Susceptibility‐weighted imaging in malignant melanoma brain metastasis

Abstract

Background The value of cerebral susceptibility‐weighted imaging (SWI) in malignant melanoma (MM) patients remains controversial and the effect of melanin on SWI is not well understood. Purpose To systematically analyze the spectrum of intracerebral findings in MM brain metastases (BM) on SWI and to determine the diagnostic value of SWI. Study Type Retrospective. Population/Subjects In all, 100 patients with melanoma BM (69 having received radiotherapy [RT] and 31 RT‐naïve) and a control group of 100 melanoma patients without BM were included. For detailed analysis of signal characteristics, 175 metastases were studied. Field Strength/Sequence Gradient echo SWI sequence at 1.5, 3.0, and 9.4 T. Assessment Signal characteristics from melanotic and amelanotic BMs on SWI with a focus on blooming artifacts were analyzed, as well as the presence and longitudinal dynamics of isolated SWI blooming artifacts in patients with and without BM. Statistical Tests Chi‐squared and Student's t‐test were used for contingency table measures and group data of signal and clinical characteristics, respectively. Results Melanotic and amelanotic metastases did not show significant differences of SWI blooming artifacts (38% vs. 43%, P = 0.61). Most metastases without an initial SWI artifact developed a signal dropout during follow‐up (80%; 65/81). Isolated SWI artifacts were detected more frequently in patients with BM (20 vs. 9, P = 0.03), of which the majority were found in patients who had received RT (17 vs. 3, P = 0.08). None of these isolated SWI blooming artifacts turned into overt metastases over time (median follow‐up: 8.5 months). Similar findings persisted as remnants of successfully treated metastases (88%; 7/8). Data Conclusion We conclude that SWI provides little additional diagnostic benefit over standard T1‐weighted imaging, as melanin content alone does not cause diagnostically relevant SWI blooming. Signal transition of SWI may rather indicate secondary phenomena like microbleeding and/or metal scavenging. Our results suggest that isolated SWI artifacts do not constitute vital tumor tissue but represent unspecific microbleedings, RT‐related parenchymal changes or posttherapeutic remnants of former metastatic lesions. Level of Evidence: 3 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2019;50:1251–1259.

Recognition of Brain Metastases Using Gadolinium-Enhanced SWI MRI: Proof-of-Concept Study

“…In the case of brain metastases from systemic melanoma or breast cancer, T1-Gd has been shown to be better than other modalities (15,20). Moreover, in direct comparison with T1-Gd for detecting melanoma metastases, SWI-U has shown no diagnostic advantage (21). To our knowledge, the present study is the first one to prospectively evaluate the added value of SWI-Gd for the potential detection of brain metastases.…”

Clinical Value of Susceptibility Weighted Imaging of Brain Metastases

“…This was first reported by Gaviani et al on T2 * -weighted imaging in three malignant melanoma patients (52). However, later studies analyzing the fate of isolated cerebral SWI artifacts in larger patient cohorts over time could not confirm the hypothesis that such "isolated SWI signals" would eventually evolve into overt brain metastases (53,54). Indeed, these studies showed that SWI signal losses without corresponding signal changes on standard sequences remained constant over time.…”

“…The SWI signal drop remains as a remnant of the preexisting metastasis (iv). Adapted from Schwarz et al (54).…”

“…brain metastases as compared to melanoma patients without metastatic brain disease (54). Of those patients, only patients after radiotherapy showed an increased number of such artifacts indicating that these findings did not constitute vital tumor tissue but may rather represent either non-specific microbleedings or radiotherapy-related parenchymal damage (56) which are both well-known phenomena in patients after radiotherapy of the brain (57).…”

High-Resolution Intratumoral Susceptibility Signal (ITSS) as an Adjunctive Imaging Tool in the Evaluation of Treatment Response of Brain Metastases Following Stereotactic Radiosurgery

“…37 These changes could be evaluated on SWI following SRS which allow for the assessment of treatment response along with T1 post-contrast images. 38,39 The purpose of our study was to extend previous work and evaluate the longitudinal change of intratumoral susceptibility signal (ITSS) on highresolution SWI as an adjunctive imaging tool to evaluate treatment response of brain metastasis following stereotactic radiosurgery. Our hypothesis is that this approach could help further stratification of the patients and guide clinical decision making.…”