POSITION FEED BACK INDICATOR FOR MEDICAL IMAGING

Abstract

The invention provides for a medical instrument (100, 300, 400, 500, 600) comprising a camera system (102, 102′, 102″) for imaging a portion (418) of a subject (108) reposing on a subject support (106). The medical instrument further comprises a display system (104) for rendering a position feedback indicator (130, 900). The display system is configured such that the position feedback indicator is visible to the subject when the subject is reposing on the subject support. The execution of the machine executable instructions (120) causes a processor (114) controlling the medical instrument to: acquire (200) a base position image (122) using the camera system; repeatedly (202) acquire a subsequent image (124) using the camera system; repeatedly (204) calculate an image transformation (126) from voxels of at least a portion of the base position image to voxels of the subsequent image by inputting the base position image and the subsequent image into an image transformation algorithm (128); and repeatedly (206) render a position feedback indicator (130, 900) on the display, wherein the position feedback indicator is controlled by the image transformation.

Claims

1. A medical instrument comprising: a camera system for imaging a portion of a subject reposing on a subject support; a display system for rendering a position feedback indicator, that represents a displacement of the subject relative to an initial position of the subject, wherein the display system is configured such that the position feedback indicator is visible to the subject when the subject is reposing on the subject support. a memory for storing machine executable instructions; a processor for controlling the medical instrument, wherein execution of the machine executable instructions causes the processor to: acquire a base position image using the camera system, the base position image corresponding to the subject initial position; repeatedly acquire a subsequent image using the camera system; repeatedly calculate an image transformation from voxels of at least a portion of the base position image to voxels of the subsequent image by inputting the base position image and the subsequent image into an image transformation algorithm; and repeatedly render a position feedback indicator on the display, wherein the position feedback indicator is controlled by the image transformation.

2. The medical instrument of claim 1, wherein execution of the machine executable instructions further causes the processor to calculate an average image transformation quantity for voxels with a region of interest of the base position image using the image transformation, wherein the position feedback indicator is controlled using the average image transformation quantity.

3. The medical instrument of claim 2, wherein any one of the following: the position feedback indicator shows a displacement of an object relative to an initial position of that object; the position feedback indicator shows a displacement of a ball relative to a circle; and the position feedback indicator shows a displacement of an animated person relative to an initial position of that animated person.

4. The medical instrument of claim 1, wherein the position feedback indicator is a rendering of the image transformation.

5. The medical instrument of claim 1, wherein the medical instrument comprises a medical imaging system configured for acquiring medical imaging data from a subject, wherein the camera system is configured for imaging the portion of the subject when the medical imaging system is acquiring the medical imaging data.

6. The medical instrument of claim 5, wherein the medical imaging system is configured for acquiring the medical imaging data in portions, wherein execution of the machine executable instructions further cause the processor to: calculate a statistical measure from the image transformation; and retrospectively validate or invalidate the portions of the medical imaging data by comparing the statistical measure to predetermined criteria.

7. The medical instrument of claim 5, wherein the medical imaging system is configured for acquiring the medical imaging data in portions, wherein execution of the machine executable instructions further cause the processor to: calculate a frame-to-frame image transformation by inputting sequentially acquired images selected from the repeatedly acquired subsequent images into the image transformation algorithm; calculate a statistical measure from the frame-to-frame image transformation; and retrospectively validate or invalidate the portions of the medical imaging data by comparing the statistical measure to predetermined criteria.

8. The medical instrument of claim 6, wherein execution of the machine executable instructions further causes the processor to perform any one of the following: reacquire invalidated portions of the medical imaging data; and reconstruct a medical image from the medical imaging data, wherein the reconstruction excludes invalidated portions of the medical imaging data.

9. The medical instrument of claim 6, wherein execution of the machine executable instructions further causes the processor to: repeatedly calculate the statistical measure; calculate a statistical variation of the repeatedly calculated statistical measure; and adjust the predetermined criteria using the statistical variation.

10. The medical instrument of claim 5, wherein the medical imaging system is a magnetic resonance imaging system.

11. The medical instrument of claim 10, wherein the camera system comprises any one of the following: one or more magnet bore mounted camera; a head coil mounted camera, one or more magnet flange mounted cameras; and combinations thereof.

