Biomedical subjects

Debiao Li

Publications and source records attributed to Debiao Li.

At least 19 recordsLinked to original sources

PubMed2007

Diffusion-prepared segmented steady-state free precession: Application to 3D black-blood cardiovascular magnetic resonance of the thoracic aorta and carotid artery walls.

This work developed a three-dimensional (3D) diffusion-prepared segmented steady-steady free precession (DP-SSFP) cardiovascular magnetic resonance (CMR) sequence for black-blood (BB) thoracic aortic and carotid wall visualization. In 14 healthy volunteers, BB CMR of the thoracic aorta (n = 7) and carotid arteries (n = 7) was performed over 12 cm and 3 cm of transversal coverage, respectively, with a single 3D DP-SSFP acquisition and multiple two-dimensional (2D) slices using a T2-weighted (T2W) double inversion-recovery fast spin-echo (DIR-FSE) sequence. Arterial wall area (WA), lumen area (LA), and wall-lumen contrast-to-noise ratio (CNR) measured from the 3D DP-SSFP images were compared to those measured from the 2D T2W DIR-FSE images. Strong agreement in WA and LA between the two techniques was observed in the thoracic aorta (WA: intraclass correlation coefficient (ICC) = 0.866, LA: ICC = 0.993; p < 0.001 for both) and carotid arteries (WA: ICC = 0.939, LA: ICC = 0.991; p < 0.001 for both). Adjusted for slice thickness and number of slices, higher effective CNR per unit time (i.e., CNR efficiency) was attained with 3D DP-SSFP than 2D T2W DIR-FSE during thoracic aortic wall imaging (11.6 +/- 1.4 vs. 2.9 +/- 0.5; p < 0.001) and carotid artery wall imaging (10.1 +/- 1.9 vs. 3.1 +/- 0.5; p < 0.001). Diffusion-prepared segmented SSFP is a promising vessel wall CMR sequence that allows for 3D acquisition of thin and contiguous slices with BB image contrast.

Adult↗

PubMed2006

Bolus characteristics based on Magnetic Resonance Angiography.

BACKGROUND: A detailed contrast bolus propagation model is essential for optimizing bolus-chasing Computed Tomography Angiography (CTA). Bolus characteristics were studied using bolus-timing datasets from Magnetic Resonance Angiography (MRA) for adaptive controller design and validation. METHODS: MRA bolus-timing datasets of the aorta in thirty patients were analyzed by a program developed with MATLAB. Bolus characteristics, such as peak position, dispersion and bolus velocity, were studied. The bolus profile was fit to a convolution function, which would serve as a mathematical model of bolus propagation in future controller design. RESULTS: The maximum speed of the bolus in the aorta ranged from 5-13 cm/s and the dwell time ranged from 7-13 seconds. Bolus characteristics were well described by the proposed propagation model, which included the exact functional relationships between the parameters and aortic location. CONCLUSION: The convolution function describes bolus dynamics reasonably well and could be used to implement the adaptive controller design.

Computer Simulation↗

PubMed2006

Generating positive contrast from off-resonant spins with steady-state free precession magnetic resonance imaging: theory and proof-of-principle experiments.

It is well known that magnetic susceptibility variations lead to signal voids in MRI. However, recent work has shown that positive-contrast imaging of susceptibility-induced field variations can provide signal enhancements rather than signal losses. In this paper, we propose a new method for generating positive contrast from off-resonant spins with steady-state free precession (SSFP) magnetic resonance imaging. Based on theory and experiments, we demonstrate that positive-contrast images can be acquired in the presence of susceptibility-shift media with low flip angle excitations that are determined by the spin relaxation time constants of the imaging medium. Compared to other techniques, this technique is substantially faster and has low specific absorption rates, permitting high-field imaging. In addition to acquiring positive-contrast images, we also show that it is possible to suppress the imaging medium to desired levels; thereby allowing for simultaneous registration of the background details surrounding the susceptibility-shift media. Among practical applications, we anticipate that the proposed technique can potentially facilitate high field magnetic-resonance-based molecular imaging.

Absorption↗

PubMed2006

Multislice dark-blood carotid artery wall imaging: a 1.5 T and 3.0 T comparison.

