Bibliographic Details
| Title: |
Reduced Computed Tomography Scan Speed Improves Alignment Errors for Patients Undergoing Thoracic Stereotactic Body Radiation Therapy. |
| Authors: |
Sadagopan, Ramaswamy, Martin-Paulpeter, Rachael M., Peeler, Christopher R., Wang, Xiaochun, Nitsch, Paige, Pollard-Larkin, Julianne M. |
| Source: |
Cancers; Aug2025, Vol. 17 Issue 16, p2646, 12p |
| Subject Terms: |
Medical protocols, Motion, Computer software, Computed tomography, Research evaluation, Radiosurgery, Retrospective studies, Descriptive statistics, Cancer patients, Vertebrae, Chest tumors, Imaging phantoms, Respiratory measurements, Patient positioning |
| Abstract: |
Simple Summary: Four-dimensional computed tomography (4DCT) has been used to account for breathing motion during the simulation of both stereotactic body radiation therapy (SBRT) and non-SBRT treatments. However, 4DCT is often unavailable, and it is impractical for image guidance. Due to its inherent slow acquisition, cone beam CT (CBCT) captures average tumor volume during multiple breathing cycles. However, CBCT's image quality for certain tumors, such as small ground glass lesions or liver lesions, is notably insufficient. While CT-on-rail is an excellent alternative to CBCT, it has motion artifacts during on-board alignment due to its fast acquisition speed. To our knowledge, our current work is the first to addresses the motion artifact problem by evaluating the use of a slow CT protocol in CT-on-rail image guidance for patients undergoing thoracic SBRT. We also suggest steps to improve the alignment accuracy when using slow CT. Objectives: We investigated the performance of a slow computed tomography (CT) protocol to reduce alignment errors arising from motion when using CT-on-rail (CTOR) for image guidance for patients receiving thoracic stereotactic body radiation therapy (SBRT). Methods: A Quasar lung phantom with a moving tumor was programmed with three breathing rates and three motion amplitudes. MIP and average 4DCT images were used for contouring and alignment, respectively. Ten CTOR images were obtained for each of the breathing rates and amplitudes, under both CT protocols. We used in-house CAT software for image guidance, centering the tumor in the lung window within the gross tumor volume contour. Longitudinal coordinate reproducibility was compared between the two protocols. We also retrospectively analyzed CBCT SBRT image guidance alignment data from 31 patients to evaluate the systematic error in the longitudinal direction between simulation and daily treatments. Results: The mean (standard deviation) alignments (mm) for the standard and slow CT protocol ranged from 0.7 (0.68) and 1.0 (0.0), respectively, for the 28 BPM breathing rate and 5 mm amplitude combination to 5.2 (2.0) and 1.6 (0.52) for the 8 BPM breathing rate and 15 mm amplitude combination. Our retrospective analysis of patient alignment data showed a notable systematic difference in the relative bone and gross tumor volume alignment between the simulation and daily cone beam CT datasets. The mean longitudinal difference was −0.19 cm (standard deviation, 0.17 cm; range, 0.28 cm to −1.14 cm). Therefore, the position of the vertebral body cannot be used as a surrogate for mean tumor position in the longitudinal direction. Longitudinal position must be accurately determined for each patient using multiple CT images. Conclusions: A slow CT protocol improved the alignment with slower breathing rates being more challenging. A 5 mm PTV is not sufficient for tumor motion greater than 9 mm. Averaging the coordinates from multiple CTOR images is recommended. [ABSTRACT FROM AUTHOR] |
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| Database: |
Complementary Index |