The Usefulness of Diffusion Tensor MRI for the Prediction of Clinical Outcome in Patients with Acute Subcortical Infarction

BACKGROUND: Diffusion tensor MRI (DTI) is a new imaging technique and enables us to analyze the structural damage of fiber pathways and to monitor the time course of Wallerian degeneration of the pyramidal tract in stroke patients. We used DTI to investigate structural changes of the infarct area and the associated descending corticospinal tract in patients with subcortical infarct. METHODS: We examined 24 consecutive patients who presented with acute single cerebral infarct in the subcortical area and who also had undergone an MRI study within 7 days after symptom onset. Clinical outcome was assessed using the National Institutes of Health Stroke Scale (NIHSS) at admission, 7 days, 14 days and 30 days and modified Rankin Scale (mRS) at admission and 30 days. Each of the indices was achieved by post processing the acquired DTI data and correlated with the NIHSS. RESULTS: In infarct region, fractional anisotropy (FA) was significantly decreased compared with matched-contralateral regions (0.39 vs. 0.53, p<0.001). In the distal to the infarct, FA was significantly decreased at internal capsule (0.62 vs. 0.64, p=0.019), not at pons (0.51 vs. 0.53, p=0.103). The decrease of anisotropy at infarct region correlated positively with the NIHSS at 7, 14 and 30 days and mRS at 30 days after stroke, but the decrease of anisotropy at internal capsule did not correlate with the NIHSS. CONCLUSIONS: This study shows the potential of DTI to detect and monitor the structural degeneration of fiber pathways and to establish the prognosis in patients with acute subcortical cerebral infarct.

Diffusion-Weighted MR Imaging of Neuro-Behcet's Disease: Initial and Follow-up Studies

PURPOSE: To assess the usefulness of diffusion-weighted MR imaging (DWI) and apparent diffusion coefficient (ADC) in the initial and follow-up studies of patients with neuro-Behcet's disease. MATERIALS AND METHODS: Six patients diagnosed with neuro-Behcet's disease were the subjects of this study. Initial and follow-up MR imaging were obtained in all six patients. Initial and follow-up DWI were also obtained in four of the six patients, with only an initial DWI in the other two. The DWI were obtained using multi-shot echo planar imaging, on a 1.5T MR unit, with two gradient steps (b values of 0, 1000 sec/mm2). The ADC value and ADC maps were obtained using commercial software. The locations and signal intensities of the lesions were analyzed on conventional MRI and DWI, respectively. The ADC values of the lesions were calculated on the initial and follow-up DWI, and compared those of lesions in the normal contralateral regions. RESULTS:The initial DWI showed iso-signal intensities in four of the six patients, with high signal intensities in the other two. In five of the six patients, including three of the four that showed isosignal intensities and the two that showed high signal intensities on the initial DWI, the ADC values of the involved lesions were higher than those of the normal contralateral regions. In three of four that showed isosignal intensities, the ADC values of the lesions were decreased and normalized on the follow-up DWI. CONCLUSION: Obtaining DWI and ADC values in patients with neuro-Behcet's disease may be helpful in the understanding of pathophysiology and differential diagnosis of this disease.

Usefulness of Apparent Diffusion Coefficient in Ovarian Cystic Tumors Using Diffusion-Weighted Magnetic Resonance Imaging

PURPOSE: To evaluate the usefulness of apparent diffusion coefficient (ADC) values using diffusion-weighted magnetic resonance imaging (DWI) in patients with ovarian cystic tumors. MATERIALS AND METHODS: During past 12 months, we studied 30 patients who were clinically suspected of having ovarian cystic tumors and who underwent DWI using a 1.5 T MR unit. Eight patients with small cystic ovarian lesions of less than 3 cm in diameter and insufficient DWI were excluded from the calculation of the ADC values. The remaining twenty-six cystic ovarian lesions in 22 patients were classified into four groups; ovarian cysts, cystadenomas, other benign tumors, and malignant tumors. DWI was obtained using single-shot spin echo planar imaging and two gradient steps (b values of 0, 800 sec/mm2). The ADC values were measured using regions-of-interest (ROI) in the cystic components of the DWI located in the same section as the T2-weighted image and away from the septation and solid components. RESULTS: The mean ADC values were 0.196+/-0.105x10(-3) mm2/sec in the ovarian cysts, 1.312+/-1.064x10(-3) mm2/sec in the cystadenomas, 0.274+/-0.124x10(-3) mm2/sec in the other benign tumors, and 1.011+/-0.080x10(-3) mm2/sec in the malignant tumors. The differences in the ADC values between the ovarian cysts and cystadenomas, the ovarian cysts and malignant tumors, the cystadenomas and other benign tumors, and the other benign tumors and malignant tumors were statistically significant (p 0.05). CONCLUSION: The calculated ADC values using DWI should be helpful in the differential diagnosis of cystic ovarian tumors.

