Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 66, Issue 7
Displaying 1-18 of 18 articles from this issue
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Opening Article
Originals
  • Evaluation of RF Heating on Hip Joint Implant in Phantom during MRI Examinations
    Hiroyuki Muranaka, Takayoshi Horiguchi, Yoshitake Ueda, Shuji Usui, No ...
    2010 Volume 66 Issue 7 Pages 725-733
    Published: November 25, 2009
    Released on J-STAGE: August 10, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.725
    JOURNAL FREE ACCESS
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    Purpose: We evaluate radiofrequency (RF) heating of two kinds of hip joint implants of different sizes, shapes and materials. Temperature rises at various positions of each implant are measured and compared with a computer simulation based on electromagnetic-field analysis. Methods: Two kinds of implants made of cobalt-chromium alloy and titanium alloy were embedded at a 2-cm depth of tissue-equivalent gel-phantom. The phantom was placed parallel to the static magnetic field of a 1.5 T MRI device. Scans were conducted at the specific absorption rate of 2.5 W/kg for 15 min, and temperatures were recorded with RF-transparent fiberoptic sensors. Temperatures of the implant surface were measured at 6 positions, from the tip to the head. Measured temperature rises were compared with the results of electromagnetic-field analysis. Results: The maximum temperature rise was observed at the tip of each implant, and it was 9.0°C for the cobalt- chromium implant and 5.3°C for the titanium implant. The simulated heating positions with electromagnetic-field analysis accorded with experimental results. However, a difference in temperature rise was seen with the titanium implant. Conclusion: RF heating was confirmed to take place at both ends of the implants in spite of their different shapes. The maximum temperature rise was observed at the tip where there is large curvature. The value was found to depend on physical properties of the implant materials. The discrepancy between experimental and simulated temperature rises was presumed to be the result of an incomplete model for the titanium implant.
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  • Investigation of Error Factors in Analysis of Digital Noise Power Spectrum
    Hiroshi Kunitomo, Katsuhiro Ichikawa, Ryo Higashide, Kazuya Ohashi, Mi ...
    2010 Volume 66 Issue 7 Pages 734-742
    Published: July 20, 2010
    Released on J-STAGE: August 10, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.734
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    The noise power spectrum (NPS) measurement is important for assessing noise properties of digital radiography systems, and its measurement method was standardized in International Electrotechnical Commission 62220-1 (IEC). However, improvement of its accuracy is not easy due to random data analysis. In this study, regarding error factors in the NPS measurement using 2-dimensional (2D) Fast Fourier transform, we investigated effects of overlap of region of interests (ROIs), number of average lines in 2D frequency space, directional dependence of frequency property, and detrending techniques. If the number of average lines was set so as to obtain a similar frequency range to IEC, total matrix size was the most important factor and error rate was decreased with increasing of the size. For images, including many trends, detrending using 256×256-pixels ROI and second-order polynomial fitting was the most effective. Consistent with the previous report, the overlap of ROIs was not effective for improving accuracy. Contrary to the previous report that indicated effectiveness of 128×128-pixels ROI for detrending, we demonstrated less affectivity of the ROI size, other than 256×256-pixels.
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Clinical Technology
  • Respiratory Management of CT-transmission for Accuracy Fusion in PET/CT: A Comparison between Normal Expiration and Free Breathing in 600 Experiences
    Atsushi Osawa, Tomohiro Takiguchi, Shintaro Tamura, Takashi Ohashi, Ke ...
    2010 Volume 66 Issue 7 Pages 743-748
    Published: July 20, 2010
    Released on J-STAGE: August 10, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.743
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    Image misregistration can occur in fusion PET/CT, because of motion artifacts caused by the management of respiration. The standard imaging protocol of the CT component of PET/CT is normal expiration (NormExp) or free breathing (FB). The objective of this study was to compare NormExp and FB for the optimal breathing protocol for PET/CT scans. A total of 600 consecutive patients were examined using lutetium oxyorthosilicate (LSO)-based PET/CT. CT was acquired during NormExp (i.e., the level reached when the patient exhaled without forcing expiration and then held the breath) in 300 patients and during FB in 300 patients. The profile of liver measured along body axis was assessed. The distance of profile centers between the PET image and the CT image was measured. The misalignment between profile centers (PET) and profile centers (CT) was compared between NormExp and FB using the histogram of patients. An F test was used to test if the variances of two misalignments are equal. Next, the relationship between misalignment and age was evaluated in two managements of respiration. There was no significant difference between NormExp and FB in the histogram. However, significant misalignments (>10 cm) were found with NormExp. Patient age may have influenced the mismatch. FB is recommended for geriatric patients during acquisition of attenuation correction CT data sets.
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  • Comparison MR Cholangiopancreatography with 3D-Fast Recovery Fast Spin Echo in Several Different Slice Thicknesses
    Hiroshi Ikenoue, Shigeki Ito, Masami Yamada, Yukinori Takikawa, Osamu ...
