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Biomedical subjects

Joon Koo Han

Publications and source records attributed to Joon Koo Han.

At least 55 records · Page 3Linked to original sources
PubMed2005

Radiofrequency thermal ablation in canine femur: evaluation of coagulation necrosis reproducibility and MRI-histopathologic correlation.

OBJECTIVE: Our purposes were to determine whether a single application of radiofrequency energy to normal bone can create coagulation necrosis reproducibly and to assess the accuracy of MRI at revealing the extent of radiofrequency-induced thermal bone injury. MATERIALS AND METHODS: Using a 200-W generator and a 17-gauge cooled-tip electrode, a total of 11 radiofrequency ablations were performed under fluoroscopic guidance in the distal femurs of seven dogs. Radiofrequency was applied in standard monopolar mode at 100 W for 10 min. During radiofrequency ablation, the changes in impedance and currents were recorded. MRI, including unenhanced T1- and T2-weighted images and contrast-enhanced fat-suppressed T1-weighted images, was performed to evaluate ablation regions. Six dogs were killed on day 4 after MRI and one dog on day 7. RESULTS: In all animals, radiofrequency ablation created a well-defined coagulation necrosis and no significant complications were noted. The mean long-axis diameter and the mean short-axis diameter of the coagulation zones produced were 45.9 +/- 5.5 mm and 17.7 +/- 2.7 mm, respectively. At gross examination, thermal ablation regions appeared as a central, light-brown area with a dark-brown peripheral hemorrhagic zone, which was surrounded by a pale-yellow rim. On MRI, the ablated areas showed multilayered zones with signal intensities that differed from normal marrow on unenhanced images and a perfusion defect on contrast-enhanced T1-weighted images. The maximum difference between lesion sizes on MR images, established by measuring macroscopic coagulation necrosis, was 3 mm. The correlation between the diameter of coagulation necrosis and lesion size at MRI was strong, with correlation coefficients ranging from 0.89 for unenhanced T1-weighted images and 0.97 for unenhanced T2-weighted images to 0.98 for contrast-enhanced T1-weighted images (p < 0.05). CONCLUSION: Radiofrequency ablation created well-defined coagulation necrosis in a reproducible manner, and MRI accurately determined the extent of the radiofrequency-induced thermal bone injury.

Animals↗
PubMed2005

Protocol optimization of multidetector computed tomography colonography using pig colonic phantoms.

OBJECTIVE: The introduction of multidetector computed tomography (CT) increases the possibility of enhanced polyp detection using CT colonography. The effects of collimation and tube currents on polyp detection were investigated in pig colonic phantoms to determine the optimal scanning parameters. MATERIALS AND METHODS: Twenty pig colons were prepared, and polyps with diameters ranging from 3 mm to 15 mm were created and randomly distributed. There was a total of 60 polyps; 20 polyps were 3 to 5 mm in size, 21 polyps 6 to 9 mm, and 19 polyps 10 to 15 mm. The pig colons were sealed, distended with air, submerged in water, and were arranged to mimic the in vivo arrangement. CT was performed using a 4-row multidetector CT scanner with collimations of 1, 2.5, and 5 mm, a pitch of 1.75, and mA of 100. A low-dose protocol (mA of 50) was added with a collimation of 1 mm. Two blinded observers independently analyzed the datasets. RESULTS: : The overall sensitivities of CT colonography were 94.2% with 1-mm collimation, 80% with 2.5-mm collimation, and 75% with 5-mm collimation. Considering the sensitivity of each protocol for the size of the polyps, the 1-mm collimation protocol had a sensitivity of 87.5% for 3- to 5-mm polyps, 95.2% sensitivity for 6- to 9-mm polyps, and 100% sensitivity for 10- to 15-mm polyps; the 2.5-mm protocol had 50%, 92.9%, and 97.4% sensitivities, respectively; and the 5-mm protocol had 47.5%, 88.1%, and 89.5% sensitivities, respectively, for the respective polyp size group. A significant difference in sensitivity among the protocols was present in the 3- to 5-mm polyps. No significant difference was seen between the standard- and the low-dose protocols. CONCLUSIONS: The sensitivity of multidetector CT colonography for detecting polyps larger than 5 mm is robust over a range of collimation in pig colonic phantoms. However, reliable detection of polyps 5 mm or smaller requires a 1-mm collimation. Sensitivity is not influenced by lowering the mA from 100 to 50.

Animals↗
PubMed2004

Four-dimensional volume contrast ultrasound imaging of the gallbladder compared with tissue harmonic imaging: preliminary experience.

