A comprehensive study of the most likely path formalism for proton-computed tomography

Erdélyi, Béla

doi:10.1088/0031-9155/54/20/005

Cited by 31 publications

(33 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We therefore recapitulate the central aspects for coherence and better legibility. Several authors have reported mathematical formalisms (Williams 2004, Schulte et al 2008, Erdelyi 2009, Collins-Fekete et al 2016 to estimate the most likely proton path when using single tracking set-ups. As a by-product, the mathematical equations also allow us to quantify the size of the uncertainty envelope around the most likely path.…”

Section: Recapitulation: Estimation Of the Most Likely Pathmentioning

confidence: 99%

A comprehensive theoretical comparison of proton imaging set-ups in terms of spatial resolution

et al. 2018

View full text Add to dashboard Cite

We present a comprehensive analytical comparison of four types of proton imaging set-ups and, to this end, develop a mathematical framework to calculate the width of the uncertainty envelope around the most likely proton path depending on set-up geometry, detector properties, and proton beam parameters. As a figure of merit for the spatial resolution achievable with each set-up, we use the frequency [Formula: see text] at which the modular transfer function of a density step decreases below 10%. We verify the analytical results with Monte Carlo simulations. We find that set-ups which track the angle and position of individual protons in front of and behind the phantom would yield an average spatial resolution of 0.3-0.35 lp mm assuming realistic geometric parameters (i.e. 30-40 cm distance between detector and phantom, 15-20 cm phantom thickness). For set-ups combining pencil beam scanning with either a position sensitive detector, e.g. an x-ray flat panel, or with a position insensitive detector, e.g. a range telescope, we find an average spatial resolution of about 0.1 lp mm for an 8 mm FWHM beam spot size. The pixel information improves the spatial resolution by less than 10%. In both set-up types, performance can be significantly improved by reducing the pencil beam size down to 2 mm FWHM. In this case, the achievable spatial resolution reaches about 0.25 lp mm. Our results show that imaging set-ups combining double scattering with a pixel detector can provide sufficient spatial resolution only under very stringent conditions and are not ideally suited for computed tomography applications. We further propose a region-of-interest method for set-ups with a pixel detector to filter out protons which have undergone nuclear reactions and discuss the impact of tracker detector uncertainties on the most likely path.

show abstract

Section: Recapitulation: Estimation Of the Most Likely Pathmentioning

confidence: 99%

A comprehensive theoretical comparison of proton imaging set-ups in terms of spatial resolution

et al. 2018

View full text Add to dashboard Cite

show abstract

“…While pCT exhibits other benefits (Schulte et al 2005, Depauw & Seco 2011, Oancea et al 2018, the achievable spatial resolution is limited due to multiple Coulomb scattering (MCS). To reduce the uncertainty introduced by MCS, in single-event pCT, the trajectory of each proton through the object is estimated during image reconstruction (Williams 2004, Li et al 2006, Schulte et al 2008, Erdelyi 2009, Collins-Fekete et al 2015, Collins-Fekete et al 2017, Krah et al 2018. The use of path reconstruction techniques requires sophisticated detector systems capable of acquiring the proton track information before and after the object to be imaged, as well as the residual energy/range on a single-event basis (Schulte et al 2004, Schulte et al 2008, Sadrozinski et al 2013.…”

Section: Introductionmentioning

confidence: 99%

Improving single-event proton CT by removing nuclear interaction events within the energy/range detector

Volz¹,

Piersimoni²,

Johnson³

et al. 2019

Phys. Med. Biol.

