Multi-Modal Imaging System and Method for Non-Invasive Examination of an Object to be Examined

Abstract

The invention relates to a multi-modal imaging system (2) for non-invasive examination of an examination object (10), comprising a multi-photon imaging system for providing high-resolution detailed images of the examination object (10), which imaging system comprises a radiation source (12), the latter generating an excitation beam (21) of near infrared femtosecond laser radiation for triggering secondary radiation emitted by the examination object (10), and a focusing optical unit (30), by means of which the radiation of the radiation source (12) is directable at a measurement position of the examination object (10), wherein the focusing optical unit (30) and a laser head (14) of the radiation source (12) are provided in a measuring head (4), which is pivotable, rotatable and flexibly positionable freely in space such that the examination of the examination object (10) is performable under any desired solid angle, and comprising at least one confocal detection device, which is at least partly integrated in the measuring head (4) as well and which is configured to receive a signal of the excitation beam (21) of near infrared femtosecond laser radiation, which was diffusely reflected by the examination object (10).

Moreover, a method is specified for non-invasive examination of an examination object (10) using a multi-modal imaging system (2), as is the use of the multi-modal imaging system (2) for examining living matter of the examination object (10)

Claims

1. A multi-modal imaging system (2) for non-invasive examination of an examination object (10), comprising a multi-photon imaging system for providing high-resolution detailed images of the examination object (10), which imaging system comprises a radiation source (12), the latter generating an excitation beam (21) of near infrared femtosecond laser radiation for triggering secondary radiation emitted by the examination object (10), and a focusing optical unit (30), by means of which the radiation of the radiation source (12) is directable at a measurement position of the examination object (10), wherein the focusing optical unit (30) and a laser head (14) of the radiation source (12) are provided in a measuring head (4), which is pivotable, rotatable and flexibly positionable freely in space such that the examination of the examination object (10) is performable under any desired solid angle, and comprising at least one confocal detection device, which is at least partly integrated in the measuring head (4) as well and which is configured to receive a signal of the excitation beam (21) of near infrared femtosecond laser radiation, which was diffusely reflected by the examination object (10).

2. The multi-modal imaging system (2) as claimed in claim 1, wherein at least parts of a detector system of the imaging system are provided in a manner integrated in the measuring head (4) as well, in particular wherein the multi-modal imaging system (2) can be battery-operated.

3. The multi-modal imaging system (2) as claimed in either of the preceding claims, comprising at least one further system for providing overview images of the examination object (10), wherein the further system is at least partly integrated in the measuring head (4) as well and wherein the further system comprises a CCD camera or CMOS camera (64) and/or an optical coherence tomography device, in particular wherein the further system is configured to use the near infrared femtosecond laser radiation as illumination radiation.

4. The multi-modal imaging system (2) as claimed in claim 3, wherein the CCD camera or CMOS camera (64) is arranged laterally at the front of the measuring head (4) in accordance with the Scheimpflug principle, or wherein the CCD camera or CMOS camera (64) uses the focusing optical unit (30) as an imaging element.

5. The multi-modal imaging system (2) as claimed in any one of the preceding claims, wherein, for reducing an amplitude of the central reflection, the confocal detection device is arranged in such a way that it taps a partly transmitted signal of a deflection mirror (60) arranged in front of the radiation source (12), wherein, for reducing an amplitude of the central reflection, a polarization beam splitter (22) for separating linearly polarized excitation radiation and diffusely reflected unpolarized secondary radiation of the examination object (10) is provided and the confocal detection device is arranged in such a way that it receives the diffusely reflected unpolarized secondary radiation of the examination object (10).

6. The multi-modal imaging system (2) as claimed in any one of the preceding claims, wherein the confocal detection device comprises an apparatus for time-resolved signal processing of the diffusely reflected signal of the excitation beam (21) of near infrared femtosecond laser radiation.

7. The multi-modal imaging system (2) as claimed in any one of the preceding claims, wherein, for the purposes of providing an autofocus function, the multi-modal imaging system (2) comprises an apparatus for determining the position of a coverslip (106) and/or of the examination object (10).

