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"Imaging with CBCT and 4D-CT of objects moving with respiratory motions"
Stockholm University, Faculty of Science, Medical Radiation Physics (together with KI). Stockholm University, Faculty of Science, Department of Physics.
2012 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]



: 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


Place, publisher, year, edition, pages
2012. , 70 p.
Keyword [en]
Medical Physicist, Radiotherapy, SBRT, CBCT, 4D-CT
Keyword [sv]
Sjukhusfysik, Strålbehandling, SBRT, CBCT, 4D-CT
National Category
Other Physics Topics
URN: urn:nbn:se:su:diva-89053OAI: diva2:615450
2012-09-20, 12:14 (English)
Physics, Chemistry, Mathematics
Available from: 2013-06-26 Created: 2013-04-10 Last updated: 2013-06-26Bibliographically approved

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Lindbäck, Elias
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