日本放射線技術学会雑誌
Online ISSN : 1881-4883
Print ISSN : 0369-4305
ISSN-L : 0369-4305
最新号
選択された号の論文の16件中1~16を表示しています
巻頭言
原著
  • 青山 貴洋, 清水 秀年, 磯村 泰己, 北川 智基, 田中 健登, 古平 毅
    2019 年 75 巻 10 号 p. 1125-1134
    発行日: 2019年
    公開日: 2019/10/20
    ジャーナル フリー

    As the couch used in external radiation therapy attenuate radiation by interaction, it is necessary to correct attenuation of radiation by inserting a couch model in the treatment planning systems. For a couch whose thickness is different in the superior-inferior direction, it is possible to perform dose calculations with an error within ±1% by using separate different couch models provided by vendors. However, it is difficult to correct attenuation correction accurately with a single couch model. In this study, we created an in-house couch model which can set couch shape and physical density in detail by acquiring CT images of actual couch. When we performed dose calculation by optimizing the physical densities of in-house and vendor couch, it was found that the difference between the measured and the calculated values can be significantly reduced by using in-house couch model. Additionally, by using in-house couch model, it is found that the dose attenuation can be corrected within ±1% for a couch whose thickness is different in the superior-inferior direction.

臨床技術
  • 松本 賢治, 樽谷 和雄
    2019 年 75 巻 10 号 p. 1135-1140
    発行日: 2019年
    公開日: 2019/10/20
    ジャーナル フリー

    Radiotherapy linear accelerators are calibrated to deliver a specific dose under standard conditions following accepted protocols (for example, JSMP12 protocol). The linear accelerator output is calibrated to deliver 1.0 cGy per 1.0 monitor unit (MU) at the depth of maximum in tissue maximum ratio. Beams of photons or electrons pass through a monitor chamber located in the linear accelerators head, which turns off the beam once the prescribed MU is delivered. The clinical outcome of radiotherapy demands that the linear accelerators output do not deviate from the calibrated level by more than a few percent. The purpose of this study is to characterize and understand the long term behavior of the output, change of flatness and symmetry from megavoltage radiotherapy linear accelerators (TrueBeam, Varian Medical Systems). Output trends of beams from three linear accelerators in two institutions over a period of more than 3 years are reported and analyzed. Output taken once per month the basis of this study. The output is measured using ionization chamber with water phantom. These are calibrated by accredited dosimetry laboratory with Japanese traceability system. When the output variation was bounded ±1%, monitor chamber was re-calibrated. The results show that the output from Linac was constantly upward trend. The output of Linac increased up to 8.0% in 1st year. However, upward trend became plateau slowly after years. Beams of same energies from another Linac are correlated with a correlation coefficient. Symmetry and flatness from one Truebeam stabled within 1%. If these adjustments are artificially removed then there is an increase in output, it is important to check the output of linear accelerator periodically.

  • 水﨑 陽仁, 今井 俊輔, 梶浦 涼, 中島 勇気, 近藤 武, 立木 秀一, 市原 隆, Nadeeka Hemachandra, 間瀬 ...
    2019 年 75 巻 10 号 p. 1141-1149
    発行日: 2019年
    公開日: 2019/10/20
    ジャーナル フリー

    Purpose: Ichihara et al. (Fujita Med J 2015; 1(1): 9–14) developed a method to simultaneously obtain both coronary computed tomography (CT) angiography and CT myocardial perfusion (CTP) using 64-multi detector CT (MDCT). An input-function (time enhancement curve, TEC) of the ascending aorta (Ao) and myocardial CT density are necessary to calculate absolute myocardial blood flow (ml/g/min) using a two-compartment model. Helical scan starting timing is important to capture the peak (P) of Ao time enhancement curve (TEC). The purpose is to search the optimal timing of starting helical scan to capture the P. Methods: We performed 14 CTPs using Definition AS+ (SIEMENS). A dynamic scan at the Ao level was started at 7 s after contrast injection and helical scan was started at various trigger on bolus tracking. Definition AS+ needs 2 s (other scanner may need 4 s) for changing from a dynamic to helical scan mode. We created TECs of pulmonary artery (PA) and Ao using the fifth function fitting. We measured the time from trigger point to the P (t200, t250, t300 and tCP). Results: Mean t200, t250, t300 and tCP were 9.1±1.9, 7.9±2.0, 6.6±1.9 and 3.9±1.2 s, respectively. In additional other 16 CTP studies using the cross point method, we can capture the P in all (100%) examinations. Conclusion: Scan starting at the cross point is best for Definition AS+, and the Ao=300 HU may be best for other scanner that needs 4 s for changing scan mode to obtain a fine input function for calculating absolute myocardial blood flow.

