x - ray digital subtraction angiography ( dsa ) has been the gold standard investigation in the evaluation of intracranial aneurysms both before and after surgical clipping [ 13 ] .
two - dimensional ( 2d ) dsa has been used over the years and has been supplemented by three - dimensional ( 3d ) rotational angiography ( ra ) which has been shown to be superior in evaluation of untreated aneurysms with regard to aneurysm detection rate , morphology delineation , and size estimation , features which have a direct implication in the treatment planning .
thus , now 3d ra is being labelled as the  new gold standard  [ 49 ] . considering the added advantage of 3d ra over 2d dsa in evaluation of native aneurysms
, it follows that the same could also be applicable to evaluation of clipped aneurysms .
we undertook the study to assess whether 3d ra compared favourably to 2d dsa in picking up aneurysm remnant / recurrence .
47 consecutive patients referred to the authors for follow up angiograms after surgical clipping were taken into study and underwent both 2d dsa and 3d ra on a neurostar biplane neuroangiography suite ( siemens , erlangen , germany ) .
the 2d views taken were anteroposterior ( ap ) , lateral ( lat ) , and right and left anterior obliques ( rao , lao ) and a view with specific angle determined by preoperative dsa showing the neck of the aneurysm .
3d ra was subsequently performed , acquired data transferred to the work station ( inspace , leonardo vb30b , siemens ag , berlin and munchen , 2003 ) automatically , and reconstruction process started immediately .
3d reconstruction and rendering : various rendering techniques [ 1014 ] were employed in each case : maximum intensity projection ( mip ) , surface shaded display ( ssd ) , volume rendered transparent ( vrt ) , and two - color coils and clips .
the aneurysm residue / recurrence was assessed by two authors ( sk and nkm ) and classified as per sindou et al .   into 5 grades : grade 1 : less than 50% of neck implantation ; grade 2 : more than 50% of neck implantation ; grade 3 : residual lobe from a multilobulated sac ; grade 4 : residual portion of the sac , less than 75% of aneurysmal size ; grade 5 : residual portion of the sac more than 75% of aneurysm 's size .  
 statistical analysis .
wilcoxon signed - rank test was used to compare the different grades of aneurysm residue / recurrence in 2d dsa and 3d ra .
a total of 47 patients were evaluated , who underwent angiograms of 51 vessels harbouring 54 aneurysms ( 4 patients had two aneurysms in the same injected vessel ) .
the patients ' age varied from 14 years to 74 years ( maximum were between 45 and 65 years ) and the male to female ratio was 1  :  1.85 .
the aneurysms ' primary distribution was anterior communicating artery20 , middle cerebral artery11 , paraclinoid internal carotid artery9 , posterior communicating artery8 , distal anterior cerebral artery3 , posterior cerebral artery , anterior inferior cerebellar artery , and basilar tip1 each .  
figure 1 shows the presence / absence and the different grades of residual / recurrent aneurysm in a head - to - head comparison of 2d dsa and 3d ra .
the residual / recurrent aneurysm detection rate was 53.70% ( 29/54 aneurysms ) with 2d dsa and 66.67% ( 36/54 aneurysms ) with 3d ra .
the results of the wilcoxon signed rank test were w = 83 , n = 17 , z = 1.95 , area between z = 0.9488 , p(1-tail ) = 0.0256 , and p(2-tail ) = 0.0512 ( just about significant ) . in 12 aneurysms ,
3d ra upgraded the residue / recurrence , among which nine had been completely not detected on 2d dsa and were found to have grade one or two residual necks on the 3d ra , and , in three aneurysms , a small neck on 2d dsa turned out to be aneurysm sac on 3d ra . in a total of 5 aneurysms , the classification was downgraded by 3d ra , one each from grade 1 to 0 , grade 2 to 0 , grade 3 to 1 , grade 3 to 2 , and grade 4 to 3 .
by simultaneously rotating the x - ray tube and the image intensifier during the intra - arterial injection of contrast media , after having taken a spin of mask images , ra and 3d reconstructed images enable us to obtain accurate information regarding the cerebral arteries and the pathologies they possess by visualizing them from different perspectives and avoiding vessel overlap .
the evaluation of the result of aneurysm clip placement is important because the complete exclusion of aneurysms from the circulation is the aim of the operation .
the incidence of recurrent aneurysm after successful clip placement has been reported to be 1.52.9% [ 16 , 17 ] , while the reported incidences of residual aneurysms are between 4% and 8% [ 1821 ] and the risk of bleeding from residual aneurysm is believed to be 1 - 2% [ 16 , 18 ] .
