Biomedical subjects

Gerhard Laub

Publications and source records attributed to Gerhard Laub.

28 records · Page 2Linked to original sources

PubMed2005

Single-session magnetic resonance coronary angiography and myocardial perfusion imaging using the new blood pool compound B-22956 (gadocoletic acid): initial experience in a porcine model of coronary artery disease.

OBJECTIVE: The objective of this study was to evaluate a new blood pool contrast agent, B-22956, for detecting myocardial perfusion abnormality and coronary artery stenosis by magnetic resonance imaging (MRI) in 1 setting. MATERIALS AND METHODS: Coronary artery atherosclerotic stenoses were created in 6 miniswine. Myocardial first-pass perfusion imaging was performed with a bolus injection of 0.015 mmol/kg B-22956 during pharmacologic stress followed by postcontrast coronary artery imaging after another injection of B-22956/1. The total doses for the 6 pigs were 0.1 mmol/kg (n=3) and 0.15 mmol/kg (n=3). Perfusion upslope maps were analyzed and MR coronary artery images were reviewed by 2 readers. RESULTS: For all 6 pigs, the normalized upslopes of the perfusion curves were 0.83+/-0.12, 0.74+/-0.15, and 0.52+/-0.05 (P<0.01 vs. normal) with normal or mild (<50% area stenosis), moderate (<50% and <75%), and severe stenosis (>75%), respectively. Mean signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in right coronary artery images improved 90% and 200%, respectively, with a total dose of 0.1 mmol/kg of B-22956. Excellent agreements (kappa=0.82) were achieved for evaluating the grade of stenosis between MR postcontrast coronary artery images and histopathology by 2 reviewers. CONCLUSION: The MR blood pool contrast agent B-22956 demonstrated the ability for detecting myocardial perfusion abnormalities and coronary artery stenosis in 1 setting.

Animals↗

PubMed2004

Self-gated cardiac cine MRI.

The need for ECG gating presents many difficulties in cardiac magnetic resonance imaging (CMRI). Real-time imaging techniques eliminate the need for ECG gating in cine CMRI, but they cannot offer the spatial and temporal resolution provided by segmented acquisition techniques. Previous MR signal-based techniques have demonstrated an ability to provide cardiac gating information; however, these techniques result in decreased imaging efficiency. The purpose of this work was to develop a new "self-gated" (SG) acquisition technique that eliminates these efficiency deficits by extracting the motion synchronization signal directly from the same MR signals used for image reconstruction. Three separate strategies are proposed for deriving the SG signal from data acquired using radial k-space sampling: echo peak magnitude, kymogram, and 2D correlation. The SG techniques were performed on seven normal volunteers. A comparison of the results showed that they provided cine image series with no significant differences in image quality compared to that obtained with conventional ECG gating techniques. SG techniques represent an important practical advance in clinical MRI because they enable the acquisition of high temporal and spatial resolution cardiac cine images without the need for ECG gating and with no loss in imaging efficiency.

Algorithms↗

PubMed2003

TrueFISP--technical considerations and cardiovascular applications.

Magnetic resonance imaging (MRI) using steady-state free precession (SSFP) sequences was described in the early years of MR imaging. However, due to hardware imperfections, these techniques were not robust enough at the time to play any significant role in clinical MRI. More recently, significant hardware improvements became widely available, and the SSFP sequences such as TrueFISP (true fast imaging with steady-state precession) became very popular for a variety of clinical applications due to the distinct improvements in signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). The purpose of this article is to give an overview on the basics of TrueFISP imaging and to demonstrate its potential for current clinical applications with a focus on cardiovascular MRI.

Cardiovascular Diseases↗

PubMed2003

Diagnostic value of maximum intensity projections versus source images for assessment of contrast-enhanced three-dimensional breath-hold magnetic resonance coronary angiography.

RATIONALE AND OBJECTIVES: We compared maximum intensity projections (MIP) versus original source images (SI) in respect to detection of coronary artery stenoses by means of magnetic resonance (MR) coronary angiography. METHODS: MR coronary angiography was performed on 61 patients. MIP and SI were independently evaluated as to presence of significant stenoses in the proximal and midcoronary segments and compared with x-ray angiography. RESULTS: A total of 315 of 427 (74%) coronary artery segments could be evaluated in MIP and 328 of 427 (77%) in SI. In segments able to be evaluated, MIP images demonstrated 84% (54/64) sensitivity and 87% (219/251) specificity, whereas SI images showed 85% (58/68) sensitivity and 90% (235/260) specificity. Overall accuracy was 87% (273/310) for MIP and 89% (293/328) for SI. There was no statistically significant difference between both modalities. CONCLUSIONS: The MIP reconstructions showed comparable accuracy to unprocessed SI. However, MIP postprocessing is compromised by a higher number of images that were unable to be evaluated due to overlap of coronary arteries with adjacent cardiac structures.

