MRSIImportance of full volumetric coverage

The advantages of MRSI as compared to MRS for tumor diagnostics cannot be overemphasized. As will be seen in the next chapters, the major breakthroughs in brain and prostate cancer diagnostics have relied heavily upon assessment of the metabolic characteristics of larger areas of suspected tumor, peritumoral regions and normal tissue. This is provided by MRSI. Spielman [10] states: "the spatial resolution of in vivo {MR} spectroscopy is simply too coarse to avoid false negative findings resulting from small lesions partially volumed with normal tissues"(p. 30) and emphasizes the need for volumetric coverage using proton MRSI for central nervous system (CNS) tumor diagnostics. Complete volumetric coverage of a suspected lesion is critical for accurate diagnosis, and Spielman notes that metabolically abnormal regions may not precisely correspond to much larger T2 abnormalities. Thus, he concluded: "sampling the most 'metabolically' abnormal tissue may be a better choice than just sampling the tissue with the highest level of contrast-enhancement" (p. 31). Vigneron et al. [11] similarly point out the weakness of single voxel techniques that "provide one spectrum {as in MRS} which is presumed to be representative of the entire tumor." They note that "this technique provides no information on the extent of the metabolic abnormality and suffers both from the inaccuracy of conventional MRI to define the exact extent of solid neoplasms and the considerable tissue heterogeneity within the tumor mass" (pp. 98-99). Thus, these authors underscore the need for 3D spectroscopic imaging for "identification of viable tumor on the basis of both morphologic and metabolic parameters ... for targeting and following local therapy" (p. 100).

References

[1] A.E. Li, D.A. Bluemke, Magnetic Resonance Imaging in: V.T. de Vita, S. Hellman, S.A. Rosenberg, Cancer Principles & Practice of Oncology 6th Edition, Lippincott Williams & Wilkins, Philadelphia, 2001, p. 669-679.

[2] R. Damadian, Tumor detection by nuclear magnetic resonance, Science 171, 1151-1153 (1971).

[3] J.A. Koutcher, M. Goldsmith, R. Damadian, NMR in cancer. X. A malignancy index to discriminate normal and cancerous tissue, Cancer 41 174-182 (1978).

[4] P. Kowalski, P. Skupin, J. Sowier, K.J. Olszewski, NMR relaxation time studies of large bowel neoplasms, Physiol. Chem. Phys. Med. NMR 29, 51-54 (1997).

[5] E. R. Danielsen, B. Ross, Magnetic Resonance Spectroscopy Diagnosis of Neurological Diseases, Marcel Dekker, Inc., New York, 1999.

[6] J. Czernin, M.E. Phelps, Positron emission tomography scanning: Current and future applications. Annu. Rev. Med. 53, 89-112 (2002).

[7] W. Negendank, Studies of human tumors by MRS: A review, NMR Biomed. 5, 303-324 (1992).

[8] N.R. Aiken, R.J. Gillies, Phosphomonoester metabolism as a function of cell proliferative status and exogenous precursors, Anticancer Res. 16, 1393-1397 (1996).

[9] J.D. Bell, KK. Bhakoo, Metabolic changes underlying 31P MR spectral alterations in human hepatic tumors, NMR Biomed. 11, 354-359 (1998).

[10] D. Spielman, In vivo proton MR spectroscopy: basic principles and clinical applications,

Section for Magnetic Resonance Technologists Educational Seminars 3, 19-37 (2000).

[11] D. Vigneron, A. Bollen, M. McDermott, et al., Three-dimensional magnetic resonance spectroscopic imaging of histologically confirmed brain tumors, Magn. Reson. Imaging 19, 89-101

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