Glucose Response Kinetics and Permeability of a Composite Hydrogel Membrane

To investigate the clinical application of diffusion weighted imaging (DWI) in uterine cervical cancer and the apparent diffusion coefficient (ADC) value in diagnosis and predicting treatment response. Twenty-eight patients with advanced primary cervical cancer confirmed by pathology and 10 cases of normal uterine cervix as control were recruited in this prospective clinical trial. To analyze the correlation between tumor volume measured in DWI and tumor maximum diameter measured according to the RECIST criteria. To compare the ADC value differences among the uterine cervical cancer, uterine myometrium, and normal uterine cervix. To compare the ADC values in 17 cancer patients before and after treatment. The illustration of tumor boundary in DWI was superior to conventional T2WI and post-enhancement T1WI. The DWI with higher b value (2000 s/mm(2)) had a better signal-to-noise ratio. The tumor volume measured in DWI has good correlation with tumor maximum diameter according to RECIST criteria (r = 0.759, P < 0.01). When b = 800 s/mm(2), the ADC values of the uterine cervical cancer, uterine myometrium, and normal uterine cervix were (9.85 ± 1.55)×10(-3) mm(2)/s, (14.20 ± 2.80)×10(-3) mm(2)/s, and (14.14 ± 0.45) ×10(-3) mm(2)/s. When b = 2000 s/mm(2), the ADC values of the uterine cervical cancer, uterine myometrium and normal uterine cervix were (7.38 ± 0.98)×10(-3) mm(2)/s, (8.52 ± 2.38)×10(-3) mm(2)/s, and (8.60 ± 0.63)×10(-3) mm(2)/s, respectively. There were significant differences between the cervical cancer and normal cervix or uterine myometrium (P < 0.001 for both). When b = 800 s/mm(2), the ADC value was (9.85 ± 1.55)×110(-3) mm(2)/s before and (13.41 ± 2.93)×10(-3) mm(2)/s after treatment (P < 0.001). When b = 2000 s/mm(2), the ADC value was (7.38 ± 0.98)×10(-3) mm(2)/s before and (8.93 ± 1.92)×10(-3) mm(2)/s after treatment (P = 0.008). Univariate logistic regression analysis showed that 25% ADC, 50%ADC, and 75%ADC in the tumor ADC value histogram before treatment were significantly correlated to the treatment outcome of cervical cancer (P < 0.05 for all). Multivariate regression analysis showed that 25%ADC, 50%ADC, and 75%ADC in the tumor ADC value histogram before treatment were not significantly correlated to the treatment outcome of cervical cancer (P > 0.05 for all). The values of ROC curves were 25%ADC = 0.818, 50%ADC = 0.775, and 75%ADC = 0.716 (P > 0.05), however, the 25% ADC showed a relatively stronger statistical power. DWI helps to confirm the morphology and exact target zone of the tumor for radiotherapy. DWI volume measurement is well correlated with RECIST criteria, particularly in volume measurement of irregular tumors. ADC value has a potential in quantitatively monitoring treatment response and predicting outcome of cervical cancers.

Wet and dry cup tests are widely used to characterize the vapor permeability (or the apparent vapor diffusion coefficient) of construction materials. From a theoretical approach, we examined the transport characteristics of such tests in detail. We precisely quantified the impact of the boundary conditions on the apparent diffusion coefficient and the time required to reach steady-state conditions, which is critical for accurate estimation of this coefficient. Finally, a major point concerns the physical meaning of the value measured through this type of test. For a homogeneous non-hygroscopic medium, the diffusion coefficient obtained represents the diffusion coefficient of vapor through the medium. For hygroscopic materials, where vapor diffusion, bound water diffusion, and sorption or desorption processes may be encountered, we demonstrate that the total water transport diffusion coefficient in the medium is strongly different from, yet proportional to, the apparent vapor diffusion coefficient. We validated and illustrated this analysis based on experiments with cellulose fiber stacks of different porosities and under different experimental conditions.

