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Abstract:Raman microspectroscopy is a powerful tool for the analysis of tissue sections providing a molecular map of the investigated samples. Nevertheless, data pre processing, and particularly the removal of broad background to the spectra remains problematic. Indeed, the physical origin of the background has not been satisfactorily determined. Using 785nm as source in a confocal geometry, it is demonstrated, that for the example of the protein kappa-elastin, the background and resulting quality of the recorded spectrum is dependent on the morphology of the sample. Whereas a fine powder yields a dominant broad background, compressed pellets and solution cast thin films produce respectively improved quality spectra with significantly reduced spectral background. As the chemical composition of the samples is identical, the background is ascribed to stray light due to diffuse scattering rather than an intrinsic photoluminescence. Recorded spectra from tissue sample exhibit a large and spatially variable background, resulting in poorly defined spectral features. A significant reduction of the background signal and improvement of the spectral quality is achieved by immersion in water, and measurement with an immersion objective. The significant improvement in signal to background is attributed to a reduction of the diffuse scattering due to a change in the effective morphology as a result of an improved index matching between the water/ tissue interface compared to the air/tissue interface. Compared to sections measured in air, the background is reduced to that of the water, and preprocessing is reduced to the subtraction of the substrate and water signal, and correction for the instrument response, all of which are highly reproducible. Data preprocessing is thus greatly simplified and the results significantly more reliable.

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The recently updated Durie/Salmon PLUS staging system published in 2006 highlights the many advances that have been made in the imaging of multiple myeloma, a common malignancy of plasma cells. In this article, we shall focus primarily on the more sensitive and specific whole-body imaging techniques, including whole-body computed tomography, whole-body magnetic resonance imaging, and positron emission computed tomography. We shall also discuss new and emerging imaging techniques and future developments in the radiological assessment of multiple myeloma.

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