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Evaluation of intrafractional motion for patients receiving whole brain radiotherapy in open-faced immobilisation masks

Falk, Sara (2023) MSFT02 20232
Medical Physics Programme
Abstract
Purpose/Background
Patients receiving whole brain radiotherapy (WBRT) today are treated with an immobilisation mask which fully covers their face and therefore might be experienced as uncomfortable and claustrophobic. In recent years, optical surface scanning (OSS) systems have been implemented for patient positioning and real-time motion monitoring [1]. OSS systems cannot track the patients surface through the closed masks and are therefore only monitoring the motion of the mask. Using open-faced immobilisation masks would allow the OSS to monitor the patient directly, but may allow for more movement. The purpose of this thesis was to evaluate the intrafractional motion of WBRT patients receiving treatment in open-faced immobilisation... (More)
Purpose/Background
Patients receiving whole brain radiotherapy (WBRT) today are treated with an immobilisation mask which fully covers their face and therefore might be experienced as uncomfortable and claustrophobic. In recent years, optical surface scanning (OSS) systems have been implemented for patient positioning and real-time motion monitoring [1]. OSS systems cannot track the patients surface through the closed masks and are therefore only monitoring the motion of the mask. Using open-faced immobilisation masks would allow the OSS to monitor the patient directly, but may allow for more movement. The purpose of this thesis was to evaluate the intrafractional motion of WBRT patients receiving treatment in open-faced immobilisation masks.

Material and Method
The accuracy of the x-ray and surface imaging system (EXTD) was investigated using two different rigid head phantoms with internal bony anatomy for matching purposes. The surface imaging is dependant on the phantoms optical characteristics [1] and therefore two different skin colours were used. The phantoms were placed on the treatment couch in nine different rotational angles and the position was verified with CBCT (Cone Beam Computed Tomography). The surface imaging and x-ray systems were compared to the CBCT using a Wilcoxon signed-rank test (α=0.05). The patients included in this study all received WBRT in open-faced immobilisation masks and were monitored using the combined surface and x-ray imaging capabilities of the ExacTrac Dynamic system. In total, 25 treatment fractions from 5 patients were analysed.

Results
Overall, both x-ray and surface imaging agreed with the CBCT within 0.4 degrees for all investigated angles. The largest deviation was 0.4 degrees and 0.3 degrees in pitch and yaw rotations for the x-ray imaging and surface imaging, respectively. No statistically significant difference was found between the x-ray and CBCT in the roll direction (p>0.05, both phantoms). For the other rotational directions there was a statistically significant difference (p<0.05) between the x-ray and the CBCT for both phantoms and all directions showed a statistically significant difference (p<0.05) between the surface and the CBCT for both phantoms.
For all five patients, the median (range) translational vector was 0.3 (0.0-1.3) mm, and 95% of the vector deviations were within 0.7 mm. For the individual translational directions, the absolute median (range) was found to be 0.1 (0.0-1.0) mm in lateral (lat), 0.2 (0.0-1.1) mm in longitudinal (long), and 0.1 (0.0-0.7) mm in vertical (vert), respectively, and for the rotational directions 0.1 (0.0-0.8) degrees in pitch, 0.1 (0.0-0.7) degrees in roll, and 0.1 (0.0-0.7) degrees in yaw, respectively. 95% of the deviations were within 0.4 mm in lat, 0.6 mm in long, 0.3 mm in vert, 0.5 degrees in pitch, 0.3 degrees in roll, and 0.5 degrees in yaw.

Conclusion
For the two head phantoms, excellent agreement was observed for both x-ray and surface imaging compared to CBCT (within 0.4 degrees), which fulfills the QA guidelines published by ESTRO-ACROP and AAPM TG-302 [1,2]. The EXTD system's accuracy showed no dependance on the colouring of the phantoms. This study shows that the surface guidance real time tracking of the patient's rigid face structures can detect submillimeter patient motion and in combination with its beam hold capabilities, deliver a high-accuracy treatment in the open face masks. The median intrafraction motion observed was 0.3 mm for all patients, and hence, open-faced masks can further be investigated for other patient groups. (Less)
Popular Abstract
Antalet cancerpatienter i Sverige ökar och varje år diagnostiseras över 60 000 fall. Den vanligaste formen av hjärncancer är hjärnmetastaser, som uppstår då cancer som har börjat någon annanstans i kroppen sprider sig till hjärnan. Hjärntumörer kan ge många symptom, såsom huvudvärk, balansproblem, illamående osv. och kan behandlas med läkemedel, kirurgi eller strålning. För patienter med många hjärnmetastaser ges en palliativ (symptomlindrande) behandling där hela hjärnan bestrålas.

För att behandlingen ska ges korrekt är det viktigt att patienten ligger stilla och att de ligger likadant vid varje behandlingstillfälle, varför patienten fixeras under behandling. För patienter som får strålbehandling mot hjärnan används konventionellt en... (More)
Antalet cancerpatienter i Sverige ökar och varje år diagnostiseras över 60 000 fall. Den vanligaste formen av hjärncancer är hjärnmetastaser, som uppstår då cancer som har börjat någon annanstans i kroppen sprider sig till hjärnan. Hjärntumörer kan ge många symptom, såsom huvudvärk, balansproblem, illamående osv. och kan behandlas med läkemedel, kirurgi eller strålning. För patienter med många hjärnmetastaser ges en palliativ (symptomlindrande) behandling där hela hjärnan bestrålas.

