Dose calculation method, dose calculation device, and computer-readable storage medium

Provided are a dose calculation method, a dose calculation device, and a computer-readable storage medium. The dose calculation method comprises: generating an intermediate image between a plurality of sequentially acquired diagnostic images; and calculating doses through a simulation using the diagnostic images and the intermediate image.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/KR2014/004470, filed May 19, 2014, and claims priority Korean Patent Application No. 10-2014-0035591 flied Mar. 26, 2014, the contents of which are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The inventive concept relates to a dose calculation method, a dose calculation device, and a computer-readable storage medium, and more particularly, to a dose calculation method, a dose calculation device, and a computer-readable storage medium calculating doses by using sequentially acquired four-dimensional (4D) computed tomography (CT) images.

BACKGROUND ART

In order to increase an effect of cancer treatment without damage of normal tissue by irradiating cancer tissue with an optimal radiation dose for cancer tissue and irradiating normal tissue around the cancer tissue with a minimum radiation dose at the same time during radiation treatment for cancer, research on radiation treatment planning (RTP) to make a plan for a radiation dose according to a state of cancer in a patient has been performed.

The RTP, which is related to calculation and verification of a radiation dose and generation of radiation treatment information, is made through a computer simulation using diagnostic images of a patient, for example, 3D computed tomography (CT) images or average intensity projection (AVE-IP) of 4D CT images.

The diagnostic images of the patient cannot reflect movement of internal organs according to breathing, and thus, may cause a difference between a dose of RTP and a dose of actual radiation treatment. A greater dose difference may occur especially when RTP about a tumor generated in an organ with a large movement, for example, a lung, a liver, or a pancreas. Furthermore, a much greater dose difference may occur when radiation treatment using charged particles irradiating a local area with many doses or spot-scanning radiation treatment irradiating a tumor of a patient with radiation by moving a beam along a shape of the tumor is performed. However, if a breathing period of a patient is further subdivided to reflect movement of the internal organ to prevent the dose difference, and thus, more diagnostic images are acquired and an exposure dose of the patient may increase.

In general, a calculation of a dose when making RTP includes a separate process of calculating a dose of each of diagnostic images of a patient by performing a computer simulation and matching each of the dose calculation results with a specific reference image. As a result, a time for RTP is longer and it is difficult to simplify and automate a dose calculation process.

DETAILED DESCRIPTION OF THE INVENTION

Technical Problem

The inventive concept provides a dose calculation method, a dose calculation device, and a computer-readable storage medium capable of reducing a dose difference according to movement of an internal organ of a patient without acquiring additional 4D computed tomography (CT) images, and capable of reducing a dose calculation time and simplifying a dose calculation process.

Technical Solution

According to an aspect of the inventive concept, there is provided a dose calculation method comprising: generating an intermediate image between a plurality of diagnostic images that are sequentially acquired; and calculating a dose through a simulation using the diagnostic images and the intermediate image.

According to an exemplary embodiment, wherein the generating the intermediate image may comprise: acquiring a deformable vector field indicating a moving direction of voxels between the diagnostic images; and generating the intermediate image based on the deformable vector field and a function representing breathing of a patient.

According to an exemplary embodiment, wherein the function representing the breathing of the patient may be acquired by measuring breathing characteristics of the patient.

According to an exemplary embodiment, wherein the calculating the dose may comprise: calculating a dose of each of the intermediate image and the diagnostic images; and recalculating the calculated dose of each of the intermediate image and the diagnostic images to correspond to a reference image by referring to the deformable vector field.

According to an exemplary embodiment, wherein the diagnostic images may be 4D computed tomography (CT) images, and the computer simulation may be a deterministic simulation or a stochastic simulation.

According to another aspect of the inventive concept, there is provided a dose calculation device comprising: an intermediate image generation unit configured to generate an intermediate image between a plurality of diagnostic images that are sequentially acquired; and a dose calculation unit configured to calculate a dose through a simulation using the plurality of diagnostic images and the intermediate image.

According to an exemplary embodiment, wherein the intermediate image generation unit may comprise a deformable vector field acquisition unit acquiring a deformable vector field indicating a moving direction of voxels between the diagnostic images, and may generate the intermediate image based on the deformable vector field.

According to an exemplary embodiment, the dose calculation device may further comprise: a storage unit configured to store a function representing breathing of a patient, wherein the intermediate image generation unit generates the intermediate image based on the function and the deformable vector field.

According to an exemplary embodiment, wherein the function representing the breathing of the patient may be acquired by measuring breathing characteristics of a patient.

According to an exemplary embodiment, wherein the dose calculation unit may calculate a dose of each of the intermediate image and the diagnostic images, and recalculate the calculated dose of each of the intermediate image and the diagnostic images to correspond to a reference image by referring to the deformable vector field.

