担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

A novel method for measuring the slice sensitivity profile (SSP) of computed tomography (CT) images reconstructed using an iterative reconstruction (IR) algorithm is proposed herein. A phantom that included a low-contrast spherical object was scanned and consecutive cross-sectional images were reconstructed. The mean CT values in a region including the sphere were measured for all images and plotted as a function of slice position along the longitudinal [Formula: see text] direction to yield a mean CT value profile [Formula: see text]. Next, we numerically generated an object function corresponding to the sphere and obtained the mean CT value profile [Formula: see text]. Subsequently, the SSP was modeled as a product of the Gaussian and cosine functions. We convolved [Formula: see text] with the modeled SSP to obtain [Formula: see text]. The difference between [Formula: see text] and [Formula: see text] was evaluated using the root mean square error (RMSE), which was minimized via optimization of the SSP model parameters. To validate the methodology, we first used filtered back projection (FBP) images to compare the SSPs determined using the proposed and standard coin methods. Subsequently, the proposed method was applied to measure the SSPs of four types of IR algorithms in two scanners. The SSPs of the FBP images determined using the proposed and coin methods showed good agreement. Additionally, in the SSP measurements using the proposed method, [Formula: see text] agreed well with [Formula: see text] for every IR algorithm. The RMSEs for all measurements were less than 0.7 HU, indicating the accuracy of the SSPs. Thus, the proposed method is effective for obtaining valid SSPs.

DOI： 10.1007/s12194-021-00636-0

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その他リンク： https://link.springer.com/article/10.1007/s12194-021-00636-0/fulltext.html

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：(公社)日本放射線技術学会  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

PURPOSE: We sought to develop machine learning models to detect multileaf collimator (MLC) modeling errors with the use of radiomic features of fluence maps measured in patient-specific quality assurance (QA) for intensity-modulated radiation therapy (IMRT) with an electric portal imaging device (EPID). METHODS: Fluence maps measured with EPID for 38 beams from 19 clinical IMRT plans were assessed. Plans with various degrees of error in MLC modeling parameters [i.e., MLC transmission factor (TF) and dosimetric leaf gap (DLG)] and plans with an MLC positional error for comparison were created. For a total of 152 error plans for each type of error, we calculated fluence difference maps for each beam by subtracting the calculated maps from the measured maps. A total of 837 radiomic features were extracted from each fluence difference map, and we determined the number of features used for the training dataset in the machine learning models by using random forest regression. Machine learning models using the five typical algorithms [decision tree, k-nearest neighbor (kNN), support vector machine (SVM), logistic regression, and random forest] for binary classification between the error-free plan and the plan with the corresponding error for each type of error were developed. We used part of the total dataset to perform fourfold cross-validation to tune the models, and we used the remaining test dataset to evaluate the performance of the developed models. A gamma analysis was also performed between the measured and calculated fluence maps with the criteria of 3%/2 and 2%/2 mm for all of the types of error. RESULTS: The radiomic features and its optimal number were similar for the models for the TF and the DLG error detection, which was different from the MLC positional error. The highest sensitivity was obtained as 0.913 for the TF error with SVM and logistic regression, 0.978 for the DLG error with kNN and SVM, and 1.000 for the MLC positional error with kNN, SVM, and random forest. The highest specificity was obtained as 1.000 for the TF error with a decision tree, SVM, and logistic regression, 1.000 for the DLG error with a decision tree, logistic regression, and random forest, and 0.909 for the MLC positional error with a decision tree and logistic regression. The gamma analysis showed the poorest performance in which sensitivities were 0.737 for the TF error and the DLG error and 0.882 for the MLC positional error for 3%/2 mm. The addition of another type of error to fluence maps significantly reduced the sensitivity for the TF and the DLG error, whereas no effect was observed for the MLC positional error detection. CONCLUSIONS: Compared to the conventional gamma analysis, the radiomics-based machine learning models showed higher sensitivity and specificity in detecting a single type of the MLC modeling error and the MLC positional error. Although the developed models need further improvement for detecting multiple types of error, radiomics-based IMRT QA was shown to be a promising approach for detecting the MLC modeling error.

