Differentiation of osteoporosis from metastasis in the vertebral fracture using chemical shift and diffusion weighted imaging Poster No.: C-0444 Congress: ECR 2012 Type: Educational Exhibit Authors: H. T. Koay, R. DUTTA, M. GEORGE ; Singapore/SG, 1 2 2 1 2 SINGAPORE/SG Keywords: Osteoporosis, Metastases, Imaging sequences, MR, Spine DOI: 10.1594/ecr2012/C-0444 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myesr.org Page 1 of 24
Learning objectives Acute benign and malignant fractures of the spine may have similar signal intensity characteristics on conventional MR imaging sequences. Apart from the routine spine evaluation on MRI by T1-weighted, T2-weighted and FSEIR sequences, chemical shift and diffusion weighted imaging may be useful in differentiating acute benign compression fractures from malignant infiltration and pathologic fractures. Background Benign vertebral lesions can occur in cancer patients. Metastatic vertebral lesions frequently account for bony metastases in patients with primary neoplasm. Differentiation between malignant and benign vertebral compression fracture in acute setting is difficult especially for patients known with or suspected primary neoplasm. Routine MRI of the spine typically includes T1-weighted, T2-weighted and FSEIR sequences, may provide useful evaluation of the benign and malignant vertebral fracture based on morphological features. Lesions with negative gadolinium enhancement were favored as benign fractures. A uniform signal change in multiple involved vertebra lesions, round, smooth margins with marked epidural compression, a paraspinal soft tissue mass, and pedicle and posterior element involvement were favored as malignant fractures. An associated paraspinal soft tissue mass was found to be significant in predicting the probability of malignancy. (Fu TS, Chen LH, Liao JC, Lai PL, Niu CC, Chen WJ. Magnetic resonance imaging characteristics of benign and malignant vertebral fractures. Chang Gung Med J. 2004 Nov;27(11):808-15) Despite the use of these features, there may be an overlap between benign fractures from malignant fractures Non routine MRI pulse sequences such as chemical shift and diffusion weighted imaging are increasingly used recently for further evaluation. Imaging findings OR Procedure details Chemical shift imaging applies principle that fat and water protons in a single voxel show slightly different precession frequencies. Page 2 of 24
Using a 1.5-T magnet, water and fat protons are in phase with one another at a TE of 4.6 milliseconds. At a TE of 2.4 milliseconds, water and fat are 180 opposed; thus, the signals of water and fat cancel each other. Page 3 of 24
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Fig. 1: Physical principles of in-phase/opposed-phase imaging References: AJNR June 2006 27: 1183-1188 In normal bone marrow with the presence of both fat and water, signal loss will occur on the out-of-phase images as compared with the in-phase images. Most malignancy completely replaces or displaces fat in the marrow space and will lack normal signal dropout on opposed phase images. While most benign conditions such as trauma, edema, marrow hyperplasia, ischemia and infection do not replace bone marrow fat and preserve some degree of signal dropout on opposed phase images. In one of the study of 30 patients, relative SI ratio to predict whether lesions were neoplastic or non neoplastic, was calculated. A 0.81 was used as cutoff value, sensitivity and specificity of 95% were achieved. This technique has also been used to differentiate acute benign versus malignant vertebral fractures. (Disler DG, McCauley TR, Ratner LM, Kesack CD, Cooper JA. In-phase and out-of-phase MR imaging of bone marrow: prediction of neoplasia based on the detection of coexistent fat and water. AJR 1997; 169:1439-1447) Page 5 of 24
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Fig. 7: T1W Fig. 8: T2W Page 7 of 24
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Fig. 9: FSEIR Page 9 of 24
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Fig. 16: In-phase Fig. 17: Opposed-phase: signal dropout Benign fracture of T12 and L1 vertebra with known metastatic colon carcinoma Page 11 of 24
