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: