JP2825091B2 - Method for measuring frequency dependence of ultrasonic absorption coefficient in ultrasonic diagnostic equipment - Google Patents
Method for measuring frequency dependence of ultrasonic absorption coefficient in ultrasonic diagnostic equipmentInfo
- Publication number
- JP2825091B2 JP2825091B2 JP60259147A JP25914785A JP2825091B2 JP 2825091 B2 JP2825091 B2 JP 2825091B2 JP 60259147 A JP60259147 A JP 60259147A JP 25914785 A JP25914785 A JP 25914785A JP 2825091 B2 JP2825091 B2 JP 2825091B2
- Authority
- JP
- Japan
- Prior art keywords
- ultrasonic
- absorption coefficient
- frequency
- regions
- echo signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
- G01S7/52023—Details of receivers
- G01S7/52036—Details of receivers using analysis of echo signal for target characterisation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
- G01S15/88—Sonar systems specially adapted for specific applications
- G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
- G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
- G01S15/895—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques characterised by the transmitted frequency spectrum
- G01S15/8952—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques characterised by the transmitted frequency spectrum using discrete, multiple frequencies
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Acoustics & Sound (AREA)
- Computer Networks & Wireless Communication (AREA)
- General Physics & Mathematics (AREA)
- Ultra Sonic Daignosis Equipment (AREA)
Description
【発明の詳細な説明】
（イ）産業上の利用分野
本発明は、超音波診断装置における超音波吸収係数の
周波数依存特性を測定する方法に関する。
（ロ）従来技術とその問題点
一般に、超音波診断装置では、トランスジューサから
超音波を生体内に放射し、生体内の各部の音響インピー
ダンスの差に応じて反射されたそのエコーを再びトラン
スジューサで受波し、受波して得られるエコー信号を輝
度変調することにより断層像をCRT等に表示する。
ところで、従来の組織性状の判定は、専らSTC調整後
の断層像の濃淡を観察することによって、医師が行なっ
ている。生体内に放射された超音波は、生体内の深さ方
向の距離とその組織性状に応じた吸収減衰を受ける。生
体内の距離による超音波の吸収減衰の影響は、近距離で
はエコー信号のゲインを低くし、遠距離では深さに応じ
てゲインを高くする、いわゆるSTC（Sensitivity Time
Control）により補正することができる。したがって、S
TC調整後のエコー信号強度に対応した断層像の輝度の違
いを観察することによってある程度の組織性状の判定が
可能である。
しかしながら、このような判定は、専門的に高度な知
識と経験を必要とし、また、定量的な評価を行なうこと
ができない。しかも、最終的には組織を切り取ってその
良否を確定する必要が生じるなど、患者に負担を強いる
ばかりでなく、不要な労力を伴なっていた。
上述のごとく、生体内に放射された超音波は、その組
織性状に応じた吸収減衰を受けるが、その吸収減衰の程
度は送受波される超音波の周波数に依存する。すなわ
ち、同じ組織でも超音波の周波数によつて吸収減衰する
程度が異なってくる。したがって、生体内の超音波の吸
収量（吸収係数）の周波数依存性を調べることによっ
て、組織性状を診断することができる。
本発明は、生体の組織性状が超音波周波数に依存する
というその特異性に着目し、超音波の周波数と吸収係数
との関係を求めることができる超音波診断装置における
超音波吸収係数の周波数依存特性測定方法を提供するこ
とを目的とする。
（ハ）問題点を解決するための手段
本発明は、上記の目的を達成するために、超音波診断
装置における超音波吸収係数の周波数依存特性測定方法
として、超音波を送受波して得られるエコー信号を互い
に周波数帯域の異なる複数のフィルタをそれぞれ通過さ
せて、各周波数ごとのエコー信号に基づく複数の断層像
を得、次いでこれらの各断層像について、その深さ方向
に２つの領域を設定し、両領域のエコー信号強度の輝度
の平均値が等しくなるようにSTCを調整した後、各領域
におけるゲイン設定値をそれぞれ読み取り、読み取った
これらの各ゲイン設定値と両領域間の距離から両領域間
の超音波の吸収係数を算出し、前記エコー信号の周波数
と吸収係数との関係を求めるようにしている。
（ニ）実施例
第１図は、本発明方法を適用するための超音波診断装
置のブロック図である。この超音波診断装置１により組
織性状を判定するには、まず、その前段階として、トラ
ンスジューサ２から生体内に超音波を放射し、生体内か
ら反射されたそのエコーをトランスジューサ２で受波す
る。トランスジューサ２からは、受波した超音波エコー
に対応したエコー信号が出力されるので、このエコー信
号を送受波回路４で増幅、検波し、次いで、マルチプレ
クサ６で互いに周波数帯域が異なる複数（本例では４
つ）のバンドパスフィルタ8a〜8dの内の一つ、たとえば
第１バンドパスフィルタ8aを選択し、選択した第１バン
ドパスフィルタ8aで所定の周波数帯域のエコー信号のみ
を通過させる。そして、第１バンドパスフィルタ8aを通
過したエコー信号のゲインをSTC調整回路10によって超
音波の深さ方向の距離に対応させて調整した後、このエ
コー信号を次段のA/Dコンバータ12でデジタル化してデ
ジタルスキャンコンバータ部14のメモリに画像データと
して格納する。
こうしてデジタルスキャンコンバータ部14に画像デー
タを格納すると、次に、演算制御部16によりこれらの画
像データをTV走査速度に同期して読み出し、この画像デ
ータをD/Aコンバータ18でアナログ化した後、CRT20に断
層像として表示する。
操作部22から断層像をフリーズさせる指令信号を入力
すると、演算制御部16は、第１バンドパスフィルタ8aを
通過した一画面分の断層像を表示する画像データがデジ
タルスキャンコンバータ部14に格納される。
次に、演算制御部16からの制御信号により、マルチプ
レクサ６を切り換えて次の第２バンドパスフィルタ8bを
選択し、上記と同じく断層像をフリーズさせてエコー信
号の周波数が異なる他の一画面分の画像データをデジタ
ルスキャンコンバータ部14に格納する。このようにし
て、第１バンドパスフィルタ8aから第４バンドパスフィ
ルタ8dをそれぞれ通過したエコー信号に基づく画像デー
タをそれぞれフリーズしてデジタルスキャンコンバータ
部14のメモリにすべて格納する。
超音波周波数の異なるエコー信号に基づく断層像が得
られると、次に、これらの各断層像について、それぞれ
単位距離当たりの吸収係数が求める。これには、まず、
第２図に示すように、第１バンドパスフィルタ8aを通過
して得られた一つの断層像F1をCRT20に表示し、その断
層像F1の深さ方向に２つの領域Ｉ、IIを設定する。これ
には、操作部22を操作して演算制御部16に領域指定信号
を与え、CRT20に領域Ｉ、II指定用のフレームを表示す
るとともに、そのフレームの大きさを各対象部位に応じ
て適宜拡大、縮小するなどして調整される。
次に、両領域Ｉ、IIのエコー信号強度の輝度の平均値
を測定する。これには、デジタルスキャンコンバータ部
14に格納されている画像データについて、演算制御部16
により、設定した各領域Ｉ、II内に存在するエコー信号
の強度値をピクセルごとに読み出してその領域内の強度
の平均値を算出することにより行なう。そして、両領域
Ｉ、IIの輝度の平均値を比較し、輝度の平均値が等しく
ない場合には、再度、第１バンドパスフィルタ8aを通過
したエコー信号について、演算制御部16からSTC調整回
路10に制御信号を与えることによりゲインを制御し、一
画面分の画像データの各領域Ｉ、IIにおける輝度が等し
くなるように調整した後、この画像データをフリーズす
る。
こうして、両領域Ｉ、IIの輝度が等しくなるように調
整すると、そのSTC調整後の両領域Ｉ、IIのゲイン設定
値を読み取る。そして、読み取った各ゲイン設定値と両
領域Ｉ、II間の距離から領域Ｉ、II間の超音波の吸収係
数を算出する。すなわち、いま両領域Ｉ、IIの各ゲイン
設定値をA1、A2、両領域Ｉ、II間の距離をＬとすると、
単位距離当たりの吸収係数μは、次式の関係で表わされ
る。
log（A2/A1）＝μＬ
よって、この式から吸収係数μが算出される。
上記動作を他のバンドパスフィルタ8b〜8dを通過した
エコー信号に基づいて得られる各断層像F2〜F4に対して
行なう。そして、各断層像F1〜F4の吸収係数μ１〜μ４
が算出されると、第３図に示すように、たとえば横軸を
各バンドパスフィルタ8a〜8dを通過したエコー信号の各
中心周波数f1〜f4、縦軸を吸収係数μ１〜μ４として両
者の関係をプロットすれば、組織性状を反映した特異な
特性曲線が得られる。すなわち、第３図中には一例とし
て、肝臓の組織（実線）と脂肪の組織（破線）について
の周波数と吸収係数との関係を示したが、このように、
組織性状には、超音波が吸収減衰される程度に特異な周
波数依存性があるので、この種のデータを蓄積すれば、
組織性状を容易に判定することができる。
なお、この実施例では４つのバンドパスフィルタ8a〜
8dを設けているが、さらに多数のバンドパスフィルタを
設ければ第３図の特性曲線が一層連続した曲線として得
られるようになる。
（ホ）効果
以上のように本発明によれば、超音波診断装置でもっ
て簡単に超音波の周波数と吸収係数との関係を求めるこ
とで超音波吸収係数の周波数依存特性が測定できる。ま
た、測定された特性は、生体内の組織性状を表らわして
いるので、高度な専門的知識がなくてもその特性より、
生体内の組織性状の診断を的確に、しかも、in vivoで
行な得る。The present invention relates to a method for measuring a frequency-dependent characteristic of an ultrasonic absorption coefficient in an ultrasonic diagnostic apparatus. (B) Conventional technology and its problems In general, in an ultrasonic diagnostic apparatus, an ultrasonic wave is radiated from a transducer into a living body, and an echo reflected according to a difference in acoustic impedance of each part in the living body is received by the transducer again. A tomographic image is displayed on a CRT or the like by modulating the intensity of an echo signal obtained by wave-receiving. By the way, the conventional determination of the tissue property is performed by a doctor exclusively by observing the density of the tomographic image after the STC adjustment. Ultrasonic waves radiated into a living body are absorbed and attenuated according to the distance in the depth direction and the tissue properties of the living body. The effect of absorption attenuation of ultrasonic waves due to the distance in the living body is that the gain of the echo signal is reduced at short distances, and the gain is increased according to the depth at long distances, so-called STC (Sensitivity Time).
Control). Therefore, S
By observing the difference in luminance of the tomographic image corresponding to the echo signal intensity after TC adjustment, it is possible to determine the tissue properties to some extent. However, such determination requires a high level of professional knowledge and experience, and cannot be quantitatively evaluated. In addition, it is necessary to cut off the tissue and finally determine the quality of the tissue, thereby imposing not only a burden on the patient but also unnecessary labor. As described above, an ultrasonic wave radiated into a living body undergoes absorption attenuation according to its tissue properties, and the extent of the absorption attenuation depends on the frequency of the transmitted and received ultrasonic waves. That is, the degree of absorption and attenuation differs depending on the frequency of the ultrasonic wave even in the same tissue. Therefore, a tissue property can be diagnosed by examining the frequency dependence of the amount of absorption (absorption coefficient) of ultrasonic waves in a living body. The present invention focuses on the peculiarity that the tissue property of the living body depends on the ultrasonic frequency, and the frequency dependence of the ultrasonic absorption coefficient in the ultrasonic diagnostic apparatus capable of obtaining the relationship between the ultrasonic frequency and the absorption coefficient. It is an object