Biomedical subjects

Gerhard Laub

Publications and source records attributed to Gerhard Laub.

At least 19 recordsLinked to original sources

PubMed2007

Pulmonary MR perfusion at 3.0 Tesla using a blood pool contrast agent: Initial results in a swine model.

PURPOSE: To prospectively evaluate the technical feasibility of a highly accelerated pulmonary MR perfusion protocol at 3.0T using a blood pool contrast agent in a swine model. MATERIALS AND METHODS: Twelve pigs underwent time-resolved pulmonary MR angiography (MRA) on a 3.0T MR system under anesthesia and controlled mechanical ventilation. After intravenous injection of 0.05 mmol/kg of Gadomer-17 at 4 mL/second, a fast time-resolved MRA sequence with temporal echo-sharing (three segmented k-space) and highly accelerated parallel acquisition was used to acquire 3D data sets with an in-plane resolution of 1 x 1 mm(2) (slice thickness = 6 mm) and temporal resolution of one second. Image quality was evaluated independently by two radiologists, and quantitative analysis of perfusion parameters was performed using pre-released perfusion software. RESULTS: All studies were identified by both readers as having diagnostic image quality (range = 2-3, median = 3) and there was excellent interobserver agreement (kappa = 0.89; 95% CI = 0.83, 0.95). A quantitative analysis of perfusion indices was performed, with excellent overall goodness-of-fit (chi(2) value = 1.4, degree of freedom (DF) = 1). Successfully derived perfusion parameters included the time to peak (TTP, 5.1 +/- 0.7 second), mean transit time (MTT, 6.6 +/- 0.9 second), maximal signal intensity (MSI, 1051.2 +/- 718.9 arbitrary units [A.U.]), and maximal upslope of the curve (MUS, 375.9 +/- 263.4 A.U./second). CONCLUSION: 3.0T pulmonary MR perfusion using a blood pool contrast agent in a swine model is feasible. The higher available signal-to-noise ratio (SNR) at 3.0T and the high T1 relaxivity of Gadomer-17 effectively support highly accelerated parallel acquisition, and improve the performance of time-resolved pulmonary MRA.

Animals↗

PubMed2006

MR imaging with remote control: feasibility study in cardiovascular disease.

The institutional review board approved this HIPAA-compliant study and waived informed consent. The purpose was to retrospectively evaluate remote control magnetic resonance (MR) imaging in complex cardiovascular procedures, whereby operational expertise was made available locally from a remote location. Thirty patients underwent cardiac (12 patients) and/or vascular (30 patients) 1.5-T MR imaging with a remote operator by using a personal computer. All patient studies were compared with 30 control studies obtained with conventional local imaging. Cardiac cine, myocardial delayed enhancement, and MR angiograms were assessed for overall image quality and motion artifact. MR angiograms were evaluated for vascular definition. Image quality was excellent in 90% (38 of 42) of remote images versus 60% (25 of 42) of control group images (P < .01). Scores for motion artifact were not significantly different (P = .11). Interactive MR imaging was successfully implemented with remote control in complex cardiovascular cases; diagnostic quality of images was superior to that of images obtained locally.

Adolescent↗

PubMed2006

Pulmonary circulation: contrast-enhanced 3.0-T MR angiography--initial results.

