Biomedical subjects

M H Han

Publications and source records attributed to M H Han.

At least 19 recordsLinked to original sources

PubMed1999

Intracranial germinomas: correlation of imaging findings with tumor response to radiation therapy.

OBJECTIVE: The purpose of this study was to correlate imaging characteristics of intracranial germinomas with response to radiation therapy. MATERIALS AND METHODS: Using tumor size at the completion of irradiation, we classified 23 patients with histologically proven germinomas in the pineal gland (n = 6), the suprasellar region (n = 7), and the basal ganglia (n = 10) into two groups: excellent response group (n = 14) and good response group (n = 9). Excellent response was defined as complete resolution or residual tumor less than 1.0 cm in diameter, and good response was defined as residual tumor of 1.0-3.0 cm in diameter. CT (n = 53) and MR (n = 32) images obtained before, during, and after radiation therapy were retrospectively analyzed with particular attention to the location, size, presence of cystic change, and CSF seeding of the tumors. RESULTS: In all 23 patients, the tumors decreased 85-100% in size at the completion of irradiation with 40-56 Gy. A significant factor in the different responses to irradiation between patients in the excellent and good response groups was cystic change of the tumor. Tumors with cystic components responded more slowly and had larger residual lesions than did tumors without cystic components (p < .01). In eight of 12 cystic tumors, the cystic portion of the tumor responded more slowly than did the solid portion and remained visible on imaging 6-12 months after irradiation. We found no significant differences between the two groups in location, size, and CSF seeding of tumors. In 12 patients with residual lesions at the completion of irradiation, the tumors proceeded to resolve after completion of treatment. CONCLUSION: In our study, tumor response to radiation therapy correlated negatively with the presence of a cystic region.

Adolescent↗

PubMed1999

Comparison of MR imaging with PET and ictal SPECT in 118 patients with intractable epilepsy.

BACKGROUND AND PURPOSE: MR imaging, PET, and ictal SPECT have been studied extensively as individual techniques in the localization of epileptogenic foci, but only a few comparative studies have been done. We evaluated the concordance rates of ictal video/EEG, MR imaging, PET, and ictal SPECT to compare the sensitivities of these imaging methods in the lateralization of epileptogenic foci. METHODS: The study included 118 consecutive patients who underwent surgery for medically intractable epilepsy and who were followed up for 12 months or more. MR imaging was compared retrospectively with ictal video/EEG, FDG-PET, ictal 99mTc-HMPAO SPECT, and invasive EEG as to their ability to localize the epileptogenic focus; the pathologic findings served as the standard of reference. RESULTS: MR imaging was concordant with video/EEG, PET, and ictal SPECT in 58%, 68%, and 58% of patients, respectively. With the pathologic diagnosis as the standard of reference, MR imaging, PET, and ictal SPECT correctly lateralized the lesion in 72%, 85%, and 73% of patients, respectively. Of the patients with good outcomes, MR imaging, PET, and ictal SPECT were correct in 77%, 86%, and 78%, respectively. In the good outcome group, MR imaging was concordant with PET and ictal SPECT in 73% and 62% of patients, respectively. Of 45 patients who underwent invasive EEG, MR imaging was concordant with the invasive study in 47%; PET in 58%; and ictal SPECT in 56%. Of 26 patients with normal MR findings, PET and ictal SPECT correctly lateralized the lesion in 80% and 55%, respectively. CONCLUSION: Overall concordance among the techniques is approximately two thirds or less in lateralizing epileptogenic foci. PET is the most sensitive, even though it provides a broad approximate nature of the epileptogenic zone, which is not adequate for precise surgical localization of epilepsy. PET and/or ictal SPECT may be used as complementary tools in cases of inconclusive lateralization with ictal video/EEG and MR imaging.

Adolescent↗

PubMed1999

Focal lesion in the splenium of the corpus callosum in epileptic patients: antiepileptic drug toxicity?

