Encrypted login | home

Program Information

Tumor Displacement-Based Binning for Respiratory-Gated Time-Independent 5DCT Treatment Planning

L Yang

L Yang*, D O'Connell , P Lee , N Shaverdian , A Kishan , J Lewis , T Dou , D Thomas , X Qi , D Low , UCLA, Los Angeles, CA


SU-F-J-135 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: A published 5DCT breathing motion model enables image reconstruction at any user-selected breathing phase, defined by the model as a specific amplitude (v) and rate (f). Generation of reconstructed phase-specific CT scans will be required for time-independent radiation dose distribution simulations. This work answers the question: how many amplitude and rate bins are required to describe the tumor motion with a specific spatial resolution?

Methods: 19 lung-cancer patients with 21 tumors were scanned using a free-breathing 5DCT protocol, employing an abdominally positioned pneumatic-bellows breathing surrogate and yielding voxel-specific motion model parameters α and β corresponding to motion as a function of amplitude and rate, respectively. Tumor GTVs were contoured on the first (reference) of 25 successive free-breathing fast helical CT image sets. The tumor displacements were binned into widths of 1mm to 5mm in 1mm steps and the total required number of bins recorded. The simulation evaluated the number of bins needed to encompass 100% of the breathing-amplitude and between the 5th and 95th percentile amplitudes to exclude breathing outliers.

Results: The mean respiration-induced tumor motion was 9.90mm ± 7.86mm with a maximum of 25mm. The number of bins required was a strong function of the spatial resolution and varied widely between patients. For example, for 2mm bins, between 1-13 amplitude bins and 1-9 rate bins were required to encompass 100% of the breathing amplitude, while 1-6 amplitude bins and 1-3 rate bins were required to encompass 90% of the breathing amplitude.

Conclusion: The strong relationship between number of bins and spatial resolution as well as the large variation between patients implies that time-independent radiation dose distribution simulations should be conducted using patient-specific data and that the breathing conditions will have to be carefully considered. This work will lead to the assessment of the dosimetric impact of binning resolution.

Funding Support, Disclosures, and Conflict of Interest: This study is supported by Siemens Healthcare

Contact Email: