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  • Original Article 2018-03-31 2018-03-31 \ 0 \ 492 \ 379

    Impact of the Respiratory Motion and Longitudinal Profile on Helical Tomotherapy

    So Hyun Park, Jinhyun Choi, JinSung Kim, Sohyun Ahn, Min Joo Kim, Ho Lee, Seo Hee Choi, Kwangwoo Park

    https://doi.org/10.14316/pmp.2018.29.1.1

    Abstract

    The TomoTherapy® beam-delivery method creates helical beam-junctioning patterns in the dose distribution within the target. In addition, the dose discrepancy results in the particular region where the resonance by pattern of dose delivery occurs owing to the change in the position and shape of internal organs with a patient’s respiration during long treatment times. In this study, we evaluated the dose pattern of the longitudinal profile with the change in respiration. The superior-inferior motion signal of the programmable respiratory motion phantom was obtained using AbChes as a four-dimensional computed tomography (4DCT) original moving signal. We delineated virtual targets in the phantom and planned to deliver the prescription dose of 300 cGy using field widths of 1.0 cm, 2.5 cm, and 5.0 cm. An original moving signal was fitted to reflecting the beam delivery time of the TomoTherapy®. The EBT3 film was inserted into the phantom movement cassette, and static, without the movement and with the original movement, was measured with signal changes of 2.0 s, 4.0 s, and 5.0 s periods, and 2.0 mm and 4.0 mm amplitudes. It was found that a dose fluctuation within ±4.0% occurred in all longitudinal profiles. Compared with the original movement, the region of the gamma index above 1 partially appeared within the target and the border of the target when the period and amplitude were changed. Gamma passing rates were 95.00% or more. However, cases for a 5.0 s period and 4.0 mm amplitude at a field width of 2.5 cm and for 2.0 s and 5.0 s periods at a field width of 5.0 cm have gamma passing rates of 92.73%, 90.31%, 90.31%, and 93.60%. TomoTherapy® shows a small difference in dose distribution according to the changes of period and amplitude of respiration. Therefore, to treat a variable respiratory motion region, a margin reflecting the degree of change of respiration signal is required.

  • Original Article 2018-03-31 2018-03-31 \ 3 \ 1123 \ 481

    Acceptance Testing and Commissioning of  Robotic Intensity-Modulated Radiation Therapy M6 System Equipped with InCiseTM2 Multileaf Collimator

    Jeongmin Yoon, Kwangwoo Park, Jin Sung Kim, Yong Bae Kim, Ho Lee

    https://doi.org/10.14316/pmp.2018.29.1.8

    Abstract

    This work reports the acceptance testing and commissioning experience of the Robotic Intensity-Modulated Radiation Therapy (IMRT) M6 system with a newly released InCise2 Multileaf Collimator (MLC) installed at the Yonsei Cancer Center. Acceptance testing included a mechanical interdigitation test, leaf positional accuracy, leakage check, and End-to-End (E2E) tests. Beam data measurements included tissue-phantom ratios (TPRs), off-center ratios (OCRs), output factors collected at 11 field sizes (the smallest field size was 7.6 mm×7.7 mm and largest field size was 115.0 mm×100.1 mm at 800 mm source-to-axis distance), and open beam profiles. The beam model was verified by checking patient-specific quality assurance (QA) in four fiducial-inserted phantoms, using 10 intracranial and extracranial patient plans. All measurements for acceptance testing satisfied manufacturing specifications. Mean leaf position offsets using the Garden Fence test were found to be 0.01±0.06 mm and 0.07±0.05 mm for X1 and X2 leaf banks, respectively. Maximum and average leaf leakages were 0.20% and 0.18%, respectively. E2E tests for five tracking modes showed 0.26 mm (6D Skull), 0.3 mm (Fiducial), 0.26 mm (Xsight Spine), 0.62 mm (Xsight Lung), and 0.6 mm (Synchrony). TPRs, OCRs, output factors, and open beams measured under various conditions agreed with composite data provided from the manufacturer to within 2%. Patient-specific QA results were evaluated in two ways. Point dose measurements with an ion chamber were all within the 5% absolute-dose agreement, and relative-dose measurements using an array ion chamber detector all satisfied the 3%/3 mm gamma criterion for more than 90% of the measurement points. The Robotic IMRT M6 system equipped with the InCise2 MLC was proven to be accurate and reliable.

  • Original Article 2018-03-31 2018-03-31 \ 1 \ 1145 \ 378

    Use of Cylindrical Chambers as Substitutes for Parallel-Plate Chambers in Low-Energy Electron Dosimetry

    Minsoo Chun, Hyun Joon An, Seong-Hee Kang, Jin Dong Cho, Jong Min Park,ΙΙ, Jung-in Kim

    https://doi.org/10.14316/pmp.2018.29.1.16

    Abstract

    Current dosimetry protocols recommend the use of parallel-plate chambers in electron dosimetry because the electron fluence perturbation can be effectively minimized. However, substitutable methods to calibrate and measure the electron output and energy with the widely used cylindrical chamber should be developed in case a parallel-plate chamber is unavailable. In this study, we measured the correction factors and absolute dose-to-water of electrons with energies of 4, 6, 9, 12, 16, and 20 MeV using Farmer-type and Roos chambers by varying the dose rates according to the AAPM TG-51 protocol. The ion recombination factor and absolute dose were found to be varied across the chamber types, energy, and dose rate, and these phenomena were remarkable at a low energy (4 MeV), which was in good agreement with literature. While the ion recombination factor showed a difference across chamber types of less than 0.4%, the absolute dose differences between them were largest at 4 MeV at approximately 1.5%. We therefore found that the absolute dose with respect to the dose rate was strongly influenced by ion-collection efficiency. Although more rigorous validation with other types of chambers and protocols should be performed, the outcome of the study shows the feasibility of replacing the parallel-plate chamber with the cylindrical chamber in electron dosimetry.

