Dedicated breast PET value to evaluate BI-RADS 4 breast lesions.

PURPOSE: To evaluate the diagnostic value of dedicated breast PET (dbPET) parallel imaging in mammographically or sonographically detected BI-RADS 4 (Breast Imaging Reporting And Data Systems) lesions. MATERIALS AND METHODS: After institutional review board and patient approvals, 50 consecutive women with 60 BI-RADS 4 breast lesions were prospectively included in the study. All patients underwent Magnetic Resonance Imaging (MRI) and dbPET before biopsy and fusion of both MRI and dbPET images was performed to better locate corresponding lesions. Final findings were compared with histological results. Sensitivity and specificity for dbPET were determined along with their respective 95%-confidence intervals. RESULTS: Histopathology examination revealed 18 malignant lesions (7 in situ and 11 invasive carcinomas) and 42 benign entities. The dedicated breast PET reported no evidence of malignancy in 41 patients, 9 of them with histological diagnosis of neoplasm. Besides, dbPET showed increased metabolically activity in 10 benign lesions and in 9 breast cancers. Two invasive carcinomas were located less than 1 cm from the pectoral muscle, which can explain that they were missed by dbPET because they were outside the field of view (FOV). There were other 6 false negative results, which corresponded to a 0.1 cm invasive lobular carcinoma and 5 in situ carcinomas. Sensitivity and specificity of dbPET were 50% and 76%, respectively. CONCLUSIONS: Our analysis does not allow the recommendation of dbPET for diagnosis of malignancy in BI-RADS 4 mammographic or US abnormalities, mainly due to its high false-negative rate for the detection of in situ carcinomas (85.7%). However, considering the lesions greater than 0.1 cm and included in the FOV, dbPET depicted all invasive carcinomas.

Estudios simulados de PET FDG para la evaluación de diferentes métodos de cuantificación de SUV / Simulated FDG-PET studies for the assessment of SUV quantification methods

Objetivo. estudiar en detalle la precisión y la repetitividad de tres métodos de uso común en la estimación del SUV de nódulos pulmonares solitarios. Material y métodos. hemos diseñado una metodología de trabajo basada en la simulación de adquisiciones de estudios PET-FDG a partir de modelos antropomórficos de actividad, que incluyen nódulos pulmonares de diferente tamaño y valor de SUV conocido. Esta metodología nos permite comparar el SUV estimado a partir de la imagen PET con el SUV teórico. La actividad del tumor fue estimada mediante tres métodos conocidos: SUVmax, SUVmean y SUV50. Resultados. nuestros resultados muestran que, por un lado SUVmax sobreestima la actividad en el tumor, mientras SUV50 subestima el valor de actividad de manera muy significa. En cambio, la cuantificación de SUV50 mostró un buen acuerdo con los valores de SUV teóricos o simulados, y únicamente mostró una ligera subestimación para lesiones muy pequeñas. Por otro lado, SUVmean mostró un mejor comportamiento que SUV50 en términos de repetitividad, proporcionando variabilidades por debajo del 5% para todos los tamaños de lesión y para dosis inyectadas tan bajas como 111 MBq. Conclusiones. nuestros hallazgos mostraron que SUV50 proporciona el mejor comportamiento para estimar la actividad en nódulos pulmonares, pero SUVmean mostró mejores resultados en términos de repetitividad (AU)

Aim. To study in detail the accuracy and repeatability of three commonly used methods for SUV estimation in solitary pulmonary nodules. Material and methods. We have designed a realistic framework based on simulated FDG-PET acquisitions from an anthropomorphic activity model that included solitary pulmonary nodules (different sizes) of well-known SUV. This framework enables us to compare the SUV values obtained from the reconstructed PET images with the real SUV values. Three commonly used methods (SUVmax, SUVmean and SUV50) were used to estimate the tumor activity. Results. Our results showed the tumor activity was overestimated using SUVmax and clearly subestimated using SUVmean. Instead, the quantification of SUV50 showed great agreement with the simulated tumor activity and only slight subestimation was found for very small lesions. On the other hand, SUVmean showed better performance than SUV50 in terms of repeatability, providing variabilities below 5% for all tumor sizes and for injected doses as low as 111 MBq. Conclusions. Our findings showed that SUV50 provided better performance for estimating accurately tumor SUV values in pulmonary nodules, but SUVmean showed better results in terms of repeatability (AU)

Simulated FDG-PET studies for the assessment of SUV quantification methods.

