Salivary Imaging - Sioloscintigram

  1. Anatomy
    2. Salivary Anatomy

    1. There two basic types of salivary glands (major and minor)
      1. There are three major pairs of gland - parotid, submandibular, and sublingual
      2. There are hundreds of other minor glands found through out the mouth cavity
    2. Each salivary gland contains two regions
      1. Acinar region - responsible for the secreting either serous or mucous
        1. Parotid - serous
        2. Sublingual - mucous
        3. Submandibular -serous and mucous
        4. Minor glands - mucous
        5. This region is water permeable and the site of all salivary production
        6. Glands secrete about 85 - 90% exocrine protein into saliva that is mostly isotonic fluid
      2. Ductal region
        1. Pathway for serous or mucous to pass from the gland into the oral cavity
        2. Water cannot permeate the ducts
        3. Reabsorb NaCl
        4. Ducts secrete about 10 - 15% exocrine protein in a hypotonic solution
      3. Salivary glands aid in digestion (starch) and swallowing

        4. https://www.youtube.com/watch?v=xGixFl0abQc

        1. The saltine cracker test is an example on how important saliva is in the aid of swallow
        2. If all the saliva is absorbed in the oral cavity, you cannot swallow solid food
    3. Physiology
      1. At rest the production of saliva occurs as follows
        1. Parotid ~30%
        2. Submandibular and sublingual ~40%
        3. All minor glands contribute ~30%
      2. During the active phase of eating the production of saliva changes
        1. Parotid ~45%
        2. Submandibular and sublingual ~45%
        3. Minor glands ~10%
        4. The amount of secretion (volume) increases 10 to 20 times more than at rest
      3. Salivation occurs in response to neural activation and is not considered spontaneous
      4. While the production of saliva will not be discussed, one must appreciate that pertechnetate replaces Cl- in the salivary production. Hence, pertechnetate is incorporated into the gland via serous production
    4. Diseases
      1. Xerostomic (dry mouth) - cause may be known or unknown
        1. When administering pertechnetate salivary glands will uptake the radiotracer, but not excrete it
        2. Dry mouth can be caused by certain pharmaceuticals - antidepressants, antihypertensive, and/or anticholinergic
        3. Radiation therapy to the head and/or neck or thyroid oblation
        4. Sjogren's syndrome is a autoimmune diseases that more normally appears in post-menopausal women
      2. Evaluation of tumor mass maybe evaluated as follows
        1. 70 - 80% are benign
          1. Smooth borders is an indication of this
          2. Irregular borders may identify cancerous cells
        2. Most tumor cells are heterogeneous
          1. Usually defined as pleomorphic adenoma
          2. Will appear cold and are not functioning when pertechnetate is administered


          3. http://jnm.snmjournals.org/content/39/1/43.long

        3. Warthin's tumor (cystadenoma lymphomastosum) 4
          1. Is usually a functioning hot mass
          2. This tumor is usually benign
          3. In the example the parotid gland indicates tumor which displays its heterogeneous nature as indicated by the arrows. Following lemon juice (C and D) shows some response to the stimuli1
      3. Sialoadenitis (inflammation)
        1. Acute phase shows increased uptake
        2. Over time, if this condition continues, tracer uptake is reduced as salivary glands become damaged
        3. Obstruction can be caused by a sialolith (stone). This can be diagnosed when pertechnetate if picked up by the gland, but the activity is not secreted
      4. Sjogren's syndrome
        1. Early development of the diseases identifies normal pertechnetate uptake with some delay in secretion
        2. As the disease progresses uptake becomes diminished and secretion of pertechnetate is further delayed
        3. At end-stage disease there is complete loss of tracer uptake
    5. Procedure 1
      1. Dose - 5 to 10 mCi
      2. Collimator - LEHR
      3. Matrix - 128 x 128
      4. Dynamic - 120 seconds/frame for 60 minutes
      5. Image Anterior head and neck
      6. At 40 minutes post injection
        1. Administer 0.5 mL sodium citrate PO
        2. Make sure the patient does not move his/her head while administering
        3. Patient should swallow the fluid after it has been in his/her mouth for 30 seconds
      7. Spot views may also be taken to evaluate tumor or other structures or 1-minute dynamics can also be taken
    6. Qualification analysis (Uptake and Washout)
      1. There are two components that are critical when evaluating salivary function
        1. How quickly the radiotracer is picked up by the gland - Uptake
        2. How much/how fast does the radiotracer excrete when lemon juice is administered - Washout

