35 research outputs found
The role of whole brain radiation therapy in the management of newly diagnosed brain metastases: a systematic review and evidence-based clinical practice guideline
QUESTION: Should patients with newly-diagnosed metastatic brain tumors undergo open surgical resection versus whole brain radiation therapy (WBRT) and/or other treatment modalities such as radiosurgery, and in what clinical settings?
TARGET POPULATION: These recommendations apply to adults with a newly diagnosed single brain metastasis amenable to surgical resection.
RECOMMENDATIONS: Surgical resection plus WBRT versus surgical resection alone Level 1 Surgical resection followed by WBRT represents a superior treatment modality, in terms of improving tumor control at the original site of the metastasis and in the brain overall, when compared to surgical resection alone. Surgical resection plus WBRT versus SRS + or - WBRT Level 2 Surgical resection plus WBRT, versus stereotactic radiosurgery (SRS) plus WBRT, both represent effective treatment strategies, resulting in relatively equal survival rates. SRS has not been assessed from an evidence-based standpoint for larger lesions (\u3e3 cm) or for those causing significant mass effect (\u3e1 cm midline shift). Level 3 Underpowered class I evidence along with the preponderance of conflicting class II evidence suggests that SRS alone may provide equivalent functional and survival outcomes compared with resection + WBRT for patients with single brain metastases, so long as ready detection of distant site failure and salvage SRS are possible. Note The following question is fully addressed in the WBRT guideline paper within this series by Gaspar et al. Given that the recommendation resulting from the systematic review of the literature on this topic is also highly relevant to the discussion of the role of surgical resection in the management of brain metastases, this recommendation has been included below
The American Board of Radiology Focused Practice Recognition in Brachytherapy (FPRB) Program: Opportunities lost, lessons learned, and future implications
Calculation of K Correction Factors with Monte Carlo Simulations in Tomotherapy Clinical Helical Deliveries for Future Ion Chamber Reference Dosimetry Protocols of Non-standard Beams
Modeling the Fluence Output Factor for TomoTherapy Dynamic Jaw Delivery
Purpose/Objective(s): The dynamic jaw delivery improves the longitudinal resolution and throughput of the TomoTherapy treatment system. This technique utilizes small jaw widths near longitudinal borders of a tumor for higher resolution and utilizes large jaw widths in the middle for higher efficiency. Due to the finite spot size of the electron source, the fluence output factor (FOF) decreases as the jaws close, which results in the longitudinal borders of the target receiving fewer doses. To address this issue, we propose a model to calculate the FOF for different jaw settings. This model provides a quick solution to convert the fluence-equivalent jaw width to the light-projected jaw width. Materials/Methods: For TomoTherapys dose calculation, the integral fluence is more relevant than the center value of the jaw fluence profile. FOF in TomoTherapy is defined as the ratio of longitudinal integral fluence to the jaw width. The dynamic jaw algorithm generates jaw trajectories based on the assumption that the FOF remains the same for different jaw widths. However, the physical, light-projected jaw width which the initial MLC open sinogram is based on does not preserve FOF. The light-projected jaw width leads to a decrease of the FOF for small jaw opening. This could result in a sinogram with hot regions near the longitudinal borders for dynamic jaw delivery. To address the issue, we define the fluence-equivalent jaw width as the jaw width that preserves FOF and propose a fluence calculation model with a radiation source of finite size. A 2D Gaussian distribution is assumed for the photon source. Photons are assumed to be absorbed immediately once they are blocked by the jaws. The fluence value of a point on the isocenter plane is the integral of the part of the source that can be seen by the point. Photons in different directions have equal weight since the angular variation is very small within a few degrees in the forward direction. Longitudinal fluence profiles for different jaw settings are calculated based on the jaw geometry. Results: As the jaws close, source occlusion makes the FOF deviate from constant and eventually drop to zero. Different spot sizes were used to test the model. The results are plotted in the FOF vs. light-projected jaw width graphs. The results match well with the Monte Carlo simulations for different spot sizes. A spot size with a FWHM of 1.1 mm fits well with measurement results. The model has adequate accuracy to calculate the integral fluence. Conclusions: The variation of the FOF is mainly due to the finite size of the radiation source and its occlusion by the jaws. The simple model based on jaw geometry can calculate the FOF with adequate accuracy. Conversion from the fluence-equivalent jaw trajectory to light-projected jaw trajectory can be built based on this model to improve the efficiency of the dynamic jaw delivery
Construction of a Dental Atlas for Automatic Teeth Segmentation to Improve Post-irradiation Dental Care Management
International Journal of Radiation Oncology Biology Physicsno abstrac