Ji Hyun Koo

Sungkyunkwan University, Seoul, Seoul, South Korea

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Publications (10)17.2 Total impact

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    ABSTRACT: To retrospectively determine the optimal b value of diffusion-weighted imaging (DWI) for predicting the presence of localized prostate cancer, and to evaluate the utility of DWI under different b values in differentiating between cancers and benign prostatic tissues. Eighty patients with suspected prostate cancer underwent MRI including DWI at 3T, followed by radical prostatectomy. DWI was examined under different b values. Apparent diffusion coefficient (ADC) maps were generated by using b = 0, and other b values of 300, 700, 1000 or 2000 s/mm(2). For predicting the presence of cancers, four different ADC maps were analyzed independently by two blinded readers. ADCs were measured in benign and malignant tissues. For predicting the presence of 110 prostate cancers, the sensitivity and area under the curve (AUC) for an experienced reader was significantly greater at b = 1000 (85% and 0.91) than b = 300, 700 or 2000 s/mm(2) (p < 0.01). For a less-experienced reader, the AUC was significantly greater at b = 700, 1000 or 2000 than b = 300 s/mm(2) (p < 0.01). Mean ADCs of the cancers in sequence from b = 300 to 2000 s/mm(2) were 1.33, 1.03, 0.88 and 0.68 × 10(-3) mm(2)/s, which were significantly lower than those of benign tissues (p < 0.001). The optimal b value for 3T DWI for predicting the presence of prostate cancer may be 1000 s/mm(2).
    Korean journal of radiology: official journal of the Korean Radiological Society 01/2013; 14(1):61-9. · 1.32 Impact Factor
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    ABSTRACT: Our aim was to determine whether sonographically guided radiofrequency ablation with superficial saline injection can minimize thermal injury of the skin without an influence on therapeutic efficacy. Institutional Animal Care Committee approval was obtained. Twelve percutaneous radiofrequency ablation procedures were performed in the thighs of 6 rabbits (control, n = 6, right thigh; experimental, n = 6, left thigh). The ablation with local anesthesia was performed in the most superficial area of the thigh muscle. In the experimental group, 1 mL of saline was injected before the ablation at the tissue layer between the skin and ablated muscle. The duration and energy of the ablation were the same in the control and experimental groups. Rabbits were compared for their gross skin state and histopathologic findings after the ablation. The degree of thermal coagulation of the muscle was similar in both groups at pathologic examination. Grossly, skin redness was mild in the experimental group but moderate in the control group. Of the 6 rabbits, 5 tended to show more frequent histopathologic changes, including an inflammatory reaction, interruption of collagen fibers, injury of the skin adnexa, and fibrosis, in the control group when compared with the experimental group. However, there was no statistically significant difference (all P> .05). One rabbit that underwent ablation at higher energy had a partially dissected epidermis in the control group only. Sonographically guided radiofrequency ablation with a saline injection superficial to a tumor might prevent skin burns and provide equivalent therapeutic efficacy for ablating superficial lesions.
    Journal of ultrasound in medicine: official journal of the American Institute of Ultrasound in Medicine 06/2012; 31(6):873-8. · 1.40 Impact Factor
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    ABSTRACT: We investigated low dose digital tomosynthesis (DT) for the evaluation of the paranasal sinus (PNS), and compared its diagnostic accuracy with a PNS radiography series (XR). We enrolled 43 patients for whom XR, PNS DT, and OMU CT were performed. We measured effective doses (EDs) of XR, DT, and OMU CT using Monte Carlo simulation software. Two radiologists performed independent observation of both XR and DT. For seven PNSs, they scored anatomic conspicuity of sinuses and confidence on the presence of sinusitis using nine point scales. OMU CT was observed by the third radiologist and the findings were regarded as reference standard. We compared scores for conspicuity and sinusitis confidence between XR and DT. Mean EDs were 29 ± 6 µSv, 48 ± 10 µSv, and 980 ± 250 µSv, respectively, for XR, DT, and CT. Mean scores for conspicuity were 6.3 and 7.4, respectively, for XR and DT. Sensitivity per patient basis for sinusitis detection were 52% and 96%, respectively, for XR and DT in observer 1 (p = 0.001) and 80% and 92% for observer 2 (p = 0.25). Specificities for sinusitis exclusion were 100% for both XR and DT for observer 1 and 89% and 100% for observer 2 (p = 0.50). Accuracies for sinusitis diagnosis were 72% and 98%, respectively, for XR and DT for observer 1 (p = 0.001) and 84% and 95% for observer 2 (p = 0.125). Patient radiation dose from low dose DT is comparable with that of PNS XR. Diagnostic sensitivity of DT for sinusitis was superior to PNS XR.
