Bill H. Warren

Prospective versus Retrospective ECG Gating for 64-Detector CT of the Coronary Arteries: Comparison of Image Quality and Patient Radiation Dose

PURPOSE To compare image quality and patient radiation dose in a group of patients who underwent 64-detector computed tomography (CT) coronary angiography performed with prospective electrocardiographic (ECG) gating with image quality and radiation dose in a group of patients matched for clinical features who underwent 64-detector CT coronary angiography performed with retrospective ECG gating. MATERIALS AND METHODS Institutional review board approval was obtained for this HIPAA-compliant study, and the informed consent requirement was waived due to the retrospective study design. Two independent reviewers separately scored coronary artery segment image quality and overall image quality for 100 cardiac CT studies (50 in each group). Interobserver variability was calculated. Patient radiation dose for the actual examination z-axis length was recorded, and a normalized dose was calculated for a 12-cm z-axis length of a typical heart. RESULTS The two groups matched well for clinical characteristics and CT parameters. There was good agreement for coronary artery segment image quality scores between the independent reviewers (kappa = 0.72). Of the 1253 coronary artery segments scored, the number of coronary artery segments that could not be evaluated in each group was similar (1.1% [seven of 614] in the prospective group vs 1.5% [10 of 647] in the retrospective group, P = .53). Image quality scores were not significantly different when matched for chest cross-sectional area (P > .05). Mean patient radiation dose was 77% lower for prospective gating (4.2 mSv) than for retrospective gating (18.1 mSv) (P < .01). CONCLUSION Use of 64-detector CT coronary angiography performed with prospective ECG gating has similar subjective image quality scores but 77% lower patient radiation dose when compared with use of retrospective ECG gating.

Fetal Skeletal Dysplasia: An Approach to Diagnosis with Illustrative Cases

Skeletal dysplasias are a heterogeneous group of conditions associated with various abnormalities of the skeleton. These conditions are caused by widespread disturbance of bone growth, beginning during the early stages of fetal development and evolving throughout life. Despite recent advances in imaging, fetal skeletal dysplasias are difficult to diagnose in utero due to a number of factors, including the large number of skeletal dysplasias and their phenotypic variability with overlapping features, lack of precise molecular diagnosis for many disorders, lack of a systematic approach, the inability of ultrasonography (US) to provide an integrated view, and variability in the time at which findings manifest in some skeletal dysplasias. US of suspected skeletal dysplasia involves systematic imaging of the long bones, thorax, hands and feet, skull, spine, and pelvis. Assessment of the fetus with three-dimensional US has been shown to improve diagnostic accuracy, since additional phenotypic features not detectable at two-dimensional US may be identified. The radiologist plays a major role in making an accurate diagnosis; however, representatives of other disciplines, including clinicians, molecular biologists, and pathologists, can also provide important diagnostic information.

Identifying, Characterizing, and Classifying Congenital Anomalies of the Coronary Arteries

The clinical manifestations of coronary artery anomalies vary in severity, with some anomalies causing severe symptoms and cardiovascular sequelae and others being benign. Cardiovascular computed tomography (CT) has emerged as the standard of reference for identification and characterization of coronary artery anomalies. Therefore, it is important for the reader of cardiovascular CT images to be thoroughly familiar with the spectrum of coronary artery anomalies. Hemodynamically significant anomalies include atresia, origin from the pulmonary artery, interarterial course, and congenital fistula. Non-hemodynamically significant anomalies include duplication; high origin; a prepulmonic, transseptal, or retroaortic course; shepherds crook right coronary artery; and systemic termination. In general, coronary arteries with an interarterial course are associated with an increased risk of sudden cardiac death. Coronary artery anomalies that result in shunting, including congenital fistula and origin from the pulmonary artery, are also commonly symptomatic and may cause steal of blood from the myocardium. Radiologists should be familiar with each specific variant and its specific constellation of potential implications.

Whole-chest 64-MDCT of emergency department patients with nonspecific chest pain: Radiation dose and coronary artery image quality with prospective ECG triggering versus retrospective ECG gating.

OBJECTIVE The purpose of this study was to compare the patient radiation dose and coronary artery image quality of long-z-axis whole-chest 64-MDCT performed with retrospective ECG gating with those of CT performed with prospective ECG triggering in the evaluation of emergency department patients with nonspecific chest pain. SUBJECTS AND METHODS Consecutively registered emergency department patients with nonspecific low-to-moderate-risk chest pain underwent whole-chest CT with retrospective gating (n = 41) or prospective triggering (n = 31). Effective patient radiation doses were estimated and compared by use of unpaired Students t tests. Two reviewers independently scored the quality of images of the coronary arteries, and the scores were compared by use of ordinal logistic regression. RESULTS Age, heart rate, body mass index, and z-axis coverage were not statistically different between the two groups. For retrospective gating, the mean effective radiation dose was 31.8 +/- 5.1 mSv; for prospective triggering, the mean effective radiation dose was 9.2 +/- 2.2 mSv (prospective triggering 71% lower, p < 0.001). Two of 512 segments imaged with retrospective gating were nonevaluable (0.4%), and two of 394 segments imaged with prospective triggering were nonevaluable (0.5%). Prospectively triggered images were 2.2 (95% CI, 1.1-4.5) times as likely as retrospectively gated images to receive a high image quality score for each segment after adjustment for segment differences (p < 0.05). CONCLUSION For long-z-axis whole-chest 64-MDCT of emergency department patients with nonspecific chest pain, use of prospective ECG triggering may result in substantially lower patient radiation doses and better coronary artery image quality than is achieved with retrospective ECG gating.

