The Abnormality of Posterior Default Mode Network in Medication-Naive Attention-Deficit Hyperactivity Disorder Children : Resting State fMRI Study

OBJECTIVES: Characteristic symptoms, including hyperactivity and easy distractibility, in children with attention-deficit hyperactivity disorder (ADHD) suggest that their brain status, even at rest, might differ from that of healthy children. This study was conducted in order to determine whether resting state brain activity is compromised in medication-naive children with ADHD. METHODS: Twenty medication-naive children with ADHD (mean age 10.3+/-2.5) and 28 age- and gender-matched healthy volunteers (mean age 10.3+/-2.0) underwent measurements for resting state brain activity using functional magnetic resonance imaging (fMRI). Among resting state related-independent components (RSICs) extracted from fMRI data using independent component analysis, a significant difference in RSICs was observed between groups, using a mixed Gaussian/gamma model. RESULTS: Except for IQ, which was higher in the healthy control group, no demographic difference was observed between the two groups (p<.001). Significantly less activation of one RSIC, which includes the bilateral precuneus/posterior cingulate cortex, occipito-temporal junction, and anterior cingulate cortex, was observed in the ADHD group, compared with the control group (p<.05). CONCLUSION: An abnormal RSIC, posterior default mode network (DMN), was observed in the medication-naive ADHD group. Results of our study suggest that abnormality of posterior DMN is one of the main pathophysiologies of ADHD.

Measurement of Precuneal and Hippocampal Volumes Using Magnetic Resonance Volumetry in Alzheimer's Disease

BACKGROUND AND PURPOSE: Alzheimer's disease (AD) is associated with structural alterations in the medial temporal lobe (MTL) and functional alterations in the posterior cortical region, especially in the early stages. However, it is unclear what mechanisms underlie these regional discrepancies or whether the posterior cortical hypometabolism reflects disconnection from the MTL lesion or is the result of local pathology. The precuneus, an area of the posteromedial cortex that is involved in the early stages of AD, has recently received a great deal of attention in functional neuroimaging studies. To assess the relationship between the precuneus and hippocampus in AD, we investigated the volumes of these two areas using a magnetic resonance volumetric method. METHODS: Twenty-three subjects with AD and 14 healthy age-matched controls underwent T1-weighted three-dimensional volumetric brain magnetic resonance imaging. Volumetric measurements were performed in the precuneus and hippocampus. RESULTS: Compared to controls, AD patients exhibited a significant reduction in total precuneal volume, which was more prominent on the right side, and significant bilateral reductions in hippocampal volume. No correlation was found between the total volumes of the precuneus and hippocampus in the AD group. CONCLUSIONS: These results suggest that volumetric measurements of both the precuneus and hippocampus are useful radiological indices for the diagnosis of AD. Furthermore, the lack of correlation is attributable to local pathology rather than being a secondary consequence of MTL pathology.

Measurement of Precuneal and Hippocampal Volumes Using Magnetic Resonance Volumetry in Alzheimer's Disease

BACKGROUND AND PURPOSE: Alzheimer's disease (AD) is associated with structural alterations in the medial temporal lobe (MTL) and functional alterations in the posterior cortical region, especially in the early stages. However, it is unclear what mechanisms underlie these regional discrepancies or whether the posterior cortical hypometabolism reflects disconnection from the MTL lesion or is the result of local pathology. The precuneus, an area of the posteromedial cortex that is involved in the early stages of AD, has recently received a great deal of attention in functional neuroimaging studies. To assess the relationship between the precuneus and hippocampus in AD, we investigated the volumes of these two areas using a magnetic resonance volumetric method. METHODS: Twenty-three subjects with AD and 14 healthy age-matched controls underwent T1-weighted three-dimensional volumetric brain magnetic resonance imaging. Volumetric measurements were performed in the precuneus and hippocampus. RESULTS: Compared to controls, AD patients exhibited a significant reduction in total precuneal volume, which was more prominent on the right side, and significant bilateral reductions in hippocampal volume. No correlation was found between the total volumes of the precuneus and hippocampus in the AD group. CONCLUSIONS: These results suggest that volumetric measurements of both the precuneus and hippocampus are useful radiological indices for the diagnosis of AD. Furthermore, the lack of correlation is attributable to local pathology rather than being a secondary consequence of MTL pathology.

