JP5261706B2 - Radiation detection apparatus and positron emission tomography apparatus having the same - Google Patents
Radiation detection apparatus and positron emission tomography apparatus having the same Download PDFInfo
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- 230000005855 radiation Effects 0.000 title claims abstract description 61
- 238000001514 detection method Methods 0.000 title claims abstract description 32
- 238000002600 positron emission tomography Methods 0.000 title claims description 7
- PGAPATLGJSQQBU-UHFFFAOYSA-M thallium(i) bromide Chemical compound [Tl]Br PGAPATLGJSQQBU-UHFFFAOYSA-M 0.000 claims abstract description 34
- 230000003321 amplification Effects 0.000 claims abstract description 22
- 238000003199 nucleic acid amplification method Methods 0.000 claims abstract description 22
- 230000010354 integration Effects 0.000 claims abstract description 4
- 230000010287 polarization Effects 0.000 claims description 5
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 claims description 4
- 230000000694 effects Effects 0.000 claims description 4
- 229910052716 thallium Inorganic materials 0.000 claims description 4
- BKVIYDNLLOSFOA-UHFFFAOYSA-N thallium Chemical compound [Tl] BKVIYDNLLOSFOA-UHFFFAOYSA-N 0.000 claims description 4
- 230000006866 deterioration Effects 0.000 claims description 3
- 239000011347 resin Substances 0.000 claims description 3
- 229920005989 resin Polymers 0.000 claims description 3
- 238000003325 tomography Methods 0.000 abstract description 3
- 239000013078 crystal Substances 0.000 description 20
- 238000010586 diagram Methods 0.000 description 10
- MARUHZGHZWCEQU-UHFFFAOYSA-N 5-phenyl-2h-tetrazole Chemical compound C1=CC=CC=C1C1=NNN=N1 MARUHZGHZWCEQU-UHFFFAOYSA-N 0.000 description 7
- 230000000630 rising effect Effects 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 229910016036 BaF 2 Inorganic materials 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- 230000005251 gamma ray Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
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Abstract
Description
本発明は、放射線検出装置及びこれを有する陽電子断層撮影装置（ＰＥＴ）に関する。 The present invention relates to a radiation detection apparatus and a positron emission tomography apparatus (PET) having the same.
ＰＥＴ等の検出部には、シンチレーション検出器と半導体検出器が使用されている。高空間分解能を得るためには、検出器サイズを小さくできる半導体検出器が用いられており、テルル化カドミウム結晶を用いた放射線検出器が使用されている。ところがテルル化カドミウム結晶は、共有結合結晶であり、融点が高く、また作製費が高いという問題点がある。例えば装置１台当たりの結晶のみの価格が数億円と高価になっている。
このためテルル化カドミウムに代わるものとして臭化タリウムが注目されている。
臭化タリウムは、その高い原子番号(Tl: 81、Br: 35)及び高密度(7.56g/cm3)、広いギャップ・エネルギー(2.68eV)及び高い光子阻止能により室温放射線検出器の素材として魅力的な半導体である。
A scintillation detector and a semiconductor detector are used for a detection unit such as PET. In order to obtain high spatial resolution, a semiconductor detector capable of reducing the detector size is used, and a radiation detector using a cadmium telluride crystal is used. However, the cadmium telluride crystal is a covalent bond crystal and has a problem that it has a high melting point and a high production cost. For example, the price of only crystals per device is as high as several hundred million yen.
For this reason, thallium bromide has attracted attention as an alternative to cadmium telluride.
Thallium bromide is attractive as a material for room temperature radiation detectors due to its high atomic number (Tl: 81, Br: 35) and high density (7.56g / cm3), wide gap energy (2.68eV) and high photon stopping power Semiconductor.