PURPOSE: To prospectively evaluate the technical feasibility of both high-spatial-resolution and time-resolved contrast material-enhanced magnetic resonance (MR) angiography of the pulmonary circulation at 3.0 T. MATERIALS AND METHODS: All examinations were HIPAA compliant. After institutional review board approval and written informed consent, time-resolved and high-spatial-resolution three-dimensional contrast-enhanced MR angiography of the pulmonary circulation was performed with a 3.0-T MR system in 31 adults (13 men, 18 women; age range, 29-87 years old): 22 volunteers and nine patients (two with mediastinal masses, seven with pulmonary arterial hypertension [PAH]). The image quality of pulmonary arterial branches and parenchymal enhancement conspicuity were evaluated independently by two radiologists. The signal-to-noise ratio and quantitative analysis of perfusion parameters was performed. Statistical analysis of data was performed by using Wilcoxon rank sum test and two-sample Student t test, and interobserver variability was tested with kappa coefficient. RESULTS: Visualization up to fourth-order pulmonary arterial branches was observed on time-resolved MR angiograms and that up to fifth-order branches was observed on high-spatial-resolution MR angiograms, with diagnostic-quality blood vessel definition and good interobserver agreement. Evaluation of parenchymal enhancement and semiquantitative analysis of perfusion parameters yielded dynamic information in all subjects. Comparative analysis of definition scores for fourth- and fifth-order pulmonary arterial branches, parenchymal enhancement, the time lag between the pulmonary arterial and parenchymal enhancement, and all of the calculated perfusion indices in patients with PAH showed statistically significant differences from volunteers (P < .05). CONCLUSION: Three-dimensional contrast-enhanced MR angiography of the pulmonary circulation was feasible at 3.0 T and provided high vascular morphologic detail and dynamic functional information. Clearly detectable abnormalities were present in patients with PAH.

Adult↗

PubMed2006

High-resolution renal MRA: comparison of image quality and vessel depiction with different parallel imaging acceleration factors.

PURPOSE: To investigate the image quality and vessel depiction of renal MRA with integrated parallel imaging techniques (iPAT) using acceleration factors of 2 and 3. MATERIALS AND METHODS: In this prospective study renal MRA was performed on 14 and 12 patients with acceleration factors of 3 and 2, respectively. For the MRA a 3D-GRE sequence with an acquired spatial resolution of 0.9 x 0.8 x 1.0 mm(3) was applied (TR/TE = 3.79 msec/1.39 msec, FOV = 400 mm x 320 mm, acquired matrix = 512 x 384, flip angle = 25 degrees) on a 32-channel 1.5T MR scanner. The acquisition time was 26 seconds with iPAT 2, and 19 seconds with iPAT3. All parameters other than acquisition time and acceleration factor were kept constant. To assess the signal-to-noise ratio (SNR) we performed repetitive phantom measurements using iPAT 2 and 3. The images were rated by two radiologists in terms of noise, artifacts, and the quality of vessel depiction for the proximal, segmental, and subsegmental renal artery. A Mann-Whitney U-test and kappa-test were used for statistical analysis. RESULTS: SNR decreased significantly with iPAT 3 in the phantom measurements. The two readers found no difference in noise, but significantly fewer artifacts with iPAT 3. The depiction of segmental vessels was significantly better for both readers with iPAT 3, and the subsegmental vessels were rated significantly better by one reader. iPAT 3 also resulted in a better interreader agreement. CONCLUSION: The use of iPAT 3 for renal MRA enables a better depiction of the distal parts of the renal artery. The decrease in SNR is not diagnostically impairing.

Adult↗

PubMed2006

Dynamic pulmonary perfusion and flow quantification with MR imaging, 3.0T vs. 1.5T: initial results.

PURPOSE: To prospectively evaluate the technical feasibility and relative performance of pulmonary time-resolved MR angiography (MRA) and pulmonary artery (PA) flow quantification at 3.0T vs. 1.5T. MATERIALS AND METHODS: Time-resolved contrast-enhanced (CE) MRA of the pulmonary circulation, and flow quantification of the main PA (MPA) were performed in 14 consecutive adult healthy volunteers at both 1.5 and 3.0 Tesla with nearly identical sequence parameters. Image quality, signal-to-noise ratio (SNR), and quantitative indices of pulmonary perfusion, flow, and velocity were evaluated and compared at both field strengths. RESULTS: Time-resolved pulmonary MRA, perfusion, and flow quantification were successfully performed at both magnetic fields. The results of pulmonary perfusion and flow indices were comparable at both magnetic fields, with no statistically significant difference. The SNR values for vascular structures were higher at 3.0T vs. 1.5T (P = 0.001). The SNR values and the definition scores for parenchymal enhancement were significantly lower (P = 0.008 and 0.001, respectively) at 3.0T. CONCLUSION: Time-resolved pulmonary MRA, perfusion, and flow quantification at 3.0T was feasible, with comparable results to 1.5T. The lower parenchymal enhancement at 3.0T is believed to reflect increased susceptibility effects at higher magnetic fields. Further work is needed to fully exploit the potential of pulmonary perfusion imaging at 3.0T and to address the current limitations.

