Enfermedad de Erdheim-Chester: el poder de las imágenes de medicina nuclear / Erdheim-Chester disease: the power of nuclear medicine imaging

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Papel de la 18F-FDG PET o PET/TC en el plasmocitoma: una revisión sistemática / 18F-FDG PET or PET/CT role in plasmacytoma: a systematic review

ANTECEDENTES: El comportamiento metabólico del plasmocitoma en la PET/TC con 18F-FDG no está claro. OBJETIVO: Realizar una revisión sistemática sobre la utilidad diagnóstica de la PET o PET/TC con 18F-FDG en pacientes afectos de plasmocitoma. MÉTODOS: Se ha realizado una búsqueda exhaustiva bibliográfica de artículos relevantes en las bases de datos de Scopus, PubMed/MEDLINE, Embase y Cochrane Library desde julio de 2019. RESULTADOS: La búsqueda exhaustiva bibliográfica ha revelado 371 artículos; al revisar los títulos y los resúmenes, se excluyeron 363 artículos porque los datos que aportaban no estaban dentro del campo de interés de esta revisión. En total, en esta revisión sistemática se incluyeron 8 artículos. Los principales hallazgos del análisis de los artículos seleccionados han sido: 1) El plasmocitoma generalmente es un tumor ávido de 18F-FDG y la PET/TC muestra un buen rendimiento diagnóstico, con alta sensibilidad; 2) en la mayoría de los casos la PET/TC con 18F-FDG ha influido en el manejo de los pacientes, permitiendo seleccionar el tratamiento y evitando terapias ineficaces; 3) el valor pronóstico de los parámetros cualitativos y semicuantitativos de la PET/TC con 18F-FDG sigue mostrando un carácter controvertido con los resultados obtenidos. CONCLUSIÓN: A pesar de las limitaciones de estos hallazgos, dado el reducido número de trabajos y pacientes estudiados, el plasmocitoma parece ser un tumor ávido de 18F-FDG en la mayoría de los casos. La PET o PET/TC con 18F-FDG muestra un buen rendimiento diagnóstico, con impacto clínico significativo en el cambio de enfoque terapéutico. Finalmente, parece existir un probable valor pronóstico de la PET/TC con 18F-FDG

BACKGROUND: The metabolic behavior of plasmacytoma at 18F-FDG PET/CT is not yet clear. OBJECTIVE: The aim of this systematic review was to analyze published data about the role of 18F-FDG PET or PET/CT in patients affected by plasmacytoma. METHODS: Acomprehensive computer literature search of the Scopus, PubMed/MEDLINE, Embase and Cochrane Library databases was conducted including articles up to July 2019 to find relevant published papers about the performance of 18F-FDG PET and PET/CT in plasmacytoma. RESULTS: The comprehensive computer literature search revealed 371 articles. On reviewing the titles and abstracts, 363 articles were excluded because the reported data were not within the field of interest of this review. Eight articles were selected and retrieved in full-text version. From the analyses of the selected studies, the following main findings have been founded: 1) plasmacytoma generally is a 18F-FDG-avid tumor and PET/CT had good diagnostic performance with high sensitivity; 2) 18F-FDG PET/CT influenced patient management in most cases avoiding useless therapies and choosing the best therapeutic approach; 3) prognostic value of PET/CT qualitative and semiquantitative parameters is only suggested with controversial reports. CONCLUSION: Despite several limitations affect this analysis, especially related to the low number of articles and patients studied, plasmacytoma looks to be an 18F-FDG-avid tumor in most of the cases; 18F-FDG PET or PET/CT had good diagnostic performance and had a significant clinical impact in change of therapeutic approach. Moreover, a possible prognostic role of PET/CT features is described

18F-FDG PET or PET/CT role in plasmacytoma: A systematic review. / Papel de la 18F-FDG PET o PET/TC en el plasmocitoma: una revisión sistemática.

