Increase In ADC Research Articles

Diffusion Tensor Magnetic Resonance Imaging Mapping the Fiber Architecture Remodeling in Human Myocardium After Infarction

Diffusion tensor magnetic resonance imaging (DT-MRI) provides a means for nondestructive characterization of myocardial architecture. We used DT-MRI to investigate changes in direction-dependent water diffusivity to reflect alterations in tissue integrity (trace apparent diffusion coefficients [ADCs] and fractional anisotropy [FA]), as well as indicators of remodeling of fiber helix angles, in patients after myocardial infarction. Thirty-seven patients (35 men, 2 women; median age, 59) after acute myocardial infarction (median interval from onset, 26 days) were enrolled. DT-MRI was performed at the midventricular level to measure trace ADC, FA, and helix angles of myofibers. Helix angles were grouped into left-handed helical fibers, circumferential fibers, and right-handed helical fibers. Measurements were correlated with viability and regional wall motion assessed by contrast-delay-enhancement and cine MRI, respectively. The infarct zone showed significantly increased trace ADC and decreased FA than the remote zone. The percentage of left-handed helical fibers increased from the remote zone (mean +/- SD, 13.3 +/- 5.8%) to the adjacent zone (19.2 +/- 9.7%) and infarct zone (25.8 +/- 18.4%) (MANOVA, P = 0.004). The percentage of right-handed helical fibers decreased from the remote zone (35.0 +/- 9.0%) to the adjacent zone (25.5 +/- 11.5%) and infarct zone (15.9 +/- 9.2%) (P < 0.001). Multiple linear regression showed that the percentage of left-handed helical fibers of the infarct zone was the strongest correlate of infarct size and predictor of ejection fraction. In vivo DT-MRI of postinfarct myocardium revealed a significant increase in trace ADC and a decrease in FA, indicating altered tissue integrity. The redistribution of fiber architecture correlated with infarct size and left ventricular function. This technique may help us understand structural correlates of functional remodeling after infarction.

Evolution of Magnetic Resonance Imaging Changes Associated with Cerebral Hypoxia-Ischemia and a Relatively Selective White Matter Injury in Neonatal Rats

We hypothesized that a combination of quantitative magnetic resonance imaging (MRI) sequences would detect a differential evolution of hypoxic-ischemic changes in white matter compared with gray matter in a recently developed model of unilateral mild cerebral hypoxia-ischemia in the 7-d-old rat. Using this model, which involved unilateral carotid artery occlusion and exposure to hypoxia for 45-50 min, maps of apparent diffusion coefficients of water (ADC), T1, T2, and cerebral blood flow (CBF) were acquired either before hypoxia-ischemia or at 1, 24, or 48 h and at 7 d post-hypoxia-ischemia followed by brain processing for histology. At 1 h post-hypoxia-ischemia, MRI changes in white matter ipsilateral to the hypoxia-ischemia were not as pronounced as those in gray matter. However, increases in T1, T2 and ADC and decreases in CBF within white matter enhanced over time, with changes being maximal at 48 h post-hypoxia-ischemia, whereas changes in the cortical gray matter normalized over this time. By 7 d post-hypoxia-ischemia, there were no differences in ADC, T1, T2, or CBF between hemispheres despite there being histologic changes in white matter within the hypoxic-ischemic hemisphere including increased glial proliferation and reactivity, reduced myelin basic protein, and increased cell death. The results demonstrate that increases in ADC and T2 observed subacutely in the days following hypoxia-ischemia are associated with rather selective white matter damage and suggest that diffuse white matter hyperintensities and increased ADC reported in infants are transient MRI changes post- hypoxia-ischemia.

