High-speed magnetic synchronization of wireless detector

Abstract

Mechanisms for synchronizing the read-out sequence of non-tethered digital X-ray detectors in a radiography system with an X-ray generator or an X-ray source for use in digital wireless detectors where a synchronization of the digital wireless detector circuitry with the start of the actual exposure is required. The mechanisms can be applied in X-ray devices that are based on digital flat panel detectors, and wherein the digital detectors do not have a tethered connection with the modality for receiving the activation signal.

Claims

1. A system for synchronizing an X-ray generator and a wireless digital X-ray sensor to initiate capturing of a single digital image or a sequence of digital images, the system comprising: a sender including a sender microcontroller connected to the X-ray generator and configured or programmed to receive a trigger signal from the X-ray generator; and a receiver including a receiver microcontroller configured or programmed to trigger the wireless digital X-ray sensor when a predetermined condition in a digital signal stream is detected; wherein the sender further includes: a sender magnetic coil that generates a magnetic field {right arrow over (H)}; and a sender magnetic coil driver for the sender magnetic coil that applies an electric current to the sender magnetic coil upon activation of the sender magnetic coil driver; the receiver further includes: a receiver magnetic coil that converts the magnetic field {right arrow over (H)} into a measurable electric current; and an electrical signal converter for the receiver magnetic coil and including an electric current amplifier and an A/D convertor that converts an amplitude of the measurable electric current into the digital signal stream; and the predetermined condition in the digital signal stream is defined by exceeding a predetermined threshold value.

2. The system according to claim 1, wherein the sender magnetic coil driver generates an alternating electric current, and the magnetic field {right arrow over (H)} is an alternating magnetic field.

3. The system according to claim 2, wherein the alternating magnetic field {right arrow over (H)} has a frequency between 10 kHz and 30 MHz.

4. The system according to claim 1, wherein the sender magnetic coil and the receiver magnetic coil include a triplet of orthogonally oriented magnetic coils; the sender magnetic coil driver includes a sender magnetic coil driver for each of the sender magnetic coils in the triplet; and the electrical signal converter includes an electrical signal converter for each of the receiver magnetic coils in the triplet.

5. The system according to claim 2, wherein the sender magnetic coil and the receiver magnetic coil include a triplet of orthogonally oriented magnetic coils; the sender magnetic coil driver includes a sender magnetic coil driver for each of the sender magnetic coils in the triplet; and the electrical signal converter includes an electrical signal converter for each of the receiver magnetic coils in the triplet.

6. The system according to claim 3, wherein the sender magnetic coil and the receiver magnetic coil include a triplet of orthogonally oriented magnetic coils; the sender magnetic coil driver includes a sender magnetic coil driver for each of the sender magnetic coils in the triplet; and the electrical signal converter includes an electrical signal converter for each of the receiver magnetic coils in the triplet.

7. The system according to claim 1, wherein the receiver magnetic coil measures a strength of the magnetic field {right arrow over (H)}.

8. The system according to claim 1, wherein the sender and the receiver further include bi-directional wireless data communicators that: communicate, from the sender to the receiver, parameter data that determine an activation sequence and timing; communicate, from the receiver to the sender, the digital signal stream including the electric current measurement data obtained by the receiver magnetic coil.

9. The system according to claim 2, wherein the sender and the receiver further include bi-directional wireless data communicators that: communicate, from the sender to the receiver, parameter data that determine an activation sequence and timing; communicate, from the receiver to the sender, the digital signal stream including the electric current measurement data obtained by the receiver magnetic coil.

10. The system according to claim 3, wherein the sender and the receiver further include bi-directional wireless data communicators that: communicate, from the sender to the receiver, parameter data that determine an activation sequence and timing; communicate, from the receiver to the sender, the digital signal stream including the electric current measurement data obtained by the receiver magnetic coil.

11. The system according to claim 1, wherein the wireless digital X-ray sensor includes the receiver magnetic coil; an X-ray tube includes the sender magnetic coil; and the wireless digital X-ray sensor and the X-ray tube include respective inoperative or rest positions that provide optimal magnetic coupling of the receiver magnetic coil and the sender magnetic coil.