To explore the utility of whole-lesion apparent diffusion coefficient (ADC) histogram analysis for differentiating parotid gland tumors following readout-segmented diffusion-weighted imaging (RESOLVE). 80 patients (40 with pleomorphic adenomas, 14 with Warthin tumors, and 26 with malignant parotid gland tumors) who underwent routine head-and-neck MRI and RESOLVE examinations, were retrospectively evaluated. RESOLVE data were acquired from a MAGNETOM Skyra 3T MR system. Eleven whole-lesion histogram parameters derived from histogram analysis (ADC_mean, ADC_minimum, ADC_maximum, ADC_1th, ADC_10th, ADC_50th, ADC_90th, ADC_99th, skewness, variance and kurtosis) were calculated for each patient using MaZda. Receiver operating characteristic (ROC) curve analysis was used to assess the diagnostic performance of the ADC for distinguishing among the three groups. In total, nine parameters (ADC_minimum, ADC_maximum, ADC_mean, ADC_10th, ADC_50th, ADC_90th, ADC_99th, variance, skewness) were statistically significant (all p < 0.05) for all three groups, in the comparison of pleomorphic adenomas to Warthin tumors; the ADC_mean, ADC_50th, and skewness revealed high diagnostic efficiency with areas under the receiver operating characteristic curve of 0.976, 0.970, and 0.970, respectively. In the comparison of pleomorphic adenomas to malignant parotid gland tumors, these nine parameters were also found to be statistically different (all p < 0.05); the ADC_mean, ADC_10th and ADC_50th revealed high diagnostic efficiency with area under the curve of 0.851, 0.866, and 0.841, respectively. However, in the comparison of Warthin tumors to malignant parotid gland tumors, only three parameters (ADC_mean, ADC_50th, skewness) were statistically significant (all p < 0.05). Whole-lesion ADC histograms are effective in differentiating common parotid gland tumors.

To compare the value of whole-lesion apparent diffusion coefficient (ADC) histogram analysis derived from readout-segmented echo-planar imaging (RS-EPI) and single-shot echo-planar imaging (SS-EPI) diffusion-weighted imaging (DWI) in evaluating normal-sized lymph node metastasis (LNM) in cervical cancer. Seventy-six pathologically confirmed cervical cancer patients (stages IB and IIA) were enrolled, including 61 patients with non-LNM (group A) and 15 patients with normal-sized LNM (group B). The recorded tumor volume on T2-weighted imaging was the reference against which both DWIs were evaluated. Each ADC histogram parameter (including ADC max , ADC 90 , ADC median , ADC mean , ADC 10 , ADC min , ADC skewness , ADC kurtosis , and ADC entropy ) was compared between SS-EPI and RS-EPI and between the 2 groups. There was no significant difference in tumor volume between the 2 DWIs and T2-weighted imaging (both P > 0.05). Higher ADC max and ADC entropy but lower ADC 10 , ADC min and ADC skewness were found in SS-EPI than those in RS-EPI (all P < 0.05). For SS-EPI, lower ADC 90 and higher ADC kurtosis were found in group B than those in group A (both P < 0.05). For RS-EPI, lower ADC 90 and higher ADC kurtosis and ADC entropy were found in group B than those in group A (all P < 0.05). Readout-segmented echo-planar imaging ADC kurtosis showed the highest area under the curve of 0.792 in the differentiation of the 2 groups (sensitivity, 80%; specificity, 73.77%). Compared with SS-EPI, the ADC histogram parameters derived from RS-EPI were more accurate, and ADC kurtosis held great potential in differentiating normal-sized LNM in cervical cancer.

