Applied Radiology

Dr. Teague is an Assistant Professor of Radiology, Department of Radiology, Indiana University School of Medicine, Indianapolis, IN. Dr. Rosenblum is Vice Chair, Department of Radiology, and Director, Interventional Radiology, MetroHealth Medical Center, and Assistant Professor of Radiology, Case Western Reserve University, Cleveland, OH. Dr. Olszewski is a Research Scientist, Ms. Dharaiya is a Research Scientist, and Mr. Popilock is a Product Manager, Computed Tomography Clinical Science, Philips Healthcare, Cleveland, OH.

The evolution of multidetector computed tomography (MDCT) throughout the past decade has established its position as the workhorse of radiology. In addition to facilitating faster and improved diagnoses in the routine examinations-such as thoracic, abdominal, pelvic, brain, neck, and spine- that make up >85% of annual CT exams, ¹ this evolution has sparked a surge in vascular imaging procedures, such as CT angiography (CTA).

From 2004 to 2007 alone, the number of annual CTA procedures in the United States more than doubled to 4.7 million. ¹ The concurrent increase in the number of sites regularly performing CTA procedures, from 44% to 67% in the same time period, ¹ further supports the adoption of MDCT as the noninvasive modality of choice for imaging the anatomy in most vascular territories. ^2,3 Despite the growing acceptance of this technology, the rapid rate of procedure growth has led to renewed concerns regarding both the radiation dose ^4-7 and the amount of intravenous contrast delivered ^6,7 to patients undergoing CTA.

Minimizing patient radiation dose is of paramount concern when using MDCT. As MDCT procedures have grown, studies have shown that CT is an increasing source of radiation exposure, ⁴ and attempts have been made to estimate the increase in cancer risk due to CTA procedures. ⁵ Imaging equipment vendors have made progress in the area of radiation dose management with the introduction of novel technologies, such as prospective electrocardiographic (ECG)-gating with advanced algorithms to handle cardiac arrhythmias, improved beam filtration technology, and dose-reducing collimators. Concurrent efforts are underway across the industry and in academia to provide recommendations for the responsible imaging of pediatric patients. ^6,7

At the same time, the amount of contrast media delivered to a patient is also of utmost concern due to the risk of complications, particularly contrast-induced nephropathy (CIN). Contrast-induced nephropathy is defined as acute renal failure occurring within 48 hours of exposure to intravascular radiographic contrast material that is not attributable to other causes, and it is the third most common cause of hospital-acquired acute renal failure. ^8,9 Prevention of CIN has been the subject of many studies ¹⁰ ; but the development of new contrast formulation, ^11,12 injection technique, ¹³ and pretreatment paradigm, ¹⁴ strategies to prevent CIN are implemented nonuniformly ¹⁵ and have shown varied results. ¹⁶

It is well-known that vessel visualization in CTA benefits from higher contrast volumes, concentrations, and injection rates; ^17,18 however, the risk of CIN increases with increased contrast volume. ^9,16 Studies using earlier generation MDCT scanners evaluated the possibility of reducing the contrast volume necessary for various types of CTA examinations, ^19-22 but it may be possible to consistently decrease contrast volumes across a wider patient population. Efforts to further reduce contrast volume per patient study may reduce the risk of CIN and provide institutions with an overall economic benefit.

This article details the clinical and economic benefits of reduced contrast doses made possible by new CT scanner technology that is enhanced for speed, power, and coverage. This combination of technologic advances may enable high-quality imaging of all patients with a consistent reduction in contrast volume of ≥35%, while maintaining image quality. Finally, the authors provide an economic analysis of potential cost savings related to further reduction in contrast-media volume.