MR imaging of iron phagocytosis in intraluminal thrombi of abdominal aortic aneurysms in humans.
OBJECTIVE
To prospectively determine if superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging could help visualize leukocyte phagocytic activities in human abdominal aortic aneurysms (AAAs).


METHODS
This study was approved by the institutional ethics committee; all patients gave informed consent. Preoperative MR imaging data, including unenhanced and SPIO-enhanced T1-, T2*-, and T2-weighted transverse images of the entire AAA, obtained 1 hour after contrast enhancement from 15 patients (mean age, 72.7 years +/- 8.2; range, 60-83 years), 10 men (mean age, 73.5 years +/- 7.9; range, 60-83 years) and five women (mean age, 71.2 years +/- 9.4; range 60-82), were retrospectively evaluated. Morphologic appearance and semiquantitative and contrast-to-noise ratio (CNR) analyses of the thrombi were performed. Thrombi were analyzed semiquantitatively at microscopy after staining with hematoxylin-eosin, CD68, and CD66b. Levels of promatrix metalloproteinase (pro-MMP)-2 and pro-MMP-9, MMP-2 and MMP-9, and their mRNA located in the thrombus were assessed by using zymography and quantitative reverse transcriptase polymerase chain reaction analysis. Nonparametric statistics of the Spearman rank correlation were calculated to evaluate correlations between the aneurysm thrombus signal level decrease after SPIO and the levels of CD68(+), CD66b(+) cells, pro-MMP-2 and pro-MMP-9, MMP-2 and MMP-9, and MMP-9 mRNA.


RESULTS
The pre-SPIO CNRs in the luminal sublayer of the thrombus and the deeper thrombus were -10.20 +/- 12.69 and -5.68 +/-10.38, respectively. After SPIO, the CNRs decreased to -21.34 +/-13.07 (P < .001) and -12.44 +/- 14.56, respectively (P < .012). There was a significant linear correlation between the thrombus signal level decrease and the levels of CD68(+) and CD66b(+) cells, pro-MMP-9, and MMP-9 mRNA (P < .05).


CONCLUSIONS
MR imaging allows in vivo demonstration of SPIO uptake at the luminal interface of the thrombus. This uptake is correlated to the abundance of leukocytes.


BACKGROUND
http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.09090657/-/DC1.
Nchimi
Alain
A
Departments of Medical Imaging and Pathology, Centre Hospitalier Chrétien, Rue de Hesbaye, 75, B-4000 Liège, Belgium. alain.nchimi@chc.be
Defawe
Olivier
O
Brisbois
Denis
D
Broussaud
Thomas K Y
TK
Defraigne
Jean-Olivier
JO
Magotteaux
Paul
P
Massart
Brigitte
B
Serfaty
Jean-Michel
JM
Houard
Xavier
X
Michel
Jean-Baptiste
JB
Sakalihasan
Natzi
N
D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001014:Aortic Aneurysm / Q000378:metabolism* / Q000503:physiopathology; D003287:Contrast Media / Q000493:pharmacokinetics; D003911:Dextrans; D004792:Enzyme Precursors / Q000378:metabolism; D005260:Female; D052203:Ferrosoferric Oxide / Q000493:pharmacokinetics; D018093:Gelatinases / Q000378:metabolism; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007150:Immunohistochemistry; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008875:Middle Aged; D010587:Phagocytosis / Q000502:physiology*; D011446:Prospective Studies; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000378:metabolism; D018709:Statistics, Nonparametric; D013927:Thrombosis / Q000378:metabolism* / Q000503:physiopathology
D003287:Contrast Media; D003911:Dextrans; D004792:Enzyme Precursors; D058185:Magnetite Nanoparticles; D012697:Serine Endopeptidases; C463979:pro-MMP-9 activator; D018093:Gelatinases; C069860:progelatinase; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; C065507:ferumoxides; D052203:Ferrosoferric Oxide