Sung Mok Kim

Coronary Calcium Screening Using Low-Dose Lung Cancer Screening: Effectiveness of MDCT with Retrospective Reconstruction

OBJECTIVE The purpose of our study was to show the usefulness of nongated low-dose chest CT for coronary screening by comparing the results of coronary artery calcium measurement with that of dedicated calcium-scoring CT. MATERIALS AND METHODS One hundred twenty-eight consecutive participants (all men; mean age, 52 +/- 7 years) underwent low-dose chest CT and calcium-scoring CT with prospective ECG gating using 40-MDCT. Low-dose chest CT volume data were reconstructed as 25-cm field of view and three slice thicknesses: 1, 2.5, and 5 mm. For each examination, the lesion area, Agatston calcium score, and calcium mass were measured at 90- and 130-H thresholds. All measurements (130-H threshold) from the calcium-scoring CT were used as reference standards. Spearmans correlation test was used to compare the results. RESULTS Among the low-dose chest CT examinations, sensitivity was best determined with a 1-mm slice thickness at 130 H and 2.5-mm slice thickness at 90 H. Specificity was best determined with a 5-mm slice thickness at 130 H. Accuracy (90%) was best determined with a 2.5-mm slice thickness at 130 H. Of all protocols, calcium area, score, and mass from a 2.5-mm slice thickness at 130 H correlated best with the reference results (r = 0.89 for all three criteria). CONCLUSION Using a low radiation dose and nongated MDCT, we can detect coronary artery calcium and obtain results comparable to those obtained with dedicated calcium-scoring CT that uses a higher dose and ECG gating.

Drug-sensitive tuberculosis, multidrug-resistant tuberculosis, and nontuberculous mycobacterial pulmonary disease in nonAIDS adults: comparisons of thin-section CT findings.

The aim of this work was to compare thin-section CT (TSCT) findings of drug-sensitive (DS) tuberculosis (TB), multidrug-resistant (MDR) TB, and nontuberculous mycobacterial (NTM) pulmonary disease in nonAIDS adults. During 2003, 216 (113 DS TB, 35 MDR TB, and 68 NTM) patients with smear-positive sputum for acid-fast bacilli (AFB), and who were subsequently confirmed to have mycobacterial pulmonary disease, underwent thoracic TSCT. The frequency of lung lesion patterns on TSCT and patients’ demographic data were compared. The commonest TSCT findings were tree-in-bud opacities and nodules. On a per-person basis, significant differences were found in the frequency of multiple cavities and bronchiectasis (P<0.001, chi-square test and multiple logistic regression analysis). Multiple cavities were more frequent in MDR TB than in the other two groups and extensive bronchiectasis in NTM disease (multiple logistic regression analysis). Patients with MDR TB were younger than those with DS TB or NTM disease (P<0.001, multiple logistic regression analysis). Previous tuberculosis treatment history was significantly more frequent in patients with MDR TB or NTM disease (P<0.001, chi-square test and multiple logistic regression analysis). In patients with positive sputum AFB, multiple cavities, young age, and previous tuberculosis treatment history imply MDR TB, whereas extensive bronchiectasis, old age, and previous tuberculosis treatment history NTM disease.

Korean Guidelines for the Appropriate Use of Cardiac CT

The development of cardiac CT has provided a non-invasive alternative to echocardiography, exercise electrocardiogram, and invasive angiography and cardiac CT continues to develop at an exponential speed even now. The appropriate use of cardiac CT may lead to improvements in the medical performances of physicians and can reduce medical costs which eventually contribute to better public health. However, until now, there has been no guideline regarding the appropriate use of cardiac CT in Korea. We intend to provide guidelines for the appropriate use of cardiac CT in heart diseases based on scientific data. The purpose of this guideline is to assist clinicians and other health professionals in the use of cardiac CT for diagnosis and treatment of heart diseases, especially in patients at high risk or suspected of heart disease.