2d dsa has been used as the standard for the follow - up imaging of clipped aneurysms . however , the small remnant / recurrent aneurysms are often difficult to detect and evaluate because of the clip mass and overlap of adjacent vessels .
kang et al .   studied 71 patients with 88 clipped aneurysms and found 37 residual aneurysms ( 42% ) with 3d ra as opposed to only 18 with 2d dsa .
they attributed this to the excellent image quality and the various viewing angles provided by 3d angiography coupled with the ability to avoid and if necessary delete the overlapping vessels . 

murakamia et al .   have also published a paper wherein they assessed 67 treated ( both coiled and clipped ) aneurysms and found good results with regard to remnant detection rate .
we had a very high residual / recurrent aneurysm detection rate ( 53.70% and 66.67% with 2d
this high percentage was possibly because many of the cases were referred to us and the operating neurosurgeon might have had a suspicion of a residue .
however , we do not have correlation with intraoperative findings available for all the patients .
3d ra excellently showed the clip - artery , clip - aneurysm , and artery - aneurysm relationship ( figure 2 ) .
in fact , most extra residues picked were type 1 or type 2 residual necks .
out of the 12 extra aneurysms picked up , 9 were advised a prolonged vigil for aneurysm regrowth and only 3 were advised retreatment ( which the patients promptly refused ) . in our study , we studied ssd , vrt , mip and two - color , coils and clips reconstructed images in all the cases in multiple viewing angles and varied thresholds .
as per our day - to - day experience , all of these commonly used techniques , namely , ssd , vrt , mip , and two - color coils and clips have to be viewed for adequate assessment .
an example ( figure 4 ) illustrates this fact , wherein two - color and mip could show the artery and clip relationship well , while ssd could not , and vrt could do so only in limited manner .
hence , a difference between these various techniques was not evaluated as all of them were found to be complementary to each other and indispensable .
the final opinion formed after analyzing all the images was compared with that of 2d dsa findings .
3d ra picks up more residual / recurrent aneurysms than 2d dsa and both 2d dsa and 3d ra should be performed in follow - up of clipped aneurysms .
 
 introduction . 3d 
 rotational angiography ( ra ) is indispensable for evaluation of intracranial aneurysms , providing infinite viewing angles and defining the aneurysm morphology . 
 its role in follow - up of clipped aneurysms remains unclear . 
 we aimed to compare the aneurysm residue / recurrence detection rate of 3d ra with 2d digital subtraction angiography ( dsa ) . 
 methods . 
 47 patients harboring 54 clipped aneurysms underwent both 2d dsa and 3d ra . 
 the residual / recurrent aneurysms were classified into five grades and the images of both modalities were compared . 
 results . 
 the residual / recurrent aneurysm detection rate was 53.70% ( 29/54 aneurysms ) with 2d dsa and 66.67% ( 36/54 aneurysms ) with 3d ra ( p = 0.05 ) . 
 in 12 aneurysms , 3d ra upgraded the residue / recurrence among which nine had been completely not detected on 2d dsa and were found to have grade one or two residual necks on the 3d ra , and , in three cases , a small neck on 2d dsa turned out to be aneurysm sac on 3d ra . in a total of 5 aneurysms , 
 the classification was downgraded by 3d ra . 
 conclusion . 
 3d ra picks up more aneurysm residue / recurrence ; hence , both 2d dsa and 3d ra should be performed in follow - up evaluation of clipped aneurysms . 
1. Introduction
2. Materials and Methods
3. Results
4. Discussion
5. Conclusion