JP2014521399A - Image guided radiation therapy - Google Patents

Abstract

  Image-guided radiation therapy systems have a radiation source that produces radiation. The radiation optical unit forms a therapeutic radiation beam from the radiation from the radiation source. The imaging system forms an image of the target zone and controls the radiation optics to direct the therapeutic radiation beam onto the target zone. The radiation optic includes an optical module configured to generate an imaged photonic beam that is provided with optical angular momentum. The imaging system includes a magnetic resonance assembly that receives a magnetic resonance signal from the target zone generated by an imaging photonic beam provided with the optical angular momentum.

Description

  The present invention relates to an image guided radiation therapy system.

  An image guided radiation therapy system is known from the international application WO 2010/067227.

  Known image guided radiation therapy systems have a magnetic resonance imaging system that acquires magnetic resonance imaging data in an imaging zone. The guide means guides a beam of charged particles to the target zone in the object. The imaging zone includes a target zone, and the target zone in the object is determined using magnetic resonance imaging data. The beam of charged particles surrounds an angle with a magnetic field line less than 30 °.

  It is an object of the present invention to provide an image guided radiation therapy system that more accurately controls a therapeutic radiation beam onto a target zone.

This object is achieved by an image guided radiation therapy system according to the invention, which system comprises:
A radiation source that generates radiation; and
A radiation optic for forming a therapeutic radiation beam from radiation from the radiation source;
An imaging system that forms an image of a target zone and controls the radiation optics to direct the therapeutic radiation beam onto the target zone;
The radiation optic comprises an optical module configured to generate an imaging photonic beam provided with optical angular momentum;
The imaging system includes a magnetic resonance assembly that receives a magnetic resonance signal from the target zone generated by an imaging photonic beam provided with the optical angular momentum.

  The imaging photonic beam given the optical angular momentum generates nuclear hyperpolarization in the tissue of the object to which the photonic beam is directed, for example the patient to be examined. Due to the generated hyperpolarization, a magnetic resonance signal is generated from the tissue to which the OAM photonic beam is directed. The magnetic resonance imaging assembly generates a magnetic resonance image of the tissue illuminated by the OAM photonic beam. This magnetic resonance image is reconstructed from magnetic resonance signals generated by the OAM photonic beam. An insight of the present invention is that magnetic resonance images generated based on OAM photonic beams can be used to image the therapeutic radiation beam. Another insight of an example of the present invention is that when both the therapeutic radiation beam and the OAM photonic beam are formed by the radiation optics, the beam path of the therapeutic radiation beam and the OAM photonic beam is well defined. It is to be. Based on this spatial relationship between the therapeutic radiation beam and the OAM photonic beam, it is realized to image the area where the therapeutic beam actually impacts the patient's anatomy. Thus, based on the magnetic resonance image generated based on the hyperpolarization generated by the OAM photonic beam, the therapeutic radiation beam can be monitored and accurately directed onto the target zone. That is, the OAM photonic beam causes the hyperpolarized region of tissue in the patient being examined to appear as a hyperintensity region in the magnetic resonance image. This hyperintensity region indicates the position and orientation of the therapeutic radiation beam relative to the patient being examined. In particular, the target zone includes a lesion, for example a tumor to be treated with a therapeutic radiation beam.

  In additional examples of the invention, the therapeutic radiation beam can be a high energy X-ray beam, a gamma ray beam, or the therapeutic radiation beam can be a particle such as a proton beam, a heavy ion beam, or a gamma radiation beam. It can be a beam.

  In a preferred mode of operation of the image guided therapy system of the present invention, the optical module generates an imaging OAM photonic beam immediately before the radiation source is activated. In this way, the position and orientation of the therapeutic radiation beam path can be accurately verified. This verification does not result in a significant radiation dose (eg, x-ray dose) deposition on the patient.

  In addition, the optical module selects a polarizing plate, a beam expander (to allow the beam to fill a branched hologram), a diffraction grating with a branched hologram pattern, and a spatial filter (diffractive element with OAM). And an optical system for generating an OAM photonic beam using a focusing lens. In order to ensure that the optical system works for high values of the optical angular momentum (l value) of the photonic beam, the size of the spatial filter and the opening of the other optical elements are the radius of the photonic beam with OAM. Need to be increased based on (increases with l value). Since only a relatively weak static magnetic field is needed to establish the hyperpolarized nuclear precession frequency (ie, hyperpolarized nuclear spin moment), the outside of the patient's body to be examined A simple magnet that can be used in is sufficient. Magnetic resonance spectrum data is obtained from the acquired magnetic resonance signal by the magnetic resonance spectrometer. The generation of a magnetic resonance signal from an OAM photonic beam itself is known from International Application No. WO2009 / 081360A1.

