First-pass Myocardial Perfusion MRI Research Articles

Towards elimination of the dark-rim artifact in first-pass myocardial perfusion MRI: removing Gibbs ringing effects using optimized radial imaging.

Subendocardial dark-rim artifacts (DRAs) remain a major concern in first-pass perfusion (FPP) myocardial MRI and may lower the diagnostic accuracy for detection of ischemia. A major source of DRAs is the "Gibbs ringing" effect. We propose an optimized radial acquisition strategy aimed at eliminating ringing-induced DRAs in FPP. By studying the underlying point spread function (PSF), we show that optimized radial sampling with a simple reconstruction method can eliminate the oscillations in the PSF that cause ringing artifacts. We conducted realistic MRI phantom experiments and in vivo studies (n = 12 healthy humans) to evaluate the artifact behavior of the proposed imaging scheme in comparison to a conventional Cartesian imaging protocol. Simulations and phantom experiments verified our theoretical expectations. The in vivo studies showed that optimized radial imaging is capable of significantly reducing DRAs in the early myocardial enhancement phase (during which the ringing effect is most prominent and may obscure perfusion defects) while providing similar resolution and image quality compared with conventional Cartesian imaging. The developed technical framework and results demonstrate that, in comparison to conventional Cartesian techniques, optimized radial imaging with the proposed optimizations significantly reduces the prevalence and spatial extent of DRAs in FPP imaging.

Evaluation of semi quantitative perfusion parameter maps generated based on a fully automated non-rigid motion correction during a first pass myocardial perfusion (FPMP) MRI

Summary The purpose of this study is to evaluate semi quantitative perfusion parameter maps generated based on a fully automated non-rigid motion correction during a first pass myocardial perfusion (FPMP) MRI in patients with suspected coronary artery disease (CAD) or coronary micro vascular disease (CMVD). Background FPMP MRI is commonly used to assess CAD and most recently to assess cardiac involvement in asymptomatic patients with CMVD such as systemic sclerosis and diabetes mellitus. FPMP MRI evaluation relies on visual inspection for qualitative analysis but quantitative analysis of rest and stress perfusion data is desired to improve diagnosis. One main challenge of qualitative analysis includes cardiac and respiratory motion. To minimize this challenge, ap reviously described inline, fully automated motion correction method [Xue, H MICCAI 2009] generates a motion corrected dataset as well as pixel-wise upslope maps. Using the image at a time point selected for peak signal change during the first pass of contrast agent as the template, all other time points were registered into the template coordinate system. We compare qualitatively and quantitatively the original free breathing images and motion correted images with the corresponding maps pixel-wise upslope maps in patients with suspected CAD or CMVD. Methods

Evaluation of fully automated motion corrected first pass myocardial perfusion MRI with semi quantitative perfusion parameter maps in patients with ischemic heart disease

Summary The purpose of the study is to evaluate a fully automated motion corrected first pass myocardial perfusion (FPMP) MRI with semi quantitative perfusion parameter maps in patients with suspected ischemic heart disease. Background Coronary heart disease is the leading cause of death and disability in the US. FPMP MRI is increasingly used to assess ischemic heart disease; however respiratory motion is one of the major problems for myocardial blood flow quantification. An algorithm for motion correction, surface coil correction, temporal denoising and robust pixel-wise parameter map generation model was previously desribed [Xue H et al MICCAI 2009).This work evaluates automated workflow in a clinical setting to diagnose ischemic heart disease comparing free breathing and motion correcteted images and corresponding pixel-wise parameter map. Methods Stress and rest FPMP images were acquired using a 1.5T scanner (MAGNETOM Avanto, Siemens Healthcare) in 39 patients with suspected ischemic heart disease. Short axis slices were acquired during infusion of 0.075 mMol/kg of Gadolinium (Magnevist, Bayer HealthCare Pharmaceuticals, USA) and adenosine (Adenoscan, AstellasPharma, USA) infusion (0.14 mg/kg/min; duration: 4 min) was administrated to induce stress. Free breathing, motion-corrected images and corresponding perfusion maps were assessed by 2 radiologists independently using the AHA 16 model and evaluated using a four point Likert scale (poor to excellent) to evaluate image quality and confidence level in presence or absence of hypo-perfusion regions. Upslope index of both free breathing and motion corrected images during stress and rest were manually calculated in nonischemic and ischemic areas and compared to the corresponding pixel-wise parameter map generated based on motion corrected images. FPMP MRI results were subsequently compared to coronary angiogram, stress echocardiography, or SPECT.