Occipito-Temporal Connectivity in Medication-Naive ADHD Children: Preliminary Diffusion Tensor Imaging Study / 신경정신의학

OBJECTIVES: Occipito-temporal connectivity was explored using diffuse tensor imaging (DTI) and its correlation to behavioral symptoms and neurocognitive functions in medication-naive attentiondeficit/hyperactivity disorder (ADHD) children and adolescents. METHODS: Eleven medication-naive children and adolescents with ADHD (mean age 11.5+/-.3) and 9 age- and gender-matched healthy volunteers (mean age 11.4+/-2.5) were measured for mean fractional anisotropy (FA) values with DTI and clinical assessments. The FA values for the region of interest (ROI) which contained both inferior longitudinal fasciculus (ILF) and inferior occipito-frontal fasciculus (IOFF), were compared in ADHD and gender- and age-matched healthy control groups and the relationship between clinical and neurocognitive variables was explored. RESULTS: The ADHD group exhibited significantly higher scores on the Korean ADHD Rating Scale (p<0.001), the Korean Conners Parent Rating Scale (p<0.001), the computerized Continuous Performance Test, and the Visual (omission error, commission error, mean time, and variability)(p<0.01), and significantly decreased scores on the Finger Window Test (p<0.01). Mean FA values from the left-side ROI were significantly lower in the ADHD group compared with healthy controls after controlling for age (p<0.05). In the ADHD group, FA values from the left-side of the ROI did not show significant correlation with clinical rating or neurocognitive tests. CONCLUSION: Our results suggest that one of the core pathophysiology hallmarks in child ADHD may be abnormal anatomical connectivity in the occipito-frontal and/or occipito-temporal pathway, both of which are related to visual information processing. To confirm such an anatomical deficit and its association with clinical or neurocognitive symptoms in ADHD, further studies using larger sample sizes are needed.

The Effect of Imaging Parameters of Diffusion Tensor Imaging on Fractional Anisotropy

PURPOSE: To evaluate the effect of changes of parameters of diffusion tensor imaging (DTI), including slice thickness/slice number, b-value and the direction number of a diffusion gradient on fractional anisotropy (FA). MATERIALS AND METHODS: Three groups of normal volunteers underwent brain diffusion tensor imaging with the use of three different imaging parameters as follows: a different slice thickness/slice number (6 mm/20 slices and 2.33 mm/54 slices), a different b-value (800 s/mm2/1000 s/mm2) and a different number of directions of the diffusion gradient (6 and 15 directions). The signal to noise ratio (SNR) and FA were measured by a ROI measurement at the anterior corona radiata, superior corona radiata, putamen and corpus callosum. We compared the mean SNR and FA in each group by the use of the paired T-test. RESULTS: The SNR decreased and the FA increased significantly according to the increase of the slice number (6 mm/20 slices vs. 2.33 mm/54 slices). The SNR of DTI with 15 diffusion gradient directions was significantly higher than DTI with six directions, without a difference of FA. There were no significant changes of the SNR and FA of DTI according to the b-value. CONCLUSION: It is essential and useful in the clinical application of DTI to understand the effect of imaging parameters on FA.

Brain Diffusion Tensor MR Imaging

The development of MR imaging techniques during the past decade has enabled researchers to use MR imaging as a noninvasive tool for evaluating structural and physiologic states in biologic tissues by measuring the diffusion process of water molecules. More recently, diffusion tensor MR imaging (DTI) technique based on the dependency of molecular diffusion on the orientation of white matter fiber tracts has been used to analyze the trajectory, shape, fiber structure, location, topology and connectivity of neuronal fiber pathways in living humans. Numerous efforts have been made by MR physicists, brain scientists, and medical doctors to advance MR techniques and computer-based algorithms which result in more accurate quantification of diffusion tensor and the generation of white matter fiber tract maps and to determine the pathophysiology of brain disease by DTI and useful clinical applications of DTI. In this article, we describe the tensor theory used to characterize molecular diffusion in white matter and a process of measuring tensor elements using diffusion-sensitive MR images to fiber mapping. We then provide review of current literature and some clinical examples that have been published and are on-going.