DOI： 10.1002/mp.14699

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/mp.14699

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

PURPOSE: A method for measuring the slice sensitivity profile (SSP) of computed tomography (CT) images reconstructed with iterative reconstruction (IR) algorithms was reported by the AAPM Task Group 233 (TG233). In this method, the phantom plane edge is slightly slanted with respect to the scan plane to obtain a composite oversampled edge-spread function (ESF). However, it is expected that a fine-sampled ESF can be obtained directly from images reconstructed with a small slice increment without slanting the edge plane. This study aimed to investigate the validity of using a non-slanted edge plane. METHODS: In the proposed non-slanted edge method, the phantom was positioned so that the plane edge was perpendicular to the longitudinal z-axis, and images were reconstructed with a 1-mm slice thickness and 0.1-mm increment. The mean CT value was obtained in each slice and plotted as a function of slice position along the z-axis, thereby generating the ESF. The SSP was calculated from the ESF by differentiation. In the TG 233-recommended slanted edge method, the SSP was obtained by following the procedure described in the TG233 report. To validate the methodology, we first used filtered back projection (FBP) images to compare SSPs obtained using the non-slanted edge method, slanted edge method, and a standard method using a high-contrast thin object (coin). Next, for two types of IR algorithms, we compared the SSPs obtained using the non-slanted and slanted edge methods. RESULTS: For the FBP images, the SSP measured using the non-slanted edge method agreed well with SSPs measured using the coin and slanted edge methods. For the IR images, the SSPs measured using the non-slanted and slanted edge methods showed good agreement. CONCLUSIONS: The non-slanted edge method was demonstrated to be valid. The simplicity and practicality of the method allows routine and accurate determination of the SSP.

DOI： 10.1002/mp.14668

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/mp.14668

記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会  

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担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.6009/jjrt.2021_JSRT_77.8.828

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記述言語：日本語   出版者・発行元：新潟大学医学部保健学科  

本研究では、CTにおける逐次近似再構成(iterative reconstruction:IR)画像のMTF測定を目的として、既報のfiltered back projection(FBP)画像におけるMTF測定法をIR画像に適応した。IR画像の空間分解能はコントラストに依存するため、コントラストの低い円柱を含んだファントムを使用した。円柱のCT画像と数値的に生成した被写体関数を逆重畳積分することでpoint spread functionを算出し、MTFを求めた。得られたMTFと被写体関数から計算画像を算出し、実際のCT画像と比較を行うことでMTFの精度を評価した。FBP画像において、標準的なMTF測定法である金属ワイヤー法と提案法のMTFを比較し、良好な一致を確認した。次に、提案法によってIR画像のMTFを測定した。このMTFから得られた計算画像は実際のCT画像に類似し、MTFの測定精度が高いことが示された。提案法を用いることでコントラストの低いIR画像から精度の高いMTFを測定できることが示唆された。(著者抄録)

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会  

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

The circular-edge technique using a low-contrast cylindrical object is commonly used to measure the modulation transfer functions (MTFs) in computed tomography (CT) images reconstructed with iterative reconstruction (IR) algorithms. This method generally entails averaging multiple images of the cylinder to reduce the image noise. We suspected that the cylinder edge shape depicted in the IR images might exhibit slight deformation with respect to the true shape because of the intrinsic nonlinearity of IR algorithms. Image averaging can reduce the image noise, but does not effectively improve the deformation of the edge shape; thereby causing errors in the MTF measurements. We address this issue and propose a method to correct the MTF. We scanned a phantom including cylindrical objects with a CT scanner (Ingenuity Elite, Philips Healthcare). We obtained cylinder images with iterative model reconstruction (IMR) algorithms. The images suggested that the depicted edge shape deforms and fluctuates depending on slice positions. Because of this deformation, image averaging can potentially cause additional blurring. We define the deformation function D that describes the additional blurring, and obtain D by analyzing multiple images. The MTF measured by the circular-edge method (referred to as MTF') can be thought of as the multiplication of the true MTF by the Fourier transformation (FT) of D. We thus obtain the corrected MTF (MTFcorrected ) by dividing MTF' by the FT of D. We validate our correction method by comparing the calculated images based on the convolution theorem using MTF' and MTFcorrected with the actual images obtained with the scanner. The calculated image using MTFcorrected is more similar to the actual image compared with the image calculated using MTF', particularly in edge regions. We describe a pitfall in MTF measurement using the circular-edge technique with image averaging, and suggest a method to correct it.

