Rationale and Objectives
The aim of this study was to prospectively assess the effect of low–tube voltage (80 kVp) 320–detector row volume computed tomographic (CT) angiography (L-VCTA) in the detection of intracranial aneurysms, with three-dimensional (3D) spin digital subtraction angiography (DSA) as the gold standard.
Materials and Methods
Forty-eight patients with clinically suspected subarachnoid hemorrhages were divided into two groups. One group underwent L-VCTA and DSA, while the other group underwent conventional–tube voltage (120 kVp) volume CT angiography (C-VCTA) and DSA. Vascular enhancement, image quality, detection accuracy of aneurysms, and radiation dose were compared between the two groups.
Results
For objective image quality, the L-VCTA group had higher mean vessel attenuation, correlated with higher image noise and lower signal-to-noise ratio, than the C-VCTA group. For subjective image quality, there were no significant differences between the two groups regarding scores for arterial enhancement, depiction of small arterial detail, interference of venous structures, and overall image quality scores. The mean effective dose for the L-VCTA group was significantly lower than for the C-VCTA group (0.56 ± 0.25 vs 1.84 ± 0.002 mSv), with a reduction of radiation dose of 69.73%. With 3D DSA as the reference standard, the sensitivity, specificity, and accuracy in the L-VCTA and C-VCTA groups were 94.12%, 100%, 94.4% and 100%, 100%, and 100%, respectively. In both groups, there were significant correlations for maximum aneurysm diameter measurements between volume CT angiography and 3D DSA; no statistical difference in the mean maximum diameter of each aneurysm was measured between volume CT angiography and 3D DSA.
Conclusions
L-VCTA is helpful in detecting intracranial aneurysms, with results similar to those of 3D DSA, but at a lower radiation dose than C-VCTA.
It has been reported that the incidence of aneurysmal subarachnoid hemorrhage in the general population is between 7% and 10%, with 30-day case fatality of about 43% to 67% . Prompt detection and evaluation of intracranial aneurysms is critical for appropriate endovascular or neurosurgical intervention for patients with subarachnoid hemorrhages. Currently, three-dimensional (3D) digital subtraction angiography (DSA) is considered the “gold standard” for the detection of intracranial aneurysms , but the technique is invasive, time consuming, demanding of technical skill, and relatively expensive, and it carries a risk for neurologic complications of up to 1% to 2.3% (even in patients without vascular disease), which that can lead to permanent deficits in up to 0.5% .
Hence, there has been increasing interest in investigating noninvasive alternatives for the accurate detection of intracranial aneurysms. Computed tomographic (CT) angiography (CTA) is a noninvasive technique and can be easily performed with a single bolus intravenous injection of contrast medium, allowing the rapid evaluation of patients with suspected intracranial aneurysms in the acute setting.
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Materials and methods
Patients
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CTA
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DSA
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Image Analysis
Image quality
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Aneurysm detection
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Radiation Exposure
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Statistical Methods
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Results
Image Quality
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Table 1
Mean Attenuation and Noise Values
Group Attenuation (HU) SD of Attenuation (HU) ICA M2 Basilar Artery Trunk ICA Brain Parenchyma L-VCTA 418.86 ± 86.17 320.85 ± 67.02 350.55 ± 73.00 38.34 ± 15.75 8.99 ± 2.45 C-VCTA 293.36 ± 53.07 220.93 ± 75.84 221.06 ± 63.39 18.69 ± 6.35 4.31 ± 0.86
C-VCTA, conventional-voltage volume computed tomographic angiography; HU, Hounsfield units; ICA, internal carotid artery; L-VCTA, low-voltage volume computed tomographic angiography; M2, second segment of the middle cerebral artery; SD, standard deviation.
In the quantitative region-of-interest analysis of HU, absolute values tended to be higher for the L-VCTA group than for the C-VCTA group. The average differences in mean attenuation were 125.5 HU in the largest vessel, 99.92 HU in the M2, and 129.49 HU in the basilar artery trunk ( P < .001). The noise level was higher and calculated signal-to-noise ratio were lower in the L-VCTA group ( P < .001).
