Quantitative Analysis Of Myocardial Perfusion Research Articles

Stress CMR in Known or Suspected CAD: Diagnostic and Prognostic Role.

The recently published 2019 guidelines on chronic coronary syndromes (CCS) focus on the need for noninvasive imaging modalities to accurately establish the diagnosis of coronary artery disease (CAD) and assess the risk of clinical scenario occurrence. Appropriate patient management should rely on controlling symptoms, improving prognosis, and guiding each therapeutic strategy as well as monitoring disease progress. Among the noninvasive imaging modalities, cardiovascular magnetic resonance (CMR) has gained broad acceptance in past years due to its unique features in providing a complete assessment of CAD through data on cardiac anatomy and function and myocardial viability, with high spatial and temporal resolution and without ionizing radiation. In detail, evaluation of the presence and extent of myocardial ischemia through stress CMR (S-CMR) has shown a high rule-in power in detecting functionally significant coronary artery stenosis in patients suspected of CCS. Moreover, S-CMR technique may add significant prognostic value, as demonstrated by different studies which have progressively evidenced the valuable power of this multiparametric imaging modality in predicting adverse cardiac events. The latest scientific progress supports a greater expansion of S-CMR with improvement of quantitative myocardial perfusion analysis, myocardial strain, and native mapping within the same examination. Although further study is warranted, these techniques, which are currently mostly restricted to the research field, are likely to become increasingly prevalent in the clinical setting with the scope of increasing accuracy in the selection of patients to be sent to invasive revascularization. This review investigates the diagnostic and prognostic role of S-CMR in the context of CAD, by analysing a strong, long-standing, scientific evidence together with an appraisal of new advanced techniques which may potentially enrich CAD management in the next future.

Cardiac Magnetic Resonance for Evaluating Nonculprit Lesions After Myocardial Infarction: Comparison With Fractional Flow Reserve

ObjectivesThis study sought to determine the agreement between cardiac magnetic resonance (CMR) imaging and invasive measurements of fractional flow reserve (FFR) in the evaluation of nonculprit lesions after ST-segment elevation myocardial infarction (STEMI). In addition, we investigated whether fully quantitative analysis of myocardial perfusion is superior to semiquantitative and visual analysis. BackgroundThe agreement between CMR and FFR in the evaluation of nonculprit lesions in patients with STEMI with multivessel disease is unknown. MethodsSeventy-seven patients with STEMI with at least 1 intermediate (diameter stenosis 50% to 90%) nonculprit lesion underwent CMR and invasive coronary angiography in conjunction with FFR measurements at 1 month after primary intervention. The imaging protocol included stress and rest perfusion, cine imaging, and late gadolinium enhancement. Fully quantitative, semiquantitative, and visual analysis of myocardial perfusion were compared against a reference of FFR. Hemodynamically obstructive was defined as FFR ≤0.80. ResultsHemodynamically obstructive nonculprit lesions were present in 31 (40%) patients. Visual analysis displayed an area under the curve (AUC) of 0.74 (95% confidence interval [CI]: 0.62 to 0.83), with a sensitivity of 73% and a specificity of 70%. For semiquantitative analysis, the relative upslope of the stress signal intensity time curve and the relative upslope derived myocardial flow reserve had respective AUCs of 0.66 (95% CI: 0.54 to 0.77) and 0.71 (95% CI: 0.59 to 0.81). Fully quantitative analysis did not augment diagnostic performance (all p > 0.05). Stress myocardial blood flow displayed an AUC of 0.76 (95% CI: 0.64 to 0.85), with a sensitivity of 69% and a specificity of 77%. Similarly, MFR displayed an AUC of 0.82 (95% CI: 0.71 to 0.90), with a sensitivity of 82% and a specificity of 71%. ConclusionsCMR and FFR have moderate-good agreement in the evaluation of nonculprit lesions in patients with STEMI with multivessel disease. Fully quantitative, semiquantitative, and visual analysis yield similar diagnostic performance.

Development and validation of a new method to diagnose apical hypertrophic cardiomyopathy by gated single-photon emission computed tomography myocardial perfusion imaging.

