Tap chi Tin hoc va Dieu khien hoc. T.26. S.4 (2010). :351-360
XLT LY A N H Y TE 4 0 - CT CHIU NEN SU" DUNG MANG NffRON TE BAG
C A P THANH TUNG ^ PHAM T H U Q N G CAT ^
^Phdng CNTT-TV. Trudng Dai hoc Su Pham Thdi Nguyen
^ Vien Cong nghe thdng tin, Vien Khoa hoc vd Cdng nghe Viet Nam.
A b s t r a c t . W i t h regards of 3D image, we use the concept of voxel(\'ohimetric cell) instead of pixel (picture cell). A single voxel consists of [x.y.z) for 3 .space dimensions. Database of voxels can describe large structures and can be applied in many fields: architecture, video game, geology, as- tronomy, satellite image ... and, especially, in processing medical image. It is noted in the research of anatomy image from computed tomography of brain, lung, heart, thorax, hips... that those struc- tures contijiuousl}' and periodically change their position and size (due to respiration rhythm, pulse break, moveiiient of muscles and articulations,..) .so the presence of time factor in parameter set of voxel is required. The processing of motion image concerns 4D-CT(4 Dimension Computed Tomog- raphy) scanning techniques and requires IR (Image Registration) techniques. There are many image registration approaches corresponding to various registration criteria (optical flow speed, calculation model, geometric feature ...). They are widely applied in analysis and calculation of medical images.
Neverthek^ss. each approach still has issues to be addressed (both accuracy and calculation sjieed op- timization). With medical image in general and with analysis of lung polyps diagnosis image, there is always considerable discrepancy. In general, the result will be rather good if intensity in image is unchanged , but this is impractical because lung is always in motion (due to respiration rhythm) and intensity- on object (lung tissue) will be changed accordingly, which in turn leads to many errors ill analysis. We call C T image of elastic tissues compressible image. Moreover, we investigate the calculation of optical flow speed of 4D-CT compressible image. This proces.sing has a large number of image data and the calculation of optical flow speed is very complicated. So high processing speed is required and this is a great challenge for the P C , In this article, in order to improve calculation s]-)ccd. we propose a processing with CNN for calculating 4D optical flow speed in real time mode,
T o m t a t . Vai anh 3 chieu, t a sii dung khai niem voxel (Volumetric Cell) thay vi pixel (Picture Cell) ciia 2D. Moi phan tii voxel d a n chira d u n g cac t h a m sd (x, y. z) cho 3 chieu khong gian. T a p hgp dfr lien ciia cac voxel co the mo ta cho cac hinh the \an. irng dung trong nhieu hnh vuc: kien tnic, liMjii iiiiih (Video Game), dia chat, thien van. anh ve tinh,... va dac biet trong xu ly anh y te. Khi nghien ciiu cac anh pliau thuat co d u g c tir cac anh chup cat lap C T (Computed Tomography): nao.
phoi, tim, long ngirc, x u a n g chau... cac klmi hinh nay con lien tuc thay ddi vi tri va kich thudc theo chu ky (nhip tlia. mach d a p . sir van dong ca, khap..,) nen can tai yen td thai gian (t) trong b(> tham ao ciia voxel. Do do \-iec xir ly anh d(?ng lien quan tai ky thuat scan 4D-CT (4 Dimention Computed Tomograpjiy), Qua trinh xir ly anh 4D-CT can den ky thuat xac nhan anh IR (Image Registration) ma biin cliat la xac dinh cac diein anh t u a n g thich gifra hai anh lien ke trong qua trinh chuyfui dong.
