Term
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Definition
| Number of photons absorbed by the detector; dependent on the physical properties of the detector face (e.g., thickness, material). |
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Term
| ACR CT Accreditation Phantom |
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Definition
| A solid phantom that contains four modules and is constructed primarily from a water-equivalent material. Each nodule is 4cm deep and 20 cm in diameter, with external alignment markings to allow centering of the phantom in the x, y, and z axes, and is used to measure different aspects of image quality. |
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Term
| Acute Renal Failure (ARF) |
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Definition
| Rapid loss of renal function caused by damage to the kidney, resulting in retention of waste products that are normally excreted by the kidney. |
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Term
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Definition
| Detector rows that have variable widths and sizes. Also called nonuniform or hybrid arrays. |
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Term
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Definition
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Term
| Advanced Display Functions |
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Definition
| Display functions that include multiplanar reformation and 3D reformation. |
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Term
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Definition
| A brief, persistent flash of scintillation that must be taken into account and subtracted before image reconstruction. |
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Term
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Definition
| Air that enters the bloodstream and can occur during an IV injection. Small quantities of air can be absorbed by the body; thus small air emboli may never be detected if patients are asymptomatic. However, large air emboli can cause seizures, permanent neurologic damage, or occasionally death. These large air emboli only occur as a result of human error. |
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Term
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Definition
| A precise set of steps to be performed in a specific order to solve a problem. Algorithms are the basis for most computer programming. |
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Term
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Definition
| Artifacts that result from insufficient projection data; cause fine stripes that appear to be radiating from a dense structure. |
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Term
| Analog to Digital Converter (ADC) |
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Definition
| Converts the analog signal to a digital format. |
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Term
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Definition
| Life-threatening reactions; symptoms include substantial respiratory distress, unresponsiveness, convulsions, clinically manifested arrhythmias, and cardiopulmonary arrest. These reactions require prompt recognition and treatment. |
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Term
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Definition
| Landmark, such as the xiphoid or the iliac crest, used as a reference point when planning the scout image. |
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Term
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Definition
| Characterized by an individual standing erect, with the palms of the hands facing forward. This position is used internationally and guarantees uniformity in description of direction. |
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Term
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Definition
| Technique that is used to dilate an area of arterial blockage using a catheter with a small, inflatable, sausage shaped balloon at its tip. |
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Term
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Definition
| Xray tube design includes a cathode, which emits electrons, and an anode, which collects electrons. |
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Term
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Definition
| Term used to describe movement forward (toward the face); also referred to as ventral. |
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Term
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Definition
| Saving studies on auxiliary devices for the purposes of future viewing. |
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Term
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Definition
| Now outdated, an array processor is a CPU design frequently used for CT image reconstruction. Also called a vector processor, this design was able to run mathematical operations on multiple data elements simultaneously. General increases in performance and processor design have made this design obsolete. |
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Term
| Arteriovenous Iodine Difference |
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Definition
| Comparison of a Hounsfield unit (HU) measurement taken within the aorta to that of a measurement taken in the inferior vena cava. Used to assess the phase of tissue enhancement after the IV injection of contrast media. |
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Term
| Arteriovenous Malformations |
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Definition
| Composed of tangles of arteries and arterialized veins. In the brain there is tissue interposed between the vessels, but it is usually abnormal and often scarred from previous tiny hemorrhages; blood is shunted directly from the arterial system to the venous system. This shunting allows oxygenated blood to enter the veins. The flow is high and the pressure is elevated within the veins. The elevated pressure can cause the vessels to rupture, resulting in a hemorrhagic stroke. |
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Term
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Definition
| Objects seen on the image but not present in the object scanned. |
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Term
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Definition
| The buildup of fat and cholesterol plaque. |
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Term
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Definition
| A disorder of the heart rate and rhythm in which the atria are stimulated to contract in a very rapid or disorganized manner rather than in an organized one. |
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Term
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Definition
| Method for reducing artifacts in the PET image. In PET, loss of counts can occur because of anomalies in attenuation, scatter and random image noise, image artifacts, and image distortion. In a dedicated PET system, attenuation correction features are built into the process using a PET transmission scan. However, when PET/CT is used, data from the CT images can be used for attenuation correction of the PET emission data, elimination the need for a separate, time consuming transmission scan. |
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Term
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Definition
| The system accounts for the attenuation properties of each ray sum and correlates it to the position of the ray. |
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