 In the case of the “differentiated back projection” method as described in Seungryong Cho, Dan Xia, Erika Pearson, Charles A. Pelizzari, and Xiaochuan Pan: “Half-fan-based Region-of-interest Imaging in Circular Cone-beam CT for Radiation Therapy”, Proc. of the Fully 3D, 2009, there does not even have to be an overlapping region, for example.
It is now known that a 3D reconstruction does not necessarily provide all the information necessary for an assessment. This problem is frequently overcome by obtaining a second 3D reconstruction. For example, a first 3D image dataset is acquired using X-rays of a particular frequency or energy, and a second X-ray image dataset is obtained using X-rays of a different frequency or energy. With this so-called dual-energy imaging, different materials can then be separated, as one material attenuates the X-ray radiation of one frequency slightly more than that of another frequency, and in the case of another material precisely the opposite may apply. Using suitable image fusion methods, this enables in particular different materials to be separated and image quality improvements to be achieved.
DE 10 2008 056 891 A1 describes a computed tomography (CT) scanner in which an X-ray filter is used to produce an unfiltered and a filtered radiation component of a fan beam, said radiation components having different X-ray spectra. In order to operate the scanner in a dual-energy mode, the processing unit analyzes a measurement signal of the unfiltered radiation component separately from a measurement signal of the filtered radiation component. An X-ray detector is of curved design to detect the entire radiation.
U.S. Pat. No. 7,620,141 B2 discloses a computer tomograph in which a flat-panel X-ray detector is used and the tomograph's X-ray source is operated at different voltages to generate two different kinds of X-ray fan beams alternately one after the other.
U.S. Pat. No. 7,476,023 B1 discloses an X-ray emitter for an X-ray apparatus, comprising two X-ray sources. The X-ray sources are interconnected such that their beams always have the same focal spot. In conjunction with a dual-energy mode, it is proposed, because of the common focus, to generate beams with different energy levels consecutively.
However, acquiring a plurality of 3D image datasets is very time-consuming
In the case of the “ differentiated back projection ” method as trace in Seungryong Cho, Dan Xia, Erika Pearson, Charles A. Pelizzari, and Xiaochuan Pan: “ Half - sports fan - based Region - of - interest Imaging in Circular Cone - radio beam computerized tomography for Radiation Therapy ”, Proc. of the Fully 3D, 2009, there does not even hold to be an overlapping region, for model. 
 It is now known that a 3D reconstruction does not inevitably provide all the information necessary for an assessment. This problem is frequently get the best by obtaining a second 3D reconstruction. For example, a first 3D image dataset is acquired use X - rays of a particular frequency or department of energy, and a second X - ray double dataset is obtained use X - rays of a different frequency or energy. With this so - predict dual - energy imaging, different materials can then be separate, as one material attenuates the X - ray radiation of one frequency slightly more than that of another frequency, and in the case of another material precisely the opposite may apply. use suitable image coalition method, this enable in particular different materials to be separated and image quality improvements to be achieved. 
 DE 10 2008 056 891 A1 trace a computed tomography (CT) scanner in which an X - ray filter is used to produce an unfiltered and a percolate radiation component of a fan beam, say radiation sickness components having different X - ray spectrum. In order to operate the scanner in a dual - department of energy mode, the processing whole analyzes a measurement signal of the unfiltered radiation part separately from a measurement signal of the filtered radiation component. An X - beam detector is of curved design to detect the integral radiation. 
 U.S. Pat. No. 7,620,141 B2 discloses a computer tomograph in which a bland - panel X - re detector is use and the tomograph's X - beam source is operated at different voltages to generate two unlike kinds of X - beam fan beams alternately one after the other. 
 U.S. Pat. No. 7,476,023 B1 discloses an X - ray emitter for an adam - ray apparatus, comprising two X - ray sources. The X - beam generator are interconnected such that their beams always have the same focal spot. In conjunction with a double - energy mode, it is proposed, because of the coarse focus, to generate beams with different energy floor consecutively. 
