Diffusion-weighted imaging of metastatic brain tumors: comparison with histologic type and tumor cellularity.
OBJECTIVE
On diffusion-weighted imaging (DWI), metastatic tumors of the brain may exhibit different signal intensities (SI) depending on their histology and cellularity. The purpose of our study was to verify the hypotheses (1) that SI on DWI predict the histology of metastases and (2) that apparent diffusion coefficient (ADC) values reflect tumor cellularity.


METHODS
We assessed conventional MR images, DWI, and ADC maps of 26 metastatic brain lesions from 26 patients, 13 of whom underwent surgery after the MR examination. Two radiologists performed qualitative assessment by consensus of the SI on DWI in areas corresponding to their enhancing portions. We measured the contrast-to-noise ratio (CNR) on T2-weighted images and normalized ADC (nADC) values, and compared them with tumor cellularity.


RESULTS
The mean SI on DWI and the CNR on T2-weighted images were significantly lower in well differentiated than in poorly differentiated adenocarcinomas and lesions other than adenocarcinoma. The mean nADC value was significantly higher in well differentiated than poorly differentiated adenocarcinomas and lesions other than adenocarcinoma. All 3 small-cell carcinomas and 1 large-cell neuroendocrine carcinoma exhibited high SI on DWI. The nADC value showed a significant inverse correlation with tumor cellularity. There was no significant correlation between the CNR and tumor cellularity.


CONCLUSIONS
The SI on DWI may predict the histology of metastases; well differentiated adenocarcinomas tended to be hypointense, and small- and large-cell neuroendocrine carcinomas showed hyperintensity. Their ADC values reflect tumor cellularity.
Hayashida
Y
Y
Department of Diagnostic Radiology, Graduate School of Medical Sciences, School of Medicine, Kumamoto University, 1-1-1 Honjo, Kumamoto 860-8556, Japan.
Hirai
T
T
Morishita
S
S
Kitajima
M
M
Murakami
R
R
Korogi
Y
Y
Makino
K
K
Nakamura
H
H
Ikushima
I
I
Yamura
M
M
Kochi
M
M
Kuratsu
J-i
JI
Yamashita
Y
Y
D000230:Adenocarcinoma / Q000473:pathology / Q000556:secondary; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000556:secondary*; D018287:Carcinoma, Large Cell / Q000473:pathology / Q000556:secondary; D018278:Carcinoma, Neuroendocrine / Q000473:pathology / Q000556:secondary; D018288:Carcinoma, Small Cell / Q000473:pathology / Q000556:secondary; D002467:Cell Nucleus / Q000473:pathology; D003287:Contrast Media; D018284:Cystadenocarcinoma, Serous / Q000473:pathology / Q000556:secondary; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005544:Forecasting; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged
D003287:Contrast Media