Split Lung Quantification

  1. This nuclear medicine procedure is done to evaluate resectability of lung tissue on patients with lung carcinoma or lung transplant
    1. The concern relates to whether or not there is enough viable lung tissue following the removal of cancerous lung tissue
    2. The rationale to perform the thoracotomy is based on:
      1. Resecting the tumor
      2. Patient's ability to tolerate the surgical results

    3. It should also be noted that a split lung procedure is very non-specific in finding lung cancer and it is unable to identify metastatic involvement
    4. The study is combined with pulmonary lung function test
      1. Forced expiratory volume in time (1 - 3 seconds) - FEV1
      2. Forced vital capacity (FVC) - volume of air forced out of lung
      3. Study should be done when the patient is not on a bronchodilator
      4. Why is a bronchodilator NOT recommended?
  2. The patient can tolerate significant amount of lung removal if the pulmonary lung function test meets the following values:
    1. FEV1 is greater than 50% of the FVC and the FVC is greater than 2 L
    2. Maximum voluntary ventilation is greater than 50% of the predicted value
    3. Ratio of residual volume to total lung capacity is less than 50%
  3. Surgery is usually not performed if the FEV1is below 0.8 L
  4. When the above criteria is/are not met, a split lung procedure using 99mTcMAA is usually ordered (Note: 2 a-c)
  5. The procedure is as follows:
    1. Inject the patient with 4 mCi IV using 99mTcMAA
    2. Camera setup
      1. 256 x 256
      2. LEHR collimator
      3. 500 to 750k counts per image
      4. Take anterior and posterior images
    3. Once the images are collected, ROIs are drawn over the R and L lungs (refer to image)

        4.  

      1. Counts are then determined
      2. Anterior R lung and posterior R lung counts are summed
      3. Posterior R lung and posterior L lung counts are summed
      4. Average counts from each lung are then determined (R and L)
      5. Geometric or arithmetic mean maybe used (arithmetic is used in the example)
      6. Ratio for L lung to R lung is determined (see image)
      7. From a nuclear medicine technologist's standpoint, the study is complete.
    4. What does the physician do with these numbers?
      1. Following a pulmonary function test the preoperative FEV1 value is determined
      2. In the example 2200 mL is used
      3. The preoperative value is then multiplied by ratio of R lung counts, since this is the lung that has no disease.
        1. The assumption is that there may be additional disease in the L lung, and that all of the L lung may be removed during surgery
        2. -- This is the more conservative approach --
      4. The postoperative predicted value is then determined and an estimation of total lung capacity is estimated (in the example used the value is 1320 L)
      5. Based on these calculations is surgical intervention recommended?
  6. Other approaches to the split lung procedures:
    1. Ventilation and perfusion may be used together for a more accurate approach
    2. Analysis of activity in each lobe may also be considered
      1. Lung counts are divided into each lung's separate lobes; that is, as opposed to counting each whole lung.
      2. The right side would have 3 regions and left side would have 2 regions
      3. The same approach is used to determine counts and ratios; however, it is done at the lobular level
      4. Literature suggests that these other applications do not improve the patient outcome, post surgery

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Reference - http://www.meddean.luc.edu/lumen/MedEd/medicine/pulmonar/lungca/man-preo.htm

End of Lung Lecture - Review Study Guide

10/22

This completes our discussion in Ventilation Perfusion Lung Imaging