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Diffusion Coefficients in Abdominal Organs and Hepatic Lesions: Evaluation with Intravoxel Incoherent Motion Echo-planar MR Imaging

Ichiro Yamada, MD1, Winn Aung, MD1, Yoshiro Himeno, MD1, Tsuneaki Nakagawa, MD1 and Hitoshi Shibuya, MD1

1 Department of Radiology, Faculty of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.



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  		Figure 1a. (a) Graph of signal attenuation versus b factor for the liver ({bigcirc}), kidney ({square}), and hepatocellular carcinoma (•) as measured at IVIM echo-planar MR imaging. The plots clearly show a curvature for low b values, which is indicative of perfusion effects, according to the IVIM theory. The dotted lines represent a least-squares fit to the last three data points. The slope of the straight line gives the diffusion coefficient D, and the deviation from the diffusion asymptote at the intercept gives the perfusion fraction f (2,3). (b) Graph of signal attenuation versus b factor for the gallbladder ({circ}) and liver cysts ({square}) as measured at IVIM echo-planar MR imaging. The plots follow a straight line, as expected for a pure diffusion process. The slope of the straight line gives the diffusion coefficient D.

 


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  		Figure 1b. (a) Graph of signal attenuation versus b factor for the liver ({bigcirc}), kidney ({square}), and hepatocellular carcinoma (•) as measured at IVIM echo-planar MR imaging. The plots clearly show a curvature for low b values, which is indicative of perfusion effects, according to the IVIM theory. The dotted lines represent a least-squares fit to the last three data points. The slope of the straight line gives the diffusion coefficient D, and the deviation from the diffusion asymptote at the intercept gives the perfusion fraction f (2,3). (b) Graph of signal attenuation versus b factor for the gallbladder ({circ}) and liver cysts ({square}) as measured at IVIM echo-planar MR imaging. The plots follow a straight line, as expected for a pure diffusion process. The slope of the straight line gives the diffusion coefficient D.

 


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  		Figure 2a. MR images in a 58-year-old man with hepatocellular carcinoma. (a) T2-weighted turbo spin-echo MR image (2,595/128 [effective]; echo train length, 23) shows a lesion (arrow) with high signal intensity in the right lobe of the liver. (b) Echo-planar MR image ({infty}/123) obtained with a low MPG (b = 30 sec/mm2) shows a high-signal-intensity lesion (arrow). This finding is due to the elongated T2 of the lesion. (c) Echo-planar MR image ({infty}/123) obtained with an intermediate MPG (b = 300 sec/mm2) shows that the signal intensity of the lesion (arrow) remains high, indicating a low diffusion coefficient. (d) Echo-planar MR image ({infty}/123) obtained with a high MPG (b = 1,100 sec/mm2) shows that the signal intensity of the lesion (arrow) remains high, indicating a low diffusion coefficient. (e) Diffusion coefficient map shows that the lesion (arrow) has a low D value (0.95 x 10-3 mm2/sec). The diffusion coefficient map was calculated on a pixel-by-pixel basis by using Equation (2).

 


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  		Figure 2b. MR images in a 58-year-old man with hepatocellular carcinoma. (a) T2-weighted turbo spin-echo MR image (2,595/128 [effective]; echo train length, 23) shows a lesion (arrow) with high signal intensity in the right lobe of the liver. (b) Echo-planar MR image ({infty}/123) obtained with a low MPG (b = 30 sec/mm2) shows a high-signal-intensity lesion (arrow). This finding is due to the elongated T2 of the lesion. (c) Echo-planar MR image ({infty}/123) obtained with an intermediate MPG (b = 300 sec/mm2) shows that the signal intensity of the lesion (arrow) remains high, indicating a low diffusion coefficient. (d) Echo-planar MR image ({infty}/123) obtained with a high MPG (b = 1,100 sec/mm2) shows that the signal intensity of the lesion (arrow) remains high, indicating a low diffusion coefficient. (e) Diffusion coefficient map shows that the lesion (arrow) has a low D value (0.95 x 10-3 mm2/sec). The diffusion coefficient map was calculated on a pixel-by-pixel basis by using Equation (2).

 


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  		Figure 2c. MR images in a 58-year-old man with hepatocellular carcinoma. (a) T2-weighted turbo spin-echo MR image (2,595/128 [effective]; echo train length, 23) shows a lesion (arrow) with high signal intensity in the right lobe of the liver. (b) Echo-planar MR image ({infty}/123) obtained with a low MPG (b = 30 sec/mm2) shows a high-signal-intensity lesion (arrow). This finding is due to the elongated T2 of the lesion. (c) Echo-planar MR image ({infty}/123) obtained with an intermediate MPG (b = 300 sec/mm2) shows that the signal intensity of the lesion (arrow) remains high, indicating a low diffusion coefficient. (d) Echo-planar MR image ({infty}/123) obtained with a high MPG (b = 1,100 sec/mm2) shows that the signal intensity of the lesion (arrow) remains high, indicating a low diffusion coefficient. (e) Diffusion coefficient map shows that the lesion (arrow) has a low D value (0.95 x 10-3 mm2/sec). The diffusion coefficient map was calculated on a pixel-by-pixel basis by using Equation (2).