INITIAL ADC PREDICTS THE OCCURRENCE AND SEVERITY OF HEMORRHAGIC TRANSFORMATION IN EXPERIMENTAL STROKE

P64 BACKGROUND: We recently reported that early lower ADC values are associated with an increased hemorrhagic transformation (HT) risk in ischemic stroke patients. The ability to predict the individual HT risk could be of considerable importance, particularly among patients candidates for thrombolysis. In this study we analyzed the relationship between initial ADC value and secondary HT in an experimental embolic model. We hypothesized that 1) initial lower ADC values would be found in lesions destined to HT and 2) the degree of the initial ADC decrease could predict the severity of HT. METHODS: Embolic strokes were created in 14 rabbits by injection of heterologous thrombi. Thrombolysis was initiated 1 hour later. DWI was performed at 0.5 h after embolization and repeated at 1.75, 3 and 5 h. We applied ADC histogram analysis to the entire ischemic hemisphere. The severity of ADC reduction was expressed as cumulative percentage of pixels below the cut-off value of 550 X 10 -6 mm 2 /sec. The brains were then histologically examined for HT 6h after embolization. RESULTS: HT was present in 10/14 brains (4 confluent, 6 petechial). As early as 30 min after embolization ADC values were lower in HT destined lesions. There was a significant correlation between ADC reduction and subsequent HT type (r 2 = 0.734, p&lt;0.001). The percentage of pixels under the cut-off ADC value was 10 ± 6% in hemispheres without HT, 17. ± 4% in those with petechial HT and 32 ± 6% in those with confluent HT. The number of pixels with severely reduced ADCs progressively increased over time in the confluent HT destined animals, but increased only slightly in the other groups. Further, the confluent HT destined group experienced a rapid ADC increase at 4 h, immediately before hemorrhage. CONCLUSION: We show that initial lower ADC values are associated with an increased risk of secondary HT. Moreover, the degree of ADC reduction correlated with the severity of HT. These findings are evident as early as 30 min after stroke onset. These results suggest that DWI may be helpful in predicting both HT occurrence and severity. This could have substantial implications for the use of MRI in acute stroke management.

The pathogenesis of lesions and normal-appearing white matter changes in multiple sclerosis: a serial diffusion MRI study.

The idea that the initiating event in the formation of all new multiple sclerosis lesions is a focal blood-brain barrier (BBB) leakage associated with perivascular inflammation has been challenged recently by the observation of subtle abnormalities in some quantitative magnetic resonance (MR) parameters (including the magnetization transfer ratio) prior to lesion enhancement. MR diffusion imaging can non-invasively quantify the average apparent diffusion coefficient (ADC(av)), a measure of water molecule random motion that is sensitive to pathological change in multiple sclerosis lesions and to abnormalities in the normal-appearing white matter (NAWM). We therefore used MR diffusion imaging to investigate the dynamic evolution of water diffusion measurements in new enhancing multiple sclerosis lesions, in the NAWM from which they arise, and in anatomically matched contralateral NAWM regions from which no visible lesions develop. Gadolinium diethylenetriaminepentaacetic acid (Gd)-enhanced MRI and MR diffusion studies were performed monthly for 1 year in five multiple sclerosis patients with clinically and radiologically active disease. The ADC(av) was calculated at each time point of the study (before, during and after lesion appearance on Gd-enhanced scans) for each new enhancing lesion, and for regions matched for size and position in the contralateral NAWM. A steady and moderate increase in ADC(av) in prelesion NAWM was observed, which was followed by a rapid and marked increase at the time of Gd enhancement and a slower decay after the cessation of enhancement. In matched contralateral NAWM regions there was a significant but milder increase in ADC(av) at the time of the first noted lesion enhancement. These findings indicate that new focal lesions associated with frank BBB leakage are preceded by subtle, progressive alterations in tissue integrity beyond the resolution of conventional MRI. The increases in ADC(av) in anatomically matched contralateral regions after lesions have appeared supports the concept that structural damage in lesions causes damage or dysfunction in connected areas of NAWM.

Changes in Polyamine Levels in Relationship to the Double-sigmoidal Growth Curve of Peaches

Polyamines and the activities of their biosynthetic enzymes were evaluated during peach (Prunus persica L. `Biscoe') mesocarp (pulp) and seed growth starting at full bloom and until full fruit maturity at 14 weeks after full bloom (AFB). Mesocarp fresh mass exhibited a double-sigmoidal pattern characteristic of peaches. Seed fresh mass increased to a maximum of≈1 g at 4 weeks AFB then remained unchanged during the remaining weeks of sampling. Free putrescine, spermidine, and spermine levels were significantly higher in the flower bud, declined in the mesocarp tissue during the first 2 weeks AFB, then exhibited another increase between 2 and 6 weeks AFB. In contrast, conjugated spermidine and spermine levels were low in flower buds, then increased to their maximum level at 6 weeks AFB, then declined at full fruit development. Ornithine decarboxylase (ODC, EC 4.1.1.17) activity was high in flower buds (89.3 nmol·h-1·mg-1 protein) and in early stages of mesocarp development then declined to its lowest level (5.8 nmol·h-1·mg-1 protein) at full-fruit development. Arginine decarboxylase (ADC, 4.1.1.19) activity did not change during the first 6 weeks of mesocarp growth but declined later, reaching its lowest (1.95 nmol·h-1·mg-1 protein) at 14 weeks AFB. During the first 5 weeks AFB, ODC activity was 3.0- to 4.5-fold that of ADC activity; however, at full-fruit maturity (14 weeks AFB) the activities of both enzymes were similar. The slowdown in mesocarp growth during pit hardening between 6 and 9 weeks AFB did not change polyamines concentrations or their biosynthetic enzymes. Free spermidine and spermine levels declined during seed development; however, between 7 and 9 weeks AFB an increase in putrescine was observed. Similarly, conjugated putrescine increased substantially during seed growth reaching its highest level of 680 nmol·g-1 fresh mass at week 8 then declined at the later weeks, while conjugated spermidine and spermine peaked at week 10 to 1,169 and 2,148 nmol·g-1 fresh mass. ODC and ADC activities declined between 3 and 5 weeks AFB. However, a significant increase in ADC but not ODC activity in the seed tissue was observed during pit hardening between 6 and 10 weeks AFB. Based on the rapid increase in putrescine and ADC activity in the seed tissue, it appears that pit hardening may be a stress-related phenomenon. Data also suggest that polyamine levels in the mesocarp and seed tissue are independently regulated.

