Tumor search with diffusion-weighted imaging: First experiences

Purpose: Assessment of fat-suppressing diffusion imaging as a tool for tumor search in primary oncological staging and follow-up after treatment. Materials and Methods: The DWIBS sequence (DWIBS: Diffusion-Weighted Whole-Body Imaging with Background Body Signal Suppression) developed by Taro Takahara et al. [1] was implemented in oncological MRI protocols. After measurement of 8 volunteers with a whole-body protocol, 47 whole-body scans were performed on 38 oncological patients. 70 exams were performed on 62 tumor patients with organ-specific protocols using parallel imaging. A total of 64 patients showed neoplastic lesions in the non-diffusion sequences. These lesions were evaluated in terms of visibility and signal intensity in DWIBS imaging. Non-malignant changes which showed high signal intensity in diffusion imaging were recorded in all examinations. Results: 113 of the 125 DWIBS examinations were judged as technically good. Diffusion imaging showed bright signal in the malignant lesions of 58 of the 64 patients. The tumors of 6 patients showed only moderately bright signal or were not discernible at all. Although partly performed with free breathing of the patients and limited spatial resolution of the sequence, lesions with sizes close to voxel-size were able to be visualized. Some of the patients were seen in follow-up examinations and showed signal decrease of their lesions in case of therapy response and signal increase in recurrent disease. Conclusion: Introduction of diffusion-weighted imaging provides a new independent parameter in oncological scanning. DWIBS meets the requirements of a fast, robust technique. Homogeneous fat suppression allows the use of maximum intensity projections which may visualize the spread of the disease at first glance. Most of the tumor entities examined in this study showed a bright signal in DWI. Exceptions were some osteoplastic metastases and hemorrhaged lesions. Although sensitive, visual evaluation of signal intensity alone showed limited specificity. Detection of lesions in physiological hyperintense structures may be difficult. DWIBS imaging seems to be a sensitive tool in the search for lymphomas and gastrointestinal tumors.