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Longitudinal Assessment of Radiation Treatment Response in Non-Small Cell Lung Cancer Using Intravoxel Incoherent Motion Model Diffusion-Weighted MRI

K Karki

K Karki*, G Hugo , J Ford , E Weiss , Virginia Commonwealth University, Richmond, VA


TH-CD-204-2 (Thursday, July 16, 2015) 10:00 AM - 12:00 PM Room: 204

Purpose: Perfusion-insensitive apparent diffusion coefficient (ADC) is obtained using intravoxel incoherent motion (IVIM) model by separating perfusion compartment. The purpose of this study is to assess the longitudinal changes in the reference-standard IVIM model ADC (ADCIVIM) values of lung tumor volumes due to treatment response and to compare the relative longitudinal changes of the monoexponential model ADC values with that of ADCIVIM.

Methods: Ten subjects had diffusion-weighted MRI (DW-MRI) scans at 0 week (pre-treatment), and 3 and 6 weeks during radiotherapy in 1.5T MRI scanner. Respiratory triggering was applied to the echo-planar DW-MRI with TR=~4500 ms, TE=74 ms, eight b-values of 0-1000 μs/μm², pixel size=1.98X1.98 mm², slice thickness/gap=6 mm/1.2 mm and 7 axial slices. The ADCIVIM values and volumes of active tumors were compared longitudinally using paired t-test. Changes in monoexponential model ADC values using the sets- 0-1000; 50-1000; 100-1000; 250-1000; 500-1000; 250, 500 and 1000; 250, 650 and 1000; 250, 800 and 1000; 250 and 800; and 250 and 1000 μs/μm² at 3 and 6 weeks relative to their corresponding baseline values at 0 week were also compared with that of ADCIVIM using all b-values.

Results: The ADCIVIM values increased significantly from 0 to 3 weeks, and from 3 to 6 weeks (p<0.05). The changes of monoexponential model ADC values relative to the baseline values for all sets were not significantly different from that of ADCIVIM at both 3 and 6 weeks (p>0.05) except for 0-1000, and 50-1000 μs/μm² sets at 3 weeks. The active tumor volume decreased significantly from 0 to 6 weeks.

Conclusion: Active tumor ADCIVIM value increased and volume decreased during radiotherapy. No significant differences between the longitudinal changes of monoexponential ADC and ADCIVIM values were generally observed. DW-MRI is efficient in showing active tumor functional and volume changes due to radiation treatment in lung cancer.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by Virginia Commonwealth University Massey Cancer Center pilot project A35242 (EW). There are no conflicts of interest.

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