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)
Imaging procedure to detect edema?
CT or MRI
CT - hypodensity
MRI - hyperintensity on T2 or FLAIR; DWI most sensitive for intracelluar edema
What is hydrocephalus?
Increased CSF volume in the ventricles
4 types of hydrocephalus?
Obstructive
Communicating
NPH
Ex-vacuo
CSF is produced in what ventricle(s) by the choroid plexus?
Lateral, 3rd, and 4th
Pathway of CSF?
Travels from lateral ventricles through the interventricular foramina -> third ventricle, through the cerebral aqueduct -> fourth ventricle, through midline foramina of Magendie and paired lateral foramina of Luschka -> subarachnoid spaces -> circulates to bathe the brain and spinal cord -> venous sinuses via arachnoid villi
Characteristics of obstructive hydrocephalus?
CSF flow blockage occurs within the ventricular system -. enlargement of ventricles proximal to the obstruction
Causes of obstructive hydrocephalus?
Congenital or acquired; common cause -> tumors
Characteristics of communicating hydrocephalus?
Impaired CSF reabsorption; clinical features like obstructive, but less pronounced, all ventricles dilated
Dx with MRI
Caused by SAH, meningitis, neoplastic meningitis
Characteristics of hydrocephalus ex-vacuo?
Shrinkage of brain substance -> ventricular dilation (symptoms due to atrophy, not hydrocephalus)
List brain tumors common in the first decade of life.
- Medulloblastoma
- Ependymoma
- Low grade astrocytoma (grade 1 = pilocystic, grade 2)
- Craniopharyngioma
Last brain tumors common in adults.
- Metastasis
- High grade gliomas (high grade astrocytomas = grade 3 and grade 4; grade 4= glioblastoma)
- Lympoma
- Benign tumors -> meningioma, schwanoma, pituitary macroadenoma
2 brain tumors common in intra-axial location?
- Metastasis
2. Astrocytoma
2 brain tumors common in intraventricular location?
- Ependymoma
2. Choroid plexus papilloma
4 brain tumors common in extra-axial locations?
- Anterior cranial fossa -> meningioma
Middle cranial fossa:
2. Pituitary fossa -> craniopharyngioma, pituitary macroadenoma
Posterior cranial fossa;
- Cerebellopontine angle -> schwannoma/meningioma
- Foramen magnum -> meningioma
Brain tumors with fat noted?
Lipoma
Dermoid
Teratoma
Brain tumors with calcium?
Meningioma
Oligodendroglioma
Craniopharyngioma
Brain tumors with cystic features?
Non-tumoral cyst (arachnoid cyst)
Tumors: pilocytic astrocytoma (grade 1 astrocytoma), craniopharyngioma
What imaging is more sensitive to detect calcification within tumors, tumors originating from the skull, and acute hemorrhage within tumors?
CT
Most tumors enhance due to breakdown of BBB. What has no enhancement?
Grade II astrocytoma
Most tumors enhance due to breakdown of BBB. What has mild enhancement?
Grade III astrocytoma
Most tumors enhance due to breakdown of BBB. What has non-homogenous irregular ring ehnahcement?
Grade IV astrocytoma (glioblastoma)
Most tumors enhance due to breakdown of BBB. What has smooth ring enhancement?
Mets
Most tumors enhance due to breakdown of BBB. What has homogenous intense enhancement?
Meningioma
5 common primary brain tumors?
- Glioblastoma
- Medulloblastoma
- Pilocytic astrocytoma
- Ependymoma
- Lymphoma
Irregular solitary mass, often with necrosis and surrounding edema?
Glioblastoma
DDx - ring enhancing lesions
Glioblastoma (irregular)
Mets, abscess (circumscribed)
Tumor originating from the roof of the 4th ventricle, common in younger people, can cause hydrocephalus
Medulloblastoma
Slow growing tumor with solid and cystic component, well-circumscribed, enhances with contrast, common in young people
Pilocystic astrocytoma
Glial tumor arising in the ventricle, may cause obstructive hydrocephlus, may occur within any ventricle, most commonly in 4th, more common in young people
Ependymoma
Common sites of primary lymphoma of the brain?
Corpus callosum
Basal ganglia
Thalamus
Periventricular white matter
Solitary or multiple, spherical lesions located at the gray-white matter junction
Mets
Primary malignant tumors that hematogenously spread to the brain?
Lung Breast Melanoma Thyroid Renal
3 common benign brain tumors?
