Using superparamagnetic iron oxide-enhanced MRI to differentiate metastatic hepatic tumors and nonsolid benign lesions.
OBJECTIVE
We evaluated the ability of superparamagnetic iron oxide (SPIO)-enhanced MRI to differentiate solid metastatic tumors and nonsolid benign lesions by clarifying the characteristic signal-intensity pattern of each lesion on SPIO-enhanced T2-weighted and heavily T1-weighted gradient-echo images.


METHODS
SPIO-enhanced MRI was performed using a 1.5-T system in 33 consecutive patients without cirrhosis who had 81 focal hepatic lesions (42 cysts, 13 hemangiomas, 26 metastatic tumors). The relative signal intensity of lesions on SPIO-enhanced heavily T1- and T2-weighted gradient-echo images was classified into one of the following three categories: high intensity, isointensity, or low intensity relative to the surrounding liver parenchyma. The diagnostic accuracy for differentiating solid metastatic tumors from nonsolid benign lesions (cysts or hemangiomas) was determined.


RESULTS
A combination of the relative signal intensity of the lesion on T2- and heavily T1-weighted gradient-echo images could be classified into the following five categories: high intensity and high intensity (category 1), high intensity and isointensity (category 2), high intensity and low intensity (category 3), isointensity and isointensity (category 4), and isointensity and low intensity (category 5). According to these categories, category 1 contained two hemangiomas, category 2 had 11 hemangiomas, category 3 had 25 metastatic tumors and two cysts, category 4 had three cysts, and category 5 had 37 cysts and one metastatic tumor. When a tumor with a relative signal intensity of categories 1 or 2 was considered to be a hemangioma (category 3 metastatic tumors and categories 4 and 5 cysts), diagnostic accuracy for characterizing such hepatic lesions was 96% (78/81).


CONCLUSIONS
When evaluating metastatic liver tumors on SPIO-enhanced MRI, we recommend that heavily T1- and T2-weighted gradient-echo images be obtained with our parameters to exclude hemangiomas or cysts.
Department of Radiology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 5650871 Japan.
Seishi
S
Kumano
Takamichi
T
Murakami
Tonsok
T
Kim
Masatoshi
M
Hori
Atsuya
A
Okada
Takashi
T
Sugiura
Yumi
Y
Noguchi
Syuji
S
Kawata
Kaname
K
Tomoda
Hironobu
H
Nakamura
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media / Q000008:administration & dosage*; D003911:Dextrans; D003937:Diagnosis, Differential; D005260:Female; D052203:Ferrosoferric Oxide; D006801:Humans; D007501:Iron / Q000008:administration & dosage*; D008113:Liver Neoplasms / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D008297:Male; D008875:Middle Aged; D010087:Oxides / Q000008:administration & dosage*
D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010087:Oxides; D007501:Iron; C065507:ferumoxides; D052203:Ferrosoferric Oxide