According to still another aspect of the inventive concept, there is provided a non-transitory computer-readable storage medium having saved thereon at least one program comprising commands for executing the aforementioned dose calculation method by a processor of a computer when the program is executed by the computer.

Advantageous Effects

According to a dose calculation method and a dose calculation device according to the inventive concept, a dose difference may be reduced without increase in an exposure of a patient by generating intermediate images between continuous 4D computed tomography (CT) images to reflect movement of an internal organ of a patient without acquiring additional images and calculating a dose, and thus, it is possible to make accurate radiation treatment planning (RTP) and radiation treatment.

Furthermore, according to a dose calculation method and a dose calculation device according to the inventive concept, doses of 4D CT images and intermediate images sequentially acquired may be calculated and each of the calculated doses of the images may be recalculated with respect to a reference image through a single computer simulation, and thus, RTP may be rapidly made by reducing the total dose calculation time and simplification and automation of a dose calculation process may be possible.

MODE OF THE INVENTION

Since the inventive concept may have diverse modified embodiments, preferred embodiments are illustrated in the drawings and are described in the detailed description. However, this does not limit the inventive concept within specific embodiments and it should be understood that the inventive concept covers all the modifications, equivalents, and replacements within the idea and technical scope of the inventive concept.

In the description of the present disclosure, certain detailed explanations of the related art are omitted when it is deemed that they may unnecessarily obscure the essence of the inventive concept. While the terms including an ordinal number, such as “first”, “second”, etc., may be used to describe various components, such components are not be limited by these terms. The terms first and second should not be used to attach any order of importance but are used to distinguish one element from another element.

Throughout the specification, it will be understood that when a unit is referred to as being “connected” to another element, it may be “directly connected” to the other element or “electrically connected” to the other element in a state in which intervening elements are present.

In addition, terms such as “ . . . unit”, “ . . . module”, or the like refer to units that perform at least one function or operation, and the units may be implemented as hardware or software or as a combination of hardware and software.

Furthermore, components of the specification are divided in accordance with a main function of each component. For example, combining two or more elements are in a single component, as needed, or may be one component configuration is subdivided into two or more components. Each of the components may further perform some or all of the functions of other components as well as its main functions, and some of the main functions may also be performed by other components.

FIG. 1is a schematic block diagram of a dose calculation device100according to an embodiment of the inventive concept. The dose calculation device100may be, by itself, a device for making radiation treatment planning (RTP), a device for verifying RTP, or a simulation treatment device, or may be a part of the device for making RTP, the device for verifying RTP, or the simulation treatment device.

Referring toFIG. 1, the dose calculation device100may include an intermediate image generation unit110, a dose calculation unit130, and a storage unit150.FIG. 1illustrates that the intermediate image generation unit110, the dose calculation unit130, and the storage unit150are separately included in the dose calculation device100. However, the inventive concept is not limited thereto. At least two of the intermediate image generation unit110, the dose calculation unit130, and the storage unit150may be formed as a single structure.

The intermediate image generation unit110may receive n (n is a natural number of 2 or more) diagnostic images D1through Dn that are sequentially acquired. The n diagnostic images D1through Dn may be images that are acquired by a imaging device, for example, a 4D computed tomography (CT) device sequentially imaging an affected part (for example, an internal organ) of a patient at a predetermined time interval. In some embodiments, the n diagnostic images D1through Dn may be images that are acquired by the imaging device imaging an affected part of a patient by dividing a breathing period of the patient into ten phases. The n diagnostic images D1through Dn may be provided from the imaging device to the intermediate image generation unit110.

The intermediate image generation unit110may include a deformable vector field acquisition unit111acquiring a deformable vector field by using the n diagnostic images D1through Dn. For example, the deformable vector field acquisition unit111may calculate a moving direction of voxels between continuous two diagnostic images from among the n diagnostic images D1through Dn such as a first diagnostic image D1and a second diagnostic image D2. The deformable vector field acquisition unit111may calculate the moving direction of the voxels by using deformable image registration (DIR) for estimating movement between the two images by matching coordinate systems of the two images with each other. The DIR may use any one of, e.g., an optical flow algorithm, a level set algorithm, a demons algorithm, a b-spline algorithm, a free-style deformation algorithm, and an iterative sum-of-squared-difference (SSD) minimization algorithm. The deformable vector field acquisition unit111may acquire the deformable vector field indicating a directional group of each vector based on the calculated moving direction of the voxels.FIG. 1shows that the deformable vector field acquisition unit111is included in the intermediate image generation unit110, but is not limited thereto. The deformable vector field acquisition unit111may also be included in the calculation device100as distinct from the intermediate image generation unit110.

