Medical imaging systems give health-care providers and researchers the information they need using high-frequency sound waves (ultrasound and echocardiography), magnetic fields (MRI), and electromagnetic radiation (conventional 2-D X-ray, 3-D computed tomography or CT scan, and fluoroscopy). Additional medical imaging techniques include molecular imaging (scintigraphy and PET scanning, for example) and breast thermography. Mobile radiography and MRI equipment is used in heath care, security, and disaster response. Continuing advances in each technique require careful consideration of pros and cons regarding scan time, image format, and clinical and research applications.