JP4822379B2 - Magnetic resonance imaging system - Google Patents

Description

上記の式にて調整されたゲイン値は、中央処理装置（ＣＰＵ）によってシーケンサをとおして受信回路へ指示（６０４）され、本計測で計測したＮＭＲ信号を効率よくデジタル信号に変換するために用いられる。
【０００６】
図７は、１計測４スライスの計測を２回連続して行う場合を例として、従来技術によるゲイン値を調整するまでの過程を流れ図で示したものである。Ｓ１１〜Ｓ１４は１計測目で計測するスライス、Ｓ２１〜Ｓ２４は２計測目で計測するスライスを示している。従来技術によるゲイン調整では、図６と同様に全スライスにおいてＮＭＲ信号を収集（７０１）し、収集した信号の中から最大信号を発生するスライスを検索（７０２）して、そのスライスポジションにてゲイン値の調整（７０３）をし、調整されたゲイン値をシーケンサをとおして受信回路へ指示していた（７０４）。
【０００７】
【発明が解決しようとする課題】
しかし、上記従来技術では、計測を行うスライス数が増加するに従って最大となるＮＭＲ信号を検索するための信号収集回数が増加するため、ゲイン調整時間が非常に長くなっていた。そこで、本発明の目的は、最大信号を検索するための信号収集回数を削減することによってゲイン調整時間を短縮し、全スライスにて最大信号を検索した場合と同等のゲイン調整結果を得ることを可能とすることで操作性を向上させた計測方法を提供することにある。
【０００８】
【課題を解決するための手段】
上記目的を達成するために、本発明は静磁場発生手段と、スライスエンコード、位相エンコード、周波数エンコードの各方向の傾斜磁場を発生する傾斜磁場発生手段と、被検体の組織を構成する原子核を励起して磁気共鳴を生じさせる高周波磁場を発生する送信手段と、磁気共鳴による被検体からのＮＭＲ信号を検出する受信手段と、前記受信手段で検出したＮＭＲ信号を用いて画像を再構成する信号処理手段と、前記傾斜磁場及び高周波磁場を複数スライスを撮像するシーケンスにて印加すると共に前記各手段を制御する制御手段とを備えて成る磁気共鳴イメージング装置において、前記制御手段は、前記複数スライスのスライス数よりも少ないスライス数で、ゲイン調整のための前計測を行なうようにしたものである。或いは、ゲイン調整のための前計測を行なうスライス間隔を、前記複数スライスのスライス間隔よりも広くするようにしたものである。
また、前記制御手段は、前記前計測により得られたＮＭＲ信号の内で、最大の信号となったスライスにおいて、前記ゲイン調整を行う。
【０００９】
【発明の実施の形態】
以下、本発明に記載の実施形態を、図面に基づいて詳細に説明する。
【００１０】
図３は、本発明を適用するＭＲＩ装置の概略の全体構成を示すブロック図である。このＭＲＩ装置は、磁気共鳴現象を利用して被験体の断層像を得るためのもので、静磁場発生手段１、傾斜磁場発生手段２、送信系３、受信系４、信号処理系５、シーケンサ６、中央処理装置７および図示しない操作部とからなっている。
【００１１】
静磁場発生手段１は、被検体８の周りのある広がりを持った空間に配置された永久磁石・常伝導磁石のいずれかからなり、被検体８の周囲にその体軸方向または被検体の体軸と直交する方向に均一な静磁場を発生させる。
【００１２】
傾斜磁場発生手段２は、Ｘ、Ｙ、Ｚの３軸方向に巻かれた傾斜磁場コイル９とこれらの各々のコイルを磁化させる傾斜磁場電源１０とからなり、シーケンサ６からの命令に従って傾斜磁場電源１０の各々のコイルを磁化させることによりＸ、Ｙ、Ｚの３軸方向の傾斜磁場Ｇｓ、Ｇｐ、Ｇｆを被検体８に印加する。この傾斜磁場の加え方により、被検体８の撮影して表示する断面が設定される。
【００１３】
送信系３は、高周波発振器１１、変調器１２、高周波増幅器１３および高周波照射コイル１４とからなり、傾斜磁場発生手段２で設定された被検体８の撮影断面の生体組織を構成する原子の原子核を励起して核磁気共鳴を起こさせるために、高周波発振器１１から出力された高周波パルスを高周波増幅器１３で増幅した後に、被検体８に近接して設置された高周波照射コイル１４に供給して被検体に照射する。
【００１４】
受信系４は、高周波受信コイル１５、受信回路１６およびアナログ／ディジタル（以下「Ａ／Ｄ」という）変換器１７とからなり、送信系３の高周波照射コイル１４から照射された電磁波による被検体８の生体組織の原子核の磁気共鳴によるエコー信号であるＮＭＲ信号を、被検体８に近接して配置された高周波受信コイル１５で検出し、受信回路１６を介してＡ／Ｄ変換器１７に入力し、ディジタル信号に変換して、さらにシーケンサ６からの命令によるタイミングでサンプリングされた収集データとして、その信号を信号処理系５に送る。
【００１５】
