RADIOLOGY Flashcards
what is an xray
form of electromagnetic energy with a very short wavelength which allows xrays to penetrate matter unlike light rays
How are xrays produced ?
xray tube consits of an evacuated glass tube with cathode and anode terminals; cathode tungsten filament in heated to incandescencce, giving off electron; electrons bombard positively charged anode target and xray are emitted
ionizing radiation
radiation that has enough energy to remove electrons from atoms or molecules; forms of ionization radiation include Xray, gamma rays, alpha particles, beta particles and neutrons
what involves ionizing radiation
xrays, nucleur medicne studis and fluroscopy
radioopaque tissue is
denser, absorbs more xrays and appears as white image on film
radiolucen tissue is
less dense, absorbs less xrays and appears as darker image on film
film cassette
patients cannot hold still long enough to obtain an image from x rays along; cassette contains flourescent screens which glow when activated by xrays and this light is used to expose the film; less radiation and exposure times are needed; the grid cuts down on scatter effect on film-like a lens
The close an object is to the film
the less magnified its image
advantages to digial radioagrphy
less storage space
multiple monitors can look at same image at the same time, difficult to Lose films, transmitted electronically, view generated can be altered by the computer
disadvantages of digital radiography
hospitals arealdy have fully functional film based imaging equipment, new equpment is expensive, may not be as sharp
flouroscopy
common radiological technique allows realtime visulaization; continous beam of xrays; common procedures used for are upper gi and lower gi, and many interventional procedures
types of GI contrast
barium sulfate or iodinated water; not absorbed
barium sulfate
dense, good images, slow to be excreted, not good is body cavity is posibile, must be dilute for CT scan
iodine based water soluble contrast
ok if spilled into cavities, less dense, less details, toxic to lung tissue,
intravenous contrast
imaging of blood vessels or urinary tract use iodinated compounds but they are toxic to kidneys
ultrasound
narrow beam of high frequency sound waves is procued by vibrating crystals; sound waves directed into the body and reflected back dependent upon tissues differing acoustic impedance
anechoic
echo-free due to absence of acoustic interfaces
sonolucent
cyst or fluid filled viscus shows as dark area
echogenic
based on internal echoes due to acoustic interfaces, solid tisues, tumors, fat or fibrous itssue show as LIGHT areas
advantages of ultrasound
no ionixing radiation safe, multiplanar imaging; ability to differentiate cystic, solid and complex tissue, cost effectv, portable and realtime analysis
disadvantages of ultrasound
air and bone produce extreme impendance; most sound is reflected prohibitng sound penetration; images not as clear as CT or MRI, and operator depedent
doppler ultrasound
can be used to calculate velocity of moving blod
computer tomography
cross sectional xray imaging
in computer tomography dense tissues are
white
