Evaluation of Ovarian Tumors by Proton Magnetic Resonance Spectroscopy at Three Tesla

Aim:The purpose of this study was to determine the feasibility of acquiring in vivo proton magnetic resonance spectroscopy of ovarian lesions at a magnetic field strength of 3 Tesla (T). The goal was to provide potentially diagnostic biochemical information that may aid in the characterization of ovarian neoplasms detected during clinical magnetic resonance imaging scanning. Methods:Fourteen patients referred to 2 gynecologic oncologic surgeons were examined in a whole-body 3.0 T clinical scanner using an 8-element phased-array surface coil. Single voxel spectroscopy (SVS) was undertaken after identification of lesions on T1-weighted and T2-weighted imaging. SVS was performed using the point resolved spectroscopy (PRESS) localization technique using a echo time (TE) of 135 milliseconds and repetition time (TR) of 2000 milliseconds and with 192 signal averages. Resonance integrals for the prominent signals from choline-containing compounds and creatine (Cr) were studied and presence of other prominent spectroscopic signals reported. Each SVS acquisition was performed in less than 8 minutes. Magnetic resonance spectral findings were correlated with the detailed pathology reports obtained after resection of each tumor. Results:Pathology revealed 7 patients with malignant surface epithelial-stromal tumors, 3 patients with germ cell tumors, 3 patients with benign serous cystadenomas, and 1 patient with a non-neoplastic endometrioma. Spectroscopic data were acquired from 16 voxels in 14 patients. Resonances attributable to choline-containing compounds and Cr were recorded in all malignant tumors and some of the benign tumors. When detected, a choline/Cr integral ratio of greater than 3 was found to indicate that a tumor was malignant in nature, whereas a choline/Cr integral ratio less than 1.5 was found to indicate that a tumor was benign in nature. There was 1 exception, a 13-cm serous cystadenofibroma, where the choline/Cr integral ratio was 3.13. Several other prominent metabolites were recorded including lactate, lipid, and an as yet unassigned resonance (possibly N-acetylaspartate or sialic acid) at 2.07 ppm. Conclusions:Spectroscopy of ovarian masses can be recorded at 3.0 T with acceptable spectral quality and good signal-to-noise ratio. There are stringent technical considerations to be considered in obtaining good spectral quality. Further experience with a larger and more biologically variable range of tumors needs to be undertaken to determine the final clinical utility of this technique, but initial results from this small cohort are promising.