Patent ID: 12210082

DETAILED DESCRIPTION OF EMBODIMENTS

FIG.1illustrates an exemplary magnetic resonance imaging system100. The magnetic resonance imaging system100comprises a magnet104such as a superconducting cylindrical type magnet with a bore106through it that is large enough to receive a subject118on a support120. Within the bore106of the cylindrical magnet104there is an imaging zone108where the magnetic field is strong and uniform enough to perform magnetic resonance imaging. Within the bore106there is also a set of magnetic field gradient coils110used for acquisition of magnetic resonance data to spatially encode magnetic spins within the imaging zone108. The magnetic field gradient coils110contain three separate sets of coils for spatially encoding in three orthogonal spatial directions. The magnetic field gradient coils110are connected to a magnetic field gradient coil power supply112which supplies current to the magnetic field gradient coils110. Adjacent to the imaging zone108is a radio-frequency antenna114for manipulating the orientations of magnetic spins within the imaging zone108and for receiving radio transmissions from spins also within the imaging zone108. The radio frequency antenna114may contain multiple coil elements. The radio-frequency coil114is connected to a radio frequency transceiver116. The radio-frequency antenna114and radio frequency transceiver116may be replaced by separate transmit and receive coils and a separate transmitter and receiver. It will be understood that the details of the magnetic resonance imaging system100are provided herein for the purposes of illustration only and that the techniques described herein are application to any MM system or to any other imaging system which is susceptible to imaging artifacts caused by patient motion. The magnetic resonance imaging system100further comprises a patient state sensing system102and optionally also an environmental control subsystem122.

The magnetic field gradient coil power supply112, the transceiver116, the patient state sensing system102, and the environmental control subsystem122are connected to a hardware interface128of a control system126.

The control system126comprises a processor130connected to the hardware interface128along with a user interface132, computer storage134, and computer memory136. The computer storage134contains, in use, sensor data310that was acquired using the patient state sensing system102. The computer storage134optionally also contains in-bore lighting control data312and music/video data314. The computer memory136contains a control module250, a monitor module252, a sequencing module254, and optionally also an environmental control module256. Each of the modules250-256contains computer-executable instructions.

The control module250contains computer-executable code which enables the processor130to control the operation and function of the magnetic resonance imaging system100in the manner described herein. In particular, the control module250is configured to control the magnetic resonance imaging system100to perform an examination comprising multiple scans. The control module250may be configured to adjust scan parameters during a said scan being performed by the magnetic resonance imaging system100according to the monitored sleep state.

The monitor module252is configured to monitor the sleep state of a patient on the basis of the sensor data310received from the patient state sensing system102. In this example, the monitor module252is configured to detect, based on the sensor data310, whether the patient is asleep (in a sleep state) or awake (in a non-sleep state). Sleep may be detected by methods such as camera-based measurements of heart rate and breathing rate and closed eye detection. The sensor data310received from the patient state sensing system102may thus comprise one or more (i) motion sensor data; (ii) patient heart rate data; (iii) patient breathing rate data; (iv) data indicating detection of patient closed eyes.

The sequencing module254is configured dynamically to determine at least part of a sequence in which the control module is to control the magnetic resonance imaging system to perform the scans. The determination is made according to the monitored sleep state of the patient and according to a sleep-appropriateness score associated with one or more of the scans. The sequencing module254may be configured to respond to the monitored sleep state of the patient indicating that the patient has entered the sleep state by prioritizing, as the next scan in the sequence, a first said scan having a first sleep-appropriateness score over a second said scan having a second sleep-appropriateness score, the first sleep-appropriateness score being higher than the second sleep-appropriateness score. Advantageously, more sleep-appropriate scans are thus prioritized to occur while the patient is asleep and other, less sleep appropriate scans, which therefore have a lower priority in terms of scheduling, may occur at any other time during the examination.

The sequencing module254may be configured to associate the one or more scans with the respective sleep-appropriateness scores using a rule-based scoring algorithm which takes as input one or more of the following parameters: (i) scan duration, (ii) scan noise level, (iii) scan type (relating to sensitivity to patient motion); (iv) level of patient interaction during the scan. The sleep-appropriateness score S may be defined as a sum of terms each comprising a weighting factor wiand a function fi(p) that depends on the parameter p. The factors wimay be adjusted empirically to set the relative weights of the parameters. The function may be any analytical function of the parameter p as a polynomial, exponential or other function. In case of scan duration, this function may simply be the identity function f(p)=p. In case of scan noise level, the function may be defined as f(p)=−p2because higher noise levels are increasingly inappropriate for sleep. The parameter scan type is introduced to the score to take into account the different sensitivities of various scan types to patient motion. More motion-sensitive scan types should deliver a high score, because they are more appropriate to be performed during sleep, and vice versa. Therefore the respective function may be a table of values each attributed to one of the scan types. For example, table values may be set for diffusion scans to 5, for all non-diffusion cartesian scans to 3, to non-diffusion radial and spiral scans to 1. The function for the parameter representing the level of patient interaction may also be implemented as a table. For example, scans requiring the patient to respond to requests as breath-hold commands may be assigned with the value −1, all other scans with 0.

