An empirical artifact correction for proton computed tomography

Dickmann, Jannis; Sarosiek, Christina; Götz, Stefanie; Pankuch, Mark; Coutrakon, G.; Johnson, R. P.; Schulte, R.; Parodi, Katia; Landry, Guillaume; Dedes, G.

doi:10.1016/j.ejmp.2021.05.018

Cited by 7 publications

(10 citation statements)

References 36 publications

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“…It is worth mentioning that both HeCT and pCT showed a similar systematic underestimation of the RSP accuracy, which has also been observed already by Dedes et al., 20 hinting at a potential bias due to the detector calibration or the reconstruction procedure. Similar problems have been observed in the recent work by Dickmann et al 50 . Using a new calibration phantom, they developed an empirical correction method which improved the accuracy of their experimental pCT results by reducing ring artifacts in the reconstructions.…”

Section: Discussionsupporting

confidence: 69%

“…Nevertheless, the here observed results for HeCT are also comparable to a previous study from our group investigating the RSP accuracy of HeCT for seven plastic materials, 28 where a MAE of 0.45% was found. Similarly, our pCT results can be compared to recent experiments with the detector at the Chicago Proton Center, 50 where a MAE of 0.87 ± 0.03% was reported for the same plastic materials before applying an empirical artifact correction method. Given the respective uncertainties, no statistically significant difference between the results reported in our work and these experiments can be concluded.…”

Section: Discussionmentioning

confidence: 63%

“…pCT and HeCT are more ambivalent; they can produce higher RSP map accuracy in situ but need more developments to be clinically usable. It is necessary that correction methods, such as the one proposed by Dickmann et al., 50 are implemented for the ring artifacts we observed with the current pCT prototype, which should not be necessary for future clinical pCT systems. In addition, significant reduction of acquisition time for single event particle imaging by about one order of magnitude compared to the current benchmarks (

\sim

6 min for a full scan at a cyclotron and with continuous data acquisition 38 ) is required for particle CT to become clinically relevant.…”

Section: Discussionmentioning

confidence: 99%

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Experimental comparison of photon versus particle computed tomography to predict tissue relative stopping powers

et al. 2021

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Purpose: Measurements comparing relative stopping power (RSP) accuracy of state-of -the-art systems representing single-energy and dual-energy computed tomography (SECT/DECT) with proton CT (pCT) and helium CT (HeCT) in biological tissue samples. Methods: We used 16 porcine and bovine samples of various tissue types and water, covering an RSP range from 0.90±0.06 to 1.78 ±0.05. Samples were packed and sealed into 3D-printed cylinders (d = 2 cm, h = 5 cm) and inserted into an in-house designed cylindrical polymethyl methacrylate (PMMA) phantom (d = 10 cm, h = 10 cm). We scanned the phantom in a commercial SECT and DECT (120 kV; 100 and 140 kV/Sn (tin-filtered)); and acquired pCT and HeCT (E ∼ 200 MeV/u, 2 • steps, ∼ 6.2 × 10 6 (p)/∼ 2.3 × 10 6 (He) particles/projection) with a particle imaging prototype. RSP maps were calculated from SECT/DECT using stoichiometric methods and from pCT/HeCT using the DROP-TVS algorithm.We estimated the average RSP of each tissue per modality in cylindrical volumes of interest and compared it to ground truth RSP taken from peak-detection measurements.Results: Throughout all samples, we observe the following root-mean-squared RSP prediction errors ± combined uncertainty from reference measurement and imaging: SECT 3.10±2.88%, DECT 0.75±2.80%, pCT 1.19± 2.81%, and HeCT 0.78±2.81%.The largest mean errors ± combined uncertainty per modality are SECT 8.22 ±2.79% in cortical bone, DECT 1.74±2.00% in back fat, pCT 1.80 ±4.27% in bone marrow, and HeCT 1.37±4.25% in bone marrow. Ring artifacts were observed in both pCT and HeCT reconstructions, imposing a systematic shift to predicted RSPs. Conclusion:Comparing state-of -the-art SECT/DECT technology and a pCT/HeCT prototype, DECT provided the most accurate RSP prediction, closely followed by particle imaging. The novel modalities pCT and HeCT have the potential to further improve on RSP accuracies with work focusing on the origin and correction of ring artifacts. Future work will study accuracy of proton treatment plans using RSP maps from investigated imaging modalities.