PURPOSE: To compare two multislice turbo spin-echo (TSE) carotid artery wall imaging techniques at 1.5 T and 3.0 T, and to investigate the feasibility of higher spatial resolution carotid artery wall imaging at 3.0 T. MATERIALS AND METHODS: Multislice proton density-weighted (PDW), T2-weighted (T2W), and T1-weighted (T1W) inflow/outflow saturation band (IOSB) and rapid extended coverage double inversion-recovery (REX-DIR) TSE carotid artery wall imaging was performed on six healthy volunteers at 1.5 T and 3.0 T using time-, coverage-, and spatial resolution-matched (0.47 x 0.47 x 3 mm3) imaging protocols. To investigate whether improved signal-to-noise ratio (SNR) at 3.0 T could allow for improved spatial resolution, higher spatial resolution imaging (0.31 x 0.31 x 3 mm3) was performed at 3.0 T. Carotid artery wall SNR, carotid lumen SNR, and wall-lumen contrast-to-noise ratio (CNR) were measured. RESULTS: Signal gain at 3.0 T relative to 1.5 T was observed for carotid artery wall SNR (223%) and wall-lumen CNR (255%) in all acquisitions (P < 0.025). IOSB and REX-DIR images were found to have different levels of SNR and CNR (P < 0.05) with IOSB values observed to be larger. Normalized to a common imaging time, the higher spatial resolution imaging at 3.0 T and the lower spatial resolution imaging at 1.5 T provided similar levels of wall-lumen CNR (P = NS). CONCLUSION: Multislice carotid wall imaging at 3.0 T with IOSB and REX-DIR benefits from improved SNR and CNR relative to 1.5 T, and allows for higher spatial resolution carotid artery wall imaging.

Adult↗

PubMed2006

Comparison between intravenous and intraarterial contrast injections for dynamic 3D MRI of liver tumors in the VX2 rabbit model.

PURPOSE: To test the hypothesis that catheter-directed intraarterial (IA) contrast agent injection increases tumor enhancement and conspicuity compared to intravenous (IV) injection. MATERIALS AND METHODS: Eight VX2 liver tumors were grown in five rabbits. After positioning a catheter in the hepatic artery, we performed 3D inversion recovery GRE MRI after IA and IV gadopentetate-dimeglumine contrast injections at doses of 0.04 and 0.1 mmol/kg, respectively. Peak enhancement (signal-to-noise ratio (SNR)) and conspicuity (contrast-to-noise ratio (CNR)) were measured for each acquisition. RESULTS: The peak SNR and CNR were 21.7 +/- 5.8 and 17.0 +/- 4.8 (mean +/- SD) after IA injection, and 16.9 +/- 10.2 and 6.2 +/- 2.6 after IV injection. The IA CNR was significantly greater than the IV CNR (P < 0.05), with a >60% increase in CNR for each tumor. For six of the eight tumors the IA SNR was greater than the IV SNR, but statistical significance was not achieved due to the small sample size of the study (P = 0.07). CONCLUSION: We demonstrated the feasibility of using IA injection techniques to improve tumor conspicuity. This strategy could be employed to enhance the detection of small liver tumors or to conserve contrast agent in future MRI-guided transcatheter liver therapies.

Animals↗

PubMed2006

Coronary artery magnetic resonance angiography (MRA): a comparison between the whole-heart and volume-targeted methods using a T2-prepared SSFP sequence.

In this study, coronary MRA was performed on 10 healthy volunteers using the whole-heart and volume-targeted scans with comparable imaging parameters. Similar results in the SNR, CNR, and vessel diameter were observed. The depicted length of coronary arteries was longer using the whole-heart scan (whole-heart: RCA/LAD = 13.4 +/- 3.9/10.5 +/- 1.6 cm; volume-targeted: RCA/LAD = 11.0 +/- 2.6/8.7 +/- 1.8 cm). Imaging times for the RCA- (3.8 +/- 1.4 minutes) and LAD-targeted (3.6 +/- 1.3 minutes) are similar, while the time required for one whole-heart scan is significantly longer (12.2 +/- 4.0 minutes). The measured vessel sharpness was higher using the volume-targeted method (whole-heart: RCA/LAD = 0.65 +/- 0.18/0.78 +/- 0.16; volume-targeted: RCA/LAD = 0.84 +/- 0.22/0.90 +/- 0.20). Combination of the whole-heart and volume-targeted methods could be potentially useful in clinical applications of coronary MRA.

Adult↗

PubMed2006

Comparison of gradient-echo and steady-state free precession for coronary artery magnetic resonance angiography using a gadolinium-based intravascular contrast agent.

