WEEK 3: Radio of the Skull, Brain and Spine Flashcards
Energy used to produce the image must be capable of
penetrating tissues. T or F?
T
High frequency sound waves
ultrasound
basically an electrode pair inside a glass
vacuum tube.
Xray machine
Anode or cathode? Electric current passes through the filament, heating it
up
o Heat sputters electrons off the filament surface
cathode
Anode or cathode? o Flat disc mode if tungsten.
o Draws electrons across the tube.
anode
negative part of the xray tube?
Cathode
Radiolucent or radiopaque?
o Transmitted radiation
▪ Passes through the patient and interacts with the
detector to create the image
Radiolucent
absorbed radiation or scattered radiation? Interacts with the tissues of the patient depositing
energy in tissues.
absorbed
what is the density of water?
1
white to black on Xray?
Bone Soft tissue Water Fat Air
T or F? the thicker the object the more radiopaque it is.
T
▪ Passes through the patient, but changes its original
path, leaving the patient along a different course
▪ Can degrade the quality of the image
▪ Can be exposure source to personnel
absorbed radiation or scattered radiation?
scattered radiation
Radiography is usually used for
- Broken bones
- Cavities
- Foreign objects
- Lungs
- Blood vessels (angiography)
- Breasts (mammography)
liquids that absorb x-rays more effectively than surrounding tissue
▪ To bring organs in the digestive tract into focus typically a barium compound will be swallowed or introduced
Contrast media
gadolinium based agents with T1 relaxation time shortening effects
MRI
micro-bubbles which have higher echogenicity compared to human tissue are injected into the patient’s vein.
Ultrasound
A narrow beam of x-ray scans across a patient in synchrony with a radiation detector on the opposite side of the patient.
• Internal structure of an object is reconstructed from multiple projections
CT
uses of angiography
Diagnosis of primary vascular disease
• Pre-operative definition of vascular anatomy
• Diagnosis of vascular complications
A quantity used in CT to express CT numbers in a standardized and convenient form
Hounsfield unit
Created by and named after Sir Godfrey Hounsfield
Radiodensity of distilled water at STP
0 HU
Radiodensity of air at STP
-1000 HU
HU of fat
-200 - -50
Aka grey-level mapping, contrast stretching, histogram modification
Windowing
o Can detect diffuse and focal changes
o Bone window can detect fracture
what CT?
Plain CT