Synopsis

Keywords: Contrast mechanisms: Perfusion

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) assesses tissue perfusion, which is crucial for diagnosing various diseases. Quantitative analysis improves accuracy but faces challenges due to inter/intra-scanner variability. Proposed solutions include using phantoms with known contrast-agent concentrations. The Point-of-care Portable Perfusion Phantom (P4) addresses this, reducing measurement variations across scanners. Challenges remain in peripheral device portability, but efforts are underway. Despite advancements, ensuring clinical advantage outweighs costs is crucial for effective implementation.

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a method utilized to evaluate tissue perfusion by observing changes in contrast-agent concentration over time. While clinical assessments of DCE-MRI often rely on qualitative interpretations, these can be prone to variability among observers. Conversely, quantitative analysis of DCE-MRI data offers a more objective and potentially more accurate approach for diagnosis, prognosis, and therapy monitoring across various conditions such as cancer, inflammation, and neurodegeneration.
However, concerns persist regarding the consistency of quantitative DCE-MRI measurements across different MRI scanners due to variations in hardware settings, pulse sequences, and post-processing methods (1). Achieving reproducible measurements across scanners is crucial for reliable data in both clinical trials and routine practice.
One proposed solution to address inter-scanner variability is the use of a phantom with known contrast-agent concentrations. This phantom serves as a reference to reduce variation in quantifying contrast-agent concentration and tissue pharmacokinetic parameters. To be effective, the phantom should ideally be small enough to be scanned alongside a human subject for on-site reference, minimizing drift in measurements due to hardware instability (2).
Initially, a static phantom comprising compartments with different contrast-agent concentrations was suggested (3). However, this approach may not adequately replicate tissue signal variations caused by microvascular flow (1), and inaccuracies in measuring flip angles can further compromise its effectiveness, particularly in high-field MRI (4-7).
In response, we developed the Point-of-care Portable Perfusion Phantom (P4), designed to be compact yet avoid partial volume effects (1). Using the P4 for error correction significantly reduced variation in quantitative DCE-MRI measurements across different 3T MRI scanners (8). Additionally, we demonstrated its clinical utility in assessing pancreatic cancer therapy response (9) and improving grade stratification of prostate cancer (2). Furthermore, the P4-based error correction showed promise in distinguishing between pseudo and true progressions of glioblastoma after chemoradiation therapy.
Despite these advancements, challenges remain regarding the portability of peripheral devices needed to activate the P4 phantoms. Efforts are underway to develop a portable phantom toolkit to address this limitation and further enhance the utility of the P4 in clinical settings.
In summary, quantitative DCE-MRI has exhibited considerable clinical promise. However, enhancing measurement accuracy may require supplementary hardware and software tools. Consequently, the effective implementation of this methodology mandates a demonstrable clinical advantage that outweighs the incurred costs.

Acknowledgements

The studies to advance the point-of-care perfusion phantom for accurate DCE-MRI measurement were funded by NIH UG3/UH3 CA232820, R03 CA245986, and R01 CA272702. Dr. Harrison Kim owned the intellectual property of the point-of-care perfusion phantom.