Dual-axis rotational coronary angiography can reduce peak skin dose and scattered dose: a phantom study

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1 JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS, VOLUME 15, NUMBER 4, 2014 Dul-xis rottionl coronry ngiogrphy cn reduce pek skin dose nd scttered dose: phntom study Huiling Liu, Zhigeng Jin, Yunpeng Deng, Limin Jing Deprtment of Crdiology, Generl Hospitl of Chinese People s Armed Police Forces, Beijing, Chin lwgjzg@sin.com Received 13 November, 2013; ccepted 12 Februry, 2014 The purpose of this study ws to evlute pek skin dose received by the ptient nd scttered dose to the opertor during dul-xis rottionl coronry ngiogrphy (DARCA), nd to compre with those of stndrd coronry ngiogrphy (SA). An nthropomorphic phntom ws used to simulte ptient undergoing dignostic coronry ngiogrphy. Cine imging ws pplied on the phntom for 2 s, 3 s, nd 5 s in SA projections to mimic clinicl situtions with norml vessels, nd uncomplicted nd complicted coronry lesions. DARCA ws performed in two curved trjectories round the phntom. During both SA nd DARCA, pek skin dose ws mesured with thermoluminescent dosimeter rrys nd scttered dose with dosimeter t predefined height (pproximtely t the level of left eye) t the opertor s loction. Compred to SA, DARCA ws found lower in both pek skin dose (rnge: 44% 82%, p < 0.001) nd scttered dose (rnge: 40% 70%, p < 0.001). The mximl reductions were observed in the set mimicking complicted lesion exmintions (82% reduction for pek skin dose, p < 0.001; 70% reduction for scttered dose, p < 0.001). DARCA reduces both pek skin dose nd scttered dose in comprison to SA. The benefit of rdition dose reduction could be especilly significnt in complicted lesion exmintions due to lrge reduction in X-ry exposure time. The use of DARCA could, therefore, be recommended in clinicl prctice to minimize rdition dose. PACS numbers: j, Bn, e, C-, cf, Dj Key words: coronry ngiogrphy, rottionl coronry ngiogrphy, dul-xis ngiogrphy, rdition dose, ptient dose, stff dose Conflict of Interest sttement The uthors declre there re no conflicts of interest. I. Introduction As interventionl crdic procedures become indispensble in the present crdiology prctice, concerns rise over potentil rdition risk to both ptients nd opertors. (1,2) There re two types of biologicl effects of rdition: stochstic effects nd tissue rections (previously clled deterministic effects). (3) Tissue rections re cused by rdition dose tht exceeds specific thresholds. Typicl exmples of tissue rections of crdiologicl interest re ctrct formtion (in opertors) nd skin injury (in ptients). Note tht dt from humn popultions under rdition exposure suggest tht ctrct occurs t doses fr lower thn the previous consensus. (4) Moreover, there hs been n incresing number of cse reports on ptient skin injuries resulting from interventionl procedures. (5-7) Thus, in order to prevent serious tissue rections in clinicl prctice, ctions to control rdition dose need to be tken. Corresponding uthor: Zhigeng Jin, Division of Crdiology, Generl Hospitl of Chinese People s Armed Police Forces, No.69, Yongding Rod, Hidin District, Beijing , Chin; phone: ; fx: ; emil: lwgjzg@sin.com

2 327 Liu et l.: Dul-xis rottionl coronry ngiogrphy 327 Recently, dul-xis rottionl coronry ngiogrphy (DARCA) hs developed s n innovtive dpttion to the stndrd coronry ngiogrphy (SA), which remins the gold stndrd for ssessing coronry stenosis. (8) During DARCA, the three-dimensionl rottion of the gntry round the ptient occurs in the left nterior oblique (LAO)/right nterior oblique (RAO) nd crnil/cudl orienttions during one cine cquisition, to obtin imges in trjectory specificlly designed to reduce vessel foreshortening. Compred to SA, this cretive technology demonstrtes significnt potentil in reducing ptient rdition dose, contrst utiliztion, nd procedure time, while enhncing the number of ngiogrphic projections obtinble with superior imging results. (8-11) However, the bove-mentioned dose reductions hve been reported with dose re product (DAP), which gives no direct informtion on pek skin dose (PSD). (12-16) Moreover, estimting skin dose from DAP hs potentil error of t lest 30% 40%. (17) The impct of DARCA on ptient skin dose, compred with SA, remins unknown. In ddition, s fr s we know, there hs been no study on the scttered dose during DARCA compred to SA. The purpose of this study ws to evlute ptient PSD nd scttered dose to the opertor in DARCA compred to SA with the use of n nthropomorphic phntom. II. Mterils nd Methods A. Coronry ngiogrphy This study ws conducted in the crdic ctheteriztion lbortory of tertiry referrl center using monoplne AllurXper FD10 fluoroscopy device (Philips Helthcre, Best, The Netherlnds). Dignostic coronry ngiogrphy ws simulted on n nthropomorphic femle phntom (ART-200; RGRMS, Chin) by n experienced interventionl crdiologist (Fig. 1). Exposure prmeters (e.g., X-ry tube voltge nd tube current) were set by the X-ry system s utomtic exposure control. SA projections ccording to our routine coronrogrphy were used. Left coronry ngiogrphy ws performed with five exposures in five projections: RAO 25 /cudl 25, RAO 25 / crnil 25, LAO 45 /crnil 25, LAO 45 /cudl 25, nd nterior posterior (AP)/crnil 25. Fig. 1. Coronry ngiogrphy performed on n nthropomorphic phntom. For scttered dose mesurements, the dosimeter ws clmped to drip stnd t the height of 170 cm (white rrow), which ws positioned t distnce of 91 cm from the exposure center of phntom. No rdition protections were used during the mesurements.

3 328 Liu et l.: Dul-xis rottionl coronry ngiogrphy 328 Right coronry ngiogrphy ws done with two exposures in two projections: LAO 45 nd AP/crnil 25. As the complexity of individul lesions cn influence the SA exposure time to the ptient, bsed on our center s imge study verges, we pplied 2, 3, nd 5 s cine imging in ech projection to represent clinicl situtions with norml, uncomplicted, nd complicted vessels, respectively. Moreover, 3 s fluoroscopy in ech projection ws included for tble pnning to position the region of interest to mimic clinicl prctice. Therefore, ech exposure consisted of 3 s fluoroscopy nd 2, 3, or 5 s cine imging. Prior to DARCA, isocentering of the imged coronry rteries is essentil. The technique ws described in previous study. (10) To simulte the workflow, seprte 5 s fluoroscopy runs were cquired t AP nd LAO 45 projections before left coronry DARCA, nd t AP projection before right coronry DARCA. Cine time required for left nd right coronry DARCA verges 6.8 s nd 4.5 s, respectively. Detiled X-ry exposure fctors for the SA nd DARCA re shown in Tble 1. T b l e 1. X-ry exposure fctors for different coronry ngiogrphic protocol. Exposure Fctors 2 s SA 3 s SA 5 s SA DARCA Fluoroscopy time per run (s) Cine time per run (s) (4.5) Totl fluoroscopy time (s) Totl cine time (s) Field of view (cm) Source imge detector distnce (cm) Source skin distnce (cm) Fluoroscopy mode Low Low Low Low Cine mode (fr/s) Number in the brcket indictes cine time for the right coronry spin; out of the brcket