Recent advances in the design of scintillation cameras have made scintillation cameras suitable for dynamic studies, such as tomographic studies. A scintillation camera, especially a wide field of view scintillation camera, such as would be expected to be used in dynamic studies is typically a very heavy device, on the order of several hundred pounds. Thus, whenever it is necessary to rotate a scintillation detector and its rotable support apparatus, a significant mass must be accelerated resulting in a rather substantial momentum. Traditional modes of braking the rotating apparatus, such as by applying a high frictional force, may result in damage to components of the system and hence are undesirable. Nonetheless, there is a need to safely decelerate the rotating apparatus subsequent to completion of a patient encircling orbit at some point beyond 360.degree. and to do so in a fail-safe manner.