- Email: [email protected]
IC-P3-181: ADNI phantom & scanner longitudinal performance
T80
Alzheimer’s Imaging Consortium IC-P3: Poster Presentations
Eleven DLB, 20 AD, and 18 control subjects underwent arterial-spin labeled perfusion MRI (ASL-pMRI) and a neuropsychological test battery that included the Mini-mental State Examination, verbal fluency, and memory testing. MRI was performed on a 3 Tesla whole body scanner using the head coil. ASL was performed using flow driven adiabatic inversion and an improved version of a previously published method for subtracting off-resonance saturation effects. The blood flow images were spatially normalized and group comparisons performed using Statistical Parametric Mapping (SPM2). Results: With a threshold of p⬍ 0.0.5 uncorrected for multiple comparisons, significant differences in rCBF were found for both the DLB and AD groups in frontal and parieto-occipital cortex. However, the magnitude in reduction in blood flow was significantly more pronounced in the DLB group compared to the AD group, despite a milder degree of cognitive impairment amongst the subjects with DLB. Conclusions: The regional pattern of decreased rCBF measured with ASL may have limited specificity for separating mild DLB from mild AD. Clinically, patients with DLB have been observed to exhibit dramatic clinical response to treatment with cholinesterase inhibitors, and a more severe cholinergic deficit is known to be present in DLB relative to AD. The hypoperfusion in association areas detected by ASL-pMRI in DLB may therefore be associated with decreased cholinergic function. IC-P3-181
ADNI PHANTOM & SCANNER LONGITUDINAL PERFORMANCE
Jeff L. Gunter1, Bret Borowski1, Paula Britson1, Matt Bernstein1, Chadwick Ward1, Joel Felmlee1, Norbert Schuff2, Michael Weiner2, Clifford R. Jack1, the Alzheimer’s Disease Neuroimaging Initiative (ADNI), 1 Mayo Clinic and Foundation, Rochester, MN, USA; 2UC San Francisco and Magnetic Resonance Unit (114M), San Francisco, CA, USA. Contact e-mail: [email protected] Background: The Alzheimer’s Disease Neuroimaging Initiative (ADNI) employs a fleet of 66 phantoms for MRI scanner characterization and to insure the integrity of data pre-processing steps. 84 different scanners (67 1.5T, 27 3T) are used in ADNI. Methods: The ADNI phantom is scanned along with every ADNI MRI subject exam, providing time locked scanner tracking. Phantom analysis returns estimates of gradient calibration (proportional an object’s size as measured by MRI), non-linearity and SNR and contrast measures. Data from a single scanner in ADNI over time is shown in Figure 1. The data may be averaged over time (where allowances are made for discrete gradient calibration changes are made) with the variance indicating scanner stability. Additionally, phantom estimates of scanner gradient calibration may be used to correct individual human subject images. The accuracy of this approach was evaluated by comparing intra-subject pairs of images with and without phantom correction. Results: Shown in Figures 2a and 2b are the gradient scaling, non-linearity estimate, SNR and contrast results by scanner. Data are grouped by vendor and vendor to vendor differences are observed. The large uncertainties in Vendor 3 data (which were only revealed by the ADNI phantom data) were tracked to a protocol error which was subsequently corrected. If using phantom estimates of gradient calibration to correct for scanner drift is valid, then the relative (registration) scaling between corrected intra-subject images should be closer to unity and narrower than without correction. Histograms of scale factors with and without correction are shown in Figure 3 for data in which the same phantom was used to correct both scans. Figure 4 shows similar data where one scan was performed on a 3T system and the other at 1.5T. Conclusions: The ADNI phantom is used to track longitudinal scanner performance. Gradient recalibration introduces changes which are typically larger than scanner drift. Longitudinal phantom measurements have proved essential for detecting protocol errors otherwise would have gone unnoticed. While phantom data may be used to correct individual human scans for gradient drift, phantom to phantom manufacturing variability is a significant confound for such corrections.
