Neuroradiology and Sectional Anatomy
Neuroradiology and Sectional Anatomy
Introduction
Objectives:
1. Understand basic types of brain imaging techniques
2. Understand the benefits of different brain imaging techniques
3. Be able to identify basic brain structures in MR images.
Introduction
Topics covered:
1. Computerized tomography
2. Magnetic resonance imaging (MRI)
3. Functional imaging techniques
4.Angiography
5.Sectional anatomy in MRI images
Computerized Tomography
Computerized tomography (CT):-CT scans measure the density of tissue (hyperdense, hypodense, isodense)
-Like a conventional X-Ray image, but the X-Ray beam is rotated around a patients head capturing images from multiple planes (TOMOGRAPHY)
-Multiple images are ‘reconstructed’ into a single image (COMPUTERIZED)
Computerized Tomography
Computerized tomography (CT):-hyperdense, hypodense, isodense
Hyperdense:
Bone - WHITE
Hypodense:
Cerebral spnal fluid (CSF) - DARK GRAY
Fat tissue, air - BLACK
Isodense:
Brain tissues - GRAY Scout Image (X-Ray) CT Scan (axial
plane)
Computerized Tomography
Computerized tomography:-Density in CT scans measured in Hounsfield Units (HU)
Air --- -1000 to -600 HU
Fat --- -100 to -60 HU
CSF --- 8-18 HU
White matter --- 30-34 HU
Gray matter --- 37-41 HU
Freshly congealed blood --- 50-100 HU
Bone --- 600-2000 HU
CT Scans (axial plane). Red arrow - Skull fracture
*** You will NOT be responsible to know the HU numbers for different brain components
Computerized Tomography
Computerized tomography:-Density in CT scans measured in Hounsfield Units (HU)
Air --- -1000 to -600 HU
Fat --- -100 to -60 HU
CSF --- 8-18 HU
White matter --- 30-34 HU
Gray matter --- 37-41 HU
Freshly congealed blood --- 50-100 HU
Bone --- 600-2000 HU
Other information obtained from CT scans:
Mass effect - anything that distorts normal brain anatomy
CT Scans (axial plane). Black arrow - left frontal acute epidural hematoma. White arrows - displaced midline (http://emedicine.medscape.com)
Computerized Tomography
Computerized tomography:
Other information obtained from CT scans:
Cerebral infarctions: Usually cannot be detected by CT scans in the first 12 hours. Subsequent cell death and edema lead to hypodensity.
Neoplasms: Can be hyper-, hypo- or isodense depending on the type, location, etc.
CT Scans (axial plane). A. Middle cerebral artery infarction with mild mass effect after 24 hrs (red arrow). B. Glioblastoma multiforme with mass effect (GBM). (http://emedicine.medscape.com)
A B
Computerized Tomography
Computerized tomography:
Specialized types of CT scans:
CT with intravenous contrast:
-material injected is denser than brain and will therefore appear hyperdense (white). Example -- iodine
CT myelography:
-iodinated injected material delivered into CSF.
-allows visualization of impingements of spinal CSF space or nerve roots
Subdural hematoma (red arrows). CT Scans obtained at the same level with or without intravenous contrast (axial plane). A. Without contrast B. With intravenous contrast. Green arrow is an enhanced vein. Blue arrow highlights border of hematoma. (http://emedicine.medscape.com)
A B
Magnetic resonance imaging
Magnetic resonance imaging (MRI)
A technique in which atomic nuclei are placed in a static electric field and then pulsed with magnetic energy
- the electric field aligns most of the protons atomic spin
- a pulse of magnetic energy flips some protons spin against the electric field
- after the pulse of energy ‘flipped’ protons ‘relax’ back into alignment with
the electric field and release energy Determinants of MRI signal:
1.Density of protons in tissue
2.Proton relaxation state (T1 and T2)
(Blumenfeld Neuroanatomy through Clinical Cases)
Magnetic resonance imaging
Magnetic resonance imaging (MRI) - Types
Axial T1-weighted, T2-weighted, and FLAIR (fluid attenuation inversion recovery) MR images at the same level in the same patient. (Blumenfeld Neuroanatomy through Clinical Cases)
T1 T2
Magnetic resonance imaging
Magnetic resonance imaging (MRI) - Types
T1-weighted (left) and T2-weighted MRIs of a patients with a glioma. (http://emedicine.medscape.com)
(*You do not need to know for exam)
Magnetic resonance imaging
Magnetic resonance imaging (MRI) - Types
Axial T1-weighted MR image with intravenous gadolinium contrast(Blumenfeld Neuroanatomy through Clinical Cases)
T1 T2
Specialized types of MRI scans:
MRI with intravenous contrast:
-paramagnetic material is injected to enhance vasculature. Example -- gadolinium
Magnetic resonance spectroscopy:
-measures abundance of brain neurotransmitters or other biochemicals.
