Experimental comparison of proton CT and dual energy x-ray CT for relative stopping power estimation in proton therapy

Dedes, Georgios; Dickmann, Jannis; Niepel, Katharina; Wesp, Philipp; Johnson, R. P.; Pankuch, Mark; Bashkirov, V.; Rit, Simon; Volz, Lennart; Schulte, R.; Landry, Guillaume; Parodi, Katia

doi:10.1088/1361-6560/ab2b72

Cited by 67 publications

(128 citation statements)

References 45 publications

(59 reference statements)

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“…Details about the modeling of physics processes can be found in literature, where the platform was validated for its fidelity in terms of RSP. 19,35 A previous study 34 improved the platform for reproducing variance levels of experimental scans. With respect to that work, the beam model was modified, and is described below.…”

Section: A Simulation Frameworkmentioning

confidence: 99%

“…RSP errors were comparable for modulated and un-modulated scans, and all below 1%, which is within the magnitude expected from literature. 12,19,35 Imaging doses in fluence-modulated scans showed local increases and doses partially spilled out of the ROI. This may have impaired results in this study and could be caused by the fact that optimization was exclusively performed with a variance objective.…”

Section: C Simulation Studymentioning

confidence: 99%

“…10 Direct imaging of RSP using proton computed tomography (pCT) [11][12][13][14][15][16] has been proposed to increase accuracy and to allow for a frequent, dose efficient acquisition in treatment position. Accuracies achievable with current prototypes are comparable to state-of-the art clinical dual energy x-ray CT. 7,[17][18][19] A further reduction of imaging dose can be achieved by modulating the imaging fluence field during the acquisition and thereby achieving a task-specific image quality. Fluencemodulated scans 20 can either aim for homogeneous variance across the whole volume, or for region-of-interest (ROI) imaging, where only the relevant part of the image is acquired at low noise and imaging dose is reduced elsewhere.…”

Section: Introductionmentioning

confidence: 99%

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An optimization algorithm for dose reduction with fluence‐modulated proton CT

et al. 2020

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Purpose: Fluence-modulated proton computed tomography (FMpCT) using pencil beam scanning aims at achieving task-specific image noise distributions by modulating the imaging proton fluence spot-by-spot based on an object-specific noise model. In this work, we present a method for fluence field optimization and investigate its performance in dose reduction for various phantoms and image variance targets. Methods: The proposed method uses Monte Carlo simulations of a proton CT (pCT) prototype scanner to estimate expected variance levels at uniform fluence. Using an iterative approach, we calculate a stack of target variance projections that are required to achieve the prescribed image variance, assuming a reconstruction using filtered backprojection. By fitting a pencil beam model to the ratio of uniform fluence variance and target variance, relative weights for each pencil beam can be calculated. The quality of the resulting fluence modulations is evaluated by scoring imaging doses and comparing them to those at uniform fluence, as well as evaluating conformity of the achieved variance with the prescription. For three different phantoms, we prescribed constant image variance as well as two regions-of-interest (ROI) imaging tasks with inhomogeneous image variance. The shape of the ROIs followed typical beam profiles for proton therapy. Results: Prescription of constant image variance resulted in a dose reduction of 8.9% for a homogeneous water phantom compared to a uniform fluence scan at equal peak variance level. For a more heterogeneous head phantom, dose reduction increased to 16.0% for the same task. Prescribing two different ROIs resulted in dose reductions between 25.7% and 40.5% outside of the ROI at equal peak variance levels inside the ROI. Imaging doses inside the ROI were increased by 9.2% to 19.2% compared to the uniform fluence scan, but can be neglected assuming that the ROI agrees with the therapeutic dose region. Agreement of resulting variance maps with the prescriptions was satisfactory. Conclusions: We developed a method for fluence field optimization based on a noise model for a real scanner used in pCT. We demonstrated that it can achieve prescribed image variance targets. A uniform fluence field was shown not to be dose optimal and dose reductions achievable with the proposed method for FMpCT were considerable, opening an interesting perspective for image guidance and adaptive therapy.

