Focal eosinophilic necrosis on superparamagnetic iron oxide-enhanced MRI.
OBJECTIVE
The purpose of our study was to evaluate the usefulness of superparamagnetic iron oxide (SPIO)-enhanced MRI for distinguishing focal eosinophilic necrosis (FEN) from hepatic metastasis.


METHODS
Forty-one cases of FEN in 41 patients and 40 hepatic metastases in 40 patients were analyzed on unenhanced and SPIO-enhanced T2-weighted MRI retrospectively. Depending on the extent of the remaining hyperintense area on SPIO-enhanced T2-weighted images compared with the unenhanced images, the lesions were classified into four categories--category 1, less than 25%; category 2, 25-49%; category 3, 50-75%; and category 4, more than 75%--by two independent readers. Contrast-to-noise ratio (CNR) was measured using the same region of interest on unenhanced and SPIO-enhanced T2-weighted images. In three pathologic specimens of FEN, the number of Kupffer cells was compared with that of background hepatic parenchyma.


RESULTS
All metastases were classified as category 4, whereas FEN showed various distributions overall (category 1, 45.2%; category 2, 24.6%; category 3, 13.4%; category 4, 17.1%). FEN showed a decrease in CNR (from 7.9 +/- 5.8 to 6.1 +/- 5.6, p < 0.05), and metastases showed an increase in CNR (from 33.7 +/- 27.0 to 55.0 +/- 44.3, p < 0.05) after SPIO administration. In biopsy specimens, FEN had many more Kupffer cells (174.7 +/- 120.3 cells/high-power field [hpf]) than background hepatic parenchyma (23.7 +/- 9.8 cells/hpf). When using signal loss categories 1, 2, or 3 or CNR decrease, the accuracy of SPIO enhancement was 88.3%.


CONCLUSIONS
Unlike hepatic metastases, most of the cases of FEN showed a reduction in the extent of hyperintense area or a decrease in CNR after SPIO administration on the T2-weighted images. Therefore, SPIO-enhanced T2-weighted MRI can help to differentially diagnose FEN from metastases.
Cho
Eun-Suk
ES
Department of Radiology, Yonsei University College of Medicine, Gangnam Severance Hospital, 612 Eonjuro, Gangnam-gu, Seoul 135-720, Republic of Korea.
Yu
Jeong-Sik
JS
Kim
Myeong-Jin
MJ
Kim
Joo Hee
JH
Chung
Jae-Joon
JJ
Kim
Ki Whang
KW
D000328:Adult; D000368:Aged; D003287:Contrast Media; D003937:Diagnosis, Differential; D004802:Eosinophilia / Q000175:diagnosis*; D005260:Female; D052203:Ferrosoferric Oxide; D006501:Hepatic Encephalopathy / Q000175:diagnosis*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008113:Liver Neoplasms / Q000175:diagnosis* / Q000556:secondary*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009336:Necrosis / Q000175:diagnosis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D003287:Contrast Media; C427127:superparamagnetic blood pool agent; D052203:Ferrosoferric Oxide