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Table 2
Subjective Image Scores at 80 and 120 kVp
Characteristic 80 kVp 120 kVp_P_ Arterial enhancement 3.92 ± 0.52 3.81 ± 0.32 .338 Depiction of small arterial detail 3.65 ± 0.60 3.50 ± 0.59 .549 Interference of venous structures 3.52 ± 0.73 3.37 ± 0.63 .542 Image noise 3.65 ± 0.54 4.00 ± 0.53 .026 Bone removal 3.73 ± 0.68 3.77 ± 0.57 .877 Overall scores 3.65 ± 0.60 3.83 ± 0.467 .268
There were no significant differences in subjective image quality between the low-voltage and conventional-voltage volume computed tomographic angiography groups regarding the scores for arterial enhancement ( P = .338), depiction of small arterial detail ( P = .549), interference of venous structures ( P = .542), and overall scores ( P = .268). Images acquired at 120 kVp were rated significantly better than images acquired at 80 kVp regarding image noise.
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Diagnostic Accuracy of Aneurysms
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Table 3
Accuracy of L-VCTA and C-VCTA in the Detection of Intracranial Aneurysms
Group Result Statistical Analysis True Positive True Negative False Positive False Negative Sensitivity Specificity Positive Predictive Value Negative Predictive Value Accuracy L-VCTA 32 280 0 2 94.12% (32/34) 100% (280/280) 100% (32/32) 99.29% (280/282) 99.36% (312/314) C-VCTA 23 291 0 0 100% (23/23) 100% (291/291) 100% (23/23) 100% (291/291) 100% (314/314)
C-VCTA, conventional-voltage volume computed tomographic angiography; L-VCTA, low-voltage volume computed tomographic angiography.
There were no significant differences in specificity, sensitivity, and diagnostic accuracy between the L-VCTA and C-VCTA groups ( P < .05).
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Radiation Dose
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Table 4
Radiation Exposure Parameters of the 80-kVp and 120-kVp Groups
Tube Voltage (kVp) Volume Computed Tomographic Dose Index (mGy) Dose-Length Product (mGy · cm) Effective Dose (mSv) 80 16.56 ± 0.71 265.63 ± 11.30 0.56 ± 0.25 120 54.57 ± 0.20 876.58 ± 0.90 1.84 ± 0.002
There was an average 69.73% reduction of estimated effective dose in the low-voltage volume computed tomographic angiography group comparing to the conventional-voltage volume computed tomographic angiography group.
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Discussion
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References
1. Lovelock C.E., Rinkel G.J.E., Rothwell P.M.: Time trends in outcome of subarachnoid hemorrhage: population-based study and systematic review. Neurology 2010; 74: pp. 1494-1501.
2. Stegmayr B., Eriksson M., Asplund K.: Declining mortality from subarachnoid hemorrhage: changes in incidence and case fatality from 1985 through 2000. Stroke 2004; 35: pp. 2059-2063.
3. Anxionnat R., Bracard S., Ducrocq X., et. al.: Intracranial aneurysms: clinical value of 3D digital subtraction angiography in the therapeutic decision and endovascular treatment. Radiology 2001; 218: pp. 799-808.
4. Jayaraman M.V., Mayo-Smith W., Tung G.A., et. al.: Detection of intracranial aneurysms: multi-detector row CT angiography compared with DSA. Radiology 2004; 230: pp. 510-518.
5. Watanabe Y., Uotani K., Nakazawa T., et. al.: Dual-energy direct bone removal CT angiography for evaluation of intracranial aneurysm or stenosis: comparison with conventional digital subtraction angiography. Eur Radiol 2009; 19: pp. 1019-1102.
6. Cloft H.J., Joseph G.J., Dion J.E.: Risk of cerebral angiography in patients with subarachnoid hemorrhage, cerebral aneurysms, and arteriovenous malformations: a meta-analysis. Stroke 1999; 30: pp. 317-320.
7. Pozzi-Mucelli F., Bruni S., Doddi M., et. al.: Detection of intracranial aneurysms with 64 channel multidetector row CT: comparison with DSA. Eur J Radiol 2007; 64: pp. 15-26.
8. Zhang L.J., Wu S.Y., Niu J.B., et. al.: Dual-energy CT angiography in the evaluation of intracranial aneurysms: image quality, radiation dose, and comparison with 3D rotational DSA. AJR Am J Roentgenol 2010; 194: pp. 23-30.
9. Siebert E., Bohner G., Dewey M., et. al.: 320-slice CT neuroimaging: initial clinical experience and image quality evaluation. Br J Radiol 2009; 82: pp. 561-570.
10. Hall P., Adami H.O., Trichopoulos D., et. al.: Effect of low doses of ionizing radiation in infancy on cognitive function in adulthood: Swedish population based cohort study. BMJ 2004; 328: pp. 19.
