How much electricity does a 4-slice CT scanner use per month?

With the little information given, it is next to impossible to determine the monthly cost of using any appliance. There are too many variables. For starters, you must know the electrical load in wattage. This is not just nameplate data. The nameplate data is usually the "maximum load" when the machine is doing what it does - in this instance taking a CT image. How many minutes a month is the machine taking CT images? Can anyone really know this in advance? There is also "standby load" when the machine is turned on but at idle. You will not usually find this info on a nameplate. Lastly, you need to know the local electric rates.