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SU‐E‐E‐11: Novel Matching Module for Respiration‐Gated Motion Tumor of Cone‐Beam Computed Tomography (CBCT) to 4DCT
Author(s) -
Yu P,
Tsai Y,
Nien H,
Chiu Y,
Chang H,
Lin C,
Fu P,
Chang C,
Wu C
Publication year - 2015
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4923933
Subject(s) - cone beam computed tomography , nuclear medicine , imaging phantom , medicine , maximum intensity projection , breathing , image guided radiation therapy , image registration , medical imaging , computed tomography , radiology , computer science , computer vision , image (mathematics) , anatomy , angiography
Purpose: Four dimensional computed tomography (4DCT) scans reliably record whole respiratory phase and generate internal target volumes (ITV) for radiotherapy planning. However, image guiding with cone‐beam computed tomography (CBCT) cannot acquire all or specific respiratory phases. This study was designed to investigate the correlation between average CT and Maximum Intensity Projection (MIP) from 4DCT and CBCT. Methods: Retrospective respiratory gating were performed by GE Discovery CT590 RT. 4DCT and CBCT data from CRIS Dynamic Thorax Phantom with simulated breathing mode were analyzed. The lung tissue equivalent material encompassed 3 cm sphere tissue equivalent material. Simulated breathing cycle period was set as 4 seconds, 5 seconds and 6 seconds for representing variation of patient breathing cycle time, and the sphere material moved toward inferior and superior direction with 1 cm amplitude simulating lung tumor motion during respiration. Results: Under lung window, the volume ratio of CBCT scans to ITVs derived from 10 phases average scans was 1.00 ± 0.02, and 1.03 ± 0.03 for ratio of CBCT scans to MIP scans. Under abdomen window, the ratio of CBCT scans to ITVs derived from 10 phases average scans was 0.39 ± 0.06, and 0.06 ± 0.00 for ratio of CBCT scans to MIP scans. There was a significant difference between lung window Result and abdomen window Result . For reducing image guiding uncertainty, CBCT window was set with width 500 and level‐250. The ratio of CBCT scans to ITVs derived from 4 phases average scans with abdomen window was 1.19 ± 0.02, and 1.06 ± 0.01 for ratio of CBCT to MIP scans. Conclusion: CBCT images with suitable window width and level can efficiently reduce image guiding uncertainty for patient with mobile tumor. By our setting, we can match motion tumor to gating tumor location on planning CT more accurately neglecting other motion artifacts during CBCT scans.