V-shaped coil for magnetic resonance imaging of pelvis part of human body and design method of V-shaped coil

Abstract

The invention relates to a V-shaped coil for magnetic resonance imaging of a pelvis part of a human body and a design method of the V-shaped coil, and belongs to the field of magnetic resonance imaging. High-quality images are the key of magnetic resonance imaging. There are many factors affecting the quality of magnetic resonance images, wherein the most direct factor is a coil for receiving magnetic resonance signals. For pelvis imaging, a cylindrical solenoid radio frequency detection coil is used in an existing magnetic resonance imaging system to wrap a detected person, due to the fact that the coil is far away from the central area of the pelvis, the detection sensitivity of the detection coil to the central area of the pelvis is low, and the signal-to-noise ratio of a final image can be reduced. According to the human lower limb structure, the V-shaped radio frequency coil structure for human pelvis magnetic resonance imaging and the design method of the V-shaped radio frequency coil structure are provided, the coil structure is represented by angles and distances, iterative optimization is carried out through mutual intersection and change of parameter groups, and finally the optimal coil structure is obtained. Therefore, the image quality of human pelvis magnetic resonance imaging is further improved.

Description

Technical Field

[0001] The invention belongs to the field of magnetic resonance imaging and relates to a V-shaped coil used for magnetic resonance imaging of a human pelvis and a design method thereof. Background Art

[0002] Magnetic resonance imaging is a widely used medical image detection tool. Compared with other imaging methods, it has the advantages of no ionizing radiation, high soft tissue resolution, and rich imaging parameters. It plays an irreplaceable role in clinical medical detection and diagnosis. Pelvic imaging is an important branch of magnetic resonance imaging. There are many soft tissues in the human pelvis, and the water content and water form of various tissues are different, so different signals will be presented in the magnetic resonance image. Using pelvic magnetic resonance images with different weighting parameters, the morphology of various tissues in the pelvis can be presented, providing a basis for further diagnosis.

[0003] Magnetic resonance images are the direct basis for clinical diagnosis, and their image quality directly affects medical workers' judgment of the type of disease and its degree of development. Therefore, high-quality images are the key to magnetic resonance imaging. There are many factors that affect the quality of magnetic resonance images, among which the most direct factor is the coil used to receive magnetic resonance signals. For pelvic imaging, existing magnetic resonance imaging systems all use cylindrical solenoid coils to cover the subject. Since the coil is far away from the central area of ​​the pelvis, its coil filling factor is small, and the signal-to-noise ratio of the final image will be reduced. In view of this, the present invention proposes a V-shaped coil for magnetic resonance imaging of the human pelvis and a design method thereof according to the structure of the lower limbs of the human body, aiming to further improve the image quality of magnetic resonance imaging of the human pelvis. Summary of the invention

[0004] In view of this, an object of the present invention is to provide a V-shaped coil for magnetic resonance imaging of the human pelvis and a design method thereof.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A V-shaped coil for magnetic resonance imaging of the human pelvis, the coil comprising two symmetrical (non-parallel) solenoid structures, respectively sleeved on the left and right thigh roots of the subject, the two solenoid wire groups are wound based on the principle of generating magnetic fields in the same direction, the magnetic fields generated by the two solenoid wire groups are in the same direction at the spatial junction, and are perpendicular to the static magnetic field. The V-shaped coil has a bilaterally symmetrical structure, with two solenoid wire groups at both ends of the coil. The coil is used to transmit radio frequency excitation signals and (or) receive magnetic resonance signals. In order to determine the optimal structure of the coil, the present invention also proposes a combined parameter genetic iterative algorithm.

[0007] First, this method takes the maximization of the coil signal-to-noise ratio as the optimization design goal. The signal-to-noise ratio calculation formula can be equivalently simplified as:

[0008]

[0009] Where SNR is the signal-to-noise ratio. av is the mean value of the magnetic induction intensity in the target area. R is the AC resistance of the entire coil. The value of the magnetic induction intensity at each field point in the target area of ​​the coil is calculated using the Biot-Savart law. The value of the coil AC resistance is characterized by the total length of the coil.