Comparison of volume contrast US imaging with tissue harmonic imaging for the evaluation of gallbladder lesions and determination of the adequate slice thickness in volume contrast US imaging were performed. Forty-one patients who had gallbladder lesions (polyps in 26, stones in 12, and sludge in 3) were enrolled in our study. A Voluson 730 Expert US scanner was used throughout. Volume contrast US imaging with slice thicknesses of 3, 5, 10 and 15 mm and tissue harmonic imaging of the gallbladder were obtained. Two abdominal radiologists reviewed the masked images and graded by consensus these images using a five-point scale [from grade 1, (best), to grade 5, (worst)], based on the sharpness of the anterior gallbladder wall, internal artifact, lesion conspicuity and acoustic shadowing from stone. Volume contrast US imaging with thin slice thicknesses (3 or 5 mm) was judged superior to both tissue harmonic imaging and with thick slice thicknesses (10 or 15 mm), with respect to the sharpness of the anterior wall and lesion conspicuity ( P<0.001). In terms of internal artifact, volume contrast imaging with thin slice thicknesses was significantly superior to both tissue harmonic imaging and volume contrast imaging with a 15 mm thickness ( P<0.001) and was judged to be marginally better than with a 10 mm thickness ( p>0.01). With regard to acoustic shadowing, volume contrast imaging with thin slice thicknesses was also significantly better than with thick slice thicknesses ( P<0.01), and it was also marginally better than tissue harmonic imaging ( P>0.01). Volume contrast US imaging with thin slice thicknesses provides a better image quality with fewer artifacts than three other types of images for the evaluation of gallbladder diseases.

Adult↗
PubMed2004

Bipolar radiofrequency ablation in ex vivo bovine liver with the open-perfused system versus the cooled-wet system.

The aim of this study was to investigate the efficacy of bipolar radiofrequency ablation (RFA) with the open-perfused electrode and cooled-wet electrode. Bipolar RF was applied for 20 min to the ex vivo bovine liver using either the Berchtold system with two 16-gauge open-perfused electrodes (group A, n=15) or the Radionics system with two 15-gauge cooled-wet electrodes (group B, n=15). In both groups, two electrodes were placed 3 cm apart. The ablation zone was created by the RF energy delivered together with the infusion of 5% hypertonic saline (2 ml/min). The dimension of the ablation zone, its shape and the changes in the impedance and W s of two groups during the RFA were examined and documented. The vertical diameter (Dv) along the probe, the long-axis diameter (Dl) perpendicular to the Dv in the longitudinal plane and the short-axis diameter of the ablation zone (Ds) in the transverse plane through the midpoint between the tips of two probes were measured. The mean accumulated energy output in the Radionics system was higher than in the Berchtold system (159,887.0+/-36,423 W s vs. 87,555.1+/-86,787 W s). The difference was statistically significant (P<0.05). In group A, the impedance intermittently rose to above 700 Omega during the RFA in all sessions, which led to a gradual decrease of the power output to lower than 30 W. In group B, on the other hand, the impedance did not change markedly. The mean Dv value of the coagulation necrosis in group B was significantly longer than in group A (5.0+/-0.4 cm vs. 4.3+/-0.6 cm, P<0.05). The mean Dl and Ds were 6.7+/-0.5 cm and 5.0+/-0.8 cm in group A, and 6.5+/-0.8 cm and 5.5+/-0.7 cm in group B, respectively (P>0.05). The data demonstrate that the cooled-wet electrode generates the more spherical ablation zone than the open-perfused electrode. With approximately doubled power output, the bipolar RFA with the cooled-wet electrodes induces a larger volume of tissue coagulation than with the open-perfused electrodes.

Animals↗
PubMed2004

Heparin-coated angiographic catheters: an in vivo comparison of three coating methods with different heparin release profiles.