Co iiiiieu p h u a n g phap xac nhan anh khac nhau. iriig vdi cac ticu chi nhau dang khac nhau (theo tdc (1() ciia hmng anh (Optical Flow), theo mo hinh tinh toan. theo dac rti(--m iiiiili hoc...). C'iiiiiig
352 CAP TH.ANH TUNC - PH.AM THUCTNG CAT
dugc ling dung rong rai trong cac phan tich va tinh toan cho dong anh y te. Tuy vay con kha nhieu ton tai trong moi phuang phap, can dugc giai quyet (ca ve do chinh xac Ian viec tdi uu hoa tdc do tinh toan). Vol cac anh y hoc noi chung va vdi viec phan tich anh cho chan doan u phdi noi rieng, luon vap phai cac sai si5 Ian do tiihi co dan cua cac te l^ao va cac nhieu tir tinh thu dugc, Nhin chung cac ket qua se kha tot neu cudng do anh sang tren moi diem Anh khong thay doi (phuang phap ciia Horn/Schunck), nhung day la dieu khdng thuc te vi phoi luon van dong theo nhip thd va vi vay cudng do sang tren vat the (md phoi) cung bien doi theo. gay ra nhieu sai sdt cho qua trinh phan tich, Ta goi cac anh CT cua cac mo chin tac d(5ng co dan la cac anh chin nen (Compressible Image), O day, ta khao sat viec tinh toan tdc do dong anh (Optical Flow) ciia anh chiu nen CT 4D, Cac anh 4D co khdi lugng diem anh Ian vai cac tinh toan dong anh co do phirc tap cua tinh toan rat Ian doi hdi tdc do xii ly cao la mot thach thiic Idn cho cac may PC xir ly tuan t u hien nay, De nang cao t(5c do tinh toan, tac gia da de xuat mot mo hinh mang naron te bao xir ly song song co kha nang tinh tdc do luong anh 4D trong che d(3 thdi gian thirc.
1. D A T V A N D E
Tir nhirng nam 198-5, ky thuat xu ly luong anh 2 cliieii da dirge de x u a t de thu nhan dfr lieu van tdc cua mdi di(;m anh chuyen ddng. Ngay nay, vdi khdng gian 3 chieu cac qua trinh xu ly t r d nen phiic tap ban vdi dan vi xii ly la cac voxel cliii khong cdn la pixel iiira. Cac anh chup cat ldp 4 chieu (4D-CT) dugc ung dung nhieu trong y ' t e , no t r g giup dac lire cho cac chan doan y lipc cung nhu qua trinh danh gia boat ddng ciia u birdu dugc cliuih xtic ban, dac biet d khu vuc long ngirc (u phoi). Ctic anh 4D-CT cd the chiia tdi 20 khdi anh (Image Volume) 3 chieu cho mdi pha, vdi kich thudc dtit tdi 512x512x200 voxel moi khoi. Ngoai khdi lugng khdng Id ve dfr lieu, ta cdn luon phai ddi mat vdi cac sai sd do qua trinh hd h a p gay ra, tao chuyen d(Diig co dan tren cac b(D phan ca the ma t a dang quan tam. Van de nay da dugc trinh bay trong hang loaf h(ii thao khoa hoc, vdi sir ddng gdp ciia nhieu nha khoa hoc: Sarut (2006) d u a ra cdng cu phan tich anh chieu xa. Kessler (2006) cd each thiic thu t h a p dir lieu anh tir nhieu p h u a n g thirc khac nhau. Guerrero. GZhang. Segar. Huang, Bilton (2007) vdi ky thuat danh gia anh 4D [8].... Rat nhieu giai phap ky thuat d u a ra da d u a t r e n . p h u a n g phap cua Horn va Schunck (de xuat cho anh 2D tir 1981) de tinh toan tdc dp cua diem anh trong luong anh (chuyen ddng) [9]. Atet sd tac gia bo sung them cac rang budc va gia thiet de giai bai toan toi uu [10]. Ngoai ra phirang phap cua Lucass Kanade de khii nhieu luong anh 3D bang pli<;p tich chap vdi ham phan bo Gauss cung dugc phdi hgp sir dung [11]. Nhirng hau het cac tac gia chi dirng lai d xu ly anh 2D chin nen, hoac 3D khdng chiu nen va giai quyet bang phuang phap lap cho tluuit toan Gauss- Seidel. Trong khudn kho bai bao, se tiep tuc phat trien va phtin tich ky h a n ve md hinh bai toan xii ly anh 3D chiu nesn, dong thdi de x u a t can tnic mang naron te bao (CNN) 3 ldp 3D cd the tinh dugc tdc dp luong anh 3D vdi toc dp cao. Cac ket qua mdi chi mang tinh ly thuyet va se tiep tuc dugc phat trien trong thdi gian tiep theo, by vong mang Itii uwt p h u a n g phap mdi cho Ihih vuc xir ly tinh ddng 4D-CT trong nganh y te.