Algorithms↗

PubMed2002

Comparison of contrast-enhanced breath-hold and free-breathing respiratory-gated imaging in three-dimensional magnetic resonance coronary angiography.

Suppression of respiratory motion is one of the major challenges of magnetic resonance (MR) coronary angiography. Two approaches to compensate for respiratory motion have often been proposed: breath-hold (BH) and free-breathing respiratory-gated (FBRG) imaging. So far, however, these approaches have never been directly compared. MR coronary angiography was performed in 32 patients with suspected coronary artery disease. MR data were acquired using contrast-enhanced BH and FBRG 3-dimensional MR coronary angiographic techniques. MR images were compared with regard to image quality using quantitative parameters and with regard to accuracy for stenosis detection in the proximal and mid-coronary segments in comparison to x-ray angiography. With regard to image quality, BH was superior to FBRG. Signal-to-noise ratio was 29.1 +/- 10.7 for BH versus 18.8 +/- 9.7 for FBRG (p <0.05) and contrast-to-noise was 18.0 +/- 7.4 for BH versus 11.3 +/- 7.9 for FBRG (p </=0.05). One hundered seventy-one of 224 coronary artery segments (76%) were evaluable in BH compared with 155 of 224 in FBRG (69%). In the evaluable segments, BH demonstrated a sensitivity of 87% (26 of 30 stenoses detected) and specificity of 92% (129 of 141 nonstenotic segments correctly identified), whereas FBRG showed a sensitivity of 60% (15 of 25) and specificity of 89% (115 of 130). Overall accuracy was 91% (155 of 171) for BH and 84% (130 of 155) for FBRG. Sensitivity was significantly higher for BH (p = 0.0320), whereas specificity and overall accuracy were not significantly different. Thus, contrast-enhanced BH MR coronary angiography compares favorably to FBRG imaging with regard to image quality and detection of coronary stenoses.

Adult↗

PubMed2002

Real-time MRI of joint movement with trueFISP.

PURPOSE: To develop a technique for dynamic magnetic resonance imaging (MRI) of joint motion based on a combination of real-time TrueFISP (fast imaging with steady state precession) imaging with surface radiofrequency (RF) coils. MATERIALS AND METHODS: The metacarpal, elbow, tarsal, and knee joint of five volunteers and the knees of four patients were examined with a real-time TrueFISP sequence during movement of the joints. RESULTS: All examined joints could be assessed under dynamic conditions with high image contrast and high temporal resolution. CONCLUSION: Dynamic MRI of joints with TrueFISP is feasible and can provide information supplemental to static joint examinations.

Elbow Joint↗

PubMed2002

Time-resolved three-dimensional pulmonary MR angiography and perfusion imaging with ultrashort repetition time.

RATIONALE AND OBJECTIVES: The purpose of this study was to implement ultrafast, multiphase three-dimensional (3D) magnetic resonance (MR) angiography and perfusion imaging after bolus injection of contrast medium to generate preliminary validation of parameters in a pig model and to illustrate potential applications in patients with lung abnormalities. MATERIALS AND METHODS: Five healthy volunteers, five patients, and three pigs underwent rapid, time-resolved pulmonary MR angiography and perfusion imaging on a 1.5-T MR imager. All patients had undergone correlative computed tomographic or conventional angiography. The pulse sequence was a 3D spin-warp, gradient-echo acquisition with a repetition time of 1.6 msec and an echo time of 0.6 msec. Each 3D acquisition lasted 2-3 seconds, and 8-16 sequential measurements were made in each study. Artificial pulmonary emboli were generated in pigs with gelatin sponge. All patients had diseases of the pulmonary circulation (as confirmed with other studies). RESULTS: Multiphasic, time-resolved pulmonary parenchymal enhancement was demonstrated in all healthy subjects and animals. All segmental (n = 100) and subsegmental (n = 200) branches were identified in the healthy subjects. Perfusion deficits were clearly demonstrated in all pigs after gelatin embolization. Perfusion defects were identified in two patients with lung disease. Abnormalities of the pulmonary vasculature were clearly identified in the patient group. CONCLUSION: Dynamic time-resolved 3D pulmonary MR angiography and perfusion imaging is feasible in humans as well as in animals. Induced perfusion deficits are identifiable after artificial embolization in pigs. Combined pulmonary MR angiography and parenchymal (perfusion) imaging may improve evaluation of the pulmonary circulation in a variety of conditions.

Adult↗

PubMed2002

A direct comparison of noninvasive coronary angiography by electron beam tomography and navigator-echo-based magnetic resonance imaging for the detection of restenosis following coronary angioplasty.

