Maximum intensity projection (MIP) or MIP imaging, invented by Jerold Wallis, "is a method for 3D data that projects in the visualization plane the voxels with maximum intensity that fall in the way of parallel rays traced from the viewpoint to the plane of projection. This implies that two MIP renderings from opposite viewpoints are symmetrical images if they are rendered using orthographic projection.

"MIP is used for the detection of lung nodules in lung cancer screening programs which use computed tomography scans. MIP enhances the 3D nature of these nodules, making them stand out from pulmonary bronchi and vasculature. MIP imaging is also used routinely by physicians in interpreting Positron Emission Tomography (PET) or Magnetic Resonance Angiography studies

In the setting of Nuclear Medicine, MIP was originally called MAP (Maximum Activity Projection). 

To view SPECT visualized by a MIP of a mouse click on the link below:

https://en.wikipedia.org/wiki/Maximum_intensity_projection#/media/File:Mouse02-spect.gif