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Variations between in-water and in-air root-mean squared spatial width of an electron pencil beam for blocked electron cutouts compared to open standard fields
Increasingly electron treatment fields are varying widely from small ocular ports to large breast square or long neck's rectangular ports. Their dose distributions are commonly calculated by pencil beam algorithms computing broad dose distributions from summing several elemental electron Pencil...
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creator | Nagappan, S. Kalend, A.M. King, G.C. Mogus, R. |
description | Increasingly electron treatment fields are varying widely from small ocular ports to large breast square or long neck's rectangular ports. Their dose distributions are commonly calculated by pencil beam algorithms computing broad dose distributions from summing several elemental electron Pencils. Accurate electron pencil modeling (Pinnacle) requires determining the pencil's critical parameters including its spatial spread (/spl tau///spl rho/) typically one value for each electron beam energy. Spreads (/spl sigma//sub RMS-air/) are deduced from penumbral decrements (i.e., ICRU-35) of the broadest electron beam profiles in air, which algorithms scale to tissue through water-to-air ratios of electron mass-scattering powers (/spl tau///spl rho/). It is possible however, to assess pencil spreads (/spl sigma//sub RMS-water/) directly by ionization scans at depths in water for narrow blocked as well as broad electron fields at different source-to-skin distances (SSD). This paper presents extensive electron pencil spreads in rising field sizes and SSD between air and water, and assesses the media pencil spreads (/spl sigma/(RMS-air) /spl sigma//sub RMS-water/) ratios changing with typical treatment cutouts versus standard open fields. Gaussian pencil spreads (/spl sigma//sub RMS-air/) in air were found in direct constant proportionality (1/[2/spl pi/]/sup 1/2/) to penumbra widths for limited broad fields, but poorly correlated for narrow beams. Water widths and spreads showed limited constant scaling yet their ratios deviated significantly from proportionality for shrinking field ports. Hence for accurate clinical dose commission, an electron pencil that models small as well as large field treatments, may demand RMS values characterized both in air and water, and also scaled empirically with rising electron field diameters or treatment distances. |
doi_str_mv | 10.1109/IEMBS.2000.901360 |
format | conference_proceeding |
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Their dose distributions are commonly calculated by pencil beam algorithms computing broad dose distributions from summing several elemental electron Pencils. Accurate electron pencil modeling (Pinnacle) requires determining the pencil's critical parameters including its spatial spread (/spl tau///spl rho/) typically one value for each electron beam energy. Spreads (/spl sigma//sub RMS-air/) are deduced from penumbral decrements (i.e., ICRU-35) of the broadest electron beam profiles in air, which algorithms scale to tissue through water-to-air ratios of electron mass-scattering powers (/spl tau///spl rho/). It is possible however, to assess pencil spreads (/spl sigma//sub RMS-water/) directly by ionization scans at depths in water for narrow blocked as well as broad electron fields at different source-to-skin distances (SSD). This paper presents extensive electron pencil spreads in rising field sizes and SSD between air and water, and assesses the media pencil spreads (/spl sigma/(RMS-air) /spl sigma//sub RMS-water/) ratios changing with typical treatment cutouts versus standard open fields. Gaussian pencil spreads (/spl sigma//sub RMS-air/) in air were found in direct constant proportionality (1/[2/spl pi/]/sup 1/2/) to penumbra widths for limited broad fields, but poorly correlated for narrow beams. Water widths and spreads showed limited constant scaling yet their ratios deviated significantly from proportionality for shrinking field ports. Hence for accurate clinical dose commission, an electron pencil that models small as well as large field treatments, may demand RMS values characterized both in air and water, and also scaled empirically with rising electron field diameters or treatment distances.