Correlation of 18F-sodium fluoride uptake and radiodensity in extraosseous metastases of medullary thyroid carcinoma

ABSTRACT Objective: Although 18F-sodium fluoride (18F-NaF) uptake is frequently observed in extraosseous metastases of medullary thyroid carcinoma (MTC) with calcification, it can also occur in metastatic sites without visible calcium deposition, leading to the hypothesis that visually undetectable calcium accumulation may be responsible for this uptake. The aim of this study was to indirectly support this hypothesis by analyzing the correlation between the degree of 18F-NaF uptake and radiodensity in extraosseous MTC metastases, since calcium deposition can increase attenuation even when not visually detectable. Subjects and methods: Extraosseous metastatic lesions of 15 patients with MTC were evaluated using 18F-NaF positron-emission tomography (PET)/computed tomography (CT) and segmented by levels of standardized uptake value (SUV). The correlation between mean SUV and mean Hounsfield unit (HU) values was assessed for the entire group of segments and for two subgroups with different mean HU values. Results: Very high correlations were observed between mean SUV and mean HU values for both the entire group of segments and the subgroup with a mean HU value greater than 130 (p = 0.92 and p = 0.95, respectively; p < 0.01). High correlation (p = 0.71) was also observed in the subgroup with mean HU values ranging from 20 to 130 (p < 0.01). Conclusion: The findings of the present study suggest that there is an association between 18F-NaF uptake and calcium deposition in extraosseous metastases of MTC, supporting the hypothesis that visually undetectable calcium accumulation may be responsible for 18F-NaF uptake in regions without visible calcium deposition.

Treatment Response Assessment of Skeletal Metastases in Prostate Cancer with ¹⁸F-NaF PET/CT / 대한핵의학회잡지

PURPOSE: To determine the utility of ¹⁸F-sodium fluoride positron emission tomography-computed tomography (¹⁸F-NaF PET/CT) in the imaging assessment of therapy response in men with osseous-only metastatic prostate cancer.METHODS: In this Institutional Review Board-approved single institution retrospective investigation, we evaluated 21 ¹⁸F-NaF PET/CTscans performed in 14 patients with osseous metastatic disease from prostate cancer and no evidence of locally recurrent or soft-tissue metastatic disease who received chemohormonal therapy. Imaging-based qualitative and semi-quantitative parameters were defined and compared with changes in serum PSA level.RESULTS: Qualitative and semi-quantitative image-based assessments demonstrated > 80% concordance with good correlation (SUV(max) κ = 0.71, SUVavg κ = 0.62, SUVsum κ = 0.62). Moderate correlation (κ = 0.43) was found between SUV(max) and PSA-based treatment response assessments. There was no statistically significant correlation between PSA-based disease progression and semi-quantitative parameters. Qualitative imaging assessment was moderately correlated (κ = 0.52) with PSA in distinguishing responders and non-responders.CONCLUSION: ¹⁸F-NaF PET/CT is complementary to biochemical monitoring in patients with bone-only metastases from prostate cancer which can be helpful in subsequent treatment management decisions.

Bone and Calcified Soft Tissue Metastases of Medullary Thyroid Carcinoma Better Characterized on ¹⁸F-Fluoride PET/CT than on ⁶⁸Ga-Dotatate PET/CT / 대한핵의학회잡지

Herein, we report a case of a 19-year-old man with multiple endocrine neoplasia type 2B (MEN2B) and medullary thyroid carcinoma (MTC) diagnosed when he was 12 years of age. The patient had previously undergone total thyroidectomy, cervical radiotherapy, and chemotherapy. He progressed with known bone, pulmonary, and lymph node metastases and was scanned with ¹⁸F-fluoride (¹⁸F-NaF) and ⁶⁸Ga-dotatate whole-body positron emission tomography/computed tomography (PET/CT) for metastatic disease monitoring.We found that the MTC bone metastases and soft tissue calcified metastases were better characterized on ¹⁸F-NaF PET/CT than on ⁶⁸Ga-dotatate PET/CT. This case illustrates that the ¹⁸F-NaF PET/CT could be helpful not only to the detection of bone metastases but also to the detection of calcified soft tissue metastases in patients with MTC.

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.

The role of low dose CT as part of the same 18F-NaF PET/CT in detecting bone metastases in lung cancer / 实用医学杂志

Objective Retrospectively evaluate low dose computed tomography (CT) as part of a combined 18F-NaF positron emission tomography (18F-NaFPET/CT) examination in lung cancer patients suspected of bone metastases. Methods 118 of 122 lesions with increased uptake of 18F-NaF were assessed. Characteristics of bone metastases on CT images were reviewed by radiologists. Results 27 of 47 metastases presented as sites of increased uptake with corresponding lytic or sclerotic changes on low dose CT. Other 20 show normal or non-specific appearing bone on CT. Most benign lesions (67 of 71,94%)have a benign appearance on low-dose CT. Conclusions Low dose CT images were useful in precisely diagnosing bone metastasis. Negative low dose CT appearance to the abnormal foci on PET may be a reliable sign of metastases.

Prevalence of exclusive lower extremity metastases at 18F-NaF PET/CT / Prevalência de metástases exclusivas em membros inferiores em exames de PET/TC com 18F-NaF

Abstract Objective: To evaluate the prevalence of exclusive lower extremity metastases, specifically in the femur and below the knee, observed at 18F-NaF PET/CT. Materials and Methods: One thousand consecutive PET/CT studies were retrospectively evaluated for the presence of exclusive uptake in lower extremities suggesting metastatic involvement. The presumptive diagnoses based on such uptakes were subsequently obtained by evaluation of other imaging studies. Results: No exclusive uptake suggestive of metastasis below the femur was observed in the present series. Exclusive uptake was observed in the proximal femur with a presumptive diagnosis of metastasis in two patients. Conclusion: The prevalence of exclusive metastasis below the femur is low and scanning from head to knees is appropriate in most cases. .

Resumo Objetivo: Avaliar a prevalência de metástases exclusivas em membros inferiores, subdivididas em lesões femorais e abaixo dos joelhos, em exames de PET/TC com 18F-NaF. Materiais e Métodos: Mil exames consecutivos foram retrospectivamente avaliados para a presença de captações exclusivas em membros inferiores sugestivas de comprometimento metastático. Os diagnósticos presuntivos dessas captações foram posteriormente obtidos pela avaliação de outros exames realizados. Resultados: Não foram observadas captações exclusivas sugestivas de metástases abaixo dos fêmures na nossa casuística. Foi observada captação exclusiva no terço superior do fêmur com diagnóstico de metástase em dois pacientes. Conclusão: A prevalência de metástase exclusiva abaixo dos fêmures é baixa e a realização do exame da cabeça até os joelhos é adequada na maioria dos casos. .

Comparison of standardized uptake values measured on 18F-NaF PET/CT scans using three different tube current intensities / Comparação dos valores de captação medidos nos estudos de 18F-NaF PET/CT utilizando três intensidades diferentes de corrente do tubo de tomografia computadorizada

Objective: To analyze standardized uptake values (SUVs) using three different tube current intensities for attenuation correction on 18FNaF PET/CT scans. Materials and Methods: A total of 254 18F-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. .