Ultrasound-Based Elastography: A Novel Approach to Assess Radio Frequency Ablation of Liver Masses Performed With Expandable Ablation Probes A Feasibility Study

Objective. The purpose of this study was to evaluate the technical feasibility of ultrasound‐based elastography as a tool for assessing the size and shape of the coagulation necrosis caused by radio frequency ablation (RFA) probes using expandable electrodes ex vivo as well as in a patient with a liver metastasis. Methods. A commercially available expandable RFA probe was used to create a 3‐cm ablation in a piece of bovine liver. The ablation probe was used in situ to induce tissue deformation for elastography before and after ablation. Ultrasonic radio frequency data were processed to generate elasticity strain images. The appearance of the ablation zone was compared with magnetic resonance imaging and a gross section specimen. One patient with malignant metastatic disease to the liver and a clinical indication for RFA was investigated for the feasibility of percutaneous elastography of RFA using the same technique. Sonographic strain images were compared with the appearance of the nonenhancing ablation zone on contrast‐enhanced computed tomography. Results. Ex vivo, the ablation zone on ultrasound‐based elastography was represented by an area of increased stiffness and was well demarcated from the nonablated surrounding tissue. The size and shape of the ablated zone on the strain image correlated well with the gross specimen and the magnetic resonance imaging appearance. Strain images obtained from the patient showed results similar to those of the ex vivo experiment and correlated well with the nonenhancing area of ablation on contrast‐enhanced computed tomography. Conclusions. Ultrasound‐based elastography may be a promising tool for displaying the ablation zone created by expandable RFA probes.

Antenatal Ultrasonic Demonstration of Fetal Bowel

Although ultrasound evaluation of the adult gastrointestinal tract is largely impossible because of bowel gas, the fetal bowel is fluid-filled and therefore not subject to this limitation. In our experience, the fetal bowel pattern can be recognized and antenatal abnormalities detected.

AIUM practice guideline for the performance of an ultrasound examination of the abdomen and/or retroperitoneum

These guidelines are an educational tool designed to assist practitioners in providing appropriate radiologic care for patients. They are not inflexible rules or requirements of practice and are not intended, nor should they be used, to establish a legal standard of care. For these reasons and those set forth below, the American College of Radiology cautions against the use of these guidelines in litigation in which the clinical decisions of a practitioner are called into question.

Pre-operative CT angiography and three-dimensional image post processing for deep inferior epigastric perforator flap breast reconstructive surgery

Autologous breast reconstructive surgery with deep inferior epigastric artery (DIEA) perforator flaps has become the mainstay for breast reconstructive surgery. CT angiography and three-dimensional image post processing can depict the number, size, course and location of the DIEA perforating arteries for the pre-operative selection of the best artery to use for the tissue flap. Knowledge of the location and selection of the optimal perforating artery shortens operative times and decreases patient morbidity.

Nonatherosclerotic Cardiovascular Findings on MDCT Coronary Angiography: A Selection of Abnormalities

OBJECTIVE Improvements in MDCT coronary angiography allow imaging of the coronary arteries that rivals invasive coronary angiography. Recent studies have shown high sensitivity and specificity in detecting coronary artery disease. But in the course of interpretation, other significant abnormalities may be encountered in addition to atherosclerotic plaques. CONCLUSION We present a selection of nonatherosclerotic cardiovascular findings that were detected with coronary CT angiography performed on a 64-MDCT scanner.

Imaging Findings in Two Cases of Fluoroquinolone-Induced Achilles Tendinopathy

Tendonitis and tendon rupture are rare but recognized complications of fluoroquinolone therapy. Most reports of this problem have appeared in the rheumatology and pharmacology literature, and this topic has received little attention in the radiologic literature. We report two cases of fluoroquinolone-induced tendinopathy and describe their magnetic resonance (MR) and sonographic findings. Although Achilles tendinopathy is generally the result of repetitive injury, it is useful to keep other causes in mind. MR or sonographic findings of Achilles tendinopathy in a patient without history of antecedent trauma should prompt the radiologist to consider fluoroquinolone treatment as a possible causative agent.