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Low Dose Rate
(LDR) The low dose rate is used in brachytherapy to estimate the use of sealed sources placed in a patient on a permanent or temporary basis to achieve the therapeutic dose of radiation.
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Brachytherapy
(Radioactive Seed Implantation Therapy) Brachytherapy is a type of radiation therapy in which a sealed source (encapsulated radionuclide) is placed inside the patient as close as possible to the area being treated. The brachytherapy source delivers usually gamma or beta radiation at a distance up to a few centimeters either by surface, intracavitary or interstitial application.

See also Low Dose Rate, Cryotherapy, RF Thermal Ablation and Prostate Ultrasound.
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.

Contrast Agents
(CA) Contrast agents are used to change the imaging characteristics, resulting in additional information about anatomy, morphology or physiology of the human body. Radiocontrast agents (also called photon-based imaging agents) are used to improve the visibility of internal body structures in x-ray and CT procedures. Contrast agents are also used to increase the contrast between different tissues in MRI (magnetic resonance imaging) and ultrasound imaging. The ideal imaging agent provides enhanced contrast with little biological interaction.
First investigations with radiopaque materials are done shortly after the discovery of x-rays. These positive contrast agents attenuate x-rays more than body soft tissues due to their high atomic weight. Iodine and barium have been identified as suitable materials with high radiodensity and are used until today in x-ray and CT contrast agents. Iodine-based contrast agents are water-soluble and the solutions are used nearly anywhere in the body. Iodinated contrast materials are most administered intravenous, but can also be introduced intraarterial, intrathecal, oral, rectal, intravesical, or installed in body cavities. Barium sulfate is only used for opacification of the gastrointestinal tract. Negative contrast agents attenuate x-rays less than body soft tissues, for example gas.

Iodinated contrast media are differentiated in;

Intravascular iodinated contrast agents are required for a large number of x-ray and CT studies to enhance vessels and organs dependent on the blood supply. Injectable contrast agents are diluted in the bloodstream and rapidly distributed throughout the extracellular fluid. The main route of excretion is through the kidneys, related to the poor binding of the agent to serum albumin. The liver (gall bladder) and small intestine provide alternate routes of elimination particularly in patients with severe renal impairment. The use of special biliary contrast agents is suitable for gallbladder CT and cholecystograms because they are concentrated by the liver to be detectable in the hepatic bile.
The introduction of fast multi-detector row CT technology, has led to the development of optimized contrast injection techniques. The amount of contrast enhancement depends on the contrast agent characteristics, such as iodine concentration, osmolality, viscosity, and the injection protocol, such as iodine flux and iodine dose. Adverse reactions are rare and have decreased with the introduction of nonionic contrast agents.
See also Contrast Enhanced Computed Tomography, Abdomen CT, Contrast Media Injector, Single-Head CT Power Injector, Multi-Head Contrast Media Injector, Syringeless CT Power Injector, CT Power Injector.
Digital Radiography
(DR) Digital radiography uses a special electronic x-ray detector, which converts the radiographic image into a digital picture for review on a computer monitor. The digital image is then stored and can be post processed by changing the magnification, orientation, brightness, and contrast. Digital radiography (also called direct radiography) is a progressive development of computed radiography (CR).
These advantages can lead to fewer 'recalls' (repeated x-ray images) including a lower radiation dose than analog or conventional radiography. DR and CR systems use no chemicals to process the x-ray images and the hazardous materials and waste associated with film development are eliminated.

Advantages of digital radiography compared with conventional radiography:
saves time and costs due to more effective imaging process and workflow;
improved diagnostic quality images also in cases of x-ray under exposition or over exposition;
lower repeat rate;
films and developing chemicals are omitted;
reduction of hazardous chemical waste.
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