Diagnostic evaluation of planar and tomographic ventilation/perfusion lung images in patients with suspected pulmonary emboli.

Transcription

1 Dignostic evlution of plnr nd tomogrphic ventiltion/perfusion lung imges in ptients with suspected pulmonry emoli. Bjc, Mrik; Olsson, Crl-Gustv; Olsson, Berit; Plmer, John; Jonson, Björn Pulished in: Clinicl Physiology nd Functionl Imging DOI: /j X x Pulished: Link to puliction Cittion for pulished version (APA): Bjc, M., Olsson, C-G., Olsson, B., Plmer, J., & Jonson, B. (2004). Dignostic evlution of plnr nd tomogrphic ventiltion/perfusion lung imges in ptients with suspected pulmonry emoli. Clinicl Physiology nd Functionl Imging, 24(5), DOI: /j X x Generl rights Copyright nd morl rights for the pulictions mde ccessile in the pulic portl re retined y the uthors nd/or other copyright owners nd it is condition of ccessing pulictions tht users recognise nd ide y the legl requirements ssocited with these rights. Users my downlod nd print one copy of ny puliction from the pulic portl for the purpose of privte study or reserch. You my not further distriute the mteril or use it for ny profit-mking ctivity or commercil gin You my freely distriute the URL identifying the puliction in the pulic portl L UNDUNI VERS I TY PO Box L und

2 Clin Physiol Funct Imging (2004) 24, pp Dignostic evlution of plnr nd tomogrphic ventiltion/ perfusion lung imges in ptients with suspected pulmonry emoli Mrik Bjc 1, Crl-Gustv Olsson 2, Berit Olsson 1, John Plmer 3 nd Björn Jonson 1 1 Center for Medicl Imging nd Clinicl Physiology, 2 Deprtment of Internl Medicine, nd 3 Deprtment of Rdition Physics, University Hospitl Lund, Lund, Sweden Summry Correspondence Mrik Bjc, Center for Medicl Imging nd Clinicl Physiology, University Hospitl Lund, Lund, Sweden E-mil: mrik.jc@klinfys.lu.se Accepted for puliction Received 20 Ferury 2004; ccepted 8 April 2004 Key words pulmonry emolism; quntifiction; RoPer; RoVent; ventiltion/perfusion SPET Plnr lung ventiltion/perfusion scintigrphy (V/P PLANAR ) is stndrd method for dignosis of pulmonry emolism (PE). The gols of this study were to test whether the dignostic informtion of ventiltion/perfusion tomogrphy (V/P SPET ) pplied in clinicl routine might enhnce informtion compred with V/P PLANAR nd to stremline dt processing for the demnds of clinicl routine. This prospective study includes 53 ptients suspected for PE referred for lung scintigrphy. After inhltion of 99m Tc-DTPA plnr ventiltion imging ws followed y tomogrphy, using dul-hed gmm cmer. 99m Tc-MAA ws injected i.v. for perfusion tomogrphy followed y plnr imging. Ptients were exmined in supine position, unchnged during V/P tomogrphy. Two reviewers evluted V/P PLANAR nd V/P SPET imges seprtely nd rndomly. Mismtch points were clculted on the sis of extension of perfusion defects with preserved ventiltion. Ptients were followed up cliniclly for t lest 6 months. With V/P SPET the numer of ptients with PE ws higher nd 53% more mismtch points were found. In V/P SPET interoserver vrition ws less compred with V/P PLANAR. Ancillry findings were oserved y oth techniques in hlf of the ptients ut more precisely interpreted with V/P SPET. V/P SPET shows more nd etter delineted mismtch defects, improved quntifiction nd less interoserver vrition compred with V/P PLANAR. V/P SPET is menle to implementtion for clinicl routine nd suitle even when there is demnd for high ptient throughput. Introduction Plnr lung scintigrphy is frequently used method for the dignosis of pulmonry emolism (PE) (Burkill et l., 1999) due to its non-invsive chrcter, ese of ppliction, low cost, low rdition urden nd high