PurposeThe usage of PET/computed tomography (CT) to monitor hepatocellular carcinoma patients following yttrium-90 (90Y) radioembolization has increased. Respiratory motion causes liver movement, which can be corrected using gating techniques at the expense of added noise. This work examines the use of amplitude-based gating on 90Y-PET/CT and its potential impact on diagnostic integrity.Patients and methodsPatients were imaged using PET/CT following 90Y radioembolization. A respiratory band was used to collect respiratory cycle data. Patient data were processed as both standard and motion-corrected images. Regions of interest were drawn and compared using three methods. Activity concentrations were calculated and converted into dose estimates using previously determined and published scaling factors. Diagnostic assessments were performed using a binary scale created from published 90Y-PET/CT image interpretation guidelines.ResultsEstimates of radiation dose were increased (P<0.05) when using amplitude-gating methods with 90Y PET/CT imaging. Motion-corrected images show increased noise, but the diagnostic determination of success, using the Kao criteria, did not change between static and motion-corrected data.ConclusionAmplitude-gated PET/CT following 90Y radioembolization is feasible and may improve 90Y dose estimates while maintaining diagnostic assessment integrity.

Given the significant different treatment strategy of glioblastoma compared to lymphoma, early non-invasive differentiation of these two malignant brain tumours is essential for treatment planning. Our study investigates the feasibility of differentiation of glioblastoma from lymphoma by measuring the apparent diffusion coefficient (ADC) values of the tumour using a very easy method on radiology PACS workstation. Forty-two (42) patients with pathology proven glioblastoma and 30 patients with pathology proven primary CNS lymphoma were retrospectively reviewed. Two different readers placed the regions of interest in the nonhaemorrhagic darkest solid area of the tumour to measure the ADC values. The median of the "Mean ADC Values" (averaged between two interpreters) in the primary CNS lymphoma group was significantly lower than the median of "Mean ADC Values" in the glioblastoma group for both readers (p < 0.0001) [582 (511,687) × 10 -6 mm 2 /s for the lymphoma group and 789 (734,896) × 10 -6 mm 2 /s for the GBM group]. Our study offers a novel, effective and easy approach for differentiation of the glioblastoma from lymphoma.

The usage of PET/CT to monitor patients with hepatocellular carcinoma following Y radioembolization has increased; however, image quality is often poor because of low count efficiency and respiratory motion. Motion can be corrected using gating techniques but at the expense of additional image noise. Amplitude-based gating has been shown to improve quantification in FDG PET, but few have used this technique in Y liver imaging. The patients shown in this work indicate that amplitude-based gating can be used in Y PET/CT liver imaging to provide motion-corrected images with higher estimates of activity concentration that may improve posttherapy dosimetry.