OBJECTIVES: Intravascular contrast agents may offer longer imaging times and better vessel visualization over conventional extravascular agents for magnetic resonance coronary angiography. The purpose of this study was to evaluate the effect of intravascular contrast (B-22956/1) on coronary visualization. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were compared in inversion-recovery (IR)-prepared FLASH (fast low-angle shot) and IR-trueFISP (true fast imaging with steady-state precession) sequences before and after contrast. MATERIALS AND METHODS: Numeric simulations were performed to compare blood signals in IR-trueFISP and IR-FLASH sequences. Coronary imaging was performed in 15 swine. RESULTS: Postcontrast CNR was improved 23% with breathhold IR-FLASH and 55% with breathhold IR-trueFISP as compared with precontrast trueFISP. With free-breathing, long TR IR-FLASH provided 131% and 55.8% higher SNR and 132% and 58.7% increased CNR compared with IR-FLASH with shorter TR and IR-trueFISP, respectively. CONCLUSION: Intravascular contrast agents improve CNR and vessel visualization in coronary magnetic resonance angiography with IR-FLASH and IR-trueFISP.

Animals↗

PubMed2006

Gadofluorine-enhanced magnetic resonance imaging of carotid atherosclerosis in Yucatan miniswine.

OBJECTIVE: The aim of this study was to determine whether gadofluorine, a paramagnetic magnetic resonance imaging (MRI) contrast agent, selectively enhances carotid atherosclerotic plaques in Yucatan miniswine. METHODS: Atherosclerotic plaques were induced in the left carotid arteries (LCA) of Yucatan miniswine (n=3) by balloon denudation and high cholesterol diet. T1-weighted MRI was performed before and 24 hours after gadofluorine injection (at a dose of 100 micromol/kg) to assess the enhancement of the balloon-injured LCA wall relative to healthy, uninjured right carotid artery (RCA) wall. Histopathology was performed to verify the presence and composition of the atherosclerotic plaques imaged with MRI. RESULTS: Gadofluorine was found to enhance LCA atherosclerotic lesions relative to RCA wall by 21% (P<0.025) 24 hours after contrast injection. Enhancement of healthy LCA wall relative to healthy RCA wall was not observed. CONCLUSION: Gadofluorine selectively enhances carotid atherosclerotic plaques in Yucatan miniswine. Gadofluorine appears to be a promising MR contrast agent for detection of atherosclerotic plaques in vivo.

Animals↗

PubMed2006

Coronary magnetic resonance angiography using magnetization-prepared contrast-enhanced breath-hold volume-targeted imaging (MPCE-VCATS).

OBJECTIVES: Coronary artery x-ray angiography (XRA) is currently the gold standard for the assessment of coronary artery disease. A substantial minority of patients referred for coronary angiography have no significant coronary artery disease. The purpose of this study is to evaluate magnetization-prepared contrast-enhanced breath-hold volume-targeted imaging (MPCE-VCATS), a new 3-dimensional breath-hold coronary magnetic resonance angiography (MRA) technique, in detecting hemodynamically significant coronary artery stenoses in a patient population, with XRA correlation. MATERIALS AND METHODS: A total of 19 subjects who were referred for conventional coronary angiography were enrolled in the study. ECG-triggered MPCE-VCATS coronary artery scans were acquired for the left main coronary artery (LCA), left anterior descending (LAD), and right coronary artery (RCA). Coronary MRA and XRA results were compared. RESULTS: The overall sensitivity, accuracy, and negative predictive value for diagnosing any hemodynamically significant coronary artery disease (> or =50% diameter reduction) was 91%, 80%, and 90%, respectively. The sensitivity of the technique in the LCA, LAD, and RCA was 100%, 100% and 78%, respectively. The negative predictive value of the technique was 100%, 100%, and 71%, respectively. DISCUSSION: MPCE-VCATS is a promising technique for coronary artery imaging. It has a relatively high sensitivity as well as a high NPV. The results of the study may indicate a future role for the technique in obviating the need for some patients to undergo XRA.

Aged↗

PubMed2006

Comparison of intraarterial MR angiography at 3.0 T with X-ray digital subtraction angiography for detection of renal artery stenosis in swine.

