CN104997512A - MRI (magnetic resonance imaging) temperature measurement magnetic field drift phase compensation method - Google Patents
MRI (magnetic resonance imaging) temperature measurement magnetic field drift phase compensation method Download PDFInfo
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- CN104997512A CN104997512A CN201510395002.XA CN201510395002A CN104997512A CN 104997512 A CN104997512 A CN 104997512A CN 201510395002 A CN201510395002 A CN 201510395002A CN 104997512 A CN104997512 A CN 104997512A
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Abstract
The invention relates to an MRI (magnetic resonance imaging) temperature measurement magnetic field phase drift compensation method. According to the method, temperature information of a temperature measuring object itself is independent from external interference factors, and external information in a compensation process and external information in a temperature measurement process can keep constant, and therefore, the effectiveness of error compensation can be ensured. In an error compensation calculation process, sampling time is fixed, a large quantity of original MR data are reconstructed; the influence of magnetic field drift on the phase information of a constant temperature object in a certain time period is calculated; average phase offset under constant temperature can be obtained, so that the average phase offset can be subtracted from each phase change quantity in an object temperature measurement magnetic field drift phase compensation process; and the accuracy of phase compensation quantity is verified by using independent data. The invention provides an effective compensation method for errors caused by magnetic field drift, and the accuracy of MRI measurement can be improved.
Description
[technical field]
The present invention relates to magnetic field drift phase compensating method in a kind of MRI system, be specifically related to utilize the phase error compensation that statistical method realizes because magnetic field drift causes in MRI temp measuring system.
[background technology]
Magnetic resonance imager (hereinafter referred to as MRI) is one of current most widely used out of contact imaging armarium, it have not damaged, can any direction fault imaging and soft tissue contrast high.Meanwhile, the method for nuclear magnetic resonance is flexible, can provide the image of various different contrast, can provide morphology and functional imaging, is mainly used in the diagnosis of clinical human's internal imaging.
In hyperthermia process, the real-time Measurement accuracy technology of temperature is a crucial core technology.It is directly connected to the treatment success or failure of patient, even the individual life security of patient.Utilize MRI technology, can realize observing therapeutic effect intuitively, again can variations in temperature effectively in monitor treatment, reach dual supervisory function bit.Therefore, in hyperthermia process, utilize MRI image to carry out thermometric, become the measuring method of prioritizing selection.MRI thermometry is a kind of noninvasive thermometry.It makes this thermometry more and more come into one's own because of can realize imaging monitoring and the dual monitoring of monitoring temperature in the thermotherapy of tumor simultaneously.
MRI temp measuring method includes Proton Resonance Frequency (Proton Resonance Frequency PRF, hereinafter referred to as PRF), longitudinal relaxation time T1, water diffusion coefficient etc.PRF method is the thermometric of the relational implementation utilizing temperature and MR image phase, is that current technology is in the world the most ripe, most widely used MRI temp measuring method.The magnetic field bump of main field, can make the change that can not reflect temperature in MR image phase information exactly.Have by inserting the imaging together with detection bodies film of multiple thermostat films at present, then the phase changing capacity of thermostat film is utilized, and the spatial relation that thermostat film and detection bodies film are put, simulate detection bodies present position to be subject to main field and to drift about the phase changing capacity caused, thus reduce magnetic field drift to the impact of temperature measurement accuracy.In real process, the size of measured object has uncertainty, and cannot guarantee has suitable reference substance to provide magnetic field drift to correct at any one MRI scanning plane.
[summary of the invention]
The object of the invention is to solve the error in MRI thermometric process caused by magnetic field drift.
To achieve these goals, the invention provides the compensation method of a kind of MRI thermometric magnetic field drift, comprising:
Step one, adopts MR equipment to scan for Constant Temperature Detection body;
Step 2, the MR equipment interval set time gathers the data in K space and stores;
Step 3, carries out Fourier transformation to the data of step 2 collection, reconstructs magnitude image and phase image respectively;
Step 4, repeatedly repeats step 2 to step 3, obtains several phase images according to time order and function order; According to the magnitude image being suitable for human eye and directly observing, chosen area 1, to with the average gray in region 2 asking for same regional location, formed objects in the phase image that magnitude image is mated, adjacent phase image is utilized to calculate the change of phase place, add up phase changing capacity in whole period, average after multiple phase changing capacity summation;
Step 5, carries out thermometric to thermometric object, the phase value of the phase image obtained in thermometric process is deducted the meansigma methods of the relevant position that step 4 obtains, thus realizes the compensation of thermometric process phase place.
