Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 68, Issue 11
Displaying 1-18 of 18 articles from this issue
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Opening Article
Originals
  • Non-contrast Magnetic Resonance Angiography for Renal Arteries Using Breath Held Inflow Inversion Recovery-Fan Shaped Inward Outward View Ordering: Impact on Image Quality by Changing Wait Recovery Time after Data Acquisition
    Yasushi Watanabe, Koichi Motoyoshi, Naoyuki Takei, Masaaki Akahane, To ...
    2012 Volume 68 Issue 11 Pages 1441-1447
    Published: November 20, 2012
    Released on J-STAGE: November 21, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.11.1441
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    Purpose: We assessed the wait time of non-contrast renal artery magnetic resonance (MR) angiography with a single breath hold using inflow inversion recovery-fan shaped inward outward view ordering technique in normal volunteers. Methods: The wait time (WT)-the duration between the data acquisition and the following inversion recovery pulse-was varied from 10 ms to 2000 ms, and the contrast ratio between the renal artery and the background structures for each WT was assessed quantitatively. A simulation was also performed. Results: The contrast ratio between the renal artery and each background structure with 2000 ms of WT was higher than that with 10 ms of WT. The contrast ratio between the renal artery and renal cortex with 1500 ms of WT was also higher than that with 10 ms of WT. In the simulation, when WT lengthened, the residual longitudinal magnetization of each background structure lowered. Conclusion: The WT affects contrast; adjustment of WT should be added to the assessment of the imaging parameter.
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  • Questions That Radiography Students Have Regarding X-ray Photography: A Qualitative Study
    Takayoshi Terashita, Kengo Kisa, Sumiko Oshima, Hidenobu Kawabata
    2012 Volume 68 Issue 11 Pages 1448-1455
    Published: November 20, 2012
    Released on J-STAGE: November 21, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.11.1448
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    Objective: To improve lectures and training programs on X-ray photography, we aimed to determine the questions that radiography students have regarding X-ray photography. Methods: We collected text data from questions on X-ray photography in radiography student reports after an X-ray photography training program. The text data were analyzed using content analysis. Codes were assigned to segments and they were categorized according to similarities. Results: From 111 reports, 348 questions were collected. Four categories and 47 subcategories were obtained. The “Required Knowledge” category comprised subcategories concerning knowledge for the X-ray photography including X-ray radiography methodology and disease knowledge. The “Radiography Service” category comprised subcategories concerning radiographers’ responsibilities in a hospital including the role of radiographer and the extent of responsibilities. The “Radiographers’ Challenges” category comprised subcategories concerning unusual situations radiographers encounter at work including accurate positioning and communication with patients. The “Patient Types” category comprised subcategories concerning patients in whom X-ray photography was considered difficult including pediatric patients and patients with serious conditions. Questions related to subcategories in “Radiographers’ Challenges” and “Patient Types” were interrelated. Radiography students had concerns regarding whether they would be able to handle difficult patients efficiently in clinical situations. Conclusion: We were able to suggest the re-orientation of radiography education according to students’ intellectual appetite regarding X-ray radiography.
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  • Slice Profile Measurement Using a Crossed Thin-ramps Method in Three-dimensional Magnetic Resonance Imaging
    Rei Yoshida, Yoshio Machida, Takahide Ogura, Hajime Tamura, Takeo Hiki ...
    2012 Volume 68 Issue 11 Pages 1456-1466
    Published: November 20, 2012
    Released on J-STAGE: November 21, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.11.1456
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    Recent progress in variable-flip-angle fast spin-echo technology has further extended the utility of three-dimensional (3D) magnetic resonance imaging (MRI) for clinical application. The slice profile in 3D MRI is the point spread function that has a sync form in principle, whereas a slice profile in 2D imaging provides information on characteristics of selective radio frequency excitation. We investigated the optimal condition to measure 3D slice profiles using a crossed thin-ramps phantom. We found that the profile data should cover a large area in order to evaluate both the main lobe and side lobes in the slice profile, and that the appropriate slice thickness was 2 mm. We also found that artifacts in the direction perpendicular to the slice create an offset error in the measured slice profile when 3D imaging. In this paper, we describe the optimal condition and some remarks on the slice profile evaluation for 3D MRI.
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  • Estimation of Activities Caused by Black Spots for Digital Radiography System: Analysis of Black Spots by the Low Concentrate Radioisotopes Adhered Directly to the Surface of the Phosphor Plate
    Hiroaki Hayashi, Sadamitsu Nishihara, Satoru Takashi, Hiroki Hanamitsu ...
