Japanese Journal of Radiological Technology
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
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Volume 67, Issue 12
Displaying 1-18 of 18 articles from this issue
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Opening Article
Originals
  • T2 Image Contrast Evaluation Using Three Dimension Sampling Perfection with Application Optimized Contrasts Using Different Flip Angle Evolution (3D-SPACE)
    Ryo Yamazaki, Masato Uchikoshi, Yukikazu Hiura, Akio Tsuji, Shigeo Nis ...
    2011 Volume 67 Issue 12 Pages 1515-1522
    Published: December 20, 2011
    Released on J-STAGE: December 21, 2011
    DOIhttps://doi.org/10.6009/jjrt.67.1515
    JOURNAL FREE ACCESS
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    Purpose: Sampling perfection with application optimized contrasts using different flip angle evolution (3D-SPACE) sequence enables one to decrease specific absorption rate (SAR) by using variable flip angle refocusing pulse. Therefore, it is expected that the contrast obtained with 3D-SPACE sequences is different from that of spin echo (SE) images and turbo spin echo (TSE) images. The purpose of this study was to evaluate the characteristics of the signal intensity and central nervous system (CNS) image contrast in T2 weighted 3D-SPACE. Method: Using 3 different sequences (SE, 3D-TSE and 3D-SPACE) with TR/TE=3500/70, 90 and 115 ms, we obtained T2 weighted magnetic resonance (MR) images of inhouse phantom and five healthy volunteers’ brain. Signal intensity of the phantom which contains various T1 and T2 value was evaluated. Tissue contrasts of white/gray matter, cerebrospinal fluid (CSF)/subcutaneous fat and gray matter/subcutaneous fat were evaluated for a clinical image study. Results: The phantom study showed that signal intensity in 3D-SPACE significantly decreased under a T1 value of 250 ms. It was markedly decreased in comparison to other sequences, as effective echo time (TE) was extended. White/gray matter contrast of 3D-SPACE was the highest in all sequences. On the other hand, CSF/fat and gray matter/fat contrast of 3D-SPACE was higher than TSE but lower than SE. Conclusion: CNS image contrasts of 3D-SPACE were comparable to that of SE. Signal intensity had decreased in the range where T1 and T2 values were extremely short.
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  • A Suggestion of New Slice Thickness Mensuration Using Partial Volume Effect in Magnetic Resonance Imaging
    Tetsuya Kimura, Mitsuji Higashida, Yasuo Takatsu, Akio Ogura
    2011 Volume 67 Issue 12 Pages 1523-1532
    Published: December 20, 2011
    Released on J-STAGE: December 21, 2011
    DOIhttps://doi.org/10.6009/jjrt.67.1523
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    The wedge and the slab methods are standard procedures as slice thickness mensuration of the MRI needs an expensive and exclusive phantom, and they are poor in versatility. We suggest a new method, that we call “differential edge response function method”. This is a modified version of the partial method which Higashida and others proposed. In this method, we use an original phantom which has an acrylic disk on the bottom, and take an image of it while moving a slice position so it includes the disk part. We established the region of interest on an image set up and got the edge response function (ERF) from the mean signal intensity and relations of the Z position of the image. In this method, the effective slice thickness is the half width of the slice profile, which is differentiated ERF. This method can be measured even if the linearity of the signal intensity is poor compared to the partial method. It is possible to correct the alignment. In this method the measurement accuracy was approximately equal to the wedge method. This method is minimally influenced by signal-to-noise ratio in comparison with the wedge method. Furthermore, versatility is high, because it is simple and relatively easy to use.
