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CT Scan Protocol for Seed Localization after Prostate Seed Implant


The objective of this CT scan protocol is to give a guideline of the scanning parameters so the CT hard copies can be used by the physics staff at the Chicago Prostate Center to localize the seeds in the prostate for the purpose of performing post-implant dosimetry.
  1. NO contrast agent is to be used.
  2. The CT scan should be performed with the following suggested parameters:
      a. KVP = 120
      b. mA = 100
      c. GT = 0
      d. FOV of 26.0 cm centered in the prostate region
  3. Please perform AP scout view (topogram) to cover the whole pelvis down to the upper thigh. This will allow viewing of the possible migrated seeds outside the prostate and facilitate the countability of the implanted seeds.
  4. For the cross-sectional scan, the TABLE INCREMENT SHOULD BE 5 MM and the SLICE THICKNESS SHOULD BE 3 MM. If possible, it should cover the region 2.0 cm superiorly from the superior edge of the prostate and the region 2.0 cm inferiorly from the inferior edge of the prostate.
  5. When the hard copies are to be produced, the desirable level (or center of CT value for display) should be 300 and the window should be 1500. This would give best visibility of the seeds without the star effect.
  6. The hard copy scout views (topogram) should be a 2 on 1 print, where one has the slice numbering lines and the other does not. While the former allows the anatomical and spacial correlation of the cross-sectional images with one another, the latter allows overall visualization of the implanted seeds in the prostate and those which have possibly migrated out of the prostate.
  7. The cross sectional images should be produced on a 6 on 1 print to allow easy identification of the I125 or Pd103 seeds. Each image should also include a scale of 10.0 cm to allow an easy and accurate calculation of the magnification factor for the images. Labeling of the right and left sides of the patients should also be included with each image.
  8. If your scanner is a helical, change to axial mode.
  9. Please put grid on each slice where seeds are present. This will not obscure the seeds.