Influence of selective photon shield combined with sinogram affirmed iterative reconstruction on image quality and radiation dose of dual-energy CT angiography for the diagnosis of intracranial aneurysms

Abstract

Objective To investigate the influence of selective photon shield combined with sinogram affirmed iterative reconstruction(SAFIRE) on image quality and radiation dose of dual-energy CTA for the diagnosis of intracranial aneurysms. Methods The study retrospectively analyzed 80 patients with spontaneous subarachnoid hemorrhage, who were diangosed having intracranial aneurysms by three-dimensional DSA and surgery and underwent cerebral CTA examination. According to CTA scanning method, the patients were divided into conventional group and experimental group (n=40 for each). All patients underwent head CTA in dual energy mode with selective photon shield (SPS) technology. The scanning protocols of conventional group were tube voltages 80 kV and sn 140 kV, tube currents 300 mAs and 150 mAs, filtered back projection (FBP) reconstruction. The scanning protocols of experimental group were tube voltages 80 kV, sn 140 kV, tube currents 200 mAs, 100 mAs, SAFIRE reconstruction. Objective image quality evaluation indexes included the average CT value of all parts (occipital lobe, the anterior cerebral artery, middle cerebral artery and posterior cerebral artery), the background noise, the signal-to-noise ratio (SNR) and contrast to noise ratio (CNR), and subjective image quality was also assessed. Radiation dose was recorded. With 3D DSA or operation findings as gold standard, coincidence rate of intracranial aneurysm detection was calculated both in experimental group and conventional group. Objective image quality evaluation index and radiation dose both in conventional group and experimental group were compared with two independent two-sample t test, subjective image scores with non parameter test of independent samples. Results The noise of occipital lobe, the anterior cerebral artery, middle cerebral artery and posterior cerebral artery were (5.34±1.22), (39.94±15.96), (39.94±15.96) and (23.17± 5.51) HU in conventional group, (4.44 ± 1.08), (24.91 ± 9.36), (35.03 ± 13.65) and (20.61 ± 5.08) in experimental group (the value of t test were 2.508,3.742,2.788 and 2.563, P 0.05). Image quality scores of the conventional group and experimental group were (4.86± 0.07) and (4.67±0.21) without statistical difference (Z=- 0.443,P=0.621). CTDIvol and ED were (20.61 ± 1.07) mGy and (0.79 ± 0.04) mSv in conventional group and (13.59 ± 1.27) mGy and (0.54 ± 0.06) mSv in experimental group (the value of t test were 24.039 and 15.813, P<0.01). With 3D DSA or operation findings as gold standard, intracranial aneurysm diagnosis coincidence of experimental group was 100.0% (29/29), while coincidence rate of conventional group was 96.0% (25/26). Conclusion SPS combined with SAFIRE techniques applied in dual energy CTA for the diagnosis of intracranial aneurysms could improve the quality of CT image and reduce the radiation dosage and have a high diagnosis accuracy. Key words: Intracranial aneurysm; Tomography, X-ray computed; Radiation dosage; Image quality