Radiation safety measures in diagnostic nuclear medicine, based on the potential radiation dose emitted by radioactive patients.

Objective: To measure the potential radiation dose emitted by patients who have recently undergone diagnostic nuclear medicine procedures, in order to establish optimal radiation safety measures for such procedures. Materials and Methods: We evaluated the radiation doses emitted by 175 adult patients in whom technetium-99m, iodine-131, and fluorine-18 radionuclides were administered for bone, kidney, heart, brain, and whole-body scans, as measured with a radiation detector. Those values served as the basis for evaluating whole-body radiopharmaceutical clearance, as well as the risk for the exposure of others to radiation, depending on the time elapsed since administration of the radiopharmaceutical. Results: The mean time to clearance of the radiopharmaceuticals administered, expressed as the effective half-life, ranged from 1.18 ± 0.30 h to 11.41 ± 0.02 h, and the mean maximum cumulative radiation dose at 1.0 m from the patients was 149.74 ± 56.72 µSv. Even at a distance of 0.5 m, the cumulative dose was found to be only half and one tenth of the limits established for exposure of the general public and family members/caregivers (1.0 mSv and 5.0 mSv per episode, respectively). Conclusion: Cumulative radiation doses emitted by patients immediately after diagnostic nuclear medicine procedures are considerably lower than the limits established by the International Commission on Radiological Protection and the International Atomic Energy Agency, and precautionary measures to avoid radiation exposure are therefore not required after such procedures.

Objetivo: O objetivo deste trabalho foi levantar o potencial de dose de radiação emitida por pacientes em procedimentos diagnósticos, visando a estabelecer cuidados de radioproteção mais otimizados. Materiais e Métodos: Taxas de dose de radiação emitidas por 175 pacientes administrados com os radionuclídeos 99mTc, 131I e 18F para cintilografias óssea, renal, cardíaca, cerebral e corpo inteiro, foram mensuradas com um detector de radiação, servindo para avaliar o clareamento do radiofármaco no organismo e risco de exposição após administração dos radiofármacos. Resultados: O clareamento, representado pela meia-vida efetiva, variou de 1,18 ± 0,30 h até 11,41 ± 0,02 h e a dose de radiação máxima acumulada oferecida pelos pacientes a 1,0 m foi de 149,74 ± 56,72 µSv. Mesmo para distâncias de 0,5 m, as doses estimadas foram, respectivamente, duas e dez vezes inferiores ao nível de restrição para o público geral (1,0 mSv) e exposição médica (5,0 mSv/episódio). Conclusão: Doses de radiação oferecidas por pacientes em procedimentos diagnósticos são inferiores aos níveis de restrição recomendados pela International Commission on Radiological Protection e International Atomic Energy Agency, e assim, cuidados de radioproteção são geralmente desnecessários.

Radiation safety measures in diagnostic nuclear medicine, based on the potential radiation dose emitted by radioactive patients / Cuidados de radioproteção em medicina nuclear diagnóstica baseados no potencial de dose de radiação emitida por pacientes radioativos

Abstract Objective: To measure the potential radiation dose emitted by patients who have recently undergone diagnostic nuclear medicine procedures, in order to establish optimal radiation safety measures for such procedures. Materials and Methods: We evaluated the radiation doses emitted by 175 adult patients in whom technetium-99m, iodine-131, and fluorine-18 radionuclides were administered for bone, kidney, heart, brain, and whole-body scans, as measured with a radiation detector. Those values served as the basis for evaluating whole-body radiopharmaceutical clearance, as well as the risk for the exposure of others to radiation, depending on the time elapsed since administration of the radiopharmaceutical. Results: The mean time to clearance of the radiopharmaceuticals administered, expressed as the effective half-life, ranged from 1.18 ± 0.30 h to 11.41 ± 0.02 h, and the mean maximum cumulative radiation dose at 1.0 m from the patients was 149.74 ± 56.72 µSv. Even at a distance of 0.5 m, the cumulative dose was found to be only half and one tenth of the limits established for exposure of the general public and family members/caregivers (1.0 mSv and 5.0 mSv per episode, respectively). Conclusion: Cumulative radiation doses emitted by patients immediately after diagnostic nuclear medicine procedures are considerably lower than the limits established by the International Commission on Radiological Protection and the International Atomic Energy Agency, and precautionary measures to avoid radiation exposure are therefore not required after such procedures.

Resumo Objetivo: O objetivo deste trabalho foi levantar o potencial de dose de radiação emitida por pacientes em procedimentos diagnósticos, visando a estabelecer cuidados de radioproteção mais otimizados. Materiais e Métodos: Taxas de dose de radiação emitidas por 175 pacientes administrados com os radionuclídeos 99mTc, 131I e 18F para cintilografias óssea, renal, cardíaca, cerebral e corpo inteiro, foram mensuradas com um detector de radiação, servindo para avaliar o clareamento do radiofármaco no organismo e risco de exposição após administração dos radiofármacos. Resultados: O clareamento, representado pela meia-vida efetiva, variou de 1,18 ± 0,30 h até 11,41 ± 0,02 h e a dose de radiação máxima acumulada oferecida pelos pacientes a 1,0 m foi de 149,74 ± 56,72 µSv. Mesmo para distâncias de 0,5 m, as doses estimadas foram, respectivamente, duas e dez vezes inferiores ao nível de restrição para o público geral (1,0 mSv) e exposição médica (5,0 mSv/episódio). Conclusão: Doses de radiação oferecidas por pacientes em procedimentos diagnósticos são inferiores aos níveis de restrição recomendados pela International Commission on Radiological Protection e International Atomic Energy Agency, e assim, cuidados de radioproteção são geralmente desnecessários.

