Purpose: To study the correlation between apparent diffusion coefficient (ADC) and pathology in patients with undefined breast lesion, to validate how accurately ADC is related to histology, and to define a threshold value of ADC to distinguish malignant from benign lesions.
Materials and Methods:Seventy-eight patients (110 lesions) were referred for positive or dubious findings. Threedimensional fast low-angle shot (3D-FLASH) with contrast injection was applied. EPI diffusion-weighted imaging (DWI) with fat saturation was performed, and ROIs were selected on subtraction 3D-FLASH images before and after contrast injection, and copied on an ADC map. Inter-and intraobserver analyses were performed.Results: At pathology 22 lesions were benign, 65 were malignant, and 23 were excluded. The ADCs of malignant and benign lesions were statistically different. In malignant tumors the ADC was (mean Ϯ SEM) 0.95 Ϯ 0.027 ϫ 10 -3mm 2 /second, and in benign tumors it was 1.51 Ϯ 0.068 ϫ 10 -3 mm 2 /second. According to receiver operating characteristic (ROC) curves, we found a threshold between malignant and benign lesions for highest sensitivity and specificity (both 86%) around 1.13 Ϯ 0.10 ϫ 10 -3 mm 2 /second. For a threshold of 0.95 Ϯ 0.10 ϫ 10 -3 mm 2 /second, specificity was 100% but sensitivity was very low. Inter-and intraobserver studies showed good reproducibility.
Conclusion:The ADC may help to differentiate benign and malignant lesions with good specificity, and may increase the overall specificity of breast MRI.
13 C NMR studies of polycrystalline C 60 •2S 8 are reported. At room temperature, the static 13 C NMR spectra are similar to the 13 C spectrum of polycrystalline C 60 , which suggests that C 60 molecules undergo fast reorientational motion within the solvate lattice as within pure crystalline C 60 . This observation seems to contradict previous x-ray results that were interpreted in terms of motionless C 60 molecules within the solvate lattice; however, it agrees with thermodynamic measurements according to which the enthalpy for the departure of sulfur from the solvate is nearly equal to that of pure sulfur sublimation. The evolution of the shielding tensor as a function of temperature is also reported: it exhibits a steep change near 150 K that corresponds to a slowing down of the C 60 rotational motion. Finally, according to the variation of the 13 C spin-lattice relaxation time T 1 vs temperature, the dynamics of C 60 molecules, which consists in jumps between symmetryequivalent orientations, can be considered as ruled by two activation energies, 15.3 and 24.8 kJ mol Ϫ1 .
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