    2012 Volume 68 Issue 11 Pages 1467-1473
    Published: November 20, 2012
    Released on J-STAGE: November 21, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.11.1467
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    Because of an accident of the nuclear power plants in the Fukushima, many radioisotopes (RI) have been diffused to the environment. As a result, black spots were appearing on the medical images which were taken by the phosphor plate. The aim of this study is to evaluate the activity (Bq) of radioactive contaminated IP based on the experiment using RI. The radioactive material (134Cs and/or 137Cs) in the form of liquid was dropped on filter paper (25 mm2), and radioactive sources having 40–240 Bq activities were made. These sources were closely attached to the IP with irradiation times of 2–22 h. Then, we obtained the relationship between pixel values and products of activities and irradiation times. Using these relationships, we evaluated the activity in the contaminated IP. The evaluated value of approximately 7 Bq was in good agreement with a value which was inhered in a chemical wiper used for the decontamination of the IP. Based on the results, we summarized that almost all black spots were created by the RI adhered directly to the IP.
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  • Development of a Computer-aided Diagnosis System for the Distinction between Benign and Malignant Gastric Elevated Lesions
    Nobumichi Nagano, Takami Matsuo, Takashi Itoh, Kenichiro Tomonari, Jun ...
    2012 Volume 68 Issue 11 Pages 1474-1485
    Published: November 20, 2012
    Released on J-STAGE: November 21, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.11.1474
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    We proposed a method for a computer-aided diagnosis system that distinguishes between benign and malignant lesions in gastrointestinal digital radiography. To begin with, the level set method was applied in order to extract a tumor region from the image which was smoothed by the bilateral filter. Next, we selected four image features with the large SN ratio among various image features obtained from a tumor region using the Mahalanobis-Taguchi method, which has been employed mainly in quality engineering. The selected four image features—circularity, irregularity, size, and perimeter—were used as input data for the artificial neural network, which was employed for distinction between benign and malignant lesions. By using 43 regions of interest cropped from the 43 clinical cases, the area under the ROC curve (AUC) of diagnostic accuracy for the classification obtained with this proposed method was 0.970, whereas the average AUC obtained with 7 human observers (3 radiologists and 4 radiological technologist) was 0.941.
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  • Positional Accuracy and Quality Assurance of Backup JAWs Required for Volumetric Modulated Arc Therapy
    Daisaku Tatsumi, Ryosei Nakada, Akinori Ienaga, Akane Yomoda, Makoto I ...
    2012 Volume 68 Issue 11 Pages 1486-1491
    Published: November 20, 2012
    Released on J-STAGE: November 21, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.11.1486
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    The tolerance of the Backup diaphragm (Backup JAW) setting in Elekta linac was specified as 2 mm according to the AAPM TG-142 report. However, the tolerance and the quality assurance procedure for volumetric modulated arc therapy (VMAT) was not provided. This paper describes positional accuracy and quality assurance procedure of the Backup JAWs required for VMAT. It was found that a gap-width error of the Backup JAW by a sliding window test needed to be less than 1.5 mm for prostate VMAT delivery. It was also confirmed that the gap-widths had been maintained with an error of 0.2 mm during the past one year.
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Notes
  • A Practical Method for Six-dimensional Online Correction System with Image Guided Radiation Therapy
    Yuji Nakaguchi, Fujio Araki, Tomohiro Kouno, Masato Maruyama
    2012 Volume 68 Issue 11 Pages 1492-1498
    Published: November 20, 2012
    Released on J-STAGE: November 21, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.11.1492
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    In this study, we developed a correction method for coordinate transformation errors that are produced in combination with the ExacTrac X-ray system (BrainLAB) and HexaPOD (Elekta) in image guided radiation therapy (IGRT). The positional accuracy of the correction method was compared between the ExacTrac Robotics (BrainLAB) and no correction. We tried to correct iBeam evo couch top (Elekta) by operating two steps drive like ExacTrac Robotics. No correction for HexaPOD showed a maximal error of 4.52 mm, and the couch did not move to the correct position. However, our correction method for HexaPOD showed the positional accuracy within 1 mm. Our method has no significant difference with ExacTrac Robotics (paired t-test, P>0.1). But, when the correction values for the rotatory directions were large, the positional accuracy tended to be poor. The smallest setup errors for the rotatory directions are important for IGRT.
