitative interpretation Contour endocardial and epicardial borders to measure the myocardial signal intensity curve Generate myocardial and LV blood signal intensity time curves Derive semi-quantitative measures such as Slope, Time to Peak, Max upslope, Peak from the signal intensity curves Calculate absolute myocardial blood flow (ml/min/g) with further fitting of the signal intensity time curve. Myocardial perfusion reserve is defined as the ratio of hyperemic flow to resting flow and also can be used clinically. MR quantification of the myocardial perfusion reserve with a Fermi function model for constrained deconvolution M. Jerosch-Herold, N. Wilke, A. Stillman, R. Wilson Med. Phys. 25 (1), 73-84, Jan 1998

Quantitative Perfusion Analysis Clinically this has been useful in extending qualitative perfusion analysis in the following ways 1. differentiating artifact from actual defects 2. differentiating microvascular disease from ischemia 3. Determining the potential degree of coronary stenosis based on perfusion reserve 4. assist in determining which coronary arteries are affected 5. more accurate comparison with follow up scans 6. eventually to determine prognostic risk as based on the MESA trial.