Imaging Flashcards
what is image registration
process of spatially aligning two images together
what info does CT provide?
great anatomical detail, enhanced with contrast
what info does RNI provide
great physiological info, but poor anatomical info, so is used alongside other modalities
what is the role of imaging
that the target volume is being treated
what info does MRI provide
greater anatomical details, enhanced with contrast, with an increased use
what info does ultrasound provide
great anatomical detail for soft tissues
why are images gathered
to avoid errors
- systematic = QA program
- random = imaging, QA programme and education
why is registration important
- follow up studies
- inflammatory disease diagnosis
- RT planning
- neurological disorders
- RT portal film comparison with ref image
why is registration important
- follow up studies
- inflammatory disease diagnosis
- RT planning
- neurological disorders
- RT portal film comparison with ref image
what is a random error
a deviation which can vary in direction and magnitude for each delivered fraction. these are not inherent within the process, normally only occur once
<2mm
what is a systematic error
an error which is introduced at the beginning of treatment and carried throughout the whole treatment. The deviation occurs in the same direction and is of similar magnitude for each fraction throughout the treatment course.
<5mm
what is a pixel
2D space
what is a voxel
3D space
what are fiducial markers
markers which are found internally or outside the treatment couch, which act as a reference point. They are used in image registration
what is localisation
location of where it is in reference with other body parts. it can act as a reference marker outside the body
what position is the same as the treatment position
CT position
what are some equipment adaptations
- couch is flat and not dish shaped
- treatment position, otherwise it could lead to geographical miss
- accessory equipment must attach directly to the couch accurately
what is a simulator
it is similar to the treatment couch, which is isocentrically mounted, but it doesn’t visualise soft tissue, all tissue looks the same
what is the ideal equipment
- treatment position
- anatomical + functional info
- minimal/no radiation dose
- localisation and position of where the tumour is active
- good image quality
- information of x-ray absorption
why are radio-opaque markers used
they are inserted in the body, which help with the alignment so that the patient is in the same position
what is contrast
it is the state of being strikingly different from something else in juxtaposition or close association. There is a difference in density
bone = white, air = black, soft tissue = grey
what is the density of darker images
greater density
what energy is used in electrons
MeV
what is a reference image
a selected standard image used against all online images, MV images are taken prior treatment
