Week 1 Flashcards
Definition of Imaging
The visual representation of an object, such as a body part or celestial body, for the purpose of medical diagnosis or data collection, using any of a variety of usually computerised techniques.
What is an example of a type of imaging method which is excluded from the ‘imaging’ definition?
A photograph because it does not have a computerised technique element
What is a type of more abstract imaging methods?
Visualisation of calcium distribution in neurons with calcium imaging
What is the definition of functional imaging?
The task of functional brain imaging is to identify regions and their temporal relationships associated with theperformance of a well-designed task
What differentiates functional imaging from non functional?
- Functional provides added information if change that is happenning to respond in response to the scientific aspect
- It is often investigating a change in response to a stimulus or experiment design to see the function
What is the smallest level of resolution?
Molecular
What is the main issue of having an imaging method whihc measures to the sub-millimere in spatial and millisecond in temporal resolution?
This would provide too much information that would take too long to analyse
Is there an ideal imaging methodology which encapsulates sub-millimetre spatial and millisecond temporal resolution?
No single method today achieves this
What is an important thing to consider when choosing an imaging method?
Need to proportionally pick the method which has the required need of resolution- there is no point using a mehtod wih extremely fast temporal resolution to measure the slow growing of cells for example
What is the definition of spatial resolution?
Is the ability to distinguish two separate objects that are positioned close to each other.
What are 3 factors that influence the spatial resolution?
- Optics
- Contrast within the images
- Blurring in the imaged tissue (point spread function)
How can you improve the contrast of something we are imaging?
Use a stain
How would blurring affect spatial resolution?
The image becomes hazy and therefore bigger so there is less intensity in the profile mapped out
(same happens when there is less contrast)
What type of relationship is there between electromagnetic properties and resolution?
Linearly to the wavelength used
Why is there a limit to imaging using electromagnetic waves?
Because of diffraction there is a theoretical limit to the spatial resolution
What are three examples of Electro-magnetic imaging?
- X-ray
- Light microscope
- Electron microscope
What is the linear equation of theoretical resolution and EM imaging?
x= λ/sin(α)
Where:
* x: Minimum distance at which two objects can be resolved (resolution).
- λ: Wavelength of the imaging source (e.g., electron wavelength in EM).
- sin(α): Sine of the aperture angle (𝛼).
What is the aperture angle?
Angle of the object going into the objective
Is a larger or smaller angle aperture required for higher resolution?
Larger (inverse to the distance)
Is a larger or smaller minimum distance objects can be resolved required for a higher resolution
Smaller
What are two tricks to improve the theoretical resolution?
- Immersion lenses
- Super-resolution microscopy
How many times better is an electron microscope compared to a light one?
10,000 times
What is the signal to noise ratio (SNR)?
- Describes the relationship between the size of the meaningful signal and the size of the recorded noise
- It is a measure of the statistical accuracyof data from an imaging device
What is the SNR in imaging described by?
Pixel Example
The mean value in a pixel compared to the standard deviation of that pixel in repeated measurements (takes the same picture again and again to see if there are changes due to noise)