Fig. 1

Sequence diagram of diffusion-weighted point resolved spectroscopy. RF denotes the radiofrequency pulse, while GX, GY, and GZ represent the gradients along the left-right, anterior-posterior, and head-foot directions, respectively. The blue color indicates the localization gradient, black represents the spoiling gradient, and green denotes the diffusion gradient. The echo time (TE) is defined as twice the sum of τ 1 and τ 2. ε denotes the duration of the applied diffusion gradient, while Δ represents the interval between the diffusion gradient pairs (i.e., the diffusion time), which is half the duration of TE

Fig. 2

Illustration of the two cycling modes. (a) Internal cycling of b-values: The b-value loop occurs within the accumulation loop, where data from different b-values are sequentially looped and collected before proceeding to the next accumulation. (b) External cycling of b-values: The b-value loop occurs outside the accumulation loop, with data for the same b-value first accumulated before moving on to the next b-value. The b0 denotes the signal when no diffusion gradient is applied. b1-LR, b1-AP, and b1-HF represent the signals when the diffusion gradient is applied in the left-right, anterior-posterior, and head-foot directions of the subject respectively. Blue, orange, yellow, and purple indicate b0, b1-LR, b1-AP, and b1-HF respectively

Fig. 3

Illustration of the volume of interest localization for diffusion-weighted magnetic resonance spectroscopy (left column) and the corresponding spectra (right column). (a) Corona radiata; (b) Posterior cingulate cortex. b0 denotes the spectrum acquired without diffusion gradient application, while b1-LR, b1-AP, and b1-HF represent spectra obtained with the diffusion gradient applied in the left-right, anterior-posterior, and head-foot directions, respectively

Fig. 4

Variations in signal intensity of the water peak in each transient spectrum acquired using different gating methods for a subject. (a) The volume of interest is located in the corona radiata region; (b) The volume of interest is located in the posterior cingulate cortex region. b0 represents the signal without diffusion gradient application, while b1-LR, b1-AP, and b1-HF denote the signals with the diffusion gradient applied in the left-right, anterior-posterior, and head-foot directions, respectively. Blue, orange, and yellow indicate the use of ECG gating, respiratory gating, and no gating, respectively

Table 1

Comparison of apparent diffusion coefficient (ADC) obtained under different gating conditions and results of linear mixed-effects model analysis in the corona radiata

Table 2

Comparison of apparent diffusion coefficient (ADC) obtained under different gating conditions and results of linear mixed-effects model results analysis in the posterior cingulate cortex

Table 3

Comparison of the apparent diffusion coefficient (ADC) obtained using the internal and external b-value cycling methods and results of linear mixed-effects model analysis

Fig. 5

The distribution of the coefficient of variation of the apparent diffusion coefficient (ADC) for three metabolites when using the internal and external b-value cycling modes. (a) tCho; (b) tCr; (c) tNAA. The LR, AP, and HF represent the coefficient of variation of the ADC when the diffusion gradient is applied in the left-right, anterior-posterior, and head-foot directions, respectively, while "mean" denotes the coefficient of variation of the averaged ADC across the three orthogonal directions. Blue indicates the internal b-value cycling mode; orange represents the external b-value cycling mode. * P < 0.05; ** P < 0.01