BACKGROUND: The metabolic behavior of plasmacytoma at 18F-FDG PET/CT is not yet clear. OBJECTIVE: The aim of this systematic review was to analyze published data about the role of 18F-FDG PET or PET/CT in patients affected by plasmacytoma. METHODS: Acomprehensive computer literature search of the Scopus, PubMed/MEDLINE, Embase and Cochrane Library databases was conducted including articles up to July 2019 to find relevant published papers about the performance of 18F-FDG PET and PET/CT in plasmacytoma. RESULTS: The comprehensive computer literature search revealed 371 articles. On reviewing the titles and abstracts, 363 articles were excluded because the reported data were not within the field of interest of this review. Eight articles were selected and retrieved in full-text version. From the analyses of the selected studies, the following main findings have been founded: 1) plasmacytoma generally is a 18F-FDG-avid tumor and PET/CT had good diagnostic performance with high sensitivity; 2) 18F-FDG PET/CT influenced patient management in most cases avoiding useless therapies and choosing the best therapeutic approach; 3) prognostic value of PET/CT qualitative and semiquantitative parameters is only suggested with controversial reports. CONCLUSION: Despite several limitations affect this analysis, especially related to the low number of articles and patients studied, plasmacytoma looks to be an 18F-FDG-avid tumor in most of the cases; 18F-FDG PET or PET/CT had good diagnostic performance and had a significant clinical impact in change of therapeutic approach. Moreover, a possible prognostic role of PET/CT features is described.

Paraganglioma no funcionante detectado incidentalmente en la 18F-FDG PET/TC y confirmado mediante gammagrafía con 123I-MIBG / Nonfunctioning paraganglioma incidentally detected by 18F-FDG PET/CT and confirmed by 123I-MIBG M scintigraphy

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Detección de grasa parda en la PET/TC con 18F-FDG: diferencias entre la población adulta y pediátrica en una experiencia de 12 años / 18F-FDG PET/CT brown fat detection: differences between adult and pediatric population in a 12 year experience

OBJETIVO: Analizar las características epidemiológicas y antropométricas de los pacientes con activación de la grasa parda detectada por tomografía por emisión de positrones con fluoruro 18-fluorodeoxiglucosa/tomografía computarizada (18F-FDG PET/TC). MATERIAL Y MÉTODOS: De 2005 a 2017, se incluyeron retrospectivamente 818 estudios PET/TC con 18F-FDG positivos para detección de grasa parda, 742 exámenes realizados en población adulta y 76 PET/TC en población pediátrica. Se realizó una prueba de Chi cuadrado para comparar la distribución de las características entre pacientes adultos y pediátricos. RESULTADOS: Los adultos mostraron una tasa más alta de detección de grasa parda en mujeres (79% vs.61%, p < 0,001) y en pacientes con hiperglucemia (> 100mg/dl) (24% vs.16%, p = 0,02), no se encontraron diferencias significativas considerando el sobrepeso (IMC>25kg/m2) (22% vs.20%, p = 0,55). Teniendo en cuenta solo a mujeres, los adultos mostraron una tasa más alta de detección de grasa parda tanto en pacientes con hiperglucemia (83% frente a 42%, p < 0,001), como en pacientes con sobrepeso (80% frente a 67%, p = 0,005). En ambas poblaciones, la activación de la grasa parda ocurrió con mayor frecuencia en las estaciones frías; no hubo diferencias significativas en la distribución considerando la temporada de nacimiento (p = 0,2). CONCLUSIONES: El sexo, la glucemia y el IMC desempeñan un papel importante en la predicción de la activación de la grasa parda, con diferencias significativas entre adultos y niños. Se confirma que la exposición al frío es un factor de predicción importante, mientras que la temporada de nacimiento no es significativa

PURPUSE: To analyze epidemiological and anthropometric features of patients with brown adipose tissue (BAT) activation detected by fluorine18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT). MATERIAL AND METHODS: From 2005 to 2017, 818 18F-FDG PET/CT studies positive for BAT detection were retrospectively included, 742 examinations performed on the adult population and 76 PET/CT on the pediatric population. A Chi-squared test was performed to compare features distribution between the adult and pediatric patients. RESULTS: Adults showed a higher rate of BAT detection in females (79% vs.61%, p < 0.001) and in hyperglycaemic patients (>100mg/dL) (24% vs.16%, p = 0.02), no significant difference was found with regard to overweight patients (BMI>25kg/m2) (22% vs.20%, P=.55). Considering females only, the adults showed a higher rate of BAT detection both in hyperglycaemic (83% vs.42%, p < 0.001) and overweight patients (80% vs.67%, p = 0.005). In both populations BAT activation happened more frequently in cold seasons; there was no significant distribution difference with regard to season of birth (p = 0.2). CONCLUSIONS: Sex, glycemia and BMI play a major role in predicting BAT activation, with significant differences between adults and pediatric patients. Cold exposure is confirmed as an important predicting factor, while season of birth is not significant

Cistitis incrustada detectada por PET/TC con 18F-FDG / Encrusted cystitis detected by 18F-FDG PET/CT

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18F-FDG PET/CT brown fat detection: Differences between adult and pediatric population in a 12 year experience. / Detección de grasa parda en la PET/TC con 18F-FDG: diferencias entre la población adulta y pediátrica en una experiencia de 12 años.

