: ^lielia^itf^rt^teahg •
Cac phifcfng phap chan doan hinh anh u trung that
PGS.TS. Ngo Quy Chau*, ThS. NguySn Thanh Hdi*
Cac khdi u trung ttiat nguyen phat it gap, ty le chinh xac cac l(hd'i u trung tha't iihong duac bie't ro, tuy nhien ty le ehung vao khoang 1/100.000 nguai. Cac khoi u trung tha't thudng gap bao gdm: u tuye'n Lie, ken trung that, u thin kinh noi tiet, cac khoi u nay chie'm khoang tren 60% so'cac trudng hap u, ken trung that. Trieu chiing lam sang u trung that chu yeu do chen ep cac cau true trung tha't. Co khoang gin mgt nvfa so' truang hgp u trung that khong co trieu chdng, viec chin doan xac djnh khdi u trung that thuang dua nhiSu vao cac ky thuat cha'n doan hinh anh. Cac ky thuat hien dugc su dung phd bien bao gdm: chup X-quang, cat ldp vi tinh (CLVT) nguc co tiem thude can quang. Khi co nghi ngd khdi co xam la'n mach mau, cd thd chi dinh chup cong hudng td hat nhan.
I. CHUP X-QUANG NGITC QUY UffC
Trung that bao gom cac tang nam giua hai phoi. Do trung that dtrgc phu bdi cac la ctia mang phoi, nen cac khdi u trung that nhin cluing c6 bd nhan, trong khi dd cac khoi u phdi do khong dtrgc phii bdi mang phdi nSn thtrdng cd bd go ghS. Cac khoi u trung that thudng dugc phlt hien tren phim chup X - quang ngirc khi thay hinh anh trung that' rong, bd trung thiit c6 hinh anh bat thudng, tuy nhiSn cung cd nhiSu trudng hgp u trung that ma chup X - quang nguc hoan toan binh thudng.
CIc cau true binh thudng cua trung that d bSn phai (tir trudc ra sau) bao gom: cac mach mau canh tay dau, tTnh mach chii trSn, quai tmh mach don, dong much chii ISn vl nhl phai. Ben trai (tir trudc ra sau) co: cac mach mlu canh tay dau, quai dong mach chii, than dong mach phdi vl thiit trii. TrSn phim chup nghieng, trung that trai rpng ttr phia sau xuong uc tdi phia trudc cac xuang sudn.
Khoang 607c cac khoi u truns that nlm d trunc
that trudc, 25% u trung that sau vl khoang 15% u trung that giua.
1. Mgt sd diiu benh ly trong u trung that [1][3]
Trung that rgng
Day la dau hieu thudng gap nhat, trSn X-quang phdi thay bdng trung that rgng hon binh thudng (hinh 1).
' Khoa Ho Hap - Benh vien Bach Mai
Hinh 1. Hinh trdn dich mdng phdi trdi, xep phdi trdi, tii goc sudn hoanh phdi (u lympho dc
tinh khong Hodgkin loai te bdo B)
6 I Y HOC LAM SANG Sd 45 (Thang 10/2009)
ChuySn de trong thing
Dau hieu bong m d
Khdi u trung thit nlm canh tim nSu xoi mat bd tim cd nghla 11 nam vS phia trudc, cdn khi bd tim khdng bi xoi cd nghTa II khdi nly nlm sit trung that sau (hinh 2).
1 • •
Hinh 2. Ddu hieu hinh bdng duong tinh, khdi ndm sdt tim vd xda bd ciia tim tren phim chup I X-quang phdi thang cho thdy khdi u trung thdt trudc
Dau hieu ed - nguc
Dau hieu nly la he qua ciia dau hieu hinh bdng.
Chi u trung that sau hoac nhirng khdi d dinh phdi mdi tiep xiic vdi nhu md phdi d trSn xuong ddn, do vay khi thay hinh anh bd ngoli ciia khoi u trung that d trSn xuong ddn, khdi u trung that dd nam d phia sau.
