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Assessment of Splenic Switch-Off With Arterial Spin Labeling in Adenosine Perfusion Cardiac MRI
Verónica Aramendía-Vidaurreta1,2, Sergio M Solis-Barquero1,2, Ana Ezponda1,2
1Department of Radiology, Clínica Universidad de Navarra, Pamplona, Navarra, Spain.
Insights
Pseudo-continuous arterial spin labeling (PCASL) effectively identifies splenic switch-off, a marker for adequate stress during myocardial perfusion MRI. This non-contrast technique offers high accuracy in assessing coronary artery disease.
Area of Science:
- Cardiovascular Imaging
- Radiology
- Medical Physics
Background:
- Myocardial perfusion imaging under rest and stress is crucial for diagnosing coronary artery disease (CAD).
- Splenic switch-off, a reduction in splenic perfusion during stress, indicates adequate pharmacological stress but was previously assessed using contrast-enhanced methods.
- Non-contrast imaging techniques are desirable for assessing splenic switch-off to avoid contrast-related risks.
Purpose of the Study:
- To evaluate the capability of pseudo-continuous arterial spin labeling (PCASL) in identifying splenic switch-off in patients with suspected CAD.
- To assess the accuracy of PCASL for determining stress adequacy using the splenic switch-off phenomenon.
Main Methods:
- A prospective study involving 5 healthy volunteers and 32 patients with suspected CAD.
- Acquisition of 1.5-T/PCASL (spin-echo) and first-pass (gradient-echo) perfusion images at rest and during adenosine stress.
- Calculation of splenic blood flow (SBF) maps and SBF stress-to-rest ratios using PCASL data; visual and quantitative classification of splenic switch-off.
Main Results:
- Splenic switch-off was observed in 84.4% of patients based on first-pass imaging.
- PCASL-derived SBF maps demonstrated a reduction in splenic perfusion during stress, consistent with splenic switch-off.
- The SBF stress-to-rest ratio derived from PCASL achieved 97% accuracy (80% sensitivity, 100% specificity, 85.2% AUC) in identifying splenic switch-off.
Conclusions:
- Pseudo-continuous arterial spin labeling (PCASL) is a feasible non-contrast technique for identifying splenic switch-off during adenosine stress perfusion MRI.
- Both qualitative and quantitative assessments using PCASL can reliably detect splenic switch-off, confirming stress adequacy in patients with suspected CAD.
- PCASL offers a valuable alternative for assessing stress adequacy in myocardial perfusion imaging.
Background:
In patients with suspected coronary artery disease (CAD), myocardial perfusion is assessed under rest and pharmacological stress to identify ischemia. Splenic switch-off, defined as the stress to rest splenic perfusion attenuation in response to adenosine, has been proposed as an indicator of stress adequacy. Its occurrence has been previously assessed in first-pass perfusion images, but the use of noncontrast techniques would be highly beneficial.
Purpose:
To explore the ability of pseudo-continuous arterial spin labeling (PCASL) to identify splenic switch-off in patients with suspected CAD.
Study Type:
Prospective.
Population:
Five healthy volunteers (age 24.8 ± 3.8 years) and 32 patients (age 66.4 ± 8.2 years) with suspected CAD.
Field Strength/Sequence:
A 1.5-T/PCASL (spin-echo) and first-pass imaging (gradient-echo).
Assessment:
In healthy subjects, multi-delay PCASL data (500-2000 msec) were acquired to quantify splenic blood flow (SBF) and determine the adequate postlabeling delay (PLD) for single-delay acquisitions (PLD > arterial transit time). In patients, single-delay PCASL (1200 msec) and first-pass perfusion images were acquired under rest and adenosine conditions. PCASL data were used to compute SBF maps and SBF stress-to-rest ratios. Three observers classified patients into "switch-off" and "failed switch-off" groups by visually comparing rest-stress perfusion data acquired with PCASL and first-pass, independently. First-pass categories were used as reference to evaluate the accuracy of quantitative classification.
Statistical Tests:
Wilcoxon signed-rank, Pearson correlation, kappa, percentage agreement, Generalized Linear Mixed Model, Mann-Whitney, Pearson Chi-squared, receiver operating characteristic, area-under-the-curve (AUC) and confusion matrix.
Significance:
P value < 0.05.
Results:
A total of 27 patients (84.4%) experienced splenic switch-off according to first-pass categories. Comparison of PCASL-derived SBF maps during stress and rest allowed assessment of splenic switch-off, reflected in a reduction of SBF values during stress. SBF stress-to-rest ratios showed a 97% accuracy (sensitivity = 80%, specificity = 100%, AUC = 85.2%).
Data Conclusion:
This study could demonstrate the feasibility of PCASL to identify splenic switch-off during adenosine perfusion MRI, both by qualitative and quantitative assessments.
Evidence Level:
2 TECHNICAL EFFICACY: 2.
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