AIM: To study in detail the accuracy and repeatability of three commonly used methods for SUV estimation in solitary pulmonary nodules. MATERIAL AND METHODS: We have designed a realistic framework based on simulated FDG-PET acquisitions from an anthropomorphic activity model that included solitary pulmonary nodules (different sizes) of well-known SUV. This framework enables us to compare the SUV values obtained from the reconstructed PET images with the real SUV values. Three commonly used methods (SUVmax, SUVmean and SUV50) were used to estimate the tumor activity. RESULTS: Our results showed the tumor activity was overestimated using SUVmax and clearly subestimated using SUVmean. Instead, the quantification of SUV50 showed great agreement with the simulated tumor activity and only slight subestimation was found for very small lesions. On the other hand, SUVmean showed better performance than SUV50 in terms of repeatability, providing variabilities below 5% for all tumor sizes and for injected doses as low as 111 MBq. CONCLUSIONS: Our findings showed that SUV50 provided better performance for estimating accurately tumor SUV values in pulmonary nodules, but SUVmean showed better results in terms of repeatability.

[18F]fluorothymidine-positron emission tomography in patients with locally advanced breast cancer under bevacizumab treatment: Usefulness of different quantitative methods of tumor proliferation / [18F]fluortimidina-PET en pacientes con carcinoma de mama localmente avanzado en tratamiento con bevacizumab: utilidad de diferentes métodos de cuantificación de la proliferación celular

Objectives. To investigate quantitative methods of tumor proliferation using 3′-[18F]fluoro-3′-deoxythymidine ([18F]FLT) PET in patients with breast cancer (BC), studied before and after one bevacizumab administration, and to correlate the [18F]FLT-PET uptake with the Ki67 index. Material and methods. Thirty patients with newly diagnosed, untreated BC underwent a [18F]FLT-PET before and 14 days after bevacizumab treatment. A dynamic scan centered over the tumor began simultaneously with the injection of [18F]FLT (385 ± 56 MBq). Image derived input functions were obtained using regions of interest drawn on the left ventricle (LV) and descending aorta (DA). Metabolite corrected blood curves were used as input functions to obtain the kinetic Ki constant using the Patlak graphical analysis (time interval 10-60 min after injection). Maximum SUV values were derived for the intervals 40-60 min (SUV40) and 50-60 min (SUV50). PET parameters were correlated with the Ki67 index obtained staining tumor biopsies. Results. [18F]FLT uptake parameters decreased significantly (p < 0.001) after treatment: SUV50 = 3.09 ± 1.21 vs 2.22 ± 0.96; SUV40 = 3.00 ± 1.18 vs 2.14 ± 0.95, Ki_LV(10-3) = 52[22-116] vs 38[13-80] and Ki_DA(10-3) = 49[15-129] vs 33[11-98]. Consistency interclass correlation coefficients within SUV and within Ki were high. Changes of SUV50 and Ki_DA between baseline PET and after one bevacizumab dose PET correlated with changes in Ki67 index (r-Pearson = 0.35 and 0.26, p = 0.06 and 0.16, respectively). Conclusions. [18F]FLT-PET is useful to demonstrate proliferative changes after a dose of bevacizumab in patients with BC. Quantification of tumor proliferation by means of SUV and Ki has shown similar results, but SUV50 obtained better results. A correlation between [18F]FLT changes and Ki67 index was observed (AU)

