BJR
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
British Journal of Radiology (1995) 68, 1230-1236
© 1995 British Institute of Radiology
doi: 10.1259/0007-1285-68-815-1230
This Article
Right arrow Full Text (PDF)
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Olsen, D R
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Olsen, D R

Calculation of the biological effect of fractionated radiotherapy: the importance of radiation-induced apoptosis

D R Olsen, MSc

Department of Medical Physics, The Norwegian Radium Hospital, Box 20, Montebello, N-0310 Oslo, Norway

The total effect (TE) has been calculated for two different fractionation formalisms: the consecutive and repetitive fractionation mechanism, using a modified linear quadratic (LQ) model which includes the effect of apoptosis. For a given total dose, an increase in TE is seen when increasing the dose per fraction as well as the apoptotic fraction (Fa). Also, the TE increases with increasing {alpha}/β ratio (of the modified LQ model). The ratio of TE for tumour tissue and TE for late reacting tissue is calculated assuming the absence of apoptosis in late reacting tissue and a common value of {alpha}/β (of the modified LQ model). The biological effect ratio (BR) is higher for a large Fa and low doses per fraction, than for large doses per fraction and a small Fa. Assuming a consecutive fractionation mechanism, the TE formalism is unable to predict a log cell kill of more than 3 for β values of 0.010–0.028. It is less dependent on dose per fraction and Fa than the repetitive fractionation mechanism. The biological effect ratio is only slightly higher than 1, and is less influenced by Fa, dose per fraction and {alpha}/β ratio. A repetitive fractionation mechanism is also consistent with the preliminary results of published fractionation experiments. The calculations indicate that designing fractionation regimes for optimization of biological effect is a process where the role of apoptotic cell inactivation must be maximized, and where the influence of mitotic cell inactivation may be of less importance.

Received for publication March 17, 1995. Revision received July 5, 1995. Accepted for publication July 21, 1995.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
BJR DMFR IMAGING  ALL BIR JOURNALS 
Copyright © 1995 by the British Institute of Radiology.