Comparison Of Radial Research Articles

Comparison of Radial and Cartesian Imaging Techniques for MR Coronary Angiography

Magnetic resonance coronary angiography (MRCA) has traditionally been performed using a Cartesian k-space data acquisition scheme. Radial k-space sampling is known to be less sensitive to motion artifacts. Thus, potential improvements may be achieved with radial k-space data acquisition using steady state free precession (SSFP) techniques. We directly compared SSFP three-dimensional (3D)-MRCA using radial and Cartesian data acquisition. Forty-four consecutive patients with suspected coronary artery disease underwent free-breathing, navigator-corrected MRCA of the left or right coronary artery using SSFP (TR/TE/flip angle: 4.5 ms/2.3 ms/90 degrees) with radial and again with Cartesian k-space filling. Quantitative MRCA was performed with a dedicated multiplanar reformatting software to determine: visual score for image quality (low=1, high=4), vessel sharpness, visible vessel length, number of visible side branches, and average vessel diameter. Diagnostic accuracy for detection of > or = 50% coronary artery stenosis was calculated in comparison to invasive X-ray angiography. Radial data acquisition resulted in a significant (p<0.01) increase in vessel sharpness (55.6+/-7.2% vs. 45.9+/-7.0%) but a decrease in average vessel diameter (2.6+/-0.5 mm vs. 3.0+/-0.4 mm), number of visible side branches (2.1+/-1.1 vs. 3.0+/-1.7) and number of assessable coronary artery segments (66% vs. 73%) compared to Cartesian approach. There was no significant difference regarding the diagnostic accuracy (80.8% vs. 83.9%), the visual score (2.6+/-0.9 vs. 3.0+/-0.9) and the visible vessel length (92.1+/-36.0 mm vs. 99.9+/-32.4 mm). MRCA with radial k-space sampling appears to be on a par with Cartesian approach with respect to the diagnostic performance in an unselected patient population. Nevertheless, with current implementations, radial sampling is inferior to Cartesian sampling regarding the visualization of side branches despite better vessel sharpness.

Comparison of Radial- and Axial-Flow Rapid Pressure Swing Adsorption Processes

Compared to axial-flow rapid pressure swing adsorption (RPSA) processes, radial-flow RPSA processes can have the larger cross section for the same volume of adsorbers. Radial-flow RPSA processes, thus, may have the advantage of a low-pressure drop for the same volumetric flow and a small particle size of the adsorbent can be used for the same pressure drop. After an innovative coordinate transformation, the governing equations of both radial- and axial-flow RPSA processes carry a similar form. Therefore, only a simulation program is needed and is developed to simulate the dynamics of the adsorbers for both systems. The simulation results of an axial-flow RPSA were compared with the experimental data in the literature. For the modeling of radial-flow RPSA processes, the parameter of effective length is equivalent to the length of the packed bed of axial-flow RPSA processes. For the same feed pressure and the same amount of adsorbent, the separation performance of the radial-flow RPSA processes would be bet...

Comparison of Radial and Femoral Arterial Pressure in Pediatric Patients Undergoing Open Heart Surgery

Comparison of Radial and Femoral Arterial Pressure in Pediatric Patients Undergoing Open Heart Surgery

Comparison of radial and sector array Endoscopic Ultrasound (EUS) for localization of Pancreatic Endocrine Tumors (PET)

Comparison of radial and sector array Endoscopic Ultrasound (EUS) for localization of Pancreatic Endocrine Tumors (PET)

A comparison of radial, brachial, and aortic pressures after cardiopulmonary bypass

Previous investigations have identified falsely low radial artery pressures after cardiopulmonary bypass (CPB). The present study investigates the relationship among radial, brachial, and aortic arterial pressures in 33 cardiac surgical patients following CPB. Two minutes after separation from CPB, clinically important (≥10 mmHg) underestimation of systolic aortic pressures occurred in 17 of 33 (52%) radial artery catheters, while occurring in seven of 33 (21%) brachial artery catheters. Radial artery mean pressure underestimated aortic mean pressure by ≥5 mmHg in 21 of 33 (61 %) patients two minutes after CPB, while an equivalent aortic-to-brachial artery mean arterial pressure difference occurred in nine of 33 (27%) patients. The incidence of aorticto-radial mean arterial pressure differences ≥5 mmHg decreased to 40% (four of ten patients) by ten minutes after CPB, although interpretation is complicated by decreased availability of aortic pressure measurements. Multivariate analysis failed to identify factors predisposed to central-to-peripheral pressure gradients. Radial and brachial arterial pressures were compared both before and after CPB in all 33 patients. Brachial artery systolic and mean pressures were higher than corresponding radial artery measurements two minutes after CPB ( P < 0.05), followed by gradual resumption of a normal brachial-to-radial pressure relationship over 60 minutes. Either vasospasm in the brachial and radial arteries or profound arteriolar vasodilation in the upper extremity might cause the observed central-to-peripheral arterial pressure differences. The progressive central-to-peripheral decrease in mean arterial pressure favors the latter mechanism. Since radial artery pressures reproduce aortic pressure unpredictably immediately after CPB, blood pressure should be measured more centrally (eg, ascending aorta or femoral artery) before initiating vasopressor therapy for hypotension upon separation from CPB. Brachial artery pressure underestimates post-CPB aortic pressure less frequently and less severely than radial artery pressure, but reproduction of aortic pressure was too inconsistent to warrant substitution of brachial artery catheters for radial artery catheters. Alternatives to radial artery pressures appear most advantageous for the first 20 minutes after CPB separation, but occasionally they facilitate accurate diagnosis of blood pressure abnormalities well beyond that period.