Quality assurance for MRI: practical experience.

Abstract

The aim of this study is to propose guidelines for quality assurance (QA) in MRI, based on a comprehensive assessment of QA parameters undertaken on a busy clinical MRI scanner over the course of 1 year. QA phantoms supplied by the scanner manufacturer were used together with the Eurospin MRI phantom set. Signal-to-noise ratio (SNR) and image uniformity were measured daily from spin echo images acquired using a quadrature send-receive head coil and from a gradient echo sequence using the Helmholtz body coil. The voltage of the transmit radiofrequency (RF) amplifier was noted. Monthly measurements of slice thickness, geometric distortion, slice position, image resolution and image ghosting were acquired using the head coil. In addition, SNR was measured monthly on a selection of commonly used coils. Apart from some drift of the RF amplifier voltage, all measurements were within acceptable limits and were stable over the course of 1 year. Satisfactory measurements of SNR were possible using the simple phantom supplied with the scanner. The SNR, geometric distortion and RF amplifier voltage are simple to determine and can be measured in less than 15 min by the scanner operator, using the scanner software. Weekly recording of these parameters is recommended for busy clinical MRI scanners, as this should allow deviations from acceptable limits to be identified early. Such in-house checks can usefully be compared with the less frequent estimations performed by the service engineer. Comprehensive QA routines are discussed for systems used for quantitative measurements.

Measurement of MRI scanner performance with the ADNI phantom

“…Here the requirement is the phantom provides validation that corrections are properly applied. These values are two to four times larger than reported [3][4][5][6][7] after data-driven corrections were made. Detailed information about the gradient hardware may or may not be present ͑and reliable͒ in the DICOM headers and incorrect gradient hardware was reported by five ADNI sites when surveyed at the start of the study.…”

Multiple-animal MR Imaging using a 3T Clinical Scanner and Multi-channel Coil for Volumetric Analysis in a Mouse Tumor Model

“…[17][18][19] Approximately 2z distortion in 2D geometry could induce 6z (in other words, (1-0.98 3 )×100 or (1.02 3 -1)× 100) error in 3D volumetric analysis. In the 4 phantoms of diŠerent volumes, volume estimated by MR imaging was highly correlated with actual volume.…”

Self-Managed Belief as Part of the “Scientific Method”: Part II—Examples From Published Scientific Work

“…Data QC should not only be performed on phantom data, but also on real (in vivo) data, as they may contain not only technical artifacts but additional sample-specific artifacts coming from magnetically inhomogeneous regions and/or physiological motions (e.g., breathing, heartbeat, involuntary bowel movements, etc.-and mixtures of those [15][16][17][18][19][20]. Only if the data quality obtained from healthy volunteers seems to be sufficient for the study statistics to enable valid patient data and group statistics, should the measurements be continued with patient groups [21].…”