Patent Description:
Respiratory information collected by a so-called "respiratory surrogate" is used until now only in dedicated 4D respiratory scan modes and protocols of CT scan systems. Here the respiratory surrogate is used to determine the respiratory phase of a patient either during the scan in order to enable phase correlated scanning or after the scan in order to perform a phase correlated reconstruction of image data based on the scanned raw data.

<CIT>, <CIT>, <CIT> and <CIT> are to be mentioned as prior art.

In standard and non-respiratory scans and reconstructions a respiratory surrogate is not recorded at all. The reason for this is that up to now a respiratory surrogate was recorded by an external measurement system, which is quite complicated and complex to attach to the patient. Currently, a new radar-based system for the recording of the respiratory surrogate is being developed. This radar-based system is integrated into a patient table of a CT scan system and is therefore always available without any complicated and time consuming installation process. This new system for the recording of the respiratory surrogate offers the possibility to make use of the information about the breathing cycle and breathing properties of a patient even in non-respiratory correlated scan processes in order to make patient specific adjustments to the breathing commands before and during the scan.

Breathing commands are contained in almost any CT protocol. Typically, those commands are given right before or during the scan in order to give an advice to the patient how to control his breathing in order to avoid artifacts in the reconstructed images. Currently, the commands are typically pre-recorded speech commands, which can be recorded and stored by the clinical users of the CT scan units. Typically, every clinical imaging task, for example cardiac, dual energy, standard contrast and non-contrast exams have their dedicated commands, which are pre-recorded and stored in specific protocols by the clinical users according to their needs and clinical practice. The drawback of those pre-recorded commands is that they do not take into account the breathing properties of the current patient and that they cannot adapt to the current breathing status of the patient. For example there is no way to detect whether the patient is following the commands or not, which can in the worst case yield to non-diagnostic images and the need for a re-scan.

Hence, a problem underlying to the invention is to improve the effectivity of a CT scan process, which is influenced by a respiratory movement of a patient.

That problem is solved by a method of adaption of a medical imaging process to an individual respiration behaviour of a patient according to claim <NUM>, by an adaption device according to claim <NUM> and by a medical imaging system according to claim <NUM>.

According to the method of adaption of a medical imaging process, the medical imaging process being a CT scan process, to an individual respiration behaviour of a patient, it is proposed to use the monitoring of a respiratory surrogate to optimize the breathing guidance prior and during scanning and to guide the clinical user after the scan about the quality of the scan as long as the patient is still on the table. The method comprises the steps of recording the respiratory movement of a patient by monitoring a respiratory surrogate and adapting the medical imaging process based on the recorded respiratory movement of the patient, wherein the adaption is performed in the scan phase of the medical imaging process.

During the scan phase, it is determined whether the patient holds his breath properly, and in case the patient does not hold his breath properly, the scan process is dynamically reparametrized by increasing the pitch.

A surrogate has to be understood as a physiological process, which can be detected using sensor technology and which is correlated to another physiological process to be monitored. Hence, the actual interesting physiological process, for example the movement of an internal organ or the movement i.e. the change of a position of a predetermined internal examination area, can be determined based on the observation of the breathing movement of a patient, by correlating the breathing movement with the movement of the interesting internal portion. In particular, the respiratory surrogate represents the respiratory movement of a patient. The information about the respiratory movement can be used as feedback information for controlling breathing commands, which are harmonized with recording time intervals of the medical imaging process such that the imaging is not disturbed by the respiratory movement of the patient. Advantageously, the quality of medical images can be improved and the operating expense and time for wasted scan processes can be reduced. Hence, the medical imaging resources can be used more effectively. Further, the comfort for the patient is increased, since the number of additional scan attempts and the time for these attempts can be reduced. Furthermore, the radiation exposure due to additional scan attempts can also be reduced.

The adaption device according to the invention, preferably for a CT system, is configured for carrying out the method according to the invention and comprises a monitoring unit for recording the respiratory movement of the patient by monitoring the respiratory surrogate and an adaption unit for adapting the imaging process based on the recorded respiratory movement of the patient. The adaption device shares the advantages of the method according to the invention.

