PET/TC con 18F-FDG en paciente con presentación atípica de angiosarcoma cardiaco / 18F-FDG PET/CT in a patient with atypical presentation of cardiac angiosarcoma

Los tumores cardíacos o pericárdicos primarios son infrecuentes siendo más habitual la afectación metastásica. El angiosarcoma cardíaco es un tumor primario infrecuente de origen mesenquimal y de mal pronóstico por presentar metástasis en el momento del diagnóstico, y por su pobre respuesta a los tratamientos oncoespecíficos. Se describe el caso de una paciente de 74 años, que presenta un angiosarcoma cardíaco primario, con una localización infrecuente a nivel de pericardio. Se revisa la literatura y la utilidad de la PET/TC con 18F-FDG en su estadificación inicial

Primary cardiac or pericardial tumors are infrequent, metastatic involvement being more common. Cardiac angiosarcoma is a rare primary malignant tumor of mesenchymal origin. It entails a poor prognosis mostly due to frequent metastases at the time of diagnosis, as well as low response to onco-specific treatments. We describe a case of a 74-year-old patient with a primary cardiac angiosarcoma with an infrequent location at pericardium level. We review the literature and the utility of 18F-FDG PET/CT in the initial staging

18F-FDG PET/CT in a patient with atypical presentation of cardiac angiosarcoma. / PET/TC con 18F-FDG en paciente con presentación atípica de angiosarcoma cardiaco.

Primary cardiac or pericardial tumors are infrequent, metastatic involvement being more common. Cardiac angiosarcoma is a rare primary malignant tumor of mesenchymal origin. It entails a poor prognosis mostly due to frequent metastases at the time of diagnosis, as well as low response to onco-specific treatments. We describe a case of a 74-year-old patient with a primary cardiac angiosarcoma with an infrequent location at pericardium level. We review the literature and the utility of 18F-FDG PET/CT in the initial staging.

Differences on metabolic behavior between intra and extrahepatic cholangiocarcinomas at 18F-FDG-PET/CT: prognostic implication of metabolic parameters and tumor markers.

BACKGROUND AND PURPOSE: Cholangiocarcinoma is an infrequent neoplasm barely studied with 18F-FDG-PET/CT. We evaluated the metabolic behavior of cholangiocarcinoma in PET/CT according to its location (intra or extrahepatic) and analyzed the relationship between metabolic parameters of the primary tumor and tumor markers (CA19-9 and CEA), determining their prognostic significance. METHODS: Retrospective study of PET/CT of 60 patients with untreated cholangiocarcinoma, divided into two groups according to tumor location. FDG uptake was evaluated visually and semiquantitatively [SUVmax and tumor-to-liver ratio (TLR)], and differences between intra and extrahepatic cholangiocarcinomas were tested, both for FDG uptake in the primary tumor and for the presence of regional or distant disease (per-patient), as well as regarding tumor marker levels. A correlation between metabolic parameters and tumor markers was performed, and prognostic value of these factors was determined (univariate and multivariate analyses). RESULTS: Intrahepatic cholangiocarcinomas were significantly more FDG-avid than extrahepatic ones (p = 0.006 for SUVmax; p = 0.002 for TLR). There were differences neither between both groups considering the capacity of PET/CT to detect regional (p = 0.261) and distant involvement (p = 0.876), nor regarding the levels of tumor markers (p = 0.160 for CA19-9; p = 0.708 for CEA). Metabolic parameters and tumor markers showed a weak positive correlation (R2 0.22-0.27). At the multivariate analysis, advanced stage (p = 0.024), increased CEA (p = 0.022), and higher TLR (p = 0.003) were significantly related with shorter overall survival. CONCLUSIONS: Intra and extrahepatic cholangiocarcinomas behave differently on PET/CT, though no differences between both groups exist in its capacity to detect regional or distant disease. Metabolic parameters and levels of tumor markers seem to relate with tumor burden, impacting in prognosis.

Diagnosing neuroleukemiosis: is there a role for 18F-FDG-PET/CT? / Diagnosticando la neuroleucemiosis: ¿existe un papel para la PET/TC con 18F-FDG?

