title: Impact of different CT slice thickness on clinical target volume for 3D conformal radiation therapy.
abstract: The purpose of this study was to present the variation of clinical target volume (CTV) with different computed tomography (CT) slice thicknesses and the impact of CT slice thickness on 3-dimensional (3D) conformal radiotherapy treatment planning. Fifty patients with brain tumors were selected and CT scans with 2.5-, 5-, and 10-mm slice thicknesses were performed with non-ionic contrast enhancement. The patients were selected with tumor volume ranging from 2.54 cc to 222 cc. Three-dimensional treatment planning was performed for all three CT datasets. The target coverage and the isocenter shift between the treatment plans for different slice thickness were correlated with the tumor volume. An important observation from our study revealed that for volume <25 cc, most of the cases were underdosed by 18% with 5-mm slice thickness and 27% with 10-mm slickness. For volume >25 cc, the target underdosage was less than 6.7% for 5-mm slice thickness and 8% for 10-mm slice thickness. For 3D conformal radiotherapy treatment planning (3DCRT), a CT slice thickness of 2.5 mm is optimum for tumor volume <25 cc, and 5 mm is optimum for tumor volume >25 cc.
authors.affiliation: Department of Radiation Oncology, Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India. prabhakar_smr@hotmail.com
authors.forename: Ramachandran
authors.initials: R
authors.lastname: Prabhakar
authors.forename: Tharmar
authors.initials: T
authors.lastname: Ganesh
authors.forename: Goura K
authors.initials: GK
authors.lastname: Rath
authors.forename: Pramod K
authors.initials: PK
authors.lastname: Julka
authors.forename: Pappiah S
authors.initials: PS
authors.lastname: Sridhar
authors.forename: Rakesh C
authors.initials: RC
authors.lastname: Joshi
authors.forename: Sanjay
authors.initials: S
authors.lastname: Thulkar
mesh_terms: D001932:Brain Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D011879:Radiotherapy Dosage / Q000592:standards; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods*; D013679:Technology, Radiologic / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods; D047368:Tumor Burden