The medical imaging system is a CT system and comprises a scan unit for carrying out a medical imaging from a patient and an adaption device according to the invention for adapting the medical imaging of the scan unit to a recorded respiratory movement of the patient. Further, the medical imaging system includes a sensor device, for example a radar sensor, for acquiring sensor data concerning the respiratory movement of the patient. The medical imaging system shares the advantages of the method according to the invention.

The essential components of the scan adaption device according to the invention can for the most part be designed in the form of software components and if required, by further adding some hardware as for example a respiratory movement sensor like a radar sensor. This applies in particular to the monitoring unit and the adaption unit of the scan adaption device but also parts of the input interfaces. In principle, however, some of these components can be implemented also in the form of software-supported hardware, for example FPGAs or the like, especially when it comes to particularly fast calculations. Likewise, the required interfaces, for example if it is only a matter of transferring data from other software components, can be designed as software interfaces. However, they can also be designed as hardware-based interfaces that are controlled by suitable software. Furthermore, some parts of the above-mentioned components may be distributed and stored in a local or regional or global network or a combination of a network and software, in particular a cloud system.

A largely software-based implementation has the advantage that medical imaging systems that have already been used, can easily be retrofitted by a software update in order to work in the manner according to the invention. In this respect, the object is also achieved by a corresponding computer program product with a computer program that can be loaded directly into a memory device of for example a control device of a medical imaging system, with program sections, in order to carry out all steps of the method according to the invention, if the program is executed in the medical imaging system, in particular the control device. In addition to the computer program, such a computer program product may contain additional components such as a documentation and/ or additional components, including hardware components such as hardware keys (dongles etc.) for using the software.

For transport to the medical imaging system and/ or for storage on or in the medical imaging system, a computer-readable medium, for example a memory stick, a hard disk or some other transportable or permanently installed data carrier is used on which the program sections of the computer program that can be read in and executed by a computer unit of the medical imaging system are stored. The computer unit can comprise for example, one or more cooperating microprocessors or the like used for this purpose.

The dependent claims and the following description each contain particularly advantageous embodiments and developments of the invention. In particular, the claims of one claim category can also be further developed analogously to the dependent claims of another claim category. In addition, within the scope of the invention, the various features of different exemplary embodiments and claims can also be combined to form new exemplary embodiments.

In a variant of the method according to the invention the adaption is performed in at least one of the following phases of the medical imaging process:.

Advantageously, the information of the individual breathing behaviour of a patient can be used for the preparation of the scan process, as real time information for a dynamic adaption of the scan process during the actual scan process and as information for the steps after having finished the scan process like the reconstruction of image data or a repetition of the scan in case it has to be expected that the image quality of reconstructed image data would be not sufficient.

In a further variant of the method according to the invention during the pre-scan phase the adaption comprises the substeps of training the patient to breathing optimally for a given scan mode or task by taking into account the patients individual breathing behaviour for the given scan mode or task. Advantageously the recorded breathing behaviour of a patient can be used as feedback information for a feedback loop for training the patient for an individual scan mode or task.

In a further variant of the method according to the invention, during the pre-scan phase the adaption comprises determining patient depended, individualized optimal timed breathing commands. For example, the reaction time of a patient can be determined based on the recorded breathing behaviour of the patient. Hence, the breathing commands can be scheduled such that the determined delay of the reaction of the patient is compensated.

Also the optimal point in time for the scan to start can be determined based on the analysis of the patient breathing pattern. The scan can be delayed, if the patient is currently in an unsuitable breathing phase to follow the given breathing command in time. That means the breathing command will be played when the time point is well suited for the patients current breathing phase.

In a further variant of the method according to the invention, during the pre-scan phase the scan process is parametrized based on the breathing behaviour. It is determined, if the patient is able to hold his breath for performing the scan in the current configuration. If not, the control unit of the medical imaging system can give a hint to decrease the scan time, e.g. increase the pitch or switch to another scan mode, e.g. from standard spirals to a high pitch flash scan,.

if the medical imaging system provides that option. In general, these switches can also be done automatically, if local standards and regulations allow for automatic adaptions of the scan parameterization.

In a variant of the method according to the invention, during the scan phase, it is detected, if the patient holds his breath properly, and in case the patient does not hold his breath properly, a command is played to remind and motivate the patient to further hold the breath. Advantageously, a feedback of the behaviour of the patient can be used to try to influence the breathing behaviour of the patient in real time to save a current scan operation in case the patient does not exactly follow the breathing commands.