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  • The Precision of Half-value Layer Measurement on Mammography
    Rie Ishii, Akira Yoshida, Mie Ishii, Shiho Fujimoto, Noriko Henmi
    2011 Volume 67 Issue 12 Pages 1533-1539
    Published: December 20, 2011
    Released on J-STAGE: December 21, 2011
    DOIhttps://doi.org/10.6009/jjrt.67.1533
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    The half-value layer (HVL) is an important index of the image quality or radiation risk in mammography. Radiation risk of the breast tissue is evaluated with the average glandular dose. The HVL index is indispensable for the average glandular dose computations. We investigated the influence of multiple factors that affect HVL value, such as thickness or purity of the aluminum attenuator, detector material of dosimeter, fluctuation of X-ray output, detector location in X-ray field and so on, for accurate average glandular dose computations. We found some aluminum plates about 20% thicker than nominal thickness. The HVL values between seven filter sets were different in about 5% at the maximum. In addition, we reduced a fluctuation of X-ray output with dose monitoring. Then, the standard deviation of HVL value decreased from 1.114% to 0.105%. HVL value obtained from a solid-state detector was statistically thicker than that measured by ionization chamber. It has been reported that there was a difference in the half-value layer under the influence of a heel effect by location of the measurement. Accompanied with alternation of detector location, HVL value of PCM (Konica Minolta) had a significant difference, while Novation (Siemens) and Senographe 2000D (GE) had no change.
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  • Computerized Estimation of a Percent Glandular Tissue Composition in Computed Radiography Mammography
    Naoko Tsujita, Sachiko Goto, Yoshiharu Azuma, Junji Shiraishi
    2011 Volume 67 Issue 12 Pages 1540-1547
    Published: December 20, 2011
    Released on J-STAGE: December 21, 2011
    DOIhttps://doi.org/10.6009/jjrt.67.1540
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    Measurement of a percent glandular tissue composition (%GTC) is important in terms of the estimation of individual patient exposure dose and the prediction of malignancy, and thus a number of reports for estimating %GTC by use of a mammogram have been published. In this study, we propose a method for estimating individual %GTC by use of computed radiography (CR) mammograms. By employing breast-equivalent phantoms that are able to create breast phantom images with various combinations of fat and glandular tissue, as well as the thickness of whole breast, we determined a reference table for converting an each pixel value on CR mammography to the glandular tissue ratio. Therefore, the %GTC for individual breast was estimated by averaging glandular tissue ratio for a whole region. The clinical image data set that consisted of 49 CR mammograms were used for estimating %GTC. A paired comparison method for determining subjective ranking of the degree of breast density was employed in order to demonstrate the validity of our method. The results indicate that the average estimated %GTC was 35.0% (ranged from 12.0% to 67.0%) and they had a increased correlation with the ranking of those obtained by observer test. Therefore, it was suggested that our proposed method would be utilized for estimating the %GTC in objective manner.
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  • Investigation for Decrease of Delivery Time for the Prostate Cancer Patient by Modifications of Treatment Planning Parameters in TomoTherapy Planning Station
    Hidetoshi Shimizu, Hiroyuki Tachibana, Takashi Kubota, Hiroshi Imamura ...
    2011 Volume 67 Issue 12 Pages 1548-1558
    Published: December 20, 2011
    Released on J-STAGE: December 21, 2011
    DOIhttps://doi.org/10.6009/jjrt.67.1548
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    The purpose of present study is to investigate the decrease of delivery time for prostate cancer patient by using the helical type accelerator, Hi-Art System. The delivery time for Hi-Art System depends on planning parameters [pitch, modulation factor (MF) and field width (FW)], which are set by the operator at the beginning of the treatment planning. If you can allow for the deterioration of the dose distribution, the delivery time is able to decrease by increasing of FW and/or by decreasing of MF. On the other hands, as the use of 5.0 cm FW tends to increase the dose for the penile bulb, enough consideration for the dose distribution is needed. In addition, pitch should be set for the gantry rotation period not to become 15 s or less to prevent the increase of delivery time.
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Clinical Technology
  • Impact of Setup Error and Anatomical Change on Dose Distribution during Conventional Radiation Therapy
    Naoko Tsujita, Saki Yamaguchi, Ryuji Murakami, Takafumi Hattori, Masat ...