  These and other aspects of the invention will be further described with reference to the embodiments defined in the dependent claims.

  According to one aspect of the invention, the optical module is configured to form a therapeutic radiation beam and an imaging photonic beam that are provided with the optical angular momentum from the radiation source. This easily realizes that the beam paths of the imaging photonic beam and the therapeutic radiation beam are in a well-defined mutual spatial relationship. Furthermore, the radiation source is used efficiently in that it is the basis for the OAM photonic beam and the therapeutic radiation beam. In a further aspect of the invention, the therapeutic radiation beam itself can be provided with optical angular momentum and function as an OAM photonic beam.

  According to a next aspect of the invention, the optical module comprises a separate imaging radiation source, for example an X-ray source. This aspect of the invention realizes that different types of radiation can be used for the therapeutic radiation beam and the imaging photonic beam, respectively. This makes it possible to use different types of radiation for the therapeutic radiation beam and the imaging photonic beam. For example, the therapeutic radiation beam can be a particle beam and the imaging photonic beam can be an x-ray beam. Thus, on the one hand, the electromagnetic radiation for the OAM photonic beam can be selected to produce good imaging results to give a high quality rendering of the target zone. On the other hand, the therapeutic radiation can be selected to achieve an optimal therapeutic effect on the irradiation of the target zone.

  In a further aspect of the invention, the imaging OAM photonic beam has an energy range. This range of energy causes hyperpolarization in elongated regions in the tissue. This is because hyperpolarization is generated by the OAM photonic beam over a wider range along its propagation direction due to the higher energy with a greater penetration depth in the tissue. On the other hand, in the direction transverse to the propagation direction, hyperpolarization is generated over a uniform range. At least this range is narrower than the range along the propagation direction. In particular, a more or less cylindrical or ellipsoidal hyperpolarization range is formed. The beam path of the OAM photonic beam then exists along an elongated region, eg, the long axis of an ellipsoid, so that the treatment radiation beam can be accurately aligned with the beam path thus visualized. This allows a simple and accurate visualization of the area covered by the therapeutic radiation beam. Also, the position and direction of the therapeutic radiation beam is well visualized by the hyperintensity region in the magnetic resonance image. For example, the therapeutic radiation beam path can be adjusted to be along the long axis of an elongated region in the tissue where hyperpolarization is generated by the imaging OAM photonic beam.

  In a further aspect of the invention, the therapeutic radiation beam has an energy range of, for example, 6-10 MeV. This range has good efficacy for treating tumors in that necrosis is created in the area where the therapeutic radiation beam is absorbed by the (cancer) tissue. The imaging OAM photonic beam has an energy range of 10 to 100 keV, for example. This range has a good penetration depth in the tissue to reach a lesion or tumor in the patient's anatomy.

  According to another aspect of the invention, the optical module is configured to generate a plurality of imaging OAM photonic beams. In particular, these imaging OAM photonic beams are directed to different locations around the beam path of the therapeutic radiation beam. This aspect of the invention achieves good boundary determination in magnetic resonance images of the area covered by the therapeutic radiation beam. In particular, the hyper-intensity region generated by a separate imaging OAM photonic beam provides a good visualization of the determination of the therapeutic radiation beam boundary in the patient's anatomy. Thus, precise control of the radiation optics is achieved to direct the therapeutic radiation beam onto the target zone to impinge on the lesion or tumor, avoiding radiation damage to sensitive healthy tissue near the target zone. Is realized.

1 is a schematic representation of an image guided radiation therapy system in which the present invention is implemented. It is a figure which shows the schematic expression of the detail of an optical module. 1 shows a schematic diagram of an image guided radiation therapy system according to the invention in the form of a hybrid LINAC-MRI system.

  These and other aspects of the invention will be described with reference to the accompanying drawings and with reference to the embodiments described below.