12. The medical instrument of claim 5, wherein the medical instrument further comprises a second medical imaging system configured for acquiring second medical imaging data from the subject, wherein the camera system is configured for imaging the portion of the subject when the second medical imaging system is acquiring the second medical imaging data.

13. The medical instrument of claim 1, wherein the medical instrument further comprises a therapy system configured for depositing energy into a target zone of the subject, wherein the camera system is configured for imaging the portion of the subject when the therapy system is depositing energy the target zone.

14. A computer program product comprising machine executable instructions for execution by a processor controlling a medical instrument, wherein the medical instrument comprises a camera system configured for imaging a portion of a subject reposing on a subject support, wherein the medial instrument further comprise a display system for rendering a position feedback indicator that represents a displacement of the subject relative to an initial position of the subject, wherein the display system is configured such that the position feedback indicator is visible to the subject when the subject is reposing on the subject support, wherein execution of the machine executable instructions causes the processor to: acquire a base position image using the camera system, the base position image corresponding to the subject's initial position; repeatedly acquire a subsequent image using the camera system; repeatedly calculate an image transformation from voxels of at least a portion of the base position image to voxels of the subsequent image by inputting the base position image and the subsequent image into an image transformation algorithm; and repeatedly render a position feedback indicator on the display, wherein the position feedback indicator is controlled by the image transformation.

15. A method of operating a medical instrument, wherein the medical instrument comprises a camera system configured for imaging a portion of a subject reposing on a subject support, wherein the medical instrument further comprises a display system for rendering a position feedback indicator, that represents a displacement of the subject relative to an initial position of the subject, wherein the display system is configured such that the position feedback indicator is visible to the subject when the subject is reposing on the subject support, wherein the method comprises: acquiring a base position image using the camera system, the base position image corresponding to the subject's initial position; repeatedly acquiring a subsequent image using the camera system; repeatedly calculating an image transformation from voxels of at least a portion of the base position image to voxels of the subsequent image by inputting the base position image and the subsequent image into an image transformation algorithm; and repeatedly rendering a position feedback indicator on the display, wherein the position feedback indicator is controlled by the image transformation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In the following preferred embodiments of the invention will be described, by way of example only, and with reference to the drawings in which:

[0061] FIG. 1 illustrates an example of a medical instrument;

[0062] FIG. 2 shows a flow chart which illustrates a method of operating the medical instrument of FIG. 1;

[0063] FIG. 3 illustrates a further example of a medical instrument;

[0064] FIG. 4 illustrates a further example of a medical instrument;

[0065] FIG. 5 illustrates a further example of a medical instrument;

[0066] FIG. 6 illustrates a further example of a medical instrument;

[0067] FIG. 7 illustrates an example of a rendering of a position feedback indicator.

[0068] FIG. 8 illustrates an example of a base position image;

[0069] FIG. 9 illustrates a further example of a rendering of a position feedback indicator; and

[0070] FIG. 10 illustrates a further example of a rendering of a position feedback indicator.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0071] Like numbered elements in these figures are either equivalent elements or perform the same function. Elements which have been discussed previously will not necessarily be discussed in later figures if the function is equivalent.

[0072] FIG. 1 illustrates an example of a medical instrument 100. The medical instrument 100 is shown as comprising a camera system 102 and a display system 104. There is a support 106 which is shown as supporting a subject 108. The camera system 102 is configured for imaging a portion of the subject 108. The display 104 is arranged for displaying a position feedback indicator in a visible manner to the subject 108. The camera system 102 and the display system 104 are connected to a hardware interface 112 of a computer system 110. The computer is further shown as comprising a processor 114 that is also in communication with a hardware interface 112, a user interface 116, and a memory 118. The memory 118 may be any combination of memory which is accessible to the processor 114. This may include such things as main memory, cached memory, and also non-volatile memory such as flash RAM, hard drives, or other storage devices. In some examples the memory 134 may be considered to be a non-transitory computer-readable medium.

[0073] The memory 118 is shown as containing machine-executable instructions 120 which enable the processor 114 to both control the operation and function of the medical instrument 100 as well as to perform calculations and manipulate data. The memory 118 is further shown as containing a base position image 122 that is acquired with the camera system 102. The memory 118 is further shown as containing a subsequent image 124 that was acquired after the base position image 122. The subsequent image 124 may be acquired repeatedly. For example, the camera system 102 could be a video system which continually provides a video feed.

