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From model-driven to knowledge- and data-based treatment planning
Published in Jun Deng, Lei Xing, Big Data in Radiation Oncology, 2019
Morteza Mardani, Yong Yang, Yinyi Ye, Stephen Boyd, Lei Xing
DVH is commonly employed as a means to statistically summarize the iso-dose distribution for a treatment plan. In reality, the DVH only provides first-order dosimetry information, that is, the volume (or fractional volume) of an organ receiving a certain dose without the spatial information of the doses. Note also that the DVH can be obtained only after an iso-dose plan has been crafted, prohibiting its usage during the process of dose optimization. Furthermore, in order to enable real-time image-guided radiotherapy, one may need more detailed dosimetry information. In essence, for real-time therapy the plan needs to be re-optimized frequently in an online fashion to track the dynamics of the tumor site over time.58,59 Recall that the current treatment planning technology, adopted, for example, by Eclipse and RapidPlan,46 relies solely on DVH and maximum/minimum dose volumes for OARs, which require a lot of tuning and replanning to assure the resulting plan meets the prescribed DVH. This can incur significant computational overhead (e.g., for VMAT) and hinders real-time planning. In principle, a detailed estimate of the dose profile serves as a valuable prior for plan optimization, which can confine the search space for the optimal plan and thus greatly accelerate the planning.
Megavoltage beam commissioning
Published in Indra J. Das, Radiochromic Film, 2017
Iori Sumida, David Barbee, Indra J. Das
RCF provides dosimetrically accurate measurement in homogeneous media; however, in 3DCRT, nearly all clinical planning situations in the human body involve inhomogeneities. The calculation algorithms should provide a high degree of accuracy in complex geometries and should be verified by measurements, wherein RCF is a very useful tool. During commissioning, it is possible to simplify the irradiation method used clinically and to investigate the accuracy of the individual dose calculation to estimate the uncertainty of the irradiation accuracy of the dose. In most cases, some simplification can be noted: the use of a rectangular irradiation fields, the use of a wedges, the tilt of the surface of the body with respect to the beam, and the presence of an inhomogeneous region (lung, air, and bone) in the irradiation field. The calculated dose profile depends on the method of dose calculation, for example, the Clarkson method, the convolution/superposition, collapsed-cone method, or the Monte Carlo method. The accuracy of some of the algorithms differs significantly as noted by Akino et al. [28] can be easily performed in phantom with RCF. Furthermore, clinical irradiation comprises a combination of many physical parameters. Therefore, it is important to investigate each of these parameters in which RCF plays an important role due to its characteristics as described earlier in Chapters 2 and 3.
Exposure Characterization
Published in Elizabeth L. Anderson, Roy E. Albert, RISK ASSESSMENT and INDOOR AIR QUALITY, 2019
Exposure and dose can be estimated in various ways. Exposure concentrations are useful when comparing peak exposures to health criteria such as the OSHA short-term exposure limits (STEL). Time-weighted averages are widely used by the OSHA for work-day occupational exposures and by the EPA in conducting carcinogen risk assessments. Exposure or dose profiles describe concentration or dose as a function of time and can be important where both concentration and time are important. Finally, integrated exposures can be useful where the total exposure rather than the exposure profile is important.
Investigation of Buildup Region and Surface Dose: Comparison of Parallel Plane Ion Chamber, Treatment Planning System, and MC Simulation
Published in Nuclear Technology, 2022
Data measurements of the PDD and lateral dose profile were obtained with a farmer ion chamber in water (PTW, Freiburg, Germany) at 10 × 10 cm2. The lateral dose profile was taken at the depth at which the dose is maximally measured dmax. These measurement data were used to verify the MC simulation method.