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Conclusion
The use of motion compensation in the delineation of
oesophageal cancers reduced delineated volumes in 2 out
of 4 patients and would be of benefit to spare surrounding
organs at risk.
EP-1719 Diagnostic DSA's, a resource for radiotherapy
treatment planning of AVM's
P. Davenport
1
, M. Javadpour
2
1
St Luke's Radiation Oncology Center, Physics, Dublin,
Ireland
2
Beaumont Hospital, Neurosurgery, Dublin, Ireland
Purpose or Objective
To validate the use of diagnostic digital subtraction
angiograms (DSA) for the radiotherapy treatment planning
of arterial venous malformations (AVM) using a specialised
registration software package.
Material and Methods
A CT, MRI & DSA compatible phantom was constructed
which was used to assist with the calculation of geometric
accuracy of the DSA-MRI registration software, SmartBrush
Angio supplied by Brainlab. This phantom was imaged
using the standard AVM patient care-path for CT, MRI and
DSA. The CT and DSA imaging in this case was imaged with
a stereotactic localisation frame in place which allowed
the scaling of the DSA’s to the CT images. An additional
set of DSA’s were acquired without the localisation frame.
In each case the phantom vessels were contoured on DSA,
MR and CT, the latter being the reference image set.
Clinical validation of the registration software was
completed for two patients. After the registration of both
the radiotherapy treatment planning ( localised) and
diagnostic (non-localised) DSA’s to the MR, the feeding
arteries and the draining veins were delineated on the
localised and non-localised imaging sets.
An analysis of the accuracy of the registrations was
calculated using the Hausdorff distance metric.
Results
The phantom vessels were divided into two sets, the upper
loop (UL) and the lower loop (LL) for analysis. The UL
consisted of a single vessel traversing the X,Y & Z planes
while the LL traversed the X & Z planes only. Using the
Hausdorff distance metric a result of 0.41 mm and 0.85
mm displacement for the UL and LL respectively was
calculated.
A similar result was found for two clinical cases analysed,
a Hausdorff distance of <0.8 mm for the feed artery and
drain vein.
Conclusion
Based on the results of both the phantom study and the
clinical data, the use of non-localised diagnostic DSA’s
could be used to assist with the radiotherapy treatment
planning of AVM’s. This negates the need to perform an
invasive localised DSA in the majority of cases thereby
reducing risks associated with this procedure.
EP-1720 Framework for Statistical Cone-Beam CT
Reconstruction with Prior Monte-Carlo Scatter
Estimation
J. Mason
1
, M. Davies
1
, W. Nailon
2
1
University of Edinburgh, Institute for Digital
Communications, Edinburgh, United Kingdom
2
Oncology Physics Department, Edinburgh Cancer Centre,
Edinburgh, United Kingdom
Purpose or Objective
Scatter from the patient and detector leads to significant
inaccuracies and artefacts in cone-beam computed
(CBCT). Monte-Carlo (MC) methods may allow the scatter
signal to be accurately estimated based on a prior scan,
but this must be matched and calculated for the new cone-
beam measurements, and incorporated appropriately into
a reconstruction method. We investigate a framework for
statistical reconstruction with these prior MC estimates,
under various work-flows.
Material and Methods