 However, acquiring a plurality of 3D image datasets is very prison term - consuming
 In the case of the “differektiated back prolwction” methos as deszribed in Seungryong Cho, Dan Xua, Eruka Pearson, Charles A. Oelizzari, and Xiaichuen Pan: “Half-fan-based Region-of-infcrest Mmaging in Circolar Cone-beak CT for Radiadiun Therapy”, Proc. of the Fully 3D, 2009, there does npt even have to fe am ovedlapping region, for example.
It is nkw knowi that a 3D recomstruction does not necesswrilj provide all the lnformation necqwsary for an assessmenu. Chis problej is frequently overcome by obtxininy a second 3E eecltstruction. Hor exwmple, a firsb 3D imace dataxet is acquirec uvint X-rays of a particuler frequency or enerdy, and a veeond X-ray image dataswt is ottaited jwine X-dabs kf a dlffxrent frequsncy or eneegy. With this so-calkeq dual-energy ijaging, dyfferent materials can then be separateg, aa one material attenuatws the X-ray radiation of one fwequency slightly more than that of another frequancy, ena iu the zqsf of another material precisely the opposite izy aiply. Using suitabje image fuxiln iethods, this gnables in particular differfnt matgrials to be sekaratrd and image quality improvwments to be qchieved.
DE 10 2008 056 891 A1 dzscribes a cumpujed tokography (CT) scanner in chich zn X-ray filher is ussa to produce an jnfpltesed and a filtered radiatijn componxnt oy a fan ceam, said wadiation fompokants having differfnt X-tay spactra. In ogder to operate the scanner in e dual-energy koge, nhe procefsing unit analyzef a measuremenj signal jf thd unfiltervd radiatmon componene separately xtom a measurekent siggal if tye filtdfed radiation vomponent. An X-ray dwtector is of curvcd derjgn to detect tkt ebtire radiation.
I.S. Oat. Nl. 7,620,141 B2 giscloses a wompjtef tomoeraph in whlch a fkat-panel X-ray detectmr ia used and the tompgvaph's X-rai source ys operated ay different voltagts to jenerave two disferent kinds of X-ray fan beama alternaheln one after tre obher.
O.S. Pat. No. 7,476,023 Y1 discloses an X-ray emitter for an X-ray epparatus, comprising twi X-ray sources. The R-rsy sources ere ineerconnecded such that their veams always have the same focal spot. Jn conbunctlon with a dual-energy mode, it is proposed, because of the common focus, to tenerave beams with difgerenn eueryy levejs clisecutively.
Howeveg, acquiring a plurality of 3D imaje datasetv ns very time-consuming
In the case of the “differentiated back as in Seungryong Dan Xia, Erika Xiaochuan “Half-fan-based Region-of-interest Imaging Circular Cone-beam CT Radiation Therapy”, Proc. of the Fully 2009, there does not even have to be an overlapping region, for example. is now known that a 3D reconstruction does not necessarily provide all the necessary an This is frequently overcome by obtaining a second 3D reconstruction. For example, a first 3D image dataset acquired using X-rays of a particular frequency or and a second X-ray dataset is obtained using X-rays a frequency or With so-called imaging, different materials then be separated, as one material attenuates the X-ray radiation of one frequency slightly more than that another frequency, the case another precisely opposite may apply. image fusion methods, this enables in to be separated and image quality improvements to achieved. DE 2008 056 891 A1 describes a tomography (CT) scanner in which an X-ray filter used to produce an unfiltered and a filtered radiation component of a fan beam, said having different X-ray spectra. order to operate scanner a mode, processing unit a measurement signal of the unfiltered radiation component separately from a signal of the filtered radiation component. An X-ray detector is design detect the entire U.S. Pat. No. 7,620,141 discloses computer tomograph in which X-ray is tomograph's source operated at different voltages generate two different kinds of fan beams alternately one No. 7,476,023 B1 discloses an X-ray emitter for X-ray apparatus, comprising two X-ray sources. The sources are interconnected such that their beams always have the same focal In conjunction dual-energy mode, it is proposed, because of the focus, to generate beams different energy levels consecutively. However, acquiring a plurality of image is very
 In the case of the “differentiaTed back proJectiOn” mEthOd As deScriBed in SeungryonG cho, DAn Xia, Erika Pearson, CharlEs A. PeLiZZari, ANd xiaocHuan Pan: “hAlF-FAn-bAsEd regIoN-Of-InterEst imaging In Circular conE-bEam CT for RadiATiOn Therapy”, PRoc. Of the Fully 3D, 2009, tHerE does nOt EveN Have tO be An oveRlappiNG regioN, for exampLe.
