Real-time energy/mass transfer mapping for online 4D dose reconstruction

In this work we describe an ultra-fast, low-latency implementation of the energy/mass transfer (EMT) mapping method to accumulate dose on deforming geometries such as lung using the central processing unit (CPU). It enables the computation of the actually delivered dose for intensity-modulated radiation therapy on 4D image data in real-time at 25 Hz. In order to accumulate the delivered dose onto a reference phase a pre-calculated deformable vector field is used. The aim of this study is to present an online dose accumulation technique that can be carried out in less than 40 ms to accommodate the machine log update rate of our research linac. Three speed optimisation strategies for the CPU are discussed: single-core optimisation, parallelisation for multiple cores and vectorisation. The single-core implementation accumulates dose in about 1.1 s on a typical high resolution grid for a lung stereotactic body radiation therapy case. Adding parallelisation decreased the runtime to about 50 ms while adding vectorisation satisfied our real-time constraint by further reducing the dose accumulation time to 15 ms without compromising on resolution or accuracy. The presented method allows real-time dose accumulation on deforming patient geometries and has the potential to enable online dose evaluation and re-planning scenarios.

[1]  Indrin J Chetty,et al.  Dose reconstruction in deforming lung anatomy: dose grid size effects and clinical implications. , 2005, Medical physics.

[2]  Harald Paganetti,et al.  Monte Carlo simulations with time-dependent geometries to investigate effects of organ motion with high temporal resolution. , 2004, International journal of radiation oncology, biology, physics.

[3]  Iwan Kawrakow,et al.  Investigation of voxel warping and energy mapping approaches for fast 4D Monte Carlo dose calculations in deformed geometries using VMC++. , 2011, Physics in medicine and biology.

[4]  M Glitzner,et al.  On-line MR imaging for dose validation of abdominal radiotherapy , 2015, Physics in medicine and biology.

[5]  G S Bauman,et al.  Tracking the dose distribution in radiation therapy by accounting for variable anatomy , 2004, Physics in medicine and biology.

[6]  S Nill,et al.  Assessment of MLC tracking performance during hypofractionated prostate radiotherapy using real-time dose reconstruction , 2016, Physics in medicine and biology.

[7]  Jan-Jakob Sonke,et al.  Adaptive radiotherapy for lung cancer. , 2010, Seminars in radiation oncology.

[8]  Hualiang Zhong,et al.  An energy transfer method for 4D Monte Carlo dose calculation. , 2008, Medical physics.

[9]  Markus Alber,et al.  Adaptive radiotherapy for advanced lung cancer ensures target coverage and decreases lung dose. , 2016, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[10]  Peter Ziegenhein,et al.  Real‐time 4D dose reconstruction for tracked dynamic MLC deliveries for lung SBRT , 2016, Medical physics.

[11]  Michael K Fix,et al.  Monte Carlo dose calculation on deforming anatomy. , 2011, Zeitschrift fur medizinische Physik.

[12]  Martin F Fast,et al.  Dynamic tumor tracking using the Elekta Agility MLC. , 2014, Medical physics.

[13]  Carri Glide-Hurst,et al.  Direct dose mapping versus energy/mass transfer mapping for 4D dose accumulation: fundamental differences and dosimetric consequences , 2014, Physics in medicine and biology.

[14]  K. Brock,et al.  Use of image registration and fusion algorithms and techniques in radiotherapy: Report of the AAPM Radiation Therapy Committee Task Group No. 132 , 2017, Medical physics.

[15]  Rafael García-Mollá,et al.  Validation of a deformable image registration produced by a commercial treatment planning system in head and neck. , 2015, Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics.

[16]  Peter Ziegenhein,et al.  Performance-optimized clinical IMRT planning on modern CPUs , 2013, Physics in medicine and biology.

[17]  Hualiang Zhong,et al.  Monte Carlo dose mapping on deforming anatomy , 2009, Physics in medicine and biology.

[18]  Stina Svensson,et al.  The ANACONDA algorithm for deformable image registration in radiotherapy. , 2014, Medical physics.

[19]  이윤석.  Report of the AAPM Radiation Therapy Committee의 Task Group No.66에 의한 전산화 단층촬영 모의치료기의 정도 관리 , 2005 .

[20]  Jan Seuntjens,et al.  A direct voxel tracking method for four-dimensional Monte Carlo dose calculations in deforming anatomy. , 2006, Medical physics.