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Section: A Simulation Frameworkmentioning

confidence: 99%

Section: C Simulation Studymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An optimization algorithm for dose reduction with fluence‐modulated proton CT

et al. 2020

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“…Several experimental and simulation studies of the Phase-II pCT scanner [113,107,110,59] note the presence of artifacts in the RSP image. In Dedes et al [59], artifacts of up to 2 % in RSP were reported.…”

Section: Pct Image Artifactsmentioning

confidence: 99%

The role of Monte Carlo simulation in understanding the performance of proton computed tomography

Dedes

Dickmann

Giacometti

et al. 2022

Zeitschrift für Medizinische Physik

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Proton computed tomography (pCT) is a promising tomographic imaging modality allowing direct reconstruction of proton relative stopping power (RSP) required for proton therapy dose calculation. In this review article, we aim at highlighting the role of Monte Carlo (MC) simulation in pCT studies. After describing the requirements for performing proton computed tomography and the various pCT scanners actively used in recent research projects, we present an overview of available MC simulation platforms. The use of MC simulations in the scope of investigations of image reconstruction, and for the evaluation of optimal RSP accuracy, precision and spatial resolution omitting detector effects is then described. In the final sections of the review article, we present specific applications of realistic Monte Carlo simulations of an existing pCT scanner prototype, which we describe in detail.

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“…Many pCT systems have been proposed and developed in the past 20 years [15,16] achieving promising results for RSP accuracy and spatial resolution with both Monte Carlo (MC) simulated and experimental setups [17][18][19][20]. Lately, the RSP accuracy of pCT was proven to be well below 1% and performs better than modern techniques such as dual energy CT scans [21,22]. Additionally, pCT has shown reduced noise level and lower dose deposition on the patient with respect to conventional X-ray CT [23,24].…”

Section: Introductionmentioning

confidence: 99%

A High-Granularity Digital Tracking Calorimeter Optimized for Proton CT

Alme¹,

Barnaföldi²,

Barthel³

et al. 2020

Front. Phys.

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A typical proton CT (pCT) detector comprises a tracking system, used to measure the proton position before and after the imaged object, and an energy/range detector to measure the residual proton range after crossing the object. The Bergen pCT collaboration was established to design and build a prototype pCT scanner with a high granularity digital tracking calorimeter used as both tracking and energy/range detector. In this work the conceptual design and the layout of the mechanical and electronics implementation, along with Monte Carlo simulations of the new pCT system are reported. The digital tracking calorimeter is a multilayer structure with a lateral aperture of 27 cm × 16.6 cm, made of 41 detector/absorber sandwich layers (calorimeter), with aluminum (3.5 mm) used both as absorber and carrier, and two additional layers used as tracking system (rear trackers) positioned downstream of the imaged object; no tracking upstream the object is included. The rear tracker's structure only differs from the calorimeter layers for the carrier made of ∼200 μm carbon fleece and carbon paper (carbon-epoxy sandwich), to minimize scattering. Each sensitive layer consists of 108 ALICE pixel detector (ALPIDE) chip sensors (developed for ALICE, CERN) bonded on a polyimide flex and subsequently bonded to a larger flexible printed circuit board. Beam tests tailored to the pCT operation have been performed using high-energetic (50-220 MeV/u) proton and ion beams at the

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Experimental comparison of proton CT and dual energy x-ray CT for relative stopping power estimation in proton therapy

Cited by 67 publications

References 45 publications

An optimization algorithm for dose reduction with fluence‐modulated proton CT

An optimization algorithm for dose reduction with fluence‐modulated proton CT

The role of Monte Carlo simulation in understanding the performance of proton computed tomography

A High-Granularity Digital Tracking Calorimeter Optimized for Proton CT

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