The Multi Slice Ct is special because the detectors are in more row next to each other so the Ct can collect data from more slice at the same time.

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 producer.
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 the different producers 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 artefact.
The beams are not parellel which reach the different detector rows, instead they have a cone format.
The appear of the artefact rises as we extend the detectors, the FOV( field of view) and the pitch.
The producers created different techniques such as the back projection with wich the number of artefacts decreased.