Energy-painted ion radiography for precision radiotherapy
Final Report Abstract
The clinical potential of the highly precise ion radiotherapy is often compromised by uncertainties of the properties of patient's tissues and its geometry. To address these uncertainties, we developed a method towards high accuracy quantitative on-couch patient imaging based on ion radiography. While the majority of ion radiographic approaches uses protons, our method is based on largely unexploited helium ions which can provide images with superior spatial resolution. We exploit a cutting-edge radiation detection technology developed at CERN called Timepix. It enables to detect single ions and assess some of their properties. At the same time, the apparatus is compact, since it uses very thin detectors (~1 mm). However, the compactness poses a challenge when it comes to measuring the full range of radiological thicknesses of objects to be imaged with high accuracy and precision. In order to image body parts with radiological thicknesses from 3 cm up to 30 cm, a unique beam-energy painting method was developed. We paved the way for imaging objects up to ~1 m, allowing to image even the thickest treated body parts. For this, the ion beam accelerator was modified and commissioned to be able to deliver helium-ion beams with energies up to 430 MeV/u that are far beyond the previous limit. Furthermore, to know the position, shape and intensity of the low-intensity helium-ion beam that is required for ion imaging, a novel and highly sensitive beammonitor detector was developed. Large amounts of measured data for precise ion images of the radiological thickness of the imaged object were processed and evaluated by means of a newly developed and comprehensive package of dedicated data processing software and image reconstruction algorithms. The performance of the entire method was tested on geometrically simple and anthropomorphic model objects under clinical conditions of the Heidelberg Ion Beam Therapy Center in Germany. To the best of our knowledge, the measured accuracies/precisions and spatial resolutions of the quantitative ion-beam radiographs are currently among the best results ever published. Image guidance of ion radiotherapy in general is currently considered to be the most promising step ahead. It may open up the possibility for better tumor targeting in the clinics, leading to lower dose to healthy tissues. In addition to the expected decrease of the treatment complication rate, it is promising to allow for higher dose to the tumor. Thus, it might represent an important step towards treatments of radioresistant tumors and helps to ensure that the great potential of ion radiotherapy is fully exploited for the benefit of cancer patients. We consider our project to be a significant contribution to this endeavour.
Publications
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A technique for spatial resolution improvement in helium‐beam radiography. Medical Physics, 47(5), 2212-2221.
Amato, C.; Martisikova, M. & Gehrke, T.
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A method for improving the spatial resolution of helium-beam radiography and its consequences for calibrations regarding water-equivalent thickness. 59th PTCOG meeting, Online (2021)
M. Metzner & al.
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Achievable image quality of helium-beam radiography (αRad) of high-WET objects with a system based on thin silicon pixel detectors. 7th Annual Loma Linda Workshop on Particle Imaging and Radiation Treatment Planning, Online (2021)
T. Gehrke & al.
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Towards quantitative helium-beam radiography (αRad) using thin silicon pixel detectors and energy painting. 59th PTCOG meeting, Online (2021)
T. Gehrke & al.
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Development of a scintillation fiber transverse profile monitor for low-intensity ion beams at HIT. 11th Int. Beam Instrum. Conf., Krakow, Poland (2022)
R. Hermann & al.
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Experimental helium‐beam radiography with a high‐energy beam: Water‐equivalent thickness calibration and first image‐quality results. Medical Physics, 49(8), 5347-5362.
Knobloch, C.; Metzner, M.; Kehrein, F.; Schömers, C.; Scheloske, S.; Brons, S.; Hermann, R.; Peters, A.; Jäkel, O.; Martišíková, M. & Gehrke, T.
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Helium-beam radiograph of an anthropomorphic head phantom using thin silicon pixel detectors and the assessment of its accuracy. 60th PTCOG meeting, Miami, USA (2022)
M. Metzner & al.
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Helium-beam radiography (αRAD): Imaging of an anthropomorphic pelvis phantom using energy painting. 4th European Conference in Medical Physics, Dublin, Ireland (2022)
Y. Xu, C. Knobloch & al.
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2.5D Imaging: obtaining additional depth information from helium-beam radiographs for applications in ion beam radiotherapy using silicon pixel detectors. 24th International Workshop on Radiation Imaging Detectors, Oslo, Norway (2023)
A. Schlechter & al.
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Advancements in the scintillation fiber beam monitoring for low-intensity ion beams at HIT. 14th International Particle Accelerator Conference, Venice, Italy (2023)
R. Hermann & al.
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Energy painting with several initial beam energies and thin silicon pixel detectors for imaging of objects with wide WET ranges. 4th ion imaging workshop, London (2023)
M. Metzner & al.
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Investigation of patient positioning feasibility based on a helium-beam radiograph (αRAD) acquired with thin silicon pixel detectors. 61st PTCOG meeting, Madrid, Spain (2023)
Y. Xu, M. Metzner & al.
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Patient positioning based on a helium-beam radiograph (αRad). 24th International Workshop on Radiation Imaging Detectors, Oslo, Norway (2023)
Y. Xu, D & al.
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Quantitative helium-beam radiograph of a head and neck model and comparison to X-ray CT projections. 24th International Workshop on Radiation Imaging Detectors, Oslo, Norway (2023)
M. Metzner & al.
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Energy painting: helium-beam radiography with thin detectors and multiple beam energies. Physics in Medicine & Biology, 69(5), 055002.
Metzner, Margareta; Zhevachevska, Daria; Schlechter, Annika; Kehrein, Florian; Schlecker, Julian; Murillo, Carlos; Brons, Stephan; Jäkel, Oliver; Martišíková, Mária & Gehrke, Tim