Adult↗

PubMed2006

Analysis of cardiac function--comparison between 1.5 Tesla and 3.0 Tesla cardiac cine magnetic resonance imaging: preliminary experience.

PURPOSE: We sought to assess the feasibility of magnetic resonance imaging to evaluate cardiac function at 3.0 T compared with 1.5 T. MATERIAL AND METHODS: In a prospective intraindividual comparative study, 12 volunteers (range, 18-54 years), and 2 patients (range, 43-53 years) underwent cardiac cine magnetic resonance at both 3.0 T and 1.5 T. Data were acquired both with a steady-state free precession sequence (SSFP) and a spoiled gradient echo (SGE) sequence. If necessary, a frequency scout was used to correct for off-resonance artifacts. For both SSFP and SGE imaging, 6-mm thick retrospectively EKG-gated short axis views were acquired with equal matrix size (192 x 163) and comparable repetition time (TR). Cardiac function parameters were determined manually by a single investigator. Cardiac function parameters, signal to noise ratio (SNR), contrast to noise ratio (CNR), and the presence of artifacts were compared between the 2 magnetic field strengths. For statistical analysis, a Pearson's correlation coefficient was calculated, and a paired Student t test was used to test statistical significance. RESULTS: Very good correlations between cardiac function parameters at 1.5 T and 3.0 T (r > 0.84, P < 0.0011) were obtained. Compared with SGE, SSFP more frequently was prone to artifacts. With SSFP/SGE at 3.0 T, a SNR gain of 9.4/16% was achieved compared with 1.5 T. CONCLUSION: Functional cardiac cine magnetic resonance imaging can be regarded as equally accurate at 3.0 T compared with 1.5 T. Compared with SSFP imaging, the SGE sequence benefits more from higher field strengths and is less affected by artifacts.

Adolescent↗

PubMed2006

Time-resolved contrast enhanced magnetic resonance angiography of the head and neck at 3.0 tesla: initial results.

OBJECTIVES: We sought to implement and evaluate a high-performance, extended field of view protocol for time-resolved contrast-enhanced magnetic resonance imaging (CEMRA) of the carotid circulation by using a dedicated neurovascular (NV) array coil. MATERIALS AND METHODS: A total of 16 adult volunteers and 20 clinical patients with suspected cerebrovascular disease (15 male, 21 female, 25-82 years of age) were scanned with a fast 3D MRA sequence (TR/TE: 2.16/1 milliseconds, sampling BW: 1090 Hz/pixel), with echo-sharing and parallel acquisition. All studies were performed on a 3.0 T MR system using an 8-channel neurovascular array coil. After injection of 6 mL of gadodiamide at 3 mL/s, a coronal 3D data set with in-plane resolution of 1 x 1.3 was implemented for 10 consecutive measurements each 1.8 seconds apart. The subjects subsequently underwent high spatial-resolution (in-plane: 0.8 x 0.9) CEMRA for comparative analysis. The quality of segmental arterial anatomy and the presence and degree of the arterial stenosis were evaluated by 2 neuroradiologists. The interobserver variability was tested by kappa statistics and comparative analysis between the TR-CEMRA and high spatial-resolution CEMRA was evaluated by mean of the Spearman rank correlation coefficient. RESULTS: Craniocervical arteries were visualized with good image quality and definition in the diagnostic range. Occlusive disease was detected in 42 (reader A) and 44 (reader B) arterial segments with excellent interobserver agreement (kappa =0.89; 95% confidence interval 0.82-0.96). There was a significant correlation between the TR-CEMRA and high spatial-resolution CEMRA (Rs = 0.91 and 0.93, for readers A and B, respectively) for the degree of stenosis. Three aneurysms, 3 AVMs, 1 AV-fistula, and 2 subclavian steals were detected by both observers and were confirmed by correlative imaging. CONCLUSION: Time-resolved CEMRA at 3.0 T is reliable and versatile, providing 3-dimensional time-resolved data sets with high spatial (in plane: 1.3 x 1 mm2) and temporal (1.8 seconds) resolution over a large field of view. The higher signal-to-noise ratio gain at 3.0 T can be used effectively to improve performance of fast imaging and to support aggressive parallel acquisition protocols, as in the present study. Further clinical studies are required to establish the range of applications and the accuracy of the technique.

