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J K Han

Publications and source records attributed to J K Han.

At least 55 records · Page 3Linked to original sources
PubMed1999

Axillary lymph node uptake of Tc-99m MIBI resulting from extravasation should not be misinterpreted as metastasis.

Ipsilateral axillary lymph node visualization due to extravasation of Tc-99m MDP intravenous injection has been well documented. A patient with suspected angina underwent Tc-99m MIBI myocardial SPECT who had extravasation of Tc-99m MIBI in the antecubital region resulting in ipsilateral axillary lymph node uptake. This finding should not be misinterpreted as lymphatic nodal metastasis in a patient with breast cancer or lung cancer.

Angina Pectoris↗
PubMed1999

Signal from hepatic hemangiomas on power Doppler US: real or artefactual?

To describe imaging findings of hepatic hemangiomas on power Doppler (PD) ultrasound (US) with revised Doppler parameters for preventing PD artefacts from stationary hyperechoic tissue, we prospectively evaluated 48 hemangiomas by PD US with predetermined PD settings to prevent artefactual signals from stationary hyperechoic tissue (pulse repetition frequency of 1000 Hz, medium wall filter, and PD gain of 60-85%). Intratumoral PD signals were not seen in 32 lesions (67%). Minimal (n = 15) or moderate (n = 1) intratumoral PD signals were seen in 16 lesions (33%) and were distributed in the peripheral portion only in 12 lesions (75%) and in the peripheral and central portion in 4 lesions (25%). Due to the lack of sensitivity of PD to detect slow flow in hemangiomas, PD US should no longer be used for the evaluation of echogenic liver masses caused by hemangiomas from other hypovascular malignant lesions of the liver.

Adult↗
PubMed1999

The involvement of cAMP signaling pathway in axis specification in Xenopus embryos.

The cAMP signaling system has been postulated to be involved in embryogenesis of many animal species, however, little is known about its role in embryonic axis formation in vertebrates. In this study, the role of the cAMP signaling pathway in patterning the body plan of the Xenopus embryo was investigated by expressing and activating the exogenous human 5-hydroxytryptamine type 1a receptor (5-HT(1a)R) which inhibits adenylyl cyclase through inhibitory G-protein in embryos in a spatially- and temporally-controlled manner. In embryos, ventral, but not dorsal expression and stimulation of this receptor during blastula and gastrula stages induced secondary axes but were lacking anterior structures. At the molecular level, 5-HT(1a)R stimulation induced expression of the dorsal mesoderm marker genes, and downregulated expression of the ventral markers but had no effect on expression of the pan mesodermal marker gene in ventral marginal zone explants. In addition, ventral expression and stimulation of the receptor partially restored dorsal axis of UV-irradiated axis deficient embryo. Finally, the total mass of cAMP differs between dorsal and ventral regions of blastula and gastrula embryos and this is regulated in a temporally-specific manner. These results suggest that the cAMP signaling system may be involved in the transduction of ventral signals in patterning early embryos.

Animals↗
PubMed1999

Tuberculous stenosis of the left main bronchus: results of treatment with balloons and metallic stents.

PURPOSE: To assess the results of treatment with balloon dilation and metallic Z stents in patients with tuberculous stenosis of the left main bronchus. MATERIALS AND METHODS: Nineteen patients with tuberculous stenosis of the left main bronchus were treated with balloon (n = 15) and self-expanding metallic Z stents (n = 4). Respiratory status and pulmonary function tests were followed up for 2-90 months. RESULTS: In the balloon group, improvements in dyspnea occurred in 73% (11 of 15 patients) immediately, 73% after 1 month, 73% after 6 months, 64% after 1 year, 64% after 3 years, and 42% after 6 years (Kaplan-Meier method). Improvement of pulmonary function (FEV1 or FVC) was achieved in 62% (eight of 13) after 1 year. In the stent group, immediate improvements of dyspnea or pulmonary function occurred in all patients. However, fracture of the stents occurred in two patients, at 4 and 18 months, respectively. Occlusion of the lumen of the stent by granulation tissue occurred in another at 18 months. CONCLUSION: Balloon dilation can be an effective method for the treatment of tuberculous stenosis of the main bronchus. Metallic Z stents should be used cautiously because of their problems of mechanical durability and overgrowth of granulation tissue.

Adolescent↗
PubMed1999

Detection of abscesses with Tc-99m HMPAO leukocyte scintigraphy depends on their stage and location.

Two abscesses were shown on CT in a 72-year-old man: one in the left hip and one in the left pelvic region that resulted from a motor vehicle collision that occurred 8 months earlier. Bone scintigraphy showed increased uptake in the left hip area. On Tc-99m HMPAO leukocyte imaging, the hip area appeared to be photopenic, and the abscess of the left pelvis was not identified. Incidental uptake in the left lung base appeared to be an active acute inflammatory process as evidenced by an infiltrating lesion in the left lower lung on a chest radiograph. Because leukocyte scintigraphy cannot detect the presence of a chronic inflammatory process in the absence of acute inflammatory cells, the patient's abscesses in the left hip and the left pelvis did not localize Tc-99m HMPAO-labeled neutrophils. The cold lesion in the left hip area was most likely caused by the lesion in the reticuloendothelial system (bone marrow); the unidentifiable pelvic lesion was related to the area(s) outside the reticuloendothelial system. In interpreting a labeled leukocyte image, clinicians should be alert to the stage (chronic or acute) and location (regardless of whether in the reticuloendothelial system) of infectious lesion(s). In this patient, a wide spectrum of manifestations was evident on leukocyte scintigraphy.

Abscess↗
PubMed1999

Normal variants of a photon-deficient area in the lower sternum demonstrated by bone SPECT.

PURPOSE: A highly variable normal appearance of the sternal area makes interpretation difficult on planar bone imaging. These normal variants occur especially in the area above the xiphoid process of the sternum in which an oval photopenic area on anterior planar images may be seen. This finding is most likely caused by localized incomplete fusion. METHODS: Of a group of 188 patients, 35 patients (33 men, 2 women; age range, 30 to 85 years; mean age, 57 years) were examined with sternal SPECT and planar bone imaging. These patients, who had no history of sternal trauma, surgery, radiation, or infection, were referred for bone scan for metastatic work-up (n = 20), back pain (n = 6), and other conditions (n = 9). Thus 11 of 35 (31%) patients had a SPECT study that showed a photopenic area in the lower sternum. RESULTS: The incidence of this normal variant was higher than the 2% to 7.7% previously reported, indicating improved detection by SPECT. The normal variant appears to be less apparent on planar bone images and is seen more clearly on SPECT images. CONCLUSION: Differentiation from malignancy appears to be related to lesion symmetry, location, midline, and evenly distributed radioactivity surrounding the edge of the photopenic area.

Adult↗
PubMed1999

Experimental hepatobiliary fascioliasis in rabbits: a radiology-pathology correlation.

RATIONALE AND OBJECTIVES: The authors sought to correlate the radiologic findings of hepatobiliary fascioliasis with pathologic features. METHODS: Serial ultrasound, computed tomography (CT), and magnetic resonance findings in seven rabbits with experimentally induced fascioliasis were obtained every other week. Direct cholangiogram was also obtained after the rabbits were killed. Radiology-pathology correlation was done in specimens. RESULTS: In the parenchymal phase (an acute phase of parenchymal invasion of a larva), CT showed subcapsular clustered areas of low attenuation. Magnetic resonance appearance was similar in shape but better than CT in characterizing the hemorrhagic nature of the lesion. Ultrasound findings were nonspecific in this phase. In the ductal phase (a stationary phase after residing in the bile duct), CT showed dilatation of central ducts with symmetric periportal hypoattenuation (periportal tracking). Magnetic resonance could not depict mild ductal dilatation. Ultrasound was most valuable in demonstrating the moving worm within the dilated duct. Pathologically, the hepatic parenchymal lesions consisted of a cluster of eosinophilic granulomas with hemorrhagic change (migratory tract of the flukes). Ductal changes were observed predominantly in the central bile ducts. Periportal lymphangiectasia was also noted. CONCLUSIONS: Computed tomography or magnetic resonance can demonstrate the characteristic evolutionary pattern of fascioliasis that reflects the unique life cycle of Fasciola hepatica. The role of ultrasound, although limited in the parenchymal phase, was most useful in the ductal phase in that it demonstrated the moving worms themselves.

Animals↗
PubMed1999

Influence of instrument settings on flow signal and background noise in power Doppler US. An experimental study using a flow phantom with hyperechoic background.

OBJECTIVE: To determine the influence of various power Doppler instrument settings on intensities of flow signal and background noise in flow with a tissue-equivalent phantom. METHODS: Power Doppler images were obtained with changing wall filter level (low, medium, high, and maximum), pulse repetition frequency (PRF; 500, 700, 1000, 1500, 3000, and 6000 Hz), and Doppler gain (60%, 70%, 80%, 90%, and 100%) at different flow velocities (13.3, 26.5, and 49.8 cm/sec). To make a quantitative comparison of different settings, the authors measured the intensities of flow signal and background noise in obtained power Doppler images using the scanner and a computer program, calculated signal-to-noise difference (SND; intensity of flow signal--intensity of background noise), and evaluated the relation between SND and power Doppler settings. RESULTS: The intensities of flow signal and background noise were proportional to flow velocity and power Doppler gain but were inversely proportional to PRF and wall filter level. At constant wall filter level (medium), changes of PRF and Doppler gain to the same directions resulted in a high SND. At constant PRF (1000 Hz), changes of wall filter and Doppler gain to the same directions also resulted in a high SND. However, at constant Doppler gain (80%), a high SND was obtained with changing wall filter level and PRF to the opposite directions. CONCLUSIONS: Three Doppler instrument settings--wall filter level, pulse repetition frequency, and Doppler gain--have reciprocal influences on SND.

Blood Flow Velocity↗
PubMed1999

A differential index assignment scheme for tree-structured vector quantization.

A differential index (DI) assignment scheme is proposed for the image encoding system in which a variable-length tree-structured vector quantizer (VLTSVQ) is adopted. Each source vector is quantized into a terminal node of VLTSVQ and each terminal node is represented as a unique binary vector. The proposed index assignment scheme utilizes the correlation between interblocks of the image to increase the compression ratio with the image quality maintained. Simulation results show that the proposed scheme achieves a much higher compression ratio than the conventional one does and that the amount of the bit rate reduction of the proposed scheme becomes large as the correlation of the image becomes large. The proposed encoding scheme can be effectively used to encode MR images whose pixel values are, in general, highly correlated with those of the neighbor pixels.

Computer Simulation↗
PubMed1999

Low-grade gastric mucosa-associated lymphoid tissue lymphoma: correlation of radiographic and pathologic findings.

PURPOSE: To describe upper gastrointestinal (Gl) examination findings of low-grade gastric mucosa-associated lymphoid tissue (MALT) lymphoma and to correlate them with pathologic examination findings. MATERIALS AND METHODS: A retrospective review of upper Gl examinations was performed in 25 patients with proved low-grade gastric MALT lymphomas. Upper Gl examinations were reviewed for common findings and most probable diagnosis, and these findings were correlated with pathologic findings in resected specimens in 15 patients. RESULTS: The common findings at upper Gl examination included mucosal nodularity (n = 13), ulcer (n = 12), rugal thickening (n = 6), mass (n = 4), and enlarged areae gastricae (n = 2). The most probable diagnoses were early gastric carcinoma (n = 7), advanced gastric carcinoma (n = 6), gastritis (n = 9), and lymphoma (n = 3). Of 17 lesions found on resected specimens, six ulcers and two masses were not depicted at barium study. Disorganized convergent rugae projecting to multiple points and vague ulcer margins were present in four and seven lesions, respectively. Multiple ulcers were seen in two patients. CONCLUSION: Although the common radiographic and pathologic findings observed in low-grade gastric MALT lymphomas were similar to those of gastric carcinomas or gastritis, disorganized convergent rugae, vague ulcer margins, and multiplicity of lesions may be helpful in differentiating them from gastric carcinomas or gastritis.

Adult↗
PubMed1999

Hepatic changes in benign obstruction of the hepatic inferior vena cava: CT findings.

OBJECTIVE: The objective of this study was to describe CT findings of changes in the liver associated with benign obstruction of the hepatic inferior vena cava (IVC). MATERIALS AND METHODS: For a 10-year period, 35 patients with benign obstruction of the hepatic IVC underwent contrast-enhanced CT of the abdomen. These patients were included in this retrospective study. CT scans were analyzed for morphologic changes and abnormal enhancement of the liver, changes in intrahepatic vessels, and additional findings that might be related to obstruction of the IVC. RESULTS: Morphologic changes of the liver included hypertrophy of the caudate lobe (91%) and the left lobe (57%), atrophy of the right lobe (49%), and a nodular surface (74%). The most common pattern of attenuation change was areas of linear, irregular, or wedge-shaped hypoattenuation predominantly located in the peripheral portion of the liver (63%). Diffuse hypoattenuation was seen in six patients (19%) and was frequently found in areas in which hepatic veins filled with hypoattenuated thrombosis (67%). On CT, segmental IVC obstruction (80%) was seen as an obliterated segment of the hepatic IVC. However, membranous IVC obstruction (20%) was not seen on CT. The IVC below the level of obstruction was often revealed as rounded (89%) and occasionally contained thrombus (37%) or calcification (26%). CONCLUSION: CT shows a broad spectrum of morphologic and attenuation changes of the liver and of the hepatic vessels in benign obstruction of the hepatic IVC.

Adult↗
PubMed1999

Limitations of characterization of hepatic hemangiomas using a sonographic contrast agent (Levovist) and power Doppler ultrasonography.

Power Doppler ultrasonography using a sonographic contrast agent (Levovist) was evaluated in 20 patients with hepatic hemangiomas with a 2-4 MHz convex transducer according to a standardized examination protocol (pulse repetition frequency, 1000 Hz; medium wall filter; power Doppler gain, 50 to 85%). Enhancement patterns were assessed and were compared with those on dynamic magnetic resonance imaging (n = 11) or computed tomography (n = 9). The most common enhancement pattern was dotlike or linear enhancement located predominantly at the periphery of the tumor (15 cases, 75%). Diffuse homogeneous enhancement was seen in one case (5%). No definite contrast enhancement was evident in four cases (20%). The enhanced area on ultrasonograms was smaller than that on dynamic MR images or CT scans in 18 cases (90%). A transient centripetal fill-in pattern was identified in six cases (30%). Persistent enhancement until 300 s was not seen in any case. Therefore, specific diagnosis of hemangioma with power Doppler ultrasonography and contrast agent may not be possible.

Adult↗
PubMed1999

Differentiation of small hyperechoic renal cell carcinoma from angiomyolipoma: computer-aided tissue echo quantification.

To assess the value of computer-aided tissue echo quantification in differentiating small hyperechoic renal cell carcinomas from angiomyolipomas, we studied ultrasonographic images of 15 renal cell carcinomas and 20 angiomyolipomas. After digitizing the images, we measured the absolute gray scale values of the renal cortex, central echo complex, and mass. The relative gray scale value (%) of the mass was calculated by setting the gray scale value of the cortex as 0% and the central echo complex as 100%. The relative gray scale value of renal cell carcinomas was in the range of 12 to 73% (mean, 28%), whereas that of angiomyolipomas was 30 to 204% (mean, 130%). The differentiation between small hyperechoic renal cell carcinomas and angiomyolipomas can be facilitated by computer-aided tissue echo quantification.

Adult↗
PubMed1999

Bone agent localization in hepatic metastases.

We present the bone scintigrams of two patients, which demonstrate diffuse extraosseous uptake of a bone agent in metastatic masses in the liver, one from a primary lung tumor and one from a primary breast tumor. The bone imaging agent did not localize in the brain metastases in these patients. CTs of the abdomen in both patients showed massive metastases in the liver with multiple areas of tumor necrosis. The CT of the abdomen of the breast cancer patient showed multiple small hepatic calcifications. Autopsy revealed massive tumor necrosis with calcifications in the enlarged liver. In routine bone scintigraphy, diffuse uptake of bone agents in the liver of a patient with a known malignancy should be considered suggestive of massive hepatic metastases.

Adenocarcinoma↗
PubMed1999

Localization of a bone imaging agent in a calcified hematoma.

A patient with chronic renal failure and secondary hyperparathyroidism had iliac bone biopsy. The procedure was complicated by a soft-tissue hematoma, which had calcified. A 3-4-cm palpable mass was visible in the lower left abdominal wall. Intense uptake of 99mTc-HMDP corresponded with the location of the calcified hematoma in this patient.

Adult↗