Objective To explore the correlation between apparent diffusion coefficient(ADC)and neonatal behavioral neurological assessment(NBNA) of newborns with hypoxic ischemic encephalopathy (HIE), and to evaluate ADC in the early diagnosis of HIE from the imaging perspective. Method One hundred and nine neonates aged 0—7 days with HIE underwent conventional MRI and DWI. According to HIE grading standards, there were 43 neonates in the mild group, 38 in the moderate group, 28 in the severe group, and meanwhile 24 normal neonates with the same ages were selected as the control group. All cases were assessed with NBNA, and ADC values of bilateral frontal white matter, parietal white matter, periventricular white matter, posterior limb of the internal capsule (PLIC), ventral lateral nucleus of thalamus, lenticular nucleus, splenium of the corpus callosum, brainstem were measured. ADC values of different groups were compared by analysis of variance, and the correlations between ADC values of all ROIs and NBNA were analyzed by Pearson correlation. Results Except lenticular nucleus and the brainstem, ADC values of frontal white matter, parietal white matter, periventricular white matter and PLIC, ventral lateral nucleus of thalamus, splenium of the corpus callosum were decreased in the mild, moderate, severe group. In the mild, moderate, and severe group, the ADC values of frontal deep white matter were (1.82±0.33)×10-3, (1.77±0.34)×10-3 and (1.62±0.31)×10-3 mm2/s, while they were (1.81±0.34)×10-3, (1.79±0.27)× 10-3 and (1.72±0.31)×10-3 mm2/s for the parietal deep white matter, (1.27±0.15)×10-3, (1.23±0.12)×10-3 and (1.15±0.17)×10-3 mm2/s for the periventricular white matter, (1.08±0.09)×10-3, (0.97±0.07)×10-3 and (0.84±0.06)×10-3 mm2/s for the PLIC, (1.13±0.07)×10-3, (1.08±0.13)×10-3 and (1.00±0.13)×10-3 mm2/s for the ventral lateral nucleus of thalamus, (1.27±0.22)×10-3, (1.18±0.16)×10-3 and (1.00±0.23)×10-3 mm2/s for the splenium of the corpus callosum. There were statistically significant differences between the 3 groups (F=61.27, 16.27, 23.26, 72.70, 26.73, 66.09, all P<0.05). In the mild, modreate and severe group, NBNA were (36.8±1.4) in the mild group, (33.5±1.6) in the moderate, and (29.3±2.6) in the severe group. There was positive correlation between ADC values of frontal white matter, parietal white matter, periventricular white matter and PLIC, ventral lateral nucleus of thalamus, splenium of the corpus callosum and NBNA scores (r=0.60, 0.49, 0.54, 0.67, 0.56, 0.65, all P<0.05). Conclusions There are correlations between ADC values of the related ROIs of HIE and NBNA scores. Combining two aspects might diagnose the brain injury of HIE more accurately and objectively. Key words: Diffusion magnetic resonance imaging; Infant, newborn; Hypoxia-ischemia, brain

To explore whether the antitumor effect of a vascular disrupting agent (VDA) would be enhanced by combining with an antiangiogenic agent, and whether such synergistic effects can be effectively evaluated with separate calculation of diffusion weighted magnetic resonance imaging (DW-MRI). Thirty-seven rats with implanted liver tumors were randomized into the following three groups: (1) ZD6126, a kind of VDA; (2) ZDTHA, ZD6126 in combination with an antiangiogenic, thalidomide; and (3) control. Morphological DW-MRI were performed and quantified before, 4 h and 2 d after treatment. The apparent diffusion coefficient (ADC) values were calculated separately for low b values (ADC(low)), high b values (ADC(high)) and all b values (ADC(all)). The tissue perfusion contribution, ADC(perf), was calculated as ADC(low)-ADC(high). Imaging findings were finally verified by histopathology. The combination therapy with ZDTHA significantly delayed tumor growth due to synergistic effects by inducing cumulative tumor necrosis. In addition to delaying tumor growth, ZDTHA caused tumor necrosis in an additive manner, which was verified by HE staining. Although both ADC(high) and ADC(all) in the ZD6126 and ZDTHA groups were significantly higher compared to those in the control group on day 2, the entire tumor ADC(high) of ZDTHA was even higher than that of ZD6126, but the significant difference was not observed for ADC(all) between ZDTHA and ZD6126. This indicated that the perfusion insensitive ADC(high) values calculated from high b value images performed significantly better than ADC(all) for the monitoring of tumor necrosis on day 2. The perfusion sensitive ADC(perf) derived from ADC(low) by excluding high b value effects could better reflect the reduction of blood flow due to the vessel shutdown induced by ZD6126, compared to the ADC(low) at 4 h. The ADC(perf) could provide valuable perfusion information from DW-MRI data. The separate calculation of ADC is more useful than conventional averaged ADC in evaluating the efficacy of combination therapy with ZD6126 and thalidomide for solid tumors.