According to the invention, the scan process is dynamically reparametrized by increasing the pitch, if the patient seems to be not able to hold the breath properly. In that case, in particular if the patient does not improve his breathing behaviour, although he has been admonished to do so, the scan process can be altered such that the speed of recordation of raw data is increased such that the shortened breath-hold time of the patient can be tolerated.

In a further variant of the method according to the invention, during the scan phase, the scan process is aborted in an early stage, if it is detected based on the recorded breathing behaviour that the scan results are likely insufficient and a rescan cannot be avoided. Advantageously, scan resources and time resources can be saved, if it is very likely that a current scan process would lead to a medical image with insufficient image quality.

Further, during the scan phase, it can be detected, if the patient holds his breath properly, and in case the patient does not hold his breath properly, the scan process can be stopped and a pause of the scan process can be carried out at a relevant z-position, where the patient is allowed to stop holding the breath. Under the z-position, it has to be understood the coordinate of the presently recorded slice in z-direction, which is the direction of the system axis of a medical imaging system, the medical imaging system being a CT system. In that case, after the pause, the patient is instructed to perform breath-hold again and the scan process is continued at the z-position, where the scan process was stopped or at a position, where the patient still hold his breath properly. Advantageously, a current scan process can be saved although the patient is transiently not able to follow the breathing commands of the medical imaging system properly.

In a further variant of the method according to the invention, in the after-scan phase the individual breathing behaviour of the patient is analysed based on a recorded breathing curve and in case it is detected that the patient did not follow the breathing commands properly during the scan phase, a re-scan is recommended, if severe artifacts are expected. Advantageously, the decision, if the scan has to be repeated or not can be automatically carried out based on the feedback information about the patients breathing behaviour. In that case, a reconstruction based on deteriorated raw data can be dismissed and hence, time resources and medical examination capacities can be saved.

Furthermore, in a variant of the method according to the invention, in at least one of the pre-scan phase, the scan phase and the after-scan-phase, it is automatically determined based on the recorded breathing behaviour how to adapt the medical imaging process. That means that it is decided which measurement or which combination of the above-mentioned measurements for an improvement of the scan process is carried out based on the information of a respiratory surrogate. The analysis for that decision can be implemented using classical signal processing approaches or by the means of deep learning-based algorithms. For example, the analysis of the respiratory curve can be done by some kind of neural network.

In a more detailed described variant of the adaption device, the adaption unit comprises a breathing training unit for emitting breathing commands based on the recorded breathing data and the determined breathing curve. Furthermore, the adaption unit can optionally include a starting point determination unit for setting the starting time point of a scan and a breathing command based on the recorded breathing curve. The adaption unit can also include a parametrization unit for adapting scan parameters and selecting an adapted scan protocol for a recorded individual breathing curve. The parametrization unit may also be able to reparametrize a scan process in real time during a running scan process. Moreover, the adaption unit may include an interrupting unit for stopping the scan process, if it has been detected that the breathing behaviour of the patient deteriorates during the scan process. The interrupting unit stops the scan process by emitting an interruption command to the scan unit of the medical imaging system and may for example determine a z-position based on the recorded breathing curve, at which the scan process can be resumed after the patient has recovered. Furthermore, the adaption unit may additionally comprise a recommendation unit for emitting a recommendation of abortion or rescanning in case severe artifacts are to be expected based on the recorded breathing curve. Hence, the adaption device according to that variant may comprise a multiplicity of functionalities for adapting a scan process to an individual breathing behaviour of a patient for improving image quality and for saving scan resources in case it is early detected that a scan process should be aborted due to a lack of quality of the recorded images.