Comparison of 18F-NaF PET/CT with Other Imaging Methods in the Detection of Bone Metastases in Patients with Medullary Thyroid Cancer: a Report of a Series of 31 Cases.

PURPOSE: To compare the 18F-NaF PET/CT studies (18F-NaF) with other imaging methods in the detection of skeletal metastases (SM) in patients with medullary thyroid cancer (MTC). METHODS: We retrospectively analyzed 31 patients with MTC who performed 18F-NaF to assess SM. The results of the 18F-NaF were compared with other imaging methods performed for metastasis detection: 99Tc-MDP bone scan (BS), magnetic resonance imaging (MRI), contrast-enhanced CT (CT), and 68Ga-Dotatate and 18F-FDG PET/CT studies. A qualitative analysis comparing the 18F-NaF findings with the ones of the other methods was performed, and the results were classified as superior (>), equal (=), and inferior (<). RESULTS: Eleven patients had no bone metastases detected on any of the imaging methods used. Twenty patients presented SM depicted on 18F-NaF. Of these 20 patients, 12 performed bone scan (in 9 18F-NaF > BS and in 3 18F-NaF = BS), 1 performed 18F-FDG (18F-NaF > 18F-FDG), 4 performed 68Ga-Dotatate (in 2 18F-NaF > 68Ga-Dotatate and in 2 18F-NaF = 68Ga-Dotatate), 20 performed CT of at least one body segment (in 15 18F-NaF = CT and in 5 18F-NaF > CT), and 16 performed MRI of at least one body segment, and in all of them, the 18F-NaF was equal to the MRI. Beside this, the 18F-NaF detected SM in body segments not routinely scanned in MRI and CT. CONCLUSION: In patients with MTC, the 18F-NaF seems to be equal or superior to other imaging modalities in the detection of SM and allows the analysis of the whole skeletal in a single study.

Ultrasonography Echotexture as a surrogate for Sialadenitis secondary to 131I Radioiodine Therapy for differentiated Thyroid Cancer: a review and metaanalysis.

To systematically review and analyze the medical literature to assess ultrasonography echotexture changes in thyroid cancer patients for the detection of chronic sialadenitis caused by radioiodine therapy. METHODS: Sources were retrieved from PubMed, Scopus, EMBASE and LILACS through November 2018. All studies that assessed ultrasonographic features before 131I administration and at 12 months after 131I administration were selected. After data extraction, statistical analysis was performed by using Stata software. RESULTS: From a total of 435 studies, 4 studies involving 665 patients were considered eligible, and echotexture heterogeneity was found with a significant difference. CONCLUSIONS: Ultrasound echotexture may detect chronic sialadenitis secondary to salivary radioiodine therapy.

Evaluation of Parotid Salivary Gland Echo Texture by Ultrasound Examinations and Correlation With Whole-Body Scintigraphy After Radioiodine Therapy in Patients With Differentiated Thyroid Carcinoma.

OBJECTIVES: This study aimed to evaluate the echo texture of the parotid salivary glands before and after radioiodine therapy (RIT) using ultrasound (US) images in patients with differentiated thyroid cancer and to evaluate the correlations between post-RIT whole-body scintigraphy (WBS) images and US image patterns in salivary and cervical areas. METHODS: A retrospective study was performed with data on demographic and clinical information, US examinations, and WBS images collected through medical recordings. RESULTS: Comparing the US features before and after RIT, significant echo texture heterogeneity was found in 31.3% of all patients evaluated. When evaluated according to the level of iodine 131 (I-131) radioactivity (<5.6, 5.6-<9.3, and ≥9.3 GBq), echo texture heterogeneity was significantly associated with the 5.6-GBq I-131 radioactivity group (P < .001). No association was found for any level of I-131 post-RIT WBS uptake intensity and changes in US feature patterns. CONCLUSIONS: Ultrasound may be a useful tool for evaluating chronic sialadenitis after RIT, and the I-131 uptake intensity using a routine post-RIT WBS is not associated with US echo texture changes.

Ultrasonography Echotexture as a surrogate for Sialadenitis secondary to 131I Radioiodine Therapy for differentiated Thyroid Cancer: a review and metaanalysis

To systematically review and analyze the medical literature to assess ultrasonography echotexture changes in thyroid cancer patients for the detection of chronic sialadenitis caused by radioiodine therapy. Methods: Sources were retrieved from PubMed, Scopus, EMBASE and LILACS through November 2018. All studies that assessed ultrasonographic features before 131I administration and at 12 months after 131I administration were selected. After data extraction, statistical analysis was performed by using Stata software. Results: From a total of 435 studies, 4 studies involving 665 patients were considered eligible, and echotexture heterogeneity was found with a significant difference. Conclusions: Ultrasound echotexture may detect chronic sialadenitis secondary to salivary radioiodine therapy.

68Ga-DOTATATE PET: temporal variation of maximum standardized uptake value in normal tissues and neuroendocrine tumours.

