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Test‐retest variability of relative tracer delivery rate as measured by [ 11 C]PiB
Author(s) -
Heeman Fiona,
Hendriks Janine,
Alves Isadora Lopes,
Tolboom Nelleke,
Van Berckel Bart N.M.,
Yaqub Maqsood,
Lammertsma Adriaan A.
Publication year - 2021
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1002/alz.051654
Subject(s) - nuclear medicine , positron emission tomography , statistical parametric mapping , cerebral blood flow , dementia , voxel , pittsburgh compound b , medicine , correlation , mann–whitney u test , cognitive impairment , mathematics , disease , radiology , magnetic resonance imaging , geometry
Background In Alzheimer’s disease (AD), reductions in cerebral blood flow (CBF) have been reported and these may be used as proxy for measuring treatment efficacy or disease progression. The gold standard technique for measuring CBF is [ 15 O]H 2 O positron emission tomography (PET). Recent studies, however, have reported high correlations between [ 11 C]PiB PET derived relative tracer delivery rate R 1 and [ 15 O]H 2 O derived relative CBF, suggesting that [ 11 C]PiB R 1 may be a good proxy of relative CBF. As longitudinal PET studies become more common for measuring disease progression, it is important to know the intrinsic variability of R 1 . The purpose of the present study was to determine R 1 test‐retest (TRT) variability. Method Previously, TRT variability of [ 11 C]PiB binding potential has been reported for a group of twelve participants (five cognitively unimpaired (CU), one with mild cognitive impairment and six with AD dementia), in which all participants underwent two 90 min [ 11 C]PiB PET scans using a Siemens ECAT EXACT HR+ scanner 1 . This dataset was reanalysed to also determine TRT variability of [ 11 C]PiB R 1 . The voxel‐based implementation of the two‐step simplified reference tissue model with cerebellar grey matter as reference tissue was used to generate R 1 images. Next, TRT variability was calculated both globally and regionally, and global R 1 measures were compared between diagnostic groups using a non‐parametric Mann‐Whitney U test. Next, correlation analysis was used to assess the relationship between TRT variability and regional volume. Finally, regional test and retest R 1 measures were compared using Linear Mixed Effect Models and Bland‐Altman analysis. Result Global relative tracer delivery ( R 1 ) was significantly lower in AD patients (test R 1 :0.82±0.04, retest R 1 :0.82±0.03) compared with CU participants (test R 1 :0.93±0.04 retest R 1 :0.91±0.03, p <0.01). TRT variability was low across regions (range:1.5‐5.8%), with a trend effect towards smaller TRT for larger regions ( R 2 =0.14, p =0.09). Furthermore, test and retest measures showed high, significant correlations ( R 2 =0.92, slope=0.98) and negligible bias (0.69±3.07%). Conclusion The high precision of [ 11 C]PiB R 1 suggests suitable applicability for cross‐sectional and longitudinal studies. This finding further demonstrates the utility of dynamic [ 11 C]PiB PET scans for dual‐biomarker imaging in AD research. Reference: Tolboom et al.(2009) Eur J Nucl Med Mol Imaging 36:1629‐38.