Multiply your image by 1000 before passing in to imagesc. A side effect though is that the pixel values reported by mousing around over the image will also be 1000 times as big (rather than the original values) if you called impixelinfo, but maybe that will be OK. I prefer imshow to imagesc since it doesn't apply some (probably undesired) colormap by default.
scaledImage = originalImage * 1000;
imshow(scaledImage, []);
colormap('turbo');
colorbar;
impixelinfo