Objetivos. Evaluar métodos cuantitativos de proliferación celular en PET con 3′-[18F]fluoro-3′-desoxitimidina ([18F]FLT), antes y después de una dosis de bevacizumab en pacientes con carcinoma de mama (CM), y correlacionar la captación de [18F]FLT con el índice Ki67. Material y métodos. Se incluyeron 30 mujeres con CM no tratado. Se realizó [18F]FLT-PET antes y 14 días después de una dosis de bevacizumab. La PET dinámica centrada en el tumor se inició simultáneamente con la infusión de [18F]FLT (385 ± 56 MBq). Se dibujaron regiones de interés en ventrículo izquierdo (VI) y aorta descendente (AD), obteniéndose funciones de entrada, que corregidas por metabolitos, se utilizaron para obtener la constante Ki de Patlak (intervalo: 10-60 min). Se calcularon valores máximos del SUV en los intervalos 40-60 min (SUV40) y 50-60 min (SUV50). Los parámetros PET se correlacionaron con el Ki67, obtenido en biopsias tumorales teñidas. Resultados. Los parámetros de la captación de [18F]FLT disminuyeron significativamente (p < 0,001) tras el tratamiento: SUV50 = 3,09 ± 1,21 vs 2,22 ± 0,96; SUV40 = 3,00 ± 1,18 vs 2,14 ± 0,95, Ki_VI(10-3) = 52[22-116] vs 38[13-80] y Ki_AD(10-3) = 49[15-129] vs 33[11-98]. Los coeficientes de correlación intraclase fueron elevados en los SUV y en los Ki. Los cambios de SUV50 y Ki_AD entre la PET basal y la PET tras bevacizumab se correlacionaron con los cambios en el Ki67 (r-Pearson = 0,35 y 0,26, p = 0,06 y 0,16, respectivamente). Conclusiones. La [18F]FLT-PET refleja los cambios en la proliferación celular tras una dosis de bevacizumab en pacientes con CM. La cuantificación de la proliferación por medio del SUV y la Ki arrojó resultados similares, si bien fueron mejores con el SUV50. Los cambios en [18F]FLT se correlacionaron con los cambios en el índice Ki67 (AU)

[¹8F]fluorothymidine-positron emission tomography in patients with locally advanced breast cancer under bevacizumab treatment: usefulness of different quantitative methods of tumor proliferation.

OBJECTIVES: To investigate quantitative methods of tumor proliferation using 3'-[(18)F]fluoro-3'-deoxythymidine ([(18)F]FLT) PET in patients with breast cancer (BC), studied before and after one bevacizumab administration, and to correlate the [(18)F]FLT-PET uptake with the Ki67 index. MATERIAL AND METHODS: Thirty patients with newly diagnosed, untreated BC underwent a [(18)F]FLT-PET before and 14 days after bevacizumab treatment. A dynamic scan centered over the tumor began simultaneously with the injection of [(18)F]FLT (385 ± 56 MBq). Image derived input functions were obtained using regions of interest drawn on the left ventricle (LV) and descending aorta (DA). Metabolite corrected blood curves were used as input functions to obtain the kinetic Ki constant using the Patlak graphical analysis (time interval 10-60 min after injection). Maximum SUV values were derived for the intervals 40-60 min (SUV40) and 50-60 min (SUV50). PET parameters were correlated with the Ki67 index obtained staining tumor biopsies. RESULTS: [(18)F]FLT uptake parameters decreased significantly (p<0.001) after treatment: SUV50=3.09 ± 1.21 vs 2.22 ± 0.96; SUV40=3.00 ± 1.18 vs 2.14 ± 0.95, Ki_LV(10-3)=52[22-116] vs 38[13-80] and Ki_DA(10-3)=49[15-129] vs 33[11-98]. Consistency interclass correlation coefficients within SUV and within Ki were high. Changes of SUV50 and Ki_DA between baseline PET and after one bevacizumab dose PET correlated with changes in Ki67 index (r-Pearson=0.35 and 0.26, p=0.06 and 0.16, respectively). CONCLUSIONS: [(18)F]FLT-PET is useful to demonstrate proliferative changes after a dose of bevacizumab in patients with BC. Quantification of tumor proliferation by means of SUV and Ki has shown similar results, but SUV50 obtained better results. A correlation between [(18)F]FLT changes and Ki67 index was observed.

Aportación del tiempo de vuelo y de la modelización de la respuesta a una fuente puntual a las características de funcionamiento del tomógrafo PET/TAC Biograph mCT / Contribution of time of flight and point spread function modeling to the performance characteristics of the PET/CT Biograph mCT scanner

