@article{WeickBreuerRichteretal.2020,
  author    = {Weick, Stefan and Breuer, Kathrin and Richter, Anne and Exner, Florian and Str{\"o}hle, Serge-Peer and Lutyj, Paul and Tamihardja, J{\"o}rg and Veldhoen, Simon and Flentje, Michael and Polat, B{\"u}lent},
  title     = {Non-rigid image registration of 4D-MRI data for improved delineation of moving tumors},
  series = {BMC Medical Imaging},
  volume    = {20},
  journal   = {BMC Medical Imaging},
  doi       = {10.1186/s12880-020-00439-6},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-229271},
  year      = {2020},
  abstract  = {Background To increase the image quality of end-expiratory and end-inspiratory phases of retrospective respiratory self-gated 4D MRI data sets using non-rigid image registration for improved target delineation of moving tumors. Methods End-expiratory and end-inspiratory phases of volunteer and patient 4D MRI data sets are used as targets for non-rigid image registration of all other phases using two different registration schemes: In the first, all phases are registered directly (dir-Reg) while next neighbors are successively registered until the target is reached in the second (nn-Reg). Resulting data sets are quantitatively compared using diaphragm and tumor sharpness and the coefficient of variation of regions of interest in the lung, liver, and heart. Qualitative assessment of the patient data regarding noise level, tumor delineation, and overall image quality was performed by blinded reading based on a 4 point Likert scale. Results The median coefficient of variation was lower for both registration schemes compared to the target. Median dir-Reg coefficient of variation of all ROIs was 5.6\% lower for expiration and 7.0\% lower for inspiration compared with nn-Reg. Statistical significant differences between the two schemes were found in all comparisons. Median sharpness in inspiration is lower compared to expiration sharpness in all cases. Registered data sets were rated better compared to the targets in all categories. Over all categories, mean expiration scores were 2.92 +/- 0.18 for the target, 3.19 +/- 0.22 for nn-Reg and 3.56 +/- 0.14 for dir-Reg and mean inspiration scores 2.25 +/- 0.12 for the target, 2.72 +/- 215 0.04 for nn-Reg and 3.78 +/- 0.04 for dir-Reg. Conclusions In this work, end-expiratory and inspiratory phases of a 4D MRI data sets are used as targets for non-rigid image registration of all other phases. It is qualitatively and quantitatively shown that image quality of the targets can be significantly enhanced leading to improved target delineation of moving tumors.},
  language  = {en}
}
@article{ZimmermannRichterWeicketal.2022,
  author    = {Zimmermann, Marcus and Richter, Anne and Weick, Stefan and Exner, Florian and Mantel, Frederick and Diefenhardt, Markus and Fokas, Emmanouil and Kosmala, Rebekka and Flentje, Michael and Polat, B{\"u}lent},
  title     = {Acute toxicities of patients with locally advanced rectal cancer treated with intensified chemoradiotherapy within the CAO/ARO/AIO-12 trial: comparing conventional versus VMAT planning at a single center},
  series = {Scientific Reports},
  volume    = {12},
  journal   = {Scientific Reports},
  doi       = {10.1038/s41598-022-25647-8},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-301255},
  year      = {2022},
  abstract  = {In locally advanced rectal cancer (LARC) neoadjuvant chemoradiotherapy is regarded as standard treatment. We assessed acute toxicities in patients receiving conventional 3D-conformal radiotherapy (3D-RT) and correlated them with dosimetric parameters after re-planning with volumetric modulated arc therapy (VMAT). Patients were randomized within the multicenter CAO/ARO/AIO-12 trial and received 50.4 Gy in 28 fractions and simultaneous chemotherapy with fluorouracil and oxaliplatin. Organs at risk (OAR) were contoured in a standardized approach. Acute toxicities and dose volume histogram parameters of 3D-RT plans were compared to retrospectively calculated VMAT plans. From 08/2015 to 01/2018, 35 patients with LARC were treated at one study center. Thirty-four patients were analyzed of whom 1 (3\%) was UICC stage II and 33 (97\%) patients were UICC stage III. Grade 3 acute toxicities occurred in 5 patients (15\%). Patients with acute grade 1 cystitis (n = 9) had significantly higher D\(_{mean}\) values for bladder (29.4 Gy vs. 25.2 Gy, p < 0.01) compared to patients without bladder toxicities. Acute diarrhea was associated with small bowel volume (grade 2: 870.1 ccm vs. grade 0-1: 647.3 ccm; p < 0.01) and with the irradiated volumes V5 to V50. Using VMAT planning, we could reduce mean doses and irradiated volumes for all OAR: D\(_{mean}\) bladder (21.9 Gy vs. 26.3 Gy, p < 0.01), small bowel volumes V5-V45 (p < 0.01), D\(_{mean}\) anal sphincter (34.6 Gy vs. 35.6 Gy, p < 0.01) and D\(_{mean}\) femoral heads (right 11.4 Gy vs. 25.9 Gy, left 12.5 Gy vs. 26.6 Gy, p < 0.01). Acute small bowel and bladder toxicities were dose and volume dependent. Dose and volume sparing for all OAR could be achieved through VMAT planning and might result in less acute toxicities.},
  language  = {en}
}