No abstract

The influence of changes in spatial and temporal resolutions on functional parameters in the left ventricle (LV) were investigated with magnetic resonance (MR) imaging with a modified true fast imaging with steady-state precession, or FISP, two-dimensional sequence that provided temporal resolution of 21-90 msec and spatial resolution of 1-3 mm. MR imaging in the heart was performed in 15 healthy volunteers. A decrease in LV functional parameters was observed with reduced spatial and temporal resolutions. The influence of temporal resolution was more relevant.

The purpose of this study was to prospectively evaluate an arterial spin-labeling technique, flow-sensitive alternating inversion-recovery (FAIR) true fast imaging with steady-state precession (FISP), for noninvasive quantification of renal perfusion in patients without a history of renal artery stenosis (RAS) and in patients with proved RAS. The study was approved by the local ethics committee, and all participants provided written informed consent. Six patients with hypertension but no history of renal artery disease and 12 patients with RAS underwent FAIR true FISP magnetic resonance (MR) imaging in a whole-body 1.5-T unit. RAS grade and scintigraphic perfusion data served as the reference standards. On the FAIR true FISP perfusion images, severe RAS (>70% luminal narrowing) could be clearly distinguished from no or mild RAS and moderate RAS (< or =70% luminal narrowing) (P < .005). Significant correlations between FAIR perfusion data and stenosis grade (r = -0.76) and between FAIR and single photon emission computed tomographic perfusion values (r = 0.83) were observed. FAIR true FISP was found to be suitable for quantitative perfusion imaging of the kidneys in patients with RAS.

Background-Perfusion imaging techniques intended to identify regional limitations in coronary flow reserve in viable myocardium need to identify 2-fold differences in regional flow during coronary vasodilation consistently. This study evaluated the suitability of current first-pass magnetic resonance approaches for evaluating such differences, which are 1 to 2 orders of magnitude less than in myocardial infarction. Methods and Results-Graded regional differences in vasodilated flow were produced in chronically instrumented dogs with either left circumflex (LCx) infusion of adenosine or partial LCx occlusion during global coronary vasodilation. First-pass myocardial signal intensity-time curves were obtained after right atrial injection of gadoteridol (0.025 mmol/ kg) with an MRI inversion recovery true-FISP sequence. The area under the initial portion of the LCx curve was compared with that of a curve from a remote area of the ventricle. Relative LCx and remote flows were assessed simultaneously with microspheres. The ratio of LCx and remote MRI curve areas and the ratio of LCx and remote microsphere concentrations were highly correlated and linearly related over a 5-fold range of flow differences (yϭ0.96xϮ0.07, PϽ0.0001, r 2 ϭ0.87). The 95% confidence limits for individual MRI measurements were Ϯ35%. Regional differences of Ն2-fold were consistently apparent in unprocessed MR images. Conclusions-Clinically relevant regional reductions in vasodilated flow in viable myocardium can be detected with 95%confidence over the range of 1 to 5 times resting flow. This suggests that MRI can identify and quantify limitations in perfusion reserve that are expected to be produced by stenoses of Ն70%. Key Words: magnetic resonance imaging Ⅲ regional blood flow Ⅲ vasodilation F irst-pass contrast-based MR perfusion imaging of the myocardium has received increasing attention as approaches providing improved temporal and spatial resolution and signal-to-noise ratio have become available. Clinical studies have focused on the identification of regional perfusion deficits indicating the presence of coronary artery disease. Because most studies have been performed during pharmacological coronary vasodilation, the perfusion deficits have included areas of both myocardial infarction and viable myocardium having limited coronary flow reserve.The identification of a regional limitation in flow reserve in viable myocardium is based on the identification of a relative reduction in perfusion during coronary vasodilation. Pharmacological vasodilation can increase resting flow 4-to 8-fold in normally perfused viable tissue, whereas a lesser increase occurs in areas supplied by stenotic arteries. 1,2 Because 70% diameter stenoses reduce vasodilated flow by only Ϸ50%, 2-5 a clinically useful technique needs to identify 2-fold regional differences in vasodilated flow consistently. This is an appreciably more demanding requirement than when perfusion imaging is used to identify areas of myocardial infarction, ie, resting blood flow in infarcted ...

Current magnetic resonance imaging (MRI) technology allows the determination of patient-individual coronary tree structure, detection of infarctions, and assessment of myocardial perfusion. Joint inspection of these three aspects yields valuable information for therapy planning, e.g., through classification of myocardium into healthy tissue, regions showing a reversible hypoperfusion, and infarction with additional information on the corresponding supplying artery. Standard imaging protocols normally provide image data with different orientations, resolutions and coverages for each of the three aspects, which makes a direct comparison of analysis results difficult. The purpose of this work is to develop methods for the alignment and combined analysis of these images. The proposed approach is applied to 21 datasets of healthy and diseased patients from the clinical routine. The evaluation shows that, despite limitations due to typical MRI artifacts, combined inspection is feasible and can yield clinically useful information.

High resolution MDCT or MRI 3D datasets can be accurately reconstructed using laser sinter technique. Teaching, research and preoperative planning may be facilitated in the future using this technique.

Purpose:To compare signal-to-noise ratio (SNR), contrastto-noise (CNR) ratio, and diagnostic accuracy of a newly developed saturation recovery (SR)-TrueFISP-two-dimensional (2D) sequence with an SR-TurboFLASH-2D sequence. Materials and Methods:In seven healthy subjects and nine patients with coronary artery disease (CAD), contrastenhanced perfusion imaging (with Gd-DTPA) was performed with SR-TrueFISP and SR-TurboFLASH sequences. Hypoperfused areas were assessed qualitatively (scale ϭ 0 -4). Furthermore, SNR and CNR were calculated and semiquantitative perfusion parameters were determined from signal intensity (SI) time curves. Standard of reference for patient studies was single-photon emission computer tomography (SPECT) and angiography. Results:The perception of perfusion deficits was superior in TrueFISP images (2.6 Ϯ 1.0) than in TurboFLASH (1.4 Ϯ 0.6) (P Ͻ 0.001). Phantom measurements yielded increased SNR (143 Ϯ 34%) and CNR (158 Ϯ 64%) values for True-FISP. In patient/volunteer studies SNR was 61% to 100% higher and signal enhancement was 110% to 115% higher with TrueFISP than with TurboFLASH. Qualitative and semiquantitative assessment of perfusion defects yielded higher sensitivities for detection of perfusion defects with TrueFISP (68% to 78%) than with TurboFLASH (44% to 59%). Conclusion:SR-TrueFISP-2D perfusion imaging provides superior SNR and CNR than TurboFLASH imaging. Moreover, the dynamic range of SIs was found to be higher with TrueFISP, resulting in an increased sensitivity for detection of perfusion defects.

Circulating endostatin levels are elevated in patients with renal carcinoma and correlate with circulating VEGF levels. Endostatin levels increase after nephrectomy, and patients with the greatest increases experience shortened survival times. These findings suggest an association between tumor aggressiveness and the production of endogenous endostatin in patients with renal carcinoma.