BACKGROUND AND PURPOSE: Image-guided on-line correction of the target position allows radiotherapy of prostate cancer with narrow set-up margins. The present study investigated the residual set-up error after on-line prostate localization and its impact on margins. MATERIALS AND METHODS: Prostate localization based on two orthogonal X-ray images of gold markers implanted in the prostate was performed with an on-board imager at four treatment sessions for 90 patients. The set-up error in the sagittal plane residual after couch adjustment was evaluated on lateral verification portal images. RESULTS: The set-up error was less than 3.0mm in 92% of the cases in the anterior-posterior (AP) direction and in 95% of the cases in the cranio-caudal (CC) direction. The set-up error was dominated by internal prostate motion taking place during the set-up procedure. Set-up margins were calculated using two formalisms: margins designed to ensure a minimum CTV dose of 95% for 90% of the patient population were 3.6mm (AP) and 3.5mm (CC). Patient-independent normal distributed set-up errors would result in margins of 4.3mm (AP) and 4.0mm (CC) to ensure complete CTV inclusion in the PTV with 90% probability. CONCLUSION: Internal prostate motion during the set-up procedure was the main contributor to residual set-up errors.
BACKGROUND AND PURPOSE: Image-guided on-line correction of the target position allows radiotherapy of prostate cancer with narrow set-up margins. The present study investigated the residual set-up error after on-line prostate localization and its impact on margins. MATERIALS AND METHODS: Prostate localization based on two orthogonal X-ray images of gold markers implanted in the prostate was performed with an on-board imager at four treatment sessions for 90 patients. The set-up error in the sagittal plane residual after couch adjustment was evaluated on lateral verification portal images. RESULTS: The set-up error was less than 3.0mm in 92% of the cases in the anterior-posterior (AP) direction and in 95% of the cases in the cranio-caudal (CC) direction. The set-up error was dominated by internal prostate motion taking place during the set-up procedure. Set-up margins were calculated using two formalisms: margins designed to ensure a minimum CTV dose of 95% for 90% of the patient population were 3.6mm (AP) and 3.5mm (CC). Patient-independent normal distributed set-up errors would result in margins of 4.3mm (AP) and 4.0mm (CC) to ensure complete CTV inclusion in the PTV with 90% probability. CONCLUSION: Internal prostate motion during the set-up procedure was the main contributor to residual set-up errors.
Authors: X J Juan-Senabre; J López-Tarjuelo; A Conde-Moreno; A Santos-Serra; A L Sánchez-Iglesias; J D Quirós-Higueras; N de Marco Blancas; S Calzada-Feliu; C Ferrer-Albiach Journal: Clin Transl Oncol Date: 2011-11 Impact factor: 3.405
Authors: S Gill; J Thomas; C Fox; T Kron; A Thompson; S Chander; S Williams; K H Tai; G Duchesne; F Foroudi Journal: Br J Radiol Date: 2011-10-05 Impact factor: 3.039
Authors: Morten Høyer; Maria Thor; Sara Thörnqvist; Jimmi Søndergaard; Yasmin Lassen-Ramshad; Ludvig Paul Muren Journal: Cancer Imaging Date: 2011-10-03 Impact factor: 3.909