IGRT Prostate – the ADHB
experience
Nicola Gordon
Imaging Specialist RT
ADHB
A little history…
• 2009 – Orthogonal EPIs #1-3 and weekly –
Radiation Oncologists reviewed images
• 2010 – Introduction of fiducial markers for
daily IGRT and RT led image review began
• Late 2010 – first CBCT capable Linac went
clinical – CBCT used for some trial patients
• 2011 – began using CBCT to monitor bowel
and bladder status on a weekly basis
• Mid 2012 – started using VMAT routinely
Why CBCT?
Evolution of process
• CBCT then kV imaging #1-3 & weekly
• kV then CBCT #1-3 & weekly
– Patients asking if it was a scan day
– General lack of understanding from patients
• kV then CBCT daily
Bladder and Bowel Advice
Bladder filling decision rule
• 50Gy Isodose curve (maroon) used as minimum bladder
filling point.
Rectal filling.
• If fiducial match fit was
good on kV imaging
then treatment
continued, with CBCT
only for feedback.
• If fiducial match fit was
not acceptable then the
CBCT was used to
assess why.
But…
• 2 imaging modalities in each fraction for
fiducial patients
• goes against ALARA principle
• Time an issue – increased risk of intrafraction
motion.
• Effectively soft tissue matching even with
fiducials
Soft tissue matching
• Some inappropriate
fiducial positioning
• Patients who were not
suitable for fiducials
• Prostate Bed patients
had soft tissue
matching
• Consultants preferred
fiducials for the
majority of patients
Asking our colleagues…
• 5 departments use Elekta XVI to match to fiducials on CBCT
daily
• 1 department using Elekta XVI to match soft tissue on
CBCT daily
• 1 department using Siemens to match soft tissue on CBCT
daily
• 2 departments using Varian/ARIA to match to soft tissue
on CBCT daily
• 5 departments using Varian/ARIA to match to fiducials on
kV daily
• 1 department using Varian/ARIA to match to fiducials on
CBCT #1-3 and weekly and using kV on the other fractions.
Using CBCT to match fiducials
• Varian OBI gives only couch corrections that
can be applied
• Matches done without rotation so need to be
‘best fit’
• If unable to align all 3 fiducials there is
probably a reason!
How to visualise
Fiducial Contour
Colour Blend
Automatch settings.
• Bounding Box to cover PTV then use Intensity range and
structure VOI of the PTV for automatch.
The process as it stands now
•
•
•
•
Automatch
Manual adjustment as required
Fiducial match fit
Decision to treat based on bladder and bowel
filling
• Dose escalation to 78 Gy
Current Rectum Decision Rules
• Rectum should not be displaced more than 1cm
anteriorly into the PTV contour.
Rectum decision rules
Before:
28 Minutes later:
Video of process
Other initiatives
•
•
•
•
Updated (simplified) Dietary Advice
Weekly MDT ‘On Treatment Chart Round’
Interventions such as ‘tubing’
MOODLEs
Time…
Post Treatment CBCT study:
• Prostate VMAT with Fiducials 6 Min
• Prostate VMAT without Fiducials 7.5 Min
• Prostate Bed VMAT 6.94 Min
• Prostate IMRT (Soft Tissue Match) 12.94 Min
Intra-Fraction Movement - Range
• Fiducials: -0.7 to +0.6 (max -0.7 vrt)
• Non Fiducials: -0.4 to +0.2 (max -0.4 vrt)
• Prostate Bed: -0.5 to +0.5 (max -0.5 vrt)
• Prostate IMRT (longer treatment time): -0.3 to
+0.4, (max +0.4 - lng)
Moving forwards…
• No more fiducial markers!
• Finish Accuracy Study
• Look at toxicity scores
Thanks
• Helen McCabe and the team on MV4 for all
their help with Data collection and feedback
• Sheonagh Nielson
• Rob Lane
• All those who responded to the questions we
sent out
References
• Moseley DJ. White EA. Wiltshire KL. Rosewall T. Sharpe MB. Siewerdsen JH.
Bissonnette JP. Gospodarowicz M. Warde P. Catton CN. Jaffray DA.
Comparison of localization performance with implanted fiducial markers
and cone-beam computed tomography for on-line image-guided
radiotherapy of the prostate. International Journal of Radiation Oncology,
Biology, Physics. 67(3):942-53, 2007 Mar 1.
• Lazos et al, (2012)
http://astro2012.abstractsnet.com/handouts/011498_Shifts_Study_ASTR
O2012_Poster.pdf
• Shi W. Li JG. Zlotecki RA. Yeung A. Newlin H. Palta J. Liu C. Chvetsov AV.
Olivier K; Evaluation of kV Cone-Beam CT Performance for Prostate IGRT
American Journal of Clinical Oncology. 34(1):16-21, 2011 Feb.
• NHS (UK) National Cancer Action Team National Radiotherapy
Implementation Group Report on IGRT – Guidance for Implementation
and Use, August 2012 – Section 18.5