Thallium-201 SPECT versus body diffusion-weighted MRI for evaluation of bone and soft tissue tumors

1659 Objectives: Some studies have demonstrated that a newly developed body diffusion-weighted (DW) MRI is useful for differentiating benign or malignant lesions in patients with bone and soft tissue tumors. Thallium-201 (Tl) SPECT has been widely used for clinically same purpose. We compared DW-MRI with Tl-SPECT to clarify the characteristics of these two methods. Methods: Both MRI and Tl-SPECT were performed on 42 bone and soft tissue tumors (12 malignant lesions and 30 benign lesions), whose final diagnosis was based on histology. DW-MRI was performed with an echo planar imaging sequence. The apparent diffusion coefficient (ADC) value (×10-3 mm2/sec) was calculated on the lesions. The early and delayed Tl-SPECT were performed, and the uptake ratio of the lesion to the contralateral normal tissue was obtained on the early images (early ratio; ER) as well as on the delayed images (delayed ratio; DR). The diagnostic accuracy of malignant lesions was evaluated by visual interpretation. The ADC values as well as ER and DR in the lesions were evaluated and compared for quantitative evaluation of DW imaging and Tl-SPECT, respectively. Results: High sensitivity was observed in both DW-MRI and Tl-SPECT in visual interpretation. Low specificity was observed on DW-MRI (44.4 %), suitable specificity was observed on Tl-SPECT (80%). In quantitative assessment, the sensitivity, specificity were calculated when the cut-off value of ADC was less than 1.7 on DW-MRI, and the cut-off value of ER was over 3.9 on Tl-SPECT. Specificity on ADC was only 36.4%, although high sensitivity 100 % was observed. There were significant differences between the uptake ratio of the benign and that of the malignant lesions (ER: 6.23 ± 2.13 vs 26.72 ± 8.91, p Conclusions: The ADC values of bone and soft tissue tumors overlapped and could not be used to differentiate between benign and malignant tumors. Whereas the ER values and delayed visual assessment of Tl-SPECT has high diagnostic ability for bone and soft tissue tumors. Therefore, Tl-SPECT has a better diagnostic ability than DW-MRI for evaluation of bone and soft tissue tumors.