Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
AB S TRACT
: To further investigate the effects of respiratory motions
on CBCT imaging, as well as 4D-CT examinations, with a future goal
of using obtained results to implement new methods for individual
margins and daily matching procedures into routine clinical practice.
: Since the implementation of CBCT combined with
modern accelerators, a higher degree of accuracy has been made possible
in RT. However, due to the slow gantry speed of linear accelerators,
the imaging procedure of CBCT is a slow process which is
thereby degraded by internal motion such as respiration.
material and methods
: Attain patient specific respiratory motion
patterns from CBCT projection data of previous examinations.
Utilize this data to perform simulations for both CBCT and 4D-CT
using a steering system which allows for arbitrary motion patterns in
the longitudinal direction.
: Various imaging with CBCT showed that the resulting
images during respiratory motion, can be described by the Probability
Density Function of the motion for as long as it does not cause related
distortions. This also meant that convolution could be implemented
as a model to estimate the CBCT images during oscillation, knowing
the object and motion pattern.
The 4D-CT examinations using the steering system showed that
irregular motion patterns were less accurately described than regular
patterns, making the actual motion an important feature to combine
together with the measured amplitude.
: It was made clear that CBCT images can be described
by the PDF, and thus can be seen as a Color Intensity Projection
of the object position. Also it has been shown that the projection
data of CBCT images contains valuable information about the respiratory
motion of the patient.
Another conclusion is that with the help of fiducials, the position
of the target within the respiratory cycle can be determined relative
to the 4D-CT examination, enabling further input data as to the daily
matching procedure, proper applied margins as well as dose to the
2012. , 70 p.
Toma-Dasu, Iuliana, Docent/Associate ProfessorWennberg, Berit, PhDSorcini, Bruno, PhD