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
When to use MRI?
• Soft tissue details in areas such as the brain, internal pelvic organs, and joints (such as knees & shoulders) can often be better evaluated by MRI.
• In pregnant women, while CT can be performed safely, other imaging exams not involving radiation, such as ultrasound or MRI, are preferred but only if they are likely be as good as CT in diagnosing your condition.
• A person who is very large may not fit into the opening of a conventional CT scanner or may be overweight the limit – usually 450 lbs. – for the moving table (gantry)
Gantry/table won’t move if px is >450 lbs.
o Can detect and characterize focal lesions
o Majority of pathological lesions have a predominantly arterial supply, and thus “enhance”
What CT
Contrast CT
Process in which the image greyscale component of an image is manipulated via CT numbers
• Will change the appearance of the picture to highlight particular structures
• Brightness of the image is adjusted via window level
• Contrast is adjusted via the window width
windowing
CT is more versatile than X-rays and usually used for
o Presence, size and location of tumors o Organs in the pelvis, chest and abdomen o Colon health (CT colonography) o Vascular condition/blood flow o Pulmonary embolism (CT angiography) o Abdominal aortic aneurysms ( CT angiography) o Bone injuries o Cardiac tissue o Traumatic injuries o Cardiovascular disease
- Does not use ionizing radiation
- Images are created using radiofrequency energy emitted by hydrogen protons when strong magnetic fields generated around a patient are manipulated
MRI
Identify if CT or MRI? x-ray beams
CT
Identify if CT or MRI? fast scan time
CT
multiplanar: CT or MRI?
BOTH
superior soft tissue differentiation: CT OR MRI?
MRI
density: CT or MRI?
CT. MRI y intensity
Lower time to relax, lower time to emit ratio. T1 or T2?
T1. T1 has lower TR and TE
Grey matter is both isointense in T1 and T2. T or F?>
t
White matter, because of their fat content (rich in myelin, lipid filled) is bright on T1 and hypointense on T2. T or F?
T
Ventricles which is mainly composed of water is black on T1 and white on T2. T or F?
T. World War 2 mnemonic WW2, water is white on T2
White areas on sulci are CSF which are in the subarachnoid space.
T
why is blood both black on T1 and T2?
Blood are both black on T1 and T2 because of the principle of how you measure, blood flows so when it’s measured the molecule measured is no longer there after few secs.
identify the intensity in T1 and t2: gray matter
isointense on T1 & T2
identify the intensity in T1 and t2: White matter
bright on T1, dark on T2
identify the intensity in T1 and t2: Ventricles/CSF
black on T1, white on T2
identify the intensity in T1 and t2: Blood vessels (flowing blood)
black on T1 & T2.
Gray Matter o Higher blood flow o Isointense on T1 ▪ Darker/brighter than ventricles? o Isointense on T2 ▪ Darker/Brighter than ventricles?
Brighter;
Darker
• CSF
o 99% water
o Black on T1
o White on T2
is this true?
T
Appearance of all cortical bone in all sequences?
DaRK
is fat bright or dark in T1?
bright;
T or F? Brain lesions usually produce edema?
T
Most lesions are dark on T2. T or F?
F. Bright
T or F? We always look on T2 first, if there’s any funny looking on T2 we confirm it on T1
T.
Identify the image characteristics on ultrasound: Air
poor qulaity d/t scatter
Identify the image characteristics on ultrasound: water
anechoic (black)
Identify the image characteristics on ultrasound: blood
Anechoic (black)