Noise characterization of “effective quiet” areas on a U.S. Navy aircraft carrier

The purpose of this investigation was to characterize noise levels in spaces designated as “effective quiet” areas on a U.S. Navy aircraft carrier. Noise dosimetry samples were collected in 15 designated spaces, representing 15 noise measurements, while at-sea during airwing carrier qualifications. Equivalent sound level (L_eq) measurements were collected during flight operations (L_{eq (flt ops)}), non-flight operations (L_{eq (non-flt ops)}), and over 24-hr periods (L_{eq (24-hr)}). These data were compared to the 70 dBA American Conference of Governmental Industrial Hygienists (ACGIH^®) Threshold Limit Value (TLV^®) for “effective quiet” areas intended for temporary threshold shift recovery when personnel live and work in a potentially noise hazardous environment for periods greater than 24?hr. The monitored areas were selected based on personnel occupancy/use during off-duty time periods. Areas were classified by either (1) leisure areas that included mess (eating areas), gyms, lounges, an internet cafe, and the fantail social area or (2) berthing (sleeping) areas. The L_eq measurements in decibels “A” weighted (dBA) were compared to determine significant differences between L_{eq (flt ops)}, L_{eq (non-flt ops)}, and L_{eq (24-hr)} and were compared between leisure area and berthing area. Measured noise levels according to time period ranged as follows: (1) L_{eq (24-hr)}: 70.8–105.4 dBA; (2) L_{eq (flt ops)}: 70–101.2 dBA; and (3) L_{eq (non-flt ops)}: 39.4–104.6 dBA. All area measurements over the 24-hr period and during flight operations and 46.7% of the areas during the non-flight operation time period exceeded the “effective quiet” 70 dBA ACGIH TLV. Mean L_eqs were 15 dBA higher during flight operations compared to non-flight operations in “effective quiet” areas (p?=?0.001). The L_eqs in leisure areas were significantly higher than berthing areas by approximately 21 dBA during non-flight operation periods (p?=?0.001). Results suggest noise levels in “effective quiet” areas frequented by aircraft carrier personnel during off-duty hours when at-sea may inhibit auditory recovery from occupational noise exposures that occur on-duty.     

Integrating in vitro testing and physiologically-based pharmacokinetic (PBPK) modelling for chemical liver toxicity assessment—A case study of troglitazone

In vitro to in vivo extrapolation (IVIVE) for next-generation risk assessment (NGRA) of chemicals requires computational modeling and faces unique challenges. Using mitochondria-related toxicity data of troglitazone (TGZ), a prototype drug known for liver toxicity, from HepaRG, HepG2, HC-04, and primary human hepatocytes, we explored inherent uncertainties in IVIVE, including cell models, cellular response endpoints, and dose metrics. A human population physiologically-based pharmacokinetic (PBPK) model for TGZ was developed to predict in vivo doses from in vitro point-of-departure (POD) concentrations. Compared to the 200–800 mg/d dose range of TGZ where liver injury was observed clinically, the predicted POD doses for the mean and top one percentile of the PBPK population were 28–372 and 15–178 mg/d respectively based on C_max dosimetry, and 185–2552 and 83–1010 mg/d respectively based on AUC. In conclusion, although with many uncertainties, integrating in vitro assays and PBPK modeling is promising in informing liver toxicity-inducing TGZ doses.     

胶片剂量测量和验证方法的研究

目的设计和实现基于通用激光扫描仪的胶片剂量测量和验证系统。方法采用胶片饱和冲洗、非线性光学校正、多分辨率阈值滤波、离散傅里叶逆变换图像复原等方法,消除了普通扫描仪用于胶片剂量学定量处理中的各种伪影、噪声和畸变;采用过响应系数校正方法消除测量胶片对低能散射光子的过响应,改善了胶片剂量测量的准确性;采用γ结合NAT指标的方法对放疗计划进行二维定量验证,给出可视化图形表达和具有定量数据的验证结果。结果和三维水箱系统、VeriSoft胶片测量系统相比较,研制系统对放疗剂量的测量结果在±2%内符合一致,对IMRT放疗计划的定量验证结果在±3%内符合一致。结论该系统能够实现对放疗剂量的高精度测量和对适形调强放疗计划剂量的可靠验证。     

个体患者适形调强放疗计划模体内剂量实测验证技术的建立

目的建立个体患者适形调强放疗（IMRT）计划的模体内剂量实测验证技术。方法选择1例鼻咽癌患者，设计IMRT计划。将患者计划转移到模体上设计杂交计划。执行杂交计划时，用针点电离室测量感兴趣点的剂量，并与该点的计算剂量比较。用胶片剂量测量系统测量杂交计划中感兴趣平面的剂量，胶片与计划剂量矩阵登记后，依次进行计划，胶片分析、计划，胶片剖面分析和计划／胶片等剂量线分析。采用复合判断标准评价验证结果。结果针点电离室测量得到杂交计划单次照射的总剂量为121．5cGy，比计算值低约4％。计划，胶片分析得到高剂量、高梯度区域的距离差别均在4mm以内；计划／胶片剖面分析显示，计划与胶片在通过靶区的剖面具有较好的一致性；计划，胶片等剂量线分析显示，计划与胶片对应值的等剂量线重合良好。按照复合判断标准，该计划验证通过。结论初步建立了个体患者IMRT计划的模体内剂量实测验证技术，建立并优化了剂量登记技术、剂量归一方法和评价方法。     