The Usefulness of 3T-TOF MR angiography in Patients with Cerebral Infarction

PURPOSE: This study was designed to evaluate the usefulness of 3T-TOF MR angiography (3T-TOF MRA) compared with transcranial Doppler sonography (TCD) and conventional angiography (CA) in patients with suspected cerebral infarction. MATERIALS AND METHODS: Fifty four patients with clinical symptoms of cerebral infarction were involved in this study, and had undergone 3T-TOF MRA and TCD, with CA in 11 patients. On the basis of divisions of the carotid artery, four groups were designated: group I, both vertebral arteries and basilar artery; group II, segment between 2 cm below bifurcation of common carotid artery and genu portion of internal carotid artery; group III, segment between petrous portion of internal carotid artery and bifurcation of anterior and middle cerebral artery; group IV, from bifurcation of anterior and middle cerebral artery to thier distal branches. Two radiologists retrospectively reviewed the vascular imaging and stenosis in 3T-TOF MRA, TCD, and CA. RESULTS: A total of 432 arteries, 108 in each group, were available. The assessment of vascular imaging quality in 3T-TOF MRA is scored 2.98, 2.96, 2.91, 2.88 in 4 groups, respectively. Agreement among 3TTOF MR angiography, TCD, and CA was high. CONCLUSION: 3T-TOF MR angiography may be useful method for the assessment of stenotic lesions of cranial vasculature in patients with cerebral infarction.

Transvenous Embolization in Patients with Dural Arteriovenous Fistula

PURPOSE: To evaluate the efficacy of transvenous embolization in patients with dural arteriovenous fistula (DAVF). MATERIALS AND METHODS: From October 2002 to July 2004, eight patients with angiographically confirmed DAVF underwent transvenous embolization of the affected dural sinuses. Concomitant transarterial embolization was performed in four patients. Patients included five men and three women aged 45-78 years (mean age, 55.4 years). The patient's medical records and angiographic features were retrospectively reviewed. Patients had follow-up periods ranging from 5 to 24 months (mean, 16.5 months). RESULTS: The locations of DAVF were transverse - sigmoid sinus in six patients and cavernous sinus in two patients. According to Cognard's classification, four of the DAVFs were Type I, two were type IIa, and two were Type IIb. Embolic materials used for the transvenous embolization were platinum detachable coils and fibered microcoils. After the transvenous embolization, there was complete obliteration of the DAVF in seven patients and significant flow reduction in one patient. All cases were clinically successful. There were no transient or permanent complications as a result of the endovascular procedures in any of the patients. One patient who had symptom recurrence 2 months after the initial treatment was successfully treated with repeated transvenous embolization. The remaining seven patients had no symptom recurrence during the follow-up period. CONCLUSION: Transvenous embolization is an effective and safe method in the treatment of patients with DAVF.

Bilateral Paramedian Thalamic Contrast Enhancement on CT after Intra-arterial Thrombolysis

A 58-year-old woman presented with an acute embolic occlusion of the distal basilar artery. She underwent angioplasty and intra-arterial thrombolysis. Angiography performed after recanalization revealed a single perforating thalamic artery. A nonenhanced CT scan carried out immediately after the procedure revealed hyperdense lesions in the bilateral paramedian portions of the thalami, which disappeared on the 24-hour follow-up CT scan. Three months later, the patient improved to functional independence, but had some memory dysfunction and vertical gaze palsy. This case suggests that contrast enhancement or extravasation can occur in the thalamus after intra-arterial thrombolysis performed to recanalize a basilar artery occlusion.

