open access

Vol 21, No 1 (2016)
Original research articles
Published online: 2016-01-01
Submitted: 2014-09-21
Get Citation

Use of planar kV vs. CBCT in evaluation of setup errors in oesophagus carcinoma radiotherapy

Liliana Martins, Jose Guilherme Couto, Barbara Barbosa
DOI: 10.1016/j.rpor.2015.10.005
·
Rep Pract Oncol Radiother 2016;21(1):57-62.

open access

Vol 21, No 1 (2016)
Original research articles
Published online: 2016-01-01
Submitted: 2014-09-21

Abstract

Aim

The aim of this study is to evaluate differences in terms of the setup errors observed using kV planar image compared to CBCT for oesophageal cancer patients.

Background

Planar kV images are quick to acquire but only allow the observation of bony structures. CBCT allows the evaluation of soft tissues, which includes the oesophagus (and tumour) and OAR, giving a more accurate verification of the positioning.

Materials and Methods

All patients were imaged with both techniques between January 2012 and March 2014 were included in the study (16 patients, 212[[ce:hsp sp="0.25"/]]kV images and 116 CBCT images). Differences between the setup errors observed on the two images modalities were studied. A correlation study between TNM staging, tumour location and immobilization systems with setup errors was also done. Finally, the calculation of systematic and random errors allowed to determine the CTV–PTV margin.

Results

A significant discrepancy (p[[ce:hsp sp="0.25"/]]<[[ce:hsp sp="0.25"/]]0.05) between the setup errors observed with kV and CBCT was observed in the lateral direction. No statistical correlation was found between setup errors and tumour location, immobilization system or TNM staging. The CTV–PTV margin was smaller with CBCT in the vertical (0.6[[ce:hsp sp="0.25"/]]cm vs. 0.9[[ce:hsp sp="0.25"/]]cm) and longitudinal (0.7[[ce:hsp sp="0.25"/]]cm vs. 1[[ce:hsp sp="0.25"/]]cm) directions and smaller with kV for the lateral directions (0.8[[ce:hsp sp="0.25"/]]cm vs. 0.9[[ce:hsp sp="0.25"/]]cm).

Conclusions

The chosen modality influences the setup error observed which will influence the correction applied. Allowing a better observation of the volumes of interest, CBCT should be the modality of choice in this pathology. The CTV–PTV margins could be shrunk if CBCT is used.

Abstract

Aim

The aim of this study is to evaluate differences in terms of the setup errors observed using kV planar image compared to CBCT for oesophageal cancer patients.

Background

Planar kV images are quick to acquire but only allow the observation of bony structures. CBCT allows the evaluation of soft tissues, which includes the oesophagus (and tumour) and OAR, giving a more accurate verification of the positioning.

Materials and Methods

All patients were imaged with both techniques between January 2012 and March 2014 were included in the study (16 patients, 212[[ce:hsp sp="0.25"/]]kV images and 116 CBCT images). Differences between the setup errors observed on the two images modalities were studied. A correlation study between TNM staging, tumour location and immobilization systems with setup errors was also done. Finally, the calculation of systematic and random errors allowed to determine the CTV–PTV margin.

Results

A significant discrepancy (p[[ce:hsp sp="0.25"/]]<[[ce:hsp sp="0.25"/]]0.05) between the setup errors observed with kV and CBCT was observed in the lateral direction. No statistical correlation was found between setup errors and tumour location, immobilization system or TNM staging. The CTV–PTV margin was smaller with CBCT in the vertical (0.6[[ce:hsp sp="0.25"/]]cm vs. 0.9[[ce:hsp sp="0.25"/]]cm) and longitudinal (0.7[[ce:hsp sp="0.25"/]]cm vs. 1[[ce:hsp sp="0.25"/]]cm) directions and smaller with kV for the lateral directions (0.8[[ce:hsp sp="0.25"/]]cm vs. 0.9[[ce:hsp sp="0.25"/]]cm).

Conclusions

The chosen modality influences the setup error observed which will influence the correction applied. Allowing a better observation of the volumes of interest, CBCT should be the modality of choice in this pathology. The CTV–PTV margins could be shrunk if CBCT is used.

Get Citation

Keywords

Setup errors; kV; CBCT; Oesophagus carcinoma; CTV–PTV margin

About this article
Title

Use of planar kV vs. CBCT in evaluation of setup errors in oesophagus carcinoma radiotherapy

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 21, No 1 (2016)

Pages

57-62

Published online

2016-01-01

DOI

10.1016/j.rpor.2015.10.005

Bibliographic record

Rep Pract Oncol Radiother 2016;21(1):57-62.

Keywords

Setup errors
kV
CBCT
Oesophagus carcinoma
CTV–PTV margin

Authors

Liliana Martins
Jose Guilherme Couto
Barbara Barbosa

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