Characterization of a computed tomography iterative reconstruction algorithm by image quality evaluations with an anthropomorphic phantom

Rampado, Osvaldo; Bossi, Linda; Garabello, Domenica; Davini, Ottavio; Ropolo, R.

doi:10.1016/j.ejrad.2012.06.017

Cited by 20 publications

(13 citation statements)

References 15 publications

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“…Various studies have set different blends of ASiR from 20% to 100%, with reported dose reductions ranging from 23% to 76% (3). In this study, we chose an optimal level of NI and ASiR percentage (NI40 and ASiR 70%) that seemed to lead to the best trade-off between dose reduction and sufficient image quality according to our phantom study and the following formula: NI ASiR 5 NI FBP /(1-0.0073*%ASiR) (14,15). We decided not to use a percentage higher than 70% because this may result in a noise-free oversmooth artifactual image appearance, with a perceived lower image quality (11,25).…”

Section: Discussionmentioning

confidence: 99%

“…Spatial resolution is of special concern in bone imaging. Use of iterative reconstruction tends to smooth the subjective appearance of images, but it seems not to affect the spatial resolution (15,25,26). Manufacturers commonly recommend an ASiR level of 40%.…”

Section: Discussionmentioning

confidence: 99%

“…For FBP CT, NI25 was used as by the manufacturer. For the ASiR CT protocol, we chose an optimal level of NI and ASiR percentage (NI40, ASiR 70%) that seemed to lead to the best trade-off between dose reduction and sufficient image quality (with a margin of safety) according to our phantom study and the following formula: NI ASiR 5 NI FBP /(1 -0.0073 · %ASiR) (14,15). Remember that the NI is a manufacturer-specific term, which is defined as the SD of the noise in the central region of a CT image of a uniform 20-cm water phantom when imaged and reconstructed with a standard reconstruction algorithm.…”

Section: Scanning Techniquesmentioning

confidence: 99%

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Impact of the Adaptive Statistical Iterative Reconstruction Technique on Radiation Dose and Image Quality in Bone SPECT/CT

et al. 2016

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The purpose of this study was to compare a routine bone SPECT/CT protocol using CT reconstructed with filtered backprojection (FBP) with an optimized protocol using low-dose CT images reconstructed with adaptive statistical iterative reconstruction (ASiR). Methods: In this prospective study, enrolled patients underwent bone SPECT/CT, with 1 SPECT acquisition followed by 2 randomized CT acquisitions: FBP CT (FBP; noise index, 25) and ASiR CT (70% ASiR; noise index, 40). The image quality of both attenuation-corrected SPECT and CT images was visually (5-point Likert scale, 2 interpreters) and quantitatively (contrast ratio [CR] and signal-to-noise ratio [SNR]) estimated. The CT dose index volume, dose-length product, and effective dose were compared. Results: Seventy-five patients were enrolled in the study. Quantitative attenuation-corrected SPECT evaluation showed no inferiority for contrast ratio and SNR issued from FBP CT or ASiR CT (respectively, 13.41 ± 7.83 vs. 13.45 ± 7.99 and 2.33 ± 0.83 vs. 2.32 ± 0.84). Qualitative image analysis showed no difference between attenuation-corrected SPECT images issued from FBP CT or ASiR CT for both interpreters (respectively, 3.5 ± 0.6 vs. 3.5 ± 0.6 and 3.6 ± 0.5 vs. 3.6 ± 0.5). Quantitative CT evaluation showed no inferiority for SNR between FBP and ASiR CT images (respectively, 0.93 ± 0.16 and 1.07 ± 0.17). Qualitative image analysis showed no quality difference between FBP and ASiR CT images for both interpreters (respectively, 3.8 ± 0.5 vs. 3.6 ± 0.5 and 4.0 ± 0.1 vs. 4.0 ± 0.2). Mean CT dose index volume, dose-length product, and effective dose for ASiR CT (3.0 ± 2.0 mGy, 148 ± 85 mGy⋅cm, and 2.2 ± 1.3 mSv) were significantly lower than for FBP CT (8.5 ± 3.7 mGy, 365 ± 160 mGy⋅cm, and 5.5 ± 2.4 mSv). Conclusion: The use of 70% ASiR blending in bone SPECT/CT can reduce the CT radiation dose by 60%, with no sacrifice in attenuation-corrected SPECT and CT image quality, compared with the conventional protocol using FBP CT reconstruction technique.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Scanning Techniquesmentioning

confidence: 99%

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Impact of the Adaptive Statistical Iterative Reconstruction Technique on Radiation Dose and Image Quality in Bone SPECT/CT

et al. 2016

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“…Pour la reconstruction des images, la principale avancée correspond aux reconstructions itératives. Cette technique consiste à appliquer des algorithmes itératifs de réduction du bruit au cours de la reconstruction des images à la fois sur les données brutes, c'est-à-dire sur les projections et sur les données de l'image (Rampado et al, 2012). Au cours de ces dernières années, un effort pour réduire la dose (principe ALARA : As-Low-As-reasonably-Achievable) en travaillant avec les algorithmes itératifs (Martinsen et al, 2012) pour la reconstruction de l'image a été engagé par la communauté médicale de radiologie.…”

