focal spot


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Related to focal spot: fovea

spot

 [spot]
a circumscribed area or place, usually distinguished by its color; see also macula and tache.
actual focal spot the section of a focal spot on which there is intersection of an electron beam with an anode of an x-ray tube.
Bitot's s's foamy gray triangular spots of keratinized epithelium on the conjunctivae, a sign of vitamin A deficiency.
blind spot
café au lait spot a light brown pigmented macule seen in neurofibromatosis and albright's syndrome.
cherry-red spot the choroid appearing as a red circular area surrounded by gray-white retina, as viewed throught the fovea centralis in tay-sachs disease. Called also Tay's spot.
cotton-wool spot white or gray soft-edged opacities in the retina composed of cytoid bodies; seen in hypertensive retinopathy, lupus erythematosus, and numerous other conditions.
effective focal spot the size of a projected focal spot in a specified direction measured with a quality assurance test tool such as the slit camera.
focal spot
1. the object of a patient's gaze during distraction techniques.
2. a small area of an x-ray target that receives the main electron stream.
Forschheimer s's a fleeting skin eruption consisting of discrete rose spots on the soft palate sometimes seen in rubella just prior to the onset of the skin rash.
Koplik's s's small, irregular, bright red spots on the buccal and lingual mucosa, with a minute bluish white speck in the center of each; they are pathognomonic of beginning measles.
liver spot
1. a lay term for senile lentigo.
2. (in pl.) tinea versicolor.
mental blind spot mental scotoma.
mongolian spot a type of congenital brown to gray-blue nevus; see also mongolian spot.
Roth's s's round or oval white spots consisting of coagulated fibrin seen in the retina in a number of diseases in which a vascular insult resulting in hemorrhage is followed by healing.
Tay's spot cherry-red spot.

fo·cal spot

the site of bombardment by electrons and emission of x-rays from the anode of an x-ray tube.
See also: focal spot size.

fo·cal spot

(fō'kăl spot)
The area made of tungsten on the anode of a diagnostic x-ray tube. The electrons interact with it to produce x-rays.

fo·cal spot

(fō'kăl spot)
The area made of tungsten on the anode of a diagnostic x-ray tube. The electrons interact with it to produce x-rays.
References in periodicals archive ?
The rotation of the X-ray source is replaced by instantly switching on and off different focal spots. No rotation mechanism/slip rings are required.
A sequential rotation technique has been applied to each 4 x 4 subarray to improve the axial-ratio performance at the focal spot. Indeed, CP radiation is commonly required for RFID antennas to achieve tag identification independently on the spatial orientation of the tag.
where [I.sub.s], [I.sub.m], and N are the excitation laser power of single- and multifocus excitations and the number of focal spots in the multifocus excitation, respectively.
The other is the FWHM of the focal spot. In our calculation, [delta] is set to below 0.05, and the FWHM was set smaller than 0.36[lambda].
Resolution was assessed using MTFs, calculated from images acquired at 40 kV using the small focal spot size.
Figure 10 shows the weld width as a function of travel speed at various power levels for PC with the 50-[micro]m focal spot lens.
The size of the focal spot can also be controlled by varying certain excitation parameters.
The greatest possibilities for regulation of temperature conditions for formation of ingots in a mold are ensured by electron beam cold hearth remelting (EBCHR) (Figure 1, d) due to size of the heating spot on surface of a metal being heated, so called focal spot [3], and non-inertance of heating by an electron beam.
Do you know the matrix size, number of lines on a grid, target material, focal spot size, software version you are using, who checks the uniformity and how often, who's on first and what's on second?
Optical interferometry also has extremely high sensitivity, with surface height accuracy down to subnanometer vertical resolution averaged over the size of the laser focal spot.
The critical concern for many medical device manufacturers is to increase x-ray intensity, improve x-ray source distribution profile, and reduce the dimensions of the focal spot. The challenge is that increasing the intensity or density of the beam causes the electrons (within the beam) to repel each other more strongly, which in turn increases focal spot dimensions.

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