Dau hieu hoi tu rdn phdi
Khi con nhin thay hinh mach mlu phia trong bd ngoli ciia dim md trung that thi dam md dd thudng la u trung that hoac u phdi xam lln trung that. Day la he qua cua dau hieu hinh bdng giiip phan biet khoi u trung that vdi cic bat thudng mach mlu viing rdn phdi. De xlc djnh nhtrng trudng hgp nly, hien nay thudng chi djnh chup CLVT ngyc cd tiSm tbudc cin quang.
2. Mot sd dau hieu khac
Dau hieu Golden hay dau hieu chir S ngmyc Nhirng trudng hgp khdi u trung thit phlt trien xam lan khi phS quan, gay xep thdy phdi cd tao ra hinh anh chtr S ngugc trong dd phln Idi ra chinh la phan khdi u, phan 1dm vio cua chir S II phln nhu md phdi xep.
Dau hieu khoi bang troi hay dau hieu nguc - bung
Khi mot khdi u trung that dudi, canh cdt sdng cd bd ngoli di chSch ra ngoli va cat ngang co hoanh thi cd nghTa la nd vua nam d long nguc vira nam trong d bung. Day cung II mgt biSu hien cua dau hieu bong md. Bd ngoai ciia khdi d phan bung khong quan sat thay vi tiSp xiic vdi cle cau true phan mSm cd ciing mat do can quang trong khi d phan ngyc, bd ngoai ciia khoi dugc the hien rd do dSp xiic vdi khong khi.
NSu bd ngoli phia thap cua khdi trd lai tien sat vio cot song va van nhin rd d dudi co hoanh thi dd II khdi chi d trong Idng ngyc.
- Hinh tran dich mang phdi, bdng tim to do tran dich mang ngoai tim.
- Hiiy xuong sudn.
- Tha bdng do di can.
II. CHUP CAT LffP VI TiNH
Chan doan benh ly trung that cd budc thay ddi rd ret vdi sy xuat hien ciia chup cit Idp vi dnh (CLVT).
Nhtrng mat phang cit ngang ciia chup cit ldp vi tinh rat phu hgp cho viec danh gia cic clu true trung thit
Chuyen de trong thing
do hau hSt cic clu triie tmng that dSu cd hudng vudng gde vdi mat phang nay. Nhiing dac diSm tdn thuong vl ty trong do dugc trSn phim chup CLVT gidp ggi y nguySn nhan u trung that.
Dya trSn ty trgng va nhtrng dac diem ciia tdn thuang xlc dinh trSn phim CLVT giup djnh hudng chan doln nguySn nhan nhtrng khdi u trung that, tir dd Iya chgn nhiing tham dd phii hgp dS xlc dinh
nguySn nhan. Nhtrng tdn thuang hinh khdi trdn, thanh mdng, nhan, ben trong chira dich thudng dugc chan doln la nang (ken dich) trung that.
Nhtrng tdn thuang dang td cbtre nlm d trung that trudc thudng II u tuySn tre, trong khi nSu trong khdi u xuat hien nhung tdn thuang dang xuong, rang, ty trgng khdng ddng nhat thudng dugc chan doln la u quai trung that.
Hinh 3. U trung thdt vdi thdnh mdng, ty trong khdng ddng nhdt. Choc hiit thdy hinh dnh sgi tdc, cdc tdn thuong dang md" (u quai)
Chup CLVT cho phep dinh gia tdt nhung cau triie cd true thang dimg nhu khi quan, thuc quan...
tuy nhiSn ky thuat lai cd ban che trong viec danh gia nhtrng cau triie nam ngang (chang ban nhung tdn thuang d cira sd chu - phdi vl nhtrng tdn thuang dtrdi carina), bSn canh dd khd khan trong viec dinh gil bd cle tdn thuang, dac biet trong phan biet tdn thuang cd xam lan mach mlu hay khdng, ngay ca khi chup cd tiem tbudc can quang tTnh mach. TrSn hinh anh chup cit Idp vi tinh khd cd the phan biet gitra tdn thuong nam canh hay da xam lan vio cic cau triie trung that, gitra khdi u trung that xam Ian vio nhu md phdi hay chi la xep phoi do khoi u trung that chen ep phS quan va gitra hach trung that do di can hay phi dai hach trung thit lanh tinh [5].