The sequencing module254may be configured to prioritize sequencing of a said scan associated with a noise level that is lower than that associated with at least one other said scan to occur at or near the beginning of the sequence, to assist the patient in falling sleep. The scans may comprise at least one interactive scan involving a degree of patient interaction. The interactive scan may be associated with a requirement for one or more of patient repositioning and patient breath holding. In such a case, the sequencing module254may be further configured to prioritize sequencing of the interactive scan to occur at a point in the sequence at which the sleep state of the patient is determined to be awake. This may occur at or near the end of the scan, advantageously prevent interactive scans from hindering the patient in falling asleep. The sequencing module254may be configured to omit from the sequence a motion-tracking part of one or more subsequent scans in response to the monitored sleep state of the patient indicating that the patient has entered the sleep state. Motion tracking may form part of many motion-sensitive scans and typically makes them longer. Omitting motion tracking within these scans when the patient is detected to be asleep thus advantageously shortens the scans.

As mentioned above, the control module250may be configured to adjust scan parameters during a said scan being performed by the magnetic resonance imaging system100according to the monitored sleep state. Most MR scan types a tradeoff to be made between shorter imaging time with resulting lower sensitivity to motion artefacts at the cost of image quality or resolution. If a patient is detected to be awake, scan parameters may be adjusted by adjusting this tradeoff in the direction of a shorter and therefore less sensitive scan, whereas longer scan times with lower noise level may be chosen for patients that are currently asleep. The rule-based scoring algorithm as disclosed herein may be used to adjust scans to achieve this tradeoff, using for example an optimization algorithm. If a patient is currently asleep, then scan parameters may be iteratively adapted to increase a sleep-appropriateness score of the corresponding scan. If a patient is currently awake, then scan parameters may be iteratively adapted to decrease the sleep-appropriateness score. Any known optimization algorithm such as the steepest gradient-descent method may be used to perform this optimization. Optimization may be performed in a user-defined parameter space. For example, the parameter space for scan duration may be given by a maximal and a minimal scan duration that the optimization algorithm shall not exceed or fall below, respectively.

The environmental control module256may be configured to instruct the environmental control subsystem122to control an in-bore lighting condition to adopt a sleep-supporting state, for example on the basis of the in-bore lighting control data312. The environmental control module256may be configured to instruct the environmental control subsystem122to play back music and/or video identified as being personal sleep triggers of the individual patient, this music and/or video having been prestored as the music/video data314, for example.

FIG.2illustrates a method performed by the control system126for controlling the magnetic resonance imaging system100. The method comprises, at step201, controlling (by the control module250) the magnetic resonance imaging system100to perform an examination comprising multiple scans. The method further comprises, at step202, monitoring (by the monitor module252) a sleep state of a patient on the basis of the sensor data310received from the patient state sensing system102of the magnetic resonance imaging system100. The method further comprises, at step203, dynamically determining (by the sequencing module254) at least part of a sequence in which the magnetic resonance imaging system100is controlled to perform the scans. The determination may be made according to the monitored sleep state of the patient and according to a sleep-appropriateness score associated with one or more of the scans.

One use case of the techniques described herein comprises one or more of the following approaches:1. Identify potential sleepers and derive personal sleep habits and sleep triggers;2. Coach patients to sleep during examination;3. Schedule patients depending on sleep habits (time of day, scanner type);4. Apply individual sleep triggers at the beginning of the examination;Reschedule scans within the examination to support sleep;6. Adjust scans depending on sleep state;7. Adjust imaging environment to support sleep (adaptive lighting).

With reference to approach 1 (“Identify sleepers and derive personal sleep habits and sleep triggers”), potential sleepers may be identified based on an app-based questionnaire that includes questions such as:“Can you fall asleep during driving or flying?”“How much do you rate noise to disturb your sleep on a scale 1-5?”“How long does it usually take you to fall asleep?”“Which is your best sleeping posture?” (if not supine disqualifies as sleeper)“Do you keep calm and confident in new situations? Rate on 1-5.”The app may also be used to produce some low level MR noise, aiding questions such as “You will hear similar sounds during your upcoming MR exam. Do you think you will be able to sleep in that exam, which will be beneficial for you and image quality?”