信号処理系５は、収集データに対しフーリエ変換およびシーケンサ６の制御を行うＣＰＵ７、本発明の補正手段を含み補正計算や収集データを断層像に再構成するために必要な処理を行う信号処理装置１８、経時的な画像解析処理および指定された計測のシーケンスのプログラムやその実行の際に用いられるパラメータ−等を記憶し、被検体に対して行った事前の計測で得た計測パラメーターや受信系４で検出したＮＭＲ信号からの収集データおよび関心領域設定に用いる画像を一時保管すると共にその関心領域を設定するためのパラメーター等を記憶するメモリ１９、再構成された画像データを記憶するデータ格納部となる磁気ディスク２０・光ディスク２１およびこれらのディスクから読み出した画像データを映像化して断層像として表示するディスプレイ２２とからなり、受信系４で検出したＮＭＲ信号を用いて画像再構成演算を行うとともに画像表示を行う。
【００１６】
シーケンサ６は、ＣＰＵ７の制御で動作しスライスエンコード、位相エンコード、周波数エンコードの各傾斜磁場および高周波磁場パルスをある所定のパルスシーケンスで繰り返し発生するためのもので、被検体８の断層像のデータ取得に必要な種々の命令を傾斜磁場発生手段２、送信系３および受信系４に送る。
操作部は、トラックボールまたはマウス、キーボード等からなり信号処理系５で行う処理の制御情報を入力する。
【００１７】
次に、前記目的を達成するため、本発明のＭＲＩ装置を用いた前計測におけるゲイン調整処理の実施例について図１と図２を用いて説明する。図１は、１計測１スライスでｎ回連続して計測する場合を例として、ゲイン値を調整するのに用いるスライスポジションの検索方法を図示し、ゲイン調整全体の流れ図とともに示したものである。ここでは最大となるＮＭＲ信号を検索するためにＮＭＲ信号を収集するスライス枚数を全計測で計測するスライス数の１／３とする例を挙げる。Ｓ１〜Ｓｎは全計測で計測するスライスを示す。Ｓ１〜Ｓｎのスライスを計測する際に、本発明では、従来技術（図６）のようにＳ１〜Ｓｎの全スライスのＮＭＲ信号を収集するのではなく、ある指定された間隔（この例では“スライス間隔×３”）で信号収集スライスを間引く方法を提供する。ＮＭＲ信号の収集スライス数を全計測で計測するスライス数の１／３としたこの例では、Ｓ１，Ｓ４，Ｓ７，…においてのみ信号収集処理（１０１）を行う。この信号を収集したスライスの中から最大信号となるスライスを検索（１０２）し、最大の信号となったスライスのポジションにおいてゲイン値の調整（１０３）をし、調整されたゲイン値をシーケンサをとおして受信回路へ指示する（１０４）。
【００１８】
図２は、１計測４スライスの計測を２回連続して行う場合を例として、本発明のＭＲＩ装置によるゲイン値を調整するまでの過程を流れ図で示したものである。Ｓ１１〜Ｓ１４は１計測目で計測するスライス、Ｓ２１〜Ｓ２４は２計測目で計測するスライスを示している。ＮＭＲ信号の収集スライス数を全計測で計測する全スライス数の１／３としたこの例では、ある指定された間隔（この例では“スライス間隔×３”）で信号収集スライスの間引きを行うため、Ｓ１１，Ｓ１４，Ｓ２３においてのみ信号収集処理（２０１）を行い、この収集したスライスの中で最大信号となるスライスを検索（２０２）して、最大の信号となったスライスのポジションにおいてゲイン値の調整（２０３）をし、調整されたゲイン値をシーケンサをとおして受信回路へ指示する（２０４）。
【００１９】
上記に１／３の間隔で計測スライスを間引く２例（図１、図２）を示したが、通常診断に用いる計測ではスライス間隔を大きくあけて撮像することはなく、スライス間で人体の構造が大きく変わることもないので、上記方法にて信号を収集して検索した最大信号が、従来の計測スライス枚数を間引かずに全スライスにて信号を収集し検索した最大信号と比較して大きく異なることはない。よって、本発明における計測スライス枚数を間引いて信号計測を行うゲイン調整方法でも問題なくゲイン値の調整が行われる。
【００２０】
以上のように最大信号を検索するためにＮＭＲ信号を収集するスライス枚数を間引くことによって信号収集処理（図１−１０１、図２−２０１）に要する時間を短縮し、ゲイン調整時間を短縮する。なお、信号収集を間引くスライス枚数は装置固定の値としてもよいし操作者が任意に可変させてもよい。
【００２１】
【発明の効果】
本発明は、以上に説明したように構成されているので、前計測にて行うゲイン調整処理に要する時間を短縮し、かつ従来調整法と同等のゲイン調整結果を得ることが可能となり、従来より操作性のよい磁気共鳴イメージング装置が提供される。
【図面の簡単な説明】
【図１】本発明によるゲイン調整処理を用いた磁気共鳴イメージング装置の１実施例についての流れ図（１）。
【図２】本発明によるゲイン調整処理を用いた磁気共鳴イメージング装置の１実施例についての流れ図（２）。
【図３】本発明による磁気共鳴イメージング装置についての概略構成図。
【図４】磁気共鳴イメージング装置による撮像全体の流れ図。
【図５】磁気共鳴イメージング装置による前計測の流れ図。
【図６】従来発明によるゲイン調整処理を用いた磁気共鳴イメージング装置の１実施例についての流れ図（１）。
