The effect of slice thickness on target and organs at risk volumes, dosimetric coverage and radiobiological impact in IMRT planning
Clin. transl. oncol. (Print)
; 18(5): 469-479, mayo 2016. ilus, graf
Article
in English
| IBECS
| ID: ibc-151180
Responsible library:
ES1.1
Localization: BNCS
ABSTRACT
Purpose:
Dose-volume histogram (DVH) has become an important tool for evaluation of radiation outcome as reflected from many clinical protocols. While dosimetric accuracy in treatment planning system (TPS) is well quantified, the variability in volume estimation is uncertain due to reconstruction algorithm that is investigated in this study. In addition, the impact of dose distribution and tumor control probability (TCP) were also investigated with CT slice thickness for IMRT planning. Materials andmethods:
A water phantom containing various objects with accurately known volume ranging from 1 to 100 cm3 was scanned with 1, 2, 3, 5, and 10 mm slice thickness. The CT data sets were sent to Eclipse TPS for contour delineation and volume estimation. The data were compared with known volume for the estimation of error in the volume of each structure. IMRT Plans were generated on phantom containing four objects with different slice thickness (15 mm) to calculate TCP. ICRU-83- recommended dose points such as D2%, D50%, D98%, as well as homogeneity and conformity index were also calculated.Results:
The variability of volumes with CT slice thickness was significant especially for small volume structures. A maximum error of 92 % was noticed for 1 cm3 volume of object with 10 mm slice thickness, whereas it was *19 % for 1 mm slice thickness. For 2 and 3 cm3 objects, the maximum error of 99 % was noticed with 10 mm slice thickness and *60 % with 5 mm. The differences are smaller for larger volumes with a cutoff at about 20 cm3. The calculated volume of the objects is a function of reconstruction algorithm and slice thickness. The PTV mean dose and TCP decreased with increasing slice thickness. Maximum variation of *5 % was noticed in mean dose and *2 % in TCP with change in slice thickness from 1 to 5 mm. The relative decrease in target volume receiving 95 % of the prescribed dose is *5 % with change in slice thickness from 1 to 5 mm. The homogeneity index increases up to 163 % and conformity index decreases by 4 % between 1 and 5 mm slice thickness, producing highly inhomogeneous and least conformal treatment plan.Conclusions:
Estimation of a volume is dependent on CT slice thickness and the contouring algorithm in a TPS. During commissioning of TPS and for all clinical protocols, evaluation of volume should be included to provide the limit of accuracy in DVH from TPS, especially for small objects. A smaller slice thickness provides superior dosimetry with improved TCP. Thus, the smallest possible slice thickness should be used for IMRT planning, especially when smaller structures are present (AU)RESUMEN
No disponible
Search on Google
Collection:
National databases
/
Spain
Database:
IBECS
Main subject:
Radiobiology
/
Dosimetry
/
Radiotherapy, Intensity-Modulated
Type of study:
Etiology study
/
Practice guideline
/
Risk factors
Limits:
Female
/
Humans
/
Male
Language:
English
Journal:
Clin. transl. oncol. (Print)
Year:
2016
Document type:
Article
Institution/Affiliation country:
Purdue University/USA