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Predicting Residual Disease for NSCLC Using Pre-Radiotherapy 4D PET/CT


Y Yue

Y Yue1,2,3*, M Aristophanous4, A Chen1,2,3, J Killoran1,2,3, J Yap2,3, R Berbeco1,2,3, (1) Brigham and Women's Hospita, Boston, MA (2) Dana-Farber Cancer Institute, Boston,MA (3) Harvard Medical School, Boston, MA (4) UT MD Anderson Cancer Center, HOUSTON, TX

WE-A-217A-7 Wednesday 8:00:00 AM - 9:55:00 AM Room: 217A

Purpose:
To quantify PET treatment response using a novel image registration approach, and to investigate the impact of 4D PET/CT pre-radiotherapy scan for predicting residual high-uptake areas toward dose-boosting in adaptive radiotherapy.

Methods:
3D and 4D FDG-PET/CT scans were obtained from ten patients with non-small cell lung cancer (NSCLC) for approximately two weeks before radiotherapy (pre-RT) and approximately one month after therapy (post-RT). The 4D scan was taken immediately following a 3D PET scan.

The areas of high uptake in the pre-RT scans were aligned with those in the post-RT scans using a novel rigid-penalized deformable registration. The global lung bronchi and chest wall were non-rigidly transformed to minimize the respiration effects while the target lesion is rigidly transformed to preserve the volume and SUV values. A region of interest (ROI) was defined by a threshold of 40% of the maximum SUV for both 3D and 4D PET scans. The maximal SUV within the ROI were measured. Volumetric overlap fraction (VOF) was calculated as the overlap volume of pre-RT and post-RT target volumes divided by the residual volume in the post-RT scans.

Results:
The maximal SUVs for 4D pre and post PET have a 16.3% increase compared to those in 3D PET. The pre-to-post maximal SUV variations showed 57% lesions has nontrivial residual uptake (SUVmax>2.5) for 3D PET, and 64% for 4D PET. The results of the VOFs showed that the residual metabolic-active areas are mainly located within the primary tumor volume, 92% for 3D and 89% for 4D.

Conclusions:
Residual metabolic-active areas have strong physiological and geometric correspondence to the primary tumor. With better signal recovery than standard 3D PET, high uptake areas of 4D PET pre-RT can predict areas where residual metabolic activity will be found after radiotherapy.


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