8. The multi-modal imaging system (2) as claimed in claim 7, comprising an OC measurement beam (92) aligned collinearly with the optical axis of the focusing optical unit (30), the position of a coverslip (106) and/or of the examination object (10) being determinable with the aid of said OC measurement beam, for the purposes of providing the autofocus function.

9. The multi-modal imaging system (2) as claimed in any one of the preceding claims, comprising a pressure sensor for finding a surface of the examination object (10) and/or for monitoring a contact pressure.

10. The multi-modal imaging system (2) as claimed in any one of the preceding claims, wherein a release controller for the excitation beam (21) is coupled to an apparatus for determining the presence of the examination object (10) in the measurement region.

11. A method for non-invasive examination of an examination object (10) using a multi-modal imaging system (2) as claimed in any one of the preceding claims, said method including the following steps: aligning the focusing optical unit (30) with a measurement position, directing the near infrared femtosecond laser radiation of the radiation source (12) at the measurement position, and measuring the emitted secondary radiation of the examination object (10) for creating a high-resolution detailed image of the examination object (10) at the measurement position, either successively or simultaneously by the multi-photon imaging system and by the confocal detection device.

12. The method as claimed in claim 11, including the following further steps: aligning the measuring head (4) with an overview region of the examination object (10), recording an overview image of the examination object (10) by the confocal detection system and/or by a CCD camera or CMOS camera (64) and/or an optical coherence tomography device (74), and selecting a measurement position in the overview region for the purposes of recording the high-resolution detailed image.

13. The method as claimed in claim 11 or 12, wherein axial movement artifacts of the examination object (10) are corrected by an autofocus function by virtue of the distance between the focusing optical unit (30) and the examination object (10) being continuously mechanically adjusted.

14. The method as claimed in any one of claims 11 to 13, wherein measurement signals are evaluated with the aim of finding the surface of the examination object (10), in particular for providing an autofocus function.

15. The method as claimed in any one of claims 11 to 14, wherein an overview image is recorded by a CCD camera or CMOS camera (64) and/or by an optical coherence tomography device (74) and wherein a greater distance between the focusing optical unit (30) and the examination object (10) is set when recording the overview image of the examination object (10) than when recording the detailed image of the examination object (10) and/or wherein the overview image is recorded as an oblique image by the CCD camera or CMOS camera (64) and/or by the optical coherence tomography device (74) in a manner not collinear with respect to the optical axis of the focusing optical unit (30).

16. The use of a multi-modal imaging system (2) as claimed in any one of claims 1 to 10 for examining living matter of the examination object (10).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0097] The figures illustrate possible exemplary embodiments of the invention.

[0098] In detail:

[0099] FIG. 1 shows a schematic illustration of a multi-modal imaging system as per one embodiment of the invention,

[0100] FIG. 2 shows a schematic illustration of a multi-modal imaging system as per a further embodiment of the invention,

[0101] FIG. 3 shows two schematic illustrations of an examination object during an examination by a multi-modal imaging system as per one embodiment of the invention at different times,

[0102] FIG. 4 shows a schematic illustration of an examination object during an examination by a multi-modal imaging system as per one embodiment of the invention,

[0103] FIG. 5 shows a schematic illustration of an examination object during an examination by a multi-modal imaging system as per a further embodiment of the invention,

[0104] FIG. 6 shows a schematic illustration of an examination object during an examination by a multi-modal imaging system as per a further embodiment of the invention,

[0105] FIG. 7 shows a schematic illustration of part of the measuring head of a multi-modal imaging system as per a further embodiment of the invention,

[0106] FIG. 8 shows a perspective illustration of an examination object during an examination by a multi-modal imaging system as per one embodiment of the invention, and

[0107] FIG. 9 shows a graph of signal strength over penetration depth.

EMBODIMENTS OF THE INVENTION

[0108] The exemplary embodiments described below with reference to figures should not be construed as restricting the subject matter of the invention. The figures represent the subject matter of the invention only schematically.

[0109] In the figures, the same or similar components have been provided with the same reference sign, with repeat mention of these components being dispensed with in the description in individual cases.