[0074] The memory 118 is further shown as containing an image transformation 126 that was calculated by inputting the base position image 122 and the subsequent image 124 into an image transformation algorithm 128. The image transformation algorithm 128 is shown as being stored in the memory 118 also. The machine-executable instructions 120 then use the image transformation algorithm 128 to generate a rendering 130 of a position feedback indicator. The position feedback indicator is configured for displaying to the subject 108 when the subject is in a different or out of position. The memory 118 is also shown as containing an optional average transformation quantity 132 that was calculated from at least a portion of the image transformation 126. The average transformation quantity 132 may for example be used for simplifying control of the position feedback indicator 130.

[0075] FIG. 2 illustrates an example of a flowchart of a method of controlling the medical instrument 100 of FIG. 1. First in step 200 the processor 114 controls the camera system 102 to acquire the base position image 122. Next in step 202 the processor 114 controls the camera system 102 to repeatedly acquire the subsequent image 124. After a subsequent image 124 has been acquired the method proceeds to step 204 where the processor repeatedly calculates an image transformation 126 from voxels of at least a portion of the base position image 122 to voxels of the subsequent image 124 by inputting the base position image 122 and the subsequent image 124 into an image transformation algorithm 128. Finally, in step 206 the processor 114 repeatedly renders the position feedback indicator 130 and displays this on the display 104. The subject 108 can use the rendering of the position feedback indicator 130 to self-adjust his or her position.

[0076] FIG. 3 illustrates a further example of a medical instrument 300. The medical instrument illustrated in FIG. 3 is similar to the medical instrument 100 of FIG. 1. In FIG. 3 the medical instrument 300 is further shown as containing one or more medical imaging systems 302 and/or a therapy system 306. The one or more medical imaging systems 302 could for example be a PET system, a CT system, an MRI system, a SPECT system or any one of the two of those. They could for example acquire medical imaging data 310 from an imaging zone 304. In the case where the medical instrument 300 comprises a therapy system 306 the therapy system could direct energy into a target zone 308. The therapy system 306 could for example be a LINAC, an X-ray therapy system, a gamma ray treatment system, a high intensity ultrasound system, or a catheter ablation system. The memory 118 is shown as containing medical imaging data 310 that was acquired using the one or more medical imaging systems 302 and the therapy system control commands 312 that are used to control the targeting of the target zone 308. In instances where there are one or more medical imaging systems 302 and also a therapy system 306, the medical imaging data 310 may for example be useful for reconstructing images which can be used to adjust and thereby control the therapy system 306. For example, medical imaging data could be used to make changes in the therapy system control commands 312. The camera 102 captures motion of the subject 108 and this is able to be displayed on the display system 104. This may help improve the accuracy of any medical imaging or therapy that is performed with the medical instrument 300.

[0077] FIG. 4 illustrates a further example of the medical instrument 400. In this example the medical instrument 400 is shown as additionally comprising a magnetic resonance imaging system 402. The magnetic resonance imaging system 402 comprises a magnet 404. The magnet 404 is a superconducting cylindrical type magnet with a bore 406 through it. The use of different types of magnets is also possible; for instance it is also possible to use both a split cylindrical magnet and a so called open magnet. A split cylindrical magnet is similar to a standard cylindrical magnet, except that the cryostat has been split into two sections to allow access to the iso-plane of the magnet, such magnets may for instance be used in conjunction with charged particle beam therapy. An open magnet has two magnet sections, one above the other with a space in-between that is large enough to receive a subject: the arrangement of the two sections area similar to that of a Helmholtz coil. Open magnets are popular, because the subject is less confined. Inside the cryostat of the cylindrical magnet there is a collection of superconducting coils. Within the bore 406 of the cylindrical magnet 404 there is an imaging zone 408 where the magnetic field is strong and uniform enough to perform magnetic resonance imaging. A region of interest 409 is shown within the imaging zone 408. The magnetic resonance data that is acquired typically acquried for the region of interest. The subject 108 is shown as being supported by the subject support 106 such that at least a portion of the subject 108 is within the imaging zone 408 and the region of interest 409.

