Method for providing adapted 4d CT data

Abstract

A method for providing adapted 4D CT data is provided. The invention relates to a computer-implemented method for providing adapted 4D CT data, the method comprising:-receiving initial 4D CT data, the initial 4D CT data corresponding to a first 4D CT scan, the first 4D CT scan relating to an anatomical structure at a first examination date,-receiving supplemental 4D CT data, the supplemental 4D CT data corresponding to a partial 4D CT scan, the partial 4D CT scan relating to an anatomical structure at a second examination date, the method comprises the steps of:-providing initial 4D CT data corresponding to a partial 4D CT scan related to an anatomical structure at a first examination date,-calculating adapted 4D CT data based on the initial 4D CT data and supplemental 4D CT data,-calculating adapted 4D CT data corresponding to a second 4D CT scan related to the anatomical structure at the second examination date,-providing the adapted 4D CT data,-calculating the adapted 4D CT data based on the initial 4D CT data and the supplemental 4D CT data, the adapted 4D CT data corresponding to the partial 4D CT scan related to the anatomical structure at the second examination date.

Description

Technical Field

[0001] In one aspect, the invention relates to a computer implemented method for providing adapted 4DCT data. In other aspects, the invention relates to a data processing system, a computer program product, a computer readable storage medium, a medical imaging apparatus and a radiation treatment planning system. Background Art

[0002] Cancer treatment, especially lung cancer treatment, is constantly evolving due to technological advances in the delivery of radiation therapy. Adaptive radiation therapy (ART) allows modification of treatment plans, with the goal of improving the dose distribution to patients due to anatomical and / or physiological deviations from initial simulations. Cancer radiation treatment planning can be based on 4D CT data (four-dimensional computed tomography data). 4D CT simulations can be applied to 4D CT data to generate snapshots of tumor size, shape, and position relative to normal tissue, which are used to create an internal total tumor volume (IGTV) or an internal target volume (ITV). Although the technology for treating these tumors allows highly conformal dose distributions, the complex geometric uncertainties involved in lung cancer treatment planning require large safety margins to create a planning target volume (PTV), which may hinder dose escalation.

[0003] In addition, since the total duration of the treatment cycle and treatment is usually quite long in radiation therapy, it may happen that there are several weeks between the acquisition of the planning image and the actual treatment. This poses a risk of poor tumor coverage and more serious off-target effects. ART addresses these weaknesses by enabling regular changes in the treatment plan. However, 4D CT image acquisition may impose a non-negligible dose burden on the patient, for example in the range of 30mGy to 60mGy. Therefore, adaptive planning for moving tumors in the liver and lungs presents the challenge of additional dose burden. This limits clinicians to follow a "plan of the day" approach, in which the initial treatment plan is adapted on the eve of each treatment to improve accuracy. Summary of the invention

[0004] The underlying technical problem of the present invention is to facilitate adaptive treatment planning in medical radiology, which is improved in particular in terms of radiation dose and image quality. This problem is solved by the technical solution of the independent claim. The dependent claims are related to further aspects of the present invention. Independent of the use of the grammatical term, individuals of male, female or other gender identity are included in the term.

[0005] The present invention relates to a computer-implemented method for providing adapted 4D CT data, the method comprising:

[0006] - receiving initial 4D CT data corresponding to a first 4D CT scan relating to an anatomical structure on a first examination date,

[0007] - receiving supplemental 4D CT data corresponding to a partial 4D CT scan relating to the anatomical structure on a second examination date,

[0008] - calculating adapted 4D CT data based on the initial 4D CT data and the supplementary 4D CT data, the adapted 4D CT data corresponding to a second 4D CT scan relating to the anatomical structure on a second examination date,

[0009] -Provide adapted 4D CT data.

[0010] In particular, the anatomical structure may be an anatomical structure of a patient. The anatomical structure may be, for example, an organ, in particular a lung or a liver. The anatomical structure may include a lesion, such as a tumor.

[0011] The 4D CT data may be associated with three dimensions of space and one dimension of time. The dimension of time may be particularly associated with a respiratory signal and / or a sequence of respiratory phases. The first 4D CT scan may be a first full-quality 4D CT scan. The partial 4D CT scan exposes the anatomical structure to less radiation dose than the first 4D CT scan, thereby compromising image quality, image resolution, temporal resolution and / or scan range. In particular, the initial 4D CT data may cover at least one 4D sampling point that is not covered by the supplemental 4D CT data.

