Nicola Abigail Rosenfelder1, Lee Corsini2, Helen McNair2, Kjell Pennert3, Alexandra Aitken2, Caroline Mary Lamb4, Michelle Long4, Enrico Clarke5, Mauricio Murcia5, Ulrike Schick5, Kevin Burke4, Sue Ashley6, Vincent Khoo5, Michael Brada6. 1. Department of Clinical Oncology, Royal Marsden NHS Foundation Trust, London, United Kingdom. Electronic address: nrosenfelder@gmail.com. 2. Department of Radiotherapy, Royal Marsden NHS Foundation Trust, London, United Kingdom. 3. Statistics Unit, Royal Marsden NHS Foundation Trust, London, United Kingdom. 4. Department of Physics, Royal Marsden NHS Foundation Trust, London, United Kingdom. 5. Department of Clinical Oncology, Royal Marsden NHS Foundation Trust, London, United Kingdom. 6. Neuro-oncology Unit, Royal Marsden NHS Foundation Trust, London, United Kingdom.
Abstract
PURPOSE: Prospectively compare patient setup accuracy and intrafraction motion of a standard 3-point thermoplastic mask with the Gill-Thomas-Cosman relocatable stereotactic frame, during fractionated cranial radiation therapy using the ExacTrac system (Brainlab AG Feldkirchen, Germany) for daily online correction. METHODS AND MATERIALS: The number of fractions with all postcorrection and post-treatment errors <2 mm was assessed in 21 patients undergoing fractionated stereotactic radiation therapy (13 frame setup, 8 mask setup) using daily online correction. Achievable patient setup accuracy and total intrafraction motion were evaluated. The relative contributions of movement during floor rotation and patient movement to intrafraction motion were calculated. RESULTS: With daily online correction, patient setup margins can be reduced from 1, 5, and 4 mm in the lateral, longitudinal, and vertical axes for mask setup and from 1-2, 2, and 1 mm, respectively, for frame setup to <1 mm isotropically for either immobilization system. Intrafraction movement was small for frame setup (mean [SD], -0.3 [0.3], -1.1[0.4], and -0.2 [0.6] in lateral, longitudinal and vertical axes, respectively; maximum, -2.7 mm [longitudinal axis]), and mask-setup (mean [SD], -0.4 [0.5], -0.8 [0.7], and 0.0 [0.3], respectively; maximum, -2.0 mm [longitudinal axis]) and is mainly due to floor rotation. Postcorrection and post-treatment errors were all <2 mm in 95% and 99% of fractions in the mask and frame, respectively, meeting the criteria for a 3-mm clinical target volume-planning target volume margin for either immobilization method. CONCLUSIONS: Daily online correction can compensate for less precise immobilization and permits stereotactic margins to be used for standard thermoplastic masks without the need for specialized mask systems.
PURPOSE: Prospectively compare patient setup accuracy and intrafraction motion of a standard 3-point thermoplastic mask with the Gill-Thomas-Cosman relocatable stereotactic frame, during fractionated cranial radiation therapy using the ExacTrac system (Brainlab AG Feldkirchen, Germany) for daily online correction. METHODS AND MATERIALS: The number of fractions with all postcorrection and post-treatment errors <2 mm was assessed in 21 patients undergoing fractionated stereotactic radiation therapy (13 frame setup, 8 mask setup) using daily online correction. Achievable patient setup accuracy and total intrafraction motion were evaluated. The relative contributions of movement during floor rotation and patient movement to intrafraction motion were calculated. RESULTS: With daily online correction, patient setup margins can be reduced from 1, 5, and 4 mm in the lateral, longitudinal, and vertical axes for mask setup and from 1-2, 2, and 1 mm, respectively, for frame setup to <1 mm isotropically for either immobilization system. Intrafraction movement was small for frame setup (mean [SD], -0.3 [0.3], -1.1[0.4], and -0.2 [0.6] in lateral, longitudinal and vertical axes, respectively; maximum, -2.7 mm [longitudinal axis]), and mask-setup (mean [SD], -0.4 [0.5], -0.8 [0.7], and 0.0 [0.3], respectively; maximum, -2.0 mm [longitudinal axis]) and is mainly due to floor rotation. Postcorrection and post-treatment errors were all <2 mm in 95% and 99% of fractions in the mask and frame, respectively, meeting the criteria for a 3-mm clinical target volume-planning target volume margin for either immobilization method. CONCLUSIONS: Daily online correction can compensate for less precise immobilization and permits stereotactic margins to be used for standard thermoplastic masks without the need for specialized mask systems.
Authors: Ashley E Rubinstein; W Scott Ingram; Brian M Anderson; Skylar S Gay; Xenia J Fave; Rachel B Ger; Rachel E McCarroll; Constance A Owens; Tucker J Netherton; Kelly D Kisling; Laurence E Court; Jinzhong Yang; Yuting Li; Joonsang Lee; Dennis S Mackin; Carlos E Cardenas Journal: J Appl Clin Med Phys Date: 2017-06-06 Impact factor: 2.102