the guglielmi detachable coil ( gdc ) is the first detachable coil approved by the food and drug administration of the united states for treating intracranial aneurysms4,7 ) .
although the gdc has been demonstrated as safe and effective for endovascular treatment of intracranial aneurysms , there have been several reports concerning thromboembolic events related to gdc use due to air bubbles and electrothrombosis when it is electrolytically detached .
han et al.4 ) reported that the electrolytic detachment mechanism of the gdc generated gas bubbles and thrombi from the coil detachment zone and this phenomenon may be a potential cause for thromboembolic complications during treatment of cerebral aneurysms . the target detachable coil ( target ; stryker , fremont ,
target coils have the same electrolytic detachment mechanism as a gdc and we had expected the new advanced coils would generate less bubbles than the conventional gdcs during the detachment .
unfortunately , according to our in vitro experiments , the target coils generate larger - sized and more considerable number of air bubbles than the gdcs ( fig .
recently , lee et al.8 ) reported that the air bubbles were larger - sized and generated most frequently in target coil system than other coils through their in vitro experiments .
introduction and detachment of the coils may take a share of the procedure after manipulation of microcatheter with microwire .
our authors were wondering the air bubbles from the coils matter seriously to patients underwent coil embolization for intracranial aneurysm .
however , there was no study for clinical correlation of the air bubbles as thromboembolic source although some authors gave a warning for formation of air bubbles from the electrolytic detachable coils , especially the gdcs or target coils .
the purpose of this study was to retrospectively evaluate and compare the incidence of diffusion - weighted imaging positive lesion ( dwil)-as practical obtainable finding - between two electrolytic detachable coils ( gdc versus target coil ) for treating unruptured intracranial aneurysm ( uia ) .
from march 2011 to december 2011 , we performed endovascular embolization for intracranial aneurysms using one or more target coils for 99 cases in 94 patients .
there were 24 men and 70 women ( age , 59.310.0 years ; range , 40 - 82 years ) .
eighty - one ( 81.8% ) cases were located in the anterior circulation , including the internal carotid artery , 31 ; posterior communicating artery , 16 ; middle cerebral artery , 14 ; anterior communicating artery , 13 ; anterior cerebral artery , five ; and 18 cases in the posterior circulation , including seven vertebral artery , three posterior inferior cerebellar artery , one anterior inferior cerebellar artery , six basilar artery , and one posterior cerebral artery .
the average size of the aneurysms was 6.563.30 mm ( range , 2.6 - 24.6 mm ) .
we performed stent - assisted coil embolization in 18 ( 18.2% ) and balloon - assisted in six ( 6.1% ) of 99 cases .
the historical control group included 132 consecutive patients , harboring 135 aneurysms , who underwent coil embolization using one or more gdcs during the period from january 2010 to march 2011 before the target coil was launched .
inclusion criteria were : 1 ) uia , 2 ) one or more gdc or target coils in use with or without other coils , 3 ) diffusion - weighted image ( dwi ) examination within 24 hours after coiling , and 4 ) coiling performed without a balloon or stent . among 222 patients , ninety patients ( 92 cases ) met the inclusion criteria .
the patients were subdivided into a gdc - treated group ( n=44 ) and a target - coil treated group ( n=48 ) ( fig .
saline and contrast medium were heparinized ( 1000 iu/100 ml ) , and both a guiding catheter and a microcatheter were placed for a continuous heparinized drip .
all patients were administered systemic heparinization ( loading dose of 3000 iu followed by 1000 iu / hour ) during the procedure .
the results of the embolization were classified into complete ( no filling of aneurismal rests without a neck remnant ) , incomplete occlusion ( saccular contrast material filling ) and neck remnant .
all procedure records were reviewed for the number of gdcs or target coils and the total other detached coils .
magnetic resonance imaging was performed within 24 hours after the coiling procedure in all cases to check for any silent thromboembolic events , regardless of neurological changes .
imaging was performed with 1.5-t system ( signa hdxt ; ge medical systems , milwaukee , wi , usa ) and a 3.0-t system ( magnetom verio ; siemens , erlangen , germany ) .
all mr images were reviewed by two neurointerventionalists ( b .- s.k , m.j.k ) . if dwi abnormalities were detected , their number and location were recorded .
aneurysm - related lesions was defined as finding location in the vascular territory downstream from the treated aneurysm , in another cases they were checked as aneurysm - unrelated lesions ( i.e. , anterior circulation versus posterior circulation , ipsilateral hemisphere territory versus contralateral hemisphere territory except lesion of anterior communicating artery including both territories ) .