DOI： 10.1002/acm2.12821

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/acm2.12821

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11323/jjmp.39.4_77

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：(公社)日本医学物理学会  

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その他リンク： https://search.jamas.or.jp/index.php?module=Default&action=Link&pub_year=2019&ichushi_jid=J03418&link_issn=&doc_id=20191114390001&doc_link_id=130007739860&url=https%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F130007739860&type=CiNii&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00003_1.gif

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：(公社)日本医学物理学会  

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その他リンク： https://search.jamas.or.jp/index.php?module=Default&action=Link&pub_year=2019&ichushi_jid=J03418&link_issn=&doc_id=20190913200001&doc_link_id=10.11323%2Fjjmp.39.2_42&url=https%3A%2F%2Fdoi.org%2F10.11323%2Fjjmp.39.2_42&type=J-STAGE&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00007_2.gif

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY  

Purpose: The aim of this feasibility study using phantoms was to propose a novel method for obtaining computer-generated realistic virtual nodules in lung computed tomography (CT).
Methods: In the proposed methodology, pulmonary nodule images obtained with a CT scanner are deconvolved with the point spread function (PSF) in the scan plane and slice sensitivity profile (SSP) measured for the scanner; the resultant images are referred to as nodule-like object functions. Next, by convolving the nodule-like object function with the PSF and SSP of another (target) scanner, the virtual nodule can be generated so that it has the characteristics of the spatial resolution of the target scanner. To validate the methodology, the authors applied physical nodules of 5-, 7- and 10-mm-diameter (uniform spheres) included in a commercial CT test phantom. The nodule-like object functions were calculated from the sphere images obtained with two scanners (Scanner A and Scanner B); these functions were referred to as nodule-like object functions A and B, respectively. From these, virtual nodules were generated based on the spatial resolution of another scanner (Scanner C). By investigating the agreement of the virtual nodules generated from the nodule-like object functions A and B, the equivalence of the nodule-like object functions obtained from different scanners could be assessed. In addition, these virtual nodules were compared with the real (true) sphere images obtained with Scanner C. As a practical validation, five types of laboratory-made physical nodules with various complicated shapes and heterogeneous densities, similar to real lesions, were used. The nodule-like object functions were calculated from the images of these laboratory-made nodules obtained with Scanner A. From them, virtual nodules were generated based on the spatial resolution of Scanner C and compared with the real images of laboratory-made nodules obtained with Scanner C.
Results: Good agreement of the virtual nodules generated from the nodule-like object functions A and B of the phantom spheres was found, suggesting the validity of the nodule-like object functions. The virtual nodules generated from the nodule-like object function A of the phantom spheres were similar to the real images obtained with Scanner C; the root mean square errors (RMSEs) between them were 10.8, 11.1, and 12.5 Hounsfield units (HU) for 5-, 7-, and 10-mm-diameter spheres, respectively. The equivalent results (RMSEs) using the nodule-like object function B were 15.9, 16.8, and 16.5 HU, respectively. These RMSEs were small considering the high contrast between the sphere density and background density (approximately 674 HU). The virtual nodules generated from the nodule-like object functions of the five laboratory-made nodules were similar to the real images obtained with Scanner C; the RMSEs between them ranged from 6.2 to 8.6 HU in five cases.
Conclusions: The nodule-like object functions calculated from real nodule images would be effective to generate realistic virtual nodules. The proposed method would be feasible for generating virtual nodules that have the characteristics of the spatial resolution of the CT system used in each institution, allowing for site-specific nodule generation. (C) 2017 American Association of Physicists in Medicine

DOI： 10.1002/mp.12503

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BRITISH INST RADIOLOGY  

Objective: We propose the application of virtual nodules to evaluate the performance of computer-aided detection (CAD) of lung nodules in cancer screening using lowdose CT.
Methods: The virtual nodules were generated based on the spatial resolution measured for a CT system used in an institution providing cancer screening and were fused into clinical lung images obtained at that institution, allowing site specificity. First, we validated virtual nodules as an alternative to artificial nodules inserted into a phantom. In addition, we compared the results of CAD analysis between the real nodules (n=6) and the corresponding virtual nodules. Subsequently, virtual nodules of various sizes and contrasts between nodule density and background density (Delta CT) were inserted into clinical images (n=10) and submitted for CAD analysis.
Results: In the validation study, 46 of 48 virtual nodules had the same CAD results as artificial nodules (kappa coefficient = 0.913). Real nodules and the corresponding virtual nodules showed the same CAD results. The detection limits of the tested CAD system were determined in terms of size and density of peripheral lung nodules; we demonstrated that a nodule with a 5- mm diameter was detected when the nodule had a Delta CT> 220 HU.
Conclusion: Virtual nodules are effective in evaluating CAD performance using site-specific scan/reconstruction conditions.
Advances in knowledge: Virtual nodules can be an effectivemeans of evaluating site-specific CAD performance. The methodology for guiding the detection limit for nodule size/density might be a useful evaluation strategy.

DOI： 10.1259/bjr.20160313

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS  

Purpose: In lung cancer computed tomography (CT) screening, the performance of a computer-aided detection (CAD) system depends on the selection of the image reconstruction kernel. To reduce this dependence on reconstruction kernels, the authors propose a novel application of an image filtering method previously proposed by their group.
Methods: The proposed filtering process uses the ratio of modulation transfer functions (MTFs) of two reconstruction kernels as a filtering function in the spatial-frequency domain. This method is referred to as MTFratio filtering. Test image data were obtained from CT screening scans of 67 subjects who each had one nodule. Images were reconstructed using two kernels: f(STD) (for standard lung imaging) and f(SHARP) (for sharp edge-enhancement lung imaging). The MTFratio filtering was implemented using the MTFs measured for those kernels and was applied to the reconstructed f(SHARP) images to obtain images that were similar to the f(STD) images. A mean filter and a median filter were applied (separately) for comparison. All reconstructed and filtered images were processed using their prototype CAD system.
Results: The MTFratio filtered images showed excellent agreement with the f(STD) images. The standard deviation for the difference between these images was very small, similar to 6.0 Hounsfield units (HU). However, the mean and median filtered images showed larger differences of similar to 48.1 and similar to 57.9 HU from the f(STD) images, respectively. The free-response receiver operating characteristic (FROC) curve for the f(SHARP) images indicated poorer performance compared with the FROC curve for the f(STD) images. The FROC curve for the MTFratio filtered images was equivalent to the curve for the f(STD) images. However, this similarity was not achieved by using the mean filter or median filter.
Conclusions: The accuracy of MTFratio image filtering was verified and the method was demonstrated to be effective for reducing the kernel dependence of CAD performance. (C) 2016 American Association of Physicists in Medicine.

