Advanced Imaging

Question 1

What is the purpose of patient data aquisition for TP?

Answer 1

• GTV, CTV and PTV definition
• OAR localisation
• field geometry and localisation (DRR)
• plan design and dose calculations
• plan evaluation

Question 2

Why do we need to consider the CT when taking CT images?

Answer 2

1. quality of the CT images will affect the entirie planning process
2. main factors to consider when determining CT parameters
   - high quality for images ensure good soft tussue contrast
   - high DRR resolution
   - minimal artefact (parital volume, motion, high density artefact)

Question 3

What is partial volume effect?

Answer 3

• due to large slice thickness when not scanning helical
• can be created when iterpolation is done (e.g. if doctor wants skull more sup computer will create more data from last image taken and is not accurate

Question 4

What is motion artefact?

Answer 4

• due to breathing
• longer can takes more motion artefact
• if large patient is saccned to quickly, excess skin will move and create artefact

Question 5

What is the voxel sixe of CT, MRI an PET

Answer 5

• CT: 0.5
• MRI: 0.9
• PET: 4.0

Question 6

Why do we need to consider the kV when not treating on normal machine?

Answer 6

• due to the kV affecting the ct number to relative electron density conversion

Question 7

What is image windowing?

Answer 7

• images are windowed to create the most optimal density for a viewing particular regions
• window level determines mid-range of CT no.
• window width determines upper and lower range of CT no. viewed

Question 8

What are the scan parameters for CT and impact on patient dose?

Answer 8

• mAs: ^ mAs means more x-rays incidnet on patient
• kV: ^ kV menas better penetration gives lower image noise but causes decrease in soft tissue contrast
• FOV
• mutli slice scanning, slice thickness and slice inteval
• pitch

Question 9

What factors impact high axial contrast?

Answer 9

• increases with increased mAs and slice thickness

Question 10

What facots impact DRR resolution?

Answer 10

• increases with small voxels

Question 11

What is the difference between single and multislice scanners?

Answer 11

• scan time is quicker for mutlislice but the scan length is longer