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Biomedical subjects

M C Han

Publications and source records attributed to M C Han.

245 records · Page 14Linked to original sources
PubMedDate not supplied

Nodular hepatocellular carcinoma: variation of tumor conspicuity on single-level dynamic scan and optimization of fixed delay times for two-phase helical CT.

PURPOSE: The purpose of this work was to determine the optimal delay times in two-phase helical CT for nodular hepatocellular carcinoma (HCC). METHOD: Twenty-four patients with nodular HCC (size 2.1-6.7 cm, mean 4.2 cm) were divided into three groups to undergo single-level dynamic CT with 150 ml of contrast material (iodine load of 45 g) at a rate of 3 ml/s. CT acquisition started 10, 30, or 60 s after the injection for each group, respectively, and lasted for 110 or 120 s. The optimal 20 s windows that allowed a tumor-to-liver contrast of >10 HU were determined in the pooled tumor-to-liver contrast curve. RESULTS: The determined temporal windows were 36-56 and 130-150 s, respectively. However, each window was not appropriate in seven (33%) and five (36%) patients because of the individual variations of the contrast curve. CONCLUSION: There is no optimal fixed delay time that is appropriate in all individual patients. The best delay times are 36 and at least 130 s with our injection protocol.

Adult↗
PubMedDate not supplied

Factors influencing vascular and hepatic enhancement at CT: experimental study on injection protocol using a canine model.

PURPOSE: The purpose of this work was to evaluate the effects of contrast medium injection parameters on aortic, portal vein, and hepatic enhancement at spiral CT and to assess optimal injection protocol for hepatic CT. METHOD: Ten 15 kg dogs underwent single level dynamic CT through the hepatic hilum at 5 s intervals just after the injection of contrast medium for 3 min. With use of different volumes (1, 2, and 3 ml/kg), injection rates (0.5, 1, and 2 ml/s), and concentrations (150, 200, and 300 mg/ml), a total of 270 spiral CT scans were performed. In each scan, time-attenuation curves of aorta, portal vein, and liver were obtained. The degree of maximum contrast enhancement (Imax), time to maximum enhancement (Tmax), and time to equilibrium phase (Teq) for to each injection protocol were analyzed. RESULTS: Alterations in contrast material volume, injection rate, and concentration had significant impact on contrast enhancement of the liver. With increasing volume of contrast medium, Imax, Tmax, and Teq of aorta, portal vein, and liver increased (p < 0.005). With increasing rate of injection, on the other hand, Imax of aorta and liver increased (p < 0.05), but Tmax and Teq decreased (p < 0.005). Change of concentration of contrast medium had a significant effect on Imax of vessels (p < 0.05). CONCLUSION: Maximum contrast enhancement of liver and vessels was influenced mainly by injection volume of contrast medium and the time to peak enhancement by injection rate of contrast medium. Under given amounts of contrast medium, therefore, the strategy of increasing volume by dilution and faster injection might give better Imax values without penalty for the duration of an optimal temporal window (Tmax and Teq).

Animals↗
PubMedDate not supplied

Hilar cholangiocarcinoma: thin-section spiral CT findings with cholangiographic correlation.

Hilar cholangiocarcinoma, a highly lethal tumor, is difficult to diagnose with conventional computed tomography (CT) because of its small size. Spiral CT allows more effective evaluation of these small lesions and better demonstrates the status of the hepatic arterial or portal venous circulation. Among 27 patients with hilar cholangiocarcinoma (infiltrative in 21, exophytic in two, polypoid in one, diffuse in three), thin-section spiral CT allowed identification of each tumor as an area of focal wall thickening that obliterated the lumen. Seventeen of the infiltrative tumors (81%) showed high attenuation. Identification of the level of biliary obstruction was possible in 63% of the patients (17 of 27). The level of obstruction was underestimated in six patients and overestimated in four. Spiral CT is a valuable method for diagnosis of hilar cholangiocarcinoma; however, spiral CT is less accurate in evaluation of intraductal tumor extent because of the limited z-axis resolution.

Adult↗
PubMedDate not supplied

Unusual gastric tumors: radiologic-pathologic correlation.

