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DOI: 10.1148/rg.265055711
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Dual Gradient-Echo In-Phase and Opposed-Phase Hepatic MR Imaging: A Useful Tool for Evaluating More Than Fatty Infiltration or Fatty Sparing1

Elmar M. Merkle, MD and Rendon C. Nelson, MD

1 From the Department of Radiology, Duke University Medical Center, Duke North, Room 1417, Erwin Rd, Durham, NC 27710. Received May 6, 2005; revision requested July 25 and received August 15; accepted August 15. All authors have no financial relationships to disclose.

Figure 1
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  		Figure 1a.  Normal appearance of the liver at opposed-phase and in-phase hepatic MR imaging in a healthy volunteer. (a) Axial opposed-phase MR image shows a sharply defined black rim around organs with a fat-water interface. Note the drop in signal intensity in the vertebra (compared with that on the in-phase image) due to fatty bone marrow. However, there is no drop in signal intensity in the liver or subcutaneous tissue. (b) Axial in-phase MR image shows increased susceptibility artifacts (compared with those on the opposed-phase image) in the gas-filled splenic flexure (arrow) and stomach (arrowhead) due to the longer echo time.

 

Figure 1
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  		Figure 1b.  Normal appearance of the liver at opposed-phase and in-phase hepatic MR imaging in a healthy volunteer. (a) Axial opposed-phase MR image shows a sharply defined black rim around organs with a fat-water interface. Note the drop in signal intensity in the vertebra (compared with that on the in-phase image) due to fatty bone marrow. However, there is no drop in signal intensity in the liver or subcutaneous tissue. (b) Axial in-phase MR image shows increased susceptibility artifacts (compared with those on the opposed-phase image) in the gas-filled splenic flexure (arrow) and stomach (arrowhead) due to the longer echo time.

 

Figure 2
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  		Figure 2.  Underlying physics of in-phase and opposed-phase imaging. The signal intensity seen on opposed-phase images reflects the magnitude of the magnetic vector but not its phase (ie, direction). For this reason, tissue that consists of mostly fat protons (eg, subcutaneous fat) shows only little or no obvious drop in signal intensity. Furthermore, voxels with 50% fat signal and 50% water signal have a signal intensity of zero on opposed-phase images.

 

Figure 3
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  		Figure 3a.  Focal fatty sparing. Opposed-phase (a–c) and corresponding in-phase (d–f) images show focal fatty sparing next to the gallbladder fossa (arrow in a and b) and the fissure of the ligamentum venosum (arrowhead in c).

 

Figure 3
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  		Figure 3b.  Focal fatty sparing. Opposed-phase (a–c) and corresponding in-phase (d–f) images show focal fatty sparing next to the gallbladder fossa (arrow in a and b) and the fissure of the ligamentum venosum (arrowhead in c).

 

Figure 3
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  		Figure 3c.  Focal fatty sparing. Opposed-phase (a–c) and corresponding in-phase (d–f) images show focal fatty sparing next to the gallbladder fossa (arrow in a and b) and the fissure of the ligamentum venosum (arrowhead in c).

 

Figure 3
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  		Figure 3d.  Focal fatty sparing. Opposed-phase (a–c) and corresponding in-phase (d–f) images show focal fatty sparing next to the gallbladder fossa (arrow in a and b) and the fissure of the ligamentum venosum (arrowhead in c).

 

Figure 3
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  		Figure 3e.  Focal fatty sparing. Opposed-phase (a–c) and corresponding in-phase (d–f) images show focal fatty sparing next to the gallbladder fossa (arrow in a and b) and the fissure of the ligamentum venosum (arrowhead in c).

 

Figure 3
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  		Figure 3f.  Focal fatty sparing. Opposed-phase (a–c) and corresponding in-phase (d–f) images show focal fatty sparing next to the gallbladder fossa (arrow in a and b) and the fissure of the ligamentum venosum (arrowhead in c).

