Black-blood Sequence Research Articles

Black-blood dynamic contrast-enhanced coronary artery wall MRI: a potential tool for kinetic-modeling-based wall inflammation assessment

Background Dynamic gadolinium contrast-enhanced (DCE) vessel wall MRI has recently been used to compute a set of model-based contrast kinetic parameters (e.g. K and Vp) that can well characterize the extent of inflammation in carotid plaques [1,2]. However, no studies have shown its feasibility in coronary artery wall, presumably due to the technical challenges in imaging such a constantly-moving, ultra-small structure and potential difficulty in visually distinguishing the wall from the hyperintense lumen with conventional DCE techniques. This work aimed to develop a black-blood navigatorgated ECG-triggered T1-weighted sequence for DCE MRI of coronary vessel wall.

A pilgrim seeking diagnosis

We present the case of an unusual presentation of Dressler’s syndrome and the important role of new imaging techniques in its diagnosis. A 42-year-old man was admitted with progressive dyspnoea and pleuritic chest pain during the last two months. Physical examination showed signs of hemodynamic instability (BP 75/40, HR 120 bpm). X-Ray showed cardiomegaly and electrocardiogram was suggestive of chronic anterior myocardial infarction. Transthoracic echocardiography showed pericardial effusion with signs of hemodynamic compromise. Emergent cardiac surgery was performed with suspicion of cardiac rupture. Only fibrinous material and serous fluid was found. 72 hours later he required reoperation because of recurrence of cardiac tamponade. Pleuropericardial window was made. Anti-inflammatory treatment was initiated. At discharge a magnetic resonance imaging study was performed. Diffuse pericardial inflammation consistent with a diagnosis of Dressler’s syndrome (DS) was demonstrated in T2- weighted black-blood and late enhancement sequences. One month later neither pleural nor pericardial effusion had recurred. Postinfarction pericardial effusions are common and magnetic resonance imaging has proven useful in determining its aetiology.

355 Which Sequences and Planes of Cardiovascular Magnetic Resonance Provide Accurate Measurements of Branch Pulmonary Artery Size in Children With Right Ventricular Outflow Track Obstruction?

Management of right ventricular outflow tract obstructive (RVOTO) lesions requires precise quantification of pulmonary artery (PA) size. Various cardiovascular magnetic resonance (CMR) sequences are available to assess PA size. This study aimed to determine which CMR sequences correlated best with cardiac catheterization and surgical measurements of branch PA size in children. Forty children with RVOTO lesions and biventricular circulation underwent CMR prior to either cardiac catheterization or surgery within 6 months. Maximal PA and stenosis (if present) diameter were measured. CMR sequences included axial black blood, axial cine, coronal-oblique cine, sagittal-oblique cine and contrast-enhanced magnetic resonance angiography (MRA) with multiplanar reformatting in axial, sagittal-oblique, coronal-oblique and cross-sectional planes. Catheterization measurements were performed in the anteroposterior plane at maximal expansion. Surgical measurements were recorded as maximal diameter of sound which was able to pass through the lumen. The mean differences (Δ) and intra class correlation (ICC) were calculated to determine agreement of CMR sequences with catheterization and surgical measurements. CMR and catheterization comparisons were made in 23 children (age 7.5 ± 5.8 years). Contrast-enhanced MRA showed better agreement (ICC.0.7) than black blood (ICC 0.4-0.6) and cine sequences (ICC 0.5-0.7). Maximal cross-sectional diameter from reformatted MRA provided the best correlate of RPA (Δ0.2 ± 2.4 mm, ICC 0.9) and LPA (Δ0.3 ± 2.3 mm, ICC 0.9) size. For stenoses, the best correlations were from coronal oblique MRA of RPA (Δ0.3 ± 0.9 mm, ICC 0.9) and sagittal cine of LPA (Δ0.1 ± 1.3 mm, ICC 0.9). CMR and surgical comparisons were made in 17 children (age 4.3 ± 5.6 years). All MRI sequences showed good agreement (ICC > 0.8) with the best correlation from axial cine for both RPA (Δ0.1 ± 2.3 mm, ICC 0.9) and LPA (Δ0.2 ± 1.3 mm, ICC 0.9). Maximal cross-sectional diameters from reformatted MRA provides the best correlate of catheterization measured PA branch size, while stenotic lesions are best measured from coronal oblique MRA (RPA) or sagittal cine (LPA). This is likely due to similar angiographic methods based on reformation techniques that transect the central axis of the arteries. In contrast, axial cine CMR was the best surgically measured correlate of PA branch size due to this being a measure of stretched diameter. Knowledge of these differences will provide precise PA measurements to aid catheter or surgical interventions of RVOTO lesions.