for the left coronry spin. SA = stndrd coronry ngiogrphy; DARCA = dul-xis rottionl coronry ngiogrphy. B. Dosimetric mesurements PSD ws mesured by thermoluminescent dosimeter (TLD) rrys (Hrshw TLD-100 chips) ttched to the phntom s upper bck (Fig. 2). For ech mesurement site, three TLDs wrpped in blck nylon film were irrdited, with the verge signl being determined. An extr set of three TLDs ws kept outside the rdition room to obtin bckground redings. The TLDs were red out using Hrshw 3500 TLD reder (Thermo Fisher Scientific Inc, Wlthm, MA). The mximum TLD reding ws regrded s the PSD. In ddition, ech ngiogrphy ws performed five times to obtin sufficient exposure to the TLDs, nd the totl dose ws divided by five. A preselected group of TLDs ws used with sensitivity vrition ± 3% to minimize vribility. The clibrtion of the TLDs ws trceble to the Ntionl Stndrd Dosimetric Lbortory. The overll uncertinty of TLD redings ws less thn 5%. Moreover, DAP, cumultive ir kerm (CAK), nd dose rte were registered from the X-ry system. Then, dose indexes (the rtio between PSD nd CAK) were clculted per mesurement. (18) Scttered dose to the opertor ws mesured with no shielding in plce by n electronic personl dosimeter (Unfors EDD-30; Unfors Instruments AB, Billdl, Sweden). This detector hs n ccurcy of ± 6% nd n mple dynmic rnge of dose rtes between 0.03 msv/h nd 2 Sv/h. To simulte clinicl ngiogrphy procedures by rdil ccess, the dosimeter ws clmped to drip stnd, which ws lterlly positioned t 44 cm from the phntom center, t height of 170 cm (pproximtely t the opertor s left eye, Fig. 1). The dosimeter ws bout 91 cm from the phntom center. In ddition, we evluted the influence of source imge detector distnce (SID) (100, 110, nd 120 cm) on fluoroscopy entrnce dose rte nd cine entrnce dose per frme t the ptient entrnce reference point in AP projection using low fluoroscopy mode nd 15 fr/s cine with

4 329 Liu et l.: Dul-xis rottionl coronry ngiogrphy 329 Fig. 2. The thermoluminescent dosimeters (TLDs) positions used in the skin dose mesurement. The TLD rry ws plced under the upper bck of the nthropomorphic phntom, beneth the hert. TLDs were spced by 9 cm from ech other nd numbered by 1 to 9. TLD = thermoluminescent dosimeter. 25 cm field of view. To ensure high relibility of the results, ll the sme experiments were repeted ten times. C. Sttisticl nlysis All mesurement results were expressed s men ± SD nd tested with repeted mesures nlysis of vrince with post hoc Student s t-test using SPSS (Version 19.0, SPSS Inc., Chicgo, IL). A p-vlue of < 0.05 ws considered sttisticlly significnt. III. Results A. Ptient dose As shown in Tble 2, PSD (mximum TLD redings), DAP, nd CAK were generlly lower in DARCA thn in SA. DARCA ccounted for 44% less PSD (p = 0.004), 27% less DAP (p = 0.006), nd 25% less CAK (p = 0.004) thn 2 s SA. When compred to 3 s nd 5 s SA, DARCA corresponded to 59% nd 82% lower PSD, 52% nd 76% lower DAP, nd 43% nd 74% lower CAK, respectively (ll p < 0.001). Note, the minimum TLD mesurement during DARCA ws higher thn during 2 s SA (p < 0.001), while the men TLD results remined comprble T b l e 2. Rdition dose to the phntom ptient during coronry ngiogrphy. Coronry TLD (mgy) DAP CAK Angiogrphy Min Mx Men (Gy cm 2 ) (mgy) Dose Index 2 s SA 0.71± ± ± ± ± ± s SA 1.33± ± ± ± ± ± s SA 1.60± ± ± ± ± ±0.01 DARCA 1.37± ± ± ± ± ±0.01 Vlues re presented s men ± SD. SA = stndrd coronry ngiogrphy; DARCA = dul-xis rottionl coronry ngiogrphy; TLD = thermoluminescent dosimeter; DAP = dose re product; CAK = cumultive ir kerm.

