Dual-slice helical CT of the thoracic aorta

ACR Appropriateness Criteria® Workup of Noncerebral Systemic Arterial Embolic Source

Noncerebral systemic arterial embolism, which can originate from cardiac and noncardiac sources, is an important cause of patient morbidity and mortality. When an embolic source dislodges, the resulting embolus can occlude a variety of peripheral and visceral arteries causing ischemia. Characteristic locations for noncerebral arterial occlusion include the upper extremities, abdominal viscera, and lower extremities. Ischemia in these regions can progress to tissue infarction resulting in limb amputation, bowel resection, or nephrectomy. Determining the source of arterial embolism is essential in order to direct treatment decisions. This document reviews the appropriateness category of various imaging procedures available to determine the source of the arterial embolism. The variants included in this document are known arterial occlusion in the upper extremity, lower extremity, mesentery, kidneys, and multiorgan distribution that are suspected to be of embolic etiology. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Mathematical modeling improves computed tomography diagnosis of traumatic aortic injury

RATIONALE AND OBJECTIVES

Acute traumatic aorta injuries (ATAIs) following blunt thoracic trauma require rapid and accurate diagnosis for institution of lifesaving treatment. The use of computed tomography (CT) in the diagnosis of such injuries continues to improve and has the potential to become the diagnostic modality of choice in many trauma centers. A standardized diagnostic model may contribute to improvements in radiologist interpretation of CT for ATAIs.

MATERIALS AND METHODS

The following diagnostic criteria were used to develop a diagnostic model for ATAIs: 11 areas of potential hematoma formation were identified in the mediastinum. Maximum short- and long-axis cross-sectional diameters of the aorta were measured. Qualitative morphologic information (contour change, intimal flap) was recorded. Smoothness of the aorta wall was assessed. These characteristics were quantified and analyzed for statistical significance, allowing for the development of an injury assessment model.

RESULTS

The diagnostic model was used to score 69 blunt thoracic trauma patient cases. Average weighted kappa was 0.74, showing strong agreement among two observers and reproducibility of the model. The model improved injury assessment by classifying equivocal cases as either positive or negative. The ROC curve calculated from the original radiologist interpretation contained 86.1% area under the curve, while the curve for the new model contained 97.5%. The likelihood ratio increased from 30.06 to 48.67. The degree to which the new measure improved prediction over the original radiologist reading was tested using a nested model and yielded a reliable increment in model fit (chi2 analysis: Deltachi2(3) = 20.929, P < or = .0001). Finally, beta weights calculated from each variable were used to create a quantitative best-fit diagnostic model for future use.

CONCLUSION

We have developed a diagnostic tool that may help radiologists better evaluate CT for ATAIs.

Role for vascular investigations in giant cell arteritis

Giant cell arteritis is characterized by diffuse arterial inflammation that selectively involves the superficial temporal arteries but can occur in larger arteries. Various vascular investigations can assist in diagnosing and evaluating the extent of giant cell arteritis. Imaging techniques, mainly Doppler ultrasonography of the superficial temporal arteries, seem less reliable for the diagnosis than temporal artery biopsy, which is safe and remains indispensable. Investigations of larger arteries can detect asymptomatic stenotic lesions, which are common, particularly in the axillary and subclavian arteries. Involvement of the aorta can cause life-threatening dissection or aneurysmal rupture. Imaging techniques useful for diagnosing aortic involvement include ultrasonography, computed tomography, magnetic resonance imaging, and aortography. Although there is no standardized strategy for aortic lesion detection, helical computed tomography may be valuable.

Takayasu's arteritis

The frequency of Takayasu's arteritis (TA) has been estimated to be 2.9 cases per 1 million people, with a female preponderance, although female-to-male ratio varies from different geographic areas. A high frequency of haplotype A24-B52-DR2 has been found in Japanese patients, without this association in other populations. TA has a striking predilection for the aortic arch and its branches. Evidence favors an autoimmune pathogenesis. Segmental inflammation (active and inactive lesions) may coexist. Due to its enhanced resolution, magnetic resonance imaging and magnetic resonance angiography eventually will replace catheterization angiography. Mortality reduction with glucocorticoid treatment has not been firmly established.