OBJECTIVES: Higher affinity of Ga compounds to somatostatin receptors (SSTRs) and PET better image resolution increased interest in Ga-labelled somatostatin analogs in the management of neuroendocrine tumours (NETs). This study aimed to evaluate the maximum standardized uptake value (SUVmax) variation in sequential somatostatin analogs-PET in NET patients and identify optimal tumour detection and characterization imaging time. METHODS: Patients with histological or biochemical NET diagnosis performed two to three PET/computed tomography (CT) scans after intravenous injection of Ga-DOTATATE: Early PET [EarlyPET: <15 minutes postinjection (p.i.)], diagnostic PET (DiagPET: 45-90 minutes p.i.) and delayed PET (DelayPE: 90-240 minutes p.i.). Up to five tumour sites and normal tissues had SUVmax determined. Time-SUVmax curves were created for the target lesions and normal organs. Ratios between tumour and liver SUVmax (SUVTU/Liver) and tumour/blood pool (SUVTU/BP) were also calculated. RESULTS: Twenty-nine patients were included, 16 female, mean age of 46.5 ± 14.3 years. Average administered activity was 129.5 ± 29.6 MBq. Kidneys SUVmax was higher in EarlyPET compared with DiagPET (P = 0.04) and DelayPET showed higher SUVmax compared with DiagPET for normal liver, pancreas and kidneys (P = 0.02). No differences were noted between EarlyPET, DiagPET and DelayPET in tumour SUVmax (P > 0.05). SUVTU/Liver and SUVTU/BP did not change between EarlyPET and DiagPET, with a slight decrease in DelayPET. CONCLUSION: Stability in tumour SUVmax values measured at different intervals independently of tumour location, as also in normal tissues as kidneys and liver suggest that a more flexible imaging protocol may be adopted.

Pediatric 131I-MIBG Therapy for Neuroblastoma: Whole-Body 131I-MIBG Clearance, Radiation Doses to Patients, Family Caregivers, Medical Staff, and Radiation Safety Measures.

PURPOSE: I-metaiodobenzylguanidine (I-MIBG) has been used in the diagnosis and therapy of neuroblastoma in adult and pediatric patients for many years. In this study, we evaluated whole-body I-MIBG clearance and radiation doses received by patients, family caregivers, and medical staff to establish appropriate radiation safety measures to be used in therapy applications. METHODS: Research was focused on 23 children and adolescents with metastatic neuroblastoma, with ages ranging from 1.8 to 13 years, being treated with I-MIBG. Based on measured external dose rates from patients, dosimetric data to patients, family members, and others were calculated. RESULTS: The mean ± SD I-MIBG activity administered was 8.55 ± 1.69 GBq. Percent whole-body retention rates of I-MIBG at 24, 48, and 72 hours after administration were 48% ± 7%, 23% ± 7%, and 12% ± 6%, with a whole-body I-MIBG effective half-life of 23 ± 5 hours for all patients. The mean doses for patients were 0.234 ± 0.096 mGy·MBq to red-marrow and 0.251 ± 0.101 mGy·MBq to whole body. The maximum potential radiation doses transmitted by patients to others at 1.0 m was estimated to be 11.9 ± 3.4 mSv, with 97% of this dose occurring over 120 hours after therapy administration. Measured mean dose received by the 22 family caregivers was 1.88 ± 1.85 mSv, and that received by the 19 pediatric physicians was 43 ± 51 µSv. CONCLUSION: In this study, we evaluated the whole-body clearance of I-MIBG in 23 pediatric patients, and the radiation doses received by family caregivers and medical staff during these therapy procedures, thus facilitating the establishment of radiation safety measures to be applied in pediatric therapy.

Bone marrow uptake of 18F-fluorodeoxyglucose in Hodgkin lymphoma without bone involvement: comparison between patients with and without B symptoms.

OBJECTIVE: To compare the degree of benign bone marrow uptake of 18F-fluorodeoxyglucose (18F-FDG) between Hodgkin lymphoma patients with and without B symptoms. MATERIALS AND METHODS: We analyzed the medical charts of 74 Hodgkin lymphoma patients who underwent 18F-FDG positron emission tomography/computed tomography (PET/CT) prior to the initiation of therapy between October 2010 and September 2013. In all of the patients, the bone marrow biopsy was negative and the 18F-FDG PET/CT images did not suggest bone marrow involvement. Of the 74 patients evaluated, 54 presented inflammatory (B) symptoms and 20 did not. Regions of interest (ROIs) were drawn on the sternum, the proximal thirds of the humeri, the proximal thirds of the femora, and both iliac wings (totaling seven ROIs per patient). To compare the patients with and without B symptoms, in terms of standardized uptake values (SUVs) for the seven ROIs, we used the Mann-Whitney U test. RESULTS: For six of the ROIs, the SUVs were higher in the patients with B symptoms than in those without, and the difference was statistically significant (p < 0.05). There was also a tendency toward a statistically significant difference between the two groups in terms of the SUV for the right iliac wing ROI (p = 0.06). CONCLUSION: In our sample, the presence of B symptoms was associated with increased 18F-FDG uptake in bone marrow.

OBJETIVO: Comparar o grau de absorção benigna de 18F-fluordesoxiglicose (18F-FDG) na medula óssea de pacientes com linfoma de Hodgkin com e sem sintomas B. MATERIAIS E MÉTODOS: Analisamos os prontuários de 74 pacientes com linfoma de Hodgkin submetidos a tomografia por emissão de pósitrons/tomografia computadorizada (PET/CT) com 18F-FDG antes do início da terapia entre outubro de 2010 e setembro de 2013. Em todos os pacientes, a biópsia da medula óssea foi negativa e as imagens de 18F-FDG PET/CT não sugeriram envolvimento da medula óssea. Dos 74 pacientes avaliados, 54 apresentaram sintomas inflamatórios (B) e 20 não. As regiões de interesse (ROIs) foram desenhadas no esterno, nos terços proximais dos úmeros, nos terços proximais dos fêmures e nas duas asas ilíacas (totalizando sete ROIs por paciente). Para comparar os pacientes com e sem sintomas B, em termos dos standardized uptake values (SUVs) para as sete ROIs, utilizamos o teste U de Mann-Whitney. RESULTADOS: Para seis das ROIs, os SUVs foram maiores nos pacientes com sintomas B do que nos pacientes sem, e a diferença foi estatisticamente significante (p < 0,05). Houve também tendência para uma diferença estatisticamente significante entre os dois grupos em termos do SUV para a ROI da asa ilíaca direita (p = 0,06). CONCLUSÃO: Na nossa amostra, a presença de sintomas B foi associada ao aumento da captação de 18F-FDG na medula óssea.

