PURPOSE: Intrafraction rotation of more than 45° and 25° has been observed for lung and prostate tumors, respectively. Such rotation is not routinely adapted to during current radiotherapy, which may compromise tumor dose coverage. The aim of the study was to investigate the geometric and dosimetric performance of an electromagnetically guided real-time dynamic multileaf collimator (DMLC) tracking system to adapt to intrafractional tumor rotation. MATERIALS/ METHODS: Target rotation was provided by changing the treatment couch angle. The target rotation was measured by a research Calypso system integrated with a real-time DMLC tracking system employed on a Varian linac. The geometric beam-target rotational alignment difference was measured using electronic portal images. The dosimetric accuracy was quantified using a two-dimensional ion chamber array. For each beam, the following five delivery modes were tested: 1) nonrotated target (reference); 2) fixed rotated target with tracking; 3) fixed rotated target without tracking; 4) actively rotating target with tracking; and 5) actively rotating target without tracking. Dosimetric performance of the latter four modes was measured and compared to the reference dose distribution using a 3 mm/3% γ-test. RESULTS: Geometrically, the beam-target rotational alignment difference was 0.3° ± 0.6° for fixed rotation and 0.3° ± 1.3° for active rotation. Dosimetrically, the average failure rate for the γ-test for a fixed rotated target was 11% with tracking and 36% without tracking. The average failure rate for an actively rotating target was 9% with tracking and 35% without tracking. CONCLUSIONS: For the first time, real-time target rotation has been accurately detected and adapted to during radiation delivery via DMLC tracking. The beam-target rotational alignment difference was mostly within 1°. Dose distributions to fixed and actively rotating targets with DMLC tracking were significantly superior to those without tracking.
PURPOSE: Intrafraction rotation of more than 45° and 25° has been observed for lung and prostate tumors, respectively. Such rotation is not routinely adapted to during current radiotherapy, which may compromise tumor dose coverage. The aim of the study was to investigate the geometric and dosimetric performance of an electromagnetically guided real-time dynamic multileaf collimator (DMLC) tracking system to adapt to intrafractional tumor rotation. MATERIALS/ METHODS: Target rotation was provided by changing the treatment couch angle. The target rotation was measured by a research Calypso system integrated with a real-time DMLC tracking system employed on a Varian linac. The geometric beam-target rotational alignment difference was measured using electronic portal images. The dosimetric accuracy was quantified using a two-dimensional ion chamber array. For each beam, the following five delivery modes were tested: 1) nonrotated target (reference); 2) fixed rotated target with tracking; 3) fixed rotated target without tracking; 4) actively rotating target with tracking; and 5) actively rotating target without tracking. Dosimetric performance of the latter four modes was measured and compared to the reference dose distribution using a 3 mm/3% γ-test. RESULTS: Geometrically, the beam-target rotational alignment difference was 0.3° ± 0.6° for fixed rotation and 0.3° ± 1.3° for active rotation. Dosimetrically, the average failure rate for the γ-test for a fixed rotated target was 11% with tracking and 36% without tracking. The average failure rate for an actively rotating target was 9% with tracking and 35% without tracking. CONCLUSIONS: For the first time, real-time target rotation has been accurately detected and adapted to during radiation delivery via DMLC tracking. The beam-target rotational alignment difference was mostly within 1°. Dose distributions to fixed and actively rotating targets with DMLC tracking were significantly superior to those without tracking.
Authors: Paul J Keall; Emma Colvill; Ricky O'Brien; Jin Aun Ng; Per Rugaard Poulsen; Thomas Eade; Andrew Kneebone; Jeremy T Booth Journal: Med Phys Date: 2014-02 Impact factor: 4.071
Authors: Tobias Pommer; Marianne Falk; Per R Poulsen; Paul J Keall; Ricky T O'Brien; Peter Meidahl Petersen; Per Munck af Rosenschöld Journal: Phys Med Biol Date: 2013-03-14 Impact factor: 3.609
Authors: Ilana Feain; Chun-Chien Shieh; Paul White; Ricky O'Brien; Sandra Fisher; William Counter; Peter Lazarakis; David Stewart; Simon Downes; Michael Jackson; Siddhartha Baxi; Brendan Whelan; Kuldeep Makhija; Chen-Yu Huang; Michael Barton; Paul Keall Journal: Adv Radiat Oncol Date: 2016-11-08
Authors: Casper Gammelmark Muurholm; Thomas Ravkilde; Robin De Roover; Simon Skouboe; Rune Hansen; Wouter Crijns; Tom Depuydt; Per R Poulsen Journal: Med Phys Date: 2022-04-25 Impact factor: 4.506