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Zhou Z, Wellinghoff J, Fan M, Hsieh S, Holmes D, McCollough CH, Yu L. Automated Web-based Software for CT Quality Control Testing of Low-contrast Detectability using Model Observers. Proc SPIE Int Soc Opt Eng 2024; 12925:129252J. [PMID: 38606000 PMCID: PMC11008424 DOI: 10.1117/12.3008777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/13/2024]
Abstract
The Channelized Hotelling observer (CHO) is well correlated with human observer performance in many CT detection/classification tasks but has not been widely adopted in routine CT quality control and performance evaluation, mainly because of the lack of an easily available, efficient, and validated software tool. We developed a highly automated solution - CT image quality evaluation and Protocol Optimization (CTPro), a web-based software platform that includes CHO and other traditional image quality assessment tools such as modulation transfer function and noise power spectrum. This tool can allow easy access to the CHO for both the research and clinical community and enable efficient, accurate image quality evaluation without the need of installing additional software. Its application was demonstrated by comparing the low-contrast detectability on a clinical photon-counting-detector (PCD)-CT with a traditional energy-integrating-detector (EID)-CT, which showed UHR-T3D had 6.2% higher d' than EID-CT with IR (p = 0.047) and 4.1% lower d' without IR (p = 0.122).
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Affiliation(s)
- Zhongxing Zhou
- Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | | | - Mingdong Fan
- Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Scott Hsieh
- Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | - David Holmes
- Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | | | - Lifeng Yu
- Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
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Harada K, Imai T, Ohashi Y, Chiba A, Numasawa K, Hayasaka S, Omori G. [Evaluation of Low-contrast Detectability Using the Digital Phantom Creation Tool in the Late Arterial Phase to Detect Liver Mass Lesions]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2023:2023-1360. [PMID: 37286500 DOI: 10.6009/jjrt.2023-1360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
PURPOSE Late arterial phase images of SD 8, SD 10, and SD 12 were acquired in the 3-phase dynamic study of the liver in combination with hybrid iterative reconstruction. We evaluated the low-contrast detectability by adding a simulated tumor to these images and aimed to formulate a standard image quality. METHODS We prepared images with and without signal for 60 series of 20 samples, each with 3 image quality types (total: 120 series). The continuous confidence method by 10 observers detected 60 simulated tumors. RESULTS The detection sensitivities were 0.765, 0.785, and 0.260 for SD 8, SD 10, and SD 12, respectively (p<0.001) with no significantly different specificities, and the areas under the curve were 0.901, 0.892, and 0.616 (p<0.001), respectively. The simulated mass detection rates were 74.5%, 75.0%, and 21.5% for SD 8, SD 10, and SD 12, respectively (p<0.001), and the intraclass correlation coefficients, which indicate interobserver reliability, were 0.697 at SD 10 without signal, and SD 12 without a signal significantly dropped to 0.185. CONCLUSION Therefore, SD 12 images increase the possibility of overlooking lesions. Hence, image quality in the late arterial phase should be SD 10 or less.