III. CHUP CONG HirdNG TIT HAT NHAN (MRI) Chup cdng hudng ttr hat nhan (MRI) II ky thuat dinh gia td chirc thdng qua viec do ludng tan suat sdng radio dugc tao ra bdi cic hat nhan
trong CO the khi dugc dat trong mdt tir trudng co cudng do ldn vl dugc cung cap nang lugng dudi dang sdng radio ngat quang. Kha nang tao hinh Inh tir trudng khdng chi cho Inh theo mat phang cat ngang ma cdn cung cap cac hinh anh theo chieu cat dgc. Ky thuat rlt thich hgp cho viec danh gil cac cau trtic theo chiSu thang diing vl bd tiSp gilp gitra cle td chuc. Cd the dS dang nhan biSt hinh Inh mach mlu trSn phim chup cdng hudng tir ma khdng can sir dung tbudc can quang [5]. Nhtrng vat lieu kim loai cd thS gay anh gia trSn phim chup cat Idp vi dnh nhung thudng khdng gay trd ngai khi chup MM, mac du nhtrng thiSt bi nly cd the bj hut rat manh.
MRI dang dugc su dung ngly cang nhiSu trong dinh gil trung thit, dac biet khi can dinh gil dnh trang xam lln cac thanh phln trung that ciia cic khdi u trung thit. Hien nay, tinh uu viet ctia ky thuat MRI so vdi chup elt ldp vi tinh trong dinh gil liSn quan ciia trung thit trong ung thu phS quan van chua rd.
8 IY HOC LAM SANG So 45 (Thang 10/2009)
Chuyen de trong thang
Mdt nghiSn cuu Idn, da so sinh vai trd ciia hai ky thuat MRI vl chup elt Idp vi tinh nhan thay, hai ky thuat cd do chinh xlc tuong tu nhau trong phlt hien bach trung thit, mac du MRI uu the hon trong viec dinh gia cic khdi u xam lln true tiSp tmng thlt[5].
Theo Tomiyama N va cdng sy (2009) chup CLVT nSn dugc xem la Iya chon dau tiSn sau chup X-quang trong chan doln cic khdi u trung that, tuy nhiSn vdi nhung tdn thuong ken trung that nghi ngd cd chay mlu hoac viem thi nen lya chgn chup MRI [6].
Tuong ty chup cat Idp vi tinh, MRI cung cd nhtrng ban chS. Ca hai ky thuat dSu khd tich biet gitra khdi bach rdn phdi vdi vung phdi xep hoac dong dac bSn canh. Ca hai ky thuat dSu cho phep xac dinh su chen ep hoac de day thyc quan hoac khi quan do u, nhung khdng chi rd cd hay khong kem theo sy xam Ian nhtrng cau true nly v l quan trgng hon ca, ca hai ky thuat dSu khong cho phep khang dinh bach trung that Ilnh tinh hay l c dnh.
IV. SIEU AM
SiSu am hiru ich trong chan doan cle khdi trung that cd ban chat ken nhu ken phe quan hoac ken mang ngoli tim, tuy nhiSn ky thuat khong cho phep phan biet rd ring ken Ilnh tinh hay ac tinh.
Ca hai dau dd siSu am xuySn tblnb ngyc vl sieu am qua ndi soi deu hiru ich trong dinh gil cic benh ly trung that. BSn canh dd, trong nhtrng trudng hgp khdi u trung thit Idn, nam sat thanh ngyc, siSu am cdn hudng dan ky thuat sinh thiSt khdi u trung that.