2. B A I T O A N T I N H T O C D O C U A A N H C H I U N E N 4 D
Khi plitiii tich anh ddug. ni(?t van de quan trpng la phai xtic dinh d u g c thih t u a n g thich
XL" LY ANH Y TE 4D - CT CHIU NEN SL'' DUNG MANG NORON TE B.AO 353 ciia cac diem anh gifra hai anh ke tiep, Tdc d(i) ciia mdi di(=m anh trong cliiidi anh cliu>'(i"n d(iiig (Optical flow) la m(it dac trung quan trpng de giai quyet van de nay, Ddi \'di anh chup cat ldp cudng dp anh sang ciia mdi diem anh I[x, y. z. t) ty le vdi mat dc) ciia cac md te bao p[x. y, z. t) trong dd x, y, z la tpa dp trong khdi khdng gian Q. ta khao siit \-a t la thai gian, Nhu vav ta cd the md ta ve mat toan hoc diem anh 4D nhir sau
/ ( x , t ) ~ p ( x , t ) , (1)
trong dd .t e[{).l\ . x e Q. va n e 3R'^ Trong liaii het cac phuang phap xu ly anh cat ldp ngudi ta deu gia dinh rang mat dp te bao t u a n g duaiig vdi cudng d(i tinh sang cim mdi voxel khdng thay ddi theo thdi gian / ( x , t) ~ /3(x. t) = con.st . Cd nghia la
trong dd , R 5 /
dt . va : V / = dt - dl -
?fi d^i
- dz -
— ^i - r V J V — \J.
=
' I.r '
ly . v = ' dx -
- Ot -
=
II
r ir
Phuang trinh (2) dugc gpi la plimrng trinh btio toan khdi lir(rng (conser\-iitioii of mass) the hien thih lii-n tuc hay gpi tat la phmnig trinh lit'ii tuc (continuity (>f|uatioii) cua tinh cd cudng cM) khdng ddi theo thdi gian lia>- cdn gpi la tinh khdng chin nen (iincoiiipressibl(> image).
Trong trudng hgp anh CT(Coinputed Tomography) long ngirc, mat d(3 tt^ bao thay doi tir dnh nay sang knh kia do cd su co ncr cua phoi trong qua trinh hd hap. Tuy nhien, cho du mat d(i te liao cue hg khdng dong deu d phoi ta van gia thiet dugc rang tdng khdi lir(/iig cim pluii khdng thay ddi trong qiui trinh hd hap
(3) /9(x, 0 ) ( i x = / /y(x. l)(ix.
Luc nay phuang trinh ]:icio toan khdi lugng cd dang
trong dd.
/f-f V / ^ v - h / d i i ' ( v ) = 0,
,. , , dvj: dvy dv, dtv[v) = — 1 — h —-—
dx dy dz
(4)
la divergence cua vecta toe dp diem tuili v(Optical Flow). P h u a n g trinh (4) cdn gpi la phirang trinh tdc dc) cha tinh chin IK>II (Compressible Image).
u{x,y,z) v{x,y,z) w[x.y.z)
tdc d() (2) hotic (4) dVui kluiiig du dieu kien. Do vay ta can tim tliimi cac dii'Mi ki(;ii lim^ biuic De tinh dugc t(5c dp luong anh v vdi 3 an sd thi dii rii^ig ])liu(nig trinh
354 C A P THANH TUNG - PHAM THL^O'NG CAT
khac de cd the tinh d u g c vecta tdc d(? luong anh v mdt each n h a t quan. Ap dung y tirdng cua Horn - Schunck [9]. phdi hgp p h u a n g trinh (4) vdi gia thiet toc d(? ciia cac voxel Ian can it thay ddi vao trong mot phieni ham (5) va tim gia tri tdi thieu hda phiem ham nay
iiiin I I \[lt + V / ^ v + Idiv[v)]' + a-J2 l | V t ' ; f \dx.
o V ' = 1 )
(5)
trong dd Q > 0 la he sd lam trail tir chon. Ta cd the tim d u g c v de tdi thieu hda phiem ham (5) bang p h u a n g phap bi(;n i-)haa(Variational Calculus). Do (5) la iii(3t phiem ham loi binh p h u a n g nen dieu kien can va du cua v tdi uu la thoa man he p h u a n g trinh Euler-Lagrange t u a n g ling
df d df dx dt dv 0.
va dieu kien bien la:
[Vv^ -h / / ? e , ) ^ n = 0:i = 1. 2. 3.
