International Journal of Medical Physics, Clinical Engineering and Radiation Oncology

Journal Information
ISSN / EISSN : 2168-5436 / 2168-5444
Published by: Scientific Research Publishing, Inc. (10.4236)
Total articles ≅ 277
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Junfang Gao
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Volume 10, pp 12-15; https://doi.org/10.4236/ijmpcero.2021.101002

Abstract:
During the implementation of clinical trials NCT00950001 and NCCTG/N107C/CEC.3 on post-operative stereotactic radiosurgery into clinic, it brought us some thinking of fundamental concept in science that the local control rate and survival rate rely on the treatment of marginal region more than resection cavity. Marginal region might still contain residual cancer cell while the resection cavity contains only water fluid most time. Radiation treatment should focus more on the margin rather than the cavity, thus treating cancer rather than water.
Huan Yao, Jenghwa Chang
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Volume 10, pp 81-93; https://doi.org/10.4236/ijmpcero.2021.102008

Abstract:
Purpose: To improve the liver auto-segmentation performance of three-dimensional (3D) U-net by replacing the conventional up-sampling convolution layers with the Pixel De-convolutional Network (PDN) that considers spatial features. Methods: The U-net was originally developed to segment neuronal structure with outstanding performance but suffered serious artifacts from indirectly unrelated adjacent pixels in its up-sampling layers. The hypothesis of this study was that the segmentation quality of the liver could be improved with PDN in which the up-sampling layer was replaced by a pixel de-convolution layer (PDL). Seventy-eight plans of abdominal cancer patients were anonymized and exported. Sixty-two were chosen for training two networks: 1) 3D U-Net, and 2) 3D PDN, by minimizing the Dice loss function. The other sixteen plans were used to test the performance. The similarity Dice and Average Hausdorff Distance (AHD) were calculated and compared between these two networks. Results: The computation time for 62 training cases and 200 training epochs was about 30 minutes for both networks. The segmentation performance was evaluated using the remaining 16 cases. For the Dice score, the mean ± standard deviation were 0.857 ± 0.011 and 0.858 ± 0.015 for the PDN and U-Net, respectively. For the AHD, the mean ± standard deviation were 1.575 ± 0.373 and 1.675 ± 0.769, respectively, corresponding to an improvement of 6.0% and 51.5% of mean and standard deviation for the PDN. Conclusion: The PDN has outperformed the U-Net on liver auto-segmentation. The predicted contours of PDN are more conformal and smoother when compared with the U-Net.
Alejandro Prado, Inés Flores, Ángel Montero, Miguel Ángel de la Casa, Leyre Alonso, Jaime Martí, Pedro Fernández-Letón, Carmen Rubio
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Volume 10, pp 132-148; https://doi.org/10.4236/ijmpcero.2021.103012

Abstract:
Aim: To compare and analyze dose constraints and target coverage results and to reduce Bladder Wall (Bwall) V18.12 for prostate Stereotactic-Body Radiation Therapy (SBRT) when Seminal Vesicles (SSVV) are included or not. Several indicators based on intersection volumes are obtained to predict constraint fulfillment. Background: Due to prostate’s low alpha-beta ratio and the possibility of increasing the therapeutic ratio several moderate and extreme hypofractionation schemes have been proposed. The scheme selected was a fivefraction urethra-sparing prostate SBRT. Materials and Methods: 150 patients divided into two groups according to the inclusion of SSVV in PTV or not were analyzed. Histograms, average values, standard deviations and degrees of fulfillment were obtained for each constraint or goal and group. A possible reduction of the Bwall V18.12 was addressed by re-optimizing fifty randomly chosen patients. Predictors of constraint fulfilling were obtained by using the intersections of Bwall and Rectum Wall (Rwall) with the PTV. Results: Significant differences in Rwall V32.62 and V29 were obtained when evaluating the influence of SSVV inclusion. A reduction of 12% in the Bwall V18.12 constraint was achieved without compromising coverage and OARs doses. No dependence on the inclusion of SSVV was found. Conclusions: Statistically significant differences have been found in Rwall intermediate-dose constraint when SSVV was included. A reduction of 12% in the Bwall V18.12 constraint has been achieved without compromising the PTV coverage and the rest of OARs constraints. Constraint fulfillment predictors could be useful to evaluate the feasibility of prostate SBRT prior to the planning process for every single patient.
, Thomas LoSasso, Maria Chan, Laura Cervino, Dale Michael Lovelock
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Volume 10, pp 119-131; https://doi.org/10.4236/ijmpcero.2021.103011

