Increasing treatment accuracy for cervical cancer patients using correlations between bladder-filling change and cervix-uterus displacements: Proof of principle

Rozilawati Ahmad, Mischa S. Hoogeman, Maria Bondar, V. Dhawtal, Sandra Quint, Ilse De Pree, Jan Willem Mens, Ben J M Heijmen

Research output: Contribution to journalArticle

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Abstract

Purpose: To investigate application of pre-treatment established correlations between bladder-filling changes and cervix-uterus displacements in adaptive therapy. Materials and methods: Thirteen cervical cancer patients participated in this prospective study. Pre-treatment, and after delivery of 40 Gy, a full bladder CT-scan was acquired, followed by voiding the bladder and acquisition of 4 other 3D scans in a 1 h period with a naturally filling bladder (variable bladder filling CT-scans, VBF-scans). For the pre-treatment VBF-scans, linear correlations between bladder volume change and displacements of the tip of the uterus (ToU) and the center of mass (CoM) of markers implanted in the fornices of the vagina relative to the full bladder planning scan were established. Prediction accuracy of these correlation models was assessed by comparison with actual displacements in CT-scans, both pre-treatment and after 40 Gy. Inter-fraction ToU and marker-CoM displacements were derived from the established correlations and twice-weekly performed in-room bladder volume measurements, using a 3D ultrasound scanner. Results: Target displacement in VBF-scans ranged from up to 65 mm in a single direction to almost 0 mm, depending on the patient. For pre-treatment VBF-scans, the linear correlation models predicted the mean 3D position change for the ToU of 26.1 mm ± 10.8 with a residual of only 2.2 mm ± 1.7. For the marker-CoM, the 8.4 mm ± 5.3 mean positioning error was predicted with a residual of 0.9 mm ± 0.7. After 40 Gy, the mean ToU displacement was 26.8 mm ± 15.8, while prediction based on the pre-treatment correlation models yielded a mean residual error of 9.0 mm ± 3.7. Target positioning errors in the fractioned treatments were very large, especially for the ToU (-18.5 mm ± 11.2 for systematic errors in SI-direction). Conclusions: Pre-treatment acquired VBF-scans may be used to substantially enhance treatment precision of cervical cancer patients. Application in adaptive therapy is promising and warrants further investigation. For highly conformal (IMRT) treatments, the use of a full bladder drinking protocol results in unacceptably large systematic set-up errors.

Original languageEnglish
Pages (from-to)340-346
Number of pages7
JournalRadiotherapy and Oncology
Volume98
Issue number3
DOIs
Publication statusPublished - Mar 2011

Fingerprint

Cervix Uteri
Uterine Cervical Neoplasms
Urinary Bladder
Uterus
Therapeutics
Vagina
Drinking
Linear Models
Prospective Studies

Keywords

  • Adaptive RT
  • Bladder volume
  • Cervix cancer
  • Internal-organ motion
  • Radiotherapy

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Hematology

Cite this

Increasing treatment accuracy for cervical cancer patients using correlations between bladder-filling change and cervix-uterus displacements : Proof of principle. / Ahmad, Rozilawati; Hoogeman, Mischa S.; Bondar, Maria; Dhawtal, V.; Quint, Sandra; De Pree, Ilse; Mens, Jan Willem; Heijmen, Ben J M.

In: Radiotherapy and Oncology, Vol. 98, No. 3, 03.2011, p. 340-346.

