Diffusion-weighted and Gd-EOB-DTPA-contrast-enhanced magnetic resonance imaging for characterization of tumor necrosis in an animal model.
OBJECTIVE
To evaluate the role of diffusion-weighted magnetic resonance imaging (MRI) in determining tumor necrosis and contrast-enhanced MRI using gadoxetic acid disodium (Gd-EOB-DTPA) in determining maximum tumor size measurement and tumor delineation compared with criterion-standard histologic measurements in the rabbit VX2 liver tumor model.


METHODS
VX2 tumors were implanted in the livers of 13 rabbits. Magnetic resonance imaging was performed using a 1.5-T MRI scanner and an extremity coil. The imaging protocol included T2-weighted fast spin-echo images, 3-dimensional T1-weighted spoiled gradient-echo with and without fat suppression after administration of Gd-EOB-DTPA, and diffusion-weighted echo planar images. Rabbits were killed, and the tumor was harvested and sliced at 4-mm intervals in the axial plane. The MRI parameters evaluated were tumor size, tumor delineation, and tumor apparent diffusion coefficient (ADC) values. Histologic sections were evaluated to quantify tumor necrosis.


RESULTS
On contrast-enhanced MRI (obtained from 11 rabbits), the mean tumor sizes were 20, 19, and 20 mm in the arterial, portal venous, and delayed phases, respectively. Tumor delineation was most distinguishable in the delayed phase. On diffusion-weighted MRI (acquired in 13 rabbits), the mean tumor ADC value was 1.84 x 10 mm/s. The mean tumor size at pathology was 16 mm. The mean percent necrosis at the tumor's pathologic condition was 36%. The correlation between ADC value and percent necrosis showed an R value of 0.68.


CONCLUSIONS
Contrast-enhanced MRI using Gd-EOB-DTPA may provide additional information about tumor outline in the liver. Moreover, we showed a remarkable correlation between ADC values and tumor necrosis. Thus, diffusion-weighted imaging may be useful to assess tumor necrosis; nevertheless, the search for new modalities remains important.
Vossen
Josephina A
JA
Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins Hospital, Baltimore, MD 21287, USA.
Buijs
Manon
M
Geschwind
Jean-Francois H
JF
Liapi
Eleni
E
Prieto Ventura
Veronica
V
Lee
Kwang Hun
KH
Bluemke
David A
DA
Kamel
Ihab R
IR
D000818:Animals; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D004195:Disease Models, Animal; D019786:Gadolinium DTPA; D007089:Image Enhancement / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008099:Liver / Q000473:pathology / Q000648:ultrastructure; D008113:Liver Neoplasms / Q000473:pathology* / Q000648:ultrastructure; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009336:Necrosis; D011817:Rabbits
D003287:Contrast Media; C073590:gadolinium ethoxybenzyl DTPA; D019786:Gadolinium DTPA