Quantification of Blood Velocity with 4D Digital Subtraction Angiography Using the Shifted Least-Squares Method.

BACKGROUND AND PURPOSE: 4D-DSA provides time-resolved 3D-DSA volumes with high temporal and spatial resolutions. The purpose of this study is to investigate a shifted least squares method to estimate the blood velocity from the 4D DSA images. Quantitative validation was performed using a flow phantom with an ultrasonic flow probe as ground truth. Quantification of blood velocity in human internal carotid arteries was compared with measurements generated from 3D phase-contrast MR imaging. MATERIALS AND METHODS: The centerlines of selected vascular segments and the time concentration curves of each voxel along the centerlines were determined from the 4D-DSA dataset. The temporal shift required to achieve a minimum difference between any point and other points along the centerline of a segment was calculated. The temporal shift as a function of centerline point position was fit to a straight line to generate the velocity. The proposed shifted least-squares method was first validated using a flow phantom study. Blood velocities were also estimated in the 14 ICAs of human subjects who had both 4D-DSA and phase-contrast MR imaging studies. Linear regression and correlation analysis were performed on both the phantom study and clinical study, respectively. RESULTS: Mean velocities of the flow phantom calculated from 4D-DSA matched very well with ultrasonic flow probe measurements with 11% relative root mean square error. Mean blood velocities of ICAs calculated from 4D-DSA correlated well with phase-contrast MR imaging measurements with Pearson correlation coefficient r = 0.835. CONCLUSIONS: The availability of 4D-DSA provides the opportunity to use the shifted least-squares method to estimate velocity in vessels within a 3D volume.

Neuroprotection by MK-801 in temperature maintained gerbils.

Hypothermia reduces ischemic brain damage, confounding interpretation of the neuroprotective effects of drugs. Specifically, the neuroprotectant MK-801 has been shown to cause hypothermia. Some have claimed that when body temperature is maintained, MK-801 is not a neuroprotectant, whereas others claim it retains its neuroprotective activity. MK-801 was evaluated for neuroprotective properties in free-regulating as well as temperature-maintained gerbils receiving 5 or 10 min of bilateral carotid occlusion. After 10 min of ischemia, free-regulating animals exhibited significant hypothermia (as low as 32 degrees C) and showed significant neuroprotection after 3 mg/kg IP MK-801. When a hyperthermic body temperature (38.5 degrees C) was maintained, no reduction in brain damage was evident after up to 10 mg/kg IP MK-801, even when occlusion time was reduced to 5 min. However, when a normothermic body temperature (36.5 degrees C) was maintained, 10 mg/kg IP MK-801 significantly reduced brain damage after 5 min of ischemia. Thus, although a higher dose of the drug is required, MK-801 can reduce ischemic brain damage in the absence of hypothermia. The need for this high dose suggests that mechanisms other than NMDA receptor complex antagonism may be involved in the neuroprotective actions of MK-801.

Assessing the differences in distance of interstate migration, 1980.

"This study examines distance of 1975-80 interstate migration [in the United States] and several explanations for the relations between distance and characteristic of migrants and locations.... Observations are individual records from the 1980 one-in-ten-thousand PUMS files. The sample is restricted to nonblack, noninstitutionalized head of households, age 25 to 64 in 1980.... We find outmigration is shaped by characteristics of individuals; however, distance of migration is shaped by characteristics at locations. Findings lend support to an interpretation of distance reflecting psychic costs and information and are consistent with a cost/benefit view of factors contributing to distance of migration."

Mild hypertension in the elderly. A comparison of prazosin and enalapril.

In a single-blind, crossover study, prazosin and enalapril monotherapies were evaluated in 15 patients, aged 55 years or older (average age, 64 years), with mild hypertension (sitting diastolic blood pressure between 90 and 104 mm Hg). After eight weeks of placebo administration, patients were randomly assigned to treatment with prazosin or enalapril and then treated with the alternate drug after a second eight-week placebo washout period. The dose was titrated from 1 mg to a maximum of 10 mg twice daily of prazosin and from 2.5 mg to a maximum of 20 mg twice daily of enalapril to achieve a reduction in diastolic blood pressure to less than 85 mm Hg, with a decrease of at least 10 mm Hg based on clinical measurements of blood pressure. Patients received maintenance therapy with each medication for at least eight weeks. The response to therapy was then evaluated with two-hour periods of automated blood pressure monitoring. Average systolic and diastolic blood pressures for all patients during these two-hour monitoring periods decreased by 10.3 +/- 1.9/8.3 +/- 1.5 mm Hg during prazosin therapy and by 9.0 +/- 5.1/5.8 +/- 3.4 mm Hg during enalapril therapy. All patients responded to one of the two drugs, but only 50 percent responded to both. Side effects were generally mild and transient, and no significant metabolic effects were observed. Both prazosin and enalapril were effective and well tolerated in this population of elderly patients with mild hypertension.

Correlates of cardiac structure and function in normotensive adolescents.

To evaluate body weight as a determinant of cardiac structure and function in adolescents, 47 normotensive 13-year-old subjects were studied with M-mode echo duplex Doppler echocardiography (DE). They were separated by body weight into standard (greater than 55 kg) and lighter (less than 55 kg) groups. No subject had a blood pressure greater than 140/90. The differences between the groups in systolic (SBP) and diastolic (DBP) blood pressures, LV mass, left atrial size (LA), and peak aortic flow velocity (PAoV) were measured. (Formula: see text). Body weight strongly correlated with SBP in the entire study group (r = 0.66, P less than 0.001) but slightly less strongly with DBP (r = 0.48, P less than 0.001). Left ventricular filling indices such as peak early diastolic flow velocity, early diastolic filling integral, peak atrial flow velocity, and atrial filling integral were not significantly different between the groups. No significant differences in blood pressure, LV mass, LA size, or peak aortic flow velocity could be demonstrated when the subjects were subdivided on the basis of gender or presence or absence of family history of hypertension. Body weight appeared to be not only a strong predictor of blood pressure but also of cardiac structural and functional characteristics in adolescents.

Chemical Feeding Deterrent Mobilized in Response to Insect Herbivory and Counteradaptation by Epilachna tredecimnotata.

Experimentally damaged leaves of Cucurbita moschata mobilize substances to the damaged region within 40 minutes. These substances stimulate feeding by Acalymma vittata (Coleoptera: Chrysomelidae) and inhibit feeding by Epilacha tredecimnotata (Coleoptera: Coccinelidae). Under natural conditions, Epilachna cuts a circular trench in the leaf before feeding on the encircled leaf material, thus preventing mobilization of the deterrent substances to the feeding area.