【図７】従来発明によるゲイン調整処理を用いた磁気共鳴イメージング装置の１実施例についての流れ図（２）。
【符号の説明】
１………静磁場発生手段
２………傾斜磁場発生手段
３………送信系
４………受信系
５………信号処理系
６………シーケンサ
７………ＣＰＵ
８………被検体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic resonance imaging (hereinafter referred to as “MRI”) apparatus that obtains a tomographic image of a subject by using a nuclear magnetic resonance phenomenon, and a gain adjustment time is set in a measurement prior to imaging (main measurement) of a subject. The present invention relates to an MRI apparatus having a shortening function.
[0002]
[Prior art]
In the MRI apparatus, a nuclear magnetic resonance signal (NMR signal) from a subject is imaged and is generally performed as shown in FIGS. First, prior to imaging of the subject, pre-measurement (401) is performed, then main measurement (402) is performed, and then reconstruction (403) is performed to obtain an image. In the pre-measurement, as preparation for the main measurement, in addition to automatic frequency lock (501), automatic tuning of the receiving coil (502), gain adjustment (503) necessary for amplifying a weak NMR signal is performed.
[0003]
Here, the gain adjustment means that the NMR signal generated from the subject 8 by driving the pulse sequence is received by the receiving coil 15, and the received NMR signal is detected and amplified by the receiving circuit 16. An amplification factor at the time of amplification is set as a gain value through the sequencer 6 in accordance with an instruction from the central processing unit (CPU) 7. This gain value is set before digital conversion so that when the NMR signal is converted into a digital signal, the digitally converted NMR signal does not overflow and digital conversion can be performed effectively using digital bits. Set the gain value of the NMR signal appropriately. Since the gain value varies depending on the imaging region of the subject 8, the size of the subject 8, the imaging conditions, the pulse sequence used for imaging, and the like, it is necessary to adjust the gain value in the pre-measurement performed prior to the main measurement. . The process for adjusting the gain value is the gain adjustment process.
