Abstract
BackgroundIn previous clinical Positron Emission Tomography (PET) studies novel approaches for application of Principal Component Analysis (PCA) on dynamic PET images such as Masked Volume Wise PCA (MVW-PCA) have been introduced. MVW-PCA was shown to be a feasible multivariate analysis technique, which, without modeling assumptions, could extract and separate organs and tissues with different kinetic behaviors into different principal components (MVW-PCs) and improve the image quality.MethodsIn this study, MVW-PCA was applied to 14 dynamic 11C-metomidate-PET (MTO-PET) examinations of 7 patients with small adrenocortical tumours. MTO-PET was performed before and 3 days after starting per oral cortisone treatment. The whole dataset, reconstructed by filtered back projection (FBP) 0–45 minutes after the tracer injection, was used to study the tracer pharmacokinetics.ResultsEarly, intermediate and late pharmacokinetic phases could be isolated in this manner. The MVW-PC1 images correlated well to the conventionally summed image data (15–45 minutes) but the image noise in the former was considerably lower. PET measurements performed by defining "hot spot" regions of interest (ROIs) comprising 4 contiguous pixels with the highest radioactivity concentration showed a trend towards higher SUVs when the ROIs were outlined in the MVW-PC1 component than in the summed images. Time activity curves derived from "50% cut-off" ROIs based on an isocontour function whereby the pixels with SUVs between 50 to 100% of the highest radioactivity concentration were delineated, showed a significant decrease of the SUVs in normal adrenal glands and in adrenocortical adenomas after cortisone treatment.ConclusionIn addition to the clear decrease in image noise and the improved contrast between different structures with MVW-PCA, the results indicate that the definition of ROIs may be more accurate and precise in MVW-PC1 images than in conventional summed images. This might improve the precision of PET measurements, for instance in therapy monitoring as well as for delineation of the tumour in radiation therapy planning.
Highlights
In previous clinical Positron Emission Tomography (PET) studies novel approaches for application of Principal Component Analysis (PCA) on dynamic PET images such as Masked Volume Wise PCA (MVW-PCA) have been introduced
FmcasFetoiireiqglnsuduutgmerbCinmenyocas1elughpoemopsflwnic0tshas–thr4ihoo5euwnmgcsohoinftrfhurMreateeVmsspWueom9n-mP–dC1ien4Adg(iMo1m5nVa–gtW4he5es-PmgwCeihn1oe)liraemantiadmegdesaesgbciygnoegsnnudemrFirst Column shows the summed images generated by summing images through frame 9–14 (15–45 min) and second column shows the corresponding MVWPC1 images generated by application of MVW-PCA on the whole imaging sequence of 0–45 minutes
This component isolates the pharmacokinetic phase in the dynamic PET sequence, which best resembled the conventional summed images based on data 15 to 45 minutes after [11C]-MTO injection but the image noise was lower and the organ and tissue separation was better
Summary
In previous clinical Positron Emission Tomography (PET) studies novel approaches for application of Principal Component Analysis (PCA) on dynamic PET images such as Masked Volume Wise PCA (MVW-PCA) have been introduced. Adrenal tumours are common incidental radiological findings in computed tomography (CT) examinations that are performed because of non-adrenal disease. For these adrenal tumours the term generally used is incidentaloma. As a result of the more frequent use and improved spatial resolution of modern multi-detector CT scanners, incidentalomas are being found more often. Because of their malignancy potential and because these tumours may cause hormonal hypersecretion, the discovery of an incidentaloma necessitates biochemical and radiological work-ups. Additional sensitive and reliable imaging methods are needed to manage the considerable clinical problem to differentiate hormone-overproducing or malignant incidentalomas or both, for which treatment is needed, from benign non-hypersecreting lesions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