View full text Add to dashboard Cite

Improving single-event proton CT by removing nuclear interaction events within the energy/range detector. Permalink https://escholarship.org/uc/item/5rg9r6rw Journal Physics in medicine and biology, 64 (15) Abstract. Data filtering is crucial for accurate relative stopping power (RSP) reconstruction in proton CT (pCT). In this work, we assess different filters and their performance for the US pCT collaboration prototype pCT system in Monte Carlo (MC) simulations. The potential of using the recently proposed ∆E-E filter for removing nuclear interactions that occurred in the energy/range detector of the pCT system is investigated.Full pCT scans were acquired with the TOPAS MC simulated version of the prototype scanner that comprises two tracking detectors and a 5 stage energy/range detector. An ideal water cylinder and a water cylinder with 5 tissue inserts were investigated. Before image reconstruction, a 3 σ WEPL filter was applied as the only filter, or in addition to filters acting on the energy deposit in each of the energy detector stages, as done currently with the prototype. The potential of the ∆E-E filter that was recently proposed for helium imaging was assessed. The results were compared to simulations for which nuclear interactions were disabled representing ground truth.The 3 σ WEPL filter alone was not sufficient to filter out all nuclear interaction events and systematic fluctuations in the form of ring artifacts were present in the pCT reconstructed images. Applying energy filters currently used with the device prior to the 3 σ WEPL filter only slightly improved the image quality. A 2 σ WEPL filter improved the mean RSP accuracy, but could not

show abstract

“…To overcome the problem of MCS, various path estimation algorithms have been proposed for protons, of which the most likely path (MLP) algorithm is the most widely used [4][5][6][7][8]. Compared to protons, heavier ions suffer less from MCS, due to on average smaller deflection angles per scattering.…”

Section: Introductionmentioning

confidence: 99%

Stopping power accuracy and achievable spatial resolution of helium ion imaging using a prototype particle CT detector system

Volz

Collins-Fekete

Piersimoni

et al. 2017

Current Directions in Biomedical Engineering

View full text Add to dashboard Cite

A precise relative stopping power map of the patient is crucial for accurate particle therapy. Charged particle imaging determines the stopping power either tomographically -particle computed tomography (pCT) -or by combining prior knowledge from particle radiography (pRad) and x-ray CT. Generally, multiple Coulomb scattering limits the spatial resolution. Compared to protons, heavier particles scatter less due to their lower charge/mass ratio. A theoretical framework to predict the most likely trajectory of particles in matter was developed for light ions up to carbon and was found to be the most accurate for helium comparing for fixed initial velocity. To further investigate the potential of helium in particle imaging, helium computed tomography (HeCT) and radiography (HeRad) were studied at the Heidelberg Ion-Beam Therapy Centre (HIT) using a prototype pCT detector system registering individual particles, originally developed by the U.S. pCT collaboration. Several phantoms were investigated: modules of the Catphan QA phantom for analysis of spatial resolution and achievable stopping power accuracy, a paediatric head phantom (CIRS) and a custommade phantom comprised of animal meat enclosed in a 2 % agarose mixture representing human tissue. The pCT images were reconstructed applying the CARP iterative reconstruction algorithm. The MTF 10% was investigated using a sharp edge gradient technique. HeRad provides a spatial resolution above that of protons (MTF10 10% =6.07 lp/cm for HeRad versus MTF 10% =3.35 lp/cm for proton radiography). For HeCT, the spatial resolution was limited by the number of projections acquired (90 projections for a full scan). The RSP accuracy for all inserts of the Catphan CTP404 module was found to be 2.5% or better and is subject to further optimisation. In conclusion, helium imaging appears to offer higher spatial resolution compared to proton imaging. In future studies, the advantage of helium imaging compared to other imaging modalities in clinical applications will be further explored.

show abstract

A comprehensive study of the most likely path formalism for proton-computed tomography

Cited by 31 publications

References 15 publications

A comprehensive theoretical comparison of proton imaging set-ups in terms of spatial resolution

A comprehensive theoretical comparison of proton imaging set-ups in terms of spatial resolution

Improving single-event proton CT by removing nuclear interaction events within the energy/range detector

Stopping power accuracy and achievable spatial resolution of helium ion imaging using a prototype particle CT detector system

Contact Info

Product

Resources

About