A technique for spatial resolution improvement in helium‐beam radiography

Amato, Carlo; Martišíková, M.; Gehrke, Tim

doi:10.1002/mp.14051

Cited by 7 publications

(18 citation statements)

References 41 publications

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“…Recently, the possibility of using helium ions for imaging has been explored due to its reduced scattering power, leading to improved spatial resolution (Hansen et al 2014, Collins-Fekete et al 2017a, Volz et al 2017, Gehrke et al 2018a, as well as its potential for online treatment monitoring (Volz et al 2020). So far, few studies on experimental helium list-mode imaging are available (Volz et al 2017, Gehrke et al 2018a, Amato et al 2020.…”

Section: Helium Imagingmentioning

confidence: 99%

Helium radiography with a digital tracking calorimeter—a Monte Carlo study for secondary track rejection

Pettersen¹,

Volz²,

Sølie³

et al. 2021

Phys. Med. Biol.

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Radiation therapy using protons and heavier ions is a fast-growing therapeutic option for cancer patients. A clinical system for particle imaging in particle therapy would enable online patient position verification, estimation of the dose deposition through range monitoring and a reduction of uncertainties in the calculation of the relative stopping power of the patient.Several prototype imaging modalities offer radiography and computed tomography using protons and heavy ions. A Digital Tracking Calorimeter (DTC), currently under development, has been proposed as one such detector. In the DTC 43 longitudinal layers of laterally stacked ALPIDE CMOS monolithic active pixel sensor chips are able to reconstruct a large number of simultaneously recorded proton tracks.In this study, we explored the capability of the DTC for helium imaging which offers favorable spatial resolution over proton imaging. Helium ions exhibit a larger cross section for inelastic nuclear interactions, increasing the number of produced secondaries in the imaged object and in the detector itself. To that end, a filtering process able to remove a large fraction of the secondaries was identified, and the track reconstruction process was adapted for helium ions.By filtering on the energy loss along the tracks, on the incoming angle and on the particle ranges, 97.5% of the secondaries were removed. After passing through 16 cm water, 50.0% of the primary helium ions survived; after the proposed filtering 42.4% of the primaries remained; finally after subsequent image reconstruction 31% of the primaries remained. Helium track reconstruction leads to more track matching errors compared to protons due to the increased available focus strength of the helium beam. In a head phantom radiograph, the Water Equivalent

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Section: Helium Imagingmentioning

confidence: 99%

Helium radiography with a digital tracking calorimeter—a Monte Carlo study for secondary track rejection

Pettersen¹,

Volz²,

Sølie³

et al. 2021

Phys. Med. Biol.

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“…In this work, a calibration curve with the purpose of converting an energy deposition image, as measured by the detection system similar to Ref. 22, into a WET image is established for a beam energy of 239.5 MeV/u, which principally enables the imaging of objects with a WET range of ∼280-310 mm. Furthermore, the performance of the method for an object with a more complex geometry (containing WETs of up to ∼290 mm) is evaluated.…”

Section: Methodsmentioning

confidence: 99%

“…22 Copper was found to be a advantageous material to be used as a degrader. 22 However, the WET is dependent on the energy of the particle for low energies 38 and potential consequences on the WET calibration accuracy have to be considered and are investigated specifically for copper.…”

Section: Detection Systemmentioning

confidence: 99%

“…21,22 To address that, our long-term aim is to use different initial beam energies for different WET ranges in an approach named energy painting. 22 The iRAD imaging system has mainly been used with helium-ion beams, since we could experimentally demonstrate that helium-beam radiography (𝛼RAD) provides an advantage over proton radiography (pRAD) in terms of spatial resolution without a drawback in WET resolution or imaging dose. 21 The potential advantages of helium ions over protons for ion imaging in general were also shown in several other theoretical and simulation-based studies.…”

Section: Introductionmentioning

confidence: 99%

“…In previous works of our group in Heidelberg, we built a prototype imaging system for i Rad consisting entirely of thin silicon pixel detectors called Timepix 20–22 . The system design is unique in the sense that the contrast of the image stems from accurate energy deposition (d E ) measurements of individual ions in 300 μm silicon.…”