BACKGROUND AND PURPOSE: Discrete focal lesions in the splenium of the corpus callosum on MR images in epileptic patients have received little attention in the literature. Our purpose was to describe these lesions, which may be related to the toxicity of antiepileptic drugs (AEDs), and to discuss the possible mechanisms of their development. METHODS: We examined six patients with epilepsy whose brain MR imaging findings showed a discrete focal nonhemorrhagic lesion in the splenium of the corpus callosum. The medical records and MR images were reviewed retrospectively with respect to the patients' clinical history, medication, and laboratory findings to determine the etiology of the lesion. RESULTS: In all six patients MR imaging showed a focal lesion in the splenium of the corpus callosum, which was ovoid in shape and 15 to 19 mm in size. In the three patients who received contrast material, there was no enhancement of the lesion. Four of six patients had a history of medication with dilantin, in two of whom the level of serum dilantin was found to be elevated (22.3 micrograms/mL and 70.4 micrograms/mL, respectively). Vigabatrin was administered in three patients, one of whom took dilantin together with vigabatrin. In two patients, the focal lesion in the corpus callosum disappeared on follow-up MR images after withdrawal of dilantin and/or vigabatrin. CONCLUSION: A discrete, focal, ovoid, nonhemorrhagic lesion in the splenium of the corpus callosum may be seen on brain MR images of patients with epilepsy. The lesion is considered to be reversible demyelination related to AEDs toxicity.

Adult↗

PubMed1998

Profiling expression patterns and isolating differentially expressed genes by cDNA microarray system with colorimetry detection.

A high-density cDNA microarray with colorimetry detection system to simultaneously monitor the expression of many genes on nylon membrane is described and characterized. To quantify the expression of genes and to isolate differentially expressed genes, the southern hybridization process on filter membranes was employed. The levels of gene expression were represented by color intensities generated by colorimetric reactions in place of hazardous radioisotopes or costly laser-induced fluorescence detection. The gene expression patterns on nylon membranes were digitized by devices such as an economical flatbed scanner or a digital camera. The quantitative information of gene expression was retrieved by image analysis software. Quantitative comparison of the northern dot-blotting method with the microarray system is described. Applications employing single-color detection as well as dual-color detection to isolate differentially expressed genes among thousands of genes are demonstrated.

Blotting, Northern↗

PubMed1998

Cloning of a phosphatidic acid-preferring phospholipase A1 from bovine testis.

We report the molecular cloning and expression of a phosphatidic acid-preferring phospholipase A1 from bovine testis. The open reading frame encoded an 875-amino acid protein with a calculated molecular mass of 97,576 daltons and a pI of 5.61. The sequence included a region similar to a lipase consensus sequence containing the putative active site serine and also included a potential, coiled-coil-forming region. Expression of the open reading frame in COS1 cells resulted in a 20-44-fold increase in phosphatidic acid phospholipase A1 activity over that of control cells. Mutation of the putative active site serine (amino acid 540) demonstrated that it was essential for this increase in enzyme activity. Northern blot analysis revealed at least five different messages with the highest overall message levels in mature testis, but detectable message in all tissues examined. Two possible alternately spliced regions in the open reading frame also were identified. Finally, a search of the data base identified six related proteins: a potential counterpart of the phospholipase A1 in Caenorhabditis elegans, two putative lipases in yeast, and three proteins separately encoded by the Drosophila retinal degeneration B gene and its mouse and human homologues.

Amino Acid Sequence↗

PubMed1998

MRI features of choroid plexitis.

Four cases of choroid plexitis of the brain (two with cryptococcosis and two with tuberculosis) are presented. The four patients showed either unilateral enlargement (3) or bilateral enlargement (1) and dense enhancement of the choroid plexus in the lateral ventricles (4) and fourth ventricle (1) in association with clinical findings of leptomeningitis. All patients had unilateral cystic dilatation of the temporal horn of the lateral ventricle presumably secondary to entrapment of the temporal horn and extensive oedema around the ipsilateral ventricle.

