JP2010213994A5

JP2010213994A5 -

Info

Publication number: JP2010213994A5
Application number: JP2009066447A
Authority: JP
Filing date: 2009-03-18
Publication date: 2012-04-19
Anticipated expiration: 2029-03-18

Description

具体的には、被検体に静磁場を与える静磁場発生手段と、装置全体を制御して撮影を実行するとともに得られた信号を処理する制御手段と、前記制御手段に指示を入力する入力手段と、を備える磁気共鳴イメージング装置であって、前記制御手段は、静磁場分布の不均一性を補正する静磁場補正手段と、前記静磁場補正手段が静磁場分布の不均一性を補正する補正領域を決定する補正領域決定手段と、を備え、前記補正領域決定手段は、前記入力手段を介して入力された撮影パラメータに従って、予め定められた計測領域内に前記補正領域を決定することを特徴とする磁気共鳴イメージング装置を提供する。 Specifically, a control means for processing the signals obtained with performing a static magnetic field generating means for applying a static magnetic field to the subject, the photographing and controls the entire apparatus, an input means for inputting an instruction to the control means The control means includes a static magnetic field correction means for correcting non-uniformity of the static magnetic field distribution, and a correction for correcting the non-uniformity of the static magnetic field distribution by the static magnetic field correction means. and a correction region determination means for determining a region, the correction area determining means, according to imaging parameters inputted through said input means, characterized in that to determine the correction region in a predetermined measurement region A magnetic resonance imaging apparatus is provided.

受信系６は、被検体１の生体組織を構成する原子の原子核スピンの核磁気共鳴により放出されるエコー信号（ＮＭＲ信号）を検出する高周波コイル（受信コイル）６１と、検出したエコー信号を増幅する増幅器６２と、増幅された信号を直交位相検波する直交位相検波器６３と、直交位相検波器６３からのアナログ出力をディジタル信号に変換するＡ／Ｄ変換器６４とを備える。Ａ／Ｄ変換器６４で変換後のディジタル信号は、計測データとして情報処理系７に送られる。 The receiving system 6 is a high-frequency coil (receiving coil) 61 that detects an echo signal (NMR signal) emitted by nuclear magnetic resonance of atomic nuclear spins constituting the biological tissue of the subject 1 and amplifies the detected echo signal. And an A / D converter 64 for converting the analog output from the quadrature detector 63 into a digital signal. The digital signal converted by the A / D converter 64 is sent to the information processing system 7 as measurement data.

撮影部７１０は、入力装置７５を介してユーザから入力された撮影条件と、予め記憶装置７２等に格納されているパルスシーケンスに従って、シーケンサ４に指示を与え、撮影条件で定められる撮影領域の撮影を実行する。現在ＭＲＩ装置の撮像対象核種は、臨床で普及しているものとしては、被検体の主たる構成物質である水素原子核（プロトン）である。プロトン密度の空間分布や、励起状態の緩和時間の空間分布に関する情報を画像化することで、人体頭部、腹部、四肢等の形態または、機能を２次元もしくは３次元的に撮像する。 The imaging unit 710 gives an instruction to the sequencer 4 in accordance with imaging conditions input from the user via the input device 75 and a pulse sequence stored in advance in the storage device 72 or the like, and captures an imaging area determined by the imaging conditions. Execute. At present, the radionuclide to be imaged by the MRI apparatus is a hydrogen nucleus (proton) which is a main constituent material of the subject as widely used clinically. Information on the spatial distribution of the proton density and the spatial distribution of the relaxation time of the excited state is imaged, thereby imaging the form or function of the human head, abdomen, limbs, etc. two-dimensionally or three-dimensionally.

補正領域決定部７３２は、静磁場分布計測領域内で、シミングを行う領域を補正領域として決定する。本実施形態では、補正領域は、撮影領域と重心が一致し、かつ、静磁場分布計測領域と底面が平行な四角柱（直方体）でとして求める。補正領域決定部７３２による補正領域の決定は、撮影条件として入力される撮影パラメータの中で、撮影領域を特定する撮影パラメータが変更される毎に行う。以下、本実施形態の補正領域決定部７３２の詳細について説明する。 The correction area determination unit 732 determines an area for shimming as a correction area in the static magnetic field distribution measurement area. In the present embodiment, the correction area is obtained as a quadrangular prism (a rectangular parallelepiped) whose centroid coincides with the imaging area and whose static magnetic field distribution measurement area and the bottom face are parallel. The determination of the correction area by the correction area determination unit 732 is performed every time the imaging parameter for specifying the imaging area is changed among the imaging parameters input as the imaging conditions. Hereinafter, details of the correction region determination unit 732 according to the present embodiment will be described.

以下、本実施形態の補正領域決定部７３２による補正領域決定処理の流れについて説明する。図７は、本実施形態の補正領域決定処理の処理フローである。本実施形態の補正領域決定部７３２は、撮影条件の中の、撮影領域４２０を特定する情報、例えば、傾き、位置、撮影面の大きさ等の撮影パラメータが変更されたことを受けて、補正領域決定処理を開始する。 Hereinafter, the flow of the correction area determination process performed by the correction area determination unit 732 according to the present embodiment will be described. FIG. 7 is a process flow of the correction area determination process of the present embodiment. The correction area determination unit 732 according to the present embodiment corrects information in response to a change in information for specifying the shooting area 420 in the shooting conditions, for example, shooting parameters such as tilt, position, and shooting plane size. The area determination process is started.

