This study included elderly subjects and was conducted using relatively low resolution PET camera system compared to recent PET systems like the high resolution research tomograph (HRRT) with 1.5?mm FWHM . per decade) was similar as the previously reported value by Fowler et al., at 7.1% per decade . One postmortem study also reported increasing of MAO-B protein in the human brain according to age . Our PET study confirmed both findings of postmortem and in vivo human brain studies. Among all regions, the hippocampus showed the highest correlation with age effect although it did not reach statistical significance and the reproducibility was relatively low as discussed above. Since the hippocampus is thought to be especially impacted in AD [30, 31], the present findings suggest the increase of MAO-B activity may have an important role about the pathology of AD. PVE should be considered in PET studies when brain atrophy is observed in aged subjects or patients with disorders such as AD. Additionally, PVE is larger using a low resolution PET camera than a high resolution one. This study included elderly subjects and was conducted using relatively low resolution PET camera system compared to recent PET systems like the high resolution research tomograph (HRRT) with 1.5?mm FWHM . In the present BSG study, %change of em K /em 1 after PVEc was correlated with age. It indicates that the brain of aged subjects was more affected by the PVE compared to younger subject due to the brain atrophy. Meanwhile, em k /em 2 and em k /em 3 did not show any clear change after PVEc. em k /em 3 was also moderately affected by PVEc and correlated with age since it is partially determined by em K /em Pidotimod 1/ em k /em 2. Nevertheless, although the value itself of em k /em 3 was increased in aged subjects, test-retest variability of em k /em 3 did not change after PVEc. This indicates that PVEc can reliably keep reproducibility even in the case of elderly subjects with brain atrophy. There are several imitations in this study. Although only six subjects were included and it is relatively small sample size, the number were similar as previous test-retest studies about [11C]-l-deprenyl-D2 by Logan et al. ( em n /em ?=?5)  and other PET radioligands ( em n /em ?=?6C8) [25, 33]. However, the studies about age effect included larger number generally [20, 34, 35]. So, the present result about the age effect might be preliminary. Additionally, only healthy control subjects were included in this study. It is difficult to extrapolate our findings about PVEc to AD patients because the elderly ones showed slight atrophy but not pathological. To more accurately estimate the effects of PVEc, further studies with AD patients and aged control subjects who showed strong atrophy will be needed. Conclusions The present results indicate that em k /em 3 and em k /em 3 of [11C]-l-deprenyl-D2 are reliable parameters for test-retest reproducibility with healthy subjects both before and after PVEc. As the number of subjects was relatively small and only healthy subjects were included, the studies with patients of larger sample size are required for further clinical applications. Acknowledgements We thank all members of the Karolinska Insitutet PET Centre for assistance with the PET experiments. RSM was recipient of a post doc fellowship (CNPq-23364/2014-7). Funding This work was partially supported by GE Healthcare Ltd., UK. Authors contributions PS, Pidotimod AT, and CH designed the study and wrote the protocol. PS and SN conducted the PET experiment. RA, PS, AT, and RSM analyzed the data. RA wrote the first draft of the manuscript. All authors approved and browse the last manuscript. Competing passions The authors declare they have no contending passions. Consent for publication Not really applicable Ethics acceptance and consent to take part The analysis was accepted by the Regional Moral Review Plank in Stockholm, Sweden, and rays Safety Committee on the Karolinska School Medical center in Solna Pidotimod in Stockholm, Sweden. After comprehensive description from the scholarly research, written up to date consent was extracted from all individuals. Publishers Be aware Springer Nature continues to be neutral in regards to to jurisdictional promises in released maps and institutional affiliations. Abbreviations 2TCMTwo tissues compartment modelAALAnatomical Auto LabelingADAlzheimers diseaseALSAmyotrophic lateral sclerosisCSFCerebrospinal fluidFWHMFull width at fifty percent maximumGMGrey matterHRRTHigh quality research tomographICCIntraclass relationship coefficientMAOMonoamine oxidaseMRIMagnetic resonance imageMSBSMean square of between subjectMSWSMean square of within subjectPETPositron emission tomographyPVEPartial quantity effectPVEcPartial volume impact correctionROIRegions of interestWMWhite matter Contributor Details Ryosuke Arakawa, Mobile phone: +46 8 517 750 15, Email: ha firstname.lastname@example.org. Per.