Research output: Contribution to journalArticle

Ahmad, Rozilawati ; Hoogeman, Mischa S. ; Bondar, Maria ; Dhawtal, V. ; Quint, Sandra ; De Pree, Ilse ; Mens, Jan Willem ; Heijmen, Ben J M. / Increasing treatment accuracy for cervical cancer patients using correlations between bladder-filling change and cervix-uterus displacements : Proof of principle. In: Radiotherapy and Oncology. 2011 ; Vol. 98, No. 3. pp. 340-346.
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abstract = "Purpose: To investigate application of pre-treatment established correlations between bladder-filling changes and cervix-uterus displacements in adaptive therapy. Materials and methods: Thirteen cervical cancer patients participated in this prospective study. Pre-treatment, and after delivery of 40 Gy, a full bladder CT-scan was acquired, followed by voiding the bladder and acquisition of 4 other 3D scans in a 1 h period with a naturally filling bladder (variable bladder filling CT-scans, VBF-scans). For the pre-treatment VBF-scans, linear correlations between bladder volume change and displacements of the tip of the uterus (ToU) and the center of mass (CoM) of markers implanted in the fornices of the vagina relative to the full bladder planning scan were established. Prediction accuracy of these correlation models was assessed by comparison with actual displacements in CT-scans, both pre-treatment and after 40 Gy. Inter-fraction ToU and marker-CoM displacements were derived from the established correlations and twice-weekly performed in-room bladder volume measurements, using a 3D ultrasound scanner. Results: Target displacement in VBF-scans ranged from up to 65 mm in a single direction to almost 0 mm, depending on the patient. For pre-treatment VBF-scans, the linear correlation models predicted the mean 3D position change for the ToU of 26.1 mm ± 10.8 with a residual of only 2.2 mm ± 1.7. For the marker-CoM, the 8.4 mm ± 5.3 mean positioning error was predicted with a residual of 0.9 mm ± 0.7. After 40 Gy, the mean ToU displacement was 26.8 mm ± 15.8, while prediction based on the pre-treatment correlation models yielded a mean residual error of 9.0 mm ± 3.7. Target positioning errors in the fractioned treatments were very large, especially for the ToU (-18.5 mm ± 11.2 for systematic errors in SI-direction). Conclusions: Pre-treatment acquired VBF-scans may be used to substantially enhance treatment precision of cervical cancer patients. Application in adaptive therapy is promising and warrants further investigation. For highly conformal (IMRT) treatments, the use of a full bladder drinking protocol results in unacceptably large systematic set-up errors.",
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AU - Bondar, Maria

AU - Dhawtal, V.

AU - Quint, Sandra

AU - De Pree, Ilse

AU - Mens, Jan Willem

AU - Heijmen, Ben J M

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N2 - Purpose: To investigate application of pre-treatment established correlations between bladder-filling changes and cervix-uterus displacements in adaptive therapy. Materials and methods: Thirteen cervical cancer patients participated in this prospective study. Pre-treatment, and after delivery of 40 Gy, a full bladder CT-scan was acquired, followed by voiding the bladder and acquisition of 4 other 3D scans in a 1 h period with a naturally filling bladder (variable bladder filling CT-scans, VBF-scans). For the pre-treatment VBF-scans, linear correlations between bladder volume change and displacements of the tip of the uterus (ToU) and the center of mass (CoM) of markers implanted in the fornices of the vagina relative to the full bladder planning scan were established. Prediction accuracy of these correlation models was assessed by comparison with actual displacements in CT-scans, both pre-treatment and after 40 Gy. Inter-fraction ToU and marker-CoM displacements were derived from the established correlations and twice-weekly performed in-room bladder volume measurements, using a 3D ultrasound scanner. Results: Target displacement in VBF-scans ranged from up to 65 mm in a single direction to almost 0 mm, depending on the patient. For pre-treatment VBF-scans, the linear correlation models predicted the mean 3D position change for the ToU of 26.1 mm ± 10.8 with a residual of only 2.2 mm ± 1.7. For the marker-CoM, the 8.4 mm ± 5.3 mean positioning error was predicted with a residual of 0.9 mm ± 0.7. After 40 Gy, the mean ToU displacement was 26.8 mm ± 15.8, while prediction based on the pre-treatment correlation models yielded a mean residual error of 9.0 mm ± 3.7. Target positioning errors in the fractioned treatments were very large, especially for the ToU (-18.5 mm ± 11.2 for systematic errors in SI-direction). Conclusions: Pre-treatment acquired VBF-scans may be used to substantially enhance treatment precision of cervical cancer patients. Application in adaptive therapy is promising and warrants further investigation. For highly conformal (IMRT) treatments, the use of a full bladder drinking protocol results in unacceptably large systematic set-up errors.

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