AbstractID: 8962 Title: QA and assessment of image registration for planning treatments
in Head and Neck.
With the advent of image registration/ fusion software in commercial treatment planning systems the widespread use of MR imaging
is becoming feasible. We are currently implementing its use for Head and Neck Radiotherapy planning, which involves its registration
with CT. The Quality Assurance (QA) of the registration process, presented here, was an initial step of this program.
A phantom was built and experiments were performed to identify appropriate materials providing clinically relevant MR T1 and T2
contrast. Distortion effects, detectable within our phantom, were shown to be minimised by choosing a suitable (≥ ± 30kHz) receiver
bandwidth. The remaining distortion was deemed clinically acceptable within ±15 cm of the magnetic field isocentre. An assessment
of the accuracy of the image registration process within our (CMS XiO) treatment planning system was performed; Each structure was
contoured using each modality, in turn, blind of the other. The position, area and perimeter of each structure were assessed as a
measure of accuracy of the entire image registration process. A coefficient of agreement (A) analysis gave values to be within 9% of
unity, where A2 = (Ra × Rp) and Ra/p is the ratio of the area/perimeter of a particular structure on CT to that on MR. The coordinates of
the centre of each structure agreed to within 1.8 mm.
A QA process has been developed to assess the accuracy of using multi-modality image registration in the planning of Radiotherapy
for the Head and Neck; We believe its introduction is feasible and safe.