Keith A Langmack1, Louise A Newton1, Suzanne Jordan2, Ruth Smith2. 1. 1 Departments of Medical Physics, City Hospital Campus, Nottingham University Hospitals NHS Trust, Nottingham. 2. 2 Departments of Radiotherapy, City Hospital Campus, Nottingham University Hospitals NHS Trust, Nottingham.
Abstract
OBJECTIVE: To use a Likert scale method to optimize image quality (IQ) for cone beam CT (CBCT) soft-tissue matching for image-guided radiotherapy of the prostate. METHODS: 23 males with local/locally advanced prostate cancer had the CBCT IQ assessed using a 4-point Likert scale (4 = excellent, no artefacts; 3 = good, few artefacts; 2 = poor, just able to match; 1 = unsatisfactory, not able to match) at three levels of exposure. The lateral separations of the subjects were also measured. The Friedman test and Wilcoxon signed-rank tests were used to determine if the IQ was associated with the exposure level. We used the point-biserial correlation and a χ(2) test to investigate the relationship between the separation and IQ. RESULTS: The Friedman test showed that the IQ was related to exposure (p = 2 × 10(-7)) and the Wilcoxon signed-rank test demonstrated that the IQ decreased as exposure decreased (all p-values <0.005). We did not find a correlation between the IQ and the separation (correlation coefficient 0.045), but for separations <35 cm, it was possible to use the lowest exposure parameters studied. CONCLUSION: We can reduce exposure factors to 80% of those supplied with the system without hindering the matching process for all patients. For patients with lateral separations <35 cm, the exposure factors can be reduced further to 64% of the original values. ADVANCES IN KNOWLEDGE: Likert scales are a useful tool for measuring IQ in the optimization of CBCT IQ for soft-tissue matching in radiotherapy image guidance applications.
OBJECTIVE: To use a Likert scale method to optimize image quality (IQ) for cone beam CT (CBCT) soft-tissue matching for image-guided radiotherapy of the prostate. METHODS: 23 males with local/locally advanced prostate cancer had the CBCT IQ assessed using a 4-point Likert scale (4 = excellent, no artefacts; 3 = good, few artefacts; 2 = poor, just able to match; 1 = unsatisfactory, not able to match) at three levels of exposure. The lateral separations of the subjects were also measured. The Friedman test and Wilcoxon signed-rank tests were used to determine if the IQ was associated with the exposure level. We used the point-biserial correlation and a χ(2) test to investigate the relationship between the separation and IQ. RESULTS: The Friedman test showed that the IQ was related to exposure (p = 2 × 10(-7)) and the Wilcoxon signed-rank test demonstrated that the IQ decreased as exposure decreased (all p-values <0.005). We did not find a correlation between the IQ and the separation (correlation coefficient 0.045), but for separations <35 cm, it was possible to use the lowest exposure parameters studied. CONCLUSION: We can reduce exposure factors to 80% of those supplied with the system without hindering the matching process for all patients. For patients with lateral separations <35 cm, the exposure factors can be reduced further to 64% of the original values. ADVANCES IN KNOWLEDGE: Likert scales are a useful tool for measuring IQ in the optimization of CBCT IQ for soft-tissue matching in radiotherapy image guidance applications.
Authors: Cathérine Gebhard; Michael Fiechter; Tobias A Fuchs; Julia Stehli; Ennio Müller; Barbara E Stähli; Caroline E Gebhard; Jelena R Ghadri; Bernd Klaeser; Oliver Gaemperli; Philipp A Kaufmann Journal: Eur Heart J Cardiovasc Imaging Date: 2013-02-20 Impact factor: 6.875
Authors: B Loutfi-Krauss; J Köhn; N Blümer; K Freundl; T Koch; E Kara; C Scherf; C Rödel; U Ramm; J Licher Journal: Strahlenther Onkol Date: 2014-09-20 Impact factor: 3.621