    Korean journal of radiology: official journal of the Korean Radiological Society 03/2012; 13(2):136-43. · 1.32 Impact Factor
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    ABSTRACT: To evaluate the performance of digital tomosynthesis (DT) of the chest for detection of lung nodules in patients with colorectal cancer (CRC). The institutional review board approved this study, and all patients provided informed consent. A commercial caesium iodide/amorphous silicon (CsI/a-Si) flat-panel detector system was used to verify the performance of the DT and chest radiography (XR) methods. DT was performed in 142 patients with CRC. All 142 patients underwent chest computed tomography (CT) within a week of DT. As a reference standard, two radiologists reviewed the chest CT in consensus and recorded the presence of pulmonary nodules. Another two radiologists independently observed the DT images and recorded the presence of pulmonary nodules. The status of all lung nodules was assessed either histologically or by follow-up over a period of 1 year. The nodules were classified into metastasis, benign, and uncertain. Statistical analysis of the results was performed. Two hundred and thirty-seven nodules from 142 patients were found at CT. These included 71 proven metastases and 126 benign nodules; 40 nodules were uncertain. Observers detected 83% of all lung nodules and 93% of proven metastases using DT. Among 237 nodules, 147 nodules were larger than 4mm in diameter on the CT images. Observers detected 87% of lung nodules that were larger than 4mm. Despite a reasonably low radiation dose, DT is a sensitive method, and is comparable to chest CT for the detection of lung nodules, particularly metastatic lung nodules in patients with CRC.
    Clinical radiology 09/2011; 67(3):232-8. · 1.65 Impact Factor
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    ABSTRACT: To evaluate the difference in diagnostic performance of hydro-stomach computed tomography (CT) to detect early gastric cancer (EGC) between blinded and unblinded analysis and to assess independent factors affecting visibility of cancer foci. Two radiologists initially blinded and then unblinded to gastroscopic and surgical-histological findings independently reviewed hydro-stomach CT images of 110 patients with single EGC. They graded the visibility of cancer foci for each of three gastric segments (upper, middle and lower thirds) using a 4-point scale (1: definitely absent, 2: probably absent, 3: probably present, and 4: definitely present). The sensitivity and specificity for detecting an EGC were calculated. Intraobserver and interobserver agreements were analyzed. The visibility of an EGC was evaluated with regard to tumor size, invasion depth, gastric segments, histological type and gross morphology using univariate and multivariate analysis. The respective sensitivities and specificities [reviewer 1: blinded, 20% (22/110) and 98% (215/220); unblinded, 27% (30/110) and 100% (219/220)/reviewer 2: blinded, 19% (21/110) and 98% (216/220); unblinded, 25% (27/110) and 98% (215/220)] were not significantly different. Although intraobserver agreements were good (weighted κ = 0.677 and 0.666), interobserver agreements were fair (blinded, 0.371) or moderate (unblinded, 0.558). For both univariate and multivariate analyses, the tumor size and invasion depth were statistically significant factors affecting visibility. The diagnostic performance of hydro-stomach CT to detect an EGC was not significantly different between blinded and unblinded analysis. The tumor size and invasion depth were independent factors for visibility.
    World Journal of Gastroenterology 02/2011; 17(8):1051-7. · 2.55 Impact Factor
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    ABSTRACT: Esophagopleural fistulas after esophageal diverticulectomy are very rare complications. Many treatment options have been reported, and the appropriate method should be chosen according to the individual's clinical status. The authors introduce a new treatment method of esophagopleural fistulas using an AMPLATZER vascular plug (AGA Medical Corporation, Plymouth, Minnesota), coils, and Histoacryl glue (B. Braun, Melsungen AG, Germany), thus avoiding extensive surgery or covered stent insertion.