DOI： 10.1118/1.4953247

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：European Society of Radiology  

DOI： 10.1594/ecr2015/C-0946

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：John Wiley and Sons Ltd  

The measurement of modulation transfer functions (MTFs) in computed tomography (CT) is often performed by scanning a point source phantom such as a thin wire or a microbead. In these methods the region of interest (ROI) is generally placed on the scanned image to crop the point source response. The aim of the present study was to examine the effect of ROI size on MTF measurement, and to optimize the ROI size. Using a 4 multidetector-row CT, MTFs were measured by the wire and bead methods for three types of reconstruction kernels designated as 'smooth', 'standard', and 'edge-enhancement' kernels. The size of a square ROI was changed from 30 to 50 pixels (approximately 2.9 to 4.9 mm). The accuracies of the MTFs were evaluated using the verification method. The MTFs measured by the wire and bead methods were dependent on ROI size, particularly in MTF measurement for the 'edge-enhancement' kernel. MTF accuracy evaluated by the verification method changed with ROI size, and we were able to determine the optimum ROI size for each method (wire/bead) and for each kernel. Using these optimal ROI sizes, the MTF obtained by the wire method was in strong agreement with the MTF obtained by the bead method in each kernel. Our data demonstrate that the difficulties in obtaining accurate MTFs for some kernels such as edge-enhancement can be overcome by incorporating the verification method into the wire and bead methods, allowing optimization of the ROI size to accurately determine the MTF.

DOI： 10.1120/jacmp.v14i4.3905

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS  

Purpose: While the acquisition of projection data in a computed tomography (CT) scanner is generally carried out once, the projection data is often removed from the system, making further reconstruction with a different reconstruction filter impossible. The reconstruction kernel is one of the most important parameters. To have access to all the reconstructions, either prior reconstructions with multiple kernels must be performed or the projection data must be stored. Each of these requirements would increase the burden on data archiving. This study aimed to design an effective method to achieve similar image quality using an image filtering technique in the image space, instead of a reconstruction filter in the projection space for CT imaging. The authors evaluated the clinical feasibility of the proposed method in lung cancer screening.
Methods: The proposed technique is essentially the same as common image filtering, which performs processing in the spatial-frequency domain with a filter function. However, the filter function was determined based on the quantitative analysis of the point spread functions (PSFs) measured in the system. The modulation transfer functions (MTFs) were derived from the PSFs, and the ratio of the MTFs was used as the filter function. Therefore, using an image reconstructed with a kernel, an image reconstructed with a different kernel was obtained by filtering, which used the ratio of the MTFs obtained for the two kernels. The performance of the method was evaluated by using routine clinical images obtained from CT screening for lung cancer in five subjects.
Results: Filtered images for all combinations of three types of reconstruction kernels ("smooth," "standard," and "sharp" kernels) showed good agreement with original reconstructed images regarded as the gold standard. On the filtered images, abnormal shadows suspected as being lung cancers were identical to those on the reconstructed images. The standard deviations (SDs) for the difference between filtered images and reconstructed images ranged from 1.9 to 23.5 Hounsfield units for all kernel combinations; these SDs were much smaller than the noise SDs in the reconstructed images.
Conclusions: The proposed method has good performance and is clinically feasible in lung cancer screening. This method can be applied to images reconstructed on any scanner by measuring the PSFs in each system. (C) 2011 American Association of Physicists in Medicine. [DOI:10.1118/1.3590363]

DOI： 10.1118/1.3590363

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担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Society of Medical Physics  

We propose a new method of converting thin-slice CT images to thick-slice images without image raw data. Slice sensitivity profiles (SSPs) were measured in the thin- and thick-slice settings. The spatial frequency property in the slice direction of the thin-slice images was converted to that of thick-slice images, based on the spatial frequency response calculated using the each SSP. In this study, we used CT images of seven subjects obtained in lung cancer screening, with a 4-slice scanner. The images were reconstructed with slice thicknesses of 5 and 8 mm, and the SSPs were measured in the scanner for the two slice settings, respectively. We calculated 8 mm-thick images from the 5 mm-thick images by the proposed method, and compared them with the actual 8 mm-thick images; this difference was evaluated by the root mean square error (RMSE). The mean value of RMSEs for seven subjects was approximately 6.0 Hounsfield Unit (HU). In addition, we obtained 8 mm-thick images by a conventional technique of weighted average from the 5 mm-thick images; the mean value of RMSEs was approximately 10.0 HU. The proposed method was demonstrated to be effective for converting thin-slice images to thick-slice images accurately.