[0078] Within the bore 406 of the magnet there is also a set of magnetic field gradient coils 410 which is used for acquisition of preliminary magnetic resonance data to spatially encode magnetic spins within the imaging zone 408 of the magnet 404. The magnetic field gradient coils 410 connected to a magnetic field gradient coil power supply 412. The magnetic field gradient coils 410 are intended to be representative. Typically magnetic field gradient coils 410 contain three separate sets of coils for spatially encoding in three orthogonal spatial directions. A magnetic field gradient power supply supplies current to the magnetic field gradient coils. The current supplied to the magnetic field gradient coils 410 is controlled as a function of time and may be ramped or pulsed.

[0079] Adjacent to the imaging zone 408 is a head coil 414 for manipulating the orientations of magnetic spins within the imaging zone 108 and for receiving radio transmissions from spins also within the imaging zone 108. A head region of the subject is shown as being within the imaging zone 408. In this example the radio-frequency coil is a head coil 414. The head coil 414 is shown as surrounding the head of the subject 108. There is a region of interest 409 that images a portion of the subject's head region. On a flange of the magnet 404 there is a camera system 102′. The camera 102′ may for example be referred to as a flange-mounted camera. The camera 102′ looks into the bore 106 of the magnet.

[0080] There is a mirror 419 positioned in the bore 406 so that the flange mounted camera 102′ is able to image a facial region 418 of the subject 108. The display system 104 is positioned such that the subject 108 can also look into the same mirror 419 and see the rendering of the position feedback indicator 130. That may be beneficial because magnetic resonance imaging protocols may take an extended duration of time and the incorporation of the position feedback indicator 130 may assist the subject 108 in remaining still and/or returning to the same position after moving. The image transformation 126 may also be used to discard portions or reacquire portions of the magnetic resonance imaging data 422. For example, sequentially acquired frames from the camera system 102 may be checked for motion between the images that can be used to validate or invalidate motions which are uncontrollably performed by the subject 108.

[0081] A mirror may be provided for imaging the facial region 419 even when there is not a head coil 414. For example, the mirror 419 may be incorporated into a headgear or support which is attached to the subject's head in other examples.

[0082] The head coil 414 (or radio frequency coil or antenna) may contain multiple coil elements. The radio frequency antenna may also be referred to as a channel or antenna. The radio-frequency coil 414 is connected to a radio frequency transceiver 416. The radio-frequency coil 414 and radio frequency transceiver 416 may be replaced by separate transmit and receive coils and a separate transmitter and receiver. It is understood that the radio-frequency coil 414 and the radio frequency transceiver 416 are representative. The radio-frequency coil 414 is intended to also represent a dedicated transmit antenna and a dedicated receive antenna. Likewise the transceiver 416 may also represent a separate transmitter and receivers. The radio-frequency coil 414 may also have multiple receive/transmit elements and the radio frequency transceiver 416 may have multiple receive/transmit channels. For example if a parallel imaging technique such as SENSE is performed, the radio-frequency coil 114 will have multiple coil elements.

[0083] The computer memory 118 is further shown as containing pulse sequence commands 420. The pulse sequence commands are configured for controlling the magnetic resonance imaging system 402 to acquire magnetic resonance imaging data 422 from the subject 108 according to a magnetic resonance imaging protocol. The memory is further shown as containing a magnetic resonance image 424 that was reconstructed from the magnetic resonance imaging data 422.

[0084] FIG. 5 illustrates a further example of a medical instrument 500. The medical instrument 500 in FIG. 5 is similar to the medical instrument 400 in FIG. 4 except in this example the head coil 414 incorporates a camera 102″ and a display system 104 that are mounted to and attached to the head coil 414. The data bus for the head coil 414 could for example also be used for the camera 102″ and the display system 104. The camera system 102″ is configured for imaging a facial region 418 of the subject 108. The display system 104 is configured so that the subject 108 can see the rendering of the position feedback indicator 130.