Unilateral Pulmonary Artery Agenesis, Angio-MR Findings

A 64-year-old female with no family history of heart disease came to our hospital due to an episode of respiratory superinfection. An x-ray (Fig. 1) showed loss of volume in the left hemithorax and an abnormal cardiac silhouette, so we decided to perform a magnetic resonance (MR) imaging study. Using a 1.5T MR imaging, black blood sequences were acquired in all three imaging planes and a multiphase angiography was performed after administering intravenous contrast (gadolinium). The multiphase MR angiography revealed agenesis of the left pulmonary artery (Fig. 2A) in the pulmonary artery phase. The systemic arterial phase (Fig. 2B) revealed a right aortic arch and left pulmonary arterial vascularization provided by systemic collateral vessels dependent on the left subclavian artery. The supra-aortic trunks originated from a left brachiocephalic trunk that gave rise to the common left carotid artery and the left subclavian artery, and from a right common carotid artery and a right subclavian artery originating independently from the aortic arch (Fig. 2C). The systemic venous phase (Fig. 2D) showed a delay in left pulmonary venous return. Volumetric reconstructions from MR data show, in different obliquities, the morphology of the right ventricular outflow tract, the trunk of the pulmonary artery and the right pulmonary artery (Fig. 3). Multiphase MR angiography, with its high temporal resolution, enables us to obtain anatomical and functional information about thoracic vascular structures with a single injection of intravenous contrast and no ionizing radiation. Figure 3. Figure 1. Figure 2.

Dual-Source Radiofrequency Transmission with Patient-Adaptive Local Radiofrequency Shimming for 3.0-T Cardiac MR Imaging: Initial Experience

To evaluate the effect of dual-source parallel radiofrequency (RF) transmission with patient-adaptive local RF shimming on image quality, image contrast, and diagnostic confidence at routine clinical cardiac magnetic resonance (MR) imaging with use of a 3.0-T dual-channel transmit whole-body MR system. Written informed consent was obtained from all patients, and the study protocol was approved by the local institutional review board. Cardiac MR imaging was performed in 28 patients by using a 3.0-T MR unit equipped with a dual-source RF transmission system. The effect of conventional versus dual-source RF transmission on steady-state free precession (SSFP) cine sequences and turbo spin-echo (TSE) black-blood (BB) sequences was evaluated. The homogeneity of the B1 field and contrast-to-noise ratios (CNRs) were measured and tested for statistical significance with the paired t test. Images were analyzed qualitatively for homogeneity, the presence of off-resonance artifacts, and diagnostic confidence independently by two readers. Statistical significance was assessed with the Wilcoxon signed rank test. Inter- and intraobserver agreement was assessed with κ statistics. Quantitative image analysis revealed that B1 homogeneity and CNR were significantly improved for images acquired with dual-source RF transmission compared with conventional RF transmission (P = .005). The quality of SSFP and TSE BB images of the left and the right ventricles showed a significant improvement with respect to image homogeneity and diagnostic confidence as evaluated by the readers (P = .0001, κ > 0.74). As a side effect, off-resonance artifacts were significantly reduced on SSFP images (P = .0001, κ > 0.76). Dual-source parallel RF transmission significantly improves image homogeneity, image contrast, and diagnostic confidence compared with conventional RF transmission of cardiac SSFP and TSE BB sequences.