MR Imaging of Solitary Fibrous Tumors in the Head and Neck

OBJECTIVE: Solitary fibrous tumor (SFT) is a very rare tumor. The purpose of this study is to determine the MR imaging features of SFT in the intracranial and extracranial head and neck regions. MATERIALS AND METHODS: We retrospectively reviewed six MR images and two CT images of six histologically proven cases of SFT that occurred in four men and two women, and their ages ranged from 46 to 59 years. These imaging findings were correlated with the microscopic findings of their surgical specimens. RESULTS: Six SFTs arose in the meninges (the petrous ridge and the pituitary fossa), the parotid gland, the parapharyngeal space, the buccal space and the maxillary sinus. On the MR images, SFTs in the intracranial and extracranial head and neck regions were mostly isointense to the muscle on the T1-weighted images, they were hyperintense on the T2-weighted images and they all had intense enhancement. On the T1- and T2-weighted images, hypointense lines were observed within in five SFTs. On the CT images, the SFTs were hypodense to the muscle on the unenhanced images and they were heterogeneously enhanced on the contrast-enhanced images. An exceptional case of pituitary SFT was hypointense on the T2-weighted images and it was hyperdense on the unenhanced CT images, which correlated with the increased collagenous component and the cellular compactness. CONCLUSION: The imaging features of SFT are nonspecific; however, SFT should be included in the differential diagnosis of masses involving the intracranial and extracranial head and neck regions.

Diagnostic Usefulness of Perilesional Edema around Intracerebral Hemorrhage in Predicting Underlying Causes

PURPOSE: We attempted to evaluate the diagnostic usefulness of the degree of perilesional edema around intracerebral hematoma in predicting the underlying cause. MATERIALS AND METHODS: This study included 54 patients with intracerebral hematoma for whom the underlying cause was confirmed by biopsy, radiological or clinical methods. Cases of subarachnoid hemorrhage, hemorrhagic transformation of cerebral infarction and intraventricular hemorrhage were excluded. The lesion size was defined as the average value of the longest axis and the axis perpendicular to this. The size of the perilesional edema was defined as the longest width of the edema. In all cases, the sizes of the lesion and edema were measured on the T2 weighted image. We defined the edema ratio as the edema size divided by the lesion size. RESULTS:23 cases were diagnosed as intracerebral hemorrhage due to neoplastic conditions, such as metastasis (n=17), glioblastoma (n=5), hemangioblastoma(n=1). 31 cases were caused by non-neoplastic conditions, such as spontaneous hypertensive hemorrhage (n=23), arteriovenous malformation (n=4), cavernous angioma (n=3), and moya-moya disease (n=1). In fourteen cases, which were confirmed as malignant intracerebral hemorrhage, the edema ratio was more than 100%. Of the other cases, only 8 were confirmed as malignant intracerebral hemorrhage. It was found that the larger the edema ratio, the more malignant the intracerebral hemorrhage, and this result was statistically significant (p<0.001). CONCLUSION: Measurement of perilesional edema and the intracerebral hematoma ratio may be useful in predicting the underlying causes.

Cerebral Activation Associated with Visually Evoked Sexual Arousal in the Limbic System: Functional MR Imaging

PURPOSE: To identify the brain centers associated with visually evoked sexual arousal in the human brain, and to investigate the neural mechanism for sexual arousal using functional MRI (fMRI). MATERIALS AND METHODS: A total of 20 sexually potent volunteers consisting of 10 males (mean age: 24) and 10 females (mean age: 23) underwent fMRI on a 1.5 T MR scanner (GE Signa Horizon). The fMRI data were obtained from 7 slices (10 mm slice thickness) parallel to the AC-PC (anterior commissure and posterior commissure) line, giving a total of 511 MR images. The sexual stimulation consisted of a 1-minute rest with black screen, followed by a 4-minute stimulation by an erotic video film, and concluded with a 2-minute rest. The brain activation maps and their quantification were analyzed by the statistical parametric mapping (SPM 99) program. RESULTS: The brain activation regions associated with visual sexual arousal in the limbic system are the posterior cingulate gyrus, parahippocampal gyrus, hypothalamus, medial cingulate gyrus, thalamus, amygdala, anterior cingulate gyrus, insula, hippocampus, caudate nucleus, globus pallidus and putamen. Especially, the parahippocampal gyrus, cingulate gyrus, thalamus and hypothalamus were highly activated in comparison with other areas. The overall activities of the limbic lobe, diencephalon, and basal ganglia were 11.8%, 10.5%, and 3.4%, respectively. In the correlation test between brain activity and sexual arousal, the hypothalamus and thalamus showed positive correlation, but the other brain areas showed no correlation. CONCLUSION: The fMRI is useful to quantitatively evaluate the cerebral activation associated with visually evoked, sexual arousal in the human brain. This result may be helpful by providing clinically valuable information on sexual disorder in humans as well as by increasing the understanding of the neuroanatomical correlates of sexual arousal.

