What is the standard prescription range according to the slides for conventional RT? correct answers1.8-2.4Gy/ 15-40 fractions, 3 to 8 weeks
What is the standard prescription range according to the slides for Stereotactic body radiotherapy? correct answersGreater than 8Gy per fraction and up to ...
What is the standard prescription range according to the slides for conventional RT? correct answers1.8-
2.4Gy/ 15-40 fractions, 3 to 8 weeks
What is the standard prescription range according to the slides for Stereotactic body radiotherapy?
correct answersGreater than 8Gy per fraction and up to 30Gy per fraction. 1-5 fractions within 1-2
weeks. Some tumours are not hypoxic and therefore do not benefit from reoxygenation time. This
method allows for less normal tissue irradiation, smaller treatment volumes/margins which is enabled
through image guided and motion management technologies
What is the abscopal effect? correct answersThe abscopal effect is the reaction to which cells that are
not directly irradiated show signs of radiation damage. This is shown by tumour regression in non
irradiated tumours. These responses indicate that the target size of the responding tissue is larger than
the treatment field
What do we treat with SBRT? correct answers- primary and secondary tumours - oligometastatic state
- less than 5cm maximum dimension
- Non metastatic conditions such as spinal cord AVM, meningioma
- Tumours generally considered radioresistent with conventionally fractionated radiotherapy such as
renal cell and melanomas
- For abaltion such as lung and liver
- for dose escalation e.g prostate, spinal cord
What is an oligometastic state? correct answersThis term indicates a state between purely localised
disease and widespread metastatic disease.
Why SABR? correct answers- it can be used to treatment inoperable diseases which are inoperable due
to tumour location or medical comorbidities
- Technological advances image guidance means that we can deliver highly conformal dosimetry, dose
delivery and improvements in motion management strategies. SABR does not have the associated cost
and patient recovery of surgery and can produce comparable results
,What is the goal of imaging? correct answersto provide visualization of patient anatomy as it will appear
at treatment in order to delineate targets AND critical normal tissues and calculate optimal dosimetry
What are some imaging types for SABR? correct answersMRI, PET, CT, 4DCT, inhale, exhale, FB, contrast,
MIP, Ave IP
• Matched to treatment position - Assess suitability, Liaise with local MI dept and scan the patient in
treatment position (e.g. limbs, prostate)
What are some imaging artefacts? correct answersmotion, metal implants (prothetics, fillings etc), CT
myelogram for spine patients with post operative hardware, image distortion for PET and MRI. PET
should not be used for tumour delineation, just to identify sites of active disease.
Registration error is a significant factor in the treatment process
What are some patient considerations for SABR treatment? correct answers1.
Comprehension/understanding - greater chance of success if the patient is a contributing participant
2. Pain control/management - should be well controlled before attempting simulation
3. Mobility/co-morbidities
--> need to hold treatment position
--> positioning aides/accessories need to be made so that the patient can readily get into and out of the
treatment position, without leaning on and potentially displacing or deforming the equipment e.g.
vacbags
4. Breath hold? > Coaching!
What are some positioning considerations for SBRT? correct answers1. Comfortable & reproducible -
treatment times can exceed 1 hour per fraction
2. Enable delivery of technique to achieve dosimetric goals
, • Allow good access to the target
• Minimise dose to normal tissues
• Minimise restrictions on beam angle choice
• Consider arm or head position, position of tubing for body fix, position of loc bars or joins in the bed
• Accommodate equipment e.g. Hexapod
frame, compression belt/bellows
• Avoid creating build up with equipment
Why is it good to have test runs for SABR treatments? correct answers- Small rotational corrections can
require large translational moves
- Poorly constructed immobilisation can result in gantry collisions
- Check breath hold reproducibility for DIBH/EEBH
- Check tumour excursion
- Check visibility of lesion & surrounding anatomy on CBCT imaging (limited FoV)
What is the patient education process? correct answers1. Patient Information sheets & Pre-CT checklist
2. Long consultation with Radiation Oncologist
3. Pre-CT consultation with Radiation Therapist (motion management,
fasting, organ filling/voiding alongside normal education for RT)
4. Post-CT and Pre-Treatment consultation with Nursing staff and
Radiation Therapists
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