You need a means of blowing loose dust off the sensors surface I use  compressed CO2 gas and to remove any stubborn particles a lens pen.  Do not use cans of compressed air such as Dust-Off, as they contain liquid propellants that can gunk-up the sensor. Also some of the compressed gas and air blowers are very strong and can blow dirt particles into deep recesses of the camera where they can cause other problems. Also, be very careful of the point of the blower. Don't let it ever touch the sensor plate surface.

A company called American Recorder makes a blower that uses compressed CO2 that is safe to use. Their replacement cylinders of gas do not contain any propellant, and the blower has a long plastic wand. Do not use CO2 cartridges intended for use with air guns, for example, as these contain a lubricant that can gunk up your sensor plate.