The Ct scan uses x-rays and can always be used when needed because the benefits of CT scan are more than the health hazards. It can harm you as much as chest x-ray. It does not cause cancer. It can damage the cells which is even good for cancer patient.
Anything which damages the cells can cause cancer. X-rays are ionizing radiation which can of themselves cause cancer. Some studies place the incidence of cancer in the US due to CT scans high, as much as 5%. Discuss the benefits and disadvantages with your doctor.