Erratum to: Amino acid PET and MR perfusion imaging in brain tumours

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Relevant tumor sink effect in prostate cancer patients receiving Lu-177-PSMA-617 radioligand therapy

Aim: In metastatic prostate cancer patients PSMA targeting radioligands have gained significant impact as theranostic probes. In this study a correlation between total tumor volume (TTV) and measured kidney dose as well as salivary glands (SG) uptake in 177Lu-PSMA-617 therapy was evaluated.Methods: Eleven consecutive prostate cancer patients receiving a first cylcle of 177Lu-PSMA-617 (administered activity of approximately 6GBq) were included. The 68Ga-PSMA-11 PET/CT scan previous to therapy was used to determine TTV and SG uptake (glandulae submandibularis) employing PMOD version 3.403 with different 68Ga-PSMA-11 thresholds based on the standardized uptake value (SUV).The kidney dose was estimated with the software ULMDOS using planar whole-body scintigrams.Results: Kidney dose and SG uptake was inversely correlated to TTV, indicating high kidney dose and high SG uptake in case of low tumor load and low kidney dose and low SG uptake in case of high tumor load.Conclusion: Our data support the hypothesis that in 177Lu-PSMA-617 therapy an individualized treatment activity based on total tumor volume could be beneficiary

Automatic derivation of an MR-PET image-based input function for quantification of 18F-FET

Fully quantitative PET data requires an input function (IF) for kinetic modelling that is often acquired via arterial blood sampling. Here, an automatic method to obtain an image-derived input function (IDIF) using MR-PET data is presented and several partial volume correction methods (PVC) are evaluated. Data from three tumour patients were acquired in a 3T MRBrainPET. A bolus of 3MBq/Kg of body weight of 18F-FET was administrated to each subject and a dynamic PET scan (dPET) was performed during 60min. PET data were reconstructed in 23 frames with variable frame length using OP-OSEM (32it, 4sub) including all the corrections. An MPRAGE scan was acquired (TE/TR/TI = 3/2250/900 ms, FA = 9°). Five venous blood samples (VBS) were drawn at the later times later times each 10min. To estimate an IDIF, internal carotid arteries were segmented automatically and these regions were transferred to dPET. After, 4 post reconstruction PVC were applied and the impact of a scaling factor based on a single VBS was also evaluated based on the area under the curve (AUC). All the tested PVC methods resulted in an under estimation of the AUC at later frames which was mitigated after scaling with a VBS at 50 min. In the earlier frames the different PVC resulted in different AUC, which were not possible to validate. The fully automated procedure presented allows one to obtain an IDIF without user interaction. Nevertheless, the initial findings regarding the PVC require further validation with a larger data set

Congruency of tumour volume delineated by FET PET and MRSI

In addition to MR imaging, PET imaging of O-(2-[18F]Fluorethyl)-L-Tyrosine (FET) uptake provides information on brain tumour extent and metabolic activity. Similarly, MRS has been shown to be of value for distinguishing high- from low-grade gliomas. Based on 2D spatially resolved MRSI, an overlap between 18FET uptake and the choline/N-acetyl-aspartate (Cho/NAA) ratio of more than 75 % has been reporte