PURPOSE: To analyze epidemiological and anthropometric features of patients with brown adipose tissue (BAT) activation detected by fluorine18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT). MATERIAL AND METHODS: From 2005 to 2017, 818 18F-FDG PET/CT studies positive for BAT detection were retrospectively included, 742 examinations performed on the adult population and 76 PET/CT on the pediatric population. A Chi-squared test was performed to compare features distribution between the adult and pediatric patients. RESULTS: Adults showed a higher rate of BAT detection in females (79% vs. 61%, P<0.001) and in hyperglycaemic patients (>100mg/dL) (24% vs. 16%, P=0.02), no significant difference was found with regard to overweight patients (BMI>25kg/m2) (22% vs. 20%, P=.55). Considering females only, the adults showed a higher rate of BAT detection both in hyperglycaemic (83% vs. 42%, P<0.001) and overweight patients (80% vs. 67%, P=0.005). In both populations BAT activation happened more frequently in cold seasons; there was no significant distribution difference with regard to season of birth (P=0.2). CONCLUSIONS: Sex, glycemia and BMI play a major role in predicting BAT activation, with significant differences between adults and pediatric patients. Cold exposure is confirmed as an important predicting factor, while season of birth is not significant.

Valor clínico y pronóstico de la PET/TC con 18F-FDG en el cáncer de endometrio recurrente / Clinical and prognostic value of 18F-FDG PET/CT in recurrent endometrial carcinoma

Objetivo: El carcinoma endometrial (CE) es un cáncer con un buen pronóstico general, excepto en los casos de CE recurrente o avanzado. El objetivo de este estudio fue evaluar el rendimiento diagnóstico y pronóstico y el impacto en el manejo terapéutico de la PET/TC con 18F-FDG en la sospecha de CE recurrente. Material y métodos: Se evaluaron retrospectivamente 157 pacientes con CE histológicamente probado y reestadificación de PET/TC con 18F-FDG por sospecha de recurrencia. Las imágenes PET se analizaron visualmente y semicuantitativamente midiendo SUVmax, VMT y GTL. Se tomó como referencia una combinación de seguimiento clínico/radiológico/histopatológico. La supervivencia libre de progresión (SLP) y la supervivencia global (SG) se calcularon usando las curvas de Kaplan-Meier. Resultados: Setenta y nueve pacientes tuvieron una PET/TC con 18F-FDG positiva que mostró la presencia de al menos una lesión hipermetabólica compatible con recurrencia, mientras que los 78 restantes fueron negativos. La sensibilidad, la especificidad, el valor predictivo positivo, el valor predictivo negativo y la precisión de la PET/TC con 18F-FDG fueron del 96, del 99, del 99, del 96 y del 97%, respectivamente, y fueron más altos en comparación con las imágenes convencionales: 97, 62, 72, 96 y 80%. Después de un seguimiento medio de 39meses, la recaída/progresión ocurrió en 58 pacientes y la muerte en 37, con un tiempo promedio de 22,1 y 27,6meses, respectivamente. Una PET/TC con 18F-FDG positiva y un estadio FIGO avanzado se asociaron significativamente con una SLP y SG más cortos. Los resultados de PET/TC tuvieron un impacto significativo en el abordaje terapéutico en 33 pacientes: evitaron terapias innecesarias en 28 y modificaron la terapia en 5. Conclusiones: La 18F-FDG-PET/TC tiene un muy buen rendimiento diagnóstico en pacientes con sospecha de CE recurrente, y tiene un importante valor pronóstico en la evaluación de SLP y SG. Además, la PET/TC permitió un cambio en la decisión de tratamiento en aproximadamente el 20% de los casos