the demographic characteristics of the aneurysms , coiling results , and lesions on dwi were compared between the gdc and target coil groups using a contingency table or mean comparison .
correlations between multiple dwils ( > 10 dots ) and distinguished risk factors in the groups were analyzed by logistic regression .
we conducted partial correlations analysis to show the statistical differences of continuous variable between dwils and each coil ratio , and adjusted by confound factors .
all statistics were performed using spss 12.0 ( spss inc . , chicago , il , usa ) , and a p - value < 0.05 was considered significant .
from march 2011 to december 2011 , we performed endovascular embolization for intracranial aneurysms using one or more target coils for 99 cases in 94 patients .
there were 24 men and 70 women ( age , 59.310.0 years ; range , 40 - 82 years ) .
eighty - one ( 81.8% ) cases were located in the anterior circulation , including the internal carotid artery , 31 ; posterior communicating artery , 16 ; middle cerebral artery , 14 ; anterior communicating artery , 13 ; anterior cerebral artery , five ; and 18 cases in the posterior circulation , including seven vertebral artery , three posterior inferior cerebellar artery , one anterior inferior cerebellar artery , six basilar artery , and one posterior cerebral artery .
the average size of the aneurysms was 6.563.30 mm ( range , 2.6 - 24.6 mm ) .
we performed stent - assisted coil embolization in 18 ( 18.2% ) and balloon - assisted in six ( 6.1% ) of 99 cases .
the historical control group included 132 consecutive patients , harboring 135 aneurysms , who underwent coil embolization using one or more gdcs during the period from january 2010 to march 2011 before the target coil was launched .
inclusion criteria were : 1 ) uia , 2 ) one or more gdc or target coils in use with or without other coils , 3 ) diffusion - weighted image ( dwi ) examination within 24 hours after coiling , and 4 ) coiling performed without a balloon or stent . among 222 patients , ninety patients ( 92 cases ) met the inclusion criteria .
the patients were subdivided into a gdc - treated group ( n=44 ) and a target - coil treated group ( n=48 ) ( fig .
all procedures were performed via a transfemoral route with general anesthesia . flushed saline and contrast medium were heparinized ( 1000 iu/100 ml ) , and both a guiding catheter and a microcatheter were placed for a continuous heparinized drip .
all patients were administered systemic heparinization ( loading dose of 3000 iu followed by 1000 iu / hour ) during the procedure .
the results of the embolization were classified into complete ( no filling of aneurismal rests without a neck remnant ) , incomplete occlusion ( saccular contrast material filling ) and neck remnant .
all procedure records were reviewed for the number of gdcs or target coils and the total other detached coils .
magnetic resonance imaging was performed within 24 hours after the coiling procedure in all cases to check for any silent thromboembolic events , regardless of neurological changes .
imaging was performed with 1.5-t system ( signa hdxt ; ge medical systems , milwaukee , wi , usa ) and a 3.0-t system ( magnetom verio ; siemens , erlangen , germany ) .
all mr images were reviewed by two neurointerventionalists ( b .- s.k , m.j.k ) .
aneurysm - related lesions was defined as finding location in the vascular territory downstream from the treated aneurysm , in another cases they were checked as aneurysm - unrelated lesions ( i.e. , anterior circulation versus posterior circulation , ipsilateral hemisphere territory versus contralateral hemisphere territory except lesion of anterior communicating artery including both territories ) .
the demographic characteristics of the aneurysms , coiling results , and lesions on dwi were compared between the gdc and target coil groups using a contingency table or mean comparison .
correlations between multiple dwils ( > 10 dots ) and distinguished risk factors in the groups were analyzed by logistic regression .
we conducted partial correlations analysis to show the statistical differences of continuous variable between dwils and each coil ratio , and adjusted by confound factors .
all statistics were performed using spss 12.0 ( spss inc . , chicago , il , usa ) , and a p - value < 0.05 was considered significant .
dwi was performed in all 90 patients ( 92 cases ; two patients underwent coil embolization for aneurysms located on different sites ) after the coil embolization .
however , all patients with dwil were asymptomatic except for one patient who underwent coil embolization using three gdcs for an unruptured posterior inferior cerebellar artery ( pica ) aneurysm and suffered headache and dizziness after the procedure .
dwils were detected in 31 ( 70.5% ) of 44 cases in the gdc group .