The aim of this study is to develop and validate a new method to diagnose apical hypertrophic cardiomyopathy (AHCM) by the integral quantitative analysis of myocardial perfusion and wall thickening from gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). Twenty-two consecutive patients, who showed T wave inversion of at least 3 mm in precordial leads and sinus rhythm in ECG, were enrolled. All the patients underwent cardiac magnetic resonance (CMR), gated rest SPECT MPI and echocardiography. According to CMR diagnostic results, 13 patients were categorized as in the AHCM group and the remaining nine patients were categorized as in the non-AHCM group. Operators who were blinded to the CMR diagnosis independently performed the diagnosis by gated SPECT MPI. The regions of interest inside the apical hotspots on the perfusion polar map were drawn and the mean values of wall thickening in the drawn region of interests were calculated. Using MRI diagnosis as the gold standard, AHCM was diagnosed based on receiver operating characteristic analysis of the mean wall thickening in the apical perfusion hotspot. The area under curve, sensitivity, specificity, and accuracy of our method were 0.97, 100%, 89%, and 95%, respectively. Our new method has high sensitivity, specificity, and accuracy against CMR diagnosis. It has great promise to become a clinical tool in the diagnosis of AHCM.

Low CT temporal sampling rates result in a substantial underestimation of myocardial blood flow measurements

The purpose of this study was to evaluate the effect of temporal sampling rate in dynamic CT myocardial perfusion imaging (CTMPI) on myocardial blood flow (MBF). Dynamic perfusion CT underestimates myocardial blood flow compared to PET and SPECT values. For accurate quantitative analysis of myocardial perfusion with dynamic perfusion CT a stable calibrated HU measurement of MBF is essential. Three porcine hearts were perfused using an ex-vivo Langendorff model. Hemodynamic parameters were monitored. Dynamic CTMPI was performed using third generation dual source CT at 70 kVp and 230–350 mAs/rot in electrocardiography(ECG)-triggered shuttle-mode (sampling rate, 1 acquisition every 2–3 s; z-range, 10.2 cm), ECG-triggered non-shuttle mode (fixed table position) with stationary tube rotation (1 acquisition every 0.5–1 s, 5.8 cm), and non-ECG-triggered continuous mode (1 acquisition every 0.06 s, 5.8 cm). Stenosis was created in the circumflex artery, inducing different fractional flow reserve values. Volume perfusion CT Myocardium software was used to analyze ECG-triggered scans. For the non-ECG triggered scans MASS research version was used combined with an in-house Matlab script. MBF (mL/g/min) was calculated for non-ischemic segments. True MBF was calculated using input flow and heart weight. Significant differences in MBF between shuttle, non-shuttle and continuous mode were found, with median MBF of 0.87 [interquartile range 0.72–1.00], 1.20 (1.07–1.30) and 1.65 (1.40–1.88), respectively. The median MBF in shuttle mode was 56% lower than the true MBF. In non-shuttle and continuous mode, the underestimation was 41% and 18%. Limited temporal sampling rate in standard dynamic CTMPI techniques contributes to substantial underestimation of true MBF.

Quantitative Myocardial Perfusion with Dynamic Contrast-Enhanced Imaging in MRI and CT: Theoretical Models and Current Implementation.

Technological advances in magnetic resonance imaging (MRI) and computed tomography (CT), including higher spatial and temporal resolution, have made the prospect of performing absolute myocardial perfusion quantification possible, previously only achievable with positron emission tomography (PET). This could facilitate integration of myocardial perfusion biomarkers into the current workup for coronary artery disease (CAD), as MRI and CT systems are more widely available than PET scanners. Cardiac PET scanning remains expensive and is restricted by the requirement of a nearby cyclotron. Clinical evidence is needed to demonstrate that MRI and CT have similar accuracy for myocardial perfusion quantification as PET. However, lack of standardization of acquisition protocols and tracer kinetic model selection complicates comparison between different studies and modalities. The aim of this overview is to provide insight into the different tracer kinetic models for quantitative myocardial perfusion analysis and to address typical implementation issues in MRI and CT. We compare different models based on their theoretical derivations and present the respective consequences for MRI and CT acquisition parameters, highlighting the interplay between tracer kinetic modeling and acquisition settings.