Trong (6) va (7) ta sir dung cac ky hieu
f = h'-+a^J:\\Vv,f,
?,=i
h = It + Vl'^v + Idiv{v),
(6)
(7)
(8)
vdi e, la vecta dan vi cua true /'. n la vecta phap tuyen cua mat bien. Sau khi thih ctic dao ham cim (6) va nit gpn. plnrang trinh Euler-Lagrange cd dang
-IVh - a V^ 16'
(9)
Tie\) tuc trien khai plnrang trinh Euler Lagrange (9) ta dugc he p h u a n g trinh (10) nhu sau I{It.r + /.rx« + 2/r»x + lyxV + /yt'x + h^^W + Lw^ + lu^,^ + I^Vy + Iv. -f I^W, + Iw,^)-\- L{Ity + IryU + 2IyUy + lyyV + I:,Uy + I,yW -h hWy + lyU:, + IU:,y + IVyy + I W, + Iw,y) + a'^Vl = 0
/ ( / ( , + I^,U + 2LW, + Iy,V + I:,U, + h,W + lyV, + I,U^ + lu^, + IVyr + hVy + IW,,) +
trong dd,
V^ la totin tir Laplace
&^U
(10)
t/r
d^ d^ &^\
dx"^ dy"^ dz'^ J d'^I , d'^I
d^I d^I
tx dtdx • ^•'•"" a ? - ^>J'- - dx-2 2- -''!/ dtdy hr
dxdy L yy d'^u
yy dy' 5 • '-^^•rij
d^I dijdx'
dHj_
dxdy De cd the tinh dugc hn^ng anh v ta can giai he plnrang trinh (10). P h u a n g jihtip so la p h u a n g phap duy iihtit hien na>- dugc dung de giai bai toan optical flow. Thong t h u d n g nguai
-XL" LY ANH ^' TE ID - CT CHIU NEN Sl> DUNG .MANG NORON TE BAO 355 ta rdi rac hda cac phep thih vi phan vdi ctic budc khdng gian diiian hda /i^. = hy — h^ = I
nhu sau
L = {T^i.j.k - I.-i.j.k) /2 : ly = {I,.j+i.k - T^j-i.k) / 2 : / , = {I,.j.k+i - I,.j.k-i)/2.
Totin tir Laplace V^ dugc rdi rac hda : V„ = 6u,,j,k — '-'i.j.k- vdi
Ui.j.k = {iM+i.j.k + Ui-i,j,A- + Ui.j-\-i.k + Ui.j-i.k + u,,j,k.+i + <Ji.j.k-i)-
V^, ; V^, cung dugc thih tinrng tu.
duij 1 N A d'^Uj J
-g^ = 2("'+i-J - ^'--L:]) = ^xu,.j: - ~ - = [2iH,j - Uj+ij - u,^ij) = A^.^.u,,j,
"*^j = 2^"'+^'-' "^ " ' - i j ) 5 uij = -Aui+i.j + Uj_ij -\- Uij+i + u,,j-i), d'^Ui,j 1
dxdy 7 ( " / - | - l . j - l - l - '"7 + l . j - l - " ; - l , j - | - l + " i - l . j - l ) = ^xyUjj.
Thay the cac phep thih xap xi tren vao plurcrng trinh (10), ta cd plnrang trinh Euler- Lagrange dudi dang rdi rac (11) nhu sau
HLx + IxxUj.j.k + 2Ij.Aj:U,j,k -\- IyxV,.j.k + Iyl\xVi.].k + IzxWi.j.k + I-AxU-'j.j.k +
2/(Wi,j,A; - K.j.k) + ^x^yVi.j.k + I^yxVj.j.k + h-^zWi.j^k + I/^zxU'i.j.k) + QQ'-{u,j_k " ~dijk) = 0 I{Ily -h IryU,,j,k + '^ly^yl'i.j.k + T/y''i.,i.k + Ix\u,.j.k + FyU>,.j.k + L^yWjjJ. + 2/(c,,;,A- - V*jf^.