DOI： 10.11323/jjmp.30.1_3

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その他リンク： https://jlc.jst.go.jp/DN/JLC/20019128137?from=CiNii

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11323/jjmp.30.2_39

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS  

A method for verifying the point spread function (PSF) measured by computed tomography has been previously reported [Med. Phys. 33, 2757-2764 (2006)]; however, this additional PSF verification following measurement is laborious. In the present study, the previously described verification method was expanded to PSF determination. First, an image was obtained by scanning a phantom. The image was then two-dimensionally deconvolved with the object function corresponding to the phantom structure, thus allowing the PSF to be obtained. Deconvolution is implemented simply by division of spatial frequencies (corresponding to inverse filtering), in which two parameters are used as adjustable ones. Second, an image was simulated by convolving the object function with the obtained PSF, and the simulated image was compared to the above-measured image of the phantom. The difference indicates the inaccuracy of the PSF obtained by deconvolution. As a criterion for evaluating the difference, the authors define the mean normalized standard deviation (SD) in the difference between simulated and measured images. The above two parameters for deconvolution can be adjusted by referring to the subsequent mean normalized SD (i.e., the PSF is determined so that the mean normalized SD is decreased). In this article, the parameters were varied in a fixed range with a constant increment to find the optimal parameter setting that minimizes the mean normalized SD. Using this method, PSF measurements were performed for various types of image reconstruction kernels (21 types) in four kinds of scanners. For the 16 types of kernels, the mean normalized SDs were less than 2.5%, indicating the accuracy of the determined PSFs. For the other five kernels, the mean normalized SDs ranged from 3.7% to 4.8%. This was because of a large amount of noise in the measured images, and the obtained PSFs would essentially be accurate. The method effectively determines the PSF, with an accompanying verification, after one scanning of a phantom.

DOI： 10.1118/1.3123762

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記述言語：日本語   出版者・発行元：(NPO)日本CT検診学会  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会-東北支部  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会-東北支部  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会-東北支部  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会-東北支部  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会-東北支部  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会-東北支部  

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記述言語：日本語   出版者・発行元：群馬県核医学研究会  

骨転移ありと診断された14例(男6例、女8例、平均62.1歳)を対象に、2機種のガンマカメラによるデータで99mTc-MDP骨シンチグラフィー診断支援ソフト(BONENAVI)処理を行い、その結果を比較した。ガンマカメラはGE Infinia Howkeye(GE)とPhilips Precedence(PP)を用い、解析はANN、BSI、Hot spot数の他、集積部位ごとのANNを用いて1症例あたりの偽陽性の数(FP)と全転移数に対する真陽性率(TPR)を算出した。転移数5ヶ所以上の多発転移群(8例)においては、TPR最大値はGEが0.87、PPが0.94、5ヶ所未満の少数転移群(6例)はそれぞれ0.96、0.47と差異が認められた。一方Patch処理が行われなかった5例(P-群)では、TPRの最大値がGE 0.85、PP 0.90で、特性曲線は比較的一致しており、ほぼ同程度の検出率となった。BSIは14例中12例でPPが、Hot spot数は9例でGEが高値となり、P-群ではこの傾向が顕著で、それぞれ5例中5例、4例であった。

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会  

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その他リンク： https://search.jamas.or.jp/index.php?module=Default&action=Link&pub_year=2012&ichushi_jid=J01192&link_issn=&doc_id=20120606500006&doc_link_id=10030431285&url=https%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F10030431285&type=CiNii&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00003_1.gif

