Anatomical Imaging of the Head and Neck Flashcards
How is an x-ray produced?
Produced by sudden deceleration of electrons hitting the anode
What are the indications for using an x-ray?
Trauma (fractures), degenerative diseases (RA), and post-operative
What are the types of xrays?
PA, AP, lateral
How is a fluoroscopy/angiography produced?
Continuous x-ray radiation passes through the body onto a fluorescent screen creating a moving x-ray image
What are the indications for using a fluoroscopy?
Swallow study, interventional radiology, arthography, and cardiac catheterization
What is injected into the vasculature for contrast in a angiography?
Barium or iodine
What are the indications for angiography?
Aneurysm, vascular malformations, fistulae, stenosis, thrombosis, dissection, stenting, and thrombolysis
What are the pros and cons of angiography?
Pros: fast, diagnostic, and therapeutic
Cons: invasive, contrast, radiation
How is a myelography produced?
Uses fluoroscopy with an intrathecal injection of contrast
What are the indications for a myelography?
Spinal stenosis, nerve root compression, and CSF leak
What are the pros and cons of myelography?
Pros: defines subarachnoid space and identifies spinal block
Cons: invasive, CSF leak, headache, radiation, and contrast
How is a computed tomography produced?
Series of x-rays scanned axially; x-rays are digitally resliced in any plane; scans are read as if looking at the patient from the feet
How is the radiodensity measured on a CT?
Measured in Hounsfield Units (HU); all densities are compared to water; water is 0 HU; hyperdense is white, hypodense is black
What are CT scans used for?
Skull, skull base, vertebrae, ventricles, intracranial masses, mass effect, hemorrhage, ischemia, and calcification
What are the indications for a CT scan?
Trauma, bone lesions, hydrocephalus, masses, mass effect, nausea, vomitting, headache, visual symptoms, stroke, mental status change, focal neurological defects, and lesion characterization
What are the pros and cons of a CT scan?
Pros: fast, relatively inexpensive, and good at detecting large pathologies
Cons: less detail than MRI, radiation exposure, and low sensitivity in posterior fossa
When is contrast on a CT indicated?
Neoplasm, infection, vascular disease, inflammatory disease, more than 3 hours after onset of symptoms
When is contrast on a CT contraindicated?
Trauma, hemorrhage, hydrocephalus, dementia, epilepsy, and within 3 hours of symptoms
What structures will enhance in the brain with IV contrast?
Cerebral blood vessels, meninges, pineal gland, pituitary gland, and choroid plexus
How is a CT angiography produced?
Rapid IV contrast bolus; scanned during arterial phase; digitally reconstructed into 2D and 3D images
What are the uses of CT angiography?
Atherosclerosis, dissection, aneurysm, and trauma
What are the pros and cons of CT angiography?
Pros: non-invasive, examine vessels from origin
Cons: contrast, radiation, lower resolution
How is an MRI produced?
Patient lies in large magnet which aligns all the protons in the body; radiowaves are then passed through the patient and the returning signals are converted into an image
What are the different radiodensities of an MRI?
Hyperintense - white
Hypointense - black
What are the uses of an MRI?
Further evaluation of CT findings, tumors, infection, and joint imaging
What are the pros and cons of an MRI?
Pros: high level of detail, safe to use in pregnancy, and vessel imaging can be obtained without the use of contrast
Cons: time consuming, contraindications (metal/implantable diseases), expensive, and claustrophobia
What is a T1 weighted MRI?
CSF is dark (hypointense), white matter is bright (hyperintense); good for imaging normal anatomy
What is a T2 weighted MRI?
CSF is bright (hyperintense), white matter is dark (hypointense); good for visualizing pathology
What is a T2 flair MRI?
Removes CSF from T2; enhances fluid with high protein content (edemal/abscesses)
FLAIR = Fluid Attenuated Inversion Recovery
How is an ultrasound produced?
Transducer emits ultrasound waves into the body; transducer then functions as a receiver that records the energy
What are the uses of ultrasound?
Evaluation of carotid arteries and placement of central lines
What are the pros and cons of an ultrasound?
Pros: non-invasive, cheap, no radiation
Cons: learning curve
