Maximum intensity projection
The maximum intensity projection (MIP, Eng. Maximum intensity projection ) is a method from image processing, which is primarily used in medical diagnostics. The maximum intensity projection anticipates three-dimensional image data sets into two-dimensional projection images by each data point with the maximum intensity is selected along the viewing direction ( direction of projection). An important application of maximum intensity projections is the representation of CT angiography and magnetic resonance angiography data; in these data have the blood vessels generally have high signal intensities and are therefore mapped easily visible by the maximum intensity projection. Other applications include the display of nuclear medicine PET or SPECT data.
Maximum intensity projections are often used to represent three-dimensional data sets as in the picture alongside examples as rotating animation. For this, the MIPs are calculated from many different angles and displayed in sequence.
Frequently results from the maximum intensity projection of a semi-transparent image impression as in the picture alongside examples. The lack of perspective is not to distinguish whether structures front ( close to the viewer ) are, or behind the object. As a result, arise from animated MIPs the impression that changes the direction of rotation.
Principle of operation
The principle of maximum intensity projection is easiest to illustrate in a two-dimensional example, are to be calculated from the one-dimensional projections. As an example data set used here is a 3 × 3 matrix; first the maximum intensity projection is calculated in the horizontal direction of projection:
For each row of the matrix of the maximum value ( marked in red), taken separately. The maximum intensity projection thus differs from an ordinary projection imaging, such as those occurring in conventional X-ray, is that the maximum instead of the average value of all values is formed in the projection direction.
Similarly, the calculation of the maximum intensity projection in the vertical direction:
By interpolation of the data, the calculation in any other projection directions.
Designation
Instead of the term maximum intensity projection of the English term maximum intensity projection is used in untranslated German texts frequently. Occasionally one also finds the term maximum intensity projection.
Variants
Often not the projection is calculated by the entire 3D data set, but only by a disk-shaped volume ( sub-volume ), which can for example consist of a certain number of successive layers. This sub-volume maximum intensity projection is also known as thin - slab MIP or shorter than ThinMIP because it consists of a thin disk ( engl. thin slab ) and is not calculated from the ( thicker ) overall record. To represent the entire data set in this manner, the total volume in a number of (parallel ) sub-volumes can be divided, in each of which a sub-volume MIP is calculated; this technique is referred to as a sub-volume sliding MIP ( Sheet sliding Thin Slab MIP).
The minimum intensity projection ( MinIP, Eng. Minimum intensity projection ), the respective minimum intensities are selected in the viewing direction instead of the maximum intensities. This method is used for example for the representation of such an MR angiographic data in which the vessels instead appear due to the technique used dark bright as in suszeptibilitätsgewichteten recordings of the cerebral veins (MR venography ). The minimum intensity projection is almost always calculated as a sub-volume - MinIP.
In computed tomography, the minimum intensity projection is used for the representation of the lungs and in particular the low signal bronchi.