Abstract:
Managing TG-51 reference dosimetry in a large hospital network can be a challenging task. The objectives of this study are to investigate the effectiveness of using Statistical Process Control (SPC) to manage TG-51 workflow in such a network. All the sites in the network performed the annual reference dosimetry in water according to TG-51. These data were used to cross-calibrate the same ion chambers in plastic phantoms for monthly QA output measurements. An energy-specific dimensionless beam quality cross-calibration factor, , was derived to monitor the process across multiple sites. The SPC analysis was then performed to obtain the mean, , standard deviation, σk, the Upper Control Limit (UCL) and Lower Control Limit (LCL) in each beam. This process was first applied to 15 years of historical data at the main campus to assess the effectiveness of the process. A two-year prospective study including all 30 linear accelerators spread over the main campus and seven satellites in the network followed. The ranges of the control limits (±3σ) were found to be in the range of 1.7% - 2.6% and 3.3% - 4.2% for the main campus and the satellite sites respectively. The wider range in the satellite sites was attributed to variations in the workflow. Standardization of workflow was also found to be effective in narrowing the control limits. The SPC is effective in identifying variations in the workflow and was shown to be an effective tool in managing large network reference dosimetry.
Yongsook C. Lee, YongBok Kim
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Volume 10, pp 16-37; https://doi.org/10.4236/ijmpcero.2021.101003

Abstract:
Purpose: The purpose of this study is to provide technical information on commissioning the TrueBeam STx 6 MV flattening-filter free (FFF) beam in the RayStation treatment planning system (TPS) for stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) treatments. Methods: For beam modeling, percent depth dose curves, profiles and output factors for jaw-collimated fields and stereotactic cones as well as X-jaws transmission were measured. For multi-leaf collimator (MLC) modeling, MLC model parameters such as offset, gain, curvature, leaf tip width, tongue and groove and transmission were determined and output factors for MLC-collimated fields were measured. Absolute dose calibration was also performed. For beam model and MLC model validation, the American Association of Physicists in Medicine Task Group-119 plans, clinical SRS and SBRT plans and end-to-end testing were performed. Results: Beam characteristics of the 6 MV FFF beam agreed well with those in the literature. Validation results showed that our beam model and MLC model were acceptable for SRS and SBRT treatments. Conclusions: The technical information and dosimetric data provided in this study will be a useful reference for other clinics/institutions which will commission the same machine energy in the RayStation TPS.
Yulin Song, Boris Mueller, Kenneth Dow, Ziad Saleh, Xiaoli Tang, Melissa Zinovoy, Daphna Gelblum, Borys Mychalczak
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Volume 10, pp 69-80; https://doi.org/10.4236/ijmpcero.2021.102007

Abstract:
The arms-up position is the most common treatment position adopted for lung cancer patients treated with radiation therapy. However, many elderly or frail patients have shoulder problems and cannot tolerate such an overstretched position for an extended period. Therefore, the arms-down position becomes the only alternative for this group of patients during radiation therapy. Even though the arms-down position is not ideal, it does provide a stable and comfortable patient immobilization position for radiation treatments that require a longer delivery time, such as stereotactic body radiation therapy (SBRT). In this study, we designed a protocol to treat lung cancer patients with VMAT stereotactic body radiation therapy (VMAT SBRT) and deep inspiration breath-hold (DIBH) in the arms-down position. Our initial clinical experience with this protocol indicates that it is reliable for patient immobilization and accurate in delivered dosimetry.
Imane Benali, Othmane Kaanouch, Asmaa Naim, Hanae El Gouach, Zineb Dahbi, Fadila Kouhen
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Volume 10, pp 111-117; https://doi.org/10.4236/ijmpcero.2021.102010

