Radiology has been in use since the discovery of X-rays by Wilhelm Conrad Roentgen in 1895. Until 1980s, radiography was the only available tool to the veterinary profession. Imaging technique such as ultrasound, CT (computerized tomography), scanning and MRI (magnetic resonance imaging) and scintigraphy are now-a-days available to the veterinarians for accurate and early diagnosis of various ailments in dogs. This non-invasive method of diagnosis is based on the application of X-rays, gamma rays, ultrasound waves and magnet. Positron emission tomography (PET) detects abnormal metabolic processes such as increased metabolic rate as in cancer cells.