Dose reduction and image quality in CT angiography for cerebral aneurysm with various tube potentials and current settings

Abstract

Objectives: The purpose of this study is to investigate the image quality on both axial and three-dimensional CT angiograms of the brain at various tube potentials and currents, and to propose the use of descriptors for evaluating the image quality of three-dimensional CT angiograms using entropy analysis. Methods: A head phantom was used as a target object. Axial CT and threedimensional CT angiograms were obtained at various effective milliampere-second values (49-350 mAs) and tube potentials (80-140 kVp) with a 64-row detector CT scanner. Lens doses were measured using a planar silicon pin-photodiode system. The signal-to-noise ratio (SNR) and streak artefacts on the axial CT angiograms were evaluated and the image quality of the three-dimensional CT angiograms was assessed using entropy analysis. Results: Lens doses increased with tube potential and effective milliampere-seconds. From the evaluation of SNR and streak artefacts on axial CT angiograms, we found that the image quality was improved by setting the tube potential at 100 kVp. However, there was little visual difference in the image quality for 100 kVp between 252 (effective value recommended by the manufacturer) and 350 mAs (maximum effective value). In the entropy analysis of the image quality of three-dimensional CT angiograms, the mutual information (information gain) per lens dose was largest at 80 kVp and 252 mAs. Conclusion: Our results suggested that the suitable tube potentials for axial CT and three-dimensional CT angiograms were 100 and 80 kVp, respectively, and the effective milliampere-second value recommended by the manufacturer was appropriate.

Feasibility of ultra-low radiation dose digital subtraction angiography: Preliminary study in a simplified cerebral angiography phantom

“…[10][11][12] Attention is needed in the reduction of doses in diagnostic cerebral angiography because of radiationsensitive structures in the head and neck region. 13 Radiation safety is an even more pressing issue with interventional procedures because these procedures typically require double the dose used for diagnosis. In a recent survey, the average DAP for an aneurysm embolization procedure was approximately double that for a typical angiography study of cerebral aneurysms (218.8 AE 164.3 Gy-cm 2 and 106.2 AE 66.4 Gy-cm 2 , respectively).…”

Metal artifacts reduction in computed tomography: A phantom study to compare the effectiveness of metal artifact reduction algorithm, model-based iterative reconstruction, and virtual monochromatic imaging

“…In this study, we evaluated fine streak artifacts using the Gumbel method devised by Imai et al [ 12 , 13 ] The method is based on the principle that variations of the CT attenuation caused by fine streak artifacts can be statistically modeled by the Gumbel distribution. In brief, the largest difference between adjacent CT numbers of one CT number profile is attributed to fine streak artifacts.…”

“…In brief, the largest difference between adjacent CT numbers of one CT number profile is attributed to fine streak artifacts. [ 12 , 13 ]…”

“…where β and γ are the location and scale parameters, respectively, the location parameter to the mode of that distribution and the scale parameter to its variance. [ 12 , 13 ] Then, the unknown cumulative probability function was also estimated using the mean rank method, which was expressed as: …”

Contrast enhancement efficacy of iodinated contrast media: Effect of molecular structure on contrast enhancement

“…The head phantom was employed as the target object for evaluating the contrast enhancement efficacy. The phantom was composed of simulated brain parenchyma, intracranial arteries with several aneurysms, and skull bone [ 19 ]. In this phantom, the brain parenchyma was made of polyurethane polymer with 2.5% calcium phosphate and its attenuation coefficient was equivalent to that of human brain parenchyma; the intracranial arteries were bored through it; and, the skull bone was made of gypsum and enveloped by polyurethane polymer having the same attenuation coefficient as soft tissue.…”