CN115546080A - Medical image processing method and device, computer equipment and storage medium - Google Patents
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Abstract
The application relates to a medical image processing method, a medical image processing device, a computer device and a storage medium. The method comprises the steps of obtaining a scanning image of an imaging area and an emission field map corresponding to the imaging area, calculating according to the emission field map to obtain an emission field factor, determining a correction factor according to an imaging sequence parameter corresponding to the scanning image and the emission field factor, and finally correcting the scanning image of the imaging area according to the correction factor. The method fully considers the source and derivation process of the signal, and can overcome the problem of poor quality of the scanned image caused by the nonuniformity of the emission field by using a corresponding data processing method only according to the signal distribution condition of the scanned image and the emission field image. Moreover, when the method removes the signal unevenness of the scanned image caused by the emitting field unevenness, the natural contrast of the scanned image is kept, the brought imaging error is avoided, and the accurate image uniformity correction can be realized.
Description
Technical Field
The present application relates to the field of medical image processing technologies, and in particular, to a medical image processing method and apparatus, a computer device, and a storage medium.
Background
The nuclear magnetic resonance imaging system comprises the following core components: the device comprises a magnet, a gradient coil, a radio frequency transmitting coil, a radio frequency receiving coil and a signal processing and reconstruction unit. In which radio-frequency transmitting coils are used to excite specific nuclei of the object being imaged, e.g. 1 H， 23 Na， 31 P, 13 C, etc. are combined withThe imaging substance sets specific parameter combination according to the physical characteristics of the imaging substance, obtains a signal with special contrast through certain time sequence derivation, receives the signal through a radio frequency receiving coil, completes signal processing through a signal processing and reconstruction unit, and finally obtains an image or a frequency spectrum signal which can guide clinical application.
However, in an actual rf excitation stage, the uniformity of excitation in the corresponding region has a great influence on the uniformity of the final overall image or spectrum, and if the difference between the excitation uniformity and the theoretical target is too large, the final image or spectrum image is modulated by amplitude values of different degrees at different positions in space to affect the imaging quality of the final overall image. In the existing scheme for correcting the nonuniformity of the transmitting field, after an image is acquired, the image is directly post-processed by using a conventional image processing algorithm based on the gray distribution of the image, so that the homogenization correction is realized, and the homogenization is basically not directly carried out from the transmitting field distribution of a coil. However, in an actual situation, because of differences in proton density of tissue components of the nuclear magnetic medical image, natural contrast exists, and characteristics of differences in control distribution of signals appear on the image, and direct algorithm normalization processing on the image may cause the natural differences to be also normalized and weakened, so that gray level errors of the image are brought, and the quality of the acquired imaging image is reduced.
Disclosure of Invention
In view of the above, it is necessary to provide a medical image processing method, an apparatus, a computer device, and a storage medium, which can effectively solve the problem of non-uniformity of an imaged image due to non-uniformity of an excitation region, and further can improve the quality of the imaged image.
In a first aspect, a method of processing a medical image, the method comprising:
acquiring a scanning image of an imaging area and a corresponding emission field map of the imaging area;
calculating to obtain a transmission field factor according to the transmission field map;
determining a correction factor according to an imaging sequence parameter corresponding to the scanned image and the emission field factor;
correcting the imaging region image according to the correction factor.
In one embodiment, the emission field map is a low resolution image, and after the emission field map corresponding to the imaging region is acquired, the method further includes:
obtaining a high-resolution emission field map according to the low-resolution image through an interpolation algorithm;
the calculating according to the transmission field map to obtain the transmission field factor comprises:
and calculating to obtain a transmission field factor according to the high-resolution transmission field map.
In one of the embodiments, the first and second parts of the device,
at least part of the emission field pattern is a high signal-to-noise ratio region, and the calculation of the emission field factor according to the emission field pattern comprises the following steps:
inputting the emission field pattern into a correction model to obtain a corrected emission field pattern; determining the transmit field factor from the rectified transmit field pattern.
In one embodiment, the determining a correction factor according to the imaging sequence parameter corresponding to the scan image and the transmission field factor includes:
determining theoretical signal distribution intensity without considering the emission field effect based on imaging sequence parameters corresponding to the scanning image according to a Bloch equation derivation rule;
determining theoretical signal distribution intensity under the emission field effect based on imaging sequence parameters corresponding to the scanning image and the emission field factor according to the Bloch equation derivation rule;
and determining the ratio of the theoretical signal distribution intensity without considering the emission field effect and the theoretical signal distribution intensity with considering the emission field effect as the correction factor.
In one embodiment, the emission field map is obtained by reconstruction of the acquired signals after applying a dual flip angle sequence or a DREAM sequence to the imaging region.
In one embodiment, the transmit field pattern is a two-dimensional transmit field pattern or a three-dimensional transmit field pattern.
