MRI

Radiology · 804 cards · 172 labeled figures

Differentiating T1 from T2

T1: normal: denser gray matter cortex darker than white matter subcortex[…]
T2: weird: less dense white matter subcortex darker than denser gray matter cortex[…]

FLAIR Sequence Below. Is it T1 or T2 - how do you know?
T2: weird, white matter subcortex darker than denser gray matter cortex[…]

T1 Sequences

Regular T1
Contrast+[…]
C+ Fat Sat[…]: fat[…] suppressed to rid artifact and better show C+[…] areas

this is done for ex with pts w/IC mass[…] lesions in skull base where extracranial extension is possible (such as skull base meningiomas[…] or CPA angle tumors[…])

T2 Weighted Sequences

T2 Fat Sat[…]

Orbits[…]: often to look at the EOM[…]
rule out of CSF leak[…]

FLAIR[…]
T2* SWI[…] or GRE[…]

these look for areas of paramagnetic[…] void

DWI[…]
ADC[…]

Ventricular System Anatomy Review

green: anterior horn, lateral ventricle[…]
red: body, lateral ventricle[…]
blue: atrium/trigone, lateral ventricle[…]
purple: occipital horn, lateral ventricle[…]
yellow: temporal horn, lateral ventricle[…]

Ventricular System Anatomy Review

green: interventricular foramen[…] aka foramen of Monroe[…]
red: 3rd ventricle[…]
blue: cerebral aqueduct of Sylvius[…]
pink: 4th ventricle[…]
yellow: lateral apertures[…] aka foramen of Luschka[…]
dark purple: median aperture[…] aka foramen of Magendie[…]

Ventricular System Anatomy Review

red: septum pellucidum[…]
green: corpus callosum[…]

Ventricular System Anatomy Review

red: caudate[…] nucleus runs here

Ventricular System Anatomy Review

red hole present in some people in 3rd ventricle: where the thalami[…] touch called an interthalamic adhesion[…]
orange: pineal gland[…]
circle: midbrain[…] with yellow mamillary bodies[…]
green: infundibular recess[…]
light blue: pituitary gland[…]
medium blue: optic chiasm[…]
dark blue: optic recess[…]
pink: lamina terminalis[…]
red circle: pons[…]
orange circle: cerebellum[…]

Ventricular System Anatomy Review (Top to Bottom) (1)

T1[T1 or T2?], Axial[cut] scan
These are the lateral ventricles[…]

Ventricular System Anatomy Review (Top to Bottom) (2)

These are the lateral ventricles[…] separated by thin membrane called septum pellucidum[…]

Ventricular System Anatomy Review (Top to Bottom) (3-4)

These are the anterior horns, lateral ventricles[…] (green) with caudate nucleus[…] (red) to the side and genu, corpus callosum[…] (orange) and splenium of corpus callosum[…] (yellow)
they connect via the interventricular foramen / foramen of monroe[…] (light blue) into the 3rd ventricle[…] (purple)

Ventricular System Anatomy Review (Top to Bottom) (5-9)

these are various cross sections of the occipital horn, lateral ventricles[…] descending until you reach the temporal[…] lobe where they turn into the temporal horns, lateral ventricles[…]

Ventricular System Anatomy Review (Top to Bottom) (10-13)

this is the third ventricle (red) flanked on either side by the thalami (orange) that descends (yellow) and narrows into the cerebral aqueduct[…] (green) at the level of midbrain[…]
this descends further until it turns into the 4th ventricle[…] (light blue) at the level of pons[…]

Ventricular System Anatomy Review (Top to Bottom) (14-16)

these are the lateral apertures[…] (red) aka the foramen of Luschka[…] (red) at the level of pons[…]
descend further and you see the median aperture[…] (orange) aka the foramen of Magendie[…] (orange) which is continuous if you go down a smidge lower with the spinal cord central canal[…] (yellow)

Ventricular System Anatomy Review (L to R) (1-2)

this is the temporal horn, lateral ventricle[…] (red, most lateral) which gives off the occipital horn, lateral ventricle[…] (orange) as you move medial

Ventricular System Anatomy Review (L to R) (3)

this is the trigone/atra, lateral ventricle[…] (red)