    2010 Volume 66 Issue 7 Pages 749-757
    Published: July 20, 2010
    Released on J-STAGE: August 10, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.749
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    Purpose: To evaluate the technical quality and visibility of the biliary tree and pancreatic duct on magnetic resonance cholangiopancreatography (MRCP) images obtained with a single-breath-hold three-dimensional (3D) fast-recovery fast spin-echo (FRFSE) sequence in several different slice thicknesses. Materials and Methods: As a fundamental study, tubes of various inside diameters filled gadolinium solutions were acquired at 1.5 T in 3D-FRFSE. We observed error rate changes of volume inside the tubes and the visibility of thinner tubes. MRCP was performed at 1.5 T in 8 consecutive patients (4 men and 4 women, aged 22-58 years). Seven radiologists graded images obtained with each slice thickness in a blind fashion. Furthermore, we compared 1.4 mm slice thickness images with 1.8 mm slice thickness images in a continuous rating scale for the same patient. We assessed differences in technical quality, overall visibility, and six individual ductal segments of the biliary tree and pancreatic duct. Results: If slice thickness were thinner relative to diameter, the error rate would be closer to zero. But, when slice thickness was 0.8 mm, the error rate became clearly higher because of low intensity. In the fundamental study, we thought that the appropriate slice thickness is between 1.0 mm and 2.4 mm. The visibility of images of thinner tubes could be improved by having a thinner slice thickness. In particular, MRCP overall images generated from a 1.4 mm slice thickness were found to be significantly superior to those generated from a 1.8 mm slice thickness (p<0.001); this was also true as regards the pancreatic duct and cystic duct (p<0.01, p<0.05). Conclusion: We conclude that a 1.4 mm slice thickness is appropriate for MRCP.
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  • Improvement of Method of Determining Fluoroscopy Loading Factor in Digital Angiographic X-ray System with a Flat Panel Detector
    Hisaya Sato, Kyoichi Kato, Masahiro Maruyama, Keigo Okada, Yoshiaki Mi ...
    2010 Volume 66 Issue 7 Pages 758-763
    Published: July 20, 2010
    Released on J-STAGE: August 10, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.758
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    A catheterization study and treatment of coronary arteriopathy are performed by investigating the coronary artery from different angles to find the region to be treated. In doing so, our system always started from the initial value of the loading factor, using this only for the first time, and the system started from the last loading factor the second time and later, at all angles. Therefore, depending on the angle, the loading factor at the start of fluoroscopy sometimes became unstable, and it took time to stabilize. This made the starting image too dark (undershoot x-ray condition) or fogged by halation (overshoot x-ray condition). With the system manufacturer, we developed a tube voltage and tube current setting method for the initial value of the loading factor. We installed software which preset the loading factor at the start of fluoroscopy depending on the angle, and an auto memory function of the last loading factor for each angle. This function allows the system to control the tube voltage and tube current for any angle. As a result, the system can acquire a more stabilized image from the start of fluoroscopy. This method of determining the initial loading factor is an effective way to stabilize the fluoroscopy image quickly.
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  • Underlying Examination in the Imaging of 89Sr Bremsstrahlung Radiation
    Hitomi Oda, Hideyuki Hara, Osamu Ueda, Hiroaki Kawamata, Hiroto Sakai, ...
    2010 Volume 66 Issue 7 Pages 764-773
    Published: July 20, 2010
    Released on J-STAGE: August 10, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.764
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    The radiopharmaceutical strontium chloride (89Sr) has been released as a new means of pain relief for painful bone metastasis in cancer patients. Because 89Sr is a pure beta-emitting nuclide, it was considered difficult to know its distribution in the body from outside. Imaging with a gamma camera using bremsstrahlung radiation has been reported as one method, but there has been little detailed basic examination. We examined the optimal energy window and collimator when imaging with a gamma camera using bremsstrahlung radiation produced from 89Sr beta rays. The results showed that setting the energy window at 75 keV, which is the peak formed by the characteristic X-ray of lead that is produced by the interaction of bremsstrahlung radiation and lead, is optimal for imaging. Also important are the material of the collimator and the use of an MELP collimator.
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  • Radiation Dose Reduction Effects of Prospective ECG-gated Helical Scan with High Helical Pitch in Coronary Multidetector Computed Tomography
    Tomonari Sano, Hideyuki Matsutani, Takeshi Kondo, Takako Sekine, Takeh ...
    2010 Volume 66 Issue 7 Pages 774-780
    Published: July 20, 2010
    Released on J-STAGE: August 10, 2010
    DOIhttps://doi.org/10.6009/jjrt.66.774
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    Background: High radiation dose of conventional retrospective ECG-gated coronary MDCT (multidetector computed tomography) with regular helical pitch (HP) continuous scan has disturbed wide clinical use. The purpose was to estimate the radiation dose reduction effects of FlashScan, which was a prospective ECG-gated helical scan with high HP. Method: Coronary MDCT was performed by Aquilion 64 Super Heart (Toshiba) in 474 patients (M/F=280/194, mean age: 65±11 years old, mean height: 161±10 cm, body weight: 62±13 kg, BMI: 23.9±3.4) with HR≤60 and without arrhythmia before scan. Result: Mean HP (BP) which was automatically decided by the FlashScan system was 15.3±1.0 (0.239±0.016) when the gantry rotation speed was 0.35 s/rot. In 6 patients, arrhythmias occurred during scan and data deficits were observed on their images. In the remaining 468 patients, image quality was excellent. Mean DLP of the FlashScan (499±119 mGy·cm) was significantly (P<0.0001) lower than that of retrospective continuous scan with regular HP (1281±286 mGy·cm) or than that of modulation scan (927±202 mGy·cm), and mean scan time of the FlashScan (6.9±0.6 s) was also significantly (P<0.0001) shorter than that of retrospective continuous scan with regular HP (8.8±0.6 s). Conclusion: The FlashScan was a useful method to reduce patients’ radiation dose and scan time in patients with HR≤60 and without arrhythmia.
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The 65th Annual Scientific Congress
Educational Lecture- Basic Thinking of Image Analysis
Educational Lecture- Research Methodology
Basic Lecture- Comprehension and Utilization of CR Image Processing
Basic Lecture- How to Make Use of Softwares
Clinical Technology Course
Science Exchange Committee Report
Committee News
Contribution
JIRA Topics
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