In one embodiment, said correcting said imaging region image according to said correction factor comprises:
and performing product operation on each pixel value of the imaging area image and the correction factor to obtain a corrected imaging area image.
In one embodiment, the imaging sequence parameters corresponding to the scan image include a type of radio frequency pulse and/or a flip angle of the radio frequency pulse.
In a second aspect, an apparatus for processing medical images, the apparatus comprising:
the device comprises an acquisition module, a processing module and a display module, wherein the acquisition module is used for acquiring a scanning image of an imaging area and an emission field map corresponding to the imaging area;
the calculation module is used for calculating and obtaining a transmission field factor according to the transmission field map;
the determining module is used for determining a correction factor according to the imaging sequence parameter corresponding to the scanning image and the transmitting field factor;
and the correcting module is used for correcting the imaging area image according to the correction factor.
In a third aspect, a computer device comprises a memory storing a computer program and a processor implementing the method of the first aspect when the processor executes the computer program.
In a fourth aspect, a computer-readable storage medium has stored thereon a computer program which, when executed by a processor, implements the method of the first aspect described above.
The medical image processing method, the medical image processing device, the computer equipment and the storage medium acquire the scanning image of the imaging area and the emission field map corresponding to the imaging area, calculate the emission field factor according to the emission field map, determine the correction factor according to the imaging sequence parameter and the emission field factor corresponding to the scanning image, and finally correct the scanning image of the imaging area according to the correction factor. The method fully considers the source and derivation process of the signal, and can overcome the problem of poor quality of the scanned image caused by the nonuniformity of the emission field by using a corresponding data processing method only according to the signal distribution condition of the scanned image and the emission field image. Moreover, when the method removes the signal nonuniformity of the scanned image caused by the nonuniformity of the emission field, the method makes optimization consideration on the physical value of the excitation source, can better keep the natural contrast of the scanned image, and can avoid the brought imaging error and realize accurate image uniformity correction compared with the traditional method for removing the nonuniformity of the emission field by an image homogenization processing algorithm.
Drawings
FIG. 1 is a diagram of an exemplary embodiment of a method for processing medical images;
FIG. 2 is a flow diagram illustrating a method for processing a medical image according to an embodiment;
FIG. 3 is a flowchart illustrating an implementation manner of S103 in the embodiment of FIG. 2;
FIG. 4 is a schematic diagram of a 2D GRE sequence in one embodiment;
FIG. 5 is a flow diagram illustrating a method for processing medical images according to one embodiment;
FIG. 5A is a schematic flow chart illustrating the determination of an emission field map from a scan image according to one embodiment;
FIG. 6 is a flow diagram illustrating a method for processing a medical image according to an embodiment;
FIG. 7 is a schematic diagram showing the configuration of a medical image processing apparatus according to an embodiment;
FIG. 8 is a schematic diagram showing the configuration of a medical image processing apparatus according to an embodiment;
FIG. 9 is a diagram showing a configuration of a medical image processing apparatus according to an embodiment;
FIG. 10 is a schematic diagram showing the configuration of a medical image processing apparatus according to an embodiment;
FIG. 11 is a schematic diagram showing the configuration of a medical image processing apparatus according to an embodiment;
FIG. 12 is a diagram illustrating an internal structure of a computer device according to an embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of and not restrictive on the broad application.
The medical image processing method provided by the application can be applied to the application environment shown in fig. 1. The imaging device 102 is connected to the terminal 104 through a network, and the imaging device 102 is configured to scan an object in an imaging area and transmit scan data of the imaging area and a related signal of an imaging process to the terminal 104, so that the terminal 104 performs imaging processing of the imaging area based on the scan data and the related information of the imaging process to obtain an imaging image. The imaging device 102 may be various types of imaging devices, such as a magnetic resonance imaging device. The terminal 102 may be, but is not limited to, various personal computers, laptops, smartphones, tablets, and portable wearable devices.
Those skilled in the art will appreciate that the application environment shown in fig. 1 is only a block diagram of a portion of the structure associated with the present application and does not constitute a limitation on the application environment to which the present application is applied, and that a particular application environment may include more or less components than those shown in the drawings, or may combine certain components, or have a different arrangement of components.
In one embodiment, as shown in fig. 2, a method for processing a medical image is provided, which is described by taking the method as an example for being applied to the terminal in fig. 1, and includes the following steps:
s101, acquiring a scanning image of an imaging area and an emission field map corresponding to the imaging area.
The scan image of the imaging area is an initial image obtained by scanning and imaging an object to be imaged in the imaging area by the imaging device, for example, a nuclear magnetic resonance image of a tissue and an organ of a human body can be obtained by scanning and imaging the tissue and the organ by the nuclear magnetic resonance device. The scan image may be a two-dimensional image or a three-dimensional image, and is not limited thereto. The emission field pattern corresponding to the imaging region is an emission field pattern obtained by reconstructing a signal acquired after applying a corresponding test sequence to the imaging region, and optionally, the emission field pattern is obtained by reconstructing a signal acquired after applying a double flip angle sequence or a Double Refocusing Echo Acquisition (DREAM) sequence to the imaging region. The emission field pattern is a two-dimensional emission field pattern or a three-dimensional emission field pattern, and is not limited herein.