-\-IyA,rU,.j.k + lA^yUjjj. -\- lyA^Wi^j^k + IA ^yW i j ,k) ^ 6a''{vjj,k - VTJM) = 0
I{Itz + IxzU,.j.k + 2I,A-,U)ij^k + lyzVjJ.k + IxA,Jli,j,k + IyA-V,j,k + IzzWjj.k + 2/((('j,j,A- - '"Ij.k, +IzA:,njj,k + I~AyV,^j^k + IA,,.Ui,j^k + IAy,v,j^k) + 6O^(U';.J.A- - u^ijj) = 0-
(11) Bai toan tinh tdc do cac diein anh 4D-CT trcr thanh bai toan giai ]\c phwang, trinh Euler- Liigrange rdi rac de tim ctic gia tri tdc dp ciia ctic diem anh rdi rac //,.y.A. r,.j.k, «'i,j,A' tnjiig klmi khdng gian klitio stit 0 . Dtiy la in(it bai totin cd dc) thih totin phirc tap va rat Idn. Vdi Anh 4D-CT cd the chiia tdi 20 khdi anh 3D cho vdi kich tlimrc dtit tdi 512x512x200 voxel mdi khdi, ta cd td'ng sd lugng voxel can tinh totin len d(;n tren 100 trien dicim anh. Day hi khdi lugng chi lieu khong l6 ma cac phuang phap xii ly anh thdng thudng tren cac may PC tuan t u khd cd the cho Idi giai nhanh chdng, nhat la vdi ctic >-(?ii can xii ly anh chuyen ddng thai gian thuc. Bai bao da de xiitit phuang pluip xir ly song song sir dung mang ncrroii te. bti.o CNN de tiiiig tdc d(^) trong \-iec gitii bai totin optical flow cho cac anh 4D-CT chin luhi nay.
3. P H U O N G P H A P X A C D I N H T O C D O L U O N G A N H C H I U N E N 4 D S t r D U N G M A N G N O R O N T E B A O
Mang lurroii te bao CNN (Cellular Neural Network) la he xir ly song song, dap ung yen cau ve mot he xu ly toc do cao, nhat la trong xii ly anh [4, 13]. Khdi mach ca ban cua CNN hi te bao (cell). Nd dura ctic phan tir mtich tuyen tinh va phi tuyen. Mdi cell chi ket ndi vdi Ciic cell Icing gieng. Ctic cell lien ke cd the anh hudng true tiep den iihtiu. Cac cell khdng lit-n k{'t irirc tiep cd the tac ddng den ctic cell khac gian tiep bdi sir ttic d(jng Ian tru>-eii ciia nit.ing CNN. Moi cell C,j cd cac te biio king gieng Ckj • Ctic iihinnig trinh ca btiii nui ta lumt dong cua mdi ((' btio cim CNN ni()l kV]) 2D nhu sau:
356 C A P THANH TUNG - PHAM THUO'NG CAT
-I- P h u a n g trinh trang thai:
iij = -x,j +z,j + Y^ A{i. j : k. l).yki+
P h u a n g trinh dau ra:
Vi.j
C t ' S S j j l r )
/ ( ^ U )
^ B{i.j:k.l).Uki.
