In vivo ¹H MRS for musculoskeletal lesion characterization: Which factors affect diagnostic accuracy?

In vivo ¹H MRS is a noninvasive imaging technique for the identification of malignancy. Musculoskeletal lesions vary in their composition, causing field inhomogeneity and magnetic susceptibility effects which may be technical and diagnostic challenges for MRS. This study investigated the factors that affect diagnostic accuracy in the use of MRS for the characterization of musculoskeletal neoplasms. During a 7-year period, 210 consecutive patients with musculoskeletal lesions larger than 1.5cm in diameter were examined. MRS of a single-voxel point-resolved spectroscopy sequence with TE=135ms was undertaken using a 1.5-T scanner. Lesions with a choline signal-to-noise ratio larger than 3.0 were considered to be malignant tumors. The diagnostic accuracy was calculated for all lesions and for subgroups on the basis of lesion type (bone and soft tissue), lesion composition (mixed and solid nonsclerotic), lesion size (≤4, >4-10 and >10cm), MR scanner (MR scanner 1 and 2) and selected voxel size (≤3, >3-8 and >8cm ³). Multivariate logistic regressions were performed to estimate the associations between each factor and diagnostic accuracy. The diagnostic accuracy was 73.3% for all lesions. The accuracy was 54.4% for mixed lesions and 80.4% for solid nonsclerotic lesions (p<0.001). The diagnostic accuracy was lower for larger lesions [86.8% for lesions of ≤4cm, 71.6% for lesions of >4-10cm (p=0.04) and 63.6% for lesions of >10cm (p=0.007)]. There was no difference in diagnostic accuracy for bone versus soft-tissue lesions or as a function of MR scanner or voxel size. By the use of multivariate logistic regression, a solid nonsclerotic lesion was 3.15 times (95% confidence interval, 1.59-6.27) more likely than a mixed lesion to have a diagnosis (p=0.001). MRS can be used to characterize musculoskeletal lesions, particularly solid nonsclerotic lesions.