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Affiliation(s)
- Kohei Harada
- Division of Radiology, Sapporo Medical University Hospital
| | - Tatsuya Imai
- Division of Radiology, Sapporo Medical University Hospital
| | - Yoshiya Ohashi
- Division of Radiology, Sapporo Medical University Hospital
| | - Ayaka Chiba
- Division of Radiology, Sapporo Medical University Hospital
| | | | - Shun Hayasaka
- Division of Radiology, Sapporo Medical University Hospital
| | - Go Omori
- Division of Radiology, Sapporo Medical University Hospital
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Abstract
BACKGROUND Computed tomography is a standard imaging procedure for the detection of liver lesions, such as metastases, which can often be small and poorly contrasted, and therefore hard to detect. Advances in image reconstruction have shown promise in reducing image noise and improving low-contrast detectability. PURPOSE To examine a novel, specialized, model-based iterative reconstruction (MBIR) technique for improved low-contrast liver lesion detection. MATERIAL AND METHODS Patient images with reported poorly contrasted focal liver lesions were retrospectively reconstructed with the low-contrast attenuating algorithm (FIRST-LCD) from primary raw data. Liver-to-lesion contrast, signal-to-noise, and contrast-to-noise ratios for background and liver noise for each lesion were compared for all three FIRST-LCD presets with the established hybrid iterative reconstruction method (AIDR-3D). An additional visual conspicuity score was given by two experienced radiologists for each lesion. RESULTS A total of 82 lesions in 57 examinations were included in the analysis. All three FIRST-LCD algorithms provided statistically significant increases in liver-to-lesion contrast, with FIRSTMILD showing the largest increase (40.47 HU in AIDR-3D; 45.84 HU in FIRSTMILD; P < 0.001). Substantial improvement was shown in contrast-to-noise metrics. Visual analysis of the lesions shows decreased lesion visibility with all FIRST methods in comparison to AIDR-3D, with FIRSTSTR showing the closest results (P < 0.001). CONCLUSION Objective image metrics show promise for MBIR methods in improving the detectability of low-contrast liver lesions; however, subjective image quality may be perceived as inferior. Further improvements are necessary to enhance image quality and lesion detection.
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Affiliation(s)
- Jonas Oppenheimer
- Department of Radiology, Charité, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany ,Jonas Oppenheimer, Charité – Universitätsmedizin Berlin, Clinic for Radiology Campus Benjamin Franklin, Hindenburgdamm 30, 12203 Berlin, Germany.
| | - Keno Kyrill Bressem
- Department of Radiology, Charité, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany ,Berlin Institute of Health at Charité, Universitätsmedizin Berlin, Berlin, Germany
| | - Fabian Henry Jürgen Elsholtz
- Department of Radiology, Charité, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Bernd Hamm
- Department of Radiology, Charité, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Stefan Markus Niehues
- Department of Radiology, Charité, Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
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Anam C, Naufal A, Fujibuchi T, Matsubara K, Dougherty G. Automated development of the contrast-detail curve based on statistical low-contrast detectability in CT images. J Appl Clin Med Phys 2022; 23:e13719. [PMID: 35808971 PMCID: PMC9512356 DOI: 10.1002/acm2.13719] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 06/21/2022] [Accepted: 06/22/2022] [Indexed: 12/25/2022] Open
Abstract
Purpose We have developed a software to automatically find the contrast–detail (C–D) curve based on the statistical low‐contrast detectability (LCD) in images of computed tomography (CT) phantoms at multiple cell sizes and to generate minimum detectable contrast (MDC) characteristics. Methods A simple graphical user interface was developed to set the initial parameters needed to create multiple grid region of interest of various cell sizes with a 2‐pixel increment. For each cell in the grid, the average CT number was calculated to obtain the standard deviation (SD). Detectability was then calculated by multiplying the SD of the mean CT numbers by 3.29. This process was automatically repeated as many times as the cell size was set at initialization. Based on the obtained LCD, the C–D curve was obtained and the target size at an MDC of 0.6% (i.e., 6‐HU difference) was determined. We subsequently investigated the consistency of the target sizes for a 0.6% MDC at four locations within the homogeneous image. We applied the software to images with six noise levels, images of two modules of the American College of Radiology CT phantom, images of four different phantoms, and images of four different CT scanners. We compared the target sizes at a 0.6% MDC based on the statistical LCD and the results from a human observer. Results The developed system was able to measure C–D curves from different phantoms and scanners. We found that the C–D curves follow a power‐law fit. We found that higher noise levels resulted in a higher MDC for a target of the same size. The low‐contrast module image had a slightly higher MDC than the distance module image. The minimum size of an object detected by visual observation was slightly larger than the size using statistical LCD. Conclusions The statistical LCD measurement method can generate a C–D curve automatically, quickly, and objectively.
