#26 Neuroimaging for Physical Therapists (FINISH)

What is neuroimaging?

Different techniques to directly/ indirectly 'image' the brain and spinal cord to understand function/physiology of the nervous system

What are types of neuroimaging?

1. Structural imaging

2. Functional imaging

How does neuroimaging fit into neurorehabilitation?

Long-term outcomes:

1. Prediction of response to treatment

2. Enhancement of plasticity

*neuroimaging here

How can we use neuroimaging for long term outcomes?

1. Predicting long term outcomes through anatomy

2. Enhancing plasticity

What are different imaging methods?

1. X-rays

2. Computerized Axial Tomography (CAT scan/CT scan)

3. Magnetic Resonance Imaging (MRI)

4. Positron Emission Tomography (PET scan)

5. Functional Magnetic Resonance Imaging (fMRI)

6. Diffusion Tensor Imaging (DTI)

What are other indirect imaging methods?

1. Magnetoencephalography (MEG) 2. Electroencephalography (EEG)

3. Transcranial magnetic stimulation (TMS)

How are x-rays produced?

1. Exposure to X-rays, very short wavelength waves which pass through many materials

2. Produces photographic or digital image of the internal composition of the exposed body

What are characteristics of x-rays?

1. Plain films or with contrasts

2. Radio-opaque or radio lucent

3. Anatomy in four shades of gray!

4. AP versus lateral versus oblique view

How do you read x-rays?

Radiodensity:

1. Air = black◦ Fat = dark grey appearance◦ Muscle = mid grey appearance◦ Bone = white◦ Contrast = white◦ Metal = white

What are implications of x-ray imaging for therapy?

1. Improved understanding of structure, injury

2. Patient Care considerations: mobility or post-surgical restrictions, healing related concerns

3. Patient education: improved care

What is the process of a CT scan?

The scanner rotates an X-ray beam around the body producing multiple X-ray images in series of slices which the computer puts together

What are CT scan advantages?

1. Faster and cheaper

2. Gives good info on anatomical features -with and without contrast

3. Helps identify many neuro conditions- also tumors, cysts, abscesses and acute bleeds

What are CT scan disadvantages?

1. Some risk of x-ray exposure

2. Tissue contrast could be an issue

3. Resolution not as good as MRI

What are CT terminology?

1. Hyper-attenuating (i.e. hyper-dense) : brighter areas

2. Hypo-attenuating (hypo-dense): darker areas

3. Iso-attenuating (iso-dense): intermediate density

Using CT terminology, how do brain structures appear?

1. Skull - hyper dense

2. Ventricles - hypo dense (dark grey)

3. Fat and fluid dense areas- hypo dense (black)

4. Brain matter - iso dense

5. White matter appears darker than grey matter

What are implications of CT scan imaging for therapy?

Similar to x-ray imaging:

1. Patient Care considerations: mobility or post-surgical restrictions, healing related concerns

2. Patient education: improved care

Improved imaging of tissue/ brain structure

1. Improved visualization of anatomy as compared to X-ray

What is the process of an MRI?

1. Strong magnet creates a magnetic field that align the protons of the hydrogen atoms in the body uniformly

2. Then, additional energy is added with a radio wave, which causes the magnetic field to deflect. When radio wave is switched off the magnetic vector of the hydrogen atoms returns to its resting stage causing a release of the additional energy.

3. Based on the tissue characteristics, the extra energy is released at different rates creating differing signals

What are advantages to an MRI?

1. No known associated health risk

2. Sophisticated and more detailed than CT scan

3. More neuro conditions detected -degenerative diseases, inflammation, infection, tumors, strokes

What are disadvantages to an MRI?

1. Expensive

2. Takes longer time than CT

Compare and contrast T1 vs T2 MRI images.

T1:

1. For normal anatomical details

2. White matter appears light grey

3. CSF appears black

4. Looks more like normal

T2:

1. Used to look at pathology

2. White matter appears dark grey

3. CSF appears white

4. Looks like a negative image

What are implications of MRI imaging for therapy?