Adult↗

PubMed2006

High-resolution magnetic resonance angiography of the renal arteries using parallel imaging acquisition techniques at 3.0 T: initial experience.

OBJECTIVE: The purpose of this prospective study was to investigate the feasibility of high-resolution magnetic resonance angiography (MRA) of the kidneys at 3.0 T using parallel data acquisition. MATERIAL AND METHODS: Contrast-enhanced MRA of the renal arteries (RA) was performed in 12 volunteers and 12 consecutive patients (mean age 47.1 +/- 16.3 years) on a 3.0 T MR scanner. For CEMRA, a high-resolution 3-dimensional GRE FLASH sequence was implemented. Images were assessed subjectively on a 0 to 5 scoring scale by 2 reviewers. Quantitative evaluation was done by measuring the contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR). RESULTS: Diagnostic image quality was acquired in all individuals. In total, 62 RA were found, consisting of 48 main and 14 accessory RA. Overall visibility score for main RA was 4.82 +/- 0.38. RA were identified up to the third-order branches in 88%. In 3 of 12 patients, a hemodynamic relevant stenosis was found and proven by conventional angiogram. CONCLUSION: CEMRA at 3.0 T is advantageous in terms of better SNR and T1 weighting; therefore, measurement time can be reduced and spatial resolution can be increased without corruption of signal yield. Consequently, high-field MRA may be preferred for the evaluation of renal vascular anatomy in potential kidney donors or for the detection of renal artery stenosis.

Adult↗

PubMed2006

High spatial-resolution CE-MRA of the carotid circulation with parallel imaging: comparison of image quality between 2 different acceleration factors at 3.0 Tesla.