臭化タリウム結晶と電荷有感型前置増幅器を用いた放射線検出装置の原理図を図１３に示す。臭化タリウム結晶の対向する面にＴｌ等の電極が形成されており、臭化タリウム放射線検出器を構成する。そして電極間には、バイアス電圧が印加されており、臭化タリウム結晶にガンマ線が入射するとこれにより電子及び正孔が生成され、これが電荷有感型前置増幅器により増幅されて出力信号として検出される。 FIG. 13 shows a principle diagram of a radiation detection apparatus using a thallium bromide crystal and a charge-sensitive preamplifier. Electrodes such as Tl are formed on the opposing surfaces of the thallium bromide crystal to constitute a thallium bromide radiation detector. A bias voltage is applied between the electrodes. When gamma rays are incident on the thallium bromide crystal, electrons and holes are generated thereby, which are amplified by a charge-sensitive preamplifier and detected as an output signal. The
臭化タリウム放射線検出器は、テルル化カドミウム放射線検出器に比べて次のような点で優れている。
（１）臭化タリウムは、イオン結合結晶であり、融点が低く、安価に作製できる。このため臭化タリウム結晶は、テルル化カドミウム結晶と比較し、１００分の１程度の値段で作製できる。
（２）臭化タリウム結晶はテルル化カドミウム結晶よりもガンマ線を止める能力が高く、テルル化カドミウムの半分程度の大きさで同程度の効果が発揮できる。このため検出器を薄くすることができる。
The thallium bromide radiation detector is superior to the cadmium telluride radiation detector in the following points.
(1) Thallium bromide is an ion-bonded crystal, has a low melting point, and can be produced at low cost. For this reason, thallium bromide crystals can be produced at a price about 1/100 of that of cadmium telluride crystals.
(2) The thallium bromide crystal has a higher ability to stop gamma rays than the cadmium telluride crystal, and can exhibit the same effect at about half the size of cadmium telluride. For this reason, a detector can be made thin.
ところが臭化タリウム放射線検出器は、このようにガンマ線の検出効率が非常に高い反面、臭化タリウム結晶中にガンマ線入射でできた電子と空孔の移動速度が極度に遅いため同時計数時間分解能が悪いというＰＥＴ応用に対しては重大な問題がある。
すなわち、同時計数時間分解能を上げるためには、負荷電圧方向の結晶の厚さを薄くし、且つ負荷電圧を高くするという相反的条件を課すため、検出器の長期使用には適さない。
このため、上記（１）及び（２）に挙げた利点を有するにもかかわらず、臭化タリウム放射線検出器のＰＥＴ等への実用化が阻害されていた。
However, the thallium bromide radiation detector has a very high gamma ray detection efficiency, but the electron and vacancies generated by the incidence of gamma rays in the thallium bromide crystal are extremely slow, so the coincidence time resolution is low. There are significant problems for PET applications that are bad.
In other words, in order to increase the resolution of the coincidence time, a reciprocal condition is imposed that the thickness of the crystal in the load voltage direction is reduced and the load voltage is increased.
For this reason, despite having the advantages listed in (1) and (2) above, the practical application of thallium bromide radiation detectors to PET and the like has been hindered.
本発明は、上記の問題点を解決し、臭化タリウム放射線検出器を用いた放射線検出装置における同時計数の時間分解能を上げることができる放射線検出装置及びこれを有する陽電子断層撮影装置を提供することを課題とするものである。 The present invention provides a radiation detection apparatus and a positron emission tomography apparatus having the same that can solve the above problems and can increase the time resolution of coincidence counting in a radiation detection apparatus using a thallium bromide radiation detector. Is an issue.
上記の課題を解決するために本発明は、次のような放射線検出装置及びこれを有する陽
電子断層撮影装置を提供するものである。
（１）ガンマ線を検出する臭化タリウム放射線検出器と、該臭化タリウム放射線検出器の一方の電極に接続され同時計数のためのタイミング信号を取得する電流増幅型前置増幅器と、該電流増幅型前置増幅器に直列接続されエネルギー信号を取得する積分回路と、他方の電極に検出器バイアスだけを印加する電源とを備えた放射線検出装置。
（２）上記臭化タリウム放射線検出器に印加する電圧の極性を切り替えることにより臭化
タリウムの分極効果による検出器性能の劣化を解消する、上記臭化タリウム放射線検出器と前記電源との間に設置された切り替えスイッチを備えることを特徴とする上記（１）に記載の放射線検出装置。
（３）上記臭化タリウム放射線検出器を複数用いた検出器群において、該検出器群のすべての一方の電極を１つの直流型定電圧電源に接続し、片方を各々の増幅回路に接続することを特徴とする上記（１）又は（２）に記載の放射線検出装置。
（４）複数の上記臭化タリウム放射線検出器を両側から接着させた、電流増幅型前置増幅器への配線が両面にプリントされた絶縁樹脂を備えることを特徴とする上記（３）に記載の放射線検出装置。
（５）上記（１）乃至（４）のいずれかに記載の放射線検出装置を有する陽電子断層撮影
装置。
In order to solve the above problems, the present invention provides the following radiation detection apparatus and a positron emission tomography apparatus having the same.
(1) A thallium bromide radiation detector that detects gamma rays, a current amplification type preamplifier that is connected to one electrode of the thallium bromide radiation detector and obtains a timing signal for coincidence counting, and the current amplification A radiation detection apparatus comprising: an integration circuit connected in series to a mold preamplifier for acquiring an energy signal; and a power supply for applying only a detector bias to the other electrode.
(2) By switching the polarity of the voltage applied to the thallium bromide radiation detector, the deterioration of the detector performance due to the polarization effect of thallium bromide is eliminated, between the thallium bromide radiation detector and the power source. The radiation detection apparatus according to (1), further comprising an installed changeover switch .
(3) at a detector group using a plurality of the above-described bromide thallium radiation detector, connects all the one electrode of the detector groups one DC constant-voltage power supply, connected to the amplifier circuit respectively one The radiation detection apparatus according to the above (1) or (2), wherein
(4) a plurality of the above bromide thallium radiation detector was adhered on both sides, according to the above (3) to wiring to current amplification preamplifier is characterized Rukoto comprising a printed insulating resin on both surfaces Radiation detection equipment.
(5) A positron emission tomography apparatus having the radiation detection apparatus according to any one of (1) to (4).
本発明によれば、ガンマ線を検出する臭化タリウム放射線検出器の電極面に発生した誘導電荷の信号を電流増幅型前置増幅器に入力して得た立ち上がり信号を、同時計数のためのタイミング信号として利用することにより、臭化タリウム放射線検出器に対して低バイアス電圧で速いタイミング信号が取得できる。
また本発明によれば、実用に耐える同時計数の時間分解能を備えた臭化タリウム放射線検出器を用いた放射線検出装置及びこれを有する陽電子断層撮影装置が得られる。
According to the present invention, a rising signal obtained by inputting an induced charge signal generated on the electrode surface of a thallium bromide radiation detector for detecting gamma rays to a current amplification type preamplifier is used as a timing signal for coincidence counting. As a result, a fast timing signal can be obtained with a low bias voltage with respect to the thallium bromide radiation detector.
In addition, according to the present invention, a radiation detection apparatus using a thallium bromide radiation detector having a practical time resolution for coincidence counting and a positron emission tomography apparatus having the same can be obtained.
本発明について、以下図面を引用して説明する。本明細書では、臭化タリウム放射線検出器をＴｌＢｒ検出器と略称する。なお本発明は以下の説明に例示したものに限定されないことは、いうまでもないことである。 The present invention will be described below with reference to the drawings. In this specification, a thallium bromide radiation detector is abbreviated as a TlBr detector. Needless to say, the present invention is not limited to those exemplified in the following description.
（本発明に係る知見）
図１の左図は3mmφ×0.5mm厚の臭化タリウムに、また右図は3mmφ×1mm厚の臭化タリウムにそれぞれバイアス電圧１００Ｖを印加したときに、臭化タリウム放射線検出器の電極面に発生した誘導電荷の信号を入力して得た立ち上がり信号を出力する電荷有感型前置増幅器としてのオペアンプ５８０Ｈからの出力信号を図示したものである。
図１に示すようにその出力信号は、電離箱における誘導電荷による電圧変化と同じように直線的に立ち上がることが分かる。
(Knowledge of the present invention)
The left figure of Fig. 1 shows the electrode surface of the thallium bromide radiation detector when a bias voltage of 100V is applied to 3mmφ x 0.5mm thickness thallium bromide, and the right figure shows the 3mmφ x 1mm thickness thallium bromide An output signal from an operational amplifier 580H serving as a charge-sensitive preamplifier that outputs a rising signal obtained by inputting a signal of the generated induced charge is illustrated.
As shown in FIG. 1, the output signal rises linearly in the same manner as the voltage change caused by the induced charge in the ionization chamber.
また、3mmφ×0.5mm厚のＴｌＢｒ検出器と3mmφ×1mm厚のＴｌＢｒ検出器とでは、出力信号の形は大きく異なる。この出力信号の１０％〜９０％の立ち上がりを測定し、そのヒストグラムを取ると、0.5mm厚のＴｌＢｒ検出器は、その立ち上がりは0.6μsec〜7μsecの間に、1mm厚のＴｌＢｒ検出器の場合は、3.5μsec〜35μsecの間に分布している。ヒストグラムは２成分を示し、ピークを為し速く立ち上がる成分と、速い立ち上がりから遅い立ち上がりまで広がっている成分が認められた（図２参照）。 In addition, the shape of the output signal differs greatly between a 3 mmφ × 0.5 mm thick TlBr detector and a 3 mmφ × 1 mm thick TlBr detector. When measuring the rise of 10% to 90% of this output signal and taking the histogram, the rise of the 0.5 mm thick TlBr detector is between 0.6 μs and 7 μs, and in the case of the 1 mm thick TlBr detector , Distributed between 3.5 μsec and 35 μsec. The histogram showed two components: a component that rises fast with a peak and a component that spreads from a fast rise to a slow rise (see FIG. 2).
２２Ｎａからの一対の陽電子消滅ガンマ線をＢａＦ２検出器と、ＴｌＢｒ検出器及び電荷有感型前置増幅器で同時計数を行ったところ、0.5mm厚のＴｌＢｒ検出器の場合は49nsecFWHMが得られた。
ＴｌＢｒ検出器及び電荷有感型前置増幅器からの出力信号が直線的に立ち上がることに注目し、ＴｌＢｒ検出器（3mmφ×0.5mm厚及び3mmφ×1mm厚）の電極面に発生した誘導電荷の信号を入力して得た立ち上がり信号を図３に示すように電流増幅型前置増幅器としてのオペアンプＡ２５０に入力した。ここで図３左図は、定圧電源に接続された電極側からの信号抽出、右図は、定圧電源に接続されてない電極側から信号抽出をそれぞれ行うものである。
その結果を図４及び図５に示す。図４は帰還抵抗値Ｒが3MΩ、図５は帰還抵抗値Ｒが300kΩのものである。図４及び図５の結果から、電荷有感型前置増幅器を用いた場合よりも速く立ち上がることが分かった。
When a pair of positron annihilation gamma rays from 22 Na were simultaneously counted with a BaF 2 detector, a TlBr detector, and a charge-sensitive preamplifier, 49 nsec FWHM was obtained in the case of a 0.5 mm thick TlBr detector. .
Paying attention to the fact that the output signal from the TlBr detector and the charge sensitive preamplifier rises linearly, the signal of the induced charge generated on the electrode surface of the TlBr detector (3mmφ × 0.5mm thickness and 3mmφ × 1mm thickness) As shown in FIG. 3, the rising signal obtained by inputting the signal is input to the operational amplifier A250 as a current amplification type preamplifier. Here, the left diagram in FIG. 3 performs signal extraction from the electrode side connected to the constant pressure power source, and the right diagram performs signal extraction from the electrode side not connected to the constant pressure power source.
The results are shown in FIGS. 4 shows a feedback resistance value R of 3 MΩ, and FIG. 5 shows a feedback resistance value R of 300 kΩ. From the results of FIG. 4 and FIG. 5, it was found that the signal rises faster than when the charge sensitive preamplifier is used.
この出力信号の１０％〜９０％の立ち上がりを測定し、そのヒストグラムを取ると、帰還抵抗値Ｒ＝3MΩの場合、0.5mm厚のＴｌＢｒ検出器は、その立ち上がりが0.2μsec〜0.7μsec、1mm厚のＴｌＢｒ検出器は、0.6μsec〜5μsecと、その信号の立ち上がりは速くなり、その分布も非常に狭くなることが分かった（図６参照）。
さらに、帰還抵抗値Ｒ＝330kΩと下げると、0.5mm厚のＴｌＢｒ検出器は、その立ち上がりが0.１6μsec〜0.32μsec、1mm厚のＴｌＢｒ検出器は、0.18μsec〜0.6μsecとさらに改善されることが分かった（図７参照）。
When the rising edge of this output signal is measured from 10% to 90% and the histogram is taken, when the feedback resistance is R = 3MΩ, the 0.5mm thick TlBr detector has a rising edge of 0.2μsec-0.7μsec, 1mm thickness. In the TlBr detector, the rise time of the signal is 0.6 μsec to 5 μsec, and the distribution thereof is found to be very narrow (see FIG. 6).
Furthermore, when the feedback resistance value R is lowered to 330 kΩ, the rise of the 0.5 mm thick TlBr detector is further improved to 0.16 μsec to 0.32 μsec, and the 1 mm thick TlBr detector is further improved to 0.18 μsec to 0.6 μsec. Was found (see FIG. 7).
図６及び図７より、電流増幅型前置増幅器の信号は、タイミング信号として電荷有感型前置増幅器のものより大きく改善されていることが分かる。
以上の平均立ち上がり時間についての結果を表１に整理する。
6 and 7, it can be seen that the signal of the current amplification type preamplifier is greatly improved as a timing signal than that of the charge sensitive type preamplifier.
The results for the above average rise time are summarized in Table 1.
表１から分かるように、0.5mm厚のＴｌＢｒ検出器及び電流増幅型前置増幅器（帰還抵抗値Ｒ＝330kΩ）を用いると、平均316nsecと他の場合よりも速い立ち上がりが得られる。
２２Ｎａからの一対の陽電子消滅ガンマ線をＢａＦ２検出器と0.5mm厚のＴｌＢｒ検出器及び電流増幅型前置増幅器（帰還抵抗値Ｒ＝330kΩ）で同時計数を行ったところ、23nsecFWHMとＰＥＴに使用できる時間分解能が得られた（図８参照）。
この値については、非特許文献２でも21.3nsecが得られている。
ところが、検出器のサイズは3×4×0.45mmと同じであるが、電荷有感型前置増幅器を用いたものであって、この値を得るのにバイアス電圧400Vを必要し、本発明が100Vで得られたのに対し、実に４倍の電圧で検出器に大きな負荷を与えている。この方法では、検出器の厚さを薄くし、しかも高電圧をかけるために検出器の耐性が損なわれる。
As can be seen from Table 1, when a 0.5 mm thick TlBr detector and a current amplification type preamplifier (feedback resistance value R = 330 kΩ) are used, an average of 316 nsec, which is faster than the other cases, can be obtained.
A pair of positron annihilation gamma rays from 22 Na were simultaneously counted with a BaF 2 detector, a 0.5 mm thick TlBr detector and a current amplification type preamplifier (feedback resistance R = 330 kΩ), and used for 23 nsec FWHM and PET. A possible time resolution was obtained (see FIG. 8).
As for this value, 21.3 nsec is obtained even in Non-Patent
However, although the size of the detector is the same as 3 × 4 × 0.45 mm, it uses a charge-sensitive preamplifier and requires a bias voltage of 400 V to obtain this value. While it was obtained at 100V, the detector is heavily loaded with four times the voltage. In this method, since the thickness of the detector is reduced and a high voltage is applied, the resistance of the detector is impaired.
（本発明に係る放射線検出装置）
図９及び図１０に、ＴｌＢｒ検出器とそのエネルギー信号及びタイミング信号同時取得回路を有する放射線検出装置の原理図を例示する。
電流増幅型前置増幅器は同時計数のためのタイミング信号取得に利用できるが、エネルギー弁別を行うことはできない。そこで、図９に示すように、もう一方の電極に電荷有感型前置増幅器をつなげ、エネルギー信号をとり、これを用いて同時計数のエネルギー閾値に使用する。ＴｌＢｒ検出器は、ＴｌＢｒ結晶自体の分極現象のために、使用途中で電極を逆転する必要がある。このため増幅系と電圧電源とは切り替えスイッチにより同時に配線を切り替えるようにする。
また、図１０に示すように、電流増幅型前置増幅器の後段に積分型増幅器を接続し、エネルギー信号とタイミング信号を同時に取り出すことができる。この場合、ＴｌＢｒ結晶自体の分極現象に対して、結晶への負荷電圧の極性を変えるだけで、信号取り出し系の回路を変更する必要がなく、複数の検出器に対して共通のバイアス電圧をかけることができる。但し、バイアス電圧の極性切り替えとともにタイミング信号、エネルギー信号の符号が逆転する。
(Radiation detection apparatus according to the present invention)
FIG. 9 and FIG. 10 illustrate a principle diagram of a radiation detection apparatus having a TlBr detector and its energy signal and timing signal simultaneous acquisition circuit.
The current amplification type preamplifier can be used for obtaining a timing signal for coincidence counting, but cannot perform energy discrimination. Therefore, as shown in FIG. 9, a charge-sensitive preamplifier is connected to the other electrode, an energy signal is taken, and this is used as an energy threshold for coincidence counting. The TlBr detector needs to reverse the electrodes during use due to the polarization phenomenon of the TlBr crystal itself. For this reason, the amplifying system and the voltage power supply are simultaneously switched by a changeover switch.
Further, as shown in FIG. 10, an integrating amplifier can be connected to the subsequent stage of the current amplification type preamplifier so that the energy signal and the timing signal can be taken out simultaneously. In this case, for the polarization phenomenon of the TlBr crystal itself, it is not necessary to change the circuit of the signal extraction system only by changing the polarity of the load voltage to the crystal, and a common bias voltage is applied to a plurality of detectors. be able to. However, the sign of the timing signal and energy signal is reversed when the polarity of the bias voltage is switched.
（本発明に係る放射線検出装置を有する陽電子断層撮影装置）
次に本発明に係る臭化タリウム放射線検出装置のＰＥＴへの適用について説明する。
ＰＥＴ用検出器としては、偶発同時計数を極力抑えるのに十分な同時計数の時間分解能を有していなければならない。 このためＴｌＢｒ結晶の電極間を薄くして高時間分解能を得る必要がある。ところが結晶が薄くなると、ガンマ線を検出できる体積が減るため、ＴｌＢｒ結晶を積み重ねた多層のＴｌＢｒ検出器が必要となる。
(Positron tomography apparatus having radiation detection apparatus according to the present invention)
Next, application of the thallium bromide radiation detection apparatus according to the present invention to PET will be described.
The detector for PET must have a sufficient time resolution for coincidence counting to suppress accidental coincidence as much as possible. For this reason, it is necessary to obtain a high time resolution by thinning the gap between the electrodes of the TlBr crystal. However, as the crystal becomes thinner, the volume in which gamma rays can be detected decreases, so a multilayer TlBr detector in which TlBr crystals are stacked is required.
図１１及び図１２に多層ＴｌＢｒ検出器とそのエネルギー信号及びタイミング信号同時取得回路を有する放射線検出装置の原理図を例示する。
ＰＥＴにおいては、多数の検出器が実装され、そのバイアス電圧は一つの電源から供給される。このため、図９の構成では、各々の検出器に独立した定電圧電源が必要とされるが、図１０の構成では、一つの定電圧電源から各々の検出器に供給できる。ある程度の大きさを持ったＴｌＢｒ検出器を図１１のように、一方の電極に溝を入れることにより、小型のＴｌＢｒ検出器の配列を作り、そのそれぞれに電流増幅型前置増幅器と積分型増幅器を直列に繋げると、各々の検出器からタイミング信号とエネルギー信号を同時に得ることができるだけでなく、どの検出器でガンマ線が検出されたか同定できる。もう片方の電極は共通のバイアス電極として使用できる。
バイアス電圧は切り替えスイッチで付加電圧を逆転することにより、分極効果による検出器性能の劣化の解消に対応でき、永久使用可能な放射線検出装置が実現できる。この極性切り替えで信号の符号も反転する。
FIG. 11 and FIG. 12 illustrate a principle diagram of a radiation detection apparatus having a multilayer TlBr detector and its energy signal and timing signal simultaneous acquisition circuit.
In PET, a large number of detectors are mounted, and the bias voltage is supplied from one power source. For this reason, in the configuration of FIG. 9, an independent constant voltage power source is required for each detector, but in the configuration of FIG. 10, a single constant voltage power source can be supplied to each detector. As shown in FIG. 11, a TlBr detector having a certain size is provided with a groove in one electrode to form a small array of TlBr detectors, each of which has a current amplification type preamplifier and an integration type amplifier. Are connected in series, the timing signal and the energy signal can be obtained simultaneously from each detector, and it is possible to identify which detector detected the gamma ray. The other electrode can be used as a common bias electrode.
By reversing the additional voltage with a changeover switch, the bias voltage can cope with elimination of deterioration of detector performance due to the polarization effect, and a radiation detector that can be used permanently can be realized. The sign of the signal is also reversed by this polarity switching.
図１１で示した検出器列を図１２のように、電流増幅型前置増幅器への配線が両面にプリントされた非常に薄い絶縁樹脂に両側から接着させ、この検出器層をさらに、その各々のバイアス電圧用電極面を接着せ、重ね合わせることにより、有感率の高い検出器ブロックが実現できる。
以上により、高空間分解能、高検出効率で永久使用できるＴｌＢｒ検出器使用のＰＥＴが実現される。
As shown in FIG. 12, the detector array shown in FIG. 11 is bonded from both sides to a very thin insulating resin in which wiring to the current amplification type preamplifier is printed on both sides. By adhering and overlaying the bias voltage electrode surfaces, a detector block with a high susceptibility can be realized.
As described above, PET using a TlBr detector that can be used permanently with high spatial resolution and high detection efficiency is realized.
Claims (5)
A positron emission tomography apparatus comprising the radiation detection apparatus according to claim 1.
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