Focal Organizing Pneumonia: CT and Pathologic Findings

The purpose of this study was to describe the CT findings of focal organizing pneumonia and to compare the findings with pathology. CT findings of histologically proven focal organizing pneumonias in 26 consecutive patients were analyzed. In 17 patients who had undergone surgical resections, the findings were correlated with pathology. Focal organizing pneumonias appeared as a nodule (n= 13) or a mass (n=13), ranging from 9 mm to 66 mm in diameter. Ground-glass opacity was seen in 6/13 (46%) nodules and 6.5/13 (50%) masses (k=.48) with an extent ranging from 5% to 75% (mean, 16%). In 4/26 (15%) patients, the extent was more than 50% of the lesion. They showed smooth (n=4), lobulated (n=8), spiculated (n=1), or lobulated and spiculated margin (n=13). On correlative analysis, nodule or mass on CT consisted histologically of intraalveolar exudate or microabscess, chronic inflammatory cell infiltration, fibrotic nodules, and polypoid granulation tissue in the alveolar or bronchiolar spaces. Ground-glass opacity consisted of interstitial fibrosis and chronic inflammatory cell infiltration and intraalveolar polypoid granulation tissue. Focal organizing pneumonia may simulate a lung cancer with variable appearances on CT and the findings reflect underlying histopathology of the disease.

Esophageal Leiomyoma: Radiologic Findings in 12 Patients

OBJECTIVE: The aim of our study was to describe and compare the radiologic findings of esophageal leiomyomas. MATERIALS AND METHODS: The chest radiographic (n = 12), esophagographic (n = 12), CT (n = 12), and MR (n = 1) findings of surgically proven esophageal leiomyomas in 12 consecutive patients [ten men and two women aged 34 - 47 (mean, 39) years] were retrospectively reviewed. RESULTS: The tumors, surgical specimens of which ranged from 9 to 90 mm in diameter, were located in the upper (n = 1), middle (n = 5), or lower esophagus (n = 6). In ten of the 12 patients, chest radiography revealed the tumors as mediastinal masses. Esophagography showed them as eccentric, smoothly elevated filling defects in 11 patients and a multilobulated encircling filling defect in one. In 11 of the 12 patients, enhanced CT scans revealed a smooth (n = 9) or lobulated (n = 2) tumor margin, and attenuation was homogeneously low (n = 7) or iso (n = 4). In one patient, the tumor signal seen on T2-weighted MR images was slightly high. CONCLUSION: Esophageal leiomyomas, located mainly in the middle or distal esophagus, are consistently shown by esophagography to be mainly eccentrically elevated filling defects and at CT, lesions showing homogeneous low or isoattenuation are demonstrated.

Basic Understanding of High-Resolution CT

No abstract available.

MR Findings of Cyclosporine Neurotoxicity

PURPOSE: To analyze the MR findings of cyclosporine-induced neurotoxicity in patients receiving high dose ofcyclosporine and to suggest the possible pathogenetic mechanism. MATERIALS AND METHODS: The cases of seven patients (2 males, 5 females ; 18-36 years old) who suffered seizures after receiving high-dose cyclosporine for bone marrow transplantation due to diseases such as a plastic anemia or leukemia were retrospectively reviewed. We evaluated the location and pattern of abnormal signal intensity seen on T2 weighted images, the presence of contrast enhancement, and the changes seen on follow-up MR performed at intervals of 12-30 days after initial MR in five of seven patients. We analyzed levels of blood cyclosporine and magnesium, and investigated the presence of hypertension at the site of the seizure. RESULTS: Locations of the lesions were bilateral(n=5),unilateral(n=2), parietal(n=6), occipital(n=6), temporal(n=4), and in the frontal lobe(n=3). Frontal lesions showed high signal intensities in the borderline ischemic zone of the frontal lobe between the territory of the anterior and middle cerebral arteries. In six of the seven patients, cortical and subcortical areas including subcortical U-fibers were seen on T2-weighted images to be involved in the parietooccipital lobes. Only one of the seven showed high signal intensity in the left basal ganglia. All lesions showed high signal intensity onT2-weighted images, and iso to low signal intensity on T1-weighted. In five of seven patients there was nodefinite enhancement, but in the other two, enhancement was slight. In four of seven patients seizures occurred within high therapeutic ranges (250 - 450 ng/ml), while others suffered such attacks at levels below the therapeutic range. After cyclospirine was administered at a reduced dosage or stopped, follow-up MR images showed the complete or near-total disappearance of the abnormal findings previously described. Only two patients had hypertension, and the others normotension. Five of the seven had hypomagnesemia(1.3 -1.74 mg/dl; N : 1.9 -3.1mg/dl). CONCLUSION: Most patients with cyclosporine neurotoxicity showed high signal intensity in the corticaland subcortical areas of the parietooccipital lobes, including subcortical U-fiber, as seen on T2 weighted images,and no abnormal enhancement after Gd-DTPA injection. These MR findings should be helpful for the diagnosis of cyclosporine neurotoxicity.

