Computed tomography in metastatic disease of the brain

15 male undergraduates were presented with 10-sided random forms which they explored visually, or one-handed haptically, or two-handed haptically. Forms were exposed for various durations and subjects were required to draw each form immediately after its removal. The results indicated that 30 sec. of one-handed exploration and 20 and 30 sec. of two-handed exploration produced performance comparable to just 2 sec. of visual exploration. Two-handed exploration was significantly superior to one-handed exploration only at the 20-sec. exposure duration. These results illustrate the disparity in the information-gathering capabilities between the visual and haptic systems.     

Smoking habits and changes in smoking habits as they relate to chronic conditions and respiratory symptoms

The relation of smoking to chronic lung disease has been documented in several studies. Several conclusions have been drawn about the type of smoking associated withdisease, including inhalation, filter tip use, and reduction in smoking. These factors were examined in a community epidemiologic study of chronic obstructive lung diseases. It was found that the community population exhibited greater filter tip use and higher rates of exsmoking than often seen elsewhere. Smoking habits and the changes in smoking habits over time were related to physician-diagnosed emphysema and/or chronic bronchitis, but not asthma. Some relation was seen also with present heart trouble. There was dose-relationship to pack-years of smoking in both present and ex-smokers. There were more ex-smokers among males. Most male ex-smokers quit due to symptoms. Ex-smokers were found to have high rates of diagnosed disease but reduced rates of symptoms. The incidence of diagnosed disease was found to be associated with smoking, both in intensity and duration. Changes in smoking over time were found to be correlated with symptomatology.     

Hypertension and the obstetrician-gynecologist

Hypertension is a major risk factor for cardiovascular-related morbidity and death. Antihypertensive therapy markedly reduces the risk caused by elevated blood pressure. Earlier treatment of hypertensive patients should reduce deaths and morbidity even further. The obstetrician-gynecologist has the opportunity and responsibility to identify hypertensive patients early in the course of their disease. He must also confront the problem of elevated blood pressure associated with the use of oral contraceptives. In addition to its impact on the general population, chronic hypertension presents special problems during pregnancy. Pregnant women with elevated blood pressure have an increased fetal mortality rate and develop pre-eclampsia more frequently and earlier than nonhypertensive women. Antihypertensive treatment possibly increases fetal survival; when used appropriately, it definitely does not decrease fetal salvage. The appropriate use of antihypertensive therapy during pregnancy requires an understanding of the mechanism of action of these agents and recognition of side effects, especially those important during pregnancy.     

Dystroglycan in development and disease

Our understanding of the structure and function of dystroglycan, a cell surface laminin/agrin receptor, has increased dramatically over the past two years. Structural studies, analysis of its binding partners, and targeted gene disruption have all contributed to the elucidation of the biological role of dystroglycan in development and disease. It is now apparent that dystroglycan plays a critical role in the pathogenesis of several muscular dystrophies and serves as a receptor for a human pathogen as well as being involved in early development, organ morphogenesis, and synaptogenesis.     

Experimental evaluation of two simple thermal models using transient temperature analysis

Thermal models are used to predict temperature distributions of heated tissues during thermal therapies. Recent interest in short duration high temperature therapeutic procedures necessitates the accurate modelling of transient temperature profiles in heated tissues. Blood flow plays an important role in tissue heat transfer and the resultant temperature distribution. This work examines the transient predictions of two simple mathematical models of heat transfer by blood flow (the bioheat transfer equation model and the effective thermal conductivity equation model) and compares their predictions to measured transient temperature data. Large differences between the two models are predicted in the tissue temperature distribution as a function of blood flow for a short heat pulse. In the experiments a hot water needle, approximately 30 degrees C above ambient, delivered a 20 s heating pulse to an excised fixed porcine kidney that was used as a flow model. Temperature profiles of a thermocouple that primarily traversed the kidney cortex were examined. Kidney locations with large vessels were avoided in the temperature profile analysis by examination of the vessel geometry using high resolution computed tomography angiography and the detection of the characteristic large vessel localized cooling or heating patterns in steady-state temperature profiles. It was found that for regions without large vessels, predictions of the Pennes bioheat transfer equation were in much better agreement with the experimental data when compared to predictions of the scalar effective thermal conductivity equation model. For example, at a location r approximately 2 mm away from the source, the measured delay time was 10.6 +/- 0.5 s compared to predictions of 9.4 s and 5.4 s of the BHTE and ETCE models, respectively. However, for the majority of measured locations, localized cooling and heating effects were detected close to large vessels when the kidney was perfused. Finally, it is shown that increasing flow in regions without large vessels minimally perturbs temperature profiles for short exposure times; regions with large vessels still have a significant effect.     

Proton T1rho-dispersion imaging of rodent brain at 1.9 T

Detection of H2(17)O with proton T1rho-dispersion imaging holds promise as a means of quantifying metabolism and blood flow with MRI. However, this technique requires a priori knowledge of the intrinsic T1rho dispersion of tissue. To investigate these properties, we implemented a T1rho imaging sequence on a 1.9-T Signa GE scanner. A series of T1rho images for different locking frequencies and locking durations were obtained from rat brain in vivo and compared with 5% (wt/vol) gelatin phantoms containing different concentrations of (17)O ranging from .037% (natural abundance) to 2.0 atom%. Results revealed that, although there is considerable T1rho-dispersion in phantoms doped with H2(17)O, the T1rho of rat brain undergoes minimal dispersion for spin-locking frequencies between .2 and 1.5 kHz. A small degree of T1rho dispersion is present below .2 kHz, which we postulate arises from natural-abundance H2(17)O. Moreover, the signal-to-noise ratios of T1rho-weighted images are significantly better than comparable T2-weighted images, allowing for improved visualization of tissue contrast. We have also demonstrated the feasibility of proton T1rho-dispersion imaging for detecting intravenous H2(17)O on a live mouse brain. The potential application of this technique to study brain perfusion is discussed.