neuroradiology Flashcards
Computed tomography (CT)
Circular gantry (donut), Xray (ionizing radiation), Axial scan (Coronal and sagittal reformats), Iodinated contrast, fast available but expensive
Axial- around the axis of the body- cuts top and bottom
Coronal- Like a crown (cuts front and back)
Viewing axial images
pt lies on their back, you pretend youre standingg at the foot end of the table
youre looking up at the undersurface of the anatomic slice in question
MRI (magnetic resonance imaging)
cylindrical magnet, strong magnetic field, radio waves, multi planar images
Gadolinium contrast
Slower (pt has to sit very still) less available, really expensive
Safety issues with metal compatibility with sick pts,
Can take axial, coronal and sagittal and oblique slices
Image types in CT and MRI
CT- scan once maybe twice with IV contrast, View images using different windows (brightness and contrast settings), brain bone soft tissue and lungs
MRI- Scan several times (3 to 8), multiple planes, different pulse sequences- TI-weighted, FLAIR, view each image set with only one window
Comparative strengths
CT- good for bone (cortex), acute hemorrhage, trauma, fast, safe with metal
MRI- soft tissues (including bone marrow), better appreciation of contrast enhancement, Much more sensitive for subtle lesions (BRAIN AND SPINE), acute infarcts (DWI)
How different substances look on CT and MRI
CT (from really bright to very dark): Bone (white), Brain (gray matter is lightler and white matter is darker more fat), CSF, Fat, AIR
MRI T1 W1(from really dark to light): Fat (is really white, then brain– White then gray), CSF then air and corrtical bone
MRI T2 W2 ( CSF–> Fat–> Brain gray–> White –> Air and cortical bone)
Contrast in CTA vs MRA
CTA- Images obtained in the arterial phase after IV injection of iodinated Contrast
Contrast is required
MRA: time of flight technique is used to creat flow related enhancement of the unmagnetized incoming blood in a saturated volume of tissue, contrast usually not required
Functional neuroimaging
Functional MRI (fMRI)- technique that localizes functional cortex Diffusion Tensor Imaging (DTI)- Technique that enables the visualization of individual White matter tracts Blood- oxygen-level dependent (BOLD) contrast: hemodynamic response, T2* EPI, signal from varying concentrations of oxy and deoxyhemoglobin
Language, motor and vision paradigms
Useful in presurgical brain mapping to avoid injury to functional networks
Neuroradiology divisions
3 main anatomical divisions (Brain, spine, head and neck)
2 main imaging modalities (Computed tomography CT), Magnetic resonance imaging MRI
Intracranial hemorrhages
Subdural- Usually crescentic, not limited by sutures, does not cross midline, tearing of bridging veins
Epidural- lentiform (, limited by sutures, mostly associated with overlying skull fracture, arterial hemorrhage
Subarachnoid- takes the shape of the sulcal/CSF spaces, it will be blood within the sulci, Traumatic or aneurysmal rupture
Intraparenchymal- no definite shape but can be rounded or oval, within parenchyma, traumatic, hypertensive tumor
Acute intracranial hemorrhage
Acute hemorrhage on CT is hyperdense (bright) while chronic hemorrhage is hypodense (dark) on CT
Locations include subarachnoid, subdural, epidural, parenchymal, and intraventricular
Knowing the location of the hemorrhage can help you work through a differential diagnosis
2 most common causes of subarachnoid hemorrhage are trama and ruptured aneurysm
To look for an aneurysm on CTA, contrast is needed, no contrast necessary for MRA
Sinus infection can spread intracraniallu
better evaluated on MRI- rim enhancing lesion with surrounding edema, restricted diffusion
Could be due to systemic or regional source- check regional sites- sinuses and mastoids
Multiple sclerosis
Unknown etiology- autoimmune, infection,
activated T cells attack myelinated axons
Affects young women
Perivenular demyelination- characteristic periventricular plaques- Dawsons fingers
MRI is the best imaging modality
T2W/FLAI hypertensive (bright) lesions in white matter
Acute lesions will show enhancement
Spine trauma
CT is the initial screening exam for trauma patients not cleard clinically
Sensitivity for cervical spine injury is increased with plain films
MR is used to evaluate for soft tissue abnormalities such as disc, ligament, nerve, or cord injuries