to provide a method for measuring characteristics. (C) Means for Solving the Problems In order to achieve the above object, the present invention is obtained by transmitting and receiving an ultrasonic wave as a method of measuring the frequency dependence characteristic of an ultrasonic absorption coefficient in an ultrasonic diagnostic apparatus. The echo signals are respectively passed through a plurality of filters having different frequency bands to obtain a plurality of tomographic images based on the echo signals for each frequency, and then, for each of these tomographic images, two regions are set in the depth direction. Then, after adjusting the STC so that the average value of the intensity of the echo signal intensities in both regions becomes equal, the gain setting values in each region are read, and both are read from these read gain setting values and the distance between the two regions. An absorption coefficient of the ultrasonic wave between the regions is calculated, and a relationship between the frequency of the echo signal and the absorption coefficient is obtained. (D) Embodiment FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus to which the method of the present invention is applied. In order to determine the tissue properties by the ultrasonic diagnostic apparatus 1, first, as a preliminary step, an ultrasonic wave is emitted from the transducer 2 into the living body, and the echo reflected from the living body is received by the transducer 2. Since the transducer 2 outputs an echo signal corresponding to the received ultrasonic echo, the echo signal is amplified and detected by the transmission / reception circuit 4, and then a plurality of multiplexers 6 having different frequency bands (this example). Then 4
One of the bandpass filters 8a to 8d, for example, the first bandpass filter 8a is selected, and only the echo signal of a predetermined frequency band is passed through the selected first bandpass filter 8a. Then, the gain of the echo signal that has passed through the first band-pass filter 8a is adjusted by the STC adjustment circuit 10 in accordance with the distance in the depth direction of the ultrasonic wave, and this echo signal is adjusted by the A / D converter 12 at the next stage. It is digitized and stored as image data in the memory of the digital scan converter unit 14. After storing the image data in the digital scan converter unit 14 in this manner, the arithmetic control unit 16 reads out the image data in synchronization with the TV scanning speed, and after converting the image data into an analog signal by the D / A converter 18, Display as tomographic image on CRT20. When a command signal for freezing a tomographic image is input from the operation unit 22, the arithmetic control unit 16 stores image data for displaying one screen of the tomographic image that has passed through the first bandpass filter 8a in the digital scan converter unit 14. You. Next, according to the control signal from the arithmetic control unit 16, the multiplexer 6 is switched to select the next second band-pass filter 8b. Is stored in the digital scan converter unit 14. In this way, the image data based on the echo signals that have passed through the first band-pass filter 8a to the fourth band-pass filter 8d, respectively, are frozen and all are stored in the memory of the digital scan converter unit 14. When tomographic images based on echo signals having different ultrasonic frequencies are obtained, the absorption coefficient per unit distance is determined for each of these tomographic images. To do this,
