Methods to Maximize CBCT Image Quality

Adult vs. Child

Child settings are significantly lower than adults. Children are 2-10 times more sensitive to radiation than adults. With smaller anatomy, less radiation is needed in children to achieve equivalent image quality.
mA (Tube Current)
Increasing mA will decrease image noise with a proportional increase in dose.

kVp (Tube Voltage)

Increasing kVp will decrease beam hardening artifact, but with disproportionate increase in dose. Increasing by 10 kV will more than double the dose.

Automatic exposure control (AEC)

Modulates mA after scout image acquisition, eliminating the need to manually adjust exposure settings based on scout data.

Field of View (FOV) Size

FOV size limitations via beam collimation improve image quality by reducing scatter radiation, also reducing patient dose.

Number of Basis Images

Basis image counts are determined by detector frame rates (projections acquired per second), trajectory arcs (180° vs. 360°), and rotation speed of the source and detector.
Higher frame rates and trajectory arcs and slower scan speeds increase spatial and contrast resolution and signal-to-noise ratio, resulting in decreased noise and metallic artifact but with a proportional increase in patient dose.

Resolution Mode

Image Matrix Size

Matrix size increases (within same-sized FOV) lead to higher spatial resolution & less volume averaging, but with more noise and less contrast-to-noise ratios.

Scout images

Minimize unnecessary image retakes by acquiring pre-scan a positioning shot to confirm the area of interest will be included within the FOV.

Detectors

Flat Panel Detector (FPD) vs. Image Intensifying Tube (IIT) – FPDs have better image quality with less distortion. IITs generate increased exposure due to the spherical shape & larger volume size.

Beam rate

Pulsed vs. Continuous – Pulsed beam reduces patient dose without affecting signal-to-noise ratio.

Film scintillator coating

Cesium iodide (CsI) vs. Gadolinium oxobromide – CsI scintillators convert x-rays to light with a higher image quality and dose efficiency because their columnar structure reduces the light spreading between the scintillators.

Reconstruction Methods

Iterative vs. Filter-back – Iterative generates a higher signal-to-noise ratio with lower dose.

Filtration

Optimized filtration decreases dose by removing low-energy x rays from the beam that would otherwise only contribute to image degradation.

Pixel Binning

1 x 1 pixel binning has higher resolution and lower noise, but larger image file size, slower transmission, and increased dose.

Quality assurance protocols ensure radiology processes function optimally to maximize diagnostic yield while minimizing patient radiation exposure.
Process requires routine use of a radiologic phantom where consistent image quality is determined through trend analysis of control charts constructed over time.
Parameters typically measured: Uniformity (Artifacts), Geometric Precision, Voxel Density Values, Noise, Low Contrast resolution, Contrast-to-Noise Ratios, and Spatial Resolution.
State Health Departments each have unique Radiation Control Regulations governing the periodicity of testing radiologic equipment.