12. A method of triggering a wireless digital X-ray sensor upon receipt of a trigger signal initiated by an X-ray generator, the method comprising: receiving the trigger signal from the X-ray generator with a microcontroller in a sender; activating a magnetic coil driver with the microcontroller; generating a current that is applied to a sender magnetic coil by the magnetic coil driver; generating a magnetic field {right arrow over (H)} with the sender magnetic coil; inducing a measurable electric current in a receiver magnetic coil at a receiver with the magnetic field {right arrow over (H)}; converting an amplitude of the measurable electric current into a digital signal stream in the receiver with an electrical signal converter including an A/D-converter connected to the receiver magnetic coil; receiving the digital signal stream from the electrical signal converter with a receiver microcontroller; and triggering the wireless digital X-ray sensor upon detecting a predetermined condition in the digital signal stream with the receiver microcontroller; wherein the predetermined condition in the digital signal stream is defined by exceeding a predetermined threshold value.

13. A method for synchronizing a start of an exposure produced by an X-ray generator with a start of an acquisition cycle for the exposure by a wireless digital X-ray sensor, the method comprising: communicating an anticipated synchronization time point from a sender to a receiver; activating a magnetic coil driver with a microcontroller of the sender when a clock time of the sender equals the anticipated synchronization time point; generating a current that is applied to a sender magnetic coil by the magnetic coil driver; generating a magnetic field {right arrow over (H)} with the sender magnetic coil; inducing a measurable electric current in a receiver magnetic coil at a receiver with the magnetic field {right arrow over (H)}; converting an amplitude of the measurable electric current into a synchronization signal; setting a clock time of the receiver to equal the anticipated synchronization time point upon receiving the synchronization signal; communicating an anticipated exposure time point to the sender and the receiver; and triggering both the X-ray generator and the digital X-ray sensor when the anticipated exposure time point equals both the clock time of the sender and the clock time of the receiver.

14. A method for synchronizing a start of an exposure produced by an X-ray generator with a start of an acquisition cycle for the exposure by a wireless digital X-ray sensor, the method comprising: communicating an anticipated synchronization time point from a sender to a receiver; activating a magnetic coil driver with a microcontroller of the sender when a clock time of the sender equals the anticipated synchronization time point; generating a current that is applied to a sender magnetic coil by the magnetic coil driver; generating a magnetic field {right arrow over (H)} with the sender magnetic coil; inducing a measurable electric current in a receiver magnetic coil at a receiver with the magnetic field {right arrow over (H)}; converting an amplitude of the measurable electric current into a digital signal stream in the receiver with an electrical signal converter including an A/D converter connected to the receiver magnetic coil; receiving the digital signal stream from the electrical signal converter with a receiver microcontroller; setting a clock time of the receiver to equal the synchronization time point upon detecting a predetermined condition in the digital signal stream by the receiver microcontroller; communicating an anticipated exposure time point to the sender and the receiver; and triggering both the X-ray generator and the digital X-ray sensor when the anticipated exposure time point equals both the clock time of the sender and the clock time of the receiver.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 gives a schematic overview of a first embodiment of the invention using only 1 magnetic coil [230] in the sender component [200] and 1 magnetic coil [330] in the receiver component [300], and showing the sender component [200] and the receiver component [300] in the context of their usage within a X-ray system. The X-ray systems generator that is responsible for giving the trigger signal [101] to the detector is here represented by the console [100] component of a typical X-ray system. The console is connected to the X-ray generator (not shown) and serves as the user as an interface through which the actual trigger command is given by the radiographer.

(2) At the other end of imaging chain of the X-ray system resides the X-ray detector, which is in our embodiment of the invention a wireless digital X-ray sensor [400]. The wireless digital X-ray sensor [400] is shown comprising an integrated and miniaturized version of the receiver component [300], and is shown as a small grey compartment in the wireless digital sensor [400]. The trigger signal that is propagated by the invention to activate the digital X-ray sensor is shown as an arrow [401], and is generated within the receiver component [300] by the analog or digital trigger component [313].

(3) It has to be understood that the wireless digital sensor [400] comprising the receiver component [300] is physically separated from the X-ray systems generator or console [100] that comprises in its own turn the sender component [200]. There is thus no physical or tethered connection between the two parts of the system.

(4) The sender component [200] is drawn showing its different components: the sender microcontroller [210], the magnetic coil driver [220] and the magnetic coil [230], generating a magnetic field {right arrow over (H)} [600]. The sender microcontroller [210] is shown comprising a digital clock [212], a digital or analog trigger module [213], and optionally comprising a wireless communications module [211].