Comparison of Myocardial Transmural Perfusion Gradient by Magnetic Resonance Imaging to Fractional Flow Reserve in Patients With Suspected Coronary Artery Disease

The goal of this study was to evaluate the diagnostic accuracy of transmural perfusion gradient (TPG) and transmural perfusion gradient reserve (TPGR) with 3.0 T cardiac magnetic resonance (CMR) against invasively determined fractional flow reserve (FFR) to detect coronary artery stenosis. Quantitative analysis of myocardial perfusion with CMR to diagnosis coronary artery disease (CAD) has been widely accepted. However, traditional transmural myocardial perfusion analysis with CMR neglects that endocardium is more vulnerable to ischemia than epicardium. TPG and TPGR can take the inhomogenous perfusion impairment into account and be more sensitive and specific for diagnosis of CAD. In this study, 71 patients (57 men, age 60.1 ± 6.4 years) with known or suspected CAD referred for invasive angiography study underwent rest and adenosine-induced stress CMR perfusion imaging scan. FFR was attempted to be measured in all major epicardial coronary arteries. FFR ≤0.75 was regarded to indicate a hemodynamic significant coronary lesion. A TPG ≤0.85 predicted significant CAD with sensitivity and specificity of 74.55% and 83.65%, respectively. Sensitivity and specificity of TPGR ≤0.81 were 90.91% and 89.94%, respectively. Area under the receiver-operating curve to detect FFR ≤0.75 was 0.86 for TPG and 0.95 for TPGR. TPGR yielded significantly better sensitivity and specificity for diagnosis of CAD than traditional myocardial blood flow, myocardial perfusion reserve, and TPG (p < 0.0001). In conclusion, TPG and TPGR analyses with MRI are capable of detecting hemodynamic stenosis of coronary artery and superior to traditional myocardial perfusion analysis. Furthermore, TPGR appears to be superior to TPG in the diagnosis of coronary artery stenosis.

Diaphragm border detection in coronary X-ray angiographies: New method and applications

X-ray angiography is widely used in cardiac disease diagnosis during or prior to intravascular interventions. The diaphragm motion and the heart beating induce gray-level changes, which are one of the main obstacles in quantitative analysis of myocardial perfusion. In this paper we focus on detecting the diaphragm border in both single images or whole X-ray angiography sequences. We show that the proposed method outperforms state of the art approaches. We extend a previous publicly available data set, adding new ground truth data. We also compose another set of more challenging images, thus having two separate data sets of increasing difficulty. Finally, we show three applications of our method: (1) a strategy to reduce false positives in vessel enhanced images; (2) a digital diaphragm removal algorithm; (3) an improvement in Myocardial Blush Grade semi-automatic estimation.

Myocardial Blood Flow Quantification from MRI – an Image Analysis Perspective

First-pass perfusion imaging allows for a very high spatial resolution, noninvasive and radiation free quantification of myocardial blood flow. True quantification of perfusion images offers a unique capability to localize and measure subendocardial ischemia. Several techniques such as semiquantitative, model independent and model dependent methods are available for calculating MBF from perfusion CMR. However, for accurate perfusion quantification a few requirements need to be addressed beforehand. These include but are not limited to the relationship between the amount of injected contrast agent and the signal intensity of the MR image, used pulse sequence, and the extraction of an arterial input function. Moreover, with the new advances in CMR perfusion imaging, high spatial resolution voxel-wise quantitative analysis of myocardial perfusion is feasible. Voxel-wise quantification has the potential to combine the advantage of visual analysis with the objective and reproducible evaluation made by true quantitative methods.

