Coulomb is the SI unit of electric charge. One coulomb is the amount of charge accumulated in one second by a current of one ampere.
The charge of a proton is 1.6 x 10^-19 coulombs. The charge of an electron is - 1.6 x 10^-19 coulombs. An atomic particle has a charge which is an integral multiple of 1.6 x 10^-19 coulombs.

(C, c, Ci) Curie is an obsolete unit of radioactivity; superseded by the SI unit becquerel.
1 curie is 3.70 x10¹⁰ disintegrations per second or 37,000 MBq. Formerly it was defined as the radiation emitted by 1 g of radium.
The curie is originated on Marie (1867-1934) and Pierre (1859-1906) Curie, (French chemists and physicists and Nobel laureates).

See Becquerel.

The industry standard of computed tomography (CT) contrast media power injectors changed over time from single-head to dual-head systems. The advantage of a power (or pressure) injector with two syringes is that a saline solution can be injected first to open the veins, followed by a second injection with contrast agent. Then the first head flushes the saline to maintain contrast flow. As a result, much less contrast agent is needed (about 30 percent less), helping to reduce costs. Dual-head contrast media injectors also provide greater patient safety by reducing the pressure of the flow rate, helping to prevent damage to the veins.
Contrast delivery is much more controlled and efficient when using a dual-head power injector (also called double-piston injector). Also, these medical devices are required to accommodate the quick imaging times typical for a multi-detector CT scanner.

See also Contrast Media Injector, Single-Head CT Power Injector, CT Power Injector, Multi-Head Contrast Media Injector, Syringeless CT Power Injector.

The dynamic range describes the range of x-ray intensities a detector can differentiate. A high dynamic range provides the discrimination between small differences in x-ray attenuation.
A current CT scanner has approximately a dynamic range of 1,000,000 to 1 and 1,100 views or projections a second.

(F) The number of cycles of a periodic process per unit time. Frequency and wavelength are inversely related. The higher the frequency the smaller the wavelength. The frequency of for example ultrasound is expressed in units of hertz (Hz), where 1 Hz = 1 cycle per second.
Usual frequencies in medical imaging are e.g., for ultrasound in the range of 1-20 MHz, for x-rays above 3x10¹⁶ Hz and for gamma rays less than 10²⁰ Hz.