Table 1.

Dual-energy acquisition methods

Dual-source dual energy	Two tubes and two sets of detectors are placed perpendicular to each other in one gantry with each tube operating independently and simultaneously at two different energy levels. The two sets of detectors register attenuation information separately
Twin beam	Single tube emitting a beam that is pre-filtered widthwise into two halves—low-energy and high-energy components—before traversing the patient. The images are acquired simultaneously by one layer of detectors with half the detectors registering high-energy and the other half absorbing low-energy data
Fast kV switching	Single tube in the gantry emits high- and low-energy beams alternatively in a single gantry rotation. The properties of high-speed sampling detectors are high light output, fast speed and low afterglow
Dual detector	Single tube with two layers of detectors—superficial layer absorbs low-energy spectrum and the deeper layer absorbs high-energy spectrum
Rapid dual rotation	Single tube with two ultrafast sequential rotations, one emitting high-energy beam and subsequent rotation emitting low-energy beam
Photon-counting detector	Single source with novel detectors that can resolve photons at specific energy levels, thus providing information about a voxel at multiple energy levels

kV, kilovoltage.