  • Original Article 2018-03-31 2018-03-31 \ 1 \ 762 \ 323

    Database for Patient Information Management in Radiation Oncology Department

    Sangwook Lim, Kyubo Kim, Sohyun Ahn, Sang Hoon Lee, Rena Lee, Samju Cho

    https://doi.org/10.14316/pmp.2018.29.1.23

    Abstract

    The purpose of this study is to build a database of patient information for efficient radiotherapy management. Microsoft Office Access was used to build the database owing to its convenience and compatibility. The most important aspect when building the patient database is to make the input and management of patient information efficient at every step of radiotherapy process. The information input starts from the patient’s first visit to the radiation therapy department and ends upon completion of the radiotherapy. The forms for each step of radiotherapy process include the patient information form, the radiotherapy schedule form, the radiotherapy information form, the simulation order form, and the patient history form. Every form is centrically connected to the radiation oncology department’s patient information form. A test revealed that the database was found to be efficient in managing patient information at each step. An important benefit of this database is improved efficiency in radiotherapy management. Information on patients who received radiotherapy is stored in a database. This means that this clinical data can be found easily and used in future, which will be helpful in research studies on the radiation oncology department. Benefits such as these will potentially contribute to improved radiotherapy quality.

  • Original Article 2018-03-31 2018-03-31 \ 1 \ 853 \ 380

    Preliminary Phantom Experiments to Map Amino Acids and Neurotransmitters Using MRI

    Jang-Hoon Oh, Hyug-Gi Kim, Dong-Cheol Woo, Sun Jung Rhee, Soo Yeol Lee, Geon-Ho Jahng

    https://doi.org/10.14316/pmp.2018.29.1.29

    Abstract

    The objective of this study was to evaluate the chemical exchange saturation transfer (CEST) effect of amino acids and neurotransmitters, which exist in the human brain, depending on the concentration, pH, and amplitude of the saturation radiofrequency field. Phantoms were developed with asparagine (Asn), γ-aminobutyric acid (GABA), glutamate (Glu), glycine (Gly), and myoinositol (MI). Each chemical had three different concentrations of 10, 30, and 50 mM and three different pH values of 5.6, 6.2, and 7.4. Full Z-spectrum CEST images for each phantom were acquired with a continuous-wave radiofrequency (RF) saturation pulse with two different B1 amplitudes of 2 μT and 4 μT using an animal 9.4T MRI system. A voxel-based CEST asymmetry was mapped to evaluate exchangeable protons based on amide (–NH), amine (–NH2), and hydroxyl (–OH) groups for the five target molecules. For all target molecules, the CEST effect was increased with increasing concentration and B1 amplitude; however, the CEST effect with varying pH displayed a different trend depending on the characteristics of the molecule. On CEST asymmetric maps, Glu and MI were well visualized around 3.0 and 0.9 ppm, respectively, and were well separated macroscopically at a pH of 7.4. The exchange rates of Asn, Glu, BABA, and Gly usually decreased with increasing pH. The CEST effect was dependent on the concentration, acidity of the target molecules, and B1 amplitude of the saturation RF pulse. The CEST effect for Asn can be observed in a 9.4T MRI system. The results of this study are based on applying the CEST technique in patients with neurodegenerative diseases when proteins in the brain are increased with disease progression.

  • Technical Report 2018-03-31 2018-03-31 \ 1 \ 850 \ 411

    Survey of Radiation Shielding Design Goals and Workload Based on Radiation Safety Report: Tomotherapy Vault

    Kwang Hwan Cho, Jae Hong Jung, Chul Kee Min, Sun Hyun Bae, Seong Kwon Moon, Eun Seog Kim, Sam Ju Cho, Rena Lee

    https://doi.org/10.14316/pmp.2018.29.1.42

    Abstract

    The purpose of this study was to perform a survey of the radiation shielding design goals (P) and workload (W) based on the radiation safety reports concerned with structural shielding design for the IMRT treatment technique in Tomotherapy vaults. The values of the P and W factors as well as of a verified concrete thickness of the ceiling, bottom, sidewalls (sidewall-1 and sidewall-2), and door have been obtained from radiation safety reports for a total of 16 out of 20 vaults. The recommended and most widely used report for P values was the NCRP No. 151 report, which stated that the P factor in controlled and uncontrolled areas was 0.1 and 0.02 mSv/week, respectively. The range of the W factor was 600~14,720 Gy/week. The absorbed dose delivered per patient was 2~3 Gy. The maximum number of patients treated per day was 10~70. The quality assurance (QA) dose was 100~1,000 Gy/week. Fifteen values of the IMRT factor (F) were mostly used but a maximum of 20 values was also used. The concrete thickness for primary structures including the ceiling, bottom, sidewalls, and door was sufficient for radiation shielding. The P and W factors affect the calculation of the structural shielding design, and several parameters, such as the absorbed dose, patients, QA dose, days and F factor can be varied according to the type of shielding structure. To ensure the safety of the radiation shielding, it is necessary to use the NCRP No. 151 report for the standard recommendation values.

Korean Society of Medical Physics

Vol.35 No.2
2018-03-31

pISSN 2508-4445
eISSN 2508-4453
Formerly ISSN 1226-5829

Frequency: Quarterly

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