          3. Qualitative Table for Salivary Gland Evaluation

          Parotid Uptake (1)
          0 - 6 minutes
          7 - 40 minutes
          >40 minutes

          Points

          2
          1
          0

          Submandibular Uptake
          0 - 6 minutes
          7 - 40 minutes
          >40 minutes

           

          2
          1
          0

          Activity in Oral Cavity
          0 - 32 minutes
          33 - 40
          >40 minutes

           

          2
          1
          0

          Parotid vs. thyroid concentration
          >50%
          <50%

           

          1
          0

          Submandibular vs. thyroid concentration >50%
          <50%
           

           

          1
          0

          Response to Lemon Juice
          Yes
          No

           

          1
          0
          Maximum Score 9
      2. Uptake and washout (qualitative approach)
        1. Activity should quickly appear in the all glands bilaterally
        2. Tracer is usually seen in parotid and submandibular glands within three minutes post injection, but is considered normal if it takes up to 6 minutes (this is equal to 2 SD)
        3. Without any lemon juice stimulation activity should appear in the oral cavity in about 13 minutes, but is still considered normal if it takes 32 minutes (this is equal to 2 SD)
        4. In all but 6% of the population tracer uptake is greater in the thyroid when compared to the major salivary glands
        5. Application of lemon juice should cause washout
        6. Apply the above grading scale to salivary scan
        7. The closer the value is to 9 the better the function of the glands
    7. Semiquantitative2
      1. Acquisition protocol is similar to the one mentioned above
        2. Flow Study for Salivary Imaging
        1. The above images shows uptake of the salivary glands appearing over time. Five mCi of pertechnetate was administered and data was acquired in a 64x64 matrix. Images were taken every 30 seconds and at 15 minutes freshly squeezed lemon juice mixed with water was given to the patient. This occurred on frame. 2 (Not all images are being displayed)
        2. Homework assignment click here

          3. Quatification of Salivary Images - Normal

      2. After the data has been collected ROIs are drawn over the left and right Submandibular/Parotid glands. Time activity curves are then generated for each gland2
        1. X - represents the the uptake value at a point where the curve is the steepest. This value defines the slope of the curve. The more positive the slope, there better the uptake
        2. Y - defines washout. How much of the activity washes out of the gland after the administration of lemon juice
        3. Z - Curve starts to increase. Why does the behavior occur?
        4. Why is the activity in the submandibular glands less than that of the parotid glands?

          5. Quantification of Salivary Images - Abnormal

        5. The above graph shows you abnormal distribution of the radiotracer. The slop of the uptake is reduces and after the administration of lemon juice there was no washout.2
      3. Another case5

        1. While this appears in another language the results are worth observing
        2. ROIs are color coded to better interpret the scan: green, light/dark blue, and purple are the salivary glands; red is the mouth; and black "fundo" is background
        3. Appreciate how there is a significant drop in salivary retention after citric acid is administered which results in a drastic increase of activity in the oral cavity
      4. Unusual Case study

        Is this the Salivary Gland?

        1. Patient was administered 16.71 mCi of 99mTcO4- with the following results. What do you think is being imaged?
        2. Hint - It migrates from the sternum

    References
    1. Most of lecture material was attended from: Nuclear Medicine Diagnosis and Therapy, Harbert, JC, Eckel man, WC, and Neumann, RD.Thieme Medical Publishers, Inc., NY,NY 1996
    2. Quantification data was acquired from: Outfit, I, Nair, MK, and Ibrahim, AK. Salivary Gland Scintigraphy: The Use of Semiquantitative Analysis for Uptake and Clearance. Society of Nuclear Medicine, TS. 2003;31:81-85
    3. Discussion of Sjogren's syndrome - A pilot study of the salivary scintigraphy diagnostic performance in a Spanish population with Sjogren's syndrome diagnosed by the European criteria
    4. Diagnostic Accuracy of Technetium-99m-Pertechnetate Scintigraphy with Lemon Juice Stimulation to Evaluate Warthin's Tumor
    5. Assessment of salivary gland function in Sjogren's syndrome: The role of salivary gland scintigraphy by Vinagre F., et al.

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