    2011 Volume 67 Issue 12 Pages 1559-1564
    Published: December 20, 2011
    Released on J-STAGE: December 21, 2011
    DOIhttps://doi.org/10.6009/jjrt.67.1559
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    The purpose of this study was to evaluate the impact of setup error and anatomical change on dose distribution during conventional radiation therapy. We performed regional irradiation (Plan1) using opposing pair fields, and then we planned local irradiation (Plan2) with a computed tomography (CT) acquired at that time in 10 patients with advanced oral cancer. To consider the setup error, a minimum dose of gross tumor volume (GTV) and a maximum dose for the spinal cord were re-calculated with isocenter shifts of ±5 mm. We also evaluated an alteration of reference dose due to anatomical changes during radiation therapy. A minimum dose of GTV was decreased with isocenter shifts; the trend was stronger in Plan2 than Plan1 (—5.7% vs. —1.2%, p=0.02). Similarly, a maximum dose of spinal cord was increased with isocenter shifts, especially in Plan2 (12.2% vs. 0.5%, p<0.01). Anatomical changes during radiation therapy were observed in all patients, and the mean difference for depth was —4 mm in Plan1; the reference dose was increased in Plan1 and Plan2. Precise setup is necessary, especially for local irradiation in spite of anatomical changes during radiation therapy. Reimaging and replanning are recommended for patients with marked anatomical changes.
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  • Efficacy of Patient Skin Dose Reduction by a Compensating Filter through of Irradiation Field Overlaps on the Area during Percutaneous Coronary Intervention
    Hiroyuki Yamasaki, Makoto Nakahara, Sadao Yamaguchi, Naomi Yamamoto, T ...
    2011 Volume 67 Issue 12 Pages 1565-1573
    Published: December 20, 2011
    Released on J-STAGE: December 21, 2011
    DOIhttps://doi.org/10.6009/jjrt.67.1565
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    Our study was involved with entrance surface dose reduction and irradiation field by the filter use of PCI, and insertion in place of an effective compensating filter to maximize entrance surface dose reduction, which we verified. The radiation dosimetry put a 6cc ion chamber on the back side of the thorax phantom, and changed the filter of the four corners (a: upper left, b: upper right, c: lower right, d: lower left) of the monitor confirmed with fluoroscopy [(0) no filter, (1) one filter, (2) two filters]. The angle of C arm was assumed to be eight directions and 0 degrees adopted by this hospital. It was compared with a corrective rate of which one was no filter. Next, the presence of filter and irradiation field overlaps on the area in monitor in the angle of C arm was verified by this hospital’s classic example. As for corrective rate, (1) becomes 0.41 and (2) become 0.25 at fluoroscopy, (1) becomes 0.26 and (2) become 0.16 at exposure. Irradiation field overlaps on the area (+) compensating filter (—) was many with d of RAO/CAU, a of RAO and c of CAU at left CAG, c of LAO at right CAG, b of LAO/CRA (left CAG), b of CRA (right CAG) and a and d of RAO (right CAG) at both CAG. Irradiation field overlaps on the area (+) compensating filter (+) was many with b of CRA at left CAG, a of LAO/CRA at right CAG, b of CRA (left CAG) and b of RAO (right CAG) at both CAG. When the compensating filter is used the entrance surface dose reduction effect was great. If automatic exposure control protects the part of irradiation field overlaps on the area in the range without operating excessively, the radiological risk can be reduced, and it is conceivable as useful clinical setting.
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Data
  • An Attitude Survey of Radiological Technologists toward Qualification Acquisition of Licentiate and Degrees in Mie Prefecture
    Satoshi Nakanishi, Akira Kamigiri, Tsuyoshi Yamada, Kazuyoshi Nanba, T ...