ij-u + l| + 2 l-^''^'
2 1|
(12)
(13) Ta thay he plnrang trinh ca ban (12). (13) cua mang naron te bao la mdt he lien tuc ve thdi gian vk rdi rac ve khdng gian. Do cau true ciia cac te bao la n h u nhau nen rat thuan Igi cho ^iec thirc hien mang tren chip. Chirang trinh xu ly trong CNN d u g c thirc hien thdng qua ctic lenli md ta sir ket ndi cue hg gifra cac te bao trong mang A , B , Z (template). Mdi lenli ling vdi ni(3t template. Trong t h u vien cua CNN cd cac template ca ban va nga\- cang dugc bo sung phong phu han. Ngirdi lap trinh cdn cd the t u tim cho mdi bai toan nliirg template dac trung tiiy theo yeu can xir ly. Khi xii ly bai toan, chiing ta plitii xay d u n g md hinh toan hoc cho bai totin vk tim cac template phii hgp. De xac dinh tdc dc) cua mdi ^'oxel ta can phai giai he p h u a n g trinh Euler-Lagrange rdi rac (11). Ta cd the nhan dugc nghiem cua (11) bang viec tim nghieni on dinh cua he p h u a n g trinh vi phan theo thdi gian ao r sau
du,
dr HLx + IxxUij.k + 2I:,AjcUjj,k + IyxV,,jM + lyA^Vij^k + IzxWi.j.k + IzAj.Wj,_ j.k
-f2/(u,j.A. -u*ii,) + IxA.yV,,j,k + IAy,rVi,j,k + IxA:,w,,jM + IA^xWi,j,k) + 6a''{ui,j,k - «,.,;•) 5 ^ = ^(-^t'y + I-ryUi.j.k + 2IyAyV,,j,k + lyyVi.j.k + IxAyU,j,k + LyWi.j.k + h^yU'i.j.k +2/(ui,j,/c - c^j A-) + LyA-,u,j,k + IAj,.yU,,j,k + IyA,w,^j_k + IA-yW,,j_k) + Qa'ivj.j.k - vijj^) _ J ^ j j ^ = I{Itz + IxzU,,j,k + 2FA,W,j,k + lyzl'i.j.k + /xA,Uj.j,A,. -f lyA-A'i.j.k + hzW^j.k +2/(wi,j,A - w*jj^) + hA.^.u.ij,k + LAyVij,k + IAxzUij,k + IAy:,v,,j,k) + 6a''{w,,j,k - W~JM)
(14) Ta xtiy dirng cau true CNN giai he p h u a n g trinh vi phan (14) tren n h u Hinh . Dtiy la nipt mang CNN 3 ldp 3D.
Ldp tren cung de tinh thanh phan toc do Uij,k ciia voxel {i,j,k) trong khdng gian 3D.
ldp gifra tinh thanh phan tdc d(3 v,,j,k vk lap dudi de tinh thanh phan tdc d(3 U',-,J.A-- Trang thai cua mang la tdc d(3 voxel v ( x . y, z). Hai anh 4D: I[x. y, z, t), I[x, y,z,t+ At) dugc dung d(:' tiiih ctic thanh phan cim cac template phi tuyen ciia mang. Gia tri ban dau cua ctic tich phtin trong mang la 0. Mang dugc tinh vdi cac dieu kien cell bien la 0. Dau ra cim mting la cac gia tri ciia cac thanh phan t(3C dp ciia voxel v[x{t),y{t), z[t)). Ta t h a y mdi quan he gifra Ctic ldp cd tinh phi tuyen vdi cac gia tri cudng dp anh sang. Tren ca sd- phan tich ctic mdi li(:m ket gifra cac thanh phan cua cac \'oxel d lie phirang trinh (14) ta cd the xac dinh dmrc Ctic ma trail trpng sd lien ket giua cac te bao nhu sau Z„ = LRx.
Au
Auz-l Auz Auz+l .
vdi Au-^i
Auz =
— Auz+l —
0 0 0 "
0 ~a' 0 0 0 0
r 0 -/./,,. - P - o-'
- Q 2 / . / „ . + 6 Q 2 + 2/2 0 / . /
, - r' - a'
0 1
- a 2
0
.XL" L^' ANH ^' TE 4D - CT CHIU NEN SU DUNG M.ANG NORON TE B A O 357
Zv.
Zu J
1 •'•, 1 1
1 1 1
1 1
1 ' 1 ' ' ;'
i 1 / 1
ly
•J * 1 \1
1 11 r
1 / 1
I k.f
*1 •\
1 \ 1 1 1
Au Duv D'.-u
T^-
^
Dv.u
Av D'.-'.v Dv.v
Aw Duv.'
