We have implemented a computerized system for relatively rapid (< 1 h) three-dimensional (3D) surface rendering of flow-sensitive (gradient refocused) magnetic resonance images. The method has been applied in 8 patients with six different clinical problems and was found to enhance understanding of normal and abnormal aortic, caval, and portosystemic venous anatomy. 3D images are useful for communicating complex anatomic information and may help with difficult diagnoses. Advantages and limitations of the present system are discussed.

Aortic Dissection↗

PubMedDate not supplied

Corticosteroid receptors in the avian kidney.

The binding in vitro of tritiated aldosterone to domestic duck (Anas platyrhynchos) kidney tissue has been investigated. Using tissue from animals on a normal diet, tritiated aldosterone was specifically bound to kidney cytosol with an apparent equilibrium dissociation constant of about 9 nM and number of binding sites in the 20 fmol/mg protein range. These values did not show statistically significant changes when the cytosol originated from animals with salt activated nasal glands. Kidney cytosols labeled with tritiated aldosterone sedimented with a single peak at 8S in a linear sucrose gradient (10--30%) and this peak was quenched by excess, radioinert aldosterone. Following incubation of labeled cytosols with crude nuclei, the cytosols became depleted of the label and aldosterone was translocated to the Tris-soluble and Tris-insoluble, 0.4 M KC1 soluble nuclear fractions. Kidney cytosols metabolized aldosterone extensively to a compound presumed to be 3alpha,5beta-tetrahydroaldosterone. However, only unchanged aldosterone became receptor-bound. It was concluded that the duck kidney possesses aldosterone receptors, though competition studies indicated that the specificity of these receptors might be different from those described in the mammalian kidney.

Adrenal Cortex Hormones↗

PubMedDate not supplied

Symmetrical and asymmetrical changes in brain tissue with age as measured on CT scans.

Age-related changes in mean CT attenuation values of brain tissue were analyzed by an objective, automated technique. Study participants included 64 healthy men ranging in age from 31 to 87 years. Five CT slices from each individual were evaluated: the last ventricular slice and the next four supraventricular slices. Regression analyses indicated that specific regions in the brain change with age. A schematic reconstruction of these regions suggests that several brain regions are selectively altered with age. On the medial aspect of the cerebral hemisphere there was bilaterally symmetrical atrophy of the cingulate gyrus and sulcus, the adjacent interhemispheric frontal gyri, the parietooccipital sulcus, and the marginal branch of the cingulate sulcus. On the convexity of the cerebral hemispheres there was asymmetrical widening of the central and postcentral sulcus on the left, and the intraparietal sulcus on the right.

Adult↗

PubMedDate not supplied

Computer-assisted, operator-interactive technique for calculating pulmonary arterial taper.

We have developed a computer-assisted, operator-interactive technique which performs fast, precise computations of pulmonary artery taper. Individual 35-mm cineframes from balloon-occlusion pulmonary arteriograms are digitized into a 640 X 480 matrix in 8-bit depth and loaded into a VAX 11/780 computer for analysis. After operator identification of the arterial segment, an automated process of caliber analysis is initiated. By fitting a cubic spline function to the densitometric profiles extracted from the arterial segment, serial arterial cross-sectional diameters are calculated from the mathematically-derived points along the fitted curves. Spurious profiles, caused by sectioning at bifurcations, can be overridden by an operator-interactive subroutine. Taper is derived from the slope of the least-squares fit of vessel caliber with respect to its distance along the arterial segment. Results obtained by calculations from the computer-assisted caliber measurements were compared with those obtained by hand-tracing the same vessel segments. Correlation between computer-traced inflection points and hand-traced taper was very significant (r = .96, n = 13, P less than 0.001).

Child, Preschool↗

PubMedDate not supplied

Statistical assessment of perceptual CT scan ratings in patients with Alzheimer type dementia.

Three neuroradiologists perceptually evaluated CT of 24 patients with Alzheimer type dementia and 22 normal control subjects and made a dichotomous judgment for each case (i.e., normal control or Alzheimer type dementia). The mean percentage of patients correctly classified was 83.3%. The neuroradiologists also completed perceptual ratings on each scan. Thirteen regions were rated for atrophy on a scale of 0-4. Discriminant function analyses of several sets of perceptual atrophy ratings (optimized on an exploratory set and evaluated on a test set) showed that the perceptual ratings of temporal lobe regions produced an average accuracy of 88.57%. In contrast, only 74.26% of the cases were correctly classified when the discriminant functions were based on perceptual ratings of midventricular and supraventricular areas. Linear measures of atrophy correctly classified only 65.20% of the subjects. The results suggest that atrophy ratings of brain regions that show the characteristic macroscopic neuropathological changes of Alzheimer disease may be used by neuroradiologists to reach more accurate diagnostic decisions.

