Published Online
on April 1, 2002

A more recent version of this article appeared on April 23, 2002

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Submitted on November 29, 2001
Revised on February 1, 2002
Accepted on February 14, 2002

Endovascular Aneurysm Repair. Magnetic Resonance Monitoring of Histological Organization Processes in the Excluded Aneurysm

Michael Bernhard Pitton MD^*, Ralf Patrick Schmenger MD, Achim Neufang MD, Moritz Anton Konerding MD, Christoph Düber MD, and Manfred Thelen MD

From the Departments of Radiology (M.B.P., R.P.S., M.T.), Cardiovascular Surgery (A.N.), and Anatomy (M.A.K.), University Hospital, Johannes Gutenberg University of Mainz, Germany, and Department of Radiology (C.D.), University Hospital Mannheim, Ruprecht-Karls University of Heidelberg, Germany.

^* To whom correspondence should be addressed. E-mail: pitton{at}radiologie.klinik.uni-mainz.de.

Background—The purpose of the present study was to systematically analyze the histopathologic organization processes in excluded aneurysms after endovascular stenting and to develop a noninvasive monitoring method for these processes using MRI.

Methods and Results—In 36 mongrel dogs, autologous aortic aneurysms were created. Endovascular treatment was performed using covered stents. Follow-up was after 1 week, 6 weeks, and 6 months. MRI was performed with T₂-weighted turbo-spin-echo sequences and T₁-weighted spin-echo sequences and was repeated after contrast bolus with gadolinium. Histopathologic findings were correlated to signal intensities (SIs) of MRI images. SIs of distinct areas were analyzed and related to the SI of the reference tissue (SI ratio). The histological organization process was gradated in the following 4 classes: class 0, detritus without organization; classes I and II, connective tissue proliferation with increasing fiber synthesis; and class III, dense fibrous connective tissue. The SI ratios of T₂-weighted images were significantly reduced from 4.76 in detritus (0) to 1.70 in dense fibrous connective tissue (III) as a function of histopathologic classes. SI ratios of T₁-weighted images were reduced from 1.84 (0) to 1.12 (III). Contrast bolus with gadolinium-DTPA showed no change of SI ratio in detritus (0.99) but an increase from 1.12 (I) to 1.70 (III) as organization increased.

Conclusions—The histological organization of excluded aneurysms can be monitored by MRI. Progressive organization is indicated by decreasing SIs in T₂- and an increasing signal increase in T₁-weighted images after gadolinium bolus.

Key words: aneurysm • grafting • stents • magnetic resonance imaging • aorta

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