Table 2 Summary of four cone-beam CT imaging protocols with gantry speed adjusted for the pretreatment CBCT scans and corresponding image quality evaluation results
From: Image quality of 4D in-treatment CBCT acquired during lung SBRT using FFF beam: a phantom study
3D | 4D | |||
|---|---|---|---|---|
Pretreatment | In-treatment | Pretreatment | In-treatment | |
Image acquisition parameters | ||||
MV treatment beam | No | Yes | No | Yes |
Tube voltage (kV) | 120 | 120 | 120 | 120 |
Tube current (mA) | 40 | 40 | 20 | 20 |
Exposure time (ms) | 40 | 40 | 16 | 16 |
Collimator | M20 | M20 | S20 | S20 |
Rotation angle (°) | 360 | 360 | 200 | 200 |
Gantry speed (°/min) | 240 | – | 254 | – |
Acquisition interval (°) | – | 0.1 | – | 0.1 |
Estimated time (s)a | 90 | 99 | 47 | 55 |
Analysis results | ||||
#projections acquired | 502 | 512 | 276 | 266 |
Contrast (%) | 9.5 | 10.1 | 7.9 | 5.5 |
Contrast-to-noise ratio | 14.9 | 9.5 | 6.3 | 2.6 |
Overall uniformity (%) | 98.7 | 98.0 | 96.4 | 89.1 |
Minimum uniformity (%) | 99.1 | 98.4 | 98.0 | 95.7 |