Xiaoming Bi

Contrast-Enhanced Whole-Heart Coronary Magnetic Resonance Angiography at 3.0-T: A Comparative Study With X-Ray Angiography in a Single Center

OBJECTIVES The purpose of this study was to prospectively evaluate the diagnostic performance of 3.0-T contrast-enhanced whole-heart coronary magnetic resonance angiography (CMRA) in patients with suspected coronary artery disease (CAD). BACKGROUND A slow-infusion, contrast-enhanced whole-heart CMRA approach has recently been developed at 3.0-T. The accuracy of this technique has not yet been determined among patients with suspected CAD. METHODS The 3.0-T contrast-enhanced whole-heart CMRA was performed in 69 consecutive patients. An electrocardiography-triggered, navigator-gated, inversion-recovery prepared, segmented gradient-echo sequence was used to acquire isotropic whole-heart CMRA with slow infusion of 0.2 mmol/kg gadobenate dimeglumine. The diagnostic accuracy of whole-heart CMRA in detecting significant stenoses (> or =50%) was evaluated using X-ray angiography as the reference. RESULTS The CMRA examinations were successfully completed in 62 patients. Acquisition time of whole-heart CMRA procedure was 9.0 +/- 1.9 min. The 3.0-T whole-heart CMRA correctly identified significant CAD in 32 patients and correctly ruled out CAD in 23 patients. The sensitivity, specificity, and accuracy of whole-heart CMRA for detecting significant stenoses were 91.6% (87 of 95), 83.1% (570 of 686), and 84.1% (657 of 781), respectively, on a per-segment basis. These values were 94.1% (32 of 34), 82.1% (23 of 28), and 88.7% (55 of 62), respectively, on a per-patient basis. CONCLUSIONS Contrast-enhanced whole-heart CMRA with 3.0-T allows for the accurate detection of coronary artery stenosis with high sensitivity and moderate specificity.

Whole-Heart Coronary Magnetic Resonance Angiography at 3 Tesla in 5 Minutes With Slow Infusion of Gd- BOPTA, a High-Relaxivity Clinical Contrast Agent

T1‐shortening contrast agents have been used to improve the depiction of coronary arteries with breath‐hold magnetic resonance angiography (MRA). The spatial resolution and coverage are limited by the duration of the arterial phase of the contrast media passage. In this study we investigated the feasibility of acquiring free‐breathing, whole‐heart coronary MRA during slow infusion of the contrast media (0.3 ml/s) for prolonged blood signal enhancement time. Ultrashort TR (3 ms) and parallel data acquisition were used to allow the whole‐heart MRA in approximately 5 min. A newly approved gadolinium (Gd)‐based high T1 relaxivity contrast agent, gadobenate dimeglumine ([Gd‐BOPTA]2–), was used and coronary MRA was performed on a whole‐body 3 Tesla (T) system to improve the signal‐to‐noise ratio (SNR). Results from eight volunteers demonstrate that this coronary MRA method is capable of imaging the whole heart in 4.5 ± 0.6 min. Major coronary arteries are well depicted with high SNR (42.4 ± 12.5) and contrast‐to‐noise ratio (CNR; 27.1 ± 7.6). Magn Reson Med 58:1–7, 2007.

Bright-Blood T2-Weighted MRI Has Higher Diagnostic Accuracy Than Dark-Blood Short Tau Inversion Recovery MRI for Detection of Acute Myocardial Infarction and for Assessment of the Ischemic Area at Risk and Myocardial Salvage

Background— T2-Weighted MRI reveals myocardial edema and enables estimation of the ischemic area at risk and myocardial salvage in patients with acute myocardial infarction (MI). We compared the diagnostic accuracy of a new bright-blood T2-weighted with a standard black blood T2-weighted MRI in patients with acute MI. Methods and Results— A breath-hold, bright-blood T2-weighted, Acquisition for Cardiac Unified T2 Edema pulse sequence with normalization for coil sensitivity and a breath-hold T2 dark-blood short tau inversion recovery sequence were used to depict the area at risk in 54 consecutive acute MI patients. Infarct size was measured on gadolinium late contrast enhancement images. Compared with dark-blood T2-weighted MRI, consensus agreements between independent observers for identification of myocardial edema were higher with bright-blood T2-weighted MRI when evaluated per patient (P<0.001) and per segment of left ventricle (P<0.001). Compared with bright-blood T2-weighted MRI, dark-blood T2-weighted MRI underestimated the area at risk compared with infarct size (P<0.001). The 95% limits of agreement for interobserver agreements for the ischemic area at risk and myocardial salvage were wider with dark-blood T2-weighted MRI than with bright-blood T2-weighted MRI. Bright blood enabled more accurate identification of the culprit coronary artery with correct identification in 94% of cases compared with 61% for dark blood (P<0.001). Conclusions— Bright-blood T2-weighted MRI has higher diagnostic accuracy than dark-blood T2-weighted MRI. Additionally, dark-blood T2-weighted MRI may underestimate area at risk and myocardial salvage.

Bright Blood T2 Weighted MRI Has Higher Diagnostic Accuracy Than Dark Blood STIR MRI for Detection of Acute Myocardial Infarction and for Assessment of the Ischemic Area-at-Risk and Myocardial Salvage

Background— T2-Weighted MRI reveals myocardial edema and enables estimation of the ischemic area at risk and myocardial salvage in patients with acute myocardial infarction (MI). We compared the diagnostic accuracy of a new bright-blood T2-weighted with a standard black blood T2-weighted MRI in patients with acute MI. Methods and Results— A breath-hold, bright-blood T2-weighted, Acquisition for Cardiac Unified T2 Edema pulse sequence with normalization for coil sensitivity and a breath-hold T2 dark-blood short tau inversion recovery sequence were used to depict the area at risk in 54 consecutive acute MI patients. Infarct size was measured on gadolinium late contrast enhancement images. Compared with dark-blood T2-weighted MRI, consensus agreements between independent observers for identification of myocardial edema were higher with bright-blood T2-weighted MRI when evaluated per patient (P<0.001) and per segment of left ventricle (P<0.001). Compared with bright-blood T2-weighted MRI, dark-blood T2-weighted MRI underestimated the area at risk compared with infarct size (P<0.001). The 95% limits of agreement for interobserver agreements for the ischemic area at risk and myocardial salvage were wider with dark-blood T2-weighted MRI than with bright-blood T2-weighted MRI. Bright blood enabled more accurate identification of the culprit coronary artery with correct identification in 94% of cases compared with 61% for dark blood (P<0.001). Conclusions— Bright-blood T2-weighted MRI has higher diagnostic accuracy than dark-blood T2-weighted MRI. Additionally, dark-blood T2-weighted MRI may underestimate area at risk and myocardial salvage.

3D Noncontrast MR Angiography of the Distal Lower Extremities Using Flow-Sensitive Dephasing (FSD)-Prepared Balanced SSFP

While three‐dimensional contrast‐enhanced MR angiography (MRA) is becoming the method of choice for clinical peripheral arterial disease (PAD) examinations, safety concerns with contrast administration in patients with renal insufficiency have triggered a renaissance of noncontrast MRA. In this work, a noncontrast‐MRA technique using electrocardiography‐triggered three‐dimensional segmented balanced steady‐state free precession with flow‐sensitive dephasing (FSD) magnetization preparation was developed and tested in the distal lower extremities. FSD preparation was used to induce arterial flow voids at systolic cardiac phase while having little effect on venous blood and static tissues. High‐spatial‐resolution MRA was obtained by means of magnitude subtraction between a dark‐artery scan with FSD preparation at systole and a bright‐artery scan without FSD preparation at mid‐diastole. In nine healthy volunteers, FSD parameters, including the gradient waveform and the first‐order gradient moment, were optimized for excellent MRA image quality. Furthermore, arterial stenosis and occlusion in two peripheral arterial disease patients were identified using the noncontrast‐MRA technique, as confirmed by contrast‐enhanced MRA. In conclusion, FSD‐prepared balanced steady‐state free precession in conjunction with electrocardiography gating and image subtraction provides a promising noncontrast‐MRA strategy for the distal lower extremities. Magn Reson Med, 2009.

