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Strahlentherapie und Onkologie

, Volume 193, Issue 6, pp 459–465 | Cite as

Prefraction displacement and intrafraction drift of the prostate due to perineal ultrasound probe pressure

  • Minglun Li
  • Nina-Sophie Hegemann
  • Farkhad Manapov
  • Anne Kolberg
  • Patrick Dominik Thum
  • Ute Ganswindt
  • Claus Belka
  • Hendrik BallhausenEmail author
Original Article

Abstract

Objective

In image-guided EBRT of the prostate, transperineal ultrasound (US) probes exert pressure on the perineum both during planning and treatment. Through tissue deformation and relaxation, this causes target and risk organ displacement and drift. In this study, prefraction shift and intrafraction drift of the prostate are quantified during robotic transperineal 4DUS.

Methods

The position of the prostate was recorded for different positions of the probe before treatment in 10 patients (16 series of measurements). During treatment (15 patients, 273 fractions), intrafraction motion of the prostate was tracked (total of 27 h and 24 min) with the transperineal probe in place.

Results

Per 1 mm shift of the US probe in the cranial direction, a displacement of the prostate by 0.42 ± 0.09 mm in the cranial direction was detected. The relationship was found to be linear (R² = 0.97) and highly significant (p < 0.0001). After initial contact of the probe and the perineum (no pressure), a shift of the probe of about 5–10 mm was typically necessary to achieve good image quality, corresponding to a shift of the prostate of about 2–4 mm in the cranial direction. Tissue compression and prostate displacement were well visible. During treatment, the prostate drifted at an average rate of 0.075 mm/min in the cranial direction (p = 0.0014).

Conclusion

The pressure applied by a perineal US probe has a quantitatively similar impact on prostate displacement as transabdominal pressure. Shifts are predominantly in the cranial direction (typically 2–4 mm) with some component in the anterior direction (typically <1 mm). Slight probe pressure can improve image quality, but excessive probe pressure can distort the surrounding anatomy and potentially move risk organs closer to the high-dose area.

Keywords

External beam radiotherapy Transperineal ultrasound Patient positioning Intrafraction motion Quality assurance 

Präfraktionelle Verschiebung und intrafraktionelle Drift der Prostata durch Druck perinealer Ultraschallköpfe

Zusammenfassung

Zielsetzung

In der bildgeführten Strahlentherapie der Prostata üben perineale Ultraschallköpfe während Planung und Behandlung Druck auf das Perineum aus. Durch Gewebedeformation verursacht dies Verschiebungen von Zielvolumen und Risikoorganen. In dieser Studie werden Verschiebungen vor und Relaxationen während der Behandlung unter transperinealem orts- und zeitaufgelöstem Ultraschall (US) quantifiziert.

Methoden

Vor der Behandlung (10 Patienten, 16 Messreihen) wurde die Lage der Prostata bei verschiedenen Schallkopfpositionen aufgezeichnet. Während der Behandlung (15 Patienten, 273 Fraktionen) mit anliegender perinealer Probe wurde die intrafraktionelle Bewegung der Prostata aufgezeichnet (insgesamt 27 h 24 min).

Ergebnisse

Pro 1 mm Verschiebung des Schallkopfs nach kranial verschob sich die Prostata um 0,42 ± 0,09 mm, ebenfalls in kranialer Richtung. Der Zusammenhang war linear (R² = 0,97) und hoch signifikant (p < 0,0001). Nach drucklosem Kontakt des US-Kopfs war für eine gute Bildqualität eine Verschiebung in das Perineum um typischerweise 5–10 mm notwendig, was einer Verschiebung der Prostata von etwa 2–4 mm in kranialer Richtung entspricht. Gewebedeformation und Prostataverschiebung waren deutlich sichtbar. Während der Behandlung driftete die Prostata mit einer mittleren Rate von 0,075 mm/min in kranialer Richtung (p = 0,0014).

Schlussfolgerung

Der Druck des perinealen Schallkopfs hat ähnlich großen Einfluss auf die Lage der Prostata, wie derjenige eines abdominellen. Verschiebungen geschehen hauptsächlich in kranialer Richtung (typisch 2–4 mm) mit einer geringen Komponente in ventraler Richtung (typisch <1 mm). Mäßiger Druck des Schallkopfs kann die Bildqualität verbessern, übergroßer Druck jedoch die umliegende Anatomie verformen und potentiell Risikoorgane in Regionen höherer Dosis verschieben.

Schlüsselwörter

Externe Strahlentherapie Transperinealer Ultraschall Patientenpositionierung  Intrafraktionelle Bewegung Qualitätssicherung 

Notes

Acknowledgements

We thank Andrea Beisel, Gabriela Danilkiewicz, Sandra Kohlhauser, and Anja Weber for their excellent technical assistance.

Funding

Funding for research with the Clarity system has been received from Elekta. Elekta was not involved in and had no influence on the study design, the collection, analysis, or interpretation of data, on the writing of the manuscript or the decision to submit the manuscript for publication.

Compliance with ethical guidelines

Conflict of interest

Elekta Germany supports research at the university hospital of Ludwig-Maximilians-Universität, chaired by Professor Belka. Elekta supported various congress presentations by C. Belka and M. Li. N.-S. Hegemann, F. Manapov, A. Kolberg, P.D. Thum, U. Ganswindt and H. Ballhausen declare that they have no competing interests.

Ethical standards

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.Department of Radiation OncologyLMU MunichMunichGermany
  2. 2.University Hospital of LMU MunichMunichGermany

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