[0004]
FIG. 6 and FIG. 7 show an embodiment and a flowchart of gain adjustment processing according to the prior art. FIG. 6 illustrates a method for searching for a slice position used to adjust the gain value, taking as an example a case where n measurements are performed continuously for one slice per measurement, and is shown together with a flowchart of overall gain adjustment. S1 to Sn indicate slices to be measured in all measurements. In the gain adjustment according to the conventional technique, the NMR signal is collected for each measurement from S1 to Sn with the phase encoding turned off, and when the signal collection for all measurements (601) is completed, the maximum signal is generated from the collected signals. The slice to be searched is searched (602), and the gain value is adjusted (603) using the following equation at each slice position.
[0005]
[Expression 1]

The gain value adjusted by the above equation is instructed (604) by the central processing unit (CPU) through the sequencer to the receiving circuit, and is used to efficiently convert the NMR signal measured in this measurement into a digital signal. It is done.
[0006]
FIG. 7 is a flowchart showing a process until the gain value is adjusted according to the conventional technique, taking as an example a case where one measurement and measurement of four slices are performed twice. S11 to S14 indicate slices measured at the first measurement, and S21 to S24 indicate slices measured at the second measurement. In the gain adjustment according to the conventional technique, NMR signals are collected in all slices (701) as in FIG. 6, and the slice that generates the maximum signal is searched from the collected signals (702), and gain is obtained at the slice position. The value was adjusted (703), and the adjusted gain value was instructed to the receiving circuit through the sequencer (704).
[0007]
[Problems to be solved by the invention]
However, in the above-described prior art, the number of signal acquisitions for searching for the maximum NMR signal increases as the number of slices to be measured increases, so that the gain adjustment time is very long. Therefore, an object of the present invention is to shorten the gain adjustment time by reducing the number of times of signal acquisition for searching for the maximum signal, and obtain a gain adjustment result equivalent to the case of searching for the maximum signal in all slices. The object is to provide a measurement method with improved operability by making it possible.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention excites a magnetic field generating means, a gradient magnetic field generating means for generating a gradient magnetic field in each direction of slice encoding, phase encoding, and frequency encoding, and an atomic nucleus constituting a tissue of a subject. Transmitting means for generating a high-frequency magnetic field for generating magnetic resonance, receiving means for detecting an NMR signal from the subject by magnetic resonance, and signal processing for reconstructing an image using the NMR signal detected by the receiving means means, in the magnetic resonance imaging apparatus comprising a control means for controlling said each means and applies in the gradient magnetic field and high frequency magnetic field to be imaged multiple slices sequence, the control unit may slice the plurality slices The pre-measurement for gain adjustment is performed with a smaller number of slices than the number . Alternatively, the slice interval for performing the pre-measurement for gain adjustment is made wider than the slice interval of the plurality of slices.
In addition, the control means performs the gain adjustment in the slice having the maximum signal among the NMR signals obtained by the previous measurement .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments described in the present invention will be described in detail with reference to the drawings.
[0010]
FIG. 3 is a block diagram showing a schematic overall configuration of an MRI apparatus to which the present invention is applied. This MRI apparatus is for obtaining a tomographic image of a subject using a magnetic resonance phenomenon, and includes a static magnetic field generation means 1, a gradient magnetic field generation means 2, a transmission system 3, a reception system 4, a signal processing system 5, and a sequencer. 6, the central processing unit 7 and an operation unit (not shown).
[0011]
The static magnetic field generating means 1 is composed of either a permanent magnet or a normal magnet arranged in a wide space around the subject 8, and the body axis direction or the body of the subject around the subject 8. A uniform static magnetic field is generated in a direction perpendicular to the axis.
[0012]
The gradient magnetic field generating means 2 comprises a gradient magnetic field coil 9 wound in the X, Y and Z axis directions and a gradient magnetic field power source 10 for magnetizing each of these coils. By magnetizing each of the 10 coils, gradient magnetic fields Gs, Gp, and Gf in the three-axis directions of X, Y, and Z are applied to the subject 8. Depending on how the gradient magnetic field is applied, a cross-section for imaging and displaying the subject 8 is set.
[0013]
The transmission system 3 includes a high-frequency oscillator 11, a modulator 12, a high-frequency amplifier 13, and a high-frequency irradiation coil 14, and atomic nuclei constituting the biological tissue of the imaging section of the subject 8 set by the gradient magnetic field generating means 2. In order to excite and cause nuclear magnetic resonance, the high-frequency pulse output from the high-frequency oscillator 11 is amplified by the high-frequency amplifier 13 and then supplied to the high-frequency irradiation coil 14 installed in the vicinity of the subject 8. Irradiate.
