Investigation of sliced body volume (SBV) as respiratory surrogate.

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The purpose of this study was to evaluate the sliced body volume (SBV) as a respiratory surrogate by comparing with the real-time position management (RPM) in phantom and patient cases. Using the SBV surrogate, breathing signals were extracted from unsorted 4D CT images of a motion phantom and 31 cancer patients (17 lung cancers, 14 abdominal cancers) and were compared to those clinically acquired using the RPM system. Correlation coefficient (R), phase difference (D), and absolute phase difference (D(A)) between the SBV-derived breathing signal and the RPM signal were calculated. 4D CT reconstructed based on the SBV surrogate (4D CT(SBV)) were compared to those clinically generated based on RPM (4D CT(RPM)). Image quality of the 4D CT were scored (S(SBV) and S(RPM), respectively) from 1 to 5 (1 is the best) by experienced evaluators. The comparisons were performed for all patients, and for the lung cancer patients and the abdominal cancer patients separately. RPM box position (P), breathing period (T), amplitude (A), period variability (V(T)), amplitude variability (V(A)), and space-dependent phase shift (F) were determined and correlated to S(SBV). The phantom study showed excellent match between the SBV-derived breathing signal and the RPM signal (R = 0.99, D= -3.0%, D(A) = 4.5%). In the patient study, the mean (± standard deviation (SD)) R, D, D(A), T, V(T), A, V(A), and F were 0.92 (± 0.05), -3.3% (± 7.5%), 11.4% (± 4.6%), 3.6 (± 0.8) s, 0.19 (± 0.10), 6.6 (± 2.8) mm, 0.20 (± 0.08), and 0.40 (± 0.18) s, respectively. Significant differences in R and D(A) (p = 0.04 and 0.001, respectively) were found between the lung cancer patients and the abdominal cancer patients. 4D CT(RPM) slightly outperformed 4D CT(SBV): the mean (± SD) S(RPM) and S(SBV) were 2.6 (± 0.6) and 2.9 (± 0.8), respectively, for all patients, 2.5 (± 0.6) and 3.1 (± 0.8), respectively, for the lung cancer patients, and 2.6 (± 0.7) and 2.8 (± 0.9), respectively, for the abdominal cancer patients. The difference between S(RPM) and S(SBV) was insignificant for the abdominal patients (p = 0.59). F correlated moderately with S(SBV) (r = 0.72). The correlation between SBV-derived breathing signal and RPM signal varied between patients and was significantly better in the abdomen than in the thorax. Space-dependent phase shift is a limiting factor of the accuracy of the SBV surrogate.





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Cai, Jing, Zheng Chang, Jennifer O'Daniel, Sua Yoo, Hong Ge, Christopher Kelsey and Fang-Fang Yin (2013). Investigation of sliced body volume (SBV) as respiratory surrogate. Journal of applied clinical medical physics, 14(1). p. 3987. 10.1120/jacmp.v14i1.3987 Retrieved from

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Jing Cai

Adjunct Associate Professor in the Radiation Oncology

Image-guided Radiation Therapy (IGRT), Magnetic Resonance Imaging (MRI), Tumor Motion Management, Four-Dimensional Radiation Therapy (4DRT), Stereotatic-Body Radiation Therapy (SBRT), Brachytherapy, Treatment Planning, Lung Cancer, Liver Cancer, Cervical Cancer.


Zheng Chang

Professor of Radiation Oncology

Dr. Chang's research interests include radiation therapy treatment assessment using MR quantitative imaging, image guided radiation therapy (IGRT), fast MR imaging using parallel imaging and strategic phase encoding, and motion management for IGRT.


Jennifer Colleen O'Daniel

Assistant Professor of Radiation Oncology

Adaptive radiotherapy
2D and 3D patient-specific quality assurance techniques


Sua Yoo

Associate Professor of Radiation Oncology

Patient positioning verification for radiation therapy using OBI/CBCT; Treatment planning for breast cancer radiotherapy;


Christopher Ryan Kelsey

Professor of Radiation Oncology

I specialize in the treatment of hematologic and thoracic malignancies. I have a special research interest in optimizing radiation therapy in lymphomas and leukemias, particularly consolidation radiation therapy in diffuse large B-cell lymphoma and total body irradiation in the setting of allogeneic stem cell transplantation. Other academic interests include cardiac toxicity after radiation therapy for lung cancer and optimizing stereotactic body radiation therapy for stage I non-small cell lung cancer.

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