記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会-東北支部  

磁化率アーチファクトによる画像歪みの影響が、静磁場(Bo)方向と脳動脈瘤クリップの長軸方向とのなす角度に依存するか検討した。磁化率アーチファクトの影響を低減させるには、バンド幅が非常に重要であることが再認識された。Boと脳動脈瘤クリップの長軸方向とのなす角度が大きくなると、磁化率アーチファクト領域は大きくなり、0度〜90度でSE系が2.3倍、GE系が1.5倍となり、Boと垂直で最大となった。また、SE系に比べGE系の撮像法は磁化率アーチファクト領域が2.5〜3倍ほど大きくなった。Bo方向に対する脳動脈瘤クリップの長軸方向の角度が、磁化率アーチファクト領域に対し依存性があることが示唆された。

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記述言語：日本語   出版者・発行元：(NPO)日本核医学技術学会  

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会  

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記述言語：日本語   出版者・発行元：(NPO)日本CT検診学会  

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記述言語：日本語   出版者・発行元：(一社)日本医学物理学会  

胸部CTによる肺内結節に対する精度の高い診断や、三次元的な評価を行う際、濃度閾値が重要な因子の一つになる場合が多い。結節を想定した球体を被写体関数に設定し、PSF(点拡がり関数)を用いた三次元画像シミュレーションに基づき、濃度閾値設定を行った。閾値設定と、それによって抽出される領域の体積との関係は、球体ファントムを用いた結果と比べ約5%の差異であったことから、シミュレーションの妥当性が確認された。結節の体積を正確に算出するための設定閾値は、結節の濃度が一定である場合でも大きさによって変動し、更に画像再構成関数、スライス厚およびスライス位置にも大きく依存することが定量的に示された。

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その他リンク： https://search.jamas.or.jp/index.php?module=Default&action=Link&pub_year=2010&ichushi_jid=J03418&link_issn=&doc_id=20101213350002&doc_link_id=10.11323%2Fjjmp.30.2_39&url=https%3A%2F%2Fdoi.org%2F10.11323%2Fjjmp.30.2_39&type=J-STAGE&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00007_2.gif

記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会  

ガドキセト酸ナトリウムを用いた肝ダイナミックMRIの動脈優位相における画像アーチファクトについてシミュレーションした。撮像は、5通りの時刻範囲(撮像タイミングt1〜t5)で行われたと想定し、いずれも撮像に要する時間は、横軸の50%に相当する時間とした。Sequential法は、いずれのタイミングにおける画像も、明らかなアーチファクトはみられなかった。Centric法の場合、t4およびt5の場合、原画像に比べ、大きなボケが生じ、t2の場合、輪郭強調のような効果がみられた。Centric法では、sequentia1法に比べ、撮像タイミングによってアーチファクトが生じやすかった。撮像時間を25%にした。Sequential法での撮像の場合、明らかなアーチファクトはみられず、Centric法での撮像の場合、t4とt5の場合にボケが生じ、t2の場合に輪郭強調の効果がみられた。

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その他リンク： https://search.jamas.or.jp/index.php?module=Default&action=Link&pub_year=2010&ichushi_jid=J01192&link_issn=&doc_id=20101001470490&doc_link_id=10026649024&url=https%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F10026649024&type=CiNii&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00003_1.gif

記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会-東北支部  

肝臓dynamic MRIにおける動脈優位相でのアーチファクトについて検討した。肝特異性造影剤Gd-EOB-DTPA(EOB)を用いたテストインジェクションのデータを参考に、模擬的に時間濃度曲線を作成した。時間濃度曲線上で、撮像時間および撮像開始のタイミングを想定し、その間の濃度曲線の変化パターンを用いた。この変化パターンに基づいて、k-spaceにおける位相エンコード方向の各データを変調した。撮像時間20秒の場合、セントリック法にて、造影剤の立ち上がり時に撮像が開始された場合、輪郭強調の影響がみられた。逆に立ち下がり時に撮像が開始された場合、ボケが生じた。これらの影響は、撮像時間が短い(10秒)方が小さかった。また、シーケンシャル法では、撮像時間、タイミングに関わらずこれらのアーチファクトはほとんどみられなかった。

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記述言語：日本語   出版者・発行元：(公社)日本放射線技術学会  

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記述言語：日本語   出版者・発行元：(NPO)日本CT検診学会  

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