Purpose: Endometrial carcinoma (EC) is a cancer with a good overall prognosis, except in cases of recurrent or advanced EC. The aim of this study was to assess the diagnostic performance, the prognostic value and the impact on therapeutic management of 18F-FDG PET/CT in suspected recurrent EC. Materials and methods: We retrospectively evaluated 157 patients with histologically proven EC and restaging 18F-FDG PET/CT for suspected recurrence. The PET images were analyzed visually and semi-quantitatively by measuring SUVmax, MTV and TLG. A combination of clinical/imaging follow-up and/or histopathology was taken as reference standard. Progression-free survival (PFS) and overall survival (OS) were computed using Kaplan-Meier curves. Results: Seventy-nine patients had positive 18F-FDG PET/CT showing the presence of at least one hypermetabolic lesion consistent with recurrence, while the remaining 78 were negative. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 18F-FDG PET/CT were 96%, 99%, 99%, 96%, 97%, respectively, and were higher compared to conventional imaging: 97%, 62%, 72%, 96%, 80%. After a mean follow-up of 39months, relapse/progression occurred in 58 patients and death in 37 with an average time of 22.1 and 27.6months, respectively. A positive 18F-FDG PET/CT and advanced FIGO stage were significantly associated with shorter PFS and OS. PET/CT results had a significant impact on therapeutic approach in 33 patients: avoiding unnecessary therapies in 28 and modifying therapy in 5. Conclusions: 18F-FDG PET/CT has a very good diagnostic performance in patients with suspected recurrent EC and has an important prognostic value in assessing PFS and OS. Moreover, PET/CT allowed for a change in treatment decision in about 20% of cases

18F-FDG PET/TC en reestadificación y seguimiento de pacientes con sarcomas uterinos / Role of 18F-FDG PET/CT in restaging and follow-up of patients with uterine sarcomas

Objetivo: Los sarcomas uterinos son tumores raros con mal pronóstico debido a las altas tasas de recurrencia. El papel actual de la 18F-FDG PET/TC en la vigilancia posterior a la terapia aún no está establecido. Material y metodos: Cuarenta y una mujeres con sarcoma uterino se sometieron a 73 estudios 18F-FDG PET/TC para la reestadificación en la presunta recurrencia o durante el seguimiento en pacientes asintomáticos. Los resultados histopatológicos y/o el seguimiento clínico/de imágenes durante al menos 12 meses se consideraron el estándar de referencia. Se calculó la precisión diagnóstica y el impacto clínico de la 18F-FDG PET/TC. Resultados: treinta y tres estudios 18F-FDG PET/TC fueron positivos, mientras que los 40 estudios restantes fueron negativos. La sensibilidad general, la especificidad, el valor predictivo positivo (VP+), el valor predictivo negativo (VP-) y la precisión de la 18F-FDG PET/TC fueron del 88%, 98%, 97%, 91% y 93%. Considerando pacientes con sospecha clínica o radiológica de recidiva (n=47) y durante el seguimiento (n=26) la sensibilidad y especificidad, VP+, VP− y precisión de 18F-FDG PET/TC fueron del 89%, 100%, 100%, 86% y 94%, y 80%, 95%, 80%, 95% y 92% respectivamente. La 18F-FDG PET/TC tuvo un impacto clínico positivo en 9/73 (12%) estudios y cambió el manejo clínico en 8/41 (20%) pacientes. Conclusion: La 18F-FDG PET/TC es un método preciso para la detección y localización de recidivas a distancia en pacientes con sarcoma uterino con buena sensibilidad y especificidad e impacto significativo en la toma de decisiones clínicas

Purpose: Uterine sarcomas are rare tumors with poor prognosis due to the high recurrence rates. The current role of 18F-FDG PET/CT in the post-therapy surveillance is not established yet. Materials and Methods: Forty-one women with uterine sarcoma underwent 73 18F-FDG PET/CT for restaging in suspected recurrence or during follow-up in asymptomatic patients. Histopathology results and/or clinical/imaging follow-up for at least 12 months were considered the reference standard. The diagnostic accuracy and clinical impact of 18F-FDG PET/CT was calculated. Results: Thirty-three 18F-FDG PET/CT were positive, while the remaining 40 studies were negative. The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of 18F-FDG PET/CT were 88%, 98%, 97%, 91% and 93%, respectively. Considering patients with clinical or radiological suspicion of recurrence (n=47) and those during follow-up (n=26), sensitivity, specificity, PPV, NPV and accuracy of 18F-FDG PET/CT were 89%, 100%, 100%, 86% and 94%, and 80%, 95%, 80%, 95% and 92%, respectively. 18F-FDG PET/CT had a positive clinical impact in 9/73 (12%) studies and changed the clinical management in 8/41 (20%) patients. Conclusions: 18F-FDG PET/CT seems to be an accurate method for detection and localization of local and distant recurrence in patients with uterine sarcoma with good sensitivity and specificity and significant impact on clinical decision making

Role of 18F-FDG PET/CT in restaging and follow-up of patients with uterine sarcomas. / 18F-FDG PET/TC en reestadificación y seguimiento de pacientes con sarcomas uterinos.

