Dacryoscintigraphy
  1. The purpose of this procedure is to evaluate lacrimal drainage.
    1. Usually the procedure is done if the patient has epiphora (water eye(s))
    2. Epiphora maybe due to excessive tear production or blockage in a tear duct that prevents drainage
    3. Perhaps the procedure of choice would be a dacryocystogram (radiology), however, this exam is a lot more invasive that its counterpart, nuclear medicine
  2. The anatomy of tear production and drainage must be reviewed

    3. Anatomy of tears

    1. Tears flow as follows
      1. Tears flow from the lacrimal gland down small ducts that bath the eyeball
      2. Tears flow towards the medial position of the eye as it passes the medial canthus
      3. Then the liquid enters opening known as the puncta
      4. Tears continue down the medial and inferior canaliculi to the nasolacrimal sac and duct
      5. The nasolacrimal duct then drains into the sinus
    2. A blockage can occur anywhere along the nasolacrimal duct system
  3. Diseases that cause obstruction

    1. Epiphora - watery eye
    2. Periocular - occurs around the eye
    3. Causes
      1. Congenital
      2. Blockage do to stone or tumor
      3. Infection
  4. Procedure

    1. Dose preparation
      1. Dose is between 100 to 200 μCi per eye
      2. To achieve correct activity you need to remember that 20 drops is about equal to 1 mL
      3. Therefore, if you take 200 μCi and multiple by 20 drops (see conversion calculator) you get a concentration of 4.0 mCi
      4. Hence a diluted vial of 99mTcO4- must have a concentration of 4.0 mCi/mL
      5. In the above example a 10 mL solution is calculated
      6. Place the solution into a small bottle that contains an eyedropper. The entire container should be placed it need a lead container until needed

      7. In the hotlab I decided to see how accurate a 200μCi dose so I prepared a 4.0 mCi/mL solution and came up with the above result. It appears that my μCi per drop is a little off?
    2. Camera/patient setup
      1. Pinhole collimator
      2. Matrix at 64 or 128
      3. Acquire 30 seconds per frame for 5 minutes
      4. Place the patient in a supine position and immobilize the head
      5. The field of view should be set to acquire both eyes yet bring the detector in, as close as possible. Remember with a pinhole the further away the collimator is the smaller the area of interest
      6. To assure that both eyes are in then FOV use a hot marker
    3. Acquisition
      1. Set the patient up before placing the drops in the eye
      2. Put one drop into the lateral ends of each canthus
      3. Start imaging
      4. Normal tear flow, the activity should appear in the nasolacrimal sac and duct within several minutes
      5. Non-filling of the sac or duct is an indication of blockage
      6. Optional maneuvers - If the flow of activity seems "sluggish"
        1. Digital massage over the nasolacrimal sac and duct, which may facilitate movement within the duct.
        2. Additional drops of saline may assist in flushing the radiopharmaceutical to into the puncta
        3. If the activity shows little movement, wash the eye out saline and a sponge. This may help to determine if there is a blockage
    4. Evaluation of the scan - Compare both eyes by observing the flow
      1. Normal shows drainage through the system in a matter of several minutes
      2. Partial blockage is seen if one side drains slower than the other
      3. Complete blockage is indicated when the activity does not move at all
  5. Dacryocystography vs. dacryoscintigraphy

    1. The radiology procedure
      1. Requires cannulation and injection of contrast into the puncta. This is usually painful procedure and may traumatize the eye as the contrast is injected into a blocked nasolacrimal duct
      2. It does give excellent anatomical detail and is considered a simple procedure
    2. Nuclear medicine
      1. Is recommended as the initial step to determine if there is a problem
      2. There is no trauma or pain in this procedure and it analyzes tear flow from a physiologic standpoint
      3. Unfortunately its anatomical detail is limited
      4. This procedure might be considered for pre and post surgery to determine if blockage has been removed
  6. Case presentation - Normal

Normal Tear Flow

  1. This procedure shows normal flow of salivary tears
  2. Compare this above image to the drawing seen at the beginning of the lecture

Abnormal Case I

Blockage of the Nasolacrimal Sac

    1. Blockage is very pronounced
    2. Blockage is greater on the left than it is on the right
    3. At 40 minutes the radiotracer does not go pass the proximal end of the nasolacrimal sac (left or right)

    Abnormal Case II

    Dacryoscintigraphy - Normal and abnormal

    1. The image on the left shows normal tear flow with generalized anatomy being identified
    2. The image on the right is abnormal with a blockage noted in the nasolacrimal duct

    Reading assignments:

    1. Homework
    2. Comparative Study on Dacryoscintigraphy and Contrast Dacryocystography
    3. Dacryoscintigraphy: A Pictorial Essay

      4. Return to the Beginning of the Page
      Return to the Table of Content

      9/23

      Lecture material and images were taken from: Nuclear Medicine Diagnosis and Therapy, Harbert, JC, Eckel man, WC, and Neumann, RD.Thieme Medical Publishers, Inc., NY,NY 1996