Qualitative and Quantitative Measurement of Human Brain Activity Using Pixel Subtraction Algorithm

PURPOSE: To develop an automated quantification program, which is called FALBA (Functional & Anatomical Labeling of Brain Activation), and to provide information on the brain centers, brain activity (%) and hemispheric lateralization index on the basis of a brain activation map obtained from functional MR imaging. MATERIALS AND METHODS: The 3-dimensional activation MR images were processed by a statistical parametric mapping program (SPM99, The Wellcome Department of Cognitive Neurology, University College London, UK) and MRIcro software (www.mricro.com). The 3-dimensional images were first converted into 2-dimensional sectional images, and then overlapped with the corresponding T1-weighted images. Then, the image dataset was extended to -59 mm to 83 mm with a 2 mm slice-gap, giving 73 axial images. By using a pixel subtraction method, the differences in the R, G, B values between the T1-weighted images and the activation images were extracted, in order to produce black & white (B/W) differentiation images, in which each pixel is represented by 24-bit R, G, B true colors. Subsequently, another pixel differentiation method was applied to two template images, namely one functional and one anatomical index image, in order to generate functional and anatomical differentiation images containing regional brain activation information based on the Brodmann's and anatomical areas, respectively. In addition, the regional brain lateralization indices were automatically determined, in order to evaluate the hemispheric predominance, with the positive (+) and negative (-) indices showing left and right predominance, respectively. RESULTS: The manual counting method currently used is time consuming and has limited accuracy and reliability in the case of the activated cerebrocortical regions. The FALBA program we developed was 240 times faster than the manual counting method: -10 hours for manual accounting and -2.5 minutes for the FALBA program using a Pentium IV processor. Compared with the FALBA program, the manual quantification method showed an average error of 0.334+/-0.007 (%). Thus, the manual counting method gave less accurate quantitative information on brain activation than the FALBA program. CONCLUSION: The FALBA program is capable of providing accurate quantitative results, including the identification of the brain activation region and lateralization index with respect to the functional and anatomical areas. Also, the processing time was dramatically shortened in comparison with the manual counting method.

Qualitative and Quantitative Measurement of Brain Activity Associated with Visual Sexual Arousal in Males and Females: 3.0 Tesla Functional MR Imaging

PURPOSE: The present study utilized 3.0 Tesla functional MR imaging to identify and quantify the activated brain regions associated with visually evoked sexual arousal, and also to discriminate the gender differences between the cortical activation patterns in response to sexual stimuli. MATERIALS AND METHODS: A total of 24 healthy, right-handed volunteers, 14 males (mean age: 24) and 10 females (mean age: 23), with normal heterosexual function underwent functional MRI on a 3.0T MR scanner (Forte, Isole technique, Korea). The sexual stimulation consisted of a 1-minute rest with black screen, followed by a 3-minute stimulation by an erotic video film, and concluded with a 1-minute rest. The fMRI data was obtained from 20 slices (5 mm slice thickness, no gap) parallel to the AC-PC (anterior commissure and posterior commissure) line on the sagittal plane, giving a total of 2,100 images. The brain activation maps and the resulting quantification were analyzed by the statistical parametric mapping program, SPM 99. The mean-activated images were obtained from each individual activation map using one sampled t-test. The FALBA program, which is a new algorithm based on the pixel differentiation method, was used to identify and quantify the brain activation and lateralization indices with respect to the functional and anatomical terms. RESULTS: In both male and female volunteers, significant brain activation showed in the limbic areas of the parahippocampal gyrus, septal area, cingulate gyrus and thalamus. It is interesting to note that the septal areas gave a relatively lower activation ratio with high brain activities. On the contrary, the putamen, insula cortex, and corpus callosum gave a higher activation ratio with low brain activities. In particular, brain activation in the septal area, which was not reported in the previous fMRI studies under 1.5 Tesla, represents a distinct finding of this study using 3.0 T MR scanner. The overall lateralization index of activation shows left predominance (LI=35.3%) in the limbic system during sexual stimulation. The gender differences of brain activation in response to sexual arousal were characterized as follows. The activation area observed in males was the hypothalamus in the limbic system, whereas in females it was the cingulate gyrus, head of caudate nucleus, insula and corpus callosum. These findings reveal dissimilarities between males and females in neuronal responses to sexual arousal. As for the overall lateralization of activation in the limbic system, male volunteers gave a lateralization index that was greater than that of females by 300%. CONCLUSION: Our findings confirmed that neuroanatomical regions are associated with visually evoked sexual arousal and also with gender differences in response to sexual stimulation. Given that data from time-course traces of activation pattern and findings are observed by different stimuli, such as tactile and olfactory sense, it might be helpful to evaluate the neurophysiological mechanism for sexual arousal, and furthermore, to develop new diagnostic tools for sexual dysfunction and disorder.

