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The Utility of In-Phase/Opposed-Phase Imaging in Differentiating Malignancy from Acute Benign Compression Fractures of the Spine

W.K. Erlya, E.S. Oha and E.K. Outwatera

a From the Department of Radiology, The University of Arizona, Tucson, Ariz


Figure 1
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  		Fig 1. Motor vehicle crash involving 31-year-old man. Images demonstrate signal intensity–to-noise measurement technique used in assessing the abnormal signal intensity in the acute T12 compression fracture (arrows).

A, T1-weighted image.

B, T2-weighted image.

C, In-phase image.

D, Opposed-phase image. Region of interest cursor is on the region of abnormal signal intensity on the T1- and T2-weighted images. SIR is 0.76, indicating the presence of fat or benign marrow. Note the suppression of signal intensity from the normal fatty marrow in the adjacent vertebra.


Figure 2
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  		Fig 2. Plot of SIR of the data points with triangle indicating the benign fractures and circle denoting the malignant marrow infiltration. While there is variation in the SIR of the benign lesion, malignant infiltration does not suppress.


Figure 3
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  		Fig 3. Illustration of the physical principles of in-phase/opposed-phase imaging.

A, At echo time (TE) of 4.6 ms, both the fat and water protons are in phase, and signal intensity is received from voxels containing both tissue types.

B, At TE of 2.4 ms, the protons on water and fat molecules are 180° opposed, and the signal intensity from one cancels the signal intensity from the other. Voxels that contain both tissue types have a reduction in signal intensity.


Figure 4
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  		Fig 4. Metastatic melanoma in a 56-year-old man.

A and B, Routine T1- and T2-weighted images of metastatic melanoma with pathologic fracture of L2 (arrows). Metastatic lesions of L1 and L3 are difficult to see on the routine sequences.

C, In-phase image (TE = 4.6 ms).

D, Opposed-phase image (echo time [TE] = 2.4 ms). Marrow replaced by tumor does not suppress (arrows), whereas the normal fatty marrow appears dark on these images (asterisks).

E, In-phase image with region of interest cursor in place. Signal intensity ratio of L2 is 0.90, indicating the absence of fat and a malignant result.

F, Opposed-phase image with region of interest cursor in place. Signal intensity ratio of L2 is 0.90, indicating the absence of fat and a malignant result.


Figure 5
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  		Fig 5. Lymphoma in a 33-year-old man. False-negative for malignancy.

A and B, T1- and T2-weighted images, respectively, done in February 2003 show abnormal decreased signal intensity (arrows) on the T1-weighted sequence and increased signal intensity (arrows) on the T2-weighted sequence compared with normal marrow. These findings were considered to be due to lymphomatous marrow infiltration.

C and D, In-phase image and opposed-phase image, respectively, done in February 2003. Signal intensity measurement is 202 on the in-phase sequence and 215 on the opposed phase, a ratio of 1.1 or a malignant result.

E–H, T1-weighted, T2-weighted, in-phase, and opposed-phase images 3 months later. Patient has received prior radiation therapy. T1- and T2-weighted images continue to show abnormal signal intensity relative to the normal marrow (arrows), though the signal intensity changes have evolved since the initial examination. Signal intensity on the in-phase image is 90 and 46 on the opposed-phase, a SIR of 0.51, a benign result in a lesion that was still considered malignant on the routine sequences.





Copyright © 2008 by the American Society of Neuroradiology. Print ISSN: 0195-6108 Online ISSN: 1936-959X