Nuclear lacrimal scintigraphy is a simple, noninvasive physiological test that evaluates patency of the lacrimal system. Scintigraphy uses a radiotracer (technetium-99m pertechnetate), which is very easily detectable with a gamma camera (Fig. 3.9).
While a DCG is usually preferred especially in a complete obstruction, scintigraphy is useful only in those patients whose lacrimal system is patent to syringing in the presence of constant epiphora. The test
A drop ot technetium-99m is instilled into each con-junctival sac of a patient sitting in front of a gamma camera. No topical anesthesia is required, and normal blinking is allowed.
The patient stares at a distant target during a 20-min test for a qualitative analysis, in the course of which images are recorded (immediately following instillation, after 3, 5, 10, 15, and 20 min).
Fig. 3.9. Nuclear lacrimal scintigraphy. a Set-up for nuclear lacrimal scan. The patients sits upright with the head fixed in front of the pinhole collimator of a gamma camera. Serial images are taken as the tracer passes through the system. b Patients with right-sided tearing and patency to syringing and nasolacrimal duct stenosis on dacryocystogram. Scan after 10 min. c Normal scintigraphy. d Scan after 20 min demonstrates significant decreased flow on the right and normal flow on the left. (From )
A quantitative, region-of-interest analysis can be obtained as well. There are pre-saccal, sac/nasolacri-mal duct junction, nasolacrimal duct, and nasal cavity areas of interest. The analysis gives percentage of drainage in mentioned areas with time and can assist in determining the area of pathology.
188.8.131.52 Nuclear Lacrimal Scan Indication
The nuclear lacrimal scan indications are as follows:
1. Interpretation of anatomical tests: if it is not possible to determine the full patency of lacrimal system or functional significant stenosis, surgery is indicated
2. Questionable lid laxity, punctal stenosis, facial nerve palsy: evaluation of lacrimal pump dysfunction or significant stenosis (indicating need for eyelid surgery)
3. Questionable epiphora: evaluation of dynamics of tear drainage; determination whether the drainage system is normal or not (if normal, no surgery is indicated)
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