Bone marrow uptake of 18F-fluorodeoxyglucose in Hodgkin lymphoma without bone involvement: comparison between patients with and without B symptoms / Captação de 18F fluordesoxiglicose na medula óssea em pacientes com linfoma de Hodgkin sem comprometimento ósseo: comparação entre pacientes com e sem sintomas B

Abstract Objective: To compare the degree of benign bone marrow uptake of 18F-fluorodeoxyglucose (18F-FDG) between Hodgkin lymphoma patients with and without B symptoms. Materials and Methods: We analyzed the medical charts of 74 Hodgkin lymphoma patients who underwent 18F-FDG positron emission tomography/computed tomography (PET/CT) prior to the initiation of therapy between October 2010 and September 2013. In all of the patients, the bone marrow biopsy was negative and the 18F-FDG PET/CT images did not suggest bone marrow involvement. Of the 74 patients evaluated, 54 presented inflammatory (B) symptoms and 20 did not. Regions of interest (ROIs) were drawn on the sternum, the proximal thirds of the humeri, the proximal thirds of the femora, and both iliac wings (totaling seven ROIs per patient). To compare the patients with and without B symptoms, in terms of standardized uptake values (SUVs) for the seven ROIs, we used the Mann-Whitney U test. Results: For six of the ROIs, the SUVs were higher in the patients with B symptoms than in those without, and the difference was statistically significant (p < 0.05). There was also a tendency toward a statistically significant difference between the two groups in terms of the SUV for the right iliac wing ROI (p = 0.06). Conclusion: In our sample, the presence of B symptoms was associated with increased 18F-FDG uptake in bone marrow.

Resumo Objetivo: Comparar o grau de absorção benigna de 18F-fluordesoxiglicose (18F-FDG) na medula óssea de pacientes com linfoma de Hodgkin com e sem sintomas B. Materiais e Métodos: Analisamos os prontuários de 74 pacientes com linfoma de Hodgkin submetidos a tomografia por emissão de pósitrons/tomografia computadorizada (PET/CT) com 18F-FDG antes do início da terapia entre outubro de 2010 e setembro de 2013. Em todos os pacientes, a biópsia da medula óssea foi negativa e as imagens de 18F-FDG PET/CT não sugeriram envolvimento da medula óssea. Dos 74 pacientes avaliados, 54 apresentaram sintomas inflamatórios (B) e 20 não. As regiões de interesse (ROIs) foram desenhadas no esterno, nos terços proximais dos úmeros, nos terços proximais dos fêmures e nas duas asas ilíacas (totalizando sete ROIs por paciente). Para comparar os pacientes com e sem sintomas B, em termos dos standardized uptake values (SUVs) para as sete ROIs, utilizamos o teste U de Mann-Whitney. Resultados: Para seis das ROIs, os SUVs foram maiores nos pacientes com sintomas B do que nos pacientes sem, e a diferença foi estatisticamente significante (p < 0,05). Houve também tendência para uma diferença estatisticamente significante entre os dois grupos em termos do SUV para a ROI da asa ilíaca direita (p = 0,06). Conclusão: Na nossa amostra, a presença de sintomas B foi associada ao aumento da captação de 18F-FDG na medula óssea.

Estimating (131)I biokinetics and radiation doses to the red marrow and whole body in thyroid cancer patients: probe detection versus image quantification.

OBJECTIVE: To compare the probe detection method with the image quantification method when estimating (131)I biokinetics and radiation doses to the red marrow and whole body in the treatment of thyroid cancer patients. MATERIALS AND METHODS: Fourteen patients with metastatic thyroid cancer, without metastatic bone involvement, were submitted to therapy planning in order to tailor the therapeutic amount of (131)I to each individual. Whole-body scans and probe measurements were performed at 4, 24, 48, 72, and 96 h after (131)I administration in order to estimate the effective half-life (Teff) and residence time of (131)I in the body. RESULTS: The mean values for Teff and residence time, respectively, were 19 ± 9 h and 28 ± 12 h for probe detection, compared with 20 ± 13 h and 29 ± 18 h for image quantification. The average dose to the red marrow and whole body, respectively, was 0.061 ± 0.041 mGy/MBq and 0.073 ± 0.040 mGy/MBq for probe detection, compared with 0.066 ± 0.055 mGy/MBq and 0.078 ± 0.056 mGy/MBq for image quantification. Statistical analysis proved that there were no significant differences between the two methods for estimating the Teff (p = 0.801), residence time (p = 0.801), dose to the red marrow (p = 0.708), and dose to the whole body (p = 0.811), even when we considered an optimized approach for calculating doses only at 4 h and 96 h after (131)I administration (p > 0.914). CONCLUSION: There is full agreement as to the feasibility of using probe detection and image quantification when estimating (131)I biokinetics and red-marrow/whole-body doses. However, because the probe detection method is inefficacious in identifying tumor sites and critical organs during radionuclide therapy and therefore liable to skew adjustment of the amount of (131)I to be administered to patients under such therapy, it should be used with caution.

