Dennis Nelson

Attention and regional cerebral blood flow in posttraumatic stress disorder patients with substance abuse histories

Performance on an attentional task was assessed in posttraumatic stress disorder patients with substance abuse histories (PTSD-SA). Positron emission tomography (PET) was used to measure concurrent regional cerebral blood flow (rCBF). Eight male PTSD-SA patients and eight normal subjects each received three serial PET scans with 15O-labeled water under the following conditions: (1) resting, (2) auditory continuous performance task (ACPT1), and (3) repeat auditory task (ACPT2). PTSD-SA patients made more errors of commission on the ACPT than normal subjects. Examination of right frontal and parietal cortex ACPT task substrates revealed decreased parietal blood flow in PTSD-SA, which may represent a pathophysiology for poor attentional task performance in PTSD-SA. Attentional problems may underlie other symptomatology in PTSD.

Preliminary report: Brain blood flow using PET in patients with posttraumatic stress disorder and substance-abuse histories

Abstract Posttraumatic stress disorder (PTSD) is defined by DSM-III-R as an anxiety disorder characterized by recurrent distressing and intrusive remembrances of a traumatic event (American Psychiatric Association 1987). Some physiological abnormalities have been found in PTSD, notably for cardiac (Blanchard et al 1991) and neuroendocrine measures (Friedman 1991), but no studies to date have directly measured regional brain function changes in PTSD using positron emission tomography (PET). This preliminary study compares PTSD patients who have histories of substance abuse (Keane et al 1983, 1988) with normal controls who did not have a history of substance abuse. PET studies of anxiety disorders (Baxter et al 1987; Nordahl et al 1989, 1990; Reiman et al 1986), and acute (London et al 1990) and recent (Volkow et al 1991) substance abuse suggested hypotheses of increased orbital frontal cortex (OFC) blood flow and decreased left/right hippocampal ratios in PTSD patients with histories of substance abuse (PTSD-SA) compared to normal control subjects.

A Digital Reference Object to Analyze Calculation Accuracy of PET Standardized Uptake Value.

PURPOSE To determine the extent of variations in computing standardized uptake value (SUV) by body weight (SUV(BW)) among different software packages and to propose a Digital Imaging and Communications in Medicine (DICOM) reference test object to ensure the standardization of SUV computation between medical image viewing workstations. MATERIALS AND METHODS Research ethics board approval was not necessary because this study only evaluated images of a phantom. A synthetic set of positron emission tomographic (PET)/computed tomographic (CT) image data, called a digital reference object (DRO), with known SUV was created. The DRO was sent to 16 sites and evaluated on 21 different PET/CT display software packages. Users were asked to draw various regions of interest (ROIs) on specific features and report the maximum, minimum, mean, and standard deviation of the SUVs for each ROI. Numerical tolerances were defined for each metric, and the fraction of reported values within the tolerance was recorded, as was the mean, standard deviation, and range of the metrics. RESULTS The errors in reported maximum SUV ranged from -37.8% to 0% for an isolated voxel with 4.11:1 target-to-background activity level, and errors in the reported mean SUV ranged from -1.6% to 100% for a region with controlled noise. There was also a range of errors in the less commonly used metrics of minimum SUV and standard deviation SUV. CONCLUSION The variability of computed SUV(BW) between different software packages is substantial enough to warrant the introduction of a reference standard for medical image viewing workstations.

A Dynamic Dual Isotope Radionuclear Method of Quantifying Penile Blood Flow

A new radionuclear method of quantifying arterial and venous blood flow of the penis is described. The technique is based on the simultaneous recording of the change in blood volume and venous outflow in the flaccid and erect states, which is produced pharmacologically. The change in penile blood volume is determined by measuring the change in the technetium-labeled red blood cell activity with time. Venous outflow is recorded with a xenon washout technique. The isotope data are used to compute arterial and venous flows with a complex computerized mathematical formula. Three basic blood flow patterns have been noted that distinguish normal patients from those with arterial insufficiency and venous leakage. The study is relatively easy and noninvasive to perform, and it appears to quantify penile blood flow accurately.

Tissue Blood Flow and Oxygenation during Large Vessel Surgery

Tissue PO2 and blood flow through gastrocnemius muscle and overlying subcutis were continuously determined in patients undergoing major vascular surgery for abdominal aneurysm or arteriosclerotic occlusive disease. Polarographic oxygen detection using paired flow-dependent and independent electrodes in each tissue allowed on-line computation of blood flow during the intraoperative and immediate perioperative periods.

Flow limited properties of teflon and silicone diffusion membranes.

The mass spectrometer equipped with a diffusion catheter can detect partial pressures of gases in tissues and blood vessels. The catheter consists of a small gauge stainless steel conduit with small openings at one end covered by a thin teflon or silicone membrane. The entire catheter can be inserted through the lumen of a sixteen gauge needle.