Imaging for Target Volume Definition Flashcards
what is gross target volume (GTV)
the gross demonstrable tumour present
what are the principles of imaging for TVD
the ability to identify a tumour and its extent depends on the contrast between it and the surrounding normal tissue
what is depth
the slice thickness manipulated after acquisition
what is a voxel
a 3D pixel with depth
when would a 5mm CT slice be appropriate?
palliative treatment
when would a 1.25mm CT slice be appropriate?
stereotactic treatment
when does partial volume effect occur?
when portions of several objects are averaged together in a single slice
if slice thickness is increased, how does it effect resolution?
resolution decreases with increasing slice thickness
what are Hounsfield units?
units of attenuation, they follow a scale centred on water (0HU)
what does black on a CT scan represent
low attenuation
air or lung tissue
what does white represent on a CT scan?
high attenuation
cartilage or bone
what does grey represent on a CT scan?
medium attenuation
organs, muscles, lymph nodes, soft tissue
what is windowing
a grey scale bar to adjust the contrast and intensity refining of the slice
what are the 3 basic types of MRI weighting used in clinical practice?
proton density (PD) weighted
T1 weighted
T2 weighted
T1 weighted MRI
fluid containing the structures are dark
good for anatomical detail, vascular changes
