Diffusion-weighted MRI versus FDG-PET/CT: Qualitative assessment of the lesion detection in patients with chest diseases

275 Objectives: Diffusion-weighted MRI is known to provide images seemingly similar to those of FDG-PET. In the present study, we examined and compared lung cancer cases using FDG-PET/CT and diffusion-weighted imaging with background body signal suppression (DWIBS) on the same day. Methods: We examined 21 lesions that were confirmed to be lung cancer with lymph node metastasis based on biopsies in addition to one pulmonary hamartoma in 13 patients who underwent follow-up longer than 6 months. The mean lesion size was 20.8±9.4 mm (range: 10-45 mm). After 5-hour fasting, FDG was intravenously injected at a dose of 3.7 MBq/kg and then its distribution was analyzed using PET/CT (Discovery ST Elite, GE) one hour later. DWIBS was performed to the consented patients, immediately prior to PET analysis, by taking images (slice thickness = 6 mm, b-factor = 1000) with a single shot EPI method using a 8-ch body array coil with 1.5T MRI (SIGNA EXCITE, GE). Both images were visually evaluated. The tracer accumulation in the liver and the signals in the spinal cord were considered to be positive for PET, DWIBS, respectively. Results: Twenty (95.2%) of the 21 malignant lesions were positive on FDG-PET/CT, whereas 19 lesions (90.5%) were positive on DWIBS. There were no significant differences between the two modalities (p = 0.565). The benign pulmonary hamartoma was negative on PET, but positive on DWIBS. Pulmonary adenocarcinoma (12.6 mm) in the right upper lobe showed false-negative findings on PET, but CT scanning of this node indicated suspicious pulmonary adenocarcinoma. In addition, left pulmonary hilar lymph node metastasis (15 mm) associated with left upper lobe cancer and pulmonary adenocarcinoma (12 mm) in the right upper lobe showed false-negative findings on DWIBS. Conclusions: Both PET and DWIBS detected malignant lesions almost the same level. However, DWIBS is less efficient in differentiating malignant lesions from benign lesions because DWIBS showed benign lesions such as pulmonary hamartoma as positive.