As shown in FIG. 2, one of the tomographic image F 1 obtained through the first band pass filter 8a displayed on CRT 20, the tomographic image F 1 in the depth direction into two areas I, II, Set. To do this, the user operates the operation unit 22 to supply an area designation signal to the arithmetic control unit 16, displays frames for area I and II designation on the CRT 20, and appropriately adjusts the size of the frame according to each target part. Adjusted by enlarging or reducing. Next, the average value of the luminance of the echo signal intensities in both regions I and II is measured. This includes the digital scan converter section
The operation control unit 16 operates on the image data stored in
By reading the intensity values of the echo signals present in the set regions I and II for each pixel, the average value of the intensities in the regions is calculated. Then, the average values of the luminances of the two regions I and II are compared. If the average values of the luminances are not equal to each other, the operation control unit 16 returns the STC adjustment circuit to the echo signal passing through the first band-pass filter 8a again. The gain is controlled by giving a control signal to 10 so that the brightness of each area I and II of the image data for one screen is adjusted to be equal, and then this image data is frozen. In this way, when the brightness of both areas I and II is adjusted to be equal, the gain setting values of both areas I and II after the STC adjustment are read. Then, the ultrasonic absorption coefficient between the regions I and II is calculated from the read gain setting values and the distance between the regions I and II. That is, assuming that the respective gain setting values of both regions I and II are A 1 and A 2 and the distance between both regions I and II is L,
The absorption coefficient μ per unit distance is represented by the following equation. log (A 2 / A 1 ) = μL Accordingly, the absorption coefficient μ is calculated from this equation. Performed for each tomographic image F 2 to F 4 obtained on the basis of the operation on the echo signal passed through the other bandpass filter 8 b to 8 d. Then, the absorption coefficients μ 1 to μ 4 of each tomographic image F 1 to F 4
When There is calculated, as shown in FIG. 3, for example, the central frequencies f 1 ~f 4 of the horizontal axis echo signal passed through the band-pass filter 8 a to 8 d, absorbs vertical axis coefficient μ 1 ~μ 4 By plotting the relationship between the two, a unique characteristic curve reflecting the tissue properties can be obtained. That is, FIG. 3 shows, as an example, the relationship between the frequency and the absorption coefficient of the liver tissue (solid line) and the fat tissue (dashed line).
Tissue properties have a peculiar frequency dependence to the extent that ultrasound is absorbed and attenuated.
The tissue properties can be easily determined. In this embodiment, four bandpass filters 8a to 8a are used.
Although 8d is provided, if more bandpass filters are provided, the characteristic curve of FIG. 3 can be obtained as a more continuous curve. (E) Effect As described above, according to the present invention, the frequency dependence of the ultrasonic absorption coefficient can be measured by easily obtaining the relationship between the ultrasonic frequency and the absorption coefficient using the ultrasonic diagnostic apparatus. In addition, since the measured properties represent the tissue properties in the living body, even if they do not have high specialized knowledge,
Diagnosis of tissue properties in a living body can be performed accurately and in vivo.
【図面の簡単な説明】
第１図は本発明方法を適用するための超音波診断装置の
ブロック図、第２図は本発明方法の説明図、第３図は超
音波の吸収量と周波数との関係を示す組織性状の特性図
である。
１……超音波診断装置、Ｉ、II……領域。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus to which the method of the present invention is applied, FIG. 2 is an explanatory diagram of the method of the present invention, and FIG. FIG. 6 is a characteristic diagram of a tissue property showing the relationship of FIG. 1 ... Ultrasonic diagnostic apparatus, I, II ... Area.