sensitivity (Mki et l., 1999). The vlue of scintigrphy is questioned, primrily ecuse of high incidence of non-dignostic findings reported in studies sed on PIOPED nd modified PIOPED interprettive strtegies (Gottschlk et l., 1993). However, recent studies show much more fvourle results ecuse of improved techniques for plnr lung ventiltion/perfusion scintigrphy (V/P PLANAR ) (Howrth et l., 1999; Brghouth et l., 2000; Tgil et l., 2000) nd lterntive interprettion strtegies (Bjc et l., 2002). Accordingly, technique llowing V/P PLANAR within 1 h fter referrl showed higher sensitivity nd similr low rtes of non-dignostic findings s compred with spirl computer tomogrphy (CT) (Bjc et l., 2002). Studies y Pll et l. (1988); Eustce et l. (1993); Corus et l. (1997); Mgnussen et l. (1999); Wenger et l. (2000); Lem & Pohleln (2001); showed tht ventiltion/perfusion tomogrphy (V/P SPET ) further improves specificity y reducing the proportion of uncertin results. Plmer et l. (2001) recently showed tht V/P SPET is cliniclly fesile with short exmintion time, low cost nd low rdition dose. Their preliminry dt indicte tht tomogrphy is superior to V/P PLANAR. The method ws vlidted on pigs using lung emoli lelled with 201 Tl s golden stndrd (Bjc et l., 2002), thus circumventing imperfections of other modlities, such s ngiogrphy. The ltter study showed tht V/P SPET ws significntly more sensitive thn V/P PLANAR with respect to detection of smll emoli. The ojective of PE dignostics is not only to confirm or deny the presence of PE, ut lso to provide quntittive dt on degree of PE so s to meet the demnds y rpidly evolving therpeutic modlities. Mssive emoliztion should e treted with thromolysis, while modest emoliztion requires inptient tretment. At low degree of PE, outptient tretment my e offered. It ppers even possile tht we in the future my Ó 2004 Blckwell Pulishing Ltd Clinicl Physiology nd Functionl Imging 24, 5,

3 250 Evlution of V/P PLANAR nd V/P SPET, M. Bjc et l. stin from tretment of single su-segmentl emoli. Accordingly, dignostic methods should llow quntittion. Also evlution nd development of new therpeutic strtegies require recognition of ll emolized res t the time of dignosis nd t follow up. The im of the present study ws to compre V/P PLANAR nd V/P SPET with respect to the dignosis of PE, quntifiction of emoli nd ncillry findings, ginst the clinicl dignosis t dischrge from hospitl. Before pplying V/P SPET in routine, we wnted to vlidte its usefulness. Bsed on initil clinicl experience of the V/P SPET technique, we wnted to improve the normliztion of imges, their mode of presenttion, nd to utomte dt processing. Ptients nd methods This prospective study emrces 51 ptients with symptoms suggestive for PE nd dditionl two ptients on tretment for PE. All were exmined with V/P PLANAR nd V/P SPET. Referred ptients were included whenever the dul hed gmm cmer ws ville. Accordingly, ptient selection ws not specific for the purpose of the study. The study included 19 inptients (one with trum, four from surgicl nd 14 from medicl specilties) nd 34 outptients. The ptients gve informed consent to e exmined oth y V/P PLANAR nd V/P SPET. Approvl ws otined from the ethicl committee. When ptients left hospitl, the responsile clinicins estlished the finl dignosis, sed on symptoms, lood specimens, chest X-ry (nd some with spirl CT), V/P scintigrphy, chnges due to therpy, ccording to locl consensus progrm on venous thromoemolism. Ptients with PE were followed during 6-month periods y one of us, up to 24 months. They were controlled t n outptient clinic with physicl exmintion, lood specimens nd scintigrphy, if considered