OBJETIVO: Comparar o desempenho dos métodos de detecção de sonda e quantificação de imagens na estimativa da biocinética do radioisótopo 131I e das doses de radiação na medula óssea vermelha e no corpo inteiro durante a radioiodoterapia em pacientes com câncer de tireoide. MATERIAIS E MÉTODOS: Catorze pacientes portadores de câncer metastático de tireoide, sem acometimento ósseo, foram submetidos ao planejamento terapêutico visando estabelecer a melhor atividade de 131I a ser empregada na radioiodoterapia. Imagens cintilográficas e captações de corpo inteiro foram adquiridas 4, 24, 48, 72 e 96 h após a administração de atividades traçadoras de 131I, visando estimar a meia-vida efetiva (T1/2ef) e o tempo de residência do 131I no organismo dos pacientes. RESULTADOS: Os valores médios de T1/2ef e tempo de residência foram, respectivamente, 19 ± 9 h e 28 ± 12 h pelo método de detecção de sonda e 20 ± 13 h e 29 ± 18 h pela quantificação de imagens. As doses médias na medula óssea vermelha e no corpo inteiro foram, respectivamente, 0,061 ± 0,041 mGy/MBq e 0,073 ± 0,040 mGy/MBq pelo método de detecção de sonda e 0,066 ± 0,055 mGy/MBq e 0,078 ± 0,056 mGy/MBq pela quantificação de imagens. A análise estatística demonstrou que os dois métodos apresentam desempenho semelhante no tocante à estimativa de T1/2ef (p = 0,801), tempo de residência (p = 0,801) e doses, tanto na medula óssea vermelha (p = 0,708) como no corpo inteiro (p = 0,811), mesmo com métodos otimizados de dosimetria que levam em consideração somente dois pontos de medida (4 h e 96 h) após a administração de 131I (p > 0,914). CONCLUSÃO: Existe excelente concordância entre o método de detecção de sonda e a quantificação de imagens quanto à estimativa da biocinética do 131I e das doses absorvidas de radiação. Contudo, o método de detecção de sonda deve ser usado com cuidado por ser incapaz de identificar regiões metastáticas e órgãos críticos durante a terapia com radionuclídeos, podendo distorcer ajustes da atividade de 131I a ser administrada durante a radioiodoterapia.

Estimating 131I biokinetics and radiation doses to the red marrow and whole body in thyroid cancer patients: probe detection versus image quantification / Estimativa da biocinética do 131I e das doses de radiação na medula óssea vermelha e no corpo inteiro em pacientes com câncer de tireoide: comparação entre o método de detecção de sonda e a quantificação de imagens cintilográficas

Abstract Objective: To compare the probe detection method with the image quantification method when estimating 131I biokinetics and radiation doses to the red marrow and whole body in the treatment of thyroid cancer patients. Materials and Methods: Fourteen patients with metastatic thyroid cancer, without metastatic bone involvement, were submitted to therapy planning in order to tailor the therapeutic amount of 131I to each individual. Whole-body scans and probe measurements were performed at 4, 24, 48, 72, and 96 h after 131I administration in order to estimate the effective half-life (Teff) and residence time of 131I in the body. Results: The mean values for Teff and residence time, respectively, were 19 ± 9 h and 28 ± 12 h for probe detection, compared with 20 ± 13 h and 29 ± 18 h for image quantification. The average dose to the red marrow and whole body, respectively, was 0.061 ± 0.041 mGy/MBq and 0.073 ± 0.040 mGy/MBq for probe detection, compared with 0.066 ± 0.055 mGy/MBq and 0.078 ± 0.056 mGy/MBq for image quantification. Statistical analysis proved that there were no significant differences between the two methods for estimating the Teff (p = 0.801), residence time (p = 0.801), dose to the red marrow (p = 0.708), and dose to the whole body (p = 0.811), even when we considered an optimized approach for calculating doses only at 4 h and 96 h after 131I administration (p > 0.914). Conclusion: There is full agreement as to the feasibility of using probe detection and image quantification when estimating 131I biokinetics and red-marrow/whole-body doses. However, because the probe detection method is inefficacious in identifying tumor sites and critical organs during radionuclide therapy and therefore liable to skew adjustment of the amount of 131I to be administered to patients under such therapy, it should be used with caution.

Resumo Objetivo: Comparar o desempenho dos métodos de detecção de sonda e quantificação de imagens na estimativa da biocinética do radioisótopo 131I e das doses de radiação na medula óssea vermelha e no corpo inteiro durante a radioiodoterapia em pacientes com câncer de tireoide. Materiais e Métodos: Catorze pacientes portadores de câncer metastático de tireoide, sem acometimento ósseo, foram submetidos ao planejamento terapêutico visando estabelecer a melhor atividade de 131I a ser empregada na radioiodoterapia. Imagens cintilográficas e captações de corpo inteiro foram adquiridas 4, 24, 48, 72 e 96 h após a administração de atividades traçadoras de 131I, visando estimar a meia-vida efetiva (T1/2ef) e o tempo de residência do 131I no organismo dos pacientes. Resultados: Os valores médios de T1/2ef e tempo de residência foram, respectivamente, 19 ± 9 h e 28 ± 12 h pelo método de detecção de sonda e 20 ± 13 h e 29 ± 18 h pela quantificação de imagens. As doses médias na medula óssea vermelha e no corpo inteiro foram, respectivamente, 0,061 ± 0,041 mGy/MBq e 0,073 ± 0,040 mGy/MBq pelo método de detecção de sonda e 0,066 ± 0,055 mGy/MBq e 0,078 ± 0,056 mGy/MBq pela quantificação de imagens. A análise estatística demonstrou que os dois métodos apresentam desempenho semelhante no tocante à estimativa de T1/2ef (p = 0,801), tempo de residência (p = 0,801) e doses, tanto na medula óssea vermelha (p = 0,708) como no corpo inteiro (p = 0,811), mesmo com métodos otimizados de dosimetria que levam em consideração somente dois pontos de medida (4 h e 96 h) após a administração de 131I (p > 0,914). Conclusão: Existe excelente concordância entre o método de detecção de sonda e a quantificação de imagens quanto à estimativa da biocinética do 131I e das doses absorvidas de radiação. Contudo, o método de detecção de sonda deve ser usado com cuidado por ser incapaz de identificar regiões metastáticas e órgãos críticos durante a terapia com radionuclídeos, podendo distorcer ajustes da atividade de 131I a ser administrada durante a radioiodoterapia.

