Suk Ki Chang

The Prevalence and Significance of Incidental Thyroid Nodules Identified on Computed Tomography

Purpose: The purpose of this study was to assess the prevalence of incidental thyroid nodules (ITN) found on computed tomography (CT) of the neck and to determine whether CT characteristics could distinguish malignant from benign thyroid lesions. Materials and Methods: We retrospectively reviewed CT scans in 734 patients without known thyroid disease (384 men and 350 women; mean age, 49.8 ± 13.7 years). The CT findings of ITN such as size, shape (anteroposterior-transverse diameter ratio [AP/T ratio]), margin, peripheral enhancing rim, intralesional calcification, and attenuation characteristics were analyzed and correlated with ultrasonographic (US) findings. Results: One hundred sixty ITNs were noted in 123 (16.8%) patients. Of 120 ITNs whose histological diagnoses were available, 15 (12.5%) were malignant. Malignant nodules more frequently showed nodular or rim calcifications (46.7% vs 13.3%; P < 0.0005), AP/T ratio of greater than 1.0 (33.3% vs 9.5%; P < 0.05), and mean attenuation value on contrast-enhanced scan of greater than 130 Hounsfield units (86.7% vs 49.5%; P < 0.05) than benign nodules. Conclusions: We found at least a 9.4% (15/160) prevalence of malignancy among ITN detected on CT. The further evaluation with US or biopsy should be performed, if an ITN shows CT features suggesting malignancy (calcification; AP/T ratio, >1.0; or mean attenuation value, >130 HU).

Peripheral Calcification in Thyroid Nodules Ultrasonographic Features and Prediction of Malignancy

The purpose of this study was to investigate the association between peripheral calcification in thyroid nodules detected on ultrasonography and thyroid malignancy.

CT, MR, 18F-FDG PET/CT, and their combined use for the assessment of mandibular invasion by squamous cell carcinomas of the oral cavity

Background: A reliable assessment of mandibular invasion is crucial for treatment planning to obtain both radical tumor resection and good functional results. Purpose: To retrospectively compare the diagnostic value of three different imaging methods – computed tomography (CT), magnetic resonance (MR) imaging, 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT – and their combined use for detection of mandibular invasion by squamous cell carcinoma (SCC) of the oral cavity. Material and Methods: Forty-six patients (39 men and 7 women; mean age, 59.4 years) suspected of having mandibular invasion by SCC of the oral cavity underwent CT, MR, and PET/CT within 2 weeks before surgery. First, each study was reviewed separately for the presence of mandibular invasion by tumors. Then, the value of combined images was assessed based on a confidence rating score for each modality assigned by observers. These results were verified with histopathologic findings. Results: Histopathologic examination revealed mandibular invasion in 12 of 46 SCCs. The sensitivity, specificity, and accuracy were 41.7%, 100%, and 84.8% for CT; 58.3%, 97.1%, and 87.0% for MR; and 58.3%, 97.1%, and 87.0% for PET/CT, respectively. The comparison of these modalities showed no statistically significant difference among them (P > 0.05). The combination of CT, MR, and PET/CT improved sensitivity (83.3%), without loss of specificity (100%) and accuracy (95.7%), although the difference failed to reach statistical significance (P > 0.05). Conclusion: The combined analysis of CT, MR, and PET/CT can improve sensitivity in the detection of mandibular invasion by SCC of the oral cavity.

Publication Rates for Abstracts Presented by Korean Investigators at Major Radiology Meetings

