Esophageal Transit

  1. Anatomy and physiology of the esophagus
    1. Approximately 20 cm in length
    2. Starts at the cricoid cartilage and extends to the stomach
    3. Esophagus is composed of different types of muscles
      1. Proximal third contains striated muscle
      2. Distal third contains smooth muscle
      3. Middle section is composed of both striated and smooth muscle
    4. Esophageal motility - swallowing
      1. Initially there is pharyngeal contraction that transfers the "bolus" of solid or liquid material to the relaxed upper esophageal sphincter
      2. As material passes the sphincter muscles, the sphincter muscle contracts initiating a primary peristaltic wave that forces the material downward
      3. Secondary contractions occur along the lining of the esophagus in response to residual solid or liquid material that may still be in the esophagus
  2. Disease – esophageal transit can be effected by
    1. Achalasia
      1. Loss of peristalsis within the muscles of the esophagus and failure of the lower esophageal sphincter to relax
      2. This results in prolonged retention of the food/liquid in the distal third of the esophagus
    2. Diffused esophageal spasm syndrome
      1. Results in spasms of the lower 2/3 of the esophagus and included intermittent chest pain or dysphasia
      2. This results in prolonged transit times and reduced esophageal emptying
      3. In addition, material within the esophagus moves within all three segments
    3. Nutcracker esophagus
      1. Exemplified by high amplitude peristaltic contractions in the body of the esophagus along with chest pain and/or dysphasia
      2. Food/liquid are retained within the mid to distal third of the esophagus
    4. Abnormal esophageal transit times have been associated with all connective tissue disorders that involve smooth muscle and striated muscles
      1. Smooth muscle disease – Scleroderma, systemic lupus erythematosus, and Raynaud’s disease
      2. Striated muscles disease – dermatopolymyositis
      3. Transit patterns show stagnation of food/liquid in the lower 2/3 of the esophagus
  3. Esophageal Transit Procedure
    1. Patient should be NPO after 12M
    2. Radiopharmaceutical
      1. Prepare 2 to 3 syringes with 15 mL water boluses in each
      2. Each bolus should contain 300 μCi of Tc99mSulfur Colloid
    3. Patient instruction (is very important)
      1. The patient will be given a syringe full of radiowater that will be placed in the patient’s mouth
      2. The patient will be asked to keep the radiowater in his/her oral cavity (don’t swallow until I tell you)
      3. When acquisition is started, the patient will be asked to swallow the bolus and then continue to dry swallow for an additional 10 minutes
    4. Patient positioning
      1. In the supine position place the camera so that the detector is in an anterior position
      2. The field of view should include the oral cavity to the base of the stomach
    5. Acquisition parameters
      1. Two sets of acquisition should be completed for each bolus administered
      2. Matrix should be set at 64 by 64
      3. Collimator – LEPH Gap or HS
      4. First set of acquisitions - 0.1 to 0.25 seconds per frame for 10 to 20 seconds
      5. Second set of images can be taken at 1 second frame for up to 10 minutes
      6. Following the swallow of the bolus, the patient should dry swallow every 10 to 15 seconds, until the study is done

        7. ets1flow.jpg - 31641 Bytes

      7. The above image identifies the first set of images collected at 0.1 seconds per frame. Note the lack of activity seen in these images.
    6. Image processing
      1. ROIs may be drawn in several ways

        2. ets1bresults.jpg - 28008 Bytes

      2. Note that the images above indicate three ROIs – mouth, cricoid cartilage, and the entire esophagus
      3. This data represents the initial images that were collected above
      4. Time activity curves are then generated
      5. According to the data above the bolus of activity arrives at the stomach within a second (normal) and no reflux or delayed transit is noted
      6. Modification of the ROIs
        1. Three ROIs can be drawn around esophagus to include upper, mid, and lower portions (1/3 each)
        2. This adds to the sensitivity of the exam by noting where the abnormal transit times might occur
        3. Consider the diseases described above and determine what might be the behavior of the radioactive bolus

        etformula.jpg - 10058 Bytes

      7. Finally, a percent transit time can also be calculated using the above formula
        1. Maximum counts represent the frame where the initial bolus is at maximum counts in the esophagus (as its passing through)
        2. "Counts At End Frame" represent the activity remaining after a period time (t)
        3. Which frame do you select for t?
        4. Remember liquid should travel down the esophagus in no more than 1 second. After that time, any residual activity represents the inability of the esophagus to get the bolus to the stomach
        5. Hence, the frame you want to selecting is going to be after 1 second
        6. Therefore the "End Frame" represents the % traveled through the esophagus or %Esophageal Transit
        7. Note - The frame that you select after 1 second will represent residual activity remaining the esophagus

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