Objective: Hyperdense lesions can frequently be observed on the CT obtained immediately after intra-arterial (IA) thrombolysis, and it is sometimes difficult to differentiate contrast extravasation from the hemorrhagic lesions. The purposes of this study are to classify the hyperdense lesions according to their morphologic features and to track the outcome of those lesions. Materials and Methods: Among the 94 patients who suffered with anterior circulation ischemic stroke and who were treated with IA thrombolysis, 31 patients revealed hyperdense lesions on the CT obtained immediately after the procedure. The lesions were categorized into four types according to their volume, shape, location and density: cortical high density (HD), soft HD, metallic HD and diffuse HD. The follow-up images were obtained 3-5 days later in order to visualize the morphologic changes and hemorrhagic transformation of the lesions. Results: Among the 31 patients with HD lesions, 18 (58%) showed hemorrhagic transformation of their lesion, and six of them were significant. All the cortical HD lesions (n=4) revealed spontaneous resolution. Seven of the soft HD lesions (n=13) showed spontaneous resolution, while the rest of the group showed hemorrhagic transformation. Among them the hemorrhage was significant in only two patients (2/6) who did not achieve successful recanalization. All the metallic HD lesions (n=10) resulted in hemorrhagic transformation; among them, three cases (30%) with a maximum CT value more than 150 HU (Hounsfield unit) subsequently showed significant hemorrhagic transformation on the follow-up CT. There were four diffuse HD lesions, and two of them showed hemorrhagic transformation. Conclusion: The parenchymal hyperdense lesions observed on the CT obtained immedicately after IA thrombolysis in ischemic stroke patients exhibited varying features and they were not always hemorrhagic. Most of the soft HD lesions were benign, and although all of the metallic HD lesions were hemorrhagic, some of them were ultimately found to be benign.

Objective: We wanted to describe the characteristic ultrasonography (US) features and clinical findings for making the diagnosis of subacute granulomatous thyroiditis. Materials and Methods: A total of 31 lesions from 27 patients were confirmed as subacute granulomatous thyroiditis by US-guided fine needle aspiration biopsy. We analyzed the ultrasonographic findings such as the lesion's size, margin and shape, the discrepancy between length and breadth and the vascularity. The clinical findings such as acute neck pain or fever were reviewed. The follow-up clinical and ultrasonographic data were reviewed for 15 patients. Results: The thyroid gland was found to be enlarged in five patients, it was normal size in 20 patients and it was smaller in two patients. All the lesions had focally ill-defined hypoechogenicity. Hypervascularity was not noted in any of the lesions. Painful neck swelling was present in 18 patients. An accompanying fever was documented in nine of the 18 patients. Twelve patients showed disappearance (n=3) or a decreased size (n=9) of their lesions on follow-up US. Conclusion: The presence of ill-defined hypoechoic thyroid lesions without a discrete round or oval shape is characteristic for subacute granulomatous thyroiditis, and particularly when this is associated with painful neck swelling and/or fever.

Objective: We wanted to assess the feasibility and diagnostic accuracy of whole heart coronary magnetic resonance angiography (MRA) with using 3D balanced turbo-field-echo (b-TFE) with SENSE and the half-Fourier acquisition technique for identifying stenoses of the coronary artery. Materials and Methods: Twenty-one patients who underwent both whole heart coronary MRA examinations and conventional catheter coronary angiography examinations were enrolled in the study. The whole heart coronary MRA images were acquired using a navigator gated 3D b-TFE sequence with SENSE and the half-Fourier acquisition technique to reduce the acquisition time. The imaging slab covered the whole heart (80 contiguous slices with a reconstructed slice thickness of 1.5mm) along the transverse axis. The quality of the images was evaluated by using a 5-point scale (0-uninterpretable, 1-poor, 2-fair, 3-good, 4-excellent). Ten coronary segments of the heart were evaluated in each case; the left main coronary artery (LM), and the proximal, middle and distal segments of the left anterior descending (LAD), the left circumflex (LCX) and the right coronary artery (RCA). The diagnostic accuracy of whole heart coronary MRA for detecting significant coronary artery stenosis was determined on the segment-by-segment basis, and it was compared with the results obtained by conventional catheter angiography, which is the gold standard. Results: The mean image quality was 3.7 in the LM, 3.2 in the LAD, 2.5 in the LCX, and 3.3 in the RCA, respectively (the overall image quality was $3.0{\pm}0.1$). 168 (84%) of the 201 segments had an acceptable image quality(${\geq}$ grade 2). The sensitivity, specificity, accuracy, negative predictive value and positive predictive value of the whole heart coronary MRA images for detecting significant stenosis were 81.3%, 92.1%, 91.1%, 97.9%, and 52.0%, respectively. The mean coronary MRA acquisition time was 9 min 22 sec (${\pm}$ 125 sec). Conclusion: Whole heart coronary MRA is a feasible technique, and it has good potential to evaluate the major portions of the coronary arteries with an acceptable image quality within a reasonable scan time.

