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Effect of NaCl-Induced Salinity and Human Urine Fertilization on Substrate Chemical Properties

Open Journal of Soil Science 2014年第1期4卷 16-25页

作者： michael yongha boh Joachim Sauerborn Institute of Plant Production and Agroecology in the Tropics and Subtropics University of Hohenheim Stuttgart Germany

We evaluated the effect of NaCl-induced salinity and successive urine fertilization on changes in cultivation substrate chemical properties in a greenhouse study. The substrate was composed of an equal volume ratio mixture of bio-waste compost, quartz sand and silty loam soil. Salinity was imitated by adding NaCl solutions to a known substrate weight achieving three target salinity treatments of ECe 1.3 (S0—no NaCl), 4.6 (S1) and 7.6 (S2) dS·m-1. Cultivation substrate had been cropped with two cycles of maize (Zea mays L.) (crop cycles I and II) and fertilized with human urine at N amounts of 0 (U0—no urine), 180 (U1) and 360 (U2) mg·kg-1 substrate in the first cycle and half of the urine-N dosages in cycle II. Substrate samples collected at the end of each cycle were analyzed for pHKCl, ECe, exchangeable and water extractable cations (Na+, K+, Ca2+, Mg2+), cation exchange capacity, water extractable anions (Cl-, , , ) and exchangeable sodium percentage (ESP). Exchangeable Na+, K+ and Ca2+ were significantly (p < 0.05) affected by salinity x urine interaction. ECe significantly increased by 7.3, 5.3 and 7.6 dS·m-1 in the S0, S1 and S2 treatments following an increase in urine from U0 to U2. In the S0 treatment, ESP increased in the order U0 and Cl- were significantly affected by crop cycle, salinity and urine interactions (p < 0.05) whereas the effect of urine fertilizer on extractable and depended on crop cycle alone. There was a tendency towards increasing soil sodicity with mounting urine fertilization. The level of NaCl salinity and the amount of urine applied are important determinants of substrate chemical properties. Adoption of appropriate management techniques to avoid salinity/sodicity build up should be included in urine fertilization planning.

关键词： Soil Sodicity Electrical Conductivity Urine Nitrogen Nutrient Recycling

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Risk Management of Clinical Reference Dosimetry of a Large Hospital Network Using Statistical Process Control

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2021年第3期10卷 119-131页

作者： Seng-boh Lim Thomas LoSasso Maria Chan Laura Cervino Dale michael Lovelock Department of Medical Physics Memorial Sloan Kettering Cancer Center New York USA

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.

关键词： TG-51 Dosimetry Process Control Risk Management Large Hospital Network

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Dosimetric Effect of Cobalt-Chrome Stabilization Hardware in Paraspinal Radiation Treatments

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2022年第3期11卷 176-187页

作者： Grace Tang Thomas LoSasso Seng-boh Lim Yoshiya Yamada Mark Bilsky Dale michael Lovelock Department of Medical Physics Memorial Sloan Kettering Cancer Center New York USA Department of Radiation Oncology Memorial Sloan Kettering Cancer Center New York USA Department of Neurosurgery Memorial Sloan Kettering Cancer Center New York USA

High density materials are assigned with an apparent density of 3.2 g/cm3 in 12-bit CT images due to saturation. This is often ignored in planning for spine tumors with titanium (density 4.40 g/cm3) spinal hardware. However, new cobalt-chrome hardware has a density of 8.11 g/cm3, which would increase dosimetric uncertainty if the true density is not utilized in planning. This effect was evaluated in this study. Calculation accuracy was examined using MapCHECK2 with a single 20 × 10 cm2 field with a titanium and a cobalt-chrome rod in a solid water phantom for 6X, 6FFF and 15X, at 2 cm and 6 cm beneath the rods. Measurement was compared to the calculation with density override (DO) with the true density and to the calculation with no-density override (NDO). Additionally, the dosimetric effect in clinical treatment plans was investigated for six IMRT and VMAT paraspinal cases. Plan quality was compared with the original NDO calculation and the DO recalculation. Compared to measurements, the treatment planning system (TPS) overestimated the dose locally by up to 13.2% for cobalt-chrome and 4.8% for titanium with NDO calculations. DO calculations improved the differences to 8.4% and 4.0%, respectively. Scatter from the rod increased the lateral dose and diminished as depth increased but was not properly accounted for by the TPS even with the correct density assigned. For the clinical plans, PTV coverage was lowered by an average of ~1.0% (range: 0.5% - 2.0%) and ~0.3% (range: 0.2% - 0.7%) in DO recalculations for cobalt-chrome and titanium, respectively. In conclusion, neglecting the true density of cobalt-chrome hardware during planning may result in an unexpected decrease in target coverage.

关键词： Cobalt-Chrome Spinal Hardware Paraspinal Radiation Therapy

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Risk Management of Clinical Reference Dosimetry of a Large Hospital Network Using Statistical Process Control

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology（医学物理学、临床工程、放射肿瘤学） 2021年第3期

作者： Seng-boh Lim Thomas LoSasso Maria Chan Laura Cervino Dale michael Lovelock

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Dosimetric Effect of Cobalt-Chrome Stabilization Hardware in Paraspinal Radiation Treatments

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology（医学物理学、临床工程、放射肿瘤学） 2022年第3期

作者： grace tang thomas losasso seng-boh lim yoshiya yamada mark bilsky dale michael lovelock

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