Biomedical subjects

D G Na

Publications and source records attributed to D G Na.

29 records · Page 2Linked to original sources

PubMed1998

Acute occlusion of the middle cerebral artery: early evaluation with triphasic helical CT--preliminary results.

PURPOSE: To evaluate use of triphasic helical computed tomography (CT) for early diagnosis of occlusion and assessment of ischemia in cases of acute middle cerebral arterial occlusion. MATERIALS AND METHODS: Thirty-five patients with acute ischemia underwent triphasic helical CT within 6 hours after symptom onset. Early arterial, perfusion, and delayed phase CT scans were obtained 18, 30, and 80 seconds, respectively, after contrast material administration. Eighteen patients had proximal middle cerebral arterial occlusion diagnosed at magnetic resonance (MR) or digital subtraction angiography. Follow-up CT or MR imaging was performed in all patients. Two independent observers interpreted images for signs of arterial occlusion, collateral vessels, and the ischemic zone. RESULTS: One observer found at least one of three signs in 17 of the 18 patients with occlusion, and the other found at least one sign in all 18: Early decreased arterial contrast enhancement was seen by both observers in 11 patients (kappa = 0.77), a nonenhancing arterial segment was seen by the two observers in 12 and 14 (kappa = 0.73), and delayed asymmetric arterial enhancement was seen in 13 and 16 (kappa = 0.49). Triphasic CT findings of the ischemic zone were consistent with follow-up CT or MR imaging findings in seven of 12 patients. CONCLUSION: Triphasic helical CT is useful for early diagnosis of acute proximal middle cerebral arterial occlusion and assessment of the ischemic zone.

Acute Disease↗

PubMed1997

Differential diagnosis of cervical lymphadenopathy: usefulness of color Doppler sonography.

OBJECTIVE: The purpose of this study was to evaluate the usefulness of color Doppler sonography in differentiating benign from malignant cervical lymphadenopathy. MATERIALS AND METHODS: We used color Doppler sonography to evaluate 117 lymph nodes in 105 patients. The patients were pathologically and clinically confirmed to have benign reactive lymphadenitis (n = 28), tuberculosis (n = 17), lymphoma (n = 14), and metastasis (n = 46). The patterns of hilar vascularity, central nodal vascularity, and peripheral vascularity were assessed. The highest resistive index and pulsatility index in 116 lymph nodes were measured from spectral waveforms. Histologic findings of nodal vessels were analyzed in 14 nodes and compared with findings on color Doppler sonograms. RESULTS: Thirty-two (94%) of 34 nodes with benign reactive disease showed normal patterns of nodal vascularity; central hilar vascularity, radial symmetric central vascularity, and no peripheral vascularity. At least one of six abnormal patterns of vascularity (eccentric or absent hilar vascularity; deformed radial, aberrant multifocal, or absent central vascularity; and peripheral vascularity) was observed in 98% (65/66) of nodes with malignant disease and in all tuberculous nodes. We established cutoff values of 0.8 for the resistive index and 1.5 for the pulsatility index that were 100% specific for malignancy. However, sensitivities for these cutoff values were 47% and 55%, respectively. Also, histologic examinations showed that most flow signals in nodes with malignant disease represented arterioles or veins in the septa between tumor nests or near the capsule. CONCLUSION: Unlike nodes with benign reactive disease, 98% of nodes with malignant disease and 100% of tuberculous nodes showed abnormal patterns of nodal vascularity. Also, high values for the resistive and pulsatility indexes were highly specific for malignant lymphadenopathy. Color Doppler sonography combined with analysis of spectral waveforms was useful in differentiating benign from malignant cervical lymphadenopathy.

Adolescent↗

PubMed1997

Kikuchi disease: CT and MR findings.

Two cases of Kikuchi disease showed variable nodal enhancing features, including homogeneous enhancement and focal or extensive nodal necrosis on contrast-enhanced CT scans. At MR imaging, the area of central necrosis was isointense or hypointense on T1-weighted images and had a lower signal than nonnecrotic areas on T2-weighted images. The CT appearance of Kikuchi disease can be variable and can mimic not only lymphoma but various nodal diseases with nodal necrosis, including metastasis and tuberculosis.

Adult↗

PubMed1995

Doppler sonography in experimentally induced acute renal failure in rabbits. Resistive index versus serum creatinine levels.

