Program Information
Total Imaged CBCT Volume as An Indicator of Weight Loss in Head and Neck IMRT Patients
D Nicewonger*, D Saenz , University of Texas HSC at San Antonio, San Antonio, Texas
Presentations
WE-RAM1-GePD-J(B)-4 (Wednesday, August 2, 2017) 9:30 AM - 10:00 AM Room: Joint Imaging-Therapy ePoster Lounge - B
Purpose: To find a cone beam CT (CBCT) metric associated with the effect of weight loss on the dose distribution for head and neck patients.
Methods: The presence of weight loss was detected by calculating the total volume in daily CBCT images. A total of nine head and neck IMRT patients with daily CBCTs were used. CBCTs were exported at least weekly to Velocity where the skin was contoured using the threshold tool to find the daily total imaged CBCT volume. The CBCT-based external patient contour of a representative fraction was then fused with the planning CT and exported to Pinnacle to re-evaluate the dose to the PTV, GTV, hot spot, spinal cord, larynx, mandible, and esophagus mean by assigning a density override to air to tissue outside the CBCT-based external patient contour.
Results: In 7 of the 9 patients, the daily imaged CBCT volume dropped by 1% to 8% and the other 2 patients either had no change or gained volume. Increases in daily total imaged CBCT volume led to dosimetric changes in mandible maximum dose (up to 4.2% increase), larynx mean dose (up to 7.4% increase), and the overall hot spot (up to 4.9% increase).
Conclusion: Preliminary results show that there is a correlation between daily total imaged CBCT volume (a metric for weight loss) of head and neck patients and an increase in some dosimetric quantities (such as the overall hot spot). Further investigations for the study include increasing the number of patients, comparing with weight measurements recorded by nursing staff, as well as improving skin contour conformality.
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