Quantification of myocardial blood flow using model based analysis of first‐pass perfusion MRI: Extraction fraction of Gd‐DTPA varies with myocardial blood flow in human myocardium

For the absolute quantification of myocardial blood flow (MBF), Patlak plot-derived K1 need to be converted to MBF by using the relation between the extraction fraction of gadolinium contrast agent and MBF. This study was conducted to determine the relation between extraction fraction of Gd-DTPA and MBF in human heart at rest and during stress. Thirty-four patients (19 men, mean age of 66.5 ± 11.0 years) with normal coronary arteries and no myocardial infarction were retrospectively evaluated. First-pass myocardial perfusion MRI during adenosine triphosphate stress and at rest was performed using a dual bolus approach to correct for saturation of the blood signal. Myocardial K1 was quantified by Patlak plot method. Mean MBF was determined from coronary sinus flow measured by phase contrast cine MRI and left ventricle mass measured by cine MRI. The extraction fraction of Gd-DTPA was calculated as the K1 divided by the mean MBF. The extraction fraction of Gd-DTPA was 0.46 ± 0.22 at rest and 0.32 ± 0.13 during stress (P < 0.001). The relationship between extraction fraction (E) and MBF in human myocardium can be approximated as E = 1 - exp(-(0.14 × MBF + 0.56)/MBF). The current results indicate that MBF can be accurately quantified by Patlak plot method of first-pass myocardial perfusion MRI by performing a correction of extraction fraction.

Systolic 3D first-pass myocardial perfusion MRI: Comparison with diastolic imaging in healthy subjects

Three-dimensional (3D) first-pass myocardial perfusion imaging (MPI) is a promising alternative to conventional two-dimensional multislice MPI due to its contiguous spatial coverage that is beneficial for estimating the size of perfusion defects. Data acquisition at mid-diastole is a typical choice for 3D MPI yet is sensitive to arrhythmia and variations in R-R interval that are common in cardiac patients. End systole is the second longest quiescent cardiac phase and is known to be less sensitive to the R-R variability. Therefore, 3D MPI with systolic acquisition may be advantageous in patients with severe arrhythmia once it is proven to be comparable to diastolic MPI in subjects with negligible R-R variation. In this work, we demonstrate the feasibility of 3D MPI with systolic data acquisition in five healthy subjects. We performed 3D MPI experiments in which 3D perfusion data were acquired at both end-systole and mid-diastole of every R-R interval and analyzed the similarity between resulting time intensity curves (TIC) from the two data sets. The correlation between systolic and diastolic TICs was extremely high (mean = 0.9841; standard deviation = 0.0166), and there was a significant linear correlation between the two time intensity curve upslopes and peak enhancements (P < 0.001).

Influence of the k‐space trajectory on the dynamic T1‐weighted signal in quantitative first‐pass cardiac perfusion MRI at 3T

The dynamic T(1)-weighted signal in first-pass myocardial perfusion MRI can vary as a function of k-space trajectory. The purpose of this study, therefore, was to compare the relative T(1)-weighted signal produced by the linear, centric, and reverse centric k-space trajectories at 3T. The centric k-space trajectory yielded higher arterial input function (AIF) than the linear and reverse centric k-space trajectories (6.21 +/- 0.84 vs. 4.75 +/- 0.75 vs. 4.39 +/- 0.85 mM, respectively; N = 9; P < 0.01), and the reverse centric k-space trajectory yielded higher myocardial signal contrast (as a fraction of equilibrium magnetization) than the linear and centric k-space trajectories (0.17 +/- 0.02 vs. 0.12 +/- 0.02 vs. 0.05 +/- 0.01, respectively; N = 9; P < 0.001). Compared to the linear k-space trajectory, the centric k-space trajectory is relatively optimal for the quantification of AIF, whereas the reverse centric k-space trajectory is relatively optimal for high contrast of myocardial wall enhancement.

Abstract 3420: Effects on Myocardial Perfusion at 3 and 15 Months in Recanalized Chronic Total Occlusions - Randomized Comparison of Blood-Derived Progenitor Cells and Inactive Serum

