Evaluation of the dosimetry approaches in ablation treatment of thyroid cancer

In this study, we aimed to evaluate dosimetric approaches in ablation treatment of Differentiated Thyroid Carcinoma (DTC) without interrupting the clinical routine. Prior to therapy, 10.7 MBq 131I in average was orally given to 24 patients suffering from DTC. MIRD formalism was used for dosimetric c...

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Bibliographic Details
Published in:Journal of applied clinical medical physics 2018-07, Vol.19 (4), p.134-140
Main Authors: Alan Selcuk, Nalan, Toklu, Turkay, Beykan, Seval, Karaaslan, Serife Ipek
Format: Article
Language:English
Subjects:
Adolescent
Adult
Aged
Bone marrow
bone marrow dosimetry
Child
Dosimetry
Female
Humans
Iodine Radioisotopes
Male
Middle Aged
Radiation Oncology Physics
Radiometry
Radiotherapy Dosage
remnant tissue dosimetry
thyroid ablation treatment
Thyroid cancer
Thyroid Neoplasms - radiotherapy
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Summary:In this study, we aimed to evaluate dosimetric approaches in ablation treatment of Differentiated Thyroid Carcinoma (DTC) without interrupting the clinical routine. Prior to therapy, 10.7 MBq 131I in average was orally given to 24 patients suffering from DTC. MIRD formalism was used for dosimetric calculations. For blood and bone marrow dosimetry, blood samples and whole‐body counts were collected at 2, 24, 72, and 120 h after I‐131 administration. For remnant tissue dosimetry, uptake measurements were performed at the same time intervals. To estimate the remnant volume, anterior and lateral planar gamma camera images were acquired with a reference source within the field of view at 24 h after I‐131 administration. Ultrasound imaging was also performed. Treatment activities determined with the fixed activity method were administered to the patients. Secondary cancer risk relative to applied therapy was evaluated for dosimetric approaches. The average dose to blood and bone marrow were determined as 0.15 ± 0.04 and 0.11 ± 0.04 Gy/GBq, respectively. The average remnant tissue dose was 0.58 ± 0.52 Gy/MBq and the corresponding required activity to ablate the remnant was approximately 1.3 GBq of 131I. A strong correlation between 24th‐hour uptake and time‐integrated activity coefficient values was obtained. Compared to fixed activity method, approximately five times higher secondary cancer risk was determined in bone marrow dosimetry, while the risk was about three times lower in lesion‐based dosimetry.
ISSN:1526-9914
1526-9914
DOI:10.1002/acm2.12350