SPECT-CT-Guided Thoracoscopic Biopsy of Sentinel Lymph Nodes in the Internal Mammary Chain in Patients With Breast Cancer: A Pilot Study.

OBJECTIVE: The objective of this study was to determine the impact of the use of single-photon emission computed tomography fused with computed tomography (SPECT-CT) on thoracoscopic biopsy of sentinel lymph nodes (SLNs) in the internal mammary chain in patients with breast cancer by evaluating resultant changes in staging and their clinical implications. METHODS: Between September 2010 and January 2014, we performed lymphoscintigraphy-assisted thoracoscopic biopsy of the internal mammary chain SLN in 20 patients with breast cancer. Single-photon emission computed tomography fused with computed tomography was also used in 13 of these patients. The sentinel nodes were surgically identified with the aid of a gamma probe. RESULTS: Sentinel lymph nodes were identified surgically in 19 of 20 patients. In the 13 patients in whom SPECT-CT was used, it readily identified SLNs, especially when they were located over an intercostal space. Change of staging occurred in three patients (15%), two of whom accordingly received adjuvant radiotherapy to the internal thoracic chain. CONCLUSIONS: Compared with lymphoscintigraphy alone, the use of SPECT-CT improves localization of the SLN in the internal mammary chain, allowing more accurate planning of each individual's treatment.

Receiver operating characteristic (ROC) curve for classification of (18)F-NaF uptake on PET/CT.

OBJECTIVE: To assess the cutoff values established by ROC curves to classify (18)F-NaF uptake as normal or malignant. MATERIALS AND METHODS: PET/CT images were acquired 1 hour after administration of 185 MBq of (18)F-NaF. Volumes of interest (VOIs) were drawn on three regions of the skeleton as follows: proximal right humerus diaphysis (HD), proximal right femoral diaphysis (FD) and first vertebral body (VB1), in a total of 254 patients, totalling 762 VOIs. The uptake in the VOIs was classified as normal or malignant on the basis of the radiopharmaceutical distribution pattern and of the CT images. A total of 675 volumes were classified as normal and 52 were classified as malignant. Thirty-five VOIs classified as indeterminate or nonmalignant lesions were excluded from analysis. The standardized uptake value (SUV) measured on the VOIs were plotted on an ROC curve for each one of the three regions. The area under the ROC (AUC) as well as the best cutoff SUVs to classify the VOIs were calculated. The best cutoff values were established as the ones with higher result of the sum of sensitivity and specificity. RESULTS: The AUCs were 0.933, 0.889 and 0.975 for UD, FD and VB1, respectively. The best SUV cutoffs were 9.0 (sensitivity: 73%; specificity: 99%), 8.4 (sensitivity: 79%; specificity: 94%) and 21.0 (sensitivity: 93%; specificity: 95%) for UD, FD and VB1, respectively. CONCLUSION: The best cutoff value varies according to bone region of analysis and it is not possible to establish one value for the whole body.

Receiver operating characteristic (ROC) curve for classification of18F-NaF uptake on PET/CT / Curva de característica de operação do receptor (ROC) para classificação da captação de 18F-NaF em PET/CT

Abstract Objective: To assess the cutoff values established by ROC curves to classify18F-NaF uptake as normal or malignant. Materials and Methods: PET/CT images were acquired 1 hour after administration of 185 MBq of18F-NaF. Volumes of interest (VOIs) were drawn on three regions of the skeleton as follows: proximal right humerus diaphysis (HD), proximal right femoral diaphysis (FD) and first vertebral body (VB1), in a total of 254 patients, totalling 762 VOIs. The uptake in the VOIs was classified as normal or malignant on the basis of the radiopharmaceutical distribution pattern and of the CT images. A total of 675 volumes were classified as normal and 52 were classified as malignant. Thirty-five VOIs classified as indeterminate or nonmalignant lesions were excluded from analysis. The standardized uptake value (SUV) measured on the VOIs were plotted on an ROC curve for each one of the three regions. The area under the ROC (AUC) as well as the best cutoff SUVs to classify the VOIs were calculated. The best cutoff values were established as the ones with higher result of the sum of sensitivity and specificity. Results: The AUCs were 0.933, 0.889 and 0.975 for UD, FD and VB1, respectively. The best SUV cutoffs were 9.0 (sensitivity: 73%; specificity: 99%), 8.4 (sensitivity: 79%; specificity: 94%) and 21.0 (sensitivity: 93%; specificity: 95%) for UD, FD and VB1, respectively. Conclusion: The best cutoff value varies according to bone region of analysis and it is not possible to establish one value for the whole body.

Resumo Objetivo: Acessar valores de corte estabelecidos pela curva ROC para classificar a captação de 18F-NaF como normal ou maligna. Materiais e Métodos: Imagens de PET/CT foram realizadas 1 hora após a administração de 185 MBq de18F-NaF e volumes de interesse (VOIs) foram desenhados em três regiões do esqueleto: diáfise umeral proximal direita (UD), diáfise femoral proximal direita (FD) e corpo da primeira vértebra lombar (VB1), em 254 pacientes, totalizando 762 VOIs. A captação nos VOIs foi classificada como normal ou maligna baseada no padrão de distribuição do radiofármaco e nas imagens de CT. Um total de 675 volumes foi classificado como normais e 52 como malignos. Trinta e cinco VOIs classificados como indeterminados ou lesões não malignas foram excluídos da análise. Os valores de captação (SUVs) medidos nos VOIs foram plotados em uma curva ROC para cada uma das três regiões. Foi calculada a área sob a curva (AUC), bem como os valores de SUV mais adequados para a classificação dos VOIs (maior resultado da soma da sensibilidade e especificidade). Resultados: As AUCs foram 0,933, 0,889 e 0,975 para UD, FD e VB1, respectivamente. Os valores de corte mais adequados de SUV foram 9,0 (sensibilidade: 73%; especificidade: 99%), 8,4 (sensibilidade: 79%; especificidade: 94%) e 21,0 (sensibilidade: 93%; especificidade: 95%)para UD, FD e VB1, respectivamente. Conclusão: O valor de corte de SUV mais adequado varia de acordo com a região óssea em análise e não é possível estabelecer um valor adequado para todo o esqueleto.

Effects of Thyroid Hormone Withdrawal and Recombinant Human Thyrotropin on Glomerular Filtration Rate During Radioiodine Therapy for Well-Differentiated Thyroid Cancer.

BACKGROUND: Renal function is related to thyroid hormonal status, and glomerular filtration rate (GFR) seems to be impaired in patients with hypothyroidism. The aim of this work was to evaluate quantitatively the effect of hypothyroidism on GFR using a (51)Cr-EDTA radioisotope assay. METHODS: Twenty-eight patients without known renal disease or dysfunction who had been referred for radioiodine therapy (RIT) after total thyroidectomy were enrolled in this study and divided into two groups. Group A underwent thyroid hormone withdrawal (THW) resulting in hypothyroidism, while group B underwent recombinant human thyrotropin (rhTSH) stimulation and hence remained euthyroid. GFR was assessed by (51)Cr-EDTA before and after THW or rhTSH. RESULTS: No clinical differences were observed between the two groups. The mean ± SD GFRs were 94 ± 19 mL/min/1.73 m(2) before THW and 76 ± 16 mL/min/1.73 m(2) after THW for group A (p = 0.009), and 91 ± 18 mL/min/1.73 m(2) before rhTSH and 93 ± 15 mL/min/1.73 m(2) after rhTSH for group B (p = 0.613). The percent decrease in GFR during hypothyroidism is approximately 18-22%. CONCLUSION: GFR decreases in patients with normal kidney function during THW for RIT, and rhTSH preserves GFR in these patients. This GFR impairment following thyroidectomy is related to hypothyroidism due to a significant reduction in thyroid hormone levels and is not due to a rise in the TSH level.

Dose Calibrator Linearity Testing: Radioisotope (99m)Tc or (18)F? An Alternative for Reducing Costs in Nuclear Medicine Quality Control.

Dose calibrator linearity testing is indispensable for evaluating the capacity of this equipment in measuring radioisotope activities at different magnitudes, a fundamental aspect of the daily routine of a nuclear medicine department, and with an impact on patient exposure. The main aims of this study were to evaluate the feasibility of substituting the radioisotope Fluorine-18 ((18)F) with Technetium-99m ((99m)Tc) in this test, and to indicate it with the lowest operational cost. The test was applied with sources of (99m)Tc (62 GBq) and (18)F (12 GBq), the activities of which were measured at different times, with the equipment preadjusted to measuring sources of (99m)Tc, (18)F, Gallium-67 ((67)Ga), and Iodine-131 ((131)I). Over time, the average deviation between measured and expected activities from (99m)Tc and (18)F were, respectively, 0.56 (±1.79)% and 0.92 (±1.19)%. The average ratios for 99(m)Tc source experimental activity, when measured with the equipment adjusted for measuring (18)F, (67)Ga, and (131)I sources, in real values, were, respectively, 3.42 (±0.06), 1.45 (±0.03), and 1.13 (±0.02), and those for the (18)F source experimental activity, measured through adjustments of (99m)Tc, (67)Ga, and (131)I, were, respectively, 0.295 (±0.004), 0.335 (±0.007), and 0.426 (±0.006). The adjustment of a simple exponential function for describing (99m)Tc and (18)F experimental activities facilitated the calculation of the physical half-lives of the radioisotopes, with a difference of about 1% in relation to the values described in the literature. Linearity test results, when using (99m)Tc, through being compatible with those acquired with (18)F, imply the possibility of using both radioisotopes during linearity testing. Nevertheless, this information, along with the high potential of exposure and the high cost of (18)F, implies that (99m)Tc should preferably be employed for linearity testing in clinics that normally use (18)F, without the risk of prejudicing either the procedure itself or the guarantee of a high-quality nuclear medicine service.

Clinical and Dosimetric Variables Related to Outcome After Treatment of Graves' Disease With 550 and 1110 MBq of 131I: Results of a Prospective Randomized Trial.

UNLABELLED: : Therapy of Graves' hyperthyroidism (HTG) with I is still mostly performed on an empirical basis. The present study was carried out to evaluate clinical and dosimetric variables associated with outcome in HTG therapy, which could contribute to planning and defining the most appropriate activity to be administered. METHODS: Patients with HTG were randomly assigned to therapy with 555 MBq (15mci) or 1110 MBq (30 mCi) of I. Estimation of thyroid radiation absorbed dose was made according to MIRD methodology. Success was defined as clinical/laboratory euthyroidism or hypothyroidism one year after therapy. The association between clinical, laboratory, and dosimetric variables with 1-year outcome was measured using bivariate analysis, followed by logistic regression. RESULTS: Ninety-one patients included completed the follow-up. Therapeutic success was observed in 77 (84.6%) of them, in a greater proportion when 1110 MBq of I was administered as compared with 550 MBq (94.8% vs 77.4%, P = 0.02). Besides administered activity, multivariate analysis indicated that outcome was related to patient age and gland mass. A higher therapeutic success rate was achieved with doses greater than 300 Gy as compared with doses less than 300 Gy (89% vs 60%, P = 0.01). CONCLUSION: Administered activity, age, and gland mass were related to the outcome. Radiation absorbed dose, although not significant according to multivariate analysis, may be used as a quantitative parameter in therapy planning, with a target dose of 300 Gy. In cases where a rapid and efficient response to radioiodine treatment is required, adoption of a simplified protocol employing high activities is justified.

