Functional MRI: evaluation of chronic kidney disease with perfusion imaging.

RATIONALE AND OBJECTIVES: To evaluate the functional alterations of chronic kidney disease (CKD) with magnetic resonance dynamic perfusion imaging. MATERIALS AND METHODS: Twenty-one healthy subjects (42 kidneys) and 20 CKD patients (40 kidneys) underwent routine scans with fat-saturated T1-weighted fast low angle shot (FLASH) and true-fast imaging with steady-state precession (FISP) sequences followed by dynamic perfusion scans using a turbo-FLASH T1-weighted sequence. Signal intensity (SI) of the cortex and medulla on images was measured and plotted as a function of time. Peak height (P) and time to peak (T) of the cortex and medulla SI were estimated, and P/T ratio and the area under the time-intensity curves were calculated. We also tested the correlation between these data and serum creatinine (sCr) levels in patients. RESULTS: P, P/T ratio, and the area under the curve of patients' cortex and medulla were significantly decreased compared to control subjects, and T was delayed. In patients, P and P/T ratio of the cortex and P of the medulla were negatively correlated with sCr levels (r = -0.469, r = -0.419, and r = -0.423, respectively; P < 0.01). CONCLUSION: Renal dysfunction in CKD can be evaluated by magnetic resonance dynamic perfusion imaging.

Diffusion tensor imaging study of the anterior limb of internal capsules in neuroleptic-naive schizophrenia.

RATIONALE AND OBJECTIVES: Abnormalities in brain structure have been implicated in psychosis. Herein, we investigated the differences in fractional anisotropy (FA) and average diffusion coefficient (ADC) in the bilateral anterior limb of internal capsules between neuroleptic-naive schizophrenic patients and appropriately matched healthy controls. MATERIALS AND METHODS: Magnetic resonance imaging was performed with a 1.5 T superconductive MR scanner, and diffusion tensor imaging was carried out in 21 neuroleptic-naive schizophrenic patients and 18 matched healthy controls. FA and ADC were measured by region of interest analysis. RESULTS: Compared with healthy controls, the neuroleptic-naive schizophrenic patients showed significantly reduced FA in the bilateral anterior limb of the internal capsule. However, the difference in the ADC values between the patients and the controls was not significant. CONCLUSIONS: FA of the bilateral anterior limb of the internal capsule was reduced in neuroleptic-naive schizophrenic patients, indicating that the integrity of the white matter of the bilateral thalamus-frontal connection or the bilateral thalamus-anterior cingulate gyrus connection was destroyed.

Perfusion-weighted MRI in evaluating the intranodular hemodynamic characteristics of dysplastic nodules and hepatocellular carcinomas in an experimental rat model.

PURPOSE: To investigate the value of perfusion-weighted MRI in the evaluation of the intranodular hemodynamic characteristics of dysplastic nodules (DNs) and hepatocellular carcinomas (HCCs) in an experimental rat model. MATERIALS AND METHODS: A total of 40 rats with chemically-induced DNs and HCCs were investigated. Single-slice gadolinium-enhanced perfusion-weighted MRI was performed to evaluate the nodules. Time to peak (Tp), maximal relative signal enhancement (REmax), and the initial slope of signal intensity (SI) vs. time curves of the nodules and cirrhotic liver were evaluated. Nodules precisely corresponding to MRI were examined histologically. Paired Student's t-tests were used to compare the difference between nodules and cirrhotic liver. RESULTS: A total of 20 HCCs and 14 DNs were evaluated. HCCs showed a significantly higher REmax, shorter Tp, and higher slope than adjacent cirrhotic liver. The REmax and slope of DNs were significantly lower than adjacent cirrhotic liver parenchyma. Although the Tp of DNs was delayed two to three seconds compared to adjacent cirrhotic liver, there was no significant difference between them. CONCLUSION: Perfusion-weighted MRI detected the intranodular hemodynamic characteristics of DNs and HCCs in an experimental rat model. DNs were hypovascular compared to cirrhotic liver, while HCCs were markedly hypervascular.

Diffusion-weighted magnetic resonance imaging of focal hepatic nodules in an experimental hepatocellular carcinoma rat model.