(5) The receiver component [300] comprises the following components: a magnetic coil [330] outputting a measurable electric current [331], an electrical signal converter [320] comprising an electric current amplifier and an A/D-convertor (indicated by the universally used symbols of said components) outputting the continuous digital signal stream [321], and receiver microcontroller [310] configured to receive said continuous digital signal stream from the electrical signal converter [320], and configured to trigger said wireless digital X-ray sensor [400] to which it is connected (or in which it is integrated). The receiver microcontroller [310] is shown comprising a digital clock [312], a digital or analog trigger module [313], and optionally comprising a wireless communications module [311].

(6) FIG. 2 gives an equivalent overview of a second embodiment of the invention, wherein multiple magnetic coils [230] are integrated in the sender component [200] and are each driven by an individual magnetic coil driver [220]. Similarly, the receiver component [300] comprises multiple magnetic coils [330] picking up individual measurable electric currents [331] by the multiple electrical signal converters [320] for each magnetic coil, and that are subsequently digitized into a continuous digital signal stream [321] or set of digital signal streams [321] for each magnetic coil. The continuous digital signal stream [321] is monitored and analysed by the microcontroller [310] that comprises an optional wireless communication module [311].

(7) In this embodiment, as can be seen in the drawing, there are three different magnetic coils [230] present that are moreover orthogonally oriented with respect to each other. A similar set of three orthogonally oriented magnetic coils [330] are also present in the receiver component.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) The purpose of the invention herein disclosed is the reliable and accurate synchronization of the start of an exposure that is produced by an X-ray generator with the start of the acquisition cycle of the same exposure by a wireless digital X-ray sensor. A trigger signal [101] given at the X-ray generator or console by a user marks the actual starting point in time to start an X-ray exposure, next to which this exposure is also characterized by a certain duration. Two different approaches or trigger methods may be chosen to ensure an accurate synchronisation of the start of the exposure by the X-ray modality and the start of the acquisition cycle of the wireless digital X-ray sensor.

(9) In a first trigger method, which we will call direct synchronization, the trigger signal [101] initiates the actual exposure in the X-ray generator, while at the exact same moment and with the lowest possible latency the same trigger [101] is propagated by the magnetic field {right arrow over (H)} [600] to the digital X-ray sensor [401]. The trigger signal thus simultaneously activates the exposure and the acquisition cycle of the digital X-ray sensor. The mechanism to wirelessly propagate this trigger signal to the digital X-ray sensor is discussed in more detail below.

(10) In a second trigger method, which we will indirect synchronization, the trigger pulse propagated by the magnetic field {right arrow over (H)} [600] may be used to synchronize the clocks of a generator and a receiver component [212] and [312], after which a timing (or sequence of timings) for future synchronized events is communicated to the respective X-ray generating and X-ray sensor components via a (less time-accurate) bi-directional wireless data communication means (such as Wi-Fi, Bluetooth, and alike). In this mechanism, the accurate synchronization mechanism is used only to accurately synchronize the clocks, and not to trigger the actual events.

(11) The duration and/or start of the exposure (or exposure time) is known upfront and chosen by the operator of the system. This exposure time and other exposure parameters are programmed in the X-ray system console prior to giving the exposure command. The X-ray generation components (X-ray generator and X-ray tube) are designed such that there is a very low latency between the moment that the trigger switch is activated (by closing an electrical contact) and that X-ray radiation is produced by the tube. This is crucial, as the operator requires the accurate control over the moment of exposure in case of direct synchronization. In case of indirect synchronization via the clocks of the generator and receiver this crucial control is guaranteed by transferring the absolute time-stamps of exposure prior to the start of the sequence. As long as the generator and receiver clocks are synchronized this enables an undelayed operation.

(12) Another important feature of the X-ray generator is that it can very accurately sustain the produced high voltage current fed into the X-ray tube for a very accurately timed duration. Also here, accuracy is very important in order to accurately control the delivered dosage to the patient during his exposure. In fact, the beam forming components are designed with low trigger latency and timing accuracy in mind.

(13) In order to optimize the digital image capture by the digital X-ray sensor, it should be ensured that the acquisition period (or dose integration period) of the DR sensor is synchronized with the actual exposure period of the X-ray source. This means that both the start and the duration of the acquisition (integration) time of the DR sensor and the exposure time of the X-ray generator should be ideally identical. This also ensures that no X-ray emission is present during read-out of the DR sensor in the digital X-ray sensor.

