RESUMEN
Imaging with positron emission tomography (PET) and (68)Ga-DOTA peptides is a promising method in intracranial meningiomas. Especially in recurrent meningioma discrimination between scar tissue and recurrent tumor tissue in magnetic resonance imaging (MRI) is often difficult. We report the first case of (68)Ga-DOTATATE-PET/computed tomography (PET/CT) imaging in recurrent spinal meningioma. A 64-year-old Caucasian female patient was referred to our department with the second recurrence of thoracic meningothelial meningioma. In MRI, it remained unclear if the multiple enhancements seen represented scar tissue or vital tumor. We offered (68)Ga-DOTATATE-PET/CT imaging in order to evaluate the best strategy. (68)Ga-DOTATATE-PET/CT imaging revealed strong tracer uptake in parts of the lesions. The pattern did distinctly differ from MRI enhancement. Multiple biopsies were performed in the PET-positive and PET-negative regions. Histological results confirmed the prediction of (68)Ga-DOTATATE-PET with vital tumor in PET-positive regions and scar tissue in PET-negative regions. Differentiating scar tissue from tumor can be challenging in recurrent spinal meningioma with MRI alone. In the presented case, (68)Ga-DOTATATE-PET imaging was able to differentiate noninvasively between tumor and scar.
RESUMEN
A small positron-generating branch in 90-Yttrium ((90)Y) decay enables post-therapy dose assessment in liver cancer radioembolization treatment. The aim of this study was to validate clinical (90)Y positron emission tomography (PET) quantification, focusing on scanner linearity as well as acquisition and reconstruction parameter impact on scanner calibration. Data from three dedicated phantom studies (activity range: 55.2 MBq-2.1 GBq) carried out on a Philips Gemini TF 16 PET/CT scanner were analyzed after reconstruction with up to 361 parameter configurations. For activities above 200 MBq, scanner linearity could be confirmed with relative error margins 4%. An acquisition-time-normalized calibration factor of 1.04 MBq·s/CNTS was determined for the employed scanner. Stable activity convergence was found in hot phantom regions with relative differences in summed image intensities between -3.6% and +2.4%. Absolute differences in background noise artifacts between - 79.9% and + 350% were observed. Quantitative accuracy was dominated by subset size selection in the reconstruction. Using adequate segmentation and optimized acquisition parameters, the average activity recovery error induced by the axial scanner sensitivity profile was reduced to +2.4%±3.4% (mean ± standard deviation). We conclude that post-therapy dose assessment in (90)Y PET can be improved using adapted parameter setups.