necessry. Ptients without PE were not given nticogulnt therpy nd were followed for t lest 6 months, y their medicl records. According to the protocol, new V/P scintigrphy should e performed in cse of recurrent symptoms, which did not occur. For the ventiltion study ptients inhled erosolized 99m Tc- DTPA (TechneScn DTPA; Mllinckrodt Medicl, Petten, The Netherlnds) in supine position, y spontneous rething from pressurized ir driven neulizer. Inhltion stopped when 30 MBq hd een deposited, s mesured y shielded Geiger Müller tue (Mini-Instruments Ltd, Burnkm-on-Crouch, Essex, UK). Plnr imges in nterior, posterior nd posterior olique projections were tken in the supine position nd followed y ventiltion tomogrphy. Immeditely therefter nd without ptient movement, 100 MBq 99m Tc -MAA (TechneScn LyoMAA; Mllinckrodt Medicl) ws given y i.v. injection for perfusion study. Then, tomogrphy ws followed y plnr imging. A lrge field-of-view dul-hed gmm cmer with low energy ll-purpose collimtors ws used (SMV DST-XLi, Buc Cedex, Frnce). For SPET mtrix ws used with 128 projections over 360. Sixty-four steps of 10 nd 5 s were used for the ventiltion nd the perfusion studies, respectively. 99m Tc-DTPA clernce ws clculted from the initil nd finl SPET projections, nd ws used for correction of the ventiltion projection set prior to reconstruction. Itertive reconstruction ws performed using OSEM with eight susets nd two itertions. The ventiltion ckground ws sutrcted from the perfusion tomogrms, nd normlized V/P imge set clculted. As mnul processing would e prohiitive in clinicl routine the procedure, from rw dt to complete set of imges for finl review ws mde fully utomtic. Tgil et l. (2000) nd Plmer et l. (2001) descried detils of the plnr nd tomogrphic techniques. In short, the min considertion in the cretion of quotient imges is to define suitle scling fctor etween the reconstructed nd ppropritely smoothened ventiltion nd perfusion dt sets. The scling ws designed with the im to produce quotient imges tht would e displyed in fixed grey-scle vlue in lung regions deemed to e norml from simple utomtic criterion. In the originl work (Plmer et l., 2001) the norml region ws selected y threshholding from the mximum count fter utomtic hotspot removl in the reconstructed volumes. In the present work, more roust normliztion threshholding ws pplied. Thus, the reconstructed volume ws first truncted t lower threshold of 10% of its mximum vlue. An upper threshold ws then otined y itertion to the count level t which 90% of the lung volume ws included. The voxels within the count rnge % of the upper threshold defined preliminry norml suvolume. This process ws pplied to ventiltion nd perfusion independently. The volume in which oth ventiltion nd perfusion were norml comprised the finl normliztion volume. When, in exceptionl cses, no such common volume ws recognized, ech region ws used seprtely. The verge voxel count in the normliztion volume ws scled to e equl for ventiltion nd perfusion. The finl disply ws set to lwys spn quotient rnge of , with equlity eing represented y Ventiltion, perfusion nd V/P quotient tomogrms were simultneously presented in 13Æ6 mm thick coronl, sgittl nd trnsverse slices, nd s rotting volume rendered Mximum Intensity Projection imges. The computer disply llowed djustment of thresholds nd colours. For clinicl purpose physicins on duty red the plnr imges. These reports were used y clinicins for tretmentdecisions nd lso, in the study, for comprison with results of the two expert reviewers. For the purpose of the study these two reviewers interpreted SPET imges. No results from SPET were given to clinicins. The clinicl reders nd the reviewers hd ccess to clinicl dt. Plnr nd tomogrphic imges were relted for interprettion to ntomicl chrts of lung segments. The two reviewers red seprtely ll plnr nd tomogrphic imges. The two modlities were interpreted with t lest 3 weeks intervl. In ech session the identifiction of ptients ws hidden nd the order ws rndomized. The time needed for V/P exmintion is out 30 min including cquisition time of 16 min. Reconstruction, utomtic Ó 2004 Blckwell Pulishing Ltd Clinicl Physiology nd Functionl Imging 24, 5,

