Refusal of blood transfusions by Jehovah's Witnesses.II.
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Blood Transfusion↗
Biomedical subjects
J C Ford
Publications and source records attributed to J C Ford.
Dependence of apparent diffusion coefficients on axonal spacing, membrane permeability, and diffusion time in spinal cord white matter.
We used a numerical simulation of water self-diffusion among permeable cylinders to predict the dependence of MR-based apparent diffusion coefficients in white matter on axonal separation, barrier permeability, and diffusion time (T). The transverse apparent diffusion coefficient (tADC), calculated with simulated diffusion-sensitizing gradients perpendicular to the axon fibers, remains a function of T down to diffusion times as short as .1 microsec for a range of diffusion barrier permeability. As the diffusion time lengthens, the response of tADC depends on axon diameter, with decreases in tADC occurring earliest, and most dramatically, for the smallest fiber diameter simulated (2 microm). For a given axonal separation, asymptotic values of ADC are determined by permeability alone and are the same for 2-microm and 11-microm fibers of equal membrane permeability. The effect of increased relative intracellular volume is manifested primarily in a decrease in tADC at short T. Increases in interaxonal spacing increase the tADC at asymptotically long diffusion times and reduce the dependence on permeability. However, at the widest plausible axonal separations, permeability remains an important determinant of tADC. These simulations may enhance interpretation of measured tADC in the context of the underlying physiologic and structural changes at the cellular level that accompany white-matter disease.
Animals↗
MR microscopy of the arterial wall in an experimental model of atherosclerosis: preliminary results.
PURPOSE: To obtain images of the arterial lumen and wall in a rabbit model of atherosclerosis with use of high-resolution magnetic resonance (MR) imaging to follow morphologic changes during the induction of atherosclerosis and, hence, develop a non-invasive tool to investigate restenosis. MATERIALS AND METHODS: In vivo microscopic MR images of rabbit aorta were acquired after balloon injury. Measurements of wall and lumen diameter from MR images area were compared with measurements obtained from histologic and angiographic examination. RESULTS: Injured rabbits exhibited an obvious thickening of the arterial wall, accompanied by an increased wall conspicuity, probably due to increases in T2. Quantitative MR morphometry corresponded well with morphologic measurements based on angiographic and histologic study. CONCLUSIONS: MR implanted coil technology affords imaging of the arterial lumen and wall, allowing temporal assessment of the morphologic changes due to intimal hyperplasia after balloon dilation and may enable the evaluation of novel techniques to eliminate restenosis.
Angioplasty, Balloon↗
Histologic estimation of coronary artery stenoses: reproducibility and the effect of training.
Histologic estimation of coronary artery stenoses (CAS) provides the 'gold-standard' for clinicopathologic correlations and medicolegal investigations, yet little evidence supports histology as a reproducible diagnostic measure, and none addresses the effect of training on its use. To study these questions, 20 randomly selected Movat-stained coronary artery cross-sections were reviewed 3 times, at 3-month intervals, by six clinical pathologists (CPs), six pathology residents (Res), seven anatomic pathologists (APs), and two cardiovascular pathologists (CVPs). Before the third iteration, a guide to CAS assessment with illustrations was provided. Inter- and intraobserver reproducibility were determined using interclass correlation coefficients (ICC) (0.40-0.75 = fair-good; > or = 0.76 = excellent agreement beyond chance). Surprisingly, all study groups had excellent interobserver reproducibility. Before training, at Time 1, the scores were CPs, 0.77; Res, 0.89; APs, 0.93; and CVPs, 0.93. After training, at Time 3, the results were CPs, 0.81; Res, 0.91; APs, 0.86; and CVPs, 0.88. Intraobserver reproducibility for CPs overall was good (ICC, 0.74), and excellent for Res, APs, and CVPs (0.89, 0.94, and 0.97, respectively). In conclusion, statistical analysis failed to demonstrate any significant effect of training or experience on observer reproducibility.
Autopsy↗
The histologic estimation of coronary artery stenoses: accuracy and the effect of lumen shape.
The authors have recently investigated the histologic estimation of coronary artery stenoses (CAS) to determine its reproducibility and the effect of training on reproducibility. The present study extends this work, examining the accuracy, the sensitivity, and the specificity of the estimation of CAS. Further, the effect of one histologic variable (i.e., arterial lumen shape) on the evaluation of CAS is examined. As described previously, 20 randomly selected Movat-stained coronary artery cross-sections were reviewed three times, at 3-month intervals, by six clinical pathologists (CPs), six pathology residents (Res), seven anatomic pathologists (APs), and two cardiovascular pathologists (CVPs). Before the third iteration, training in CAS assessment was provided. In the present study, for comparison with observer estimates, image analysis was used to establish the actual percent CAS and determine observer accuracy. The results of this study showed, paradoxically, that greater experience did not correlate with greater accuracy: The CPs consistently had the highest accuracy scores and the CVPs consistently had the lowest. Training, however, improved the accuracy scores of all groups. Stenotic arterial cross-sections with residual lumens showing concentric or eccentric polymorphous shapes were consistently underestimated compared to image analysis, while lumens with a eccentric slitlike shape were consistently overestimated.
Arteries↗
Experimental spinal cord injury: MR correlation to intensity of injury.
OBJECTIVE: This study was conducted to determine the association between lesion length measured on MRI and the severity of mechanical injury in a rat model of spinal cord trauma. MATERIALS AND METHODS: Sprague-Dawley rats were subjected to a modified Allen weight drop injury and killed 4 h after injury. Their fixed, exercised cords were studied with MRI at 1.9 T. RESULTS: There were strong correlations between lesion length on MR images and weight drop height and square root of drop height (r2 = 0.55, p < 0.0001 and r2 = 0.63, p < 0.0001, respectively). The lesion length differences were significant versus controls for all drop heights at p values of < or = 0.002 and for the 2.5 cm animals versus the 5 and 15 cm animals (p = 0.01 and p = 0.0002, respectively), but the lengths of the 5 vs. 15 cm groups only approached significance (p = 0.06). CONCLUSION: These results suggest that lesion length determined on MR images is a reliable indicator of the severity of trauma among animals subjected to weight drop injury.
Animals↗