title: MRI of blood volume with superparamagnetic iron in choroidal melanoma treated with thermotherapy.
abstract: Functional magnetic resonance imaging (MRI) with a new intravascular contrast agent, monocrystalline iron oxide nanoparticles (MION), was applied to assess the effect of transpupillary thermotherapy in a rabbit model of choroidal melanoma. 3D-spoiled gradient recalled sequences were used for quantitative assessment of blood volume. The MRI-parameters were 5/22/35 degrees (time of repetition (TR)/echo delay (TE)/flip angle (FA)) for T(1)- and 50/61/10 degrees for T(2)-weighted sequences. Images were collected before and at different times after MION injection. In all untreated tissues studied, MION reduced the T(2)-weighted signal intensity within 0.5 h and at 24 h (all p <== 0.012), whereas no significant changes were detected in treated tumors. T(1)-weighted images also revealed differences of MION-related signal changes between treated tumors and other tissues, yet at lower sensitivity and specificity than T(2). The change of T(2)-weighted MRI signal caused by intravascular MION allows early distinction of laser-treated experimental melanomas from untreated tissues. Further study is necessary to determine whether MRI can localize areas of tumor regrowth within tumors treated incompletely.
authors.affiliation: Massachusetts General Hospital-Nuclear Magnetic Resonance (MGH-NMR) Center, Harvard Medical School, Charlestown, MA, USA.
authors.forename: Matthias H J
authors.initials: MH
authors.lastname: Krause
authors.forename: Kenneth K
authors.initials: KK
authors.lastname: Kwong
authors.forename: Evangelos S
authors.initials: ES
authors.lastname: Gragoudas
authors.forename: Lucy H Y
authors.initials: LH
authors.lastname: Young
mesh_terms: D000818:Animals; D001810:Blood Volume; D002830:Choroid Neoplasms / Q000503:physiopathology* / Q000628:therapy*; D003287:Contrast Media; D005260:Female; D052203:Ferrosoferric Oxide; D006979:Hyperthermia, Induced; D007501:Iron; D008279:Magnetic Resonance Imaging; D008546:Melanoma, Experimental / Q000503:physiopathology* / Q000628:therapy*; D023421:Models, Animal; D010087:Oxides; D011817:Rabbits; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media; D010087:Oxides; D007501:Iron; D052203:Ferrosoferric Oxide