4 Evlution of V/P PLANAR nd V/P SPET, M. Bjc et l. 251 processing including ll slices nd 3D rendered cine imges tke 9 min. Interprettion nd reporting tkes 5 10 min. Interprettion criteri Ventiltion nd perfusion defects were quntified with respect to segmentl/susegmentl chrcter of defects, RoVent points (reduction of ventiltion) nd RoPer points (reduction of perfusion) (Plmer et l., 2001; Olsson et l., 2002). A segmentl reduction or susegmentl totl deficiency ws ttriuted 1 point; segmentl totl deficiency ws ttriuted 2 points. For ech lung, we clculted the numer of points reflecting P defect with preserved V, to totl mismtch score. Within holistic principle of imge reding the following guidelines were pplied. No emolism, PE): sence of unmtched perfusion defects. Emolism, PE+: >1 segmentl or susegmentl defect of mismtch, i.e. t lest 2 points. Other pthology thn PE: mtched defects with typicl ptterns for other lung diseses. Non-dignostic, ND: Grve V/P defects rendering the judgement of mismtch impossile. We dhere to holistic principle of clinicl imge reding, in line with concepts recently descried y Freemn et l. (2001). Accordingly, ncillry scintigrphic findings nd clinicl dt were considered in the interprettion. The reders considered the numer of mismtched res, their distinctness, peripherl or centrl position, s well s segmentl or non-segmentl loction. Signs of ostructive or prenchyml lung disese, tumour nd hert filure were included in clinicl nd reviewed reports. Incresed clernce of DTPA from the lungs ws considered to indicte lveolr inflmmtion. Sttistics: liner regression ws used for comprison etween reders. Wilcoxon Signed Rnk Test ws used for comprisons etween V/P SPET nd V/P PLANAR, using Sigm Stt, Sttisticl Softwre, version 2, SPSS Inc. Results According to the finl clinicl dignosis, 11 ptients were treted for recent PE. Another two ptients were on continuous tretment since previous episode of PE (Tle 1). In the 11 cses of recent PE the dignosis reflected positive reding of the routine V/P PLANAR. The reviewers judged the V/P PLANAR positive for PE in the sme 11 nd 10 cses, respectively. In the 11th cse, one reviewer expressed strong suspicion for PE nd recommended CT to confirm the suspicion. In two ptients with old PE the routine nd the reviewers report on V/P PLANAR were negtive. On V/P SPET oth reviewers reported PE in ll 11 new cses with clinicl dignosis of PE nd in two ptients lredy on therpy for PE (Fig. 1). In the remining 40 ptients ll routine nd review reports of V/P PLANAR were negtive. In three of these 40 ptients V/P SPET showed PE ccording to one reviewer. The other reviewer reported two of these, while the third ws considered ND (Tle 1). The inter-oserver greement etween reviewer A nd B, with respect to the numer of mismtch points recognized for ech ptient, MMP A nd MMP B, respectively ws illustrted with regression nlysis: For V/P PLANAR : MMP B ¼ 0 79ð0 04Þ; MMP A 0 2ðR 2 ¼ 0 88Þ For V/P SPET : MMP B ¼ 0 96ð0 03Þ; MMP A 0 2ðR 2 ¼ 0 95Þ Numers in rckets indicte stndrd error. The intercept 0Æ2 ws not significntly different from zero. On