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44 results on '"Takeda, Hiromitsu"'

3. Benchmark of EGS5 for 125I brachytherapy

Author

Tanaka, Kenichi, primary, Tateoka, Kunihiko, additional, Asanuma, Osamu, additional, Kamo, Ken-ichi, additional, Sato, Kaori, additional, Takeda, Hiromitsu, additional, Takagi, Masaru, additional, Hareyama, Masato, additional, and Takada, Jun, additional

Published
2014
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5. A dosimetry study of the Oncoseed 6711 using glass rod dosimeters and EGS5 Monte Carlo code in a geometry lacking radiation equilibrium scatter conditions

Author

Tanaka, Kenichi, primary, Tateoka, Kunihiko, additional, Asanuma, Osamu, additional, Kamo, Ken-ichi, additional, Bengua, Gerard, additional, Sato, Kaori, additional, Ueda, Toshikazu, additional, Takeda, Hiromitsu, additional, Takagi, Masaru, additional, Hareyama, Masato, additional, and Takada, Jun, additional

Published
2011
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40. Strength estimation of a moving 125Iodine source during implantation in brachytherapy: application to linked sources

Author

Tanaka, Kenichi, Endo, Satoru, Tateoka, Kunihiko, Asanuma, Osamu, Hori, Masakazu, Takagi, Masaru, Bengua, Gerard, Kamo, Ken-ichi, Sato, Kaori, Takeda, Hiromitsu, Hareyama, Masato, Sakata, Koh-ichi, and Takada, Jun

Abstract

This study sought to demonstrate the feasibility of estimating the source strength during implantation in brachytherapy. The requirement for measuring the strengths of the linked sources was investigated. The utilized sources were 125I with air kerma strengths of 8.38–8.63 U (μGy m2 h–1). Measurements were performed with a plastic scintillator (80 mm × 50 mm × 20 mm in thickness). For a source-to-source distance of 10.5 mm and at source speeds of up to 200 mm s–1, a counting time of 10 ms and a detector-to-needle distance of 5 mm were found to be the appropriate measurement conditions. The combined standard uncertainty (CSU) with the coverage factor of 1 (k = 1) was ∼15% when using a grid to decrease the interference by the neighboring sources. Without the grid, the CSU (k = 1) was ∼5%, and an 8% overestimation due to the neighboring sources was found to potentially cause additional uncertainty. In order to improve the accuracy in estimating source strength, it is recommended that the measurment conditions should be optimized by considering the tradeoff between the overestimation due to the neighboring sources and the intensity of the measured value, which influences the random error.

Published
2014
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41. A dosimetry method for low dose rate brachytherapy by EGS5 combined with regression to reflect source strength shortage

Author

Tanaka, Kenichi, Tateoka, Kunihiko, Asanuma, Osamu, Kamo, Ken-ichi, Sato, Kaori, Takeda, Hiromitsu, Takagi, Masaru, Hareyama, Masato, and Takada, Jun

Abstract

The post-implantation dosimetry for brachytherapy using Monte Carlo calculation by EGS5 code combined with the source strength regression was investigated with respect to its validity. In this method, the source strength for the EGS5 calculation was adjusted with the regression, so that the calculation would reproduce the dose monitored with the glass rod dosimeters (GRDs) on a water phantom. The experiments were performed, simulating the case where one of two 125I sources of Oncoseed 6711 was lacking strength by 4–48%. As a result, the calculation without regression was in agreement with the GRD measurement within 26–62%. In this case, the shortage in strength of a source was neglected. By the regression, in order to reflect the strength shortage, the agreement was improved up to 17–24%. This agreement was also comparable with accuracy of the dose calculation for single source geometry reported previously. These results suggest the validity of the dosimetry method proposed in this study.

Published
2014
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43. [Development of a Lead-covered Case for a Wireless X-ray Output Analyzer to Perform CT Half-value Layer Measurements].

Author

Akaishi H, Takeda H, Kanazawa Y, Yoshii Y, and Asanuma O

Subjects
Radiation Dosage, Radiation Injuries prevention & control, Lead, Radiometry instrumentation, Tomography, X-Ray Computed instrumentation, X-Rays adverse effects
Abstract

Measurement of the half-value layer (HVL) is a difficult task in computed tomography (CT) , because a nonrotating X-ray tube must be used. The purpose of this study is to develop a lead-covered case, which enables HVL measurements with a rotating CT X-ray tube. The lead-covered case was manufactured from acrylic and lead plates, which are 3 mm thick and have a slit. The slit-detector distance can be selected between 14 mm and 122 mm. HVL measurements were performed using a wireless X-ray output analyzer "Piranha." We used the following exposure conditions: tube voltages of 80, 100, and 120 kV; a tube current of 550 mA; and an exposure time of 1.0 s. The HVLs were measured by using the following two methods: (a) Nonrotating method-a conventional method that uses the nonrotating exposure mode. (b) Rotating method-a new method that uses the lead-covered case and the rotating exposure mode. As a result, when the slit-detector distance was 58 mm, the HVL values obtained by the nonrotating and rotating methods were 4.38 and 4.24 mmAl at 80 kV, 5.51 and 5.37 mmAl at 100 kV, 6.61 and 6.48 mmAl at 120 kV, respectively. A lead-covered case, which enables the measurement of the HVL in a rotating X-ray tube, was developed. The case is useful in measuring the HVLs at facilities that cannot fix the X-ray tube.

Published
2016
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44. [Study of radiation dose to the eye lens by multi-detector row computed tomography of the temporal bone].

Author

Hirakuri A, Numasawa K, Takeishi H, Satomura M, Takeda H, Harada K, Asanuma O, and Sakata M

Subjects
Humans, Male, Middle Aged, Phantoms, Imaging, Radiation Protection, Radiometry instrumentation, Temporal Bone anatomy & histology, Lens, Crystalline radiation effects, Multidetector Computed Tomography adverse effects, Radiation Dosage, Temporal Bone diagnostic imaging
Abstract

The exposure of the eye lens caused by multi-detector row computed tomography (MDCT) of the temporal bone is a serious problem. Our aim was to evaluate the radiation dose to the eye lens by different scan baselines (orbitomeatal line; OML, acanthiomeatal line; AML) and examine the difference of the depiction of the temporal bone structures. Measurement of the exposure to the eye lens was performed by means of MDCT of the temporal bone with a radio-photoluminescence glass dosimeter using a rand phantom. Moreover, we studied only one volunteer (58-year-old male) who had no symptom and was not suspected of having any ear abnormalities with a two scan baseline. Visualization of the major anatomical structures of the temporal bone (the tympanic portion of the facial nerve canal, the body of the incus, stapes superstructures, vestibule etc.) was performed on the volunteer. The average absorbed dose was 6.42 mGy by the OML and 1.59 mGy by the AML, respectively. With regard to visualization of the temporal bone structures, all structures were of equal quality with the two scan baseline. With the AML line, the radiation dose to the eye lens was reduced to 75%. Therefore, the authors recommended an AML for use for MDCT of the temporal bone. In clinical practice, the optimization of scanning factor (kVp, mAs etc.) and the use of the radio-protection should be implemented for radiation dose reduction of the eye lens by MDCT of the temporal bone.

Published
2012
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