Correlation of MR imaging and histologic findings in mouse melanoma

Abstract

M2R melanoma tumors in male C57 black mice were used to correlate magnetic resonance (MR) images with the corresponding histologic slices and to determine if analysis of the achievable correlation can provide a basis for predicting gross histologic features with MR imaging alone. The MR imaging sections obtained at 4.7 T were each 680 microns thick, with an in-plane resolution of 195 microns. The distribution of melanin within the histologic slices correlated well with the high-signal-intensity regions on the T1-weighted images (T1WIs), while these regions had low signal intensity on the T2-weighted images (T2WIs), providing evidence that melanin or melanin-associated paramagnetic species are responsible for the observed proton relaxation rate enhancement. Viable melanoma cells typically showed intermediate signal intensity on T2WIs, T1WIs, and proton-density images. Necrosis typically had high signal intensity on T2WIs, T1WIs, and proton-density images. Quantitation of the MR imaging results, followed by statistical analysis, demonstrated statistically significant differences between melanin-rich, viable-melanoma, and necrotic regions on MR images.

Influence of paramagnetic melanin on the MRI contrast in melanoma: a combined high‐field (11.7 T) MRI and EPR study

“…The results we obtained at high field are not in agreement with some previous studies done at lower magnetic field, which pointed out the efficiency of T 1 W or T 2 W sequences to distinguish pigmented tumors or pigmented areas from the non‐pigmented ones. Still, it is interesting to note that the results obtained so far were quite controversial as studies that obtained significant results with T 1 W sequences failed to observe a correlation between melanin and the T 2 , and reciprocally.…”

Vaccinia virus-mediated melanin production allows MR and optoacoustic deep tissue imaging and laser-induced thermotherapy of cancer

“…We speculated that introduction of melanogenesis into tumor cells might render them visible as a result of melanin overproduction by optical as well as optoacoustic imaging (6) and might facilitate therapy. Furthermore, it is well known that melanotic melanomas generate high signal on T1-weighted magnetic resonance images (7,8), probably as a result of trapping of paramagnetic transition metal ions (9). Previously published cell culture data also encouraged us to use the production of melanin as a reporter for MRI (9)(10)(11).…”

Monitoring acute inflammatory processes in mouse muscle by MR imaging and spectroscopy: a comparison with pathological results

“…T 2 , T 1 , proton-density weighting, magnetization transfer, inversion recovery, etc., or the use of contrast agents, which have all been useful in predicting certain pathological findings in other cases. [2][3][4][17][18][19][20] Thus the intermediate stage, with a higher percentage of coagulative necrosis and a central abscess, was mainly observed during the evolution from initial infection towards well-established acute inflammation (days 3-7 after inoculation). The accumulation of A. fumigatus in necrotic areas resulted in MRI hypointensities in those slice areas, which may go to support some reports that put the hypointense signals down to low water concentration, as seen in some fibrous lesions with scar tissue, large amounts of collagen, densely mineralized masses, air, and foreign bodies.…”