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Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists | Page 2

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https://read.qxmd.com/read/31901300/a-sliding-window-approach-for-improved-vmat-dose-calculation-accuracy
#21
Haitham N Alahmad, Ji-Yeon Park, Nicholas J Potter, Bo Lu, Guanghua Yan, Chihray Liu, Jonathan G Li
The continuous delivery of volumetric modulated arc therapy (VMAT) plans is usually approximated by discrete apertures at evenly-spaced gantry angles for dose calculation purposes. This approximation can potentially lead to large dose calculation errors if the gantry angle spacings are large and/or there are large changes in the MLC apertures from one control point (CP) to the next. In this work, we developed a sliding-window (SW) method to improve VMAT dose calculation accuracy. For any 2 adjacent VMAT CPs ni and ni + 1, the dose distribution was approximated by a 2-CP SW IMRT beam with the starting MLC positions at CP ni and ending MLC positions at CP ni + 1, with the gantry angle fixed in the middle of the 2 VMAT CPs...
December 31, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31870600/proton-pencil-beam-scanning-treatment-with-feedback-based-voluntary-moderate-breath-hold
#22
Peng Wang, Shikui Tang, Karla Leach, Victor Mangona, Charles B Simone, Katja Langen, Chang Chang
Introduction The aim of this article is to introduce a novel protocol for proton pencil beam scanning treatment with moderate deep inspiration breath hold (mDIBH) and report on our clinical implementation results. Methods Three computed tomography (CT) scannings to build the patient's anatomy model were performed during the patient's voluntary mDIBH. All 3 CT scans were used in the optimization during the treatment planning process. Both orthogonal kV imaging and cone-beam computed tomography (CBCT) were implemented for patient alignment with BH prior to the treatment...
December 20, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31864819/small-bowel-dose-in-subserosal-tandem-insertion-during-cervical-cancer-brachytherapy
#23
Yu-Lun Tsai, Pei-Chieh Yu, Louis Tak Lui, Suzun Shaw, Ching-Jung Wu
Cervical cancer patients may sometimes experience subserosal tandem insertions during brachytherapy, which can lead to increased but unnoticed irradiations to the small bowel (SB). In this study, we aimed to quantify and further predict individual SB dose increase and to increase focus on the SB in subserosal tandem insertions. Images and dosimetry data of cervical cancer brachytherapy with subserosal insertion (SI) were reviewed. The percentage increases in the SB dose compared with intracavitary insertion (II) at 8 points of D(x)cc with 10 cc intervals were assessed...
December 18, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31843470/functional-cranio-spinal-irradiation-a-hippocampal-and-hypothalamic-pituitary-axis-sparing-radiation-technique-using-two-imrt-modalities
#24
Jack Zheng, Saif Aljabab, Patricia Lacasse, Jamie Bahm, Katie Lekx-Toniolo, Laval Grimard
Cranio-spinal irradiation (CSI) treatment of embryonal tumors is associated with long-term endocrine and neuro-cognitive sequelae. As an example, the radiation regiment for standard risk medulloblastoma is 23.4 Grays (Gy) CSI followed by a boost of 30.6Gy to the tumor bed. We hypothesize that a novel CSI technique, which we named "Functional" CSI (F-CSI) can reduce the dose to the hypothalamic-pituitary axis (HPA) and hippocampi compared to standard CSI (S-CSI) without sacrificing coverage. In this study, we compared the efficacy of Volumetric Modulated Arc Therapy (VMAT) and Helical Tomotherapy (HT) in delivering this novel CSI technique...
December 13, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31822373/optimization-of-the-accelerated-partial-breast-brachytherapy-fractionation-considering-radiation-effect-on-planning-target-and-organs-at-risk
#25
Weihua Fu, Mohammed Saiful Huq
The same fractionation scheme of accelerated partial breast irradiation (APBI) with brachytherapy is usually applied to APBI patients without considering the radiaton effect on the planning target and organs at risk (OARs) for an individual patient. The purpose of this study is to report the results of optimization of the fractionation scheme by evaluating the radiation effect on target and OARs with a modified linear-quadratic model, universal survival curve (USC), based on dose-volume histograms (DVHs). Ten breast patients treated with multilumen balloon brachytherapy were selected...