Objetivo. Caracterizar el funcionamiento del tomógrafo PET/TAC Biograph mCT TrueV que incorpora el tiempo de vuelo (TOF) y modeliza la respuesta a una fuente puntual (PSF). Material y métodos. El tomógrafo combina un TAC de 64 cortes y un PET que reconstruye tomográficamente con TOF y PSF. Las características de funcionamiento PET se evaluaron siguiendo el estándar NEMA NU-2-2007, ampliando algunas pruebas. Adicionalmente se evaluaron diferentes algoritmos de reconstrucción y se midieron la radiación intrínseca y la uniformidad tomográfica. Resultados. La resolución espacial (FWHM) a 1 y 10cm del eje fue de 4,4 y 5,3mm, mejorando al introducir la PSF a 2,6 y 2,5mm. La sensibilidad fue de 10,9 y 10,2 kcps/MBq a 0 y 10cm del eje. La fracción de dispersión fue inferior al 34% a bajas concentraciones y la tasa de sucesos equivalentes al ruido (NECR) fue máxima en 182 kcps a 27,8 kBq/mL. La radiación intrínseca produjo 4,42 coincidencias verdaderas por segundo. El coeficiente de variación de la uniformidad del volumen y del sistema fue del 4,7 y 0,8%. La prueba de calidad de imagen mostró mejores resultados al incluir conjuntamente PSF y TOF. Específicamente, la PSF mejoró el contraste de las esferas calientes y la variabilidad del fondo, mientras que el TOF aumentó el contraste de las esferas frías. Conclusiones. El tomógrafo tiene muy buenas características de funcionamiento, además la calidad de la imagen mejora al incorporar la información de la PSF y del TOF en la reconstrucción tomográfic (AU)

Objective. To characterize the performance of the Biograph mCT PET/CT TrueV scanner with time of flight (TOF) and point spread function (PSF) modeling. Material and methods. The PET/CT scanner combines a 64-slice CT and PET scanner that incorporates in the reconstruction the TOF and PSF information. PET operating characteristics were evaluated according to the standard NEMA NU 2-2007, expanding some tests. In addition, different reconstruction algorithms were included, and the intrinsic radiation and tomographic uniformity were also evaluated. Results. The spatial resolution (FWHM) at 1 and 10cm was 4.4 and 5.3mm, improving to 2.6 and 2.5mm when PSF is introduced. Sensitivity was 10.9 and 10.2 Kcps/MBq at 0 and 10cm from the axis. Scatter fraction was less than 34% at low concentrations and the noise equivalent count rate (NECR) was maximal at 27.8 kBq/mL with 182 Kcps, the intrinsic radiation produced a rate of 4.42 true coincidences per second. Coefficient of variation of the volume and system uniformity were 4.7 and 0.8% respectively. The image quality test showed better results when PSF and TOF were included together. PSF improved the hot spheres contrast and background variability, while TOF improved the cold spheres contrast. Conclusions. The Biograph mCT TrueV scanner has good performance characteristics. The image quality improves when the information from the PSF and the TOF is incorporated in the reconstruction (AU)

[Contribution of time of flight and point spread function modeling to the performance characteristics of the PET/CT Biograph mCT scanner]. / Aportación del tiempo de vuelo y de la modelización de la respuesta a una fuente puntual a las características de funcionamiento del tomógrafo PET/TAC Biograph mCT.

OBJECTIVE: To characterize the performance of the Biograph mCT PET/CT TrueV scanner with time of flight (TOF) and point spread function (PSF) modeling. MATERIAL AND METHODS: The PET/CT scanner combines a 64-slice CT and PET scanner that incorporates in the reconstruction the TOF and PSF information. PET operating characteristics were evaluated according to the standard NEMA NU 2-2007, expanding some tests. In addition, different reconstruction algorithms were included, and the intrinsic radiation and tomographic uniformity were also evaluated. RESULTS: The spatial resolution (FWHM) at 1 and 10cm was 4.4 and 5.3mm, improving to 2.6 and 2.5mm when PSF is introduced. Sensitivity was 10.9 and 10.2 Kcps/MBq at 0 and 10cm from the axis. Scatter fraction was less than 34% at low concentrations and the noise equivalent count rate (NECR) was maximal at 27.8 kBq/mL with 182 Kcps, the intrinsic radiation produced a rate of 4.42 true coincidences per second. Coefficient of variation of the volume and system uniformity were 4.7 and 0.8% respectively. The image quality test showed better results when PSF and TOF were included together. PSF improved the hot spheres contrast and background variability, while TOF improved the cold spheres contrast. CONCLUSIONS: The Biograph mCT TrueV scanner has good performance characteristics. The image quality improves when the information from the PSF and the TOF is incorporated in the reconstruction.