Image-based dosimetry for 225Ac-PSMA-I&T therapy using quantitative SPECT

Purpose!#!After a decade of PET/MR, the case of attenuation correction (AC) remains open. The initial four-compartment (air, water, fat, soft tissue) Dixon-based AC scheme has since been expanded with several features, the latest being MR field-of-view extension and a bone atlas. As this potentially changes quantification, we evaluated the impact of these features in PET AC in prostate cancer patients.!##!Methods!#!Two hundred prostate cancer patients were examined with either !##!Results!#!High correlation and no visually perceivable differences between all evaluated methods (r > 0.996) were found. The mean relative difference in lesion uptake of !##!Conclusions!#!Based on these results and the encountered bone atlas registration inaccuracy, we deduce that including bones and extending the MR field-of-view did not introduce clinically significant differences in PSMA diagnostic accuracy and tracer uptake quantification in prostate cancer pelvic lesions, facilitating the analysis of serial studies respectively. However, in the absence of ground truth data, we advise against atlas-based methods when comparing serial scans for bone lesions

Dosimetry and optimal scan time of 18FSiTATE-PET/CT in patients with neuroendocrine tumours

PURPOSE Radiolabelled somatostatin analogues targeting somatostatin receptors (SSR) are well established for combined positron emission tomography/computer tomography (PET/CT) imaging of neuroendocrine tumours (NET). 18FSiTATE has recently been introduced showing high image quality, promising clinical performance and improved logistics compared to the clinical reference standard 68Ga-DOTA-TOC. Here we present the first dosimetry and optimal scan time analysis. METHODS Eight NET patients received a 18FSiTATE-PET/CT (250 ± 66~MBq) with repeated emission scans (10, 30, 60, 120, 180~min after injection). Biodistribution in normal organs and SSR-positive tumour uptake were assessed. Dosimetry estimates for risk organs were determined using a combined linear-monoexponential model, and by applying 18F S-values and reference target masses for the ICRP89 adult male or female (OLINDA 2.0). Tumour-to-background ratios were compared quantitatively and visually between different scan times. RESULTS After 1 h, normal organs showed similar tracer uptake with only negligible changes until 3 h post-injection. In contrast, tracer uptake by tumours increased progressively for almost all types of metastases, thus increasing tumour-to-background ratios over time. Dosimetry resulted in a total effective dose of 0.015 ± 0.004~mSv/MBq. Visual evaluation revealed no clinically relevant discrepancies between later scan times, but image quality was rated highest in 60 and 120~min images. CONCLUSION 18FSiTATE-PET/CT in NET shows overall high tumour-to-background ratios from 60 to 180~min after injection and an effective dose comparable to 68Ga-labelled alternatives. For clinical use of 18FSiTATE, the best compromise between image quality and tumour-to-background contrast is reached at 120~min, followed by 60~min after injection

Correction to: Influence of dosimetry method on bone lesion absorbed dose estimates in PSMA therapy: application to mCRPC patients receiving Lu-177-PSMA-I&T

An amendment to this paper has been published and can be accessed via the original article.Medicine, Faculty ofNon UBCRadiology, Department ofReviewedFacult

Imaging and biochemical biomarkers of psychiatric comorbidities in a rat epilepsy model

Aims: Biomarkers of epilepsy-associated psychiatric comorbidities represent a powerful tool for an early diagnosis and personalized therapy in patients with epilepsy. Here, in order to identify new candidates as biomarkers of epilepsy comorbidities, alterations in brain metabolic activity and serotonergic neurotransmission in a rat post-status epilepticus model were explored and cross-correlated with alterations in various neurobehavioral and biochemical parameters. Methods: Status epilepticus was induced in twelve female Sprague Dawley rats by lithium chloride-pilocarpine treatment. µPET analysis to determine [18F]FDG uptake and [18F]MPPF binding were performed in the chronic phase of epilepsy, followed by the assessment of alterations in several behavioral paradigms and biochemical markers. A Spearman cross-correlation analysis was performed including all µPET, behavioral and biochemical data. Results: Epileptic rats showed a reduction in thalamic [18F]FDG uptake, indicating regional hypometabolism, and increased septal [18F]MPPF binding suggesting changes in serotoninergic neurotransmission. Both, thalamic [18F]FDG and septal [18F]MPPF data correlate with behavioral alterations including decreases in burrowing behavior, in social interaction, and changes in anxiety-related behaviors. Moreover, thalamic [18F]FDG correlate with seizure frequency. Importantly, thalamic [18F]FDG and septal [18F]MPPF data correlate with BDNF serum levels, which were decreased in epileptic rats. Conclusions: µPET data suggest that alterations in septal 5HT1a receptor binding can be employed as imaging biomarker of epilepsy-associated neuropsychiatric comorbidities, as well as BDNF, which might be used as a peripheral circulatory biomarker. In contrast [18F]FDG uptake, which reflects epilepsy severity, might not represent a specific biomarker for psychiatric comorbidities. Project supported by Deutsche Forschungsgemeinschaft grants (FOR 2591, GZ: PO681/9-1

Anpassentwicklung Windenergieanlage MONOPTEROS 50

With 49 refs., 193 figs.TIB Hannover: RO 8091(0001-89PUB) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman