Choline-containing compounds quantification by 1H NMR spectroscopy using external reference and noise measurements

A straightforward multiparametric quality control protocol for proton magnetic resonance spectroscopy: Validation and comparison of various 1.5 T and 3 T clinical scanner systems

PURPOSE

The aim of this study was to propose and validate across various clinical scanner systems a straightforward multiparametric quality assurance procedure for proton magnetic resonance spectroscopy (MRS).

METHODS

Eighteen clinical 1.5 T and 3 T scanner systems for MRS, from 16 centres and 3 different manufacturers, were enrolled in the study. A standard spherical water phantom was employed by all centres. The acquisition protocol included 3 sets of single (isotropic) voxel (size 20 mm) PRESS acquisitions with unsuppressed water signal and acquisition voxel position at isocenter as well as off-center, repeated 4/5 times within approximately 2 months. Water peak linewidth (LW) and area under the water peak (AP) were estimated.

RESULTS

LW values [mean (standard deviation)] were 1.4 (1.0) Hz and 0.8 (0.3) Hz for 3 T and 1.5 T scanners, respectively. The mean (standard deviation) (across all scanners) coefficient of variation of LW and AP for different spatial positions of acquisition voxel were 43% (20%) and 11% (11%), respectively. The mean (standard deviation) phantom T₂values were 1145 (50) ms and 1010 (95) ms for 1.5 T and 3 T scanners, respectively. The mean (standard deviation) (across all scanners) coefficients of variation for repeated measurements of LW, AP and T₂ were 25% (20%), 10% (14%) and 5% (2%), respectively.

CONCLUSIONS

We proposed a straightforward multiparametric and not time consuming quality control protocol for MRS, which can be included in routine and periodic quality assurance procedures. The protocol has been validated and proven to be feasible in a multicentre comparison study of a fairly large number of clinical 1.5 T and 3 T scanner systems.

Accuracy of 2-hydroxyglutarate quantification by short-echo proton-MRS at 3 T: a phantom study

PURPOSE

We set out to investigate the potential confounding effect of variable concentration of N-acetyl-l-aspartate (NAA) and Glutamate (Glu) on measurement of the brain oncometabolite 2-hydroxyglutarate (2HG) using a standard MRS protocol. This issue may arise due to spectral overlap at clinical magnetic field strengths and thus complicate the usage of 2HG as a putative biomarker of gliomas bearing mutations of the isocitrate dehydrogenase (IDH) 1 and 2 genes.

METHODS

Spectra from 25 phantoms (50 mL falcon test tubes) containing a range of known concentrations of 2HG, NAA and Glu were acquired using a clinical 3 T scanner with a quadrature head coil, single-voxel point-resolved spectroscopy sequence with TE = 30 ms. Metabolite concentrations were estimated by linear combination analysis and a simulated basis set.

RESULTS

NAA and Glu concentrations can have a significant confounding effect on 2HG measurements, whereby the negative changes in concentration of these metabolites typically observed in (peri)lesional areas can lead to under-estimation of 2HG concentration with respect to spectra acquired in presence of physiological levels of NAA and Glu.

CONCLUSION

The confounding effect of NAA and Glu concentration changes needs to be considered: in patients, it may mask the presence of 2HG at low concentrations, however it is not expected to lead to false positives. 2HG data acquired using standard short echo-time MRS protocols should be considered with caution.