X-ray alternative is a term used to describe medical imaging techniques that are used instead of X-rays. Ultrasound (10 letters) is a type of imaging technique that uses sound waves to create an image of the inside of the body. Magnetic Resonance Imaging (MRI, 3 letters) is another type of imaging technique that uses magnetic fields and radio waves to create detailed images of the body. Positron Emission Tomography (PET Scan, 7 letters) is a type of imaging technique that uses radioactive substances to create images of the body's organs and tissues. All three of these imaging techniques are used as alternatives to X-rays in medical imaging.