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  • A Method for Evaluating the Mechanical Isocenter of Gantry of a Radiotherapy Machine with Motion Picture Trace Analysis Software
    Nobutaka Yanano, Toshioh Fujibuchi
    2012 Volume 68 Issue 11 Pages 1499-1507
    Published: November 20, 2012
    Released on J-STAGE: November 21, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.11.1499
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    In recent years, development of advanced radiotherapy technology has resulted in an improvement in radiotherapy. Although the radiotherapy system has improved, the effect of the gap, the gyration center, and distortion of the rotation orbit cannot be neglected. Therefore, a verification method for a geometrical isocenter and rotation orbit in a three-dimension (3D) space is required. We developed a verification method for determination of the geometrical isocenter. In this method, the rotation of the gantry that applied the measured target from two directions was imaged and analyzed using animation pursuit analysis software. The measurement targets were pursued by analysis, and the rotation orbit of the target was visually evaluated from obtained coordinates and displacement distance. The gyration center in 3D space was calculated from pursued coordinates and compared with the intersection in the side laser and crosshair. In this verification method, the rotation orbit and geometrical isocenter in the 3D space were confirmed, and visually evaluated. Thus, this method was effective in verifying the geometrical isocenter by solving the problem of the measurement precision and reproducibility.
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  • The Characteristic of the Image by Image Reconstruction Method Applied to Successive Approximation Method
    Yoshihiro Yukimura, Keisuke Isotani, Tomoyuki Uto, Kiyoaki Kouduki, At ...
    2012 Volume 68 Issue 11 Pages 1508-1518
    Published: November 20, 2012
    Released on J-STAGE: November 21, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.11.1508
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    In recent years, an applied successive approximation method has emerged as a new reconstruction technique of the computed tomography (CT). The CT unit of our hospital is equipped with an adaptive statistical iterative reconstruction (ASiR) which applies this method. This time, we have investigated the feature of the images through the ASiR. A subtraction of the filtered back projection (FBP) image from the ASiR image of various phantoms took place, and the structure marginal region was evaluated by varying the blend rate of ASiR and the display field of view (DFOV). By varying the CT value difference with the surroundings (using iodinated contrast medium) the structure marginal region of the subtraction image was evaluated. Modulation transfer function (MTF) and noise power spectrum (NPS) measurements were carried out to make evaluations. The result was that the CT value of the marginal unit structure was elevated with an increase of the blend ratio of ASiR and DFOV. When the CT value difference with surroundings was high, an edge was formed in the structure near the marginal region, and when it was low, a slowdown in the peripheral zone was observed. The value of MTF and NPS showed the change. The formation of the edge and slowdown in the peripheral zone can be seen in clinical images, we fully need to understand this result and make use of it in the clinical field.
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  • Quality Assurance for Respiratory-gated Stereotactic Body Radiation Therapy in Lung Using Real-time Position Management System
    Yuji Nakaguchi, Fujio Araki, Tomohiro Kouno, Masato Maruyama
    2012 Volume 68 Issue 11 Pages 1519-1524
    Published: November 20, 2012
    Released on J-STAGE: November 21, 2012
    DOIhttps://doi.org/10.6009/jjrt.2012_JSRT_68.11.1519
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    In this study, we investigated comprehensive quality assurance (QA) for respiratory-gated stereotactic body radiation therapy (SBRT) in the lungs using a real-time position management system (RPM). By using the phantom study, we evaluated dose liberality and reproducibility, and dose distributions for low monitor unite (MU), and also checked the absorbed dose at isocenter and dose profiles for the respiratory-gated exposure using RPM. Furthermore, we evaluated isocenter dose and dose distributions for respiratory-gated SBRT plans in the lungs using RPM. The maximum errors for the dose liberality were 4% for 2 MU, 1% for 4–10 MU, and 0.5% for 15 MU and 20 MU. The dose reproducibility was 2% for 1 MU and within 0.1% for 5 MU or greater. The accuracy for dose distributions was within 2% for 2 MU or greater. The dose error along a central axis for respiratory cycles of 2, 4, and 6 sec was within 1%. As for geometric accuracy, 90% and 50% isodose areas for the respiratory-gated exposure became almost 1 mm and 2 mm larger than without gating, respectively. For clinical lung-SBRT plans, the point dose at isocenter agreed within 2.1% with treatment planning system (TPS). And the pass rates of all plans for TPS were more than 96% in the gamma analysis (3 mm/3%). The geometrical accuracy and the dose accuracy of TPS calculation algorithm are more important for the dose evaluation at penumbra region for respiratory-gated SBRT in lung using RPM.
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Clinical Technology
The 68th Annual Scientific Congress Technical Seminar
Educational Lecture—Statistical Methods for Radiologic Research
Basic Lecture—From Diagnosis of the Breast to Treatment
Basic Lecture—Three-dimensional Computer Graphics
JIRA Topics
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