PURPOSE: Uterine sarcomas are rare tumors with poor prognosis due to the high recurrence rates. The current role of 18F-FDG PET/CT in the post-therapy surveillance is not established yet. MATERIALS AND METHODS: Forty-one women with uterine sarcoma underwent 73 18F-FDG PET/CT for restaging in suspected recurrence or during follow-up in asymptomatic patients. Histopathology results and/or clinical/imaging follow-up for at least 12 months were considered the reference standard. The diagnostic accuracy and clinical impact of 18F-FDG PET/CT was calculated. RESULTS: Thirty-three 18F-FDG PET/CT were positive, while the remaining 40 studies were negative. The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of 18F-FDG PET/CT were 88%, 98%, 97%, 91% and 93%, respectively. Considering patients with clinical or radiological suspicion of recurrence (n=47) and those during follow-up (n=26), sensitivity, specificity, PPV, NPV and accuracy of 18F-FDG PET/CT were 89%, 100%, 100%, 86% and 94%, and 80%, 95%, 80%, 95% and 92%, respectively. 18F-FDG PET/CT had a positive clinical impact in 9/73 (12%) studies and changed the clinical management in 8/41 (20%) patients. CONCLUSIONS: 18F-FDG PET/CT seems to be an accurate method for detection and localization of local and distant recurrence in patients with uterine sarcoma with good sensitivity and specificity and significant impact on clinical decision making.

Clinical and prognostic value of 18F-FDG PET/CT in recurrent endometrial carcinoma. / Valor clínico y pronóstico de la PET/TC con 18F-FDG en el cáncer de endometrio recurrente.

PURPOSE: Endometrial carcinoma (EC) is a cancer with a good overall prognosis, except in cases of recurrent or advanced EC. The aim of this study was to assess the diagnostic performance, the prognostic value and the impact on therapeutic management of 18F-FDG PET/CT in suspected recurrent EC. MATERIALS AND METHODS: We retrospectively evaluated 157 patients with histologically proven EC and restaging 18F-FDG PET/CT for suspected recurrence. The PET images were analyzed visually and semi-quantitatively by measuring SUVmax, MTV and TLG. A combination of clinical/imaging follow-up and/or histopathology was taken as reference standard. Progression-free survival (PFS) and overall survival (OS) were computed using Kaplan-Meier curves. RESULTS: Seventy-nine patients had positive 18F-FDG PET/CT showing the presence of at least one hypermetabolic lesion consistent with recurrence, while the remaining 78 were negative. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 18F-FDG PET/CT were 96%, 99%, 99%, 96%, 97%, respectively, and were higher compared to conventional imaging: 97%, 62%, 72%, 96%, 80%. After a mean follow-up of 39months, relapse/progression occurred in 58 patients and death in 37 with an average time of 22.1 and 27.6months, respectively. A positive 18F-FDG PET/CT and advanced FIGO stage were significantly associated with shorter PFS and OS. PET/CT results had a significant impact on therapeutic approach in 33 patients: avoiding unnecessary therapies in 28 and modifying therapy in 5. CONCLUSIONS: 18F-FDG PET/CT has a very good diagnostic performance in patients with suspected recurrent EC and has an important prognostic value in assessing PFS and OS. Moreover, PET/CT allowed for a change in treatment decision in about 20% of cases.

