Week 2 - Emerging IGRT Technology Flashcards
Define IGRT
The use of any imaging to aid decision making, whether to treat how to treat and when to treat, gives confidence in treatment delivery
rationale for IGRT in RT
- Increase precision and accuracy in RT planning and radiation delivery leading to reduced toxicity with potential for dose escalation and improved tumour control
- Assess random and systematic errors
- Account for intra and inter fraction error
- Allow for dose escalation
List the benefits of MVCBCT
- Uses standard linac hardware
- Images high density structures without artefact
- Same isocentre of imaging and treatment
List the disadvantages of MVCBCT
- Dose greater than kV
- Low contrast
List the benefits for kV imaging
- Better resolution and contrast than MV
- Lower imaging dose
- Widely available and utilised
List the disadvantage for kV imaging
requires additional LINAC hardware
Discuss the strengths of FMs
- Surrogate of prostate motion
- Very fast method of localisation
- Staff have good confidence when aligning
Discuss the weaknesses of FMs
- Associated expense
- Invasive procedure
- Some patients are ineligible
- Rely on few (3) discrete points to localise the prostate
- Evaluation of nearby organs and deformation of the target is difficult
What is a half fan and full fan filter used for?
Half - chest, abdomen, pelvis
Full - head
Does varian haylacon have MV or KV imaging
Both kV-CBCT (15 seconds) and MV imaging (7 seconds)
What does the Varian Ethos system allow?
- uses AI and machine learning to create contours and generate adapted plans for physician review within minutes, while a patient is on the couch
- Provides diagnostic-quality CBCT images and ability to register images to PET/MR in adaptive workflow using artificial intelligence and machine learning
- assist with decision making guided by AI
What are the differences between CyberKnife and ExacTrac?
ExacTrac has floor mounted kV sources and ceiling mounted aSi detectors
List the benefits of CT based imaging technologies
- Excellent soft tissue visualisation
- Great potential to improve treatment delivery
Describe the confounding factors of CT-on-rails
- Motion between imaging and treatment
- couch sag
- lag between image acquisitions (prostate motion)
- Differences between in-room CT and EPI
- the action of rotating the couch
- EPI image quality and outlining uncertainties
Explain the use of helical tomotherapy
An MV beam source is placed on a ring gantry, a xenon ion chamber array allows CT reconstruction from treatment beam, providing less tissue contrast than kV CT but less artefacts from high-Z material
What were some challenges in the development of MR linacs
- Radiofrequency interference between linac and magnetic filed which affects radiation dose distribution and MR image quality
- increased complexity of imaging will impact clinical decision making
- safety and QA implications
- education (RO and RT staff)
List 4 non-ionising technologies
- Calypso
- 3D ultrasound - clarity
- Optical surface scanning
- MR linac
How is Clarity used in RT?
- US probe calibrated to the same isocentre as the CT
- Reflective markers used to track position
- Volumetric US fused with CT
- Can be used to position patient for treatment
- Verify target position and monitor
when to replan
- disease progression
- disease response
- weight loss
halcyon features
- multi-arc VMAT
- IMRT
- dose rate 800MU/min
- 6MV FFF
- rotations - 4 revolutions per minute
- 100cm bore
clarity system
- 3D ultrasound system
- used for planning and treatment
- can be employed at CT simulation to aid soft tissue visualisation
- ultrasound probe is calibrated to the same isocentre as the CT system
cyberknife process
- fiducial placement
- set up and imaging
- planning
- treatment and follow up
HT imaging
helical tomotherapy
- MV beam source placed on a ring gantry
- xenon ion chamber array allows CT reconstruction from treatment beam
- provides less tissue contrast than kV CT, but less artefacts from high Z material such as metal hips
how does the calypso system work
- was only limited prostate
- continuous, real time imaging of prostate
- non ionising –> no additional dose the the patient
- permanently implanted in the prostate prior to external
beam therapy - transmits RF waves to the Calypso System
- inactive until energised by the Calypso System