[0014]
The reception system 4 includes a high-frequency reception coil 15, a reception circuit 16, and an analog / digital (hereinafter referred to as “A / D”) converter 17, and the subject 8 caused by electromagnetic waves irradiated from the high-frequency irradiation coil 14 of the transmission system 3. NMR signals, which are echo signals generated by magnetic resonance of the nuclei of the living tissue, are detected by the high-frequency receiving coil 15 arranged close to the subject 8 and input to the A / D converter 17 via the receiving circuit 16. Then, the signal is converted into a digital signal, and the signal is sent to the signal processing system 5 as collected data sampled at a timing according to a command from the sequencer 6.
[0015]
The signal processing system 5 includes a CPU 7 that performs Fourier transformation and control of the sequencer 6 on the collected data, and a signal processing device that includes correction means of the present invention and performs processing necessary for reconstructing correction calculations and collected data into tomographic images. 18. The time-lapse image analysis process and the specified measurement sequence program, parameters used for the execution, etc. are stored, and the measurement parameters and the receiving system obtained by the previous measurement performed on the subject 4, a memory 19 for temporarily storing the collected data from the NMR signal detected in 4 and an image used for setting the region of interest, and storing parameters for setting the region of interest, and a data storage unit for storing the reconstructed image data The magnetic disk 20 and the optical disk 21 and the image data read from these disks are visualized and displayed as tomographic images. Consists displaying 22. displays an image performs image reconstruction operation using the NMR signal detected by the receiving system 4.
[0016]
The sequencer 6 operates under the control of the CPU 7 and repeatedly generates slice encode, phase encode, and frequency encode gradient magnetic fields and high frequency magnetic field pulses in a predetermined pulse sequence, and acquires tomographic image data of the subject 8. Various commands necessary for the above are sent to the gradient magnetic field generating means 2, the transmission system 3, and the reception system 4.
The operation unit includes a trackball, a mouse, a keyboard, or the like, and inputs control information for processing performed by the signal processing system 5.
[0017]
Next, in order to achieve the above object, an embodiment of gain adjustment processing in the pre-measurement using the MRI apparatus of the present invention will be described with reference to FIGS. FIG. 1 illustrates a method of searching for a slice position used for adjusting a gain value, taking as an example a case where n measurements are continuously performed in one measurement and one slice, and is shown together with a flowchart of overall gain adjustment. Here, an example is given in which the number of slices from which NMR signals are collected in order to search for the maximum NMR signal is 1/3 of the number of slices measured in all measurements. S1 to Sn indicate slices to be measured in all measurements. When measuring the slices of S1 to Sn, the present invention does not collect the NMR signals of all the slices of S1 to Sn as in the prior art (FIG. 6), but instead of collecting the NMR signals of all the slices of S1 to Sn (in this example, “ A method of thinning out signal acquisition slices at a slice interval × 3 ″) is provided. In this example in which the number of NMR signal acquisition slices is 1/3 of the total number of slices measured in all measurements, signal acquisition processing (101) is performed only in S1, S4, S7,. The slice that becomes the maximum signal is searched from the slices from which this signal has been collected (102), the gain value is adjusted (103) at the position of the slice that has become the maximum signal, and the adjusted gain value is taken through the sequencer. Then, the reception circuit is instructed (104).
[0018]
FIG. 2 is a flowchart showing a process until the gain value is adjusted by the MRI apparatus of the present invention, taking as an example a case where measurement of one slice and four slices is performed twice. S11 to S14 indicate slices measured at the first measurement, and S21 to S24 indicate slices measured at the second measurement. In this example in which the number of NMR signal acquisition slices is 1/3 of the total number of slices measured in all measurements, signal acquisition slices are thinned out at a specified interval (in this example, “slice interval × 3”). In S11, S14, and S23, the signal acquisition process (201) is performed, and the slice that becomes the maximum signal among the acquired slices is searched (202), and the gain value is determined at the position of the slice that becomes the maximum signal. Adjustment (203) is performed, and the adjusted gain value is instructed to the receiving circuit through the sequencer (204).
