The Multi Slice Ct is special because multiple detectors are placed next to each other so the Ct can collect multiple slice data at the same time (single scan) .

The Multi slice can work sequental and spiral mode also.
In the simpliest Multi slice Ct there are 2 rows of detectors. In these, the radiographer/ assistant can set the slice thickness with the help of the collimator just as the conventional Ct.
In the four or multi slice Ct there are special detector system, which differ with the different manufacturer.
The GE uses matrixdetector at their 4 and 8 slices Ct, which consists of detectors of the same size.
The Siemens and the Philips uses the so called "adaptive array" arrangement, in which in the middle of the examining area there are narrower and at the sides there are wider detectors.
The adjustment of the slice thickness is with the electrical interlock of the different detectors.
An important thing is that, usually the number of measurable slices is differ from the number of detectors.

Earlier each manufacturer had their own definition of "pitch" but now the standard definition is the following:
a pitch is the quotient of the speed of the table and one slice collimation.

With extending the number of detectors a new problem come up: the cone beam artifact.
The beams are not parallel which reach the different detector rows, instead they have a cone format.
The appearance of the artifact will be more pronounced with the number of parallel detectors, the FOV( field of view) and the pitch.
The manufacturers' created different techniques such as the back projection with which the number of artifacts can be reduced.