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US 12,678,108 B2Granted
Acquisition of proton computed tomography images
AssigneeRhode Island Hospital
InventorUlrich Langner
Life of this patent
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Abstract
A method includes providing a proton computed tomography (CT) scanner, and measuring sigma with a scintillator screen at an exit beam for each pencil beam scanned across an object for each gantry angle necessary to determine a total energy loss as the beam traverses an object of unknown thickness or material.
Claims6
A method of proton computed tomography, comprising:
- providing a proton computed tomography (CT) scanner;
- configured to deliver a scanning proton pencil beam and to rotate relative to an object;
- for a proton pencil beam of a first known entrance energy, scanning the pencil beam over the object at a plurality of gantry angles and, for each pencil-beam position of a scan pattern at each gantry angle, measuring on a fluorescent scintillator screen located in air downstream of the object a one-dimensional intensity profile of an exit proton beam by acquiring, with an optical camera or an electronic portal imaging device of a type used for quality assurance of proton therapy beams, an image of the scintillator screen and determining a beam-width parameter σ_exit from a Gaussian fit to the one-dimensional intensity profile, wherein σ_exit is computed from a full width at half maximum (FWHM) of the fit;
- using a Monte Carlo model of proton transport to generate, for the first entrance energy, a correlation between σ_exit and residual beam energy for proton beams traversing objects of different thickness and composition and, for each respective pencil-beam path, determining a total energy loss along the path by a applying the correlation to the measured σ_exit for that path;
- reconstructing, from the total-energy-loss values for the pencil-beam paths, a first three-dimensional map of relative stopping power of the object corresponding to the first entrance energy;
- repeating the scanning, measuring, determining and reconstructing steps for at least a second entrance proton energy different from the first entrance energy to obtain a second three-dimensional map of relative stopping power of the object;
- and
- comparing the first and second three-dimensional maps of relative stopping power to determine, for voxels of the object, information about material composition based on a dependence of σ_exit on entrance energy;
- wherein the method determines the total energy loss without measuring a Bragg-peak depth using an ion-chamber array.
6 more elements
A method comprising:
- providing a proton computed tomography (CT) scanner;
- configured to deliver a scanning proton pencil beam and to rotate relative to an object;
- for a proton pencil beam of a first known entrance energy entering the object, inserting a fluorescent scintillator screen in air downstream of the object and acquiring a beam profile of an exit proton beam by recording, with an optical camera or an electronic portal imaging device of a type used for quality assurance of proton therapy beams, an image of the fluorescent scintillator screen, and determining a sigma (σ_exit) for the exit beam by determining a full width at half maximum (FWHM) of a Gaussian distribution of a one-dimensional intensity profile of the beam recorded on the image;
- using a Monte Carlo model of proton transport to generate, for the first entrance energy, a correlation between σ_exit and exiting energy of the beam for proton beams traversing objects of different thickness and composition;
- scanning the pencil beam over the object in a plane and over 360 degrees around the object, using the fluorescent scintillator screen and the optical camera or electronic portal imaging device to measure σ_exit of each pencil beam at the exit, and
- determining a total energy loss for each beam path from the correlation;
- repeating the scanning, measuring, and determining steps for at least a second entrance energy different from the first entrance energy so as to obtain, for each beam path, σ_exit values as a function of entrance energy;
- and
- using differences in a dependence of σ_exit on entrance energy to determine, for voxels along the beam paths, information about material composition including atomic number and mass number;
- wherein determining the total energy loss is performed without measuring a Bragg-peak depth using an ion-chamber array.
7 more elements
Dependencies are inferred from the claim text.