 

Figure 4
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  		Figure 4a.  Focal fatty sparing. Opposed-phase (a) and in-phase (b) images show wedge-shaped focal fatty sparing in the subcapsular region of segment VIII (arrow in a). It is important to rule out an underlying tumor near the apex of the focal sparing. Note the hemorrhagic cyst in segment VII (arrowhead).

 

Figure 4
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  		Figure 4b.  Focal fatty sparing. Opposed-phase (a) and in-phase (b) images show wedge-shaped focal fatty sparing in the subcapsular region of segment VIII (arrow in a). It is important to rule out an underlying tumor near the apex of the focal sparing. Note the hemorrhagic cyst in segment VII (arrowhead).

 

Figure 5
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  		Figure 5a.  Diffuse steatosis hepatis with focal intensification. Opposed-phase (a) and in-phase (b) images show diffuse steatosis hepatis, which is markedly pronounced in the caudate lobe (arrow in a).

 

Figure 5
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  		Figure 5b.  Diffuse steatosis hepatis with focal intensification. Opposed-phase (a) and in-phase (b) images show diffuse steatosis hepatis, which is markedly pronounced in the caudate lobe (arrow in a).

 

Figure 6
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  		Figure 6a.  Focal fatty sparing. Opposed-phase (a) and in-phase (b) images show subcapsular focal fatty sparing, which produces a hepatic pseudotumor (arrow in a).

 

Figure 6
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  		Figure 6b.  Focal fatty sparing. Opposed-phase (a) and in-phase (b) images show subcapsular focal fatty sparing, which produces a hepatic pseudotumor (arrow in a).

 

Figure 7
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  		Figure 7a.  Geographic steatosis hepatis. Opposed-phase (a) and in-phase (b) images show geographic steatosis hepatis. Note that the course of the vessel (arrows in b) is unaltered by the steatosis.

 

Figure 7
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  		Figure 7b.  Geographic steatosis hepatis. Opposed-phase (a) and in-phase (b) images show geographic steatosis hepatis. Note that the course of the vessel (arrows in b) is unaltered by the steatosis.

 

Figure 8
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  		Figure 8a.  Liver metastasis with peritumoral fatty sparing in a patient with breast cancer. Opposed-phase (a) and in-phase (b) images show a large right-sided subcapsular liver metastasis (arrow in b). The opposed-phase image shows a bright peritumoral rim, which represents peritumoral fatty sparing in an otherwise steatotic liver. Note that the peritumoral fatty sparing is not specific for malignant lesions but can also be seen in conjunction with benign masses such as hemangiomas.

 

Figure 8
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  		Figure 8b.  Liver metastasis with peritumoral fatty sparing in a patient with breast cancer. Opposed-phase (a) and in-phase (b) images show a large right-sided subcapsular liver metastasis (arrow in b). The opposed-phase image shows a bright peritumoral rim, which represents peritumoral fatty sparing in an otherwise steatotic liver. Note that the peritumoral fatty sparing is not specific for malignant lesions but can also be seen in conjunction with benign masses such as hemangiomas.

 

Figure 9
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  		Figure 9a.  Transfusional hemosiderosis. Opposed-phase (echo time of 1.5 msec) (a) and in-phase (echo time of 4.9 msec) (b) images, obtained with an ultrahigh-field-strength 3-T MR system, show a marked drop in signal intensity in the liver (from 65 to 8 [arbitrary units]) and spleen (from 126 to 13) on the image with the longer echo time (b). Iron storage causes significant local distortion of the nearby magnetic field, resulting in significant shortening of T2*.

 

Figure 9
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  		Figure 9b.  Transfusional hemosiderosis. Opposed-phase (echo time of 1.5 msec) (a) and in-phase (echo time of 4.9 msec) (b) images, obtained with an ultrahigh-field-strength 3-T MR system, show a marked drop in signal intensity in the liver (from 65 to 8 [arbitrary units]) and spleen (from 126 to 13) on the image with the longer echo time (b). Iron storage causes significant local distortion of the nearby magnetic field, resulting in significant shortening of T2*.

