Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 70, Issue 4
Displaying 1-11 of 11 articles from this issue
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Opening Article
Originals
  • Comparison of 18F-fluoro-2-deoxy-D-glucose Positron Emission Tomography/Computed Tomography Image Quality between Commercial and In-house Supply of FDG Radiopharmaceuticals
    Kei Wagatsuma, Kenta Miwa, Noriaki Miyaji, Taisuke Murata, Takuro Umed ...
    2014 Volume 70 Issue 4 Pages 339-345
    Published: 2014
    Released on J-STAGE: April 22, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.4.339
    JOURNAL FREE ACCESS
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    Objective: PET images are affected by scanner model, reconstruction conditions, injected dose, scan duration, patient health status and FDG radiopharmaceutical supply systems. The present study compares images of 40 patients using commercial and in-house FDG systems with one PET scanner (Aquiduo). Methods: The PET images were evaluated using the physical indexes of NECpatient, NECdensity and SNRliver proposed by the Japanese guidelines for oncological FDG-PET/CT, and by visual assessment. Results: There were no significant differences in the physical indexes between PET images generated using commercial and in-house FDG. The physical indexes were also acceptable according to the recommended Japanese guidelines. NECdensity was higher when a higher dose/body weight of commercial FDG was injected (correlation coefficient: r=0.576, p<0.001) and lower when BMI was lower and in-house FDG was injected (r=−0.786, p<0.0001). These results suggest that scan duration should be increased if the injected dose of commercial FDG/body weight is <5.5 MBq/kg, and if individuals with BMI >21.4 kg/m2 are injected with in-house FDG. Conclusions: Scan duration should be varied depending on FDG supply systems to ensure more accurate image quality and quantitative values during evaluations of response to therapy and prognostic prediction.
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  • A Method of Measuring Presampled Modulation Transfer Function Using a Rationalized Approximation of Geometrical Edge Slope
    Michitaka Honda
    2014 Volume 70 Issue 4 Pages 346-358
    Published: 2014
    Released on J-STAGE: April 22, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.4.346
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    Several improvements were implemented in the edge method of presampled modulation transfer function measurements (MTFs). The estimation technique for edge angle was newly developed by applying an algorithm for principal components analysis. The error in the estimation was statistically confirmed to be less than 0.01 even in the presence of quantum noise. Secondly, the geometrical edge slope was approximated using a rationalized number, making it possible to obtain an oversampled edge response function (ESF) with equal intervals. Thirdly, the final MTFs were estimated using the average of multiple MTFs calculated for local areas. This averaging operation eliminates the errors caused by the rationalized approximation. Computersimulated images were used to evaluate the accuracy of our method. The relative error between the estimated MTF and the theoretical MTF at the Nyquist frequency was less than 0.5% when the MTF was expressed as a sinc function. For MTFs representing an indirect detector and phase-contrast detector, good agreement was also observed for the estimated MTFs for each. The high accuracy of the MTF estimation was also confirmed, even for edge angles of around 10 degrees, which suggests the potential for simplification of the measurement conditions. The proposed method could be incorporated into an automated measurement technique using a software application.
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Notes
  • Winston-Lutz Test and Acquisition of Flexmap Using Rotational Irradiation
    Toshikazu Imae, Akihiro Haga, Naoya Saotome, Shigeharu Takenaka, Yukar ...
    2014 Volume 70 Issue 4 Pages 359-368
    Published: 2014
    Released on J-STAGE: April 22, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.4.359
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    Purpose: IGRT (image guided radiation therapy) is a useful technique for implementing precisely targeted radiation therapy. Quality assurance and quality control (QA/QC) medical linear accelerators with a portal imaging system (electronic portal imaging device: EPID) are the key to ensuring safe IGRT. The Winston-Lutz test (WLT) provides an evaluation of the MV isocenter, which is the intersection of radiation, collimator, and couch isocenters. A flexmap can indicate a displacement of EPID from the beam center axis as a function of gantry angles which can be removed from the images. The purpose of this study was to establish a novel method for simultaneously carrying out WLT and acquiring a flexmap using rotational irradiation. We also observed long-term changes in flexmaps over a period of five months. Method: We employed rotational irradiation with a rectangular field (30×30 mm). First, the displacement of EPID from the beam center axis, indicated by the ball bearing (BB) center, was evaluated using an in-house program. The location of the BB center was then modified according to WLT. Second, a second irradiation was used to acquire a flexmap. We performed this examination regularly and evaluated long-term changes in the flexmap. Results and discussion: It proved feasible to perform WLT and flexmap measurements using our proposed methods. The precision of WLT using rotational irradiation was 0.1 mm. In flexmap analysis, the maximum displacement from the mean value for each angle was 0.4 mm over five months. Conclusion: We have successfully established a novel method of simultaneously carrying out WLT and flexmap acquisition using rotational irradiation. Maximum displacement from the mean in each angle was 0.4 mm over five months.
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  • Examination of the Orbitomeatal Basal Line-Anthropological Basal Line Crossing Angle and Acanthiomeatal Line-Anthropological Basal Line Crossing Angle
    Akio Hashimoto, Hirosi Inatsu, Susumu Ogashiawa, Yukimitsu Teranishi, ...
    2014 Volume 70 Issue 4 Pages 369-374
    Published: 2014
    Released on J-STAGE: April 22, 2014
    DOIhttps://doi.org/10.6009/jjrt.2014_JSRT_70.4.369
    JOURNAL FREE ACCESS
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    Orbitomeatal basal line-anthropological basal line (OML-ABL), and the acanthiomeatal line (AML)-ABL crossing angles were measured using profile pictures. There were 219 volunteers in total: 42 people four years old, 44 people nine years old, 45 people 14 years old, 43 people 19 years old, and 45 people 40 years or older (48±7.4 years). The average OML-ABL crossing angle was 14.3 degrees in the 4-year-old group, while that of the 40-year or older group was 11.1 degrees. The deviation width of the 4-year-old group was 4.8 degrees, and that of the 40-year or older group was 2.4 degrees. The average AML-ABL crossing angle was 12.3 degrees in the 4-year-old group, while that of the 40-year or older group was 15.7 degrees. There were differences between males and females. The deviation width of the 4-year group was 5.4 degrees, and that of the 40-year or older group was 2.7 degrees. The results showed that 14.0 degrees for around 4-year-old, and 12.0 degrees for around 9- to 14-year-olds, could be used as OML-ABL crossing angles as a practical proposition.
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The 41st Autumn Scientific Congress
Special Plan—Member Interview: The People Who Contributed to the Academic Society—
Special Article for Vol. 70
Basic Lecture—Heart Disease: From Diagnosis to Treatment
Basic Lecture—Image Reconstruction: Basic and Clinical Application
JIRA Topics
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