Takayasu Arteritis: Assessment of Coronary Arterial Abnormalities with 128-Section Dual-Source CT Angiography of the Coronary Arteries and Aorta

PURPOSE To evaluate coronary arterial lesions and to assess their correlation with clinical findings in patients with Takayasu arteritis (TA) by using coronary computed tomographic (CT) angiography. MATERIALS AND METHODS This retrospective study was approved by the hospital internal review board, and informed consent was waived. A total of 111 consecutive patients with TA (97 female, 14 male; mean age, 44 years ± 13.8 [standard deviation]; age range, 14-74 years) underwent CT angiography of the coronary arteries and aorta with 128-section dual-source CT. CT angiographic, clinical, and laboratory findings of each patient were retrospectively reviewed. Statistical differences between coronary CT angiographic findings and clinical parameters were examined with univariate analysis. RESULTS Of 111 patients, 32 (28.8%) had cardiac symptoms and the remaining 79 (71.2%) had no cardiac symptoms. Fifty-nine patients (53.2%) had coronary arterial lesions at coronary CT angiography. Three main radiologic features were detected: coronary ostial stenosis (n = 31, 28.0%), nonostial coronary arterial stenosis (n = 41, 36.9%), and coronary aneurysm (n = 9, 8.1%). Coronary artery ostial or luminal stenosis of 50% or more or coronary aneurysms were observed in 26 (23.4%) patients with TA. Patients with coronary arterial abnormalities at coronary CT angiography had higher incidences of hypertension (P = .02), were older at the time of CT (P = .01), and had longer duration of TA (P = .02) than those without coronary artery abnormalities. The presence of cardiac symptoms, disease activity, and other comorbidities was not associated with differences in coronary artery involvement. CONCLUSION In patients with TA, there is a high prevalence of coronary arterial abnormalities at coronary CT angiography, regardless of disease activity or symptoms. Thus, coronary CT angiography may add information on coronary artery lesions in patients with TA.

Dual-energy CT perfusion during pharmacologic stress for the assessment of myocardial perfusion defects using a second-generation dual-source CT: a comparison with cardiac magnetic resonance imaging.

Objectives This study aimed to assess the diagnostic performance of adenosine-stress dual-energy myocardial computed tomography perfusion (DECTP) imaging using 128-slice dual-source computed tomography (CT) for the detection of myocardial perfusion defects in comparison with stress-perfusion magnetic resonance imaging (MRI). Methods This prospective study included 50 patients (mean age, 66 [9] years; 64% men) with suspected coronary artery disease who underwent adenosine-stress DECTP using 128-slice dual-source CT as well as adenosine-stress cardiac MRI using a 1.5-T scanner. Estimates of diagnostic accuracy in detecting myocardial perfusion defects were calculatedand compared with those of cardiac MRI. Results The estimates of diagnostic accuracy in detecting myocardial perfusion defects using DECTP were as follows: sensitivity, 77% (95% confidence interval [CI], 67%–87%); specificity, 94% (95% CI, 92%–95%); positive predictive value, 53% (95% CI, 44%–63%); and negative predictive value, 98% (95% CI, 97%–99%). The results of DECTP imaging were positively correlated with those of cardiac MRI (r = 0.602, P < 0.001). Mean effective radiation doses for stress DECTP imaging and rest coronary CTA were 6.5 (2.2) and 4.9 (1.7) mSv, respectively. Conclusions Adenosine-stress DECTP imaging enables detection of myocardial ischemia. However, further technical developments are necessary to reduce artifacts and improve the sensitivity of DECTP.

Right ventricular fat infiltration in asymptomatic subjects: observations from ECG-gated 16-slice multidetector CT.

