The image quality of ion computed tomography at clinical imaging dose levels

Hansen, David C.; Bassler, Niels; Sørensen, Thomas Sangild; Seco, Joao

doi:10.1118/1.4897614

Cited by 30 publications

(55 citation statements)

References 69 publications

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“…This prior knowledge combined with the information from the proton radiographs allows for accurate patient stopping power reconstruction. 27 MRI has high spatial accuracy and high sensitivity to radiation-induced tissue dynamics. MRI as a dose monitor has been applied, post-treatment, to assess dose response in craniospinal treatment, where vertebral bone marrow is transformed into fat, 62 and in liver, where radiation damage inhibits enzymatic uptake and allows for distinct imaging of irradiated tissues vs nonirradiated tissues possibly within the treatment course.…”

Section: Radiobiological Considerationsmentioning

confidence: 99%

“…The stopping power uncertainty thus has a large impact on our ability to place a Bragg peak spot in the patient, and the uncertainty must be mitigated. Physical mitigations include measuring the stopping power in patient directly through proton transmission imaging (analogous to X-ray or CT imaging), 23,24 measuring the proton penetration in vivo through measurement of gamma emissions produced in the proton interactions, 25 multispectral CT 26 or combined CT and proton radiography, 27 improved dose transport calculations with Monte Carlo (MC) (also limited by stopping power values) 28 and, most immediately practical and perhaps most effective, uncertainty mitigation in treatment planning and consistent on-treatment imaging (below).…”

Section: Physicsmentioning

confidence: 99%

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Intensity modulated proton therapy

Kooy¹,

Grassberger²

2015

BJR

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Intensity modulated proton therapy (IMPT) implies the electromagnetic spatial control of well-circumscribed "pencil beams" of protons of variable energy and intensity. Proton pencil beams take advantage of the charged-particle Bragg peak-the characteristic peak of dose at the end of range-combined with the modulation of pencil beam variables to create target-local modulations in dose that achieves the dose objectives. IMPT improves on X-ray intensity modulated beams (intensity modulated radiotherapy or volumetric modulated arc therapy) with dose modulation along the beam axis as well as lateral, in-field, dose modulation. The clinical practice of IMPT further improves the healthy tissue vs target dose differential in comparison with X-rays and thus allows increased target dose with dose reduction elsewhere. In addition, heavy-charged-particle beams allow for the modulation of biological effects, which is of active interest in combination with dose "painting" within a target. The clinical utilization of IMPT is actively pursued but technical, physical and clinical questions remain. Technical questions pertain to control processes for manipulating pencil beams from the creation of the proton beam to delivery within the patient within the accuracy requirement. Physical questions pertain to the interplay between the proton penetration and variations between planned and actual patient anatomical representation and the intrinsic uncertainty in tissue stopping powers (the measure of energy loss per unit distance). Clinical questions remain concerning the impact and management of the technical and physical questions within the context of the daily treatment delivery, the clinical benefit of IMPT and the biological response differential compared with X-rays against which clinical benefit will be judged. It is expected that IMPT will replace other modes of proton field delivery. Proton radiotherapy, since its first practice 50 years ago, always required the highest level of accuracy and pioneered volumetric treatment planning and imaging at a level of quality now standard in X-ray therapy. IMPT requires not only the highest precision tools but also the highest level of system integration of the services required to deliver high-precision radiotherapy.

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Section: Radiobiological Considerationsmentioning

confidence: 99%

Section: Physicsmentioning

confidence: 99%

Intensity modulated proton therapy

Kooy¹,

Grassberger²

2015

BJR

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“…addition, there are several new algorithms in development that can be applied to proton CT, which should also be thoroughly evaluated and compared with our DROP-TVS algorithm. 8,9,24,25 Plots of the MTF 10% 's for all edges for the stepped experimental scan [ Fig. 5(b)] are given in Fig.…”

Section: Figures 5(a) and 5(b)mentioning

confidence: 99%

“…These measurements are made at many angles between 0 • and 360 • in order to reconstruct a 3D map of proton RSP, using an appropriate image reconstruction algorithm. [7][8][9] The spatial resolution of proton CT images is fundamentally limited by multiple Coulomb scattering (MCS), which determines the uncertainty of the MLP prediction. Due to MCS, straight-line projections are not accurate enough for clinically acceptable spatial resolution.…”