Objective: To evaluate how changes in lung volume affect volumetric measurements of lung nodules using a multi-detector row CT. Materials and Methods: Ten subjects with asthma or chronic bronchitis who had one or more lung nodules were included. For each subject, two sets of CT images were obtained at inspiration and at expiration. A total of 33 nodules (23 nodules ${\geq}3mm$) were identified and their volume measured using a semiautomatic volume measurement program. Differences between nodule volume on inspiration and expiration were compared using the paired t-test. Percent differences, between on inspiration and expiration, in nodule attenuation, total lung volume, whole lung attenuation, and regional lung attenuation, were computed and compared with percent difference in nodule volume determined by linear correlation analysis. Results: The difference in nodule volume observed between inspiration and expiration was significant (p<0.01); the mean percent difference in lung nodule volume was 23.1% for all nodules and for nodules ${\geq}3mm$. The volume of nodules was measured to be larger on expiration CT than on inspiration CT (28 out of 33 nodules; 19 out of 23 nodules ${\geq}3mm$). A statistically significant correlation was found between the percent difference of lung nodule volume and lung volume or regional lung attenuation (p<0.05) for nodules ${\geq}3mm$. Conclusion: Volumetric measurements of pulmonary nodules were significantly affected by changes in lung volume. The variability in this respiration-related measurement should be considered to determine whether growth has occurred in a lung nodule.

Objective: The aim of our study was to compare the accuracy of CT and $^{18}F-FDG$ PET for detecting peritoneal metastasis in patients with gastric carcinoma. Materials and Methods: One-hundred-twelve patients who underwent a histologic confirmative exam or treatment (laparotomy, n=107; diagnostic laparoscopy, n=4; peritoneal washing cytology, n=1) were retrospectively enrolled. All the patients underwent CT and $^{18}F-FDG$ PET scanning for their preoperative evaluation. The sensitivities, specificities and accuracies of CT and $^{18}F-FDG$ PET imaging for the detection of peritoneal metastasis were calculated and then compared using Fisher's exact probability test (p<0.05), on the basis of the original preoperative reports. In addition, two board-certified radiologists and two board-certified nuclear medicine physicians independently reviewed the CT and PET scans, respectively. A receiver-operating characteristic curve analysis was performed to compare the diagnostic performance of CT and $^{18}F-FDG$ PET imaging for detecting peritoneal metastasis. Results: Based on the original preoperative reports, CT and $^{18}F-FDG$ PET showed sensitivities of 76.5% and 35.3% (p=0.037), specificities of 91.6% and 98.9% (p=0.035), respectively, and equal accuracies of 89.3% (p=1.0). The receptor operating characteristics curve analysis showed a significantly higher diagnostic performance for CT (Az=0.878) than for PET (Az=0.686) (p=0.004). The interobserver agreement for detecting peritoneal metastasis was good (${\kappa}$ value = 0.684) for CT and moderate (${\kappa}$ value = 0.460) for PET. Conclusion: For the detection of peritoneal metastasis, CT was more sensitive and showed a higher diagnostic performance than PET, although CT had a relatively lower specificity than did PET.

Objective: We wanted to investigate the prevalence and causative factors of extrahepatic arterial blood supply to hepatocellular carcinoma (HCC) at its initial presentation and during chemoembolization. Materials and Methods: Between February 1998 and April 2000, consecutive 479 patients with newly diagnosed HCC were prospectively enrolled into this study. A total of 1629 sessions of transcatheter arterial chemoembolization (TACE) were performed in these patients (range: 1-15 sessions; mean: 3.4 sessions) until April 2004. For each TACE procedure, we determined the potential extrahepatic collateral arteries (ExCAs) depending on the location of the tumor, and we performed selective angiography of all suspected collaterals that could supply the tumor. The prevalence of ExCAs and the causative factors were analyzed. Results: At initial presentation, 82(17%) of these 479 patients showed 108 ExCAs supplying tumors. Univariate analysis showed that tumor size (p<0.01), patient age (p=0.02), a surface location (p<0.01), and a bare area location (p<0.01) were significantly associated with the presence of ExCAs. Multiple logistic regression analysis showed that only tumor size was predictive of ExCAs formation (p<0.01, odds ratio=1.737, confidence interval: 1.533 to 1.969). During repeated TACE sessions, 97 additional ExCAs were detected in 70 (14%) patients. The cumulative probability of ExCAs in patients with a large tumor $({\geq}5cm)$ was significantly higher than that for those patients with a small tumor (<5cm) (p<0.01). Conclusion: The presence of ExCAs supplying HCC is rather common, and the tumor size is a significant causative factor for the development of these collateral arteries.