PURPOSE: To compare the accuracy of catheter-directed intraarterial (IA) magnetic resonance (MR) angiography at 3.0 T with that of x-ray digital subtraction angiography (DSA) for the measurement of renal artery stenosis (RAS) in swine. MATERIALS AND METHODS: Unilateral hemodynamically significant RAS (>50%) was induced surgically in six pigs with use of reverse cable ties. One to two weeks after surgery, each pig underwent x-ray DSA and MR angiography before and after percutaneous transluminal balloon angioplasty (PTA). X-ray DSA was performed before and after PTA of RAS by injection of iodinated contrast agent through a 5-F multiple-side hole angiographic catheter placed in the abdominal aorta under fluoroscopic guidance. MR angiography of RAS was performed before and after PTA of RAS on a 3.0-T clinical MR imager with use of gadolinium-based contrast agent. MR angiography and DSA images were analyzed with the full width at half maximum method. Percent stenosis measurements between x-ray DSA and MR angiography were compared with a paired t test and were correlated with linear regression and Bland Altman analysis (alpha = 0.05). RESULTS: Six cases of RAS were induced and imaged successfully with DSA and MR angiography techniques before and after PTA. On x-ray DSA, median stenoses was 64% (95% CI 57%-80%) before PTA and 20% (95% CI 5%-32%) after PTA. Corresponding MR angiography median stenosis measurement was 69% (95% CI 58%-80%) before PTA and 26% (95% CI 16%-36%) after PTA. A paired t test comparison did not show a difference between DSA and MR angiography (P = .16). RAS measurements on MR angiography correlated closely (P < .01) with DSA measurements (r(2) = 0.92). CONCLUSION: In swine, the accuracy of catheter-directed IA MR angiography with use of a clinical 3.0-T MR imaging unit for the measurement of RAS was similar to that of conventional x-ray DSA.

Angiography, Digital Subtraction↗

PubMed2006

MR imaging- versus conventional X-ray fluoroscopy-guided renal angioplasty in swine: prospective randomized comparison.

PURPOSE: To test the hypothesis that the technical success rates, complication rates, and procedural times for magnetic resonance (MR) imaging-guided percutaneous transluminal angioplasty (PTA) and conventional (x-ray) fluoroscopy-guided PTA for treatment of renal artery stenosis are similar. MATERIALS AND METHODS: The study was animal care and use committee approved. After surgically inducing bilateral renal artery stenosis in 11 swine, the authors performed baseline digital subtraction angiography. They transferred each animal to a 1.5-T MR imaging unit and randomly decided which artery would be treated with MR-guided PTA. With MR imaging guidance, angioplastic devices were tracked by using active and passive techniques. Vascular depiction was achieved by using catheter-directed MR angiography. Stenotic vessels were dilated by using 5-6-mm-diameter balloon catheters. PTA was then performed in the contralateral artery by using conventional fluoroscopy-guided techniques. With the intention to treat, the authors compared the technical success (residual stenosis < 50%) rates, complication rates, and procedural times for each guidance method. They compared technical successes and complications by using the McNemar test and procedural times by using a paired t test, with P < .05 indicating a significant difference. RESULTS: The authors successfully dilated nine (82%) of 11 renal arteries with MR guidance and all 11 arteries (100%) with conventional fluoroscopic guidance. The difference was not significant (P = .5). Complications occurred in three (27%) arteries with MR guidance and in one (9%) artery with fluoroscopic guidance, with no significant differences (P = .5). The mean MR-guided PTA procedural time was 46 minutes longer than the fluoroscopy-guided PTA procedural time; this difference was significant (P = .01). CONCLUSION: In a small cohort of swine, the authors did not observe a significant difference between MR imaging- and conventional fluoroscopy-guided renal artery PTA in terms of success and complication rates. However, no evidence of similarity between the techniques should be assumed. Procedural times differed significantly.

Angioplasty↗

PubMed2005

Coronary artery wall imaging: initial experience at 3 Tesla.

PURPOSE: To assess the feasibility of black-blood turbo spin-echo imaging of the left anterior descending coronary artery wall at 3 Tesla under free-breathing and breath-hold conditions. MATERIALS AND METHODS: Proton density-weighted black-blood turbo spin-echo imaging of the left anterior descending coronary artery was performed on 15 volunteers on a 3 T whole body scanner with an eight channel phased array coil. Volunteers were imaged during free-breathing (with navigators, N = 5), or with breath-hold (N = 5), or both (N = 2). Imaging was not possible in three volunteers due to either gradient or radiofrequency (RF) coupling with the electrocardiogram (ECG). Images were analyzed to determine coronary artery wall thickness, wall area, lumen diameter, and lumen area. Signal-to-noise and contrast-to-noise ratios were calculated. RESULTS: Coronary artery wall thickness, wall area, lumen diameter, and lumen area measurements were consistent with previous magnetic resonance (MR) measurements of the coronary wall at 1.5 Tesla. CONCLUSION: Coronary wall imaging using free-breathing and breath-hold two-dimensional black-blood TSE is feasible at 3 T. Further improvement in resolution and image quality is required to detect and characterize coronary plaque.

