chapter 4 ct nguc - page 148 - 182

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  • 1. CHNG IVNGUYN TC CHUNG V K THUT CHP CT LP VI TNH LNG NGC Gio s Hong c Kit148

2. Chp ct lp vi tnh u tin c p dng cho s no vi thit b ct lp qui c , thi gian qut 360o quanh trc c th ca bng X quang t 2-4sec v thi gian gia hai lp ct t 11 n 16sec hn ch kt qu chn on ca chp ct lp lng ngc . T khi cng ngh chp ct lp xon c ra i , phm vi ng dng ca chp ct lp vi tnh cho ton thn ngy cng m rng v hiu qu hn . Vi nhng th h my mi cho php qut lin tc 30sec hoc di hn, loi tr c nhng thay i gii phu gia hai ln nhn th ca bnh nhn v cho php t c nng thuc cn quang mch mu mc cao mt cch n nh , li ch ca chp ct lp vi tnh (CLVT) i vi bnh l ngc tr nn khng thua km so vi s no v c th tm tt vo ba im sau : 1. Loi b c vn chng lp ca cc cu trc gii phu bng k thut to nh thng dng nh chp X quang chun vi nhng lp ct ngang t mng cn thit cho chn on . 2. Cho php to nh c i quang t chc rt cao so vi phim X quang qui c nhng vn m bo phn gii khng gian cn thit cho chn on . 3. Kh nng ti to nh 3D v nhng hng cn thit khc i vi ton b lng ngc c bit quan trng trong chn on bnh l mch mu trung tht . Nh nhng u th ni trn , chn on hnh nh bng chp CLVT ni chung thun li v t ph thuc vo ngi c hn so vi k thut to nh khc .Ch nh chp CLVT lng ngc : Chp X quang chun vn l khm xt thng qui hiu qu nht cho chn on v i quang ca cc cu trc trong ngc cao , d thc hin , liu x v gi thnh thp . Chp CLVT c p dng tip theo khi tn ti nhng cu hi chn on m phim Xquang chun khng gii p c . Di y l mt s ch dn thc hnh : ng b bt thng trung tht hay rn phi cha r do bm sinh , bt thng gii phu , phnh hay phnh tch ng mch hoc chn y ca khi u gy ra .Hnh khi , hnh thm nhim hay hnh nt m nhu m phi cn c nh gi y hn v cu trc v hnh thi ; nu nghi ng ung th , cn phn bc khi u c ch nh iu tr hp l .Nghi ng mt hnh bt thng vng c-ngc hay ngc-bng v X quang chun khng c kh nng hin nh chn on cc vng ny .Nhng trng hp kh phn bit hnh m gi nhu m phi vi mng phi trn phim chun .Bnh l thnh ngc hay ct sng c lin quan ti mng phi v phi .149 3. Hnh bt thng lan to trn phim ngc chun cn c lm sng t tn thng thuc nhu m hay ng th nh , c im v lan rng ca tn thng . Trng hp ny nn chp ct lp phn gii cao .Chp CLVT cn c ch nh khi phim X quang ngc chun bnh thng hoc gn nh bnh thng nhng trn lm sng vn rt nghi ng mt bnh l kn o trong ngc nh : Khi u c tnh ngoi phi cn tm nt di cn ti phi . Cc bt thng ni tit hoc ho sinh lin quan ti lng ngc nh nhc c nghi c bt thng tuyn c ; ri lon chuyn ho calci nghi bt thng tuyn bng gip trng ; tng catecholamin tng huyt p nghi u bt mu chrom ngoi thng thn hoc hi chng ni tit cn u nghi ung th ph qun ...Ho ra mu khng tm c nguyn nhn , c t bo c tnh trong m , c ting rt thng xuyn khi th , thm nhim phi iu tr khng hiu qu .Nhim khun phi ti pht bnh nhn khng c suy gim min dch .Lm sng nghi nghn mch phi hoc d dng ng-tnh mch phi .Bt thng chc nng h hp nhng khng thy bt thng trn phim ngc chun .au ngc cp tnh hoc au ngc ko di m khng tm thy bt thng trn in tm .Ch nh chp CLVT ngc hin m rt rng nn khng th c mt chng trnh khm xt chung cho mi yu cu chn on . Da trn tnh nng k thut ca my chp c di tay cng vi phn tch k cu hi chn on , ngi bc s chuyn khoa phi quyt nh cc thng s k thut v chng trnh khm xt cho tng bnh nhn da trn nguyn tc gi tr chn on cao nht vi nguy c v gi thnh thp nht . Cn c gng t c kt lun ca khm xt trc khi cho bnh nhn ri khi my chp .K THUT KHM XT Ba k thut khm CLVT lng ngc thng dng c th la chn tu theo tnh nng k thut ca thit b c di tay v yu cu chn on ca tng bnh nhn : 1. Chp ct lp qui c vi dy lp ct t 3-10mm v bn bnh nhn chuyn dch tng bc sau mi vng qut ca bng X quang , qut lin tip 2. Chp ct lp phn gii cao vi dy lp ct nh hn 2mm v thi gian qut mt vng 360o ca bng nh hn 2sec ; khng cn lin tip . 