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Osmole
(Osm) A unit of osmotic pressure used in physical chemistry, cell biology, and medicine.
Definition: 1 osmole is the osmotic pressure of a one molar solution (that is, a solution with a concentration of one mole per liter of solvent) of a substance that does not dissociate.
If chemical solutions are separated by a semipermeable membrane (a membrane that resists the passage of dissolved substances but permits the passage of the solvent, usually water), then the solvent will diffuse across the membrane to equalize the concentrations. This process is called osmosis.
Solutions with higher concentrations of dissolved substances are said to have higher osmotic pressure than solutions having lower concentrations; thus the solvent moves from an area of low osmotic pressure to an area of higher osmotic pressure.
Osmotic pressure depends on the total number of dissolved particles, so for a substance that dissociates into two ions, such as ordinary salt (sodium chloride), a one molar solution has an osmotic pressure of 2 osmoles. In practice, most measurements are in milliosmoles (mOsm). Typical values range from 20 mOsm for fresh water through 290 mOsm for typical human blood plasma to 1010 mOsm for salt water from the open ocean.
See also Part Per Million.
CT Power Injector
A computed tomography (CT) power injector (also named pressure injector) is used to deliver contrast agents during CT imaging procedures with high-flow, high-volume, fixed-rate injection at relatively high pressures. The use of power injectors allows precise administration of contrast agent to obtain consistent high quality CT images. A dual-head CT power injector permits loading of contrast and saline onto the same injector. Contrast injection systems manage injector protocol data, improve patient safety, and workflow efficiency. When combined with pressure monitoring systems and hardware to prevent extravasation (accidental leakage of IV material into the surrounding tissue) these CT injectors can simultaneously mitigate risk.

See also Contrast Media Injector, Single-Head CT Power Injector, Multi-Head Contrast Media Injector, Syringeless CT Power Injector.
Contrast Media Injector
Contrast media injectors are part of the medical equipment used to deliver fluids in examinations such as CT, MRI, fluoroscopy and angiography. Many of these diagnostic imaging procedures include the administration of intravenous contrast agents to enhance the blood and perfusion in tissues.

Mainly there are two types of injector technology:
Piston-based systems use a plunger/piston to move a piston in the cylinder of a reservoir, which works in two directions to first fill the reservoir and then deliver the fluid from the reservoir to the patient, similar to a hand-held syringe.
Peristaltic-pump-based systems operate as rotary pumps that use rollers to compress sections of flexible tubing, drawing fluid directly from the supply source and delivering it to the patient.

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

The use of x-ray contrast agents in computed tomography (CT) began with a hand injection by the radiologist in the scan room. During its history, CT scanners have made great improvements in speed and image quality. Actual CT systems with multiple detectors allow scan times of a few seconds per body region. Some CT protocols require multiphase scans, where a body region is imaged with a single bolus of contrast in different blood flow phases. Automatic power (pressure) contrast media injectors are required to provide precise control of flow rate, volume and timing of injection. The use of a saline bolus following contrast administration reduces the volume of contrast required.

Most relevant topics for the use of a power injector in medical imaging procedures such as contrast enhanced computed tomography (CECT):
Avoidance of microbiologic contamination;
workflow efficiency in the use of the contrast media injector;
contrast cost and waste volume;
reimbursement.

Must have basic injector control options:
Flow rate with a usual range from 0.1 to 10 mL/sec in 0.1 mL/sec increments; some injectors can be set to inject in ml/min or ml/hour;
volume range from 1 mL to 200 mL for contrast and saline phases;
pressure limit typically programmable from 50 psi to 300 psi in 1 psi increments (also displayable in kPa and kg/cm²).

Examples of other injector control options:
Warmer/heater; an increase in temperature of the contrast medium results in a decrease in its viscosity; warmed contrast media are less viscous and offer lesser resistance;
pre-filled syringes; the compatibility with many selected syringes makes it easy to change and select the appropriate contrast medium for each patient;
injection reports accessible via RIS/PACS for dose management systems and records of prior injections.

Decibel
(dB) A customary logarithmic measure most commonly used (in various ways) for measuring sound. Decibel is a way to express the ratio of two sound intensities: dB=10log10I1/I2 being I1 the reference. If one sound is 1 bel (10 decibel) 'louder' than another, this means the louder sound is 10 times louder than the fainter one. A difference of 20 decibel corresponds to an increase of 10 x 10 or 100 times in intensity.
The intensity of ultrasound is measured in db/cm and decreases during the propagation.
For sound pressure (the pressure exerted by the sound waves) 0 decibel equals 20 micropascal (µPa), and for ultrasonic power 0 decibel sometimes equals 1 picowatt.
See also Phon, Pascal, Logarithms, Proportionality Constant, Watt, Diagnostic Imaging.
Dual-Head CT Power Injector
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.
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