Neuroimaging

Question 1

medical imaging used to be limited to a small number of elite hospitals associated with teams of researchers who provide the expertise for its application and interpretation but now…

Answer 1

this is changing since commercial vendors are now offering products that make advanced brain imaging accessible to a much wider range of physicians and insti- tutions.

Question 2

To treat a brain tumor patient using invasive surgery and/or radiotherapy, there are three key issues

Answer 2

1. Where is the tumor ad how far has it spread
2. How bad is it? (pathology/heterogenous or not/where is it most aggresive
   • What’s at risk? Is there eloquent cortex or key white matter (tracts) near with key fnx?

Question 3

overall clinical goal:

Answer 3

effective treatment with minimal risk of causing neurological deficits that could compromise the patient’s quality of life.

Question 4

“deck” of 5 different types of imag- ing information layered into a single view that provides the surgeon with detailed infor- mation for planning a maximal resection of the tumor without damaging gray and white matter structures critical for vision.

Answer 4

Advanced imaging advantage

Question 5

This shows the anatomy at high resolution with good gray/white matter differentiation.

Answer 5

T1-weighted magnetic resonance image (MRI).

Question 6

Issue with T1 weighted magnetic resonace image MRI

Answer 6

However, some types of pathology are not well differentiated in this type of image.

Question 7

(SPoiled, Gradient Recalled at steady state)

Answer 7

SPGR

Question 8

The deck allows you to individually adjust each type of image and to re-arrange their stacking order. You can think of this as analogous to a deck of cards in which you can re-arrange the order of the cards.

Answer 8

SPGR

Question 9

an MRI image that highlights the tumor better. This type of image also reveals edema within the tumor and surrounding tissue. However, the gray/white matter anatomy is less well de- fined.

Answer 9

(Fluid Attenuated Inversion Recovery = FLAIR

Question 10

We can “threshold” the FLAIR image to allow the detailed SPGR anatomy to show through thus getting both the detailed anatomy and a good image of the tumor bed.

Answer 10

Multiparameter Imaging: Threshold FLAIR + SPGR

Question 11

_______ is a mathematical manipulation of the image so that only voxels with intensities above the threshold limit are displayed.

Answer 11

Thresholding

Question 12

= a small 3-dimensional imaging volume or the 3-dimensional equivalent of a “pixel”,

Answer 12

Voxel

Question 13

The more voxels the _____ the spatial reso- lution, that is, the more detial in the MR im- age.)

Answer 13

higher

Question 14

Functional MRI provides images of highly localized changes in blood flow and oxygenation that are driven by changes in net neural activity due to a sensory, motor or cognitive event.

Answer 14

BOLD fMRI: Brain Function

Question 15

______ triggers local vasodilation and resultant increase in highly oxygenated hemoglobin
in BOLD fMRI: Brain Function

Answer 15

Neural activity

Question 16

BOLD fMRI: Water protons within the blood and tissue are induced to emit radio frequency signals that are ________when the local magnetic field created by the scanner is undisturbed but _______when the local field is disrupted by the presence of poorly oxygenated hemoglobin.

Answer 16

high (strong) 
are low (weak)

Question 17

(BOLD fMRI) Neural activity causes increased blood flow which removes poorly oxygenated hemoglobin which allows

Answer 17

the protons to emit a strong signal.

Question 18

How neural activity triggers the
blood flow changes is poorly under- stood and may reflect a complex interplay of excitatory and inhibitory effects and may reflect both

Answer 18

post- synaptic and action potential activity.

Question 19

in BOLD fMRI the fMRI signals are slow compared to ______so typically reflect changes in neural activity integrated over several seconds.

Answer 19

neural events

Question 20

technique for mapping the representation of the visual field in a relatively short scanning session of 10-15 min.

