Technische Evaluierung, Verifikation und klinische Einführung eines Patienten-Oberflächen-Überwachungssystems für strahlentherapeutische Behandlungen im Bereich des Kopfes
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Philipps-Universität Marburg
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Abstract
For radiotherapies in the region of the head, a precise positioning and stable alignment of the patient is necessary. The usage of a surface guidance system in combination with a system to immobilize the patient, which is suitable for the detection of the patient's surface, represents a solution for the positioning and the monitoring of this position. State of the art of immobilizations for radiotherapies in the region of the head are thermoplastic mask systems. But there is a collective of patients, who does not tolerate the usage of a conventional thermoplastic mask system. A surface guidance system got the potential make a radiotherapy for these patients possible. Nevertheless, before the usage of such a system, the stability and accuracy for the south art of patient positioning has to be evaluated under clinical circumstances.
The aims of this work lead to the clinical implementation of a surface guidance system for radiotherapies in the region of the head under the usage of different immobilization systems. It will be investigated, which amount of accuracy and stability can be reached with a surface guidance system installed at the University Hospital of Marburg. Furthermore, the question will be answered, if such a system offers the possibility to treat patients, which do not tolerate any type of thermoplastic mask. Another point of this work is the question, under which circumstances the rate of imaging using ionizing radiation can be reduced under the usage of a reduced of a thermoplastic mask leaving the face open.
To evaluate the accuracy and stability of the system, different measurements in terms of time and different positions where performed using an anthropomorphic head phantom. For a time period of 15 minutes it was shown that the stability of the system is within 0.10° and 0.1mm, if the field of view is not in blocked in any part. In the case of such a blockage, the stability still lies within 0.10° and 0.2mm. In terms of the accuracy, deviations showed a maximum of 0.3° and 1.1mm$, however this amount of deviations occurred for extreme differences between the sought and the actual position. Under clinical circumstances, the errors resulting from the deviations could be determined about 0.1° and a maximum of 0.32mm. Moreover, a certain systematic was detected between rotational and translational movements.
The investigation of a collective of 14 volunteers showed a maximum movement of the head of 0.22° and 2.2mm on average away from the original position. With the examination of 17 therapies of a collective of patients immobilized with an open mask, it was shown that the accuracy and stability of this positioning is clearly more precise than the positioning with a conventional mask with markers on it. Within common durations of a radiotherapy, the movement of this patients was below 1 mm and thus comparable to the possible movements inside a conventional mask. For different scenarios regarding lesions of different dimensions inside the region of the head and different rates of imaging using ionizing radiation, the margins needed between the clinical and the planning target volume where calculated. For example, for a 10 cm cerebral lesion treated with fractionated radiotherapy, the imaging can be reduced to every other day with an expansion of the margins below 1 mm and with an expansion of about 1,5 mm, only imaging once a week is necessary. Additionally, a case study with the treatment of two patients, which did not tolerate any type of thermoplastic mask, was performed.
Overall, trough the technical evaluation of the surface guidance system, a better understanding of the system has arisen. Additionally, it was shown that the systems accuracy and stability meet the requirements for correct and precise positioning for radiotherapy in the region of the head. Also, it was shown, that a stable positioning without the usage of an individual immobilization system is possible. Furthermore, the usage of the surface guidance system eliminates the possibility of human failure. It was pointed out, that the margins for the usage of a conventional mask system and the investigated open mask system are equivalent. Nevertheless, with the usage of this surface guidance system, the margins can be increased in a small amount to reduce the rate of imaging using ionizing radiation. In single cases, this can lead to the same success of the therapy following the ALARA principles. Additionally, it was shown that a successful treatment of patients not tolerating any thermoplastic mask is suitable with the usage of a surface guidance system. Inferring, all goals of this work were reached successfully and a routine for the implementation of the investigated surface guidance systems in the clinical workflow of the University Hospital Marburg was developed.
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Created: 2020Issued: 2025-06-23Updated: 2025-06-23
Faculty
Medizin
Publisher
Philipps-Universität Marburg
Language
ger
Data types
DoctoralThesis
Keywords
Oberflächengestützte StrahlentherapieSurface Guided Radiation TherapyRadiotherapyStereotactic Radiotherapy
DFG-subjects
StereotaxieStrahlentherapie
DDC-Numbers
610
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Rauwald-Josephs, Patrick: Technische Evaluierung, Verifikation und klinische Einführung eines Patienten-Oberflächen-Überwachungssystems für strahlentherapeutische Behandlungen im Bereich des Kopfes. : Philipps-Universität Marburg 2025-06-23. DOI: https://doi.org/10.17192/z2020.0426.