Objective To determine the publication rate of abstracts presented by Korean investigators at national and international radiological meetings, and to identify predictive factors of publication. Materials and Methods Abstracts presented at the annual meetings of the Korean Radiological Society (KRS), and abstracts presented by Korean investigators at the annual meetings of the Radiological Society of North America (RSNA) and European Congress of Radiology (ECR) from 2001 to 2002 were searched for subsequent publication, using PubMed and the Korean Medical Database. The following variables were evaluated. 1) The overall publication rate; 2) the publication rates according to the radiological subspecialty, presentation type (oral or poster), sample size (≤ 20, 21-50, or > 50), study design (prospective or retrospective), statistical analysis (present or absent), and study outcome (positive or negative); 3) the time to publication; 4) the journal where the study was published; 5) consistency between the abstract and the final publication. Results Of 1,097 abstracts, 301 (27.4%) were subsequently published, at an average of 15.8 ± 13.8 months after presentation in 48 journals. The publication rates for studies presented at the RSNA (35.4%) and ECR (50.5%) conferences were significantly higher than that for the KRS conference (23.6%, p < 0.05). Vascular/interventional radiology studies had the highest publication rate (33.1%), whereas musculoskeletal radiology studies had the lowest publication rate (17.1%). Other factors associated with subsequent publication were prospective design, use of statistical testing, and a positive study outcome. Conclusion The publication rate is significantly lower for the KRS (23.6%) meeting abstracts as compared to those of the RSNA (35.4%) and ECR (50.5%). Prospective design, use of statistical testing, and positive study outcome have a statistically significant effect on the publication rate.

Effects of right- versus left-arm injections of contrast material on computed tomography of the head and neck.

Objective: To investigate the effects of the right- and left-arm injections of contrast material on image quality in computed tomography of the head and neck. Methods: Sixty patients were prospectively and randomly assigned into 2 groups. Eighty milliliters of contrast material (iodine concentration, 300 mg/mL) was administered into the right (n = 30) or the left (n = 30) antecubital vein at a 2-mL/s injection rate. The attenuation of the carotid artery (CA) and the internal jugular vein (IJV) was measured at 1.5-second intervals in each patient. The mean attenuation values for CA and IJV, the time to reach peak attenuation, the duration of diagnostic window (both CA and IJV enhancement were greater than 150 HU), the perivenous artifacts, and the retrograde flow of contrast material column from the subclavian or brachiocephalic vein were statistically compared between patients with right-arm injection and those with left-arm injection. Results: The mean attenuation values in CA and IJV were slightly higher in patients with right-arm injection than in those with left-arm injection, although no significant difference was reached (P = 0.06 for CA and 0.07 for IJV). The right-arm injection resulted in significantly reduced perivenous artifacts and retrograde flow of contrast material column. There were no significant differences in the time to reach the peak attenuation and in the duration of the diagnostic window between the 2 groups. Conclusions: The right-arm injection of contrast material may provide better image quality in the computed tomography of the head and neck when compared with the left-arm injection.

Combination of magnetic resonance cholangiopancreatography and computed tomography for preoperative diagnosis of the Mirizzi syndrome.

Objective: To determine the diagnostic accuracy of combined magnetic resonance cholangiopancreatography (MRCP) and computed tomography (CT) for preoperative diagnosis of Mirizzi syndrome. Materials and Methods: Fifty-two patients with surgically proven Mirizzi syndrome (n = 13) and cholecystitis without evidence for Mirizzi syndrome (n = 39) underwent both MRCP using single-shot turbo spin echo and 3-dimensional turbo spin echo sequences and CT. Two blinded observers independently and retrospectively reviewed the combination of MRCP and CT images and CT images alone. Diagnostic accuracy for a combined protocol and CT was evaluated. Results: The overall sensitivity, specificity, positive and negative predictive values, and accuracy of the combination of MRCP and CT were 96.0%, 93.5%, 83.5%, 98.5%, and 94.0%, respectively. Corresponding values of CT were 42.0%, 98.5%, 93.0%, 83.5%, and 85.0%, respectively. The sensitivity, negative predictive value, and accuracy of combined protocol were significantly higher than those of CT alone (P = 0.000, 0.001, and 0.042, respectively). Interobserver agreement was better for combined images (&kgr; = 0.906) than for CT images alone (&kgr; = 0.812). Conclusions: A combination of MRCP and CT is useful for preoperative diagnosis of Mirizzi syndrome.