An imaging case is presented on a patient referred to our department for an 18F-FDG-PET/CT, as a paraneoplastic syndrome was suspected due to his clinical situation. He had a history of acute myeloid leukemia (AML) treated two years earlier, with sustained complete remission to date. 18F-FDG-PET/CT findings revealed hypermetabolism in almost all nerve roots, suggesting meningeal spread, consistent with the subsequent MRI findings. Cerebrospinal fluid (CSF) findings confirmed a leptomeningeal reactivation of AML. Although not many studies have evaluated the role of 18F-FDG-PET/CT in leukemia, it is a noninvasive tool for detecting extramedullary sites of disease and a good imaging alternative for those patients on whom an MRI cannot be performed (AU)

Presentamos el caso de un paciente remitido a nuestro servicio para la realización de una PET/TC con 18F-FDG por sospecha clínica de un síndrome paraneoplásico Entre sus antecedentes destacaba el de una leucemia mieloide aguda tratada 2 años antes y en remisión completa en los controles sucesivos. La PET/TC con 18F-FDG mostró hipermetabolismo en prácticamente todas las raíces nerviosas, apuntando a enfermedad meníngea diseminada, en concordancia con los hallazgos de la RM realizada posteriormente. El análisis del líquido cefalorraquídeo confirmó una reactivación leptomeníngea de la leucemia mieloide aguda. A pesar de los pocos estudios existentes sobre el papel de la PET/TC con 18F-FDG en la leucemia, es una herramienta no invasiva para localizar recidivas extramedulares de la enfermedad y una buena técnica de imagen alternativa para aquellos pacientes a los que no se les puede realizar una RM (AU)

18F-FDG PET/CT in the detection of a primary radiation-induced metastatic angiosarcoma / 18F-FDG PET/TC en la detección de angiosarcoma primario radioinducido metastásico

No disponible

Diagnosing neuroleukemiosis: Is there a role for 18F-FDG-PET/CT?

An imaging case is presented on a patient referred to our department for an 18F-FDG-PET/CT, as a paraneoplastic syndrome was suspected due to his clinical situation. He had a history of acute myeloid leukemia (AML) treated two years earlier, with sustained complete remission to date. 18F-FDG-PET/CT findings revealed hypermetabolism in almost all nerve roots, suggesting meningeal spread, consistent with the subsequent MRI findings. Cerebrospinal fluid (CSF) findings confirmed a leptomeningeal reactivation of AML. Although not many studies have evaluated the role of 18F-FDG-PET/CT in leukemia, it is a noninvasive tool for detecting extramedullary sites of disease and a good imaging alternative for those patients on whom an MRI cannot be performed.

Tomografía por emisión de positrones con 18F-FDG en oncología: principales indicaciones / 18F-FDG positron emission tomography in oncology: main indications

El desarrollo de la imagen molecular y funcional con nuevas técnicas de tomografía computarizada, resonancia magnética o tomografía por emisión de positrones (PET), entre otras, ha mejorado de forma muy significativa la detección de tumores, su estadificación, la monitorización de la respuesta al tratamiento y la detección de posibles recidivas. Además, la combinación de estas diferentes modalidades de imagen y el continuo desarrollo de radiofármacos para PET han permitido avanzar en el entendimiento y conocimiento de los diferentes procesos fisiopatológicos en el cáncer y, de este modo, poder ser más eficaces en su tratamiento, mejorando la calidad de vida de los pacientes y aumentado su supervivencia. La PET es una de las técnicas de imagen que más interés ha suscitado en los últimos años por su capacidad diagnóstica. Su habilidad para localizar anatómicamente los focos patológicos de actividad metabólica ha supuesto una revolución en la detección y estadificación de muchos tumores, ampliando, de forma exponencial, sus potenciales indicaciones no solo en oncología, sino también en otros campos como la cardiología, la neurología o las patologías inflamatorias e infecciosas (AU)

The development of molecular and functional imaging with new imaging techniques such as computed tomography, magnetic resonance imaging, and positron emission tomography (PET) among others, has greatly improved the detection of tumors, tumor staging, and the detection of possible recurrences. Furthermore, the combination of these different imaging modalities and the continual development of radiotracers for PET have advanced our understanding and knowledge of the different pathophysiological processes in cancer, thereby helping to make treatment more efficacious, improving patients’ quality of life, and increasing survival. PET is one of the imaging techniques that has attracted the most interest in recent years for its diagnostic capabilities. Its ability to anatomically locate pathologic foci of metabolic activity has revolutionized the detection and staging of many tumors, exponentially broadening its potential indications not only in oncology but also in other fields such as cardiology, neurology, and inflammatory and infectious diseases (AU)

18F-FDG positron emission tomography in oncology: main indications. / Tomografía por emisión de positrones con 18F-FDG en oncología: principales indicaciones.

