1. Neuroradiology and Sectional Anatomy

2. Understand basic types of brain imaging techniques
Introduction
Objectives:
Understand basic types of brain imaging techniques
Understand the benefits of different brain imaging techniques
Be able to identify basic brain structures in MR images.

3. Computerized tomography Magnetic resonance imaging (MRI)
Introduction
Topics covered:
Computerized tomography
Magnetic resonance imaging (MRI)
Functional imaging techniques
Angiography
Sectional anatomy in MRI images

4. 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)

5. 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)

6. Computerized Tomography
Density in CT scans measured in Hounsfield Units (HU)
Air to -600 HU
Fat to -60 HU
CSF HU
White matter HU
Gray matter HU
Freshly congealed blood HU
Bone HU
*** You will NOT be responsible to know the HU numbers for different brain components
CT Scans (axial plane). Red arrow - Skull fracture

7. Computerized Tomography
Density in CT scans measured in Hounsfield Units (HU)
Air to -600 HU
Fat to -60 HU
CSF HU
White matter HU
Gray matter HU
Freshly congealed blood HU
Bone 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 (

8. Computerized TomographyB
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). (

9. Computerized TomographyB
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. (

10. 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:
Density of protons in tissue
Proton relaxation state (T1 and T2)
(Blumenfeld Neuroanatomy through Clinical Cases)

11. Magnetic resonance imaging
Magnetic resonance imaging (MRI) - Types T2 T1
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)

12. Magnetic resonance imaging
Magnetic resonance imaging (MRI) - Types
(*You do not need to know for exam)
T1-weighted (left) and T2-weighted MRIs of a patients with a glioma. (

13. Magnetic resonance imaging
Magnetic resonance imaging (MRI) - Types
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. T2 T1
Axial T1-weighted MR image with intravenous gadolinium contrast
(Blumenfeld Neuroanatomy through Clinical Cases)

14. Magnetic resonance imaging
CT vs MRI
(Blumenfeld Neuroanatomy through Clinical Cases)

15. Functional imaging techniques
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

16. Functional imaging techniques
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]) T2 T1
PET
PET/MRI

17. Functional imaging techniques
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

18. Neuro-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.
(Blumenfeld Neuroanatomy through Clinical Cases)
con
(Blumenfeld Neuroanatomy through Clinical Cases)

19. Neuro-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.
MRA
(Blumenfeld Neuroanatomy through Clinical Cases)
CTA

20. Sectional anatomy in MRI images
Self-study with:
Purves Neuroscience. “Atlas” pages
MRIs in Sylvius4
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.

21. Sectional anatomy in MRI images
Be able to identify the following structures in MR images:
Amygdala
Angular gyrus
Anterior commissure
Calcarine sulcus
Caudate nucleus
Central sulcus
Cerebellar peduncles, superior
Cerebellar peduncle, middle
Cerebellar peduncles, inferior
Cerebellum
Cerebral aqueduct
Cerebral peduncles
Cingulate gyrus
Corpus callosum, genu
Corpus callosum, splenium
Corpus callosum, body
Cuneus gyrus
Fornix
Fourth ventricle
Globus pallidus
Hippocampus
Hypothalamus
Inferior colliculus
Inferior frontal gyrus
Inferior temporal gyrus
Insular lobe (insular gyri)
Internal capsule, anterior limb
Internal capsule, posterior limb
Lateral ventricles
Lingual gyrus
Longitudinal fissure
Medulla oblongata
Midbrain
Middle frontal gyrus
Middle temporal gyrus
Optic chiasm
Optic nerve
Orbital gyri
Parietooccipital sulcus
Pons
Postcentral gyrus
Precentral gyrus
Putamen
Spinal cord
Superior colliculus
Superior frontal gyrus
Superior temporal gyrus
Supramarginal gyrus
Thalamus