Objective: To analyze the computed tomography (CT) findings of fatty replacement in the right ventricle (RV) of asymptomatic subjects and to correlate the CT findings with electrocardiogram (ECG) abnormalities. Methods: This prospective study included 996 subjects who underwent ECG-gated 16-slice CT for determination of coronary calcium scores. The CT findings were analyzed in terms of location, pattern, and degree of RV fat infiltration, along with the shape and dimension of RV. The RV fat was regarded present when a region showed less than or equal to −30 Hounsfield units as revealed by CT. Results: Computed tomography features suggestive of RV fat were found in 169 subjects (17%; 136 men and 33 women; mean age, 56.3 years). The most frequent location of fat was the basal superior wall (93%); next was the middle superior wall (72%); and then, the RV outflow tract (44%). Subjects with moderate to severe involvement were older than those with mild involvement (P = 0.012). In 3 subjects, the RV wall thickening with fat was more than 5 mm. Angular deformity and undulating appearance of the RV also occurred in 25 (15%) and 20 subjects (12%), respectively. However, these were not patients with ECG findings positive for arrhythmogenic RV dysplasia. Conclusions: Asymptomatic subjects may have fat in RV on CT. However, these subjects show no RV dysfunction or significant ECG-abnormalities consistent with the diagnosis of arrhythmogenic RV dysplasia.

Efficacy of Femoral Vascular Closure Devices in Patients Treated with Anticoagulant, Abciximab or Thrombolytics during Percutaneous Endovascular Procedures

Objective This study assessed the outcomes of using vascular closure devices following percutaneous transfemoral endovascular procedures in the patients who were treated with heparin, abciximab or thrombolytics (urokinase or t-PA) during the procedures. Materials and Methods From March 28, 2003 to August 31, 2004, we conducted a prospective and randomized study in which 1,676 cases of 1,180 patients were treated with one of the two different closure devices (the collagen plug device was Angio-Seal™; the suture-mediated closure device was The Closer S™) at the femoral access site after instituting percutaneous endovascular procedures. Among the 1,676 cases, 108 cases (the drug group) were treated with heparin only (n = 94), thrombolytics only (n = 10), heparin and thrombolytics (n = 3), or abciximab and thrombolytics (n = 1) during the procedures; 1,568 cases (the no-drug group) were treated without any medication. We compared the efficacy and complications between the two groups. Of the drug group, 42 cases underwent arterial closures with the collagen plug devices and 66 cases underwent arterial closures with the suture-mediated closure devices. We also compared the efficacy and complications between these two groups. Results The immediate hemostasis rates were 92.9% (1,456/1,568) in the no-drug group and 91.7% (99/108) in the drug group. Early complications occurred in four cases of the drug group. These included two episodes of rebleeding with using the Closer S, which required manual compression for at least 10 minutes, and two episodes of minor oozing with using one Angio-Seal and one Closer S, which required two hours of additional bed rest. There was no late complication. So, the total success rates were 90.8% (1,423/1,568) in the no-drug group and 88.0% (95/108) in the drug group. These results were not significantly different between the two groups (p = 0.34). In the drug group, the difference of the successful hemostasis rate between the collagen plug devices and the suture-mediated devices was also not statistically significant (92.9% vs. 84.8%, respectively; p = 0.21). Conclusion Arterial closure of the femoral access site with using vascular closure devices is both safe and effective, even in the patients who received heparin, abciximab or thrombolytics.

Noninvasive evaluation of coronary collateral arterial flow by coronary computed tomographic angiography

Background—Coronary collateral flow is an alternative source of myocardial perfusion in patients with totally occluded coronary arteries. Clinical evaluation of collateral flow has been limited by the need of invasive measurements. We investigated whether noninvasive coronary computed tomographic angiography can evaluate the angiographic extent of coronary collateral flow. Methods and Results—We enrolled 325 coronary computed tomographic angiography cases with angiographically confirmed chronic total occlusion (median age, 63 years; men 83%). Transluminal attenuation gradient (TAG), which reflects the kinetics of contrast media in coronary artery, of an entire artery as well as of a distal vessel was assessed to evaluate the flow in entire vessel and distal vessel. TAGs were validated against visually assessed angiographic collateral connection and Rentrop grading. TAG of an entire artery increased consistently according to the angiographic extent of collateral flow (P<0.001). Well-developed collaterals, defined by highest collateral connection and Rentrop grades (n=103), could be predicted by TAG of an entire artery (cutoff, ≥−7.6 Hounsfield units/10 mm; c-statistics, 0.72; sensitivity, 65%; specificity, 73%; positive predictive value, 52%; negative predictive value, 82%). TAG of a distal vessel could discriminate the antegrade (n=143) and retrograde (n=182) flows in distal artery (cutoff, 0.0 Hounsfield unit/10 mm; c-statistics, 0.88; sensitivity, 78%; specificity, 85%; positive predictive value, 87%; negative predictive value, 75%). Conclusions—TAG, an intracoronary attenuation-based analysis of coronary computed tomographic angiography, moderately reflected the functional extent and direction of collateral flow.