The intermediate image generation unit110, based on the deformable vector field acquired by the deformable vector field acquisition unit111and a function FU representing breathing of a patient, may generate an intermediate image between continuous two diagnostic images from among the sequentially acquired n diagnostic images D1through Dn. For example, the intermediate image generation unit110may generate an intermediate image corresponding to a gap between the first and second diagnostic images D1and D2through interpolation using the deformable vector field acquired by using the first and second diagnostic images D1and D2and the function FU. The function FU may be provided from the storage unit150. A plurality of intermediate images may be generated one by one between each of continuous two diagnostic images. However, the inventive concept is not limited thereto, and each intermediate image between continuous two diagnostic images may be at least two. Hereinafter, for convenience of description, it will be described that m (m is a natural number) intermediate images I1through Im in total are generated as intermediate images are generated one by one between continuous two diagnostic images.

The dose calculation unit130may receive the n diagnostic images D1through Dn. As illustrated inFIG. 1, the dose calculation unit130receives the n diagnostic images D1through Dn through the intermediate image generation unit110, however, the dose calculation unit130is not limited thereto. The dose calculation unit130may directly receive the n diagnostic images D1through Dn from the imaging device (not shown).

The dose calculation unit130may receive the m intermediate images I1through Im from the intermediate image generation unit110. Furthermore, the dose calculation unit130may receive the deformable vector field from the intermediate image generation unit110.

The dose calculation unit130may calculate a dose through a simulation of the n diagnostic images D1through Dn and the m intermediate images I1through Im. In detail, the dose calculation unit130may calculate a dose of each of the n diagnostic images D1through Dn and the m intermediate images I1through Im based on a position of an affected part of a patient in each of the n diagnostic images D1through Dn and the m intermediate images I1through Im. Next, the dose calculation unit130may recalculate the calculated dose of each of the n diagnostic images D1through Dn and the m intermediate images I1through Im to correspond to a reference image. In other words, the dose calculation unit130may estimate a converted position of the affected part of the patient corresponding to the reference image from any one of the n diagnostic images D1through Dn and the m intermediate images I1through Im by referring to the deformable vector field, and may further recalculate a dose calculated based on the estimated converted position of the affected part to correspond to the reference image. The reference image may be any one of the n diagnostic images D1through Dn and/or the m intermediate images I1through Im.

The dose calculation unit130may calculate a dose of each of the n diagnostic images D1through Dn and the m intermediate images I1through Im through, e.g., a deterministic simulation or a stochastic simulation. The deterministic simulation, which is a simulation using superposition/convolution, may be a simulation excluding probability application. The stochastic simulation may use probability. The stochastic simulation may be, for example, a Monte Carlo simulation. The Monte Carlo simulation may use, for example, a code for a GEometry ANd Tracking (GEANT4) code, a Monte Carlo N-particle (MCNP) code, an Electron-Gamma Shower (EGS) code, a FLUKA code, or a Particle and Heavy Ion Transport code System (PHITS) code.

The storage unit150may store the function FU representing breathing of a patient. The function FU representing breathing of a patient may indicate movement of an affected part (for example, an internal organ) of a patient according to the breathing of the patient. The function FU representing breathing of a patient may be acquired by directly measuring breathing characteristics of a patient. Alternatively, the function FU representing breathing of a patient may be selected from previously stored functions corresponding to breathing characteristics of a patient.

The storage unit150may provide the function FU representing breathing of a patient to the intermediate image generation unit110, and accordingly, the intermediate image generation unit110may generate an intermediate image reflecting movement of an internal organ of a patient.

As such, the dose calculation device100may reduce a difference between a calculated dose and a dose of actual radiation treatment by generating the m intermediate images I1through Im reflecting the movement of the internal organ of the patient in gaps between the n diagnostic images D1through Dn without acquiring additional diagnostic images or more diagnostic images, and by using the m intermediate images I1through Im generated during dose calculation with the n diagnostic images D1through Dn. Therefore, the dose calculation device100may improve reliability during dose calculation in RTP, and may maximize an effect of radiation treatment by improving accuracy of radiation treatment.

Furthermore, the dose calculation device100may simplify and automate a dose calculation process by calculating doses of images corresponding to a reference image through a single simulation, and may rapidly make RTP by reducing a dose calculation time.

FIG. 2is a flowchart for describing a dose calculation method according to an embodiment of the inventive concept, andFIGS. 3 through 8are views for describing operations of the dose calculation method ofFIG. 2in detail. Hereinafter, the dose calculation method according to an embodiment of the inventive concept will be described referring toFIGS. 2 through 8as well asFIG. 1. The dose calculation method according toFIG. 2may be implemented as a program and recorded on a non-transitory computer-readable recording medium, and the program may be installed in or downloaded to the dose calculation device100as described inFIG. 1, and thus, corresponding functions may be executed by a processor of the dose calculation device100.