Similar to X-ray and CT imaging:

1. Patient Care considerations: mobility or post-surgical restrictions, healing related concerns

2. Patient education: improved care

Additional advantages

1. Improved visualization of anatomy as comparted to X-ray and CT scans

2. Improved localization of anomalies/pathologies/lesions

Improved visualization of progression/recovery of injury

What is a functional MRI (fMRI)?

Creates a functional map of brain activity mostly by imaging the ratio of oxygenated to deoxygenated hemoglobin secondary to neural activity

What can fMRI be used for?

To determine where and with what intensity brain activity occurs during a functional task

What are strengths of fMRI?

1. Validated technique for good spatial localization

2. Non-invasive

3. Can be replicated

What are weaknesses of fMRI?

1. Complex data processing required

2. Expensive and time consuming

What are implications of fMRI for therapists?

1. Currently still research focused

2. In future, possibly used to identify residual functional areas post stroke/ brain injury; predict treatment effects

What is diffuse tensor imaging (DTI)?

MRI used to monitor axonal bundles that connect regions of the central nervous system

- Based on the principle that water molecules diffuse along the length of an axon rather than perpendicular to it

What are strengths of DTI?

1. Detects problems in neural tracts (e.g. DAI)

What are limitations of DTI?

1. Intricate software processing

2. Expensive

What are implications of DTI for neurorehabilitation?

1. Sensitive to detect DAI and microstructural damage of white matter tracts

2. Visual memory deficits, working memory deficits and motor learning can be predicted from white matter tracts

3. Relationship between clinical outcomes measures (GCS, PTA) and DTI measures

What are relationships between clinical outcome measures (GCS, PTA) and DTI measures?

1. Lower GCS and reduced DTI in Corpus Callosum, midbrain and brainstem pathways

2. PTA measurements associated with hippocampal pathways

What is positron emission tomography (PET)?

Detects gamma rays emitted by a positron-emitting radio-isotopes (tracer) which is injected intravenously or inhaled

What can a PET scan provide?

Depending on the tracer's uptake, PET scan provides measurements of blood flow, brain glucose metabolism and neuroreceptor /neurotransmitter issues

What is the future of neuroimaging in neurorehabilitation?

1. To predict treatment pathways

2. To predict dose of treatment

3. To enhance neuroplasticity post injury

4. Improve understanding of the mechanisms of recovery and treatment

5. Provide targeted or individualized therapy

How should you systematically read x-rays?

Determine if radiographs are normal or abnormal based on the following criteria:

1. Alignment

2. Bone Density

3. Spaces

4. Visualize/predict soft tissue injuries

What are basic suggestions on reading CTs and MRI?

1. Knowledge of normal anatomy

2. Correlate with signs and symptoms... what's obvious on an image might not be the cause of the patient's main problems

What are the 5 assessment areas are used by radiologists?

1. Identify

2. Examine

3. Localize

4. Analyze

5. Conclude

What do you identify?

Subject of the exam and some technical details

1. Patient name, date

2. Plane of scan: Transverse, sagittal or coronal

3. Orientation: Right/Left, Anterior/Posterior

4. Image characteristics: CT- with or without contrast; MRI - T1 or T2

What do you examine?

Search for radiological findings such as size, shape, symmetry, density, displacement, integrity, and lesions

What do localize?

Just exactly where are the relevant findings anyway?

What do you analyze?

If anything abnormal is suspected, what are the likely pathological, etiologic, and chronological features?

What do you conclude?

A format for a concise summary report to think, say, or write?

What regions do you inspect?

1. Midline

2. Ventricles, cisterns, sulci

3. Brain structures

4. Lobes, gyri, corona radiata

5. Basal ganglia, thalami, capsules, corpus callosum

6. Brain stem, cerebellum

7. Bone

What are used for qualities?

1. Shift

2. Size

3. Shape

4. Symmetry

5. Density

6. Displacement

7. Integrity

8. Grey-white differentiation

9. Lesions

What are descriptor words/phrases for shift?