In this embodiment, an imaging device, such as a magnetic resonance imaging device, may be used to scan an object to be imaged in an imaging region to obtain scan data of the imaging region, and obtain a signal corresponding to a test sequence of an emission field, such as a signal corresponding to a conventional double-flip angle sequence or a DREAM sequence, and then transmit the scan data and the signal corresponding to the test sequence to a terminal, where the terminal performs image reconstruction based on the scan data to obtain a scan image of the imaging region, and performs image reconstruction based on the signal corresponding to the test sequence to obtain an emission field map of the imaging region.
In one embodiment, the scan image of the imaging region and/or the transmit field map corresponding to the imaging region employ a dual flip angle sequence comprising a first RF pulse and a second RF pulse disposed after the first RF pulse, wherein the flip angle of the first RF pulse is θ, the flip angle of the second RF pulse is 2 θ, and θ = γ B 1 T，B 1 T represents the duration of the first RF pulse as the strength of the RF field. The corresponding magnetic resonance signal of the test subject after application of the first RF pulse may be denoted Mxy (θ), and the corresponding magnetic resonance signal of the test subject after application of the second RF pulse may be denoted Mxy (2 θ), then θ may be approximated as:
θ＝arccos(Mxy(2θ)/2Mxy(θ))
by the above formula, the strength of each location in the RF field can be determined.
In one embodiment, the transmit field pattern may also be generated by using a stimulus echo (STEAM) sequence comprising three RF pulses with flip angles θ 1 、θ 2 、θ 3 And satisfies theta 1 ＝θ 2 ＝θ 3 (= theta) detecting spin echo in the imaging region of the objectAnd the stimulus echo signal strength can be expressed as follows:
wherein ρ 0 Denotes longitudinal magnetization, T 1 Longitudinal relaxation time, T, of hydrogen protons 2 Transverse relaxation time of hydrogen proton,. Tau 1 And τ 2 Is the time interval from the rf pulse to the acquisition window. Combined use of signal intensity S from spin echo SE And stimulus echo signal strength S STE The flip angle can be determined, and then the emission field pattern corresponding to the imaging region is determined.
And S102, calculating to obtain a transmission field factor according to the transmission field map.
When the terminal acquires the emission field map corresponding to the imaging area, for example, the B1 emission field map, the emission field factor can be calculated according to the signal distribution intensity of the emission field map. In one application, the transmit field map may be input into a correction model to obtain a corrected transmit field map; a transmit field factor is determined from the rectified transmit field pattern. In this embodiment, the transmit field factor represents the strength of the RF field formed by the RF pulses experienced at any location in space.
S103, determining a correction factor according to the imaging sequence parameter and the emission field factor corresponding to the scanned image.
The imaging sequence parameters corresponding to the scanned image comprise the type of the radio frequency pulse and/or the flip angle of the radio frequency pulse. When the terminal acquires the type and the transmission field factor of the radio frequency pulse, a signal derivation process corresponding to the type of the radio frequency pulse can be further simulated through a Bloch derivation rule, and a correction factor for optimizing the distribution uniformity of the spatial signal and the distribution uniformity of each pixel value on a scanning image of an imaging area can be calculated by combining the transmission field factor which is actually influenced by the nonuniformity of the transmission field. When the terminal acquires the flip angle and the transmission field factor of the radio frequency pulse, the flip angle and the transmission field factor can be further substituted into a Bloch equation representing a Bloch derivation rule to calculate the signal distribution intensity, and then a correction factor is calculated according to the signal distribution intensity.
And S104, correcting the scanned image of the imaging area according to the correction factor.
When the terminal needs to correct the scanned image of the imaging area, the gray value or the pixel value of each pixel point on the scanned image of the imaging area can be corrected according to the correction factor, so that the gray value or the pixel value of each pixel point on the corrected scanned image can be basically consistent with the gray value or the pixel value of each pixel point on the scanned image which is imaged without being influenced by the nonuniformity of the emission field, and the nonuniformity of the pixel value or the gray value of each pixel point on the scanned image caused by the nonuniformity of the emission field can be removed.
In the medical image processing method, a scanning image of an imaging area and an emission field map corresponding to the imaging area are obtained, an emission field factor is obtained through calculation according to the emission field map, a correction factor is determined according to an imaging sequence parameter and the emission field factor corresponding to the scanning image, and finally the scanning image of the imaging area is corrected according to the correction factor. The method fully considers the source and derivation process of the signal, and can overcome the problem of poor quality of the scanned image caused by the nonuniformity of the emission field by using a corresponding data processing method only according to the signal distribution condition of the scanned image and the emission field pattern. Moreover, when the method removes the signal nonuniformity of the scanned image caused by the nonuniformity of the emission field, the method takes optimization consideration from the physical value of the excitation source, can better keep the natural contrast of the scanned image, and can avoid the brought imaging error and realize accurate image uniformity correction compared with the traditional method for removing the nonuniformity of the emission field by an image homogenization processing algorithm.