Hepatic Enhancement on Gd-BOPTA-enhanced MR Imaging: Comparison between Cirrhotic and Normal Livers

PURPOSE: To compare the enhancement features of hepatic parenchyma between cirrhotic and normal liver, using Gd-BOPTA-enhanced delayed MR imaging. MATERIALS AND METHODS: The 60 patients (35 with cirrhotic and 25 with normal liver) included in our study underwent Gd-BOPTA-enhanced MR imaging using a 1.5T system with a phase-array multicoil. In all cases, T1-weighted in-phase and opposed-phase gradient-echo MR imaging was performed before and 60 minutes after intravenous administration of a bolus of Gd-BOPTA. All images were quantitatively analysed by comparing the signal-to-noise ratio (SNR) and signal enhancement (SE) of cirrhotic and normal liver before and after contrast enhancement, and in cirrhotic patients, SNR and SE were also compared in terms of the Child-Pugh classification. For qualitative analysis, the hepatic enhancement patterns of cirrhotic and normal liver were classified as homogeneous or heterogeneous according to the consensual findings of two radiologists. RESULTS: At contrast-enhanced imaging, both cirrhotic (p<0.001) and normal liver (p<0.001) showed substantially increased SNR relative to unenhanced images, and the SNR of cirrhotic liver was significantly lower than that of normal livers at both in-phase (p<0.001) and opposed-phase (p<0.001) imaging. The SE of cirrhotic liver was significantly lower than that of normal liver (in-phase: p=0.002; opposed phase: p=0.011). Both Child-Pugh class A (p<0.001) and B (p<0.001) cirrhotic liver showed a substantial increase in SNR at contrast-enhanced imaging relative to unenhanced imaging and the SNR of Child-Pugh class A was significantly higher than that of Child-Pugh class B at both in-phase (p<0.001) and opposed-phase (p=0.022) imaging. In addition, the SE of class A was significantly higher than that of class B at in-phase imaging (p=0.004). Cirrhotic liver showed heterogeneous enhancement in 20 of 35 patients (57%), whereas normal liver showed homogeneous enhancement in all patients. CONCLUSION: At Gd-BOPTA-enhanced delayed MR imaging, cirrhotic liver showed less enhancement than normal liver. In cirrhotic patients, hepatic enhancement and hepatic function decreased in tandem. Gd-BOPTAenhanced delayed MR imaging may be useful for evaluating the functional reserve of the liver.

Three-Dimensional Computed Tomographic Angiography with Volume Rendering Technique in the Evaluation of Intracranial Aneurysms: Comparison with Three-Dimensional Digital Subtraction Angiography

PURPOSE: The author compared three-dimensional computed tomographic angiography with combined volume rendering technique (3D-CTA VR) with three-dimensional digital subtraction angiography (3D-DSA) in the detection and characterization of intracranial aneurysms, in order to assess the diagnostic capability of 3D-CTA VR. MATERIALS AND METHODS: This study included 50 patients with suspected intracranial aneurysm who underwent both 3D-CTA VR and 3D-DSA, and who were subsequently confirmed as having aneurysms by intracranial operation or other neurointerventional procedures. The detectability and the characteristics of the aneurysms, such as their aneurysmal neck, direction, and vasospasm of the adjacent vessels, were evaluated retrospectively. RESULTS: Sixty-five intracranial aneurysms were detected through surgery or other interventional procedures. 3D-DSA was more sensitive (96.92%) than 3D-CTA VR in the detection of the aneurysms. All of the aneurysms that were more than 3mm in size were detected with both techniques. 3D-DSA failed to reveal one posterior communicating artery aneurysm, while 3D-CTA VR missed three aneurysms. The aneurysmal necks were clearly visualized in 58 of 61 aneurysms (95.1%) on 3D-CTA VR, but all of the aneurysmal necks(100%) were clearly identified on 3D-DSA. CONCLUSION: 3D-CTA combined with VR technique showed good sensitivity for the depiction of intracranial aneurysms greater than 3 mm in size, and its usefulness in characterizing the aneurysms for surgical or endovascular treatment planning was equal to or less than that of 3D-DSA.

