Imaging Science and Image Processing Flashcards
What is a medical image?
A representation of the human body at a point in time that can be interpreted by an observer. The content of the image depends upon the physics of the imaging process, meaning that each medical image is just one representation of the ‘truth’.
Define planar imaging
The acquisition of 2D images.
Define tomographic imaging
A method of producing a three-dimensional image of the internal structures of a solid object by sectioning that uses any kind of penetrating wave.
Which 2 imaging modalities produce planar images?
- Planar X-ray
- Nuclear medicine (but can be tomographic)
Which 5 imaging modalities produce tomographic images?
- X-ray CT
- MRI
- Nuclear medicine (but can be planar)
- PET/CT
- Ultrasound
Which 5 imaging modalities produce anatomical images?
- Planar X-ray
- X-ray CT
- MRI (but can be functional)
- PET/CT (but can be functional)
- Ultrasound
Which 3 imaging modalities produce functional images?
- MRI (but can be anatomical)
- Nuclear medicine
- PET/CT (but can be anatomical)
What are the pros and cons of planar X-ray?
+ Quick
+ Inexpensive
- Poor soft tissue contrast
What are the pros and cons of X-ray CT?
+ Quick
+ Reproducible
+ Good soft tissue contrast
- Difficult to manipulate contrast
What are the pros and cons of MRI?
+ Very good soft tissue contrast
- Can be slow
- Not always reproducible
What are the pros and cons of nuclear medicine?
+ Early disease detection
+ Functional imaging
- No anatomical information
- Low resolution
- Slow
- Potential for high dose
What are the pros and cons of PET/CT?
+ Whole body scans are easy
- Expensive
- Low resolution
What are the pros and cons of ultrasound?
+ Quick
+ Inexpensive
- Difficult to interpret
Which imaging modalities use ionising radiation?
- Planar X-ray
- X-ray CT
- Nuclear medicine
- PET/CT
Which imaging modalities use non-ionising radiation?
- MRI
- Ultrasound
When beginning a clinical investigation, what is the best imaging modality to use?
The quickest, most accessible, and least invasive one
Define image fusion
The co-registration and visualisation of multiple imaging modalities by bringing the images together into the same geometrical context on the same screen.
Often, information from ______ imaging modalities is considered to develop an overal picture of the patient’s condition.
Multiple
What is a digital image?
An array (2D matrix) of numbers mapped onto the pixels of an output device, visualising data collected by an imaging device.
What are the key disadvantages of a digital image?
- It is rare to see all of the information from a single ‘visualisation’ of the image
- Information can be lost if a mapping scheme is used to increase image size
What is windowing?
The selection of a range of raw data values (the window width) and stretching these values across all available pixel values on the display of the device. This makes the image easier to visualise.
Why is CT windowing often preset?
To allow clinicians to choose the appropriate window for the organs being visualised and to provide consistent results between patients and scanners.
What makes a good quality image?
An image that is appropriate for the clinical application and balances (optimises) all competing factors, including:
- Image quality (contrast, resolution, etc.)
- Patient dose burden
- Meets the requirements of each stage of the clinical process (i.e. answers the clinical question)
True or false: an image is only good quality if it is the best possible image that can be acquired.
False
