Tear transit time evaluation using real-time technique for dynamic MR dacryocystography

Purpose: To explore the utility of a novel real-time dynamic magnetic resonance dacryocystography (MRDCG) technique to assess the transit times through the lacrimal drainage system (LDS). Methods: Twenty-six patent LDS of 13 normal and asymptomatic individuals underwent MRDCG using a dynamic recalled three-dimensional spoiled gradient sequence (3DSPGR) on 1.5-Tesla magnetic resonance (1.5T MR) scanner while pre-determined diluted gadolinium drops were instilled into the eyes simultaneously. MR images of 0.8 mm thickness were captured every 9.4 s for 10 min. Evaluated parameters include the time taken for contrast to first appear in lacrimal sac, nasolacrimal duct (NLD), and inferior meatus (IM). Results: Dynamic MRDCG demonstrated contrast outflow in all cases with good structural delineation. The mean transit time for contrast to appear in lacrimal sac was 15.2 s (9.4-66 s; SD, 11.9), 50.4 s for nasolacrimal duct (18.9-151; SD, 32), and 150.5 s for inferior meatus (37.8-490; SD, 135). Contrast appeared in the IM in less than 2 min in 62% (16/26) systems, and only 19% (5/26) required more than 5 min. The maximum time taken for the contrast to reach IM was 6.2 min and all the LDS eventually showed the contrast into the nasal cavity. No statistically significant differences were noted in the transit times between the right and left sides. Conclusion: Dynamic MR-DCG using real-time 3DSPGR sequence reliably demonstrates the structural and physiological assessment of LDS and could be further explored to study the physiology and pathologies of the LDS.