Perfusion and molecular diffusion-weighted MR imaging of the brain: in vivo assessment of tissue alteration in cerebral ischemia.

The combined use of perfusion imaging (PI) and diffusion-weighted imaging (DWI) is opening a new window into the processes that occur during the first hours of ischemia. DWI detects changes in molecular diffusion associated with cytotoxic edema. PI characterizes the degree of regional hypoperfusion. Regions showing mismatches between DWI and PI, i.e. hypoperfused areas with normal diffusion behavior are considered potentially salvageable. We present results of 11 patients with an occlusion of the middle cerebral artery stem and spontaneous stroke evolution. Whereas the infarct was clearly visible on initial DWI and PI, surrounding tissue at risk of infarction was marked in all patients by an increased blood volume and transit time, but only in a subgroup (n = 3) where alteration were more pronounced this tissue at risk was progressively infarcted. These human DWI and PI data show alterations in the area of tissue at risk which correlates with infarct progression.

In-vivo proton MR-spectroscopy of the human brain: assessment of N-acetylaspartate (NAA) reduction as a marker for neurodegeneration.

Proton magnetic resonance spectroscopy ((1)H-MRS) is a non-invasive method to investigate changes in brain metabolite composition in different cerebral diseases. We performed proton spectroscopy in patients with dementia of the Alzheimer's type (AD) and in patients with motor neuron disease (MND) with the aim to detect the specific metabolic pattern for these neurodegenerative disorders. In the MND group we found a significant reduction of NAA/tCr metabolite ratios in the motor cortex, which correlates with the disease severity and the clinical lateralization of neurological symptoms and further decreases in the time course of the disease. In AD patients a reduction of NAA/tCr was observed in the medial temporal lobe. Since NAA is exclusively expressed in neurons as shown by immunohistochemical studies, reduced NAA levels suggest neuronal loss or dysfunction in the observed regions. The observed regional metabolic alterations reflect the neuronal basis of the characteristic neurological symptoms in AD (dementia) and MND (muscular palsy) and mirrors the disease progress over time.

Adaptive management on public lands in the United States: commitment or rhetoric?

Adaptive management (AM) is the process of implementing land management activities in incremental steps and evaluating whether desired outcomes are being achieved at each step. If conditions deviate substantially from predictions, management activities are adjusted to achieve the desired outcomes. Thus, AM is a kind of monitoring, an activity that land management agencies have done poorly for the most part, at least with respect to ground-based monitoring. Will they do better in the future? We doubt it unless costs, personnel, and future commitment are seriously addressed. Because ecosystem responses to management impacts can ripple into the distant future, monitoring programs that address only the near future (e.g., 10-20 years), are probably unreliable for making statements about resource conditions in the distant future. We give examples of this. Feedback loops between ecosystem response and adjustment of management actions are often broken, and therefore AM again fails. Successful ground-based monitoring must address these and other points that agencies commonly ignore. As part of the solution, publics distrustful of agency activities should be included in any monitoring program.

Single breath-hold 3D contrast-enhanced method for assessment of cardiac function.

Cardiac MRI function measurements are typically performed using 2D sequences and require multiple breath-holds to image the entire heart. A single 3D acquisition using a T(1)-shortening agent has many potential advantages over techniques that acquire multiple 2D images, including more consistent contrast and precise slice coverage. However, 3D techniques currently require much longer than a single breath-hold to complete. It has been shown that for MR angiography undersampled projection reconstruction can acquire much higher resolution per unit time than Fourier imaging with acceptable artifacts. By employing a gated, undersampled projection technique, high-resolution 3D multiphase volumes of the heart can be acquired in a single breath-hold. Short repetition times result in good myocardial suppression and a temporal aperture of 60 ms.

Ultra-fast three-dimensional MR perfusion imaging of the entire brain in acute stroke assessment.

We sought to evaluate a three-dimensional (3D) whole-brain perfusion technique based on echo-shifting (PRESTO) for its performance in evaluation of acute stroke. Twenty-six patients were scanned within 6 hours after onset of hemispheric symptoms, and the results were compared with results of diffusion-weighted imaging (DWI) and digital subtraction angiography (DSA). The signal-to-noise ratio of the images was 61 +/- 3 pre-contrast and 47 +/- 3 at the bolus peak. Brain coverage on perfusion parameter maps was 95% +/- 2% compared with that displayed on T2-weighted images, with only minor artifacts related to susceptibility at the skull base. Measured regional cerebral blood volume (rCBV) reduction closely correlated to lesion size on initial DWI and to final clinical outcome (P = 0.006), consistent with results previously reported for 2D perfusion methods. Mismatches between DWI and perfusion imaging characterized the total extent of tissue at risk, and the contrast timing correlated with the amount of collateral circulation as shown on DSA. In conclusion, 3D imaging using the PRESTO technique permits high-quality perfusion imaging of the entire brain.

Nutritional indexes of clients in a maternity and infant care project. I. The target population.

The Detroit Maternity and Infant Care Project (DMICP) is funded under Title V of the Social Security Act. Records of 198 pregnant women and their infants seen by a project nutritionist in fiscal 1971-72 were studied. The women were predominantly young (below twenty years of age), black, and not enrolled in school. Most were pregnant for the first time. About a third were overweight. Mean scores on the APGAR scale for the infants at birth were high (7 to 10). More than half of these young mothers brought their infants to the project center for check-ups six to ten times during the first year.