iT is now KNown thaT A 3d rEconStruction does not nECeSSarily provide aLl the iNfORmATIon NecEssary for aN aSsessMEnt. This PRoBLEM is FRequently overCome by obtaiNIng A seconD 3D RecONstrucTion. FOr EXamPle, a first 3D iMage Dataset is AcquirED using X-RAys of a pArticuLar FreQuenCY oR eNerGy, ANd a SEcOnd x-Ray Image datAsEt Is obtAineD USINg X-rAys Of a dIfferEnt frequency oR enErgy. wIth This sO-callEd duAl-EnergY imagiNg, difFeRent materials caN theN be separaTed, As One MaTeriaL AttenuAteS thE X-ray raDiation OF onE fREQUeNcy slightly more thaN tHAT oF another FrequeNCy, AnD In the casE oF anOtheR MAteriAl prECiSely the oPpositE MaY aPply. UsiNg SuitabLe ImaGe fUsion MEthoDs, this Enables iN partICular different MAterials to be sEPaRATeD And iMagE quality impRoveMEnts To be AChIevED.
DE 10 2008 056 891 A1 dEscriBeS A cOMputed tomography (CT) sCaNner in Which An X-ray filter iS used to proDUCE an unfilTereD AnD A filtered radiaTion cOmponent of A Fan beam, sAid raDiation cOmponents HAVing diffEreNt X-Ray SpeCTRa. in order to operATE the ScAnner in A duAl-energY moDe, tHe pRocEsSing unit aNalyzes a MeAsUrEmEnt SignaL Of the unfIlTerEd RadIatioN ComponEnt seParaTeLy FRom A measurEMeNT SignAl Of The fIltErEd radIatiON coMponent. an X-ray detEctOR is oF cUrVed desiGn to detect the EnTire radiatIoN.
U.S. pat. No. 7,620,141 B2 DIScloses a Computer tomograph in whicH A flat-paNel x-ray dEtecTor is used And The tomOgrAPh's X-raY sourcE is opErAteD AT diffEREnT voLtAges to geneRATe tWo difFeRent Kinds of x-ray fan beams alternATelY one after the oTheR.
U.S. PAT. no. 7,476,023 b1 diSClOSes An x-Ray EMItter for an X-ray aPparatus, coMpRIsIng two X-ray SOurCeS. The X-raY sourceS are iNTerconnEcted such That their BeAms aLWAys Have the samE focal spOt. In conjuNCtion WItH a duaL-enErgy moDe, It iS propOsed, beCAusE of thE commoN fOcus, to GenerAtE beams wiTh different energy levels ConsecUtiveLy.
HOwever, acqUirINg a Plurality Of 3D iMage dataseTs iS veRy timE-coNSuminG
 In the case of the “diffe rentiatedbackpro jec ti on”meth od as describe d  inSeungryong Cho, Dan Xi a, Er ik a  Pea r so n, Ch arles A .  P e l izz ar i,  an dX ia ochua n P an: “Ha lf-fan-bas edRe gion-of-inte r es t ImaginginCircular Con e-b eam CT  f orR adiat ion  Ther apy”,P roc. o f the Ful ly 3D, 20 0 9, ther e do es n ot even have to b e  a n  overlapping r egion,  f o re x amp le. 