3. Chp ct lp xon c lng ngc vi rng ca chm tia X ( dy lp ct ) t 3-10mm v bn bnh nhn chuyn dch lin tc theo tc nh trc . Chp ct lp qui c b hn ch v to nh 3D v MPR nn hin t s dng . Trng hp thit b khng c tnh nng qut xon c , bc s khm xt cn bit150 4. nhng hn ch ca k thut , nht l kh nng b st tn thng nh do phi di chuyn khi th . Chp ct lp phn gii cao thng thc hin nghin cu chi tit cu trc phi nh trong bnh l lan to hoc khu tr ca nhu m phi nh bnh t chc k , gin ph qun , gin ph nang , x phi . Hnh nh thu c khng thun li cho phn tch cc cu trc ca trung tht , khng p dng cht cn quang tnh mch trong k thut ny . Cn t cc thng s ca chng trnh ti to c phn gii khng gian cao . Nn t trng quan st t 15-20cm , dy lp ct 1-2mm bc chuyn bn 10-20mm t c nh phn gii cao nhng mc chiu x trn bnh nhn khng qu cao . Chp ct lp xon c nn lu mt s chi tit di y: Pitch : l t l gia tc di chuyn bnh nhn (s) vi rng ca b chun trc (w) , cng chnh l dy lp ct , trong mi tng quan vi thi gian qut 360o ca bng Xquang (t)s (mm/s) P = -------------t (sec)w (mm) Theo Wang v Vannier , nn chn pitch nh hn cn bc 2 ca 2 tc l di 1,4 . Pitch cng ln th thi gian khm xt cng ngn nhng nhiu nh tng theo . Pitch > 2 s to ra nhng khoang hp khng c d kin gia cc lp ct . Cc my chp CLVT hin c thi gian qut t 0.8 n 2sec/360o . Nu t thi gian qut 1sec/360o , tnh pitch rt n gin : khi chuyn bn vi tc 12mm/s v dy lp ct 8mm , pitch=1,5 . Trng quan st (FOV) : l rng ca ma trn ti to nh . t FOV cng rng th phn gii khng gian ca nh cng gim do nn t FOV va bng chiu ngang lng ngc ca bnh nhn c c phn gii tt nhtt ca s nh L v W : Lng ngc l c khc bit ln nht v t trng cc cu trc gii phu , thng phi c 2 ca s cho mt lp ct l ca s m mm cho trung tht - thnh ngc v ca s cho nhu m phi ; nu cn thit c th phi t thm ca s xng . Nn lu ba im khi t ca s c nh tt nht cho chn on : 1- phn bit mt cu trc cn quan tm vi cc cu trc ln cn , cn t L mc gia ca t trng chnh lch th d mt nhn phi c t trng +50 gia nhu m phi c m 800 th L tt nht 375. 2- Mc ca s cng phi tng khi dy lp ct cng gim.3- rng W phi bao trm c t trng mi cu trc cn phn tch trn nh: ca s m mm phi c rng W t 500-600 mi c th xem c t m n151 5. xng; ca s nhu m phi phi t W t 1300-2000 mi c th xem c t nhu m phi n xng . Thuc cn quang: i vi lng ngc, tim thuc cn quang tnh mch ch cn thit khi cn phn bc mt ung th ph qun-phi , nghi ng bt thng mch mu hoc c mt tn thng phc tp phi-mng phi. Nn dng thuc cn quang c nng Iode t 240 n 300 mg/ml trnh nhiu nh tnh mch di n v tnh mch ch trn ; loi khng in tch (non-ionic ) c a dng v him gy phn ng ph lm gin on khm xt.TIM V TRUNG THT a- Nhc li v gii phu Trung tht c chia lm ba khoang d nhn bit cc cu trc bn trong v ccbnh hay gp ca tng khoang; l trung tht trc, gia v sau. Trung tht trc l khoang ngc t sau xng c cho ti mng tim trc; trung tht sau l mng tim sau cho ti thnh ngc sau. Cc thnh phn khc gia trung tht v trung tht sau ( tr khoang mng tim v mng phi) hnh thnh khoang trung tht gia. T trn xung di, trung tht chon t h thng c cho ti vm honh. Rn phi kh xc nh gii hn c th hc, l vng b mt