Document Type : Original Paper
Assistant professor of medical physics, Department of Radiology Technology, School of Paramedicine, Hamadan University of Medical Sciences, Hamadan, Iran.
General Practitioner, Hamadan University of Medical Sciences, Hamadan, Iran Sciences, Hamadan, Iran.
Assistant Professor of Radiology, Department of Radiology, School of Medicine, Farshchian Cardiovascular Subspecialty Medical Center, Hamadan University of Medical Sciences, Hamadan, Iran.
PhD of medical physics, Department of Radiology Technology, School of Paramedicine, Hamadan University of Medical Sciences, Hamadan, Iran
Introduction: This study aimed to compare the image quality and volume dose index of head CT scan between two adaptive statistical iterative reconstructions (ASIR) and the filtered back projection (FBP) algorithms.
Materials and methods: CT number, noise and signal to noise ratio(SNR) for white matter(WM), gray matter(WM), cerebrospinal fluid(CSF( and skull bone were investigated in brain CT scans of 60 patients. All images were reconstructed by FBP and ASIR 40% algorithms. A water phantom was also used to compare the average CT number; noise, signal-to-noise (SNR), and contrast-to-noise ratio (CNR) between algorithms under different acquisition parameters. Volume computed tomography dose index (CTDIvol) and (dose-length product) DLP were obtained from scanner software. Data were analyzed by T-test and Mann-Whitney statistical test with a significance level of less than 0.05.
Results: Image noise of gray matter, CSF and skull bone was significantly lower for ASIR algorithm (P<0.05). The difference in SNR for white matter and gray matter was not significant between the two algorithms but it was higher for CSF and bone for ASIR. In phantom study, Image noise, CTDIvol and DLP in both axial and spiral scan modes were higher for FBP algorithm (P<0.05). In addition, there was no significant difference in SNR and CNR between the two algorithms (P>0.05).
Conclusion: ASIR algorithm reduces the dose and image noise in head CT scan compared to the filtered back projection. Also, using ASIR algorithm the image noise does not increase with lower mA.