5 330 Liu et l.: Dul-xis rottionl coronry ngiogrphy 330 (p > 0.05). In ddition, DARCA ws ssocited with smller dose index in comprison to SA (ll p < 0.05). Skin dose distribution ws plotted in Fig. 3 per TLD mesurement nd per ngiogrphic protocol. During SA, the most irrdited TLDs were No. 4, 5, 6, 8, nd 9, mong which No. 8 received the highest dose. During DARCA, the most irrdited TLDs were No. 5, 6, 8, nd 9, with No. 6 exposed to the highest dose. Fig. 3. Skin dose distribution in the thermoluminescent dosimeter rrys seprted by different ngiogrphic protocol. 2 s, 3 s, nd 5 s cine time ws pplied in ech projection during the 2 s, 3 s, nd 5 s SA, which represents evluting norml vessels, uncomplicted, nd complicted coronry lesions in clinicl prctice, respectively. TLD = thermoluminescent dosimeter; SA = stndrd coronry ngiogrphy; DARCA = dul-xis rottionl coronry ngiogrphy. B. Opertor dose Tble 3 shows comprison of scttered dose to the opertor. DARCA ws found to reduce 40%, 53%, nd 70% of scttered dose thn tht in 2 s, 3 s, nd 5 s SAs, respectively (ll p < 0.001). T b l e 3. Scttered dose to the opertor during coronry ngiogrphy. Coronry Dose in Fluoroscopy Dose in Cine Totl Dose Angiogrphy (μsv) (μsv) (μsv) 2 s SA 2.45± ± ± s SA 2.44± ± ± s SA 2.48± ± ±0.28 DARCA 1.75± ± ±0.07 Vlues re presented s men ± SD. SA = stndrd coronry ngiogrphy; DARCA = dul-xis rottionl coronry ngiogrphy.

6 331 Liu et l.: Dul-xis rottionl coronry ngiogrphy 331 C. The influence of SID on entrnce dose rte nd dose per frme Entrnce dose rte in fluoroscopy nd dose per frme in cine both significntly incresed with greter SID (p < 0.001, Tble 4). T b l e 4. Entrnce dose rte during fluoroscopy nd dose per frme during cine for different source-imge detector distnces. Source imge Fluoroscopy Cine Detector Distnce Dose Rte Dose per Frme (cm) (mgy/min) (μgy/fr) ± ± ± ± ± ±3.00 Entrnce dose rte nd dose per frme were mesured t the ptient entrnce reference point in the nterior posterior projection (in the low fluoroscopy mode with 25 cm field of view nd 15 fr/s for both fluoroscopy nd cine) IV. DISCUSSION The present study hs used n nthropomorphic phntom for rdition dose mesurements during coronry ngiogrphy simultions. It llows controlled mesurement pproch to void clinicl vribilities (e.g., ptient differences or clinicl procedurl fctors), nd, therefore, results in relible dosimetry ssessment of DARCA nd SA. To our knowledge, this is the first study tht focuses on PSD nd scttered dose in DARCA in comprison to SA. This study demonstrtes tht the PSD during DARCA is significntly lower thn tht during SA. Severl fctors my contribute to lower the PSD. During DARCA exms, less fluoroscopy time nd cine frmes re needed thn in SA. This results in considerbly lower DAP nd CAK (i.e., much less rdition energy) to the ptient. Moreover, the results show tht using DARCA leds to lower dose index thn in SA. This, in turn, indictes tht DARCA is more effective in reducing PSD, s it could spred the dministered rdition over lrge skin re. A mjor finding of this work is tht complicted lesion exmintions could benefit the most from PSD reduction with DARCA. This is of prcticl importnce. Ptients with complicted lesions re likely to undergo reoccurring invsive tretments in the ner future becuse of disese recurrence. The limits of skin tolernce to rdition my then be exceeded, resulting in skin injuries. (19) By pplying DARCA insted of SA, the risk could be lowered. While most of coronry ngiogrphy procedures hve PSD well below the 2 Gy threshold for skin injuries (erly trnsient erythem), (3) procedures tht use ionizing rdition should be performed in ccordnce with the As Low As Resonbly Achievble (ALARA) philosophy. Even when the skin dose is below the threshold, the probbility of stochstic effects shll not be neglected. In ddition, lthough 2 Gy is the threshold to cuse the erliest detectble effect on the skin, the ctul rdition needed to cuse injury vries, depending on individul biologicl sensitivity nd the presence of coexisting diseses (e.g., dibetes mellitus nd connective tissue disorders). (3,20) For this reson, some ptients could show signs of deterministic injury t reltively low dose. Moreover, sensitive ptients re likely to experience more severe injury thn typicl ptients t equl doses. Thus, it is of gret relevnce to pply DARCA for lowering ptient rdition. Compred to the 2 s SA (i.e., ngiogrphy of norml vessels), DARCA seems to hve higher minimum skin dose despite less exposure time nd comprble men skin dose. Figure 3 shows tht, except for No. 4 nd No. 8 TLDs, ll the other TLD redings re higher in DARCA thn in 2 s SA. It suggests tht during DARCA, the TLDs (except No. 4 nd No. 8) my hve more incidences of being irrdited due to more imging projections thn in SA, resulting in higher minimum TLD reding. We lso observed tht, lthough the skin dose distribution on the body surfce is different between DARCA nd SA, the most irrdited body re is similr,

