Echo-planar imaging for MRI evaluation of intrathoracic tumors in murine models of lung cancer

Purpose: To evaluate the efficacy of fast cardiac- and respiratory-gated MRI acquisition methods for noninvasive assessment of tumor volume in murine models of lung cancer. Materials and Methods: A total of 21 mice bearing either human small-cell (N417) or non-small-cell (H460) lung tumors were scanned using combinations of respiratory-gated computed tomography (CT) imaging, cardiac- and respiratory-gated multishot spin-echo echo-planar imaging (SE-EPI), and cardiac- and respiratory-gated spoiled gradient echo (SPGR). Tumor depiction at 4.7T was qualitatively and quantitatively compared with CT and tissue cross sections. MRI-based measures of tumor volume were compared with ex vivo measurement of tumor mass. Results: Tumors appeared hyperintense on T ₂-weighted EPI images, providing positive intrinsic contrast between tumors and surrounding tissues. Tumor boundaries were better distinguished by EPI and SPGR with T₁-reducing contrast enhancement when tumor abutted other tissues than by CT or SPGR without contrast. Tumor volumes measured from EPI images correlate well with ex vivo measurements of tumor mass (P < 0.001, r² = 0.99) and volume (P < 0.01, r² = 0.98) over a wide range of tumor sizes. Conclusion: Respiratory- and cardiac-gated multishot EPI enables accurate, noninvasive assessment of tumor in murine models of lung cancer using a sequence that requires approximately two minutes to complete.