Detection of Hemorrhagic Transformation in Patients with Acute Cerebral Infarction: Comparison of CT with T1WI, FLAIR, and Gradient-Echo MR Imaging

PURPOSE: To determine the diagnostic accuracy of T1-weighted, FLAIR, and GRE MR imagings in the detection of hemorrhagic transformation in patients with acute cerebral infarction and to compare it with CT. MATERAILS AND METHODS: Fifty-three patients with acute territorial cerebral infarction were studied prospectively. All patients underwent nonenhanced CT and MRI including the T1-weighted, FLAIR, and GRE. Lesion conspicuity of hemorrhage was scored as follows: 0-none; 1-suspicious; 2-sure. CT and MR imagings were reviewed two radiologists respectively. The mean value of the lesion conspicuity in each CT and MR sequences was compared by means of a Wilcoxon signed ranks test. The time intervals between CT and MR imagings ranged from 3 to 14 hours (mean; 7.6 hours). RESULTS: Hemorrhagic transformation was detected on nonenhanced CT in 26 of 53 patients. In the detection of hemorrhage in patients with acute cerebral infarction, T1-weighted and FLAIR MR imagings were inferior to NECT (p<0.05). By contrast, lesion conspicuity of GRE MR imaging was not different from that of CT (p=0.5). In addition, lesion conspicuity of GRE MR imaging was greater than that of CT in five patients on reader A and two patients on reader B. CONCLUSION: GRE MR imaging was superior to T1-weighted and FLAIR MR imagings, equal to nonenhanced CT in the detection of hemorrhagic transformation in patients with acute cerebral infarction.

The Usefulness of Perfusion CT in Acute Cerebral Ischemic Infarction

PURPOSE: To determine the usefulness of cerebral perfusion computed tomography (CT) in patients with acute cerebral ischemic infarction. MATERIALS AND METHODS: Twelve patients with acute middle cerebral artery infarction underwent conventional CT and cerebral perfusion CT within 25 hours of the onset of symptoms. For each patient, perfusion CT scans were obtained at the levels of the basal ganglia and 1 cm caudal to them. Using special imaging software, perfusion imaging maps for cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time to peak (TTP) were created, and the infarcted lesion was evaluated on each map. MTT and TTP delay times were measured in the perfusion defect lesion and symmetric contralateral normal cerebral hemisphere. Lesion size on each perfusion map was determined and compared with the value obtained by diffusionweighted MR imaging (DWMRI). RESULTS: In all patients, perfusion CT maps depicted the perfusion defect lesion, for which the MTT and TTP delay was remarkable. A comparison of lesion size between each perfusion map and DWMR images showed that the closest correlation involved CBF maps (8/12, 67%). On MTT maps, the lesion was larger than at DWMRI, suggesting that MTT mapping can be used to evaluate ischemic penumbra. CONCLUSION: Perfusion mapping facilitates the evaluation not only of the ischemic core and ischemic penumbra, but also of hemodynamic status in the area of the perfusion defect. This finding demonstrates that perfusion CT can be useful for the diagnosis and treatment of patients with acute cerebral ischemic infarction.

