Assessment of Melanin Content and its Influence on Susceptibility Contrast in Melanoma Metastases
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ORIGINAL ARTICLE
Assessment of Melanin Content and its Influence on Susceptibility Contrast in Melanoma Metastases Sina Straub1 · Frederik B. Laun1,2 · Martin T. Freitag3 · Christian Kölsche4,5 · Andreas von Deimling4,5 · Michael Denoix1 · Martin Bendszus8 · Heinz-Peter Schlemmer3 · Mark E. Ladd1,6,7 · Till M. Schneider3,8 Received: 3 May 2019 / Accepted: 8 July 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract Purpose To quantify the influence of melanin content on magnetic susceptibility of cerebral melanoma metastases. Methods Patients with non-hemorrhagic metastases were included based on the absence of susceptibility blooming artifacts. Susceptibility maps were calculated from 3D gradient echo data, using Laplacian-based phase unwrapping, sophisticated harmonic artefact reduction for phase data (V-SHARP) with varying spherical kernel sizes for background field removal and the iLSQR algorithm for the inversion of phase data. Susceptibility maps were referenced to cerebrospinal fluid. Non-hemorrhagic metastases were identified on contrast-enhanced T1-weighted images and susceptibility weighted images. Metastases masks were drawn on T1-weighted post-contrast images and used to compute mean susceptibility values of each metastasis. Results A total of 33 non-hemorrhagic melanoma brain metastases in 20 patients were quantitatively evaluated. Metastases without and with hyperintense signal on T1-weighted images, which corresponds to the melanin content, showed median susceptibility values of –0.028 ppm and –0.020 ppm, respectively. The susceptibility differences between metastases without and with T1-weighted hyperintense signal was not statistically significant (p ≥ 0.05). Conclusion Non-hemorrhagic cerebral melanoma metastases showed weak diamagnetic susceptibility values and susceptibility did not significantly correlate to T1-weighted signals. Therefore, melanin does not seem to be a major contributor to susceptibility in cerebral melanoma metastases.
Keywords Magnetic resonance imaging · Malignant melanoma · Neoplasm metastasis · Melanin · Magnetic susceptibility
Introduction Among all primary neoplasms in adults, melanomas have the highest propensity to metastasize to the brain [1] and it has been shown that high melanin levels in melanoma lesions attenuate the response to chemotherapy and radiotherapy [2]. Therefore, an improved understanding of the
Till M. Schneider
contrast mechanisms of melanin in melanoma metastases in magnetic resonance imaging (MRI) can be of clinical importance. Outside the spectrum of melanoma metastases, melanin is additionally clinically important with respect to Parkinson’s disease where depletion of neurons containing neuromelanin in the substantia nigra correlates with disease progression [3]. 4
Department of Neuropathology, Institute of Pathology, University of Heidelberg, Im Neuenheimer Feld 224, 69120 Heidelberg, Germany
5
German Cancer Consortium (DKTK), CCU Neuropathology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120
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