RATIONALE AND OBJECTIVES: The purpose of this study is to investigate the temporal relation between the change in the resistive index (RI) from renal Doppler sonography and that of serum creatinine values in the course of experimentally induced reversible acute renal failure (ARF) in rabbits. METHODS: Reversible ARF was induced in 10 New Zealand white rabbits by injecting a glycerol solution (6.0 mL/kg) into the thigh muscle. Doppler sonography was performed before injection, and 6, 12, and 24 hours, and 3, 5, 7, and 14 days after injection of glycerol. Blood samples for measuring serum creatinine levels were obtained in the same time sequence. Three rabbits, which died during the course of the experiment, were excluded from the study group. RESULTS: The RI elevated rapidly after glycerol injection, peaked at 12 hours, and then decreased to normal values by 7 days. Conversely, serum creatinine values were elevated and peaked at 1 day and then decreased to normal by 14 days. The change in the RI preceded the change in serum creatinine levels in the course of reversible ARF. There was a weak linear correlation between RI and serum creatinine levels, with a correlation coefficient of 0.33. CONCLUSION: Doppler sonography with measurement of resistive index may be useful in predicting the course of ARF.

Acute Kidney Injury↗

PubMed1995

Cystic expansile masses of the maxilla: differential diagnosis with CT and MR.

PURPOSE: To describe the CT and MR findings of various entities causing cystic expansile masses in the maxilla and the significance of the cortical bony plate between the lesions and sinus cavities in the differential diagnosis. METHODS: CT findings of 28 patients with cystic expansile masses of the maxilla, including 20 cases of maxillary mucoceles (17 postoperative mucoceles, 2 mucoceles of a septated compartment of the maxillary sinuses, and 1 maxillary antral mucocele with inflammatory ostial obstruction), 3 cases of fissural cyst, 4 cases of odontogenic cyst, and 1 case of maxillary cystic ameloblastoma, were reviewed. Six cases (4 postoperative mucoceles and 2 odontogenic cysts) were also examined with MR. RESULTS: A thin bony plate between the lesion and antral cavity was demonstrated in every extraantral lesion (ameloblastoma, fissural cysts, and odontogenic cysts) and distinguishing these abnormalities from the antral lesions (mucoceles). All mucoceles showed findings of antral lesions except 2 cases of mucoceles at the septated compartments of the sinuses, in which thin bony septa were identified between the lesions and remaining sinus cavities. Postoperative mucoceles showed hyperostotic and retracted bony walls caused by previous surgery and localized erosion of bony walls with localized bulging of the cystic masses in every case. CONCLUSION: In the differential diagnosis of cystic masses of the maxilla, careful identification of the bony walls of the antrum and bony septa may allow one to locate the origin of a mass as antral or extraantral. This is important to an appropriate differential diagnosis.

Adult↗

PubMedDate not supplied

Direct invasion of urinary bladder from sigmoid colon cancer: CT findings.

Radiological findings in three cases of sigmoid colon carcinoma invading the urinary bladder are reported. An irregular spiculated margin or nodular indentations in region of bladder dome were seen on intravenous urography. A soft tissue mass contiguous with an irregularly thickened urinary bladder wall and a circumferentially thickened sigmoid colon wall were demonstrated on CT and sonography and led to the correct diagnosis.

Adenocarcinoma↗

PubMedDate not supplied

Primary adenoid cystic carcinoma of the cervical trachea mimicking thyroid tumor: CT evaluation.

OBJECTIVE: Our goal was to describe the CT characteristics of adenoid cystic carcinomas of the trachea mimicking thyroid tumors. MATERIALS AND METHODS: Computed tomography of four patients with pathologically proved adenoid cystic carcinomas extending into the thyroid gland was retrospectively reviewed. One case was also examined with MR. RESULTS: The masses encircling the trachea and circumferential thickening of the tracheal wall were demonstrated in all four cases. The longitudinal extent of the tracheal wall thickening was also demonstrated in all cases. The tumors had a broad base on the trachea and convex margin on the thyroid gland. They were all homogeneous, generally smoothly marginated, and isoattenuating on postcontrast CT scans. CONCLUSION: Adenoid cystic carcinomas were usually seen on CT scans as homogeneous masses encircling the posterolateral trachea with thickening of the tracheal wall in the transverse and longitudinal planes. These CT characteristics may be helpful in the differential diagnosis of adenoid cystic carcinomas mimicking thyroid tumors.

Adult↗

PubMedDate not supplied

Focal cortical dysplasia: comparison of MRI and FDG-PET.

PURPOSE: The purpose of this work was to compare the use of MRI and [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) in the diagnosis of focal cortical dysplasia (FCD). METHOD: Nineteen patients with surgically proven FCD were analyzed retrospectively. MRI was performed in all patients, and FDG-PET was performed in 17 patients. We compared the MR and FDG-PET findings of FCD according to the histologic findings that were classified into three grades. RESULTS: Four cases were classified as Grade I, 4 cases as Grade II, and 11 cases as Grade III FCD. The lesions were detected on MRI in 9 (82%) of the 11 patients with Grade III FCD and in only 1 (13%) of the 8 patients with Grade I and II FCD. Cortical hypometabolism of the lesion was revealed on FDG-PET in 6 (86%) of the 7 patients with Grade I and II FCD and in 9 (90%) of the 10 patients with Grade III FCD. The extent of the cortical abnormality was larger on FDG-PET than on MRI in 11 (65%) of the 17 patients. CONCLUSION: FDG-PET is more useful in delineating the cortical abnormality in patients with mild degrees of FCD. The extent of the lesion was larger or similar on FDG-PET compared with that of the MRI.