December 7, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31757715/the-mean-absolute-dose-deviation-a-common-metric-for-the-evaluation-of-dose-volume-histograms-in-radiation-therapy
#26
Vincent Vinh-Hung, Nicolas Leduc, Dirk Verellen, Claire Verschraegen, Giovanna Dipasquale, Nam P Nguyen
Radiation therapy needs to balance between delivering a high dose to targets and the lowest possible dose to the organs at risk. Dose-volume histograms (DVHs) summarize the distribution of radiation doses in the irradiated structures. The interpretation can however be a challenge when the number of structures is high. We propose the use of a simple summary metric. We define the mean absolute dose deviation (MADD) as the average of absolute differences between a DVH and a reference dose. The properties are evaluated through numerical analysis...
November 19, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31740043/comparison-of-dose-distributions-between-transverse-magnetic-fields-of-0-35-t-and-1-5-t-for-radiotherapy-in-lung-tumor-using-monte-carlo-calculation
#27
Takahiro Kubota, Fujio Araki, Takeshi Ohno
We investigated the impact of the transverse magnetic fields of 0.35 T and 1.5 T on the dose distributions for a 6 MV beam, by using a thorax phantom with a lung tumor. First, the dose distributions in the magnetic flux densities of 0 T, 0.35 T, and 1.5 T were compared by increasing the number of irradiation fields. Next, the dose distributions for stereotactic body radiotherapy (SBRT) with 5-fields for an isolated lung tumor was compared in transverse magnetic fields. All dose distributions were calculated by the Monte Carlo method...
November 15, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31740042/rapidplan-development-of-vmat-plans-for-cervical-cancer-patients-in-low-and-middle-income-countries
#28
Marisol Tinoco, Erika Waga, Kevin Tran, Hieu Vo, Jamie Baker, Rachel Hunter, Christine Peterson, Nicolette Taku, Laurence Court
Cervical cancer has a high incidence and mortality rate in low- and middle-income countries (LMICs) largely due to limited resources and insufficient staffing. Knowledge-based planning (KBP) could alleviate understaffing issues by streamlining the radiotherapy treatment planning process. Varian's KBP system (RapidPlan) was used to develop a model capable of producing volumetric modulated arc therapy (VMAT) plans for cervical cancer patients. Plan data from 46 patients previously treated at MD Anderson Cancer Center (MDACC) were used to create and train the model which was then applied to 32 patients excluded from the training process...
November 15, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31727550/improving-tbi-lung-dose-calculations-can-the-treatment-planning-system-help
#29
Narottam Lamichhane, Matthew T Studenski
Lung toxicity is a serious concern during total body irradiation (TBI). Therefore, evaluation of accurate dose calculation when using lung blocks is of utmost importance. Existing clinical treatment planning systems can perform the calculation but there are large inaccuracies when calculating volumetric dose at extended distances in the presence of high atomic number materials. Percent depth dose and absolute dose measurements acquired at 400 cm SSD with a cerrobend block were compared with calculated values from the Eclipse treatment planning system using AAA and Acuros...
November 12, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31718856/surface-dose-and-acute-skin-reactions-in-external-beam-breast-radiotherapy
#30
Patrick N McDermott
The biologically relevant depth for acute skin reactions in radiotherapy is 70 µm. The dose at this depth is difficult to measure or calculate and can be quite different than the dose at a depth of as little as 1 mm. For breast radiotherapy with medial and lateral tangential beams, the skin dose depends on both the contribution from the entrance beam and the exit beam. The skin dose has been estimated in a breast model hemi-ellipse accounting for field size, beam energy, obliquity, lack of backscatter, fractionation, size and shape of the hemi-ellipse...
November 9, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31629601/evaluation-of-the-raystation-electron-monte-carlo-dose-calculation-algorithm
#31
Neil Richmond, Vincent Allen, Jonathan Wyatt, Richard Codling
The aim of this work was to evaluate the accuracy of the RayStation treatment planning system electron Monte Carlo algorithm against measured data for a range of clinically relevant scenarios. This was done by comparing measured percentage depth dose data (PDD) in water, profiles at oblique incidence and with heterogeneities in the beam path, and output factor data and that generated using the RayStation treatment planning system Monte Carlo VMC++ based calculation algorithm. While electron treatments are widely employed in the radiotherapy setting accurate modelling is challenging (TPS) in the presence of patient being both heterogeneous and nonrectangular...
October 17, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31606269/dosimetric-evaluation-of-the-intrabeam-system-for-breast-intraoperative-radiotherapy-a-single-institution-experience
#32
Mubin Y Shaikh, Adrian Nalichowski, Michael C Joiner, Jay Burmeister
Breast intraoperative radiotherapy (IORT) with the INTRABEAM system uses a 50 kV x-ray source to deliver a single fraction of radiation therapy to the lumpectomy cavity during breast-conserving surgery. We seek to perform a dosimetric analysis of the lumpectomy cavity for rigid spherical applicators. Water phantom measurements were acquired to validate the vendor-provided x-ray calibration. The planning target volume (PTV) was defined as a 10 mm expansion beyond the spherical applicator, a dose-volume histogram (DVH) was generated and dose-volume parameters [Dmin , D1mm , V90 , V80 , V50 , HI] were reported...
October 9, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31570239/dosimetric-comparison-between-volumetric-modulated-arc-therapy-and-a-hybrid-volumetric-modulated-arc-therapy-and-segmented-field-in-field-technique-for-postmastectomy-chest-wall-and-regional-lymph-node-irradiation
#33
Karen Lang, Brianne Loritz, Adam Schwartz, Ashley Hunzeker, Nishele Lenards, Lee Culp, Randi Finley, Kimberly S Corbin
Decreasing radiotoxicity to the heart, lungs, and contralateral breast has proven to lower the risk of secondary malignancy and improve overall outcomes when treating chest wall (CW) and regional lymph nodes in postmastectomy breast cancer patients. In this retrospective study, 11 postmastectomy patients were selected and planned with a novel hybrid treatment method and a traditional volumetric arc therapy (VMAT) approach for comparison. This hybrid technique was able to optimize tangential beams to minimize heart dose and the VMAT contribution to improve dose conformity around the planning target volume (PTV)...
September 27, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31562018/comparison-of-dose-statistics-for-bladder-wall-and-rectum-wall-vs-whole-organs-for-vmat-prostate-treatment
#34
Andree Desrochers, Sunita Ghosh, Matthew Parliament, Rhea Garraway, Leanne Kellogg, Matthew P Larocque
Dose-wall histograms (DWHs) have been used as alternatives to dose-volume histograms (DVHs) for hollow organs, with the rationale that the dose delivered to the interior of a hollow organ would be unrelated to the level of radiation damage. The purpose of this study is to conduct a statistical comparison of dose statistics for both walled and solid structure contours for both bladder and rectum in the treatment of intermediate risk prostate cancer with volumetric arc therapy (VMAT). Ten intermediate risk prostate cases were randomly selected...
September 24, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31548101/a-novel-technique-for-treating-deep-seated-breast-cavity-boosts
#35
David Pearson, Jui Wan, Jonathan Bogue
Breast boost irradiation is an integral component to the standard of care for early staged breast cancer. The use of reduced tangents is common for deep seating tumor bed; however, reduced tangents result in non-conformal plans delivering prescription dose to large volumes of breast tissue. To improve conformity, a novel technique of integrating a single conformal arc with reduced tangents has been developed. With this technique, a conformal arc was placed between a pair of reduced tangents to better conform the prescription dose to the target volume...