Answer 20

fMRI Mapping of the Visual Field

Question 21

How do you get a visual stimulus for fMRI Mapping of the Visual Field

Answer 21

visual stimulus = flickering, checkered annulus slowly ex- pands over a 32 second period and then repeats 5 times during the fMRI scan.

Question 22

In the fMRI of the occipital cortex, we see the layout of the visual field eccentricity with the center of gaze represented at the

Answer 22

occipital pole

Question 23

In the fMRI of the occipital cortex, we see the layout of the visual field eccentricity with the more eccentric locations represented

Answer 23

represented more anteriorly.

Question 24

The colors in the fMRI of the visual field identify

Answer 24

locations in the visual field not the amplitude of the fMRI response.

Question 25

By adding distance contours, you show an estimated

Answer 25

“no-fly zone” around the tumor

Question 26

``` Different colors within the no-fly zone mark “shells” at different distances from the tumor: Red orange yellow green ```

Answer 26

Red < 5 mm, orange < 10 mm, yellow < 15 mm, green < 20 mm.

Question 27

Gray and white matter structures within _____mm of a resection site are likely to be at risk for damage caused by the surgery.

Answer 27

5-10

Question 28

When looking at a no-fly zone we see the peripheral visual field is in the red zone around the tumor.. would the physician opt for compete excision of the tumor?

Answer 28

Yes, Loss of vision in the peripheral visual field is often well tolerated so the surgeon and patient may elect to accept such a functional loss to ensure complete excision of the tumor.

Question 29

When evaluating imaging, doc noticices the close proximit of white matter tracts along the margin of the tumor including optic radiations. Why do those tracts show up green?

Answer 29

these are optic radiations which are supplying the visual input that is driving the fMRI activity in the occipital cortex

Question 30

arterio- venous malformation (AVM) in the ______These typically congenital malformations of the vasculature can ____ or _____

Answer 30

precentral sulcus bleed or induce epileptic activity.

Question 31

Tx option for AVM

Answer 31

surgical removal

Question 32

superior longitudinal fasciculus is also known as

Answer 32

arcuate fasiculus

Question 33

connects Wiernicke’s and Broca’s speech are- as in the temporal and frontal lobes respectively

Answer 33

arcuate fasiculus

Question 34

Option a surgeon can use when the the tumor is close to structures for movement and language function

Answer 34

Gamma knife

Question 35

__________is essential in complicated cases to allow the surgeon to plan both the route of access to the tumor and the key structures “at risk”

Answer 35

Advanced multiparamter imaging

Question 36

Advanced multiparameter imaging allows sugeons to be more or less aggressive

Answer 36

allows them to be MORE aggressive with the resection because they don’t have to guess where the crucial structures are located.

Question 37

Treatment was to involve sub-threshold electrical stimulation of the face area in motor cortex using epi- dural electrodes, (direct visualization was not possible) What kind of tx was this?

Answer 37

Therapeutic brain stimulation

Question 38

placement of the electrodes in therapeutic brain stimulation is critical not only to achieve maximum therapeutic effect but also

Answer 38

avoid stimulation of other nearby areas

Question 39

fMRI data can be used to

Answer 39

identify the optimal location of the stimulating electrodes relative to the fiducial markers on the scalp.

Question 40

Once a surgical plan is constructed, key images showing the critical features of the case are loaded into a system for

Answer 40

intra-operative navigation.

Question 41

Such systems can track the location of a surgical instrument (eg. aspi- rator) relative to the images of the brain thereby assisting the surgeon in orienting to features that are invisible to the naked eye but that are evident in the medical images

Answer 41

intra-operative navigation

Question 42

______ is rapidly affecting all stages of health care from diagnosis to treatment planning to treatment delivery and follow up monitoring for tumor recurrence

Answer 42

medial imaging technology

Question 43

capabilities are currently rudimentary but will advance rapidly allowing custom “shaping” of the radiation field... the purpose is

Answer 43

to maximally impact the tumor while minimizing dosage to eloquent cortex nearby