Positron emission tomography-computed tomography evaluation for recurrent differentiated thyroid carcinoma.

OBJECTIVES: Recurrence is observed in 15-20% of patients under surveillance following treatment of differentiated thyroid cancer (DTC). However, due to cell dedifferentiation, the recurrence may be iodine-negative, thereby compromising detection. For this reason, new methods of exploration are indispensable to enable localization of such recurrences. The purpose of this work is to review the contribution of positron emission tomography-computed tomography (PET-CT) in the exploration of iodine-negative recurrent DTC. METHOD: A comprehensive review and discussion of the medical literature was carried out. RESULTS: Depending on the report, the sensitivity of PET-CT ranged from 70% to 85%, with up to 90% specificity. However, the large number of false negatives, which can reach 40%, is the disadvantage of this examination. PET-CT results lead to change in the therapeutic strategy in approximately 50% of patients with isolated raised serum thyroglobulin levels, and surgical exploration of a precise anatomical area in the neck. CONCLUSION: As post-treatment recurrence of a DTC can affect patient survival, a thorough diagnostic work-up is required in these cases. Where thyroglobulin levels are elevated with no uptake on 131-iodine scans, PET-CT can be a useful complementary exploration, especially for localizing the site of recurrence.

Assessment of liver metastases from colorectal adenocarcinoma following chemotherapy: SPIO-MRI versus FDG-PET/CT.

PURPOSE: This study compared superparamagnetic iron-oxide-enhanced magnetic resonance imaging (SPIO-MRI) and combined fluorodeoxyglucose positron emission tomography and computed tomography (FDG-PET/CT) in evaluating liver metastases from colorectal adenocarcinoma following chemotherapy. MATERIALS AND METHODS: Nineteen patients were included in this retrospective study. SPIO-MRI and PET/CT results were compared with surgery, intraoperative ultrasound and pathology results in 11 patients and with the follow-up in eight patients. RESULTS: SPIO-MRI and PET/CT identified 125 and 71 metastases, respectively. False negative lesions were 11 for SPIO-MRI and 65 for PET/CT. In the whole study population, the per-lesion analysis of SPIO-MRI and PET/CT showed a sensitivity of 92% and 52% (p<0.001) and the per-segment analysis a sensitivity of 99% and 79% (p<0.001), respectively. In patients who underwent surgery, the per-lesion analysis of SPIO-MRI and PET/CT showed a sensitivity of 85% and 58% (p<0.05) and the per-segment analysis a sensitivity of 97% and 63% (p<0.05), respectively. In patients who underwent follow-up, the per-lesion analysis of SPIO-MRI and PET/CT showed a sensitivity of 97% and 47% (p<0.001) and the per-segment analysis a sensitivity of 100% and 63% (p<0.007), respectively. For lesions ≥15 and <30 mm and for lesions <15 mm, SPIO-MRI demonstrated a higher sensitivity than PET/CT (p<0.001). CONCLUSIONS: SPIO-MRI appears superior to PET/CT in evaluating liver metastases from colorectal adenocarcinoma following chemotherapy.

Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: a preliminary study.

The aim of this preliminary study was to evaluate the accuracy of left and right ventricular output computed from a semi-automatic processing of tomographic radionuclide ventriculography data (TRVG) in comparison with the conventional thermodilution method. Twenty patients with various heart diseases were prospectively included in the study. Thermodilution and TRVG acquisitions were carried out on the same day for all patients. Analysis of gated blood pool slices was performed using a watershed-based segmentation algorithm. Right and left ventricular output measured by TRVG correlated well with the measurements obtained with thermodilution (r = 0.94 and 0.91 with SEE = 0.38 and 0.46 l/min, respectively, P < 0.001). The limits of agreement for TRVG and thermodilution measurements were -0.78-1.20 l/min for the left ventricle and -0.34-1.16 l/min for the right ventricle. No significant difference was found between the results of TRVG and thermodilution with respect to left ventricular output (P = 0.09). A small but significant difference was found between right ventricular output measured by TRVG and both left ventricular output measured by TRVG (mean difference = 0.17 l/min, P = 0.04) and thermodilution-derived cardiac output (mean difference = 0.41 l/min, P = 0.0001). It is concluded that the watershed-based semi-automatic segmentation of TRVG slices provides non-invasive measurements of right and left ventricular output and stroke volumes at equilibrium, in routine clinical settings. Further studies are necessary to check whether the accuracy of these measurements is good enough to permit correct assessment of intracardiac shunts.