skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Monitoring real-time aerosol distribution in the breathing zone

Abstract

A prototype air sampling, data recording, and data retrieval system was developed for monitoring aerosol concentrations in a worker's breathing zone. Three continuous-reading, light-scattering aerosol monitors and a tape recorder were incorporated into a specially designed and fabricated backpack for detailed field monitoring of both temporal and spatial variability in aerosol concentrations within the breathing zone. The backpack was worn by workers in a beryllium refinery. The aerosol which passed through each monitor was collected on a back-up filter for later chemical analysis for Be and Cu. The aerosol concentrations were recorded on magnetic tape as a function of time. The recorded signals were subsequently transcribed onto a strip chart recorder, then evaluated using a microcomputer with graphics capability. Field measurements made of the aerosol concentration at the forehead, nose, and lapel of operators during the melting and casting of beryllium-copper alloy demonstrated that there is considerable variability in concentration at different locations within the breathing zone. They also showed that operations resulting in worker exposure can be identified, and the precise time and duration of exposure can be determined.

Authors:
; ; ;
Publication Date:
Research Org.:
New York University Medical Center
OSTI Identifier:
5746167
Resource Type:
Journal Article
Resource Relation:
Journal Name: Am. Ind. Hyg. Assoc. J.; (United States); Journal Volume: 44:4
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; INDUSTRIAL PLANTS; AEROSOL MONITORING; PERSONNEL MONITORING; SAMPLERS; DESIGN; BERYLLIUM; CHEMICAL ANALYSIS; COPPER; DATA ANALYSIS; MEASURING METHODS; REFINING; SPATIAL DISTRIBUTION; TESTING; VARIATIONS; ALKALINE EARTH METALS; DISTRIBUTION; ELEMENTS; EQUIPMENT; METALS; MONITORING; PROCESSING; RADIATION MONITORING; TRANSITION ELEMENTS; 500200* - Environment, Atmospheric- Chemicals Monitoring & Transport- (-1989)