Comparison of 3D Free-Breathing Coronary MR Angiography and 64-MDCT Angiography for Detection of Coronary Stenosis in Patients with High Calcium Scores

OBJECTIVE The objective of our study was to compare the diagnostic performance of coronary MR angiography (MRA) and 64-MDCT angiography (MDCTA) for the detection of significant stenosis (> or = 50%) in patients with high calcium scores. MATERIALS AND METHODS Eighteen patients (12 men, six women; mean age, 56 y; age range, 38-77 y) who had at least one calcified plaque with a calcium score of > 100 underwent coronary MRA and conventional coronary angiography (CAG) within 2 weeks of MDCTA. Coronary MRA image quality of the calcified segments was assessed by two observers in consensus on a 4-point scale (1 = not visible, 2 = poor, 3 = good, 4 = excellent) using a 10-segment model from the modified American Heart Association classification. Three experienced radiologists, unaware of the results of conventional CAG, independently assessed for the presence of significant stenosis on MDCTA images and the corresponding MRA images. Receiver operating characteristic (ROC) curves were calculated for each reader using conventional CAG as the gold standard. RESULTS Thirty-three calcified plaques with a calcium score of > 100 were detected on MDCTA in the 18 patients. The coronary segments with nodal calcification (n = 17) showed a higher mean image quality score than the segments with diffuse calcification (n = 16) (3.47 +/- 0.62 vs 2.94 +/- 0.77, respectively; p < 0.05). Of the 33 coronary segments with calcification, 12 significant stenoses were identified on conventional CAG. The sensitivity, specificity, and area under the ROC curve (AUC) for MRA and MDCTA, respectively, were as follows: reader 1, 75%, 81%, 0.82 versus 75%, 48%, 0.68; reader 2, 83%, 71%, 0.82 versus 67%, 52%, 0.63; and reader 3, 83%, 71%, 0.85 versus 83%, 43%, 0.65, respectively. The average AUC of MRA for the three readers was significantly higher than that of MDCTA (p = 0.030). CONCLUSION Coronary MRA has higher image quality for coronary segments with nodal calcification than for coronary segments with diffuse calcification. Coronary MRA has better diagnostic performance than coronary MDCTA for the detection of significant stenosis in patients with high calcium scores.

Contrast-Enhanced Whole-Heart Coronary Magnetic Resonance Angiography at 3.0-T

OBJECTIVES The purpose of this study was to prospectively evaluate the diagnostic performance of 3.0-T contrast-enhanced whole-heart coronary magnetic resonance angiography (CMRA) in patients with suspected coronary artery disease (CAD). BACKGROUND A slow-infusion, contrast-enhanced whole-heart CMRA approach has recently been developed at 3.0-T. The accuracy of this technique has not yet been determined among patients with suspected CAD. METHODS The 3.0-T contrast-enhanced whole-heart CMRA was performed in 69 consecutive patients. An electrocardiography-triggered, navigator-gated, inversion-recovery prepared, segmented gradient-echo sequence was used to acquire isotropic whole-heart CMRA with slow infusion of 0.2 mmol/kg gadobenate dimeglumine. The diagnostic accuracy of whole-heart CMRA in detecting significant stenoses (> or =50%) was evaluated using X-ray angiography as the reference. RESULTS The CMRA examinations were successfully completed in 62 patients. Acquisition time of whole-heart CMRA procedure was 9.0 +/- 1.9 min. The 3.0-T whole-heart CMRA correctly identified significant CAD in 32 patients and correctly ruled out CAD in 23 patients. The sensitivity, specificity, and accuracy of whole-heart CMRA for detecting significant stenoses were 91.6% (87 of 95), 83.1% (570 of 686), and 84.1% (657 of 781), respectively, on a per-segment basis. These values were 94.1% (32 of 34), 82.1% (23 of 28), and 88.7% (55 of 62), respectively, on a per-patient basis. CONCLUSIONS Contrast-enhanced whole-heart CMRA with 3.0-T allows for the accurate detection of coronary artery stenosis with high sensitivity and moderate specificity.