Detection of cardiac myxomas with non-contrast chest CT

Background Cardiac myxomas are sources of systemic embolism. Currently a large volume of chest CT and calcium-scoring CT scans are performed without contrast injection. Purpose To evaluate the diagnostic capability of non-contrast CT covering heart in detecting cardiac myxomas. Material and Methods This retrospective study included 36 non-contrast CT scans of 36 consecutive patients (16 men, 20 women) who underwent CT scan before surgery for left atrial myxomas and 20 patients without myxoma as a control group. Two independent readers who were blinded to medical information reviewed non-contrast CT scans of 36 patients with cardiac myxomas and 20 scans in the control group patients. They determined the presence of lesions suspicious of myxomas using a five-point scale. The other reader measured attenuation number in the non-calcific areas of the tumors and sizes of the masses on the non-contrast CT images. Results The average attenuation of cardiac myxoma (22.5 Hounsfield units [HU]; range, 8.9–32.9 HU) and adjacent unopacified blood (44.6 HU; range, 31.5–57 HU) were significantly different (P < 0.001). Twelve cardiac myxomas (31.6%) had internal calcification and all of them were detected by both of readers. Cardiac myxomas were measured smaller on non-contrast CT (mean, 3.5 cm; range, 1.1–9.7 cm) than on pathologic specimens (mean, 4.1 cm, 1.4–10.0 cm) (P < 0.001). Considering grade 3–5 on a five-grade scale as the detectability, the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of non-contrast CT in detecting cardiac myxomas were 88.8%/86.1%, 95.0%/100%, 96.9%/100%, 82.6%/80.0%, and 91.1%/91.1%, by reader 1 and reader 2, respectively and there was good inter-observer reliability (kappa value = 0.92, P = 0.157). Conclusion Non-contrast CT scan is useful for detecting cardiac myxomas. Therefore, radiologists should be familiar with imaging findings of cardiac myxomas on non-contrast CT.

Digital tomosynthesis of the thorax: the influence of respiratory motion artifacts on lung nodule detection

Background Digital tomosynthesis considerably reduces problems created by overlapping anatomy compared with chest X-ray (CXR). However, digital tomosynthesis requires a longer scan time compared with CXR, and thus may be vulnerable to motion artifacts. Purpose To compare the diagnostic performance of digital tomosynthesis in subjects with and without respiratory motion artifacts. Material and Methods The institutional review board approved this retrospective study, and the requirement for written informed consent was waived. A total of 46 subjects with imaging containing respiratory motion artifacts were enrolled in this study, 18 of whom were positive and 28 of whom were negative for lung nodules on computed tomography (CT). The control group was comprised of 92 age-matched subjects with imaging devoid of motion artifacts. Of these, 36 were positive and 56 were negative for lung nodules on subsequent CT scan. The size criteria of nodules were 4–10 mm. Three chest radiologists independently evaluated the radiographs and digital tomosynthesis images for the presence of pulmonary nodules. Multireader multicase receiver-operating characteristic (ROC) analyses was used for statistical comparisons. Results Within the control group, the areas under curve (AUC) for observer performances in detecting lung nodules on digital tomosynthesis was higher than that on CXR (P = 0.017). Within the study group, there were no significant differences in AUCs for observer performances (P = 0.576). Conclusion When no motion artifacts are present, the detection performance of nodules (4–10 mm) on digital tomosynthesis is significantly better than that on CXR, whereas there is not a significant difference in cases with motion artifacts.