On-Treatment Imaging Two

Question 1

What is Surface Tracking?

Answer 1

• Use the surface of the patient to tract movement
• AlignRT uses a 2/3 camera system
• Images are monitored and automatic shut off occurs

Question 2

How does surface tracking work?

Answer 2

• Reference model is required and is taken at the time of scanning
• System needs to be calibrated with respect to the linac
• Real time analysis is possible so beam is gated
• Can detect movements as low as 0.8mm

Question 3

What are Infrared Fiducials?

Answer 3

• Tracks position of infrared markers similar to tracking of optical box on RPM system
• Cameras track markers
• 1.1mm accuracy

Question 4

What are transponders?

Answer 4

• Implanted beacons
• Externally energised by electromagnetic radiation
• Markers position relative to the isocentre is determined after planning and position with respect to detector array
• Gating can be used

Question 5

How is ultrasound used with radiotherapy?

Answer 5

• Locates prostate, borders between bladder, prostate and rectum noticable
• Guidance of permanent prostate seeds
• Monitoring changes in bladder volume
• Guidance of electron boost and partial breast treatments