RATIONALE AND OBJECTIVES: To compare electron beam tomography (EBT) with MR imaging (MRI) for detection of restenosis after coronary angioplasty (PTCA). METHODS: One hundred eighteen patients after PTCA were investigated. By EBT, 50 axial images were acquired (3-mm slice thickness, 120-160 mL radiographic contrast agent). MRI was performed using respiratory-gated sequences (24-48 cross-sections, 2-mm slice thickness, 20 mL Gd-DTPA). EBT and MRI images were evaluated concerning high-grade post-PTCA restenosis (> or = 70%) and validated against coronary angiography. RESULTS: In EBT, 28 patients and in MRI, 31 patients were not evaluable. In the remaining patients, sensitivity for restenosis detection was 90% in EBT (17/19) and 73% in MRI (11/15; P = 0.370). In EBT, specificity was significantly higher (66% vs. 49%, P = 0.043). Overall accuracy was 71% for EBT and 53% for MRI (P = 0.014). CONCLUSIONS: For the detection of high-grade restenosis after PTCA, EBT demonstrated significantly higher accuracy than MRI.

Angioplasty, Balloon, Coronary↗

PubMed2002

Coronary MR angiography: experimental results with a monomer-stabilized blood pool contrast medium.

PURPOSE: To evaluate the signal-enhancing characteristics of monomer-coated very small superparamagnetic iron oxide (SPIO) particles used as a blood pool contrast medium for magnetic resonance (MR) angiography in the coronary arteries. MATERIALS AND METHODS: The particles used in this study were coated with citrate as the monomer (VSOP-C91). The particles have a total diameter of 7 nm and show the following relaxivities at 0.47 T: T1, 19 L/mmol. sec(-1); T2, 29 L/mmol. sec(-1). Fifteen cardiac MR examinations were performed at 1.5 T in five pigs. Images were acquired from immediately to 35 minutes (equilibrium phase) after intravenous injection of gadopentetate dimeglumine, gadobenate dimeglumine, and the very small SPIO particles (n = 5 for each substance). RESULTS: Immediately after administration of gadopentetate dimeglumine, gadobenate dimeglumine, and the very small SPIO particles, respectively, increases in the signal-to-noise ratio in blood were 94%, 103%, and 102% and in myocardium were 83%, 83%, and 29% (P <.05, very small SPIO particles versus the low-molecular-weight gadolinium-based compounds). Differences in the blood-to-myocardium contrast-to-noise ratio and visualization of the coronary arteries and their branches were also significant. CONCLUSION: VSOP-C91 significantly improves visualization of the coronary arteries at MR angiography from immediately to 35 minutes after injection.

Analysis of Variance↗

PubMed2002

High-resolution breath-hold contrast-enhanced MR angiography of the entire carotid circulation.

OBJECTIVE: The purpose of this study was to evaluate the effect of breathing on image quality of the aortic arch and carotid vessels during contrast-enhanced MR angiography and to show that high-resolution breath-hold contrast-enhanced MR angiography combined with a timing-bolus technique can produce high-quality images of the entire carotid circulation. MATERIALS AND METHODS: Forty patients underwent high-resolution contrast-enhanced MR angiography on a 1.5-T Magnetom Symphony. A coronal three-dimensional (3D) gradient-echo sequence (TR/TE, 4.36/1.64; flip angle, 25 degrees) with asymmetric k-space acquisition was used. The 136 x 512 matrix yielded voxel sizes of 1.33 x 0.64 x 1.0 mm. A timing-bolus acquisition, orientated in the coronal plane to include the aortic arch, was obtained initially during free-breathing. Twenty milliliters of gadopenetate dimeglumine was injected at 2 mL/sec. Unenhanced and enhanced 3D volumes were recorded. A subtracted 3D set was calculated and subjected to a maximum-intensity-projection algorithm. Half of the patients held their breath during angiography and the other half did not. Aortic arch motion was measured on the timing-bolus acquisition as the distance moved by a single pixel in both the x and y directions. Maximum-intensity-projection MR images were assessed independently by two observers, and vessel sharpness was scored on a scale of 1-5. Sharpness was also assessed quantitatively by generating a signal intensity profile across the aortic arch vessel wall and calculating the average of the upslope and downslope at full-width half maximum. Visualization of carotid branch vessels was scored on a scale of 0-5, and venous contamination was scored on a scale of 0-3. RESULTS: Average in-plane aortic arch movement was 10.3 mm in the x direction and 8.7 mm in the y direction. Quantitative and qualitative sharpness of the aortic arch and great vessel origins was better (p < 0.05) during breath-holding than during non-breath-holding. No difference in the sharpness of the carotid vessels was noted between the two groups. Carotid branch vessels were well visualized from the aortic arch to the intracerebral circulation. The average venous contamination score was 0.56. CONCLUSION: Breath-holding greatly improves the sharpness of the aortic arch and great vessel origins but has no effect on visualization of the carotid vessels. High-resolution breath-hold contrast-enhanced MR angiography can produce high-quality, artifact-free images of the entire carotid circulation from the aortic arch to the intracerebral circulation.

Aged↗