Clinical considerations in the use of missing tissue compensators for head and neck cases

The irregular shape or contour of the patient’s surface in the treatment field can alter the dose distribution resulting in non-uniformity of dose in the treatment volume. Missing tissue compensators have been most commonly used to improve this non-uniformity, especially in head & neck, breast, lung and supraclavicular regions. Two or three dimensional compensators have been typically designed to make the dose uniform at a specific depth. This compensation shifts the dose distribution within the treatment volume so that some structures may be under or over compensated. This study will examine how various sites in head and neck cases are affected by compensators. We have also analyzed the uncertainty in compensated dose due to the daily variations in patient repositioning. Computer isodose plans using Cobalt-60 gamma rays and 6 and 18 MV x-rays were generated using coronal contours. Results show that the dose uniformity is improved for the treatment sites, especially for the thinner sites, like the larynx and the anterior cervical neck nodes. Finally, patient movement or positioning errors of ±1.0 cm will cause a change in dose distribution.     

脑转移瘤同期加量混合调强放疗与调强放疗的剂量学比较

目的:探讨同时运用三维适形与调强的混合调强放疗（Hybrid-IMRT）与调强放疗（IMRT）用于脑转移瘤同期加量的剂量学差异。方法:选取20例进行头颅放疗的患者，分别设计Hybrid-IMRT计划和IMRT计划。Hybrid-IMRT计划包括全脑行三维适形（两野对穿）3 600 cGy/20 F、脑转移灶行IMRT同期加量至5 000 cGy/20 F；IMRT计划全程运用IMRT给予全脑照射3 600 cGy/20 F、脑转移灶5 000 cGy/20 F。在满足临床要求的前提下，比较两组计划靶区的均匀性指数、适形度指数、平均剂量和机器跳数，危及器官脑干、视神经、晶体、视交叉、眼球的最大剂量和平均剂量。结果:两种计划均能满足临床要求。Hybrid-IMRT计划的PGTV均匀性优于IMRT计划（P<0.001）；Hybrid-IMRT计划的脑干、视交叉、左右晶体的最大剂量与平均剂量，左右眼球的平均剂量以及左右视神经的最大剂量均低于IMRT计划（P<0.05）；Hybrid-IMRT计划的机器跳数比IMRT计划减少了约70%（P<0.001）。结论:两种计划均能满足临床要求，Hybrid-IMRT计划相较IMRT计划靶区剂量更加均匀，治疗时间缩短，也能更好地保护危及器官。     

独立准直器位置精度对半野联合处剂量的影响

目的:介绍在乳腺癌和鼻咽癌放射治疗中的单一等中心半野联合放疗技术,并对独立准直器位置精度对半野联合处剂量的影响进行研究,提出对策.方法:用带独立准直器的直线加速器,以一个等中心,上下半野技术照射体模,用胶片剂量仪分析半野衔接处剂量分布情况,并将研究结果应用于乳腺癌和鼻咽癌病人的放射治疗.结果:受加速器独立准直器位置精度的影响,半野衔接处可能存在最大不超过2mm的过剂量区或欠剂量区.如果消除该系统误差的影响,则半野衔接处可得到均匀的剂量分布.结论:单一等中心半野联合照射,半野衔接处处于照射靶区,必须重视独立准直器位置精度对衔接处剂量的影响,并加以修正.     

Determination of ionisation chamber collection efficiency in a swept electron beam by means of thermoluminescent detectors and the "two-voltage" method

Two methods for determining the collection efficiency of a 0.6 cm3 thimble ionisation chamber exposed to the swept electron beam of a linear accelerator Therac 20 Saturne (CGR MeV) have been compared. In one method the chamber signal has been compared to that of simultaneously exposed thermoluminescent LiF dosemeters (TLD), in the other the "two-voltage" method of Boag, adapted for swept beams, has been used. By variation of the electron energy between 20 and 13 MeV, of the focus-skin-distance (FSD) between 200 and 100 cm and of the monitor rate between 400 monitor units (m.u.) and 100 m.u. per minute, different values could be produced for the peak charge density M. The collection efficiency of the chamber, operating at a standard voltage of 250 V, decreases from 0.99 to 0.84 for a charge density increasing from 0.3 X 10(-4) C/m3 to 7.5 X 10(-4) C/m3, respectively. The maximum deviation observed between the TLD and the "two-voltage" method adopted for similar M is never more than 2% and mostly smaller than 1%. It can be concluded that, under the present experimental conditions, the calculated ionisation chamber collection efficiency is confirmed by the experimental method using TL dosimetry.     

Radiopharmacokinetics and radiation dose from 99mTc-HM-PAO (Preliminary report)

Whole body retention measurements were performed in volunteers after i.v. injection of ^99mTc-HM-PAO (Ceretec^®). The organ accumulation was measured in mice and data were transferred to standard man according to ICRP. Absorbed dose calculations were made with these data by using the concept of absorbed fractions (MIRD method). In man, the whole body retention and the retention in the brain could be calculated by direct measurement, absorbed doses to the other organs could only be derived from animal data. The absorbed dose to the brain derived from human data (10.3 Gy/MBq) is greater by a factor of 2 than that derived from animal data. The highest absorbed dose was received by the thyroid (24.4 Gy/MBq), the absorbed dose to the ovaries, testes and whole body ranged from 2.8 to 4.2 Gy/MBq.Dedicated to Professor Dr. Guenter Liess on the occasion of his 65th anniversary