7 332 Liu et l.: Dul-xis rottionl coronry ngiogrphy 332 owing to ll the trditionl coronry ngiogrphic views re encompssed by the trjectories of DARCA. (10) Note tht greter SID is used during DARCA compred to SA (120 cm vs. 100 cm). This, in principle, would led to higher entrnce dose rte or dose per frme to the ptient (i.e., 51% nd 48% for fluoroscopy nd cine, respectively). However, the exposure time for the SA is much longer thn tht for the DARCA (fluoroscopy: 21 s vs. 15 s; cine: 23.3 s (verge) vs s). The reltive increses in rdition dose cused by the longer exposure time during SA re 40% nd 106% for fluoroscopy nd cine, respectively. As cine imging contributes more to the totl mount of rdition dose during dignostic coronry ngiogrphy becuse of higher dose rte, (21) lower totl rdition dose is expected in DARCA, even with greter SID. The lens of the eye is one of the most rdiosensitive tissues in the body. Exposure of the lens to ionizing rdition cn cuse ctrct t pproximtely 2 Gy. (22) Recent studies hve indicted n even lower threshold in the order of 0.5 Gy, or tht risk increses linerly with rdition dose, with no pprent threshold. (4,23) Moreover, prior study hs found high percentge of lens opcities in interventionl crdiologists ttributble to occuptionl rdition exposure. (24) Thus, there is n urgent need to pply vrious rdition protection strtegies to reduce the risk of ctrct formtion. The present study indictes tht scttered dose t the level of the opertor s left eye during DARCA is significntly lower thn during SA, prticulrly while exmining complicted lesions. As commonly greed, stff dose is lrgely relted to ptient dose since it results from secondry scttered rdition rising minly from the ptient. We cn infer tht scttered dose reduction would lso exist in the other sites of the opertor s body, s lower ptient rdition dose is ssocited with DARCA when compred to SA. This would hve significnt impct on the nnul dosge for the opertors, especilly for the high-volume opertors. Therefore, this new imging technique could be used widely for ssessing coronry stenosis, in order to reduce the rdition doses both to the ptient nd the opertor. Note tht this study my benefit from greter rnge of positionl vrition in the opertor dose mesurements due to the inherent differences in bem projections. However, this effect my be limited. The resons re s follows. For one thing, ll the trditionl coronry ngiogrphic views re encompssed by the trjectories of DARCA. For nother, the DAP-normlized opertor dose (μsv/gy cm 2 ) (opertor dose divided by the DAP), which is relible estimtion of locl scttered dose by simple documenttion of DAP, (25) ws comprble between SA nd DARCA in the present study (men 1.92 for SA nd 2.06 for DARCA). Accordingly, the lower scttered dose ssocited with DARCA in this study ws minly s result of smller ptient rdition exposure during DARCA. We should py ttention to the fct tht both ptient nd stff doses noted in this study re mrkedly lower thn those in clinicl prctice described previously. For SA, in the study of vn de Putte et l., (12) they hve reported higher DAP nd PSD vlues (61 Gy cm 2 for DAP nd 412 mgy for PSD) thn those in the present study (verge: 8 Gy cm 2 nd 22 mgy, respectively). Recent studies hve reported 21 Gy cm 2 nd 160 mgy for DAP nd PSD, respectively. (10,16) Moreover, Politi et l. (26) hve reported tht the opertor s left eye exposure ws 297 μsv during trnsrdil SA, which ws significntly greter thn tht in our study (verge: 15 μsv). For DARCA, the DAP rnged from 9 to 24 Gy cm 2. (10,11) However, to the best of our knowledge, no dt were vilble for PSD nd scttered dose during DARCA. These lower rdition exposures cn be