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Trade-off between the conflicting planning goals in correlation with patient’s anatomical parameters for intensity-modulated radiotherapy of prostate cancer patients

Published online by Cambridge University Press:  11 April 2019

Amin Banaei ,
Bijan Hashemi ,
Mohsen Bakhshandeh  and
Bahram Mofid
Amin Banaei
Affiliation:
Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
Bijan Hashemi*
Affiliation:
Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
Mohsen Bakhshandeh
Affiliation:
Department of Radiology Technology, Faculty of Allied Medical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Bahram Mofid
Affiliation:
Department of Radiation Oncology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
*
Author for correspondence: Bijan Hashemi, Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Al-Ahmad and Chamran Cross, Tehran 1411713116, Iran. Tel: +98-21-82883892. Fax: +98-21-88006544. E-mail: [email protected]
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Abstract

Aim

To quantify the relationship between the planning target volume (PTV) dose homogeneity and organs at risk (OARs) sparing in correlation with anatomical parameters in prostate intensity-modulated radiotherapy (IMRT).

Materials and methods

Nine IMRT plans with various target dose constraints’ priorities were created for 15 prostate cancer patients. Selected PTV and OARs parameters were calculated for the patients. A trade-off was assessed between homogeneity index (HI) and OAR sparing. Several anatomical parameters were evaluated to investigate their effects on the OAR sparing and HI.

Results

Inverse exponential relationships were found between the OAR sparing and HI (average R2 of 0·983 and 0·994 for bladder and rectum, respectively). Decreasing the priority led to more OARs sparing (normal tissue complication probability reduction: 97·6 and 74·5%; mean dose reduction: 16·3 and 11·3% for bladder and rectum, respectively) and worsening of the HI (0·095–0·322) but with no significant effect on tumour control probability. Furthermore, OARs volumes, distances between OARs and PTV and their joint volumes had stronger correlations with OARs’ mean doses.

Conclusion

Enforcement of target dose constraints was more effective on the improvement of HIs for the patients with initial high HI values at low dose constraints’ priorities. Reducing the priority had more effects on the OARs sparing compared to HI, especially for the patients with high OAR doses in high priority plans. This can be attributed to smaller distances or greater joint volumes between the OARs and PTV.

Keywords

IMRTOAR sparingprostate cancerPTV dose homogeneitytreatment planning
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 18 , Issue 3 , September 2019 , pp. 232 - 238
Copyright
© Cambridge University Press 2019 

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Footnotes

Cite this article: Banaei A, Hashemi B, Bakhshandeh M, Mofid B. (2019). Trade-off between the conflicting planning goals in correlation with patient’s anatomical parameters for intensity-modulated radiotherapy of prostate cancer patients. Journal of Radiotherapy in Practice18: 232–238. doi: 10.1017/S1460396919000025

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