PET/CT calibration for post-treatment standard body scan acquisition with yttrium-90 resin micro-SPHERES.

INTRODUCTION: Among the objectives in treatments with yttrium-90 spheres, is to demonstrate that the tumoricidal dose is achieved and that hepatotoxic doses are avoided, as well as that there is no extrahepatic deposition. MATERIAL AND METHODS: We use different amounts of yttrium-90 resin micro-spheres and a NEMA NU2-2007 phantom to check if the scanner maintains a response that allows real dosimetric calculations. RESULTS: The Gemini tomograph responds linearly in a wide range of activities with R2 = 0.9983. CONCLUSION: The detection capacity of the PET equipment allows us to carry out standard body studies with dosimetric purposes with times of five minutes per bed. It also make possible to verify the absence of extrahepatic deposition of significant amounts of yttrium 90 spheres.

Utility of low dose (18)F-FDG PET-CT in patients with suspected colorectal carcinoma recurrence in conventional diagnostic methods.

OBJECTIVE: To evaluate the efficacy of (18)F-FDG PET-CT in the diagnosis of recurrence of colorectal cancer (CRC) in patients with elevated values of carcinoembryonic antigen (CEA) and/or signs of recurrence in the multidetector CT (MDCT), and to demonstrate that good results can be obtained applying the ALARA principles. MATERIAL AND METHODS: A retrospective study of 54 patients with suspected CRC, who underwent an (18)F-FDG PET-CT, administering a mean dose of 222 MBq (6 mCi) of (18)F-FDG, from 07/2007 to 01/2011 was carried out. Seven patients were excluded, thus studying 47 (27 males, 20 females, mean age 63 years). Recurrence was confirmed by histopathology study in 14 cases and by clinical evolution in 33. The patients were divided into 4 groups. A: patients with elevation of CEA and suspected recurrence in the MDCT. B: elevation of CEA, without suspicious lesions in the MDCT. C: normal levels of CEA and positive MDCT. D: normal levels of CEA and uncertain MDCT. RESULTS: We found sensitivity, specificity, PPV, NPV and overall accuracy of 91%, 69%, 89%, 75% and 85% respectively. For group A, we found 100% sensitivity, in group B, 75% sensitivity with 100% specificity%, for C, sensitivity was 89% with 71% specificity. Finally, in group D, sensitivity was 100% and specificity 60%, respectively. CONCLUSION: Applying a low dose, the (18)F-FDG PET-CT has high diagnostic performance in patients with suspicion of CRC, approaching in a higher grade the ALARA criteria.

[Thymic uptake of 18FFDG following radioiodine ablation therapy]. / Captación de 18F-FDG en timo tras terapia ablativa de restos tiroideos con 131I.

We report the case of a 47 year-old woman with a history of non-Hodgkin's lymphoma. During the course of her disease, we performed various (18F)FDG PET/CT that identified several significant incidental findings. First, we incidentally identified a hypermetabolic nodule in the left thyroid lobe, whose final diagnosis was differentiated thyroid carcinoma. Second, metabolic activity was visualized in the thymus secondary to ablative treatment with radioiodine. This uptake disappeared in subsequent studies. Several papers have reported thymic rebound following chemotherapy but we have found only one case report of (18F)FDG uptake after radioiodine treatment. On the other hand, this case is of interest because it supports the benefit of studying the hypermetabolic thyroid nodules incidentally detected on the PET/CT performed for other reasons.

[Utility of diuretic renography in the detection of an enteroureteral fistula]. / Utilidad del renograma diurético en la detección de una fístula enteroureteral.

After a 2-year-old male with left impairment underwent surgery for a left vesicoureteral stenosis, his renal function was followed up by means of dynamic renal scintigraphy with 99mTc-DTPA. Incidental radiotracer accumulation was observed in left hemiabdomen tracing the descending and sigmoid colon. A vesico-colonic fistula was suspected. However, ultrasonography and cystography studies showed no presence of a vesico-enteric fistula. Because the patient persisted without symptoms, an expectant approach was adopted. One year later, he began to suffer watery diarrhoea episodes. 99mTc-DTPA renography was again performed to re-evaluated renal function and explore presence of urinary-enteric fistula. Diuretic renography demonstrated the presence of a vesical leak to sigmoid gut, which was confirmed by recovery of fecal matter from the patient. Both isotopic renograms evidenced the presence of uretero-sigmoid fistula, an uncommon postsurgical that was not detected by cystography, ultrasonography or RMN. The patient subsequently underwent surgery for fistula repair.