Dose response of the intravascular contrast agent gadofosveset trisodium in MR perfusion imaging of the myocardium using a quantitative evaluation

This study was performed to determine the best concentration of gadofosveset at 1.5 and 3 T MRI for quantitative myocardial perfusion analysis. 18 healthy volunteers have been examined at a 1.5 and a 3 T MRI system assigned to one of three dose groups: low dose (0.00375 mmol/kg), medium dose (0.0075 mmol/kg), high dose (0.0150 mmol/kg). A T1-weighted saturation recovery turboFLASH sequence with parallel imaging was used. Two perfusion scans were performed for each field strength and volunteer. Peak signal-to-noise-ratio, maximum contrast-enhancement-ratio and myocardial blood flow (MBF) were calculated. MBF values were significantly higher at 1.5 T in the medium and the high dose groups than in the low dose group (p < 0.001). Higher MBF values could be found at 3 T for the second perfusion scan in the medium and both perfusion scans in the high dose group compared to the low dose group. Optimal dose of gadofosveset for quantitative perfusion analysis at 1.5 T is 0.00375 mmol/kg as higher doses caused overestimation of the MBF. At 3 T 0.0075 mmol/kg seems to be the best dose for a single perfusion scan, while for a second perfusion scan MBF may be overestimated.

3 Tesla is the preferred field strength for perfusion imaging in coronary artery disease – a comparison to 1.5 Tesla and fractional flow reserve

Background Adenosine perfusion imaging at 1.5 Tesla (T) has been shown to yield good diagnostic values in comparison to quantitative coronary angiography. Perfusion imaging at 3 T has the potential benefit of higher contrast- and signalto-noise ratios. However, little is known about diagnostic performance of 3 T perfusion imaging in comparison to 1.5 T and in comparison to invasive measurement of fractional flow reserve (FFR). We sought to evaluate visual and quantitative assessment of adenosine perfusion at 3 T in comparison to 1.5 T and to coronary angiography in patients presenting with suspected coronary artery disease (CAD). Methods 86 consecutive patients with suspected CAD were enrolled in this study. All patients underwent adenosine perfusion at 3 T (Achieva, Philips Medical Systems) and 1.5 T (Intera, Philips Medical Systems) within 72 hours with subsequent coronary angiography within 72 hours. Two independent patient groups were formed. In group 1 1 (N=52) quantitative coronary analysis (QCA) was compared to qualitative perfusion MRI imaging. Group 2 (N=34) underwent FFR measurement in all three major coronary arteries in comparison to quantitative myocardial perfusion reserve (MPR). Results In both groups a significant (p<0.05) higher sensitivity and specificity (group 1: 0.88 vs 0.80 and 0.96 vs. 0.89, p<0.01; group 2 0.91 vs. 0.62 and 1.0 vs. 0.77, p<0.001) was found for 3 T when compared to 1.5 T. Conclusions 3 T appears to be the superior field strength for visual or quantitative analysis of myocardial perfusion in CAD as shown in our two consecutive patient groups.

Quantitative Myocardial Contrast Supine Bicycle Stress Echocardiography for Detection of Coronary Artery Disease

If compared with two-dimensional echocardiography (2DE), quantitative myocardial contrast echocardiography (MCE) improves detection of coronary artery disease (CAD) during pharmacological stress, but there is paucity of data regarding quantitative MCE performed during supine bicycle stress. To determine the feasibility and accuracy of quantitative MCE and assess its incremental benefit over 2DE for detection of CAD during supine bicycle stress. Sixty-one consecutive patients (47 males, 14 females, mean age 57 ± 12 years) with suspected CAD, who were scheduled for coronary angiography, underwent 2DE and MCE supine bicycle stress. The diagnosis of obstructive CAD (≥50% stenosis) was based on inducible wall-motion and myocardial perfusion abnormalities. For quantitative myocardial perfusion analysis, A, β, and Aβ reserve were derived from myocardial contrast replenishment curves. Quantitative coronary angiography revealed ≥50% stenosis in 41, ≥70% stenosis in 18, single vessel disease in 24, and multivessel disease in 17 patients. If compared with 2DE, quantitative MCE was more sensitive (71% vs. 93%; P < 0.05) and more accurate (74% vs. 89%; P < 0.05) to detect obstructive CAD. The sensitivity of 2DE and quantitative MCE was 61% and 91% (P < 0.05) in 50-69% stenosis, and 63% and 92% (P < 0.05) in single vessel disease. No difference in sensitivity between 2DE and quantitative MCE was found in subjects with ≥70% stenosis (83% vs. 94%, P = NS) and multivessel disease (82% vs. 94%, P = NS). Quantitative MCE enhances sensitivity and accuracy of supine bicycle stress 2DE for detection of obstructive CAD, and this incremental benefit is especially present in less severe disease.