Abstract:
Background: Intensity Modulated Radiation Therapy (IMRT) is currently employed as a major arm of treatment in multiforme glioblastoma (GBM). The present study aimed to compare 3D-CRT with IMRT to assess tumor volume coverage and OAR sparing for the treatment of malignant gliomas. Materials and methods: We assessed 22 anonymized patients datasets with High Grade Glioblastoma who had undergone post-operative Intensity Modulated Radiotherapy (IMRT) and 3D Conformal Radiotherapy (3D-CRT), This study will compare and contrast treatment plans Rapidarc and 3D-CRT to determine which technology improves significantly dosimetric parameters. Results: Plans will be assessed by reviewing the coverage of the PTV using mean, maximum and minimum doses while the OAR doses will be compared using the maximal doses for each, as set out in the QUANTEC dose limits. Conclusion: The use of IMRT seems a superior technique as compared to 3D-CRT for the treatment of malignant gliomas having the potential to increase the dose to the PTV while sparing OARs optimally.
Sudeb Kumar Roy, Pretam Kumar Das, Rajada Khatun, Ashikur Rahman, Shirin Akter, Tushar Kumar, Mohammad Monjur Ahasan
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Volume 10, pp 38-46; https://doi.org/10.4236/ijmpcero.2021.101004

Abstract:
Dosimetric characteristic is one of the essential parameters of a medical linear accelerator (LINAC), which must be obtained before clinical use. The dosimetric characteristics for 6 MV photon beam were measured and compared with the corresponding published data. The study was done using a Varian linear accelerator (Model Clinac-iX) at the Institute of Nuclear Medical Physics (INMP), AERE, Savar, Dhaka, under the Bangladesh Atomic Energy Commission (BAEC). The data is taken for 10 field sizes (2 × 2, 3 × 3, 5 × 5, 7 × 7, 10 × 10, 15 × 15, 20 × 20, 25 × 25, 30 × 30 and 40 × 40 cm2) at same conditions. The measured Percent Depth Dose (PDD) curves were obtained for 6 MV photon beams with the field as mentioned above and compared with the calculated PDD curves. The measured depth dose (Dmax) for reference field size (FS) 10 × 10 cm2 is 15.99 mm, and the PDD at 10 cm depth (D10) is 66.87% for 6 MV photon energies that are found to be compatible with the published report BJR supplement 25. The measured PDD curves for photon energies show a good agreement with the standard PDD curves. The photon beam dosimetry data found in the current study are compatible and all the tolerances are within the clinically acceptable tolerance limit.
Bosco Giap, Thorsten Ostrander, Angie Waldinger, Fantine Giap, Huan Giap
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Volume 10, pp 1-11; https://doi.org/10.4236/ijmpcero.2021.101001

Abstract:
Patients with recurrent breast cancer to chest wall, who had previous irradiation, are difficult to manage and have limited options. Several reports described the use of photon therapy, hyperthermia, and brachytherapy. This is a case report of a 72-year-old female with Stage IIIA (pT3N1M0) invasive ductal carcinoma of the right breast status post modified radical mastectomy. The patient developed recurrence to the chest wall and one internal mammary lymph node one year later. She received 3-D conformal photon radiation therapy for this recurrence. Two years later, she had progression of the recurrence at the right chest wall and axillary and internal mammary lymph nodes. She was treated with intensity modulated proton therapy (IMPT) for a total of 6600 cGy in 33 fractions. However, four months later, she was found to have biopsy-proven isolated metastatic disease at her right bicep, which was again treated with IMPT for a dose of 6000 cGy in 20 fractions. Proton beam therapy was used in this case to spare dose to the brachial plexus, heart and lung while optimally irradiating the recurrent tumors. At last follow up, the patient is alive and has been disease free for 39 months. This report describes the technique and dosimetry for this unique case, which also reviewed recent series of re-irradiation using proton beam.
Yulin Song, Miao Zhang, Laszlo Voros, Xiaoli Tang, Ziad Saleh, Weixing Cai, Jeho Jeong, Boris Mueller, Borys Mychalczak
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, Volume 10, pp 59-68; https://doi.org/10.4236/ijmpcero.2021.102006

Abstract:
Each year, 170,000 cancer patients in the United States develop brain metastases. Many of them present with multiple small lesions. Historically, Linac-based stereotactic radiosurgery (SRS) was used to treat single solitary brain metastasis with a diameter of less than 3.0 cm, while whole brain radiation therapy (WBRT) was used to treat multiple brain metastases mainly as palliative therapy. Evidence-based practices reveal that WBRT results in poor treatment outcomes, with high local recurrence rates, decreased cognitive function, and even the onset of dementia. Recently, volumetric modulated arc therapy (VMAT) SRS has been tested as an alternative treatment to WBRT. Owing to its inherent complexity and high risk, it is imperative to perform rigorous testing prior to its clinical implementation. In this paper, we present a novel technique for dosimetry validation of VMAT SRS.
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