Objective To evaluate the feasibility of whole body diffusion weighted imaging （DWI） in the diagnosis of metastatic tumor. Methods Fifty-six patients （40 males and 16 females

age ranging from 29 to 84 years with a mean age of 57 years） with a variety of primary tumors were investigated by whole body DWI combined with computed tomography （CT） and/or conventional magnetic resonance imaging （MRI） scans. Twelve patients underwent positron emission tomography. The final diagnosis was made on the basis of CT or high resolution CT result for lung lesion and MRI or CT result for skull

abdomen and other parts. All tumors were classified into four groups by their diameter: below 1.0 cm

1.0-1.9 cm

2.0-2.9 cm

and above 3.0 cm. The sensitivity and specificity of whole body DWI in the detection of metastatic tumor were analyzed. Results The sensitivities of whole body DWI for screening metastasis of the four groups were 38%

75%

97%

and 100%

respectively. Whole body DWI showed the highest sensitivity and specificity for detecting metastasis of the skeletal system. It was difficult to find metastatic tumor whose diameter was below 1.0 cm

or lymph nodes located in the pelvis with diameter below 2.0 cm. Conclusions Whole body DWI is a promising method in the diagnosis of metastastic tumors. With the perfection of scanning parameter

whole body DWI should be a new effective whole body technique for tumor detection.