Hyun Woo Goo

Xenon Ventilation CT with a Dual-Energy Technique of Dual-Source CT: Initial Experience

Institutional review board approval and written informed consent were obtained. Although xenon (Xe) ventilation CT has been introduced as a potential method with which to depict regional ventilation, quantification of Xe enhancement has been limited by the variability of lung attenuation caused by different lung volumes between scans. The purpose of this study was to assess the feasibility of Xe ventilation CT with a dual-energy technique. Dual-energy CT was performed in 12 subjects after Xe inhalation. With use of a dual-energy technique, the Xe component could be extracted without any influence from lung volume. Dynamic and static regional ventilation function can be displayed with an exact match to the thin-section CT image.

Computed tomography for the diagnosis of congenital heart disease in pediatric and adult patients.

The development of multi-slice spiral computed tomography (CT) has increased the clinical use of cardiac CT imaging in patients with congenital heart disease. Multi-slice CT has the advantages of fast scan speed; high spatial resolution, enabling the acquisition of isotropic volume data; and simultaneous evaluation of airways and lung parenchyma, thus increasing the ability to answer most clinical questions about structural abnormalities in patients with congenital heart disease. When coupled with electrocardiography-gating, multi-slice spiral CT can be used in functional evaluations, including ventricular wall motion, ventricular ejection fraction, and motion of cardiac valves, as well as enabling the performance of high-quality coronary CT angiography. In this article, we review imaging techniques of multi-slice spiral CT and imaging findings in pediatric and adult patients with various congenital heart diseases.

CT Radiation Dose Optimization and Estimation: an Update for Radiologists

In keeping with the increasing utilization of CT examinations, the greater concern about radiation hazards from examinations has been addressed. In this regard, CT radiation dose optimization has been given a great deal of attention by radiologists, referring physicians, technologists, and physicists. Dose-saving strategies are continuously evolving in terms of imaging techniques as well as dose management. Consequently, regular updates of this issue are necessary especially for radiologists who play a pivotal role in this activity. This review article will provide an update on how we can optimize CT dose in order to maximize the benefit-to-risk ratio of this clinically useful diagnostic imaging method.

State-of-the-Art CT Imaging Techniques for Congenital Heart Disease

CT is increasingly being used for evaluating the cardiovascular structures and airways in the patients with congenital heart disease. Multi-slice CT has traditionally been used for the evaluation of the extracardiac vascular and airway abnormalities because of its inherent high spatial resolution and excellent air-tissue contrast. Recent developments in CT technology primarily by reducing the cardiac motion and the radiation dose usage in congenital heart disease evaluation have helped expand the indications for CT usage. Tracheobronchomalacia associated with congenital heart disease can be evaluated with cine CT. Intravenous contrast injection should be tailored to unequivocally demonstrate cardiovascular abnormalities. Knowledge of the state-of-the-art CT imaging techniques that are used for evaluating congenital heart disease is helpful not only for planning and performing CT examinations, but also for interpreting and presenting the CT image findings that consequently guide the proper medical and surgical management.

Coronary artery anomalies and clinically important anatomy in patients with congenital heart disease: multislice CT findings.

In patients with congenital heart disease, coronary artery anomalies are common and have different clinical importance from individuals with structurally normal hearts. Visibility of the coronary arteries by CT has markedly improved due to high temporal resolution and ECG-synchronized data acquisition. In this article we describe current multislice CT techniques for coronary artery imaging and illustrate coronary artery anomalies and clinically important coronary artery anatomy from the point of view of congenital heart disease.

Xenon ventilation imaging using dual-energy computed tomography in asthmatics: initial experience.

Purpose:To assess the feasibility of xenon ventilation computed tomography (CT) for evaluating ventilation abnormality in asthmatics. Materials and Methods:Twenty-two, stable asthmatics (M:F = 10:12; mean age, 57.6) were included. Single-phase, whole-thorax, dual-energy CT was performed using dual-source CT (Somatom Definition, Siemens) after subjects had inhaled 30% xenon for 90 seconds. Parameters include 512 × 512 matrix; 14 × 1.2 mm collimation; 40/140 eff. mAs at 140/80 kV; 0.45 pitch; and 0.33 seconds rotation time. On the color-coded xenon map, the extent of the ventilation defect was visually assessed using a 5-point scale in each lobe (0, absent defect; 1, 0%–25%; 2, 25%–50%; 3, 50%–75%; and 4, 75%–100%), which was defined as defect score. On the weighted average image, airway wall dimensions were measured at 4 segmental bronchi in both upper and lower lobes. Patients were classified into a defect group and a defect-free group based on the presence of defects shown on the xenon map. Pulmonary function test parameters and airway wall dimensions were compared in those 2 groups. Correlation analyses between the defect score, pulmonary function test, and airway wall dimensions were performed. Results:Sixteen asthmatics showed peripheral ventilation defects on the xenon map (defect score, 6.6 ± 4.2). The defect group had a significantly lower forced expiratory volume in 1 second (FEV1) and thicker airway wall than that of the defect-free group (P = 0.04 and 0.02, respectively). The defect score correlated negatively with a ratio of FEV1 and forced vital capacity (FEV1/FVC) (r = −0.44, P = 0.04) and corrected diffusing capacity (r = −0.76, P = 0.04) and correlated positively with total lung capacity, functional residual volume, and residual volume (r = 0.90, P = 0.005; r= 0.99, P < 0.001; r = 0.88, P = 0.008, respectively). Conclusions:The ventilation defects appeared on xenon ventilation CT in asthmatics with more severe airflow limitation and airway wall thickening. The extent of the ventilation defects showed correlations with parameters of pulmonary function test.

