In vivo absolute quantification of carnosine in the vastus lateralis muscle with 1 H MRS using a surface coil and water as internal reference

Objective To standardize a method for 1 H MRS intramuscular absolute quantification of carnosine in the thigh, using a surface coil and water as internal reference. Materials and methods Carnosine spectra were acquired in phantoms (5, 10, and 15 mM) as well as in the right gastrocnemius medialis (GM) and right vastus lateralis (VLM) muscles of young team sports athletes, using volume (VC) and surface (SC) coils on a 3 T scanner, with the same receiver gain. Water spectra were used as internal reference for the absolute quantification of carnosine. Results Phantom’s experiments showed a maximum error of 7%, highlighting the validity of the measurements in the study setup. The carnosine concentrations (mmol/kg ww, mean ± SD) measured in the GM were 6.8 ± 2.2 with the VC (C car VC) and 10.2 ± 3.0 with the SC (C car SC) ( P = 0.013; n = 9). Therefore, a correction was applied to these measurements (C car VC = 0.6582*C car SC), to make coils performance comparable (6.8 ± 2.2 for VC and 6.7 ± 2.0 for SC, P = 0.97). After that, only the SC was used to quantify carnosine in the VLM, where a concentration of 5.4 ± 1.5 ( n = 30) was found, with significant differences between men (6.2 ± 1.3; n = 15) and women (4.6 ± 1.2; n = 15). The error in quantitation was 5.3–5.5% with both coils. Conclusion The method using the SC and water as internal reference can be used to quantify carnosine in voluminous muscles and regions of the body in humans, where the VC is not suitable, such as the VLM.