[0019]
Two examples (FIGS. 1 and 2) in which measurement slices are thinned out at intervals of 1/3 are shown above, but in the measurement used for normal diagnosis, imaging is not performed with a large interval between slices, and the structure of the human body between slices Therefore, the maximum signal that is collected and searched by the above method is larger than the maximum signal that is collected and searched for all slices without thinning out the number of conventional measurement slices. There is no difference. Therefore, the gain adjustment is performed without any problem even in the gain adjustment method in which the number of measurement slices in the present invention is used to perform signal measurement.
[0020]
As described above, the time required for the signal collection process (FIGS. 1-101 and 2-201) is shortened by thinning out the number of slices from which NMR signals are collected in order to search for the maximum signal, and the gain adjustment time is shortened. Note that the number of slices from which signal acquisition is thinned may be a fixed value of the apparatus, or may be arbitrarily changed by the operator.
[0021]
【The invention's effect】
Since the present invention is configured as described above, it is possible to shorten the time required for the gain adjustment processing performed in the previous measurement, and obtain a gain adjustment result equivalent to the conventional adjustment method. A magnetic resonance imaging apparatus with good operability is provided.
[Brief description of the drawings]
FIG. 1 is a flowchart (1) of an embodiment of a magnetic resonance imaging apparatus using gain adjustment processing according to the present invention.
FIG. 2 is a flowchart (2) of an embodiment of a magnetic resonance imaging apparatus using gain adjustment processing according to the present invention.
FIG. 3 is a schematic configuration diagram of a magnetic resonance imaging apparatus according to the present invention.
FIG. 4 is a flowchart of overall imaging by a magnetic resonance imaging apparatus.
FIG. 5 is a flowchart of pre-measurement by the magnetic resonance imaging apparatus.
FIG. 6 is a flowchart (1) of an embodiment of a magnetic resonance imaging apparatus using gain adjustment processing according to the conventional invention.
FIG. 7 is a flowchart (2) of an embodiment of a magnetic resonance imaging apparatus using gain adjustment processing according to the conventional invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ......... Static magnetic field generating means 2 ......... Gradient magnetic field generating means 3 ......... Transmission system 4 ......... Reception system 5 ......... Signal processing system 6 ......... Sequencer 7 ......... CPU
8 ……… Subject

Claims (2)

A static magnetic field generating means;
Gradient magnetic field generating means for generating gradient magnetic fields in each direction of slice encoding, phase encoding, and frequency encoding;
Transmitting means for generating a high-frequency magnetic field that excites the nuclei constituting the tissue of the subject to generate magnetic resonance;
Receiving means for detecting NMR signals from the subject by magnetic resonance;
Signal processing means for reconstructing an image using the NMR signal detected by the receiving means;
A control unit that applies the gradient magnetic field and the high-frequency magnetic field in a sequence of imaging a plurality of slices by repeating measurement of a single measurement multi-slice method multiple times with different slice positions for each measurement, and controlling each of the units; ,
In a magnetic resonance imaging apparatus comprising:
The control means, the slice interval of the previous measurement for gain adjustment, the wider than the slice spacing a plurality of slices, wherein the relatively different to the slices for performing front measurement between each measurement Magnetic resonance imaging device. A static magnetic field generating means;
Gradient magnetic field generating means for generating gradient magnetic fields in each direction of slice encoding, phase encoding, and frequency encoding;
Transmitting means for generating a high-frequency magnetic field that excites the nuclei constituting the tissue of the subject to generate magnetic resonance;
Receiving means for detecting NMR signals from the subject by magnetic resonance;
Signal processing means for reconstructing an image using the NMR signal detected by the receiving means;
Control means for applying the gradient magnetic field and the high-frequency magnetic field in a sequence for imaging a plurality of slices and controlling the means;
In a magnetic resonance imaging apparatus comprising:
The control means performs a pre-measurement for gain adjustment at a number of slices smaller than the number of slices of the plurality of slices or at a slice interval wider than the slice interval of the plurality of slices, and is obtained by the previous measurement. A magnetic resonance imaging apparatus , wherein the gain adjustment is performed on a slice having the maximum signal among NMR signals, and the adjusted gain value is applied to gain values of other slices .

Images