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Longitudinal Change of T2 Map During MR-Guided SBRT for Pancreatic Cancer

X Chen*, H Nasief, E Paulson, E Ahunbay, P Prior, W Hall, B Erickson, X Li, Medical College of Wisconsin, Milwaukee, WI


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Both anatomic and functional MRIs are being acquired in each fraction during MR-guided adaptive radiation therapy (MRgART) on 1.5T MR-Linac. These longitudinal functional MRIs (e.g., T2 map) may provide patient specific treatment response data that may potentially be used for response guided adaptive treatments. In this study, we investigate if there is consistent change in delta-radiomic features of the daily T2 map collected during MRgART/SBRT for pancreatic cancer.

Daily T2 maps for four pancreatic cancer (3 pancreatic head and 1 pancreatic body) patients treated on a 1.5T MR-Linac were included in this initial study. These patients were treated with 5-fraction SBRT with prescription doses ranging from 33 Gy to 35 Gy. The gross tumor volumes (GTV) were delineated by treating physician during the online adaptation in every fraction. Change of a variety of radiomic feature (delta radiomics) in the target on the T2 maps were extracted. The T2 maps were preprocessed prior to radiomic feature extraction. Preprocessing involved bias correction, denoising with a gaussian filter and histogram equalization. Radiomics features that were found independent of motion were obtained in each fraction from the segmented GTVs. The relative net change of the radiomic features compared to first fraction was calculated. Features were examined to determine those with trend repeatedly among different patients.

Seven radiomic features from 3 different matrices (inverse difference normalized, Correlation, gray level non uniformity, skewness, dissimilarity, long run emphasis, homogeneity) showed consistent longitudinal trends. For example, the correlation metric changed on average 102%, up to 139% for a patient.

Longitudinal consistent changes of radiomic metrics on daily T2 maps were observed during the short course of MR-guided SBRT for pancreatic cancer. With further studies based on larger datasets, the daily T2 maps may be developed as an image biomarker for response-guided adaptive radiation treatment.


Not Applicable / None Entered.


IM- MRI : Functional MRI (fMRI)

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