Simultaneous 18F- FDG PET/MRI in Autoimmune Limbic Encephalitis.

Limbic encephalitis is an autoimmune disorder characterized by inflammation of the brain with rapidly progressing dementia which requires definitive neurological evaluation. We describe both clinical as well as imaging findings in a case of limbic encephalitis using positron emission tomography/magnetic resonance imaging.

Effect of Combined 68Ga-PSMAHBED-CC Uptake Pattern and Multiparametric MRI Derived With Simultaneous PET/MRI in the Diagnosis of Primary Prostate Cancer: Initial Experience.

OBJECTIVE: The purpose of this study is to assess whether temporal changes in 68Ga-prostate-specific membrane antigen (PSMA)-HBED-CC uptake and multiparametric MRI parameters derived using PET/MRI can aid in characterization of benign and malignant prostate lesions. MATERIALS AND METHODS: Thirty-five men with 29 malignant and six benign prostate lesions undergoing complete clinical workup including histologic analysis were enrolled for this retrospective study. All had undergone simultaneous whole-body 68Ga-PSMAHBED-CC PET/MRI. Prostate Imaging Reporting and Data System version 2 (PI-RADSv2) assessment was made using a 5-point scale showing the likelihood of cancer with the combination of multiparametric MRI findings. Gallium-68-PSMA uptake was recorded at two time points: early (7 minutes) and delayed (54 minutes), adopting a copy-and-paste function of the ROI defined on MR images. ROC curve analysis was performed to test the diagnostic accuracy of early versus delayed PSMA uptake (measured as maximum standardized uptake value [SUV]). A multiple-ROI analysis was done to obtain ROCs for combined PET SUV and multiparametric MRI datasets. Spearman analysis was performed to assess the correlations. RESULTS: There was a significant difference between early and delayed PSMA uptake in malignant prostatic lesions (p < 0.01), which was able to characterize prostate lesions with an AUC of 0.83 and 0.94. Combined ROC analysis of PI-RADSv2 category derived from multiparametric MRI and differential PSMA uptake in characterizing prostatic lesions improved the AUC to 0.99. CONCLUSION: Dual-phase PSMA uptake improves accuracy of classifying malignant versus benign prostate lesions and complements multiparametric MRI in the diagnosis of prostate cancer.

68Ga-Prostate-Specific Membrane Antigen-Avid Tubercular Lesions Mimicking Prostate Cancer Metastasis on Simultaneous Prostate-Specific Membrane Antigen PET/MRI.

Ga-prostate-specific membrane antigen (PSMA) has gained increasing interest as a target molecule in imaging of prostate cancer because of its selective overexpression in local prostate cancer lesions and metastasis. We report a case of a 62-year-old man with raised serum prostate-specific antigen levels who presented for Ga-PSMA HBED-CC simultaneous PET/MRI for prostate cancer evaluation. A PSMA-nonavid PI-RADS 5 (Prostate Imaging-Reporting and Data System) lesion was confirmed as adenocarcinoma on histopathology. The PSMA-avid lesions were noted in the calvarium and lung, with the calvarial lesion confirmed to be of tubercular etiology on biopsy, and both lesions subsequently responded to antitubercular treatment.

Association of pharmacokinetic and metabolic parameters derived using simultaneous PET/MRI: Initial findings and impact on response evaluation in breast cancer.

PURPOSE: To study relationships among pharmacokinetic and 18F-fluorodeoxyglucose (18F-FDG) PET parameters obtained through simultaneous PET/MRI in breast cancer patients and evaluate their combined potential for response evaluation. METHODS: The study included 41 breast cancer patients for correlation study and 9 patients (pre and post therapy) for response evaluation. All patients underwent simultaneous PET/MRI with dedicated breast imaging. Pharmacokinetic parameters and PET parameters for tumor were derived using an in- house developed and vendor provided softwares respectively. Relationships between SUV and pharmacokinetic parameters and clinical as well as histopathologic parameters were evaluated using Spearman correlation analysis. Response to chemotherapy was derived as percentage reduction in size and in parameters post therapy. RESULTS: Significant correlations were observed between SUVmean, max, peak, TLG with Ktrans (ρ=0.446, 0.417, 0.491, 0.430; p≤0.01); with Kep(ρ=0.303, ρ=0.315, ρ=0.319; p≤0.05); and with iAUC(ρ=0.401, ρ=0.410, ρ=0.379; p≤0.05, p≤0.01). The ratio of ve/iAUC showed significant negative correlation to SUVmean, max, peak and TLG (ρ=0.420, 0.446, 0.443, 0.426; p≤0.01). Ability of SUV as well as pharmacokinetic parameters to predict response to therapy matched the RECIST criteria in 9 out of 11 lesions in 9 patients. Maximum post therapy quantitative reduction was observed in SUVpeak, TLG and Ktrans. CONCLUSION: Simultaneous PET/MRI enables illustration of close interactions between glucose metabolism and pharmacokinetic parameters in breast cancer patients and potential of their simultaneity in response assessment to therapy.