Objective: We wanted to evaluate whether tumors located in a segmental border zone are predisposed to local recurrence after performing segmental transarterial chemoembolization for hepatocellular carcinoma. Materials and Methods: Seventy-three hepatocellular carcinoma nodules were retrospectively analyzed for local tumor recurrence after performing segmental transarterial chemoembolization by using follow-up CT studies (median follow-up period: 20 months, range: 4-77 months). The tumors were divided into two groups according to whether the lesions were located at the segmental border zone (Group I) or not (Group II). Comparison of the tumor characteristics and chemoembolization methods between the two groups was performed using the chi-square test. The local recurrence rates were compared by Kaplan-Meyer method and analyzed with the log rank test. Results: Local tumor recurrence occurred for 25 hepatocellular carcinoma nodules (42.9%). The follow-up periods, tumor characteristics and chemoembolization methods between Groups I and II were comparable. The local recurrence rate was 64.0% (16/25) in Group I and 18.8% (9/48) in Group II. The difference was statistically significant on the univariate and multivariate analyses (p=0.000 for both). Conclusion: Tumor location in a segmental border zone was a significant risk factor for local tumor recurrence after performing segmental transarterial chemoembolization for hepatocellular carcinoma.

Objective: To evaluate the effect of thin overlapping reconstruction on the attenuation of small $({\leq}3cm)$ renal cysts in the nephrographic phase of multidetector CT (MDCT). Materials and Methods: We scanned a phantom kidney containing spheres of various sizes (10,20, and 30 mm) using both 4- and 16-channel MDCT scanners, and reconstructed images with various slice thickness (T, mm) and intervals (I, mm). The attenuation increase (AI) was measured for each sphere in 240-HU diluted solution of contrast material and compared with the attenuation in 35-HU solution. Results: On the 4-channel MDCT, thin overlapping reconstruction (T/I =3/1, compared with 5/5) lowered the AI as much as 17 HU in the 10 mm-sphere and 6 HU in the 20mm-sphere (p<0.05). Thin slicing alone was also effective; however overlapping alone was not. On the 16-channel MDCT, AI in the 10 mm-sphere was significantly lower than on the 4-channel MDCT with T/I = 5/5 (p<0.05), however thinner slicing or overlapping did not affect the attenuation significantly in all of the spheres. Conclusion: The effect of thin overlapping reconstruction on minimizing falsely elevated attenuation in the nephrographic phase was significant only in cysts ${\leq}20$ mm on the 4-channel MDCT.

Objective: The study was performed to present the sonographic findings of uterine endometrial stromal sarcoma (ESS). Materials and Methods: We conducted a retrospective review of sonographic findings of 10 cases that were diagnosed as uterine ESS. The patients' ages ranged from 25 to 51 years (mean age: 36.1 years). The reviews focused on the location, margin, size, number and echotexture of the lesions. Hysterectomy (n=9) and myomectomy (n=1) were performed and a pathologic diagnosis was obtained in all cases. Results: The masses were located in the uterine wall (n=6), or they presented as a polypoid mass protruding into the endometrial cavity from the myometrium (n=3) or as a central cavity mass (n=1). The lesion margins were smooth (n=5), ill defined (n=2), or smooth with partially nodular extensions (n=3). The maximal mass length was 38 mm to 160 mm with a mean mass length of 83.5 mm. There were single lesions in eight cases and multiple lesions in two cases. The lesion echotextures were hypoechoic solid (n=3), heterogeneously intermediate echoic (n=5), diffuse myometrial thickening with heterogeneous echogenicity (n=1) and septated cystic (n=1). Conclusion: Endometrial stromal sarcoma presents with four patterns of its sonographic appearance; a polypoid mass with nodular myometrial extension, an intramural mass with an ill defined margin and heterogeneous echogenicity, an ill defined large central cavity mass or, diffuse myometrial thickening.

Generalized lymphangiomatosis is a rare disease that is characterized by widespread bony and soft tissue involvement of lymphangioma. Radiological evaluation is crucial because the site and extent of the lymphangioma are important prognostic factors. We reported here on three cases of generalized lymphangiomatosis and all three cases showed similar radiologic findings, but a different clinical course. The CT, US and MR images showed sharply defined, nonenhanced cystic lesions involving the mediastinum, bones, spleen, lung and lower neck. The whole body MR imaging with the short tau inversion recovery (STIR) sequence showed good capability for evaluating the extent of disease.

We report here on a rare case of carotid artery angioplasty and stenting in a patient with spontaneous recanalization after complete occlusion of the proximal internal carotid artery (ICA). The patient initially showed severe stenosis at the left proximal ICA on MR angiography (MRA). Digital subtraction angiography (DSA) performed three days after MRA showed complete occlusion of the proximal ICA. The follow-up DSA after four weeks showed recanalization of the ICA, and then carotid artery stenting was successfully performed. There has been no neurologic complication during more than one year follow-up.

Ectopic stomal varices are an unusual cause of gastrointestinal hemorrhage. The term "ectopic stomal varices" means abnormally dilated veins that have developed in the stomal mucosa. We describe the 20 reformatted and 30 volume rendered images by MDCT in a patient with an episode of acute bleeding from the colonic stoma. This case indicates that the 20 reformatted and 3D volume rendered images are useful to detect this rare complication of portal hypertension, and they help to tailor adequate treatment for the patients with bleeding from stomal varices.