Predictors Of Positivity Of [F-18]F-Choline PET-CT In Prostate Cancer Recurrence. Preliminary Results

EP-173 Aim/Introduction: To analyze the validity of [18F]F-Choline PET-CT results in prostate cancer recurrence in our daily practice, based on theoretical cut-off points of prostatespecific antigen (PSA), its kinetic, and PSA doubling time (PSADT), to identify predictors of positivity and modify the indication criteria. Materials and Methods: Prior to the validity analysis, a descriptive, prospective analysis of consecutive patients with prostate cancer treated with curative intent by radical prostatectomy (RP) or radiotherapy (RT), who underwent PET-CT scan with recurrence criteria: PSA =1 or PSA 0.4-1 with PSADT Nadir + 2 after RT, was performed. Results: From April to December 2019, 69 patients were included, 40 were treated with RP (58%) and 29 with RT (42%). In 45 patients (65%) PET-CT was able to identify recurrence of the disease (positive PET) and in 24 it was not (negative PET). Of patients treated with RP, 82, 5% (33/40) had PSA>1, and of those, 61% were positive PET. 17, 5% (7/40) had PSA6months (28/69), in 71% if PSADT6 months, in 61% and 92% if PSADT<6 months and in 77% and 100% if PSADT<3 months. Conclusion: Preliminarily and awaiting validation, it seems that PSA>1 after RP or Nadir +2 after RT is an indicator of PET-CT. There seems to be a tendency that shows that PSA<1 after RP is an indicator of PET-CT if PSADT<3 months. PSADT <3 or <6 months could be the best predictor of positivity of PET-CT with [18F]F-Choline in recurrent prostate cancer

Correlation between the findings in the first post-transplantation Renogram and the allograft renal function twelve months after surgery

EP-061 Aim/Introduction: To study the correlation between findings in the first renogram post-trasplantation, and the evolution of the renal function of the graft twelve months after surgery. Materials and Methods: 20-minute duration renogram with [99mTc]Tc-MAG3, performed in the first 72 hours post-kidney transplantation, of patients attended at the Nuclear Medicine Service between January-December of 2018 are reviewed, extracting: a) the concentration angle (CA) that measures the inclination of the ascent section of the concentration phase with respect to the vertical axis (cutoff thershold <40° vs =40°); b) the time, in minutes (Tmax), at which the maximum concentration occurs (<10 vs =10min); and c) the percentage of cortical retention (CR) at the end of the study (<80% vs =80%). These 3 parameters are correlated with renal function at 12 months post-transplantation, through the need or not of dialysis. Results: A total of 62 renograms were obtained, excluding 7 due to death as a result of intercurrent diseases and 2 due to vascular complications and graft loss, before the first year after surgery. 53 patients, 15 female and 38 male, aged between 20-80 years, were included in the analysis. Functional failure (dialysis) of the graft one year after the transplantation ocurred in 15% (8/53). In patients with CA =40° the probability of failure was 28% (5/18) and in CA <40° 8.6% (3/35), with relative risk (RR) of 3.2. 7/34 (20, 6%) patients incluided in the group with Tmax =10 min were on dialysis one-year after, unlike just 1/19 (5, 3%) if Tmax<10min (RR 3, 8). Among the 37 patients with CR =80%, 8/37 (22%) were dialyzed one year after, while none of the 16 in the group of patients with CR <80% (0% probability if CR <80%). The matching of parameteres CA =40°, Tmax =10 min and CR =80% together do not improve the prediction of dialysis one year after (27%, 5/18). Conclusion: 1. Renogram parameters 72 hours post-transplantation, such as concentration phase angle =40°, time at maximun concentration =10min and percentage of cortical retention =80%, allow recognize a group of patients with greater probability of needing dialysis in the first year after surgery, but they do not are capable of indentify in which specific patients it will occur. 2. The parameter that best predicts the viability of the graft is cortical retention <80%

Analysis of results of effective dose estimation obtained from RADAR 2017 dose assessment model for nuclear medicine procedures

EP-296 Aim/Introduction: To analyze the results of effective dose (E) estimation of the most frequent procedures using photon emitters in Nuclear Medicine, obtained from RADAR 2017 dose assessment model. To compare these results with those obtained from ICRP 128 (2015) recommendations, and to assess how using each dose assessment model can change E results. Materials and Methods: E estimation data was collected from photon emitter procedures performed during the last year in our department, obtained from RADAR 2017 dose estimation model for age groups: = 1 year old; >1-5 years old ; >5- 10 years old, >10- 15 years old and adults. Injected activity was the one recommended by international guidelines and EANM Pediatric and Dosimetry Committees. Hybrid exams (SPECT / CT) and procedures for which there is no RADAR 2017 dosimetry estimation were excluded. Results for (E) were compared with those obtained by using ICRP 128 (2015) recommendations. Results: With RADAR 2017 dose evaluation model we obtained a lower mean value of E on most of the procedures that were analyzed, being significantly lower for Renogram, Renal scintigraphy on >10-15 years old, Thyroid scintigraphy, Meckel’s scan and Bone Scan (0.12 to 1.16 mSv, 25% to 67%). Brain perfusion and Renal scintigraphy on ages under 10 obtained a significantly greater difference for E (0.33 to 2.85 mSv, 26% to 29%). Conclusion: These results are an updated collection of estimated E values for photon-emitting radiopharmaceuticals commonly used in Nuclear Medicine, considering RADAR 2017 dose assessment model compared to ICRP 128) recommendations. Methodological changes on estimation lead to lower E for most of diagnostic procedures using photon emitters, this is of special interest for patients undergoing repeated ionizing radiation (dosimetry history)