Visualization of myocardial infarction six hours after injection of 111 In-antimyosin antibodies using an image subtraction technique.

111 In-antimyosin antibodies are capable of visualizing acute myocardial infarction (MI). Because of slow blood clearance, images are usually recorded 24 or 48 h postinjection. This pilot study was aimed at validating a blood pool subtraction technique, which makes it possible to visualize MI 6 h postinjection. Twenty-five patients with proven MI (16 anterior, 9 inferior) were imaged 10 minutes, 6 and 24 h after an injection of 110 MBq 111 In-labelled antimyosin antibodies, with a mean delay of two weeks after infarction. Three planar views were obtained each time. Using software which performs geometric registration, grey level normalization and subtraction of images, the blood pool image (obtained 10 minutes postinjection) was subtracted from the 6 hour image. The resulting image was the blood pool corrected 6 h image. The 24 h images and the blood pool corrected 6 h images were interpreted blindly and the number of correct, incorrect and indeterminate MI localizations were tabulated. The number of correct localizations was 19/25 for the standard 24 h images and 22/25 for the blood pool corrected 6 h images. With this blood pool subtraction method it was possible to visualize MI 6 h postinjection. Theoretically, this method could be applied six hours after myocardial infarction.