Ventricular System Anatomy Review (L to R) (4)

this is the body, lateral ventricle[…] (red) and anterior horn, lateral ventricle[…] (orange) with its laterally running caudate nucleus[…] (green)

Ventricular System Anatomy Review (L to R) (7)

this is the interventricular foramen / foramen of monroe[…] (red) connecting the lateral ventricle[…] (orange) to the 3rd ventricle[…] (green)

Ventricular System Anatomy Review (L to R) (7)

3rd ventricle[…] (red)
lateral ventricle[…] (orange)
fornix[…] (yellow)
lamina terminalis[…] (green)
optic chiasm[…] (light blue)
mamillary bodies[…] (intermediate blue)
pineal gland[…] (dark blue)
infundibular recess[…] (purple) coming down toward the pituitary gland[…] (pink) sitting in the sella turcica[…] (pink)

anterior to that is sphenoid sinus[…] (dark pink/red)

Ventricular System Anatomy Review (L to R) (8)

orange: 3rd ventricle[…]
red arrow: cerebral aqueduct of Sylvius[…]
yellow: 4th ventricle[…]
green: median aperture (foramen of Magendie)[…]

Ventricular System Anatomy Review (L to R) (9)

Choroid Plexus[…] Course

red: starts in temporal horn, lateral ventricle[…]
orange: runs along the roof[…] of this structure all the way around
yellow: runs along the floor[…] of the lateral ventricle (body)[…]
green: runs into the 3rd ventricle[…] and runs along the roof[…] of it
note 1: there's no choroid plexus in the anterior horns[…] or occipital horns[…] of the lateral ventricles
purple - note 2: there's also choroid plexus on the floor[…] of the 4th ventricle[…]

Ventricular System Anatomy Review (L to R) (10)

Choroid Plexus Arterial Supply

The anterior part of the choroid plexus and ventricles are supplied by the Anterior Choroidal (AChA)[…] Artery which branches off the Communicating ICA (C7 segment)[vessel, segment?]
The posterior part of the choroid plexus and ventricles are supplied by the

(1) Posterior Choroidal[…] Artery which typically branches off the PCA (P2 Segment)[vessel, segment?]
(2) Choroid[…] branch of the PICA[…] which itself branches off the Vert[…]

Subarachnoid Cisterns Anatomy Review (Sagittal)

the cisterns are areas where the pia mater[…] is pressed against the brain surface but the arachnoid mater[…] is stretched out and allowing for some space away from the brain surface, generally in the folds[…] of the brain - they generally hold CSF[…] where flow is continuous
red (line structure) is the lamina terminalis[…]
orange cistern: cistern of the lamina terminalis[…]
yellow: optic chiasm[…] (light), infindibular stalk[…] (medium), pituitary gland[…] (dark)
light green: suprasellar[…] aka chiasmatic[…] cistern
dark green: interpeduncular[…] cistern located anterior to the midbrain[…] and between the cerebral peduncles[…]
light blue: quadrigeminal[…] cistern posterior to the midbrain tectum[…]
medium blue dotted line (seen on axial but imagined here): ambient[…] cisterns wrapping around the midbrain[…] to connect the interpeduncular[…] cistern anteriorly > to the quadrigeminal[…] cistern posteriorly
dark blue: superior cerebellar[…] cistern
light purple: prepontine[…] cistern
dark purple: cerebellopontine angle (CPA)[…] cistern connecting the pons[…] lateral surface > to the cerebellum[…] anterior surface -- into which the lateral apertures (foramen of Luschka)[…] of the 4th ventricle[…] flow into
light pink: premedullary[…] cistern
medium pink: cerebellomedullary[…] cistern
dark pink/red: the largest cistern at the base of the brain coming through the foramen magnum[structure] which is the cisterna magna[…] - this is often obliterated in situations of high or low ICP[…] with low-lying cerebellar tonsils

Subarachnoid Cisterns Anatomy Review (Axial)

red: mamillary bodies[…]

Subarachnoid Cisterns Anatomy Review (Axial)

light yellow: optic chiasm[…]

Subarachnoid Cisterns Anatomy Review (Axial)

dark yellow: pituitary stalk[…]
light green: supracellar[…] aka chiasmatic[…] cistern