The adaption device according to the invention may be part of a control unit, which is for example part of a medical imaging system, the medical imaging system being a computed tomography system. The control unit can optionally comprise a data storage unit, which stores scan protocols, which can be used for a particular scan mode. Such a scan protocol is transmitted to a driving unit. The driving unit, which may be also part of the control unit, generates control instructions for controlling a scan process. The control instructions are sent to the scan unit of the medical imaging system. The control unit may also include a reception unit, which receives raw data from the scan unit during a scan process and which also receives breathing data from a sensor system, for example a radar sensor system, which may be installed in a patient table of the medical imaging system, and monitors the breathing movement of the patient. Then, the breathing data are transmitted to an adaption device according to a variant of the invention, which may be also part of the control unit. The adaption device may modify the currently used scan protocol and may then transmit a modified scan protocol to the driving unit. The scan adaption device can also directly transmit instructions to the driving unit, for example a stop instruction, i.e. an interruption command or a start instruction or movement instruction for the patient table or the movable part of the scan unit of the medical imaging system. The scan adaption device can also emit a modified breathing command to the driving unit, which is sent to the scan unit and is emitted by an audio system of the scan unit such that the patient can follow the modified breathing command. Further, the scan adaption device may further send a breathing curve to a reconstruction unit, which may be also part of the control unit and reconstructs image data based on the received raw data and the breathing curve. Furthermore, the scan adaption device can emit a recommendation to the user for abortion or rescanning, in case the breathing curve leads to the conclusion that the image quality of the reconstructed medical images would likely be not high enough for a particular application of the medical images generated by the scan process.

The invention is explained below with reference to the figures enclosed once again. The same components are provided with identical reference numbers in the various figures. The figures are usually not to scale.

<FIG> shows s schematic representation of a computed tomography system <NUM> comprising an adaption device according to an embodiment of the invention as later discussed in detail in context with <FIG> and which may be included by a computer <NUM> of the computed tomography system <NUM>. The arrangement of the computed tomography system <NUM> comprises a gantry also called as scan unit <NUM> with a stationary part <NUM>, also referred to as a gantry frame, and with a part <NUM>, which can be rotated about a system axis z, also referred to as a rotor or drum. The rotating part <NUM> has an imaging system (X-ray system) 4a, which comprises an X-ray source <NUM> and an X-ray detector <NUM>, which are arranged on the rotating part <NUM> opposite one another. The X-ray source <NUM> and the X-ray detector <NUM> form the imaging system 4a. When the computed tomography system <NUM> is in operation, the X-ray source <NUM> emits X-rays <NUM> in the direction of the X-ray detector <NUM>, penetrates a measurement object P, for example a patient P, and is transmitted by the X-ray detector <NUM> in the form of measurement data or measurement signals recorded.

In <FIG>, a patient table <NUM> for positioning the patient P can also be seen. The patient table <NUM> comprises a bed base <NUM>, on which a patient support plate <NUM>, which is provided for actually positioning the patient P, is arranged. The patient support plate <NUM> can be adjusted relative to the bed base <NUM> in the direction of the system axis z, i.e. in the z direction, so that it enters an opening <NUM> such that the patient P can be introduced into the opening <NUM> of the scan unit <NUM> for recording X-ray projections from the patient P. A computational processing of the X-ray projections recorded with the imaging system 4a or the reconstruction of sectional images, 3D images or a 3D data set based on the measurement data or measurement signals of the X-ray projections is carried out in an image computer <NUM> of the computed tomography device <NUM>, wherein the sectional images or 3D images can be displayed on a display device <NUM>. The image computer <NUM> can also be designed as a control unit for controlling an imaging process and for controlling the scan unit <NUM> and in particular the imaging system 4a of the scan unit <NUM>. In <FIG>, also a sensor device, which works as a surrogate monitoring unit RS, is depicted. The surrogate monitoring unit RS emits radar waves (symbolised as dashed lines in <FIG>) to the area to be scanned, which is the breast of the patient P.

<FIG> shows a flow chart diagram <NUM>, which illustrates the method of adaption of a medical imaging process to an individual respiration behaviour of a patient P according to an embodiment of the invention.

In step <NUM>. I a pre-scan adaption is carried out. Step <NUM>. I comprises a breathing training of a patient P, an adaption of breathing commands RI, a selection of an appropriate scan mode SCM and an adaption of parameters SP of the selected scan mode SCM based on the patient's individual breathing behaviour. Further details of step <NUM>. I are described in context with <FIG>.

In step <NUM>. II a during-scan adaption is carried out, wherein raw data RD are acquired from the patient. Step <NUM>. II comprises a real time adaption of the scan process during the scanning. As explained in detail in context with <FIG>, the scan process can be dynamically reparametrized, the scan can be aborted in an early stage or the scan can be interrupted, until the patient P has recovered and then the scan process can be resumed at a z-position, at or after which the breathing curve BC shows an aberration of the breathing behaviour of the patient P from a predetermined breathing curve.

