Principles and applications of balanced SSFP techniques.

During the past 5 years balanced steady-state free precession (SSFP) has become increasingly important for diagnostic and functional imaging. Balanced SSFP is characterized by two unique features: it offers a very high signal-to noise ratio and a T2/T1-weighted image contrast. This article focuses on the physical principles, on the signal formation, and on the resulting properties of balanced SSFP.

Background suppression using magnetization preparation for contrast-enhanced 3D MR angiography of the pelvic and lower leg arteries.

Purpose: To develop and evaluate non-slab-selective magnetization preparation in contrast-enhanced 3D-MR angiography.

Methods: An ultrafast spoiled mr angiography sequence (FLASH) with non-selective inversion prepulses for background suppression was implemented on a 1.5 T MR system.

Assessment of pulmonary perfusion with ultrafast projection magnetic resonance angiography in comparison with lung perfusion scintigraphy in patients with malignant stenosis.

Rationale And Objective: The aim of this study was to demonstrate and measure perfusion deficits caused by central bronchogenic carcinoma and to compare magnetic resonance angiography (MRA) perfusion data with data of perfusion scintigraphy. The diagnostic value of 2D MRA in detection of malignant pulmonary artery stenosis in comparison with conventional DSA was investigated.

Materials And Methods: Eighteen patients were included in the study.

Pulmonary sequestration: demonstration of blood supply with 2D and 3D MR angiography.

Pulmonary sequestration is a relatively rare but clinically significant congenital anomaly. This disease is a spectrum of disorders involving the pulmonary airways, the arterial supply to the lungs, the lung parenchyma and its venous drainage. Traditionally, the diagnosis of pulmonary sequestration has been made definitively with arterial angiography.

Diagnosis of the hypothenar hammer syndrome by high-resolution contrast-enhanced MR angiography.

Our objective was to describe the imaging features of hypothenar hammer syndrome using minimally invasive contrast-enhanced MR angiography in comparison with oscillography study. In five patients with hypothenar hammer syndrome Gd-BOPTA-enhanced elliptically reordered 3D pulse sequence MR was compared with oscillography findings and clinical symptoms focusing on angiographic appearance of vessel injury, distribution pattern of hand vasculature and joining branches between the radial and ulnar artery supply. All patients showed segmental occlusion at the site of trauma impact with varying involvement of the superficial palmar arch, common volar digital arteries.

Contrast enhanced MR angiography in the assessment of relevant stenoses in occlusive disease of the pelvic and lower limb arteries: diagnostic value of a two-step examination protocol in comparison to conventional DSA.

Introduction/objectives: Contrast-enhanced MRA (ce-MRA) has been claimed by many authors as a replacement of conventional angiography evaluating peripheral arterial occlusive disease. However, reliable detection of relevant stenoses (>70%) has to be provided for planning vascular interventions. Only few data in the literature focuses on this crucial problem.

Fast functional MRA using time-resolved projection MR angiography with correlation analysis.

Most recently, time-resolved 2D MRA after injection of a contrast agent bolus for various applications has been proposed. Similar to conventional digital subtraction angiography (DSA), 2D MR DSA offers the ability to observe the dilution of the bolus in the vascular system during the passage with a temporal resolution considerably below 1 sec. The purpose of this paper is to present strategies to improve the inherent low signal-to-noise ratio of 2D angiograms while retaining some temporal resolution.

MRI of heart morphology. Comparison of nongradient echo sequences with single- and multislice acquisition.

Rationale And Objectives: A large variety of cardiac MRI sequences have been introduced for heart morphology evaluation. The aim of this study was to establish a practicable and robust examination protocol for standard high-field systems applying nongradient echo sequences with single- and multi-slice acquisition.

Methods: Fifty-one patients received electrocardiogramgated MRI of the heart with "black-blood" preparation, comparing three single-slice and three multislice sequences with a T1-weighted turbo spin echo reference sequence.

In vivo effect of asparagine in the hydrophobic region of the signal sequence.

On the basis of the biophysical studies on the synthetic mutant (Ile-8----Asn) OmpA signal peptide in the preceding paper (Hoyt, D. C., and Gierasch, L.

Enhancement of protein translocation across the membrane by specific mutations in the hydrophobic region of the signal peptide.

The hydrophobic region of the signal peptide of the OmpA protein of the Escherichia coli outer membrane was extensively altered in its hydrophobicity and predicted secondary structure by site-specific mutagenesis. The mutated signal peptides were fused to nuclease A from Staphylococcus aureus, and the function of the signal peptide was examined by measuring the rate of processing of the signal peptide. Six of the 12 mutated signal peptides in the nuclease hybrid were processed faster than the wild-type.

Modulation of the effects of mutations in the basic region of the OmpA signal peptide by the mature portion of the protein.

Oligonucleotide-directed site-specific mutagenesis was used to study the structure-function relationship of the positively charged amino terminus of the Escherichia coli outer membrane protein OmpA signal peptide. Mutations were isolated which reduced the overall charge of the amino-terminal region from +2 (wild type) to +1, 0, and -1, as well as one mutation from Thr to Ser at position 4. DNA encoding the wild type and mutant OmpA signal peptides was then fused in-frame to DNA encoding the mature regions of Staphylococcus aureus nuclease A and TEM beta-lactamase.

The differential effect on two hybrid proteins of deletion mutations within the hydrophobic region of the Escherichia coli OmpA signal peptide.

Oligonucleotide-directed site-specific mutagenesis was used to systematically shorten the hydrophobic region within the signal peptide of the Escherichia coli outer membrane protein OmpA. DNA encoding the wild type and mutant OmpA signal peptides were then fused in frame to DNA encoding the mature regions of Staphylococcus aureus nuclease A and TEM beta-lactamase. The ability of these signal peptides to direct processing of the resulting hybrid proteins was dependent on both their length and the protein to which they were fused.