フロントページの続き (56)参考文献 特開 昭60−29137（ＪＰ，Ａ) 特開 昭50−70083（ＪＰ，Ａ) 特開 昭60−36038（ＪＰ，Ａ) 特開 昭60−24829（ＪＰ，Ａ) 特開 昭60−212150（ＪＰ，Ａ) 特開 昭60−203090（ＪＰ，Ａ) 医用超音波機器ハンドブック （社) 日本電子機械工業会編 Ｓ60．４．20 Ｐ22Continuation of front page (56) References JP-A-60-29137 (JP, A) JP-A-50-70083 (JP, A) JP-A-60-36038 (JP, A) JP-A-60-24829 (JP, A) JP-A-60-212150 (JP, A) JP-A-60-203090 (JP, A) Medical Ultrasound Equipment Handbook (company) Japan Electronic Machinery Manufacturers Association S60.4.20 P22
Claims (1)
波数帯域の異なる複数のフィルタをそれぞれ通過させ
て、各周波数ごとのエコー信号に基づく複数の断層像を
得、次いでこれらの各断層像について、その深さ方向に
２つの領域を設定し、両領域のエコー信号強度の輝度の
平均値が等しくなるようにSTCを調整した後、各領域に
おけるゲイン設定値をそれぞれ読み取り、読み取ったこ
れらの各ゲイン設定値と両領域間の距離から両領域間の
超音波の吸収係数を算出して前記エコー信号の周波数と
吸収係数との関係を求めることを特徴とする、超音波診
断装置における超音波吸収係数の周波数依存特性測定方
法。(57) [Claims] Echo signals obtained by transmitting and receiving ultrasonic waves are respectively passed through a plurality of filters having different frequency bands to obtain a plurality of tomographic images based on the echo signals for each frequency, and then, for each of these tomographic images, After setting two areas in the depth direction and adjusting the STC so that the average value of the intensity of the echo signal intensity in both areas is equal, the gain setting values in each area are read, and the read gain setting values are read. Calculating the absorption coefficient of the ultrasonic wave between the two regions from the value and the distance between the two regions to determine the relationship between the frequency of the echo signal and the absorption coefficient, the ultrasonic absorption coefficient of the ultrasonic diagnostic apparatus Frequency-dependent characteristic measurement method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60259147A JP2825091B2 (en) | 1985-11-18 | 1985-11-18 | Method for measuring frequency dependence of ultrasonic absorption coefficient in ultrasonic diagnostic equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60259147A JP2825091B2 (en) | 1985-11-18 | 1985-11-18 | Method for measuring frequency dependence of ultrasonic absorption coefficient in ultrasonic diagnostic equipment |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62117536A JPS62117536A (en) | 1987-05-29 |
| JP2825091B2 true JP2825091B2 (en) | 1998-11-18 |
Family
ID=17329986
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60259147A Expired - Fee Related JP2825091B2 (en) | 1985-11-18 | 1985-11-18 | Method for measuring frequency dependence of ultrasonic absorption coefficient in ultrasonic diagnostic equipment |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2825091B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5185921B2 (en) * | 2006-03-31 | 2013-04-17 | 日立アロカメディカル株式会社 | Method and apparatus for ultrasound imaging |
| CN107405136A (en) * | 2015-03-31 | 2017-11-28 | 奥林巴斯株式会社 | The working procedure of ultrasound observation apparatus, the method for work of ultrasound observation apparatus and ultrasound observation apparatus |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU6842074A (en) * | 1973-05-03 | 1975-10-30 | Commonwealth Of Australia, The | Ultrasonic echogram display |
| JPS6024829A (en) * | 1983-07-21 | 1985-02-07 | 株式会社東芝 | Ultrasonic diagnostic apparatus |
| JPS6029137A (en) * | 1983-07-27 | 1985-02-14 | 株式会社東芝 | Ultrasonic diagnostic apparatus |
| JPS60203090A (en) * | 1984-03-27 | 1985-10-14 | Shimadzu Corp | Picture processor |
| JPS60212150A (en) * | 1984-04-06 | 1985-10-24 | 富士通株式会社 | Measurement of living body tissue characteristics by ultrasonic wave |
-
1985
- 1985-11-18 JP JP60259147A patent/JP2825091B2/en not_active Expired - Fee Related
Non-Patent Citations (1)
| Title |
|---|
| 医用超音波機器ハンドブック （社）日本電子機械工業会編 Ｓ６０．４．２０ Ｐ２２ |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62117536A (en) | 1987-05-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |