NEURODIAGNOSTIC EVALUATION p1

Based on image reconstruction from sets of quantitative x-ray measurements

Computed Tomography (CT or CAT Scan)

 contains x-ray source and detectors; tilts from axial to coronal

Gantry

Differential absorption of x-ray beam by different tissues produce varied levels of density in the image which are measured in?

Hounsfield units (HU)

These tissues are considered HYPODENSE

Air, Fat, Water/CSF

Hounsfield units of:

• Air

• Fat

• Water/CSF

• -1000

• -120

• 0

The following are considered HYPERDENSE:

Hemorrhage, Calcification, Bone

Hounsfield units of:

• Hemorrhage

• Calcification

• Bone

• 70-80

• 80-100

• +400

This tissue is between hyperdense and hypodense

White matter

Hounsfield units of white matter

22-32

Tissue/s considered black on the CT gray scale

Air, CSF, Fat

Tissue/s considered white on the CT gray scale

Extravasated blood, Calcium

Tissue/s considered dark gray on the CT grayscale

Inflammation (contrast enhancing), Edema

Tissue/s considered gray on the CT grayscale

Brain, Tumor (can be white and contrast enhancing)

Tissue/s considered very white on the CT grayscale

Bone

Type of CT scan used for identifying acute hemorrhage (gold standard for acute neurotrauma)

non-contrast CT (NCCT)

Advantages: Fast - identifies blood - shows bony structures

Sign/s associated with loss of insular cortex

Insular ribbon sign

Sign/s associated with hyperattenuating vessel filled with acute thrombus

dense MCA and dot sign

During a stroke, there is a loss of gray-white matter __________ in the NCCT image

differentiation

Sign/s associated with decreased density of basal ganglia

disappearing basal ganglia sign

This CT scan type is used to enhance differences in tissue density, demonstrate vasculature and vascular pathology and detects areas of BBB breakdown

Contrast Enhanced CT (CECT)

IV iodinated water-soluble contrast is given through IV line

Contraindications or limiting factors of CECT

• Allergic reaction

• Contrast induced nephropathy (increased creatinine)

CT scans are more reliable for ______ brain parenchymal or _______ hemorrhage especially _______ (aneurysm that popped)

• acute

• extra axial

• SAH

Indications for emergency CT:

• Acute or chronic FND 

• Head or facial trauma

• Headache 

  • Abrupt or worsening

  • SAH traumatic vs. non-traumatic 

• Change in mental status 

• New-onset seizure

Limitations of CT scan

• Imaging of posterior fossa → linear artifacts (not as clear) 

• Ionizing radiation → pregnant

Advantages of CT-scan

• Speed

• Cost 

• Availability

Repeating scan during a bolus of IV contrast that produces a dynamic set of images that are real time 4D images of blood flow through the intracranial vessels

CTA

CT scan that produces functional images of brain parenchymal blood flow

CTP

True or False:

Catheter Angiography is more widely available, less specialized are required and there is no risk of dissection or stroke.

False:

CTA to boi

True or False:

Catheter angiography is more time consuming than CTA

False:

False, CTA has a time-consuming process requiring to edit and generate rendering 

CTP allows quantitative measures of the following:

• cerebral blood volume

• cerebral mean transmit time

• time to peak

• cerebral blood flow 

CTP can be used as a quick screening method to assess _______ and for differentiating ________ and __________

• Acute cerebral ischemia

• Infarct

• Penumbra

Infarct signs:

• _____ MTT

• Decreased _____ and _____

Infarct signs:

• prolonged MTT

• Decreased CBV and CBF

Ischemic penumbra signs:

• prolonged _____ and _____

• normal or increased ______

• mildly reduced _____

• ____________

• Salvageable

Ischemic penumbra signs:

• prolonged MTT and TTP

• normal or increased CBV

• mildly reduced CBF

• compensatory vasodilation

• Salvageable

This imaging tech has the ability to distinguish between pathologic soft tissues and identify pathologic abnormalities

MRI

Origin of MRI signal:

hydrogen nuclei

consist of a single proton that is constantly spinning 

Most precise and sensitive imaging for detecting CNS tissue pathology

MRI agen

MRI demonstrates a ____________ contrast between different tissues compared to CT or UTZ

Significantly higher

Limitations of MRI:

• ____ (broke boi boi boi)

• Lengthy (________ min for cranial CT) 

• Distortion of images by ________

• _________ and level of cooperation of patient 

• _________ (i.e. pacemakers, infusion pumps, cochlear implants, aneurysm clips) 

• _________ (i.e. ventilators) 

• ________ → possibility of developing _______ of fetuses of animal (not 100%)

Limitations of MRI:

• Cost

• Lengthy (30-40 min for cranial CT) 

• Distortion of images by artifacts 

• Claustrophobia and level of cooperation of patient 

• Implanted devices (i.e. pacemakers, infusion pumps, cochlear implants, aneurysm clips) 

• Machines (i.e. ventilators) 

• Pregnant → possibility of developing cataracts of fetuses of animal (not 100%)

Safety Concerns of MRI:

• Powerful magnetic field (its in the name bozo)

• Gadolinium chelates

Gadolinium chelates can cause what in patients with renal dysfunctions?

Nephrogenic Systemic Fibrosis

Basic sequences of MRI:

• Displays brain and spinal cord anatomy

• Evaluates subacute hemorrhage, lipids, paramagnetic metals, or proteinaceous composition of lesions

• Baseline for comparison of CE images

T1 WEIGHTED

What color is the CSF in T1 weighted MRI

Dark

T2-Weighted:

• Display brain and spinal cord ________

• Emphasize long T2 relaxation times = _____

• Emphasize short T2 relaxation times = ______

T2-Weighted:

• Display brain and spinal cord pathology

• Emphasize long T2 relaxation times = bright

• Emphasize short T2 relaxation times = dark

Brain:

• CT GRAYSCALE

• MRI T1 SIGNAL

• MRI T2 SIGNAL

All gray

Air:

• CT GRAYSCALE

• MRI T1 SIGNAL

• MRI T2 SIGNAL

All black

CSF:

• CT GRAYSCALE

• MRI T1 SIGNAL

• MRI T2 SIGNAL

CSF:

• Black

• Black

• White

Fat:

• CT GRAYSCALE

• MRI T1 SIGNAL

• MRI T2 SIGNAL

Fat:

• Black

• White

• Less white

Calcium:

• CT GRAYSCALE

• MRI T1 SIGNAL

• MRI T2 SIGNAL

Calcium:

• White

• Black

• Black

Bone:

• CT GRAYSCALE

• MRI T1 SIGNAL

• MRI T2 SIGNAL

Bone:

• VERY white

• Black

• Black

Extravasated blood:

• CT GRAYSCALE

• MRI T1 SIGNAL

• MRI T2 SIGNAL

Extravasated blood:

• White

• White

• Black

Inflammation:

• CT GRAYSCALE

• MRI T1 SIGNAL

• MRI T2 SIGNAL

Inflammation:

• Dark gray, contrast enhancing

• Gray, gadolinium enhancing

• White

Edema:

• CT GRAYSCALE

• MRI T1 SIGNAL

• MRI T2 SIGNAL

Edema:

• Dark gray

• Gray

• White

Tumor:

• CT GRAYSCALE

• MRI T1 SIGNAL

• MRI T2 SIGNAL

Tumor:

• Gray or white, contrast enhancing

• Gray or white, gadolinium enhancing

• White

MRI sequence used to eliminate signal from CSF

T2 sequenced (T2 flair)

T2 Flair highlights subtle brain pathology; specifically useful for _________ diseases and lesions that are near CSF compartments

White matter diseases

T2 flair demonstrates ________ tumor components as well as associated mass effect and edema

non-enhancing

Presents as a periventricular white matter lesion, radially oriented to bodies of lateral ventricles

Multiple Sclerosis

These lesions can be found periventricular, deep and subcortical/juxtacortical white matter and corpus callosum

Supratentorial lesions

• Used to eliminate signal from fat

• Useful in dx fat containing lesions like lipoma and dermoid cyst 

Short Tau Inversion Recovery (STIR)

For detection of early ischemic brain injury
can help with identifying chronicity of infarct

Diffusion Weighted Imaging (DWI)

This measures the extent to which diffusivity of water is restricted from free diffusion, presumably due to structural barriers such as cell membranes or association of water with larger molecules that have lower diffusion coefficients

Interpreted along with DWI

Apparent Diffusion Coefficient (ADC)

A hyperintense DWI can mean?