The development of molecular and functional imaging with new imaging techniques such as computed tomography, magnetic resonance imaging, and positron emission tomography (PET) among others, has greatly improved the detection of tumors, tumor staging, and the detection of possible recurrences. Furthermore, the combination of these different imaging modalities and the continual development of radiotracers for PET have advanced our understanding and knowledge of the different pathophysiological processes in cancer, thereby helping to make treatment more efficacious, improving patients' quality of life, and increasing survival. PET is one of the imaging techniques that has attracted the most interest in recent years for its diagnostic capabilities. Its ability to anatomically locate pathologic foci of metabolic activity has revolutionized the detection and staging of many tumors, exponentially broadening its potential indications not only in oncology but also in other fields such as cardiology, neurology, and inflammatory and infectious diseases.

[Positron emission tomography-computed tomography in tumors of the locomotor apparatus]. / La tomografía por emisión de positrones asociada con la tomografía computarizada en tumores del aparato locomotor.

Positron emission tomography/computed tomography (PET/CT) is a hybrid imaging technique that combines the anatomic information from CT with the metabolic information acquired from PET after the administration of specific radiotracers, the most commonly used of which is F18-fluorodeoxyglucose (FDG). In oncology, this technique is based on the increased uptake of FDG by malignant lesions. In the locomotor apparatus, some uptake by bones and soft tissues is physiological or benign and this uptake must be differentiated from uptake by malignancies, whether primary or secondary. The most important limitations are active inflammatory or infectious processes, which are positive on PET images, and malignant lesions that are smaller than 1cm, cystic, necrotic, or low-grade, which are negative on PET images. PET/CT in the locomotor apparatus is especially useful for the detection of metastases from the most common tumors. It is also used for staging and monitoring the response to treatment of some hematological tumors like lymphoma, where it is fundamental to determine whether the bone marrow has been infiltrated, or myeloma. Lastly, although it is not yet an established indication, PET/CT is being increasingly used to study sarcomas, because it can provide additional information that can be useful for the characterization and grading of tumors, for guiding biopsies, for staging and re-staging, and for evaluating the response to neoadjuvant therapy as well as for evaluating new drugs in clinical trials.

La tomografía por emisión de positrones asociada con la tomografía computarizada en tumores del aparato locomotor / Positron emission tomography-computed tomography in tumors of the locomotor apparatus

La tomografía por emisión de positrones asociada con la tomografía computarizada (PET/TC) es una técnica de imagen híbrida que combina la información anatómica de la TC con la metabólica tras la administración de radiofármacos específicos, de los cuales el más usado es la 18F-fluordesoxiglucosa (FDG). La mayor captación de FDG de las lesiones malignas es la base para la aplicación de la técnica en oncología. En el aparato locomotor hay captaciones óseas y en partes blandas que son fisiológicas o benignas y que se deben diferenciar de las malignas, secundarias o primarias. Las limitaciones más importantes son los procesos inflamatorios o infecciosos activos (positivos en PET) y las lesiones de tamaño inferior a un centímetro, quísticas, necróticas o de bajo grado (negativos en PET). La PET/TC en el aparato locomotor permite especialmente la detección de metástasis de los tumores más frecuentes. También se utiliza en la estadificación y monitorización de la respuesta al tratamiento de algunos tumores hematológicos como el linfoma (donde la determinación de la infiltración de la médula ósea es fundamental) o el mieloma. Por último, aunque no de forma generalizada, es creciente el uso en sarcomas ya que puede aportar información adicional para la caracterización y gradación tumoral, la guía de biopsia, la estadificación y reestadificación, y la evaluación de la respuesta al tratamiento neoadyuvante y de nuevos fármacos en ensayos clínicos (AU)