In one embodiment, an implementation manner of the above S103 is provided, and as shown in fig. 3, the above S103 "determining a correction factor according to the imaging sequence parameter and the transmission field factor corresponding to the scan image" includes:
s201, according to a Bloch equation derivation rule, determining theoretical signal distribution intensity without considering an emission field effect based on imaging sequence parameters corresponding to a scanned image.
The Bloch equation derivation rule can be expressed by using a Bloch equation, and different types of radio frequency pulses correspond to different Bloch derivation results. The theoretical signal distribution strength refers to the regional signal strength distribution calculated by using the Bloch equation when a receiving field is ideally transmitted under corresponding sequence parameters.
In this embodiment, when the terminal obtains the imaging sequence parameter corresponding to the scanned image, the imaging sequence parameter is directly analyzed according to the derivation rule of the Bloch equation to obtain the theoretical signal distribution intensity corresponding to the actual emission field without considering the emission field effect.
S202, determining theoretical signal distribution intensity under the consideration of an emission field effect based on imaging sequence parameters and emission field factors corresponding to the scanned image according to a Bloch equation derivation rule.
The theoretical signal distribution strength under the field emission effect refers to the distribution strength of a signal subarea which is calculated by using a Bloch equation and corresponds to an actual emission field and is subjected to signal modulation after the actual imaging sequence parameters and the actual imaging sequence parameters are modulated by emission field factors.
In this embodiment, when the terminal obtains the imaging sequence parameter and the transmission field factor corresponding to the scanned image, the imaging sequence parameter and the transmission field factor are directly analyzed according to the derivation rule of the Bloch equation to obtain the theoretical signal distribution strength under the transmission field effect.
S203, determining the ratio of the theoretical signal distribution intensity without considering the emission field effect and the theoretical signal distribution intensity with considering the emission field effect as a correction factor.
When the terminal calculates the theoretical signal distribution intensity without considering the transmission field and the theoretical signal distribution intensity with considering the transmission field, the ratio operation can be carried out on the values of the two signal intensities, and the finally obtained ratio is determined as the correction factor. .
The method described in S201-S203 is exemplified by the 2D GRE sequence described in fig. 4, if the transmission field (B1 field) is in an ideal state, the transverse magnetization vector M will be generated after the RF excitation is finished, and the transverse magnetization vector M can be obtained by the following relation (1):
M＝ρ 0 *sinα (1)；
in the above formula, M represents that the signal generates a transverse magnetization vector after the RF excitation is finished; rho 0 Representing a spatial voxel proton density distribution matrix; α denotes the RF excitation flip angle.
Over a duration t1
After attenuation, the theoretical signal distribution intensity without considering the emission field effect corresponding to the sequence can be obtained based on the derivation rule of Bloch equation and can be expressed by the relation (2):
in the above formula, S ACQ Representing the theoretical signal distribution intensity without considering the field effect of the emission; t is t 1 Represents a duration of time;
representing a pixel spatial distribution matrix.
When considering the influence of the nonuniformity factor of the actual transmission field, the flip angles alpha of different space voxels will be transmitted by the transmission field factor S B1+ Modulated to become corresponding S B1+ * α, the theoretical signal distribution strength corresponding to the sequence obtained based on the derivation rule of Bloch equation can be expressed by the following relation (3):
in the above formula, S ACQ-B1 Indicating the theoretical signal distribution strength taking into account the effect of the emitted field.
Obtaining the theoretical signal distribution intensity S after being adjusted by the actual transmitting field ACQ-B1 And a theoretical signal distribution strength S not adjusted by the transmission field ACQ Then, a ratio operation may be performed to obtain a correction factor, for example, the correction factor may be determined by the following relation (4):
in the above equation, γ represents a correction factor.
In practical application, the transmission field nonuniformity only affects the signal strength generated during radio frequency transmission, and has no additional influence during spatial coding. Therefore, after the space coding signals are converted into corresponding space pixel signals after Fourier change, the signal intensity of the corresponding space position is adjusted according to the factors of the transmitting field and the radio frequency type and the flip angle in the corresponding sequence time sequence, and the problem of data uniformity caused by non-uniform transmitting field can be solved. Based on the thought, the spatial excitation generated by the emission field nonuniformity is nonuniform, and the method provided by this embodiment can calculate the acquired theoretical signal distribution intensity without considering the emission field distribution and the acquired theoretical signal distribution intensity with considering the emission field distribution according to the relation (4) by the Bloch equation derivation rule to obtain the correction factor, and then perform the inverse compensation adjustment on each pixel gray value on the obtained actual imaging image by using the correction factor, so as to eliminate the influence of the B1 emission field nonuniformity.