Diffusion tensor imaging (DTI):
-permits the sensitive assessment of white matter tracts.
Magnetic resonance imaging
CT vs MRI
(Blumenfeld Neuroanatomy through Clinical Cases)
Functional imaging
Functional imaging techniques
T1 T2
Functional imaging techniques capitalize on detecting differential levels of blood flow and/or metabolism.
Regions of high brain activity = regions with high levels of blood flow/metabolism
Functional imaging
Functional imaging techniques
T1 T2
Positron emission tomography (PET) Scans:
-Short-lived radio-active isotopes (typically conjugated to biological agents, such as glucose analogs [eg. fluorodeoxyglucose]) are delivered into the blood stream
-Isotopes undergo positron emission decay and emit 2 gamma photons at 180˚ from each other allowing localization.
-Images of isotope density within tissues are generated like CT Scans
(A similar technique is Single-Photon Emission Computerized Tomography [SPECT])
http://en.wikipedia.org/wiki/Positron_emission_tomography
PET PET/MRI
Functional imaging
Functional imaging techniques
T1 T2
Functional MRIs (fMRI or blood oxygen level-dependent [BOLD] fMRI):
Predicated on the principle that differences in hemoglobin levels distort magnetic resonance properties of tissues.
No radioactivity required
Non-invasive
Angiography
Conventional angiography:
An invasive technique that delivers iodinated contrast material into the vasculature and detects it with X-rays
Interventional angiography:
Wada test: Injection of amobarbital instead of (or with) contrast material.
con
Neuro-Angiography
(Blumenfeld Neuroanatomy through Clinical Cases)
(Blumenfeld Neuroanatomy through Clinical Cases)
Angiography
Magnetic resonance angiography (MRA):
A less invasive technique that takes advantage of changes in magnetic resonance signals that occur as a result of blood flow. Gadolinium may be used to enhance contrast.
CT angiography (CTA):
A rapid injection of iodinated contrast material is injected and CT scans are quickly obtained.
Neuro-Angiography
(Blumenfeld Neuroanatomy through Clinical Cases)
MRA
http://emedicine.medscape.com
CTA
Sectional anatomy in MRI images
Sectional Anatomy
Self-study with:
1. Purves Neuroscience. “Atlas” pages 846-853
2. MRIs in Sylvius4
3. Chapter 6 of “Digital Neuroanatomy” on the eCurriculum website
***A list of structures to identify is in your syllabus. Be able to identify these structures in axial, coronal and sagital MRI images.