Adolescent↗

PubMed1998

A brain MRI study in subjects with borderline personality disorder.

BACKGROUND: There have been only a few brain computed tomography imaging studies, with mostly negative findings, in subjects with borderline personality disorder (BPD). This is the first MRI study which evaluated the structural abnormalities of the brain in subjects with the sole diagnosis of BPD. METHODS: Twenty-five subjects with BPD were compared with age-, gender-matched healthy comparison subjects (n=25) on volumes of the frontal lobes, the temporal lobes, the lateral ventricles, and the cerebral hemispheres in brain magnetic resonance imaging. RESULTS: Subjects with BPD had a significantly smaller frontal lobe compared to comparison subjects (multivariate regression analysis, t=2.225, df=46, P=0.031). There were no significant differences in volumes of the temporal lobes, the lateral ventricles, and the cerebral hemispheres between subjects with and without BPD. LIMITATIONS: Strict inclusion and exclusion criteria employed in the present study may make it difficult to generalize our findings. The gray matter and white matter of the brain were not measured separately. Differences in head tilt during image acquisition were not corrected. CONCLUSIONS: The current study reports a smaller frontal lobe volume on brain MRI in subjects with BPD compared with healthy comparison subjects. This finding may serve as a potentially useful biological variable that may allow for subtyping BPD.

Adolescent↗

PubMed1998

The significance of CT scan or MRI in the evaluation of salivary gland tumors.

Imaging modalities such as CT scan or MRI are frequently employed for the diagnosis of neoplastic lesions in the salivary glands. To evaluate the efficacy of the CT scan and the MRI in differentiating malignant neoplasm from benign lesions, 120 CT scans and 31 MRIs were retrospectively analyzed from 147 patients with salivary gland masses. All images were analyzed focusing on the presence of several relevant features. The pathologic results were matched with radiological features and also tabulated with radiological assessment. For the CT scans, the contour and margin of the lesion and tissue plane obliteration were found to be statistically significant indicators for malignant neoplasms. Among 69 CT scans interpreted as 'benign' by a radiologist, five cases (7%) were histologically diagnosed as 'malignant'. On the other hand, 20 out of 51 CT scans (39%) were misinterpreted as 'malignant'. For MRI, two out of 14 cases (14%) were radiologically misdiagnosed as 'benign' and six out of 17 patients (35%) as 'malignant'. In conclusion, whereas both the CT and MRI showed a similar level of accuracy in evaluation of salivary gland tumors, they showed a considerable tendency of misdiagnosis, especially by interpreting benign tumors as 'malignant'.

Biopsy↗

PubMed1998

Half-dose gadolinium-enhanced MR imaging with magnetization transfer technique in brain tumors: comparison with conventional contrast-enhanced MR imaging.

OBJECTIVE: The purpose of this study was to determine whether half-dose enhanced MR imaging with magnetization transfer (MT) saturation can replace standard-dose enhanced MR imaging without MT saturation in patients who have brain tumors. SUBJECTS AND METHODS: Three sets of enhanced T1-weighted MR images were prospectively obtained for each of 25 patients with 32 brain tumors; the first conventional MR images without MT were obtained after administration of standard-dose (0.1-mmol/kg) gadopentetate dimeglumine. Within 1 week, patients underwent administration of one half-dose (0.05 mmol/kg) of the contrast medium, and then two sets of enhanced T1-weighted images were obtained with and then without MT. The degree of contrast enhancement was assessed qualitatively for all 32 tumors and quantitatively for 26 tumors. In the quantitative analysis, we compared mean values for tumor-brain contrast-to-noise ratios in three sets of images. RESULTS: The visual conspicuity of enhancing lesions in half-dose T1-weighted MR images with MT was comparable with that of standard-dose conventional T1-weighted MR images in 43% of cases including most extraaxial tumors. In approximately 75% of cases, the degree of enhancement of the lesions was similar for half-dose T1-weighted images obtained with and without MT. Overall, mean values for tumor-brain contrast-to-noise ratios were significantly lower in half-dose T1-weighted images with MT than in standard-dose T1-weighted images. Also, mean values for tumor-brain contrast-to-noise ratios were significantly higher in half-dose T1-weighted images with MT than in half-dose T1-weighted images without MT. CONCLUSION: Because half-dose enhanced MR imaging with MT yields enhancement comparable with that of standard-dose enhanced conventional MR imaging in less than 50% of cases, the former technique would replace the latter in only limited cases such as selected extraaxial tumors.