  • 原田 高行, 武村 哲浩
    2019 年 75 巻 10 号 p. 1150-1157
    発行日: 2019年
    公開日: 2019/10/20
    ジャーナル フリー

    In this paper, we proposed an efficient quality assurance method which can measure direct tissue maximum ratio (TMRDir), total scatter factor (Scp, Dir), wedge factor (WFDir), tissue phantom ratio 20/10 (TPR20/10Dir) by using a calibration water phantom and a Farmer chamber. The TMRDir was compared with the calculated TMR (TMRCal) that was calculated from the percentage depth dose at the time of the linear accelerator installation. Scp, Dir, WFDir and TPR20/10Dir calculated from TMRDir were compared with Scp, BD, WFBD, and TPR20/10BD measured at the time of the linear accelerator installation. The difference between TMRDir and TMRCal was approximately within 1% except for using 60° wedge filter. The difference between Scp, Dir and Scp, BD was within 1%, between WFDir and WFBD was within 2%, between TPR20/10Dir and TPR20/10BD was within 1%, these differences were acceptable levels of AAPM TG-142 report. Also, coefficient of variation (CV) of TMRDir, ScpDir, WFDir and TPR20/10Dir when changing days and measuring multiple times were approximately within 1%, these CVs were reference levels of AAPM TG-106 report. We validated that was an efficient quality assurance method by measuring direct tissue maximum ratio, but the propose method has limited in measurable field size.

  • 北 章延, 杉本 勝也, 小坂 信之, 小野口 昌久, 澁谷 孝行, 安達 登志樹
    2019 年 75 巻 10 号 p. 1158-1164
    発行日: 2019年
    公開日: 2019/10/20
    ジャーナル フリー

    Purpose: To calculate the quantitative values in bone single-photon emission computed tomography, it is necessary to measure the amount of syringe radiation before and after the administration of a radiopharmaceutical. We proposed a method to omit the measurement of radioactivity. In this study, we clarified the effects of adopting this method and calculated its influence on quantitative values in a clinical setting. Methods: We derived a relational expression of the administration time and dose of radioactivity from the measured value and the administration time of the syringe dose before and after the administration in each patient. Next, we determined the differences for radioactivity calculated from this relational expression (estimated dose) and actual administered radioactivity (actual dose). Furthermore, we calculated the differences in the quantitative values of a normal region (the fourth lumbar vertebra) on adopting these data. Results: No significant differences between the estimated dose and actual dose were noted. Additionally, no significant differences in the quantitative values were observed. Conclusion: Our findings suggest that adoption of the estimated dose does not affect the quantitative value. When the estimated dose is adopted, it can be administered with an accuracy of 0.80%. Thus, it is possible to omit the actual measurement of radioactivity by using our proposed method.

  • 北野 哲哉, 金子 雅一, 山田 茂樹
    2019 年 75 巻 10 号 p. 1165-1172
    発行日: 2019年
    公開日: 2019/10/20
    ジャーナル フリー

    There are many variations in branching and running of pulmonary artery (PA) and pulmonary vein (PV). It is desirable to separate as a surgical simulation of lung cancer and important to grasp before video-assisted thoracic surgery (VATS) to perform quick and safe. Therefore, the purpose of this study was to evaluate objective and subjective image quality (contrast attenuation, separation ability, and vascular visualization) of PA and PV of splitbolus single-phase protocol (SBSPP) in preoperative three-dimensional computed tomography angiography (3DCTA). CT value of PA was 410.2±71.0 Hounsfield unit (HU), PV was 245.1±24.8 HU, difference between CT value of PA and CT value of PV was 164.5±60.9 HU. Subjective image quality of PA and PV could be visualized until more than the segmental branch level. SBSPP can obtain sufficient CT value for separate visualization of PA and PV, and before VATS useful PA and PV 3D-CTA imaging.

  • 郡 倫一, 加藤 崇英, 倉田 和馬
    2019 年 75 巻 10 号 p. 1173-1176
    発行日: 2019年
    公開日: 2019/10/20
    ジャーナル フリー

    Recently, tumor differentiation in various tissues has been performed by using the apparent diffusion coefficient (ADC) value. However, the influence of ADC value due to the different inversion time (TI) of fat suppression methods has not been reported yet. Therefore, the purpose of our study was to verify the influence of the different TI of fat suppression methods on the ADC value. ADC values were compared for diffusion-weighted imaging (DWI), using the short-TI inversion recovery (STIR) method and the spectral attenuated inversion recovery (SPAIR) method. For the STIR method, when TI was closed to the null point of each phantom, signal intensity decreased, and the ADC value thereby decreased. However, by the SPAIR method, signal intensity and ADC value were not affected by the inversion time. When using the STIR method, signal intensity decreased when the null point for each phantom was approached, which was thought to decrease the ADC value. In conclusion, when using STIR-DWI after contrast agent administration, the ADC value might have been affected by the TI.

第75回総会学術大会「JSRT-JSMP 合同企画」
第75回総会学術大会教育講演
教育講座─放射線技術学を用いた先端生命科学研究─
教育講座─放射線治療装置を立ち上げよう─
教育講座─放射線技術学におけるImageJの活用─
教育講座─放射線技術学における研究の進め方:研究計画から論文発表まで─
基礎講座─定量とその不確かさ─
JIRAトピックス
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