verge mismtch points in V/P SPET were for oth reviewers 53% higher thn in V/P PLANAR. This difference etween the methods ws significnt (reviewer A, P ¼ 0Æ003 nd B, P ¼ 0Æ001). No ptient developed signs or symptoms of new PE during the follow up period of 6 months. Ancillry findings The reviewers together renlysed V/P PLANAR nd V/P SPET imges with respect to ncillry findings indicting other diseses thn PE. Ancillry findings were concordnt etween V/P PLANAR nd V/P SPET in 25 ptients. V/P chnges were of ostructive type, i.e. centrl deposition of erosols nd mtched ventiltion perfusion chnges in 12 (Fig. 2). Lor V/P defects were oserved in 4, nd minor Tle 1 Clinicl dignosis nd scintigrphic findings. Clinicl dignosis of PE Routine reding of V/P PLANAR Reviewers reding of V/P PLANAR Reviewers reding of V/P SPET Reviewer A Reviewer B Reviewer A Reviewer B 13 PE+ 11 New 11 PE+ 11 PE+ 10 PE+ 1 ND 11 PE+ 11 PE+ 2 Old 1 PE) 1ND 2PE) 2PE) 2 PE+ 2 PE+ 40 PE) 40 PE) 40 PE) 40 PE) 37 PE) 3 PE+ 37 PE) 2 PE+ 1 ND PE+, ptient with nd PE), ptient without pulmonry emolism; ND, non-dignostic. Ó 2004 Blckwell Pulishing Ltd Clinicl Physiology nd Functionl Imging 24, 5,

5 252 Evlution of V/P PLANAR nd V/P SPET, M. Bjc et l. A Ventiltion Anterior Posterior RPO LPO B Ventiltion Sgittl, right lung Post Ant V/P quotient Figure 1 Ptient with known PE, 6 month fter therpy: (A) plnr imges: reduction nd uneven distriution of V nd P in lower loe of right lung (rrows); (B) tomogrphy: sgittl slices from nterior to posterior perfusion defect in lower loe is clerly visile, enhnced y V/P quotient (rrows). Ó 2004 Blckwell Pulishing Ltd Clinicl Physiology nd Functionl Imging 24, 5,

6 Evlution of V/P PLANAR nd V/P SPET, M. Bjc et l. 253 A Ventiltion Anterior Posterior B Ventiltion Frontl V/P quotient Figure 2 Ptient with known ostructive lung disese: (A) plnr imges: V/P re uneven nd reduced in some segments () nd centrl deposition of erosol; (B) tomogrphy: coronl slices reduction of V nd P () nd lso cler mismtch on V/P quotient typicl for susegmentl PE (). Ó 2004 Blckwell Pulishing Ltd Clinicl Physiology nd Functionl Imging 24, 5,

7 254 Evlution of V/P PLANAR nd V/P SPET, M. Bjc et l. defects of the sme type in 5 (Fig. 3). Two others hd pttern of hert filure, i.e. diminished ventiltion nd perfusion in dorsl nd sl prt of the lung. Alveolitis ws dignosed y high clernce of DTPA in two ptients. Ancillry findings were discordnt in four ptients. In one ptient ostruction ws only recognized on V/P SPET. Two ptients with enlrged herts nd one ptient with uptke in oesophgus clerly oserved on V/P SPET showed flse V/P chnges on V/P PLANAR. Discussion In this study, we compre plnr nd tomogrphic imging in clinicl mteril. In previous experimentl study we showed tht oth sensitivity nd specificity ws enhnced y tomogrphy (Bjc et l., 2002). In tht study rtificil emoli were mrked with 201 Tl providing true gold stndrd. A limittion of clinicl studies is tht no similr stndrd is ville. Trditionlly, pulmonry ngiogrphy hs een regrded s the gold stndrd for dignostics of PE. However, ccording to recent rticle on stte of the rt the sttus of pulmonry ngiogrphy s the stndrd of reference for dignosis of PE is in dout (Schoepf & Costello, 2004). A similr opinion hs since severl yers een dvocted y the British Thorcic Society, Stndrds of Cre Committee, These considertions were sed upon severl studies showing limited sensitivity nd high inter-oserver nd intr-oserver vriility. Ethicl concerns would lso e rised ginst n invsive technique with some rdition hzrds used for purely scientific resons. In the sence of stndrd reference for the dignosis PE the outcome