ABSTRACT
BACKGROUND: The purpose of this study was to qualitatively and quantitatively evaluate the effects of a metal artifact reduction for orthopedic implants (O-MAR) for brain computed tomographic angiography (CTA) in patients with aneurysm clips and coils. METHODS: The study included 36 consecutive patients with 47 intracranial metallic implants (42 aneurysm clips, 5 coils) who underwent brain CTA. The computed tomographic images with and without the O-MAR were independently reviewed both quantitatively and qualitatively by two reviewers. For quantitative analysis, image noises near the metallic implants of non-O-MAR and O-MAR images were compared. For qualitative analysis, image quality improvement and the presence of new streak artifacts were assessed. RESULTS: Image noise was significantly reduced near metallic implants (P < 0.01). Improvement of implant-induced streak artifacts was observed in eight objects (17.0%). However, streak artifacts were aggravated in 11 objects (23.4%), and adjacent vessel depiction was worsened in eight objects (17.0%). In addition, new O-MAR-related streak artifacts were observed in 32 objects (68.1%). New streak artifacts were more prevalent in cases with overlapping metallic implants on the same axial plane than in those without (P = 0.018). Qualitative assessment revealed that the overall image quality was not significantly improved in O-MAR images. CONCLUSION: In conclusion, the use of the O-MAR in patients with metallic implants significantly reduces image noise. However, the degree of the streak artifacts and surrounding vessel depiction were not significantly improved on O-MAR images.
Subject(s)
Humans , Aneurysm , Angiography , Artifacts , Brain , Noise , Orthopedics , Quality ImprovementABSTRACT
Objective To investigate the feasibility of low-tube-voltage in combination with the three-dimensional adaptive iterative dose reduction (AIDR-3D) algorithm in performing lower extremity computed tomography angiography (CTA).Methods A total of 60 patients suspicious of lower extremity arterial occlusion were randomized into control group (120 kV,a =30) and experimental group (100 kV,n =30).The CTA was undertaken with a 320-row scanner (Toshiba Aquilion ONE),and the images was reconstructed with filtered back projection (FBP) algorithm in control group and FBP as well as the AIDR-3D algorithm in experimental group.The subjective image quality,vascular density (VD),noise,signal-to-noise ratio (SNR),contrast-to-noise ratio (CNR),and dose length product (DLP) were compared between two groups.Results The DLP was significantly lower in experimental group than that in control group [(503.5± 104.7) vs.(1 099.4 ± 151.7) mGy·cm,t =15.7,P ＜0.05].The images in experimental group with 100 kV and FBP protocol had significantly increased VD and noise (t =-3.13,-3.61,P ＜ 0.05) than that in the control.The images in experimental group with AIDR-3D had significantly lower noise and higher SNR and CNR than that with FBP (t =13.59,2.14,P ＜ 0.05),also significantly lower noise and significantly higher VD,SNR,and CNR than that in the control (t =-3.75,-4.19,-4.15,P ＜ 0.05).Conclusions Low-tube-voltage (100 kV) combined with AIDR-3D reconstruction could significantly improve the image quality and reduce radiation dose in lower extremity CTA with a 320-row CT scanner.Trial registration Chinese clinical trial registry,ChiCTR-DPD-16008054.
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Objective To evaluate retrospectively the image quality and detection of nodules with low-dose chest computed tomography (LDCT)by photon detector and iterative reconstruction (IR).Methods Sixty-six patients with lung nodules underwent routine LDCT with image reconstruction using filtered back projection (FBP).These patients were followed up by LDCT with photon detector 6 months later with image reconstruction using FBP and SAFIRE.Image quality and detection rate of the nodules were compared among groups including routine LDCT,photon decector+FBP and photon Decector+IR groups.Results Noise was decreased and SNR was increased in turn for routine LDCT,photon detector+FBP and photon detector +IR,exhibiting statistical differences (all P0.05).14 ground glass nodules (GGN )in routine LDCT group and 15 in other two groups were identified with the average diameter of (6.44±1.86)mm, (7.23±1.74)mm and (7.31±1.68)mm,respectively.The ability of routine LDCT to detect the GGNs was lower than that of the others.Conclusion Photon detector and IR are able to decrease image noise,improve image quality,and increase detection rate and measurement accuracy of GGN.
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Objective To study elimination of the Micro CT projective image noise and improve the quality of the recon-structed image for the Micro CT system.Methods The forming factors of the Micro CT projective image noise were analyzed,and proposed the Micro CT projective image correction method to correct the random noise,dark field,light field,response nonuniformity and defect picture element and eliminate the random noise and the ring artifact respectively.Results Through the comparative study,it proposes a simple and practical correction method for the actual response nonuniformity which combines the corrections of light field,dark current and gain inconsistency and settles the three corrections with one circu-lation.The method can enhance the algorithm efficiency greatly and the validity of the correction protocol can be proved through experiments.Conclusion The Micro CT projective image noise is eliminated effectively and the good basis for the following work are established such as three-dimensional reconstruction.