[0010] Furthermore, the coil structure is abstracted into a parameter combination model, which specifically includes: the number of coil turns, the distance between the closest points of adjacent turns under a given number of turns, and the angle formed between adjacent turns under a given number of turns. Due to the symmetrical structure of the coil, the above parameters are only for the turns on one side, and the parameters of the turns on the opposite side can be mirrored.

[0011] Furthermore, in order to make the design parameters feasible, the coil parameter values ​​are discretized, specifically: the value range of the coil turns C is [c1, c2…, c n ]; the value range of the distance L between the nearest points of adjacent turns under a given number of turns is [l1,l2…,l n ]; the value range of the angle D formed between adjacent turns under a given number of turns is [d1, d2…, d n ]. Given the number of coil turns C, there are C-1 L values ​​that need to be taken, and C-1 D values ​​that need to be taken, that is, the total number of parameters is 1+(C-1)+(C-1)=2C-1. Any combination of parameters uniquely determines a coil structure, and also uniquely determines the signal-to-noise ratio of the coil in the target area under the structure.

[0012] Furthermore, the above coil combination parameters are subjected to genetic iterative optimization, specifically including the following steps:

[0013] S1. Select a coil turn number C.

[0014] S2. Under the selected number of coil turns, P parameter combinations are randomly generated, and each parameter combination is regarded as an individual.

[0015] S3. Calculate the signal-to-noise ratio values ​​of all P individuals.

[0016] S4. Select two individuals from P individuals, and the probability of each individual being selected is proportional to the signal-to-noise ratio value of the individual. The parameter values ​​of the corresponding positions of the two selected individuals are exchanged with probability p1, and after the exchange, a new individual is generated based on the original individual group. This step is repeated (PN) times to generate (PN) new individuals, so that the number of new individual groups is equivalent to the number of original individual groups.

[0017] S5. For the newly generated (PN) individuals, a parameter change is performed at a random position of each individual with probability p2. Parameter change means that the parameter at that position changes from the original value to another value within the value range. At this point, the (PN) new individuals and the retained N individuals together form the next generation of individuals.

[0018] S6. Repeat S3-S5 until the number of generations of the individual group reaches the set upper limit or the optimal individual signal-to-noise ratio value of several consecutive generations of the individual group does not change, then the iteration is terminated. The optimal individual after the termination of the iteration is the optimal design parameter of the coil under the number of coil turns.

[0019] S7. Select another value for the number of coil turns, repeat S2-S6, compare the signal-to-noise ratio results between the numbers of turns, and obtain the optimal coil design result.

[0020] Furthermore, after determining the optimal combination parameters of the coil, a coil housing is manufactured according to the wiring path of the coil parameters, and a connecting beam is used on the housing to connect the two sections of the solenoid structure on both sides of the V-shaped coil to form a whole V-shaped coil.

[0021] The beneficial effects of the present invention are:

[0022] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0024] Figure 1 A schematic diagram of the V-shaped coil structure proposed by the present invention and its relative position to the human body;

[0025] Figure 2 It is the forward projection view of the V-shaped coil and the schematic diagram of the magnetic field direction;

[0026] Figure 3 It is a partial enlarged view of the forward projection view of the 4-turn coil on one side of the V-shaped coil and a schematic diagram of the structural parameters;

[0027] Figure 4 This is the image formed by a traditional solenoid coil;

[0028] Figure 5 This is the image formed by the V-shaped coil of the present invention. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0030] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0031] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0032] See also Figure 1 to Figure 5 , is a V-shaped coil for magnetic resonance imaging of the human pelvis and its design method. Figure 1 As shown, the entire V-shaped coil is a bilaterally symmetrical structure, and both sides of the coil can be regarded as a form of a solenoid coil with several turns (non-parallel), and the solenoid coil groups at both ends are respectively placed on the left and right thigh roots of the subject.

[0033] like Figure 2 As shown in the forward projection view of the V-shaped coil, the winding direction of the V-shaped coil is such that the solenoid coil groups on both sides generate magnetic fields in the same direction, so as to superimpose a uniform magnetic field in the same direction at the hip position of the human body.

