Volumetric and dosimetric effects of different slice thickness in radiotherapy planning Computed Tomography for head and Neck cancer
Introduction: Accurate estimation of target and Organ at Risk Volume is required to ensuretreatment efficacy and minimal normal tissue toxicity in radiotherapy planning. ComputedTomography slice thickness plays a vital role in volume estimation. It highly impacts smaller volumeorgans such as 1-3cm3.
Materials and Methods: CT datasets of 20 head and neck cancer patientswere recruited for this study in each CT data three CT series with a slice thickness of 1.5mm, 3mmand 5mm were imported to the TPS. Eclipse TPS of version 13.6 was used for delineation andtreatment planning.
Results: The variability of volumes with CT slice thickness was significant,especially for small volume structures. The maximum volume error of 63% was found in >3ccvolume structures with 5mm slice thickness. Whereas in larger volume structures the differenceswere observed 2%in terms of volume and mean dose. And in terms of homogeneity and conformity,there is no significant difference was found.
Conclusion: This study concludes that for head andneck cancer which has many smaller volume structures 1.5mm slice thickness will accuratelyestimate the volume which is clinically useful for OAR near the PTV.
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