Section: Introductionmentioning

confidence: 99%

“…The acceptability of any proton imaging system depends on the relative importance assigned to visual quality of an image (spatial resolution and noise) and RSP accuracy. 1 A theoretical study of spatial resolution in proton and carbon radiography using Monte Carlo simulations was performed by Seco et al, 14 and theoretical estimates of spatial resolution in proton CT have been published by Schneider et al and Hansen et al, 9,15 but, to the authors' knowledge, no comprehensive study of spatial resolution of an experimental proton CT scanner has been published. In this paper, we present the radial and azimuthal MTFs for a prototype proton CT scanner to characterize the spatial resolution that can be achieved with such a system using 200 MeV protons.…”

Section: Introductionmentioning

confidence: 99%

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An evaluation of spatial resolution of a prototype proton CT scanner

et al. 2016

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Purpose: To evaluate the spatial resolution of proton CT using both a prototype proton CT scanner and Monte Carlo simulations. Methods: A custom cylindrical edge phantom containing twelve tissue-equivalent inserts with four different compositions at varying radial displacements from the axis of rotation was developed for measuring the modulation transfer function (MTF) of a prototype proton CT scanner. Two scans of the phantom, centered on the axis of rotation, were obtained with a 200 MeV, low-intensity proton beam: one scan with steps of 4• , and one scan with the phantom continuously rotating. In addition, Monte Carlo simulations of the phantom scan were performed using scanners idealized to various degrees. The data were reconstructed using an iterative projection method with added total variation superiorization based on individual proton histories. Edge spread functions in the radial and azimuthal directions were obtained using the oversampling technique. These were then used to obtain the modulation transfer functions. The spatial resolution was defined by the 10% value of the modulation transfer function (MTF 10% ) in units of line pairs per centimeter (lp/cm). Data from the simulations were used to better understand the contributions of multiple Coulomb scattering in the phantom and the scanner hardware, as well as the effect of discretization of proton location. Results: The radial spatial resolution of the prototype proton CT scanner depends on the total path length, W , of the proton in the phantom, whereas the azimuthal spatial resolution depends both on W and the position, u − , at which the most-likely path uncertainty is evaluated along the path. For protons contributing to radial spatial resolution, W varies with the radial position of the edge, whereas for protons contributing to azimuthal spatial resolution, W is approximately constant. For a pixel size of 0.625 mm, the radial spatial resolution of the image reconstructed from the fully idealized simulation data ranged between 6.31 ± 0.36 lp/cm for W = 197 mm i.e., close to the center of the phantom, and 13.79 ± 0.36 lp/cm for W = 97 mm, near the periphery of the phantom. The azimuthal spatial resolution ranged from 6.99 ± 0.23 lp/cm at u − = 75 mm (near the center) to 11.20 ± 0.26 lp/cm at u − = 20 mm (near the periphery). Multiple Coulomb scattering limits the radial spatial resolution for path lengths greater than approximately 130 mm, and the azimuthal spatial resolution for positions of evaluation greater than approximately 40 mm for W = 199 mm. The radial spatial resolution of the image reconstructed from data from the 4• stepped experimental scan ranged from 5.11 ± 0.61 lp/cm for W = 197 mm to 8.58 ± 0.50 lp/cm for W = 97 mm. In the azimuthal direction, the spatial resolution ranged from 5.37 ± 0.40 lp/cm at u − = 75 mm to 7.27 ± 0.39 lp/cm at u − = 20 mm. The continuous scan achieved the same spatial resolution as that of the stepped scan.

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In vivo range verification in particle therapy

2018

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Exploitation of the full potential offered by ion beams in clinical practice is still hampered by several sources of treatment uncertainties, particularly related to limitations of our ability to locate the position of the Bragg peak in the tumour. To this end, several efforts are ongoing to improve the characterization of patient position, anatomy and tissue stopping power properties prior to treatment, as well as to enable in-vivo verification of the actual dose delivery, or at least beam range, during or shortly after treatment. This contribution critically reviews methods under development or clinical testing for verification of ion therapy, based on pre-treatment range and tissue probing as well as detection of secondary emissions or physiological changes during and after treatment, trying to disentangle approaches of general applicability from those more specific to certain anatomical locations. Moreover, it discusses future directions, which could benefit from integration of multiple modalities or address novel exploitation of the measurable signals for biologically adapted therapy.

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The image quality of ion computed tomography at clinical imaging dose levels

Abstract: The method presented for comparing various ion CT modalities is feasible for practical use. While all studied ions would improve upon x-ray CT for particle range estimation, helium appears to give the best results and deserves further study for imaging.

Cited by 30 publications

References 69 publications

Intensity modulated proton therapy

Intensity modulated proton therapy

An evaluation of spatial resolution of a prototype proton CT scanner

In vivo range verification in particle therapy

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