CT angiography safely visualizes pediatric vascular anomalies

Catheter angiography's two main risk factors, ionizing radiation and invasiveness, present a particular challenge in young patients with vascular anomalies. Advances in CT technology, including speed, lower radiation exposure, and postprocessing, have increased CT's utility for diagnosing children with vascular problems.

Until recently, defining the venous anatomy using available CT scanners and axial imaging was almost impossible, and patients with vascular anomalies were routinely referred to conventional angiography. Multislice CTA with 3D reconstruction is enabling visualization of both arterial and venous anatomy and has become the modality of choice for younger patients, said Dr. Marilyn J. Siegel, a U.S. professor of radiology and pediatrics at the Mallinckrodt Institute of Radiology in St. Louis, Missouri.

Siegel, along with lead author Dr. Edward Y. Lee and colleagues at Mallinckrodt, enrolled six patients with pulmonary sequestration, a congenital malformation that compromises lung tissue's connectivity with the tracheobronchial tree and the pulmonary arteries (AJR 2004;183:183-188). Axial and 3D images showed the vascularity related to the area of interest in all patients. Axial views, for instance, identified an anomalous draining vein and its course in a patient with extralobar sequestration. Three-D reconstruction made it easier to visualize the arterial supply in one patient, and allowed visualization of the veins draining from intralobar sequestrations in three patients and from extralobar sequestration in one.

Most intralobar sequestrations require lobectomy or segmentectomy of the affected lung. Earlier research suggested that identifying the aberrant artery helps in planning surgical excision. Visualization of the anatomy of the venous drainage, however, can also be helpful to plan the surgical procedure and to explain the child's abnormality to parents, Siegel said.

In another study, Dr. Musturay Karcaaltincaba and colleagues at Hacettepe University School of Medicine in Ankara, Turkey, imaged six children with congenital extremity malformations that included polydactyly, Volkmann's ischemic contracture, and suspected stenosis/ occlusion of the arteries of the arms and legs (AJR 2004;183:189-192). They performed CTA studies with an average iodinated contrast volume of 43 mL, coverage area of 29 cm, and acquisition time of 21 seconds. Arterial opacification with no significant venous contamination was achieved in 83% of the patients.

The researchers concluded that multislice CTA can be used in small hospitals and outpatient centers where a pediatric interventional specialist may not be available to perform conventional angiography.

Three-D CTA offers an alternative to ultrasound, which is mainly restricted to newborns due to its limited acoustic window, and MRA, which requires longer imaging times and sedation. CTA radiation dose is three times lower than that of conventional catheter angiography and can be further reduced by following appropriate scanning protocols. The use of a single phase of contrast material and low exposure factors-30 to 50 mAs, 80 kVp, for instance-helps reduce radiation exposure without compromising the study's diagnostic quality, Siegel said.