[0034] by Figure 3The combined parameter genetic iterative optimization design method proposed by the present invention is illustrated by taking the single-sided 4-turn coil as an example. Since the entire coil is a bilaterally symmetrical structure, the single-sided structure is used as an example. After the single-sided structure is determined, the opposite side structure is also determined. For a single-sided 4-turn coil, the angle between each turn of the coil and the horizontal direction and the distance between the closest points of adjacent turns are all parameters that can be optimized. For a 4-turn coil group, there are 4 angle parameters and 3 distance parameters, a total of 7 parameters.

[0035] First, several (eg, 100) parameter combinations are randomly generated, each parameter group is called an individual, and each individual represents a coil structure.

[0036] Next, among the initial 100 individuals, the signal-to-noise ratio of each individual is calculated using the signal-to-noise ratio calculation formula, and a certain proportion (eg, 20%) of the best individuals is retained.

[0037] Next, two individuals are randomly selected and parameters are exchanged at any three of the seven parameter positions in the two individuals. The purpose of this step is to generate new individuals based on the original individuals. This step is repeated 40 times to obtain 80 new individuals on the basis of retaining the 20 original optimal individuals, keeping the total number of individuals unchanged at 100.

[0038] Next, a small probability p (eg 0.01) is used to change any parameter position of each individual. The purpose of this step is also to obtain new individuals based on existing individuals.

[0039] After the above steps are completed, one iteration is completed, and then the above process is repeated until the signal-to-noise ratio value of the optimal individual does not increase after several consecutive (for example, 10) iterations, then the iteration is stopped and the current optimal result is used as the structural optimization result of the coil.

[0040] It should be noted that the above is the iterative optimization process after the number of turns is determined. For different numbers of turns, only the number of each individual parameter is different. For example, for a single-sided 4-turn coil, there are a total of 7 parameters; for a single-sided 5-turn coil, there are a total of 9 parameters; for a single-sided 6-turn coil, there are a total of 11 parameters, and so on. The ideas and steps of iterative optimization used for different numbers of coil turns are the same. In actual operation, you can try different numbers of coil turns to get the optimal result under each number of turns, and then compare the differences between different numbers of turns and choose the best one.

[0041] To prove the effectiveness and advancement of the present invention, the V-shaped coil of the present invention and the traditional solenoid coil were imaged and compared. The image comparison results are shown in FIG. Figure 4 and Figure 5 shown. Figure 4 This is the image formed by a traditional solenoid coil; Figure 5This is the image formed by the V-shaped coil of the present invention.

[0042] The pelvic image formed by the traditional solenoid coil has a lot of noise points and the overall signal-to-noise ratio of the image is low. The image formed by the V-shaped coil designed by the method described in the present invention greatly improves the image signal-to-noise ratio, which proves the effectiveness and advancement of the present invention.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A V-shaped coil for magnetic resonance imaging of the human pelvis, characterized in that: The coil comprises two symmetrical, non-parallel solenoid structures, which are respectively used to be placed on the left and right thigh roots of the subject; The two-section solenoid coil group is wound based on the principle of generating a magnetic field in the same direction. The magnetic field generated by the two-section solenoid coil group is in the same direction at the spatial combination point and is perpendicular to the static magnetic field. The V-shaped coil has a bilaterally symmetrical structure, with two solenoid-shaped wire groups at both ends of the coil; The coil is used to transmit radio frequency excitation signals or receive magnetic resonance signals.

2. The V-shaped coil for magnetic resonance imaging of the human pelvis according to claim 1, characterized in that: The signal-to-noise ratio of the coil is: Where SNR is the signal-to-noise ratio; B av is the average value of the magnetic induction intensity in the target area; R is the AC resistance of the entire coil.

3. The V-shaped coil for magnetic resonance imaging of the human pelvis according to claim 2, characterized in that: The value of the magnetic induction intensity at each field point in the target area is calculated using the Biot-Savart law; the value of the coil AC resistance is characterized by the total length of the coil.