Aged↗

PubMedDate not supplied

Discriminability of fracture and nonfracture cases based on the spatial distribution of spinal bone mineral.

PURPOSE: The purpose of our study is to demonstrate that spinal mineral distribution measured with CT can distinguish normal from osteoporotic individuals. METHOD: CT studies of lumbar vertebrae (L1-L3) from 121 clinically normal women without fractures and 57 women with one or more atraumatic fractures somewhere in the skeleton were evaluated with discriminant analysis based on indices of the spatial distribution and noise properties of spinal bone mineral density (BMD). RESULTS: The use of discriminant analysis for all of the normal and osteoporotic women (L1-L3) resulted in a classification accuracy of 87.1% for fracture cases and 83.2% for nonfracture cases. In contrast, using the conventional method in the same patient population, 62.5% of BMD values of osteoporotics overlapped with those of normals whose BMD was below the 90th centile of osteoporotics. CONCLUSIONS: CT-based measures of the spinal mineral distribution can increase the accuracy of discriminating fracture and nonfracture cases almost to 90% accuracy, even in a region below the fracture threshold. This shows that in this region the risk of fracture is not completely random but has a stochastic component as well.

Adult↗

PubMedDate not supplied

Effect of intervertebral changes of the spinal trabecular and cortical mineral content on the precision requirements in longitudinal single and dual energy computed tomography examinations.

Statistical considerations related to the measuring and analyzing procedures in computed tomography (CT) scans indicate that determination of a 2.5% change in spinal mineral content (SMC) which is assumed necessary in clinical practice, requires a 0.9% combined precision in setting the location and direction of the scan plane through the vertebral body, and defining the region of interest. In single energy examinations the short-term precision of CT scanners was found to be sufficiently high to achieve this goal, but the variability due to subjective finding of scan direction requires the automation of slice selection and additional averaging of data from more than one scan slice. The precision of calcium images was much lower, and one conclusion of this study is that dual energy technology is not suitable for longitudinal examinations, where small changes in SMC have to be determined. The SMC of the vertebrae T12, L1, L2, and L3 as measured in 41 subjects was compared and a significant decrease in trabecular bone in single energy examinations and increase in cortical bone was found from T12 to L3. This suggests that the comparison of SMC data should be done over time for each vertebra separately, in order to preserve diagnostic information.

Adult↗

PubMedDate not supplied

Vasomotion of renal blood flow in essential hypertension. Oscillations in xenon transit.

To assess the frequency and magnitude of phasic renal blood flow changes in essential hypertension, we applied an analytical method based on the estimation of power spectral density to xenon transit through the kidney. Despite similar age and gender distribution of the patients and exclusion of those with accelerated hypertension, mean renal blood flow was significantly lower in 100 patients with essential hypertension (299 +/- 8 ml/100 g/min) than in the 144 normal subjects (335 +/- 6 ml/100 g/min; p less than 0.001). Normalized power, the index of oscillatory behavior, was more than twice normal in patients with essential hypertension (p less than 0.001), but there was no difference in the frequency or cycle length of the oscillation. Two maneuvers that induced renal vasoconstriction, the application of cuffs to the thighs which were then inflated to diastolic blood pressure and an emotional provocation, reduced renal blood flow much more in patients with essential hypertension (p less than 0.01) in association with a striking increase in normalized power (p less than 0.001). The oscillations, which reflected not the phasic blood pressure change but rather the phasic change in renal perfusion, provided additional evidence that renal vasoconstriction plays an active role in the pathogenesis of essential hypertension.

Blood Pressure↗

PubMedDate not supplied

Use of computerized CT analysis to discriminate between Alzheimer patients and normal control subjects.

A newly developed computerized technique was used to analyze the CT scans of 49 patients with dementia of the Alzheimer type and 31 normal control subjects. Nine brain regions distributed across five CT slices were evaluated for each individual. For the purpose of analysis, the patients and controls were divided into an exploratory set and a test set. Several discriminant functions were conducted on the exploratory set and applied to the test set. The combination of variables that focused on regions in the temporal lobe was most accurate in differentiating Alzheimer patients from controls (94%). This degree of accuracy was achieved only when subjects younger than 65 years old were analyzed separately from those 65 years old and older. The newly developed computer software program was able to discriminate between independently selected groups of Alzheimer patients and control subjects. The program was most effective when the analysis emphasized regions in the temporal lobe and when subjects younger than 65 years old were analyzed separately from those 65 years old and older.

Aged↗