PURPOSE: We sought to evaluate and compare the image quality and vessel delineation of the carotid arteries with high spatial-resolution contrast-enhanced MRA (CE-MRA) at 3.0 T using integrated parallel acquisition (iPAT) with acceleration factors of 2 and 4. MATERIALS AND METHODS: Using an 8-channel neurovascular array coil, we performed prospective high-spatial resolution CE-MRA at 3.0 T of the head and neck on 24 patients (11 men, 13 women, ages 37-89) with suspected arterio-occlusive disease who were assigned randomly to 2 groups. Twelve patients (group A) were examined with a 3D-GRE sequence using iPAT with acceleration factor of 2. For the next 12 patients (group B) a near-identical sequence with an acceleration factor of 4 was applied. Higher iPAT factors were used to increase the spatial-resolution while keeping scan time unchanged. Two volunteers were scanned by both protocols. Phantom measurements were performed to assess the signal-to-noise ratio (SNR). The presence of artifact, noise, image quality of the arterial segments, and the presence and degree of arterial stenosis were evaluated independently by 2 radiologists. Statistical analysis of data was performed by using Wilcoxon rank sum test and 2-sample Student t test (P < 0.05 was indicative a statistically significant difference). The interobserver variability was tested by kappa coefficient. RESULTS: SNR values were significantly lower when iPAT with acceleration factor of 4 was used (P < 0.001). There was no significant difference between 2 groups in regards to image noise (P = 0.67) and artifact (P = 0.8). Both readers visualized the majority of carotid circulation with good image quality in both groups. For smaller intracranial arteries, such as the second-division of anterior and middle cerebral artery, anterior communicating artery, and superior cerebellar artery, the image quality and vessel delineation was significantly better at an iPAT factor of 4 (P < 0.01). The overall interobserver agreement for both the vessel depiction, and detection of arterial stenoses was higher in group B compared with group A. CONCLUSION: Use of parallel acquisition techniques with a high acceleration factor (iPAT-4) results in superior depiction of small intracranial arterial segments. Imaging at higher magnetic field strength, in addition to the use of an optimized 8-channel array coil, provides sufficient SNR to support faster parallel acquisition protocols, leading to improved spatial-resolution. More extensive clinical studies are warranted to establish the range of applications and confirm the accuracy of the technique.

Adult↗

PubMed2006

Isotropic high spatial resolution magnetic resonance angiography of the supra-aortic arteries using two-dimensional parallel imaging (iPAT2) at 3 Tesla: a feasibility study.

OBJECTIVES: We sought to assess the feasibility of isotropic 3-dimensional contrast-enhanced magnetic resonance angiography (MRA) covering the supra-aortic and intracranial arteries with a MR sequence using parallel-imaging in phase- and slice-encoding directions. MATERIALS AND METHODS: Six volunteers and 5 patients with suspected cerebrovascular disease were examined at 3.0 T using a 16-element head-neck array. Contrast-enhanced 3-dimensional MRA (repetition time 3.2 milliseconds, echo time 1.2 milliseconds, flip angle 30 degrees , bandwidth 390 Hz/pixel) was acquired with integrated generalized autocalibrating partially parallel acquisition (GRAPPA), in both phase- and slice-encoding direction. Images were evaluated independently by 2 radiologists. Signal-to-noise ratio was calculated from phantom measurements. RESULTS: Signal-to-ratio levels of 8.7 +/- 2.2/48.7 +/- 10.2 with and without parallel-imaging (GRAPPA x 6) were measured, respectively. Scoring of image quality by observer 1/observer 2 on a 4-point-scale (range 0-3) yielded 2.5 +/- 1.0/2.4 +/- 1.0 and 2.1 +/- 1.0/2.0 +/- 1.1 for extracranial and intracranial vessel segments in volunteers and 2.8 +/- 0.6/2.7 +/- 0.7 and 2.0 +/- 1.2/2.1 +/- 1.1 in patients, respectively. The interobserver agreement was excellent (k = 0.82). CONCLUSIONS: This study shows that contrast-enhanced MRA, applying parallel-imaging in both phase- and slice-encoding direction (iPAT), is feasible at 3.0 T. Coverage of the carotid and vertebro-basilar circulation was achieved.

Adolescent↗

PubMed2006

Cardiac cine imaging at 3 Tesla: initial experience with a 32-element body-array coil.

