JOSE WILLEGAIGNON DE AMORIM DE CARVALHO
Projetos de Pesquisa
Unidades Organizacionais
LIM/43 - Laboratório de Medicina Nuclear, Hospital das Clínicas, Faculdade de Medicina
5 resultados
Resultados de Busca
Agora exibindo 1 - 5 de 5
- Comparison of different dosimetric methods for red marrow absorbed dose calculation in thyroid cancer therapy(2012) WILLEGAIGNON, Jose; SAPIENZA, Marcelo T.; BUCHPIGUEL, Carlos A.Several dosimetric methods have been proposed for estimating red marrow absorbed dose (RMAD) when radionuclide therapy is planned for differentiated thyroid cancer, although to date, there is no consensus as to whether dose calculation should be based on blood-activity concentration or not. Our purpose was to compare RMADs derived from methods that require collecting patients' blood samples versus those involving OLINDA/EXM software, thereby precluding this invasive procedure. This is a retrospective study that included 34 patients under treatment for metastatic thyroid disease. A deviation of 10 between RMADs was found, when comparing the doses from the most usual invasive dosimetric methods and those from OLINDA/EXM. No statistical difference between the methods was discovered, whereby the need for invasive procedures when calculating the dose is questioned. The use of OLINDA/EXM in clinical routine could possibly diminish data collection, thus giving rise to a simultaneous reduction in time and clinical costs, besides avoiding any kind of discomfort on the part of the patients involved.
- Influence on voxel-based dosimetry: noise effect on absorbed dose dosimetry at single time-point versus sequential single-photon emission computed tomography(2023) FONDA, Uysha de S.; LEITAO, Andre L. A.; PAIVA, Marcia M. D. P.; WILLEGAIGNON, Jose; JOSEFSSON, Anders; BUCHPIGUEL, Carlos A.; SAPIENZA, Marcelo T.ObjectiveThe purpose of this study was to evaluate how statistical fluctuation in single-photon emission computed tomography (SPECT) images propagate to absorbed dose maps. MethodsSPECT/computed tomography (CT) images of iodine-131 filled phantoms, using different acquisition and processing protocols, were evaluated using STRATOS software to assess the absorbed dose distribution at the voxel level. Absorbed dose values and coefficient of variation (COV) were analyzed for dosimetry based on single time-point SPECT images and time-integrated activities of SPECT sequences with low and high counts. ResultsConsidering dosimetry based on a single time-point, the mean absorbed dose was not significantly affected by total counts or reconstruction parameters, but the uniformity of the absorbed dose maps had an almost linear correlation with SPECT noise. When high- and low-count SPECT sequences were used to generate an absorbed dose map, the absorbed dose COV for each of the temporal sequences was slightly lower than the absorbed dose COV based on the single SPECT image with the highest count included in the sequence. ConclusionThe impact of changes in SPECT counts and reconstruction parameters is almost linear when dosimetry is based on isolated SPECT images, but less pronounced when dosimetry is based on sequential SPECTs.
- 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]
- Prediction of iodine-131 biokinetics and radiation doses from therapy on the basis of tracer studies: an important question for therapy planning in nuclear medicine(2016) WILLEGAIGNON, Jose; PELISSONI, Rogerio A.; LIMA, Beatriz C. G. D.; SAPIENZA, Marcelo T.; COURA-FILHO, George B.; BUCHPIGUEL, Carlos A.ObjectivesThis study aimed to present a comparison of iodine-131 (I-131) biokinetics and radiation doses to red-marrow (rm) and whole-body (wb), following the administration of tracer and therapeutic activities, as a means of confirming whether I-131 clearance and radiation doses for therapy procedures can be predicted by tracer activities.MethodsEleven differentiated thyroid cancer patients were followed after receiving tracer and therapeutic I-131 activity. Whole-body I-131 clearance was estimated using radiation detectors and OLINDA/EXM software was used to calculate radiation doses to rm and wb.Results and discussionTracer I-131 activity of 86 (14)MBq and therapeutic activity of 8.04 (+/- 1.18)GBq were administered to patients, thereby producing an average wb I-131 effective half-time and residence time of, respectively, 13.51 (+/- 4.05) and 23.13 (+/- 5.98)h for tracer activities and 13.32 (+/- 3.38) and 19.63 (+/- 4.77)h for therapy. Radiation doses to rm and wb were, respectively, 0.0467 (+/- 0.0208) and 0.0589 (+/- 0.0207)mGy/MBq in tracer studies and 0.0396 (+/- 0.0169) and 0.0500 (+/- 0.0163)mGy/MBq in therapy. Although the differences were not considered statistically significant between averages, those between the values of effective half-times (P=0.906), residence times (P=0.145), and radiation doses to rm (P=0.393) and to wb (P=0.272), from tracer and therapy procedures, large differences of up to 80% in wb I-131 clearance, and up to 50% in radiation doses were observed when patients were analyzed individually, thus impacting on the total amount of I-131 activity calculated to be safe for application in individual therapy.Conclusion(131)I biokinetics and radiation doses to rm and wb in therapy procedures are well predicted by diagnostic activities when average values of a group of patients are compared. Nonetheless, when patients are analyzed individually, significant differences may be encountered, thus implying that nuclear medicine therapy-planning requires due consideration of changes in individual patient-body status from initial tracer to final therapy procedures to thus provide appropriate adjustments in therapeutic activities.
- Diagnostic reference level: an important tool for reducing radiation doses in adult and pediatric nuclear medicine procedures in Brazil(2016) WILLEGAIGNON, Jose; BRAGA, Luis F. E. F.; SAPIENZA, Marcelo T.; COURA-FILHO, George B.; CARDONA, Marissa A. R.; ALVES, Carlos E. R.; GUTTERRES, Ricardo F.; BUCHPIGUEL, Carlos A.ObjectivesThis study aimed to establish a concise method for determining a diagnostic reference level (DRL) for adult and pediatric nuclear medicine patients on the basis of diagnostic procedures and administered radioisotope as a means of controlling medical exposure.MethodsA screening was carried out in all Brazilian Nuclear Medicine Service (NMS) establishments to support this study by collecting the average activities administered during adult diagnostic procedures and the rules applied to adjust these according to the patient's age and body mass. Percentile 75 was used in all the activities administered as a means of establishing DRL for adult patients, with additional correction factors for pediatric patients. Radiation doses from nuclear medicine procedures on the basis of average administered activity were calculated for all diagnostic exams.Results and DiscussionA total of 107 NMSs in Brazil agreed to participate in the project. From the 64 nuclear medicine procedures studied, bone, kidney, and parathyroid scans were found to be used in more than 85% of all the NMSs analyzed. There was a large disparity among the activities administered, when applying the same procedures, this reaching, in some cases, more than 20 times between the lowest and the highest. Diagnostic exams based on Ga-67, Tl-201, and I-131 radioisotopes proved to be the major exams administering radiation doses to patients. On introducing the DRL concept into clinical routine, the minimum reduction in radiation doses received by patients was about 15%, the maximum was 95%, and the average was 50% compared with the previously reported administered activities.ConclusionVariability in the available diagnostic procedures as well as in the amount of activities administered within the same procedure was appreciable not only in Brazil, but worldwide. Global efforts are needed to establish a concise DRL that can be applied in adult and pediatric nuclear medicine procedures as the application of DRL in clinical routine has been proven to be an important tool for controlling and reducing radiation doses received by patients in medical exposure.