The overlap of radiologic findings in many gastric tumors makes differentiation difficult. However, some unusual gastric tumors have characteristic radiologic features that may suggest a specific diagnosis. At barium study, lipomas typically manifest as a smooth submucosal mass or an ulcerated lesion with a "bull's-eye" appearance that is indistinguishable from other mesenchymal tumors. At computed tomography (CT), lipomas usually manifest as well-circumscribed submucosal masses with fat attenuation. At radiology, glomus tumors appear as smooth submucosal masses with or without ulceration and may contain tiny flecks of calcification. These tumors frequently demonstrate strong enhancement on early-phase contrast material-enhanced images. At barium study, lymphangiomas may appear as smooth intramural masses that are indistinguishable from other mesenchymal tumors. At CT, they manifest as non-enhancing extramucosal masses with homogeneous low attenuation. Diffuse lesions in Brunner gland hamartoma manifest as multiple small nodules, producing a characteristic "cobblestone" appearance. Lymphomas may have typical imaging features (eg, more pronounced and homogeneous mural thickening) that can help differentiate them from adenocarcinoma. In addition, adenocarcinomas may demonstrate unusual findings such as transpyloric spread, unusually large polyps, or intratumoral calcifications. Familiarity with these radiologic features of gastric tumors can help ensure correct diagnosis and proper management.

Adenocarcinoma↗
PubMedDate not supplied

Sinonasal psammomatoid ossifying fibromas: CT and MR manifestations.

Five cases of pathologically proved psammomatoid ossifying fibromas of the sinonasal area are presented. All five cases were examined by CT and in three cases MR imaging was performed before and after injection of gadopentetate dimeglumine. The lesions were located in the sphenoethmoidal area and extended over the nasal cavity or orbit in four cases. In one case, the lesion occurred at the perpendicular plate of the ethmoid bone with preservation of the ethmoidal sinus. On CT, all the lesions were expansile and circumscribed by a thick bony wall. Internal septations of bone density (four cases) or enhancing soft-tissue density (one case) were seen and internal content was low in density in all but one from which blood was aspirated. On MR, the bony walls were isointense with gray matter on T1-weighted images and were seen as areas of low intensity on T2-weighted images. The lesions significantly enhanced after injection of contrast material. A well-circumscribed multiloculated expansile mass with a thick wall of bone density on CT scans and enhancement of this area on postcontrast MR images is strongly suggestive of psammomatoid ossifying fibroma.

Adolescent↗
PubMedDate not supplied

The role of contrast-enhanced MR imaging in the diagnosis of neurocysticercosis.

Pre- and postcontrast MR images of 17 patients with the diagnosis of neurocysticercosis were reviewed to evaluate the role of gadopentetate dimeglumine in MR imaging of this disease. The MR images, which were obtained on either a 0.5-T or 2.0-T superconducting system, revealed a total of 92 cysticerci in 17 patients. On contrast-enhanced T1-weighted images, 23 parenchymal cysticerci showed contrast enhancement. Ring-shaped enhancement was seen in only 6% (3/54) of cysticerci with intensity paralleling the CSF, while it was noted in 67% (16/24) of the cysticerci with intensity higher than CSF. Nodular enhancement was seen in granulomatous lesions with surrounding edema (29%, 4/14). Of 18 cysticerci with surrounding edema, 17 showed contrast enhancement. Basal meningeal enhancement, indicating meningitis, was observed in three patients. The results indicate that contrast enhancement usually occurs in patients in whom precontrast MR findings have shown active inflammatory reaction in the degenerating stage of the worm. Thus, postcontrast imaging is useful in a limited number of patients with neurocysticercosis; it should be used selectively in those whose clinical or precontrast MR studies show meningitis, granulomatous lesions, or cysts with surrounding edema.

Adult↗
PubMedDate not supplied

Gd-DTPA-enhanced MR imaging of the brain in patients with meningitis: comparison with CT.

Plain and Gd-DTPA-enhanced MR images of the brain were obtained in 18 consecutive patients with meningitis (eight with tuberculous, five with bacterial, three with viral, and two with fungal infections); the MR images were compared with CT scans. MR images were obtained on a 2.0-T superconducting unit with both T1- and T2-weighted pulse sequences before injection and with a T1-weighted sequence after injection of Gd-DTPA (0.1 mmol/kg) in all patients. In tuberculous meningitis, MR imaging depicted ischemia/infarct, hemorrhagic infarct of basal ganglia, meningeal enhancement at either basal cistern or convexity surface of brain, and associated small granulomas in a few more patients than CT did. In bacterial meningitis, primary foci of extracranial inflammation (i.e., mastoid, paranasal sinuses) and adjacent intracranial lesions including localized dural inflammation, subdural fluid collection, and/or brain parenchymal lesions were demonstrated much better on MR than on CT. Otherwise, MR images generally matched the CT scan. Although the plain MR images, both T1- and T2-weighted, were the most sensitive in delineating ischemia/infarct, hemorrhage, and edema, they were not as specific as Gd-DTPA-enhanced T1-weighted images and postcontrast CT scans in defining the active inflammatory process of the meninges and focal lesions precisely. We conclude that if Gd-DTPA is used, MR imaging appears to be superior to CT in the evaluation of patients with suspected meningitis. Precontrast MR is needed to delineate ischemia/infarct, edema, and subacute hemorrhage.