Meningioma
Pituitary macroadenoma
Craniopharyngioma
Most common intra-cranial benign tumor?
Meningioma
Extra-axial, dural-based, often calcified, located along the dura, falx, and tentorium?
Meningioma
Suprasellar tumor, usually cystic, contains calcium, capsule enhances with contrast
Craniopharyngioma
5 HIV-related infections of the brain?
HIV encephalitis Toxoplasmosis Cryptococcosis TB CMV ependymitis
Ring enhancing mass with a central cavity that involves the brain parenchyma with surrounding edema and mass effect?
Abscess
Causes of bacterial brain abscess?
Staph
Strep
Pneumococcus
Causes of granulomatous brain abscess?
M. tuberculosis
Causes of fungal brain abscess?
Cryptococcosis
Aspergillosis
Mucormycosis
Causes of parasitic brain abscess?
Toxoplasmosis
Cysticercosis
DDx - brain abscess?
Glioblastoma
Mets
(central portion not as bright as abscess)
Imaging findings of meningitis?
Intense enhancement of basal cisterns
Meningeal enhancement (non-specific)
Can be normal
Imaging of choice for MS?
MRI (flair in particular)
Imaging findings in MS?
Asymmetric periventricular and subcortical lesions in the white matter
DDx for white matter lesions?
Microvascular disease (predisposing factors include HTN, DM, HLD, vasculitis)
MS
HIV-related infections (HIV encephalitis, PML)
Radiation-induced leukoencephalopathy
Chemo-induced leukoencephalopathy
Common conditions presenting as back pain?
Vertebral body pathology (mets, fracture, osteoporosis)
Disc disease (herniation)
Spinal cord tumor
Retroperitoneal structure disease (AAA, renal pathology, retroperitoneal LAD)
Imaging for lower backache?
CT or MRI if severe or prolonged pain, focal neuro deficits, history of cancer or febrile illness -> commonly used to identify disc or vertebral body abnormality (MRI is more accurate)
XR - r/o gross fracture, spinal instability
Bone scan - mets
DEXA - BMD
Features of osteoporotic fracture of vertebral body on XR?
Wedge shaped, decreased density
If compression fracture -> biconcave vertebral body due to central end-plate collapse
Common primary malignancies that met to bones?
Breast Lung Renal Thyroid Prostate (most commonly blastic) Lymphoma Multiple myeloma (lytic)
What is a T-score?
of SD the BMD is above or below the young (30 y/o) normal mean
What is a Z-score?
Age-matched
Use of T-score?
Dx osteoporosis:
- 1 to 1 = normal
- 1 to -2.5 = osteopenia
- 2.5 or less = osteoporosis
Use of z-score?
Concern for secondary cause
Imaging findings of osteomyelitis?
Abnormal low signal intensity involving adjacent vertebral bodies and the disc space (T1), hyperintense (T2)
Extradural tumors of the spinal cord?
Metastatic involvement of vertebral bodies
Primary vertebral body tumors (osteoma, osteogenic sarcoma, chondroma, chondrosarcoma, chordoma)
Intradural tumors of the spinal cord?
Intramedullary: ependymoma, astrocytoma, hemangioblastoma, mets
Extramedullary: meningioma, neurofibroma
Alternative procedure to evaluate spinal cord compression if MRI cannot be done?
CT myelography
Features of meningioma (SC)?
Dural-based intradural tumor
Intensely enhances with contrast
May be calcified
Can produce cord compression
Features of schwannoma (SC)?
Intradural nerve sheath tumor that enhances
Dumb-bell shaped tumor
SC meningioma vs. schwannoma?
Schwannoma: follows the exiting nerve root as it exits and enlarges the neural foramina
Meningioma: dural-based, limited to SC, does not follow the nerve root
Obstruction at the aqueduct of sylvius results in?
Dilation of the lateral and third ventricles
Medulloblastoma arises in the floor or roof of the 4th ventricle?
Roof; ependymoma arises in the floor
Tumors that can occur more commonly in the corpus callosum?
Glioblastoma multiforme
Lymphoma
The rim of brain abscess enhances with contrast. The rim thins towards the cortex or ventricle?
Ventricle; it is thick toward the cortex
True or false - in metastatic disease, the intervertebral disc is normal.
True
Tumor located in the center of the spinal cord?
Ependymoma (arise from ependymal lining of central canal)
When the cord expands in both sagittal and axial views, the tumor is ___.
Intramedullary