Radiologic Placement of Tunneled Central Venous Catheter

PURPOSE: To evaluate the efficacy and safety of fluoroscopy-guided, radiologic placement of a tunneled central venous catheter into the superior vena cava (SVC). MATERIALS AND METHODS: Thirty five patients underwent tunneled central venous catheter placement to facilitate long-term chemotherapy. They included 33 leukemicpatients, one colon cancer patient, and one multiple myeloma patient. After confirming central venous patency witha injection of contrast media via the peripheral cephalic or basilic vein in the wrist joint, the subclavian veinwas punctured under fluoroscopic guidance. A 7F double lumen TPN catheter was placed into the SVC through asubcutaneous tunnel in the anterior chest wall. RESULTS: Catheter placements were successful in all patients. The mean procedure time was 17.2 minutes, mean fluoroscopy time was 1.3 minutes, mean number of punctures was 1.4, and mean volume of injected contrast media was 43.5 cc. Only two of all leukemic patients developed mild hematomas atthe puncture site, but these soon resolved themselves. None of the patients developed pneumothorax or hemothorax.but late complications included local infection in two patients (6%) and thrombotic occlusion of the catheter inone (3%). The occluded catheter was successfully recanalized with Urokinase infusion. CONCLUSION: Fluoroscopy-guided, radiologic placement of a tunneled central venous catheter is an easy and safe method, anduseful for patients requiring long-term venous access.

Marrow Pattern in the Proximal Femoral Metaphysis of Patients with Osteonecrosis of Femoral Head and Normal Subjects: Comparison on MR Images

PURPOSE: To predict early risk of osteonecrosis of the femoral head by comparison of the bone marrow pattern of the proximal femoral metaphysis(PFM) in normal subjects and patients with osteonecrosis of the femoral head on T1-weighted magnetic resonance (MR) images. MATERIALS AND METHODS: The authors retrospectively reviewed T1 (TR525/TE 25 msec) weighted coronal MR images of 67 hips with osteonecrosis and 65 normal hips in 39 patients with osteonecrosis of the femoral head and in 27 normal subjects. On the basis of bright signal intensity of fat, the proportion of remaining hematopoietic marrow in PFM was subdivided into 4 grades (0 to 3) by two radiologists. No evidence of remaining hematopoietic marrow was assigned grade 0, and grades 1, 2 and 3 represented scanty, moderate, and prominent hematopoietic marrow, respectively. Grades 0 and 1 were collectively defined as "predominantly fatty", grades 2 and 3 as "predominantly hematopoietic". The frequency of the predominantly fatty marrow in PFM was analyzed in relation to three age groups(<25,25-50,50<) and both sexes. RESULTS: The overall frequency of predominantly fatty marro in PFM was higher in hips with osteonecrosis than in normal hips (p<0.001). Especially in the male population under the age of 50, the frequency was apparently higher in hips with osteonecrosis, compared with normal hips (p<0.001). However, the male population aged over 50 or female population showed no statistically significant difference in our series. CONCLUSION: In proximal femoral metaphysis with osteonecrosis of the femoral head, fatty marrow conversion occurs apparently earlier than in normal subject. T1-weighted MR imaging could therefore be useful in predictiong early risk of osteonecrosis of the femoral head because of early fatty marrow conversion of the proximal femoral metaphysis.