Adolescent↗

PubMedDate not supplied

Functional MR imaging of working memory in the human brain.

OBJECTIVE: In order to investigate the functional brain anatomy associated with verbal and visual working memory, functional magnetic resonance imaging was performed. MATERIALS AND METHODS: In ten normal right handed subjects, functional MR images were obtained using a 1.5-T MR scanner and the EPI BOLD technique. An item recognition task was used for stimulation, and during the activation period of the verbal working memory task, consonant letters were used. During the activation period of the visual working memory task, symbols or diagrams were employed instead of letters. For the post-processing of images, the SPM program was used, with the threshold of significance set at p <.001. We assessed activated brain areas during the two stimulation tasks and compared the activated regions between the two tasks. RESULTS: The prefrontal cortex and secondary visual cortex were activated bilaterally by both verbal and visual working memory tasks, and the patterns of activated signals were similar in both tasks. The superior parietal cortex was also activated by both tasks, with lateralization to the left in the verbal task, and bilaterally without lateralization in the visual task. The inferior frontal cortex, inferior parietal cortex and temporal gyrus were activated exclusively by the verbal working memory task, predominantly in the left hemisphere. CONCLUSION: The prefrontal cortex is activated by two stimulation tasks, and this is related to the function of the central executive. The language areas activated by the verbal working memory task may be a function of the phonological loop. Bilateral prefrontal and superior parietal cortices activated by the visual working memory task may be related to the visual maintenance of objects, representing visual working memory.

Adult↗

PubMedDate not supplied

Diffusion-weighted MR imaging of intracerebral hemorrhage.

OBJECTIVE: To document the signal characteristics of intracerebral hemorrhage (ICH) at evolving stages on diffusion-weighted images (DWI) by comparison with conventional MR images. MATERIALS AND METHODS: In our retrospective study, 38 patients with ICH underwent a set of imaging sequences that included DWI, T1-and T2-weighted imaging, and fluid-attenuated inversion recovery (FLAIR). In 33 and 10 patients, respectively, conventional and echo-planar T2* gradient-echo images were also obtained. According to the time interval between symptom onset and initial MRI, five stages were categorized: hyperacute (n=6); acute (n=7); early subacute (n=7); late subacute (n=10); and chronic (n=8). We investigated the signal intensity and apparent diffusion coefficient (ADC) of ICH and compared the signal intensities of hematomas at DWI and on conventional MR images. RESULTS: DWI showed that hematomas were hyperintense at the hyperacute and late subacute stages, and hypointense at the acute, early subacute and chronic stages. Invariably, focal hypointensity was observed within a hyperacute hematoma. At the hyperacute, acute and early subacute stages, hyperintense rims that corresponded with edema surrounding the hematoma were present. The mean ADC ratio was 0.73 at the hyperacute stage, 0.72 at the acute stage, 0.70 at the early subacute stage, 0.72 at the late subacute stage, and 2.56 at the chronic stage. CONCLUSION: DWI showed that the signal intensity of an ICH may be related to both its ADC value and the magnetic susceptibility effect. In patients with acute stroke, an understanding of the characteristic features of ICH seen at DWI can be helpful in both the characterization of intracranial hemorrhagic lesions and the differentiation of hemorrhage from ischemia.

Acute Disease↗

PubMedDate not supplied

MR imaging of central diabetes insipidus: a pictorial essay.

Central diabetes insipidus (DI) can be the outcome of a number of diseases that affect the hypothalamic-neurohypophyseal axis. The causes of the condition can be classified as traumatic, inflammatory, or neoplastic. Traumatic causes include postoperative sella or transection of the pituitary stalk, while infectious or inflammatory causes include meningitis, lymphocytic hypophysitis, and granulomatous inflammations such as sarcoidosis and Wegener's granulomatosis. Various neoplastic conditions such as germinoma, Langerhans cell histiocytosis, metastasis, leukemic infiltration, lymphoma, teratoma, pituitary adenoma, craniopharyngioma, Rathke cleft cyst, hypothalamic glioma, and meningioma are also causes of central DI. In affected patients, careful analysis of these MR imaging features and correlation with the clinical manifestations can allow a more specific diagnosis, which is essential for treatment.

Adolescent↗