Positron emission tomography/computed tomography (PET/CT) is a hybrid imaging technique that combines the anatomic information from CT with the metabolic information acquired from PET after the administration of specific radiotracers, the most commonly used of which is F18-fluorodeoxyglucose (FDG). In oncology, this technique is based on the increased uptake of FDG by malignant lesions. In the locomotor apparatus, some uptake by bones and soft tissues is physiological or benign and this uptake must be differentiated from uptake by malignancies, whether primary or secondary. The most important limitations are active inflammatory or infectious processes, which are positive on PET images, and malignant lesions that are smaller than 1cm, cystic, necrotic, or low-grade, which are negative on PET images. PET/CT in the locomotor apparatus is especially useful for the detection of metastases from the most common tumors. It is also used for staging and monitoring the response to treatment of some hematological tumors like lymphoma, where it is fundamental to determine whether the bone marrow has been infiltrated, or myeloma. Lastly, although it is not yet an established indication, PET/CT is being increasingly used to study sarcomas, because it can provide additional information that can be useful for the characterization and grading of tumors, for guiding biopsies, for staging and re-staging, and for evaluating the response to neoadjuvant therapy as well as for evaluating new drugs in clinical trials (AU)

Utilidad de la PET-TC en la valoración de la respuesta precoz al tratamiento en el linfoma B difuso de celula grande. Resultados preliminares / Utility of the PET-CT in the evaluation of early response to treatment in the diffuse large B-cell lymphoma. Preliminary results

Objetivo. Valorar la utilidad de la PET-TC con FDG tras los primeros ciclos de quimioterapia en la predicción de la respuesta al tratamiento en pacientes con linfoma B difuso de célula grande. Metodologia. Se incluyeron 20 pacientes (edad media: 48), 16 en la estadificación inicial y 4 por recidiva. La PET-TC se realizó en tres tiempos: 1) Basal, 2) Tras el primer-tercer ciclo (valoración de respuesta precoz), y 3) Al finalizar el tratamiento (valoración de respuesta final). Los hallazgos de la valoración precoz fueron correlacionados con la valoración final y el seguimiento. La valoración de la respuesta se estableció según la disminución de la captación de las lesiones (SUVmax). En la valoración precoz el indicador de buena respuesta (IBR) fue la reducción del SUVmax > 50% o la desaparición. Al final del tratamiento se determinó la respuesta metabólica completa (RMC) en ausencia de focos. El seguimiento fue superior a los 19 meses, estableciendo progresión/recidiva o sin evidencia de enfermedad (SEE). Resultados. La valoración precoz fue IBR en 16/16 pacientes de estadificación inicial (100%) y en 2/4 de recidiva (50%). Al final del tratamiento, en el primer grupo 14/16 pacientes con IBR consiguieron RMC y 1/16 RMP; 14 continuaron SEE y uno recidivó. En el segundo grupo 2/2 pacientes con IBR consiguieron RMC; uno continuó SEE y otro recidivó. Conclusion. La PET-TC tras los primeros ciclos de quimioterapia es útil para monitorizar el tratamiento debido a su elevado valor predictivo negativo (87,5%), modificando la terapia precozmente en los no respondedores(AU)

Objective. To assess the role of FDG-PET/CT performed after the first cycles of chemotherapy in the prediction of response to treatment in patients with diffuse large B-cell lymphoma. Methods. Twenty patients (mean age: 48 years) were included, 16 initial staging and 4 relapse. All patients underwent PET/CT at 3 times: 1) Baseline, 2) After 1-3 cycles of chemotherapy (early response assessment), and 3) End of treatment (evaluation of final response). Early PET/CT findings were correlated to the end-treatment PET/CT and follow-up. The evaluation of the response was established according to the decrease in uptake of the lesions (SUVmax). In the early assessment, a good response indicator (GRI) was obtained when the lesion disappeared or had more than 50% reduction in SUVmax. At the end of the treatment, a complete metabolic response (CMR) was determined in negative PET scans. Follow-up was superior to 19 months and final outcome was established as progression/relapse or no evidence of disease (NED). Results. At the early treatment evaluation, 16/16 patients of initial staging (100%) and 2/4 of relapse (50%) achieved GRI. At the end of treatment evaluation, 14/16 patients of initial staging with GRI achieved CMR and 1/16 PMR: 14 were alive with NED in the follow-up while 1 relapsed. In the second group, 2/2 patients with GRI achieved CMR (100%): 1 continued with NED in the follow-up and another relapsed. Conclusion. FDG-PET/CT after the first cycles of chemotherapy is useful to monitor treatment due to its high negative predictive value (87.5%), using it to modify treatment early in the non-responders(AU)

Utility of the PET-CT in the evaluation of early response to treatment in the diffuse large B-cell lymphoma. Preliminary results.

