In 121 patients 150 aneurysms were detected. In 101 patients was detected one aneurysm (83%),
in 14 two aneurysms (12%),
in 4 patients three aneurysms (3%),
in 1 patient four and in 1 five aneurysms (1%).
Most of aneurysms were diagnose on MCA (41%),
and were medium size (60%) (Table 1.)
Table 1.
Aneurysms diagnosed on surgery and DSA („gold standard“)
|
≤ 3mm
|
4-10mm
|
11-24mm
|
≥25mm
|
|
ACA
|
9
|
33
|
5
|
0
|
47 31%
|
MCA
|
12
|
36
|
13
|
1
|
62 41%
|
PCA
|
0
|
0
|
1
|
0
|
1 1%
|
ICA
|
5
|
15
|
11
|
2
|
33 22%
|
VBA
|
1
|
6
|
0
|
0
|
7 5%
|
|
27
18%
|
90
60%
|
30
20%
|
3
2%
|
150
100%
|
On MIP CT angiography were diagnosed 7 fals negativ and 4 fals positive aneurysms and sensitivity/ specificity/PPV/NPV/ accuracy was 95.3/87.9/97.3/80.6/93.9%.
On VR CTangiography were diagnosed 3 fals negative and 3 fals positive aneurysms,
and sensitivity/ specificity/PPV/NPV/ accuracy was 98.0/90.9/98.0/90.9/96.7%.
For MIP+VR algorithm sensitivity/ specificity/PPV/NPV/ accuracy was 98.0/84.8/96.7/90.3/95.6%,
respectively.
(Table 2)
Table 2.
|
MIP
|
VR
|
MIP + VR
|
Sensitivity (%)
|
95.3 (92 – 97 )
|
98 (95 – 99.3)
|
98 (95 – 99)
|
Specificity (%)
|
87.9 (74.6 – 95.5)
|
90.9 (79 – 96.7)
|
84.8 (72.5 – 91)
|
Pozitive predictive value PPV(%)
|
97.3 % (94.4 – 99 %)
|
98 % (95.4 – 99.3 %)
|
96.7 % (94 – 98 %)
|
Negative predictive value NPV(%)
|
80.6 % (68.4 – 87.6 %)
|
90.9 % (79 – 96.7 %)
|
90.3 % (77 – 97 %)
|
Accuracy (%)
|
93.9
|
96.7
|
95.63
|
*Intervals with 95% confidence
|
Area under Roc curve for MIP algorithm is 0.916,
for VR is 0.945 in relation to gold standard and show high accuracy for both tests (MIP and VR) ,
but there is no significant different between thise two methods and gold standard (OP,
DSA) p=0.18.
All aneurysms larger than 3mm were diagnosed on CT angiography on both MIP and VR reconstruction.
Using Wilcoxon Signed Rank Test,
p=0.057,
there was no significant different between VR vs.
DSA finding in size of aneurysms, but there was significant different between VR vs.
surgical finding in size of aneurysms (p=0.005).
On surgery,
anurysms were found significantly large then on VR CT angiography.
Disscusion
Table 3.
Localization of aneurysms
|
ACA (%)
|
MCA (%)
|
ICA (%)
|
PCA (%)
|
VBA (%)
|
Merhemic
|
31
|
41
|
22
|
1
|
5
|
Osborn
|
30-35
|
20
|
30-35
|
|
10
|
Numminen
|
22
|
39
|
31
|
3
|
5
|
Zhang
|
29
|
16
|
48
|
1
|
6
|
Hwang
|
36.5
|
28.5
|
28
|
0.5
|
6.5
|
Donmez
|
30
|
32
|
30
|
|
8
|
Merhemic
|
26.5
|
34.5
|
28
|
3
|
8
|
In our study most aneurysms were found on MCA,
like in Numminen et al.
study.
There was significant different between VR vs.
surgical finding in size of aneurysms (p=0.005).
On surgery,
anurysms were found significantly large then on VR CT angiography.
Despide the fact that surgical finding is gold standard,
we can not rely on that when size of aneurysm is questioned.
Surgent does not measure aneurysms with any instrument and their finding is approximative,
rely on expirience.(Fig.1.)
All aneurysms larger than 3mm were diagnosed on CT angiography on both MIP and VR reconstruction.
Three aneurysms smaller then 4mm (one on PICA,
and two on ICA) were not diagnosed on VR algorithm CT angiography (Fig.2),
and three aneurysms on MCA were fals positive diagnosed.
Table 4.
Intracranial aneurysms: CTA findings in different studies
|
Sensitivity
|
Specificity
|
PPV
|
NPV
|
Accuracy
|
Merhemic MIP
|
95.3
|
87.9
|
97.3
|
80.6
|
83.2
|
VR
|
98.0
|
90.92
|
98.0
|
90.9
|
96.7
|
MIP+VR
|
98.0
|
84.8
|
96.7
|
90.3
|
95.63
|
McKinney
|
97.4
|
90.0
|
97.4
|
90.0
|
95.63
|
Donmez
|
95.1
|
94.1
|
|
|
95.0
|
Yoon
|
92.5
|
93.3
|
|
|
92.6
|
Zhang
|
91.5
|
95.0
|
97.7
|
82.6
|
92.5
|
|
95.7
|
95.0
|
97.8
|
90.5
|
95.5
|
Ramasudara
|
94.0
|
80.0
|
94.0
|
80.0
|
|
Li
|
98.1
|
100
|
100
|
85.7
|
|
|
99.0
|
100
|
100
|
92.3
|
|
Hiratsuka
|
87
|
79.0
|
|
|
85.0
|
Most of studies were performed on 64-row spiral CT unit.
In our study, only 30 patient underwent CTA on 64-row unit,
and all others on 4-row CT unit.In our study all patients were evaluated by two radiologist with more than 10 years of experience,
and this is the reason that our results were very good.
In all studies only small aneurysms were not diagnosed on CTA,
like in our study.
Volume rendering (VR) reconstruction has much higher sensitivity,
specificity,
PPV,
NPV and accuracy than MIP.
(Fig.3.)