Author/Authors :
Yavari, S Department of Nuclear Medicine - Vali-Asr Hospital - Tehran University of Medical Sciences, Tehran, Iran - Department of Technology of Radiology and Radiotherapy - Allied Medical Sciences School - Tehran University of Medical Sciences, Tehran, Iran , Geramifar, P Research Center for Nuclear Medicine - Shariati Hospital - Tehran University of Medical Sciences, Tehran, Iran , Fallahpoor, M Department of Nuclear Medicine - Vali-Asr Hospital - Tehran University of Medical Sciences, Tehran, Iran , Changizi, V Department of Technology of Radiology and Radiotherapy - Allied Medical Sciences School - Tehran University of Medical Sciences, Tehran, Iran , Gholami, M Department of Pharmacology and Toxicology - Faculty of Pharmacy - Pharmaceutical Sciences Research Center - Tehran University of Medical Sciences, Tehran, Iran , Meysamie, A Department of Community and Preventive Medicine - Faculty of Medicine - Tehran University of Medical Sciences, Tehran, Iran , Farzanehfar, S Department of Nuclear Medicine - Vali-Asr Hospital - Tehran University of Medical Sciences, Tehran, Iran , Abbasi, M Department of Nuclear Medicine - Vali-Asr Hospital - Tehran University of Medical Sciences, Tehran, Iran
Abstract :
Background: Pretreatment with lithium in thyroid cancer patients before radioiodine therapy (RIT) has been suggested to improve the results of therapy in terms of higher radiation to thyroid tissue and limiting extrathyroid irradiation. Materials and Methods: The beta and gamma radiation to
the thyroid gland and lungs in 8 female New Zealand rabbits weighing 2.7 to
3.6 kg were simulated employing GATE Monte Carlo code. The study design
was before-after and crossover; rabbits were orally treated with 165 to 288
μCi 131I with or without pretreatment with 60 mg per day lithium. SPECT/CT
imaging was done 20 to 24 hours after RIT providing the distribution and
attenuation maps for simulation. The S-values were calculated and compared
between the rabbits prepared with and without lithium before RIT by analysis
of covariance. Results: For beta radiation, the thyroid to lung S-value ratios
(TLR) was 10.5 ± 1.6 with lithium pretreatment and 15.9 ± 12.5 without it. For
gamma rays, TLR was 4.8 ± 1.8 vs. 6.7 ± 3.1 in rabbits with and without lithium
pretreatment. The values of TLR were higher without lithium pretreatment
but statistically insignificant. Conclusion: Lithium demonstrated no
improvement in radioiodine uptake in thyroid tissue. Pretreatment of
differentiated thyroid cancer patients with lithium before RIT, which is backed by old literature, should be reconsidered.
Keywords :
Monte Carlo simulation , lithium , 131I , specific dosimetry