OBJECTIVE: To assess the role of FDG-PET/CT performed after the first cycles of chemotherapy in the prediction of response to treatment in patients with diffuse large B-cell lymphoma. METHODS: Twenty patients (mean age: 48 years) were included, 16 initial staging and 4 relapse. All patients underwent PET/CT at 3 times: 1) Baseline, 2) After 1-3 cycles of chemotherapy (early response assessment), and 3) End of treatment (evaluation of final response). Early PET/CT findings were correlated to the end-treatment PET/CT and follow-up. The evaluation of the response was established according to the decrease in uptake of the lesions (SUVmax). In the early assessment, a good response indicator (GRI) was obtained when the lesion disappeared or had more than 50% reduction in SUVmax. At the end of the treatment, a complete metabolic response (CMR) was determined in negative PET scans. Follow-up was superior to 19 months and final outcome was established as progression/relapse or no evidence of disease (NED). RESULTS: At the early treatment evaluation, 16/16 patients of initial staging (100%) and 2/4 of relapse (50%) achieved GRI. At the end of treatment evaluation, 14/16 patients of initial staging with GRI achieved CMR and 1/16 PMR: 14 were alive with NED in the follow-up while 1 relapsed. In the second group, 2/2 patients with GRI achieved CMR (100%): 1 continued with NED in the follow-up and another relapsed. CONCLUSION: FDG-PET/CT after the first cycles of chemotherapy is useful to monitor treatment due to its high negative predictive value (87.5%), using it to modify treatment early in the non-responders.

[Impact of (18)F-FDG PET/CT on the therapeutic management in the initial staging of the esophageal cancer]. / Impacto clínico de la PET/TAC con (18)F-FDG en el manejo terapéutico de pacientes con diagnóstico inicial de cáncer de esófago.

OBJECTIVE: The incidence of esophageal cancer has increased considerably over recent years, it now being the 6th most frequent cause of cancer-related death. Our study has aimed to compare the clinical value of PET/CT and CT scan in the initial staging of patients with esophageal cancer. MATERIAL AND METHODS: Fifty nine patients (6 women) diagnosed of esophageal cancer were assessed retrospectively. All patients underwent diagnostic CT scan and PET/CT for initial staging within 3 to 15 days following clinical diagnosis. RESULTS: PET/CT showed intracellular (18)F-FDG entrapment having pathological significance in all the tumors (100%), signs of locoregional lymph node infiltration (N1) in 34 and a total of 19 lesions consistent with metastasis (M1) in 14 patients (23.72%). The CT scan detected malignancy in 57 patients (96.6%), abnormal lymph node in 32 patients and 17 N1 in 12 patients (20.33%). In three cases, CT- PET detected synchronous esophageal lesion in staging studies for other neoplastic processes (lung and ear-nose-throat). CONCLUSION: PET/CT showed a higher detection rate of primary malignant lesions, abnormal lymph nodes and distant metastases. A change in stage was only observed in two patients.

Impacto clínico de la PET/TAC con 18F-FDG en el manejo terapéutico de pacientes con diagnóstico inicial de cáncer de esófago / Impact of 18F-FDG PET/CT on the therapeutic management in the initial staging of the esophageal cancer

