Radiation Protection Dosimetry Advance Access published online on May 27, 2007
Radiation Protection Dosimetry, doi:10.1093/rpd/ncm243
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QUANTITATIVE ANALYSIS OF THE FACTORS RESPONSIBLE FOR OVER OR UNDER DOSE OF 131I THERAPY PATIENTS OF HYPERTHYROIDISM
1 Institute of Nuclear Medicine Oncology and Radiotherapy (INOR), PO Box 110, Abbottabad, NWFP, Pakistan
2 Nuclear Medicine, Oncology and Radiotherapy Institute (NORI), Islamabad, Pakistan
3 Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
* Corresponding author: wazir90{at}hotmail.com
Received December 19, 2006, amended April 18, 2007, accepted April 18, 2007
Radioiodine (131I) therapy has been in use for more than 60 y. Several protocols have been suggested and used for prescribing the activity to be administered to the patients for the treatment of hyperthyroidism; application of these protocols may result in an under or over dose of the hyperthyroid patients. The main objective of this study was to carry out quantitative analysis of the factors responsible for possible under or over dosage of the patients. In this regard, a total of 59 patients [15 diffuse goitre (DG) and 44 nodular goitre (NG) cases] were studied. In order to compare the thyroid doses calculated by using different protocols, the dosimetric approach was followed. 131I uptakes were measured after 24 and 48 h, respectively, by giving 0.5 MBq of 131I to each patient. Thyroid mass and effective half-life were also calculated for each patient and the variations in the thyroid doses were analysed. According to the results 28 and 54% patients were under dosed and 72 and 46% patients were over dosed with DG and NG, respectively. The protocols, which have not taken into account the thyroid mass, multi pre-therapeutic 131I uptakes and the effective half-life of 131I of the individual patient, showed a higher degree of deviation from the required thyroid dose. Besides these parameters, some fundamental factors such as radiosensitivity, previous exposure to thyroid drugs and duration of the disease are recommended to be incorporated, which can certainly affect the clinical out comes.