In step <NUM>. III an after-scan adaption of the imaging process is carried out and it is determined based on the recorded breathing curve BC, whether the patient P followed the breathing commands properly during the scan time or not. If that is the case, which is symbolized in <FIG> with "y", step <NUM>. IV can be carried out, wherein a reconstruction based on the recorded raw data RD of the scan is performed and image data BD are reconstructed. If it is determined in step <NUM>. III that the patient did not follow properly enough to the breathing instructions, which is symbolized in <FIG> with "n", it is decided that the image data BD have to be discarded and the scan process has to be repeated and the method goes further with step <NUM>. Further details concerning step <NUM>. III are discussed in context with <FIG>.

In <FIG> a flow chart diagram of step <NUM>. I is illustrated. In sub step <NUM>. Ia, a breathing training is performed, wherein a patient P gets some instructions RI for the point of time, when he should hold his breath and for the point of time, when he can proceed with breathing. The training process comprises a feedback loop. That means that in sub step <NUM>. Ib the patient P is monitored and a reaction of the patient P to an instruction RI is recorded. Particularly, a breathing curve BC is recorded. The training can also be used for taking into account the patient's individual breathing behaviour. For example, if the patient P needs some time for reacting to an instruction RI, the individual reaction time of the patient P can be considered for setting the starting time point of a scan process. In sub step <NUM>. Ic based on the recorded breathing curve BC, a scan mode SCM or an adapted set SP of parameters for a scan process is determined. Thereafter, the scan process is carried out with step <NUM>. II, which is described in context with <FIG> in detail.

In <FIG> a flow chart diagram is illustrated for a detailed description of step <NUM>. In sub step <NUM>. IIa, the actual scan process is started and some raw data RD from a scan area of the patient P are recorded. At the same time, a breathing curve BC, describing the breathing behaviour of the patient P, is recorded. At sub step <NUM>. IIb it is determined, if the breathing curve BC is conform with a predetermined breathing curve. If that is the case, which is represented in <FIG> with "y", the scan process can be continued with sub step <NUM>. If the breathing curve BC deviates from the predetermined breathing curve, which is represented with "n" in <FIG>, in sub step <NUM>. IIc a command AI is played out to remind and motivate the patient P to further hold the breath. If it is helpful, the scan process can be dynamically reparametrized, by for example increasing the pitch, if the patient P seems to be not able to hold the breath long enough, or amending some other scan parameters SP. In sub step <NUM>. IId it is determined, if the recorded breathing curve BC is conform with a possibly amended predetermined breathing curve, which, where appropriate, has been adapted to the amended parameters SP. If that is the case, which is symbolized with "y" in <FIG>, the scan process proceeds with sub step <NUM>. If the recorded breathing BC still deviates from the amended breathing curve, which is symbolized with "n" in <FIG>, the method goes further with sub step <NUM>. In sub step <NUM>. IIe it is determined, if the scan SC has to be aborted. An abortion can be reasonable, for example in an early stage of a scan process, if it is obvious that the scan result is insufficient and a rescan cannot be avoided. If that is the case, which is symbolized with "y" in <FIG>, the scan process ends with sub step <NUM>. In case the scan SC has not been finished, which is symbolized with "n" in <FIG>, in sub step <NUM>. IIg the scan SC is stopped such that the patient P can recover. After a recovering pause, a z-position is determined, at which the measured breathing curve BC was conform enough with a predetermined breathing curve. Then the scan SC is resumed with sub step <NUM>. IIa at the determined z-position. It is confirmed that most of the sub steps of step <NUM>. II, for example sub step <NUM>. IIe or sub step <NUM>. IIg are optional and can be leaved out in other embodiments of the invention or arranged in another combination as described in context with <FIG>.

In <FIG> a flow chart is illustrated, which describes step <NUM>. III of the adaption method visualized in <FIG> in detail.

In sub step <NUM>. IIIa, after the actual scan process, the recorded breathing curve BC is analysed and compared with a predetermined breathing curve. In sub step <NUM>. IIIb, it is determined, if the recorded breathing curve BC is conform enough with the predetermined breathing curve. If that is the case, which is symbolised with "y" in <FIG>, the process ends with sub step <NUM>. IIIc, wherein the reconstruction of recorded raw data RD is carried out. In case the recorded breathing curve BC is not conform enough with the predetermined breathing curve, which is symbolised with "n" in <FIG>, the scan process ends with sub step <NUM>. IIId, wherein the recorded raw data RD are dismissed and a new scan is recommended.

