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A new index: Triple Point Conformity Scale (CS3) and its implication in qualitative evaluation of radiotherapy plan

Published online by Cambridge University Press:  26 July 2018

Shahnawaz Ansari ,
Subrat K. Satpathy ,
Imteyaz Ahmad ,
Priyanka K. Singh ,
Santosh Lad ,
Nimish Thappa  and
B. K. Singh
Shahnawaz Ansari*
Affiliation:
Department of Medical Physics, Apollo Hospitals Bilaspur, Bilaspur, Chhattisgarh, India
Subrat K. Satpathy
Affiliation:
Department of Medical Physics, Apollo Hospitals Bilaspur, Bilaspur, Chhattisgarh, India
Imteyaz Ahmad
Affiliation:
Department of Medical Physics, Apollo Hospitals Bilaspur, Bilaspur, Chhattisgarh, India
Priyanka K. Singh
Affiliation:
Department of Medical Physics, Apollo Hospitals Bilaspur, Bilaspur, Chhattisgarh, India
Santosh Lad
Affiliation:
Department of Medical Physics, Apollo Hospitals Bilaspur, Bilaspur, Chhattisgarh, India
Nimish Thappa
Affiliation:
Department of Medical Physics, Apollo Hospitals Bilaspur, Bilaspur, Chhattisgarh, India
B. K. Singh
Affiliation:
Department of Medical Physics, Apollo Hospitals Bilaspur, Bilaspur, Chhattisgarh, India
*
Author for correspondence: Shahnawaz Ansari, Department of Medical Physics, Apollo Hospitals Bilaspur, Bilaspur, Chhattisgarh 495006, India. Tel: +91 775224833451. E-mail: [email protected]
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Abstract

Background

Across the history of radiotherapy, with gradual technological progress and various methods of irradiation, the purpose has always been to deliver homogeneously 100% of the prescribed dose to 100% of the target volume containing the identifiable tumour and/or tumour cells potentially present while limiting the dose to adjacent normal tissues.

Material and methods

The formula for triple point conformity scale is: CS3=(V95+V100+V105)/3VT. (a) Lower limit determination: CS3=(VT+0·93 VT+0·0)/3VT=0·643; (b) Upper limit determination: in order to find out an empirical relation in between V105 and VT, we studied over 593 cancer patients of various sites by taking planning target volume as target, and an empirical relation is derived out as: V105/VT=0·0007. Hence, CS3=(VT+VT+0·0007 VT)/3VT=0·6667~0·667.

Result

Upper and lower limits of CS3 have been calculated at 0·643 and 0·667, respectively. Maximum value of CS3 index is recorded 0·656 while minimum value is 0·478.

Discussion

The CS3 scale constitutes an attractive tool because it could facilitate decisions during analysis of various treatment plans proposed for conformal radiotherapy. Its major advantages are its simplicity and integration of multiple parameters.

Conclusion

The triple point conformity scale (CS3) provides better qualitative information about radiotherapy plans as compared to other conformity indices. This study advises the users to use the CS3 scale to evaluate a conformal radiotherapy plan which encompasses a wide range of relevant clinical volumes, and is able to extract qualitative dosimetric information.

Keywords

conformity indexevaluation toolisodose linepanning target volume
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 17 , Issue 3 , September 2018 , pp. 309 - 312
Copyright
© Cambridge University Press 2018 

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