TY - JOUR
T1 - Using four-dimensional computed tomography images to optimize the internal target volume when using volume-modulated arc therapy to treat moving targets
AU - Yakoumakis, Nikolaos
AU - Winey, Brian
AU - Killoran, Joseph
AU - Mayo, Charles
AU - Niedermayr, Thomas
AU - Panayiotakis, George
AU - Lingos, Tania
AU - Court, Laurence
PY - 2012
Y1 - 2012
N2 - In this work we used 4D dose calculations, which include the effects of shape deformations, to investigate an alternative approach to creating the ITV. We hypothesized that instead of needing images from all the breathing phases in the 4D CT dataset to create the outer envelope used for treatment planning, it is possible to exclude images from the phases closest to the inhale phase. We used 4D CT images from 10 patients with lung cancer. For each patient, we drew a gross tumor volume on the exhale-phase image and propagated this to the images from other phases in the 4D CT dataset using commercial image registration software. We created four different ITVs using the N phases closest to the exhale phase (where N = 10, 8, 7, 6). For each ITV contour, we created a volume-modulated arc therapy plan on the exhale-phase CT and normalized it so that the prescribed dose covered at least 95% of the ITV. Each plan was applied to CT images from each CT phase (phases 1-10), and the calculated doses were then mapped to the exhale phase using deformable registration. The effect of the motion was quantified using the dose to 95% of the target on the exhale phase (D95) and tumor control probability. For the three-dimensional and 4D dose calculations of the plan where N = 10, differences in the D95 value varied from 3% to 14%, with an average difference of 7%. For 9 of the 10 patients, the reduction in D95 was less than 5% if eight phases were used to create the ITV. For three of the 10 patients, the reduction in the D95 was less than 5% if seven phases were used to create the ITV. We were unsuccessful in creating a general rule that could be used to create the ITV. Some reduction (8/10 phases) was possible for most, but not all, of the patients, and the ITV reduction was small.
AB - In this work we used 4D dose calculations, which include the effects of shape deformations, to investigate an alternative approach to creating the ITV. We hypothesized that instead of needing images from all the breathing phases in the 4D CT dataset to create the outer envelope used for treatment planning, it is possible to exclude images from the phases closest to the inhale phase. We used 4D CT images from 10 patients with lung cancer. For each patient, we drew a gross tumor volume on the exhale-phase image and propagated this to the images from other phases in the 4D CT dataset using commercial image registration software. We created four different ITVs using the N phases closest to the exhale phase (where N = 10, 8, 7, 6). For each ITV contour, we created a volume-modulated arc therapy plan on the exhale-phase CT and normalized it so that the prescribed dose covered at least 95% of the ITV. Each plan was applied to CT images from each CT phase (phases 1-10), and the calculated doses were then mapped to the exhale phase using deformable registration. The effect of the motion was quantified using the dose to 95% of the target on the exhale phase (D95) and tumor control probability. For the three-dimensional and 4D dose calculations of the plan where N = 10, differences in the D95 value varied from 3% to 14%, with an average difference of 7%. For 9 of the 10 patients, the reduction in D95 was less than 5% if eight phases were used to create the ITV. For three of the 10 patients, the reduction in the D95 was less than 5% if seven phases were used to create the ITV. We were unsuccessful in creating a general rule that could be used to create the ITV. Some reduction (8/10 phases) was possible for most, but not all, of the patients, and the ITV reduction was small.
KW - ITV
KW - Treatment margins
UR - http://www.scopus.com/inward/record.url?scp=84873535063&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84873535063&partnerID=8YFLogxK
U2 - 10.1120/jacmp.v13i6.3850
DO - 10.1120/jacmp.v13i6.3850
M3 - Article
C2 - 23149778
AN - SCOPUS:84873535063
SN - 1526-9914
VL - 13
SP - 181
EP - 188
JO - Journal of applied clinical medical physics
JF - Journal of applied clinical medical physics
IS - 6
ER -