TomoTherapy® CTrue™ Adaptive Lung Case

This clinical case study demonstrates how the TomoTherapy® Hi·Art® treatment system's CTrue™ technology provides true dose guidance. Only TomoTherapy's daily 3D imaging reveals anatomical changes and their dosimetric impact at every fraction.

Original Treatment Plan

Figure 1

  • 50 Gy in 25 fractions is prescribed to a mass in the right posterior lung.
  • Excellent cord sparing (maximum of approx. 8 Gy) is achieved via optimization of a helical IMRT delivery.

Figure 2

 

Hypothetical Delivery

Figure 3a
Original plan image
Figure 3b
Five days into treatment (~1cGy MVCT)
Figure 3c
Registered image
(Green= Daily CT;
Grey=Planning CT)
  • Over a one week period, a progressive posterior shift of the tumor occurs due to reduced pleural effusion.
  • Daily patient alignment via external marks or bony anatomy would lead to a severe under-dosage of the tumor due to geographic miss.
Figure 4
Dose calculation showing the results if treated by aligning to bone
 

Actual Delivery Using CTrue Technology

Figure 5a
Registered images using PTV contour & dose to position tumor for treatment
Figure 5b
  • Using CTrue technology, the shifting tumor can be correctly aligned before every fraction and dose can be overlaid to check target coverage and organ sparing.
  • Spinal cord dose remains within tolerance thanks to the TomoTherapy Hi·Art system’s helical delivery, and treatment is continued with the initial plan up to and including the 5th fraction.
  • Taking advantage of CTrue images and adaptive therapy technology, the clinician decided that after the 5th treatment session, the plan will be re-optimized for the remaining fractions.
Figure 6
Dose calculated on the daily CT image.
 

Adapted Plan

Figure 7

  • Using CTrue technology, every daily image is suitable for treatment planning since pixel values are true representations of tissue density.
  • The day-5 CTrue image is used to re-plan the case using the true anatomy.
  • After re-optimization, the cord is once again spared effectively along with excellent dose coverage of the target at its new location.
Figure 8
DVH for re-optimized plan, showing low cord dose and homogeneous target dose.
 

* Original treatment plan and images courtesy of Richard Hudes, MD, St. Agnes Cancer Center, Baltimore, MD. Used by permission.