The Very Basics of X-Ray Images Flashcards
What are radiographs?
Images created by passing x-ray beam through part of patient
Record images on film/digital detector
Image formed based on amount of x-rays penetrating each part of body
What other modalities use x-rays?
Fluoroscopy
Angiography
CT
What other modalities don’t use x-rays?
Ultrasound
Nuclear medicine radi-isotope imaging
MRI
What does x-ray production require?
Creation of free electrons
Acceleration across large voltage potential
Rapid deceleration by suitable target, like tungsten
What does absorption of x-ray beams in tissues depend on?
Thickness of tissue
Density of tissue
Atomic number of tissue (to 4th power)
List the different tissue types in order of increasing x-ray absorption
Air
Fat
Soft tissues, muscle, solid organs, fluids
Bone
How do we improve on the natural differences in x-ray absorption?
Alter absorption
- Introduce radiographic contrast medium
Measure absorption by more sensitive method
What are positive contrast agents?
Increase x-ray absorption
Most commonly used
What are negative contrast agents?
Decrease x-ray absorption; eg:
- Air
- Carbon dioxide
How is contrast media injected in endoscopic retrograde cholangiopancreatography?
Endoscope passed through stomach > ampulla in duodenum cannulated > contrast injected into bile and pancreatic duct
What are intravascular contrast agents made of?
Organic salts containing iodine
What happens to intravascular contrast agent when it enters the body?
Some becomes extravascular
Excreted by kidneys
Why are angiographies performed?
To see blood vessels
How are angiographies performed?
Narrow catheter inserted into artery/vein of interest > contrast injected quickly > rapid series of images taken