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Affiliation(s)
- Choirul Anam
- Department of Physics, Faculty of Sciences and Mathematics, Diponegoro University, Semarang, Central Java, Indonesia
| | - Ariij Naufal
- Department of Physics, Faculty of Sciences and Mathematics, Diponegoro University, Semarang, Central Java, Indonesia
| | - Toshioh Fujibuchi
- Department of Health Sciences, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Kosuke Matsubara
- Department of Quantum Medical Technology, Faculty of Health Sciences, Institute of Medical Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - Geoff Dougherty
- Department of Applied Physics and Medical Imaging, California State University Channel Islands, Camarillo, California, USA
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Washio H, Ohira S, Funama Y, Ueda Y, Morimoto M, Kanayama N, Isono M, Inui S, Nitta Y, Miyazaki M, Teshima T. Dose Reduction and Low-Contrast Detectability Using Iterative CBCT Reconstruction Algorithm for Radiotherapy. Technol Cancer Res Treat 2022; 21:15330338211067312. [PMID: 34981989 PMCID: PMC8733359 DOI: 10.1177/15330338211067312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Introduction: Several studies have reported the relation between the imaging dose and secondary cancer risk and have emphasized the need to minimize the additional imaging dose as low as reasonably achievable. The iterative cone-beam computed tomography (iCBCT) algorithm can improve the image quality by utilizing scatter correction and statistical reconstruction. We investigate the use of a novel iCBCT reconstruction algorithm to reduce the patient dose while maintaining low-contrast detectability and registration accuracy. Methods: Catphan and anthropomorphic phantoms were analyzed. All CBCT images were acquired with varying dose levels and reconstructed with a Feldkamp-Davis-Kress algorithm-based CBCT (FDK-CBCT) and iCBCT. The low-contrast detectability was subjectively assessed using a 9-point scale by 4 reviewers and objectively assessed using structure similarity index (SSIM). The soft tissue-based registration error was analyzed for each dose level and reconstruction technique. Results: The results of subjective low-contrast detectability found that the iCBCT acquired at two-thirds of a dose was superior to the FDK-CBCT acquired at a full dose (6.4 vs 5.4). Relative to FDK-CBCT acquired at full dose, SSIM was higher for iCBCT acquired at one-sixth dose in head and head and neck region while equivalent with iCBCT acquired at two-thirds dose in pelvis region. The soft tissue-based registration was 2.2 and 0.6 mm for FDK-CBCT and iCBCT, respectively. Conclusion: Use of iCBCT reconstruction algorithm can generally reduce the patient dose by approximately two-thirds compared to conventional reconstruction methods while maintaining low-contrast detectability and accuracy of registration.
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Affiliation(s)
- Hayate Washio
- 53312Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan.,13205Graduate School of Health Sciences, Kumamoto University, Kumamoto, Japan
| | - Shingo Ohira
- 53312Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan
| | - Yoshinori Funama
- Department of Medical Radiation Sciences, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Yoshihiro Ueda
- 53312Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan
| | - Masahiro Morimoto
- 53312Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan
| | - Naoyuki Kanayama
- 53312Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan
| | - Masaru Isono
- 53312Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan
| | - Shoki Inui
- 53312Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan.,Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Japan
| | - Yuya Nitta
- 53312Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan
| | - Masayoshi Miyazaki
- 53312Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan
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Omigbodun A, Vaishnav JY, Hsieh SS. Rapid measurement of the low contrast detectability of CT scanners. Med Phys 2021; 48:1054-1063. [PMID: 33325033 PMCID: PMC8058889 DOI: 10.1002/mp.14657] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 09/07/2020] [Accepted: 11/30/2020] [Indexed: 12/25/2022] Open
Abstract
PURPOSE Low contrast detectability (LCD) is a metric of fundamental importance in computed tomography (CT) imaging. In spite of this, its measurement is challenging in the context of nonlinear data processing. We introduce a new framework for objectively characterizing LCD with a single scan of a special-purpose phantom and automated analysis software. The output of the analysis software is a "machine LCD" metric which is more representative of LCD than contrast-noise ratio (CNR). It is not intended to replace human observer or model observer studies. METHODS Following preliminary simulations, we fabricated a phantom containing hundreds of low-contrast beads. These beads are acrylic spheres (1.6 mm, net contrast ~10 HU) suspended and randomly dispersed in a background matrix of nylon pellets and isoattenuating saline. The task was to search for and localize the beads. A modified matched filter was used to automatically scan the reconstruction and select candidate bead localizations of varying confidence. These were compared to bead locations as determined from a high-dose reference scan to produce free-response ROC curves. We compared iterative reconstruction (IR) and filtered backpropagation (FBP) at multiple dose levels between 40 and 240 mAs. The scans at 60, 120, and 180 mAs were performed three times each to estimate uncertainty. RESULTS Experimental scans demonstrated the feasibility of our technique. Our metric for machine LCD was the area under the exponential transform of the FROC curve (AUC). AUC increased monotonically from 0.21 at 40 mAs to 0.84 at 240 mAs. The sample standard deviation of AUC was approximately 0.02. This measurement uncertainty in AUC corresponded to a change in tube current of 4% to 8%. Surprisingly, we found that AUCs for IR were slightly worse than AUCs for FBP. While the phantom was sufficient for these experiments, it contained small air bubbles and alternative fabrication methods will be necessary for widespread utilization. CONCLUSIONS It is feasible to measure machine LCD using a search task on a phantom with hundreds of beads and to obtain tight error bars using only a single scan. Our method could facilitate routine quality assurance or possibly enable comparisons between different protocols and scanners.