RATIONALE AND OBJECTIVES: We sought to investigate the value of diffusion-weighted MR imaging in evaluating focal hepatic nodules in an experimental hepatocellular carcinoma (HCC) rat model. MATERIALS AND METHODS: Forty rats with chemically induced primary hepatic nodules ranging pathologically from regenerative nodules (RNs) to dysplastic nodules (DNs) to HCC were examined with diffusion-weighted imaging. The apparent diffusion coefficient (ADC) values of hepatic nodular lesions were calculated. Tukey's HSD post hoc test was used to compare the difference in ADC values between different hepatic nodular lesions. RESULTS: Eight RNs, 16 DNs, 7 well-differentiated HCCs (HCCwell), 11 moderately differentiated HCCs (HCCmod), and 14 poorly differentiated HCCs (HCCpoor) were evaluated. There was no significant difference between RNs and DNs (P > 0.05). Although the ADC values of HCCwell were slightly lower than those of DNs, there was no significant difference between them (P > 0.05). The ADC values of HCCmod and HCCpoor were significantly higher (P < 0.05) than those of other nodules, and no significant difference was seen between HCCmod and HCCpoor (P > 0.05). CONCLUSION: Diffusion-weighted magnetic resonance imaging can be useful in characterizing focal hepatic nodular lesions, but ADC values cannot be used efficiently to distinguish HCCwell from DNs.

In vivo 1H MR spectroscopy in the evaluation of the serial development of hepatocarcinogenesis in an experimental rat model.

RATIONALE AND OBJECTIVES: We used a 1.5-T MR scanner to investigate in vivo hydrogen 1 ((1)H) MRS to evaluate metabolic changes in the hepatocarcinogenesis experimental rat model. MATERIALS AND METHODS: Hepatocellular carcinoma (HCC) was induced by diethylnitrosamine in 70 treated rats with 20 normal rats used as controls. Single-voxel (1)H MRS is performed to obtained the relative choline-to-lipid (Cho/lipid) ratio. The liver and tumor tissues are incised for the histologic examination. Based on the histologic result, the progression of hepatocarcinogenesis of the animal model was divided into three stages: fibrosis stage, cirrhosis stage, and HCC stage. The mean (+/-SD) ratio values are calculated and compared at various stages between the treated group and the control group. RESULTS: In control group, the calculated mean (+/-SD) Cho/lipid ratio was 0.15 +/- 0.05. With the progression of hepatocarcinogenesis, the Cho/lipid ratio increased significantly, to 0.18 +/- 0.05, 0.24 +/- 0.07, and 0.38 +/- 0.19, respectively. CONCLUSION: The (1)H MRS is technically feasible for evaluation of the metabolic changes in the animal model. A significant increase in choline-containing compounds level was observed in the HCC stage in the treated group.

[Assessment of acute mesenteric ischemia with multi-slice spiral CT].

OBJECTIVE: To explore the clinical value of multi-slice spiral CT (MSCT) in diagnosis of acute mesenteric ischemia. METHODS: MSCT, including plain scan, the arterial phase scan, and the portal vein phase scan, was performed in 18 patients who were suspected of acute intestinal ischemia. The mesenteric arteries and portal veins were imaged with techniques including volume-rendered technique, multi-planar reconstruction, and maximum intensity projection-thin. All of them were also examined with digital subtractive angiography (DSA). The diagnostic results of MSCT were compared with those of DSA, and the abnormal MSCT findings were analyzed. RESULTS: Bowel wall thickening, mesenteric edema, and ascites were most commonly seen in venous thromboses, while luminal dilatation and air-fluid levels were commonly seen in arterial embolization. Except that pneumatosis was only seen in transmural infarction, all the abnormal CT findings were found in different patterns and different degrees of ischemia. CONCLUSIONS: The integrated MSCT examination is a valuable tool in diagnosis of acute intestinal ischemia. It can accurately diagnose acute intestinal ischemia and is also useful to assess the degrees of ischemia.

Evaluation of cirrhotic liver with perfusion-weighted magnetic resonance imaging: a preliminary experimental study in animal models with half-liver cirrhosis.

OBJECTIVE: To investigate the role of perfusion-weighted magnetic resonance imaging (MRI) in evaluation of cirrhotic liver. METHODS: With a 4F catheter, 1% diluted carbon tetrachloride (1 ml/kg) was selectively injected into right or left hepatic artery of 12 dogs fortnightly. The half liver into which carbon tetrachloride was injected was called as study side (SS), while the other half liver without carbon tetrachloride injection was called as study control side (SCS). Conventional and perfusion-weighted MRI were performed in every 4 weeks. Via a 4F catheter, 5ml gadolinium diethylentriamine pentaaceti acid (Gd-DTPA) dilution was injected into superior mesenteric artery at the 5th scan. The signal intensity-time curves of SS, SCS, and portal vein were completed in MR workstation. The maximal relative signal increase (MRSI), peak time (tp), and slope of the curves were measured. RESULTS: On conventional MR images, no abnormalities of externality and signal intensity were observed in both SS and SCS of liver at each stage. The mean tp, MRSI, and slope of intensity-time curves in normal liver were 10.56 seconds, 1.01, and 10.23 arbitrary unit (au)/s, respectively. Three parameters of curves didn't show obvious change in SCS of liver at every stage. Abnormal perfusion curves occurred in SS of liver at the 12th week after the 1st injection. The abnormality of perfusion curve in SS was more and more serious as the times of injection increased. The mean tp, MRSI, and slope intensity-time curves in SS of liver were 19.45 seconds, 0.43, and 3.60 au/s respectively at the 24th week. CONCLUSION: Perfusion-weighted imaging can potentially provide information about portal perfusion of hepatic parenchyma, and to some degree, reflect the severity of cirrhosis.