trung tht ln vo phi v cc mch mu, ph qun v dy thn kinh i vo phi . Hai rn phi khng i xng nhau nn khi xc nh mt cu trc bt thng vng ny l hch hay mch mu cn phn tch nh mt cch h thng `v tim thuc cn quang gip phn bit r rng hn v cng d nhn bit khi chon ch bnh l hn. Hch bch huyt rn phi c ng knh ngang bnh thng t 0,3 n 0,6 cm v c th thy c trn cc lp ct. Ch khi ng knh ngang ca hch ln hn 1cm mi c th coi l bnh l v hch bch huyt thng nm dc theo ph qun v mch mu. Tuyn c tr nh v thiu nin c m ca m mm v sau 20 tui dn dn c thay th bng t chc m. Hnh dng tuyn c thay i tng ngi; hai thu tri v phi ca tuyn c khi tch ri c khi ho nhp lm mt. dy ca t chc tuyn tr em khng qu 1,8cm v ngi ln khng qu 1,3cm. Tuyn c c th to ln ngi cng gip hoc sau iu tr bng Corticoid, ho cht. Khm xt tim thng dng siu m nhng chp CLVT c th s dng : -nh gi hnh dng v kch thc tim. -nh gi s lin quan v tr gia cc bung tim v mch gc. -Pht hin khi chon ch trong bung tim. 152 6. -nh gi chc nng cu ni ng mch ch vnh. Cn mun nh gi c nng cc van tim, cc bung tim ch c my CT siu m nhanh mi thc hin c. Cc vi ho trong lng ngc (ngoi mch mu) thng l di chng ca mt qu trnh bt thng i trc, chng c th gp nhu m phi, trung tht, rn phi v cc hch bch huyt, mng phi, thnh ngc. Nguyn nhn cc vi ho c th d on nh v tr, hnh dng ca vi km theo nhng kin thc v nhng bnh l lm sng phi hp. Tr cc thm vi thnh ng mch ch v ng mch vnh, nguyn nhn hay gp nht l do mt qu trnh nhim trng c; t gp hn l do u ri n cc ri lon chuyn ho, bnh ngh nghip hoc do mt qu trnh iu tr.B- bnh l trung tht v rn phi: 1-ng mch ch ngc:a. Hp eo ng mch ch do qu sn lp gia ca thnh mch gy hp lng ng mch gy tng huyt p chi trn v gim huyt p chi di; v tr hp hay sau quai ng mch ch, di ch pht xut ng mch di n tri. Chp CLVT c tim nhanh thuc cn quang mi pht hin c hnh hp lng ng mch. b. thoi.Phnh ng mch ch: c hai dng phnh ng mch ch l hnh ti v hnhBnh thng ng mch ch ngc c khu kch t 3 3,5cm. nu ng knh ng mch ch ln hn 4cm c th coi l phng ng mch ch hnh thoi. C khi khu knh ng mch ch khng qu 4cm nhng vn l phng ng mch v b khng i xng, l trng hp phng hnh ti. Khu knh ca vng ng mch ch b phnh nu khng qu 5cm, kh nng v rt him; nu t 5 10 cm rt d v. V tr ca phnh ng mch ch hay gp on MC xung v y thc qun sang bn phi. D hay v ti phnh ng mch ch cho thy mu t t trng c hiu trong trung tht. c.Phnh tch ng mch ch l bnh cp cu tng i hay gp do hu qu vt nt thnh ng mch ch gy bc tch lp ni mc to ra mt lng mch gi trong lp o gia ca thnh mch. Phnh tch ng mch ch ngc c chia thnh hai th khc nhau: Tip A l loi phnh tch ng mch ch ln v chim 60 70% cc trng hp. Tip B t gp hn, c v tr phnh tch ng mch ch xung, t eo ng mch ch lan xung di. Tip A hay lan ti van ng mch ch v l pht xut ng mch vnh tim v thng khng m c. Chn on phnh tch ng mch ch c hai tiu chun l: -ng mch c 2 lng, lng gi v lng tht; lng tht ngm thuc cn quang mnh hn. Lng gi c khi rng hn lng tht.153 7. -Thy l ni mc gia hai lng gi v tht, nhiu khi nh vi ho ni mc cho php nhn bit l ni mc ngay c trn phim khng tim thuc. 2- Kn: a) Kn ph qun hay gp nht trung tht gia nhng cng c khi trung tht sau v trc, kn c m dch nhng cng c khi l cht nhy vi m cao hn. Kn c hnh trn hoc bu dc, b r v mng, khng ngm thuc cn quang. Thng thy kn di chc ba khi ph qun v pht trin lch sang phi. b) Kn mng tim thng khng c triu chng lm sng. Kn c b mng, khng ngm thuc cn quang, hay gp nht gc tm honh phi v cha ng t trng dch trong kn. y chnh l c s phn bit kn vi khi m