Gelatin film cross-linked with laccase-catalyzed purple cauliflower extract and coated with Zn-carbon dots exhibits excellent physicochemical properties and functionality for intelligent and active packaging

BACKGROUNDThe value of conventional magnetic resonance imaging in the differential diagnosis of thyroid nodules is limited; however, the value of multi-parameter diffusion-weighted imaging (DWI) in the quantitative evaluation of thyroid nodules has not been well determined. AIMTo determine the utility of multi-parametric DWI including mono-exponential, bi-exponential, stretched exponential, and kurtosis models for the differentiation of thyroid lesions.METHODSSeventy-nine patients (62 with benign and 17 with malignant nodules) underwent multi-b value diffusion-weighted imaging of the thyroid. Multiple DWI parameters were obtained for statistical analysis.RESULTSGood agreement was found for diffusion parameters of thyroid nodules. Malignant lesions displayed lower diffusion parameters including apparent diffusion coefficient (ADC), the true diffusion coefficient (D), the perfusion fraction (f), the distributed diffusion coefficient (DDC), the intravoxel water diffusion heterogeneity (α) and kurtosis model-derived ADC (Dapp), and higher apparent diffusional kurtosis (Kapp) than benign entities (all P < 0.01), except for the pseudodiffusion coefficient (D*) (P > 0.05). The area under the ROC curve (AUC) of the ADC(0 and 1000) was not significantly different from that of the ADC(0 and 2000), ADC(0 to 2000), ADC(0 to 1000), D, DDC, Dapp and Kapp (all P > 0.05), but was significantly higher than the AUC of D*, f and α (all P < 0.05) for differentiating benign from malignant lesions.CONCLUSIONMultiple DWI parameters including ADC, D, f, DDC, α, Dapp and Kapp could discriminate benign and malignant thyroid nodules. The metrics including D, DDC, Dapp and Kapp provide additional information with similar diagnostic performance of ADC, combination of these metrics may contribute to differentiate benign and malignant thyroid nodules. The ADC calculated with higher b values may not lead to improved diagnostic performance.

Objective To study the effect of diffusion-weighted magnetic resonance imaging (DW-MRI) in the differential diagnosis of hydronephrosis and pyonephrosis. Methods From March 2015 to October 2017, 50 patients with renal stone and highly suspected infectious hydronephrosis underwent renal DW-MRI, and clinical materials were collected and analyzed retrospectively. Seventeen male and 33 female patients were enrolled with a mean age of (49.40±10.51) years. The median maximum diameter of renal stone was 30.30 (17.38, 56.01) mm and hydronephrosis was 46.39 (34.33, 56.55) mm. No pyonephrosis was diagnosed by preoperative ultrasound or CT, while 29 cases of hydronephrosis and 21 cases of pyonephrosis were reported by preoperative DW-MRI. Final diagnoses of hydronephrosis and pyonephrosis were made according to whether the pelvic urine drainage was purulent or not during the surgery. DW-MRI reports and characteristics of DW images were analyzed retrospectively. Apparent diffusion coefficient (ADC) was calculated and ADC map constructed, which was compared between the two groups. Receiver operating characteristic curve (ROC) was drawn to analyze the area under curve (AUC) and the optimal cutoff of ADC value, with sensitivity and specificity. Results Thirty-three patients of hydronephrosis and 17 pyonephrosis were confirmed intraoperatively. The overall accuracy of diagnosis using DW-MRI was 84.00% (42/50), with sensitivity of 88.24% (15/17) and specificity of 81.82% (27/33). Among 30 patients who underwent CT scan in our hospital, mean CT value of 18 hydronephrosis was (7.03±3.26) HU and that of 12 pyonephrosis was (8.67±3.52) HU, with no statistical significance (P>0.05). On DW image, when b≥500 s/mm2, hydronephrosis signal intensity was lowered apparently, whereas pyonephrosis signal intensity was intensified. On ADC map, hydronephrosis appeared as hyperintensity, whereas pyonephrosis appeared as hypointensity. The mean ADC value of pyonephrosis group was lower than hydronephrosis group [(1.53±0. 58)×10-3 mm2/s vs. (2.86±0.56)×10-3 mm2/s, P<0.01]. ROC analysis revealed that AUC=0.92(95%CI 0.80-0.98), and the cut-off value of ADC for pyonephrosis diagnosis was 1.39×10-3 mm2/s, of which the sensitivity and specificity was 94.12% and 84.85% respectively. Conclusions Signal of pyonephrosis was enhanced on DW image, while decreased on ADC image. The ADC value of pyonephrosis was much lower than that of hydronephrosis, with which the differential diagnosis between pyonephrosis and hydronephrosis could be made efficiently. Key words: Hydronephrosis; Pyonephrosis; Urosepsis; Diffusion-weighted imaging; Apparent diffusion coefficient

