Radiological Sciences, David Geffen School of Medicine at UCLA, 10945 Peter V Ueberroth Building, Suite#1417A, Los Angeles, CA, 90095, USA.
Physics and Biology in Medicine IDP, University of California Los Angeles, Los Angeles, CA, USA.
Sci Rep. 2023 Oct 5;13(1):16809. doi: 10.1038/s41598-023-43356-8.
Acquisition duration of correlated spectroscopy in vivo can be longer due to a large number of t increments along the indirect (F) dimension. Limited number of t increments on the other hand leads to poor spectral resolution along F. Covariance transformation (CT) instead of Fourier transform along t is an alternative way of increasing the resolution of the 2D COSY spectrum. Prospectively undersampled five-dimensional echo-planar correlated spectroscopic imaging (EP-COSI) data from ten malignant patients and ten healthy women were acquired and reconstructed using compressed sensing. The COSY spectrum at each voxel location was then generated using FFT, CT and a variant of CT called Inner Product (IP). Metabolite and lipid ratios were computed with respect to water from unsuppressed one-dimensional spectrum. The effects of t-ridging artifacts commonly seen with FFT were not observed with CT/IP. Statistically significant differences were observed in the fat cross peaks measured with CT/IP/FFT. Spectral resolution was increased ~ 8.5 times (~ 19.53 Hz in FFT, ~ 2.32 Hz in CT/IP) without affecting the spectral width along F was possible with CT/IP. CT and IP enabled substantially increased F resolution effectively with significant gain in scan time and reliable measure of unsaturation index as a biomarker for malignant breast cancer.
由于间接（F）维度上大量的 t 增量，相关谱在体内的采集时间可能会更长。另一方面，t 上的 t 增量有限会导致 F 方向上的光谱分辨率较差。协方差变换（CT）而不是沿 t 的傅里叶变换是提高 2D COSY 光谱分辨率的另一种方法。前瞻性欠采样的来自 10 名恶性肿瘤患者和 10 名健康女性的五维回波平面相关光谱成像（EP-COSI）数据采用压缩感知进行采集和重建。然后使用 FFT、CT 和称为内积（IP）的 CT 变体在每个体素位置生成 COSY 谱。未抑制的一维谱的水相对于代谢物和脂质比进行计算。未观察到 FFT 常见的 t 削波伪影的影响。使用 CT/IP/FFT 测量的脂肪交叉峰存在统计学显著差异。通过 CT/IP 可以在不影响 F 方向上的光谱宽度的情况下将光谱分辨率提高约 8.5 倍（FFT 中为 19.53 Hz，CT/IP 中为 2.32 Hz）。CT 和 IP 能够有效地显著提高 F 分辨率，同时显著增加扫描时间，并可靠地测量不饱和指数作为恶性乳腺癌的生物标志物。