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Affiliation(s)
| | | | - Scott S. Hsieh
- Department of Radiological Sciences, UCLA, Los Angeles, CA 90024, USA
- Department of Radiology, Mayo Clinic, Rochester, MN 55902, USA
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Sakai Y, Shirasaka T, Kondo M, Hamasaki H, Mikayama R, Matsumoto R, Hioki K, Onizuka Y, Yoshikawa H. [Improvement of Image Quality in the Axial Section Using High-resolution Scan Mode and Hybrid Iterative Reconstruction in Ultra-high-resolution Computed Tomography]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2018; 74:1419-1427. [PMID: 30568092 DOI: 10.6009/jjrt.2018_jsrt_74.12.1419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of this study is to compare the physical characteristics and visibility of high-resolution and conventional images acquired with the same X-ray dose, and to investigate the superiority of super high-resolution imaging. A Catphan phantom was scanned in the normal resolution (NR), high-resolution (HR), and super high-resolution (SHR) modes of ultra-high-resolution computed tomography at 120 kV and 75 mAs. All images were reconstructed into a 5-mm thick image slices with filtered back-projection (FBP) and hybrid image reconstruction (HIR), which included normal and enhanced adaptive iterative dose reduction 3D (AIDR and eAIDR, respectively). The modulation transfer function (MTF) and noise power spectrum (NPS) were measured using the circular edge method and radial frequency method, respectively. The signal-to-noise ratio (SNR) was then calculated. High-contrast resolution and low-contrast detectability were evaluated visually by five radiological technologists. The MTFs of HReAIDR and HRFBP images were higher than those of NRFBP images. However, the NPSs of HReAIDR and HRFBP images were larger than those of NRFBP images. The SNR of HReAIDR images was higher than that of NRFBP and HRFBP images. The scores of high-contrast resolution of HReAIDR, NRFBP, and HRFBP images were 13, 8, and 13 cycles/cm, respectively, and the scores of low-contrast detectability were 5, 5, and 6 mm, respectively. Hence, an improvement in high-contrast resolution of signal more than 400 HU in the axial section can be achieved without increasing the radiation dose and decreasing low-contrast detectability with 10 HU using the HR mode and eAIDR.