Sectional anatomy in MRI images
Be able to identify the following structures in MR images:
AmygdalaAngular gyrusAnterior commissureCalcarine sulcusCaudate nucleusCentral sulcusCerebellar peduncles, superiorCerebellar peduncle, middleCerebellar peduncles, inferiorCerebellumCerebral aqueductCerebral pedunclesCingulate gyrusCorpus callosum, genuCorpus callosum, spleniumCorpus callosum, bodyCuneus gyrusFornixFourth ventricle
Globus pallidusHippocampusHypothalamusInferior colliculusInferior frontal gyrusInferior temporal gyrusInsular lobe (insular gyri)Internal capsule, anterior limbInternal capsule, posterior limbLateral ventriclesLingual gyrusLongitudinal fissureMedulla oblongataMidbrain Middle frontal gyrusMiddle temporal gyrusOptic chiasmOptic nerveOrbital gyri
Parietooccipital sulcusPonsPostcentral gyrusPrecentral gyrusPutamenSpinal cordSuperior colliculusSuperior frontal gyrusSuperior temporal gyrusSupramarginal gyrusThalamus
Sectional anatomy in MRI images
T1-weighted MRIUnstained brain T2-weighted MRI
Basal ganglia:Caudate nucleusGlobus pallidusPutamen
Cortical features:Inferior, middle, superior frontal gyriInferior, middle, and superior temporal gyriCingulate gyriInsular gyri (lobes)Longitudinal fissure
Ventricles:Lateral ventriclesThird ventricle
Axon tracts:Corpus Callosum, bodyAnterior commissureInternal capsule, anterior limbOptic chiasm
Other:Amygdala
Purves Digital NADigital NA
Sectional anatomy in MRI images
T1-weighted MRIUnstained brain T2-weighted MRIPurves Digital NADigital NA
Basal ganglia:Caudate nucleus
Cortical features:Inferior, middle, superior frontal gyriInferior, middle, and superior temporal gyriCingulate gyriInsular gyri (lobes)Longitudinal fissureParahippocampal gyrus
Ventricles:Lateral ventriclesThird ventricle
Axon tracts:Corpus Callosum, bodyInternal capsule, posterior limbCerebral peduncle (crus cerebri)
Other:ThalamusHippocampusPons
Sectional anatomy in MRI images
T1-weighted MRIUnstained brainPurvesDigital NA
Cortical features:Cingulate gyriCalcarine sulcusParieto-occipital sulcusCuneus gyrusLingual gyrus
Axon tracts:Corpus Callosum(body, genu, spleium)FornixSuperior and inferior cerebellar peduncles
Dienchephalon:ThalamusHypothalamus
Brainstem:MidbrainInferior colliculusSuperior colliculusPonsMedulla oblongata
Ventricles:Lateral ventriclesFourth ventricle Spinal cord
Cerebellum
Sectional anatomy in MRI images
Cortical features:Superior frontal gyriMiddle frontal gyriPrecentral gyriPostcental gyriCentral sulcusLongitudinal fissure
T1-weighted MRIPurves
Sectional anatomy in MRI images
Cortical features:Insular gyriParieto-occipital sulcusCuneus gyriSupramarginal gyriAngular gyri
Axon tracts:Corpus callosum, spleniumInternal capsule, anterior limbInternal capsule, posterior limb
Ventricles:Lateral ventriclesThird ventricle
T1-weighted MRIUnstained brainPurvesDigital NA
Subcortical:Caudate nucleusGlobus pallidusPutamenThalamus
Sectional anatomy in MRI images
Cortical features:Orbital gyriSuperior temporal gyrusMiddle temporal gyrusCuneus gyrusLingual gyrusCalcarine sulcusLongitudinal fissure Axon tracts:
Optic nerveOptic chiasmCerebral peduncle
Ventricles:Lateral ventricles
T1-weighted MRI
Other:AmygdalaHippocampus
Purves
Midbrain:Superior colliculusCerebral aqueductCerebral peduncle
Sectional anatomy in MRI images
T1-weighted MRI
PonsCerebellumMiddle cerebellar peduncleInferior cerebellar peduncleFourth ventricle
PurvesA B B
A
Sectional anatomy in MRI images
The structure marked by the tip of the arrow is the:
A.Caudate nucleus
B.Internal capsule, posterior limb
C.Globus pallidus
D.Putamen
E.Internal capsule, anterior limb
Sectional anatomy in MRI images
The structure marked by the tip of the arrow is the:
A.Insular gyrus
B.Orbital gyri
C.Amygdala
D.Hippocampus
E.Parahippocampal gyrus
Sectional anatomy in MRI images
The structure marked by the tip of the arrow is the:
A.Superior colliculus
B.Superior cerebellar peduncle
C.Pons
D.Inferior colliculus
E.Middle cerebellar peduncle