(14) In fixed, tethered DR-based X-ray systems, this can easily be achieved by transmitting the trigger signal over a wired connection to activate the digital X-ray sensor, as for such a wired connection there is close to no latency in the transmitted signal. Our invention however allows for transmitting a comparable low latency trigger signal in a wireless setup.

(15) In a first embodiment, the transmission of a single trigger signal is performed by the transmission of a single magnetic pulse between a sending and receiving part of the invention. The advantage of using a magnetic pulse to carry the signal is that there is close to no latency between the generation of the magnetic pulse, signal or sequence of signals and the reception of such a signal by a magnetic coil in the receiver component.

(16) The operating principle of the invention comes from the surprising effect that the latency of a transmitted trigger signal based on magnetic principles is very low, and thus can fulfil the application requirements of traditional (still) X-ray acquisitions or dynamic imaging. For dynamic images, the requirements towards low latency and consequently low jitter are even more stringent, so that the advantages of applying the invention are even more pronounced.

(17) Nevertheless, in order to ensure reliable operation of such a magnetic pulse based transmission system, certain measures have to be taken to ensure that the magnetic trigger signal is sufficiently strong and detectable by the receiver electronics.

(18) In this first embodiment of the invention, a single magnetic coil [230] produces a single magnetic field [600] of which the direction is oriented in the direction of the axis of the coil. As soon as the magnetic field is generated by energizing the magnetic coil by an electric current, the magnetic field raises and has a particular strength and orientation (mathematically represented as the magnetic field vector {right arrow over (H)}). The detection of the magnetic field by a magnetic field detector [330] is direction dependent, and depends on the coupling efficiency between the 2 magnetic coils. In certain positions and under certain orientations a magnetic detector may measure an optimal signal (with maximal signal amplitude) as the consequence of an optimal coupling between the two magnetic coils [230] and [330]. The coupling efficiency of two magnetic coils depends on their mutual orientation and relative distance. So there are relative orientations between a generator magnetic coil and a receiver magnetic coil which result in very small signals even when they are close to each other. So, our first embodiment of the invention (when using a set of single coils) can only work reliably on condition that the relative positions and orientations of the sender and receiver coils can be controlled. Therefore, this first embodiment should be used preferably for application in an indirect synchronization trigger method, wherein the digital X-ray sensor would be temporarily brought into a known position relative to the sender component during the synchronizing process of the clocks of the sender and receiver components. This known synchronization position is specifically chosen to ensure an optimal magnetic coupling between sender and receiver coils.

(19) This can be practically achieved by making sure that the magnetically coupling coils are brought physically close together and in the right orientation when bringing the modality in its parking position. A parking position of a modality is an inoperative or rest position, and is the physical configuration in which a mobile X-ray modality can be brought by flexing the tube arm in a specific position in order to make the system more compact for more easy transportation, to avoid collisions and to provide more stability when moving the system around. Such a parking position brings the collimator head in a particular and predefined position close to which a storage location can be foreseen to carry and store the digital X-ray sensor. The magnetic coils of the sender component would in this configuration typically be integrated in (or close to) the collimator head, while the magnetic coils of the receiver component are integrated into the digital X-ray sensor. The orientation of the coils can then be chosen such that the optimal magnetic coupling is achieved.

(20) Another problem relating to the measurement of magnetic field strengths is the influence by external magnetic disturbances, such as the presence of metallic objects in the vicinity of the sensor coil. Such disturbances have not so much an impact on the amplitude component of the magnetic field vector, but rather on the direction of the magnetic field vector. This means that such disturbances nevertheless can have a significant impact on the measured amplitude by the sensor coil in a certain position. This is another reason why relying on the amplitude measurement of a single magnetic sensor alone is not sufficient to reliably transmit a trigger signal, unless such disturbances are being actively avoided by preventing their occurrences such as for instance when using a known calibration position of the digital X-ray sensor as explained above.

(21) External magnetic disturbances could occur due to a positioning of the magnetic sensor coil near electric transformers or other electronic equipment, or even due to the presence of the static magnetic fields, such as the earth's magnetic field. Also, metallic objects in the vicinity of the magnetic coil of the receiver component may cause undesired magnetic disturbances, or shield off the intended magnetic field trigger pulse.