Adipose Tissue↗

PubMed2005

Coronary arteries at 3.0 T: Contrast-enhanced magnetization-prepared three-dimensional breathhold MR angiography.

PURPOSE: To evaluate the efficacy of contrast-enhanced coronary magnetic resonance angiography (MRA) at 3.0 T. MATERIALS AND METHODS: Nine healthy human volunteers were studied on a 3.0-T whole-body MR system. A three-dimensional, breathhold, magnetization-prepared, segmented, gradient-echo sequence was used, with injection of 20 mL gadopentetate dimeglumine for each three-dimensional slab. Imaging parameters were optimized based on computer simulations. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), depicted coronary artery length, lumen diameter, and imaging sharpness with contrast agent were evaluated. SNR and CNR were compared to the results from a previous 1.5-T study. RESULTS: A 53% increment in SNR and a 305% enhancement in CNR were measured with contrast. Vessel length and sharpness depicted were higher and the lumen diameter was lower (all P values < 0.05) in postcontrast images. Compared to previous results from 1.5-T, the SNR, CNR, and vessel sharpness were enhanced at 3.0 T with higher spatial resolution. CONCLUSION: Contrast-enhanced, three-dimensional, coronary MRA at 3.0 T is a promising technique for diagnosing coronary artery diseases. Patient studies are necessary to evaluate its clinical utility.

Adult↗

PubMed2005

Three-dimensional breathhold SSFP coronary MRA: a comparison between 1.5T and 3.0T.

PURPOSE: To assess the feasibility of three-dimensional breathhold coronary magnetic resonance angiography (MRA) at 3.0T using the steady-state free precession (SSFP) sequence, and quantify the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) gains of coronary MRA from 1.5T to 3.0T using whole-body and phased-array cardiac coils as the signal receiver. MATERIALS AND METHODS: Eight healthy volunteers were scanned on 1.5T and 3.0T whole-body systems using the SSFP sequence. Numerical simulations were performed for the SSFP sequence to optimize the flip angle and predict signal enhancement from 1.5T to 3.0T. Coronary artery images were acquired with the whole-body coil in transmit-receive mode or transmit-only with phased-array cardiac coil receivers. RESULTS: In vivo studies of the same volunteer group at both field strengths showed increases of 87% in SNR and 83% in CNR from 1.5T to 3.0T using a whole-body coil as the signal receiver. The corresponding increases using phased-array receivers were 53% in SNR and 92% in CNR. However, image quality at 3.0T was more variable than 1.5T, with increased susceptibility artifacts and local brightening as the result of increased B(0) and B(1) inhomogeneities. CONCLUSION: Coronary MRA at 3.0T using a three-dimensional breathhold SSFP sequence is feasible. Improved SNR at 3.0T warrants the use of coronary MRA with faster acquisition and/or improved spatial resolution. Further investigations are required to improve the consistency of image quality and signal uniformity at 3.0T.

Adult↗

PubMed2005

Three-dimensional contrast-enhanced steady-state free precession for improved catheter-directed coronary magnetic resonance angiography.

PURPOSE: To demonstrate the feasibility of three-dimensional thick-partition, contrast-enhanced, catheter-directed coronary artery magnetic resonance angiography (MRA) and test the hypothesis that three-dimensional imaging improves coronary artery background contrast-to-noise ratio (CNR) compared to two-dimensional imaging. MATERIALS AND METHODS: Catheters were advanced into the coronary arteries of swine (N = 6) under MR guidance. Three-dimensional coronary MRA was performed after intracoronary injection of a small dose of contrast media using magnetization-prepared steady-state free precession (SSFP) with two thick partitions. For comparison, two magnetization-prepared two-dimensional SSFP scans were also performed, one with no signal averaging and one with two signal averages. All sequences had the same coverage and in-plane spatial resolution. RESULTS: The coronary artery was successfully catheterized in all (6/6) animals. CNR for three-dimensional imaging was 11.1 +/- 1.2 for proximal arterial segments and 4.3 +/- 0.4 for distal segments. Without averaging, two-dimensional imaging CNRs for proximal and distal segments were 5.0 +/- 0.7 and 1.2 +/- 0.2, respectively. With averaging, two-dimensional imaging CNRs for proximal and distal segments were 9.4 +/- 1.5 and 2.9 +/- 0.4, respectively. Three-dimensional imaging showed a statistically significant increase in CNR over all two-dimensional imaging for both proximal and distal segments (P < 0.05). CONCLUSION: Three-dimensional thick-partition, contrast-enhanced, catheter-directed coronary MRA is feasible and improves CNR over two-dimensional projection imaging.