[0110] FIG. 1 shows a schematic illustration of a multi-modal imaging system 2 as per a first embodiment of the invention.

[0111] The multi-modal imaging system 2 comprises a measuring head 4 which is pivotable, rotatable and flexibly positionable freely in space such that an examination of an examination object 10 is performable under any desired solid angle.

[0112] For the purposes of positioning the measuring head 4 freely, the latter is fastened to a mobile base device 6 by means of an articulated arm 8.

[0113] The multi-modal imaging system 2 comprises a radiation source 12, which comprises a laser head 14 arranged in the measuring head and a laser driver 16 arranged in the mobile base device 6. The laser head 14 and the laser driver 16 are interconnected by way of a first light guide 18, for example an optical fiber. In some embodiments (not illustrated), the first light guide 18 can be integrated in the articulated arm 8.

[0114] By way of example, the laser driver 16 comprises the power supply of the laser and pump diodes. By way of example, the laser head 14 comprises an SHG unit, which doubles the frequency of the radiation emitted by the laser driver 16 for the purposes of generating a linearly polarized excitation beam 21.

[0115] The excitation beam 21 passes a power setting unit 20 and a polarization beam splitter 22 and is steered to a focusing optical unit 30 via a scanning unit 24 and via two lenses 26, 28, said focusing optical unit focusing the excitation beam 21 on the examination object 10. The scanning unit 24 allows an angular deflection of the excitation radiation in two planes, which is converted into a two-dimensional translational movement of the excitation volume by means of the focusing optical unit 30.

[0116] The focusing optical unit 30 is adjustable in a z-direction, which is indicated by arrows, by means of a linear actuator 32. To this end, the linear actuator 32 comprises a motor. In the illustrated exemplary embodiment, the z-direction corresponds to the optical axis of the focusing unit 30.

[0117] The entire measuring head 4 is locked at any desired position in space by the articulated arm 8. An adapter plate 36, which comes into contact with the examination object 10, is provided between the focusing optical unit 30 and the examination object 10. The adapter plate 36 is described in more detail with reference to FIG. 8. An xy-translation stage 34 is configured to laterally move the adapter plate 36 and the examination object 10 coupled to the adapter plate 36 with respect to the measuring head 4. To this end, the xy-translation stage 34 comprises appropriate motor-driven actuators.

[0118] The excitation beam 21 interacts with the examination object 10. Thereupon, the examination object 10 emits secondary radiation, for example reflected radiation, fluorescence radiation, in particular TPF, SHG or THG, which is received by the focusing optical unit 30. In the illustrated exemplary embodiment, two dichroic beam splitters 38, 42 are provided between the second lens 28 and the focusing optical unit 30, said dichroic beam splitters transmitting the TPF, SHG or THG signals to a first and a second detector 40, 44. By way of example, the first detector 40 can be embodied to capture the SHG signals and the second detector 44 can be embodied to capture the TPF signals. In some embodiments (not illustrated), it is possible that only one of the dichroic beam splitters 38, 42 is positioned between the lens 28 and the focusing optical unit 30. In this embodiment, the spectral separation of the signals can be implemented in one of the coupled first and second beam paths 150, 151 using further beam splitters.

[0119] In the illustrated exemplary embodiment, a confocal detection device is integrated in the multi-modal imaging system 2. The confocal detection device comprises the polarization beam splitter 22, a lens 46, a pinhole 49, and a confocal radiation detector 52. The confocal detection device receives part of the unpolarized reflection radiation triggered by the excitation beam 21 at the examination object 10. After passing the scanning unit 24, the reflection radiation is tapped in descanned fashion to this end. After passing the scanning unit 24, the signal is reflected at the polarization beam splitter 22 and guided via the lens 46 and the pinhole 49 to the confocal radiation detector 52, which is also referred to as a CLSM detector. In the illustrated exemplary embodiment, the confocal radiation detector 52 is situated in the measuring head 4. The radiation source 12 serves as the illumination for the confocal detection device.