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Fig. 10: T1W Fig. 11: T2W Page 13 of 24
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Fig. 12: FSEIR Fig. 13: T1W + contrast Page 15 of 24
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Fig. 18: In-phase Malignant fracture of L1 vertebra with known metastatic lung carcinoma There are several pitfalls in chemical shift imaging. Radiation therapy may normalize the signal-to-noise ratio in treated lesions, whereas marrow fibrosis may result in a false-positive interpretation. Susceptibility artifact associated with sclerotic metastases and fracture-related hematoma may result in a false-positive result. On the other hand, metastases containing fat such as renal cell carcinoma and infiltrative multiple myeloma, may result in a false-negative interpretation. (Lubdha M. Shah, Christopher J. Hanrahan. MRI of spinal bone marrow: part 1, techniques and normal age-related appearances. AJR 2011; 197:1298-1308) Diffusion-weighted imaging (DWI) is a special technique using very strong magnetic gradients, effectively canceling signal from protons in free moving water. All benign vertebral compression fractures were hypo- to isointense to adjacent normal vertebral bodies. Pathologic compression fractures were hyperintense to normal vertebral bodies. (Baur A, Stäbler, Brüning R, et al. Diffusion weighted MR imaging of bone marrow: differentiation of benign versus pathologic compression fractures. Radiology 1998; 207:349-356) Page 17 of 24
Fig. 5: T2W Page 18 of 24
Fig. 4: T1W Fig. 23: DWI: restricted diffusion Page 19 of 24
Fig. 22: ADC: low value Expansile bony metastasis at L2 vertebra with known metastatic renal cell carcinoma Quantitative diffusion imaging with ADC (apparent diffusion coefficiency) mapping improved the distinction between benign and malignant lesions. It is known that ADC is sensitive to cell volume fraction and cellularity in biologic tissue. In metastatic lesions, the cellularity can be high, especially in actively growing tumors. The lower ADC values in the metastases with high cellularity are seen. On the other hand, the cellularity in benign fractures can be lower than that of metastatic lesions and leads to a higher ADC value. The mean ADC value of benign lesions was 68% higher than that of the metastases. (Xiaohong Joe Zhoua, Norman E. Leedsa, Graeme C. McKinnonb, Ashok J. Kumara. Characterization of Benign and Metastatic Vertebral Compression Fractures with Quantitative Diffusion MR Imaging. AJNR 2002 23: 165-170) Page 20 of 24
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Fig. 2: T1W References: TTSH, Singapore Fig. 3: T2W References: TTSH, Singapore Page 22 of 24
Fig. 20: DWI: no restricted diffusion References: TTSH, Singapore Page 23 of 24
Fig. 21: ADC: high value References: TTSH, Singapore Acute benign compression fracture of L1 vertebral body with known metastatic cervical carcinoma Conclusion Chemical shift and diffusion-weighted MR imaging can provide excellent distinction between malignant and benign acute vertebral compression fractures especially for the patient with known metastatic tumor. Personal Information References Fu TS, Chen LH, Liao JC, Lai PL, Niu CC, Chen WJ. Magnetic resonance imaging characteristics of benign and malignant vertebral fractures. Chang Gung Med J. 2004 Nov;27(11):808-15. Disler DG, McCauley TR, Ratner LM, Kesack CD, Cooper JA. In-phase and out-of-phase MR imaging of bone marrow: prediction of neoplasia based on the detection of coexistent fat and water. AJR 1997; 169:1439-1447 Lubdha M. Shah, Christopher J. Hanrahan. MRI of spinal bone marrow: part 1, techniques and normal age-related appearances. AJR 2011; 197:1298-1308 Baur A, Stäbler, Brüning R, et al. Diffusion weighted MR imaging of bone marrow: differentiation of benign versus pathologic compression fractures. Radiology 1998; 207:349-356 Xiaohong Joe Zhoua, Norman E. Leedsa, Graeme C. McKinnonb, Ashok J. Kumara. Characterization of Benign and Metastatic Vertebral Compression Fractures with Quantitative Diffusion MR Imaging. AJNR 2002 23: 165-170 Page 24 of 24