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CN-114340728-B - Pseudo CT image generation

CN114340728BCN 114340728 BCN114340728 BCN 114340728BCN-114340728-B

Abstract

A method for generating a calibrated pseudo-CT image of at least a portion of a patient for radiation treatment planning is disclosed herein. The method includes obtaining radiation intensity data indicative of attenuation characteristics of tissue within a patient and calibrating a first pseudo-CT image of at least a portion of the patient using the radiation intensity data to produce a calibrated pseudo-CT image.

Inventors

  • BROWN KEVIN

Assignees

  • 伊利克塔有限公司

Dates

Publication Date
20260508
Application Date
20200827
Priority Date
20190830

Claims (16)

  1. 1. A system for generating a calibrated pseudo-CT image of at least a portion of a patient for radiation treatment planning, the system comprising: a radiation source configured to generate a radiotherapy beam for delivering radiation to the patient, and a radiation detector arranged to detect the intensity of radiation passing through the patient; A controller, and A computer readable medium comprising computer executable instructions that, when executed by the controller, cause the system to: obtaining a first pseudo CT image of at least a portion of the patient; obtaining radiation intensity data indicative of attenuation characteristics of tissue within the patient using the radiation therapy beam, and The first pseudo CT image of at least a portion of the patient is calibrated using the radiation intensity data to produce the calibrated pseudo CT image.
  2. 2. The system of claim 1, wherein the first pseudo CT image is generated based on MR data obtained by imaging the patient with an MR imager.
  3. 3. The system of claim 2, wherein obtaining the first pseudo-CT image includes imaging the patient with the MR imager to obtain the MR data.
  4. 4. The system of claim 3, wherein the patient is positioned on a patient support surface when the MR data and radiation intensity data are obtained.
  5. 5. The system of any of the preceding claims, wherein the first pseudo CT image is further generated based on MR data and radiation intensity data obtained prior to generating the first pseudo CT image.
  6. 6. The system of any one of claims 1 to 4, wherein the first pseudo CT image includes a plurality of voxels, each respective voxel being associated with a pseudo CT value, and wherein, Generating the calibration phantom CT image includes comparing the obtained radiation intensity data with estimated radiation intensity data, the estimated radiation intensity data being based on at least one of the phantom CT values, and updating each phantom CT value of the first phantom CT image based on the comparison to generate the calibration phantom CT image.
  7. 7. The system of any one of claims 1 to 4, wherein the computer-executable instructions further cause the system to deliver radiation from the radiation source to the patient and obtain the radiation intensity data from the radiation detector.
  8. 8. The system of claim 7, wherein delivering the radiation to the patient further comprises irradiating a target area within the patient to deliver a dose of radiation to the target area according to a radiation treatment plan.
  9. 9. The system of claim 8, wherein the computer-executable instructions further cause the system to generate the radiation treatment plan based on the first pseudo-CT image.
  10. 10. The system of claim 8, wherein the computer-executable instructions further cause the system to: A second radiation is delivered to the patient according to a second radiation treatment plan to deliver a second radiation dose to the target region, the second radiation treatment plan being based on the calibrated pseudo-CT image.
  11. 11. The system of any of claims 1-4, wherein the computer-executable instructions further cause the system to deliver radiation to the patient according to a treatment plan and update the treatment plan a plurality of times in an iterative process, each iteration of the iterative process comprising: delivering radiation to the patient according to the treatment plan to deliver a dose of radiation to a target area; obtaining radiation intensity data indicative of attenuation characteristics of tissue within the patient; Updating the calibration phantom CT image using the radiation intensity data, and The treatment plan is updated based on the updated calibration phantom CT image.
  12. 12. The system of any one of claims 1 to 4, wherein the radiation intensity data comprises a calibrated CT image of the at least a portion of the patient, the calibrated CT image having a lower resolution than the first pseudo CT image.
  13. 13. The system of any one of claims 1-4, wherein the first pseudo-CT image includes a plurality of voxels, each respective voxel being associated with a pseudo-CT value and a tissue type, and Wherein generating the calibration pseudo CT image further comprises updating the pseudo CT values for each voxel based on the radiation intensity data and the tissue type.
  14. 14. The system of claim 1, further comprising an MR imager configured to obtain MR data.
  15. 15. The system of claim 14, further comprising a patient support surface, wherein the MR imager is configured to obtain the MR data and the radiation detector is configured to detect a radiation intensity passing through the patient when the patient is positioned on the patient support surface.
  16. 16. A computer readable medium for use in a system according to any one of claims 1 to 15, comprising computer executable instructions which, when executed by a processor, cause the processor to perform: Obtaining a first pseudo-CT image of at least a portion of a patient; Obtaining radiation intensity data indicative of attenuation characteristics of tissue within the patient using a radiation therapy beam, and The first pseudo-CT image of at least a portion of the patient is calibrated using the radiation intensity data to produce a calibrated pseudo-CT image.

