The effects of molar activity on [18F]FDOPA uptake in patients with neuroendocrine tumors.

BACKGROUND: 6-[18F]fluoro-L-3,4-dihydroxyphenyl alanine ([18F]FDOPA) is a commonly used PET tracer for the detection and staging of neuroendocrine tumors. In neuroendocrine tumors, [18F]FDOPA is decarboxylated to [18F]dopamine via the enzyme amino acid decarboxylase (AADC), leading to increased uptake when there is increased AADC activity. Recently, in our hospital, a new GMP compliant multi-dose production of [18F]FDOPA has been developed, [18F]FDOPA-H, resulting in a higher activity yield, improved molar activity and a lower administered mass than the conventional method ([18F]FDOPA-L). AIMS: This study aimed to investigate whether the difference in molar activity affects the [18F]FDOPA uptake at physiological sites and in tumor lesions, in patients with NET. It was anticipated that the specific uptake of [18F]FDOPA-H would be equal to or higher than [18F]FDOPA-L. METHODS: We retrospectively analyzed 49 patients with pathologically confirmed NETs and stable disease who underwent PET scanning using both [18F]FDOPA-H and [18F]FDOPA-L within a time span of 5 years. A total of 98 [18F]FDOPA scans (49 [18F]FDOPA-L and 49 [18F]FDOPA-H with average molar activities of 8 and 107 GBq/mmol) were analyzed. The SUVmean was calculated for physiological organ uptake and SUVmax for tumor lesions in both groups for comparison, and separately in subjects with low tumor load (1-2 lesions) and higher tumor load (3-10 lesions). RESULTS: Comparable or slightly higher uptake was demonstrated in various physiological uptake sites in subjects scanned with [18F]FDOPA-H compared to [18F]FDOPA-L, with large overlap being present in the interquartile ranges. Tumor uptake was slightly higher in the [18F]FDOPA-H group with 3-10 lesion (SUVmax 6.83 vs. 5.19, p < 0.001). In the other groups, no significant differences were seen between H and L. CONCLUSION: [18F]FDOPA-H provides a higher activity yield, offering the possibility to scan more patients with one single production. Minor differences were observed in SUV's, with slight increases in uptake of [18F]FDOPA-H in comparison to [18F]FDOPA-L. This finding is not a concern for clinical practice, but could be of importance when quantifying follow-up scans while introducing new production methods with a higher molar activity of [18F]FDOPA.

Evaluación clínica de la correlación entre el volumen prostático, el flujo urinario, la edad y el residuo posciccional en 250 pacientes con trastornos miccionales / Clinical evaluation of the correlation between prostatic volume (PV), peak flow rate (PFR), age, and post void residual urine (PVR) in 250 patients with lower urinary tract symptoms (LUTS)

Objetivo: Interpretar clínicamente los resultados de la correlación existente entre los parámetros objetivos que utilizamos en la evaluación de pacientes portadores de síntomas urinarios, en relación con la presencia de HPB. Material y métodos: se evaluó la variación de las relaciones entre el tscto rectal, la flujometría, el volumen prostático, la edad y el residuo, en 250 pacientes con síntomas urinarios. Resultados: El tamaño de la próstata aumentó con la edad, con un brusco incremento en la década de los 50 años (p<0,01), el Qmax fue menor (p<0,01) y el residuo fue más frecuente (p<0,01) cuanto más grande ( o más pesada) fue la próstata; del mismo modo se relacionó el menor flujo con la mayor prevalencia de residuo (p<0,01). mientras que la edad no demostró una influencia significativa (p>0.05) para condicionar estos resultados. Conclusión En los pacientes que consultan por trastornos miccionales en asociación con HPB clínicamente demostrable se observa una correlación estadísticamente significativa entre el mayor tamaño de la misma, un flujo bajo, menor de 10ml/s y la presencia de residuo posmicional clínicamente significativo, independientemente de la edad