補正領域決定部７３２は、撮影パラメータの変更を受け、まず、上記の補正領域底面決定法を用いて補正領域の底面４３０を決定する（ステップＳ２０１）。次に、補正領域決定部７３２は、決定法データベースを参照し、撮影パラメータで指定された撮影部位に従っていずれの高さ決定法を用いるか決定する（ステップＳ２０２）。 The correction area determination unit 732 receives the change of the imaging parameter, and first determines the bottom surface 430 of the correction area using the correction area bottom surface determination method (step S201). Next, the correction area determination unit 732 refers to the determination method database and determines which height determination method to use in accordance with the imaging region specified by the imaging parameters (step S202).

Claims

Magnetic comprising: a static magnetic field generating means for applying a static magnetic field to the subject, and a control means for processing the signals obtained and executes the photographing and controls the entire apparatus, an input means for inputting an instruction to the control means, the A resonance imaging apparatus comprising:
The control means includes
Static magnetic field correction means for correcting non-uniformity of the static magnetic field distribution;
The static magnetic field correction means comprises a correction area determination means for determining a correction area for correcting the non-uniformity of the static magnetic field distribution,
The correction region determining means, according to imaging parameters inputted through said input means, magnetic resonance imaging apparatus characterized by determining the correction region in a predetermined measurement region.

The magnetic resonance imaging apparatus according to claim 1,
The measurement region is an internal region of a quadrangular prism whose axial direction is one axial direction of three predetermined orthogonal axes,
The correction area is an internal area of a polygonal column that has the same axial direction as the measurement area and has the same center as the shooting area specified by the shooting parameters,
The correction area determining means includes
A bottom surface shape determining means that uses a shape including at least a projection shape obtained by projecting the imaging region on a surface orthogonal to the axial direction as a bottom surface shape of the polygonal column;
A height determining unit that uses any one of a length that is the same as the height of the imaging region and a length obtained by projecting the height of the imaging region in the axial direction, as the height of the polygonal column. A magnetic resonance imaging apparatus.

The magnetic resonance imaging apparatus according to claim 2,
A magnetic resonance imaging apparatus characterized in that, for each imaging target region specified by the imaging parameters, it is predetermined which of the two types of lengths is determined as the height of the polygonal column.

The magnetic resonance imaging apparatus according to claim 2,
A static magnetic field distribution measuring means for measuring the static magnetic field distribution in the measurement region ;
The static magnetic field distribution measuring means measures the static magnetic field strength of a plurality of predetermined lattice points in the measurement region as the static magnetic field distribution,
When the number of the lattice points included in the correction area when the length equal to the height of the imaging area is the height of the polygonal prism is a predetermined value or more, the height determining means A magnetic resonance imaging apparatus, wherein the height of the polygonal column is the same length as the height of the polygonal column.

A magnetic resonance imaging apparatus according to any one of claims 2 to 4,
The magnetic resonance imaging apparatus characterized in that the bottom surface shape is a rectangle that includes the projection shape and is a rectangle that is parallel to two axes orthogonal to the axial direction and has the smallest area.

A magnetic resonance imaging apparatus according to any one of claims 2 to 4,
The magnetic resonance imaging apparatus, wherein the bottom surface shape is the projected shape.

The magnetic resonance imaging apparatus according to claim 3,
A static magnetic field distribution measuring means for measuring the static magnetic field distribution in the measurement region ;
The static magnetic field distribution measuring means measures the static magnetic field strength of a plurality of predetermined lattice points in the measurement region as the static magnetic field distribution,
When the number of the grid points included in the correction area when the length equal to the height of the imaging area is the height of the polygonal prism is less than a predetermined value, the height determining means Even when the part is determined to have the same length as the height of the imaging region as the height of the polygonal prism, the length of the height of the imaging region projected in the axial direction is the polygonal prism. A magnetic resonance imaging apparatus characterized by having a height of.

The magnetic resonance imaging apparatus according to any one of claims 1 to 7,
The magnetic resonance imaging apparatus characterized in that the correction area determination means determines the correction area every time the imaging area is changed by changing the imaging parameter.

A static magnetic field generating means for applying a static magnetic field to the subject, input means for inputting a control means for processing the signals obtained and executes the photographing and controls the entire apparatus, an instruction to the control means, the static magnetic field In a magnetic resonance imaging apparatus comprising a static magnetic field homogeneity correction unit that corrects the homogeneity of the static magnetic field, the static magnetic field homogeneity correction unit determines a correction region for correcting the static magnetic field homogeneity. A decision method,
A bottom surface calculating step for calculating a bottom surface of the correction region;
A height calculating step of calculating the height of the correction area according to the imaging region specified by the imaging parameter input via the input means;
A correction area determining step for determining, as the correction area, an area having the same center of gravity as the imaging area determined by the imaging parameters, using the bottom surface calculated in the bottom surface calculating step and the height calculated in the height calculating step; With
In the bottom surface calculating step, a shape including at least a projection shape obtained by projecting the imaging region onto a surface parallel to the bottom surface of the measurement region is calculated as the bottom surface.
In the height calculation step, either one of the same length as the height of the imaging region and the length obtained by projecting the height of the imaging region in the axial direction perpendicular to the bottom surface of the measurement region according to the imaging region A method for determining a static magnetic field homogeneity correction region, wherein the length is calculated as the height.