for ptients should e regrded s pproprite endpoint (Fennerty, 1998). The study reflects trnsitory phse in our deprtment during improvement nd implementtion of the tomogrphic method, previously descried (Plmer et l., 2001). A minimum of technicin intervention is now needed for reconstruction nd V/P quotient clcultions. The interpreter is helped y new presenttion form suitle for qulity control nd reviewing. Three sets of tomogrphic dt (V, P nd V/P quotient), viewed in coronl, sgittl nd trnsverse plne s well s in simultneous 3D volume imges re directly ville for interprettion. Exmintion in supine position offered stle nd comfortle procedure even for criticlly ill ptients. Moreover, it ws convenient for the stff. Immoiliztion needed during the short cquisition time ws well tolerted y ll ptients. There were only four ptients tht moved during exmintions thus cusing rtefcts on V/P quotient imges, which re esy to recognize. The dministered ctivity used here, 30 MBq for ventiltion nd 100 MBq for perfusion, were found to e dequte in most cses. Exceptionlly we use up to 50 MBq for ventiltion nd up to 150 MBq for perfusion. The Procedure Guideline y the Society of Nucler Medicine suggests, implicitly for plnr technique, MBq for ventiltion, nd totl count rte t perfusion of t lest four times tht t ventiltion (ACCP, 1998). Interprettion of lung scintigrphy ccording to initil nd revised PIOPED criteri hs cused confusion in nucler nd clinicl medicine (Gry, 2002). The criteri for PE re sed on the judgement of size of perfusion defects nd ventiltion, if studied, hs not een stndrdized nd often een performed with 133 Xe which we find indequte. This hs cused high proportion of intermedite, non-dignostic reports (Gottschlk et l., 1993). Difficulties re lso cused y the reports expressed s proilities nd to use these in clinicl context. Recognition of ptterns typicl for PE represents step forwrd s evidenced y the PISA-PED studies, even if ventiltion ws not studied (Miniti et l., 1996). Giordno & Angiolillo (2001), stressed tht ventiltion, if used should e performed using erosols or Technegs. Finlly, holistic pproch should e dopted for interprettion of scintigrphic imges y using clinicl informtion, segmentl chrts, nd recognition of ptterns typicl for PE nd for other diseses (Freemn et l., 2001; Plmer et l., 2001; Bjc et l., 2002). Such strtegy hs drmticlly reduced the numer of non-dignostic reports nd in generl incresed the dignostic vlue of V/P scintigrphy (Bjc et l., 2002). V/P SPET used in recent studies showed prticulrly low numers of non-dignostic findings nd high sensitivity nd specificity for PE (Corus et l., 1997; Lem & Pohleln, 2001). In this respect our results re similr to these oservtions. In the present study the comprison etween V/P PLANAR nd V/P SPET ws sed on the sme holistic interprettion principles. The methods differed with respect to imging technique. V/P PLANAR showed dignostic results superior to studies sed on proilistic criteri s y PIOPED. V/P SPET further enhnced dignostic ccurcy oth y visulizing remnnts of PE in two ptients under tretment nd lso y reveling findings typicl for PE in nother three ptients, who were not treted (clinicins were not informed on the results of V/P SPET ). However, these results should e cutiously considered s the mteril is smll nd rel gold stndrd is not ville. V/P defects were quntified to descrie the extent of PE in terms of new prmeters RoVent nd RoPer. Using this strtegy V/P SPET showed 53% more mismtch points thn V/P PLANAR. Furthermore, V/P SPET with 3D visuliztion elimintes the influence of superimposed structures, thus clrifying segmentl nd susegmentl