    Journal of vascular and interventional radiology: JVIR 12/2010; 21(12):1905-10. · 1.81 Impact Factor
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    ABSTRACT: The purpose of our study was to provide sonographic findings of cystic nodules, which can mimic malignancies, after fine-needle aspiration (FNA) and to determine the differential points from malignancies. We retrospectively reviewed the sonographic findings of 33 lesions in 32 patients who had FNA for predominantly cystic nodules or cysts and showed suspicious findings during sonographic follow-up, as well as findings of 47 surgically confirmed papillary thyroid carcinomas (PTCs) in 45 consecutive patients. We evaluated the size, shape, presence of shadowing and a halo, margin, echogenicity, and presence of echogenic dots for each nodule. The final diagnosis of cystic nodules was confirmed by FNA, surgery, or follow-up sonography. Of the 33 cystic lesions, 31 (94%) were adequate with benign results, and 2 (6%) were inadequate specimens at the initial FNA. There were no malignancies in the cystic nodules at follow-up. The average interval between the initial FNA and suspicious sonographic findings was 26 months (range, 1-92 months). The average size of the suspicious nodules was 0.8 cm (range, 0.3-1.8 cm). Cystic nodules after aspiration were similar to PTCs in their sonographic findings, but the former frequently showed shadowing and a halo (85% versus 21%; P < .0001). With further follow-up, 29 lesions (88%) showed additional decreases in size. Benign cystic nodules after aspiration can have suspicious malignant features. However, shadowing and a halo associated with malignant features are characteristic findings of cystic nodule shrinkage. Awareness of these findings and correlation with the FNA history can aid in preventing unnecessary FNA.
    Journal of ultrasound in medicine: official journal of the American Institute of Ultrasound in Medicine 10/2010; 29(10):1415-21. · 1.40 Impact Factor
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    ABSTRACT: This study was designed to compare the diagnostic performance of gadoxetic acid-enhanced magnetic resonance imaging (MRI) with gadobenate dimeglumine-enhanced MRI for preoperatively detecting hepatocellular carcinoma (HCC). Eighteen consecutive patients (17 men and one woman, age range: 31-73 years) with 22 HCCs underwent examinations with gadoxetic acid enhanced MRI and gadobenate dimeglumine-enhanced MRI on a 3.0-Tesla unit. The diagnosis of HCC was established after surgical resection and pathological conformation. Three observers independently reviewed each MR image in a random order on a tumor-by-tumor basis. The diagnostic accuracy of these techniques for the detection of HCC was assessed by performing an alternative free-response receiver operating characteristic (ROC) analysis. The sensitivity and positive predictive values were evaluated. The average value of the area under the ROC curve (Az) for gadoxetic acid enhanced MRI (0.887) was not significantly different from the Az (0.899) for gadobenate dimeglumine-enhanced MRI (p > 0.05). The overall sensitivities of gadoxetic acid enhanced MRI and gadobenate dimeglumine-enhanced MRI were 80% and 83%, respectively, with no significant difference (p > 0.05). The differences of the positive predictive values for the two contrast agents for each observer were not statistically significant (p > 0.05). The diagnostic performance of gadoxetic acid-enhanced MRI and gadobenate dimeglumine-enhanced MRI for preoperatively detecting HCC is quite similar.
    Korean journal of radiology: official journal of the Korean Radiological Society 01/2010; 11(4):433-40. · 1.32 Impact Factor
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    ABSTRACT: We aimed to retrospectively compare CT, PET, and histopathologic (the extent of bronchioloalveolar carcinoma [BAC] components) findings of solitary pulmonary nodular (SPN) adenocarcinomas of the lung to determine their value as prognostic determinants. We reviewed CT and PET characteristics of tumors and pathologic specimens from 65 consecutive patients who underwent surgical resection for SPN adenocarcinomas. Nodule size and TDR (tumor shadow disappearance rate) were assessed from CT scans, and maximum standardized uptake value (SUVmax) of tumors was measured at PET. On pathologic examination, BAC, non-BAC, and central fibrous scar ratios were quantified. Prognosis was evaluated by noting disease recurrence during a minimum 12-month follow-up period after curative resection. The interrelationships between TDR, SUVmax, BAC, and non-BAC ratio were studied, and relationships between recurrence and various variables were analyzed. The median follow-up time was 33 months, and seven patients (11%) developed disease recurrence after surgical resection. TDR at CT and SUVmax at PET correlated well with pathologic BAC and non-BAC ratios. Between subgroups with and without recurrence, there were significant differences in SUVmax and BAC and non-BAC ratios. Based on univariate survival analyses, pathologic BAC and non-BAC ratios were risk factors significantly related to recurrence, but only high non-BAC ratio remained as an independent factor associated with recurrence in the multivariate analysis (hazard ratio [HR]=0.956, P=0.013). Among the factors examined, pathologic non-BAC ratio is the only independent risk factor for poor prognosis in patients with SPN adenocarcinomas.
    Lung cancer (Amsterdam, Netherlands) 04/2009; 66(3):379-85. · 3.14 Impact Factor
  • Article: Response.
    Korean journal of radiology: official journal of the Korean Radiological Society 14(5):866-7. · 1.32 Impact Factor