Development and commissioning of a full‐size prototype fixed‐beam radiotherapy system with horizontal patient rotation

PURPOSE Compared to conventional linacs with rotating gantries, a fixed-beam radiotherapy system could be smaller, more robust and more cost-effective. In this work, we developed and commissioned a prototype x-ray radiotherapy system utilizing a fixed vertical radiation beam and horizontal patient rotation. METHODS The prototype system consists of an Elekta Synergy linac with gantry fixed at 0° and a custom-built patient rotation system (PRS). The PRS was designed to immobilize patients and safely rotate them about the horizontal axis. The interlocks and emergency stops of the linac and PRS were connected. Custom software was developed to monitor the system status, control the motion of the PRS and modify treatment plans for the fixed-beam configuration. Following installation, the prototype system was commissioned for three-dimensional (3D) conformal therapy based on guidelines specified in AAPM TG-45 and TG-142, with modifications for the fixed-beam geometry made where necessary. RESULTS The system and control software was tested in a variety of machine states and executed motion, stop and beam gating commands as expected. Interlocks and emergency stops of the linac and PRS were found to correctly stop PRS motion and both kV and MV radiation beams when triggered. For 3D conformal treatments, the prototype system met all AAPM TG-45 and TG-142 specifications for geometric and dosimetric accuracy. Motion of the PRS was within 0.6 ± 0.3 mm and 0.10° ± 0.07° of input values for translation and rotation respectively. The axis of rotation of the PRS was coincident with the radiation beam axis to less than 1 mm. End-to-end treatment verification for 6 MV conformal treatments showed less than 2% difference between planned and delivered dose for all fields. CONCLUSION In this work, we have developed and commissioned a radiotherapy system that utilizes a fixed vertical radiation beam and horizontal patient rotation. This system is a proof-of-concept prototype for a fixed-beam treatment system without a rotating gantry. Fixed-beam systems that are smaller and more cost-effective could help in improving global access to radiotherapy.

[1]  Paul J Keall,et al.  The first clinical implementation of real-time image-guided adaptive radiotherapy using a standard linear accelerator. , 2018, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[2]  Paul J Keall,et al.  Cone-beam CT reconstruction with gravity-induced motion. , 2018, Physics in medicine and biology.

[3]  Ilana Feain,et al.  Technical Note: The design and function of a horizontal patient rotation system for the purposes of fixed‐beam cancer radiotherapy , 2017, Medical physics.

[4]  Timothy P Hanna,et al.  Estimating the demand for radiotherapy from the evidence: a review of changes from 2003 to 2012. , 2014, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[5]  Paul J Keall,et al.  The Nano-X Linear Accelerator , 2015, Technology in cancer research & treatment.

[6]  David M. Shepard,et al.  Delivery efficiency of an Elekta linac under gated operation , 2014, Journal of applied clinical medical physics.

[7]  Jan-Jakob Sonke,et al.  The first implementation of respiratory triggered 4DCBCT on a linear accelerator , 2016, Physics in medicine and biology.

[8]  Fang-Fang Yin,et al.  Task Group 142 report: quality assurance of medical accelerators. , 2009, Medical physics.

[9]  G Baroni,et al.  Commissioning and Quality Assurance of an Integrated System for Patient Positioning and Setup Verification in Particle Therapy , 2014, Technology in cancer research & treatment.

[10]  Michael Baumann,et al.  Expanding global access to radiotherapy. , 2015, The Lancet. Oncology.

[11]  Paul J Keall,et al.  A CBCT study of the gravity-induced movement in rotating rabbits , 2018, Physics in medicine and biology.

[12]  P J Keall,et al.  Technical Note: Real‐time image‐guided adaptive radiotherapy of a rigid target for a prototype fixed beam radiotherapy system , 2018, Medical physics.

[13]  Yolande Lievens,et al.  Cost evaluation to optimise radiation therapy implementation in different income settings: A time-driven activity-based analysis. , 2017, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[14]  Paul Keall,et al.  Functional imaging equivalence and proof of concept for image-guided adaptive radiotherapy with fixed gantry and rotating couch , 2016, Advances in radiation oncology.

[15]  Thomas Bortfeld,et al.  Evolution of technology to optimize the delivery of proton therapy: the third generation. , 2013, Seminars in radiation oncology.

[16]  Fang-Fang Yin,et al.  Dosimetric feasibility of cone-beam CT-based treatment planning compared to CT-based treatment planning. , 2006, International journal of radiation oncology, biology, physics.

[17]  Jürgen Debus,et al.  Robotic-based carbon ion therapy and patient positioning in 6 degrees of freedom: setup accuracy of two standard immobilization devices used in carbon ion therapy and IMRT , 2012, Radiation Oncology.

[18]  Lei Dong,et al.  Advantages of simulating thoracic cancer patients in an upright position. , 2014, Practical radiation oncology.

[19]  Ning Wang,et al.  Commissioning of a proton gantry equipped with dual x-ray imagers and a robotic patient positioner, and evaluation of the accuracy of single-beam image registration for this system. , 2015, Medical physics.

[20]  L. Feldkamp,et al.  Practical cone-beam algorithm , 1984 .

[21]  Michael B. Sharpe,et al.  IAEA Technical Reports Series No. 430: Commissioning And Quality Assurance Of Computerized Planning Systems For Radiation Treatment Of Cancer , 2006 .

[22]  D. L. Friesel,et al.  The Midwest Proton Radiation Institute project at the Indiana University Cyclotron Facility , 2002 .

[23]  P J Biggs,et al.  AAPM code of practice for radiotherapy accelerators: report of AAPM Radiation Therapy Task Group No. 45. , 1994, Medical physics.

[24]  Paul Keall,et al.  An MRI‐compatible patient rotation system — design, construction, and first organ deformation results , 2017, Medical physics.

[25]  Paul Keall,et al.  Patient reported outcomes of slow, single arc rotation: Do we need rotating gantries? , 2017, Journal of medical imaging and radiation oncology.

[26]  P. Keall,et al.  The first clinical treatment with kilovoltage intrafraction monitoring (KIM): a real-time image guidance method. , 2014, Medical physics.

[27]  P. Keall,et al.  Review of Real-Time 3-Dimensional Image Guided Radiation Therapy on Standard-Equipped Cancer Radiation Therapy Systems: Are We at the Tipping Point for the Era of Real-Time Radiation Therapy? , 2018, International journal of radiation oncology, biology, physics.