Estimating 3-dimensional surface areas of small scleractinian corals.

Stressor-response research on stony corals in the laboratory relies on detecting relatively small changes in the size of coral fragments throughout the course of an experiment. Coral colonies are complex, three-dimensional (3D) communities of organisms, so small changes in size are best detected by changes in 3D surface area. Traditional methods to estimate 3D coral surface area commonly require destruction of the sample, thereby eliminating repeat measurements and the ability to calculate growth rate. However, non-destructive two-dimensional (2D) photogrammetry can be used if defensible relationships with 3D surface area can be established. In this study, 165 coral skeletons representing four stony coral species (Pocillopora damicornis, Madracis mirabilis, Orbicella faveolata, Porites porites) were photographed in 2D (top and side views) and then imaged with 3D laser scanning. Significant linear relationships were found between the 3D surface areas (laser) and the sum of various combinations of top and side view surface areas captured by 2D digital photography. The relationships were very strong for simple colony shapes and more variable as coral fragments increased in size and complexity. This study demonstrates an efficient method for obtaining estimates of 3D coral surface area from non-destructive 2D photogrammetry, allowing measurement of growth rate throughout experimental exposure periods.

Perfusion-weighted imaging of interictal hypoperfusion in temporal lobe epilepsy using FAIR-HASTE: comparison with H(2)(15)O PET measurements.

To detect perfusion abnormalities in areas of high magnetic susceptibility in the brain, an arterial spin-labeling MRI technique utilizing flow-sensitive alternating inversion recovery (FAIR) and half-Fourier single shot turbo spin-echo (HASTE) for spin preparation and image acquisition, respectively, was developed. It was initially tested in a functional study involving visual stimulation, and was able to detect significant activation with an increase (approximately 70%) in relative cerebral blood flow. Subsequently, it was applied in a clinical situation in eight patients with temporal lobe epilepsy (TLE). The perfusion-weighted images obtained showed no susceptibility artifacts even in the region of the inferior temporal lobe and were able to detect interictal hypoperfusion in TLE. The results were compared with those derived from H(2)(15)O PET perfusion imaging in each patient. A statistically significant correlation (r = 0.75, P < 0.05) was found between results acquired from these two modalities. Magn Reson Med 45:431-435, 2001.

Detection of the brain response during a cognitive task using perfusion-based event-related functional MRI.

Event-related (ER) fMRI has evoked great interest due to the ability to depict the dynamic features of human brain function during various cognitive tasks. Thus far, all cognitive ER-fMRI studies have been based on blood oxygenation level-dependent (BOLD) contrast techniques. Compared with BOLD-based fMRI techniques, perfusion-based fMRI is able to localize the region of neuronal activity more accurately. This report demonstrates, for the first time, the detection of the brain response to a cognitive task using high temporal resolution perfusion-based ER-fMRI. An English verb generation task was used in this study. Results show that perfusion-based ER-fMRI accurately depicts the activation in Broca's area. Average changes in regional relative cerebral blood flow reached a maximum value of 30.7% at approximately 6.5 s after the start of stimulation and returned to 10% of the maximum value at approximately 12.8 s. Our results show that perfusion-based ER-fMRI is a useful tool for cognitive neuroscience studies, providing comparable temporal resolution and better localization of brain function than BOLD ER-fMRI.