To right or left in cm or mm

What are descriptor words/phrases for size?

1. Enlarged

2. Small

3. Compressed

4. Distended

5. Hypertrophic

6. Atrophic

What are descriptor words/phrases for shape?

1. Wedge shaped

2. Lobular

3. Spherical

4. Ovoid

5. Elliptical

6. Irregular

7. Flat

What are descriptor words/phrases for symmetry?

1. Symmetric

2. Asymmetric

What are descriptor words/phrases for density?

1. Hyperdense

2. Hypodense

What are descriptor words/phrases for displacement?

1. Superior

2. Inferior

3. Anterior

4. Posterior

5. Lateral

6. Medial

What are descriptor words/phrases for integrity?

1. Absent

2. Atrophic

3. Fractured

4. Infarction, etc.

What are descriptor words/phrases for grey-white differentiation?

1. Intact

2. Present

3. Absent

4. Reduced

What are descriptor words/phrases for lesions?

1. Present or absent

2. Location

3. Number

4. Enhancement characteristics

5. Size

6. Shape

How should you assess image content?

1. Inspect all of the images quickly. Some pathology jumps off the scan and announces itself!

2. Look again more methodically. Some very important things are subtle (until you see them!)

What midline structures do you assess?

1. Anterior falx cerebri

2. Septum pellucidum

3. Third ventricle

4. Pineal

5. Posterior falx cerebri

6. Fourth ventricle

What do midline shifts usually indicate?

Raised intracranial pressure

- They can be associated with intra-axial or extra-axial pathology

- Different processes can shift more the anterior, middle, or posterior midline structures

How do you measure midline shift?

1. Draw an imaginary line between the midline protuberances

2. Determine the midline structure most displaced

3. Measure the distance from line through the displaced midline structure

4. Measure the midline shift distance in mm (or cm)

5. Check the right-left marker on the image for direction of the shift

6. Look for signs of mass effect on one side or atrophy on the other as either can lead to a midline shift.

What do you assess looking at ventricles?

1. Changes in size, shape, and density are frequent abnormalities in the ventricles. They can involve only parts of the ventricular system and may be symmetric or asymmetric

2. Mass lesions often displace all or part of a ventricle

3. Hydrocephalus = ventricular enlargement = ventriculomegaly can be due to CSF flow problems OR to cerebral atrophy OR a normal variant if mild or moderate

4. Intraventricular hemorrhage shown by intraventricular hyperdensity if acute

5. Intraventricular mass lesions such as meningioma, colloid cyst, etc. are unusual but important

6. Asymmetry in size suggesting mass effect OR atrophy focal or diffuse OR normal variant OR developmental anomalies

What do you assess looking at sulci?

1. Cerebral sulci are the subarachnoid spaces between the gyri. Normally they contain blood vessels and CSF. They are subject to changes in size, symmetry, and density

2. Sulci can fill with blood due to subarachnoid hemorrhage whether aneurysmal, traumatic, hypertensive, or of other origin

3. They commonly enlarge in cases of brain injury of any etiology when the pathology has evolved into its chronic state

What do you assess looking at brain abnormalities?

Look at the brain in 3 areas, searching each in turn for changes in size, shape, symmetry, density, displacement, gray-white differentiation, integrity, and the presence of lesions

1. Lobes, Gyri, and White matter

2. Basal structures including basal ganglia, internal capsules, thalami, corpus callosum

3. Cerebellum and brain stem

What questions do you ask when there is a space occupying lesion/bleed?

1. Is there blood present?

2. Is there a space occupying lesion?

3. Where?

4. What effect is it having?

What does blood look like on a CT image?

1. Acute blood = bright white (once clots)

2. Blood becomes isodense at approx 1 week

3. Blood becomes hypodense at approx 2 weeks

What are some concepts that are useful in analyzing CT scans of the brain?

1. Common hyperdensities include blood, calcification or mineralization, foreign bodies, enhancing lesions such as tumors and subacute infarctions and contusions

2. Common hypodensities include edema, non-enhancing tumors, infarctions, air, chronic hematoma