In practical applications, the emission field map in S101 is usually a low-resolution image acquired in a short-time fast sequence, and based on this, the method in the embodiment of fig. 2 further includes the steps of: and obtaining a high-resolution transmitting field pattern according to the low-resolution image through an interpolation algorithm, and then calculating to obtain a transmitting field factor based on the high-resolution transmitting field pattern. Optionally, the terminal may also train a conversion network based on the low-resolution transmission field pattern in advance, so that the conversion network can convert the low-resolution transmission field pattern into the high-resolution transmission field pattern, and in actual application, the trained conversion network is directly used to convert the acquired transmission field pattern to obtain the transmission field pattern with the corresponding high resolution. It should be noted that, in the embodiment of the present application, the low-resolution image refers to an image whose resolution is less than a first set threshold, and the high-resolution image refers to an image whose resolution is greater than or equal to a second set threshold, that is, the low-resolution image has a relatively low resolution relative to the high-resolution image.
In one embodiment, the transmit field map may also be obtained from a neural network model. The neural network model is obtained by training a neural network through a plurality of paired prior scanning images and prior B1 transmitting field maps, as shown in FIG. 5A, in a training stage, the input end of the neural network model comprises a water film positioning image/initial scanning image with low resolution, the output end of the neural network model is the B1 transmitting field map (B1 field map) of an RF field corresponding to the water film positioning image/initial scanning image, and the neural network model can be obtained by continuously optimizing parameters of the neural network.
In the using stage, only the scanning image of the imaging area can be obtained, the scanning image of the imaging area can be a quick positioning image, a pre-scanning image and the like, and the quick positioning image, the pre-scanning image and the like are input into the neural network model, so that the emission field image corresponding to the imaging area can be obtained. In the embodiment of the application, the emission field pattern corresponding to the imaging area does not need to be detected by adopting the test sequence, so that the absorption of the detection object to the radio frequency energy can be reduced, the scanning time is saved, and the scanning efficiency is improved.
In practical applications, the transmission field pattern portion in S101 is a high snr region, and the transmission field factor of a low snr region near the high snr region may not be very accurate, and the transmission field pattern needs to be corrected. Illustratively, the transmit field pattern may be input into a rectification model to obtain a rectified transmit field pattern; a transmit field factor is determined from the rectified transmit field pattern. The emission field map is limited by the influence of different proton density distribution and tissue structures in the body of the detected object, and in the area with low proton density (such as a bone area and a lung area), the emission field map correspondingly shows a low signal-to-noise ratio (SNR) area; and in the area with high proton density, the emission field pattern is correspondingly expressed as a high signal-to-noise ratio, namely a high signal-to-noise ratio area. Alternatively, the low snr region is often located around or near the high snr region, and theoretically, the rf field strength experienced by the two regions is similar, i.e., the transmission field factors of the two regions are the same or similar. Optionally, the correction model may be a correction network obtained based on a machine learning method, or may be a mathematical model obtained by using a fitting algorithm.
In one embodiment, an implementation of S102 is provided, as shown in fig. 5, the method includes:
s301, calculating to obtain a first transmission field factor according to a high signal-to-noise ratio region of the transmission field map. Of course, there are also regions of low signal-to-noise ratio in the transmitted field pattern, and the regions of low signal-to-noise ratio are located around the regions of high signal-to-noise ratio.
The first transmission field factor is calculated according to a high signal-to-noise ratio region of a transmission field map. When the terminal acquires the emission field map corresponding to the imaging area, the first emission field factor can be calculated according to the signal distribution intensity of the emission field map.
S302, inputting the transmission field pattern into the correction model, obtaining a corrected transmission field pattern, and determining a second transmission field factor of a low signal-to-noise ratio region according to the corrected transmission field pattern.
And the second transmission field factor is the transmission field factor corrected by the transmission field factor corresponding to the low signal-to-noise ratio region image. In this embodiment, the terminal may obtain a correction network based on the transmission field pattern training in advance through a machine learning method, so that the correction network may obtain a corrected transmission field pattern based on the input transmission field pattern, and pixels of a low signal-to-noise ratio region of the corrected transmission field pattern are corrected and equal to or capable of being connected with pixels of a high signal-to-noise ratio region in the transmission field pattern.
It should be noted that, in this embodiment, the manner of obtaining the second transmission field factor in the low snr region is not particularly limited, and in other embodiments, the second transmission field factor can also be obtained directly by an interpolation method: determining a low signal-to-noise ratio region in the emission field map, determining a first emission field factor corresponding to a pixel which is located around the low signal-to-noise ratio region and belongs to the high signal-to-noise ratio region, and determining a second emission field factor through a linear interpolation method according to the first emission field factor corresponding to the pixel which is located around the low signal-to-noise ratio region and belongs to the high signal-to-noise ratio region.