[0085] FIG. 6 shows a further example of a medical instrument 600 that is similar to the medical instruments 500 in FIGS. 5 and 400 in FIG. 4. In this example the camera system 102 comprises multiple bore mounted cameras 102″. The subject 108 can simply be inserted into the bore of the magnet 406 and then any one of the multiple bore mounted cameras 102″ can be chosen for generating or acquiring the base position image 122 and any subsequent images 124. There is a radio-frequency coil 414 on the chest of the subject 108 that is connected to the transceiver 416. The display system 104 may for example also be mounted on the bore 406 of the camera or be provided as a camera or other wearable device to position the rendering of the position feedback indicator 130 in a position visible by the eyes of the subject 108.

[0086] FIG. 7 illustrates an example of a display system 104 which is a rendering of the position feedback indicator 130. On this display are two circles 700, 702 visible. The circle 700 represents the initial position of the subject. The circle with the dashed line 702 indicates a current position of the subject. If a region of interest of the image transformation 126 is used to calculate an average transformation quantity 132 such a rendering 130 can be easily calculated. The vector 132 illustrates a vector distance between the circles 700 and 702. The vector 132 may be the average transformation quantity 132 that is calculated from the image transformation 126.

[0087] As was mentioned above, motion management is important for many tomographic imaging modalities such as CT or MRI. Triggering and gating mechanisms are widely used to reduce motion artifacts. MRI Navigators can be used to track the motion but they require measurement time. External sensors and cameras can be used to circumvent this but can have limitations as a surrogate of the actual motion to be compensated. In addition, triggering and gating reduces scan efficiency significantly. Prospective gating and triggering is often used however this changes the steady state of the acquisition and can be difficult to apply in some patients. Monotonous scanning also frequently leads to patients falling asleep which can strongly deteriorate compliance.

[0088] Examples may use a camera sensor (e.g. camera system 102, 102′, 102″) to calculate and provide highly sensitive three-dimensional displacement visual feedback (e.g. the position feedback indicator 130) to the subject 108 which it can use to freeze the gross subject or target anatomy pose as much as possible. This is combined with retrospective gating of transient motion like eye blinking, swallowing, coughing, pulse and so forth. By retrospective data validation and invalidation, the steady state and contrast is unchanged for a given sequence. Scan efficiency is high since to a large extent only data where transient motion had occurred has to be invalidated.

[0089] In one example a two-dimensional in-bore camera 102″ is used for acquiring video data 122, 124 from a relevant part of the patient surface. An additional mirror 419 or other means to guide the visual feedback to the patient's eyes is used. From the camera frames a reference frame is extracted at the start of k-space traversal. Motion displacement is calculated from subsequent frames relative to the reference frame. The motion magnitude field (e.g. vector mapping or image transformation 126) may be displayed as false color image, the patient's task is to make the motion magnitude as low and flat as possible by keeping the target anatomy as close to the reference as possible. The mean magnitude is calculated and transmitted to the scanner for validation/invalidation of the MRI data along with a calculated reasonable threshold for the subject. For additional guidance, the motion vectors are displayed so the patient can revert e.g. eventual accidental head motion. The divergence field of the two-dimensional motion vector field is computed to detect through-plane displacement and the mean divergence is displayed to the patient yielding a sensitive measure for the z-component along the projection direction of the camera. This is possible because the lighting can be fully controlled in a MRI scanning environment and motion to be tracked is very small with minimal variation in the scene, thus vector field divergence can be almost fully contributed to through-plane motion. Overall this results in a very sensitive three-dimensional displacement detector which allows the subject to correct for very tiny motion and thus freeze the pose. Alternatively, more sophisticated three-dimensional sensing technology could be used (three-dimensional ToF, three-dimensional structured light, stereo/multi vision).

[0090] Visual feedback (via a position feedback indicator) may have the advantage of actively including the subject in the scanning procedure. Simplified or adapted feedback like Gamification can be used to add an entertainment component or for simplification as needed depending on the subject. It is proposed to have a set of feedback variants to choose to accommodate to the patient's preferences and capabilities.

[0091] Instead of only using a static reference image (base position image) acquired at the start of the scan, also frame-to-frame motion can be calculated to detect transient motion events and invalidate respective k-space data. For this mode it is assumed that the subject returns into the original resting state after transient motion has occurred. Typical examples include tremor, coughing, eye blinking, swallowing. It is also possible to switch to this mode or adapt motion thresholds for invalidation on-the-fly during scanning which can be desirable in case the subject is not able follow the visual feedback. This can also be done automatically in case scan efficiency drops too much.