Treatment of pemphigus vulgaris with mycophenolate mofetil

different pattern of diffusion changes in a 51-year-old woman with chronic epilepsy and recurrent episodes of focal status epilepticus, for whom no aetiology could be established. Status consisted of clonic jerking of the right leg, which continued for 22 days and was followed by transient paresis. DWI during status showed decreased diffusion in the motor cortex of the right leg (relative decrease in ADC of 27%, see figure). Surprisingly, the diffusion was increased in the subcortical white matter (relative increase in ADC of 31%). On the T2-weighted image (not shown), both cortex and subcortical white matter of the corresponding region returned a high signal similar to previously reported cases. 4 After cessation of the status, during transient paresis, repeat DWI and T2-weighted imaging showed resolution of these abnormalities. Resolution of diffusion changes preceded functional recovery. The pattern of diffusion changes observed by us differed from the changes observed so far in brain ischaemia and experimental status, since the decrease in cortical diffusion was associated with increased diffusion in the subcortical white matter. A possible explanation for the pattern of diffusion changes is water shifts associated with protracted epileptic activity. During epileptic activity, the extracellular space shrinks due to a water flux into cells at the area of maximum neuronal activity (in the cortex), 5 which would

Biphasic pathophysiological response of vasogenic and cellular edema in traumatic brain swelling.

The objective of this study was to quantify the temporal water content changes and document the type of edema (cellular versus vasogenic) that is occurring during both the acute and the late stages of edema development following closed head injury. Adult Sprague rats (n = 50) were separated into two groups: Group I: Sham (n = 8), Group II: Trauma (n = 42). The measurement of brain water content (BWC) was based on T1, whereas the differentiation of edema on the measurement of the random, translational motion of water protons (apparent diffusion coefficients-ADC) by MRI. In trauma animals, we found a significant increase in ADC (105%) as well as in BWC (0.7 +/- 0.3%) during the first 60 minutes post injury indicating vasogenic edema formation. This transient increase; however, was followed by a continuing decrease in ADC beginning at 45 minutes post injury and reaching a minimum at days 7-14 (-103%). Since the BWC continued to increase during the next day (10.3%), it is suggested cellular edema formation started to develop soon after injury and became dominant between 1-2 weeks post injury. In conclusion we may consider, that there is a predominantly vasogenic edema formation immediately after injury and later a more widespread and slower edema formation due to a predominantly cellular swelling.

Influence of intestinal resection and type of diet on the digestive and metabolic utilization of fats in rats

The effects of the quality of dietary fat, and the influence of ursodeoxycholic acid, an exogenous bile acid, on the digestive and metabolic utilization of fat were studied in rats in which 50% of the distal small intestine was resected. The fat content of the diets was quantitatively equivalent (4%), and differed only in the type of fat: olive oil (diet A) or 1/3 medium chain triglycerides (MCT), 1/3 sunflower oil and 1/3 olive oil (diet B). The removal of 50% of the distal small intestine led to a highly significant decline in the digestive utilization of fat (ADC) in animals given diet A. Rats fed diet B showed an increase in ADC to values approaching those seen in control animals. The addition of ursodeoxycholic acid to diet B failed to cause a further rise in the ADC of fat. After intestinal resection, serum levels of triglycerides and cholesterol fell more markedly in animals given diet A than in the diet B group, while the addition of ursodeoxycholic acid to diet B led to no further change. Serum lipid levels showed no significant influence of intestinal resection, but did accurately reflect the differences in fat composition between the two types of diet tested.