And S303, determining a transmission field factor according to the first transmission field factor and the second transmission field factor.
And when the terminal acquires the first transmission field factor and the second transmission field factor, the transmission field factors of all the transmission fields can be obtained. Of course, for the low snr region of the transmission field map, the initial transmission field factor and the second transmission field factor obtained by calculating the transmission field map may be further subjected to an average value operation, or a weighted sum operation, and the final operation result is used as the low snr region transmission field factor. Similarly, for all transmission fields, the mean value obtained by averaging the first transmission field factor and the second transmission field factor can be used as the transmission field factor.
In an embodiment, when the computer device executes the above S104, the following steps are specifically performed: and performing product operation on each pixel value of the scanned image of the imaging area and the correction factor to obtain a corrected imaging area image.
When the correction factor is calculated by the ratio of the theoretical signal distribution intensity and the actual signal distribution intensity, when the scanned image is corrected, the product operation can be specifically performed on each pixel value of the scanned image and the correction factor to obtain a corrected image of the imaged region; when the correction factor is calculated by the ratio of the actual signal distribution intensity to the theoretical signal distribution intensity, when the scanned image is corrected, the product operation may be specifically performed on each pixel value of the scanned image and the reciprocal of the correction factor to obtain a corrected image of the imaging region.
In summary, in the above embodiments, a method for processing a medical image is provided, as shown in fig. 6, the method includes:
s401, acquiring a scanning image of the imaging area.
S402, reconstructing the acquired signals after applying the double flip angle sequence or the DREAM sequence to the imaging area to obtain an emission field map of the imaging area.
And S403, calculating a transmission field factor according to the transmission field map.
And S404, determining the theoretical signal distribution intensity without considering the emission field effect based on the imaging sequence parameters corresponding to the scanning image according to the Bloch equation derivation rule.
S405, according to the Bloch equation derivation rule, determining the theoretical signal distribution intensity under the consideration of the emission field effect based on the imaging sequence parameters and the emission field factors corresponding to the scanned image.
And S406, determining the ratio of the theoretical signal distribution intensity without considering the emission field effect to the theoretical signal distribution intensity with considering the emission field effect as a correction factor.
And S407, performing product operation on each pixel value of the imaging area image and the correction factor to obtain a corrected imaging area image.
In the existing scheme for correcting the nonuniformity of the high-field B1 transmitting field (excitation nonuniformity), after an image is acquired, the image is directly post-processed by using a conventional image processing algorithm based on the gray distribution of the image, so that the homogenization correction is realized, and the homogenization is basically not directly carried out from the transmitting field distribution of the coil. However, the conventional image processing algorithm does not consider signal sources and derivation processes, and only uses a data processing algorithm according to the signal distribution condition of the image, so that the image is more uniformly approximate to the whole distribution. In practical situations, a nuclear magnetic medical image has natural contrast due to differences in proton density of tissue components and T1 or T2 attributes of the components, and exhibits a characteristic of difference in spatial distribution of signals on the image, and direct algorithmic homogenization processing on the image may weaken these natural differences by homogenization, and further bring errors. The medical image processing method provided by this embodiment is a method for obtaining a correction factor based on Bloch simulation signal derivation, and obtains a more optimal spatial signal uniformity distribution correction on the basis of retaining the original contrast factor of the signal as much as possible.
It should be understood that although the various steps in the flow charts of fig. 2-6 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 2-6 may include multiple steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, which are not necessarily performed in sequence, but may be performed in turn or alternately with other steps or at least some of the other steps.
In one embodiment, as shown in fig. 7, there is provided a medical image processing apparatus including:
the acquiring module 11 is configured to acquire a scan image of an imaging area and an emission field map corresponding to the imaging area.
And the calculating module 12 is configured to calculate a transmission field factor according to the transmission field map.
And the determining module 13 is configured to determine a correction factor according to the imaging sequence parameter corresponding to the scanned image and the transmission field factor.
A correction module 14 for correcting the scanned image of the imaging region according to the correction factor.
In one embodiment, if the emission field pattern is a low resolution image acquired in a short time fast sequence, as shown in fig. 8, the apparatus further comprises:
the interpolation module 15 is used for obtaining a high-resolution emission field map according to the low-resolution image through an interpolation algorithm;
correspondingly, the calculating module 12 is specifically configured to calculate the transmission field factor according to the high-resolution transmission field map.
In an embodiment, as shown in fig. 9, if the transmission field pattern is a transmission field pattern with a high snr, the calculating module 12 includes:
the calculation unit 121 is configured to calculate a first transmission field factor according to a high signal-to-noise ratio region of a transmission field map, where a low signal-to-noise ratio region also exists in the transmission field map, and the low signal-to-noise ratio region is located around the high signal-to-noise ratio region;
a correcting unit 122, configured to input the transmission field pattern into the correction model, obtain a corrected transmission field pattern, and determine a second transmission field factor of the low signal-to-noise ratio region according to the corrected transmission field pattern;
a determining factor unit 123 for determining the transmission field factor from the first transmission field factor and the second transmission field factor.