Objetivos: La incidencia del carcinoma de esófago se ha incrementado considerablemente en los últimos años, siendo en la actualidad la sexta causa más frecuente de muerte por cáncer. El objetivo de nuestro estudio es comparar la utilidad de la PET/TAC con 18F-FDG y la TAC en la estadificación inicial en pacientes con carcinoma esofágico. Material y método: Se han valorado de manera retrospectiva 59 pacientes (6 mujeres) diagnosticados de una neoplasia esofágica. A todos los pacientes se les realizó una TAC y una PET/TAC de estadificación inicial entre 3 y 15 días después del diagnóstico. Resultados: La PET/TAC mostró el atrapamiento intracelular de 18F-FDG de significación patológica en todos los tumores (100%), signos de infiltración ganglionar locorregional (N1) en 34 y un total de 19 lesiones compatibles con metástasis (M1) en 14 pacientes (23,72%). La TAC mostró la lesión tumoral en 57 pacientes (96,6%), infiltración ganglionar en 32 pacientes y 17 M1 en 12 pacientes (20,33%). En tres casos la PET/ TAC detectó la lesión esofágica de manera sincrónica en estudios de estadificación de otros procesos neoplásicos (pulmón y área otorrinolaringológica). Conclusión: La PET/TAC mostró una mayor detección de lesiones tumorales primarias, así como adenopatías infiltradas y metástasis a distancia. Sólo se observó un cambio de estadificación en dos pacientes(AU)

Objective: The incidence of esophageal cancer has increased considerably over recent years, it now being the 6th most frequent cause of cancer-related death. Our study has aimed to compare the clinical value of PET/CT and CT scan in the initial staging of patients with esophageal cancer. Material and methods: Fifty nine patients (6 women) diagnosed of esophageal cancer were assessed retrospectively. All patients underwent diagnostic CT scan and PET/CT for initial staging within 3 to 15 days following clinical diagnosis. Results: PET/CT showed intracellular 18F-FDG entrapment having pathological significance in all the tumors (100%), signs of locoregional lymph node infiltration (N1) in 34 and a total of 19 lesions consistent with metastasis (M1) in 14 patients (23.72%). The CT scan detected malignancy in 57 patients (96.6%), abnormal lymph node in 32 patients and 17 N1 in 12 patients (20.33%). In three cases, CT- PET detected synchronous esophageal lesion in staging studies for other neoplastic processes (lung and ear-nose-throat). Conclusion: PET/CT showed a higher detection rate of primary malignant lesions, abnormal lymph nodes and distant metastases. A change in stage was only observed in two patients(AU)

Metástasis suprarrenal metacrónica de cáncer de pulmón no microcítico en paciente con adenomas adrenales bilaterales / No disponible

No disponible

[Influence of radioactive concentration and storage time on radiochemical purity of 18F-FDG]. / Influencia de la concentración radiactiva y el tiempo de almacenamiento sobre la pureza radioquímica de la 2-[18F]-fluoro-2-desoxi-D-glucosa.

OBJECTIVE: To study the influence of the 18F-FDG radioactive concentration and the usual greatest storage time of the radiopharmaceutical at the Radiopharmacy Unit (RU) over its radiochemical purity. MATERIAL AND METHODS: Thirty 18F-FDG preparations coming from different batches were studied. The radiochemical purity was determined at the RU by means of TLC to saline-diluted (1:10) and undiluted samples of each preparation, in the early 30 minutes since its arrival and 5 hours later. The radiochemical purity of the original 18F-FDG was determined at the PET radiopharmaceutical producer Laboratory (PETL) by means of HPLC in the early hour since the 18F-FDG dispensing. RESULTS: The increase of 18F-Fluoride found in the (5 h-30 min) period was significantly greater in the samples without diluting than in the diluted ones (p < 0.0001). We found a significant correlation between the percent of this increase of 18F-Fluoride (y) and the radioactive concentration of the 18F-FDG (x): y = 0.00061x + 0.1759 (R2 = 0.198; p < 0.0005). The percent of 18F-Fluoride determined at the RU was significantly higher than the percent of 18F-Fluoride determined at the PETL (p < 0.0001). A significant correlation between the differences of the percent of 18F-Fluoride determined by TLC and HPLC (y) and the radioactive concentration (x) was found: y = 0.0139x + 0.3146 (R2 = 0.196; p = 0.016). A significant correlation among the differences of percent 18F-Fluoride determined by TLC and HPLC ([%F] RU - [%F] PETL), the radioactive concentration (RC) and the time since the radiopharmaceutical dispensing (t) was found: [%F] RU - [%F] PETL = 0.01159*RC (mCi/mL) + 0.250*t (h) - 0.01903 (R2 = 0.226; p < 0.014). CONCLUSIONS: The stability of the 18F-FDG preparations with time increases when diminishing its concentration. We recommended the dilution of these preparations with physiological saline solution.

