Validating a robust double‐quantum‐filtered ¹H MRS lactate measurement method in high‐grade brain tumours

Abstract

1H MRS measurements of lactate are often confounded by overlapping lipid signals. Double‐quantum (DQ) filtering eliminates lipid signals and permits single‐shot measurements, which avoid subtraction artefacts in moving tissues. This study evaluated a single‐voxel‐localized DQ filtering method qualitatively and quantitatively for measuring lactate concentrations in the presence of lipid, using high‐grade brain tumours in which the results could be compared with standard acquisition as a reference.Paired standard acquisition and DQ‐filtered 1H MR spectra were acquired at 3T from patients receiving treatment for glioblastoma, using fLASER (localization by adiabatic selective refocusing using frequency offset corrected inversion pulses) single‐voxel localization. Data were acquired from 2 × 2 × 2 cm3 voxels, with a repetition time of 1 s and 128 averages (standard acquisition) or 256 averages (DQ‐filtered acquisition), requiring 2.15 and 4.3 min respectively.Of 37 evaluated data pairs, 20 cases (54%) had measureable lactate (fitted Cramér–Rao lower bounds ≤ 20%) in either the DQ‐filtered or the standard acquisition spectra. The measured DQ‐filtered lactate signal was consistently downfield of lipid (1.33 ± 0.03 ppm vs 1.22 ± 0.08 ppm; p = 0.002), showing that it was not caused by lipid breakthrough, and that it matched the lactate signal seen in standard measurements (1.36 ± 0.02 ppm). In the absence of lipid, similar lactate concentrations were measured by the two methods (mean ratio DQ filtered/standard acquisition = 1.10 ± 0.21). In 7/20 cases with measurable lactate, signal was not measureable in the standard acquisition owing to lipid overlap but was quantified in the DQ‐filtered acquisition. Conversely, lactate was undetected in seven DQ‐filtered acquisitions but visible using the standard acquisition.In conclusion, the DQ filtering method has proven robust in eliminating lipid and permits uncontaminated measurement of lactate. This is important validation prior to use in tissues outside the brain, which contain large amounts of lipid and which are often susceptible to motion.

Spectral editing in 1H magnetic resonance spectroscopy: Experts' consensus recommendations

“…However, in the presence of large lipid signals or small subject/system instabilities, lactate detection via MQF editing is recommended over J-difference editing. 40 A common coediting partner of lactate, and a valid editing target in its own right, is BHB. 20 BHB, together with acetone and acetoacetate, is a ketone body that can function as an alternative substrate to glucose.…”

In vitro singlet state and zero-quantum encoded magnetic resonance spectroscopy: Illustration with N-acetyl-aspartate

“…It is worth to mention that although double quantum and zero quantum (DQ/ZQ) filters are used in MRS [ 66 ] the SISTEM approach is quite different. LLS filtering techniques select not only multi-spin systems but the systems with the specific values of chemical shift and J-coupling constant ( Fig 2 ).…”

Lactate concentration in breast cancer using advanced magnetic resonance spectroscopy

“… 19 Water and lactate amplitudes were quantified from reference and lactate spectra, respectively, using corresponding prior knowledge databases. 20 The lactate concentration in the tumour was then computed from water and lactate amplitudes, literature breast tissue biochemical composition and relaxation properties on the 3 T scanner. 21 The quantification of lactate concentration was conducted following written procedure and blinded from group allocation.…”