 


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  		Figure 2d. MR images in a 58-year-old man with hepatocellular carcinoma. (a) T2-weighted turbo spin-echo MR image (2,595/128 [effective]; echo train length, 23) shows a lesion (arrow) with high signal intensity in the right lobe of the liver. (b) Echo-planar MR image ({infty}/123) obtained with a low MPG (b = 30 sec/mm2) shows a high-signal-intensity lesion (arrow). This finding is due to the elongated T2 of the lesion. (c) Echo-planar MR image ({infty}/123) obtained with an intermediate MPG (b = 300 sec/mm2) shows that the signal intensity of the lesion (arrow) remains high, indicating a low diffusion coefficient. (d) Echo-planar MR image ({infty}/123) obtained with a high MPG (b = 1,100 sec/mm2) shows that the signal intensity of the lesion (arrow) remains high, indicating a low diffusion coefficient. (e) Diffusion coefficient map shows that the lesion (arrow) has a low D value (0.95 x 10-3 mm2/sec). The diffusion coefficient map was calculated on a pixel-by-pixel basis by using Equation (2).

 


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  		Figure 2e. MR images in a 58-year-old man with hepatocellular carcinoma. (a) T2-weighted turbo spin-echo MR image (2,595/128 [effective]; echo train length, 23) shows a lesion (arrow) with high signal intensity in the right lobe of the liver. (b) Echo-planar MR image ({infty}/123) obtained with a low MPG (b = 30 sec/mm2) shows a high-signal-intensity lesion (arrow). This finding is due to the elongated T2 of the lesion. (c) Echo-planar MR image ({infty}/123) obtained with an intermediate MPG (b = 300 sec/mm2) shows that the signal intensity of the lesion (arrow) remains high, indicating a low diffusion coefficient. (d) Echo-planar MR image ({infty}/123) obtained with a high MPG (b = 1,100 sec/mm2) shows that the signal intensity of the lesion (arrow) remains high, indicating a low diffusion coefficient. (e) Diffusion coefficient map shows that the lesion (arrow) has a low D value (0.95 x 10-3 mm2/sec). The diffusion coefficient map was calculated on a pixel-by-pixel basis by using Equation (2).

 


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  		Figure 3a. MR images in a 72-year-old man with a liver cyst. (a) T2-weighted turbo spin-echo MR image (2,595/128 [effective]; echo train length, 23) shows a lesion (arrow) with markedly high signal intensity in the left lobe of the liver. (b) Echo-planar MR image ({infty}/123) obtained with a low MPG (b = 30 sec/mm2) shows very high signal intensity in the lesion (arrow). This is due to the markedly elongated T2 of the lesion. (c) Echo-planar MR image ({infty}/123) obtained with an intermediate MPG (b = 300 sec/mm2) shows that the signal intensity of the lesion (arrow) is reduced, indicating a high diffusion coefficient. (d) Echo-planar MR image ({infty}/123) obtained with a high MPG (b = 1,100 sec/mm2) shows that the signal intensity of the lesion (arrow) is markedly reduced, indicating a high diffusion coefficient. (e) Diffusion coefficient map shows that the cyst (arrow) has a high D value (2.98 x 10-3 mm2/sec). The diffusion coefficient map was calculated on a pixel-by-pixel basis by using Equation (2).

 


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  		Figure 3b. MR images in a 72-year-old man with a liver cyst. (a) T2-weighted turbo spin-echo MR image (2,595/128 [effective]; echo train length, 23) shows a lesion (arrow) with markedly high signal intensity in the left lobe of the liver. (b) Echo-planar MR image ({infty}/123) obtained with a low MPG (b = 30 sec/mm2) shows very high signal intensity in the lesion (arrow). This is due to the markedly elongated T2 of the lesion. (c) Echo-planar MR image ({infty}/123) obtained with an intermediate MPG (b = 300 sec/mm2) shows that the signal intensity of the lesion (arrow) is reduced, indicating a high diffusion coefficient. (d) Echo-planar MR image ({infty}/123) obtained with a high MPG (b = 1,100 sec/mm2) shows that the signal intensity of the lesion (arrow) is markedly reduced, indicating a high diffusion coefficient. (e) Diffusion coefficient map shows that the cyst (arrow) has a high D value (2.98 x 10-3 mm2/sec). The diffusion coefficient map was calculated on a pixel-by-pixel basis by using Equation (2).