Adult↗

PubMed1998

Brain abscess and necrotic or cystic brain tumor: discrimination with signal intensity on diffusion-weighted MR imaging.

OBJECTIVE: The purpose of this study was to determine the differences in signal intensity between brain abscesses and necrotic or cystic tumors on diffusion-weighted MR imaging. CONCLUSION: Five consecutive patients with proven brain abscesses and four patients with proven cystic or necrotic brain tumors were prospectively evaluated with diffusion-weighted imaging. On diffusion-weighted imaging, brain abscesses showed markedly hyperintense signal in all five patients, whereas necrotic or cystic brain tumors revealed hypointense signal in all four patients. Diffusion-weighted imaging may allow the differentiation of brain abscess from necrotic or cystic brain tumor.

Adolescent↗

PubMed1998

In vivo single-voxel proton MR spectroscopy in intracranial cystic masses.

PURPOSE: Our objective was to evaluate the proton MR spectroscopic pattern of the cystic contents of various intracranial masses and to report characteristic spectral patterns that may be helpful in the differential diagnosis of these lesions. METHODS: We evaluated 40 proton MR spectra obtained from cystic contents of various intracranial cystic masses in 39 patients, including gliomas (n = 14), metastases (n = 3), abscesses (n = 8), cysticercosis (n = 4), epidermoids (n = 3), and others (n = 7). Proton MR spectroscopy was performed on a 1.5-T MR unit using a point-resolved spectroscopic sequence with a 2 x 2 x 2 cm3 volume of interest. Assignment of the resonance peaks was based on previous studies. RESULTS: Adequate proton MR spectroscopic data were obtained in 35 cases (88%). In most gliomas and metastases, only a lactate resonance was observed. There was a trend toward a higher lactate peak in high-grade gliomas. A few tumors, including malignant gliomas and metastases, showed lipid signal combined with lactate signal. In abscesses, there were various combinations of lactate, acetate, succinate, amino acids (including valine, alanine, and/or leucine), and/or unassigned resonances. In cysticercosis, resonances of lactate, succinate, alanine, acetate, and/or unassigned resonances were observed. Three epidermoid cysts showed only lactate signal. There were no identifiable resonances from the arachnoid and porencephalic cysts. CONCLUSION: Only lactate is commonly observed in a variety of intracranial cystic masses, except for abscess and cysticercosis, in which resonances of acetate, succinate, amino acids, and/or unassigned metabolites can be seen in addition to a lactate peak.

Adult↗

PubMed1998

MR of hippocampal sclerosis: comparison of qualitative and quantitative assessments.

PURPOSE: Our goal was to compare the diagnostic accuracy of subjective visual assessment versus MR volumetry in evaluating hippocampal sclerosis and to determine whether MR volumetry is needed in the lateralization of this disease process. METHODS: MR imaging findings were studied retrospectively in 48 patients who underwent surgery for temporal lobe epilepsy and were compared with findings at MR volumetry on an Allegro workstation. Both visual assessment and volumetry were carried out in a blinded fashion with oblique coronal T1-weighted three-dimensional MP-RAGE images obtained on either 1.0-T or 1.5-T units. Normal right-left volumetric differences were recorded in 30 control subjects. The optimum cutoff threshold value for right-left volumetric differences in the sensitivity and specificity of volumetric measurement was obtained from receiver operating characteristic analysis. RESULTS: Sensitivity, specificity, positive and negative predictive values, and accuracy of visual assessment were 86%, 83%, 86%, 83%, and 85%, respectively. For MR volumetry, with the optimum cutoff threshold value of right-left difference at 0.3 cm3, sensitivity, specificity, positive and negative predictive values, and accuracy were 81%, 82%, 87%, 83%, and 85%, respectively. CONCLUSION: Visual assessment was slightly superior to or similar to MR volumetry in assessing unilateral hippocampal sclerosis. MR volumetry of the hippocampus may not be needed for the evaluation of most cases of suspected hippocampal sclerosis.