Animals↗

PubMed2005

Artifact and noise suppression in GRAPPA imaging using improved k-space coil calibration and variable density sampling.

A parallel imaging technique, GRAPPA (GeneRalized Auto-calibrating Partially Parallel Acquisitions), has been used to improve temporal or spatial resolution. Coil calibration in GRAPPA is performed in central k-space by fitting a target signal using its adjacent signals. Missing signals in outer k-space are reconstructed. However, coil calibration operates with signals that exhibit large amplitude variation while reconstruction is performed using signals with small amplitude variation. Different signal variations in coil calibration and reconstruction may result in residual image artifact and noise. The purpose of this work was to improve GRAPPA coil calibration and variable density (VD) sampling for suppressing residual artifact and noise. The proposed coil calibration was performed in local k-space along both the phase and frequency encoding directions. Outer k-space was acquired with two different reduction factors. Phantom data were reconstructed by both the conventional GRAPPA and the improved technique for comparison at an acceleration of two. Under the same acceleration, optimal sampling and calibration parameters were determined. An in vivo image was reconstructed in the same way using the predetermined optimal parameters. The performance of GRAPPA was improved by the localized coil calibration and VD sampling scheme.

Algorithms↗

PubMed2005

Preliminary investigation of respiratory self-gating for free-breathing segmented cine MRI.

Segmented cine MRI generally requires breath-holding, which can be problematic for many patients. Navigator echo techniques, particularly successful for free-breathing coronary MRA, are incompatible with the acquisition strategies and SSFP pulse sequences commonly used for cine MRI. The purpose of this work is to introduce a new self-gating technique deriving respiratory gating information directly from the raw imaging data acquired for segmented cine MRI. The respiratory self-gating technique uses interleaved radial k-space sampling to provide low-resolution images in real time during the free-breathing acquisition that are compared to target expiration images. Only the raw data-producing images with high correlation to the target images are included in the final high-resolution reconstruction. The self-gating technique produced cine series with no significant differences in quantitative image sharpness to series produced using comparable breath-held techniques. Because of the difficulties associated with breath-holding, the respiratory self-gating technique represents an important practical advance for cardiac MRI. , Inc.

Algorithms↗

PubMed2005

Accurate myocardial T1 measurements: toward quantification of myocardial blood flow with arterial spin labeling.

In this study, we investigated a method for accurately measuring myocardial T(1) for the quantification of myocardial blood flow (MBF) with arterial spin labeling (ASL). A single-shot gradient-echo (GE)-based ASL sequence with an adiabatic hyperbolic secant inversion recovery pulse was modified to acquire a pair of myocardial T(1)'s within a breath-hold. A multivariable regression algorithm that accounted for the magnetization saturation effects was developed to calculate T(1). The MBF was then determined with a well-developed model. The accuracy of our T(1) calculation was first evaluated in a phantom, and then in six dogs for the MBF calculation, with (N = 4) and without (N = 2) coronary artery stenosis. In the phantom study, the accuracy of T(1) measured with a slice-selective inversion prepared pulse was within 2.5% of error. In healthy dogs, the MBF increased 2-5 times during vasodilation. In contrast, regional differences of MBF were well visualized in the stenotic dogs during vasodilation (perfusion reserve of 2.75 +/- 0.83 in normal myocardium, and 1.46 +/- 0.75 in the stenotic area). A correlation analysis revealed a close agreement in MBF between the ASL and microsphere (MS) in both healthy and stenotic dogs. In summary, the modified ASL technique and T(1) regression algorithm proposed here provide an accurate measurement of myocardial T(1) and demonstrate potential for reliably assessing MBF at steady state.

Algorithms↗