AbstractID: 8078 Title: Lung Tumor Target Respiratory Deformation and Translation Assessed by Venturi
There are three primary methods used for respiratory gating in radiation therapy: 1) nonbreath-hold, 2) deep inspiration breath hold, and 3) active breathing control. A venturi
technology – non-invasive method by remote sensing of the patient larynx respiratory
sound tracks – was developed. This technology was used to evaluate the displacement of
tumor target movement and the deformation of its volume in between virtual CT
simulation acquired shallow breathing and deep breathing.
The patient with a lung tumor underwent CT scanning under shallow and deep breathing
conditions. Each gross tumor volume (GTV) was contoured separately. Treatment plans
were constructed and beam ports were generated to compare the two breathing patterns.
The minimum doses to the GTV were then calculated.
The shift in the GTV was 5 mm in x-direction, 3 mm in y-direction, and 5 mm in zdirection. The total volume of the target was changed by 5%. The minimum doses to
GTV were less than 90% of the isocenter dose.
It has been found that the tumor displacements due to the respiration movement and the
consequent target shape deformations were significant between two extreme respiratory
conditions. Proper treatment planning should consider both the movement and the
deformation of CT target in lung. Advances in online portal imaging, image registration,
and dynamic field shaping may soon permit shaped fields that encompass the target in
either position at the time of simulation or treatment delivery. This will allow for the use
of smaller fields while ensuring proper target coverage.