the average number of dwils was 5.08.7 ( range , 1 - 40 ) in aneurysm - related territory and 0.81.2 ( range , 1 - 4 ) in aneurysm - unrelated territory . in the target coil group ,
the number of lesions was 2.15.4 ( range , 1 - 32 ) in aneurysm - related territory and 1.43.1 ( range , 1 - 14 ) in aneurysm - unrelated territory ( table 2 ) .
the target coil group tended to reveal fewer aneurysm - related dwils , however , it was not significant .
no association between multiple dwils with high signal dots over 10 and any of the risk factors ( involving group , aneurismal size and occlusion results ) was found ( table 3 ) .
a ratio of the gdcs in total coils was 45.8% ( range , 10.0 - 100% ) and the target coils were 67.8% ( range , 15.4 - 100% ) in each the gdc / target coil group .
there was no significant correlation between the number of dwils and a ratio of the coils in gdcs or target group ( fig .
since the endovascular treatment using gdcs was first introduced in 1991 , several coil materials have been developed and used for treating intracranial aneurysms . the safety and efficacy of the endovascular technique using coil materials
in particular , the coils improved rapidly , which made it possible to improve anatomic and clinical outcomes of endovascular coiling9,11,12,19 ) .
although the treatment has world - wide acceptance for intracranial aneurysms , thromboembolic complications still remain as procedure - related main events10,14,17 ) .
several studies have shown that thromboembolic events including stroke and transient ischemic attacks occur at a rate of 2.4 - 28%3,10,14 ) .
those series defined complications as new focal neurological deficits , mentality changes , or abnormal findings detected on a post - procedural imaging study .
pelz et al.14 ) reported that thromboembolic events associated with conventional coil embolization using gdcs occurred in 28% of cases , with permanent deficits affecting approximately 5% in their study group .
rordorf et al.16 ) detected embolic infarctions that were related to the coil placement procedure in eight ( 61% ) of 14 patients , and they were all asymptomatic .
soeda et al.18 ) reported that dwi showed high signal lesions in 40 ( 61% ) of 66 patients , with 16 patients ( 40% ) eventually developing neurological symptom . in our series , a symptomatic thromboembolism occurred in only one ( 1.1% ) of 90 patients ; however , new high signal lesions on dwi were detected at the aneurysm - related territory in 61.1% ( 55/90 ) of patients without neurological symptoms , suggesting silent thromboembolic events .
thromboembolic events may be caused by thrombus formation from the delivery system , endosaccular thrombosis , protruding coils into the parent vessel , or other supporting devices for endosaccular stabilization of the coils5 ) .
some studies have documented that balloon- or stent - assisted coil embolization increases thromboembolic risk , but this remains controversial1,5 ) .
several authors have reported that thromboembolic events are associated with gdc embolization and the use of dwi6,17,18 ) . among the causative factors ,
rordorf et al.16 ) suggested that air bubbles in the fusion solutions may act as emboli , and padolecchia et al.13 ) and han et al.4 ) investigated the role of electrothrombosis in embolizations performed with gdcs .
these studies suggest that thrombi might form during the procedure , as well as immediately after detachment of the coils .
the clots that form during the detachment process around the detachment zone or adjacent to the coils may be dislodged during withdrawal of the delivery wire , repositioning of the microcatheter , or repetitive endosaccular introduction of the coil1 ) .
the gdc , which is the most commonly used electrolytic detached coil system , has frequent thromboembolic complications due to its detachment system4,13,16 ) .
the target coil , which is a new version of the gdc , has been in use since early 2011 .
several changes and improvements have been implemented over the conventional gdcs . however , according to our in vitro experiment and microscopic examination of target coils , air bubbles were still observed when it is electrolytically detached ( fig .
1 ) . in addition , the air bubbles from detach zone of the coils were considerable amount more than the conventional gdcs on the contrary our expectation . in our results , there was no significant correlation between the ratio of gdc and/or target coils and detected high signal dots on dwi ( p=0.704 ) .
the number of electrolytic detachable coils was not significant for the number of dwil between the two groups .
considering these results adjusted by confounding factors ( aneurismal size and occlusion results ) , we suggest that the electrolytic detached coil system may be not a significant factor for thromboembolic events . nevertheless , as electrothrombosis during embolization occurs with gdcs4,13 ) , our results also revealed many cases with dwil . however , the relationship between the electrolytic detachable system and dwil was unclear , and all cases were silent events except one case with mild neurological deterioration .
our author reviewed the results in only single gdc ( n=5 ) , target ( n=17 ) or other kind ( n=6 ) of coils - using 28 cases in spite of a few cases . there were also no significant correlation between the number of coils and the dwils ( 4.23.7 ; 1.52.1 ; 0.70.8 , p=0.104 ) .