Adolescent↗

PubMed1997

A novel variant of staphylokinase gene from Staphylococcus aureus ATCC 29213.

The processes of hemostasis and thrombolysis are elegantly regulated in order to ensure normal functions of vascular system. A search for new plasminogen activators as thrombolytic agents has been carried out for the purpose of clinical applications to modulate thrombolytic processes. In the current work, several strains and clinical isolates of Staphylococcus aureus were screened for the fibrinolytic activity. The DNA sequences of staphylokinase gene in the strains expressing 15 kDa protein with staphylokinase activity were determined and subsequently compared with three known staphylokinase gene sequences. From the sequence comparison a new variant of staphylokinase gene has been identified in ATCC 29213 strain. The gene product needs to be further characterized and tested for the therapeutic potential.

Amino Acid Sequence↗

PubMed1997

Desensitizing GABAC receptors on carp retinal bipolar cells.

Bicuculline- and baclofen-insensitive GABA receptors (GABAC receptors) on bipolar cells acutely dissociated from carp retina were investigated with using the whole-cell patch-clamp recording technique. The currents of these cells mediated by GABAC receptors showed striking desensitization, even at low concentrations of GABA. Both the time constant tau of the GABAC current decay and the extent of desensitization were significantly different from that of GABAC receptors previously observed in other retinas and elsewhere in the CNS, suggesting that the GABAC receptors of carp bipolar cells might be distinct in intracellular mechanisms and subunit composition.

Animals↗

PubMed1997

Re-evaluation of optimal dose of contrast medium for vascular enhancement in CT of the head and neck.

Adequate contrast enhancement of major neck vessels is more important than that of a tumour itself in CT of most head and neck tumours because of differentiation from neck node metastases. Our purpose was to re-evaluate the dosage of contrast medium for adequate vascular enhancement in CT of the head and neck. In a blind prospective fashion, 60 patients with a variety of head and neck lesions were randomised into three equal groups receiving 0.75, 1.0, or 1.25 ml/kg of meglumine ioglycate, 300 mg/ml. Contrast medium was administered by injector at 2 ml/s. The scan time and interscan delay were each 1 s, and total scan time 50-180 s. The scan was started immediately after administration of two-thirds of the contrast medium. The degree of vascular enhancement was assessed visually and quantitatively. We visually scored the degree of vascular enhancement as excellent (4 points), good (3), fair (2) or poor (1). For quantitative study, after measuring the CT numbers of the common or internal carotid artery (CA), internal jugular vein (IJV) and adjacent muscle at three levels, were calculated mean vessel/muscle contrast ratios. The degree of enhancement of the CA and IJV tended to increase with dose of the contrast media, but no examination was rated as showing poor enhancement in any group. The mean visual assessment scores for 0.75, 1.0, and 1.25 ml/kg were 2.7, 2.9 and 3.1, respectively; the mean ICA/muscle contrast ratios were 1.58, 1.55 and 1.63, and those of IJV/ muscle 1.65, 1.59 and 1.59. There was no significant difference between visual and quantitative assessment in any group. The results suggest that 0.75 ml/kg of contrast medium appears sufficient for vascular opacification for head and neck lesions when the CT scan can be completed in about 120 s.