[0012] An initial treatment plan may be calculated based on the initial 4D CT data. For example, a first representation of the anatomical structure may be calculated based on the initial 4D CT data, the first representation of the anatomical structure relating to the anatomical structure on a first examination date. In particular, based on the initial 4D CT data, first information relating to a size and / or a motion of a tumor of the anatomical structure and / or to an anatomical and / or morphological condition in the patient may be calculated. For example, an initial treatment plan may be calculated based on the first representation and / or based on the first information.

[0013] An adapted treatment plan may be calculated based on the adapted 4D CT data. For example, a second representation of the anatomical structure may be calculated based on the adapted 4D CT data, the second representation of the anatomical structure relating to the anatomical structure on a second examination date. In particular, based on the adapted 4D CT data, second information relating to a size and / or a motion of a tumor of the anatomical structure and / or to an anatomical and / or morphological condition in the patient may be calculated. For example, an adapted treatment plan may be calculated based on the second representation and / or based on the second information.

[0014] In order to reduce the dose burden for adaptive re-planning, in particular for updating the treatment plan immediately before the actual treatment (to create a "day plan") or at defined time points during treatment, the initial 4D CT data can be used as prior information and modified based on the latest information from the supplementary 4D CT data. The use of prior information from the initial 4D CT data can help reduce the dose burden of adaptively updating the 4D CT planning dataset during radiation treatment planning, in particular in the form of incremental re-planning.

[0015] For example, the second 4D CT scan may be substantially equivalent to a repetition of the first 4D CT scan on a second examination date. In particular, the second examination date may be later in time than the first examination date. For example, the second examination date may occur at least two days after the first examination date, at least one week after the first examination date, and / or at least one month after the first examination date.

[0016] The proposed method can realize a dose reduction workflow for 4D CT imaging, which will allow adaptive recalculation of the treatment plan during different fractions of treatment in order to adapt the radiation plan to changes during treatment. These changes can be related to, for example, tumor size, tumor motion, condition and / or morphology of tissue surrounding the tumor.

[0017] Since there may be many weeks between the acquisition of the initial 4D CT data and the actual treatment, this approach can help significantly improve the quality, effectiveness, and accuracy of radiation treatment planning while keeping the additional dose burden low.

[0018] The radiation dose of the partial 4D CT scan may be reduced, in particular significantly reduced, compared to the first 4D CT scan. In particular, the partial 4D CT may reduce the dose by an order of magnitude relative to the first 4D CT scan, for example to enable methods like performing 4D CT-based adaptive replanning or even going in the direction of a "day plan". The radiation dose of the second 4D CT scan may be comparable, in particular substantially equal, in particular equal to the radiation dose of the first 4D CT scan.

[0019] The radiation dose of the first 4D CT scan may be higher than 10 mGy, in particular higher than 30 mGy, and / or lower than 100 mGy, in particular lower than 60 mGy. The radiation dose of the partial 4D CT scan may be lower than 50% of the radiation dose of the first 4D CT scan, in particular lower than 25% of the radiation dose of the first 4D CT scan, in particular lower than 10% of the radiation dose of the first 4D CT scan. The radiation dose of the second 4D CT scan may be higher than 50% of the radiation dose of the first 4D CT scan, in particular higher than 75% of the radiation dose of the first 4D CT scan, in particular equal to the radiation dose of the first 4D CT scan.

[0020] Since the adapted 4D CT data corresponds to the second 4D CT scan, the method does not require explicitly or implicitly applying the second 4D CT scan to the anatomical region.The second 4D CT scan may be understood as an artifact for characterizing the adapted 4D CT data.

[0021] Compared to the first 4D CT scan, the scanned volume fraction of the anatomical structure of the partial 4D CT scan may be reduced, in particular significantly reduced. Throughout this specification, significantly reduced may be understood as at least reduced by a factor of two, in particular at least reduced by a factor of four, such as at least reduced by a factor of ten. The scanned volume fraction of the second 4D CT scan may be comparable, in particular substantially equal, in particular equal to the scanned volume fraction of the first 4D CT scan. In order to generate the supplementary 4D CT data, the partial 4D CT scan may be performed only for the most relevant regions, such as those containing the tumor.

[0022] A scan range of the partial 4D CT scan may be selected based on the initial 4D CT data, the scan range of the partial 4D CT scan being reduced, in particular significantly reduced, compared to the scan range of the first 4D CT scan. The scan range of the second 4D CT scan may be comparable, in particular substantially equal, in particular equal to the scan range of the first 4D CT scan. In order to reduce the volume fraction that is scanned and thus irradiated during the partial 4D CT scan, one possible approach would be to reduce the scan range of the 4D CT scan and to adjust it such that only areas of tumor motion are irradiated during the scan.

[0023] Compared to the first 4D CT scan, the extension of the irradiation field of the partial 4D CT scan along the X-ray fan direction can be reduced, in particular significantly reduced. The extension of the irradiation field of the second 4D CT scan along the X-ray fan direction can be comparable, in particular substantially equal, in particular equal to the extension of the irradiation field of the first 4D CT scan along the X-ray fan direction. If the CT scanner used is also capable of adjusting its irradiation field along the fan direction, this would be a further source of possible radiation reduction potential. In this case, the first 4D CT scan can be used in order to perform a truncation of the partial 4D CT scan.

[0024] Once the partial 4D CT scan with the reduced irradiation range is completed, it is proposed to combine the supplementary 4D CT data with the initial 4D CT data. Thus, the tumor region in the initial 4D CT data can be replaced and / or updated by the supplementary 4D CT data. In order to adjust the initial 4D CT data and the supplementary 4D CT data in the transition region, a non-rigid registration or any other suitable image registration algorithm can be used.

[0025] The scanned fraction of the respiratory cycle of the partial 4D CT scan may be reduced, in particular significantly reduced, compared to the first 4D CT scan. The scanned fraction of the respiratory cycle of the second 4D CT scan may be comparable, in particular substantially equal, in particular equal to the scanned fraction of the respiratory cycle of the first 4D CT scan. In particular, the respiratory cycle may be a respiratory cycle of the patient. For example, the partial 4D CT scan may be applied to a fraction of the respiratory cycle, in particular only to the exhalation or inspiration phase, rather than to a scan range of the partial 4D CT scan that is equal to the scan range of the first 4D CT scan.

[0026] The adapted 4D CT data can be calculated based on the initial 4D CT data and the supplementary 4D CT data by applying image registration, in particular a non-rigid transformation, from a given phase of the respiratory cycle scanned during the first 4D CT scan to its corresponding phase in the portion of the respiratory cycle skipped during the partial 4D CT scan. Thus, the missing portion on the respiratory cycle in the partial 4D CT scan can be filled to obtain adapted 4D CT data covering the entire respiratory cycle. Thus, image information about the missing phase is acquired from the original full-quality 4D CT. The respiratory signal for the adapted 4D CT data can be fully acquired during, before and / or after the partial 4D CT scan. Another option is to acquire a partial respiratory signal that only covers the scanned fraction of the respiratory cycle of the partial scan and use it to calculate the missing portion of the respiratory signal, for example, based on the assumption that the inspiratory movement is substantially opposite to the expiratory movement to calculate the missing portion of the respiratory signal.

[0027] The partial 4D CT scan may be a prospective phase-selective 4D CT scan of a single phase of the respiratory cycle. In particular, the prospective phase-selective 4D CT scan may be a phase-selective 4D CT scan that is triggered prospectively. In this case, the 3D volume information will be acquired from the supplementary 4D CT data, while the information of the respiratory motion will be acquired from the initial 4D CT data.

[0028] A motion vector field for the respiratory motion of the anatomical structure can be calculated based on the initial 4D CT data, wherein the adapted 4D CT data is calculated based on the motion vector field and the supplementary 4D CT data, in particular the supplementary 4D CT data for a single phase of the respiratory cycle. The motion vector field for the respiratory motion can be calculated based on the initial 4D CT data and used to calculate the adapted 4D CT data based on the supplementary 4D CT data obtained from a partial 4D CT scan of the single phase. By using information from the initial 4D CT data, the entire motion vector field for the respiratory motion can be calculated, which allows each phase to be transformed into each other phase of the cycle.

[0029] Initial radiation treatment planning data regarding the anatomical structure may be calculated based on the initial 4D CT data, and / or adapted radiation treatment planning data regarding the anatomical structure may be calculated based on the adapted 4D CT data.

[0030] The present invention also relates to a computer program product or a computer-readable storage medium, comprising instructions, which, when executed by a computer, cause the computer to perform a method according to one of the aspects of the present invention.

[0031] The invention further relates to a data processing system comprising a data interface and a processor, the data processing system being configured to execute a method according to one of the aspects of the invention.