Vdi su xuat hien ciia siSu am qua ndi soi thyc quIn hoac khi quan giiip chan doln cle tdn thuang trung that, bSn canh dd cdn budng din sinh thiSt xuySn tblnb thyc quIn hoac khi quIn cho cle khdi u trung that tya sit thInh thyc quan hoac khi quan, hoac chgc, sinh tbiSt cic bach trung thit d cira sd chii phdi, bach canh khi quan, canh thyc quan vdi ty IS chan doln xlc dinh dat 63 - 98%.
V. CAC KY THUAT XA HINH
1. PET Scan (Positron Emission Tomography Scan) [2]
PET Scan la ky thuat chan doln hinh anh dua tren boat tinh sinh hgc cua tS bao ung thu. CIc tS bio ung thu cd kha nang hap thu chuySn hoi glucose cao hon cic tS bao binh thudng. Dya vao dac tinh nay, sir dung cle chat phdng xa gan glu- cose (18FDG = 18F-fluoro-deoxy-D-gIucose), chat nay chuySn h o i theo con dudng chuySn hoi glucose thong thudng. CIc glucose cd gin chat phdng xa, sau khi dugc phosphoryl hoi, chiing khong bi chuySn boa tiSp va dugc luu gitr trong tS bio. Sir dung miy quet PET dS phlt hien sy tich liiy bat thudng cua c l e chat phdng xa. PET Scan do vay dugc xem la ky thuat chan doan hinh anh chuySn boa dya tren chuc nang cua td chirc ban II cau triic giai phau. TiSu chuan dinh gil cd bat thudng tren PET scan bao gdm:
- Gil tri hap thu cua td cbtre u > 2,5 Ian gia trj chuan binh thudng.
- Gil tri hap thu ciia td chirc tdn thuong > boat ddng hap thu nen cila trung that.
Sau khi tiSm tTnh mach mdt liSu 18FDG, chat nly dugc phan bd vio trong mlu va dugc chii ddng van chuySn qua mang tS bao. Budc dau tiSn cua qui trinh chuySn hoi la sy phosphoryl hoi glucose vdi men hexokinase, men nly chuySn glucose tblnb glucose 6 phosphate (G6P) vl fluorodesoxyglucose thanh fluorodesoxygIucose-6-phosphate (18FDG- 6P). Tuy nhien d qui trinh chuyen hoi binh thudng, men glucose-6-isomerase chuySn glucose-6-phos- phate thInh fmctose-6-phosphate. Trong khi dd men gIucose-6-isomerase khdng cd tic ddng tren 18FDG-6P: chat nly clng tap trung nhiSu khi cd tang van chuyen te bao. Rlt it 18FDG-6P dugc tiSu huy vdi qui trinh phosphoryl boa do vay nd dugc tich tu lai, do dd dugc phlt hien. Sy cd djnh ciia 18FDG phu thugc vao nhiSu ySu td, sy cd dinh nly tiing ISn khi khdi u dugc tudi mlu tdt, nhieu mach mlu vl viem quanh khdi u. Chinh vi ySu td cudi
Chuyen de trong thang
ciing nay lam cho ky thuat rlt nhay nhung khong dac hieu. PET scan cd bieu qua trong chan doln phan biet td chtic u ac dnh vdi to chirc binh thudng vdi do nhay khoang 96%, do dac hieu 79%, do chinh xlc 91 %. Tuy nhiSn ky thuat nly khdng hieu qua trong nhtrng trudng hgp u nang, cic benh ly viSm ciing nhu nhiSm trung. Cac benh ly nay cting cho kSt qua PET scan duong tinh.
PET cd the cd kSt qua am tinh gil d nhtrng khdi u cd chuySn hda thap nhu u carcinoid, ung thu tiSu phe quan phS nang hoac am tinh d nhUng khdi u cd kich tbudc dudi 1cm. BSn canh dd cd thS gap PET duong tinh trong viSm phoi, Ip xe phoi, aspergillosis phdi, cle benh u hat nhu sarcoidosis, lao, histoplasmosis, coccid- iomycosis, u hat Wegener.
