[Comparison of 3T dacryo-MRI by instillation with dacryo-CT scan for evaluation of epiphora].

OBJECTIVES: Epiphora is frequently related to stenosis of the lacrimal drainage pathways. In the evaluation of stenosis, dacryo-CT scan remains the gold standard, despite the need for radiation and catheterization of the lacrimal passages. Evaluation by high field 3T MRI compared to the gold standard in the morphological study of the lacrimal passages and quantification of the stenosis is attractive considering the lack of radiation and non-invasive nature of the technique.

METHODS: Twenty-four patients were included, including 9 with bilateral epiphora, representing 33 pathological drainage systems out of 48. Twenty-three drainage systems underwent subsequent surgery (18 patients, 5 patients bilaterally).

RESULTS: The average diameter on CT scan images of the superior canaliculus was 0.70 mm (± 0.46), of the inferior canaliculus 0.69 (±0.42), the common canaliculus 0.68 (± 0.58), the lacrimal sac 4.32 (± 2.10), and the nasolacrimal duct 1.15 mm (±1.42). 3T dacryo-MRI overestimated the diameters by 0.35 to 1mm (up to 20 % of the lacrimal sac size), and the concordance between dacryo-CT scan and 3T dacryo-MRI was of average value (kappa 0.5, P<0.05) concerning the diagnosis of stenosis. Furthermore, dacryo-CT scan demonstrated higher sensitivity (72.7 %) than 3T dacryo-MRI (42.4 %).

CONCLUSIONS: The two techniques are not equivalent in the diagnosis of stenosis. An optimization of protocols and an evaluation on a larger cohort remain necessary before dacryo-CT scan can be replaced by dacryo-MRI in routine practice.