För att behandlingen ska ges korrekt är det viktigt att patienten ligger stilla och att de ligger likadant vid varje behandlingstillfälle, varför patienten fixeras under behandling. För patienter som får strålbehandling mot hjärnan används konventionellt en heltäckande plastmask som gjuts efter patientens huvud och fästs i britsen. De övervakas också under behandling med ett optiskt ytskanningssystem (OSS-system), som skannar av patientens yta och beräknar dennes position i rummet kontinuerligt. Eftersom fixationsmasken täcker patientens huvud kommer OSS-systemet endast att upptäcka hur masken rör sig, vilket inte nödvändigtvis är detsamma som patienten. För en noggrann rörelseövervakning vill vi kunna övervaka patienten direkt. Dessutom är fixationsmasken ofta obehaglig för patienter och en källa till behandlingsrelaterad ångest för många.

På grund av detta finns en önskan att börja använda så kallade öppna masker istället som har en öppning över patientens ansikte. Det skulle möjliggöra OSS-systemet att övervaka patientens yta över ansiktet och därmed upptäcka patientens rörelser, inte bara maskens. En öppen mask är även mindre obehaglig för patienten. Dessa masker skulle dock kunna tillåta att patienten rör sig mer inuti masken jämfört med en heltäckande mask.

Detta examensarbete undersöker mängden rörelse under behandling för patienter som får strål-behandling mot hela hjärnan i en öppen fixationsmask. Under behandlingen övervakas patienterna med OSS-systemet som då också samlar in data om patienternas rörelser. 5 patienter som fick behandling under 5 tillfällen vardera inkluderades i studien och därmed kunde rörelsedata från 25 behandlingstillfällen analyseras. Den eventuella påverkan på kvaliteten på behandlingen från patienternas rörelser undersöktes även.

Arbetets resultat visar på att patienternas rörelser under behandling i den öppna masken ligger inom gränserna för vad som kliniskt kan accepteras och att påverkan på behandlingskvaliteten var försumbar. Detta innebär att dessa masker kan börja användas för alla patienter som får behandling mot hela hjärnan i kliniken, i kombination med ett OSS-system som övervakar patienten i real-tid. (Less)
Please use this url to cite or link to this publication:
author
Falk, Sara
supervisor
organization
course
MSFT02 20232
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
9139558
date added to LUP
2023-10-04 19:59:58
date last changed
2023-10-04 19:59:58
@misc{9139558,
  abstract     = {{Purpose/Background
Patients receiving whole brain radiotherapy (WBRT) today are treated with an immobilisation mask which fully covers their face and therefore might be experienced as uncomfortable and claustrophobic. In recent years, optical surface scanning (OSS) systems have been implemented for patient positioning and real-time motion monitoring [1]. OSS systems cannot track the patients surface through the closed masks and are therefore only monitoring the motion of the mask. Using open-faced immobilisation masks would allow the OSS to monitor the patient directly, but may allow for more movement. The purpose of this thesis was to evaluate the intrafractional motion of WBRT patients receiving treatment in open-faced immobilisation masks.

Material and Method
The accuracy of the x-ray and surface imaging system (EXTD) was investigated using two different rigid head phantoms with internal bony anatomy for matching purposes. The surface imaging is dependant on the phantoms optical characteristics [1] and therefore two different skin colours were used. The phantoms were placed on the treatment couch in nine different rotational angles and the position was verified with CBCT (Cone Beam Computed Tomography). The surface imaging and x-ray systems were compared to the CBCT using a Wilcoxon signed-rank test (α=0.05). The patients included in this study all received WBRT in open-faced immobilisation masks and were monitored using the combined surface and x-ray imaging capabilities of the ExacTrac Dynamic system. In total, 25 treatment fractions from 5 patients were analysed.

Results
Overall, both x-ray and surface imaging agreed with the CBCT within 0.4 degrees for all investigated angles. The largest deviation was 0.4 degrees and 0.3 degrees in pitch and yaw rotations for the x-ray imaging and surface imaging, respectively. No statistically significant difference was found between the x-ray and CBCT in the roll direction (p>0.05, both phantoms). For the other rotational directions there was a statistically significant difference (p<0.05) between the x-ray and the CBCT for both phantoms and all directions showed a statistically significant difference (p<0.05) between the surface and the CBCT for both phantoms.
For all five patients, the median (range) translational vector was 0.3 (0.0-1.3) mm, and 95% of the vector deviations were within 0.7 mm. For the individual translational directions, the absolute median (range) was found to be 0.1 (0.0-1.0) mm in lateral (lat), 0.2 (0.0-1.1) mm in longitudinal (long), and 0.1 (0.0-0.7) mm in vertical (vert), respectively, and for the rotational directions 0.1 (0.0-0.8) degrees in pitch, 0.1 (0.0-0.7) degrees in roll, and 0.1 (0.0-0.7) degrees in yaw, respectively. 95% of the deviations were within 0.4 mm in lat, 0.6 mm in long, 0.3 mm in vert, 0.5 degrees in pitch, 0.3 degrees in roll, and 0.5 degrees in yaw.

Conclusion
For the two head phantoms, excellent agreement was observed for both x-ray and surface imaging compared to CBCT (within 0.4 degrees), which fulfills the QA guidelines published by ESTRO-ACROP and AAPM TG-302 [1,2]. The EXTD system's accuracy showed no dependance on the colouring of the phantoms. This study shows that the surface guidance real time tracking of the patient's rigid face structures can detect submillimeter patient motion and in combination with its beam hold capabilities, deliver a high-accuracy treatment in the open face masks. The median intrafraction motion observed was 0.3 mm for all patients, and hence, open-faced masks can further be investigated for other patient groups.}},
  author       = {{Falk, Sara}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Evaluation of intrafractional motion for patients receiving whole brain radiotherapy in open-faced immobilisation masks}},
  year         = {{2023}},
}