Whole-body Diffusion-weighted MRI In The Staging Of Malignant Tumors: Comparison With PET-CT In A Pilot Study

ObjectiveThe mortalities of oncological patients depend on the type of tumors and metastasis. Radiological methods play an important role in staging, monitoring and discovering of reoccurrence of tumors. Positron emission tomography (PET)/computed tomography (CT) with high sensitivity and specificity has become an established imaging technique for diagnosis and staging of cancer. However, PET/CT has its own limitations such as expensiveness, complicated procedure, ionizing radiation, and limited resources. For these reasons, PET/CT could not be a routine clinical method at present. Diffusion-weighted imaging (DWI) provides image contrast through measurement of the diffusion properties of water within tissues. The new magnetic resonance whole body diffusion-weighted imaging with background body signal suppression (DWIBS) uses short tau inversion recovery-echo planar imaging sequence under normal respiration. We compared the two modalities regarding the accuracy in staging of malignant tumors and tried to determine the value of ADC measurements in differentiating lymph nodes.MethodsFrom January 2009 to September 2009, we enrolled 8 consecutive patients with malignant tumors (288 observing sites in total), and 6 healthy volunteers. The primary tumors were the following:lung cancer (n=5), gastric cancer (n= 2), ovarian cancer (n= 1), and colon cancer (n= 1). The mid age was 57 years; age range 45-65 years. The DWIBS and PET/CT images were interpreted visually by two radiologists. The whole body of every patient was divided into 36 sites. The malignant lesions were confirmed to be malignant by biopsy, surgery, or through observations of malignant behavior during at least 6 months of clinical follow-up. We calculated the accuracy of DWIBS and PET/CT. The differences in ADC value between metastatic lymph nodes and normal lymph nodes were compared using the two-tailed Student's t test for unpaired data. P< 0.05 was considered statistically significant.Results1.The sensitivity of DWIBS was 95.2%, the specificity 98.1%, the positive predictive value 80%, and the negative predictive value 99.6%; for PET-CT, the sensitivity was 100%, the specificity 97.4%, the positive predictive value 74.1%, the negative predictive value 100%.2. The differences in ADC values between metastatic lymph nodes (1.28±0.33, n=11)and normal lymph nodes(1.89±0.65, n=12)had statistical significance(t=2.80, P=0.011)ConclusionThe sensitivity and specificity of DWIBS were both similar with PET-CT. The measurements of ADC values were helpful for differentiating lymph nodes. However, because of the different enrolling tumors and our small sample, further study should be needed to testify the clinical value of DWIBS for tumor staging.