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Affiliation(s)
- Yuki Sakai
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital
| | - Takashi Shirasaka
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital
| | - Masatoshi Kondo
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital
| | - Hiroshi Hamasaki
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital
| | - Ryoji Mikayama
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital
| | - Ryoji Matsumoto
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital
| | - Kazuhito Hioki
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital
| | - Yasuhiro Onizuka
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital
| | - Hideki Yoshikawa
- Division of Radiology, Department of Medical Technology, Kyushu University Hospital
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Racine D, Viry A, Becce F, Schmidt S, Ba A, Bochud FO, Edyvean S, Schegerer A, Verdun FR. Objective comparison of high-contrast spatial resolution and low-contrast detectability for various clinical protocols on multiple CT scanners. Med Phys 2018; 44:e153-e163. [PMID: 28901621 DOI: 10.1002/mp.12224] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 02/03/2017] [Accepted: 03/07/2017] [Indexed: 11/06/2022] Open
Abstract
PURPOSE We sought to compare objectively computed tomography (CT) scanner performance for three clinically relevant protocols using a task-based image quality assessment method in order to assess the potential for radiation dose reduction. METHODS Four CT scanners released between 2003 and 2007 by different manufacturers were compared with four CT scanners released between 2012 and 2014 by the same manufacturers using ideal linear model observers (MO): prewhitening (PW) MO and channelized Hotelling (CHO) MO with Laguerre-Gauss channels for high-contrast spatial resolution and low-contrast detectability (LCD) performance, respectively. High-contrast spatial resolution was assessed using a custom-made phantom that enabled the computation of the target transfer function (TTF) and noise power spectrum (NPS). Low-contrast detectability was assessed using a commercially available anthropomorphic abdominal phantom providing equivalent diameters of 24, 29.6, and 34.6 cm. Three protocols were reviewed: a head (trauma) and an abdominal (urinary stones) protocol were applied to assess high-contrast spatial resolution performance; and another abdominal (focal liver lesions) protocol was applied for LCD. The liver protocol was tested using fixed and modulated tube currents. The PW MO was proposed for assessing high-contrast detectability performance of the various CT scanners. RESULTS Compared with older generation CT scanners, three newer systems displayed significant improvements in high-contrast detectability over that of their predecessors. A fourth, newer system had lower performance. The CHO MO was appropriate for assessing LCD performance and revealed that an excellent level of image quality could be obtained with newer scanners at significantly lower dose levels. CONCLUSIONS This study shows that MO can objectively benchmark CT scanners using a task-based image quality method, thus helping to estimate the potential for further dose reductions offered by the latest systems. Such an approach may be useful for adequately and quantitatively comparing clinically relevant image quality among various scanners.
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Affiliation(s)
- Damien Racine
- Institute of Radiation Physics, Lausanne University Hospital, Rue du Grand-Pré 1, 1007, Lausanne, Switzerland
| | - Anaïs Viry
- Institute of Radiation Physics, Lausanne University Hospital, Rue du Grand-Pré 1, 1007, Lausanne, Switzerland
| | - Fabio Becce
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital, Rue du Bugnon 46, 1011, Lausanne, Switzerland
| | - Sabine Schmidt
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital, Rue du Bugnon 46, 1011, Lausanne, Switzerland
| | - Alexandre Ba
- Institute of Radiation Physics, Lausanne University Hospital, Rue du Grand-Pré 1, 1007, Lausanne, Switzerland
| | - François O Bochud
- Institute of Radiation Physics, Lausanne University Hospital, Rue du Grand-Pré 1, 1007, Lausanne, Switzerland
| | - Sue Edyvean
- Medical Dosimetry Group, Centre for Radiation Chemicals and Environmental Hazards, Public Health England, Didcot, OX11, UK
| | - Alexander Schegerer
- Department of Medical and Occupational Radiation Protection, Federal Office for Radiation Protection (BfS), Ingolstädter Landstrasse 1, 85764, Neuherberg, Germany
| | - Francis R Verdun
- Institute of Radiation Physics, Lausanne University Hospital, Rue du Grand-Pré 1, 1007, Lausanne, Switzerland
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Harada K, Ohashi Y, Chiba A, Numasawa K, Imai T, Hayasaka S, Katagiri Y. [Development of New Digital Phantom Creation Tool for Evaluation of Low-contrast Detectability Using Iterative Reconstruction]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2018; 74:769-778. [PMID: 30122741 DOI: 10.6009/jjrt.2018_jsrt_74.8.769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
PURPOSE We developed a novel digital phantom-creation tool that will help formulate the standard shooting method for a three-phase dynamic liver study. Here, we present data demonstrating the usefulness of this tool in the assessment of low-contrast detectability and visibility. METHODS We performed a visual evaluation by adding a spherical digital phantom with a diameter of 8 mm and a computed tomography (CT) value difference of 10 Hounsfield unit (HU) to images taken using filtered back projection and seven types of adaptive iterative dose reduction 3D (Weak, Mild, eMild, Standard, eStandard, Strong, and eStrong). We also examined the partial-volume effect by drawing a profile curve using a digital phantom with a CT value difference of 30 HU and a diameter of 5 mm. Furthermore, a digital phantom with two kinds of filters (smoothing and Gaussian) was added to the image of the home-made simulated tumor phantom to visual valuate its visibility in the phantom's low-contrast module and the digital phantom. RESULTS Detection sensitivity was significantly decreased in Standard, eStandard, Strong, and eStrong, and the area under the curve also decreased in a similar fashion. We confirmed that the partial-volume effect was due to the different maximum CT values in the profile curve at 4 and 5 mm thickness. The visibility of the low-contrast module and digital phantom was most consistent when using the Gaussian filter. CONCLUSION This tool can be used for low-contrast detection ability evaluation.