Voxel‐wise quantification of myocardial perfusion by cardiac magnetic resonance. Feasibility and methods comparison

The purpose of this study is to enable high spatial resolution voxel-wise quantitative analysis of myocardial perfusion in dynamic contrast-enhanced cardiovascular MR, in particular by finding the most favorable quantification algorithm in this context. Four deconvolution algorithms--Fermi function modeling, deconvolution using B-spline basis, deconvolution using exponential basis, and autoregressive moving average modeling--were tested to calculate voxel-wise perfusion estimates. The algorithms were developed on synthetic data and validated against a true gold-standard using a hardware perfusion phantom. The accuracy of each method was assessed for different levels of spatial averaging and perfusion rate. Finally, voxel-wise analysis was used to generate high resolution perfusion maps on real data acquired from five patients with suspected coronary artery disease and two healthy volunteers. On both synthetic and perfusion phantom data, the B-spline method had the highest error in estimation of myocardial blood flow. The autoregressive moving average modeling and exponential methods gave accurate estimates of myocardial blood flow. The Fermi model was the most robust method to noise. Both simulations and maps in the patients and hardware phantom showed that voxel-wise quantification of myocardium perfusion is feasible and can be used to detect abnormal regions.

Quantitative myocardial perfusion imaging with a MR cold pressor test

The response of myocardial blood flow to sympathetic stimulation with cold is modulated by endothelium-related factors. As endothelial dysfunction is an early step in patients with coronary artery disease, the aim of this study was to establish a cold pressor test (CPT) setting for quantitative analysis of myocardial perfusion in a MR scanner. First pass perfusion studies were performed in 10 healthy volunteers using a 1.5 T MR scanner with a multislice steady state free precession perfusion trueFISP sequence in prebolus technique (1 cc/4 cc gadobenate dimeglumine). MR-CPT was established using an over head ice-water bath of the left hand. First pass perfusion imaging was started after 1 min to assure an adequate stimulus followed by a second series after 15 min to evaluate the rest perfusion. After motion correction images were segmented with an adapted, automated tool, myocardial contours were determined. Perfusion was quantitatively evaluated after contamination and baseline correction by deconvolution with the arterial input function using an exponential function model as residuum. All data could be evaluated. Mean myocardial perfusion rose from 0.61 ± 0.22 cc/g/min at rest to 1.15 ± 0.34 cc/g/min under CPT. MR myocardial perfusion values show a comparable increase under CPT as published positron emission tomography data. Consequently, CPT for the presence of endothelial dysfunction is feasible in the MR environment.

Effect of improving spatial or temporal resolution on image quality and quantitative perfusion assessment with k‐t SENSE acceleration in first‐pass CMR myocardial perfusion imaging

k-t Sensitivity-encoded (k-t SENSE) acceleration has been used to improve spatial resolution, temporal resolution, and slice coverage in first-pass cardiac magnetic resonance myocardial perfusion imaging. This study compares the effect of investing the speed-up afforded by k-t SENSE acceleration in spatial or temporal resolution. Ten healthy volunteers underwent adenosine stress myocardial perfusion imaging using four saturation-recovery gradient echo perfusion sequences: a reference sequence accelerated by sensitivity encoding (SENSE), and three k-t SENSE–accelerated sequences with higher spatial resolution (“k-t High”), shorter acquisition window (“k-t Fast”), or a shared increase in both parameters (“k-t Hybrid”) relative to the reference. Dark-rim artifacts and image quality were analyzed. Semiquantitative myocardial perfusion reserve index (MPRI) and Fermi-derived quantitative MPR were also calculated. The k-t Hybrid sequence produced highest image quality scores at rest (P = 0.015). Rim artifact thickness and extent were lowest using k-t High and k-t Hybrid sequences (P < 0.001). There were no significant differences in MPRI and MPR values derived by each sequence. Maximizing spatial resolution by k-t SENSE acceleration produces the greatest reduction in dark rim artifact. There is good agreement between k-t SENSE and standard acquisition methods for semiquantitative and fully quantitative myocardial perfusion analysis. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.