Background: While it is known that a reduction of blood flow leads to a decrease in apparent diffusion coefficient (ADC), how ADC evolves as a function of time from ischemia onset is unclear. We evaluated ADC signal change in brain tissue with temporally stable hypoperfusion, examining the relationship between severity of hypoperfusion and the rate of ADC decline during acute ischemia. Methods: Ischemic stroke patients were sequentially imaged with diffusion-perfusion weighted imaging at &lt;4.5hr (tp1) and at 6hr (tp2) after stroke onset, to directly assess the temporal evolution of ADC. One month FLAIR provided the final infarct region. Registration aligned all images for each patient. Dynamic susceptibility contrast method allowed calculation of mean transit time (MTT). Hypoperfusion was defined as tissue with MTT &gt; 4sec + the contralateral median MTT. In tissue with stable hypoperfusion on tp1 and tp2, ADC regions of interest (ROIs) with normal or moderate reduction on tp1 were evaluated. To avoid capturing tp1 ADC voxels that had already maximally declined (floor effect, &lt;30 ×10 -5 mm 2 /s), ADC values &lt; 60 were excluded. To assess how ADC declined with varying degrees of hypoperfusion, tissue was divided into 6 MTT ranges: 3-6 (ROI1), 6-9 (ROI2), 9-12 (ROI3), 12-15 (ROI4), 15-18 (ROI5) and &gt;18 (ROI6) seconds. Paired t-tests compared tp1 and tp2 ROIs for each patient. Infarct probability based on tp3 FLAIR was computed for each ROI. Results: 43 patients were imaged at 2.9 (tp1) and 6.4 hrs (tp2) after stroke onset, of which 37 returned for 1 month FLAIR. The 6 ROIs with increasing MTT severity were found in 41, 27, 19, 12, 6, and 10 patients for ROI’s 1-6, respectively. ADC values for all ROIs were similar at tp1 (near normal), despite different tp1 MTT. For ROI1-3, ADC values did not decline between tp1 and tp2 or decreased mildly (ROI3, P=0.079). For severe hypoperfusion, ADC decreased significantly: ROI4 (p=0.006), ROI5 (P=0.038), and ROI6 (P=0.0001). Using linear regression to approximate the ADC decline, the slopes were significantly different from zero with ADC decay rates of -1.87×10 -5 mm 2 /s/hr (R=0.58), -2.86×10 -5 mm 2 /s/hr (R=0.65) and -4.51×10 -5 mm 2 /s /hr (R=0.82) for ROI4-6, respectively ( Figure ). The median infarct probabilities for the 6 ROI’s increased with increasing MTT severity: 16%, 53%, 57%, 87%, 100%, and 90% for ROI1-6, respectively. Conclusions: ADC remained normal after ischemic stroke in regions with stable, moderate hypoperfusion. In contrast, with stable, severe hypoperfusion (MTT&gt;12s), ADC decreased from 3-6 hours and the rate of decline was highly dependent on the degree of hypoperfusion.

Vapor and “nonvapor” diffusion of lindane was measured in Gila silt loam at various soil‐water contents. The apparent vapor diffusion coefficient ( D v ′) increased rapidly as water content increased to 4%. There was a gradual decrease in D v ′ as water content increased from 4 to 20% and then a rapid decrease at water contents greater than 20%. The “nonvapor” apparent diffusion coefficient ( D s ′) also reached a maximum at 4% water content and declined at water contents between about 4 and 20%. D s ′ increased as water content was increased above 20%. Apparently diffusion in the “nonvapor” phase occurs at the water‐air and water‐solid interface as well as in the water. The contribution of these pathways to the total transfer is dependent upon water content. It was assumed that the water‐solid diffusion coefficient would be constant at water contents above 4%. The air‐water interface diffusion was highest at 4% water content and decreased at higher water contents. Diffusion in water was essentially zero at water contents below 15% and increased with increasing water contents above this value.