Adolescent↗

PubMed1997

An experimental study of embolic effect according to infusion rate and concentration of suspension in transarterial particulate embolization.

RATIONALE AND OBJECTIVES: The authors evaluate the embolic effect according to infusion rate and concentration of particulate suspension, focusing on arterial occlusion level. METHODS: The renal arteries of 14 rabbits were embolized with 150 to 250 microns polyvinyl alcohol (PVA) particles, divided into four groups according to two different infusion rates (1 mg/second and 0.1 mg/second) and two different concentrations of suspension (10 mg/mL and 2.5 mg/mL). Arteriograms obtained immediately and a week after embolization were assessed for occlusion level. For the nephrograms obtained a week after embolization, the opacifying areas were graded from 0 to 4. Median coronal sections of each kidney specimen were investigated for the presence of peripheral infarct grossly and for the presence of PVA particles in the small artery microscopically. RESULTS: Arteriograms showed various occlusion levels. Using a 0 to 4 grading system, the opacifying area of the nephrogram obtained 1 week after embolization was noted to be smaller in the low infusion rate group (P < 0.05). In gross and microscopic pathologic examination, the number of cases with peripheral infarct or PVA particles in the small artery (< 300 microns) was greater in the group with the low infusion rate and low concentration (P < 0.05). CONCLUSIONS: In transarterial particulate embolization, slower infusion of more diluted suspension provides for a more distal arterial occlusion.

Animals↗

PubMed1997

Fibrosing inflammatory pseudotumors of the central skull base.

The most important step in the differential diagnosis of mass lesions of the central skull base is to rule out malignant neoplasms. However, nonneoplastic lesions, such as infections or nonspecific inflammatory lesions of the skull base, can mimic malignant processes. In this study, the authors analyzed seven cases of nonneoplastic noninfectious mass-forming lesions involving the central skull base. In most cases, malignant processes were suspected at the initial phase of diagnostic work-up, but subsequent histologic examinations revealed that these lesions consisted of inflammatory cells and fibrosis without neoplastic cells. Common manifestations were pain and other neurological symptoms related to the involved anatomical sites. A variety of neurological dysfunctions of the cranial nerves not including the olfactory and spinal accessory nerves were observed. No patient developed separate lesions outside the head and neck region. After the pathologic diagnosis, most of the patients were treated with oral steroid therapy, with initial doses of prednisolone, 60 to 100 mg/d. It was difficult to relate responsiveness to steroid therapy with the histologic degree of sclerosis, fibrosis, or chronicity of the disease in these cases. Otolaryngologists should be aware of this disease when making treatment decisions for their patients with skull base lesions.

Adult↗

PubMed1997

Brain abscess and brain tumor: discrimination with in vivo H-1 MR spectroscopy.

PURPOSE: To determine the ability to differentiate brain abscess from cystic or necrotic brain tumor with hydrogen-1 magnetic resonance (MR) spectroscopy. MATERIALS AND METHODS: H-1 MR spectroscopy was prospectively performed in seven consecutive patients with pyogenic brain abscess and in seven consecutive patients with necrotic or cystic brain tumor (five patients with glioblastoma and one each with pilocytic astrocytoma and metastasis from lung cancer) in whom radiologic images depicted ring-shaped areas of contrast material enhancement (indicative of a cystic or necrotic mass). Assignment of resonance peaks to metabolites was based on reports in the literature. RESULTS: In six of seven patients with abscess, there were various resonances attributed to lactate, valine, alanine, leucine, acetate, succinate, and unidentified metabolites (2.2, 2.9, 3.2, 3.4, and 3.8 ppm). In six of seven patients with tumor, there was only a resonance attributed to lactate. One patient with a tumor had an unidentified peak at 0.9 ppm (presumably attributed to lipid) in addition to the peak attributed to lactate. CONCLUSION: Spectral patterns from in vivo H-1 MR spectroscopy may permit differentiation of brain abscess from necrotic or cystic tumor.

Adult↗