Kobus Thiele, Wright Alan J, Weiland Elisabeth, Heerschap Arend, Scheenen Tom W J
Radboud University Medical Centre, Radiology Department, Nijmegen, The Netherlands.
Siemens Healthcare, Erlangen, Germany.
Magn Reson Med. 2015 Jan;73(1):1-12. doi: 10.1002/mrm.25122. Epub 2014 Jan 31.
In (1)H MR spectroscopic imaging ((1)H-MRSI) of the prostate the spatial distribution of the signal levels of the metabolites choline, creatine, polyamines, and citrate are assessed. The ratio of choline (plus spermine as the main polyamine) plus creatine over citrate [(Cho+(Spm+)Cr)/Cit] is derived from these metabolites and is used as a marker for the presence of prostate cancer. In this review, the factors that are of importance for the metabolite ratio are discussed. This is relevant, because the appearance of the metabolites in the spectrum depends not only on the underlying anatomy, metabolism, and physiology of the tissue, but also on acquisition parameters. These parameters influence especially the spectral shapes of citrate and spermine resonances, and consequently, the (Cho+(Spm+)Cr)/Cit ratio. Both qualitative and quantitative approaches can be used for the evaluation of (1)H-MRSI spectra of the prostate. For the quantitative approach, the (Cho+(Spm+)Cr)/Cit ratio can be determined by integration or by a fit based on model signals. Using the latter, the influence of the acquisition parameters on citrate can be taken into account. The strong overlap between the choline, creatine, and spermine resonances complicates fitting of the individual metabolites. This overlap and (unknown, possibly tissue-related) variations in T1, T2, and J-modulation hamper the application of corrections needed for a "normalized" (Cho+(Spm+)Cr)/Cit ratio that would enable comparison of spectra measured with different prostate MR spectroscopy protocols. Quantitative (Cho+(Spm+)Cr)/Cit thresholds for the evaluation of prostate cancer are therefore commonly established per institution or per protocol. However, if the same acquisition and postprocessing protocol were used, the ratio and the thresholds would be institution-independent, promoting the clinical usability of prostate (1)H-MRSI.
在前列腺的氢磁共振波谱成像（¹H-MRSI）中，对代谢物胆碱、肌酸、多胺和柠檬酸盐的信号水平的空间分布进行评估。胆碱（加上作为主要多胺的精胺）与肌酸之和与柠檬酸盐的比值[（Cho+(Spm+)Cr）/Cit]由这些代谢物得出，并用作前列腺癌存在的标志物。在本综述中，讨论了对代谢物比值重要的因素。这很重要，因为光谱中代谢物的出现不仅取决于组织的基础解剖结构、代谢和生理学，还取决于采集参数。这些参数尤其会影响柠檬酸盐和精胺共振的光谱形状，进而影响（Cho+(Spm+)Cr）/Cit比值。定性和定量方法均可用于评估前列腺的¹H-MRSI光谱。对于定量方法，（Cho+(Spm+)Cr）/Cit比值可通过积分或基于模型信号的拟合来确定。使用后者，可以考虑采集参数对柠檬酸盐的影响。胆碱、肌酸和精胺共振之间的强烈重叠使单个代谢物的拟合变得复杂。这种重叠以及T1、T2和J调制中（未知的、可能与组织相关的）变化阻碍了对“归一化”（Cho+(Spm+)Cr）/Cit比值所需校正的应用，而这种校正将使不同前列腺磁共振波谱协议测量的光谱能够进行比较。因此，评估前列腺癌的定量（Cho+(Spm+)Cr）/Cit阈值通常是每个机构或每个协议确定的。然而，如果使用相同的采集和后处理协议，该比值和阈值将与机构无关，从而提高前列腺¹H-MRSI的临床实用性。
