Objective To evaluate the value of whole-body diffusion weighted imaging（WB-DWI） on detection of malignant metastasis.Methods Forty-six patients with malignant tumors underwent WB-DWI examinations between April 2007 and August 2007 in our hospital.Before WB-DWI examination

the primary cancers of all the patients were confirmed by pathology

and the TNM-stage was assessed with conventional magnetic resonance imaging（MRI） or computed tomography（CT）.WB-DWI was performed using short TI inversion recovery echo-planar imaging（STIR-EPI） sequence.Abnormal high signal intensities on WB-DWI were considered as metastases.The results of WB-DWI were compared with other imaging modalities.For the assessment of the diagnostic capability of WB-DWI

WB-DWI were compared with CT for demonstrating mediastinal lymph node metastases and lung metastases

and with conventional MRI for demonstrating metastases in other locations.Results WB-DWI demonstrated 143 focuses

14 of which were diagnosed to be benign lesions in routine imaging.The number of bone metastases depicted on WB-DWI and routine imaging was 85 and 86;lymph node metastases was 17 and 18;liver metastases was 14 and 14;lung metastases was 4 and 8;and brain metastases was 6 and 8

respectively.WB-DWI failed to detect 12 metastatic lesions including 3 osteoplastic bone metastases

4 lung metastases

3 mediastinal lymph node metastases

and 2 brain metastases.Four metastatic lesions including 2 deltopectoral lymph nodes and 2 rib metastases were detected with WB-DWI alone

all of which evolved greatly during clinical follow-up for more than 6 months.WB-DWI had higher detection rates for metastatic lesions in liver

bone

and lymph nodes than those in lung and brain（χ2=30

P<0.001）.Conclusions WB-DWI could detect most of metastatic lesions that were diagnosed with conventional MRI and CT.The limitations of WB-DWI might be had high false-positive rate and low efficiency in detecting mediastinal lymph node

brain

and lung metastases.