The comparison of MR intragate and electrocardiogram-respiration triggered fast low-angle shot in imaging the structure and function of the heart

Objective A comparison between intragate and ECG-respiration triggered techniques was performed to determine their differences in measuring the structure and function of the heart at 7.0 T.Methods Ten normal ICR mice aged five to six weeks were examined on a 7.0 T MR scanner.A central slice with papillary muscle included at the short-axis view was scanned with a FLASH-cine bright blood sequence,FLASH-cine black blood sequence,IG-FLASH-sat-cine black blood sequence,and IG-FLASH-cine bright blood sequence.The area of the left ventricle of the end systole and end diastole ( including and excluding the myocardium) was measured with manually outlined ROIs.The increased area of the left ventricle and the myocardium from the end systolic to end diastolic phases was calculated.The signal intensity was measured from 8 ROIs which were evenly located at the myocardium of the end systole,and the mean and standard deviation were then determined.The coefficient of variation ( CV ) was derived by dividing the mean into the standard deviation.Results There was no significant difference ( the increased area of the myocardium t =0,P =1,the increased area of the left ventricle t =2.12,P =0.06) in the function index between the ECG-triggered black blood sequences [the increased area of the myocardium (0.100 ±0.018) cm2,the increased area of the left ventricle (0.060 ± 0.024) cm2] and intragate black blood sequences[the increased area of the myocardium (0.090 ± 0.014) cm2,the increased area of the left ventricle (0.060 ±0.012) cm2].No significant difference(the increased area of the myocardium t =1.56,P =0.15,the increased area of the left ventricle t =2.08,P =0.07 ) in the function index was observed between the ECG-triggered bright blood sequences [the increased area of the myocardium ( 0.100 ±0.018) cm2,the increased area of the left ventricle(0.060 ±0.014) cm2]and intragate bright blood sequences [the increased area of the myocardium (0.090 ±0.019) cm2,the increased area of the left ventricle (0.050 ±0.015) cm2].Furthermore,there was no significant difference(t =1,P =0.34) in the CV of the myocardium signal intensity of bright blood sequences between the ECG-triggering ( 0.050 ± 0.013 ) and intragate (0.040 ± 0.015 ),but significant difference ( t =4.51,P =0.001 ) in the CV of the myocardium signal intensity of black blood sequences between the ECG-triggering ( 0.070 ± 0.033 ) and intragate ( 0.160 ± 0.046 ) was obtained.Conclusions The intragate sequences could take the place of the ECG gate sequences in functional analysis of the heart( including bright blood and black blood sequences).The bright blood intragate sequences also could replace the bright blood ECG-triggered sequences in analyzing the signal of the myocardium. Key words: Heart; Magnetic resonance imaging; Animal experimentation

Zoom imaging for rapid aortic vessel wall imaging and cardiovascular risk assessment

To demonstrate the utility of a "reduced field-of-view" (zoom imaging) technique to accelerate free-breathing, ECG-triggered, turbo-spin-echo black-blood sequences, which have been previously described to detect subclinical aortic atherosclerosis. Fifteen healthy volunteers underwent MRI of the thoracic and abdominal aorta. Imaging with the conventional full field-of-view sequence was compared with zoom imaging. Total scan time, image quality (i.e., contrast-to-noise ratio and vessel wall sharpness) and vessel wall thickness were analyzed. A subgroup of 10 volunteers also underwent acceleration of imaging using sensitivity encoding (SENSE) for comparison. Zoom imaging significantly reduced imaging time from a mean of 41 ± 9 min (conventional imaging) to 15 ± 0.5 min (P<0.01). There was no difference in image quality between conventional and zoom imaging with respect to CNR (10.1 ± 6 versus 10.1 ± 6) or vessel wall sharpness (38 ± 4% versus 39 ± 4%). Furthermore, Bland Altman plots showed excellent agreement in vessel wall thickness measurements using the two methods. In comparison, SENSE not only reduced CNR but also resulted in underestimation of vessel wall thickness compared with the conventional sequence. Zoom imaging allows accurate and time-efficient imaging of the abdominal and thoracic aorta for cardiovascular risk prediction. In this application, it is preferable to SENSE.

