Melanin-based agents for image enhancement

Abstract

The present invention involves an image-enhancing agent comprising melanin combined with an essentially non-dissociable signal-inducing metal. The signal-inducing metal has an association constant for its melanin combination of at least about 10.sup.20. Upon suspension or dissolution in water the metal remains undissociated. A preferred signal-inducing metal is paramagnetic or superparamagnetic, of course for magnetic resonance imaging. A preferred paramagnetic or superparamagnetic metals are gadolinium, iron, nickel, copper, erbium, europium, praseodymium, dysprosium, holmium, chromium or manganese. Gadolinium is the most effective metal. The metal is incorporated into the melanin in an ionic or particulate form. Metals may be utilized which are particularly useful to modify ultrasound images by the enhancement of the image obtained from emission and detection of high-frequency soundwaves. Metals emitting gamma particles may also be utilized to enhance images resulting from gamma particle emission scanning. .sup.51 Chromium, .sup.68 gallium, .sup.99m technitium and .sup.111 indium are preferred metals for gamma particle scanning. Additionally, native or synthesized melanin, in and of itself is an effective MRI image-enhancing agent.

Dependencies are inferred from the claim text.