PURPOSE: We sought to assess the feasibility of cardiac cine imaging and evaluate image quality at 3 T using a body-array coil with 32 coil elements. MATERIALS AND METHODS: Eight healthy volunteers (3 men; median age 29 years) were examined on a 3-T magnetic resonance scanner (Magnetom Trio, Siemens Medical Solutions) using a 32-element phased-array coil (prototype from In vivo Corp.). Gradient-recalled-echo (GRE) cine (GRAPPAx3), GRE cine with tagging lines, steady-state-free-precession (SSFP) cine (GRAPPAx3 and x4), and SSFP cine(TSENSEx4 andx6) images were acquired in short-axis and 4-chamber view. Reference images with identical scan parameters were acquired using the total-imaging-matrix (Tim) coil system with a total of 12 coil elements. Images were assessed by 2 observers in a consensus reading with regard to image quality, noise and presence of artifacts. Furthermore, signal-to-noise values were determined in phantom measurements. RESULTS: In phantom measurements signal-to-noise values were increased by 115-155% for the various cine sequences using the 32-element coil. Scoring of image quality yielded statistically significant increased image quality with the SSFP-GRAPPAx4, SSFP-TSENSEx4, and SSFP-TSENSEx6 sequence using the 32-element coil (P < 0.05). Similarly, scoring of image noise yielded a statistically significant lower noise rating with the SSFP-GRAPPAx4, GRE-GRAPPAx3, SSFP-TSENSEx4, and SSFP-TSENSEx6 sequence using the 32-element coil (P < 0.05). CONCLUSION: This study shows that cardiac cine imaging at 3 T using a 32-element body-array coil is feasible in healthy volunteers. Using a large number of coil elements with a favorable sensitivity profile supports faster image acquisition, with high diagnostic image quality even for high parallel imaging factors.

Adult↗

PubMed2006

Renal magnetic resonance angiography at 3.0 Tesla using a 32-element phased-array coil system and parallel imaging in 2 directions.

PURPOSE: The aim of the present study was to assess the feasibility of renal magnetic resonance angiography at 3.0 T using a phased-array coil system with 32-coil elements. Specifically, high parallel imaging factors were used for an increased spatial resolution and anatomic coverage of the whole abdomen. MATERIALS AND METHODS: Signal-to-noise values and the g-factor distribution of the 32 element coil were examined in phantom studies for the magnetic resonance angiography (MRA) sequence. Eleven volunteers (6 men, median age of 30.0 years) were examined on a 3.0-T MR scanner (Magnetom Trio, Siemens Medical Solutions, Malvern, PA) using a 32-element phased-array coil (prototype from In vivo Corp.). Contrast-enhanced 3D-MRA (TR 2.95 milliseconds, TE 1.12 milliseconds, flip angle 25-30 degrees , bandwidth 650 Hz/pixel) was acquired with integrated generalized autocalibrating partially parallel acquisition (GRAPPA), in both phase- and slice-encoding direction. Images were assessed by 2 independent observers with regard to image quality, noise and presence of artifacts. RESULTS: Signal-to-noise levels of 22.2 +/- 22.0 and 57.9 +/- 49.0 were measured with (GRAPPAx6) and without parallel-imaging, respectively. The mean g-factor of the 32-element coil for GRAPPA with an acceleration of 3 and 2 in the phase-encoding and slice-encoding direction, respectively, was 1.61. High image quality was found in 9 of 11 volunteers (2.6 +/- 0.8) with good overall interobserver agreement (k = 0.87). Relatively low image quality with higher noise levels were encountered in 2 volunteers. CONCLUSION: MRA at 3.0 T using a 32-element phased-array coil is feasible in healthy volunteers. High diagnostic image quality and extended anatomic coverage could be achieved with application of high parallel imaging factors.

Adult↗

PubMed2006

Three-dimensional cerebral contrast-enhanced magnetic resonance venography at 3.0 Tesla: initial results using highly accelerated parallel acquisition.