  FIG. 1 shows a schematic diagram of an image guided radiation therapy system in which the present invention is implemented. The radiation source 11 emits therapeutic radiation to the radiation optics 12 that forms the treatment beam 14. The therapeutic radiation can be high energy electromagnetic radiation such as gamma radiation, hard X-rays, for example. The radiation optic is configured to direct the toe treatment beam onto the target zone 16 in the patient being treated, for example. In particular, the radiation source and the radiation optics can be formed as a linear accelerator (LINAC) system that generates a high energy electron beam directed to the anode target to generate a high energy electromagnetic radiation emission from the anode target. . In the LINAC example, the radiation source 11 includes a cathode formed as emitting a high energy electron beam to the anode. An electromagnetic lens system for directing the electron beam to the anode is provided at the radiation source 11. The impinging high-energy electrons cause the anode material to emit high-energy x-rays that in this example form therapeutic radiation. The radiation optics 12 includes a beam collimator, preferably in the form of a multi-leaf collimator that forms a high energy radiation beam 14 from the high energy radiation emitted from the anode.

  An imaging system 13 is provided to monitor the precise aim of the high energy radiation beam 14 onto the target zone 16. The imaging system 13 includes a magnetic resonance assembly 131 that generates a magnetic resonance image of the illuminated object. A magnetic resonance signal at the object, in particular at the target zone, is generated by an OAM photonic radiation beam 15 generated by an optical module 121 included in or attached to the radiation optics 12. Alternatively, the optical module can be mounted on a common gantry 137 on the opposite side of the radiation source. Thus, the beam paths of the high energy radiation beam and the OAM photonic beam 15 can be aligned in that a fixed and stable geometric relationship exists between both beam paths. Details of the optical module are shown in FIG. The OAM photonic beam 15 is given an optical angular momentum. This beam can interact with the material (tissue) in the target zone 16 and creates (nuclear) hyperpolarization in the target zone 16. From the magnetic resonance signal acquired from the target zone, a magnetic resonance image is reconstructed by the reconstructor 132 using, for example, a fast Fourier transform method. The magnetic resonance image is displayed on the monitor 133. The magnetic resonance assembly generates a main magnet 134 that generates a baseline static magnetic field to determine the Larmor precession frequency of the hyperpolarized nucleus, and a gradient magnetic field that spatially encodes (frequency and phase encode) the magnetic resonance signal. A gradient coil 135 and an RF coil for acquiring a magnetic resonance signal are included. In particular, the gradient coil 135 is a split gradient with two gradient coil cross sections separated by an aperture that allows not only the high energy beam 14 but also the OAM photonic beam 15 to travel relative to the target zone 16. Realized as a coil. The OAM photonic beam 15 is aligned with the high energy beam 14. As a result, the region where hyperpolarization is generated by the optical angular momentum corresponds to the region where the high energy radiation beam is absorbed by the material, ie, tissue. The hyperpolarized region appears as a hyperintensity region in the magnetic resonance image. This allows a simple and accurate adjustment of the beam path of the high energy radiation to coincide with the target zone 16 to be irradiated. Adjustment of the beam path of the high energy radiation beam is performed using a control unit 122 that receives image information of the magnetic resonance image from the reconstructor. From the direction and position with respect to the hyper-intensity region and the treatment plan representing the irradiated target zone 16, the control unit calculates the required beam path and a high-energy radiation beam onto the target zone along the calculated beam path. To control the radiation source.

  FIG. 2 shows a schematic representation of the details of the optical module. In FIG. 2, an exemplary configuration of optical elements for providing OAM to light is shown. It should be understood that OAM can be applied to any electromagnetic radiation, not necessarily just visible light. The above embodiment uses soft X-rays. This interacts with the molecule of interest and has no damaging effect on living tissue. However, light / radiation above and below the visible spectrum is also envisaged. The X-ray source 22 generates X-rays that are transmitted to the beam expander 24. Preferably, the X-ray has an energy n in the range of 10-100 keV that provides a suitable depth of penetration into the tissue of the patient being treated. The beam expander 24 includes an entrance collimator 251, which collimates the emitted light into a narrow beam, a concave or dispersive lens 252, a refocus lens 253, and an exit collimator 254 from which light with the least dispersion frequency is emitted. Including. In some embodiments, the exit collimator 254 narrows the beam to a 1 mm beam.

  After the beam expander 24, the light beam is circularly polarized by the linear polarizer 26. The linear polarizer is followed by a quarter wave plate 28. The linear polarizer 26 takes unpolarized light and gives it a single linear polarization. The quarter-wave plate 28 shifts the phase of the linearly polarized light by a quarter wavelength and polarizes it into a circle. The use of circularly polarized light is not important. However, it has the additional advantage of polarizing electrons.