(22) In a second embodiment, the problem of magnetic disturbances is resolved by means of using alternating magnetic fields for propagating the trigger signal, rather than a single static magnetic field. The reason for using alternating magnetic fields as opposed to static magnetic fields is that this approach compensates for the presence of any static magnetic field, such as the earth's magnetic field in case that the amplitude of the received signal is taken as the parameter for distance measurement. Also when choosing the appropriate frequency of the alternating magnetic signal, the effect of disturbances by alternating magnetic fields can be suppressed. The appropriate frequency should be chosen such that it stays away from potentially interfering alternating magnetic fields, such as the frequency at which electrical appliances such as transformers operate (50-60 Hz). The frequency should preferably be higher then 1 kHz (as the lower boundary), and should also not exceed 30 MHz, the point after which water and human tissue starts to absorb energy Within this very wide frequency band, radio frequencies should be avoided for obvious reasons.

(23) For the application of this improvement, it is contemplated to use resonant magnetic signal generator- and sensor-pairs to optimize the magnetic signal transfer for triggering. In a preferred embodiment, the signal generator is a coil through which an alternating electric current is sent by a magnetic coil driver. The alternating electric current induces an alternating magnetic field of the same frequency that can be detected at a distance from the magnetic coil of the sender component. A similar or smaller coil is used as the signal sensor of the receiver component and picks up the alternating magnetic field passing though it; inversely the alternating magnetic field induces an alternating current in the sensor coil that can be picked up and measured. The detector coil may be smaller in size and have a different winding number in comparison with the generator coil. The circuit that reads out the alternating electric current in the sensor coil is tuned to the frequency of the generator (hence the name resonant) by means of the selection of the correct capacitor and resistor network, in order to optimize the sensitivity to the generator signal frequency.

(24) While in the above preferred embodiment, the magnetic generator and resonant magnetic sensors are coils, different types of magnetic sensors may be used as alternatives, such as MEMS, Hall effect based sensors, magneto-resistive sensors, or alike . . . .

(25) The amplitude of the measured alternating current in the resonant magnetic sensor has a relation with the distance between the signal generator and signal sensor. The amplitude is approximately inversely proportional to the cubic distance from the signal generated, when measured in radial direction from the generator. When the sensor coil is kept at the same distance to the generator but its orientation and/or the relative orientation is changed the received signal ranges from 100% to 0%.

(26) In a third and preferred embodiment, instead of one single magnetic coil to generate the magnetic field, a set of differently oriented magnetic coils is used to overcome the earlier described problem of the direction sensitivity of the signal amplitude. Where it was described above that the successful detection of a magnetic trigger signal using a single magnetic coil is strongly dependent on the respective orientation of the magnetic coil in the sender component relative to the orientation of the magnetic coil in the receiver component, the following embodiment tries to overcome this problem, by proposing a solution wherein the trigger signal is no longer direction dependent.

(27) In this embodiment, a combination of differently oriented magnetic coils is applied both in the sender component and/or in the receiver component. Preferably, an orthogonally arranged triplet of magnet coils is used both in the sender as in the receiver component.

(28) In case that such a triplet of orthogonally oriented magnetic coils would be used in the sender component, to generate a magnetic field for transmitting the trigger signal, it can be shown that by means of activating different combinations of said orthogonally oriented magnetic coils, differently oriented magnetic fields will be generated. This implies that for a coil triplet, 7 (=2.sup.31) differently orientated magnetic fields can be generated, amongst which one particular combination of activated coils can be chosen to achieve the highest amplitude of measured signal at a magnetic coil of the receiver component.

(29) In case that such a triplet of orthogonally oriented magnetic coils would be used in the receiver component, it can be shown that there will always be a detectable signal in at least one of the orthogonally oriented magnetic coils of the receiver component.

(30) The preferred combination of coils to be activated in the sender component in order to achieve the optimal trigger signal amplitude can be conveniently tested by iterating through the different activated coil combinations. This testing cycle has to be understood as a calibration step to find the optimal activation and read-out configuration of the coil triplets. This preferred coil combination, which can be the activation of a single coil up to all 3 coils at the same time, can then be used as the preferred trigger signal for a particular setup.

(31) For this scenario to work, the receiver component has to be signalled and made aware of an upcoming calibration cycle, during which it can expect to detect different magnetic field strengths depending on the combination of coils being activated. These measurements are then recorded and afterwards compared with each other in order to select the preferred combination for triggering. The data about the configuration of choice has to be transferred back to the sender component for preparing a future trigger action offering the optimal trigger signal amplitude.

