JOSE WILLEGAIGNON DE AMORIM DE CARVALHO
Projetos de Pesquisa
Unidades Organizacionais
LIM/43 - Laboratório de Medicina Nuclear, Hospital das Clínicas, Faculdade de Medicina
2 resultados
Resultados de Busca
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- Graves' disease radioiodine-therapy: Choosing target absorbed doses for therapy planning(2014) WILLEGAIGNON, J.; SAPIENZA, M. T.; COURA-FILHO, G. B.; WATANABE, T.; TRAINO, A. C.; BUCHPIGUEL, C. A.Purpose: The precise determination of organ mass (m(th)) and total number of disintegrations within the thyroid gland ((A) over tilde) are essential for thyroid absorbed-dose calculations for radioiodine therapy. Nevertheless, these parameters may vary according to the method employed for their estimation, thus introducing uncertainty in the estimated thyroid absorbed dose and in any dose-response relationship derived using such estimates. In consideration of these points, thyroid absorbed doses for Graves' disease (GD) treatment planning were calculated using different approaches to estimating the m(th) and the (A) over tilde. Methods: Fifty patients were included in the study. Thyroid I-131 uptake measurements were performed at 2, 6, 24, 48, 96, and 220 h postadministration of a tracer activity in order to estimate the effective half-time (T-eff) of I-131 in the thyroid; the thyroid cumulated activity was then estimated using the Teff thus determined or, alternatively, calculated by numeric integration of the measured time-activity data. Thyroid mass was estimated by ultrasonography (USG) and scintigraphy (SCTG). Absorbed doses were calculated with the OLINDA/EXM software. The relationships between thyroid absorbed dose and therapy response were evaluated at 3 months and 1 year after therapy. Results: The average ratio (+/- 1 standard deviation) between m(th) estimated by SCTG and USG was 1.74 (+/- 0.64) and that between (A) over tilde obtained by Teff and the integration of measured activity in the gland was 1.71 (+/- 0.14). These differences affect the calculated absorbed dose. Overall, therapeutic success, corresponding to induction of durable hypothyroidism or euthyroidism, was achieved in 72% of all patients at 3 months and in 90% at 1 year. A therapeutic success rate of at least 95% was found in the group of patients receiving doses of 200 Gy (p = 0.0483) and 330 Gy (p = 0.0131) when m(th) was measured by either USG or SCTG and (A) over tilde was determined by the integration of measured I-131 activity in the thyroid gland and based on T-eff, respectively. No statistically significant relationship was found between therapeutic response and patients' age, administered I-131 activity (MBq), 24-h thyroid I-131 uptake (%) or T-eff (p >= 0.064); nonetheless, a good relationship was found between the therapeutic response and mth (p >= 0.035). Conclusions: According to the results of this study, the most effective thyroid absorbed dose to be targeted in GD therapy should not be based on a fixed dose but rather should be individualized based on the patient's m(th) and (A) over tilde. To achieve a therapeutic success (i.e., durable euthyroidism or hypothyroidism) rate of at least 95%, a thyroid absorbed dose of 200 or 330 Gy is required depending on the methodology used for estimating m(th) and (A) over tilde. (C) 2014 American Association of Physicists in Medicine.
- Determining thyroid I-131 effective half-life for the treatment planning of Graves' disease(2013) WILLEGAIGNON, Jose; SAPIENZA, Marcelo T.; COURA FILHO, George Barberio; TRAINO, Antonio C.; BUCHPIGUEL, Carlos A.Purpose: Thyroid I-131 effective half-life (T-eff) is an essential parameter in patient therapy when accurate radiation dose is desirable for producing an intended therapeutic outcome. Multiple I-131 uptake measurements and resources from patients themselves and from nuclear medicine facilities are requisites for determining T-eff, these being limiting factors when implementing the treatment planning of Graves' disease (GD) in radionuclide therapy. With the aim of optimizing this process, this study presents a practical, propitious, and accurate method of determining T-eff for dosimetric purposes. Methods: A total of 50 patients with GD were included in this prospective study. Thyroidal I-131 uptake was measured at 2-h, 6-h, 24-h, 48-h, 96-h, and 220-h postradioiodine administration. T-eff was calculated by considering sets of two measured points (24-48-h, 24-96-h, and 24-220-h), sets of three (24-48-96-h, 24-48-220-h, and 24-96-220-h), and sets of four (24-48-96-220-h). Results: When considering all the measured points, the representative T-eff for all the patients was 6.95 (+/- 0.81) days, whereas when using such sets of points as (24-220-h), (24-96-220-h), and (24-48-220-h), this was 6.85 (+/- 0.81), 6.90 (+/- 0.81), and 6.95 (+/- 0.81) days, respectively. According to the mean deviations 2.2 (+/- 2.4)%, 2.1 (+/- 2.0)%, and 0.04 (+/- 0.09)% found in T-eff, calculated based on all the measured points in time, and with methods using the (24-220-h), (24-48-220-h), and (24-96-220-h) sets, respectively, no meaningful statistical difference was noted among the three methods (p > 0.500, t test). Conclusions: T-eff obtained from only two thyroid I-131 uptakes measured at 24-h and 220-h, besides proving to be sufficient, accurate enough, and easily applicable, attributes additional major cost-benefits for patients, and facilitates the application of the method for dosimetric purposes in the treatment planning of Graves' disease. (c) 2013 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4788660]