Described Constant Temperature Detection body adopts the detection bodies not being subject to or being subject to the impact of less measures ambient temperature in data acquisition.
Gather environment in the process of MR devices collect data and keep unified.
Described Constant Temperature Detection body is in vitro tissue or biological tissue.
Described thermometric object is in vitro tissue or biological tissue.
Be organized as constant temperature object under not heating, in heating process, be organized as thermometric object.
The present invention in terms of existing technologies, for the error in MRI thermometric process caused by magnetic field drift provides a kind of effective compensation method, improves the accuracy that MRI measures.
[accompanying drawing explanation]
Fig. 1 is the flow chart of MRI thermometric magnetic field drift phase compensating method in the embodiment of the present invention;
Fig. 2 is the flow chart checking MRI thermometric magnetic field drift phase compensating method effectiveness in the embodiment of the present invention;
Fig. 3 is the temperature-measuring results curve (in this experiment, constant temperature object keeps room temperature 27 DEG C) checking MRI thermometric magnetic field drift phase compensating method in the embodiment of the present invention.
[detailed description of the invention]
Below, carry out further describing to technical scheme of the present invention with accompanying drawing, embodiment only for explaining explanation, and is not intended to limit the scope of the invention in conjunction with the embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making other embodiments all obtained under creative work prerequisite, belong to the scope of protection of the invention.
In the examples below, the MR equipment of employing is Superscan-1.5T.
The embodiment of the present invention provides the compensation method of a kind of MRI thermometric magnetic field drift, and the thermometric experiment proof the method passing through to be correlated with effectively can solve the temperature error problem that magnetic field drift causes.Below be described in detail respectively.
Embodiment 1
Please refer to Fig. 1, Fig. 1 is the flow chart of MRI thermometric magnetic field drift compensation method in the embodiment of the present invention.Method comprises following step:
Step 101, is statically placed in shielding house a period of time Constant Temperature Detection body, such as 5 hours etc.; Constant Temperature Detection body adopts the detection bodies not being subject to or being subject to the impact of less measures ambient temperature in data acquisition, and this is clearly for those skilled in the art,
Step 102, sets MR device parameter, and scanning adopts gradin-echo (hereinafter referred to as GRE sequence), sweep parameter TR/TE=50/5ms, FOV=230 × 230mm
2, Matrix=128 × 128, Slicenumber=1;
Step 103, starts scanning;
Step 104, at interval of set time T, gathers 1 secondary data, such as at interval of 15s; Gather environment in the process of MR devices collect data and keep unified;
Step 105, carries out Fourier transformation to the K space data that step 104 gathers, reconstructs two groups of magnitude image and phase image respectively;
Step 106, repeatedly repeats step 104 to 105, obtains several phase images according to time order and function order.According to the magnitude image being suitable for human eye and directly observing, choose a certain size, as the rectangle area-of-interest 1 of 5 × 5,10 × 10, to with the average gray of area-of-interest 2 asking for same regional location, formed objects in the phase image that magnitude image is mated, adjacent phase image is utilized to calculate the change of phase place, add up phase changing capacity in whole period, average after multiple phase changing capacity summation.The magnitude image being suitable for eye-observation custom is utilized to select area-of-interest 1, then in phase image, area-of-interest 2 is found, magnitude image after region 1 and region 2 undergo reconstruction from a same scan-data respectively and phase image, region 1 and region 2 position in respective image, size are identical, in whole process, region 1 does not participate in concrete calculating process, and it is the calibration in order to the region 2 in auxiliary phase image.
Step 107, within the quite a while, within 30 minutes, the phase value of the phase image obtained in thermometric process is deducted the meansigma methods of the relevant position that step 106 obtains by us, thus realizes the compensation of thermometric process phase place.
Constant Temperature Detection body in compensation process and thermometric object are not limited in vitro tissue, and the method is equally applicable to the temperature survey of biological tissue in heating process.Tissue under wherein not heating can think constant temperature object, and the tissue in heating process can think Measuring Object.
Meansigma methods in this compensation method varies with each individual, because of time and different, its effective time be enough to cover user treat service time.The core that this patent proposes is this compensation method, instead of some numerical value.