[0120] A reduction in the amplitude of the central reflection is advantageously achieved by the above-described tapping of the signal whose polarization state differs from that of the excitation beam. In some embodiments, a further reduction or complete compensation can be implemented by way of a time-resolved detection of the confocal signal, with the confocal radiation detector 52 comprising appropriate apparatuses to this end, for example a gate circuit.

[0121] In an alternative embodiment, not shown, for capturing the confocally detected fluorescence, the polarization beam splitter 22 can be replaced by a dichroic mirror, the dichroic beam splitters 38, 42 removed, and the detection beam path 160 supplemented by a fluorescence bandpass filter.

[0122] In addition to the laser driver 16, the mobile base device 6 typically also comprises signal inputs (not shown) for the signals or images for multi-photon and CLSM imaging, received by the detectors 40, 44 and by the confocal radiation detector 52.

[0123] Moreover, the mobile base device 6 comprises a control unit 54, by means of which user inputs, for example, can be processed, the individual components, such as the power sources, can be controlled, and by means of which, also, a change between the overview image and detailed image of the examination object 10, as initiated by a user or by a trigger unit, can be processed. As part of the interface for the user, the mobile base device comprises a display 56, for example a touchscreen or a monitor.

[0124] Moreover, wheels 58 are indicated in order to show that the multi-modal imaging system 2 is mobile. A battery unit 23 is provided as a power supply for the multi-modal imaging system 2.

[0125] FIG. 2 shows an alternative embodiment of the multi-modal imaging system 2. The multi-modal imaging system 2 illustrated in FIG. 2 likewise comprises a confocal detection device.

[0126] The excitation beam 21 generated by the radiation source 12 is initially deflected by a deflection mirror 60 with a high reflectivity, for example more than 90% or more than 95%, but less than 100%, in this embodiment. The further beam path of the excitation beam 21 is as described with reference to FIG. 1. The secondary signal captured by the focusing optical unit 30 at the examination object 10 is guided back by the scanning unit 24 as descanned signal.

[0127] The confocal detection device taps the secondary signal as partially transmitted signal of the deflection mirror 60. To this end, after passing the deflection mirror 60, the partially transmitted signal is guided via an analyzer 62, which is aligned such that the polarization states of the excitation radiation 21 and the transmitted detection radiation 100 are polarized orthogonal to one another (crossed polarization). In the exemplary embodiment illustrated here, the transmitted detection radiation 100 is coupled into a second light guide 50 at an input coupling point 48, which is situated in the measuring head 4, via the lens 46, the core diameter of said second light guide corresponding to the diameter of, e.g., an Airy disk, and said transmitted detection radiation is supplied to the confocal radiation detector 52. In the illustrated exemplary embodiment, the confocal radiation detector 52 is situated in the base device 6. This exemplary embodiment with detection in a crossed polarization arrangement also facilitates an effective suppression of the central reflection.

[0128] FIG. 3 shows an examination object 10 during an examination by a multi-modal imaging system 2 according to one embodiment of the invention at different times, with part of the measuring head 4 being illustrated in each case, said measuring head facilitating imaging as described with reference to FIG. 1 or 2, for example.

[0129] The left half of FIG. 3 illustrates the camera-based overview imaging. To this end, a camera 64 is coupled to the adapter plate 36. In the illustrated exemplary embodiment, the camera 64 comprises a further radiation source 70 for generating visible radiation (VIS), e.g., white light, and a camera lens 154.

[0130] Following the overview recording, the camera 64 is removed and the measuring head 4 with the device for high-resolution microscopic imaging is positioned with respect to the examination object 10, as illustrated on the right in FIG. 2.

[0131] FIG. 4 shows an alternative embodiment of a multi-modal imaging system 2, which couples the multi-photon imaging with the confocal detection device and, additionally, with camera-based imaging.

