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Published on: June 7, 2020
MRI of blood volume with MS 325 in experimental choroidal melanoma
Matthias H J Krause1, Kenneth K Kwong, Jing Xiong
1Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
Abstract:
Functional magnetic resonance imaging (MRI) allows quantitative blood volume imaging in vivo at high tissue resolution. The purpose is to apply this technique for untreated and hyperthermia-treated experimental choroidal melanoma. MS 325 was used as new intravascular albumin-bound gadolinium-based contrast agent. Pigmented choroidal melanomas were established in albino rabbits. MRI was performed in 7 untreated eyes and 7 eyes treated with a Neodymium:Yttrium-Lanthanum-Fluoride-laser at 1047 nm. 3D-spoiled gradient echo pulse sequences were used to acquire T' weighted axial images. First, a set of images was collected without contrast agent. MS 325 was then injected i.v. and images were obtained within 12 min after injection. Signal intensities were measured within tumor, ciliary body, choroid, and iris and relative signal intensities were determined for these tissues in relation to vitreous. In untreated tumors, the relative signal intensity was higher after injection of MS 325 (5.61+0.70) than without MS 325 (2.90+0.33; p = 0.0002). In contrast, the relative signal intensity of treated tumors did not differ significantly before and after MS 325 (6.19+1.59 and 6.13+1.64). Histopathological sections indicated vascular occlusion in treated tumors. All other studied tissues of untreated and treated eyes showed a significant increase of relative signal intensities in the presence of MS 325. An animal model for the research on contrast agents in MRI is presented. Blood volume measurement with MS 325 was adapted for experimental choroidal melanomas. Reduced change of relative signal intensity indicates compromised blood volume after vascular occlusion in hyperthermia-treated melanoma. Further studies are needed to investigate whether this technique allows the evaluation of tumor viability following treatments.
Insights
Functional magnetic resonance imaging (MRI) quantifies blood volume in choroidal melanoma. Hyperthermia treatment reduced blood volume changes, indicating vascular occlusion and potential for evaluating treatment efficacy.
Area of Science:
- Ophthalmology
- Medical Imaging
- Oncology
Background:
- Functional magnetic resonance imaging (fMRI) enables in vivo quantitative blood volume imaging.
- Choroidal melanoma is a significant ocular tumor requiring effective treatment monitoring.
- Intravascular contrast agents are crucial for enhancing MRI-based blood volume assessments.
Purpose of the Study:
- To apply quantitative blood volume imaging using fMRI in experimental choroidal melanoma.
- To assess the impact of hyperthermia treatment on tumor blood volume.
- To evaluate a novel gadolinium-based contrast agent (MS 325) for this application.
Main Methods:
- An animal model of experimental choroidal melanoma in albino rabbits was utilized.
- MRI was performed before and after intravenous injection of MS 325 contrast agent.
- 3D-spoiled gradient echo pulse sequences acquired T' weighted axial images for signal intensity analysis.
Main Results:
- Untreated tumors showed significantly higher relative signal intensity after MS 325 injection compared to baseline.
- Hyperthermia-treated tumors exhibited no significant change in relative signal intensity post-contrast, correlating with histopathological findings of vascular occlusion.
- Other ocular tissues demonstrated significant signal intensity increases with MS 325, validating its use in this model.
Conclusions:
- Quantitative blood volume measurement with MS 325 is feasible in experimental choroidal melanoma.
- Reduced blood volume changes post-treatment indicate vascular compromise in hyperthermia-treated melanomas.
- Further research is needed to determine if this fMRI technique can assess tumor viability after treatment.
