Beschreibung:
<jats:p>The purpose was to study correlations amongst IMRT DVH evaluation points and how their relaxation impacts the overall plan. 100 head‐and‐neck cancer cases, using the Eclipse treatment planning system with the same protocol, are statistically analyzed for PTV, brainstem, and spinal cord. To measure variations amongst the plans, we use (i) interquartile range (IQR) of volume as a function of dose, (ii) interquartile range of dose as a function of volume, and (iii) dose falloff. To determine correlations for institutional and ICRU goals, conditional probabilities and medians are computed. We observe that most plans exceed the median PTV dose (average <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/acm20044-math-0001.png" xlink:title="urn:x-wiley:15269914:media:acm20044:acm20044-math-0001" /> prescribed dose). Furthermore, satisfying <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/acm20044-math-0002.png" xlink:title="urn:x-wiley:15269914:media:acm20044:acm20044-math-0002" /> reduced the probability of also satisfying <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/acm20044-math-0003.png" xlink:title="urn:x-wiley:15269914:media:acm20044:acm20044-math-0003" />, constituting a negative correlation of these goals. On the other hand, satisfying <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/acm20044-math-0004.png" xlink:title="urn:x-wiley:15269914:media:acm20044:acm20044-math-0004" /> increased the probability of satisfying <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/acm20044-math-0005.png" xlink:title="urn:x-wiley:15269914:media:acm20044:acm20044-math-0005" />, suggesting a positive correlation. A positive correlation is also observed between the PTV <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/acm20044-math-0006.png" xlink:title="urn:x-wiley:15269914:media:acm20044:acm20044-math-0006" /> and <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/acm20044-math-0007.png" xlink:title="urn:x-wiley:15269914:media:acm20044:acm20044-math-0007" />. Similarly, a positive correlation between the brainstem <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/acm20044-math-0008.png" xlink:title="urn:x-wiley:15269914:media:acm20044:acm20044-math-0008" /> and <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/acm20044-math-0009.png" xlink:title="urn:x-wiley:15269914:media:acm20044:acm20044-math-0009" /> is measured by an increase in the conditional median of <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/acm20044-math-0010.png" xlink:title="urn:x-wiley:15269914:media:acm20044:acm20044-math-0010" />, when <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/acm20044-math-0011.png" xlink:title="urn:x-wiley:15269914:media:acm20044:acm20044-math-0011" /> is violated. Despite the imposed institutional and international recommendations, significant variations amongst DVH points can occur. Even though DVH aims are evaluated independently, sizable correlations amongst them are possible, indicating that some goals cannot be satisfied concurrently, calling for unbiased plan criteria.</jats:p><jats:p>PACS number(s): 87.55.dk, 87.53.Bn, 87.55.Qr, 87.55.de.</jats:p>