Omar El-Sherif1, Edward Yu2, Ilma Xhaferllari3, Stewart Gaede4. 1. Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada; Department of Physics, London Regional Cancer Program, London, Ontario, Canada. Electronic address: Omar.ElSherif@lhsc.on.ca. 2. Department of Radiation Oncology, London Regional Cancer Program, London, Ontario, Canada. 3. Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada; Department of Physics, London Regional Cancer Program, London, Ontario, Canada. 4. Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada; Department of Physics, London Regional Cancer Program, London, Ontario, Canada; Department of Radiation Oncology, London Regional Cancer Program, London, Ontario, Canada.
Abstract
PURPOSE: To use 4-dimensional computed tomography (4D-CT) imaging to predict the level of uncertainty in cardiac dose estimates of the left anterior descending artery that arises due to breathing motion during radiation therapy for left-sided breast cancer. METHODS AND MATERIALS: The fast helical CT (FH-CT) and 4D-CT of 30 left-sided breast cancer patients were retrospectively analyzed. Treatment plans were created on the FH-CT. The original treatment plan was then superimposed onto all 10 phases of the 4D-CT to quantify the dosimetric impact of respiratory motion through 4D dose accumulation (4D-dose). Dose-volume histograms for the heart, left ventricle (LV), and left anterior descending (LAD) artery obtained from the FH-CT were compared with those obtained from the 4D-dose. RESULTS: The 95% confidence interval of 4D-dose and FH-CT differences in mean dose estimates for the heart, LV, and LAD were ±0.5 Gy, ±1.0 Gy, and ±8.7 Gy, respectively. CONCLUSION: Fast helical CT is a good approximation for doses to the heart and LV; however, dose estimates for the LAD are susceptible to uncertainties that arise due to intrafraction breathing motion that cannot be ascertained without the additional information obtained from 4D-CT and dose accumulation. For future clinical studies, we suggest the use of 4D-CT-derived dose-volume histograms for estimating the dose to the LAD.
PURPOSE: To use 4-dimensional computed tomography (4D-CT) imaging to predict the level of uncertainty in cardiac dose estimates of the left anterior descending artery that arises due to breathing motion during radiation therapy for left-sided breast cancer. METHODS AND MATERIALS: The fast helical CT (FH-CT) and 4D-CT of 30 left-sided breast cancerpatients were retrospectively analyzed. Treatment plans were created on the FH-CT. The original treatment plan was then superimposed onto all 10 phases of the 4D-CT to quantify the dosimetric impact of respiratory motion through 4D dose accumulation (4D-dose). Dose-volume histograms for the heart, left ventricle (LV), and left anterior descending (LAD) artery obtained from the FH-CT were compared with those obtained from the 4D-dose. RESULTS: The 95% confidence interval of 4D-dose and FH-CT differences in mean dose estimates for the heart, LV, and LAD were ±0.5 Gy, ±1.0 Gy, and ±8.7 Gy, respectively. CONCLUSION: Fast helical CT is a good approximation for doses to the heart and LV; however, dose estimates for the LAD are susceptible to uncertainties that arise due to intrafraction breathing motion that cannot be ascertained without the additional information obtained from 4D-CT and dose accumulation. For future clinical studies, we suggest the use of 4D-CT-derived dose-volume histograms for estimating the dose to the LAD.
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