MR perfusion-weighted imaging and quantitative analysis of cerebral hemodynamics with symptom provocation in unmedicated patients with obsessive-compulsive disorder.

We evaluated the potential effectiveness of dynamic contrast-enhanced perfusion-weighted images (PWI) in determining hemodynamic activation in brain structures that may be involved in mediating the symptomatology of patients with obsessive-compulsive disorder (OCD), as manifested by contamination obsessions with washing compulsions. Ten unmedicated female patients with OCD were subjected to PWI, and relative cerebral blood flow (rCBF) in each region of interest (ROI) and self-ratings of OCD symptoms were compared before and after symptom provocation. We found that increases in the Anxiety Analogue Scale (AAS) and OCD Analogue Scale (OCDAS) scores were each significantly associated with provocation. The correlations between OCDAS and AAS scores were also statistically significant during both the control and provoked conditions. Compared with the control state, there was a significant increase in rCBF during the symptomatic state in the right head of caudate nucleus, thalamus, and bilateral orbitofrontal cortices (OFC). No statistical changes in rCBF were found in the bilateral anterior cingulate cortices (ACC). These findings demonstrate that OCD symptomatology is accompanied by anxiety, and that abnormal features are particularly apparent in the orbitofrontal-subcortical circuits.

Improvements in the intraluminal thread technique to induce focal cerebral ischaemia in rabbits.

Although the intraluminal thread technique has been used to induce focal cerebral ischaemia in rabbits, its success rate is not high. We, therefore, attempted to improve the stability and reproducibility of this method by using thread tips of appropriate diameter as determined from the anatomical characteristics of the carotid and cerebral arteries of New Zealand white rabbits. Following intraarterial injection of casting material, we tested threads of four different tip diameters to determine the optimal thread tip that could occlude the middle cerebral artery (MCA). 2,3,5-Triphenyltertrazolium chloride (TTC) staining showed that, consistent with the intraluminal diameter of the MCA from the arterial casts ( 0.50 +/- 0.06 mm), thread with 0.51-0.55 mm tip diameter was optimal for the occlusion of the MCA. Ability to induce focal cerebral ischaemia was also dependent on variations in the anatomy of the internal carotid artery (ICA), especially the origin of the occipital artery. Our results suggest that use of appropriately sized thread and accurate manipulation of its tip significantly improves the stability and reproducibility of this model.

Functional evaluation of normothermic ischemia and reperfusion injury in dog kidney by combining MR diffusion-weighted imaging and Gd-DTPA enhanced first-pass perfusion.

PURPOSE: To evaluate functional alterations of renal ischemia and reperfusion injury using MR diffusion-weighted imaging and dynamic perfusion imaging. MATERIALS AND METHODS: Twelve dogs were randomly divided into four groups. Animal renal ischemia was respectively induced for 30 (group 1), 60 (group 2), 90 (group 3), and 120 (group 4) minutes by left renal artery ligation under anesthesia. Using a 1.5 T MR system, true-FISP, TSE, EPI, and DWI sequences were acquired in five different periods; specifically, pre-ischemia, onset-ischemia, late ischemia, onset-reperfusion, and post-reperfusion. Moreover, a turbo-FLASH sequence (TR/TE/TI/FA = 5.8/3.2/400 msec/10 degrees ) with a temporal resolution of 1.16 seconds was acquired. Signal intensity (SI) was measured in the cortex, outer medulla, and inner medulla of kidney. Apparent diffusion coefficient (ADC) values were calculated, and SI was plotted as a function of time. RESULTS: In all animals, significant SI changes of the left kidney on T2/T2*WI were detected following ischemia-reperfusion insult compared to corresponding values of the right kidney. Following ligation, the ADC values decreased in all layers of the left kidney. Immediately after the release of ligation, ADC values in both outer and inner medulla of the left kidney remained lower than those of the right kidney in those animals which were induced with renal ischemia for 60, 90, and 120 minutes. In all groups, a uniphasic enhancement pattern was observed in the outer and inner medulla of the left kidney, accompanied by a decrease of the area under the curve. CONCLUSION: Our results suggest that MR diffusion-weighted imaging and dynamic perfusion imaging are useful in identifying renal dysfunction following normothermic ischemia and reperfusion injury.