[0132] The beam path of the multi-photon imaging and the confocal detection device can be configured as described with reference to FIG. 2. The camera 64 is completely integrated in the measuring head 4. The camera 64 uses the focusing optical unit 30 as imaging element and the radiation source 12 as illumination. The imaging condition for the camera-based imaging is satisfied by virtue of a greater working distance being set between the focusing optical unit 30 and the examination object 10. By way of example, using the linear actuator 32 to position the focusing optical unit 30 at a distance of approximately 10 mm from the examination object 10 is advantageous here. As a result of the large object distance and the high numerical aperture of the focusing optical unit 30, a large-area illumination of the tissue is provided by the excitation beam 21 of the radiation source 12. The signal passes the scanning unit 24 and is reflected at an intensity beam splitter 152. For this purpose, the intensity beam splitter 152 has an asymmetric reflection/transmission ratio, e.g., less than 20/80, preferably less than 10/90, e.g., 05/95. A beam blocker component 153 is inserted for the purposes of blocking a back side reflection of the intensity beam splitter 152. Then, the signal is fed via a fourth and a fifth lens 66, 68 to the camera 64 and detected there in spatially resolved fashion by the camera sensor. In this configuration, the examination object 10 is situated in the object plane and the camera chip is situated in the image plane of the imaging optical system. The fourth and fifth lens 66 and 68 can also be supplemented by a significantly more complex lens system. It is understood that the measuring head 4 can have appropriate interfaces (not illustrated) for transferring the camera image to the mobile base device 6.

[0133] FIG. 5 shows a multi-modal imaging system 2 as per a further embodiment. In addition to the components of the multi-photon imaging and the confocal detection device described with reference to FIG. 1 or 2, for example, the multi-modal imaging system 2 comprises a camera 64 that is integrated laterally on or in the measuring head 4, wherein the arrangement of the camera sensor 64, the imaging lens 66 and the examination object 10 is implemented according to the Scheimpflug principle, in which the object plane, image plane and lens plane have a common axis of intersection. The camera 64 can use the radiation source 12 as illumination. As an alternative or in addition thereto, the further radiation source 70 for generating VIS light is separately arranged on the side as an independent unit, integrated on or in the measuring head.

[0134] The focusing optical unit 30 can be adjusted in the z-direction by way of the linear actuator 32, two different settings being illustrated in FIG. 5. At a first distance, the multi-modal imaging system 2 is aligned for recording detailed images of the examination object 10 and has an object distance d1 of, e.g., 0.2 mm (indicated by the reference signs with apostrophes 30, 32 for the linear actuator and the focusing optical unit). At a second object distance d2 of, e.g., 10 mm (illustrated by reference signs without apostrophes), the multi-modal imaging system 2 is configured to record the camera-based overview images. In the second case, the lateral and tilted arrangement offers the necessary optical accessibility for the camera-based imaging, without the object-side aperture angle of the camera-based imaging system being clipped by the external dimensions of the focusing optical unit 30.

[0135] As a further system, the multi-modal imaging system 2 moreover comprises an optical coherence tomography device, which is indicated in FIG. 5 by an optical coherence measurement system 74, comprising an interferometric measurement structure, spectrometer, illumination, and evaluation unit, and a further focusing optical unit 76. To integrate the optical coherence measurement, superluminescent diodes with a central wavelength around 1060 nm and a bandwidth of 70 nm are used for illumination purposes. The optical coherence measurement system 74, the further focusing optical unit 76 and an OC measurement beam 92 of the optical coherence tomography device are tilted at an angle of, e.g., 30 to 60, preferably from 40 to 50, particularly preferably from 42 to 48, in particular for example 45 in relation to the optical axis of the excitation beam 21. As a result of this, the optical coherence tomography device can make an overview recording of the examination object, for example of the order of 5 mm5 mm1 mm when the second distance d2 is set. The lateral and tilted arrangement offers the necessary optical accessibility for the optical coherence tomography device.

[0136] There can be a two-dimensional deflection of the OC measurement beam 92 by way of two galvanometer scanners (not shown). Alternatively, there can be a one-dimensional deflection of the measurement beam 92 using only one galvanometer scanner, for example. In the latter case, the 3D imaging can be implemented by synchronizing the resultant line scan with the feed movement of the X- or Y-axis of the motor-driven xy-translation stage 34.

[0137] Naturally, there can be embodiments which only comprise the system with the laterally integrated camera 64 or only comprise the optical coherence tomography device that is arranged laterally in tilted fashion.

