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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

Computed Tomographic Scan of Phantom With Esophagus Applicator
© Copyright Policy - open-access
Related In: Results  -  Collection

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A2330FIG4: Computed Tomographic Scan of Phantom With Esophagus Applicator

Mentions: In order to plan the phantom for considered treatment, CT scans were acquired from the phantom with applicator placed into phantom. During CT scanning, external markers were used to avoid any mismatch between the planned and the treated phantom set up (Figure 4). All CT data were sent to the Flexiplan 3D TPS (Pars radiotherapy center, Tehran, Iran) and then the 192Ir sources were remotely loaded into the phantom while TLDs were placed at considered locations (10 on surface and six in depths) (Figure 4). Dwelling times and positions of the single 192Ir source were planned to deliver 5 Gy to the specific target volume with length of 4 cm and volume of 23 cm3 in the upper thoracic esophagus lumen. Target volume was CTV with 1 cm distal and proximal margins. The considered locations for TLDs were eye, right parotid (skin surface and 1-cm depth), left parotid (skin surface and 1-cm depth), left submandibular, right submandibular, left thyroid (skin surface and 1-cm depth), and right thyroid glands (skin surface and 1cm depth), trachea (skin surface and 4-cm depth), manubrium of sternum, spine (inside the phantom and skin surface).


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)

Computed Tomographic Scan of Phantom With Esophagus Applicator
© Copyright Policy - open-access
Related In: Results  -  Collection

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

A2330FIG4: Computed Tomographic Scan of Phantom With Esophagus Applicator
Mentions: In order to plan the phantom for considered treatment, CT scans were acquired from the phantom with applicator placed into phantom. During CT scanning, external markers were used to avoid any mismatch between the planned and the treated phantom set up (Figure 4). All CT data were sent to the Flexiplan 3D TPS (Pars radiotherapy center, Tehran, Iran) and then the 192Ir sources were remotely loaded into the phantom while TLDs were placed at considered locations (10 on surface and six in depths) (Figure 4). Dwelling times and positions of the single 192Ir source were planned to deliver 5 Gy to the specific target volume with length of 4 cm and volume of 23 cm3 in the upper thoracic esophagus lumen. Target volume was CTV with 1 cm distal and proximal margins. The considered locations for TLDs were eye, right parotid (skin surface and 1-cm depth), left parotid (skin surface and 1-cm depth), left submandibular, right submandibular, left thyroid (skin surface and 1-cm depth), and right thyroid glands (skin surface and 1cm depth), trachea (skin surface and 4-cm depth), manubrium of sternum, spine (inside the phantom and skin surface).

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