 

Figure 10
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  		Figure 10a.  Transfusional hemosiderosis. Opposed-phase (a) and in-phase (b) images obtained with a high-field-strength 1.5-T MR system show iron deposition in the spleen and liver. The iron deposition is much more severe in the spleen; as a result, the drop in signal intensity on the image with the longer echo time (b) is much more pronounced in the spleen than in the liver.

 

Figure 10
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  		Figure 10b.  Transfusional hemosiderosis. Opposed-phase (a) and in-phase (b) images obtained with a high-field-strength 1.5-T MR system show iron deposition in the spleen and liver. The iron deposition is much more severe in the spleen; as a result, the drop in signal intensity on the image with the longer echo time (b) is much more pronounced in the spleen than in the liver.

 

Figure 11
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  		Figure 11a.  Susceptibility artifact from a cholecystectomy surgical clip. Opposed-phase (a) and in-phase (b) images show a susceptibility artifact caused by a surgical clip (arrow). The artifact is larger on the image with the longer echo time (14 x 27 mm on the in-phase image vs 10 x 22 mm on the opposed-phase image).

 

Figure 11
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  		Figure 11b.  Susceptibility artifact from a cholecystectomy surgical clip. Opposed-phase (a) and in-phase (b) images show a susceptibility artifact caused by a surgical clip (arrow). The artifact is larger on the image with the longer echo time (14 x 27 mm on the in-phase image vs 10 x 22 mm on the opposed-phase image).

 

Figure 12
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  		Figure 12a.  Pneumobilia in a patient who underwent hepaticojejunostomy. (a, b) Opposed-phase (echo time of 1.5 msec) (a) and in-phase (echo time of 4.9 msec) (b) images, obtained with an ultrahigh-field-strength 3-T MR system, show susceptibility artifact caused by pneumobilia in the left hepatic lobe (arrows). The artifact is larger on the image with the longer echo time (7 mm perpendicular to the bile duct on the in-phase image vs 5 mm on the opposed-phase image). Arrowheads = simple hepatic cysts. (c) Axial turbo spin-echo T2-weighted image shows a normal peripheral intrahepatic duct (thick arrow). Note that the pneumobilia cannot be seen (thin arrow).

 

Figure 12
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  		Figure 12b.  Pneumobilia in a patient who underwent hepaticojejunostomy. (a, b) Opposed-phase (echo time of 1.5 msec) (a) and in-phase (echo time of 4.9 msec) (b) images, obtained with an ultrahigh-field-strength 3-T MR system, show susceptibility artifact caused by pneumobilia in the left hepatic lobe (arrows). The artifact is larger on the image with the longer echo time (7 mm perpendicular to the bile duct on the in-phase image vs 5 mm on the opposed-phase image). Arrowheads = simple hepatic cysts. (c) Axial turbo spin-echo T2-weighted image shows a normal peripheral intrahepatic duct (thick arrow). Note that the pneumobilia cannot be seen (thin arrow).

 

Figure 12
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  		Figure 12c.  Pneumobilia in a patient who underwent hepaticojejunostomy. (a, b) Opposed-phase (echo time of 1.5 msec) (a) and in-phase (echo time of 4.9 msec) (b) images, obtained with an ultrahigh-field-strength 3-T MR system, show susceptibility artifact caused by pneumobilia in the left hepatic lobe (arrows). The artifact is larger on the image with the longer echo time (7 mm perpendicular to the bile duct on the in-phase image vs 5 mm on the opposed-phase image). Arrowheads = simple hepatic cysts. (c) Axial turbo spin-echo T2-weighted image shows a normal peripheral intrahepatic duct (thick arrow). Note that the pneumobilia cannot be seen (thin arrow).

 




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