11. Diekmann S., Siebert E., Juran R., et. al.: Dose exposure of patients undergoing comprehensive stroke imaging by multidetector-row CT: comparison of 320-detector row and 64-detector row CT scanners. AJNR Am J Neuroradiol 2010; 31: pp. 1003-1009.
12. Klingebiel R., Siebert E., Diekmann S., et. al.: 4-D imaging in cerebrovascular disorders by using 320-slice CT: feasibility and preliminary clinical experience. Acad Radiol 2009; 16: pp. 123-129.
13. Salomon E.J., Barfett J., Willems P.W., et. al.: Dynamic CT angiography and CT perfusion employing a 320-detector row CT. Clin Neuroradiol 2009; 19: pp. 187-196.
14. Ertl-Wagner B.B., Hoffmann R.T., Bruning R., et. al.: Multi-detector row CT angiography of the brain at various kilovoltage settings. Radiology 2004; 231: pp. 528-535.
15. Hunt W., Hess R.: Surgical risk as related to time of intervention in the repair of intracranial aneurysms. J Neurosurg 1968; 28: pp. 14-20.
16. Lubicz B., Levivier M., Francois O., et. al.: Sixty-four-row multisection CT angiography for detection and evaluation of ruptured intracranial aneurysms: interobserver and intertechnique reproducibility. AJNR Am J Neuroradiol 2007; 28: pp. 1949-1955.
17. Kaufmann T.J., Huston J., Mandrekar J.N., et. al.: Complications of diagnostic cerebral angiography: evaluation of 19,826 consecutive patients. Radiology 2007; 243: pp. 812-819.
18. Dawkins A.A., Evans A.L., Wattam J., et. al.: Complications of cerebral angiography: a prospective analysis of 2,924 consecutive procedures. Neuroradiology 2007; 49: pp. 753-759.
19. Waaijer A., Prokop M., Velthuis B.K., et. al.: Circle of Willis at CT angiography dose reduction and image quality-reducing tube voltage and increasing tube current settings. Radiology 2007; 242: pp. 832-839.
20. Tomandl B.F., Hammen T., Klotz E., et. al.: Bone-subtraction CT angiography for the evaluation of intracranial aneurysms. AJNR Am J Neuroradiol 2006; 27: pp. 55-59.
21. Wintermark M., Maeder P., Verdun F.R., et. al.: Using 80 kVp versus 120 kVp in perfusion CT measurement of regional cerebral blood flow. AJNR Am J Neuroradiol 2000; 21: pp. 1881-1884.
22. Bahner M.L., Bengel A., Brix G., et. al.: Improved vascular opacification in cerebral computed tomography angiography with 80 kVp. Invest Radiol 2005; 40: pp. 229-234.
23. Wintersperger B., Jakobs T., Herzog P., et. al.: Aortoiliac multidetector-row CT angiography with low kV settings: improved vessel enhancement and simultaneous reduction of radiation dose. Eur Radiol 2005; 15: pp. 334-341.
24. Mckinney A.M., Palmer C.S., Truwit C.L., et. al.: Detection of aneurysms by 64-section multidetector CT angiography in patients acutely suspected of having an intracranial aneurysm and comparison with digital subtraction and 3D rotational angiography. AJNR Am J Neuroradiol 2008; 29: pp. 594-602.
25. Lee E.J., Lee S.K., Agid R., et. al.: Comparison of image quality and radiation dose between fixed tube current and combined automatic tube current modulation in craniocervical CT angiography. AJNR Am J Neuroradiol 2009; 30: pp. 1754-1759.
26. Funama Y., Awai K., Nakayama Y., et. al.: Radiation dose reduction without degradation of low-contrast detectability at abdominal multisection CT with a low tube voltage technique: phantom study. Radiology 2005; 237: pp. 905-910.
27. Nakayama Y., Awai K., Funama Y., et. al.: Lower tube voltage reduces contrast material and radiation doses on 16-MDCT aortography. AJR Am J Roentgenol 2006; 187: pp. W490-W497.
28. Yang C.Y., Chen Y.F., Lee C.W., et. al.: Multiphase CT angiography versus single-phase CT angiography: comparison of image quality and radiation dose. AJNR Am J Neuroradiol 2008; 29: pp. 1288-1295.
29. Westerlaan H.E., van Dijk M.J., Jansen-van der Weide M.C., et. al.: Intracranial aneurysms in patients with subarachnoid hemorrhage: CT angiography as a primary examination tool for diagnosis—systematic review and meta-analysis. Radiology 2011; 258: pp. 134-145.