ESTRO 2022 - Abstract Book

S48

Abstract book

ESTRO 2022

sFoV which was not observed using HDeepFoV. In addition, a CT radiopaque placed on the skin of a patient was reconstructed inside the body in one slice whilst another marker was suspended in the air in another slice obtained with HDFoV. The reconstructions obtained with HDeepFoV placed the markers in more realistic positions (Figure 2).

Conclusion eFoV reconstruction is an important resource since there is no alternative to the use of truncation in the eFoV region. However, it should be used carefully since there is ground truth for patients and results depend on several aspects such as the volume within eFoV. Our results obtained with phantom and patients indicate HDeepFoV is more accurate and resulted in better quality images than current commercial versions.

PD-0073 Development of a new automated data-driven gated (DDG) CT for radiation treatment planning

T. Pan 1 , D. Luo 2

1 University of Texas, M.D. Anderson Cancer Center, Imaging Physics, Houston, USA; 2 University of Texas, M.D. Anderson Cancer Center, Radiation Physics, Houston, USA Purpose or Objective A new automated data-driven gated (DDG) CT was developed on the GE CT to provide average (AVG), minimum (MIN) and maximum (MAX) intensity projection, end expiratory (EE) and end inspiratory (EI) CT images for radiotherapy treatment planning (RTP) without any hardware gating. Comparison was made among the new DDG CT, GE D4D (also data-driven gated) and GE 4D CT on a cohort of 38 patients. Materials and Methods The AVG, MIN and MAX images were from the average, minimum and maximum pixel values of cine CT images, respectively. The lung region was calculated by (1) thresholding the body region of ≥ -350 HU containing the soft tissues and bones, and the regions of < -350 HU containing the lungs inside and the air space outside the body region, (2) removing the air space and the imaging table by a mask of 50 cm diameter, and (3) removing the small unconnected air space in the abdomen from the lung region with a 3D connected component analysis. The cine CT images with the largest and smallest average HU in the lung region were identified as the EE and EI images, respectively. For the image slices without any lung region present, the largest and smallest expansions of the body outline contour with thresholding of -350 HU were selected to be the EE and EI phases, respectively. Finally, a consistency check was conducted to ensure the selection of EE and EI phase images across the slice locations acquired at the same time per cine CT step were matched together. The new DDG CT was compared to two commercial CT gating methods: 1) D4D (DDG based) and 2) 4D CT (external device based) in 38 patient data sets with respect to selection of EI and EE respiratory phases, lung HU, lung volume, and image artifacts. Results In the EE phase, the images selected by DDG CT and 4D CT were identical 62.5±21.6% of the time, while DDG CT and D4D CT were 6.5±9.7%, and 4D CT and D4D CT were 8.6±12.2%. These differences in EE phase image selection were significant (p<0.0001). In the EI phase, the images selected by DDG CT and 4D CT were identical 68.2±18.9% of the time, DDG CT and D4D CT were 63.9±18.8%, and 4D CT and D4D CT were 61.2±19.8%. These differences were not significant. The average lung HU values for EE (EI) were -497±73 (-530±76), -497±73 (-527±77), -501±76 (-530±76) for DDG, 4D and D4D CT, respectively. The lung volumes for EE (EI) in liters were 1.85±0.45 (2.29±0.50), 1.87±0.46 (2.28±0.50), 1.95±0.48 (2.26±0.53) for DDG, 4D and D4D CT, respectively. The lung HU and volumes were not statistically different (p > 0.1) among the three methods. DDG CT was better than D4D or 4D CT in appropriate selection of the EE and EI phases. D4D CT could reverse the EE and EI phases or not select the correct images in some cases. Conclusion A new automatic DDG CT was developed for RTP without any hardware gating. The utility is available on the hospital network and enables all GE CT scanners for RTP. The new DDG CT provides the benefits of 4D CT without the need for external hardware gating.