Background: MRI is an excellent diagnostic tool for serial assessment of changes in myocardial perfusion, left ventricular function, and infarct size. In chronic total occlusions (CTO) the effects of recanalization on perfusion and function are contradictory and might depend primarily on viability. Circulating progenitor cells (CPC) injected intracoronarily after successful CTO recanalization might improve perfusion and function. Methods and results: Twenty-eight patients with reperfused CTO were randomized to either CPC’s or inactive serum (control), which were infused into the target vessel. First-pass myocardial perfusion MRI at rest and stress using adenosine at standard dose revealed a significant improvement of the myocardial perfusion reserve index (MPRI) in the affected segments. The baseline MPRI in affected segments was 1.50±0.17 in CPC versus 1.46±0.16 in control (p=0.62). In CPC the MPRI improved to 1.76±0.16 (p&lt;0.001) at 3 and 1.82±0.20 (p&lt;0.001) at 15 months; in control the change was 1.58±0.10 (p=0.01) at 3 and 1.61±0.08 (p=0.004) at 15 months follow-up. However, the MPRI recovery was significantly better in CPC as compared to control at 3 (p=0.004) and 15 months (p=0.005). In remote myocardium the MPRI was 1.70±0.30 and 1.69±0.25 (p&lt;0.01 versus affected segments), respectively. At follow-up there was no significant improvement for both groups. The change in MPRI at 3 and 15 months was correlated with a change in overall infarct size for CPC (3 months: r=−0.68, p&lt;0.02; 15 months: r=−0.81, p=0.001), whereas in control there was no correlation (r=−0.38, p=0.26; 15 months: r=−0.21, p=0.56). Infarct transmurality influenced MPRI improvement at follow-up. CPC patients had a trend towards more improved segments in particular those with higher transmurality (p=0.06). Conclusions: Analysis of serial contrast-enhanced MRI suggests that intracoronary application of CPC post recanalization of CTO is associated with improved myocardial perfusion and subsequent improved recovery of left ventricular function as compared to a control group at mid- and long-term follow-up. Further investigations of the pathophysiological CPC effects on macro- and microvascular function are required.

Kardio-MRT

Cardiovascular magnetic resonance imaging (CMR) is increasingly accepted for the assessment of coronary artery disease (CAD). Pharmacological stress testing can be performed as first-pass myocardial perfusion MRI after injection of adenosine i.v. The protocol allows visualisation of LV function, myocardial perfusion and viability within a single examination. CMR respresents the gold standard concerning LV function and myocardial viability. CMR results are promising concerning myocardial first-pass perfusion imaging. Myocardial scintigraphy with technetium-99m sestamibi performed as a first-pass perfusion study applying adenosine i.v. or during bicycle ergometry represents an alternative modality. When comparing both methods advantages, disadvantages, as well as complementary aspects should be mentioned. CMR does not involve x-ray radiation and may be preferred to scintigraphy in some patients. First-pass myocardial perfusion MRI is now an officially recognized method according to the recently published "Nationale Versorgungs-Leitlinie Chronische KHK" [2] in Germany. Taking into account published data, CMR is suitable for patients with an intermediate risk for CAD.

Diagnostic Accuracy of Stress First-Pass Contrast-Enhanced Myocardial Perfusion MRI Compared with Stress Myocardial Perfusion Scintigraphy

The purpose of this study was to determine the diagnostic accuracy of stress perfusion MRI acquired with saturation-recovery prepared turbo fast low-angle shot (turbo FLASH) compared with stress myocardial perfusion scintigraphy. Recent studies show that first-pass contrast-enhanced myocardial perfusion MRI can provide noninvasive detection of low-limiting stenosis in the coronary artery. First-pass contrast-enhanced MR images were acquired at rest and during stress in 40 patients with suspected coronary artery disease. All patients underwent thallium-201 SPECT without attenuation correction and coronary angiography. Two reviewers independently assigned one of five confidence grades without knowing the results of coronary angiography for receiver operating characteristic (ROC) analysis. Luminal stenosis >70% on coronary angiography was used as a reference standard. On coronary angiography, 70% or greater diameter stenosis of the coronary artery was observed in 21 (52.5%) of 40 patients. The areas under the ROC curve for detection of significant stenosis in the individual coronary artery were 0.86 (observer 1) and 0.84 (observer 2) for MRI. These values were 0.79 (observer 1, p = not significant) and 0.72 (observer 2, p = not significant) for 201Tl SPECT. The diagnostic accuracy of stress perfusion MRI acquired with saturation-recovery-prepared turbo FLASH was comparable with that of stress 201Tl SPECT. Stress first-pass contrast-enhanced MRI is a noninvasive technique that can be used as an alternative to stress myocardial perfusion scintigraphy.

Whole-heart dipyridamole stress first-pass myocardial perfusion MRI for the detection of coronary artery disease with and without prior myocardial infarction

Whole-heart dipyridamole stress first-pass myocardial perfusion MRI for the detection of coronary artery disease with and without prior myocardial infarction