Magnetic resonance quantification of the myocardial perfusion reserve with a Fermi function model for constrained deconvolution

Abstract

The myocardial perfusion reserve, defined as the ratio of hyperemic and basal myocardial blood flow, is a useful indicator of the functional significance of a coronary artery lesion. Rapid magnetic resonance (MR) imaging for the noninvasive detection of a bolus-injected contrast agent as a MR tracer is applied to the measurement of regional tissue perfusion during rest and hyperemia, in patients with microvascular dysfunction. A Fermi function model for the distribution of tracer residence times in the myocardium is used to fit the MR signal curves. The myocardial perfusion reserve is calculated from the impulse response amplitudes for rest and hyperemia. The assumptions of the model are tested with Monte Carlo simulations, using a multiple path, axially distributed mathematical model of blood tissue exchange, which allows for systematic variation of blood flow, vascular volume, and capillary permeability. For a contrast-to-noise ratio of 6:1, and over a range of flows from 0.5 to 4.0 ml/min per g of tissue, the ratio of the impulse response amplitudes for hyperemic and basal flows is linearly proportional to the ratio of model blood flows, if the mean transit time of the input function is shorter than approximately 9 s. The uncertainty in the blood flow reserve estimates grows both at low (< 1.0 ml/min/g) and high (> 3-4 ml/min/g) flows. The predictions of the Monte Carlo simulations agree with the results of MR first pass studies in patients without significant coronary artery lesions and microvascular dysfunction, where the perfusion reserve in the territory of the left anterior descending coronary artery (LAD) correlates linearly with the intracoronary Doppler ultrasound flow reserve in the LAD (r = 0.84), in agreement with previous PET studies.

Factors associated with false‐negative cardiovascular magnetic resonance perfusion studies: A Clinical evaluation of magnetic resonance imaging in coronary artery disease (CE‐MARC) substudy

“…Furthermore, 31% of false‐negative MR studies with inadequate hemodynamic response had inducible ischemia on SPECT, which used the same adenosine protocol. Myocardial perfusion reserve, the ratio of hyperemic to resting myocardial blood flow,15 was similar between false‐negative studies and normal controls. These results all suggest that adenosine response was similar in the two groups.…”

“…MPR estimation was performed offline using PMI v. 0.4 software 14. Deconvolution was performed on MR stress and rest perfusion images using a Fermi model applied to the first pass,15, 16 with arterial input defined in the LV blood pool, and the whole mid‐LV short axis myocardial slice as tissue response. Regions of interest were carefully selected by an experienced reader (4 year' experience) to be as large as possible but to avoid dark rim artifact, trabeculations, and papillary muscles, and manually corrected to account for respiratory motion.…”

Quantification of pulmonary blood flow (PBF): Validation of perfusion MRI and nonlinear contrast agent (CA) dose correction with HO positron emission tomography (PET)

“…For reliable quantification of perfusion, a low CA dose was chosen in order to obtain a pseudolinear dependence of the SI and CA concentration (11) in the lung parenchyma. Hence, the CA gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA, Magnevist; Schering, Berlin, Germany) dose was less than 0.025 mmol/kg body weight (BW) in all cases (injection rate ϭ 3 ml s -1 ).…”

“…One of those parameters is the contrast agent (CA) dose. which has to be chosen small enough to obtain the ideal pseudolinear relationship between signal intensity (SI) and CA (11) while achieving a sufficient signal-to-noise ratio (SNR) in lung parenchyma.…”

In vivo assessment of absolute perfusion and intracapillary blood volume in the murine myocardium by spin labeling magnetic resonance imaging

“…Although this techniqe allows absolute quantification in principle (8), its reported usage in mice is currently confined to the relative assessment of perfusion changes in mouse hindlimbs after application of a vascular growth factor (9). In addition, contrast-enhanced MRI was used to study perfusion defects in murine myocardium (10).…”