Prog Med Phys.  2013 Mar;24(1):35-40.

Evaluation of Absorbed Dose and Skin Dose with MDCT Using Ionization Chamber and TLD

• Jeon KS
• Oh YK
• Baek JG
• Kim OB
• Kim JH
• Choi TJ
• Jeong DH
• Kim JK

Abstract

Recently, the uses of Multi-Detector Computed Tomography (MDCT) for radiation treatment simulation and planning which is used for intensity modulated radiation therapy with high technique are increasing. Because of the increasing uses of MDCT, additional doses are also increasing. The objective of this study is to evaluate the absorbed dose of body and skin undergoing in MDCT scans. In this study, the exposed dose at the surface and the center of the cylindrical water phantom was measured using an pencil ionization chamber, 30 cc ionization chamber and TL Powder. The results of MDCT were 31.84 mGy, 33.58 mGy and 32.73 mGy respectively. The absorbed dose at the surface showed that the TL reading value was 33.92 mGy from MDCT. These results showed that the surface dose was about 3.5% from the MDCT exposure higher than a dose which is located at the center of the phantom. These results mean that the total exposed dose undergoing MDCT 4 times (diagnostic, radiation therapy planning, follow-up et al.), is about 14 cGy, and have to be considered significantly to reduce the exposed dose from CT scan.

Keyword

MDCT; CTDI; Pencil ion chamber; 30 cc ion-chamber; TLD

MeSH Terms

Skin
Water
Water

Figure

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  Fig. 1. Schematics and photograph of cylindrical water phantom.

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  Fig. 2. Pencil ionization chamber.

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  Fig. 3. (a) 30 cc cylindrical ionization chamber. (b) Diode detector.

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  Fig. 4. Thermoluminescence (TL) as a function of absorbed dose in mGy.

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  Fig. 5. Fan beam profile of CT with 2 mm-collimator and 130 kVp-peak voltage.

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  Fig. 6. Fan beam film scan with 130 kVp, Collimation 2 mm, pitch 1.0.

Reference

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