BACKGROUND AND PURPOSE: For cervical cancer patients the CTV consists of multiple structures, exhibiting complex inter-fraction changes. The purpose of this study is to use weekly MR imaging to derive PTV margins that accommodate these changes. MATERIALS AND METHODS: Twenty patients with cervical cancer underwent a T2-weighted MRI exam before and weekly during IMRT. The CTV, GTV and surrounding organs were delineated. PTV margins were derived from the boundaries of the GTV and CTV in the six main directions and correlated with changes in the volumes of organs at risk. RESULTS: Around the GTV a margin of 12, 14, 12, 11, 4 and 8mm to the anterior, posterior, right lateral, left lateral, superior and inferior directions was needed. The CTV required margins of 24, 17, 12, 16, 11 and 8 mm. The shift of the GTV and CTV in the AP directions correlated weakly with the change in rectal volume. For the bladder the correlations were even weaker. CONCLUSIONS: We used weekly MRI scans to derive inhomogeneous PTV margins that accommodate changes in GTV and CTV. The weak correlations with rectum and bladder volume suggest that measures to control filling status of these organs may not be very effective.
BACKGROUND AND PURPOSE: For cervical cancerpatients the CTV consists of multiple structures, exhibiting complex inter-fraction changes. The purpose of this study is to use weekly MR imaging to derive PTV margins that accommodate these changes. MATERIALS AND METHODS: Twenty patients with cervical cancer underwent a T2-weighted MRI exam before and weekly during IMRT. The CTV, GTV and surrounding organs were delineated. PTV margins were derived from the boundaries of the GTV and CTV in the six main directions and correlated with changes in the volumes of organs at risk. RESULTS: Around the GTV a margin of 12, 14, 12, 11, 4 and 8mm to the anterior, posterior, right lateral, left lateral, superior and inferior directions was needed. The CTV required margins of 24, 17, 12, 16, 11 and 8 mm. The shift of the GTV and CTV in the AP directions correlated weakly with the change in rectal volume. For the bladder the correlations were even weaker. CONCLUSIONS: We used weekly MRI scans to derive inhomogeneous PTV margins that accommodate changes in GTV and CTV. The weak correlations with rectum and bladder volume suggest that measures to control filling status of these organs may not be very effective.
Authors: Karen Lim; Beth Erickson; Ina M Jürgenliemk-Schulz; David Gaffney; Carien L Creutzberg; Akila Viswanathan; Lorraine Portelance; Sushil Beriwal; Aaron Wolfson; Walter Bosch; Jennifer De Los Santos; Catheryn Yashar; Anuja Jhingran; Mahesh Varia; Issam El Naqa; Bronwyn King; Anthony Fyles Journal: Pract Radiat Oncol Date: 2015-07-02
Authors: Yvette Seppenwoolde; Katarina Majercakova; Martin Buschmann; Elke Dörr; Alina E Sturdza; Maximilian P Schmid; Richard Pötter; Dietmar Georg Journal: Strahlenther Onkol Date: 2021-04-30 Impact factor: 3.621