Radiology Flashcards
What can be evaluated with skull x-ray?
Skull bones -> fractures, metastatic lesions, multiple myeloma, Paget’s disease, alteration in the pituitary fossa
Base of skull
Sinuses -> sinus problems
Advantages of CT scan of the brain?
- Imaging modality of choice in patients with a history of trauma and acute neurologic emergencies
- Detects acute blood better than MRI (study of choice if deciding to give fibrinolytic therapy to r/o hemorrhage)
- Fast (can be done in as little as 30 seconds)
- Detailed evaluation of the bone (trauma, malignant vs. benign tumors)
- No risk in patients with implanted medical devices
- Cheaper
- Useful for routine follow-up of hydrocephalus following shunt placement
What is the purpose of IV contrast in CT scan of the brain?
- Visualize vessels = CTA
2. Detect whether the BBB is broken (lesions will enhance if this is the case)
Disadvantages to CT?
- Radiation exposure (not preferred in children or repeated evaluation)
- Iodinated contrast -> allergic reactions
Advantages to MRI of the brain?
- Imaging of choice for any patient with a neurological deficit
- More sensitive for sub-acute to chronic hemorrhage, early stroke and cerebral abscess (DWI), structural etiology for seizures
- Greater range of soft tissue contrast, depicts anatomy in details (superior to CT)
- No radiation
- Gadolinium contrast causes fewer allergic reactions
Disadvantages to MRI?
- Takes longer
- Cannot be used if magnetic implanted devices
- Gadolinium can cause nephrogenic system fibrosis in patients with compromised renal function
Indications to use U/S of the brain?
Children when fontanelles are not closed; neurologic abnormalities like congenital issues, brain tumors, hydrocephalus
Advantages of digital subtraction contrast angiogram?
- Procedure of choice toe valuate extracranial and intracranial vessels
- More precise evaluation of intracranial aneurysm, AV malformation, arterial occlusion, especially when interventional treatment is contemplated
- To diagnose vaculitis
Disadvantages of digital subtraction contrast angiogram?
- Radiation
- Contrast allergy
- Requires an arterial puncture
Advantages of CTA?
Same as digital subtraction contrast angiogram; also procedure of choice to evaluate smaller vessels
Disadvantages of CTA?
Same as CTA except, does not require arterial puncture (injected into veins)
How does MRA differ from CTA and invasive digital subtraction angiogram?
Does not display the lumen of the vessel, but rather the blood flowing through the vessel
Advantages and disadvantages of MRA?
A: does not require contrast, good screening test
D: less sensitive in detecting smaller intracranial vessels compared to CTA
What are plain films of the spine used for?
R/o gross fractures, vertebral pathology, or spina instability
Can detect fractures, displacement, alignment problems, metastatic lesions, osteoporosis, vertebral collapse, vertebral infections
Typical work-up of back pain?
Initial - plain films
CT if bony lesions
MRI if spinal cord, dura, nerve root, or disc lesions
What is used to rule out bone mets to the entire skeleton?
Bone scan
Common indications for brain imaging studies?
Symptoms: headache, N/V, change in mental status (acute or chronic), seizures, head trauma
Signs: focal neuro deficits, signs of increased ICP, signs and symptoms suggestive of acute stroke, SAH, brain tumor, meningitis/abscess, demyelinating disease
Common indications for MRI spine?
Symptoms: back pain, neck pain, weakness of arms/legs
Signs: UE/LE weakness, focal neuro deficits, congenital disorders, demyelinating disease, suspected spinal trauma, infection, cord tumor, cord compression
How does blood appear on plain films, CT, T1, T2, and U/S?
Plain films: white CT: hyperdense (bright) T1: hypointense (dark) T2: N/A U/S: anechoic
How does air appear on plain films, CT, T1, T2, and U/S?
Plain films: dark CT: hypodense/dark T1: dark T2: dark U/S: does not transmit
How does fat appear on plain films, CT, T1, T2, and U/S?
Plain films: dark CT: hypodense/dark T1: hyperintense/bright T2: hyperintense/bright U/S: hyperechoic or does not transmit
How does CSF appear on plain films, CT, T1, T2, and U/S?
Plain films: N/A CT: hypodense/dark T1: hypointense/dark T2: hyperintense/bright U/S: anechoic
How does bone appear on plain films, CT, T1, T2, and U/S?
Plain films: white CT: hyperdense/bright T1: hypointense/dark T2: hypointense/dark U/S: hyperechoic/does not transmit
Imaging procedure of choice with head trauma?
CT
Imaging procedure of choice to evaluate skull lesion?
CT
Imaging procedure of choice to evaluate brain and intracranial contents?
MRI
Imaging procedure of choice for evaluating brain and intracranial contents in a patient with prior aneurysmal clips?
CT
Risk of radiation is relatively high in?
CT
Edema is described as an area of lucency or low attenuation on what?
CT (hypodense)
Emergency evacuation of blood is necessary with…
Epidural hematoma
When does cytotoxic edema occur following a stroke?
Immediately - hence why DWI images can reveal the area of acute infarction quickly
What type of edema is seen in an acute stroke in the area of infarct?
Intracellular; BBB is intact, edema is due to a cytotoxic effect and inadequate functioning of sodium and potassium pump
What type of edema is seen in brain tumors and other lesions?
Extracellular - non-specific, due to loss of BBB; does not enhance with contrast
Optimal imaging to evaluate suspected ICH?
Pre-contrast CT scan -> acute hematoma appears as high density
Findings of epidural hematoma?
Biconvex
Acute blood is hyperdense
Does not cross suture lines
Mass effect due to hemorrhage and edema
Acute vs. subacute vs. chronic subdural hematoma?
Acute: 0-2 days, hyperdense
Sub-acute: 3-14 days, isodense
Chronic: 2+ weeks, hypodense
Most common cause of SAH
Rupture of arterial aneurysms which release blood into the CSF (trauma most commonly)
Common causes of stroke?
- Ischemic (atherosclerotic, emboli, decreased perfusion pressure)
- Hemorrhagic
- Venous sinus thrombosus
- Vasculitis
- Traumatic arterial dissection
Imaging to evaluate stroke?
CT first to r/o hemorrhage
MRI for diagnosis of acute stroke
Does a normal CT r/o stroke?
No
Non-contrast CT findings of acute infarction
Can be normal
Hypodense area
Loss of gray-white matter differentiation
Cortical sulcal effacement
Blurred basal ganglia
Insular ribbon sign (blurred insular cortex due to edema)
Dense MCA sign (hyperdense MCA, hyperdense basilar artery due to thrombus)
Hemorrhage
MRI findings of acute infarction?
DWI: hyperintensity
T2: may be normal within 4-6 hours of acute stroke
Imaging findings of subacute stroke (24 hours to 1 week)?
CT and MRI will show edema, mass effect +/- midline shift
Cortical gyral enhancement
May see hemorrhagic transformation
Imaging findings of subacute to chronic infarct (1 week to 2 months)
Resolution of edema, mass effect, parenchymal enhancement
Imaging findings of chronic old infarct (>2 months)?
Focal well-defined wedge shaped area of low attenuation involving a vascular distribution
Sulci adjacent to an old infarcted area enlarge secondary to parenchymal volume loss
Ventricular enlargement also seen if infarcted area is adjacent to the ventricle
Residual old blood may persist (better on MRI)