Stroke

This MRI shows sensitivity to small amounts of blood and blood breakdown products (hypointense)

to detect bleeding

Gradient Recalled Echo (GRE)

Tissue components characterized in Gradient Recalled Echo (GRE):

calcification or iron content

MRI that signifies breakdown of BBB 

Gadolinium Contrast Enhancement

Gadolinium Contrast Enhancement characterizes:

• brain tumors

• metastases

• Infections

• Inflammation

Takes pictures while blood is flowing, signal is related to flow phenomenon

Magnetic Resonance Angiography (MRA)

MRA is used to detect:

• Stenosis

• Thrombosis 

• Dissections 

• Aneurysms

evaluation following interventions for aneurysm cerebrovascular malformations (AVM)

CE

evaluate neck vasculature 

CE + MRA

• For viewing sinuses

• Evaluate for patency of dural venous sinuses in venous sinus stenosis or thrombosis 

Magnetic Resonance Venography (MRV)

• Use of magnetic resonance for localization of cerebral activation

• Used to obtain functional information by visualizing cortical activity

• Detects subtle changes in blood flow or blood oxygenation in response to stimuli or actions

Functional MRI

Clinical applications of Functional MRI

• Cortical mapping of known cognitive and motor functional units (researches) 

• Presurgical and pre-therapeutic planning 

MRI technique that measures water molecule diffusion and its direction

Diffusion Tensor Imaging (DTI)

Clinical applications of Diffusion tensor imaging

Clinical applications: 

• Asses integrity of white matter tracts

• Presurgical and pre therapeutic planning 

map of neural connections 

human connectome

Used to differentiate lesions (i.e Tumor recurrence (higher choline to creatine ratio) vs. radiation necrosis)

MR Spectroscopy (MRS)

Metabolite that signifies normal neuronal tissue / neuronal integrity

Decreases in destructive lesions and decreased neuron density

N-acetyl- aspartate (NAA)

Metabolite that signifies energy stores

Creatine

Metabolite that signifies components of the cell membrane and myelin/ membrane turnover

Increases in rapidly dividing tumors

Choline (Cho)

Metabolite that signifies anaerobic metabolism

Lactate

Marker of astrocytes/astrogliosis seen in Multiple Sclerosis

Inositol or Myoinositol

MRI that quantifies blood flow through biologic tissues

(cerebral blood volume, cerebral blood flow and mean transit time)

MR Perfusion Imaging

Clinical applications of MR Perfusion Imaging

• Cerebrovascular disease

• Brain tumors and metastasis

Memorize:

Molecular imaging used to better understand the biochemical processes that underlie disease

Positron Emission Tomography (PET)  And Single-Photon Emission Computed Tomography (SPECT)

A radioactive compound, in trace amounts with a pharmaco- kinetic behavior that targets a molecular pathway related to the pathology of a certain disease

 radioligand

Screening extracranial carotid and vertebral arteries for atherosclerosis 

Real-time imaging of anatomy, physiology (hemodynamics) and pathophysiology of extracranial circulation

Extracranial Ultrasound (Duplex Ultrasound or Color Doppler)

True or False:

Extracranial ultrasound can be used for carotid imaging to detect carotid stenosis after surgery or stenting, it has a sensitivity of 87% and a specificity of 86%

False:
it has a sensitivity of 86% and a specificity of 87%

haha parang tanga oh

Extracranial ultrasound can also be used to determine carotid _______ size, morphology and carotid ________ thickness

• Plaque

• Intima media

If these are seen in extracranial ultrasound there is an inc risk of stroke or MI 

• Plaque surface irregularity

• Echoluscent carotid plaque (Soft)

If these are seen in extracranial ultrasound there is an dec risk of stroke or MI 

Echodense carotid plaque (calcified)

may be a marker of presence of active plaque in other vascular beds

True or False:

Vertebral arteries can also be examined using extracranial ultrasound but is limited d/t bony structures of the neck

True

Non-invasive US technology that monitors blood flow velocity and blood flow direction in large intracranial arteries

Intracranial Ultrasound (Transcranial Doppler or TCD)

Clinical applications of Intracranial US: 

• Stenosis or occlusion of a major intracranial artery in COW or VB system and monitoring of thrombolytic activity in acute stroke 

• Vasospasm in SAH → increased blood flow velocity 

• Brain death

Limitations of intracranial US:

• ____________ dependent

• ___________ rate of inability to perform TCD due to inadequate windows 

• Limited to ________

• Operator dependent

• 10-15% rate of inability to perform TCD due to inadequate windows 

• Limited to large cerebral arteries

Transducer placed over open fontanelles or thin calvarium 

Ultrasound in Babies

Ultrasound in babies is used to detect:

• Intracerebral and subdural hemorrhages

• mass lesions

• congenital defects 

• High resolution images of extracranial and intracranial vasculature 

• Accessing femoral nerve and threading a catheter into the precerebral vessels 

• Gold standard for viewing cerebral blood vessels 

Cerebral Angiography

This is the process where soft tissue is eliminated from image leaving only the contrast enhanced vasculature (DSA) 

Digital subtraction process