Using pathologically proven tumors and 3 methods of apparent diffusion coefficient (ADC) measurement, we examined the potential of diffusion-weighted imaging (DWI) to differentiate adrenal tumors. We evaluated adrenal tumors of 52 patients who underwent magnetic resonance (MR) examination including DWI and adrenal resection or biopsy between July 2006 and August 2011. Tumors included 25 cortical adenomas, 14 pheochromocytomas, 6 adrenal metastases, and seven others. We defined the tumor's "solid" region as an enhancing area on contrast-enhanced MR or computed tomography (CT) and measured the ADC of the tumor's "entire" and "solid" regions within a region of interest (ROI) placed on an ADC map ("entire" and "solid" ADCs). We obtained a "minimum" ADC by placing an ROI in an area showing the lowest ADC within the "solid" region. We also calculated the ratio of "non-solid" area to "entire" tumor and compared the average "entire," "solid," and "minimum" ADCs and the ratio of "non-solid" area to "entire" tumor between benign and malignant groups. The average "entire" ADC was significantly higher for the benign (1.35 ± 0.38 × 10(-3) mm2/s) than malignant group (1.01 ± 0.17 × 10(-3) mm2/s), and the average "solid" and "minimum" ADC and the ratio of "non-solid" area to "entire" tumor did not differ significantly between the benign and malignant groups. The higher "entire" ADC value of the benign group, which might be obtained incidentally, can be considered dependent on the condition of necrosis, hemorrhage, and degeneration. ADC measurement of a tumor's "solid" region was not useful for differentiating pathologically proven adrenal tumors.

Objective To investigate the value of diffusion tensor imaging (DTI) at high b value for unilateral middle cerebral artery (MCA) occlusive disease in patients without obvious infarct lesions on conventional MR imaging.Methods DTI at high b value (2200 s/mm2 ) was performed using a 3.0 Tesla MR scanner in 34 patients with unilateral middle cerebral artery occlusion,who had no obvious infarct lesions on conventional MR imaging. Fractional anisotropy (FA),apparent diffusion coefficient (ADC),axial diffusivity (eigenvalue λ1) and radial diffusivity (eigenvalues λ2,λ3) were measured at the ipsilateral and contralateral corona radiata,anterior and posterior limbs of the internal capsule,cerebral peduncle and pons in all subjects.Mean ADC,FA,λ1,λ2 and λ3 values of corona radiata,anterior and posterior limbs of the internal capsule,cerebral peduncle and pons were compared between the ipsilateral and contralateral MCA territory by t test. Results Among the 34 patients,left MCA occlusion in M1 segment occurred in 16 patients and right MCA occlusion in Ml segment occurred in 18 patients.At the ipsilateral corona radiata,mean FA,ADC,λ1,λ2 and λ3 were 0.419 ±0.032,(5.975 ±0.272) × 10 3,(5.704 ±0.365) ×10-3,(6.412 ±0.368) × 10-3 and (6.605 ±0.343) × 10-3 mm2/s,respectively.At the contralateral corona radiata,mean FA,ADC,λ1,λ2 and λ3 were 0.443 ± 0.033,(5.804 ± 0.282) × 10 -3,(5.651 ±0.350) × 10-3,(6.099 ±0.353) × 10-3 and(6.372 ±0.355) × 10-3 mm2/s,respectively.At the ipsilateral corona radiata,mean FA was significantly decreased(t =11.614,P ＜0.01),and mean ADC (t=12.421,P＜0.01),λ1(t =7.447,P＜0.01),λ2(t=10.244,P＜0.01) and λ3(t=9.890,P＜0.01) were significantly increased.At the ipsilateral anterior and posterior limb of the internal capsule,mean FA were 0.609 ±0.026 and 0.674 ±0.033,λ1 were(5.330 ±0.462) × 10 -3 and(5.171 ±0.456) ×10-3 mm2/s,respectively.At the contralateral anterior and posterior limb of the internal capsule,FA were 0.622 ±0.026 and 0.694 ±0.034,λ1 were(5.064 ± 0.448) × 10 -3 and(4.924 ± 0.365) × 10 -3 mm2/s,respectively.Mean FA was significantly decreased (t =7.823,8.013,all P ＜ 0.01) and mean λ1 was significantly increased (t =7.811,8.800,all P ＜0.01) at the ipsilateral anterior and posterior limbs of the internal capsule.There was no significant difference in ADC,λ2 and λ3 value between the ipsilateral and contralateral sides.And all the DTI parameters,including mean ADC,FA,λ1,λ2 and λ3 values,showed no statistical difference between both sides of cerebral peduncle and pons.Conclusion DTI at high b valuc can provide useful information for visualizing ischemic white matter injury in patients without obvious infarct lesions on conventional MR imaging. Key words: Infarction, middle cerebral artery; Diffusion magnetic resonance imaging