Accuracy of CT angiography in the assessment of the circle of Willis: comparison of volume-rendered images and digital subtraction angiography:

Background Computed tomography angiography (CTA) is increasingly used for non-invasive imaging of the cerebrovascular diseases. Purpose To evaluate the accuracy of CTA in the assessment of the variation of the segment calibers of the circle of Willis. Material and Methods One hundred and 17 patients with acute SAH (51 men and 66 women, mean age 50.9 years) who underwent CTA using a 16 detector-row CT scanner and DSA were evaluated retrospectively. The CTA and DSA studies were performed within 24 h after the onset of symptoms and within 24 h of each other. A total of 819 arterial segments (A-comA, right and left A1 segment, right and left P-com A, and right and left P1 segment) of the circle of Willis were determined to be aplastic (grade 1), hypoplastic (grade 2), or normal-sized (grade 3) by blinded observers evaluating CTA volume-rendered images. The CTA results were then compared with findings on the corresponding DSA images (reference standard). Results The overall agreement between CTA and DSA was 92.4%. We had 62 (7.6%) cases of disagreement (58 cases of under-estimation and four cases of over-estimation by CTA) between tow modalities. The sensitivity and specificity of CTA in the detection of aplastic and normal-sized segments were more than 90%. In contrast, subgroup analysis of the hypoplastic segments showed a sensitivity of 52.6% and a specificity of 98.2%. Conclusion CTA is highly accurate in the assessment of anatomical variations of the circle of Willis; however, its sensitivity is limited in depicting hypoplastic segments.

CHANGES IN THE ABDOMINAL FAT DISTRIBUTION AFTER GASTRECTOMY: COMPUTED TOMOGRAPHY ASSESSMENT

Background:  We investigated the postoperative changes in visceral fat, as compared with subcutaneous fat in patients who underwent total gastrectomy (TG) or subtotal gastrectomy (STG).

CT, MR, and angiography findings of a solitary fibrous tumor of the larynx: a case report.

This report details the CT, MR, and angiography findings of a solitary fibrous tumor involving the larynx of a 34-year-old man. A precontrast CT scan revealed a well-defined isodense mass in the submucosal region of the supraglottic larynx. The tumor appeared as a mixed intensity lesion on the T1- and T2-weighted MR images. A T2-weighted MR image showed a central, round, and low signal intensity area within the mass. For both the CT and MR images, the mass demonstrated heterogeneous enhancement following the administration of contrast material. The angiography showed a hypervascular tumor with heterogeneous persistent staining.

Anaplastic Thyroid Carcinoma: Computed Tomographic Differentiation from Other Thyroid Masses

Background: Anaplastic thyroid carcinoma is rare but is one of the most aggressive malignancies. Therefore, accurate diagnosis is important in order to provide appropriate therapy. Purpose: To establish useful computed tomographic (CT) criteria for differentiating anaplastic carcinoma from other thyroid masses. Material and Methods: The CT scans of nine patients with anaplastic carcinomas were retrospectively reviewed and compared with those of 32 patients with papillary carcinomas (n = 12) or benign lesions (n = 20) exceeding a maximum diameter of 2.0 cm. Image analysis was performed according to the following CT parameters: size, margin (well defined or ill defined), composition (cystic, mixed, or solid), mean attenuation value, ratio of attenuation of the mass to that of the adjacent muscle (M/m attenuation ratio), necrosis (present or absent), and calcification (stippled, nodular, or absent) of the thyroid mass; and tumor-spreading patterns including the presence of surrounding normal thyroid tissue in the involved lobe, involvement of the contralateral thyroid lobe, extension into the adjacent structures, and cervical lymphadenopathy. Results: Anaplastic carcinomas appeared as large (average 4.6 cm), solid (100%), and ill-defined (88.9%) masses accompanied by necrosis (100%), nodular calcification (44.4%), direct invasion into the adjacent organs (55.6%), and cervical lymph node involvement (77.8%). Tumor necrosis was the most valuable parameter in differentiating anaplastic carcinomas from other thyroid masses. Patient age (>70 years) and low attenuation value on postcontrast scan (attenuation value <100 HU, or M/m attenuation ratio <1.3) are also helpful predictors for anaplastic carcinoma. Conclusion: If a patient is older than 70 years of age and has a large necrotic thyroid mass of low attenuation, anaplastic carcinoma should be included in the differential diagnosis.