@article{SterzingEngenhartCabillicFlentjeetal.2011,
  author    = {Sterzing, Florian and Engenhart-Cabillic, Rita and Flentje, Michael and Debus, J{\"u}rgen},
  title     = {Image-Guided Radiotherapy : A New Dimension in Radiation Oncology},
  series = {Deutsches {\"A}rzteblatt International},
  volume    = {108},
  journal   = {Deutsches {\"A}rzteblatt International},
  number    = {16},
  doi       = {10.3238/arztebl.2011.0274},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-140771},
  pages     = {274-280},
  year      = {2011},
  abstract  = {Background: The vital importance of imaging techniques in radiation oncology now extends beyond diagnostic evaluation and treatment planning. Recent technical advances have enabled the integration of various imaging modalities into the everyday practice of radiotherapy directly at the linear accelerator, improving the management of inter-and intrafractional variations. Methods: We present the topic of image-guided radiotherapy (IGRT) on the basis of a selective review of the literature. Results: IGRT can be performed with the aid of ultrasound, 2D X-ray devices, and computed tomography. It enables instant correction for positioning deviations and thereby improves the precision of daily radiotherapy fractions. It also enables immediate adjustment for changes in the position and filling status of the internal organs. Anatomical changes that take place over the course of radiotherapy, such as weight loss, tumor shrinkage, and the opening of atelectases, can be detected as they occur and accounted for in dosimetric calculations. There have not yet been any randomized controlled trials showing that IGRT causes fewer adverse effects or improves tumor control compared to conventional radiotherapy. Conclusion: IGRT is more precise and thus potentially safer than conventional radiotherapy. It also enables the application of special radiotherapeutic techniques with narrow safety margins in the vicinity of radiosensitive organs. Proper patient selection for IGRT must take account of the goals of treatment and the planning characteristics, as well as the available technical and human resources. IGRT should be used for steep dose gradients near organs at risk, for highly conformal dose distributions in the gastrointestinal tract where adjustment for filling variations is needed, for high-precision dose escalation to avoid geographic miss, and for patients who cannot lie perfectly still because of pain or claustrophobia.},
  language  = {en}
}
@article{BratengeierGaineyFlentje2011,
  author    = {Bratengeier, Klaus and Gainey, Mark B. and Flentje, Michael},
  title     = {Fast IMRT by increasing the beam number and reducing the number of segments},
  series = {Radiation Oncology},
  volume    = {6},
  journal   = {Radiation Oncology},
  number    = {170},
  doi       = {10.1186/1748-717X-6-170},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-137994},
  year      = {2011},
  abstract  = {Purpose The purpose of this work is to develop fast deliverable step and shoot IMRT technique. A reduction in the number of segments should theoretically be possible, whilst simultaneously maintaining plan quality, provided that the reduction is accompanied by an increased number of gantry angles. A benefit of this method is that the segment shaping could be performed during gantry motion, thereby reducing the delivery time. The aim was to find classes of such solutions whose plan quality can compete with conventional IMRT. Materials/Methods A planning study was performed. Step and shoot IMRT plans were created using direct machine parameter optimization (DMPO) as a reference. DMPO plans were compared to an IMRT variant having only one segment per angle ("2-Step Fast"). 2-Step Fast is based on a geometrical analysis of the topology of the planning target volume (PTV) and the organs at risk (OAR). A prostate/rectum case, spine metastasis/spinal cord, breast/lung and an artificial PTV/OAR combination of the ESTRO-Quasimodo phantom were used for the study. The composite objective value (COV), a quality score, and plan delivery time were compared. The delivery time for the DMPO reference plan and the 2-Step Fast IMRT technique was measured and calculated for two different linacs, a twelve year old Siemens Primus™ ("old" linac) and two Elekta Synergy™ "S" linacs ("new" linacs). Results 2-Step Fast had comparable or better quality than the reference DMPO plan. The number of segments was smaller than for the reference plan, the number of gantry angles was between 23 and 34. For the modern linac the delivery time was always smaller than that for the reference plan. The calculated (measured) values showed a mean delivery time reduction of 21\% (21\%) for the new linac, and of 7\% (3\%) for the old linac compared to the respective DMPO reference plans. For the old linac, the data handling time per beam was the limiting factor for the treatment time reduction. Conclusions 2-Step Fast plans are suited to reduce the delivery time, especially if the data handling time per beam is short. The plan quality can be retained or even increased for fewer segments provided more gantry angles are used.},
  language  = {en}
}