4. The V-shaped coil for magnetic resonance imaging of the human pelvis according to claim 2, characterized in that: Fitting the coil into a combination model of parameters, specifically including: the number of coil turns, the distance between the nearest points of adjacent turns under a given number of turns, and the angle formed between adjacent turns under a given number of turns, wherein the combination model of the above parameters is only for single-side wire turns; Discretize the coil parameter values, specifically: the value range of the coil turns C is [c1, c2…, c n ]; the value range of the distance L between the nearest points of adjacent turns under a given number of turns is [l1,l2…,l n ]; the value range of the angle D formed between adjacent turns under a given number of turns is [d1, d2…, d n ]; given the number of coil turns C, there are C-1 L values ​​that need to be taken, and C-1 D values ​​that need to be taken, that is, the total number of parameters is 1+(C-1)+(C-1)=2C-1; any combination of parameters uniquely determines a coil structure and uniquely determines the signal-to-noise ratio of the coil in the target area under the coil structure.

5. A method for designing a V-shaped coil for magnetic resonance imaging of the human pelvis, characterized in that: The following steps are involved: Determine the maximization of coil signal-to-noise ratio as the optimization design goal; The coil structure is abstracted into a combined model of parameters, including the number of coil turns, the distance between the closest points of adjacent turns under a given number of turns, and the angle formed between adjacent turns under a given number of turns; Discretize the coil parameter values; The genetic iterative optimization algorithm is used to optimize the coil combination parameters, including: Select a coil number of turns; Under the selected number of coil turns, multiple parameter combinations are randomly generated, and each parameter combination is regarded as an individual; Calculate the signal-to-noise ratio values ​​of all individuals; Two individuals are selected from multiple individuals. The probability of each individual being selected is proportional to the signal-to-noise ratio value of the individual. The parameter values ​​of the corresponding positions of the two selected individuals are exchanged with probability. After the exchange, a new individual is generated based on the original individual group. This step is repeated multiple times to generate multiple new individuals, so that the number of new individual groups is equivalent to the number of original individual groups. For multiple newly generated individuals, parameters are changed at random positions of each individual with probability; Repeat the above steps until the number of generations of the individual group reaches the set upper limit or the optimal individual signal-to-noise ratio value of the individual group for several consecutive generations does not change, then the iteration terminates; Select another number of coil turns, repeat the above steps, compare the signal-to-noise ratio results between each number of turns, and obtain the optimal coil design result.

6. The method for designing a V-shaped coil for magnetic resonance imaging of the human pelvis according to claim 5, characterized in that: The genetic iterative optimization algorithm is used to optimize the coil combination parameters, specifically: S1: Select a coil turn number C; S2: Under the selected number of coil turns, P parameter combinations are randomly generated, and each parameter combination is regarded as an individual; S3: Calculate the signal-to-noise ratio of all P individuals; S3: retain the best N parameter combinations and directly enter the next generation; S4: Select two individuals from P individuals, and the probability of each individual being selected is proportional to the signal-to-noise ratio value of the individual; The parameter values ​​of the two selected individuals at the corresponding positions are exchanged with probability p1, and after the exchange, a new individual is generated based on the original individual group; this step is repeated (PN) times to generate (PN) new individuals, so that the number of the new individual group is equal to the number of the original individual group; S5: For the newly generated (PN) individuals, a parameter change is performed at a random position of each individual with probability p2; parameter change means that the parameter at that position changes from the original value to another value within the value range; at this point, the (PN) new individuals and the retained N individuals together form the next generation of individuals; S6: Repeat S3-S5 until the number of generations of the individual group reaches the set upper limit or the optimal individual signal-to-noise ratio value of several consecutive generations of the individual group does not change, then the iteration is terminated; the optimal individual after the termination of the iteration is the optimal design parameter of the coil under the number of coil turns; S7: Select another value for the number of coil turns, repeat S2-S6, compare the signal-to-noise ratio results between the numbers of turns, and obtain the optimal coil design result.

7. The method for designing a V-shaped coil for magnetic resonance imaging of the human pelvis according to claim 6, characterized in that: After the V-shaped coil is designed, a coil housing is manufactured according to the coil wiring path, and a connecting beam is used on the housing to connect the two solenoid structures on both sides of the V-shaped coil to form a whole V-shaped coil.

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