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Affiliation(s)
- Kohei Harada
- Division of Radiology and Nuclear Medicine, Sapporo Medical University Hospital
| | - Yoshiya Ohashi
- Division of Radiology and Nuclear Medicine, Sapporo Medical University Hospital
| | - Ayaka Chiba
- Division of Radiology and Nuclear Medicine, Sapporo Medical University Hospital
| | - Kanako Numasawa
- Division of Radiology and Nuclear Medicine, Sapporo Medical University Hospital
| | - Tatsuya Imai
- Division of Radiology and Nuclear Medicine, Sapporo Medical University Hospital
| | - Shun Hayasaka
- Division of Radiology and Nuclear Medicine, Sapporo Medical University Hospital
| | - Yoshimi Katagiri
- Division of Radiology and Nuclear Medicine, Sapporo Medical University Hospital
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Hashimoto J, Abe S, Ishimori Y, Monma M, Tsumuraya A, Miyauchi K. [Proposal of a New Index Based on Signal-to-Noise Ratio for Low-contrast Detectability in Computed Tomographic Imaging]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2017; 73:537-547. [PMID: 28724865 DOI: 10.6009/jjrt.2017_jsrt_73.7.537] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The low-contrast detectability of computed tomography (CT) images is commonly evaluated by the contrast-to-noise ratio (CNR) because of its convenience to measure. However, the correlation between CNR and visual detectability is poor because the CNR is a simple index determined by both the contrast of the object and the standard deviation of the image noise. On the other hand, the signal-to-noise ratio (SNR), especially SNR based on the statistical decision theory model (SNRS, D) and SNR based on the matched-filter model (SNRM) are considered superior to CNR. In this study, we investigated a new physical image quality index for evaluating low-contrast detectability (SNRA), which is approximately derived from SNRS, D and SNRM. The new index, which was calculated using the object size, contrast of the object and the noise power spectrum, provided good approximations when the diameter of the rod object was equal and >5 mm. The diameter dependency of the SNRA was also found to provide better sensitivity than the sensitivities of CNR and object-specific CNR, similar to SNRS, D and SNRM. The results suggested that the proposed convenient index should be useful for evaluating the low-contrast detectability of CT images.
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Affiliation(s)
- Junichi Hashimoto
- Department of Radiology, Tokyo Medical University Ibaraki Medical Center
- Graduate School of Health Sciences, Ibaraki Prefectural University of Health Sciences
| | - Shinji Abe
- Graduate School of Health Sciences, Ibaraki Prefectural University of Health Sciences
| | - Yoshiyuki Ishimori
- Graduate School of Health Sciences, Ibaraki Prefectural University of Health Sciences
| | - Masahiko Monma
- Graduate School of Health Sciences, Ibaraki Prefectural University of Health Sciences
| | - Akio Tsumuraya
- Department of Radiology, Tokyo Medical University Ibaraki Medical Center
| | - Kaneyoshi Miyauchi
- Department of Radiology, Tokyo Medical University Ibaraki Medical Center
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