Influencia de la concentración radiactiva y el tiempo de almacenamiento sobre la pureza radioquímica de la 2- (18F) -fluoro-2-desoxi-D-glucosa / Influence of radioactive concentration and storage time on radiochemical purity of 18F-FDG

Objetivo. Determinar la influencia de la concentración radiactiva de la 2-[ 18F]-fluoro-2-desoxi-D-glucosa ( 18F-FDG) y el tiempo de almacenamiento máximo habitual del radiofármaco en la Unidad de Radiofarmacia (UR) sobre su pureza radioquímica. Material y métodos. Se estudiaron 30 preparaciones de 18F-FDG procedentes de lotes diferentes. Se determinó la pureza radioquímica en la UR dentro de los 30 minutos siguientes a su recepción y a las 5 horas mediante cromatografía en capa fina (TLC) a las muestras diluidas con suero salino fisiológico (1:10) y sin diluir. La pureza radioquímica también se determinó en el Laboratorio de radiofármacos PET (LPET) dentro de la primera hora posterior a su dispensación por cromatografía líquida a alta presión (HPLC). Resultados. El aumento de porcentaje de 18F-Fluoruro a las 5 horas fue significativamente mayor en las muestras sin diluir que en las diluidas (p < 0,0001), encontrándose una correlación significativa entre el aumento de porcentaje de 18F-Fluoruro con el tiempo (y) respecto a la concentración radiactiva (x): y = 0,0061x + 0,1759 (R 2 = 0,1977; p < 0,0005). El porcentaje de 18F-Fluoruro determinado en la UR fue significativamente mayor que el determinado en el LPET (p < 0,0001), obteniéndose una correlación significativa entre el aumento de porcentaje de 18F-Fluoruro (y) y la concentración radiactiva (x): y = 0,0139x + 0,3146 (R 2 = 0,196; p = 0,016). Se obtuvo una correlación significativa entre este aumento ([ %F] UR ­ [ %F] LPET), la concentración radiactiva (CR) y el tiempo desde la dispensación (t): [ %F] UR ­ [ %F] LPET = 0,01159*CR (mCi/ml) + 0,250*t (h) ­ 0,01903 (R 2 = 0,226; p = 0,014). Conclusiones. La estabilidad de las preparaciones de 18F-FDG aumenta al disminuir su concentración. Aconsejamos la dilución de estas preparaciones con solución salina fisiológica

Objective. To study the influence of the 18F-FDG radioactive concentration and the usual greatest storage time of the radiopharmaceutical at the Radiopharmacy Unit (RU) over its radiochemical purity. Material and methods. Thirty 18F-FDG preparations coming from different batches were studied. The radiochemical purity was determined at the RU by means of TLC to saline-diluted (1:10) and undiluted samples of each preparation, in the early 30 minutes since its arrival and 5 hours later. The radiochemical purity of the original 18F-FDG was determined at the PET radiopharmaceutical producer Laboratory (PETL) by means of HPLC in the early hour since the 18F-FDG dispensing. Results. The increase of 18F-Fluoride found in the (5 h-30 min) period was significantly greater in the samples without diluting than in the diluted ones (p < 0,0001). We found a significant correlation between the percent of this increase of 18F-Fluoride (y) and the radioactive concentration of the 18F-FDG (x): y = 0,00061x + 0,1759 (R 2 = 0,198; p < 0,0005). The percent of 18F-Fluoride determined at the RU was significantly higher than the percent of 18F-Fluoride determined at the PETL (p < 0,0001). A significant correlation between the differences of the percent of 18F-Fluoride determined by TLC and HPLC (y) and the radioactive concentration (x) was found: y = 0,0139x + 0,3146 (R 2 = 0,196; p = 0,016). A significant correlation among the differences of percent 18F-Fluoride determined by TLC and HPLC ([ %F] RU ­ [ %F] PETL), the radioactive concentration (RC) and the time since the radiopharmaceutical dispensing (t) was found: [ %F] RU ­ [ %F] PETL = 0,01159*RC (mCi/mL) + 0,250*t (h) ­ 0,01903 (R 2 = 0,226; p < 0,014). Conclusions. The stability of the 18F-FDG preparations with time increases when diminishing its concentration. We recommended the dilution of these preparations with physiological saline solution