title: Image-guided radiotherapy: a new dimension in radiation oncology.
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.
  
  
  CONCLUSIONS
  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.
authors: Abteilung für Radio onkologie und Strahlentherapie, Universitätsklinikum Heidelberg, Germany. Florian.Sterzing@med.uni-heidelberg.de
authors: Florian
authors: F
authors: Sterzing
authors: Rita
authors: R
authors: Engenhart-Cabillic
authors: Michael
authors: M
authors: Flentje
authors: Jürgen
authors: J
authors: Debus
references: Phys Med Biol. 2005 Sep 21;50(18):4259-76
references: 16148392
references: Med Dosim. 2006 Summer;31(2):91-112
references: 16690451
references: Radiologe. 2004 May;44(5):484-90
references: 15107979
references: JOP. 2006 Jul 10;7(4):372-81
references: 16832134
references: Int J Radiat Oncol Biol Phys. 2009 Nov 1;75(3):933-40
references: 19596172
references: Int J Radiat Oncol Biol Phys. 2009 Feb 1;73(2):610-7
references: 19147025
references: Radiother Oncol. 2006 Apr;79(1):59-64
references: 16584794
references: Strahlenther Onkol. 2009 Jul;185(7):469-73
references: 19714309
references: Strahlenther Onkol. 2007 Dec;183 Spec No 2:35-7
references: 18167007
references: Strahlenther Onkol. 2006 Sep;182(9):531-6
references: 16944375
references: Br J Radiol. 2006 Sep;79 Spec No 1:S79-86
references: 16980687
references: Lancet Oncol. 2006 Oct;7(10):848-58
references: 17012047
references: Med Dosim. 2006 Summer;31(2):113-25
references: 16690452
references: Future Oncol. 2006 Aug;2(4):477-92
references: 16922615
references: Front Radiat Ther Oncol. 2007;40:132-142
references: 17641506
references: Int J Radiat Oncol Biol Phys. 2008 Mar 15;70(4):1247-55
references: 18313531
references: Expert Rev Anticancer Ther. 2007 Jan;7(1):89-103
references: 17187523
references: Int J Radiat Oncol Biol Phys. 2007 Mar 1;67(3):670-7
references: 17197123
references: Int J Radiat Oncol Biol Phys. 2008 Mar 15;70(4):1151-7
references: 17892920
references: Technol Cancer Res Treat. 2009 Oct;8(5):343-52
references: 19754210
references: Strahlenther Onkol. 2009 Apr;185(4):241-7
references: 19370427
references: Br J Radiol. 2006 Sep;79 Spec No 1:S87-98
references: 16980688
references: Med Phys. 1993 Nov-Dec;20(6):1709-19
references: 8309444
references: Int J Radiat Oncol Biol Phys. 2008 Aug 1;71(5):1563-71
references: 18538505
references: Semin Radiat Oncol. 1999 Jan;9(1):108-17
references: 10196402
references: Radiother Oncol. 2009 Dec;93(3):419-23
references: 19782418
references: Int J Radiat Oncol Biol Phys. 2007 Mar 15;67(4):1201-10
references: 17336221
references: Med Dosim. 2006 Spring;31(1):51-61
references: 16551529
references: Radiother Oncol. 2009 Jun;91(3):288-95
references: 18835650