Contrast-Enhanced Whole-Heart Coronary Magnetic Resonance Angiography at 3.0 T : Comparison With Steady-State Free Precession Technique at 1.5 T

Objectives:To compare contrast-enhanced whole-heart coronary MR angiography (MRA) at 3.0 T and noncontrast steady-state free precession coronary MRA at 1.5 T in the same volunteers. Materials and Methods:Nine healthy volunteers underwent both coronary MRA using 3D FLASH with slow infusion of MultiHance at 3.0 T and 3D TrueFISP sequence at 1.5 T. Neither β-blockers nor nitroglycerine was administered in any of the imaging sessions. The same spatial resolution and heart coverage were used at both field strengths. Acquisition time, signal-to-noise ratio of coronary blood, contrast-to-noise ratio (CNR) between coronary blood and surrounding myocardium or connecting tissue, scores of image quality, coronary artery sharpness, and coverage of coronary segments for the 2 techniques were analyzed and statistically compared. Results:There were no significant differences in heart rate (68 ± 10 vs. 63 ± 6 beats/min, P > 0.05) and navigator efficiency (34.1% ± 7.7% vs. 34.8% ± 9.2%, P > 0.05) at 3.0 T and 1.5 T coronary MRA during the data acquisition. The average acquisition time of the 3.0 T coronary MRA was significantly shorter than that of the1.5 T coronary MRA (9.7 ± 2.3 vs. 14.6 ± 3.5, P < 0.05). The mean score of image quality and vessel sharpness at 3.0 T was similar to that at 1.5 T (2.8 ± 1.0 vs. 3.0 ± 1.0 and 0.63 ± 0.15 vs. 0.61 ± 0.13, respectively. P > 0.05). There was no significant difference between the number of visible coronary segments of the major coronary arteries at 3.0 T and 1.5 T (64/81 vs. 62/81, P > 0.05). However, the number of visible main coronary branches at 3.0 T was significantly higher than that at 1.5 T (18/54 vs. 7/54, P < 0.05). The overall signal-to-noise ratio at 3.0 T was significantly lower than that at 1.5 T (40.9 ± 4.7 vs. 60.9 ± 3.4, P < 0.01), whereas the overall CNR at 3.0 T was significantly higher than that at 1.5 T (35.4 ± 3.3 vs. 28.8 ± 6.4, P < 0.05). Conclusion:Contrast-enhanced whole-heart coronary MRA at 3.0 T demonstrated less acquisition time, higher CNR, and better depiction of coronary segments compared with steady-state free precession coronary MRA at 1.5 T. Patient studies are required to evaluate the clinical value of the technique.

Three-dimensional breathhold SSFP coronary MRA: A comparison between 1.5T and 3.0T†

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.

ECG-gated Nonenhanced 3D Steady-State Free Precession MR Angiography in Assessment of Transplant Renal Arteries: Comparison with DSA

PURPOSE To evaluate noncontrast material-enhanced steady-state free precession (SSFP) magnetic resonance (MR) angiography in the assessment of transplant renal arteries (RAs) by using digital subtraction angiography (DSA) as the reference standard. MATERIALS AND METHODS This prospective study was approved by the institutional review board; written informed consent was obtained from all participants. In 20 renal allograft recipients scheduled for DSA, the transplant RAs were assessed with electrocardiographically gated nonenhanced SSFP MR angiography performed at 1.5 T; the degree of stenosis was compared with that of DSA. Subjective image quality for SSFP MR angiography was assessed independently by two radiologists on a four-point scale (from 1, nondiagnostic to 4, excellent) in four predefined segments (I, the iliac artery; II, the main transplant artery; III, segmental branches; and IV, parenchymal branches). Sensitivity, specificity, and accuracy of SSFP MR angiography for the detection of relevant (> or =50%) transplant RA stenosis (TRAS) were calculated on a per-artery basis. RESULTS One patient was excluded because SSFP MR angiography failed to adequately visualize the allograft vasculature owing to low cardiac output. The mean image quality assessed by both readers was 3.98 +/- 0.16 (standard deviation), 3.5 +/- 0.68, 2.71 +/- 1.12 and 2.03 +/- 1.09 for segments I, II, III, and IV, respectively (kappa = 0.80). DSA helped identify eight relevant (> or =50%) stenoses in six transplant RAs. Kinking of the transplant artery without relevant stenosis was found in seven patients. The degree of stenosis was overestimated in three patients by using SSFP MR angiography. As compared with DSA, the sensitivity, specificity, and accuracy of SSFP MR angiography to help detect relevant TRAS were 100% (six of six), 88% (14 of 16), and 91% (20 of 22), respectively. CONCLUSION Nonenhanced SSFP MR angiography is a reliable alternative imaging technique for the assessment of transplant RAs in patients for whom contrast-enhanced MR angiography is contraindicated.