 


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  		Figure 3c. MR images in a 72-year-old man with a liver cyst. (a) T2-weighted turbo spin-echo MR image (2,595/128 [effective]; echo train length, 23) shows a lesion (arrow) with markedly high signal intensity in the left lobe of the liver. (b) Echo-planar MR image ({infty}/123) obtained with a low MPG (b = 30 sec/mm2) shows very high signal intensity in the lesion (arrow). This is due to the markedly elongated T2 of the lesion. (c) Echo-planar MR image ({infty}/123) obtained with an intermediate MPG (b = 300 sec/mm2) shows that the signal intensity of the lesion (arrow) is reduced, indicating a high diffusion coefficient. (d) Echo-planar MR image ({infty}/123) obtained with a high MPG (b = 1,100 sec/mm2) shows that the signal intensity of the lesion (arrow) is markedly reduced, indicating a high diffusion coefficient. (e) Diffusion coefficient map shows that the cyst (arrow) has a high D value (2.98 x 10-3 mm2/sec). The diffusion coefficient map was calculated on a pixel-by-pixel basis by using Equation (2).

 


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  		Figure 3d. MR images in a 72-year-old man with a liver cyst. (a) T2-weighted turbo spin-echo MR image (2,595/128 [effective]; echo train length, 23) shows a lesion (arrow) with markedly high signal intensity in the left lobe of the liver. (b) Echo-planar MR image ({infty}/123) obtained with a low MPG (b = 30 sec/mm2) shows very high signal intensity in the lesion (arrow). This is due to the markedly elongated T2 of the lesion. (c) Echo-planar MR image ({infty}/123) obtained with an intermediate MPG (b = 300 sec/mm2) shows that the signal intensity of the lesion (arrow) is reduced, indicating a high diffusion coefficient. (d) Echo-planar MR image ({infty}/123) obtained with a high MPG (b = 1,100 sec/mm2) shows that the signal intensity of the lesion (arrow) is markedly reduced, indicating a high diffusion coefficient. (e) Diffusion coefficient map shows that the cyst (arrow) has a high D value (2.98 x 10-3 mm2/sec). The diffusion coefficient map was calculated on a pixel-by-pixel basis by using Equation (2).

 


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  		Figure 3e. MR images in a 72-year-old man with a liver cyst. (a) T2-weighted turbo spin-echo MR image (2,595/128 [effective]; echo train length, 23) shows a lesion (arrow) with markedly high signal intensity in the left lobe of the liver. (b) Echo-planar MR image ({infty}/123) obtained with a low MPG (b = 30 sec/mm2) shows very high signal intensity in the lesion (arrow). This is due to the markedly elongated T2 of the lesion. (c) Echo-planar MR image ({infty}/123) obtained with an intermediate MPG (b = 300 sec/mm2) shows that the signal intensity of the lesion (arrow) is reduced, indicating a high diffusion coefficient. (d) Echo-planar MR image ({infty}/123) obtained with a high MPG (b = 1,100 sec/mm2) shows that the signal intensity of the lesion (arrow) is markedly reduced, indicating a high diffusion coefficient. (e) Diffusion coefficient map shows that the cyst (arrow) has a high D value (2.98 x 10-3 mm2/sec). The diffusion coefficient map was calculated on a pixel-by-pixel basis by using Equation (2).

 


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  		Figure 4a. (a) Graph of diffusion coefficient D values ({bigcirc}) for the hepatic lesions in 78 patients. The D values for hepatocellular carcinoma (HCC) were significantly lower than those for other hepatic lesions (P < .05), and the D values for cysts were significantly higher than those for other hepatic lesions (P < .01). Error bars = SDs, • = mean D value. (b) Graph of perfusion fraction f values ({bigcirc}) for the hepatic lesions in 78 patients. The perfusion fractions for hemangiomas were significantly higher than those for other hepatic lesions (P < .05). Error bars = SDs, HCC = hepatocellular carcinoma, • = mean f value.

 


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  		Figure 4b. (a) Graph of diffusion coefficient D values ({bigcirc}) for the hepatic lesions in 78 patients. The D values for hepatocellular carcinoma (HCC) were significantly lower than those for other hepatic lesions (P < .05), and the D values for cysts were significantly higher than those for other hepatic lesions (P < .01). Error bars = SDs, • = mean D value. (b) Graph of perfusion fraction f values ({bigcirc}) for the hepatic lesions in 78 patients. The perfusion fractions for hemangiomas were significantly higher than those for other hepatic lesions (P < .05). Error bars = SDs, HCC = hepatocellular carcinoma, • = mean f value.

 




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