In one embodiment, as shown in fig. 10, the determining module 13 includes:
a first determining unit 131, configured to determine a theoretical signal distribution intensity based on an imaging sequence parameter corresponding to the scan image according to a Bloch derivation rule;
a second determining unit 132, configured to determine an actual signal distribution strength based on the imaging sequence parameters corresponding to the scan image and the emission field factor according to the Bloch derivation rule;
a third determining unit 133, configured to determine a ratio of the theoretical signal distribution strength and the actual signal distribution strength as the correction factor.
In one embodiment, the emission field map is obtained by reconstruction of the acquired signals after applying a dual flip angle sequence or a DREAM sequence to the imaging region.
In one embodiment, the emission field pattern is a two-dimensional emission field pattern or a three-dimensional emission field pattern.
In one embodiment, as shown in fig. 11, the medical image processing apparatus further includes:
the operation module 15 is configured to perform interpolation operation on the transmission field map to obtain a high-resolution transmission field map;
correspondingly, the calculating module 12 is specifically configured to calculate the transmission field factor according to the high-resolution transmission field map.
In an embodiment, the correction module 14 is specifically configured to perform a product operation on each pixel value of the imaging area image and the correction factor to obtain a corrected imaging area image.
In one embodiment, the imaging sequence parameters corresponding to the scan image include a type of radio frequency pulse and/or a flip angle of the radio frequency pulse.
For specific limitations of the processing apparatus for medical images, reference may be made to the above limitations of the processing method for medical images, which are not described herein again. The modules in the medical image processing apparatus may be wholly or partially implemented by software, hardware and a combination thereof. The modules can be embedded in a hardware form or independent from a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules.
In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as shown in fig. 12. The computer device comprises a processor, a memory, a communication interface, a display screen and an input device which are connected through a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The communication interface of the computer device is used for carrying out wired or wireless communication with an external terminal, and the wireless communication can be realized through WIFI, an operator network, NFC (near field communication) or other technologies. The computer program is executed by a processor to implement a method of processing a medical image. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, a key, a track ball or a touch pad arranged on the shell of the computer equipment, an external keyboard, a touch pad or a mouse and the like.
Those skilled in the art will appreciate that the architecture shown in fig. 12 is merely a block diagram of some of the structures associated with the disclosed aspects and is not intended to limit the computing devices to which the disclosed aspects apply, as particular computing devices may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.
In one embodiment, a computer device is provided, comprising a memory and a processor, the memory having a computer program stored therein, the processor implementing the following steps when executing the computer program:
acquiring a scanning image of an imaging area and an emission field map corresponding to the imaging area;
calculating to obtain a transmission field factor according to the transmission field map;
determining a correction factor according to the imaging sequence parameter corresponding to the scanning image and the emission field factor;
correcting the scanned image of the imaging region according to the correction factor.
In one embodiment, the processor, when executing the computer program, further performs the steps of:
obtaining a high-resolution emission field map according to the low-resolution image through an interpolation algorithm;
the calculating according to the transmission field map to obtain the transmission field factor comprises:
and calculating to obtain a transmission field factor according to the high-resolution transmission field map.
In one embodiment, the processor, when executing the computer program, further performs the steps of:
inputting the emission field map into a correction model to obtain a corrected emission field map; a transmit field factor is determined from the rectified transmit field pattern.
In one embodiment, the processor when executing the computer program further performs the steps of:
determining theoretical signal distribution intensity without considering emission field effect based on imaging sequence parameters corresponding to the scanning image according to a Bloch equation derivation rule;
determining theoretical signal distribution intensity under the emission field effect based on imaging sequence parameters corresponding to the scanning image and the emission field factor according to the Bloch equation derivation rule;
and determining the ratio of the theoretical signal distribution intensity without considering the emission field effect and the theoretical signal distribution intensity with considering the emission field effect as the correction factor.
In one embodiment, the processor, when executing the computer program, further performs the steps of:
and performing product operation on each pixel value of the imaging area image and the correction factor to obtain a corrected imaging area image.
The implementation principle and technical effect of the computer device provided by the above embodiment are similar to those of the above method embodiment, and are not described herein again.
In one embodiment, a computer-readable storage medium is provided, having a computer program stored thereon, which when executed by a processor, performs the steps of:
acquiring a scanning image of an imaging area and an emission field map corresponding to the imaging area;
calculating to obtain a transmission field factor according to the transmission field map;
determining a correction factor according to the imaging sequence parameter corresponding to the scanning image and the emission field factor;
correcting the scanned image of the imaging region according to the correction factor.
