Purpose: For post-mastectomy radiation therapy, skin dose must be accurately estimated to assess skin reactions, such as: erythema, desquamation, and necrosis. Even with advanced algorithms, planning systems do not al...Purpose: For post-mastectomy radiation therapy, skin dose must be accurately estimated to assess skin reactions, such as: erythema, desquamation, and necrosis. Even with advanced algorithms, planning systems do not always provide accurate dosimetry for target volumes distal to skin. Methods and Materials: In this study, a female anthropomorphic (ART) phantom and the newest generation of optically stimulated luminescence dosimeters (OSLD) (nanoDots, Landauer Inc.) were deployed to measure chest wall dose distribution. Since actual dose to patients’ lung and heart cannot be measured using in-vivo dosimetry, film was also used to verify the dose distribution to the left lung and heart. The treatment planning was performed using tolerance limits of 95% to 107% of prescription dose. The ART phantom was irradiated according to 3 three-dimensional (3D) conformal radiotherapy plans for 200 cGy dose per fraction using 6 MV medial and lateral tangential photon beams. The dose distribution provided by treatment planning was studied using nanoDots and film. Results: Results show that the largest surface dose difference between nanoDots measurement and prescribed dose for medial and lateral tangential beams, are 3.8% and 9.8%, respectively. This difference may be due to higher effective point of measurement and angular dependence of the nanoDots. The maximum differences in measured dose compared with prescribed dose, using film for heart and the left lung, were 6.2% and 7.5% respectively. Conclusions: Both nanoDots and film provided reasonable estimation of dose distribution in post-mastectomy radiation therapy.展开更多
Objectives: Early detection and treatment provide the opportunity to decrease the mortality rate from breast cancer. Quasi-monochromatic technique can enhance low contrast lesion detection by eliminating beam-hardenin...Objectives: Early detection and treatment provide the opportunity to decrease the mortality rate from breast cancer. Quasi-monochromatic technique can enhance low contrast lesion detection by eliminating beam-hardening artifacts. We hypothesized that this technique would be feasible and can be used to assist in breast cancer early detection. Methods: The performance of stationary Digital Breast Tomosynthesis with quasi-monochromatic X-ray sources was evaluated using both simulated and physical phantoms. Normalized spectra in the fraction of total photons vs. photon energy were generated. Results: As expected, the peaked energies from sources, from smallest to largest, are Mo/Mo, W/Ag-1000, and W/Ce-10, W/Ce-100. For contrast vs. noise standard deviation on the simulated CIRS phantom, W/Ce-100 and W/Ce-10 have similar performance on both low and high contrast objects. For low contrast object, W/Ce-100 is barely noticeably better than W/Ce-10, and they are better than both W/Ag-1000 and Mo/Mo. For high contrast objects W/Ce-10 is slightly better than W/Ce-100. The spectra of the implemented W/Ce-10 X-ray source were measured, which matched the simulation well. The contrast noise ratios of reconstructed objects in American College of Radiology mammographic phantom with and without using W/Ce-10 combination are 7.1 and 5.4, respectively. Conclusions: The combination of stationary digital breast tomosynthesis and quasi-monochromatic technique can compensate the loss of X-ray flux due to heavy K-edge filtering. This technique can enable the stationary DBT scanners to operate at acceptable scanning times with better low contrast lesion detectability. Advances in Knowledge: The stationary digital breast tomosynthesis can provide high quality images within short scanning time by using X-ray source array, which makes quasi-monochromatic technique feasible.展开更多
文摘Purpose: For post-mastectomy radiation therapy, skin dose must be accurately estimated to assess skin reactions, such as: erythema, desquamation, and necrosis. Even with advanced algorithms, planning systems do not always provide accurate dosimetry for target volumes distal to skin. Methods and Materials: In this study, a female anthropomorphic (ART) phantom and the newest generation of optically stimulated luminescence dosimeters (OSLD) (nanoDots, Landauer Inc.) were deployed to measure chest wall dose distribution. Since actual dose to patients’ lung and heart cannot be measured using in-vivo dosimetry, film was also used to verify the dose distribution to the left lung and heart. The treatment planning was performed using tolerance limits of 95% to 107% of prescription dose. The ART phantom was irradiated according to 3 three-dimensional (3D) conformal radiotherapy plans for 200 cGy dose per fraction using 6 MV medial and lateral tangential photon beams. The dose distribution provided by treatment planning was studied using nanoDots and film. Results: Results show that the largest surface dose difference between nanoDots measurement and prescribed dose for medial and lateral tangential beams, are 3.8% and 9.8%, respectively. This difference may be due to higher effective point of measurement and angular dependence of the nanoDots. The maximum differences in measured dose compared with prescribed dose, using film for heart and the left lung, were 6.2% and 7.5% respectively. Conclusions: Both nanoDots and film provided reasonable estimation of dose distribution in post-mastectomy radiation therapy.
文摘Objectives: Early detection and treatment provide the opportunity to decrease the mortality rate from breast cancer. Quasi-monochromatic technique can enhance low contrast lesion detection by eliminating beam-hardening artifacts. We hypothesized that this technique would be feasible and can be used to assist in breast cancer early detection. Methods: The performance of stationary Digital Breast Tomosynthesis with quasi-monochromatic X-ray sources was evaluated using both simulated and physical phantoms. Normalized spectra in the fraction of total photons vs. photon energy were generated. Results: As expected, the peaked energies from sources, from smallest to largest, are Mo/Mo, W/Ag-1000, and W/Ce-10, W/Ce-100. For contrast vs. noise standard deviation on the simulated CIRS phantom, W/Ce-100 and W/Ce-10 have similar performance on both low and high contrast objects. For low contrast object, W/Ce-100 is barely noticeably better than W/Ce-10, and they are better than both W/Ag-1000 and Mo/Mo. For high contrast objects W/Ce-10 is slightly better than W/Ce-100. The spectra of the implemented W/Ce-10 X-ray source were measured, which matched the simulation well. The contrast noise ratios of reconstructed objects in American College of Radiology mammographic phantom with and without using W/Ce-10 combination are 7.1 and 5.4, respectively. Conclusions: The combination of stationary digital breast tomosynthesis and quasi-monochromatic technique can compensate the loss of X-ray flux due to heavy K-edge filtering. This technique can enable the stationary DBT scanners to operate at acceptable scanning times with better low contrast lesion detectability. Advances in Knowledge: The stationary digital breast tomosynthesis can provide high quality images within short scanning time by using X-ray source array, which makes quasi-monochromatic technique feasible.