    2011 Volume 67 Issue 12 Pages 1574-1582
    Published: December 20, 2011
    Released on J-STAGE: December 21, 2011
    DOIhttps://doi.org/10.6009/jjrt.67.1574
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    We conducted a questionnaire consciousness survey concerning qualification acquisition of licentiate and degrees among 406 radiological technologists working for medical facility in Mie Prefecture. We employed a mail-back questionnaire method. Then we analyzed relationships between progressive purpose and gender, age, and membership of the Japanese Society of Radiological Technology (JSRT). Results derived note the most common licentiate the participants wanted to acquire was the license concerning emergency medical care. On the other hand, they had limited interest in radiation therapy, nuclear medicine areas and the working environment measurement expert class I. In conclusion, the results of this study revealed the present condition that the necessity of qualification acquisition of licentiate is not recognized incorrectly. In addition, there was a mountain of issues for working radiological technologists to attend graduate school to get degrees. It is important to utilize the results of this study to enlighten their consciousness for limited interest licentiate, and interest them in attending graduate schools.
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  • Effects of Computed Tomography Contrast Medium Factors on Contrast Enhancement
    Kazuaki Terasawa, Atsushi Hatcho, Itsuko Okuda
    2011 Volume 67 Issue 12 Pages 1583-1591
    Published: December 20, 2011
    Released on J-STAGE: December 21, 2011
    DOIhttps://doi.org/10.6009/jjrt.67.1583
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    The various nonionic iodinated contrast media used in contrast computed tomography (CT) studies differ in terms of their composition, characteristics, and iodine concentration (mgI/ml), as well as the volume injected (ml). Compared with ionic iodinated contrast media, nonionic iodinated contrast media are low-osmolar agents, with different agents having different osmotic pressures. Using a custom-made phantom incorporating a semipermeable membrane, the osmotic flow rate (HU/s) could easily be measured based on the observed increase in CT numbers, and the relationship between the osmotic pressure and the osmotic flow rate could be obtained (r2=0.84). In addition, taking the effects of patient size into consideration, the levels of contrast enhancement in the abdominal aorta (AA) and inferior vena cava (IVC) were compared among four types of CT contrast medium. The results showed differences in contrast enhancement in the IVC during the equilibrium phase depending on the type of contrast medium used. It was found that the factors responsible for the differences observed in enhancement in the IVC were the osmotic flow rate and the volume of the blood flow pathways in the circulatory system. It is therefore considered that the reproducibility of contrast enhancement is likely to be reduced in the examination of parenchymal organs, in which scanning must be performed during the equilibrium phase, even if the amount of iodine injected per unit body weight (mgI/kg) is maintained at a specified level.
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Work in Progress
  • Dosimetric Correction for a Six Degrees Carbon Fiber Couch
    Yuji Nakaguchi, Ryuji Murakami, Masato Maruyama, Kiyotaka Kakei, Nozom ...
    2011 Volume 67 Issue 12 Pages 1592-1597
    Published: December 20, 2011
    Released on J-STAGE: December 21, 2011
    DOIhttps://doi.org/10.6009/jjrt.67.1592
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    We investigated experimentally and clinically the influence of a six degree (6D) carbon fiber couch on conventional radiation therapy. We used 4, 6 and 10 MV X-rays and compared dose distributions based on correction methods, i.e. monitor unit (MU) addition, including computed tomography (CT) couch, and the couch modeling. Additionally, we evaluated the clinical value of dosimetric correction for the 6D couch in 30 patients treated with multi-field irradiation. In the phantom study, the maximum difference of isocenter doses attributable to the 6D couch was 5.1%; the difference was reduced with increasing X-ray energy. Although the isocenter dose based on each correction method was precise within ±1%, MU addition underestimated the surface dose. In the clinical study, the maximum difference of isocenter doses attributable to the 6D couch was 2.7%. The correction methods for the 6D couch provide for highly precise treatment planning. However, the clinical indication of complicated correction methods should be considered for each institution or each patient, because the influence of the 6D couch was reduced with multi-field irradiation.
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Moum
Special Plan—Member Interview: The People Who Contributed to the Academic Society—
Educational Lecture—Radiation Measurement in the Clinical Setting
Basic Lecture—Radiation Therapy Technology: Basic Strategy
Virtual Interview for Graduate School and Laboratories
Science Exchanges Committee News
JIRA Topics
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