Medical Imaging How can we peer into body without cutting it open?

X-Rays Visualize bony structures Locate abnormally dense structures (tumors, etc.) First medical imaging tool; still accounts for over half of all imaging

Computed Tomography (CT) formally called CAT Refined version of Xray Confines beam to thin slice of body (about size of a dime) CT machine has Xray tube that rotates around body Different tissues absorb radiation in varying amounts Use of CT scanners eliminates exploratory surgery

DSR Dynamic Spatial Reconstruction Ultrafast CT able to produce three dimensional images Heart beating/ blood flow through vessels

Digital Subtraction Angiography (DSA) Another computer assisted Xray technique Unobstructed view of diseased blood vessels Conventional radiographs are taken before and after a contrast medium is injected into artery…then computer subtracts before image from after image, leaving just the blood vessels to view

Positron Emission Tomography (PET) Patient given an injection of short lived radioisotopes that are tagged to biological molecules like glucose As the glucose is picked up by the most active cells, gamma rays are produced and the computer picks up this emission to create a picture of biochemical activity Provides insights into brain activity for people with mental illness, Alzheimer’s and epilepsy.

Ultrasound Imaging or Ultrasonography Advantages: equipment is inexpensive, employs high-frequency sound waves, ultrasound has no harmful effects on living tissues. Works by machine picking up the echoes from ultrasound and constructing an image. Can’t pick up air-filled spaces well, like lungs and space around spinal cord

Magnetic Resonance Imaging (MRI) Uses magnetic fields up to 60,000 times stronger than Earth’s Patient lies in huge chamber with magnet which causes H molecules to spin. Computer picks up the energy released to make a visual image

MRI Benefits of MRI: dense structures like bones don’t show up so don’t obstruct view of soft issue Particularly good at detecting degenerative disease, like multiple sclerosis plaques, brain development and behavior change, and blood vessel obstructions Problem: magnet so strong can “suck” metal objects such as implanted pacemakers & loose tooth fillings through body

Functional MRI Tracks blood flow into the brain in real time

Quick Quiz Which imaging uses short lived radioisotopes tagged to glucose? Which imaging uses high frequency sound waves? Which imaging uses a refined X-ray beam to “see” a thin slice of body? Which imaging uses a strong magnet to create a magnetic field that gets H spinning? Which imaging is the oldest and still accounts for over half of imaging tests?

Answers 1.PET uses short lived isotopes…and makes the pretty pictures 2.Ultrasound uses high frequency sound waves 3.CT (or CAT) is the thin slice of X-ray 4.MRI uses a strong magnet 5.X-ray is the oldest imaging test