Klinisk strålebiologi - normalvev

Tidlig reaksjon

teleangiectasi Sen reaksjon

Basis for dose-respons-kurver

Stigetallet for dose-responskurven

Gaussian distribution of radiation sensitivity Dose response curve Uniquely described by two parameters:  - gradient at 50% response level D 50% - dose to achieve 50% response Gaussian distribution of technical and dosimetrical factors  biolo >  clin Pettersen M et al Radiotherapy and Oncology 2008 Clinical dose response curve

Uniquely described by two parameters:  - gradient at 50% response level D 50% - dose to achieve 50% response  is linked to the standard deviation, , of the Gaussian distribution by: Pettersen M et al Radiotherapy and Oncology 2008  and  

Steepness of clinical dose-response curve is depending of the dose variation Pettersen M et al Radiotherapy and Oncology 2008 Roué et al 2004 ESTRO-Equal external audit 102 centres, 235 beams in France 3% beams had deviations >  5% 24 centres had deviations >  5%

Design of a randomised clinical study The null hypothesis is that the two treatment options produce no different outcome To prove a difference, the null hypothesis has to be rejected The number of patients needed is linked to , the difference in response (  R), the level of significance (  ) and the power (  )  = 0.2  = 0.05 Pettersen M et al Radiotherapy and Oncology 2008

The number of patients required Conclusions: To keep the number of patients required for RCT as low as possible, the standard deviation of the dosimetry should be kept below 5%.

Volumeffet for rektumblødning

Strandqvist plot

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