Each of these questions may be rated with a weight, and a pro-sleep answer adds the corresponding weight to an overall score. If the overall score exceeds a limit, the patient is identified as sleeper.

Criteria for the decision sleeper/non-sleeper (weights, overall limit) may be set heuristically when the product is launched and may be continuously refined during use of the product. Therefore, the pre-exam decision may be compared against data on the sleep status obtained during the actual exam for each patient. Criteria may then be updated such that the number of correct decisions over all patients is maximized. Correct here means that the patient fell asleep after the decision was taken that he is a sleeper.

If a patient qualifies as “sleeper” based on the current criteria, then sleep habits and sleep triggers may be derived from patient characteristics, personal device usage, and an extended questionnaire. An example for characteristics is that sleep times typically change with age, and depending on the age of a particular patient, this allows most likely sleep times. Times of personal device usage may also be evaluated to derive personal sleep times.

With reference to approach 2 (“Encourage and coach patient to sleep during exam”), information may again be supplied to the patient via an app on a personal device stating that sleep is helpful both for good image quality and patient experience. The app may be used to play MR noise so that the patient can accustom themselves to this sound. The sound may be played at low volume shortly after the patient falls asleep at home.

With reference to approach 3 (“Schedule patients depending on sleep habits and apply sleep triggers”), personal sleep habits may be used to schedule patients. “Night owls” are scheduled in the morning, “early birds” in the afternoon or evening. Non-sleepers are preferably scheduled on high field systems (e.g. 3T), where scans are generally shorter than on mid or low field systems and therefore less sensitive to motion artifacts. Personal sleep triggers may be applied at the beginning of the MR exam (personal piece of music or video, some personal belongings, usual evening drink e.g. night time tea and food).

With reference to approach 4 (“Reschedule scans within exam to induce or maintain sleep”), loud scans may be avoided at the beginning of the MR exam to allow the patient to fall asleep or during actual sleep to not wake the patient up. Loud scans may be rescheduled to the end of the exam to wake the patient up again. Similarly, any scans that require active patient interaction (breath-hold scans, repositioning, etc.) may be avoided at the beginning of the MR exam or during sleep.

With reference to approach 5 (“Reschedule motion sensitive scans within exam depending on sleep state”), this is based on the insight that MR scans have very different motion sensitivity. Longer scans, diffusion scans, and functional scans are examples with very high motion sensitivity. Such scans may be rescheduled to detected sleep phases.

With reference to approach 6 (“Adjust scans depending on sleep habit and sleep state”), most MR scan types allow a trade-off to be made between shorter imaging time with associated lower sensitivity to motion artifacts and image quality or resolution. For non-sleepers scans may be shortened, whereas longer scan times may be chosen for sleeping patients. Many scan types acquire additional MR data to track motion and discard affected MR image data (such as PROPELLER, RADIAL acquisitions, MR Navigators). The additional acquisition requires additional imaging time. The scan may be adjusted to avoid this additional acquisition during sleep phases of the patient, saving imaging time.

With reference to approach 7 (“Adjust imaging environment to support sleep”), room and in-bore lighting conditions may be adjusted to support sleep. Patient communication may be avoided if patient is asleep.

Aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “module” or “system”. Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer executable code embodied thereon. Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A “computer-readable storage medium” as used herein encompasses any tangible storage medium which may store instructions which are executable by a processor of a computing device. The computer-readable storage medium may be referred to as a non-transitory computer-readable storage medium. “Computer memory” or “memory” is an example of a computer-readable storage medium. Computer memory is any memory which is directly accessible to a processor. “Computer storage” or “storage” is a further example of a computer-readable storage medium. Computer storage is any non-volatile computer-readable storage medium. In some embodiments computer storage may also be computer memory or vice versa. A “processor” as used herein encompasses an electronic component which is able to execute a program or machine executable instruction or computer executable code. References to the computing device comprising “a processor” should be interpreted as possibly containing more than one processor or processing core.

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. 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 SIGNS

100magnetic resonance imaging system102patient state sensing system104magnet106bore108imaging zone110magnetic field gradient coils112magnetic field gradient coil power supply114radio-frequency antenna116radio frequency transceiver118subject120support122environmental control subsystem126control system128hardware interface130processor132user interface134computer storage136computer memory201-203method steps250control module252monitor module254sequencing module256environmental control module310sensor data312-314other data