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High-Dose-Rate (192)Ir Brachytherapy Dose Verification: A Phantom Study.

Nikoofar A, Hoseinpour Z, Rabi Mahdavi S, Hasanzadeh H, Rezaei Tavirani M - Iran J Cancer Prev (2015)

Bottom Line: Because of some concerns about adverse effects due to absorbed radiation dose, it is important to estimate absorbed dose in risky organs during this treatment.In closer regions (≤ 16 cm), the absorbed dose might be as high as 113 cGy.Our study showed similar depth and surface doses; in closer regions, the surface and depth doses differed significantly due to the role of primary radiation that had imposed a high-dose gradient and difference between the plan and measurement, which was more severe because of simplifications in tissue inhomogeneity, considered in TPS relative to phantom.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Iran University of Medical Sciences, Tehran, IR Iran.

ABSTRACT

Background: The high-dose-rate (HDR) brachytherapy might be an effective tool for palliation of dysphagia. Because of some concerns about adverse effects due to absorbed radiation dose, it is important to estimate absorbed dose in risky organs during this treatment.

Objectives: This study aimed to measure the absorbed dose in the parotid, thyroid, and submandibular gland, eye, trachea, spinal cord, and manubrium of sternum in brachytherapy in an anthropomorphic phantom.

Materials and methods: To measure radiation dose, eye, parotid, thyroid, and submandibular gland, spine, and sternum, an anthropomorphic phantom was considered with applicators to set thermoluminescence dosimeters (TLDs). A specific target volume of about 23 cm(3) in the upper thoracic esophagus was considered as target, and phantom planned computed tomography (CT) for HDR brachytherapy, then with a micro-Selectron HDR ((192)Ir) remote after-loading unit.

Results: Absorbed doses were measured with calibrated TLDs and were expressed in centi-Gray (cGy). In regions far from target (≥ 16 cm) such as submandibular, parotid and thyroid glands, mean measured dose ranged from 1.65 to 5.5 cGy. In closer regions (≤ 16 cm), the absorbed dose might be as high as 113 cGy.

Conclusions: Our study showed similar depth and surface doses; in closer regions, the surface and depth doses differed significantly due to the role of primary radiation that had imposed a high-dose gradient and difference between the plan and measurement, which was more severe because of simplifications in tissue inhomogeneity, considered in TPS relative to phantom.

No MeSH data available.


Related in: MedlinePlus

High-Dose-Rate 192Ir Brachytherapy Source Type Designs
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A2330FIG1: High-Dose-Rate 192Ir Brachytherapy Source Type Designs

Mentions: The micro-Selectron HDR was remote after-loading unit, a treatment system developed by Flexitron International. The TPS used the American Association of Physicists in Medicine (AAPM), Task Group 43 (TG-43) formalism for dose calculation, which includes different methods of optimization of the treatment’s dose distribution such as geometrical/graphical optimization and adjustment of dwell positions/times. The 192Ir source in this unit has an active length of 3.5 mm and active diameter of 0.6 mm. The source is enclosed in a cylindrical stainless steel capsule of external diameter 1.1 mm and length 5.0 mm (14, 17, 18) (Figure 1). The 48FR esophagus applicator with length of 50 cm and diameter of 1.6 cm was inserted in esophagus lumen of phantom, which was used to place dummy source in-place to take computed tomographic (CT) scans of thorax for treatment planning. In this study, the prescribed dose per fraction was 5 Gy at 1 cm from the surface of the esophageal applicator with the treatment length including the tumor plus a 2 cm margin at both ends (4).


High-Dose-Rate (192)Ir Brachytherapy Dose Verification: A Phantom Study.

Nikoofar A, Hoseinpour Z, Rabi Mahdavi S, Hasanzadeh H, Rezaei Tavirani M - Iran J Cancer Prev (2015)

High-Dose-Rate 192Ir Brachytherapy Source Type Designs
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4581367&req=5

A2330FIG1: High-Dose-Rate 192Ir Brachytherapy Source Type Designs
Mentions: The micro-Selectron HDR was remote after-loading unit, a treatment system developed by Flexitron International. The TPS used the American Association of Physicists in Medicine (AAPM), Task Group 43 (TG-43) formalism for dose calculation, which includes different methods of optimization of the treatment’s dose distribution such as geometrical/graphical optimization and adjustment of dwell positions/times. The 192Ir source in this unit has an active length of 3.5 mm and active diameter of 0.6 mm. The source is enclosed in a cylindrical stainless steel capsule of external diameter 1.1 mm and length 5.0 mm (14, 17, 18) (Figure 1). The 48FR esophagus applicator with length of 50 cm and diameter of 1.6 cm was inserted in esophagus lumen of phantom, which was used to place dummy source in-place to take computed tomographic (CT) scans of thorax for treatment planning. In this study, the prescribed dose per fraction was 5 Gy at 1 cm from the surface of the esophageal applicator with the treatment length including the tumor plus a 2 cm margin at both ends (4).

Bottom Line: Because of some concerns about adverse effects due to absorbed radiation dose, it is important to estimate absorbed dose in risky organs during this treatment.In closer regions (≤ 16 cm), the absorbed dose might be as high as 113 cGy.Our study showed similar depth and surface doses; in closer regions, the surface and depth doses differed significantly due to the role of primary radiation that had imposed a high-dose gradient and difference between the plan and measurement, which was more severe because of simplifications in tissue inhomogeneity, considered in TPS relative to phantom.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Iran University of Medical Sciences, Tehran, IR Iran.

ABSTRACT

Background: The high-dose-rate (HDR) brachytherapy might be an effective tool for palliation of dysphagia. Because of some concerns about adverse effects due to absorbed radiation dose, it is important to estimate absorbed dose in risky organs during this treatment.

Objectives: This study aimed to measure the absorbed dose in the parotid, thyroid, and submandibular gland, eye, trachea, spinal cord, and manubrium of sternum in brachytherapy in an anthropomorphic phantom.

Materials and methods: To measure radiation dose, eye, parotid, thyroid, and submandibular gland, spine, and sternum, an anthropomorphic phantom was considered with applicators to set thermoluminescence dosimeters (TLDs). A specific target volume of about 23 cm(3) in the upper thoracic esophagus was considered as target, and phantom planned computed tomography (CT) for HDR brachytherapy, then with a micro-Selectron HDR ((192)Ir) remote after-loading unit.

Results: Absorbed doses were measured with calibrated TLDs and were expressed in centi-Gray (cGy). In regions far from target (≥ 16 cm) such as submandibular, parotid and thyroid glands, mean measured dose ranged from 1.65 to 5.5 cGy. In closer regions (≤ 16 cm), the absorbed dose might be as high as 113 cGy.

Conclusions: Our study showed similar depth and surface doses; in closer regions, the surface and depth doses differed significantly due to the role of primary radiation that had imposed a high-dose gradient and difference between the plan and measurement, which was more severe because of simplifications in tissue inhomogeneity, considered in TPS relative to phantom.

No MeSH data available.


Related in: MedlinePlus