Improved correction of spatial inhomogeneities of surface coils in quantitative analysis of first‐pass myocardial perfusion imaging

To test whether image normalization using either a separate 3D proton-density (PD)-weighted prescan, or 2D PD-weighted images prior to the perfusion series, improves correction of differences in spatial sensitivity induced by radiofrequency (RF) surface receiver coils. Originally, this correction was applied using the baseline signal in the myocardium before arrival of the contrast agent. This is of importance, as quantitative analysis of magnetic resonance (MR) myocardial perfusion using deconvolution with the arterial input assumes equal signal sensitivity over the heart. First-pass myocardial perfusion measurements were obtained in 13 patients without known coronary artery disease. Absolute perfusion values were assessed for 18 myocardial segments without any normalization and using the three different normalization methods. Using 2D or 3D PD-weighted normalization, similar mean perfusion values were found, but with reduced spatial variance over the 18 segments. The relative dispersion of perfusion at rest was 23% and 35% for the 3D prescan normalization and the baseline normalization, respectively. With 2D and 3D PD-weighted prescan normalization the relative dispersion was closer to the expected physiological heterogeneity. PD-weighted prescan normalization proved to be a valuable addition to quantitative analysis of myocardial perfusion, and better than baseline-based normalization.

Quantitative analysis of myocaridal perfusion in rabbits by tansthoracic real-time myocardial contrast echocardiography

To evaluate the feasibility of real-time myocardial contrast echocardiography (RTMCE) by quantitative analysis of myocardial perfusion in rabbits, transthoracic RTMCE was performed in 10 healthy rabbits by using continuous infusion of SonoVue into the auricular vein. The short axis view at the papillary muscle level was obtained. The duration of the time that the contrast took to appear in right heart, left heart and myocardium was recorded. The regional myocardial signal intensity (SI) versus refilling time plots were fitted to an exponential function: y(t) =A(1-e(-beta(t-t0))) + C, where y is SI at any given time, A is the SI plateau that reflects myocardial blood volume, and beta is the slope of the refilling curve that reflects myocardial microbubble velocity. The A, beta and Axbeta values at different infusion rate of SonoVue were analyzed and the A, beta and Axbeta values in each segment in the short axis view at the papillary muscle level were compared. All the animal experiments were successful and high-quality images were obtained. The best intravenous infusion rate for SonoVue was 30 mL/h. The contrast appeared in right heart, left heart and myocardium at 7.5+/-2.2 s, 9.1+/-2.4 s and 12.2+/-1.6 s respectively. After 16.6+/-2.3s, myocardial opacification reached a steady state. The mean A, beta and Axbeta value in the short axis view at the papillary muscle level were 9.8+/-3.0 dB, 1.4+/-0.5 s(-1) and 13.5+/-3.6 dBxs(-1) respectively. A, beta and Axbeta values showed no significant differences among 6 segments. It was suggested that RTMCE was feasible for quantitative analysis of myocardial perfusion in rabbits. It provides a non-invasive method to evaluate the myocardial perfusion in rabbit disease models.

Comparison of MRI and positron emission tomography for measuring myocardial perfusion reserve in healthy humans

Myocardial perfusion reserve (MPR, defined as the ratio of the maximum myocardial blood flow (MBF) to the baseline) is an indicator of coronary artery disease and myocardial microvascular abnormalities. First-pass contrast-enhanced magnetic resonance imaging (CE-MRI) using gadolinium (Gd)-DTPA as a contrast agent (CA) has been used to assess MPR. Tracer kinetic models based on compartmental analysis of the CA uptake have been developed to provide quantitative measures of MBF by MRI. To study the accuracy of Gd-DTPA first-pass MRI and kinetic modeling for quantitative analysis of myocardial perfusion and MPR during dipyridamole infusion, we conducted a comparison with positron emission tomography (PET) in 18 healthy males (age = 40 +/- 14 years). Five planes were acquired at every second heartbeat with a 1.5T scanner using a saturation recovery turboFLASH sequence. A perfusion-related parameter, the unidirectional influx constant (Ki), was computed in three coronary artery territories. There was a significant correlation for both dipyridamole-induced flow (0.70, P = 0.001) and MPR (0.48, P = 0.04) between MRI and PET. However, we noticed that MRI provided lower MPR values compared to PET (2.5 +/- 1.0 vs. 4.3 +/- 1.8). We conclude that MRI supplemented with tracer kinetic modeling can be used to quantify myocardial perfusion.

