MRI DACRYOCYSTOGRAPHY

Technique: 

• First normal T1 and T2 to rule out any tumor or lesions
• Then do the high resolution Dynamic T2 weighted thick slice (20-30mm) images while an admixture of saline-lidocaine hydrochloride solution was injected

Magnetic resonance imaging dacryocystography is a technique used to evaluate patients with epiphora. It is comparable with digital dacryocystography in detection and localization of nasolacrimal system obstruction. MRI dacryocystography has significant advantages over digital and CT dacryocystography in terms of superior soft tissue contrast resolution and lack of ionizing radiation. However, CT dacrocystography remains superior for evaluation of congenital bony stenosis, atresia of the bony segment of the nasolacrimal duct, and detection of intracanicular bony fragments in facial trauma. MRI dacryocystography is performed by topical administration of a diluted mixture of Gd-based contrast agents,which provides similar results to catheterization of the lacrimal canaliculi. It may be the best technique for evaluation of the lacrimal system in children.

MR dacryocystography uses stationary or slowly flowing water injected into the lacrimal draining system as a substitute for contrast media. The imaging strategy of MR dacryocystography involves the acquisition of a series of heavily T2-weighted images. Because fluidfilled nasolacrimal ducts have long longitudinal and transverse relaxation times, they have high signal intensity on T2-weighted images. In these hydrographic images, everything looks black and white. Observers can evaluate the nasolacrimal abnormalities indirectly using these “all or nothing” images. The fast spin-echo sequence used in the current study is relatively immune to local magnetic field inhomogeneity. Thus, the sequence is less affected by field inhomogeneity created by air in the maxillary sinus or artificial teeth in the oral cavity. 

-->
A saline-lidocaine solution is less viscous than iodinated contrast media and flows readily through a thin catheter with a narrow lumen; thus patients can easily self-inject an appropriate amount of the solution while lying on a cradle in the small bore of the MR imager. This solution's lower viscosity helps fill any narrowed lumen in the lacrimal pathways and enables the use of thinner and softer cannulas for intubation of the lacrimal canaliculi, which ensures maximum patient comfort. Concerning safety margins, a saline-lidocaine solution is safe and minimally irritating.