Evaluation of three presets for four-dimensional cone beam CT in lung radiotherapy verification by visual grading analysis.
OBJECTIVE
To evaluate three image acquisition presets for four-dimensional cone beam CT (CBCT) to identify an optimal preset for lung tumour image quality while minimizing dose and acquisition time.


METHODS
Nine patients undergoing radical conventionally fractionated radiotherapy for lung cancer had verification CBCTs acquired using three presets: Preset 1 on Day 1 (11 mGy dose, 240 s acquisition time), Preset 2 on Day 2 (9 mGy dose, 133 s acquisition time) and Preset 3 on Day 3 (9 mGy dose, 67 s acquisition time). The clarity of the tumour and other thoracic structures, and the acceptability of the match, were retrospectively graded by visual grading analysis (VGA). Logistic regression was used to identify the most appropriate preset and any factors that might influence the result.


RESULTS
Presets 1 and 2 met a clinical requirement of 75% of structures to be rated "Clear" or above and 75% of matches to be rated "Acceptable" or above. Clarity is significantly affected by preset, patient, observer and structure. Match acceptability is significantly affected by preset.


CONCLUSIONS
The application of VGA in this initial study enabled a provisional selection of an optimal preset (Preset 2) to be made.


CONCLUSIONS
This was the first application of VGA to the investigation of presets for CBCT.
1 Royal Marsden NHS Foundation Trust, London, UK.
Sally A
SA
Kember
1 Royal Marsden NHS Foundation Trust, London, UK.|2 The Institute of Cancer Research, London, UK.
Vibeke N
VN
Hansen
1 Royal Marsden NHS Foundation Trust, London, UK.|2 The Institute of Cancer Research, London, UK.
Martin F
MF
Fast
1 Royal Marsden NHS Foundation Trust, London, UK.|2 The Institute of Cancer Research, London, UK.
Simeon
S
Nill
1 Royal Marsden NHS Foundation Trust, London, UK.|2 The Institute of Cancer Research, London, UK.
Fiona
F
McDonald
1 Royal Marsden NHS Foundation Trust, London, UK.
Merina
M
Ahmed
1 Royal Marsden NHS Foundation Trust, London, UK.
Karen
K
Thomas
1 Royal Marsden NHS Foundation Trust, London, UK.|2 The Institute of Cancer Research, London, UK.
Helen A
HA
McNair
D054893:Cone-Beam Computed Tomography / Q000379:methods*; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D015203:Reproducibility of Results