Quantitative myocardial perfusion analysis with a dual‐bolus contrast‐enhanced first‐pass MRI technique in humans

To compare fully quantitative and semiquantitative analysis of rest and stress myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) using a dual-bolus first-pass perfusion MRI method in humans. Rest and dipyridamole stress perfusion imaging was performed on 10 healthy humans by administering gadolinium contrast using a dual-bolus protocol. Ventricular and myocardial time-signal intensity curves were generated from a series of T1-weighted images and adjusted for surface-coil intensity variations. Corrected signal intensity curves were then fitted using fully quantitative model constrained deconvolution (MCD) to quantify MBF (mL/min/g) and MPR. The results were compared with semiquantitative contrast enhancement ratio (CER) and upslope index (SLP) measurements. MBF (mL/min/g) estimated with MCD averaged 1.02 +/- 0.22 at rest and 3.39 +/- 0.59 for stress with no overlap in measures. MPR was 3.43 +/- 0.71, 1.91 +/- 0.65, and 1.16 +/- 0.19 using MCD, SLP, and CER. Both semiquantitative parameters (SLP and CER) significantly underestimated MPR (P < 0.001) and failed to completely discriminate rest and stress perfusion. Rest and stress MBF (mL/min/g) and MPR estimated by dual-bolus perfusion MRI fit within published ranges. Semiquantitative methods (SLP and CER) significantly underestimated MPR.

Quantitative Analysis of Myocardial Perfusion in Rats by Contrast Echocardiography

The ability to assess myocardial perfusion in small animals is important, especially to investigate models of myocardial ischemia. Myocardial perfusion is usually assessed by postmortem techniques, eliminating the possibility of follow-up. We sought to evaluate whether contrast echocardiography was able to quantify myocardial perfusion in rats. Twenty-four rats divided in 3 groups (sham-operated, and 8 and 21 days after left anterior descending coronary artery stenosis) underwent myocardial contrast echocardiography using intermittent triggered imaging. Peak plateau intensity and slope of refilling were compared with myocardial blood flow achieved with fluorescent microspheres. High-quality images were easily obtained for each experiment. Close correlation was found between myocardial contrast echocardiography and myocardial blood flow, especially for measurements of peak plateau intensity x slope of refilling relative to the control area (y = 1.15 x -0.14, r = 0.86). Quantification of myocardial perfusion in rats is feasible by myocardial contrast echocardiography using intermittent triggered imaging.

Simultaneous real-time echocardiographic imaging of myocardial perfusion and regional function using color-encoded, contrast-enhanced power modulation

We hypothesized that color-encoded, contrast-enhanced, power modulation imaging could allow simultaneous quantification of myocardial perfusion and regional left ventricular function. We studied 12 anesthetized, closed-chest pigs at baseline, during acute ischemia, and during reperfusion, and 8 patients after acute myocardial infarction. Color kinesis was used to color encode endocardial motion during real-time contrast perfusion imaging with high-energy ultrasound pulses. Wall motion was assessed by calculating regional fractional area changes. Translation-free perfusion analysis was performed in automatically identified myocardial regions of interest. Steady-state intensity and postimpulse rate of contrast replenishment were calculated. In all animals, ischemia caused reversible changes in the images and the perfusion- and function-calculated indices. A significant decrease in pixel intensity (14%) and contrast replenishment rate (66%) in left anterior descending coronary artery segments, in agreement with fluorescent microspheres measurements, coincided with a decrease in fractional area change (34%). For patients, respective perfusion and function indices were 61%, 51%, and 58% lower in segments where perfusion defects, regional wall-motion abnormalities, or both were noted in gray scale images. Color-encoded, contrast-enhanced power modulation allows simultaneous real-time imaging and quantitative analysis of myocardial perfusion and regional left ventricular function.