Khdng chi dya vio gil tri hap thu FDG dS phan biet cic tS bio Ilnh tinh va lc tinh, m l c6 thS dya c l vao tdc do hap thu FDG. Do ludng hap thu FDG d hai thdi diSm 1 va 2 gid sau tiSm FDG, neu gil trj hap thu FDG d thdi diem 2 gid sau tiSm ldn hon gil tri hap thu FDG d thdi diem 1 gid sau tiSm trSn 10% thi cd thS xlc dinh II tdn thuang lc dnh.
Sir dung so sanh vS tdc do hap thu FDG dugc xem II chinh xlc ban gil tri ngudng FDG 2,5 va dugc xem la se dugc su dung phd biSn trong tuong lai.
Chup cat Idp vi tinh rat c6 gil tri trong danh gil kich tbudc khdi u, tinh trang xam Ian tdi cic to chirc bSn canh, PET co do nhay cao trong danh gil tdn thuang xam Ian hoac di can tdi cic co quan khlc. Tuy nhiSn ky thuat chup cat Idp vi tinh dya trSn viec tao anh khdng gian 3 chiSu, con ky thuat PET tao hinh anh dya chu ySu trSn boat ddng chuc nang ciia cle tS bio. He thdng kSt hgp PET/CT lam gia tang muc do chinh xlc trong chan doln, bSn canh dd cdn llm gilm ding ke thdi gian tham khIm.
Sy ket hgp PET/CT cho phep xlc dinh chinh xlc kich thude khdi u, bSn canh dd cdn cho phep dinh gil dnh trang l c tinh ciia khdi u. PET/CT cung cap nhiSu thdng tin hiiu ich trong chan
doln ban la sir dung PET hoac chup cat Idp vi tinh dan thuin. Vdi nhung khdi u cd kich thude dudi 1cm hoac nhirng khdi u cd chuySn hda te bao thip (u carcinoid, ung thu tiSu phe quan phe nang) co thS' bi bd sdt chan doan khi chi dinh PET don thuin, nhung lai dugc chan doln chinh xlc khi sir dung he thdng PET/CT. Nhtrng ban chS khlc ciia PET trong viec dinh gil xam lan thanh ngyc, trung thit hoac cle cau true liSn kS cung bi loai bd khi sir dung kSt hgp he thdng nay. Ben canh dd, nhtrng han che ciia chup cat ldp vi tinh trong viec phan biet gitra khdi u phdi vdi nhu md phdi bj xep do tac nghen phS quan Cling bj loai bo.
He thdng'chup PET/CT cho phep chin doln giai doan hach trung that trong ung thu phoi chinh xac ban khi sir dung PET hoac CT don thuin. Theo Antoch G v l cdng sy (2003), ty IS xac dinh di can bach chinh xlc vdi CT la 63%, vdi PET II 89% v l vdi PET/CT la 93%. BSn canh dd, sir diing PET/CT cdn cd thS phlt hien c l dtrgc hach thugng ddn do di can ung thu (N3) khdng thay dugc khi kham lam sang, nhirng trudng hgp nay thudng bj bd sdt khi chup cat Idp vi tinh hoac ngi soi trung that [2].
Sir dung kSt hgp PET/CT lam gia tang ty le chan doln chinh xlc nhtrng trudng hgp khoi u trung that cd di can, bSn canh dd cdn lam gia tang sd vj tri dugc phat hien cd di can.
Nhu vay, viec sir dung kSt hgp PET/CT cung cap nhieu thdng tin hiru ich ban cho chan doln, giup phan giai doan ung thu phdi vdi do nhay vl do dac hieu cao ban ban khi sir dung chi PET hoac CT dan thuan. Tuy nhiSn, PET/CT khdng thay the hoan toan dugc cic tham dd chan doln giii phau benh.
