X-rays. Electromagnetic Spectrum 10 -1 to 10 nm 400 to 700 nm 10 -4 to 10 -1 nm 10 to 400 nm 700 to...
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Transcript of X-rays. Electromagnetic Spectrum 10 -1 to 10 nm 400 to 700 nm 10 -4 to 10 -1 nm 10 to 400 nm 700 to...
X-rays
Electromagnetic Spectrum
10-1 to 10 nm
400 to 700 nm
10-4 to 10 -1 nm
10 to 400 nm
700 to 104 nm
X-ray radiation was discovered by Roentgen in 1895. X-rays are generated by bombarding electrons on an metallic anode
Emitted X-ray has a characteristic wavelength depending upon which metal is present.e.g. Wavelength of X-rays from Cu-anode = 1.54178 Å
E= hn= h(c/l)
(l Å)= 12.398/E(keV)
NMR 10 um - 10 mm
Definition
• Transmission based technique in which x-rays from a source pass through the patient
• The x-rays are detected by film or an ionization chamber on the other side of the body.
• Image is a simple 2D image of tissues lying between the x-ray source and film.
X-Ray• Noninvasive medical test used to produce images of
the inside of the body to help diagnose medical conditions.
• X-rays are a form of electromagnetic radiation that is sent through the body.
• Structures that are dense, such as bone, will block most of the X-ray particles and appear white.
• Metal and contrast media, a special dye used to highlight areas of the body, will appear white.
• Structures containing air will appear black and muscle, fat, and fluid will appear gray.
X-Ray• Produces two-
dimensional images.• Examines bones, teeth,
lungs, breasts, heart, blood vessels, and the digestive tract.
• Uses ionizing radiation which can increase risk of developing cancer.
©iStockphoto.com
X-Ray – The Procedure
• X-ray is performed by a machine that sends individual X-ray particles, called photons, through the body.– The photons pass
through the body and the resulting images are recorded on a computer or special film.
©iStockphoto.com
Advantages and Disadvantages
Advantages– Quick, painless,
noninvasive test– Relatively inexpensive
Disadvantages– Small amount of
radiation exposure– Contrast materials
sometimes used might produce an allergic reaction
Uses
• Particularly effective in bone– Not good for analyzing tissue– Colors:
• Bone = white• Air = black• Soft Tissue = gray
Types of X-Rays
• Angiography• Upper and Lower Gastrointestinal• Bone Density• Mammography
X-Ray Source• 1st Piece of X-ray
– Also referred to as x-ray tube– This piece accelerates a beam of electrons to
strike the surface of a metal target.– It contains a cathode (creates electrons) and a
anode (deflects electrons)– http://www.crtsite.com/page5-2.html
X-Ray Collimator• 2nd piece of X-ray
– X-ray beam is a divergent beam based on the anode– A collimator reduces the size of the beam
• It restricts the size of the beam for the image
X-ray Principles
• Radiation– Primary Radiation
• X-rays go all the way through the body with no interactions (THIS IS WHAT WE WANT!)
– Secondary Radiation• Electrons in outer shells of tissue atoms• X-rays hit these shells and then scatter
– Photoelectric Effect• X-rays are absorbed by the tissue
• All Radiation ATTENUATION must be accounted for: