PET/ CT [Positron Emission Tomography]

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    NIDUNG

    Gii thiu

    PET v dc chtphng x

    CT

    ng dngPET/CT

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    GII THIU

    PET==Positron Emission Tomography.

    Nm1945:bt uc nhngnghin cu v ng dng capositron trong lnh vcy hc.

    Nm1951: cc nh khoa hc ca bnh vinMassachusetts thc hin vicghi nhpositronbng k thuttrng phng.

    T nm 1992 n nay: kt hp gia chp nh cu trc(CT) v chp nh chc nng (PET), my PET/CT rai.

    PET

    CT Hnhchc nng

    Hnhcu trc

    Hnhcu trc vchc nng

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    Mtpositron pht ra t htnhn nguyn t tn ti rt ngn, ch i c mtqungng cc ngn ri kt hp vi mt in t tdo tch inm trong m v vo mttrngthi kch thch gil positronium. Positronium tn ti rt ngnv gn nhngay lp tc chuynho thnh 2 photon cnang lng511 keV v pht ra theo 2 chiu ngcnhau trn cng mt trc vi imxutpht Ngita gi l hin tng hu ht(annihilation).

    Nu t 2 detector i din ngun pht positron v dng mch trng phng(coincidence) th c thghi nhn2 photon ng thi . Do vycc u m nhpnhy c thxc nh vtr pht ra positron (cacc photon ). Vtr phi nmtrn ng ni lin2 detectorghi nhnchng.Ngita gi l ngtrng phng (coincidence line). Trong cng mt thi im my c thghi nhn chng triu s liu nh vy, to

    nn hinh anh phn b hot phng x(PX) trong khng gian ca i tng nhduPX trc (thu thpdu liuv ti tohinh anh).

    I.1 NGUYNLPET

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    detector

    detector

    e-

    e+

    Ht nhn khngbn

    pht positronPositron kt hpelectron v hy

    2 gama 511 keV

    ngc nhau

    Trng phng tht

    I.1 NGUYNLPET

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    I.2 CU TO PET

    CT

    PET

    CT PET

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    MCH IN TTRNG PHNG

    400-650 keV

    4-16 ns

    I.2 CU TO PET

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    My PET hin ibao gm mts lng lncc tinh th(4000n24.000) c sp xp thnhhnh tr gm ccvng ring lvi ng knh vng in hnh85 cm v trc trng chiu l16 cm. Cc vng N tinh thxc nh tng cng2N-1 lt (ticctrung tm vng v ti im

    gia cacc vng). Kch thcvtl ca mitinh th thngl4-8 mm mt ct ngang v dy t20 n30 mm

    Trng phng tht(T),Trng phng ngu nhin (R),Trng phng tn x(S).

    I.2 CU TO PET

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    Cc tinh th thng c dng trong my PET nh:

    Sodium iode pha thm tp cht thallium: NaI(Tl)

    Bismuth germinate hay BGO: Bi4Ge3O12

    Lutetium oxyorthosilicate pha thm tp cht Cerium hay LSO:Lu2SiO5(Ce)

    Ytrium oxyorthosilicate pha thm tp cht Cerium hay YSO:Y2SiO5(Ce)

    Gadolinium oxyorthosilicate pha thm tp cht Cerium hayGSO: Gd2SiO5(Ce)

    Barium fluoride: BaF2

    Cesium fluoride: CsF

    I.2 CU TO PET

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    Tinh th no c s dng cn ty thuc thit b ang sdng cn tc m cao hay phn gii hnh nh cao,thng da trn nhng c im sau y ca tinh th:

    nhy cadetector

    Tc m ngu nhin

    Tc m tn x

    Hiu sutnh sng

    Thigian pht x nhpnhy

    I.2 CU TO PET

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    CC TNG TC CA CA PHOTON GAMMA VI

    M C TH

    C 3 kiu tngtc chnh: Hiu ng quang in (nng lng gamma