We evaluated in vivo anti-thrombogenic effects of three different heparin-coated angiographic catheters with different heparin release profiles. Three different types of heparin-coated 5 French angiographic catheters (rapidly-heparin-releasing, slowly-heparin-releasing, and heparin-adherent catheters) were prepared by coating amphiphilic or hydrophobic heparin derivatives in order to regulate heparin elution. After incubation time of 30 minutes in the arteries of dogs, the amount of thrombus deposition, measured as dry weight, was compared in 10 sets of the three heparin-coated catheters and a non-coated catheter used as control. The surface morphology of catheters after their withdrawal was studied by scanning electron microscopy. The amount of thrombus deposition on the non-coated catheter (374.6 +/- 11.6 mg, mean +/- SD) was significantly larger than those on the rapidly-heparin-releasing (52.0 +/- 12.6), slowly-heparin-releasing (70.4 +/- 23.1), and heparin-adherent catheters (103.7 +/- 39.9) ( p < 0.001, each). The thrombus weights in the three heparin-coated catheters were not statistically different. The scanning electron microscopy showed crusts on the catheter surface, which were thickest in the non-coated catheters. We concluded that the thrombus formation inside a catheter is significantly decreased if the catheter is treated with any of the three heparin-coating methods used in this study. The in vivo anti-thrombogenic effects of these coating methods are not significantly different despite their different heparin release profiles.

Angiography↗
PubMed2004

Experimentally induced small-bowel tumor in rabbits: US-guided percutaneous 18-gauge core biopsy.

PURPOSE: To evaluate the safety and diagnostic yield of percutaneous 18-gauge core biopsy for an experimentally induced small-bowel tumor in a rabbit model. MATERIALS AND METHODS: Small-bowel tumors were induced by injecting VX2 tumor into 20 rabbits. After 3 weeks, the small bowel was filled with 100 mL of 2% diluted contrast agent containing methylene blue by using a 5-F catheter. Fifty biopsy firings for small-bowel tumor were performed with ultrasonographic (US) guidance by using an 18-gauge automatic gun. Computed tomography (CT) was performed before and immediately after biopsy. Any procedure-related complications, including leakage of air or fluid, hematoma, and perforation as seen at CT and identified at laparotomy, which was performed 48 hours after biopsy, were evaluated. White blood cell (WBC), red blood cell, and platelet counts; hemoglobin and hematocrit levels; and erythrocyte sedimentation rate were also obtained before and 48 hours after biopsy. Comparison was performed with paired t test. The diagnostic yield was calculated, and the specimen was evaluated whether fragments of mucosa were included or not. RESULTS: No contrast agent leakage or pneumoperitoneum suggesting perforation was identified at CT or laparotomy. Fluid leakage was observed with manual squeezing at two biopsy sites (4%). In two rabbits, hemoperitoneum was observed at CT or laparotomy. Hematoma larger than 3 cm was observed in six rabbits. WBC count and erythrocyte sedimentation rate slightly increased, and red blood cells, hemoglobin, hematocrit, and platelets counts had decreased slightly after biopsy but were not significant (P >.05). Definitive histologic diagnosis of tumor was obtained in 44 (88%) of 50 biopsy sites. Fragments of mucosa were observed in 13 (28%) specimens of 10 rabbits. CONCLUSION: Core biopsies of small-bowel tumor can be performed safely with an 18-gauge gun without severe complications and allow histologic diagnosis of small-bowel tumor with a good diagnostic yield.

Animals↗
PubMed2004

Cyst fluid analysis for the differential diagnosis of pancreatic cysts.

Pancreatic cystic neoplasms comprise a pathologically heterogeneous group with many shared clinical features. We assessed the reliability of cyst fluid analysis for the differential diagnosis of pancreatic cysts. Cyst fluid was obtained by fine-needle aspiration from 78 pancreatic cysts. The lesions studied consisted of 17 mucinous cystic tumors (MCTs), 13 serous cystadenomas (SCAs), 5 solid pseudopapillary tumors (SPTs), 8 intraductal papillary mucinous tumors (IPMTs), 6 ductal adenocarcinomas (ACAs) with cystic degeneration, and 29 pseudocysts (PCs). Epithelial cells were observed in 27 (81%) of 33 successful aspirates of cystic neoplasms. Cytologic diagnosis was possible in 5 (31%) out of 16 MCTs. Mucicarmine staining was positive in five out of nine MCTs, one out of one ACA, and one out of two IPMTs, but in none of the SCAs, SPTs, or PCs. Cyst fluid carcinoembryonic antigen (CEA) levels of more than 467 ng/mL had a 87% sensitivity and a 98% specificity for detecting MCTs, and amylase levels of more than 479 U/L had a 73% sensitivity and a 90% specificity for detecting PCs. In conclusion, cyst fluid analysis for cytology, mucin staining, CEA, and amylase levels are useful in the differential diagnosis of pancreatic cysts.

Amylases↗
PubMed2004

Volumetric tumor measurement using three-dimensional ultrasound: in vitro phantom study on measurement accuracy under various scanning conditions.