September 20, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31537421/dose-perturbation-due-to-dental-amalgam-in-the-head-and-neck-radiotherapy-a-phantom-study
#36
Pegah Saadatmand, Alireza Amouheidari, Ahmad Shanei, Iraj Abedi
Dental amalgam, causes perturbation in photon dose distribution of head and neck (H&N) radiotherapy. The aim of this study was to evaluate the effects of dental amalgam on dose distribution of H&N radiotherapy and accuracy of dose calculations algorithm of commercial treatment planning system (TPS). In this study, the measurements were performed using a constructed H&N anthropomorphic. The sample of healthy teeth and teeth filled by amalgam inserted in the desired segment of the phantom in turn...
September 17, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31521451/correlation-of-hot-spot-to-breast-separation-in-patients-treated-with-postlumpectomy-tangent-3d-crt-using-field-in-field-technique-and-mixed-photon-energies
#37
Nancy R Gustafson, Teri Burrier, Brittany Butler, Ashley Hunzeker, Nishele Lenards, Lee Culp
Radiotherapy to an intact breast was previously determined to have a positive correlation between breast separation measurement and hot spot dose. As breast separation measurement increased, hot spot dose increased. The purpose of this retrospective study was to determine if this correlation persisted despite current techniques including field-in-field (FiF) blocking and mixed photon energies. Radiation treatment plans on unilateral intact breasts from 90 female, early stage breast cancer patients treated with lumpectomy were analyzed...
September 11, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31477438/comparing-medical-grade-to-commercial-grade-display-in-a-radiation-oncology-environment
#38
Adi Robinson, Mark D Fairchild
Electronic displays are used in every modern day medical clinic. They are used to view images that are needed to diagnose, treat, and follow-up on patients with a variety of conditions. The type of electronic display used varies from department to department. Currently, a type of displays called medical grade displays are used to evaluate and diagnose disease and conditions. Alternatively, commercial or entry level professional displays are used for almost everything else. In the field of radiation oncology medical images are often used to plan the treatment course for each patient...
August 31, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31466736/feasibility-of-5-mm-vs-2-5-mm-width-multileaf-collimator-in-noncoplanar-volumetric-modulated-arc-stereotactic-radiotherapy-for-multiple-brain-metastases
#39
Kotaro Yoshio, Akihisa Wakita, Kento Hisazumi, Takahiro Kitayama, Nobuhisa Tajiri, Tsuyoki Shiode, Shiro Akaki, Susumu Kanazawa
The aim of this study was to examine the feasibility of noncoplanar volumetric modulated arc stereotactic radiotherapy (VMAT-SRT) using a 5-mm multileaf collimator (MLC) for multiple brain metastases. We identified 34 multiple-target cases (3 to 19 targets in each case) with a total of 257 of targets and constructed noncoplanar VMAT-SRT plans using 5-mm and 2.5-mm MLCs with 4-arc. The prescribed dose was 36 Gy/6 fr. Plans were evaluated using the Paddick conformity indices (PCI), Paddick gradient index (PGI), and normal brain dose (NBD, equal to the mean brain dose minus gross tumor volume)...
August 26, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://read.qxmd.com/read/31466735/dosimetric-evaluation-of-automatic-and-manual-plans-for-early-nasopharyngeal-carcinoma-to-radiotherapy
#40
Quanbin Zhang, Yingying Peng, Xianlu Song, Hui Yu, Linjing Wang, Shuxu Zhang
To investigate dosimetric differences and plan qualities between manual plans and automatic plans for nasopharyngeal carcinoma (NPC) in early stage, and provide better options to maximize the benefits. Sixteen cases diagnosed with early NPC were retrospectively investigated. Conventional step and shoot IMRT with 7-fields and full arc volumetric-modulated arc therapy (VMAT) with double arcs were manually generated by experienced planners and automatically generated by Auto-Planning module in Pinnacle3 respectively, such as IMRT manual-planning (mIMRT), IMRT auto-planning (aIMRT), VMAT manual-planning (mVMAT), and VMAT auto-planning (aVMAT) for each patient...
August 26, 2019: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
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