In <FIG> an adaption device <NUM> is schematically illustrated. The adaption device <NUM> comprises a monitoring unit <NUM> for recording breathing data BRD of a respiratory movement of a patient and generating a breathing curve BC based on the recorded breathing data BRD. Further, the adaption device <NUM> also comprises a breathing training unit <NUM> for emitting breathing commands RI based on the recorded breathing data BRD and the determined breathing curve BC. Furthermore, the adaption device <NUM> includes a starting point determination unit <NUM> for setting the starting time point STP of a scan and a breathing command RI based on the determined breathing curve BC.

The adaption device <NUM> also includes a parametrization unit <NUM> for adapting scan parameters SP and selecting an adapted scan protocol MSCP for a determined individual breathing curve BC. The parametrization unit <NUM> is also able to reparametrize a scan process in real time during a running scan process. Moreover, the adaption device <NUM> has an interrupting unit <NUM> for stopping the scan process, if it has been detected that the breathing behaviour of the patient deteriorates during the scan process. The interrupting unit <NUM> stops the scan process by emitting an interruption command IC to the scan unit <NUM> and determines a z-position based on the recorded and determined breathing curve BC, at which the scan process can be resumed after the patient P has recovered. Furthermore, the adaption device <NUM> comprises a recommendation unit <NUM> for emitting a recommendation RC of abortion or rescanning in case severe artifacts are to be expected based on the breathing curve BC.

In <FIG>, a control unit <NUM> is illustrated, as it is for example part of the computed tomography system <NUM> shown in <FIG>. The control unit <NUM> comprises a data storage unit 13a, which stores scan protocols SCP, which can be used for a particular scan mode. Such a scan protocol SCP is transmitted to a driving unit 13b. The driving unit 13b, which is also part of the control unit <NUM>, generates control instructions CI for controlling a scan process. The control instructions CI are sent to the scan unit <NUM> (shown for example in <FIG>). The control unit <NUM> also includes a reception unit 13c, which receives raw data RD from the scan unit <NUM> during a scan process and which also receives breathing data BRD from a radar sensor system RS (as depicted in <FIG>), which is installed in the patient table <NUM> of the computed tomography system <NUM>, and monitors the breathing movement of the patient P. The breathing data BRD are transmitted to an adaption device <NUM>, which is also part of the control unit <NUM> and is composed of the parts described in context with <FIG>. The adaption device <NUM> modifies the currently used scan protocol SCP and transmits a modified scan protocol MSCP to the driving unit 13b. The scan adaption device <NUM> can also directly transmit instructions to the driving unit 13b, for example a stop instruction, i.e. an interruption command IC or a start instruction or movement instruction for the patient table <NUM> or the movable part 4a of the scan unit <NUM>. The scan adaption device <NUM> can also emit a modified breathing command RI to the driving unit 13b, which is sent to the scan unit <NUM> and emitted by an audio system of the scan unit <NUM> such that the patient P can follow the modified breathing command RI. Further, the scan adaption device <NUM> also sends a breathing curve BC to a reconstruction unit 13d, which reconstructs image data BD based on the received raw data RD and the breathing curve BC. Furthermore, the scan adaption device <NUM> emits a recommendation RC to the user for abortion or rescanning, in case the breathing curve BC leads to the conclusion that the image quality of the reconstructed medical images would likely be not high enough for a particular application of the medical images generated by the scan process.

Claim 1:
Method of adaption of a medical imaging process to an individual respiration behaviour of a patient (P), the medical imaging process being a CT scan process, the method comprising the steps of:
- recording a respiratory movement (BRD) of a patient (P) by monitoring a respiratory surrogate,
- adapting the medical imaging process based on the recorded respiratory movement (BRD) of the patient (P), wherein the adaption is performed in the scan phase of the medical imaging process,
- characterised in that during the scan phase, it is determined whether the patient (P) holds his breath properly, and in case the patient (P) does not hold his breath properly, the scan process is dynamically reparametrized by increasing the pitch.