Factors influencing volumetric tumor measurement using 3-D ultrasound (US) were investigated. A 3-D US unit equipped with 4- to 8-MHz curved-array and 5- to 10-MHz linear-array mechanical volume transducers, and a US phantom made of 20 ham pieces (8.6 approximately 10.5 mL) embedded in agar gel that simulated hyperechoic tumors, were used. Volumetric tumor measurement was significantly affected by the position of US focus and tumor depth. When focus was at 2 cm and 8 cm below the transducer, 5-cm-deep tumors were measured 5.6% +/- 2.8% (mean +/- SD) and 8.3% +/- 2.2% bigger, respectively, than when focus was at 5 cm below the transducer, the same position as tumors (p < 0.01). Tumors were measured 11.8% +/- 2.9% bigger when they were 8-cm deep below the transducer than when they were 5-cm deep below the transducer (p < 0.001). Setting focus at the same position as tumors and keeping tumor depth consistent during serial 3-D US examinations may be necessary for reliable volumetric assessment of tumors.

Agar↗
PubMed2004

Pyogenic hepatic abscesses: distinctive features from hypovascular hepatic malignancies on contrast-enhanced ultrasound with SH U 508A; early experience.

The aim of this study was to investigate the feasibility of contrast-enhanced US (conE US) in differentiating pyogenic hepatic abscesses (PyHAs) from hypovascular hepatic malignancies. conE US images of 16 PyHAs in 12 patients were evaluated retrospectively and were compared with those of 22 hypovascular hepatic malignancies in 12 patients. The conE US images were obtained at 30, 90, 150 and 270 s after a bolus injection of 4 g of SH U 508A (Levovist, Schering; 300 mg/mL). The images were specifically analyzed for the shape (round or ovoid, lobulating or coalescent according to the complexity), the margin (sharp or ill-defined), and the pattern of contrast agent enhancement of the lesion (internal and rim enhancement). In our experience, as to the shape of the lesion, PyHAs were usually coalescent (94%), and hepatic malignancies were more frequently round or ovoid (36%) or lobulating (50%) (p < 0.0001). The margin of the lesion was usually sharp in PyHAs (81%), whereas it was more commonly ill-defined (59%) in hepatic malignancies (p = 0.02). Whereas PYHAs usually produced no internal enhancement (94%), diffuse (73%) or peripheral (27%) hypoechoic intratumoral enhancement was seen in hepatic malignancies (p < 0.0001). This study shows that conE US is potentially useful in differentiation of PyHAs from hypovascular hepatic malignancies. PyHAs usually produce characteristic features, such as coalescent appearance, sharp boundary of necrotic cavity, and lack of internal enhancement on conE US.

Adult↗
PubMed2004

Palliation of anastomotic obstructions in recurrent gastric carcinoma with the use of covered metallic stents: clinical results in 25 patients.

BACKGROUND: The purpose of this study was to investigate the technical feasibility and the clinical effectiveness of the placement of covered self-expandable metallic stents for the treatment of anastomotic obstructions in recurrent gastric carcinoma. METHODS: With fluoroscopic guidance, covered stents were placed in 25 patients with recurrent gastric carcinoma for the palliation of obstructions at anastomotic sites (14 gastrojejunostomy, 11 esophagojejunostomy). All patients had severe nausea and recurrent vomiting before the stent placement. RESULTS: Stent placement was technically successful in 24 patients (96%). After stent placement, symptoms improved in all 24 patients. During the follow-up of 2 to 65 weeks (mean, 13.7 weeks), stent migration occurred in 1 patient 16 days after the procedure. He needed percutaneous catheter drainage because of an abscess, which was followed by esophagojejunostomy site rupture during a second stent trial. Stricture recurred in 4 patients because of tumor overgrowth 10 to 55 weeks after the procedure; all patients underwent coaxial placement of a second stent and had good oral intake. CONCLUSIONS: The placement of covered expandable metallic stents seems to be both technically feasible and an effective means for the palliation of anastomotic obstructions in recurrent gastric carcinoma. This procedure can be considered to be the primary choice for the palliation in those patients.

Adult↗
PubMed2004

Dual-probe radiofrequency ablation: an in vitro experimental study in bovine liver.