[0032] The present invention also relates to a medical imaging device, comprising a data processing system according to one of the aspects of the present invention and configured for performing a first 4D CT scan related to the anatomical structure to obtain initial 4D CT data, and / or for performing a partial 4D CT scan related to the anatomical structure to obtain supplementary 4D CT data.

[0033] The medical imaging device may be, for example, a computed tomography device and / or a cone-beam CT device.

[0034] The present invention further relates to a radiation treatment planning system comprising a data processing system according to one of the aspects of the present invention and configured for providing initial radiation treatment planning data regarding an anatomical structure and / or for providing adapted radiation treatment planning data regarding an anatomical structure.

[0035] Any algorithms and / or models mentioned in this article can be based on one or more of the following architectures: deep convolutional neural networks, deep belief networks, random forests, deep residual learning, deep reinforcement learning, recurrent neural networks, Siamese networks, generative adversarial networks, or autoencoders.

[0036] The computer program product may be, for example, a computer program, or include another element in addition to the computer program. The other element may be hardware, such as a memory device on which the computer program is stored, a hardware key for using the computer program, etc., and / or software, such as a software key or documentation for using the computer program. The computer-readable storage medium may be embodied as a non-permanent main memory (e.g., random access memory) or a permanent mass storage device (e.g., a hard disk, a USB stick, an SD card, a solid state drive).

[0037] The data processing system may include, for example, at least one of a cloud computing system, a distributed computing system, a computer network, a computer, a tablet computer, a smart phone, etc. The data processing system may include hardware and / or software. The hardware may be, for example, a processor system, a memory system, and combinations thereof. The hardware may be configurable and / or operable by software. The calculations for performing the actions of the method may be performed in a processor.

[0038] Data, in particular initial 4D CT data and supplementary 4D CT data, may be received, in particular via a data interface, e.g. by receiving a signal carrying the data and / or by reading the data from a computer memory and / or by manual user input, e.g. via a graphical user interface. Data, in particular adapted 4D CT data and / or radiation treatment planning data may be provided, in particular via a data interface, e.g. by sending a signal carrying the data and / or by writing the data into a computer memory and / or by displaying the data on a display.

[0039] In the context of the present invention, the expression "based on" may in particular be understood to mean "among other things, using". In particular, accordingly, the wording that a first feature is calculated (or generated, determined, etc.) based on a second feature does not exclude the possibility of calculating (or generating, determining, etc.) the first feature based on a third feature.

[0040] Reference is made to the fact that the described method and the described system are only preferred exemplary embodiments of the invention and that variations may be made thereto by a person skilled in the art without departing from the scope of the invention as specified by the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The invention will be explained below using exemplary embodiments with reference to the accompanying drawings. The illustrations in the figures are schematic and highly simplified and are not necessarily to scale.

[0042] Figure 1 A flow chart of a computer-implemented method for providing adapted 4D CT data is shown.

[0043] Figure 2 The anatomical structures are shown.

[0044] Figure 3 A diagram of the respiratory cycle is shown.

[0045] Figure 4 A medical imaging device is shown. DETAILED DESCRIPTION

[0046] Figure 1 A flow chart of a computer-implemented method for providing adapted 4D CT data is shown.

[0047] Figure 2 An anatomical structure N including a lesion L is shown. The irradiation field RL of the partial 4D CT scan is significantly reduced compared to the irradiation field R of the first 4D CT scan. The scanning range of the first 4D CT scan is the extension of the irradiation field R along the scanning direction Z. The scanning range of the partial 4D CT scan is the extension of the irradiation field RL along the scanning direction Z and is significantly smaller than the scanning range of the first 4D CT scan.

[0048] for Figure 2 In the example shown in FIG, the radiation dose of the partial 4D CT scan is reduced compared to the first 4D CT scan, the scanned volume fraction of the anatomical structure N of the partial 4D CT scan is reduced compared to the first 4D CT scan, the scanning range of the partial 4D CT scan is reduced compared to the scanning range of the first 4D CT scan, and the extension of the irradiation field of the partial 4D CT scan along the X-ray fan direction X is reduced compared to the first 4D CT scan.

[0049] Figure 3 A diagram of the respiratory cycle of amplitude M over time T is shown, covering the inspiration phase PI, the expiration phase PE and the individual phases P1, P2, P3 and P4. A prospective phase selective 4D CT scan can, for example, be prospectively triggered to cover the individual phase P2 maximum inspiration state at time point T2. In this case, the scanned fraction of the respiratory cycle of the partial 4D CT scan is reduced compared to the first 4D CT scan, which covers the entire respiratory cycle.