Embodiment 2
Please refer to Fig. 2, Fig. 2 is the flow chart checking MRI thermometric magnetic field drift phase compensating method effectiveness in the embodiment of the present invention.Method comprises following step:
Step 201, is statically placed in shielding house 3 hours another detection bodies, asks the detection bodies of compensation dosage to be homogeneity in this detection bodies and step 101;
Step 202, MR device parameter is set, arranging of parameter needs to keep consistent with step 102 in MRI thermometric magnetic field drift compensation embodiment, namely in the present embodiment, scanning adopts gradin-echo (hereinafter referred to as GRE sequence), sweep parameter TR/TE=50/5ms, FOV=230 × 230mm2, Matrix=128 × 128, Slice number=1;
Step 203, starts scanning;
Step 204, at interval of set time T, gathers 1 secondary data, such as at interval of 15s;
Step 205, carries out Fourier transformation to the K space data that step 204 gathers, reconstructs two groups of magnitude image and phase image respectively;
Step 206, phase alignment: repeatedly repeat step 104 to 105, obtain several phase images according to time order and function order.According to the magnitude image being suitable for human eye and directly observing, choose a certain size, as the rectangle area-of-interest 1 of 5 × 5,10 × 10, to with the average gray of area-of-interest 2 asking for same regional location, formed objects in the phase image that magnitude image is mated, adjacent phase image is utilized to calculate the change of phase place, add up phase changing capacity in whole period, average after multiple phase changing capacity summation.Within the quite a while, within 30 minutes, the phase value of the phase image obtained in thermometric process is deducted the meansigma methods of the relevant position that step 106 obtains by us, thus realizes the compensation correction of thermometric process phase place.
Step 207, PRF thermometric: utilize at present MRI thermometric in the world conventional numerical algorithm---Proton Resonance Frequency (Proton Resonance Frequency, PRF) chemical shift method carries out temperature survey.In the present embodiment, profit in this way, directly embodies magnetic field drift phase compensating method described in this patent to the lifting of temperature measurement accuracy.
Claims (6)
1. a MRI thermometric magnetic field drift compensation method, comprising:
Step one, adopts MR equipment to scan for Constant Temperature Detection body;
Step 2, the MR equipment interval set time gathers the data in K space and stores;
Characterized by further comprising following steps:
Step 3, carries out Fourier transformation to the data of step 2 collection, reconstructs magnitude image and phase image respectively;
Step 4, repeatedly repeats step 2 to step 3, obtains several phase images according to time order and function order; According to the magnitude image being suitable for human eye and directly observing, chosen area 1, to with the average gray in region 2 asking for same regional location, formed objects in the phase image that magnitude image is mated, adjacent phase image is utilized to calculate the change of phase place, add up phase changing capacity in whole period, average after multiple phase changing capacity summation;
Step 5, carries out thermometric to thermometric object, the phase value of the phase image obtained in thermometric process is deducted the meansigma methods of the relevant position that step 4 obtains, thus realizes the compensation of thermometric process phase place.
2. MRI thermometric magnetic field drift according to claim 1 compensation method, is characterized in that described Constant Temperature Detection body adopts the detection bodies not being subject to or being subject to the impact of less measures ambient temperature in data acquisition.
3. MRI thermometric magnetic field drift according to claim 1 compensation method, is characterized in that the collection environment that the process of MR equipment thermometric image data and constant temperature compensate image data process is consistent.
4. MRI thermometric magnetic field drift according to claim 1 compensation method, is characterized in that described Constant Temperature Detection body is in vitro tissue or biological tissue.
5. MRI thermometric magnetic field drift according to claim 1 compensation method, is characterized in that described thermometric object is in vitro tissue or biological tissue.
6. MRI thermometric magnetic field drift according to claim 1 compensation method, is characterized in that being organized as constant temperature object under not heating, and is organized as thermometric object in heating process.
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| CN110133553A (en) * | 2019-05-10 | 2019-08-16 | 浙江大学 | A kind of ultrashort echo time magnetic resonance fingerprint relaxation time measurement method |
| CN110244245A (en) * | 2019-06-10 | 2019-09-17 | 苏州润蓝医疗科技有限公司 | A kind of the magnetic field drift antidote and device of optimization |
| WO2022001841A1 (en) * | 2020-06-30 | 2022-01-06 | 杭州佳量医疗科技有限公司 | Dual-mode magnetic resonance thermometry method based on multi-gradient-echo sequence |
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| WO2022001841A1 (en) * | 2020-06-30 | 2022-01-06 | 杭州佳量医疗科技有限公司 | Dual-mode magnetic resonance thermometry method based on multi-gradient-echo sequence |
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