^ i
\'
'-''
Hinh 1. Md hinh CNN 3 ldp-3D tuili tdc dp voxel
D ruz-l
Dvv D„
D,,,,,
. vdi D,.u--i = D,.„:^i
0 0 0 0 0 0 0 0 0
D,.az -
/-' - / . / , - P
.1
zU^ I I LI
2 .'A'' 9
-/-' /./•; P
- 1 2 4
Dwu
D wuz — i
Du-uz Bwuz+l
D iriiz—l
o 0 0
J -II,
-7- u 0 0
358 C A P THANH TUNG - PHAM THL'O'NG CAT
Dwuz+1 —
0 ^ 0 0 ^ 0 0 ^ 0
Dauz
Av
-"W-i Arz
^ f Z - l - l
v d i ^ 1 , 2 ^ 1 = A ( , ; + l =
0 ' ^ 0 0 /.7-x 0 0 ^ 0 Zv = I.Iuj.
" 0 0 0 0 - a - 0 0 0 0
Ar. I.Iy-r--a'- /./yy + 6Q2 + 2/2 I.Iy-^r-^a'-
- Q -
Duv
Duvz-1 4-'uvz
D U l ' 2 - f - l
vdi Duuz-i = Duvz+i
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XL- LY ANH ^- TE 4D - CT CHIU NEN SU DUNG M.ANG NORON TE B A O 359 Mting CNN 3 \dp 3D (Hinh 1) vdi cac templates phi tu>'c>n dan dat a tren cd the giai
dugc bai toan thih tdc d(3 luong anh (Optical Flow) cho anh chin ne^n 4D nhir tiiili 4D-CT long ngirc. So vdi cac p h u a n g phap tinh trude daj' phirang phap nay cho nhfeu tinh nang
\-ircrt trgi. Thuc te. tdc dp tinh toan ciia mang CNN khdng phu thiKDC vao kich thudc anh Vii chi phu thucic vao quti trinh qua d(3 cua mach dien nen riit iihauli. Vdi cdng nghe CMOS liif'u iia>' toc dc) nay klioang 5-7fj.s . Tdc do nay nhanh ban nhien so \-di Ciic phuang pimp tinh tren may PC ke ca cac phuang phap loc khdng giaii-thdi gian (Spatio-Temporal Filter).
Nliugc diem cim phirang phiip de xuiit la mang CNN cd ctic trpng sd ket ndi phi tm-en ddi hoi khi thiet ke mach tren CMOS hoac FPGA can phiii thiet ke rat than trpng de btio dam miring gpn. chtiy on dinh va cd d(i chinh xtic cao.
4. K E T L U A N
Xii ly anh d(3iig cho ctic anh 4D-CT long ngirc la iiKit viin de thdi su do thih co dan cim cac te bao phoi trong qua trinh hd hap. Cac gia thiet cudng d(p anh sang cua ctic di(5'iii anh CT khdng tliiiy ddi theo thdi gian nhu cac phuang phtip xir ly hien nay deu gti\" nhieu sai sd d ciic iiiili chiu nen. O day. ta da khao sat va xay dung md hinh tdc d(i luong tinh cho cac tinh 4D chiu nen trong iiiih CT long ngirc ndi rieng va cac anh y te ndi chimg. Ctic \-tin de lien quan nhu phuang trinh toc dp luong anh, tdi thieu hda phiem ham theo mo hinh Horn-Schnnck. phiro-ng trinh Euler-Lagrange rdi rtic diro-c tip dung va phtit trien cho tinh chiu nen 4D-CT. De tang tdc do thih toiiii bai btio de xutit mdt mang iKjroii te bao 3 kip 3D gii^ii he phuang trinh Euler-Lagrange rdi rac cua iinli 4D-CT de tinh dmrc tdc dp cua ctic \-oxel tir 2 tuih ke tiep. Day la mc)t phirang phap iii('ri xir ly song song dio tdc do tinh totin rtit ctio xiiiit phtit tir diic thili cua mting lurroii t("' liao \'ii kliti nang cfriig hdii nmiig tren nen chip FPGA. Cd the tich hgp them vdi ni(jt sd i^lnrang phtip va ky thuat khtic nham giiiin nhien, ciii thien chat lugng cho Ciic knh thu dugc tir scan 4D-CT. Van de nay se dugc dc cap dt;n trong ni(3t bai btio khtic, vdi by vpng cd the di den hoan thien han ky thuat xir ly anh d(iiig chiu nen trong y te khi sir dung cdng iigh(!' CNN,
T A I LIEU T H A M K H A O
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360 C A P THANH TUNG - PH.-\.M THL'O'NG C A T
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