no significant difference was observed between the target coil group and the gdc group for aneurysm - related dwil .
manufacturers officially announced that the target detachable coil is an advanced model of the gdc coil detachment system .
however , target detachable coils still have the electrolytic detachable system and may be not superior to previous generation gdcs for electrothrombosis during conventional coil embolization .
as high signal dots in dwi were also detected in the aneurysm - unrelated territory , dwils were not always located in the vascular territory of a parent artery of the aneurysm .
lesions can develop from collateral flow through the anterior or posterior communicating artery or from other sites before the coil embolization procedure2,17 ) .
the choice of coil material was likely to be influenced by practitioner 's preference at that time during procedure .
in addition , we acknowledge that our study is a retrospective analysis with a selection bias because of inclusion of the results in cases used few gdcs or target coils - even if at least the coil was used - to our data
. it may be unreasonable to draw exactly the effect of the electrolytic detachable system on the rate of ischemic events on dwi because some other factors ( e.g. , catheter and coil manipulation , procedural time and experience of practitioner ) could affect the environment .
therefore , in this study , to exclude the other factors , relatively narrow inclusion criteria ( unruptured aneurysm , no supporting devices and simple technique ) were applied .
moreover , total target detachable coils were used more than one third and the semi - results only involving the gdc or target coils more than fifty percentage were parallel to the overall result .
therefore , our results suggest that it may support in a degree the relation between electrolytic detachable coils and dwils . however , for the more significant data coincided with our purpose , prospective study should be performed using unitary detachable coils under unitary environment except other factors .
the choice of coil material was likely to be influenced by practitioner 's preference at that time during procedure .
in addition , we acknowledge that our study is a retrospective analysis with a selection bias because of inclusion of the results in cases used few gdcs or target coils - even if at least the coil was used - to our data
. it may be unreasonable to draw exactly the effect of the electrolytic detachable system on the rate of ischemic events on dwi because some other factors ( e.g. , catheter and coil manipulation , procedural time and experience of practitioner ) could affect the environment . therefore , in this study , to exclude the other factors , relatively narrow inclusion criteria ( unruptured aneurysm , no supporting devices and simple technique ) were applied .
moreover , total target detachable coils were used more than one third and the semi - results only involving the gdc or target coils more than fifty percentage were parallel to the overall result .
therefore , our results suggest that it may support in a degree the relation between electrolytic detachable coils and dwils . however , for the more significant data coincided with our purpose , prospective study should be performed using unitary detachable coils under unitary environment except other factors .
our study has shown a relatively high prevalence of dwil that occurred after coil embolization for uia using gdcs / target electrolytic detachable coils .
no difference in the incidence of dwil was observed between the gdc and the newly developed target coil in a similar environment .
our results suggest that electrolytic detachment of the coil may not be a significant contributor to the incidence of dwil during endovascular coil embolization .
 objectivethe purpose of this study was to retrospectively evaluate and compare the incidence of diffusion - weighted image ( dwi ) lesions between the guglielmi detachable coil ( gdc ) and the target coil for treating unruptured intracranial aneurysm.methodsfrom 2010 to 2011 , consecutive 222 patients with an intracranial aneurysm underwent coil embolization . 
 inclusion criterias were : 1 ) unruptured intracranial aneurysm , 2 ) one or more gdc or target coils used with or without other coils , 3 ) dwi examination within 24 hours after coiling , and 4 ) coiling performed without a balloon or stent.resultsninety patients ( 92 cases ) met the inclusion criteria . 
 dwi lesions were detected in 55 ( 61.1% ) of 90 patients . in the gdc group ( n=44 ) , 
 dwi lesions were detected in 31 ( 70.5% ) . 
 the average number of dwi lesions was 5.08.7 ( meansd ; range , 1 - 40 ) in aneurysm - related territory . in the target coil group ( n=48 ) , 
 dwi lesions were detected in 24 ( 50.0% ) . 
 the number of dwi lesion was 2.15.4 ( range , 1 - 32 ) in aneurysm - related territory . 
 there was no significant correlation between a number of coils and dwi lesions . 
 no significant differences were also observed in the number of dwi lesions in each group.conclusionthe gdc and target coils , which have an electrolytic detachable system , showed no differences in the incidence of dwi lesion . 
INTRODUCTION
MATERIALS AND METHODS
Patients
Endovascular treatment
DWI evaluation
Statistical analysis
RESULTS
DISCUSSION
Limitations of our study
CONCLUSION