OBJECTIVE: The objective of this study was to evaluate a high spatial resolution 3-dimensional (3D) contrast-enhanced magnetic resonance (CE-MR) venography protocol for evaluation of intracranial venous system using highly accelerated parallel imaging at 3.0 T. MATERIALS AND METHODS: Ten patients (4 male, 6 female; age, 38-76 years) with suspected cerebrovascular disease were prospectively studied on a 32-channel 3.0 T MR system. After a single intravenous contrast injection, high spatial resolution 3D CE-MR angiography of the entire supraaortic arteries was performed followed immediately by 3D cerebral CE-MR venography. By using a fast 3D gradient-recalled-echo sequence with elliptic centric k-space ordering and highly accelerated parallel acquisition (acceleration factor 3 and 2 in phase and slice encoding direction, respectively), 3D cerebral CE-MR venography was acquired with voxel dimensions of 0.7 x 0.7 x 0.8 mm in 24 seconds. Image evaluation was performed independently by 2 neuroradiologists for overall image quality, presence of noise, and artifacts. The image quality of 30 venous segments was evaluated in each subject using a 1 to 4 scoring scale. In 2 patients, catheter angiography was available for correlation. Statistical analysis of data was performed by using Wilcoxon rank sum test and kappa coefficient. RESULTS: All studies were determined to be of diagnostic image quality by both observers. The majority (90%) of cerebral venous segments were evaluated to be of diagnostic image quality (median, 3; range, 3-4) by both readers and with excellent interobserver agreement (kappa = 0.86; 95% confidence interval, 0.79-0.93). One meningioma invading the superior sagittal sinus and one superior sagittal sinus fistula were detected subsequently confirmed by conventional angiography. CONCLUSION: High spatial resolution 3D cerebral CE-MR venography is feasible and promising. Using a 32-channel 3.0 T system combined with multichannel array coils effectively supports highly accelerated parallel imaging, enabling subsequent acquisition of both high spatial resolution CE-MR angiography and CE-MR venography after a single contrast injection without impairing the image quality. More extensive clinical studies are warranted to establish the range of applications and confirm the accuracy of this technique.

Adult↗

PubMed2006

3 T contrast-enhanced magnetic resonance angiography for evaluation of the intracranial arteries: comparison with time-of-flight magnetic resonance angiography and multislice computed tomography angiography.

PURPOSE: We sought to prospectively evaluate the image quality and visualization of the intracranial arteries using high spatial resolution contrast-enhanced magnetic resonance angiography (CE-MRA) at 3 T and to perform intraindividual comparison with time-of-flight (TOF) MRA and multislice CT angiography (CTA). MATERIALS AND METHODS: Twelve patients (5 men, 7 women, 37-71 years of age) with suspected cerebrovascular disease prospectively underwent MRA and CTA. MRA was performed on a 3 T MR system, including both 3-dimensional (3D) TOF (Voxel dimension: 0.6 x 0.5 x 0.9 mm in 5 minutes and 40 seconds) and 3D CE-MRA (voxel dimension: 0.7 x 0.7 x 0.8 mm in 20 seconds, using parallel acquisition with an acceleration factor of 4). CTA images were acquired on a 16-slice CT scanner (voxel dimension: 0.35 x 0.35 x 0.8 mm in 17 seconds). The image quality and visualization of up to 26 intracranial arterial segments in each study was evaluated by 2 experienced radiologists. The arterial diameter for selective intracranial arteries was measured independently on each of the 3 studies, and statistical analysis and comparative correlation was performed. RESULTS: A total of 312 arterial segments were examined by CE-MRA, TOF-MRA, and CTA. The majority of intracranial arteries (87%) were visualized with diagnostic image quality on CE-MRA with a significant correlation to TOF (R values = 0.84; 95% confidence interval 0.79-0.86, P < 0.0001), and to CTA (R values = 0.74; 95% confidence interavl 0.68-0.78, P < 0.001). The image quality for small intracranial arteries, including the anterior-inferior cerebellar artery, the posterior communicating artery, and the M3 branch of the middle cerebral artery, was significantly lower on CE-MRA compared with TOF and CTA (P < 0.03). There was a significant correlation for the dimensional measurements of arterial diameters at CE-MRA with TOF (r = 0.88, 95% confidence interval 0.81-0.93), and CTA (r = 0.83, 95% confidence interval 0.73-0.90). CONCLUSION: The described 3 T CE-MRA protocol, spanning from the cervical to the intracranial vessels, visualized and characterized the majority of intracranial arteries with image quality comparable with that obtained using TOF-MRA and CTA. Further clinical studies are required to establish the accuracy of the technique in a broader clinical setting.