[0092] Generally using the image transformation calculation, an estimate or prediction of image quality is possible. This estimate of the image quality may be provided to the operator. The operator may decide what action to take based on the prediction of the image quality. Alternatively, this can be used to adapt algorithm parameters such as invalidation threshold automatically.

[0093] Above detection of intermittent short motion events using frame-to-frame displacement measurement can be also used to trigger the acquisition of a short scout scan to measure the new resting state and eventually adapt the acquisition.

[0094] Examples may find application for high quality brain imaging, fMRI, pediatric scanning Examples may also be applied to head scanning but also to general breathing motion management, e.g. breathing sensing, breathing type classification and highly precise reproduction of breath-holds. Such precise control of breath-holds or breathing in general is very relevant to avoid morphologic distortion and diagnostic failure/misinterpretation (e.g. hypertrophy in cardiac MRI) or to ensure accurate lesion localization.

[0095] FIG. 8 illustrates an example of a base position image 122. A subject 108 is visible in the image. The image was taken from outside the bore of the magnetic resonance imaging system. A mirror 419 visible in the image 122 shows a reflection of the subject 108. There is a region of interest 800 that has been selected to identify motion of the subject.

[0096] FIG. 9 shows an example of a rendering of the image transformation 900 in this case the image transformation is a vector mapping. The top portion of the rendering 900 is identical with the region of interest 800. This vector mapping 900 has been successfully used as the position feedback indicator for several magnetic resonance imaging experiments. With some practice the subject 108 was able to control and maintain his position during the acquisition of magnetic resonance imaging data.

[0097] FIG. 10 illustrates another use of the images that were taken subsequent to image 122 in FIG. 8. By comparing adjacent images, a grayscale image was used to indicate the magnitude of motion between subsequent images. The regions labeled 1002 are lighter than the rest of the image and correspond to regions of high motion. These regions 1002 correspond to the position of the eyes and eyelids of the subject 108. The image 1000 may be used to identify when the subject 108 performs involuntary or quick motions which are only temporary. The image 1000 could for example be used to decide which portions of magnetic resonance imaging to discard and which to use during image reconstruction.

[0098] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

[0099] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

LIST OF REFERENCE NUMERALS

[0100] 100 medical instrument [0101] 102 camera system [0102] 102′ flange mounted camera [0103] 102″ multiple bore mounted cameras [0104] 104 display system [0105] 106 support [0106] 108 subject [0107] 110 computer system [0108] 112 hardware interface [0109] 114 processor [0110] 116 user interface [0111] 118 memory [0112] 120 machine executable instructions [0113] 122 base position image [0114] 124 subsequent image [0115] 126 image transformation [0116] 128 image transformation algorithm [0117] 130 rendering of position feedback indicator [0118] 132 average transformation quantity [0119] 200 acquire a base position image using the camera system [0120] 202 repeatedly acquire a subsequent image using the camera system [0121] 204 repeatedly calculate a image transformation from voxels of at least a portion of the base position image to voxels of the subsequent image by inputting the base position image and the subsequent image into a image transformation algorithm [0122] 206 repeatedly render a position feedback indicator on the display [0123] 300 medical instrument [0124] 302 one or more medical imaging system [0125] 304 imaging zone [0126] 306 therapy system [0127] 308 target zone [0128] 310 medical imaging data [0129] 312 therapy system control commands [0130] 400 medical instrument [0131] 402 magnetic resonance imaging system [0132] 404 magnet [0133] 406 bore of magnet [0134] 408 imaging zone [0135] 409 region of interest [0136] 410 magnetic field gradient coils [0137] 412 magnetic field gradient coil power supply [0138] 414 head coil [0139] 414′ radio-frequency coil [0140] 416 transceiver [0141] 418 facial region [0142] 419 mirror [0143] 420 pulse sequence commands [0144] 422 magnetic resonance imaging data [0145] 424 magnetic resonance image [0146] 700 base position [0147] 702 current position [0148] 800 region of interest [0149] 900 rendering of vector mapping [0150] 1000 image