The Goldilocks Zone for 3‐T MRS Studies Using Semi‐LASER: Determining the Optimal Balance Between Repetition Time and Scan Time

Le résumé fourni par la source

ABSTRACT 1 H‐MR spectroscopy studies often use a short TR to reduce scan time. However, this causes significant T 1 ‐weighting (T 1 w), which can alter metabolite estimates due to acquisition factors rather than biochemistry. Our goal was to determine the optimal balance between scan time and TR that minimizes T 1 w effects in semi‐LASER MRS at 3 T. Spectra were acquired in the posterior cingulate cortex of five healthy volunteers (2 male/3 female, mean age 25 ± 2 years) and analyzed using FSL‐MRS. The SNR and metabolite estimates of five metabolites were compared at TR = 2, 5, and 8 s, under conditions of “similar scan time” with varying acquisition numbers and “constant number of acquisitions” with varying scan times. T 1 relaxation times derived from metabolite estimates were compared to literature. With a 25% longer scan time, SNR TR = 5s was 34% higher and SNR TR = 2s was 29% higher than SNR TR = 8s for data with “similar scan times.” Using a TR = 5 s or longer, the SNR per minute is consistent for metabolites with T 1 s less than 2 s. Metabolite estimate trends were similar for the two different scenarios of “similar scan time” and “same number of acquisitions,” where all metabolite estimates were obtained without metabolite T 1 correction. The largest metabolite estimates were found at TR = 8 s, they were 10–15% lower at TR = 5 s and 15–30% lower at TR = 2 s. T 1 values agreed with literature values. At TR = 2 s, SNR per minute and metabolite estimates were lower due to reduced signal availability via T 1 w effects. TR = 8 s had the least amount of T 1 w effects, but results in lower SNR per minute. TR = 5 s had enough signal recovery to be robust to T 1 w effects, and yielded the largest SNR for similar scan times, with a clinically feasible scan time of 5 m 40 s. Using semi‐LASER MRS with a TR = 5 s is recommended to improve the sensitivity of MRS to changes in metabolite estimates.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.