journal article
LitStream Collection
Home
doi: N/Apmid: N/A
The potential risk of a radiologic procedure often is compared with the potential benefit of the procedure. While risk vs. benefit analysis has been useful as a step toward increased communication and understanding among radiologists, referring physicians, and the general public, it has the disadvantage that risk and benefit are fundamentally different quantities. Hence, their juxtaposition for purposes of comparison presents contextual difficulties. In this article, the concept is presented of comparing the risk of doing a procedure with the risk of choosing not to do the procedure. An example of risk vs. risk analysis of screening mammography for women over the age of 50 is given, with the conclusion that the risk of having yearly mammograms is less than 1/10 the risk of early death caused by failure to diagnose breast cancer by x-ray mammography. This approach to risk analysis would yield interesting data for examinations that are part of more complicated diagnostic pathways.
doi: N/Apmid: N/A
The effects of postextrasystolic potentiation during spontaneous ventricular ectopy on both left and right ventricular function were studied in 12 patients with the aid of list-mode radionuclide ventriculography. The left ventricular ejection fraction showed a significant increase (+ 11.0 ± 5.0%; p < .001) with associated mild increases in end-diastolic volumes (+ 4.9 ± 4.6; p<.01) and significant decreases in end-systolic volumes (—13.4% ± 7.3%; p<.001). A more heterogeneous response was seen for the right ventricle. Right ventricular ejection increased significantly in 8/12 patients (+ 3.3 ± 3.0%; p<.02). Despite a large increase in end-diastolic volumes (+ 10 ± 7.9%; p<.001), there were only mild changes in end-systolic volumes (+ 2.2 ± 9.0; p=NS). It is concluded that, for spontaneous ventricular ectopy in man, the increase in right ventricular ejection fraction reflects improved ventricular filling whereas the increase in left ventricular ejection fraction is linked to improved emptying.
doi: N/Apmid: N/A
Hexakis (alkylisonitrile) technetium(I) complexes are a new class of cationic, lipophilic myocardial perfusion imaging agents. To further evaluate the effect of lipophilicity on myocardial uptake characteristics, the authors systematically synthesized and tested Tc-isonitrile complexes of varying lipophilicity in both cellular and whole animal systems. In chick heart cells in monolayer culture, cellular plateau level uptake in general correlated with lipophilicity of the complexes (determined by reverse phase high performance liquid chromatography) (r=.71) as well as with scintigraphic intensity of imaged rabbit hearts (r=.91). Exceptions to this trend indicated that additional factors such as size of the complex and form of the terminal alkyl chain branching also may have influenced uptake. The data indicated that neither the lipophilic properties nor the cation charge alone were sufficient to predict myocardial uptake. In addition, intravenous injection of complexes into rabbits showed optimal myocardial images with agents of intermediate lipophilicity. Results indicated that, following intravenous administration, complexes of low lipophilicity yielded suboptimal myocardial images because of low heart cell uptake, whereas complexes of high lipophilicity yielded poor relative myocardial visualization because of excessive binding to additional organs and compartments.
doi: N/Apmid: N/A
The authors present a numerical deconvolution technique to compensate for image degrading effects caused by scattered photons in radiographic chest images. Fourier transform techniques are used to deconvolve a shift invariant model of the two dimensional point spread response functions of the scattered radiation. This approach uses a digitized radiograph acquired with a standard chest imaging protocol, so no specialized imaging equipment is required. While the shift variant shape of the scatter model is optimized for the lung field, effective compensation is provided when this model shape is applied to other chest regions. Preliminary evaluation suggests that this technique can provide improved image contrast over the entire chest region.
doi: N/Apmid: N/A
The effects of diatrizoate, iohexol, and ioxilan on the blood-brain barrier (BBB) were investigated in normal and hypertensive rats. Anesthetized Wistar rats received 14C-inulin as an indicator for BBB disruption. Diatrizoate, iohexol, or ioxilan (350 and 175 mgl/mL) or normal saline was then injected into the carotid artery (2 mL in 30 seconds). Twenty minutes later, the cardiovascular system was flushed, the brain removed, and each hemisphere was digested. BBB disruption, expressed as counts/minute/mg protein, was compared for each hemisphere in each group by analysis of variance. BBB damage in the diatrizoate-350 group was significantly greater than that in all other groups. No significant BBB damage resulted from iohexol or ioxilan relative to normal saline.
doi: N/Apmid: N/A
The value of rapid, contrast-enhanced, diuretic magnetic resonance (MR) imaging (using ferrioxamine B and furosemide) in demonstrating partial unilateral ureteral obstruction and the potential of such MR imaging in differentiating obstructive from nonobstructive hydronephrosis was assessed in six micropigs. MR imaging (0.35 Tesla, partial-flip technique with repetition time [TR] of 125 milliseconds, echo-delay time [TE] of 20 milliseconds, and flip angle of 70°) was performed before, and at 5, 12, and 19 days after partial ureteral obstruction. Additionally, MR images were acquired 5, 12, and 19 days after release of obstruction. The diuretic was injected 10 minutes after the contrast medium. MR findings were correlated with results from nuclear scintigraphy (
Showing 1 to 10 of 23 Articles