Term
| indications for plain x-ray |
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Definition
| useful in demonstrating bone changes: fractures, changes in contour of the skull, bony erosions or hyperostoses, and infection in the paranasal sinuses or mastoids |
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Term
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Definition
30,000 x-rays are collected and measured on electronic sensors and interpreted by a computerized algorithm. X-rays are attenuated by dense structures:
1. bone, acute blood - very white
2. contrast enhanced (tumor) - very white
3. subacute blood - light grey
4. grey matter - light grey
5. white matter - medium grey
6. CSF - dark grey to black
7. Air, fat - black |
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Term
| what is visualized on a CT? |
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Definition
| CTs demonstrate the size and position of ventricles, the position and width of sulci, the location of masses within and around the brain, and clearly show the presence extravasated blood in hematomas and contusions. |
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Term
| Magnetic Resonance Imaging (MRI) |
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Definition
| images are produced by placing the patient in a magnetic field - causes the protons of tissues and CSF to align in the orientation of the magnetic field. A radio frequency pulse causes the protons to change their axis of alignment; when the pulse is removed, they return to their original alignment, reradiating the RF energy absorbed. T1 - relaxation is parallel to magnetic field. T2 - relaxation is perpendicular to magnetic field |
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Term
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Definition
1. bone, air - very black
2. muscle - dark grey
3. white matter - light grey
4. grey matter - dark grey
5. fat - white
6. CSF - very black
7. edema - dark grey
8. enhanced tumor (gadolinium) - white
9. infarct, ischemia - dark grey |
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Term
| dark on T1-weighted image |
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Definition
1. increased water: edema, tumor, infarction, inflammation, infection, hemorrhage
2. low proton density
3. calcification
4. flow void - blood moving quickly in a vessel |
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Term
| bright on T1-weighted image |
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Definition
| fate, subacute hemorrhage, melanin, protein-rich fluid, slowly flowing blood, paramagnetic substances (gadolinium, manganese, copper), laminar necrosis of cerebral infarction |
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Term
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Definition
1. bone, air - very black
2. muscle - dark grey
3. white matter - dark grey
4. grey matter - light grey
5. fat - grey
6. CSF - very white
7. edema - light grey to white
8. enhanced tumor (gadolinium) - not used
9. infarct, ischemia - light grey to white |
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Term
| Dark on T2-weighted image |
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Definition
| low proton density, calcification, fibrous tissue, paramagnetic substances (deoxyhemoglobin, methemoglobin, iron, ferritin, hemosiderin, melanin), protein-rich fluid, flow void |
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Term
| bright on T2-weighted image |
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Definition
increased water: edema, tumor, infarction, inflammation, infection, subdural collection
methemoglobin (extracellular) in subacute hemorrhage |
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