Bone and soft tissue lesions: Diagnosis with combined H–1 MR imaging and P–31 MR spectroscopy

The authors studied the feasibility and diagnostic yield of combined magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) in 34 patients with bone and soft tissue masses located in the extremities or trunk. There were 17 an benign 17 malignant lesions; all studies were performed before bi opsy. but four lesions had been excised previously. A 1.5-T in strument was used. Magnetic resonance imaging consisted of Tl wcightcd coronal and sagittal images and T2-weighted axial images; in both instances, standard parameters were used. There is no description of the method of analysis of these images; presum ably. standard clinical interpretations were made. Magnetic reso nance spectroscopy was performed using circular surface coils with diameters chosen based on the size and location of the lesion. No additional localization method was employed. Transmitter gain was based on phantom studies done with each coil. Distributions of tissue types within the sensitive volume of the surface coil were estimated by planimetry of tissues within a hemispherical region of interest, with radius equal to the coil radius. The spectra were quantified using standard techniques. Magnetic resonance imaging was unable confidently to assign most lesions to a benign or a malignant group. However, the phosphomonocstcr (PME) nucleo side triphosphate (NTP) ratio was able to make this discrimination with a sensitivity of 1.00 and specificity of 0.93 if the threshold was set at 2 SDs above the mean ratio for the benign group. The mean peak area ratios for benign and malignant groups were dif ferent by unpaired t test (adjusted for multiple comparisons) for PME and phosphodicstcr (PDE) ratios to NTP.