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Daily isocenter correction with electromagnetic-based localization improves target coverage and rectal sparing during
Ramji Ramaswamy Rajendran1, John P Plastaras, Rosemarie Mick
1Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA 19104, USA.
Summary
Daily isocenter correction using the Calypso 4D localization system in prostate cancer radiation therapy significantly reduces rectal dose. This improves treatment accuracy, potentially lowering side effects and enhancing outcomes.
Area of Science:
- Radiation oncology
- Medical physics
- Image-guided radiation therapy
Background:
- Prostate cancer radiation therapy requires precise targeting.
- Daily setup variations can lead to inaccurate dose delivery.
- The Calypso 4D localization system offers real-time target tracking.
Purpose of the Study:
- To assess the dosimetric impact of daily isocenter corrections during prostate cancer radiotherapy.
- To evaluate the effectiveness of the Calypso 4D localization system for isocenter alignment.
Main Methods:
- Analyzed data from 28 patients with implanted prostate transponders.
- Compared isocenter locations from skin tattoos versus electromagnetic localization.
- Calculated daily isocenter shifts and their dosimetric consequences.
Main Results:
- Significant daily isocenter shifts (up to 62% beyond 0.5 cm) were observed in vertical, longitudinal, and lateral axes.
- Without daily localization, rectum received 10 Gy excess dose, and PTV had a 10 Gy deficit.
- Isocenter shifts were not correlated with patient or organ volumes.
Conclusions:
- Daily isocenter localization with the Calypso system improves rectal dose sparing.
- Implementing daily corrections enhances dose delivery accuracy.
- This approach may reduce treatment-related side effects and improve patient outcomes.