  Next, the circularly polarized light passes through the phase hologram 30. The phase hologram 30 gives OAM and spin to the incident beam. The OAM value “l” is a parameter depending on the phase hologram 30. In some embodiments, an OAM value l = 40 is provided for incident light. However, higher values of l are theoretically possible. The phase hologram 30 is a computer-generated element that is physically implemented in a spatial light modulator such as a 1280 × 720 pixel, 20 × 20 μm 2 liquid crystal on silicon (LCoS) panel with a cell gap of 1 μm. Alternatively, the phase hologram 30 can be realized in other optical elements, for example a combination of cylindrical lenses or wave plates. Spatial light modulators have the additional advantage of being able to change even between scans using simple instructions for LCoS panels.

  Not all of the light that passes through the holographic plate 30 is given OAM and spin. In general, when an electromagnetic wave with the same phase passes through an opening, it is diffracted and projected into a concentric pattern some distance away from the opening (Airy pattern). This bright spot in the center (Airy disk) represents the 0th order diffraction. In this case, it is light without OAM. The circle adjacent to the bright spot represents the different harmonic diffracted beams carrying the OAM. This distribution occurs because the probability of OAM interaction with the molecule decreases to zero at points far from the center of the light beam or at the center of the light beam. The greatest chance for interaction occurs on the radius corresponding to the maximum magnetic field distribution, ie for a circle close to the Airy disk. Thus, the maximum probability of OAM interaction is obtained with a light beam having a radius as close as possible to the Airy disk radius.

  Spatial filter 36 is placed after the holographic plate to selectively pass only light with OAM and spin. The zero order spot 32 always appears in a predictable spot and can therefore be blocked. As shown, the filter 36 allows light with OAM to pass through. Note that filter 36 also blocks the circle that occurs below and to the right of bright spot 32. Since the OAM of the system is saved, this light has an OAM equal and opposite to the OAM of the light that the filter 36 allows to pass. Passing all the light is counterproductive. This is because the net OAM transferred to the target molecule is zero. Thus, the filter 36 allows only light having one polarity of OAM to pass. The diffracted beam carrying the OAM is collected using a concave mirror 38 and focused on the region of interest using a high speed microscope objective 40. If coherent light is used, the mirror 38 is not necessary. A faster lens (with a high F number) is desirable to meet the beam waist condition as close as possible to the size of the Airy disk. In another embodiment, the lens 40 can be replaced or supplemented with alternative light guides or fiber optics.

  FIG. 3 shows a schematic diagram of the image guided radiation therapy system of the present invention in the form of a hybrid LINAC-MRI system. A radiation source 11 having an accelerator for generating an electron beam is attached to the gantry 137. The therapeutic radiation beam 14 is, in this example, a high energy x-ray beam emitted from the anode in the radiation source that is struck by the electron beam. The beam path of the therapeutic radiation beam 14 travels between the main magnet coils 134 of the magnetic resonance examination assembly. The cross section of the therapeutic radiation beam is shaped by a multi-leaf collimator (MLC) built into the radiation source 11. The optics module 12 also provides an OAM photonic beam that is integrated into the radiation source and guided along its beam path. The optical module is mounted at the radiation source in such a way that the beam paths of the OAM photonic beam and the therapeutic radiation beam have essentially the same central longitudinal axis. This ensures that the OAM photonic beam produces (nuclear) hyperpolarization in the region where the radiation source deposits its high energy radiation.

Claims (7)

An image guided radiation therapy system,
A radiation source that generates radiation; and
A radiation optic for forming a therapeutic radiation beam from radiation from the radiation source;
An imaging system that forms an image of a target zone and controls the radiation optics to direct the therapeutic radiation beam onto the target zone;
The imaging system includes an optical module configured to generate an imaging photonic beam provided with optical angular momentum;
The imaging system comprises a magnetic resonance assembly that receives a magnetic resonance signal from the target zone generated by an imaging photonic beam provided with the optical angular momentum.   The image-guided radiation therapy system according to claim 1, wherein the optical module is attached to the radiation optical unit.   The image-guided radiation therapy system of claim 1, wherein the optical module is configured to form an imaging photonic beam that is imparted with the optical angular momentum from the radiation source.   The image-guided radiation therapy system according to claim 1, wherein the optical module comprises an imaging radiation source.   The image-guided radiation therapy system of claim 1, wherein the imaging photonic beam provided with the optical angular momentum has a range of energy.   The image-guided radiation therapy system according to claim 1, wherein the imaging photonic beam provided with the optical angular momentum has an energy range of 10 to 100 keV, and the therapeutic radiation beam has an energy range of 6 to 10 MeV.   The image-guided radiation therapy of claim 1, wherein the optical module is configured to generate a plurality of the optical angular momentum provided imaging photonic beams that are directed to different locations around the therapeutic radiation beam path. system.

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