OBJECTIVE: To determine whether alternative radiofrequency (RF) application with dual probes has advantages over sequential or simultaneous RF application for creating larger coagulation necrosis. MATERIALS AND METHODS: Using 2 17-gauge internally cooled electrodes and a 200-watt generator (CC-3 model, Radionics), RF energy was applied sequentially (group A, n = 20), simultaneously (group B, n = 20), or alternately (group C, n = 20) to explanted bovine liver. After preliminary experiments with a probe distance of 2-5 cm, a distance of 2 cm and 3 cm were chosen for main experiments. Total duration of the RF application was 10 minutes. In the alternative mode, the energy was applied alternately to both RF electrodes in 2-second intervals. Changes occurring in tissue impedance, current, power output, and temperature at the midpoint between the 2 electrodes were measured. The technical parameters, temperatures, and dimension of the ablated area were compared in the 3 groups using analysis of variance or Kruskal-Wallis test. RESULTS: In the groups B and C, the impedance was gradually decreased during RF application and the mean current flow of both groups was 1550 +/- 130 mA and 1375 +/- 175 mA, respectively. However, in the group A, the impedance was markedly increased during RF application, and the mean current was 940 +/- 484 mA (P < 0.05, between groups A and B, and groups A and C). With 3-cm spacing, the alternative RF application created oval-shaped ablation zones with larger shortest axis diameter at the midpoint than either the sequential or simultaneous RF application: 12.0 +/- 7.1 mm in group A; 27.0 +/- 3.1 mm in group B; 34.9 +/- 3.4 mm in group C (P < 0.05). With 2 cm spacing, the corresponding figures were 25.3 +/- 7.8 mm in group A; 34.9 +/- 7.8 mm in group B; 41.5 +/- 1.8 mm in group C (P < 0.05): the differences between groups A and B, and between groups A and C were statistically significant (P < 0.05). With 3-cm spacing, the temperature at the midpoint between the 2 probes was higher in group C (102 degrees C) than in either the group A (62 degrees C) or the group B (78 degrees C; P < 0.05). With 2-cm spacing, groups B and C showed higher temperature than group A (P < 0.05), but the difference between groups B and C was not significant (P > 0.05). CONCLUSION: The alternative RF application creates larger, more regular ablation zones than either the sequential or simultaneous RF application. This result suggests that use of an alternating RF power application will improve the results of RF ablation for the treatment of larger tumors.

Animals↗
PubMed2004

Clonorchiasis and cholangiocarcinoma: etiologic relationship and imaging diagnosis.

Despite a gradual decrease in prevalence, clonorchiasis is still prevalent in East Asia. A large and compelling body of evidence links clonorchiasis and cholangiocarcinoma, although the mechanisms involved are not completely understood. Clonorchiasis induces biliary epithelial hyperplasia and metaplasia, and this could facilitate at least one stage of the carcinogenesis, which is promoting effect. In areas of endemic infection, more clonorchiasis cases are now diagnosed incidentally during radiological examinations such as cholangiography, ultrasonography, and computed tomography. Radiological findings are regarded as pathognomonic for clonorchiasis since they reflect the unique pathological changes of this disorder. These radiological examinations currently play important roles in the diagnosis, staging, and decision-making process involved in the treatment of cholangiocarcinoma. The morphological features and radiological findings of clonorchiasis-associated cholangiocarcinoma are essentially combinations of the findings for the two diseases. The morphological features of clonorchiasis- associated cholangiocarcinoma, observed in radiological examinations, do not differ from those of the usual cholangiocarcinoma. In patients diagnosed with or suspected to have clonorchiasis, radiological findings should be carefully scrutinized for occult cholangiocarcinoma.

Adult↗
PubMed2004

Contrast-enhanced sonography for hepatocellular carcinoma.

It is well known that contrast-enhanced sonography is valuable for the evaluation of tumoral vascularity in hepatocellular carcinoma (HCC). The knowledge of tumoral vascularity is important to diagnose HCC, to decide treatment method, and to assess therapeutic response after various treatments. Until now, various techniques of contrast-enhanced sonography have been investigated with HCCs. The purpose of this review is to describe various contrast-enhanced sonographic techniques for HCC in sequence of their development and to outline the advantages and limitation of each technique.

Aged↗
PubMed2004

Primary gastrointestinal stromal tumors in the omentum and mesentery: CT findings and pathologic correlations.

OBJECTIVE: This study was undertaken to describe the CT features of primary gastrointestinal stromal tumors in the omentum and mesentery and to identify any pathologic correlation. CONCLUSION: On contrast-enhanced CT, primary gastrointestinal stromal tumors in the omentum and mesentery are usually well-defined, huge masses that contain large areas of low-attenuation necrosis and hemorrhage and that lack central gas.

Adult↗