An alternative contrast medium for computed tomographic angiography: gadolinium.

Abstract

Sir: Computed tomography is the mainstay for perforator flap angiographic mapping. There is an increasing foundation of evidence in the literature for the use of computed tomographic angiography in the planning of free flaps, able to guide the surgical approach and improve operative outcomes. Iodinated contrast is the gold standard contrast medium for angiographic imaging. Used in either an oil- or water-soluble form, the radiopaque medium is administered intravenously to improve visibility of the vasculature on radiographic images. However, iodinated contrasts are associated with nephrotoxicity and are strongly contraindicated in patients with poor renal function.1 Magnetic resonance angiography has been suggested for use in such a scenario, when iodinated contrast media are not suitable. However, magnetic resonance angiography is also contraindicated in some settings, particularly where there are implanted metallic devices (such as some breast implants). In these cases, options for high-resolution preoperative imaging are limited. We describe the use of gadolinium as an alternative to iodinated contrast media for use in computed tomographic angiography for preoperative flap imaging. This enables the use of the gold standard modality in patients that otherwise would be unable to undergo imaging with computed tomography. Although this has not been described before, gadolinium has been tested as a contrast medium in computed tomography previously.2,3 Gadolinium, with an atomic number of 64, is a rare earth metal that, because of its paramagnetic properties, is an extremely efficacious contrast agent. In its chelated form, gadolinium has been shown to be considerably less nephrotoxic and allergenic than iodinated contrast compounds1 and is not associated, as previously thought, with any increased risk of the development of nephrogenic systemic fibrosis.4 The use of gadolinium (gadolinium diethylenetriaminepentaacetic acid)-enhanced computed tomographic angiography has been described in aortography and other large vessel angiography. The results have been verified with other forms of imaging and the conclusions have been predominantly positive. Chryssidis et al. describe the use of gadolinium for thoracic aortic aneurysm diagnosis, with vascular enhancement concluded to be sufficient for the confident exclusion of an intimal flap with confirmation of findings by magnetic resonance imaging.5 These findings are consistent across thoracic, abdominal, and cerebral vessel imaging. We have used this imaging in two patients who both required vascular mapping for preoperative flap planning, and who were both unable, for various indications, to receive either iodinated contrast or undergo magnetic resonance imaging. The images below are from a woman presenting for unilateral breast reconstruction, for whom iodinated contrast was contraindicated because of impaired renal function and for whom magnetic resonance imaging was also contraindicated because of her breast expander in situ (Mentor 550 cc Tall height model 354/6313; Mentor Corp., Santa Barbara, Calif.), which is incompatible with magnetic resonance imaging because of a magnetic port. Figures 1 and 2 clearly demonstrate the right lateral thoracic and thoracodorsal arteries, imaged for use in a breast-sharing procedure.Fig. 1: Computed tomographic angiogram, maximum-intensity projection software reconstruction, with gadolinium contrast medium, highlighting opacification of the lateral thoracic artery (blue arrow) and thoracodorsal artery (red arrow).Fig. 2: Computed tomographic angiogram, three-dimensional volume-rendered technique software reconstruction, with gadolinium contrast medium, highlighting opacification of the lateral thoracic artery (blue arrow).In both cases, accurate and relevant angiographic data were gained. Despite these being the first two scans of this type obtained, the contrast injections were able to be timed effectively and gadolinium was shown to be a valuable contrast agent when other forms of scanning are contraindicated. DISCLOSURE The authors declare that there is no source of financial or other support or any financial or professional relationship that might pose a competing interest. There was no source of funding for this article. Phaethon Karagiannis, M.B.B.S. Vachara Niumsawatt, M.B.B.S. Department of Surgery Monash University Monash Medical Centre Clayton, Victoria, Australia Warren M. Rozen, M.B.B.S., M.D., Ph.D. Department of Surgery Monash University Monash Medical Centre Clayton, Victoria, and Department of Surgery School of Medicine and Dentistry James Cook University Clinical School Townsville, Queensland, Australia [email protected]