Adolescent↗
PubMedDate not supplied

Tuberculous arachnoiditis of the spine: findings on myelography, CT, and MR imaging.

Tuberculosis (TB) is a rare cause of spinal arachnoiditis. It may occur primarily or secondary to intracranial or vertebral infection; unlike other types of arachnoiditis, it frequently involves the spinal cord as well as the meninges and the nerve roots. We retrospectively reviewed 13 conventional myelograms, eight CT myelograms, and five Gd-DTPA-enhanced MR images in 13 patients with spinal TB radiculomyelitis (arachnoiditis). Eleven patients had intracranial TB meningitis at the time of diagnosis or before. Ten patients were less than 30 years old. Conventional myelographic findings included a block of the CSF (11/13), most commonly at the level of the conus medullaris; irregular or indistinct thecal sac contour (9/13); multiple fine and/or coarse nodular defects (8/13); nerve-root thickening (7/13); and vertical bandlike adhesive defects (4/13). CT myelography showed intradural nodular masses suggesting tuberculomas at or just above the level of the block (4/8), irregularity of the spinal cord surface (4/8), irregular filling or obliteration of subarachnoidal space (6/8), and root thickening (5/8). Gd-DTPA-enhanced MR images revealed enhancing nodules suggesting tuberculomas (2/5); enhancement of the dura-arachnoid complex around the cord (3/5); and segmental enhancement of the thoracic cord, suggesting either infarction caused by vasculitis or TB myelitis in association with diffuse cord swelling (1/5). Plain MR findings were much less conspicuous, showing only an indistinct or irregular dura-arachnoid-cord complex (4/5). In conclusion, the conventional myelographic findings are considered to be virtually diagnostic of spinal TB radiculomyelitis in young patients with antecedent or coexisting TB meningitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Pituitary atrophy in Korean (epidemic) hemorrhagic fever: CT correlation with pituitary function and visual field.

Eleven patients with Korean (epidemic) hemorrhagic fever were each studied three times with high-resolution CT in order to demonstrate necrosis of the pituitary gland and to correlate the CT findings with the patients' pituitary function and visual fields. Seven of the 11 patients showed varying degrees of progressive decrease in the height of the pituitary gland: one severe, two moderate, and four mild. The visual fields of all the patients were checked at the time of the third (last) follow-up CT. Six of the 11 patients had bitemporal superior quadrantanopsia. In five patients, the decreased height (atrophic change) of the pituitary gland and the visual-field defect were coincidental. The visual-field defects in those patients were not improved on follow-up examination 5 weeks later. Two patients in whom a 1-year follow-up examination was performed showed no interval changes in the defects. Pituitary function tests were performed in nine of the 11 patients (six with atrophic pituitary glands and three without atrophic changes) at the time of the third CT. Five of the six patients with atrophy showed decreased pituitary reserve function for follicle-stimulating hormone, cortisol, or human growth hormone, while only one patient showed decreased reserve function for cortisol among the three patients without atrophic change. The pituitary atrophic changes observed on follow-up sellar CT are thought to be the result of the ischemic necrosis of the gland. The high probability (five of seven) of visual-field defects in those patients with atrophic glands suggests optochiasmatic and pituitary ischemia as the basic pathogenesis.

Adult↗
PubMedDate not supplied

Comparative evaluation of brain CT and ELISA in the diagnosis of neurocysticercosis.

This study compares the results of cysticercus-specific IgG antibody levels, as measured by enzyme-linked immunosorbent assay (ELISA), with brain CT findings in suspected neurocysticercosis and to assess the clinical significance of ELISA. One hundred twenty-three neurologic patients were examined by both brain CT and ELISA. Sensitivity and specificity of ELISA in confirmed cases were 94% and 91%, respectively. Patients with multiple cysts without enhancement on CT, which were thought to represent viable cysticerci, were positive by ELISA. Those with cysts with enhancement or poorly defined low densities or enhancing nodules, which represented cysticerci on degeneration, were also positive by ELISA. Those with multiple spotty calcifications, which represent cysticerci in the inactive stage, were negative by ELISA. Those with mixed CT findings of the above, which represent the various stages of infection in a patient, were positive by ELISA. Those with only enhancing nodules with surrounding edema, which were thought to be other inflammatory granulomas, were negative by ELISA. If patients with only hydrocephalus on CT are positive by ELISA, they can be confidently diagnosed as having ventricular cysticercosis. The results indicate that ELISA is useful as a complementary diagnostic tool, especially in patients with equivocal CT findings of neurocysticercosis. Provision of etiologic information on a biologic basis was the advantage of this serologic test.

Adolescent↗