Subarachnoid Cisterns Anatomy Review (Sagittal)

dark yellow: pituitary stalk[…]
light green: supracellar[…] cistern

Subarachnoid Cisterns Anatomy Review (Axial)

dark yellow: pituitary gland[…]

Subarachnoid Cisterns Anatomy Review (Axial)

dark green: interpeduncular[…] cistern
medium blue: ambient[…] cisterns (only one side pictured) >

connecting into the light blue: quadrigeminal[…] cistern posterior to the superior[…] colliculi at this level of the midbrain tectum[structure]

white: cerebral peduncles[…]

Subarachnoid Cisterns Anatomy Review (Axial)

light blue: quadrigeminal[…] cistern posterior to the inferior[…] colliculi at this level of the midbrain tectum[structure]
dark blue: superior cerebellar[…] cistern

Subarachnoid Cisterns Anatomy Review (Axial)

light blue: quadrigeminal[…] cistern
dark blue: superior cerebellar[…] cistern

Subarachnoid Cisterns Anatomy Review (Axial)

light purple: prepontine[…] cistern
dark purple: cerebellopontine[…] cisterns through which the trigeminal[…] nerve runs (white arrows)

Subarachnoid Cisterns Anatomy Review (Axial)

light pink: premedullary[…] cistern
medium pink: cerebellomedullary[…] cisterns

Subarachnoid Cisterns Anatomy Review (Axial)

dark pink: cisterna magna[…]

Standard MRIb wo order typically includes the following sequences (6):
T1, T2, FLAIR, DWI, ADC, GRE[…]

Edema Pathophysiology and Imaging

normal neurovascular unit aka "BBB[…]": comprised of astrocyte[…] foot processes wrapped around capillary endothelial[…] cells connected by tight[…] junctions with parenchymal neurons[…] located inside and outsode of the capillary endothelial cells; all with capillary lumen[…] carrying RBCs[…] within
Cytotoxic[…] Edema:

ischemia[…] to astrocytes / capillary endothelial cells / parenchymal neurons > these cells can't maintain their Na-K[…] gradients > toxic to cells but the BBB[…] remains intact
you can better see this if you subtract out CSF[…] bright signal - this is aka the T2 FLAIR[…] sequence

Vasogenic[…] Edema: often seen with tumors[…], abscesses[…], PRES[…]/HTNsive emergency, and more

tight junctions[…] become leaky > plasma[…] escapes into the interstitial[…] space while preserving the gray-white[…] junction

Stroke Imaging Sequences

It takes several hours[…] for T2-FLAIR[…] to reveal hyperintensity signal change (>6-8)
It takes <30mins[…] for DWI/ADC[…] to reveal hyper/hypointense signal change

DWI[…] is closely related to T2-FLAIR[…]; both will be bright

Pathophysiology for why we see ovoid lesions in Dawson's Fingers in MS?
immune cells move through & exit central veins moving perpendicular to lateral ventricles[…]

Describe the evolution of a bleed on MRI over time

Acute[…] (1[…]-3[…] days)

iso[…]intense on T1[…]
hypo[…]intense on T2[…]
contains deoxyHgb[…]

Subacute[…] (3[…]-14[…] days)

hyper[…]intense on T1[…]
hyper[…]intense on T2[…]
contains MetHgb[…]

Chronic[…] (>14[…] days)

hypo[…]intense on T1[…] as the site of hemorrhage is replaced by CSF[…]-filled slit-like hole as if the brain were "stabbed[…]"
hyper[…]intense on T2[…] (think of it like a "fingerprint[…]" left by a chronic hemorrhage
contains Hemosiderin[…]

What's the stage of this hematoma?

late subacute: both T1 T2 bright[…]

Rapid Review

"eye of the tiger[…]" sign
c/f PKAN (Pantothenate Kinase-Associated Neurodegeneration)[…] aka Hallervorden Spatz[…] Syndrome

Pantothenate = Vitamin B5

Stage this bleed time-course

acute[…] (1-3[…] days) hemorrhage containing deoxyHgb[what substance?]