Citation Formats

Martinelli, C.A., Harley, N.H., Lippmann, M., and Cohen, B.S. Monitoring real-time aerosol distribution in the breathing zone. United States: N. p., 1983. Web. doi:10.1080/15298668391404806.
Martinelli, C.A., Harley, N.H., Lippmann, M., & Cohen, B.S. Monitoring real-time aerosol distribution in the breathing zone. United States. doi:10.1080/15298668391404806.
Martinelli, C.A., Harley, N.H., Lippmann, M., and Cohen, B.S. Sat . "Monitoring real-time aerosol distribution in the breathing zone". United States. doi:10.1080/15298668391404806.
@article{osti_5746167,
title = {Monitoring real-time aerosol distribution in the breathing zone},
author = {Martinelli, C.A. and Harley, N.H. and Lippmann, M. and Cohen, B.S.},
abstractNote = {A prototype air sampling, data recording, and data retrieval system was developed for monitoring aerosol concentrations in a worker's breathing zone. Three continuous-reading, light-scattering aerosol monitors and a tape recorder were incorporated into a specially designed and fabricated backpack for detailed field monitoring of both temporal and spatial variability in aerosol concentrations within the breathing zone. The backpack was worn by workers in a beryllium refinery. The aerosol which passed through each monitor was collected on a back-up filter for later chemical analysis for Be and Cu. The aerosol concentrations were recorded on magnetic tape as a function of time. The recorded signals were subsequently transcribed onto a strip chart recorder, then evaluated using a microcomputer with graphics capability. Field measurements made of the aerosol concentration at the forehead, nose, and lapel of operators during the melting and casting of beryllium-copper alloy demonstrated that there is considerable variability in concentration at different locations within the breathing zone. They also showed that operations resulting in worker exposure can be identified, and the precise time and duration of exposure can be determined.},
doi = {10.1080/15298668391404806},
journal = {Am. Ind. Hyg. Assoc. J.; (United States)},
number = ,
volume = 44:4,
place = {United States},
year = {Sat Jan 01 00:00:00 EST 1983},
month = {Sat Jan 01 00:00:00 EST 1983}
}
  • This paper identifies the data requirements for real-time monitoring and control of distribution systems. It points out that in addition to having supervisory control and data acquisition on switches and control equipment, methods are needed to obtain an accurate estimation of data needed for feeder automation functions. A meter placement method is proposed for this purpose. It is shown that the measurements from such a metering scheme can be used with a state estimator to provide the real-time data needed for real-time monitoring of distribution system.
  • Utilities currently use historical customer load data to forecast the loads in their distribution feeders for real-time feeder analysis and control. In this paper a three-phase state estimation method is developed to increase the accuracy of this load data. The method is based on the weighted least square approach and uses a three-phase node voltage formulation. The method can handle power, voltage, and current measurements. Test results indicate that state estimation can improve the forecasted load data by using real-time measurements. The effectiveness of branch current measurements were also tested.
  • Purpose: Dose-rate-regulated tracking (DRRT) is a tumor tracking strategy that programs the MLC to track the tumor under regular breathing and adapts to breathing irregularities during delivery using dose rate regulation. Constant-dose-rate tracking (CDRT) is a strategy that dynamically repositions the beam to account for intrafractional 3D target motion according to real-time information of target location obtained from an independent position monitoring system. The purpose of this study is to illustrate the differences in the effectiveness and delivery accuracy between these two tracking methods in the presence of breathing irregularities. Methods: Step-and-shoot IMRT plans optimized at a reference phase weremore » extended to remaining phases to generate 10-phased 4D-IMRT plans using segment aperture morphing (SAM) algorithm, where both tumor displacement and deformation were considered. A SAM-based 4D plan has been demonstrated to provide better plan quality than plans not considering target deformation. However, delivering such a plan requires preprogramming of the MLC aperture sequence. Deliveries of the 4D plans using DRRT and CDRT tracking approaches were simulated assuming the breathing period is either shorter or longer than the planning day, for 4 IMRT cases: two lung and two pancreatic cases with maximum GTV centroid motion greater than 1 cm were selected. In DRRT, dose rate was regulated to speed up or slow down delivery as needed such that each planned segment is delivered at the planned breathing phase. In CDRT, MLC is separately controlled to follow the tumor motion, but dose rate was kept constant. In addition to breathing period change, effect of breathing amplitude variation on target and critical tissue dose distribution is also evaluated. Results: Delivery of preprogrammed 4D plans by the CDRT method resulted in an average of 5% increase in target dose and noticeable increase in organs at risk (OAR) dose when patient breathing is either 10% faster or slower than the planning day. In contrast, DRRT method showed less than 1% reduction in target dose and no noticeable change in OAR dose under the same breathing period irregularities. When {+-}20% variation of target motion amplitude was present as breathing irregularity, the two delivery methods show compatible plan quality if the dose distribution of CDRT delivery is renormalized. Conclusions: Delivery of 4D-IMRT treatment plans, stemmed from 3D step-and-shoot IMRT and preprogrammed using SAM algorithm, is simulated for two dynamic MLC-based real-time tumor tracking strategies: with and without dose-rate regulation. Comparison of cumulative dose distribution indicates that the preprogrammed 4D plan is more accurately and efficiently conformed using the DRRT strategy, as it compensates the interplay between patient breathing irregularity and tracking delivery without compromising the segment-weight modulation.« less
  • Purpose: The aim is to minimize frame-wise difference errors caused by respiratory motion and eliminate the need for breath-holds in magnetic resonance imaging (MRI) sequences with long acquisitions and repeat times (TRs). The technique is being applied to perfusion MRI using arterial spin labeling (ASL). Methods: Respiratory motion prediction (RMP) using navigator echoes was implemented in ASL. A least-square method was used to extract the respiratory motion information from the 1D navigator. A generalized artificial neutral network (ANN) with three layers was developed to simultaneously predict 10 time points forward in time and correct for respiratory motion during MRI acquisition.more » During the training phase, the parameters of the ANN were optimized to minimize the aggregated prediction error based on acquired navigator data. During realtime prediction, the trained ANN was applied to the most recent estimated displacement trajectory to determine in real-time the amount of spatial Results: The respiratory motion information extracted from the least-square method can accurately represent the navigator profiles, with a normalized chi-square value of 0.037±0.015 across the training phase. During the 60-second training phase, the ANN successfully learned the respiratory motion pattern from the navigator training data. During real-time prediction, the ANN received displacement estimates and predicted the motion in the continuum of a 1.0 s prediction window. The ANN prediction was able to provide corrections for different respiratory states (i.e., inhalation/exhalation) during real-time scanning with a mean absolute error of < 1.8 mm. Conclusion: A new technique enabling free-breathing acquisition during MRI is being developed. A generalized ANN development has demonstrated its efficacy in predicting a continuum of motion profile for volumetric imaging based on navigator inputs. Future work will enhance the robustness of ANN and verify its effectiveness with human subjects. Research supported by National Institutes of Health National Cancer Institute Grant R01 CA159471-01.« less
  • Purpose: To demonstrate real-time dose calculation of free-breathing MRI guided Co−60 treatments, using a motion model and Monte-Carlo dose calculation to accurately account for the interplay between irregular breathing motion and an IMRT delivery. Methods: ViewRay Co-60 dose distributions were optimized on ITVs contoured from free-breathing CT images of lung cancer patients. Each treatment plan was separated into 0.25s segments, accounting for the MLC positions and beam angles at each time point. A voxel-specific motion model derived from multiple fast-helical free-breathing CTs and deformable registration was calculated for each patient. 3D images for every 0.25s of a simulated treatment weremore » generated in real time, here using a bellows signal as a surrogate to accurately account for breathing irregularities. Monte-Carlo dose calculation was performed every 0.25s of the treatment, with the number of histories in each calculation scaled to give an overall 1% statistical uncertainty. Each dose calculation was deformed back to the reference image using the motion model and accumulated. The static and real-time dose calculations were compared. Results: Image generation was performed in real time at 4 frames per second (GPU). Monte-Carlo dose calculation was performed at approximately 1frame per second (CPU), giving a total calculation time of approximately 30 minutes per treatment. Results show both cold- and hot-spots in and around the ITV, and increased dose to contralateral lung as the tumor moves in and out of the beam during treatment. Conclusion: An accurate motion model combined with a fast Monte-Carlo dose calculation allows almost real-time dose calculation of a free-breathing treatment. When combined with sagittal 2D-cine-mode MRI during treatment to update the motion model in real time, this will allow the true delivered dose of a treatment to be calculated, providing a useful tool for adaptive planning and assessing the effectiveness of gated treatments.« less