explined by the following resons. First, the nthropomorphic phntom used in our study is without rms nd legs, nd the body mss index of this phntom is bout 21. It cnnot represent the verge crdic ptients in clinicl prctice who usully hve lrger vlues of body mss index, (1,10) which is positively correlted with rdition dose. (10) In ddition, phntom studies tend to underestimte the opertor s rdition exposure, since movements of the personnel during exmintions re difficult to simulte. (27) Second, the rdition required to dvnce the ctheter cross the ortic rch, engge the coronry osti, exchnge ctheters, nd perform noncoronry ngiogrphy were excluded from the nlysis in this study, becuse they re confounding fctors for the comprison of rdition dose between the two coronry

8 333 Liu et l.: Dul-xis rottionl coronry ngiogrphy 333 ngiogrphy modlities. Third, s insufficient experience in performing the procedure nd rdition protection techniques cn result in higher rdition dose, (28) this phntom study hd eliminted these fctors from the nlysis. Finlly, the dditionl coronry cquisitions re usully pplied in clinicl prctice t the discretion of the opertor beyond the stndrd ngiogrphy protocol. This study hs used the stndrd ngiogrphy protocols only, which re routinely pplied in our ctheteriztion lb. Although the ptient rdition dose noted in this study is obviously lower thn tht in clinicl prctice, the prior study hs reported men DAP vlue of 7 Gy cm 2 when optimized rdition protection techniques re used for SA, (29) which is t similr level s reported in this study. To some extent, the results of this study my represent the differences between the two techniques in this context. The present study is limited by few fctors. Firstly, our study ws performed in simulted crdic ctheteriztion lb environment, nd cnnot fully ccount for the vribles nd conditions present in clinicl prctice. Secondly, s mentioned bove, the nthropomorphic phntom used in this study is lcking rms nd legs nd is of smll body mss index. The morphology of rel ptient is not fully resembled. Smller DAP is lso expected here when compred with vlues from verge crdic ptients with lrger body mss index. Moreover, phntom studies tend to underestimte the opertor s rdition exposure. Thirdly, it is well known tht PSD is not esy to mesure. With the number of TLDs nd mesurement points used in our study, potentilly higher skin doses might not hve been detected. With lrger numbers of TLDs, further investigtions could be more ccurtely done on ptient skin dose distribution. Finlly, opertor position my vry between centers during the procedure, which could influence individul rdition exposure. During our study, the distnce to the X-ry source ws fixed nd, therefore, the mesured dosge should be judged s n verge vlue. In generl, lthough the bove mesurements might be distinct from the ctul rdition doses, the results in reltive reductions between SA nd DARCA re still credible nd evident. V. Conclusions The present study demonstrtes tht, compred to SA, DARCA cn reduce 44% 82% of PSD to the ptient nd 40% 70% of scttered dose to the opertor. The benefit of rdition dose reduction could be especilly significnt in complicted lesion exmintions due to lrge reduction in X-ry exposure time. The use of DARCA could, therefore, be recommended in clinicl prctice to minimize the ptient rdition dose nd stff dose. Acknowledgments We grtefully thnk the following people in Ntionl Institute for Rdiologicl Protection of Chinese Center for Disese Control nd Prevention: Kedo Wei nd Jincho Wng, for ccess to their fcilities nd help with the mesurements. References 1. Strtis AI, Anthopoulos PL, Gvlitsis IP, et l. Ptient dose in crdic rdiology. Hellenic J Crdiol. 2009;50(1): Kim KP, Miller DL, Blter S, et l. Occuptionl rdition doses to opertors performing crdic ctheteriztion procedures. Helth Phys. 2008;94(3): Stewrt FA, Akleyev AV, Huer-Jensen M, et l. ICRP publiction 118: ICRP sttement on tissue rections nd erly nd lte effects of rdition in norml tissues nd orgns--threshold doses for tissue rections in rdition protection context. Ann ICRP. 2012;41(1-2): Worgul BV, Kundiyev YI, Sergiyenko NM, et l. Ctrcts mong Chernobyl clen-up workers: implictions regrding permissible eye exposures. Rdit Res. 2007;167(2):

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