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Imaging Highlights Imaging Techniques • Used to visualize and examine internal body structures The three most common: 1.Radiography (x-ray) 2.Computed Tomography (CT) 3.Magnetic resonance imaging (MRI) X-ray • Many imaging techniques use x-ray which is invisible, odorless, and can’t be felt. • Used to radiate cancer- yet overexposure can cause death. • (See x-ray PP Google docs) X-ray • Image of hard-tissue. Internal structures created by the exposure of sensitized film to x-radiation. Resulting film known as an x-ray or radiograph • Radiograph made up of shades of gray • Radiopaque hard tissues, such as bone and tooth enamel, do not permit x-rays to pass through and appear white or light gray on radiograph • Radiolucent air and soft tissues do permit x-rays to pass through, and appear as shades of gray to black on the radiograph Positioning • Describes the body placement and the part of the body closest to the film. • Example: left lateral position, the left side of the body is placed nearest the film • http://www.rtstudents.com/radiologypositions.htm • Hand out PROJECTION • Refers to the path the beam takes through part Anteroposterior projection (AP) • Beam enters the front surface and exits the back surface of the part Posteroanterior projection (PA) • Beam enters the back and exits the front of the part AP projection in supine position PA projection in prone position Lateral Projections • Normally the positioning terminology is used rather than projection – torso and head • Right to left lateral projection • Left to right lateral projection – extremities • Mediolateral projection • Lateromedial projection L lateral erect position R to L lateral projection Oblique Projections • Normally the positioning terminology is used – example RPO position = right anterior to right posterior projection (oblique AP) Radiographpy vs Nuclear Medicine Radiography – source of radiation is external. Gamma rays pass through body and form radiograph Nuclear Medicine – source of radiation is radiopharmaceutical taken internally. X-rays pass out of body and form scan image. Ionization • Ability of x-rays to change substances thru which they pass • Used to make radiographs and treat cancer • May cause cell damage and even death Nuclear Scan • Radioactive isotope tagged to substance absorbed by specific tissue and injected into the blood • Shows gross fx of organ • Good for images of tumors or lesions Common Scans • Bone – fractures, tumors, inflammation, bone growth • Brain – tumors, blood flow • Liver – cirrhosis, hepatitis, tumors, cysts, abscesses • Lung – blood clots, tumors • Thyroid – function, tumors • heart Radioimmunoassay • Mix blood with radioactive substance to determine specific blood protein concentrations • Find antibodies and antigens (titers) Radiation Therapy • Treatment of CA with external radiation • Stereotactic – focusing multiple beams at the same spot Teletherapy vs Bradytherapy Teletherapy – radiation source is external Bradytherapy – radiation source is internal Tomography • Imaging method that produces tomes (cross sections) of body along any plane • Shows structure • Good for images of tumors- especially when contrast medium used Mammography • X-ray examination of the internal breast tissue • Helps in diagnosing breast abnormalities PET Scan • Positron Emission Tomography • Radioactive isotope is tagged to substance used by specific cells and injected into the blood • Best way to show metabolism or specific functional areas, good for determining how well an organ is functioning, especially the brain and heart CAT vs PET • CAT – 2D tomes are reconstructed to show 3D images of structure • PET – radiopharmecuticals are used to give 2D and 3D images of function Magnetic Resonance Imaging • Image produced when body is surrounded by powerful electromagnetic waves • Best way to show structure in minute detail Magnetic Resonance Imaging • Gives good image of soft tissues • Cannot use if metal is implanted in body • Good for images of any type of structural damage Sonogram • sound waves bounced off organs produces image of deep structures • Only imaging procedure safe for fetus • Also used for thyroid, abdominal masses, inner heart structure, blood vessels Contrast Medium • Radio-opaque substance used to make hard-to-see structure show up on image • Used in CAT scans and fluoroscopy Radio-opaque vs Radiolucent Radio-opaque Block x-rays Shows up as light color Radiolucent – Passes x-rays through Shows up as dark color Fluoroscopy Visualization of moving structures as contrast medium moves through body Used with radioopaque substances GI series, arteriograms Cineradiography • Filming images on fluroscope screen with a video camera How to process an imaging request • Check for allergies- if allergic to seafood the pt. might be allergic to iodine found in many radioopaque dyes • Age- below 12 may need extra help or sedation • Weight- older MRI machines limited to max 300lb • Pacemaker- may be damaged by exposure to MRI • Metal items in body- artificial joints or internal fixation devices may contain metal that will heat up or be dislodged by the test Image quality • Target structures must be visualized • Proper view must be shown • Image must be clear ***The imager must make sure the image is of good quality before releasing the patient from the unit**** Unit Preparation • Safety- equipment and safety monitors working properly • Supplies- everything needed on hand Commonly Visualized structures radiographic and fluoroscopic • Chest x-ray (CXR)- heart lungs ribs • Upper GI series- esophagus, stomach, small intestine • Lower GI - colon Patient Safety • Check for previous imaging to prevent repeat exposure • Give instructions and check for understanding • Position correctly to prevent repeat • Use gonadal shielding on children and patients of reproductive age • Ask all women for LMP Worker safety • Reduce exposure time • Stay as far from radiation source as possible and position body at right angle • Use shielding appropriate for the test- lead apron, lead gloves • Wear appropriate radiation detection device (dosimeter on front of body 1. Film badge- least accurate, good for 1 month 2. Thermoluminescent dosimeter- good for 3 months 3. Pocket ionizing chamber- most accurate Workplace safety • Geiger-Muller detector- detects quantity of radiation in the workplace • Victoreen condenser R-meter- used to calibrate radiography equipment Thermogram • Media – infrared camera captures surface body heat • Newer forms relate metabolic activity (function) to heat given off