Biomedical subjects

M A Guttman

Publications and source records attributed to M A Guttman.

4 recordsLinked to original sources

PubMed2001

Techniques for fast stereoscopic MRI.

Stereoscopic MRI can impart 3D perception with only two image acquisitions. This economy over standard multiplanar 3D volume renderings allows faster frame rates, which are needed for real-time imaging applications. Real-time 3D perception may enhance the appreciation of complex anatomical structures, and may improve hand-eye coordination while manipulating a medical device during an image-guided interventional procedure. To this goal, a system is being developed to acquire and display stereoscopic MR images in real-time. A clinically used, fast gradient-recalled echo-train sequence has been modified to produce stereo image pairs. Features have been added for depth cueing, view sharing, and bulk signal suppression. A workstation was attached to a clinical MR scanner for fast data extraction, image reconstruction and stereoscopic image display.

Humans↗

PubMed1998

Catheter-tracking FOV MR fluoroscopy.

Recent improvements in intravascular magnetic resonance imaging techniques mandate an accurate method of monitoring the introduction of MR catheter probes into the vessel of interest. For this purpose, a novel imaging protocol and a display method have been designed. First, a roadmap 3D image data set with standard pulse sequences is obtained using an external imaging coil. Subsequently, using very narrow rectangular-FOV fast-spoiled gradient recalled (SPGR), a movie of the percutaneous placement procedure of an MR catheter probe is acquired at a rate of 7.3 frames/second. In this protocol, the probe is used to transmit RF pulses and receive MR signal. A computer program was written for image unwrapping and for displaying the unwrapped movie frames on the roadmap image. In an alternative protocol, the movie frames in two projection angles were acquired in an interleaved fashion. Frames were unwrapped and combined with a 3D roadmap and displayed on a Silicon Graphics workstation equipped with stereovision goggles. Using these methods, percutaneous catheter placement in a phantom and a dog was examined. In conclusion, a new visualization technique for MR catheter placement is proposed. Combining this technique with high resolution intravascular MRI techniques may result in a very useful diagnostic tool for the evaluation of atherosclerosis and other vessel diseases.

Algorithms↗

PubMed1998

Precision of myocardial contour estimation from tagged MR images with a "black-blood" technique.

RATIONALE AND OBJECTIVES: The authors determined whether blood presaturation of tagged magnetic resonance (MR) images affects identification of left ventricular endocardial borders. MATERIALS AND METHODS: Three healthy volunteers underwent MR imaging performed with a breath-hold segmented spoiled gradient-recalled-echo sequence with tissue tagging. Two saturation pulses (in the basal and apical regions) were used to generate black-blood images. Manual segmentation of endocardial contours on black-blood and white-blood images was performed independently by five observers. RESULTS: Endocardial borders were better identified on black-blood images compared with white-blood images, especially in the early systolic phases. Interobserver variability in contour estimation was significantly higher for white-blood images (P < .001) and was twice that for corresponding black-blood images during early systole. Contour variability appeared to be affected mainly by tag-to-myocardium contrast (P = .009) and myocardium-to-chamber contrast (P = .05). CONCLUSION: Blood presaturation of tagged MR images improves reliability of contour segmentation.

Adult↗

PubMed1994

Impact of semiautomated versus manual image segmentation errors on myocardial strain calculation by magnetic resonance tagging.

RATIONALE AND OBJECTIVES: Accurate image segmentation is essential for the study of mechanical properties of the myocardium by tagged magnetic resonance imaging (MRI). The relative accuracy of three methods of segmentation of myocardial borders and tags and their impact on myocardial strain calculations were evaluated. METHODS: Radially tagged, spin-echo magnetic resonance (MR) images of dog hearts were segmented manually, automatically, and semiautomatically. The variability of segmentation methods was separately determined for myocardial contours and tags. Error propagation assessment for strain calculation was estimated. RESULTS: The variability of the segmentation of the contours was five times greater than that of the tags. The error propagation is nonuniform in all directions, maximal for the radial component of strain. CONCLUSION: Errors in the segmentation of myocardial contours are significantly greater than those of the tags. Strain calculations should be based solely on segmentation of MR tags to avoid significant errors, particularly in radial strain estimates.

Animals↗