</description><identifier>ISSN: 1094-687X</identifier><identifier>ISBN: 9780780364653</identifier><identifier>ISBN: 0780364651</identifier><identifier>EISSN: 1558-4615</identifier><identifier>DOI: 10.1109/IEMBS.2000.901360</identifier><language>eng</language><publisher>IEEE</publisher><subject>Breast ; Cancer ; Computational modeling ; Convolution ; Distributed computing ; Electron beams ; Energy measurement ; Ionization ; Neck ; Water resources</subject><ispartof>Proceedings of the 22nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (Cat. 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No.00CH37143)</title><addtitle>IEMBS</addtitle><description>Increasingly electron treatment fields are varying widely from small ocular ports to large breast square or long neck's rectangular ports. Their dose distributions are commonly calculated by pencil beam algorithms computing broad dose distributions from summing several elemental electron Pencils. Accurate electron pencil modeling (Pinnacle) requires determining the pencil's critical parameters including its spatial spread (/spl tau///spl rho/) typically one value for each electron beam energy. Spreads (/spl sigma//sub RMS-air/) are deduced from penumbral decrements (i.e., ICRU-35) of the broadest electron beam profiles in air, which algorithms scale to tissue through water-to-air ratios of electron mass-scattering powers (/spl tau///spl rho/). It is possible however, to assess pencil spreads (/spl sigma//sub RMS-water/) directly by ionization scans at depths in water for narrow blocked as well as broad electron fields at different source-to-skin distances (SSD). This paper presents extensive electron pencil spreads in rising field sizes and SSD between air and water, and assesses the media pencil spreads (/spl sigma/(RMS-air) /spl sigma//sub RMS-water/) ratios changing with typical treatment cutouts versus standard open fields. Gaussian pencil spreads (/spl sigma//sub RMS-air/) in air were found in direct constant proportionality (1/[2/spl pi/]/sup 1/2/) to penumbra widths for limited broad fields, but poorly correlated for narrow beams. Water widths and spreads showed limited constant scaling yet their ratios deviated significantly from proportionality for shrinking field ports. Hence for accurate clinical dose commission, an electron pencil that models small as well as large field treatments, may demand RMS values characterized both in air and water, and also scaled empirically with rising electron field diameters or treatment distances.</description><subject>Breast</subject><subject>Cancer</subject><subject>Computational modeling</subject><subject>Convolution</subject><subject>Distributed computing</subject><subject>Electron beams</subject><subject>Energy measurement</subject><subject>Ionization</subject><subject>Neck</subject><subject>Water resources</subject><issn>1094-687X</issn><issn>1558-4615</issn><isbn>9780780364653</isbn><isbn>0780364651</isbn><fulltext>true</fulltext><rsrctype>conference_proceeding</rsrctype><creationdate>2000</creationdate><recordtype>conference_proceeding</recordtype><sourceid>6IE</sourceid><recordid>eNp9kM1KxTAQhYM_4EX7ALqaF2hNbNPbbpUrunCliLvL3HaK0TRTk5Ti0_iqxh9cCgPDcM53DowQp0oWSsn2_HZzd3lfXEgpi1aqspZ7YqW0bvKqVnpfZO26kWnKuqp1eZA02VZ53ayfjkQWwkviZKWTJlfi4xG9wWjYBdhRXIgcGJcvGMkDuv7rQOPBM8d8JHQQ3mb01EOYEoYWFtPHZ-AhuYEsddGzg4lcZ2xKxBEG9rCz3L0m6M_QzZHnGKDjcfqOiwycKAgxtaLvYTBk-3AiDge0gbLffSzOrjcPVze5IaLt5M2I_n3784XyX_ET05Ngew</recordid><startdate>2000</startdate><enddate>2000</enddate><creator>Nagappan, S.</creator><creator>Kalend, A.M.</creator><creator>King, G.C.</creator><creator>Mogus, R.</creator><general>IEEE</general><scope>6IE</scope><scope>6IH</scope><scope>CBEJK</scope><scope>RIE</scope><scope>RIO</scope></search><sort><creationdate>2000</creationdate><title>Variations between in-water and in-air root-mean squared spatial width of an electron pencil beam for blocked electron cutouts compared to open standard fields</title><author>Nagappan, S. ; Kalend, A.M. ; King, G.C. ; Mogus, R.