Comparison of standardized uptake values measured on F-NaF PET/CT scans using three different tube current intensities.

OBJECTIVE: To analyze standardized uptake values (SUVs) using three different tube current intensities for attenuation correction on (18)FNaF PET/CT scans. MATERIALS AND METHODS: A total of 254 (18)F-NaF PET/CT studies were analyzed using 10, 20 and 30 mAs. The SUVs were calculated in volumes of interest (VOIs) drawn on three skeletal regions, namely, right proximal humeral diaphysis (RH), right proximal femoral diaphysis (RF), and first lumbar vertebra (LV1) in a total of 712 VOIs. The analyses covered 675 regions classified as normal (236 RH, 232 RF, and 207 LV1). RESULTS: Mean SUV for each skeletal region was 3.8, 5.4 and 14.4 for RH, RF, and LV1, respectively. As the studies were grouped according to mAs value, the mean SUV values were 3.8, 3.9 and 3.7 for 10, 20 and 30 mAs, respectively, in the RH region; 5.4, 5.5 and 5.4 for 10, 20 and 30 mAs, respectively, in the RF region; 13.8, 14.9 and 14.5 for 10, 20 and 30 mAs, respectively, in the LV1 region. CONCLUSION: The three tube current values yielded similar results for SUV calculation.

OBJETIVO: Analisar os valores de captação (SUVs) utilizando três diferentes intensidades de mAs para realização de correção de atenuação na 18F-NaF PET/CT. MATERIAIS E MÉTODOS: Um total de 254 exames de 18F-NaF PET/CT foi estudado utilizando 10, 20 e 30 mAs. Os SUVs foram calculados utilizando volumes de interesse (VOIs) desenhados em três regiões do esqueleto: diáfise proximal do úmero direito (UD), diáfise proximal do fêmur direito (FD) e primeira vértebra lombar (VB1), totalizando 712 VOIs. Desse total, 675 regiões classificadas como normal foram analisadas (236, 232 e 207 na UD, FD e VB1, respectivamente). RESULTADOS: A média dos SUVs para cada região óssea foi 3,8, 5,4 e 14,4 para UD, FD e VB1, respectivamente. Quando os exames foram agrupados pelo valor da corrente mAs, a média de valores de captação foi 3,8, 3,9 e 3,7 para 10, 20 e 30 mAs, respectivamente, na UD; 5,4, 5,5 e 5,4 para 10, 20 e 30 mAs, respectivamente, na FD; e 13,8, 14,9 e 14,5 para 10, 20 e 30 mAs, respectivamente, na VB1. CONCLUSÃO: As três correntes analizadas apresentaram resultados similares para o cálculo de SUV.

Dose calibrator linearity test: (99m)Tc versus (18)F radioisotopes.

OBJECTIVE: The present study was aimed at evaluating the viability of replacing (18)F with (99m)Tc in dose calibrator linearity testing. MATERIALS AND METHODS: The test was performed with sources of (99m)Tc (62 GBq) and (18)F (12 GBq) whose activities were measured up to values lower than 1 MBq. Ratios and deviations between experimental and theoretical (99m)Tc and (18)F sources activities were calculated and subsequently compared. RESULTS: Mean deviations between experimental and theoretical (99m)Tc and (18)F sources activities were 0.56 (± 1.79)% and 0.92 (± 1.19)%, respectively. The mean ratio between activities indicated by the device for the (99m)Tc source as measured with the equipment pre-calibrated to measure (99m)Tc and (18)F was 3.42 (± 0.06), and for the (18)F source this ratio was 3.39 (± 0.05), values considered constant over the measurement time. CONCLUSION: The results of the linearity test using (99m)Tc were compatible with those obtained with the (18)F source, indicating the viability of utilizing both radioisotopes in dose calibrator linearity testing. Such information in association with the high potential of radiation exposure and costs involved in (18)F acquisition suggest (99m)Tc as the element of choice to perform dose calibrator linearity tests in centers that use (18)F, without any detriment to the procedure as well as to the quality of the nuclear medicine service.

OBJETIVO: Avaliar a viabilidade de substituir o radioisótopo 18F pelo 99mTc no teste de linearidade em medidores de atividade. MATERIAIS E MÉTODOS: O teste foi realizado empregando-se fontes de 99mTc (62 GBq) e 18F (12 GBq), cujas atividades foram mensuradas até valores abaixo de 1 MBq. As razões e desvios entre as atividades experimentais e teóricas foram calculados e comparados. RESULTADOS: Os desvios médios entre as atividades experimentais e teóricas para o 99mTc e 18F foram, respectivamente, 0,56 (± 1,79)% e 0,92 (± 1,19)%. A razão média entre as atividades indicadas pelo equipamento para a fonte de 99mTc quando mensurada no equipamento pré-ajustado para medir o 99mTc e 18F foi 3,42 (± 0,06), e para o 18F este valor foi 3,39 (± 0,05), razões consideradas constantes ao longo de todo o período de medida. CONCLUSÃO: Os resultados do teste utilizando o 99mTc são compatíveis com os adquiridos com o 18F, implicando na possibilidade de utilização de ambos os radioisótopos na realização do teste de linearidade. Esta informação, aliada ao elevado potencial de exposição e custos de aquisição do 18F, sugere que o 99mTc seja empregado na realização do teste de linearidade para clínicas que utilizam 18F, sem prejuízo para o procedimento e garantia da qualidade de um serviço de medicina nuclear.