Time‐resolved three‐dimensional contrast‐enhanced magnetic resonance angiography in patients who have undergone a Fontan operation or bidirectional cavopulmonary connection: Initial experience

To evaluate the usefulness of time‐resolved three‐dimensional (3D) magnetic resonance angiography (MRA) using diluted contrast agent (CA) in patients who had undergone a Fontan operation or bidirectional cavopulmonary connection (BCPC).

Utility of spiral and cine CT scans in pediatric patients suspected of aspirating radiolucent foreign bodies

Objective To review our experience with spiral and cine CT imaging for the diagnosis of foreign body aspiration. Study Design and Setting Fifty-one consecutive pediatric patients suspected of aspirating radiolucent FBs underwent chest radiography and a 3-dimensional spiral CT scan with 12 also undergoing a cine CT scan within 24 hours before rigid bronchoscopy. Bronchoscopic and CT results were compared. Results Rigid bronchoscopy showed that FBs were present in the main bronchus or bronchus intermedius of 42 patients. Spiral CT scans localized airway FBs in these same 42 patients. In the remaining nine patients without FBs, six were true-negatives and three were false-positives on CT scan interpretation, making the overall sensitivity, specificity, accuracy, and positive and negative predictive values of CT scans 100% (95% confidence interval, 91%–100%), 66.7% (29%–92%), 94.1% (64%–99%), 93.3% (81%–98%), and 100% (54%–100%), respectively. The cine CT scan correctly diagnosed nine of 12 patients as true-positives and three as true-negatives with identification of air trapping and secondary lung changes. Conclusion These findings suggest that CT scans may be used in airway FB management of pediatric patients, especially with diagnostic dilemmas, and further prospective evaluations should be considered to assess its overall efficacy.

A spectrum of neuroradiological findings in children with haemophagocytic lymphohistiocytosis

BackgroundHaemophagocytic lymphohistiocytosis (HLH) is a rare multisystem disorder. CNS involvement is a frequent and poor prognostic component. Better neuroradiological surveillance may be beneficial for patient management and outcome.ObjectiveTo describe various neuroradiological findings in nine patients with HLH with an emphasis on correlation with disease activity and treatment response.Materials and methodsBetween 1996 and 2007, nine children with HLH with CNS involvement were identified in a single centre. Neuroradiological findings from CT, MRI, and proton MR spectroscopy, and the clinical records of the nine children were retrospectively reviewed. The frequency, distribution, characteristics of abnormal neuroradiological findings and changes during follow-up were correlated with clinical findings.ResultsInitial abnormal findings included multiple nodular or ring-enhancing parenchymal lesions, a laminated pattern of nodular parenchymal lesions on T2-weighted images, leptomeningeal enhancement, confluent parenchymal lesions, mild ventriculomegaly, and diffuse brain oedema. On follow-up imaging studies, haemorrhagic transformation and atrophy were seen where brain parenchymal lesions had been previously. These abnormal neuroradiological findings showed good correlation with clinical findings. Proton MR spectroscopy also demonstrated typical changes of metabolites during the course of the disease.ConclusionA spectrum of neuroradiological findings in children with HLH is well matched with the clinical course of the disease and, therefore, a comprehensive analysis of the findings is useful to monitor disease activity and treatment responses.

Whole-body MRI of neuroblastoma

Whole-body MRI (WBMRI) is an emerging imaging method that has a great potential in pediatric oncologic imaging. It appears useful in staging and monitoring neuroblastoma although its clinical impact has not been thoroughly evaluated. Among various imaging techniques currently available for WBMRI, coronal and sagittal STIR imaging with a quadrature body coil at 1.5T MR system is recommended for a standard protocol. Nevertheless, further technical improvements are anticipated at 3.0T MR system and multi-channel surface coil system. Scan time of WBMRI is reasonably short ranging from 20 min to 60 min. In localized neuroblastoma, WBMRI may help in predicting surgical risks by evaluating image-defined risk factors accurately. In addition, WBMRI is quite useful in detecting distant metastasis, assessing initial treatment responses, and identifying tumor recurrence of neuroblastoma. We should understand limitations of WBMRI in the evaluation of lymph node involvement, in the differentiation between viable tumor and non-viable residual lesion, and in the detection of calcified lesion. Diffusion-weighted imaging may improve diagnostic accuracy of WBMRI. Complementary use of WBMRI and other metabolic imaging method such as MIBG scintigraphy or PET probably increases diagnostic accuracy and, subsequently, improves clinical outcome of children with neuroblastoma.