Date Published: January 31, 2017
Publisher: Public Library of Science
Author(s): A. M. den Harder, D. Suchá, R. W. van Hamersvelt, R. P. J. Budde, P. A. de Jong, A. M. R. Schilham, C. Bos, J. M. P. J. Breur, T. Leiner, Stephan Meckel.
Complications might occur after great vessel stent implantation in children. Therefore follow-up using imaging is warranted.
To determine the optimal imaging modality for the assessment of stents used to treat great vessel obstructions in children.
Five different large vessel stents were evaluated in an in-vitro setting. All stents were expanded to the maximal vendor recommended diameter (20mm; n = 4 or 10mm; n = 1), placed in an anthropomorphic chest phantom and imaged with a 256-slice CT-scanner. MRI images were acquired at 1.5T using a multi-slice T2-weighted turbo spin echo, an RF-spoiled three-dimensional T1-weighted Fast Field Echo and a balanced turbo field echo 3D sequence. Two blinded observers assessed stent lumen visibility (measured diameter/true diameter *100%) in the center and at the outlets of the stent. Reproducibility of diameter measurements was evaluated using the intraclass correlation coefficient for reliability and 95% limits of agreement for agreement analysis.
Median stent lumen visibility was 88 (IQR 86–90)% with CT for all stents at both the center and outlets. With MRI, the T2-weighted turbo spin echo sequence was preferred which resulted in 82 (78–84%) stent lumen visibility. Interobserver reliability and agreement was good for both CT (ICC 0.997, mean difference -0.51 [-1.07–0.05] mm) and MRI measurements (ICC 0.951, mean difference -0.05 [-2.52 –-2.41] mm).
Good in-stent lumen visibility was achievable in this in-vitro study with both CT and MRI in different great vessel stents. Overall reliability was good with clinical acceptable limits of agreement for both CT and MRI. However, common conditions such as in-stent stenosis and associated aneurysms were not tested in this in-vitro study, limiting the value of the in-vitro study.
Great vessel stents are commonly implanted in children with congenital heart disease. Complications after stent implantation may include in-stent stenosis and aneurysm formation . Although these complications are relatively rare they require lifelong patient monitoring [2,3]. Computed tomography (CT) is often the preferred imaging modality because it is readily available, rapid, non-invasive and correlates highly with invasive angiography for the detection of stenosis . However, CT is also associated with ionizing radiation which is a well-known concern especially in paediatric imaging as children are more susceptible to the effects of radiation and have a longer expected lifetime to develop harmful radiation effects [4–7]. Furthermore, stent evaluation requires contrast-enhanced imaging with iodinated contrast agents, which carries a small but non-negligible risk of contrast nephropathy and allergic reactions. Magnetic resonance imaging (MRI) offers a potential solution for the abovementioned issues, since no ionizing radiation is used and gadolinium, a paramagnetic contrast-agent, is considered relatively safe . The use of MRI has however been limited, since most large vessel stents were made of stainless steel, which leads to MRI susceptibility artifacts hampering in-stent evaluation. New stent materials like platinum are associated with less susceptibility artifacts and may allow for MRI assessment [9,10]. Furthermore, over the past years there has been a shift towards more paediatric-friendly imaging with MRI, for example by reducing the in-bore sound pressure and creating a more comfortable atmosphere .
The effective radiation dose per CT acquisition was 1.2 mSv (CTDIvol 7.7 mGy, DLP 51.2 mGy*cm).
This in vitro study showed that it is possible to achieve good in-stent lumen visibility with both CT and MRI in different pediatric great vessel stents. Overall reliability for stent lumen visibility assessment was good with both CT and MRI. For each stent, interobserver results for diameter measurements differed per MRI sequence. In this study, optimal stent lumen visibility was achieved using a T2-weighted sequence for all great vessel stents.