On T1[T1 or T2?] imaging, chronic[acute or chronic] MS lesions appear as hypointensities ("black holes")[…]

Common Patterns of Enhancement - Ring

if confused between say brain abscess and GBM / other ring enhancing lesions, use DWI/ADC[sequences?] to differentiate

Common Patterns of Enhancement

dural: meningioma[…] & schwannoma[…]
leptomeningeal: meningitis[…] & LMM[…]
subcortical nodular: mets[…] & acute MS ovoid lesions[…]
ring enhancing: abscess[…], toxo[…], PCNSL[…]
paraventricular: PCNSL[…]
mural nodule: pilocytic astrocytoma[…]

MRI Brain Anatomy

red: midbrain[…]
orange: pons[…]
yellow: medulla[…]
green: cerebellum[…]
light blue: posterior fossa[…]
medium blue: cerebrum[…] + cerebellum[…]

MRI Brain Anatomy

red deep gray matter: head of caudate[…]
orange white matter: anterior limb, genu, posterior limb of IC[…]
green deep gray matter: lentiform nucleus (Gpi/e + putamen)[…]
light blue: corpus striatum (lentiform nucleus + head of caudate)[…]
yellow: thalamus[…]
medium blue: external capsule[…]

MRI Brain Anatomy
2 ways to ID the central sulcus

look for the sulcus that reaches the midline[…]
look for the omega[…] sign
everything anterior to it is frontal[…] lobe; posterior is parietal[…] lobe

MRI Brain Anatomy

red: central sulcus[…]
orange: precentral gyrus[…] of frontal[…] lobe
yellow: postcentral gyrus[…] of parietal[…] lobe

MRI Brain Anatomy

yellow: superior frontal gyrus[…]
red: superior frontal sulcus[…]
green: middle frontal gyrus[…]
orange: inferior frontal sulcus[…]
light blue: inferior frontal gyrus[…]

MRI Brain Anatomy

red: sylvian fissure[…]

everything above it: frontal[…] (orange) or parietal[…] (yellow) lobe
everything below it: temporal[…] lobe

MRI Brain Anatomy

red: insula[…] covered by

orange: frontal operculum[…]
green: temporal operculum[…]
yellow: parietal operculum[…]

MRI Brain Anatomy

occipital[…] lobes

MRI Brain Anatomy

ID this: occipital horns, lateral ventricle[…]

MRI Brain Anatomy

yellow: corpus callosum[…]
red: pericallosal sulcus[…]
green: cingulate gyrus[…]
orange: cingulate sulcus[…]
light blue: parieto-occipital sulcus[…] separating the parietal[…] lobe from the occipital[…] lobe

MRI Brain Anatomy

middle[…] cerebellar peduncles connecting cerebellum[…] to pons[…]

MRI Brain Anatomy

superior[…] cerebellar peduncles connecting cerebellum[…] to midbrain[…]

MRI Brain Anatomy

inferior[…] cerebellar peduncles (not very visible) connecting cerebellum[…] to medulla[…]

MRI Brain Anatomy - name this structure

insular[…] cortex
we are slightly lateral to midline; we know this because we are cutting the eye[…] through the middle

MRI Brain Anatomy - name this structure

right substantia nigra[midbrain anterior structure] which is split further into the pars compacta/reticularis[structures within that you cannot visualize on axial cut MRI]
the structure slightly posterior to it is the red nucleus[…]
we are at the level midbrain (mickey mouse)[…] and top of cerebellum[…]

MRI Brain Anatomy - name this structure

head of caudate[…] running lateral to the lateral ventricles[…] which encompasses part of the corpus striatum[this structure + lentiform nucleus]
we know we're lateral to midline because we are not seeing the entirety of the lateral ventricle[…] but rather the structure running laterally to it

MRI Brain Anatomy - name this structure

left central sulcus[…]

as we go further up in the brain, this sulcus gets pushed further posterior[…]ly

the midline marginal[…] sulcus creates the "mustache[…]" sign nearby

anterior to this is the postcentral gyrus[…]
anterior to this is the central sulcus[…]
anterior to this is the precentral gyrus[…]

MRI Brain Anatomy - name this structure

this is the left carotid canal[…]
posterior to it immediately is the jugular spine[…]

MRI Brain Anatomy - name this structure

this is the left PCA[…]