Comparison of the Region-Based and Pixel-Wise Methods for Cardiac T2* Analysis in 50 Transfusion-Dependent Thai Thalassemia Patients

To compare the observer variability of the conventional region-based (RB) to the typical and proposed pixel-wise (PW) methods for cardiac T2* analysis in thalassemia patients. Fifty thalassemia major patients were enrolled for the study. Short-axis bright- and black-blood sequences were acquired and analyzed using the RB and PW methods. Regions were defined using the whole septum (WS) or partial septum (PS). From the same PS region, results were reported by mean (PS-PW) and median (MPS-PW). Intraobserver and interobserver variabilities were investigated on all data set by 2 independent observers blinded to the result. The T2* values from the PS-PW and MPS-PW methods were comparable to the conventional WS-RB method on both scanning techniques. When comparing the interobserver variability from the WS-RB to the PS-PW method, the coefficient of variation of the PS-PW method was equivalent (4.5% vs 4.7%, P = NS) for the bright-blood technique but 31% lower (4.0% vs 2.8%, P = 0.21) for the black-blood technique. The proposed MPS-PW method performed even better with respect to the conventional WS-RB method, decreasing interobserver coefficient of variation by 24% (4.5% vs 3.5%, P = 0.08) and 42% (4.0% vs 2.4%, P = 0.02), respectively. Intraobserver reproducibility followed the same trend. The proposed PW method using the median of T2* values calculated from partial interventricular septum region provided lower intraobserver and interobserver variabilities compared with the conventional RB or typical PW methods.

SAR reduced black-blood cine TPM for increased temporal resolution at 3T

The objective was to improve the temporal resolution in black-blood CINE tissue phase mapping sequences at high field MR systems. The temporal resolution is limited due to SAR constraints causing idle times into the sequence. The aim was to avoid these idle times and therefore providing an increased number of heart phases. Thirteen volunteers were enrolled in this study. Each volunteer underwent different myocardial short-axis scans comprising scans with application of both presaturation pulses, with alternating application of presaturation pulses and with an attenuation of the excitation angle. The last two approaches enable a SAR reduction or increased temporal resolution. The contrast to noise ratio (CNR) between myocardium and blood and the influence on the measured tissue motion were investigated. High CNR between myocardium and blood could be obtained with the application of alternating presaturation-pulses. Reduction of the flip angle of the presaturation-pulses provided reduced CNR relative to both the original and the alternated presaturation-pulses approach. More details of the myocardial motion were observed with increased temporal resolution. It is feasible to increase the temporal resolution at high field strength by reducing the SAR with either alternating presaturation-pulses or decreased flip angle of these pulses.

Carotid plaque assessment using fast 3D isotropic resolution black‐blood MRI

Black-blood MRI is a promising tool for carotid atherosclerotic plaque burden assessment and compositional analysis. However, current sequences are limited by large slice thickness. Accuracy of measurement can be improved by moving to isotropic imaging but can be challenging for patient compliance due to long scan times. We present a fast isotropic high spatial resolution (0.7×0.7×0.7 mm3) three-dimensional black-blood sequence (3D-MERGE) covering the entire cervical carotid arteries within 2 min thus ensuring patient compliance and diagnostic image quality. The sequence is optimized for vessel wall imaging of the carotid bifurcation based on its signal properties. The optimized sequence is validated on patients with significant carotid plaque. Quantitative plaque morphology measurements and signal-to-noise ratio measures show that 3D-MERGE provides good blood suppression and comparable plaque burden measurements to existing MRI protocols. 3D-MERGE is a promising new tool for fast and accurate plaque burden assessment in patients with atherosclerotic plaque.

A fast black-blood sequence for four-dimensional cardiac manganese-enhanced MRI in mouse

The increasing number of mouse models of cardiac diseases requires improvements in the current MRI tools. Anatomic and functional cardiac phenotyping by MRI calls for both time and space resolution in three dimensions. Black-blood contrast is often needed for the accurate delineation of myocardium and chambers, and is consistent with manganese contrast enhancement. In this article, we propose a fast, three-dimensional, time-resolved (four-dimensional), black-blood MRI sequence that allows mouse heart imaging at 10 periods of the cardiac cycle within 30 min at an isotropic resolution of 200 µm. Two-dimensional imaging was possible within 80 s. Blood cancellation was achieved by employing bipolar gradients without the use of a double inversion recovery preparation scheme. Saturation slices were added in two-dimensional experiments for better blood nulling. The rapidity of the two-dimensional acquisition protocol allowed the measurement of the time course of contrast enhancement on manganese infusion. Owing to the very high contrast-to-noise ratio, manganese-enhanced MRI in four dimensions made possible the accurate assessment of regional cardiac volumes in healthy animals. In experimentally infarcted mice, the size of the ischemic zone could be measured easily with this method. The technique might be valuable in evaluating mouse heart diseases and their follow-up in longitudinal studies.

Improvement of hyperemic myocardial oxygen extraction fraction estimation by a diffusion‐prepared sequence

Myocardial oxygen extraction fraction (OEF) during hyperemia can be estimated using a double-inversion-recovery-prepared T(2)-weighted black-blood sequence. Severe irregular electrocardiogram (ECG) triggering due to elevated heart rate and/or arrhythmias may render it difficult to adequately suppress the flowing left ventricle blood signal and thus potentially cause errors in the estimates of myocardial OEF. Thus, the goal of this study was to evaluate another black-blood technique, a diffusion-weighted-prepared turbo spin echo sequence for its ability to determine regional myocardial OEF during hyperemia. Control dogs and dogs with acute coronary artery stenosis were imaged with both the double-inversion-recovery- and diffusion-weighted-prepared turbo spin echo sequences at rest and during either dipyridamole or dobutamine hyperemia. Validation of MRI OEF estimates was performed using blood sampling from the artery and coronary sinus in control dogs. The two methods showed comparable correlations with blood sampling results (R(2) = 0.9). Similar OEF estimations for all dogs were observed, except for the group of dogs with severe coronary stenosis during dobutamine stress. In these dogs, the diffusion-weighted method provided more physiologically reasonable OEF (hyperemic OEF = 0.75 +/- 0.08 versus resting OEF of 0.6) than the double-inversion-recovery method (hyperemic OEF = 0.56 +/- 0.10). Diffusion-weighted preparation may be a valuable alternative for more accurate oxygenation measurements during irregular ECG-triggering.

Hybrid of Opposite-Contrast Magnetic Resonance Angiography of the Brain by Combining Time-of-Flight and Black Blood Sequences

We assessed the value of a new magnetic resonance angiography (MRA) technique named hybrid of opposite-contrast (HOP) MRA in the diagnosis of moyamoya disease. Using a dual-echo sequence, we obtained the first echo for time-of-flight (TOF) MRA followed by the second echo for black blood MRA. We then subtracted the black blood MRA data set from that of the TOF MRA followed by maximum-intensity projection. In 14 patients, we performed HOP MRA and compared the findings with those on 3-dimensional TOF MRA and MR images. The HOP MRA was also compared with a radionuclide perfusion study (7 patients). The HOP MRA technique improved the demonstration of distal arteries in 13 patients. The findings in HOP MRA correlated with MR images in 9 patients as well as with the perfusion study in 6 patients. The HOP MRA technique demonstrated the distal arterial branches in moyamoya disease well and facilitated the perfusion assessment with MR imaging.