chrcter of PE defects. Also the stripe sign indicting defects of other nture thn PE is more ovious (Fig. 3). These qulities of V/P SPET re prticulrly vlule when PE is comined with other diseses nd explin the higher sensitivity oserved y others nd y us. An incresed numer of plnr projections would proly mrginlly incresed the sensitivity of plnr technique t the cost of longer time for the whole procedure. Anywy with our plnr technique the sensitivity is higher thn tht of CT (Bjc et l., 2002). Another dvntge of our V/P SPET is the V/P quotient tht fcilittes oth recognition nd quntifiction of PE (Figs 1 3). Quntifiction is ecoming importnt for choice of therpy, i.e. thromolysis or conventionl nticogulnts, nd more importntly for identifying ptients suitle for outptient tretment (Kovcs Ó 2004 Blckwell Pulishing Ltd Clinicl Physiology nd Functionl Imging 24, 5,

8 Evlution of V/P PLANAR nd V/P SPET, M. Bjc et l. 255 A Ventiltion Anterior Posterior RPO LPO B Ventiltion Right Left V/P quotient Figure 3 Ptient with known pneumoni nd PE: (A) plnr imges: reduced V nd P posterior in left lung (); (B) tomogrphy: sgittl slices right to left lung V nd P defects posterior in the left lung re clerly delineted nd stripe sign typicl for pneumoni (). defect in lingul nd middle loe re visile ut mismtches re ovious from the V/P quotient (). et l., 2000; Olsson et l., 2002; Beer et l., 2003). The significntly lower interoserver vrition nd higher sensitivity oserved y V/P SPET compred with V/P PLANAR is due to its more cler ptterns representing PE or other diseses. These qulities of V/P SPET re importnt for proper dignosis, for the choice of therpy nd for follow up of ptients. A prolem Ó 2004 Blckwell Pulishing Ltd Clinicl Physiology nd Functionl Imging 24, 5,

9 256 Evlution of V/P PLANAR nd V/P SPET, M. Bjc et l. which cnnot e ddressed on the ses of this study is the clinicl significnce nd the indiction to tret isolted susegmentl emoli. The holistic ttitude including ncillry findings should e used to recognize vrious differentil dignoses (Freemn et l., 2001). Both V/P PLANAR nd V/P SPET imging showed such findings in out hlf of the ptients. The importnce of ventiltion studies is not limited to identifiction of mismtch ut lso llows the identifiction of ptterns typicl for lterntive dignoses such s ostructive disese, prenchyml diseses nd tumours, hert filure nd in our study lso lveolitis. Experience from more thn 1200 V/P SPET exmintions until tody, comined with dily clinicl feedck hs for us confirmed the superiority of V/P SPET. Conclusion V/P SPET performed with recommended, low ctivity llows excellent imging lso of V/P quotient. V/P SPET showed higher sensitivity with respect to demonstrtion of more emoli reveling more perfusion defects nd hd less interoserver vrition thn V/P PLANAR. V/P SPET enles etter quntifiction tht hs impct on choice of therpy nd improves follow up. Ancillry findings were more clerly delineted nd correctly explined. Acknowledgments This work ws supported y the Swedish Medicl Reserch Council (02872) nd y the Swedish Hert Lung Foundtion. References ACCP. Consensus Committee on Pulmonry Emolism Opinions Regrding the Dignosis nd Mngement of Venous Thromoemolic Disese. Chest (1998); 113: Bjc M, Alrechtsson U, Olsson CG, Olsson B, Jonson B. Comprison of ventiltion/perfusion scintigrphy nd helicl CT for dignosis of pulmonry emolism; strtegy using clinicl dt nd ncillry findings. Clin Physiol Funct Imging (2002); 22: Bjc M, Bitzen U, Olsson B, Perez de S V, Plmer J, Jonson B. Lung ventiltion/perfusion SPECT in the rtificilly emolized pig. 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