Assessment of Angiogenesis of Hepatic VX2 Carcinoma: Usefulness of Perfusion CT

PURPOSE: To investigate the perfusion characteristics of VX2 carcinoma and liver parenchyma in an animal model, and to evaluate the usefulness of perfusion CT in assessing the angiogenesis of hepatic VX2 carcinoma. MATERIALS AND METHODS: Ten rabbits (control, 5; VX2 carcinoma, 5) weighing 2.5 to 3.5 (average, 3.1) Kg were involved in this study. Between 7 and 14 days after implanting VX2 carcinoma, ultrasonography and CT were performed for the purpose of detecting this. Using the cine mode and involving four simultaneous sections, four perfusion CT images were obtained every second for 60 seconds. One radiologist measured the size of the region of interest (ROI) at each liver location, and using the time-density curves for each tumor and normal liver, semi-quantitative perfusion parameters -namely blood volume, mean transit time (MTT), blood flow, and time-to-peak enhancement-were determined. The microvascular densities (MVD) of VX2 tumors and normal liver were correlated with the perfusion CT findings. RESULTS: In the control group, there were no significant differences in perfusion parameters between the left and right hepatic lobes. In the VX2 carcinoma group, there were significant differences between the lobe containing the tumor and adjacent hepatic lobes with respect to blood volume (34.80 vs. 27.2 ml/100 g), MTT (14.1 vs. 19.4 sec), blood flow (119.7 vs. 84.3 ml/100 g/min), and time-to-peak (32.4 vs. 36.9 sec) (p<0.05). The blood volume (27.2 ml/100g) of the hepatic lobe with the VX2 tumor was higher than that of normal liver (22.8 ml/100 g) (p< 0.05), but blood flow (84.3 vs. 66.8 ml/100 g/min), MTT (19.4 vs. 21.3 sec) and time-to-peak (36.9 vs. 38.7 sec) values were not different. The MVD of VX2 tumors was higher than that of normal liver (p<0.05), and significantly higher than that of adjacent and contralateral liver (p<0.05). CONCLUSION: At perfusion CT, blood volume and blood flow of VX2 carcinomas increased more than those of normal liver, as were both mean transit time and time-to-peak. It was confirmed histopathologically that the angiogenesis of VX2 carcinoma was higher than that of normal liver. In conclusion, perfusion CT may be a practically useful diagnostic tool capable of reflecting the neoplastic angiogenesis of the liver.

The Change of Cerebral Metabolites in Patients with Parkinson's Disease Measured by Proton Magnetic Resonance Spectroscopy

BACKGROUND: Parkinson's disease is a progressive, common neuro-degenerative disorder of the extrapyramidal system leading to specific motor symptoms, but there is no specific early diagnostic tool. This study was aimed to investigate the change of cerebral metabolites in patients with parkinson's disease by 1H magnetic resonance spectroscopy (MRS). METHODS: Eighteen patients with idiopathic unilateral symptomatic parkinson's disease underwent MRS study to compare metabolites of basal ganglia and thalamus, in ipsilateral and contralateral to the clinically affected side. RESULTS: In patients with unilateral symptomatic parkinson's disease, N-acetyl aspartate (NAA)/Creatine (Cr) ratio was significantly lower in contralateral side to the clinically affected side than in ipsilateral side (p=0.023). Other cerebral metabolites (Cho, mI, alpha-Glx, beta-Glx, lactate, lipid) were showed no significant difference in patients with parkinson's disease. CONCLUSIONS: The comparison and quantification of cerebral metabolites by using MRS may be helpful to diagnosis and investigation of parkinson's disease.

Acute Cerebral Infarction in a Rabbit Model: Perfusion and Diffusion MR Imaging

PURPOSE: The present study was undertaken to evaluate the usefulness of cerebral diffusion (DWI) and perfusion MR imaging (PWI) in rabbit models with hyperacute cerebral ischemic infarction. MATERIALS AND METHODS: Experimental cerebral infarction were induced by direct injection of mixture of Histoacryl glue, lipiodol, and tungsten powder into the internal cerebral artery of 6 New-Zealand white rabbits, and they underwent conventional T1 and T2 weighted MR imaging, DWI, and PWI within 1 hour after the occlusion of internal cerebral artery. The PWI scan for each rabbit was obtained at the level of lateral ventricle and 1cm cranial to the basal ganglia. By postprocessing using special imaging software, perfusion images including cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) maps were obtained. The detection of infarcted lesion were evaluated on both perfusion maps and DWI. MTT difference time were measured in the perfusion defect lesion and symmetric contralateral normal cerebral hemisphere. RESULTS: In all rabbits, there was no abnormal signal intensity on T2WI. But on DWI, abnormal high signal intensity, suggesting cerebral infarction, were detected in all rabbits. PWI (rCBV, CBF, and MTT map) also showed perfusion defect in all rabbits. In four rabbits, the calculated square of perfusion defect in MTT map is larger than that of CBF map and in two rabbits, the calculated size of perfusion defect in MTT map and CBF map is same. Any rabbits do not show larger perfusion defect on CBF map than MTT map. In comparison between CBF map and DWI, 3 rabbits show larger square of lesion on CBF map than on DWI. The others shows same square of lesion on both technique. The size of lesion shown in 6 MTT map were larger than DWI. In three cases, the size of lesion shown in CBF map is equal to DWI. But these were smaller than MTT map. The calculated square of lesion in CBF map, equal to that of DWI and smaller than MTT map was three. And in one case, the calculated square of perfusion defect in MTT map was largest, and that of DWI was smallest. CONCLUSION: DWI and PWI may be useful in diagnosing hyperacute cerebral ischemic infarction and in evaluating the cerebral hemodynamics in the rabbits.