Section: Introductionunclassified

Scanner abdominal : étude comparative de l’exposition patient en routine clinique sur des appareils avec et sans reconstruction itérative

et al. 2013

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Résumé -Objectif : comparer la dose délivrée aux patients et la qualité d'image en routine clinique lors de la réalisation d'un scanner abdominal ne disposant pas des techniques de reconstructions itératives (RI) par rapport à un examen réalisé sur un scanner disposant des RI. Matériels et méthodes : il s'agit d'une étude rétrospective incluant 30 patients ayant eu deux examens abdominaux sur un scanner 40 coupes (TDM40) et sur un scanner 256 coupes avec RI (TDM256). Les patients, suivis pour une pathologie abdominale chronique, ont eu un examen de même indication sur chaque scanner avec un protocole comprenant une phase abdomino-pelvienne au temps portal. La longueur d'acquisition, la dose efficace et le Produit Dose Longueur (PDL) ainsi que des évaluations quantitatives et qualitatives de l'image ont été comparés. Résultats : la dose efficace moyenne pour un examen était de 17,3 mSv avec le TDM40 (PDL : 1019 mGy.cm) contre 11,1 mSv avec le TDM256 (PDL : 654 mGy.cm) soit une réduction de 35,8 % (p < 0,001). Les longueurs d'acquisitions et l'évaluation quantitative étaient comparables dans les deux groupes. L'évaluation qualitative était légèrement supérieure sur le TDM40 mais aucun examen n'a été considéré comme sous-optimal. Conclusion : l'utilisation d'un scanner équipé de RI permet une réduction significative de la dose efficace tout en préservant une bonne qualité d'image.Abstract -Abdominal CT scan: A comparative study of patient exposure in clinical routine on devices with and without iterative reconstruction. Objective: compare the dose delivered to patients and image quality in clinical routine to perform an abdominal CT scan with no iterative reconstruction techniques (IR) relative to an examination conducted on a scanner with IR. Materials and methods: this is a retrospective study of 30 patients who underwent two abdominal examinations: one on a 40-slice scanner (TDM40) without IR and another one on a 256-slice scanner with IR (TDM256). The patients, on medical follow-up for a chronic abdominal disease, had an exam on each scanner using the same protocol comprising an abdominopelvic time portal phase. The length of acquisition, the effective dose and the dose length product (DLP) as well as quantitative and qualitative assessments of the image were compared. Results: the average effective dose per examination was 17.3 mSv with the TDM40 (PDL: 1019 mGy.cm) against 11.1 mSv with the TDM256 (PDL: 654 mGy.cm), hence a reduction of 35.8% (p < 0.001). The length of acquisition and quantification were comparable in both groups. The qualitative assessment was slightly higher on the TDM40 but no examination was considered suboptimal. Conclusion: using a scanner equipped with IR significantly reduces the effective dose while maintaining image quality.

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“…Hence, when radiation dose is further reduced for extremely low-dose protocols (such as renal stone CT), a higher level of iteration is needed to offset the associated increase in image noise. For example, a higher ASIR of 70%-80% can be used to enhance noise reduction with extremely low-dose protocols (38). The optimal level of iterative reconstruction depends on the degree of radiation dose reduction used for scanning and the desired spatial resolution and differs among scanning protocols.…”

Section: Statistical Iterative Reconstructionmentioning

confidence: 99%

Emerging Techniques for Dose Optimization in Abdominal CT

Kaza¹,

Platt²,

Goodsitt

et al. 2014

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Recent advances in computed tomographic (CT) scanning technique such as automated tube current modulation (ATCM), optimized x-ray tube voltage, and better use of iterative image reconstruction have allowed maintenance of good CT image quality with reduced radiation dose. ATCM varies the tube current during scanning to account for differences in patient attenuation, ensuring a more homogeneous image quality, although selection of the appropriate image quality parameter is essential for achieving optimal dose reduction. Reducing the x-ray tube voltage is best suited for evaluating iodinated structures, since the effective energy of the x-ray beam will be closer to the k-edge of iodine, resulting in a higher attenuation for the iodine. The optimal kilovoltage for a CT study should be chosen on the basis of imaging task and patient habitus. The aim of iterative image reconstruction is to identify factors that contribute to noise on CT images with use of statistical models of noise (statistical iterative reconstruction) and selective removal of noise to improve image quality. The degree of noise suppression achieved with statistical iterative reconstruction can be customized to minimize the effect of altered image quality on CT images. Unlike with statistical iterative reconstruction, model-based iterative reconstruction algorithms model both the statistical noise and the physical acquisition process, allowing CT to be performed with further reduction in radiation dose without an increase in image noise or loss of spatial resolution. Understanding these recently developed scanning techniques is essential for optimization of imaging protocols designed to achieve the desired image quality with a reduced dose.

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Characterization of a computed tomography iterative reconstruction algorithm by image quality evaluations with an anthropomorphic phantom

Cited by 20 publications

References 15 publications

Impact of the Adaptive Statistical Iterative Reconstruction Technique on Radiation Dose and Image Quality in Bone SPECT/CT

Impact of the Adaptive Statistical Iterative Reconstruction Technique on Radiation Dose and Image Quality in Bone SPECT/CT

Scanner abdominal : étude comparative de l’exposition patient en routine clinique sur des appareils avec et sans reconstruction itérative

Emerging Techniques for Dose Optimization in Abdominal CT

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