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Updated: Jul 20, 2026
Identification of Disease-related Spatial Covariance Patterns using Neuroimaging Data
Published on: June 26, 2013
Arterial spin labeling-based Z-maps have high specificity and positive predictive value for neurodegenerative
David Fällmar1, Sven Haller2,3,4,5, Johan Lilja6,7
1Department of Surgical Sciences, Radiology, Uppsala University, Uppsala, Sweden. david.fallmar@radiol.uu.se.
Objective:
Cerebral perfusion analysis based on arterial spin labeling (ASL) MRI has been proposed as an alternative to FDG-PET in patients with neurodegenerative disease. Z-maps show normal distribution values relating an image to a database of controls. They are routinely used for FDG-PET to demonstrate disease-specific patterns of hypometabolism at the individual level. This study aimed to compare the performance of Z-maps based on ASL to FDG-PET.
Methods:
Data were combined from two separate sites, each cohort consisting of patients with Alzheimer's disease (n = 18 + 7), frontotemporal dementia (n = 12 + 8) and controls (n = 9 + 29). Subjects underwent pseudocontinuous ASL and FDG-PET. Z-maps were created for each subject and modality. Four experienced physicians visually assessed the 166 Z-maps in random order, blinded to modality and diagnosis.
Results:
Discrimination of patients versus controls using ASL-based Z-maps yielded high specificity (84%) and positive predictive value (80%), but significantly lower sensitivity compared to FDG-PET-based Z-maps (53% vs. 96%, p < 0.001). Among true-positive cases, correct diagnoses were made in 76% (ASL) and 84% (FDG-PET) (p = 0.168).
Conclusion:
ASL-based Z-maps can be used for visual assessment of neurodegenerative dementia with high specificity and positive predictive value, but with inferior sensitivity compared to FDG-PET.
Key Points:
• ASL-based Z-maps yielded high specificity and positive predictive value in neurodegenerative dementia. • ASL-based Z-maps had significantly lower sensitivity compared to FDG-PET-based Z-maps. • FDG-PET might be reserved for ASL-negative cases where clinical suspicion persists. • Findings were similar at two study sites.
Insights
Arterial spin labeling (ASL) MRI Z-maps show high specificity for neurodegenerative dementia but lower sensitivity than FDG-PET. FDG-PET may be best for persistent clinical suspicion in ASL-negative cases.
Area of Science:
- Neurology
- Radiology
- Medical Imaging
Background:
- Arterial spin labeling (ASL) MRI offers potential for cerebral perfusion analysis in neurodegenerative diseases.
- Z-maps, used with FDG-PET, demonstrate disease-specific hypometabolism patterns.
- Comparing ASL-based Z-maps to FDG-PET is crucial for evaluating diagnostic performance.
Purpose of the Study:
- To compare the diagnostic performance of Z-maps generated from ASL MRI against FDG-PET in patients with neurodegenerative diseases.
- To assess the specificity, sensitivity, and positive predictive value of ASL-based Z-maps.
Main Methods:
- Combined data from two sites including patients with Alzheimer's disease, frontotemporal dementia, and controls.
- Subjects underwent pseudocontinuous ASL and FDG-PET imaging.
- Four experienced physicians visually assessed 166 Z-maps, blinded to modality and diagnosis.
Main Results:
- ASL-based Z-maps demonstrated high specificity (84%) and positive predictive value (80%) for discriminating patients from controls.
- Sensitivity for ASL-based Z-maps was significantly lower (53%) compared to FDG-PET (96%) (p < 0.001).
- Correct diagnoses were made in 76% of true-positive ASL cases versus 84% of true-positive FDG-PET cases (p = 0.168).
Conclusions:
- ASL-based Z-maps are valuable for visual assessment of neurodegenerative dementia, offering high specificity and positive predictive value.
- However, ASL-based Z-maps exhibit inferior sensitivity compared to FDG-PET-based Z-maps.
- FDG-PET may be reserved for ASL-negative cases with persistent clinical suspicion.
