Strahlentherapie und Onkologie

, Volume 190, Issue 1, pp 94–99 | Cite as

Interfractional variability in intensity-modulated radiotherapy of prostate cancer with or without thermoplastic pelvic immobilization

  • J.A. Lee
  • C.Y. Kim
  • Y.J. Park
  • W.S. Yoon
  • N.K. Lee
  • D.S. Yang
Original article

Abstract

Purpose

To determine the variability of patient positioning errors associated with intensity-modulated radiotherapy (IMRT) for prostate cancer and to assess the impact of thermoplastic pelvic immobilization on these errors using kilovoltage (kV) cone-beam computed tomography (CBCT).

Materials and methods

From February 2012 to June 2012, the records of 314 IMRT sessions in 19 patients with prostate cancer, performed with or without immobilization at two different facilities in the Korea University Hospital were analyzed. The kV CBCT images were matched to simulation computed tomography (CT) images to determine the simulation-to-treatment variability. The shifts along the x (lateral)-, y (longitudinal)- and z (vertical)-axes were measured, as was the shift in the three dimensional (3D) vector.

Results

The measured systematic errors in the immobilized group during treatment were 0.46 ± 1.75 mm along the x-axis, − 0.35 ± 3.83 mm along the y-axis, 0.20 ± 2.75 mm along the z-axis and 4.05 ± 3.02 mm in the 3D vector. Those of nonimmobilized group were − 1.45 ± 7.50 mm along the x-axis, 1.89 ± 5.07 mm along the y-axis, 0.28 ± 3.81 mm along the z-axis and 8.90 ± 4.79 mm in the 3D vector. The group immobilized with pelvic thermoplastics showed reduced interfractional variability along the x- and y-axes and in the 3D vector compared to the nonimmobilized group (p < 0.05).

Conclusion

IMRT with thermoplastic pelvic immobilization in patients with prostate cancer appears to be useful in stabilizing interfractional variability during the planned treatment course.

Keywords

Image-guided radiotherapy Organs at risk Cone-beam computed tomography Immobilization Dose–response relationship 

Interfraktionelle Variabilität der intensitätsmodulierten Strahlentherapie bei Prostatakrebs mit oder ohne thermoplastische Beckenfixierung

Zusammenfassung

Ziel

Ziel der Studie war es, die Fehlervariabilität der intensitätsmodulierten Strahlentherapie (IMRT) bei der Patientenpositionierung bei Prostatakrebs zu bestimmen und die Auswirkungen der thermoplastischen Beckenfixierung auf diesen Fehler mit der Kilovolt-(KV-)Cone-Beam-Computertomographie (CBCT) zu beurteilen.

Material und Methoden

Von Februar 2012 bis Juni 2012 wurden die Datensätze von 314 Sitzungen von 19 Patienten mit Prostatakrebs, die mittels IMRT mit oder ohne Immobilisierung an zwei verschiedenen Einrichtungen des Korea University Hospital behandelt wurden, analysiert. Die KV-CBCT-Bilder wurden mit der Simulation der Computertomographie-(CT-)Bilder abgestimmt, um die Variabilität zwischen Simulation und Behandlung zu bestimmen. Es wurden die Verschiebungen entlang der x-(lateral), y-(Längs-), z-Achse (vertikal) und im 3-D-Vektor gemessen

Ergebnisse

Die gemessenen systematischen Fehler der immobilisierten Gruppe während der Behandlung waren 0,46 ± 1,75 mm entlang der x-Achse, − 0,35 ± 3,83 mm entlang der y-Achse, 0,20 ± 2,75 mm entlang der z-Achse und 4,05 ± 3,02 mm im 3-D-Vektor. Die Fehler der nichtimmobilisierten Gruppe waren − 1,45 ± 7,50 mm entlang der x-, 1,89 ± 5,07 mm entlang der y-, 0,28 ± 3,81 mm entlang der z-Achse und 8,90 ± 4,79 mm im 3-D-Vektor. Im Vergleich zur nichtimmobilisierten Gruppe zeigte die mittels Becken-Thermoplast fixierte Gruppe eine geringere interfraktionelle Variabilität in der x- und y-Achse sowie im 3-D-Vektor (p < 0,05).

Schlussfolgerungen

Bei Patienten mit Prostatakrebs scheint die IMRT mit thermoplastischer Beckenfixierung bei der Stabilisierung der interfraktionellen Variabilität während der geplanten Behandlung nützlich zu sein.

Schlüsselwörter

Intensitätsmodulierte Strahlentherapie Risikoorgane Cone-Beam-Computertomographie Fixierung Dosis-Antwort-Beziehung 

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Copyright information

© Springer Heidelberg Berlin 2013

Authors and Affiliations

  • J.A. Lee
    • 1
  • C.Y. Kim
    • 1
  • Y.J. Park
    • 1
  • W.S. Yoon
    • 1
  • N.K. Lee
    • 1
  • D.S. Yang
    • 1
  1. 1.Department of Radiation OncologyKorea University Guro Hospital, Korea University College of MedicineSeoulRepublic of Korea

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