Development of a whole body magnetic resonance imaging protocol in normal dogs and canine cancer patients.

Whole body magnetic resonance imaging (whole body MR imaging) could potentially provide accurate cancer staging as a single imaging modality. This study was done to develop a whole body MR imaging protocol for a 1.5T MR instrument using four normal Beagle dogs (Phase 1) and then to assess the protocol's feasibility in cancer-bearing dogs (Phase II). In Phase I, anesthetized dogs were placed in dorsal recumbency with limbs flexed along the torso. T1, T2, and short tau inversion recovery sequences were acquired by spin echo or fast spin echo, and also using the more rapid single shot fast spin echo and gradient echo pulse sequences. Three large overlapping fields of view (FOV) were used to visualize the entire body and the sagittal and dorsal imaging planes were compared. Relative examination time, image quality, organ visibility and signal intensity were evaluated. Phase I results were used to establish a protocol that balanced image quality with examination time. In Phase II, whole body MR imaging was done on 10 dogs with cancer. Examination times were 60-75 min. Image quality was sufficient for all known lesions to be visualized, including mass lesions, pulmonary infiltrate, and lymphadenomegaly. Skeletal detail was sufficient to visualize known neoplastic lesions of the appendicular skeleton, yet it was suboptimal because of the large FOV and use of the body coil. Additional modifications of a whole body MR imaging protocol and continued technological improvements in MR imaging will further increase its potential for veterinary cancer staging.