Clinical CMR at 3.0 Tesla using parallel RF transmission with patient-adaptive B1 shimming: initial experience

Introduction The clinical implementation of high-field CMR systems has introduced new challenges for cardiac imaging due to B0 and B1 field inhomogeneities. TSE Black-Blood sequences (BB) are compromised by dielectric artifacts, whereas SSFP cine-sequences are known to suffer from dark-band artifacts. The flip-angle non-uniformity across the field of view affects image homogeneity of both sequences. The use of a multi-source RF transmission system may help reduce dielectric effects, improve flip-angle uniformity and avoid local SAR peaks, thus allowing a shorter minimum TR/TE in SSFP-sequences.

Accuracy of phase contrast, black‐blood, and bright‐blood pulse sequences for measuring compliance and distensibility coefficients in a human‐tissue mimicking phantom

To assess the accuracy of MR-derived luminal diameter variations and its implications for compliance (CC) and distensibility coefficients (DC) by comparison with high-resolution digital photography (HRDP) in a tissue-mimicking phantom with pulsatile flow. Diameters, CC, and DC extracted using cine phase-contrast (CPC), cine bright-blood (CBrB), and a cine black-blood (CBB) sequence were compared. The diameter in the left-right direction was compared against HRDP, as the gold-standard. The experiments were performed using 256(2) and 512(2) matrix sizes. Bland-Altman analysis was performed to compare each sequence with the gold-standard in terms of diameter changes over the simulated cardiac cycle. The bias and 95% limits of agreement (LOA) for CBB and CBrB were comparable. The bias for CPC was larger, however, the LOA were comparable. Increasing spatial resolution improved agreement with HRDP for all sequences. CBrB-derived CC and DC were within 3% of the high resolution CBB values while CPC CC and DC were underestimated but still within 11%. CPC images were found to underestimate the luminal area over the cardiac cycle. CBrB-derived diameters were more accurate in diastole while CBB-derived diameters gave the best results in systole. CC and DC varied depending on the pulse sequence.

Hybrid of opposite‐contrast MRA of the brain by combining time‐of‐flight and black‐blood sequences: Initial experience in major trunk stenoocclusive diseases

To assess the feasibility of a new MR angiography (MRA) technique named hybrid of opposite-contrast MRA (HOP MRA) that combined the time-of-flight (TOF) MRA with a flow-sensitive black-blood (FSBB) sequence in the diagnosis of major trunk stenoocclusive diseases. On a 1.5 Tesla imager using a dual-echo three-dimensional (3D)-gradient-echo sequence, we obtained the first echo for TOF MRA followed by the second echo for FSBB. We then subtracted the FSBB data set from that of TOF MRA followed by maximum intensity projection. In four normal volunteers and 19 patients with chronic stenoocclusive disease of the major trunk, we performed HOP MRA along with 3D-TOF MRA and compared the findings. In the volunteer group, the HOP MRA technique improved the demonstration of distal arterial branches. In 12 of the 19 patients, the HOP MRA better visualized branches distal to the lesion as well as distal branches of normal trunks than 3D-TOF MRA, while both techniques provided equivalent depiction of branches distal to the lesion but better depiction of normal distal branches in three patients. The HOP-MRA technique is promising in major trunk stenoocclusive diseases as it better demonstrates distal branches probably representing collaterals than 3D-TOF MRA.