[0138] FIG. 6 shows a further configuration of a multi-modal imaging system 2 with multi-photon imaging and an optical coherence tomography device, as described with reference to FIG. 5. As a third system, the camera 64 in this embodiment is not arranged to the side but completely integrated in the measuring head. The camera 64 uses the focusing optical unit 30 as imaging element. In this configuration, the examination object 10 is situated in the object plane and the camera chip in the image plane of the imaging optical system. Reference sign 78 indicates a dichroic beam splitter. A separate further radiation source 70 which is coupled to the focusing unit 30 or to the translation stage 34 (illustrated in FIG. 6) is used for illumination purposes. Here, the spectral range of the excitation radiation 21 and the spectral range of the further radiation source 70 are disjoint. An illuminated region 72 of the further radiation source 70 for overview imaging is also illustrated.

[0139] FIG. 7 shows the integration of an autofocus unit by applying optical coherence without imaging. Here, the OC measurement beam 92 from the above-described optical coherence measurement system 74 is coupled into the beam path of the excitation radiation 21 by way of a third dichroic beam splitter 90. Here, the OC measurement beam and the optical axis of the focusing optical unit 30 are aligned in collinear fashion. By way of example, the optical layer of the dichroic beam splitter 90 facilitates the transmission for the illumination radiation with the excitation beam 21 in the spectral range of, e.g., 710 to 950 nm. The detected secondary signals in the spectral range below 710 nm and the spectral range for the OC measurement beam 92 are reflected. In order to obtain only a small effective numerical aperture and consequently a long Rayleigh length of the OC measurement beam 92, the exit pupil of the focusing optical unit 30 is not illuminated completely, but only to about 10% or less.

[0140] To integrate the optical coherence measurement, superluminescent diodes with a central wavelength around 1060 nm and a bandwidth of 70 nm are used for illumination purposes. Here, the interferometer is a constituent part of the optical coherence measurement system 74.

[0141] FIG. 8 shows a perspective view of a measuring head 4 with an adapter plate 36 and an examination object 10, part of human skin in this case. The adapter plate 36 comprises a metallic coupling ring 104, a coverslip 106, and an adhesive ring 108, in this order. A first immersion liquid, for example an oil, is provided between the focusing optical unit 30 of the measuring head 4 and the metallic coupling ring 104 in order to increase the value of the numerical aperture of the focusing optical unit 30. A second immersion liquid 110, for example water, is provided between the adhesive ring 108 and the examination object 10.

[0142] FIG. 9 shows measurement signals for finding the surface of the examination object 10. The surface of the examination object 10 can be defined by the transition from the low-signal coverslip or immersion fluid to the fluorescing sample. By way of example, the turning point from low-signal to high-signal regions is defined as the tissue surface.

TABLE-US-00001 List of reference signs 2 Multi-modal imaging system 4 Measuring head 6 Mobile base device 8 Articulated arm 10 Examination object 12 Radiation source 14 Laser head 16 Laser driver 18 First light guide 20 Power setting unit 21 Excitation beam 22 Polarization beam splitter 23 Battery unit 24 Scanning unit 26 First lens 28 Second lens 30 Focusing unit 32 Linear actuator 34 xy-translation stage 36 Adapter plate 38 First dichroic beam splitter 40 First detector 42 Second dichroic beam splitter 44 Second detector 46 Third lens 48 Coupling point 49 Pinhole 50 Second light guide 52 Confocal radiation detector 54 Control unit 56 Display 58 Wheel 60 Deflection mirror 62 Analyzer 64 Camera 68 Fifth lens 70 Further radiation source 72 Illuminated region 74 Optical coherence measurement system 76 Further focusing optical unit 78 Third dichroic beam splitter 90 Fourth dichroic beam splitter 92 OC measurement beam 100 Transmitted detection radiation 102 First immersion liquid 104 Metallic coupling ring 106 Coverslip 108 Adhesive ring 110 Second immersion liquid 150 First beam path 151 Second beam path 152 Intensity beam splitter 153 Beam blocker component 154 Camera lens 160 Detection beam path d1 First object distance d2 Second object distance