Chemical shift imaging: preliminary experience as an alternative sequence for defining the extent of a bone tumor

Objective: To investigate chemical shift imaging (CSI) with in-phase and opposed-phase (OP) gradientecho sequences as an alternative sequence to spin-echo T1 imaging for defining intra-medullary skeletal tumor extent. Methods and materials: This retrospective HIPAA-compliant study was approved by our institutional institutional review board (IRB). Twenty-three subjects with histologically-proven tumors (17 appendicular, 6 axial) underwent magnetic resonance imaging (MRI) with T1-weighted spin echo (T1SE), fluid-sensitive, CSI, and contrast-enhanced T1 sequences. One observer recorded intra-medullary tumor extent (millimeters), with 153 total measurements on each sequence. Red marrow grade [0 (none), 1 (< 50%), 2 (50-75%) and 3 (> 75%)] in each bone was recorded. Tumor extent on different sequences was compared (Student's t-test); the impact of red marrow grade on measurements was assessed (Spearman's correlation coefficient). Results: There was good agreement between measurements of tumor extent on T1SE and CSI sequences in all cases (T1SE-CSI measurement difference range 0-13.2 mm, P>0.05). Measurements from other sequences were significantly different from those of T1SE (P<0.05). As red marrow grade in the bone increased, a significant increase in measurement difference obtained on T1SE and CSI sequences was observed (P<0.001). Conclusions: CSI is a potential alternative technique to T1SE imaging for defining the intra-medullary extent of a bone tumor, possibly especially useful in regions with abundant red marrow. Advance in knowledge: CSI could be an alternative technique to T1SE imaging for defining the intra-medullary extent of bone tumor by abundant red marrow in the surrounding bone.