837 Technical Developments Rendon C. Nelson, MD Frederick A. Anderson, Jr, PhD Bernard A. Blrnbaum, MD Judith 1. Chezmar, MD Seth N. Click, MD Contrast Media Extravasation during Dynamic CT: Detection with an Extravasation C 1 Detection Accessory Index terms: Computed tomography (CT), contrast media Contrast media, complications Interventional procedures, complications, 1 0.431 3, 70.719, 80.41 2, 90.458 Radiology 1998; 209:837-843 1 From the Department of RadioIog Duke University Medical Center, Box 3808, Durham, NC 27710 (R.C.N.); the Department of Surgery, University of Massachusetts Medical Center, Worchester, Mass (F.A.A.); the Depart- ment of Radiology, Hospital of the University of Pennsylvania, Philadel- phia (B.A.B.); the Department of Radi- ology, Emory University Hospital, At- lanta, Ga (J.L.C.); and the Department of Radiology, Hahneman University Medical Center, Philadelphia, Pa (S.N.G.). Received December 30,1997; revision requested March 24, 1998; revision received May 1 1; accepted August 11 . Address reprint requests to R.C.N. CRSNA, 1998 Author contributions: Guarantors of integrity of entire study, all authors; study concepts, R.C.N., F.A.A.; study design, all authors; defini- tion of intellectual content, all authors; literature research, R.C.N.; clinical stud- ies, R.C.N.; experimental studies, F.A.A.; data acquisition and analysis, F.A.A.; statistical analysis, F.A.A.; manuscript preparation, R.C.N., F.A.A.; manu- script editing and review, all authors. To detect extravasation of contrast media during mechanical power in- jection at dynamic computed to- mography, a5 x 8-cm pliable adhe- sive patch was applied to the skin over the intravenous cannula and connected to the power injector with a cable to monitor electrical skin impedance. If the rate of change or the slope of impedance over time indicated an extravasation event, the power injector was set into a pause mode. In animal and human studies, monitoring with the device was suc- cessful. Extravasation of ionic con- trast agents decreased impedance and that of nonionic agents increased impedance. The use of iodinated contrast material with computed tomography (CT) has dna- matically improved diagnostic efficacy in the central nervous system, the torso, and the extremities. Although contrast media can be administered manually as a bolus (so-called hand bolus), it can be delivered safely, in a more uniform fashion, and at a higher flow rate by using a mechanical power injector (i). These higher rates of injection are particularly important for helical CT, in which contrast media are often administered at rates of 3-5 rnL/sec followed by imaging during both the arterial dominant and portal dominant phases of enhancement (2-6). Extravasa- tion of contrast media at the site of percutaneous injection is relatively un- common, with an occurrence rate esti- mated at 0.04%-0.40% (i,7-9). In a busy CT practice, a few of these episodes may be encountered every month. Although most extravasations are of low volume (i,7-i2), the higher volumes and flow rates associated with dual-phase helical CT have increased both the prevalence of extravasation events and the volume of extravasated contrast material (9). As a result, radiologists in many practices have hesitated to incorporate these state-of-the- art helical CT techniques despite their diagnostic efficacy. The vast majority of soft-tissue injuries are mild, regardless of the volume of extravasated contrast mate- nial, and require only supportive care (7,10-17). However, injuries resulting in severe damage to the skin and subcutane- ous tissue do occur on occasion. These catastrophic events usually require plas- tic surgery and place the radiologist per- forming the examination at risk for litiga- tion. Extravasation of nonionic contrast agents can result in a less severe soft- tissue injury than is caused by extnavasa- tion of ionic agents (7, 18-21). However, the effects of extravasation of a nonionic agent are by no means unimportant (ii,i2,17). The purpose of this technical note is to introduce a commercially avail- able device that has the potential to elimi- nate clinically noticeable contrast media extravasations during dynamic CT. U Materials and Methods Equipment The extnavasation detection accessory is a small pliable patch that is 2 x 3 inches [5 x 8 cml and consists of four flat metallic electrodes embedded within a clear flexible plastic sheet (Fig 1). Adhe- sive backing is applied to the patch so it can be attached directly to the skin over- lying the tip of the intravenous cannula. The nature of the cannula can be either metallic, such as a butterfly, or nonmetal- lic, such as a flexible angiocatheten. Once in place, the accessory is attached to a small, lightweight electrode connector that is coupled to a dedicated mechanical power injector by a thin electrical cord