IC-P3-182
NEURAL CORRELATES OF LONG-TERM DECLARATIVE MEMORIES REVEAL AGEDEPENDENT DIFFERENCES
Vjera A. Holthoff1, Markus Donix2, Katrin Poettrich2, Peter Weiss3, Gereon Fink4, Ruediger von Kummer2, 1University of Technology, University Hospital, Dpt. Psychiatry, Dresden, Germany; 2University of Technology, Dresden, Germany; 3Institut fu¨r Neurowissenschaften und Biophysik - Medizin (INB-3), Juelich, Germany; 4University of Cologne, Cologne, Germany. Contact e-mail: [email protected] Background: Autobiographical episodic memory is considered to be the most complex subsystem of human long-term declarative memory combining information of multiple sources including the general knowledge of one⬘s past and episodic event memories in a specific temporal, spatial and emotionally meaningful context. The purpose of the present study was to investigate whether age influences the neural activity associated with content (episodic versus semantic) and remoteness (recent versus remote) of memories. Methods: We performed fMRI in 12 healthy elderly (mean age 60.5 years, SD 5.7) and 12 young subjects (mean age 28.0 years, SD 3.3) and analysed neural activity related to memory content and remoteness (remote events from the time when they were 5-15 years old and recent events from the last five years). The stimuli used during the fMRI study were based on autobiographical episodic memory items that included recollection and re-experiencing context-rich events of the participant’s own life (episodic memories) and were contrasted with the retrieval of semantic memory items including public events of the same time period. Results: When comparing both age groups many commonalities in the activated network subserving declarative long-term memory and specifically autobiographic memory were revealed, however, two key differences emerged. In the elderly, retrieval of declarative long-term memories irrespective of remoteness led to a significant activation of parieto-occipital areas bilaterally when compared to the young. During re-experience of recent autobiographical and semantic event memories both groups significantly activated left posterior cingulate areas. Young subjects but not the elderly additionally activated hippocampus and orbitofrontal cortex. Conclusions: Our data suggest that there are age-dependent differences in the neural networks underlying declarative long-term memory and retrieval of recent autobiographical episodic and semantic event memories. IC-P3-183
PHYSICAL FITNESS IS ASSOCIATED WITH PRESERVATION OF BRAIN VOLUME IN ALZHEIMER’S DISEASE
Robyn A. Honea, George Thomas, Amith Harsha, Benjamin Cronk, Joseph Donnelly, William M. Brooks, Jeffrey M. Burns, University of Kansas Medical Center, Kansas City, MO, USA. Contact e-mail: [email protected]
Alzheimer’s Imaging Consortium IC-P3: Poster Presentations
Eleven DLB, 20 AD, and 18 control subjects underwent arterial-spin labeled perfusion MRI (ASL-pMRI) and a neuropsychological test battery that included the Mini-mental State Examination, verbal fluency, and memory testing. MRI was performed on a 3 Tesla whole body scanner using the head coil. ASL was performed using flow driven adiabatic inversion and an improved version of a previously published method for subtracting off-resonance saturation effects. The blood flow images were spatially normalized and group comparisons performed using Statistical Parametric Mapping (SPM2). Results: With a threshold of p⬍ 0.0.5 uncorrected for multiple comparisons, significant differences in rCBF were found for both the DLB and AD groups in frontal and parieto-occipital cortex. However, the magnitude in reduction in blood flow was significantly more pronounced in the DLB group compared to the AD group, despite a milder degree of cognitive impairment amongst the subjects with DLB. Conclusions: The regional pattern of decreased rCBF measured with ASL may have limited specificity for separating mild DLB from mild AD. Clinically, patients with DLB have been observed to exhibit dramatic clinical response to treatment with cholinesterase inhibitors, and a more severe cholinergic deficit is known to be present in DLB relative to AD. The hypoperfusion in association areas detected by ASL-pMRI in DLB may therefore be associated with decreased cholinergic function. IC-P3-181
ADNI PHANTOM & SCANNER LONGITUDINAL PERFORMANCE