Functional MR Imaging Using BOLD Technique in Patients with Brain Tumors

PURPOSE: To reveal clinical usefulness of functional MRI (fMRI) using sensorymotor and language stimuli for demonstrating anatomic relationship between sensorimotor or language cortices and lesions in the planning of brain tumor surgery. MATERIALS AND METHODS: This study included 12 right-handed patients with brain tumors in or around sensorimotor or language cortices. Eleven patients were evaluated with primary motor and sensory stimuli. Of these patients, six patients were also evaluated with language stimuli. One patient was evaluated with language stimuli only. For fMR imaging, a 1.5T scanner was used and the EPI BOLD technique was employed. For postprocessing image, the SPM99 program and a program made by our department was utilized. We evaluated whether sensorimotor and language stimuli activate sensorimotor and language cortices. And also, clinical efficacy of revealing anatomic relationship between cerebral cortices and lesions for planning neurosurgical operation were evaluated. Finally, we compared post-operative neurologic function with pre-operative neurologic function in same patients. RESULTS: The fMRI examination was successful in identifying the functional cortices and depicting anatomic relationship between functional cortices and lesions in all patients. In nine patients of 11 patients with identified sensorimotor cortices, postoperative grade of manual motor test was not changed, compared with preoperative grade. Whereas postoperative improved than preoperative grade in one patient of remaining two patients, postoperative aggravated than preoperative grade in the other. This result was due to atherosclerotic lacunar infarction, regardless of tumor resection. Postoperative deficit of language function was not found in seven patients with identified language cortices. CONCLUSION: fMRI could be a helpful method for determining the best approach to neurosurgical treatment in patients with brain tumors in or around sensorimotor or language cortices.

Neural Mechanism of Implicit and Explicit Memory Retrieval: Functional MR Imaging

PURPOSE: To identify, using functional MR imaging, distinct cerebral centers and to evaluate the neural mechanism associated with implicit and explicit retrieval of words during conceptual processing. MATERIALS AND METHODS: Seven healthy volunteers aged 21-25 (mean, 22) years underwent BOLD-based fMR imaging using a 1.5T Signa Horizon Echospeed MR system. To activate the cerebral cortices, a series of tasks was performed as follows: the encoding of two-syllable words, and implicit and explicit retrieval of previously learned words during conceptual processing. The activation paradigm consisted of a cycle of alternating periods of 30 seconds of stimulation and 30 seconds of rest. Stimulation was accomplished by encoding eight twosyllable words and the retrieval of previously presented words, while the control condition was a white screen with a small fixed cross. During the tasks we acquired ten slices (6 mm slice thickness, 1 mm gap) parallel to the AC-PC line, and the resulting functional activation maps were reconstructed using a statistical parametric mapping program (SPM 99). RESULTS: A comparison of activation ratios (percentages), based on the number of volunteers, showed that activation of Rhs-35, PoCiG-23 and ICiG-26, 30 was associated with explicit retrieval only; other brain areas were activated during the performance of both implicit and explicit retrieval tasks. Activation ratios were higher for explicit tasks than for implicit; in the cingulate gyrus and temporal lobe they were 30% and 10% greater, respectively. During explicit retrieval, a distinct brain activation index (percentage) was seen in the temporal, parietal, and occipital lobe and cingulate gyrus, and PrCeG-4, Pr/PoCeG-43 in the frontal lobe. During implicit retrieval, on the other hand, activity was greater in the frontal lobe, including the areas of SCA-25, SFG/MFG-10, IFG-44, 45, OrbG-11, 47, SFG-6, 8, and MFG-9, 46. Overall, activation was lateralized mainly in the left hemisphere during both implicit and explicit retrieval tasks. For explicit retrieval, the lateralization index was more than twice as high as for implicit retrieval. CONCLUSION: Our findings indicate that there is neuro-anatomical dissociation between implicit and explicit retrieval of words during conceptual processing, suggesting, on the basis of cognitive neuroscience, that the performance of implicit and explicit memory-related tasks involves different mechanisms.