[0050] Figure 4A medical imaging device 1 in the form of a computed tomography device is shown, comprising a gantry 20, a support frame 21, a tilt frame 22, a rotor 24, an opening 9 for receiving a patient support structure 12, a radiation interaction region 4 (the radiation interaction region 4 is located in the opening 9), a radiation source 26 for generating an X-ray fan 27, and a radiation detector 28. The medical imaging device 1 also comprises a patient table 10, which comprises a patient table pedestal 11 and a patient support structure 12 in the form of a patient table top. The patient table structure 12 is movably mounted on the patient pedestal 11 along a system axis AS of the radiation interaction region 4. A patient 13 is located on the patient support structure 14. The medical imaging device 1 comprises a data processing system, which comprises a data interface and a processor, which is configured to perform a method for providing adapted 4D CT data. The medical imaging apparatus 1 is configured for performing a first 4D CT scan relating to an anatomical structure N to obtain initial 4D CT data, and for performing a partial 4D CT scan relating to the anatomical structure N to obtain supplementary 4D CT data.

Claims

1. A computer-implemented method for providing adapted 4D CT data, the method comprising: - receiving (S1) initial 4D CT data corresponding to a first 4D CT scan relating to an anatomical structure (N) on a first examination date, - receiving (S2) supplementary 4D CT data corresponding to a partial 4D CT scan relating to said anatomical structure (N) on a second examination date, - calculating (S3) the adapted 4D CT data based on the initial 4D CT data and the supplementary 4D CT data, the adapted 4D CT data corresponding to a second 4D CT scan relating to the anatomical structure (N) on the second examination date, - Providing (S4) said adapted 4D CT data.

2. The method according to claim 1, - The radiation dose of the partial 4D CT scan is reduced compared to the first 4D CT scan.

3. The method according to claim 1 or 2, - the scanned volume fraction of the anatomical structure (N) of the partial 4D CT scan is reduced compared to the first 4D CT scan.

4. The method according to claim 1, - a scanning range of the partial 4D CT scan is selected based on the initial 4D CT data, - The scan range of the partial 4D CT scan is reduced compared to the scan range of the first 4D CT scan.

5. The method according to one of claims 1 to 4, - The extension of the irradiation field along the X-ray fan direction (X) of the partial 4D CT scan is reduced compared to the first 4D CT scan.

6. The method according to one of claims 1 to 5, - The scanned fraction of the respiratory cycle of the partial 4D CT scan is reduced compared to the first 4D CT scan.

7. The method according to claim 6, - the adapted 4D CT data are calculated based on the initial 4D CT data and the supplementary 4D CT data by applying image registration from a given phase of the respiratory cycle scanned during the first 4D CT scan to its corresponding phase in the portion of the respiratory cycle skipped during the partial 4D CT scan.

8. The method according to one of claims 1 to 7, - The partial 4D CT scan is a prospective phase-selective 4D CT scan of a single phase of the respiratory cycle.

9. The method according to one of claims 1 to 8, - wherein a motion vector field of the respiratory motion of the anatomical structure (N) is calculated based on the initial 4D CT data, - wherein the adapted 4D CT data are calculated based on the motion vector field and the supplementary 4D CT data.

10. The method according to one of claims 1 to 9, - wherein initial radiation treatment planning data for said anatomical structure (N) are calculated based on said initial 4D CT data, and / or - wherein adapted radiation treatment planning data regarding said anatomical structure (N) are calculated based on said adapted 4D CT data.

11. A computer program product or a computer readable storage medium comprising instructions which, when executed by a computer, cause the computer to perform the method according to one of claims 1 to 10.

12. A data processing system comprising a data interface and a processor, the data processing system being configured to perform the method according to one of claims 1 to 10.

13. A medical imaging device (1), comprising a data processing system according to claim 12, and configured to perform the first 4D CT scan related to the anatomical structure (N) to obtain the initial 4D CT data, and / or to perform the partial 4D CT scan related to the anatomical structure (N) to obtain the supplementary 4D CT data.

14. The medical imaging device (1) according to claim 13, which is a computed tomography device and / or a cone beam CT device.

15. A radiation treatment planning system comprising the data processing system according to claim 12 and configured for providing the initial radiation treatment planning data regarding the anatomical structure and / or for providing the adapted radiation treatment planning data regarding the anatomical structure.

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