MRI Brain Anatomy - name this structure

this is the cerebral aqueduct of Sylvius[…]
at the level of midbrain[…]

can see the SN[…] anteriorly and Red Nucleus[…] posteriorly at this level

posteriorly can see the superior portion of the cerebellum[…]

MRI Brain Anatomy - name this structure

this is the cisterna magna[…], the largest cistern

MRI Brain Anatomy - name this structure

this is the left AICA[…] coming off the Basilar[…]

MRI Brain Anatomy - name this structure

these are the quadrigeminal bodies[…] sitting on the quadrigeminal plate[…] located on the midbrain tectum[…]

includes the superior colliculi[…] and inferior colliculi[…]

MRI Brain Anatomy - name this structure

this is the dentate nucleus[…] of cerebellum

MRI Brain Anatomy - name this structure

this is the body of fornix[…]

this structure runs anteriorly then inferiorly along the column[…] of fornix[…] to the mammillary bodies[…] then up to the ATN[…] of thalamus[…] as part of the papez[…] circuit

we are inferior to corpus callosum[…]

MRI Brain Anatomy - name this structure

this is the R petrous ICA (C2)[vessel, segment]

MRI Brain Anatomy - name this structure

this is the posterior falx cerebri[…] where it invaginates and gives rise to the SSS[…]

MRI Brain Anatomy - name this structure

this DTI image shows the forceps minor (anterior forceps)[…] which are white matter tracts that connect the frontal lobe[…] > genu of CC[…] > contralateral frontal lobe[…] to connect them

MRI Brain Anatomy - name this structure

this is the septum pellucidum[…]

at rest they are 2[…] separate tissue planes with a potential[…] space in between them
sometimes if these planes of tissue are separated physiologically this is called cavum septum pellucidum[…]

MRI Brain Anatomy - name this structure

this is the cingulate gyrus[…] which helps us regulate emotions

MRI Brain Anatomy - name this structure

this is the right cerebellar tonsil[…] located at the level of foramen magnum[…]

in cases of high ICP[…], see how far it pushes down via foramen magnum

MRI Brain Anatomy - name this structure

this is the right trigeminal nerve[…] that extends into Meckel's Cave[…]

MRI Brain Anatomy - name this structure

this is the straight sinus[…] (red) where the inferior sagittal sinus[…] (yellow) connects with the Great Cerebral Vein of Galen[…] (light green)

this then joins with the SSS[…] (dark pink) to form the Confluence of Sinuses[…] which is then drained away by the Transverse Sinuses[…] (light blue) into the Sigmoid Sinuses[…] (dark blue) into the IJV[…] (medium pink)

MRI Brain Anatomy - name this structure

this is the R choroid plexus[…]

MRI Brain Anatomy - name this structure

this is the R temporal horn, lateral ventricle[…]

remember the 3D shape of the ventricle

MRI Brain Anatomy - name this structure

this is an intraosseous arachnoid granulation[…]

these are physiologic variants

MRI Brain Anatomy - name this structure

the 3 cisterns pictured here are

interpeduncular[…] anteriorly
ambient[…] laterally wrapping around the midbrain[…]
quadrigeminal[…] posteriorly

MRI Brain Anatomy - name this structure

this is the right cerebral peduncle[…]

the cistern anteriorly is the interpeduncular[…] cistern

MRI Brain Anatomy

red: body of caudate[…] running posteriorly and laterally to the lateral ventricles[…] > down to the occipital horns where it becomes the tail of caudate nucleus[…]

MRI Brain Anatomy

inferiorly we see that the putamen[…] and the head of caudate[…] start off almost touching
as we rise superiorly, the putamen[…] ends up more separated posteriorly with the IC[…] now splitting the 2 structures

MRI Brain Anatomy

red: putamen[…]
orange: Gpe/i[…]
yellow: anterior limb/genu/posterior limb IC[…]
green: thalamus[…]

MRI Brain Anatomy

red: cerebral peduncles[…] containing the

orange: SN[…]
yellow: red nuclei[…]

light green: ambient cisterns[…]
light blue: mammillary bodies[…] which form the inferior[…] border of the hypothalamus[…]
dark blue: anterior to the mamillary bodies[…] is the optic chiasm[…]