Linfoma de Burkitt etmoidal y extranodal en un niño con lesiones renales bilaterales de linfoma de Burkitt detectadas por 18F-FDG PET/TC / Ethmoidal and extranodal Burkitt lymphoma in a child with bilateral kidney Burkitt lymphoma lesions incidentally detected by 18F-FDG PET/CT

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Diferente captación de 123I-MIBG en los 2 lóbulos hepáticos principales: un misterio persistente sin resolver / Different uptake of 123I-MIBG in the two main liver lobes: A persistant unsolved mistery

Objetivo: Después de la inyección del radiofármaco se observa con frecuencia una concentración incrementada de 123I-MIBG en el lóbulo hepático izquierdo en comparación con el derecho, pero la razón de este hallazgo sigue siendo desconocida. Nuestro objetivo fue analizar retrospectivamente el patrón de absorción de 123I-MIBG entre los 2 lóbulos hepáticos y correlacionar nuestros resultados con algunas características epidemiológicas/clínicas. Material y métodos: Se seleccionaron 94 gammagrafías 123I-MIBG de 71 pacientes. Las regiones de interés se dibujaron en los lóbulos derecho e izquierdo utilizando secciones tomográficas transversales y se calcularon relaciones de actividad de izquierda a derecha (relación I/D) a las 6 y 24horas de la administración del radiofármaco. Resultados: Veintisiete exámenes fueron positivos para lesiones hipermetabólicas, mientras que los 67 restantes fueron negativos. En todos los casos las relaciones medias de I/D temprana y tardía fueron superiores a 1; la relación I/D temprana media fue de 1,37 y la relación I/D tardía de 1,52. La relación I/D tardía fue significativamente mayor que la precoz. No hubo diferencias en la relación I/D con respecto a la edad, sexo, enfermedad primaria y resultado de la gammagrafía. Conclusiones: La absorción de 123I-MIBG fue mayor en el lóbulo hepático izquierdo en comparación con el derecho, y esta relación no se correlacionó con ninguna característica epidemiológica o clínica. La razón de este metabolismo todavía no se ha explicado, y algunas hipótesis biomoleculares podrían ser probadas en modelos 3D dinámicos in vitro

Purpose: After radiopharmaceutical injection, a heightened 123I-MIBG concentration is frequently observed in the left hepatic lobe compared to the right one, but the reason of this finding remains unknown. Our aim was to retrospectively analyze the different 123I-MIBG uptake pattern between the two hepatic lobes and correlate our results with some epidemiological/clinical features. Material and methods: Ninety-four 123I-MIBG scintigraphies from 71 patients were selected. Regions of interest were drawn in the right and left lobes using transverse tomographic sections and left to right activity ratios (L/R ratio) were calculated at 6 and 24h after radiotracer administration. Results: Twenty-seven examinations were positive for hypermetabolic lesions while the remaining 67 were negative. In all cases mean early and delayed L/R ratios were greater than 1.00; average early L/R ratio was 1.37 and delayed L/R ratio 1.52. The delayed L/R ratio was significantly higher than the early one. There was no difference in the L/R ratios with regard to age, gender, primary disease and result of scintigraphy. Conclusions: 123I-MIBG uptake was higher in left hepatic lobe compared to right and this ratio did not correlate with any epidemiological or clinical feature. The reason of this metabolic is not yet explained and some biomolecular hypotheses could be tested in 3D dynamic in vitro models

Different uptake of 123I-MIBG in the two main liver lobes: A persistant unsolved mistery. / Diferente captación de 123I-MIBG en los 2 lóbulos hepáticos principales: un misterio persistente sin resolver.

PURPOSE: After radiopharmaceutical injection, a heightened 123I-MIBG concentration is frequently observed in the left hepatic lobe compared to the right one, but the reason of this finding remains unknown. Our aim was to retrospectively analyze the different 123I-MIBG uptake pattern between the two hepatic lobes and correlate our results with some epidemiological/clinical features. MATERIAL AND METHODS: Ninety-four 123I-MIBG scintigraphies from 71 patients were selected. Regions of interest were drawn in the right and left lobes using transverse tomographic sections and left to right activity ratios (L/R ratio) were calculated at 6 and 24h after radiotracer administration. RESULTS: Twenty-seven examinations were positive for hypermetabolic lesions while the remaining 67 were negative. In all cases mean early and delayed L/R ratios were greater than 1.00; average early L/R ratio was 1.37 and delayed L/R ratio 1.52. The delayed L/R ratio was significantly higher than the early one. There was no difference in the L/R ratios with regard to age, gender, primary disease and result of scintigraphy. CONCLUSIONS: 123I-MIBG uptake was higher in left hepatic lobe compared to right and this ratio did not correlate with any epidemiological or clinical feature. The reason of this metabolic is not yet explained and some biomolecular hypotheses could be tested in 3D dynamic in vitro models.