Independent dose calculations for commissioning, quality assurance and dose reconstruction of PBS proton therapy

Pencil beam scanning proton therapy allows the delivery of highly conformal dose distributions by delivering several thousand pencil beams. These beams have to be individually optimised and accurately delivered requiring a significant quality assurance workload. In this work we describe a toolkit for independent dose calculations developed at Paul Scherrer Institut which allows for dose reconstructions at several points in the treatment workflow. Quality assurance based on reconstructed dose distributions was shown to be favourable to pencil beam by pencil beam comparisons for the detection of delivery uncertainties and estimation of their effects. Furthermore the dose reconstructions were shown to have a sensitivity of the order of or higher than the measurements currently employed in the clinical verification procedures. The design of the independent dose calculation tool allows for a high modifiability of the dose calculation parameters (e.g. depth dose profiles, angular spatial distributions) allowing for a safe environment outside of the clinical treatment planning system for investigating the effect of such parameters on the resulting dose distributions and thus distinguishing between different contributions to measured dose deviations. The presented system could potentially reduce the amount of patient-specific quality assurance measurements which currently constitute a bottleneck in the clinical workflow.

[1]  H Paganetti,et al.  Accurate Monte Carlo simulations for nozzle design, commissioning and quality assurance for a proton radiation therapy facility. , 2004, Medical physics.

[2]  Martin Grossmann,et al.  More than 10 years experience of beam monitoring with the Gantry 1 spot scanning proton therapy facility at PSI. , 2009, Medical physics.

[3]  L. Xing,et al.  Retrospective IMRT dose reconstruction based on cone-beam CT and MLC log-file. , 2008, International journal of radiation oncology, biology, physics.

[4]  Bijan Arjomandy,et al.  Patient-specific quality assurance for prostate cancer patients receiving spot scanning proton therapy using single-field uniform dose. , 2011, International journal of radiation oncology, biology, physics.

[5]  E Pedroni,et al.  Experimental characterization and physical modelling of the dose distribution of scanned proton pencil beams , 2005, Physics in medicine and biology.

[6]  E Pedroni,et al.  Performance of a fluorescent screen and CCD camera as a two-dimensional dosimetry system for dynamic treatment techniques. , 2000, Medical physics.

[7]  Christian Hilbes,et al.  The PSI Gantry 2: a second generation proton scanning gantry. , 2004, Zeitschrift fur medizinische Physik.

[8]  L. Xing,et al.  Independent monitor unit calculation for intensity modulated radiotherapy using the MIMiC multileaf collimator. , 2002, Medical physics.

[9]  E. Lazzaro,et al.  Phase Space Analysis , 2000 .

[10]  M. V. van Herk,et al.  Replacing pretreatment verification with in vivo EPID dosimetry for prostate IMRT. , 2007, International journal of radiation oncology, biology, physics.

[11]  A. Lomax,et al.  Intensity modulation methods for proton radiotherapy. , 1999, Physics in medicine and biology.

[12]  Cancer Therapy with Protons at Paul Scherrer Institut , 2007, 2007 15th IEEE-NPSS Real-Time Conference.

[13]  Harald Paganetti,et al.  Relative biological effectiveness (RBE) values for proton beam therapy. , 2002, International journal of radiation oncology, biology, physics.

[14]  Alessandra Bolsi,et al.  Treatment planning and verification of proton therapy using spot scanning: initial experiences. , 2004, Medical physics.

[15]  E Pedroni,et al.  Monte Carlo dose calculations for spot scanned proton therapy , 2005, Physics in medicine and biology.

[16]  Michael Fenech,et al.  Mitigating the risk of radiation-induced cancers: limitations and paradigms in drug development , 2014, Journal of radiological protection : official journal of the Society for Radiological Protection.

[17]  E. Pedroni,et al.  Dose calculation models for proton treatment planning using a dynamic beam delivery system: an attempt to include density heterogeneity effects in the analytical dose calculation. , 1999, Physics in medicine and biology.

[18]  Heng Li,et al.  Use of treatment log files in spot scanning proton therapy as part of patient-specific quality assurance. , 2013, Medical physics.

[19]  S Safai,et al.  Proton beam monitor chamber calibration , 2014, Physics in medicine and biology.

[20]  E. Pedroni,et al.  The calibration of CT Hounsfield units for radiotherapy treatment planning. , 1996, Physics in medicine and biology.

[21]  R. Siddon.  Fast calculation of the exact radiological path for a three-dimensional CT array. , 1985, Medical physics.

[22]  M van Herk,et al.  Three-dimensional dose reconstruction of breast cancer treatment using portal imaging. , 2003, Medical physics.

[23]  S B Jiang,et al.  Monte Carlo verification of IMRT dose distributions from a commercial treatment planning optimization system. , 2000, Physics in medicine and biology.