22. Sectional anatomy in MRI images
Unstained brain
T1-weighted MRI
T2-weighted MRI
Digital NA
Purves
Digital NA
Cortical features:
Inferior, middle, superior frontal gyri
Inferior, middle, and superior temporal gyri
Cingulate gyri
Insular gyri (lobes)
Longitudinal fissure
Ventricles:
Lateral ventricles
Third ventricle
Axon tracts:
Corpus Callosum, body
Anterior commissure
Internal capsule, anterior limb
Optic chiasm
Basal ganglia:
Caudate nucleus
Globus pallidus
Putamen
Other:
Amygdala

23. Sectional anatomy in MRI images
Unstained brain
T1-weighted MRI
T2-weighted MRI
Digital NA
Purves
Digital NA
Axon tracts:
Corpus Callosum, body
Internal capsule, posterior limb
Cerebral peduncle (crus cerebri)
Cortical features:
Inferior, middle, superior frontal gyri
Inferior, middle, and superior temporal gyri
Cingulate gyri
Insular gyri (lobes)
Longitudinal fissure
Parahippocampal gyrus
Ventricles:
Lateral ventricles
Third ventricle
Other:
Thalamus
Hippocampus
Pons
Basal ganglia:
Caudate nucleus

24. Sectional anatomy in MRI images
Unstained brain
T1-weighted MRI
Digital NA
Purves
Cortical features:
Cingulate gyri
Calcarine sulcus
Parieto-occipital sulcus
Cuneus gyrus
Lingual gyrus
Axon tracts:
Corpus Callosum(body, genu, spleium)
Fornix
Superior and inferior cerebellar peduncles
Brainstem:
Midbrain
Inferior colliculus
Superior colliculus
Pons
Medulla oblongata
Ventricles:
Lateral ventricles
Fourth ventricle
Dienchephalon:
Thalamus
Hypothalamus
Spinal cord
Cerebellum

25. Sectional anatomy in MRI images
T1-weighted MRI
Purves
Cortical features:
Superior frontal gyri
Middle frontal gyri
Precentral gyri
Postcental gyri
Central sulcus
Longitudinal fissure

26. Sectional anatomy in MRI images
Unstained brain
T1-weighted MRI
Digital NA
Purves
Cortical features:
Insular gyri
Parieto-occipital sulcus
Cuneus gyri
Supramarginal gyri
Angular gyri
Subcortical:
Caudate nucleus
Globus pallidus
Putamen
Thalamus
Ventricles:
Lateral ventricles
Third ventricle
Axon tracts:
Corpus callosum, splenium
Internal capsule, anterior limb
Internal capsule, posterior limb

27. Sectional anatomy in MRI images
T1-weighted MRI
Purves
Cortical features:
Orbital gyri
Superior temporal gyrus
Middle temporal gyrus
Cuneus gyrus
Lingual gyrus
Calcarine sulcus
Longitudinal fissure
Other:
Amygdala
Hippocampus
Axon tracts:
Optic nerve
Optic chiasm
Cerebral peduncle
Ventricles:
Lateral ventricles
Midbrain:
Superior colliculus
Cerebral aqueduct
Cerebral peduncle

28. Sectional anatomy in MRI images
T1-weighted MRI A A B
Purves B
Pons
Cerebellum
Middle cerebellar peduncle
Inferior cerebellar peduncle
Fourth ventricle

29. Sectional anatomy in MRI images
The structure marked by the tip of the arrow is the:
Caudate nucleus
Internal capsule, posterior limb
Globus pallidus
Putamen
Internal capsule, anterior limb

30. Sectional anatomy in MRI images
The structure marked by the tip of the arrow is the:
Insular gyrus
Orbital gyri
Amygdala
Hippocampus
Parahippocampal gyrus

31. Sectional anatomy in MRI images
The structure marked by the tip of the arrow is the:
Superior colliculus
Superior cerebellar peduncle
Pons
Inferior colliculus
Middle cerebellar peduncle