Imaging of the walls of saccular cerebral aneurysms with double inversion recovery black‐blood sequence

In this study, we evaluated the wall of saccular cerebral aneurysms (SCAs) using two-dimensional double inversion recovery black-blood sequence (BBDI). We examined 14 patients with an unruptured SCA (USCA). The BBDI was peripheral-pulse gated, and was acquired during the mid-diastolic period. We evaluated whether the aneurysmal wall could be visualized with BBDI, and the wall thickness in the neck and dome portion of the aneurysm was measured in cases with acceptable imaging quality. BBDI demonstrated the USCA walls in ten patients. In four patients, the USCA walls were poorly delineated from the adjacent brain parenchyma or cerebrospinal fluid. The mean aneurysm size was 8.0 mm. The mean thickness of the aneurysmal wall in the neck portion was 0.60 +/- 0.13 mm in 10 cases. The mean thickness at the dome portion was 0.46 +/- 0.05 mm in five cases. In this study, BBDI revealed some portion of the USCA wall, despite the limited spatial and contrast resolution for delineation of the entire USCA wall. In our opinion, this technique may be used as an additional imaging tool for the evaluation of the aneurysmal wall.

Black and bright-blood sequences magnetic resonance angiography and gross sections of the canine thorax: An anatomical study

In this study, images of the canine thorax in transverse, dorsal and sagittal planes were obtained by black-blood T1 spin-echo pulse sequence and bright-blood gradient-echo sequence magnetic resonance imaging. The images were correlated with macroscopic cryosections and anatomical dissection of cadavers with blood vessels containing latex. Non-contrast-enhanced magnetic resonance angiography was obtained from two mature Beagle breed dogs. Macroscopic sections and dissections were performed in three dogs. Black and bright-blood angiography diagnostic methods are complementary and provide an accurate depiction of the vascular canine thorax.

Cine cardiac imaging using black‐blood steady‐state free precession (BB‐SSFP) at 3T

To propose a new black-blood (BB) pulse sequence that provides BB cine cardiac images with high blood-myocardium contrast. The proposed technique is based on the conventional steady-state free precession (SSFP) sequence. Numerical simulations of the Bloch equation were conducted to compare the resulting signal-to-noise ratio (SNR) to that of conventional BB imaging, including the effects of changing the imaging flip angle and heart rates. Simulation results were verified using a gel phantom experiment and five normal volunteers were scanned using the proposed technique. The new sequence showed higher SNR and contrast-to-noise ratio (CNR) (approximately 100%) compared to the conventional BB imaging. Also, the borders of the left ventricle (LV) and right ventricle (RV) appear more distinguishable than the conventional SSFP. We were also able to cover about 80% of the cardiac cycle with short breath-hold time (approximately 10 cardiac cycles) and with reasonable SNR and CNR. Based on an SSFP conventional sequence, the new sequence provides BB cines that cover most of the cardiac cycle and with higher SNR and CNR than the conventional BB sequences.

Variability of carotid artery measurements on 3-Tesla MRI and its impact on sample size calculation for clinical research

Carotid MRI measurements are increasingly being employed in research studies for atherosclerosis imaging. The majority of carotid imaging studies use 1.5 T MRI. Our objective was to investigate intra-observer and inter-observer variability in carotid measurements using high resolution 3 T MRI. We performed 3 T carotid MRI on 10 patients (age 56 +/- 8 years, 7 male) with atherosclerosis risk factors and ultrasound intima-media thickness > or =0.6 mm. A total of 20 transverse images of both right and left carotid arteries were acquired using T2 weighted black-blood sequence. The lumen and outer wall of the common carotid and internal carotid arteries were manually traced; vessel wall area, vessel wall volume, and average wall thickness measurements were then assessed for intra-observer and inter-observer variability. Pearson and intraclass correlations were used in these assessments, along with Bland-Altman plots. For inter-observer variability, Pearson correlations ranged from 0.936 to 0.996 and intraclass correlations from 0.927 to 0.991. For intra-observer variability, Pearson correlations ranged from 0.934 to 0.954 and intraclass correlations from 0.831 to 0.948. Calculations showed that inter-observer variability and other sources of error would inflate sample size requirements for a clinical trial by no more than 7.9%, indicating that 3 T MRI is nearly optimal in this respect. In patients with subclinical atherosclerosis, 3 T carotid MRI measurements are highly reproducible and have important implications for clinical trial design.