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Temporal relationship between apparent diffusion coefficient and absolute measurements of cerebral blood flow in
Weili Lin1, Jin-Moo Lee, Yueh Z Lee
1Department of Radiology and Biomedical Engineering, University of North Carolina at Chapel Hill, 27599, USA. weili_lin@med.unc.edu
Background And Purpose:
Diffusion-weighted imaging (DWI) has been established as a marker of acute ischemic brain injury. We sought to determine the relationship between cerebral blood flow (CBF) and apparent diffusion coefficient (ADC) and to explore whether the elapsed time between MRI acquisition and symptom onset alters this relation in acute stroke patients.
Methods:
Sixteen acute stroke patients were studied with DWI and perfusion-weighted imaging, from which ADC and CBF were calculated. ADC values were normalized (nADC) to the contralateral, nonischemic hemisphere and then correlated pixel by pixel with CBF within a region of interest defined by abnormal transit time. To explore potential temporal effects on the relationship between CBF and nADC, patients were divided into 2 groups based on the duration between symptom onset and MR imaging for data analysis: group A, 2 to 4 hours (n=8), and group B, 4.5 to 6.5 hours (n=8).
Results:
nADC was plotted against CBF for each pixel in all 16 subjects, and a composite relationship was derived. After a gradual decline, an abrupt drop in nADC occurred below a CBF threshold value of 21 mL x min(-1) x 100 g(-1). When subjects were divided into early and late imaging groups, the group of patients imaged earlier (group A) had a lower threshold (15 mL x min(-1) x 100 g(-1)) than the group imaged later (group B, 24 mL x min(-1) x 100 g(-1)).
Conclusions:
Our results demonstrate that a relationship between nADC and CBF exists in the ischemic brain and that ADC values alone may provide useful information in predicting perfusion status. However, this relationship may change with elapsing time between stroke onset and imaging.
Insights
The apparent diffusion coefficient (ADC) and cerebral blood flow (CBF) are related in acute stroke, but this relationship changes over time. Early imaging reveals a lower threshold for ADC changes, indicating altered perfusion status.
Area of Science:
- Neurology
- Radiology
- Medical Imaging
Background:
- Diffusion-weighted imaging (DWI) is a key tool for detecting acute ischemic brain injury.
- Understanding the interplay between cerebral blood flow (CBF) and apparent diffusion coefficient (ADC) is crucial for stroke assessment.
Purpose of the Study:
- To investigate the relationship between CBF and ADC in acute stroke patients.
- To determine if the time elapsed since symptom onset influences the CBF-ADC relationship.
Main Methods:
- Sixteen acute stroke patients underwent DWI and perfusion imaging.
- Apparent diffusion coefficient (ADC) values were normalized (nADC) and correlated with CBF.
- Patients were stratified into early (2-4 hours) and late (4.5-6.5 hours) imaging groups.
Main Results:
- A composite relationship showed an abrupt drop in nADC below a CBF threshold of 21 mL x min(-1) x 100 g(-1).
- The early imaging group (Group A) exhibited a lower CBF threshold (15 mL x min(-1) x 100 g(-1)) compared to the late imaging group (Group B, 24 mL x min(-1) x 100 g(-1)).
Conclusions:
- A significant relationship exists between normalized ADC (nADC) and CBF in ischemic brain tissue.
- ADC values can potentially predict perfusion status in acute stroke.
- The time interval between stroke onset and MRI acquisition impacts the nADC-CBF relationship.