Referring toFIGS. 1 to 3, in operation S110, a plurality of diagnostic images are sequentially acquired by a imaging device (not shown). The imaging device may be a 4D CT device, and the diagnostic images may be a 4D CT images. The plurality of diagnostic images, which are acquired by imaging an affected part (for example, an internal organ) of a patient, may include n (n is a natural number of 2 or more) diagnostic images that are acquired by sequentially imaging the affected part of the patient at a predetermined time interval.

Referring toFIGS. 1 and 2, and 4, in operation S120, acquired is a deformable vector field between the n diagnostic images sequentially acquired by the dose calculation device100. For example, the dose calculation device100may calculate a moving direction of voxels between continuous rth (r is a natural number less than n) diagnostic image and r+1th diagnosis image from among the n diagnostic images by using DIR, and may acquire the deformable vector field denoting a directional group of each vector. Similarly, the dose calculation device100may acquire a deformable vector field between other continuous diagnostic images from among the n diagnostic images.

Referring toFIGS. 1 and 2, and 5, in operation S130, an intermediate image between diagnostic images is generated based on the deformable vector field acquired by the dose calculation device100and the function FU representing breathing of a patient. For example, the dose calculation device100may generate an sth (s is a natural number less than m) intermediate image between an rth diagnostic image and an r+1th diagnostic image through interpolation using the acquired deformable vector field and the function FU representing the breathing of the patient. Similarly, the dose calculation device100may generate an s+1th intermediate image between an r+1th diagnostic image and an r+2th diagnostic image based on a corresponding deformable vector field and the function FU representing the breathing of the patient. The dose calculation device100may generate m (m is a natural number) intermediate images in total by repeating operation S130. The function FU, which is acquired by measuring breathing characteristics of a patient, may indicate movement of an affected part of a patient according to the breathing of the patient.

Referring toFIGS. 1 and 2, andFIGS. 6 to 8, in operation S140, a dose is calculated by the dose calculation device100through a simulation using the n diagnostic images and the m intermediate images. For example, the dose calculation device100may calculate a dose of an affected part of a patient from each of the n diagnostic images including the rth and r+1th diagnostic images and the m intermediate images including the sth and s+1th intermediate images. Next, when the reference image is the r+1th diagnostic image, the dose calculation device100may refer to a deformable vector field between the rth diagnostic image and the r+1th diagnostic image and recalculate the calculated doses of the rth diagnostic image and the sth intermediate image to correspond to the r+1th diagnostic image. The dose calculation device100may recalculate the calculated doses of other images to correspond to the r+1th diagnostic image that is the reference image.

Further referring toFIG. 8illustrating a dose calculation process with respect to the rth diagnostic image in detail, in operation S140, the dose calculation device100may calculate a dose based on a position of an affected part of a patient in the rth diagnostic image (FIG. 8(a)), may estimate a converted position of the affected part of the patient in the rth diagnostic image corresponding to the reference image by referring to a deformable vector field with respect to the reference image (r+1th diagnostic image) from the rth diagnostic image (FIG. 8(b)), and may recalculate the calculated dose of the rth diagnostic image based on the estimated converted position of the affected part (seeFIG. 8(c)).

As such, the dose calculation method may improve reliability during dose calculation in RTP by reducing a dose difference, and may maximize an effect of radiation treatment by improving accuracy of radiation treatment. Furthermore, the dose calculation method may calculate doses of images corresponding to the reference image through one simulation, and thus, may rapidly make RTP by reducing a dose calculation time.

FIG. 9is a schematic block diagram of a medical system10according to an embodiment of the inventive concept. Referring toFIG. 9, the medical system10may include a imaging device200and a dose calculation device300. The imaging device200may be, for example, a 4D CT device, and the dose calculation device300may correspond to the dose calculation device100ofFIG. 1.

FIG. 9illustrates that the dose calculation device300is independent from the imaging device200. However, the inventive concept is not limited thereto. The dose calculation device300may be included in the imaging device200.

The medical system10may rapidly and simply make RTP having improved reliability by reducing a dose difference.

FIG. 10is a schematic block diagram of a medical system20according to another embodiment of the inventive concept. Referring toFIG. 10, the medical system20may include a dose calculation device400and a treatment device500. The dose calculation device400may correspond to the dose calculation device100ofFIG. 1, and the treatment device500may perform radiation treatment on a patient based on dose calculation information (DCI) provided from the dose calculation device400. The DCI may be information generated based on a dose calculated by the dose calculation device400.

FIG. 10illustrates that the dose calculation device400is independent from the treatment device500. However, the inventive concept is not limited thereto. The dose calculation device400may be included in the treatment device500.

The medical system20may perform radiation treatment, by which the effect is maximized, based on DCI having improved reliability.