To prospectively determine apparent diffusion coefficient (ADC) values of normally developing fetal lungs over gestation, as obtained by diffusion-weighted (DW) magnetic resonance imaging (MRI) and to investigate its potential application in fetuses with congenital diaphragmatic hernia (CDH). Informed consent was obtained for this cross-sectional study of 93 fetuses with normal lungs and 14 with isolated left-sided CDH, assessed between 18 and 40 weeks of gestation. MRI delineation of left and right lungs was performed on the native DW image, b0, and three values of ADC, corresponding to the overall value (ADC(avg)), and values for low and high values of b (ADC(low) and ADC(high), respectively) were calculated. Regression analysis was used to assess the relationship between gestational age and b0-values as well as calculated ADC values. The b0 and ADC values of normal and CDH fetuses were compared with normal ranges using the Mann-Whitney U-test. In fetuses with normal lungs, there was a negative correlation between gestational age and b0 values as well as with ADC(high), a positive correlation with ADC(low) but no correlation with ADC(avg). When measurable, ADC(high) values were lower in CDH as compared to fetuses with normal lungs and ADC(low) values were higher. ADC(low) was unrelated to lung volume. There is a significant relationship between ADC(low) and ADC(high) values and gestational age in normal fetal lungs. This relationship is most probably explained by developmental changes during the last three stages of lung development, which involve intense peripheral growth of airways and vessels as well as maturation. In CDH, measurement of ADC(low) might be useful as a predictor of postnatal outcome that is independent of lung volume.

Although brain ischemia has been extensively studied using diffusion-weighted magnetic resonance imaging, most studies performed so far have not had adequate time resolution to follow the temporal changes in the water apparent diffusion coefficient (ADC) in hyperacute ischemia. Using diffusion echo planar imaging, we obtained ADC maps (calculated from measurements made with 8 b-values) with a time resolution of 43 s in a feline model of global brain ischemia and reperfusion. Different protocols were performed: 10-min hypoperfusion, 10- and 22-min ischemia followed by reperfusion, and cardiac arrest. ADC values were obtained from white matter of the internal capsule and from the thalamus. Cortical gray matter measurements were not deemed reliable due to the close proximity of CSF in the cortical sulci. Following occlusion, the ADC declined in the thalamus to < 2 SD of its normal baseline value within 1.5-2.5 min. This decay was exponential with a time constant (tau +/- SD) of 6.0 +/- 2.6 min; no further decrease in the ADC was observed 10 min following ischemia. Following reperfusion, in animals that showed ADC recovery, the ADC began increasing immediately, returning to its preischemic value in approximately 15 min. No significant ADC changes were observed during hypoperfusion. Following cardiac arrest, the decay of ADC was more rapid in the thalamus (tau = 2.6 +/- 0.6 min) than in white matter (tau = 6.6 +/- 1.8 min). We observed that the ADC at 40 min after cardiac arrest was similar to the ADC at 10 min after ischemia. Given that all animals subjected to 10-min ischemic episodes showed ADC recovery with reperfusion, doubt is cast on whether it is possible to define a threshold value of the ADC below which brain tissue is irreversibly damaged. Finally, despite variability in the time constants of the ADC decay induced by ischemia, the ADC values at 10 min were very similar in all the animals. This suggests that when blood flow is diminished sufficiently to induce an ADC reduction, differences in perfusion affect the rapidity of the decrease but not the final asymptotic value reached.