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For the parotids a median dose of 22 Gy was allowed and for the spinal cord a maximum dose of 35 Gy. The maximum DVO to the external contour of the patient was set to 59 Gy. The treatment plans were optimized with the direct machine parameter optimization (\"Direct Step &amp; Shoot\", DSS, Raysearch Laboratories, Sweden) newly implemented in Masterplan v1.5 and the fluence modulation technique (\"Intensity Modulation\", IM) which was available in previous versions of Masterplan already. The two techniques were compared with regard to compliance to the DVO, plan quality, and number of monitor units (MU) required per fraction dose.<\/jats:p>\n              <\/jats:sec><jats:sec>\n                <jats:title>Results<\/jats:title>\n                <jats:p>The plans optimized with the DSS technique met the DVO for the PTV significantly better than the plans optimized with IM (p = 0.007 for the min DVO and p &lt; 0.0005 for the max DVO). No significant difference could be observed for compliance to the DVO for the organs at risk (OAR) (p &gt; 0.05). Plan quality, target coverage and dose homogeneity inside the PTV were superior for the plans optimized with DSS for similar dose to the spinal cord and lower dose to the normal tissue. The mean dose to the parotids was lower for the plans optimized with IM. Treatment plan efficiency was higher for the DSS plans with (901 \u00b1 160) MU compared to (1151 \u00b1 157) MU for IM (p-value &lt; 0.05).<\/jats:p>\n                <jats:p>Renormalization of the IM plans to the mean of the dose to 95% of the PTV (D<jats:sub>95<\/jats:sub>) of the DSS plans, resulted in similar target coverage and dose to the parotids for both strategies, at the cost of a significantly higher dose to the normal tissue and maximum dose to the target. The relative volume of the PTV receiving 107% or more of the prescription dose V<jats:sub>107<\/jats:sub> increased to 35.5% \u00b1 20.0% for the IM plan as compared to a mean of 0.9% \u00b1 0.9% for the DSS plan.<\/jats:p>\n              <\/jats:sec><jats:sec>\n                <jats:title>Conclusion<\/jats:title>\n                <jats:p>The direct machine parameter optimization is a major improvement compared to the fluence modulation with subsequent leaf sequencing in Oncentra Masterplan v1.5. The resulting dose distribution complies better with the DVO and better plan quality is achieved for identical specification of DVO. An additional asset is the reduced number of MU as compared to IM.<\/jats:p>\n              <\/jats:sec>","DOI":"10.1186\/1748-717x-2-33","type":"journal-article","created":{"date-parts":[[2007,9,6]],"date-time":"2007-09-06T18:13:20Z","timestamp":1189102400000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":36,"title":["Comparison of direct machine parameter optimization versus fluence optimization with sequential sequencing in IMRT of hypopharyngeal carcinoma"],"prefix":"10.1186","volume":"2","author":[{"given":"Barbara","family":"Dobler","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fabian","family":"Pohl","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ludwig","family":"Bogner","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Oliver","family":"Koelbl","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2007,12,1]]},"reference":[{"key":"81_CR1","doi-asserted-by":"publisher","first-page":"61","DOI":"10.1016\/S0360-3016(03)00361-4","volume":"57","author":"A Lin","year":"2003","unstructured":"Lin A, Kim HM, Terrell JE, Dawson LA, Ship JA, Eisbruch A: Quality of life after parotid-sparing IMRT for head-and-neck cancer: a prospective longitudinal study. 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