Cac ky thuat xa hinh khac
Xa hinh hai chiSu vdi gaIIium-67 (67Ga) dugc sir dung trong dinh g i l trung that trudc md d cac benh nhan ung thu phe quan, tuy nhiSn kSt qua it kha quan. Trong nghiSn cuu so sanh xa
1 0 IY HOC LAM SANG So 45 (Thang 10/2009)
Chuydnd^ trong thang
binh 67Ga vdi chup X - quang phdi chuan v l chup cat ldp vi tinh. Dooms va Hricak cho rang nhirng ky thuat tham dd phdng xa hat nhan cd do chinh xlc thap. Xa hinh 67Ga cd q u i nhiSu kSt qui duong tinh gia do sy hap thu thuoc khdng dac hieu ciia nhtrng bach viSm llnb tinh v l bd sdt nhirng bach ung thu nhd.
Mdt sd ky thuat xa hinh ddi khi dugc sir dung danh gil trung that trong nhtrng benh ly cu thS, nhu xa hinh iodine thudng dugc chi dinh khi nghi ngd tuySn gilp lac chd trong trung that. NhiSu nghiSn cuu cho thay xa hinh nuclide cd thS dugc sir dung dS xlc dinh nhtrng khdi u trung that dac biet.
Chup cat Idp phlt xa dan photon (SPECT) sir dung dau dd phlt tia gamma chuan giiip tao anh cat ngang tuong tu nhu chup cat ldp vi tinh thdng thudng. Ky thuat giiip cai thien do nhay trong chan doln nhd do phan giai hinh anh va cic thdng tin giii phau tuong ung vdi hinh anh hai chiSu. Do chinh xlc ciia 201TI-SPECT trong xlc dinh lien quan ciia bach trung that vdi benh ly ung thu phdi tuong tu nhu vdi chup cat Idp vi tinh, tuy nhiSn khong dii do nhay va do dac hieu de phan giai doan phau thuat cho benh nhan.
VI. MOT SO KY THUAT CHAN DOAN HINH ANH KHAC Chup thyc quIn cd barit cho phep xlc dinh nhirng ton thuang chen ep thyc quan ttr ngoli, tdn thuang bSn trong thyc quan hay tdn thuang d thInh thyc quan (kS ca Id dd thyc quIn). Chup mach CO thS hiru ich trong nhirng trudng hgp chen ep hoac cd xam Ian mach mlu, xac djnh nhtrng mach mau nudi khdi u. Chup tiiy sdng giiip xlc djnh chen ep tiiy sdng ciia nhirng khdi u trung that sau, phan biet gitra u than kinh v l tholt vj ming nao, tuy nhiSn, nhiing ky thuat nay hien dugc thay thS nhiSu bdi chup elt Idp vi dnh v l chup cdng hudng tir.
Nhirng ky tbuat bom khi hien it dugc Ip dung trong chin doln d My, nhung btru ich trong mdt
sd trudng hgp. Nhirng tham dd chan doln nly bao gdm gay trin khi ming phdi dS xlc dinh khdi u trung that cd dinh vdi trung that hoac thanh ngyc. Bom khi d bung dS xlc dinh tholt vj CO hoanh d phia trudc (tholt vj Morgagni) hay tholt vi phia sau (tholt vi Bochdaiek). Gay tran khi trung that cd thS giiip phan biet rd cle thanh phan trung that •
TAI LIEU THAM KHAO
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3. Jannette C; Eric SJ. (2008). Mediastinal Masses.
Chest radiology: The Essentials, 2nd edition. (6), 79 - 100.
4. Link KM, Samuels U, Reed JC. et al. (1993).
Magnetic resonance imaging of the mediastinum and its contents. J Thorac Imaging; 8:34-53.
5. Martini N, Heelan R, Westcott J, et al (1985).
Comparative merits of conventional, computed tomographic, and magnetic resonance imaging in assessing mediastinal involvement in surgically confirmed lung carcinoma. J Thorac Cardiovasc Surg; 90:639-648.
6. Tomiyama N, Honda O, Tsiibamoto M, et al. (2009).
Anterior mediastinal tumors: diagnostic accuracy of CTand MRI. Eur J Radiol 69 (2). 280-8.