eprintid: 35770
rev_number: 21
eprint_status: archive
userid: 8627
dir: disk0/00/03/57/70
datestamp: 2025-03-26 15:07:26
lastmod: 2025-04-10 07:05:01
status_changed: 2025-03-26 15:07:26
type: doctoralThesis
metadata_visibility: show
creators_name: Weidner, Artur
title: An abdominal phantom with anthropomorphic
organ motion and multimodal imaging
contrast for magnetic-resonance-guided
radiotherapy
subjects: ddc-004
subjects: ddc-530
subjects: ddc-540
subjects: ddc-610
subjects: ddc-620
subjects: ddc-660
divisions: i-911400
adv_faculty: af-05
abstract: The continuous progress in the field of radiation therapy has led to significant improvements
in the diagnosis and treatment of cancer, resulting in enhanced quality of life and increased life
expectancy. The development of the MR-Linac marked a paradigm shift in radiation therapy.
This advancement enables real-time visualization of tumors during radiation therapy using
magnetic resonance imaging. Consequently, treatment plans can be adjusted to account for
changes in tumor size between sessions, such as tumor shrinkage, and to incorporate tumor
movements during each radiation session, for example, due to breathing. This precision allows
for the delivery of a higher radiation dose directly to the target volume while minimizing
radiation exposure to nearby organs.
The aim of this work was to develop an anthropomorphic abdominal phantom that meets
several requirements: reproducible breathing motions with induced organ motions in a
composite, realistic image contrast in both magnetic resonance imaging and computed
tomography, anthropomorphically shaped organ models, and an MRI-compatible motion
control unit.
In this thesis, an innovative anthropomorphic abdominal phantom for medical imaging and
radiation therapy applications was developed. Through a series of experiments and analyses,
the capabilities and usefulness of the phantom were rigorously evaluated.
The organ models used in the experiments demonstrate remarkable accuracy in replicating the
relaxation times and Hounsfield Units of real human organs. This validation underscores the
suitability of the phantom for medical imaging research, with the results showing close
agreement with reference values without significant differences.
Comparisons between the phantom and patient/volunteer data showed good agreement in
simulating respiration-induced organ motions in a composite during various breathing patterns
(shallow, free, and deep breathing), anatomical shapes, image contrast, and radiological
characteristics.
Furthermore, the analysis of organ motion under different breathing patterns highlights the
phantom's ability to simulate human organ movements, emphasizing the importance of
considering organ motions in treatment planning and imaging procedures.
In summary, this work demonstrated that the developed phantom effectively simulates various
respiratory movements and corresponding organ motions within a composite structure.
Additionally, compared to volunteer data, the phantom exhibited comparable image contrast
in magnetic resonance imaging and computed tomography imaging, and stability of image
contrast over a period of more than 400 days was demonstrated. Moreover, the phantom proved
suitable for an end-to-end test, encompassing the entire radiation therapy process from imaging
and radiation planning to dose calculation and delivery. This included the insertion of
dosimetric EBT3 films into the liver tumor model. An important outcome was that the
phantom's liver tumor model was successfully detected by the MR-Linac and radiation was
stopped as soon as the tumor moved outside the target volume due to breathing motion.
Ultimately, a dose of 5.3 ± 0.42 Gy was calculated within the tumor model, which demonstrates
excellent alignment with the planned dose of 5 Gy, considering the minimal deviation.
date: 2025
id_scheme: DOI
id_number: 10.11588/heidok.00035770
ppn_swb: 1922047406
own_urn: urn:nbn:de:bsz:16-heidok-357700
date_accepted: 2025-02-14
advisor: HASH(0x55602a801898)
language: eng
bibsort: WEIDNERARTANABDOMINA20250214
full_text_status: public
place_of_pub: Heidelberg
citation:   Weidner, Artur  (2025) An abdominal phantom with anthropomorphic organ motion and multimodal imaging contrast for magnetic-resonance-guided radiotherapy.  [Dissertation]     
document_url: https://archiv.ub.uni-heidelberg.de/volltextserver/35770/1/Weidner_Artur_08_12_1990_Dissertation.pdf