Section: Introductionmentioning

confidence: 99%

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Experimental helium‐beam radiography with a high‐energy beam: Water‐equivalent thickness calibration and first image‐quality results

et al. 2022

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A clinical implementation of ion-beam radiography (iRAD) is envisaged to provide a method for on-couch verification of ion-beam treatment plans. The aim of this work is to introduce and evaluate a method for quantitative waterequivalent thickness (WET) measurements for a specific helium-ion imaging system for WETs that are relevant for imaging thicker body parts in the future. Methods: Helium-beam radiographs (𝛼Rads) are measured at the Heidelberg Ion-beam Therapy Center with an initial beam energy of 239.5 MeV/u. An imaging system based on three pairs of thin silicon pixel detectors is used for ion path reconstruction and measuring the energy deposition (dE) of each particle behind the object to be imaged. The dE behind homogeneous plastic blocks is related to their well-known WETs between 280.6 and 312.6 mm with a calibration curve that is created by a fit to measured data points. The quality of the quantitative WET measurements is determined by the uncertainty of the measured WET of a single ion (single-ion WET precision) and the deviation of a measured WET value to the well-known WET (WET accuracy). Subsequently, the fitted calibration curve is applied to an energy deposition radiograph of a phantom with a complex geometry. The spatial resolution (modulation transfer function at 10 % -MTF 10% ) and WET accuracy (mean absolute percentage difference-MAPD) of the WET map are determined. Results: In the optimal imaging WET-range from ∼280 to 300 mm, the fitted calibration curve reached a mean single-ion WET precision of 1.55 ± 0.00%. Applying the calibration to an ion radiograph (iRad) of a more complex WET distribution, the spatial resolution was determined to be MTF 10% = 0.49 ± 0.03 lp/mm and the WET accuracy was assessed as MAPD to 0.21 %. Conclusions: Using a beam energy of 239.5 MeV/u and the proposed calibration procedure, quantitative 𝛼Rads of WETs between ∼280 and 300 mm can be measured and show high potential for clinical use. The proposed approach with the resulting image qualities encourages further investigation toward the clinical application of helium-beam radiography.

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The accuracy of helium ion CT based particle therapy range prediction: an experimental study comparing different particle and x-ray CT modalities

et al. 2021

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This work provides a quantitative assessment of helium ion CT (HeCT) for particle therapy treatment planning. For the first time, HeCT based range prediction accuracy in a heterogeneous tissue phantom is presented and compared to single-energy x-ray CT (SECT), dual-energy x-ray CT (DECT) and proton CT (pCT). HeCT and pCT scans were acquired using the US pCT collaboration prototype particle CT scanner at the Heidelberg Ion-Beam Therapy Center. SECT and DECT scans were done with a Siemens Somatom Definition Flash and converted to RSP. A Catphan CTP404 module was used to study the RSP accuracy of HeCT. A custom phantom of 20 cm diameter containing several tissue equivalent plastic cubes was used to assess the spatial resolution of HeCT and compare it to DECT. A clinically realistic heterogeneous tissue phantom was constructed using cranial slices from a pig head placed inside a cylindrical phantom (ø150 mm). A proton beam (84.67 mm range) depth-dose measurement was acquired using a stack of GafchromicTM EBT-XD films in a central dosimetry insert in the phantom. CT scans of the phantom were acquired with each modality, and proton depth-dose estimates were simulated based on the reconstructions. The RSP accuracy of HeCT for the plastic phantom was found to be 0.3 ± 0.1%. The spatial resolution for HeCT of the cube phantom was 5.9 ± 0.4 lp cm−1 for central, and 7.6 ± 0.8 lp cm−1 for peripheral cubes, comparable to DECT spatial resolution (7.7 ± 0.3 lp cm−1 and 7.4 ± 0.2 lp cm−1, respectively). For the pig head, HeCT, SECT, DECT and pCT predicted range accuracy was 0.25%, −1.40%, −0.45% and 0.39%, respectively. In this study, HeCT acquired with a prototype system showed potential for particle therapy treatment planning, offering RSP accuracy, spatial resolution, and range prediction accuracy comparable to that achieved with a commercial DECT scanner. Still, technical improvements of HeCT are needed to enable clinical implementation.

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A technique for spatial resolution improvement in helium‐beam radiography

Cited by 7 publications

References 41 publications

Helium radiography with a digital tracking calorimeter—a Monte Carlo study for secondary track rejection

Helium radiography with a digital tracking calorimeter—a Monte Carlo study for secondary track rejection

Experimental helium‐beam radiography with a high‐energy beam: Water‐equivalent thickness calibration and first image‐quality results

The accuracy of helium ion CT based particle therapy range prediction: an experimental study comparing different particle and x-ray CT modalities

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