Description

Pseudo CT image generation Technical Field The present invention relates to radiation therapy techniques, and in particular to systems and methods for generating calibrated pseudo-CT images of at least a portion of a subject suitable for use in radiation therapy planning. Background Radiation therapy can be described as the use of ionizing radiation (e.g., X-rays) to treat the human or animal body. In general, radiation therapy is used to treat tumors in a patient or subject. In such treatments, ionizing radiation is used for irradiation, thus destroying or damaging the cells forming part of the tumor. However, in order to apply a prescribed dose to a tumor or other target area in a subject, the radiation must pass through healthy tissue, irradiating it during the process and thus potentially damaging it. A general objective in this field is to minimize the dose received by healthy tissue during radiation therapy. There are many different radiation therapy techniques that allow radiation to be applied from different angles, at different intensities and for specific periods of time. Prior to radiation treatment, a radiation treatment plan is created to determine how and where radiation should be applied. Typically, such treatment plans are created with the aid of medical imaging techniques. For example, a CT (computed tomography) scan of the patient may be performed in order to generate a three-dimensional image of the region to be treated. The three-dimensional image allows the treatment planner to view and analyze the target area and identify surrounding tissue. Different structures within the patient (e.g., bones, lungs, muscles, etc.) will attenuate and absorb radiation to varying degrees based on their respective densities. In other words, different tissues within the human body have different radiodensities and thus attenuate and/or absorb radiation to different extents. Bone is an example of a tissue that is particularly radiation dense or radiopaque. In contrast, soft tissue (e.g., lung tissue) is radiolucent. The radiodensity of various tissues can be quantified in a manner known to the skilled artisan using, for example, the Hounsfield scale. In order to plan radiation treatment, it is necessary to obtain information about the radiodensity of not only the target region but also of the surrounding tissue and any region of the body through which the radiation treatment beam will pass. Traditionally, a CT scan is performed on a patient prior to treatment, which not only provides information about the patient geometry via a three-dimensional image of the patient, but also about the radiodensity of different tissues and structures within the patient. CT scanning typically produces a three-dimensional image consisting of voxels, wherein each voxel is assigned a CT value. Each voxel is associated with a specific location within the patient, and the CT values of the voxels together describe the radiodensity of tissue within the patient. CT values are determined using CT scanning techniques and are indicative of attenuation characteristics of tissue within the patient. The CT value may be expressed in Hunter units and directly related to the electron density information required for the radiation dose calculation. However, CT scanning involves illuminating the patient from multiple angles in order to produce a three-dimensional image. Thus, a disadvantage of CT scanning is that the radiation dose is increased to the patient even before the treatment is started. Moreover, while CT scans can provide the necessary information about tissue density for radiation treatment planning, CT scans provide poor soft tissue contrast. This makes it difficult for the treatment planner to distinguish between certain kinds of soft tissue. For example, it is difficult to see a tumor in a CT scan of the prostate, as the tumor and the prostate have very similar density and attenuation characteristics and thus look similar, or even identical, in the CT image. By comparison, obtaining a magnetic resonance (Magnetic Resonance, MR) image does not involve exposing the patient to ionizing radiation, and therefore does not provide any dose to the patient. In contrast, MR scanners use magnetic fields to excite atoms (typically hydrogen atoms) to emit radio frequency signals that can be detected and processed to form a three-dimensional image of the patient. MR images provide good soft tissue contrast, allowing the treatment planner to better distinguish between, for example, tumor tissue and prostate tissue. A disadvantage of MR scanning is that it does not indicate the attenuation characteristics of tissue within the subject, i.e. the tissue radiodensity information of the patient, which is required for creating a radiation treatment plan. MR and CT data can already be combined to facilitate the treatment planning process. It is known that MR images and CT images can be obtained independently and then aligned with each other, for exam