Adult↗

PubMed2006

Cardiac MR imaging: state of the technology.

Recent developments in magnetic resonance (MR) imaging of the heart have refocused attention on the potential of MR and continue to attract intense interest within the radiology and cardiology communities. Improvements in speed, image quality, reliability, and range of applications have evolved to the point where cardiac MR imaging is increasingly seen as a practical clinical tool. As is often the case with MR imaging, not all of the most powerful techniques are necessarily easy to master or understand, and many-nonspecialists and specialists alike-are challenged to stay abreast. This review covers some of the major milestones that have led to the current state of cardiac MR and attempts to put into context some concepts that, although technical, have a real impact on the diagnostic power of cardiac MR imaging. Topics discussed include functional imaging, myocardial viability and perfusion imaging, flow quantification, and coronary artery imaging. A review such as this can only scratch the surface of what is a dynamic interdisciplinary field, but the hope is that sufficient information and insight are provided to stimulate the motivated reader to take his or her interest to the next level.

Contrast Media↗

PubMed2006

High-spatial-resolution contrast-enhanced MR angiography of abdominal arteries with parallel acquisition at 3.0 T: initial experience in 32 patients.

OBJECTIVE: The objective of our study was to evaluate an isotropic high-spatial-resolution 3D contrast-enhanced MR angiography (CE-MRA) protocol with high acceleration parallel acquisition at 3.0 T for the display of the abdominal vasculature. SUBJECTS AND METHODS: Thirty-two consecutive patients (13 men, 19 women; age range, 28-88 years) with suspected abdominal arterial disease underwent abdominal 3D CE-MRA on a 3.0-T MR system, using a high-spatial-resolution (0.7 x 0.82 x 0.8 mm3) 3D gradient-refocused echo (GRE) sequence, integrated with a generalized autocalibrating partially parallel acquisitions (GRAPPA) technique with an acceleration factor of 3. Two vascular radiologists evaluated image quality and the presence and degree of arterial stenoses. Interobserver variability was calculated, using the kappa coefficient. The sensitivity and specificity of the technique were calculated and comparative analysis was performed with those of conventional catheter angiography (in eight patients) as the standard of reference. RESULTS: The abdominal arterial vasculature was visualized with diagnostic image quality in all subjects. Arterial stenoses were detected in 148 and 142 arterial segments by observer 1 and observer 2, respectively, with good interobserver agreement (kappa = 0.75; 95% confidence interval [CI]: 0.69-0.81). The sensitivity and specificity values for CE-MRA for the detection of significant (> 50%) arterial stenoses were 100% and 96% for observer 1 and 100% and 92% for observer 2, respectively. There was a significant correlation between CE-MRA and conventional angiography (R = 0.96 and 0.93 for observers 1 and 2, respectively) for the assessment of the degree of stenosis. CONCLUSION: The outlined MR angiography protocol at 3.0 T combined with parallel acquisition technique renders highly reliable and isotropic high-spatial-resolution imaging of the abdominal vasculature.

Abdomen↗

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 MR angiography of the thoraco-abdominal vessels.

With the strategies presented in this article,relevant disease involving the thoraco-abdominal vessels can be well depicted by 3D CEMRA. Aneurysms, dissections, occlusions, congenital lesions, and anatomic anomalies are readily assessed. Time-resolved MRA provides supplemental information in shunts, dissections, aneurysms, and AVMs. Velocity-encoded imaging may help fur-ther characterize lesions and may provide useful functional information to grade and monitor the progression of stenotic disease. 3.0T imaging and recent development in multicoil RF technology will further improve the performance of 3D CEMRAin terms of temporal and spatial resolution.

Abdomen↗