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Abstract
Purpose
To evaluate and compare the accuracy of magnetic resonance imaging (MRI) and ultrasound (US) for detection and estimation of invasion depth of colorectal carcinoma (CRC) by correlation with histopathologic findings in vitro, and to find out the best MR pulse sequence for accurate delineation of tumor from surrounding normal tissue.
Materials and Methods
Resected specimens of CRC from 45 patients were examined about tumor detectability and invasion depth of US using high frequency (5-17 MHz) linear transducer in a tube filled with normal saline and MRI in a 8-channel quadrate head coil. The institutional review board approved this study and informed consent was waived. MRI with seven pulse sequences of in- and out-of-phases gradient echo T1 weighted images, fast spin echo T2 weighted image and its fat suppression image, fast imaging employing steady-state acquisition (FIESTA) and its fat suppression image, and diffusion weighted image (DWI) were performed. In each case, both imaging findings of MRI and US were evaluated independently for detection and estimation of invasion depth of tumor by consensus of two radiologists and were compared about diagnostic accuracy according to the histopathologic findings as reference standard. Seven MR pulse sequences were evaluated on the point of accurate delineation of tumor from surrounding normal tissue in each specimen.
Results
In specimens of CRC, both imaging modalities of MRI (91.1%) and US (86.7%) showed relatively high diagnostic accuracy to detect tumor and evaluate invasion depth of tumor. In early CRC, diagnostic accuracy of US was 87.5% and that of MRI was 75.0%. There was no statistically significant difference between two imaging modalities (p > 0.05). The best pulse sequence among seven MR sequences for accurate delineation of tumor from surrounding normal tissue in each specimen of CRC was fast spin echo T2 weighted image.
Figures and Tables
Fig. 1
Rectal cancer (T1, polypoid type).
a-b, g. T1 in- and out-of-phases and DWI don't show exact layer of tumor involvement.
c-f. FSE T2, FSE T2 fat-suppression, FIESTA and FIESTA fat-suppression show tumor involvement of submucosal layer with preserved proper muscle layer (arrows).
h. US shows hypoechoic tumor involvement (arrow) of echogenic submucosa with preserved hypoechoic proper muscle layer.
i. Histopathology of the tumor (H & E, ×10) is confined to submucosa.
Fig. 2
Rectal cancer (T2, ulcerative type).
a, e. T1in-phase and FIESTA don't show exact layer of tumor involvement.
b-c, d, f-g. T1 out-of-phase, FSE T2, FSE T2 fat-suppression, FIESTA fat-suppression and DWI show tumor involvement of submucosal layer with disruption of proper muscle layer (arrows).
h. US shows hypoechoic tumor involvement of echogenic submucosa with just thickened inner hypoechoic muscle layer (arrow).
i. Histopathology of the tumor (H & E, ×10) is invasion to proper muscle layer.
Fig. 3
Sigmoid colon cancer (T3, ulcerofungating type).
a-b, g. T1 in- and out-of-phases and DWI don't show exact layer of tumor involvement.
c-f. FSE T2, FSE T2 fat-suppression, FIESTA and FIESTA fat-suppression show tumor infiltration into pericolic fat tissue (arrows).
h. US shows hypoechoic tumor infiltration into echogenic pericolonic fat tissue (arrow).
i. Histopathology of the tumor (H & E, ×10) is infiltration into pericolic fat tissue.
Fig. 4
Sigmoid colon cancer (T3, ulceroinfiltrative type).
a-c, e-f. T1 in- and out-of-phases, FSE T2, FIESTA and FIESTA fat-suppression show infiltrative tumor invasion to pericolic fat tissue (arrows).
d, g. FSE T2 fat-suppression and DWI don't show exact layer of tumor involvement.
h. US shows ill-defined hypoechoic tumor infiltration into echogenic pericolic fat tissue (arrow).
i. Histopathology of the tumor (H & E, ×10) is invasion into pericolic fat tissue.
Table 2
Ratio of Satisfying Imaging among Seven MR pulse Sequences
Note.-T1-in : gradient echo T1 weighted in-phase image
T1-out : gradient echo T1 weighted out-of-phase image
FSE T2 : fast spin echo heavily T2 weighted image
FSE T2 fat-sup : fast spin echo heavily T2 weighted fat suppression image
FIESTA : fast imaging employing steady-state acquisition image
FIESTA fat-sup : fast imaging employing steady-state acquisition with fat suppression image
DWI : diffusion weighted image (b = 1000)
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