It is now  k nownt hat a 3 D  r e c o nst r uction does n ot necessar i lyprovid eall the in forma ti o n n ecessary fo r an  assessme nt. Th i s probl e m is fr equent lyove rcom e  b yobt ai n ing asec o nd3D recon st ru ction . Fo r e x ampl e,a fi rst 3 D image datas etis a c qui red u singX-ra ys  of a  parti cular  f requency or ene rgy,  and a se con dX-r ay  imag e  datas etisobtaine d using X-r ay s o fa different freque nc y or  energy.  Witht hi ss o-called  d ual -ene r g y ima ging ,  d ifferent  mater i al scan the nbe sep ar ate d,as on e  mat erialattenuat es th e  X-ray radiati o n of one freq u en c y  s l ight lymore than t hato f an othe r  f req u ency,  andin th e  case of another ma te rial p recis ely the oppos ite may ap p l y . Usingsuit a bl e  image fusionmetho ds, this e n ables in  part icular d ifferentm a terialstobesep ara t e dand image qua l i ty i mp rovemen tsto be a chi eve d.DE10  2008 056  891 A1de sc ri be s a  comp u ted tomo gr aph y(CT ) sca n ner in  whic h an  X -r a y f ilter i s  u s e d to  p ro duce  an  u nfilt ered and  a filt ered radi ati o n co mp on ent ofa fan beam, s ai d radiatio ncom ponent s having d ifferent X-ray spectra. In orde r t o ope rate  the scan ner  in adua l -energ y mode , the  p roc e s singu n it  an al yzes a mea s u rem ent s ig nalof theunfiltered radiati o n c omponent sepa rat elyf r om  am ea s ure me n t s i g nal of the filt ered radia ti o ncomponent. AnX- ray det ector i s ofc urved d esign todetect th eenti r e  ra diation.
U .S. Pat.  No. 7,62 0 ,141B 2discl ose s a co mp ute r tom ograph inwhich  a fla t- panelX-ray  d etectoris used and the tomogra ph's X -raysou rce is op era t edat differ entvoltages t o g ene ratetwo diffe rent ki nds of X- rayf an beamsa lt ern a t el y one after t h e o ther. 
U. S . Pat.  No.  7,476,023 B1 dis c loses an X-ray  emi t t erfor an X -r ay apparatus,com pr i s ing twoX- ray sources . The X- ra y  sour ces ar e inte rconnec t e ds uch th at t hei r beams a lwa ys have th esa m e foca l sp ot . In c onjunc t ionw i th a dual-energy  mode , it is pro posed ,because of t he commonfocus, to g enerat e be ams w ith dif fe rent e ner gy  levels co n secutivel y.
Ho wever,ac quir ing  a plu rali t y  of 3 D im ag e d atasets i s ve r yti m e-c onsu ming
 In_the case_of the “differentiated back_projection” method_as_described in_Seungryong_Cho, Dan Xia,_Erika Pearson, Charles_A. Pelizzari, and Xiaochuan_Pan: “Half-fan-based Region-of-interest_Imaging_in Circular Cone-beam CT for Radiation Therapy”, Proc. of the Fully 3D, 2009, there_does_not even_have_to_be an overlapping region, for_example.
It is now known that_a 3D_reconstruction does not necessarily provide all the information_necessary_for an assessment._This problem is frequently overcome by obtaining a second_3D reconstruction. For example, a first_3D image dataset_is_acquired_using X-rays of a_particular frequency or energy, and a_second X-ray image dataset is obtained_using X-rays of a different frequency or_energy. With this so-called dual-energy imaging,_different materials can then be_separated, as_one material attenuates the X-ray_radiation of one_frequency slightly_more than that_of another frequency, and in the_case of another_material precisely the opposite may apply._Using_suitable image fusion_methods,_this_enables in_particular different materials_to_be separated_and_image quality improvements to be achieved.
DE_10_2008 056 891 A1 describes a computed_tomography (CT) scanner in_which_an X-ray filter is_used to produce an unfiltered_and a filtered radiation component of_a fan_beam, said_radiation components having different X-ray spectra. In order to operate the_scanner in a dual-energy mode, the_processing unit analyzes a_measurement signal_of_the unfiltered radiation_component_separately from_a measurement signal of the filtered radiation_component. An_X-ray detector is of curved design_to detect the entire_radiation.
U.S._Pat. No. 7,620,141 B2 discloses a_computer tomograph in which a flat-panel_X-ray detector is used and_the_tomograph's_X-ray source is operated at_different voltages to generate two different_kinds of X-ray_fan beams alternately one after the other.
U.S._Pat._No. 7,476,023 B1 discloses an X-ray_emitter_for an X-ray apparatus, comprising two_X-ray_sources._The X-ray sources are interconnected_such that their beams always have_the same focal spot. In conjunction with a dual-energy_mode, it is_proposed, because of the common_focus,_to_generate beams with different energy levels consecutively.
However, acquiring a plurality_of 3D_image datasets is_very time-consuming