Jeff L. Gunter1, Bret Borowski1, Paula Britson1, Matt Bernstein1, Chadwick Ward1, Joel Felmlee1, Norbert Schuff2, Michael Weiner2, Clifford R. Jack1, the Alzheimer’s Disease Neuroimaging Initiative (ADNI), 1 Mayo Clinic and Foundation, Rochester, MN, USA; 2UC San Francisco and Magnetic Resonance Unit (114M), San Francisco, CA, USA. Contact e-mail: [email protected] Background: The Alzheimer’s Disease Neuroimaging Initiative (ADNI) employs a fleet of 66 phantoms for MRI scanner characterization and to insure the integrity of data pre-processing steps. 84 different scanners (67 1.5T, 27 3T) are used in ADNI. Methods: The ADNI phantom is scanned along with every ADNI MRI subject exam, providing time locked scanner tracking. Phantom analysis returns estimates of gradient calibration (proportional an object’s size as measured by MRI), non-linearity and SNR and contrast measures. Data from a single scanner in ADNI over time is shown in Figure 1. The data may be averaged over time (where allowances are made for discrete gradient calibration changes are made) with the variance indicating scanner stability. Additionally, phantom estimates of scanner gradient calibration may be used to correct individual human subject images. The accuracy of this approach was evaluated by comparing intra-subject pairs of images with and without phantom correction. Results: Shown in Figures 2a and 2b are the gradient scaling, non-linearity estimate, SNR and contrast results by scanner. Data are grouped by vendor and vendor to vendor differences are observed. The large uncertainties in Vendor 3 data (which were only revealed by the ADNI phantom data) were tracked to a protocol error which was subsequently corrected. If using phantom estimates of gradient calibration to correct for scanner drift is valid, then the relative (registration) scaling between corrected intra-subject images should be closer to unity and narrower than without correction. Histograms of scale factors with and without correction are shown in Figure 3 for data in which the same phantom was used to correct both scans. Figure 4 shows similar data where one scan was performed on a 3T system and the other at 1.5T. Conclusions: The ADNI phantom is used to track longitudinal scanner performance. Gradient recalibration introduces changes which are typically larger than scanner drift. Longitudinal phantom measurements have proved essential for detecting protocol errors otherwise would have gone unnoticed. While phantom data may be used to correct individual human scans for gradient drift, phantom to phantom manufacturing variability is a significant confound for such corrections.
IC-P3-182
NEURAL CORRELATES OF LONG-TERM DECLARATIVE MEMORIES REVEAL AGEDEPENDENT DIFFERENCES
Vjera A. Holthoff1, Markus Donix2, Katrin Poettrich2, Peter Weiss3, Gereon Fink4, Ruediger von Kummer2, 1University of Technology, University Hospital, Dpt. Psychiatry, Dresden, Germany; 2University of Technology, Dresden, Germany; 3Institut fu¨r Neurowissenschaften und Biophysik - Medizin (INB-3), Juelich, Germany; 4University of Cologne, Cologne, Germany. Contact e-mail: [email protected] Background: Autobiographical episodic memory is considered to be the most complex subsystem of human long-term declarative memory combining information of multiple sources including the general knowledge of one⬘s past and episodic event memories in a specific temporal, spatial and emotionally meaningful context. The purpose of the present study was to investigate whether age influences the neural activity associated with content (episodic versus semantic) and remoteness (recent versus remote) of memories. Methods: We performed fMRI in 12 healthy elderly (mean age 60.5 years, SD 5.7) and 12 young subjects (mean age 28.0 years, SD 3.3) and analysed neural activity related to memory content and remoteness (remote events from the time when they were 5-15 years old and recent events from the last five years). The stimuli used during the fMRI study were based on autobiographical episodic memory items that included recollection and re-experiencing context-rich events of the participant’s own life (episodic memories) and were contrasted with the retrieval of semantic memory items including public events of the same time period. Results: When comparing both age groups many commonalities in the activated network subserving declarative long-term memory and specifically autobiographic memory were revealed, however, two key differences emerged. In the elderly, retrieval of declarative long-term memories irrespective of remoteness led to a significant activation of parieto-occipital areas bilaterally when compared to the young. During re-experience of recent autobiographical and semantic event memories both groups significantly activated left posterior cingulate areas. Young subjects but not the elderly additionally activated hippocampus and orbitofrontal cortex. Conclusions: Our data suggest that there are age-dependent differences in the neural networks underlying declarative long-term memory and retrieval of recent autobiographical episodic and semantic event memories. IC-P3-183
PHYSICAL FITNESS IS ASSOCIATED WITH PRESERVATION OF BRAIN VOLUME IN ALZHEIMER’S DISEASE
Robyn A. Honea, George Thomas, Amith Harsha, Benjamin Cronk, Joseph Donnelly, William M. Brooks, Jeffrey M. Burns, University of Kansas Medical Center, Kansas City, MO, USA. Contact e-mail: [email protected]