In one embodiment, the computer program when executed by the processor further performs the steps of:
obtaining a high-resolution emission field map according to the low-resolution image through an interpolation algorithm;
the calculating of the transmission field factor according to the transmission field map comprises:
and calculating to obtain a transmission field factor according to the high-resolution transmission field map.
In one embodiment, the computer program when executed by the processor further performs the steps of:
calculating to obtain a first transmission field factor according to a high signal-to-noise ratio region of a transmission field pattern, wherein a low signal-to-noise ratio region also exists in the transmission field pattern, and the low signal-to-noise ratio region is positioned around the high signal-to-noise ratio region;
inputting the transmission field pattern into a correction model to obtain a corrected transmission field pattern, and determining a second transmission field factor of a low signal-to-noise ratio region according to the corrected transmission field pattern;
determining the transmit field factor from the first transmit field factor and the second transmit field factor.
In one embodiment, the computer program when executed by the processor further performs the steps of:
determining theoretical signal distribution intensity without considering emission field effect based on imaging sequence parameters corresponding to the scanning image according to a Bloch equation derivation rule;
determining theoretical signal distribution intensity under the emission field effect based on imaging sequence parameters corresponding to the scanning image and the emission field factor according to the Bloch equation derivation rule;
and determining the ratio of the theoretical signal distribution intensity without considering the emission field effect and the theoretical signal distribution intensity with considering the emission field effect as the correction factor.
In one embodiment, the computer program when executed by the processor further performs the steps of:
and performing product operation on each pixel value of the imaging area image and the correction factor to obtain a corrected imaging area image.
The implementation principle and technical effect of the computer-readable storage medium provided by the above embodiments are similar to those of the above method embodiments, and are not described herein again.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database or other medium used in the embodiments provided herein can include at least one of non-volatile and volatile memory. Non-volatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical storage, or the like. Volatile Memory can include Random Access Memory (RAM) or external cache Memory. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), among others.
All possible combinations of the technical features in the above embodiments may not be described for the sake of brevity, but should be considered as being within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent application shall be subject to the appended claims.
Claims (10)
1. A method of processing a medical image, the method comprising:
acquiring a scanning image of an imaging area and an emission field map corresponding to the imaging area;
calculating to obtain a transmission field factor according to the transmission field map;
determining a correction factor according to the imaging sequence parameter corresponding to the scanning image and the emission field factor;
correcting the scanned image of the imaging region according to the correction factor.
2. The method of claim 1, wherein the emission field map is a low resolution image, and after the acquiring the emission field map corresponding to the imaging region, the method further comprises:
obtaining a high-resolution emission field map according to the low-resolution image through an interpolation algorithm;
the calculating according to the transmission field map to obtain the transmission field factor comprises:
and calculating to obtain a transmission field factor according to the high-resolution transmission field map.
3. The method of claim 1, wherein at least a portion of the transmit field pattern is a high signal-to-noise ratio region, and wherein calculating a transmit field factor from the transmit field pattern comprises:
inputting the emission field map into a correction model to obtain a corrected emission field map; determining the transmit field factor from the rectified transmit field pattern.
4. The method of claim 1, wherein determining a correction factor based on the imaging sequence parameters and the transmit field factor for the scan image comprises:
determining theoretical signal distribution intensity without considering emission field effect based on imaging sequence parameters corresponding to the scanning image according to a Bloch equation derivation rule;
determining theoretical signal distribution intensity under the emission field effect based on imaging sequence parameters corresponding to the scanning image and the emission field factor according to the Bloch equation derivation rule;
and determining the ratio of the theoretical signal distribution intensity without considering the emission field effect and the theoretical signal distribution intensity with considering the emission field effect as the correction factor.
5. The method of claim 1, wherein the emission field map is obtained by reconstruction of acquired signals after applying a dual flip angle sequence or a DREAM sequence to the imaging region.
6. The method of claim 1, wherein the transmit field pattern is a two-dimensional transmit field pattern or a three-dimensional transmit field pattern.
7. The method of claim 5, wherein said correcting the imaging region image according to the correction factor comprises:
and performing product operation on each pixel value of the imaging area image and the correction factor to obtain a corrected imaging area image.
8. An apparatus for processing medical images, the apparatus comprising:
the device comprises an acquisition module, a detection module and a display module, wherein the acquisition module is used for acquiring a scanning image of an imaging area and an emission field map corresponding to the imaging area;
the calculation module is used for calculating and obtaining a transmission field factor according to the transmission field map;
the determining module is used for determining a correction factor according to the imaging sequence parameter corresponding to the scanning image and the transmitting field factor;
and the correction module is used for correcting the scanning image of the imaging area according to the correction factor.
9. A computer device comprising a memory and a processor, the memory storing a computer program, wherein the processor when executing the computer program performs the steps of the method according to any of claims 1 to 7.
10. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 7.
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