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IMRT and VMAT
Published in Eric Ford, Primer on Radiation Oncology Physics, 2020
Inverse planning is an optimization problem, the goal of which is to find the best planning solution given the goal of treating the target volume with a uniform dose while sparing the organs at risk (OAR). To drive this optimization, some metric for plan quality is needed. A critical measure for this is the dose volume histogram (DVH) as described in Section 13.1.5.
Data standardization and informatics in radiation oncology
Published in Jun Deng, Lei Xing, Big Data in Radiation Oncology, 2019
Changing practice norms to include the construction of ATPS for all patients is a cultural shift. Valuing the ability to automate the extraction of dose–volume histogram (DVH) curves for all treated patients is distinct from regarding treatment plans solely as objects needed to enable patient treatments to proceed. For example, in some clinics, electron boost plans may not be planned on the CT scan at all. This means that when questions arise around cumulative dose distributions (e.g., heart and lung doses for breast patients), an extensive effort is required to return to charts and manually create the ATPS. Generally, this manual effort is only carried out for certain subsets of patients. Shifting practice norms to include creation of ATPS as part of routine practice means that the information is available for all patients.
Fully Exploiting the Benefits of Protons *
Published in Harald Paganetti, Proton Therapy Physics, 2018
Peter van Luijk, Marco Schippers
Direct comparison of 3D dose distributions of alternative treatment plans is very inconvenient. Therefore, present practice is to summarize the 3D dose distribution in a dose–volume histogram (DVH). For each (relative) dose level, this histogram gives the volume that receives that dose (Figure 23.1D). In practice, the cumulative DVH, giving the volume receiving more than a certain dose as a function of that dose, is reported by treatment planning systems (Figure 23.1E). Even though a DVH discards a lot of information as compared to the 3D dose distribution, at present, this DVH is the starting point for the derivation of figures of merit, based on which the treatment plan can be optimized. Classically, individual DVH points, the mean dose or generalized forms of the mean dose are used for this. However, since the relation of these figures of merit to clinical outcome is not trivial, large efforts have been made to develop and use models explicitly describing the risk of normal tissue damage instead.
Relative contributions of radiation and cisplatin-based chemotherapy to sensorineural hearing loss in head-and-neck cancer patients
Published in Acta Oto-Laryngologica, 2021
Nidhin Das, Darwin Kaushal, Sourabha Kumar Patro, Puneet Pareek, Abhinav Dixit, Kapil Soni, Nithin Prakasan Nair, Bikram Choudhury, Amit Goyal
All patients were planned for RT using volumetric arc therapy (VMAT) treatment plans with a 6 MV flat photon beam. To achieve the best treatment plan, patients were planned using both coplanar and non-coplanar orientations using an optimized couch angle, considering the achievable gantry-couch-patient clearance and dose fluences for better target dose coverage and maximum OARs dose sparing. Treatment plans were qualitatively evaluated for each patient and the dosimetric data were taken from the Dose-volume histogram (DVH) data. Both the coplanar and non-coplanar plans were generated by a double arc (clockwise and anti-clockwise direction) plans with an increment angle of 20 degrees. To allow sufficient modulation and acceptable duration for the plan optimization process, the maximum number of control points per arc was selected as 180 with a minimum segment width of 1 cm. According to the beam angle alignment, the collimator angle was fixed to avoid tongue and groove effects and to cover the entire target region sparing the nearby OARs. In VMAT, the Segment Shape Optimization (SSO) technique was used where the target dose rate was automatically selected by the planning system itself, creating segments. According to the International Commission on Radiation Units and Measurements (ICRU) 83, 95% of planning target volume should receive 95% of the prescribed dose [8].
Microspheres Encapsulating Immunotherapy Agents Target the Tumor-Draining Lymph Node in Pancreatic Ductal Adenocarcinoma
Published in Immunological Investigations, 2020
Booyeon J. Han, Joseph D. Murphy, Shuyang Qin, Jian Ye, Taylor P. Uccello, Jesse Garrett-Larsen, Brian A. Belt, Peter A. Prieto, Nejat K. Egilmez, Edith M. Lord, David C. Linehan, Bradley N. Mills, Scott A. Gerber
All radiation was delivered using the Small Animal Radiation Research Platform (SARRP, XStrahl) using a 5-mm collimator. Mice were anesthetized with vaporized isoflurane for the duration of all radiation treatments. Stereotactic body radiation therapy (SBRT) was administered to tumor-bearing mice following a schedule of 4 fractions of 6 Gy radiation each on days 6–9 posttumor implantation, yielding a BED of 38.4 for tumor and 72 for normal tissue (assuming an α/β ratio of 10 for tumor and 3 for normal). Localized delivery was performed using visualization of previously mentioned titanium fiducial markers via computed tomography (CT) scans. The dosing isocenter was positioned using a beam angle designed to avoid major organs. In each case, a dose volume histogram (DVH) was generated to confirm full dose deposition to the tumor and negligible amounts to surrounding organs (e.g., liver and TDLN).
Definitive re-irradiation using intensity-modulated radiation therapy in cancers of the head and neck, focusing on rare tumors
Published in Acta Oto-Laryngologica, 2018
Hiroshi Doi, Kenji Uemoto, Norihisa Masai, Daisaku Tatsumi, Hiroya Shiomi, Ryoong-Jin Oh
The radiation dosage was calculated to deliver the prescribed dose to cover 95% of the PTV during IMRT, using a 6-MV linear accelerator (Novalis BrainLAB AG, Feldkirchen, Germany), with a prescription dose equivalent to a biologically effective dose (BED), the α/β values of 10 were used for the tumors, of ≥80 Gy. Fractionated regimens were scheduled to reduce BED for organs at risks. Figure 1 indicates a typical case of re-irradiation and how IMRT was provided. The dose–volume histogram (DVH) of all treatment plans was acquired from the radiotherapy planning system. Each physical dose was then converted into the BED by using the α/β value of 2 or 3 for normal tissues. The total dose distribution of each treatment plan was exported in terms of BED to be used in the digital imaging and communications in medicine-radiation therapy (DICOM-RT) image fusion software (ShioRISTM 2.0, Osaka, Japan) to determine the exposed radiation doses to organs at risk (Figure 1).