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-ieee_primary_9013603</frbrgroupid><rsrctype>conference_proceedings</rsrctype><prefilter>conference_proceedings</prefilter><language>eng</language><creationdate>2000</creationdate><topic>Breast</topic><topic>Cancer</topic><topic>Computational modeling</topic><topic>Convolution</topic><topic>Distributed computing</topic><topic>Electron beams</topic><topic>Energy measurement</topic><topic>Ionization</topic><topic>Neck</topic><topic>Water resources</topic><toplevel>online_resources</toplevel><creatorcontrib>Nagappan, S.</creatorcontrib><creatorcontrib>Kalend, A.M.</creatorcontrib><creatorcontrib>King, G.C.</creatorcontrib><creatorcontrib>Mogus, R.</creatorcontrib><collection>IEEE Electronic Library (IEL) Conference Proceedings</collection><collection>IEEE Proceedings Order Plan (POP) 1998-present by volume</collection><collection>IEEE Xplore All Conference Proceedings</collection><collection>IEEE/IET Electronic Library</collection><collection>IEEE Proceedings Order Plans (POP) 1998-present</collection></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext_linktorsrc</fulltext></delivery><addata><au>Nagappan, S.</au><au>Kalend, A.M.</au><au>King, G.C.</au><au>Mogus, R.</au><format>book</format><genre>proceeding</genre><ristype>CONF</ristype><atitle>Variations between in-water and in-air root-mean squared spatial width of an electron pencil beam for blocked electron cutouts compared to open standard fields</atitle><btitle>Proceedings of the 22nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (Cat. No.00CH37143)</btitle><stitle>IEMBS</stitle><date>2000</date><risdate>2000</risdate><volume>4</volume><spage>2554</spage><epage>2556 vol.4</epage><pages>2554-2556 vol.4</pages><issn>1094-687X</issn><eissn>1558-4615</eissn><isbn>9780780364653</isbn><isbn>0780364651</isbn><abstract>Increasingly electron treatment fields are varying widely from small ocular ports to large breast square or long neck's rectangular ports. Their dose distributions are commonly calculated by pencil beam algorithms computing broad dose distributions from summing several elemental electron Pencils. Accurate electron pencil modeling (Pinnacle) requires determining the pencil's critical parameters including its spatial spread (/spl tau///spl rho/) typically one value for each electron beam energy. Spreads (/spl sigma//sub RMS-air/) are deduced from penumbral decrements (i.e., ICRU-35) of the broadest electron beam profiles in air, which algorithms scale to tissue through water-to-air ratios of electron mass-scattering powers (/spl tau///spl rho/). It is possible however, to assess pencil spreads (/spl sigma//sub RMS-water/) directly by ionization scans at depths in water for narrow blocked as well as broad electron fields at different source-to-skin distances (SSD). This paper presents extensive electron pencil spreads in rising field sizes and SSD between air and water, and assesses the media pencil spreads (/spl sigma/(RMS-air) /spl sigma//sub RMS-water/) ratios changing with typical treatment cutouts versus standard open fields. Gaussian pencil spreads (/spl sigma//sub RMS-air/) in air were found in direct constant proportionality (1/[2/spl pi/]/sup 1/2/) to penumbra widths for limited broad fields, but poorly correlated for narrow beams. Water widths and spreads showed limited constant scaling yet their ratios deviated significantly from proportionality for shrinking field ports. Hence for accurate clinical dose commission, an electron pencil that models small as well as large field treatments, may demand RMS values characterized both in air and water, and also scaled empirically with rising electron field diameters or treatment distances.</abstract><pub>IEEE</pub><doi>10.1109/IEMBS.2000.901360</doi></addata></record> |
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source | IEEE Electronic Library (IEL) Conference Proceedings |
subjects | Breast Cancer Computational modeling Convolution Distributed computing Electron beams Energy measurement Ionization Neck Water resources |
title | Variations between in-water and in-air root-mean squared spatial width of an electron pencil beam for blocked electron cutouts compared to open standard fields |
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