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Section: Discussionsupporting

confidence: 69%

Section: Discussionmentioning

confidence: 63%

\sim

6 min for a full scan at a cyclotron and with continuous data acquisition 38 ) is required for particle CT to become clinically relevant.…”

Section: Discussionmentioning

confidence: 99%

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Experimental comparison of photon versus particle computed tomography to predict tissue relative stopping powers

et al. 2021

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“…A well‐established calibration method of the measured signal is key to accurate WET maps. As WET accuracies below 1% should be aimed at, usually many effects specific to the given detector have to be taken into account 23,24,33 .…”

Section: Introductionmentioning

confidence: 99%

“…A well-established calibration method of the measured signal is key to accurate WET maps. As WET accuracies below 1% should be aimed at, usually many effects specific to the given detector have to be taken into account 23,24,33 . In this work, the newly established calibration procedure is demonstrated for homogeneous objects and an object with a more complex, but well-known WET map.…”

Section: Introductionmentioning

confidence: 99%

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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A likelihood‐based particle imaging filter using prior information

et al. 2023

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Background: Particle imaging can increase precision in proton and ion therapy. Interactions with nuclei in the imaged object increase image noise and reduce image quality, especially for multi-nucleon ions that can fragment, such as helium.Purpose: This work proposes a particle imaging filter, referred to as the Prior Filter, based on using prior information in the form of an estimated relative stopping power (RSP) map and the principles of electromagnetic interaction, to identify particles that have undergone nuclear interaction. The particles identified as having undergone nuclear interactions are then excluded from the image reconstruction, reducing the image noise. Methods:The Prior Filter uses Fermi-Eyges scattering and Tschalär straggling theories to determine the likelihood that a particle only interacts electromagnetically. A threshold is then set to reject those particles with a low likelihood. The filter was evaluated and compared with a filter that estimates this likelihood based on the measured distribution of energy and scattering angle within pixels, commonly implemented as the 3σ filter. Reconstructed radiographs from simulated data of a 20 cm water cylinder and an anthropomorphic chest phantom were generated with both protons and helium ions to assess the effect of the filters on noise reduction.The simulation also allowed assessment of secondary particle removal through the particle histories. Experimental data were acquired of the Catphan CTP 404 Sensitometry phantom using i the U.S. proton CT (pCT) collaboration prototype scanner. The proton and helium images were filtered with both the prior filtering method and a state-of-the-art method including an implementation of the 3σ filter. For both cases a dE-E telescope filter, designed for this type of detector, was also applied. Results:The proton radiographs showed a small reduction in noise (1 mm of water equivalent thickness) but a larger reduction in helium radiographs (up to 5-6 mm of water equivalent thickness) due to better secondary filtering. The proton and helium CT images reflected this, with similar noise at the center of the phantom (0.02 RSP) for the proton images and an RSP noise of 0.03 for the proposed filter and 0.06 for the 3σ filter in the helium images. Images reconstructed from data with a dose reduction, up to a factor of 9, maintained a lower noise level using the Prior Filter over the state-of-the-art filtering method. Conclusions:The proposed filter results in images with equal or reduced noise compared to those that have undergone a filtering method typical of current particle imaging studies. This work also demonstrates that the proposed filter maintains better performance against the state of the art with up to a nine-fold dose reduction.

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An empirical artifact correction for proton computed tomography

Cited by 7 publications

References 36 publications

Experimental comparison of photon versus particle computed tomography to predict tissue relative stopping powers

Experimental comparison of photon versus particle computed tomography to predict tissue relative stopping powers

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

A likelihood‐based particle imaging filter using prior information

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