(32) Since this technique requires a bidirectional communication for transferring the configuration data between sender component and the receiver component, a communication means [211] and [311] has to be foreseen between both components. In a preferred embodiment, this communication means is a standard communication module capable of supporting Wi-Fi or Bluetooth, or alike.

(33) Said communication means is not restricted by the same latency requirement as for the trigger signal itself, as it only serves to communicate parameter data relating to the initiation of the calibration cycle (or pre-synchronisation mode) and the feedback of the results of said calibration cycle, between the 2 components. This communication may be done in an asynchronous way.

(34) In another embodiment, the communication of above mentioned configuration data may also be contemplated by means of encoding a digital signal into the alternating magnetic field. In this case, a sequence of on-off pulses is used to encode information. The pulse length of a single bit of digital information would in this case be chosen to be at least 10 the period of the alternating field. The information would in this case only flow in one direction only from the sender component to the receiver component (no bi-directional communication is possible).

(35) The different steps of how such a system would work are listed below:

(36) 1) The microcontroller of the sender component sends a command (using the wireless communication module [211], or by means of encoding the signal into the alternating magnetic field) to signal the microcontroller of the receiver component that it should be set to a calibration mode; this command may include parameters that define which functions of the digital X-ray sensor should be configured and activated upon triggering (the digital X-ray sensor may support different functions which should be chosen in advance).
2) The microcontroller of the sender component awaits a handshake or confirmation message from the receiver component (which is integrated in or connected to the digital X-ray sensor) signalling its readiness. This handshake or confirmation message is passed on to the generator allowing it to prepare itself for an exposure (this communication is performed using the wireless communication modules).
3) The microcontroller of the receiver component confirms pre-synchronization mode (via Wi-Fi protocol); this step can include communication with the DR sensor to define the function which shall be executed upon a trigger signal. The receiver component is now ready to detect the calibration signals.
4) To find maximum signal: the sender component systematically powers the magnetic coils in the generator triplet, iterating through the different activated coil combinations (e.g.: coil1 on others off; coil2 on others off; coil3 on others off; coil1&2 on other off . . . coil1&3 on others off . . . all coils on). The time between signals must be large enough to allow Wi-Fi communication between the pulses (>100 ms). The microcontroller of the receiver component analyses the induced voltages and gives feedback about the signal strength to the microcontroller of the sender component (via the Wi-Fi communication means).
5) The microcontroller of the sender component selects the strongest signal and sets the microcontroller of the receiver component to synchronization mode (WiFi protocol). The microcontroller of the receiver component confirms the synchronization mode and readiness to accept a trigger signal (via the WiFi protocol). Now the system is ready to synchronize components and Digital X-ray sensor wirelessly.
6) The microcontroller of the sender component receives a trigger signal from the X-ray systems console or X-ray generator and activates the magnetic coil driver to energize the magnetic preferred coil combination. This produces a single magnetic pulse to trigger the pre-set Digital X-ray sensor function (e.g. start read-out).
7) The electrical signal converters [320] of the different magnetic coils in the receiver component detect the trigger signal on the rising edge of the induced signalswhich is the sum of all available receiver coils. The trigger signal threshold is determined upfront from the measurement to select the preferred combination of generator coil(s). (see steps 4-5)
8) When the trigger event is detected, the microcontroller of the receiver component commands the digital or analog trigger module [313] to send a trigger signal to the Digital X-ray sensor electronics to which it is electrically connected. This signal starts the pre-defined Digital X-ray sensor function.
9) The previous steps (5 to 8) can be repeated to record an image sequence of a dynamic imaging sequence.
10) In order to terminate the sequence, the microcontroller of the sender component ends the synchronization mode by sending a Wi-Fi command to the receiver component such that both microcontrollers switch to normal mode.

(37) The method above allows to transmit a single trigger signal between the X-ray system and digital X-ray sensor, or may also be used to transmit consecutive individual trigger signals.

(38) In another embodiment of the method, the transmission of the magnetic trigger signal may be used only to synchronize the two clocks of the X-ray system and of the digital X-ray sensor, after which a timed sequence of programmed exposure events may be communicated over the asynchronous digital data communication means. The actual synchronization of the events will rely on the accurately synchronized clocks. The initiation of the sequence may then be communicated as a time point in the near future by means of the less time-accurate wireless data communication means.