QASPER
Quantitative Arterial Spin Labelling Perfusion Reference
Calibration and quality assurance standard for ASL perfusion MRI
Why use QASPER?
- To ensure consistency of your ASL acquisition over time
- To help with the development of new ASL pulse sequences
- To compare the values from ASL sequences across scanners
Are you using ASL to track disease progression? Do you wonder if quantitative ASL values vary because of hardware or physiology?
How does QASPER work?
QASPER provides a reliable, reproducible reference standard for Arterial Spin Labelling perfusion MRI. The phantom accurately replicates the physiological process of arterial blood delivery to tissue through a sophisticated three-compartment design. At its core, a porous polyethylene substrate with capillary-scale pores (≈10μm) is fed by 60 arteriole-scale tubes arranged in a ring configuration, creating a toroidal perfusion region that closely mimics in vivo capillary perfusion. The key advantage over volunteer scanning is absolute consistency: the flow rate of perfusate remains stable to within 3% throughout every measurement, providing a traceable ground truth for validating ASL sequences, tracking scanner performance over time, and harmonising measurements across multiple sites.
Flow Path Components
The first simulates the feeding arteries and arterioles that supply blood to an organ. Vessel geometry and flow velocities within this region match those found in the human body.
Compartment two uses a porous polymer substrate to simulate the microvascular, incoherent flow observed at the capillary bed.
The third compartment represents the remainder of the cardiovascular system; venous return from the organ to the heart where it is pumped back. A deliberately long, labyrinthine flow path ensures that none of the labelled bolus is recirculated before the label decays and ensures fully developed equilibrium magnetisation.
At the heart of the QASPER phantom is an MRI compatible pump that delivers liquid at a known flow rate to a simulated capillary bed. During operation, fluid is pumped around a closed system that is simply placed on the patient couch of an MRI scanner; it is not necessary to put tubing through the waveguides or to empty and re-fill the system at each use. The phantom continuously reports via wireless connection to a computer application its real-time operating state such as flow rate, temperature, battery drain etc, and can also be controlled by the user, for example to set the flow rate set point to a specified value.
Key Features
Consistency
Reliable, repeatable measurements for long-term quality assurance
- The same system flow rate is maintained at all times, to within 3% of the desired value
- Benchmark ASL perfusion measurements across ASL measurement techniques and MRI systems
Calibration
Traceable standards for quantitative ASL measurements
- Internal flow metre is calibrated with traceability to internationally recognised standards
- The phantom connects wirelessly to phantom control software, providing real time control, monitoring and recording of the flow rate and temperature
- The exact flow rate and temperature during an MR acquisition can be determined, and cross-referenced for Quality Assurance validation
Assurance
Validate your ASL protocols and sequences
- Compare measurements with ground truth reference data
- Use as part of an ASL Quality Control procedure
Technical Specifications
Flow Rate Performance
Accuracy
±3% of set value
Range
0-500 ml/min
Calibration
NIST-traceable calibration
System Components
- pump
- MRI-compatible peristaltic pump
- flow Meter
- Calibrated Turbine Flow Meter
- perfusion Chamber
- 60 arteriole-scale tubes feeding porous substrate
- capillary Bed
- Porous polyethylene (≈10μm pore size)
- communication
- Remote connection to control software
Physical Properties
- dimensions
- Fits within standard head coil
- weight
- Portable system with integrated battery
- material
- MRI-compatible materials throughout
Performance
- consistency
- Flow rate maintained to ±3%
- calibration Traceability
- Traceable to international standards
- temperature Control
- Real-time flow and temperature monitoring
Downloads
Documentation
Publications
QASPER has been featured in multiple peer-reviewed publications and conference proceedings. Below are key publications demonstrating the phantom's use in ASL research and quality assurance.
X Golay et al.
"How to quantify ASL values in a perfusion phantom"
A-1672. Magn Reson Mater Phy (2019) 32(Suppl 1): 373.
A Oliver-Taylor et al.
"A multi-site round robin assessment of ASL using a perfusion phantom"
In: Proceeding of ISMRM 2019. 2653. 2019.
A Oliver-Taylor et al.
"A Calibrated Perfusion Phantom for Quality Assurance of Quantitative Arterial Spin Labelling"
In: Proceedings of ISMRM 2017. 0681. 2017.
Warnert EAH, Steketee RME, Vernooij MW, Ikram MA, Vogel M, Hernandez Tamames JA, Kotek G.
"Implementation and validation of ASL perfusion measurements for population imaging"
Magn Reson Med. 2020 Oct;84(4):2048-2054. doi: 10.1002/mrm.28271.
Xu F, Zhu D, Fan H, Lu H, Liu D, Li W, Qin Q.
"Magnetic resonance angiography and perfusion mapping by arterial spin labeling using Fourier transform-based velocity-selective pulse trains: Examination on a commercial perfusion phantom"
Magn Reson Med. 2021 Sep;86(3):1360-1368. doi: 10.1002/mrm.28805.
Ready to standardise your ASL measurements?
Get in touch to learn more about QASPER and how it can improve your ASL quality assurance workflow.