The actual focal spot is
the area of the focal spot on the radiographic target (anode)
as viewed at right angles to the plane of the target.
What is focal spot in radiography?
Focal spot is
the area of the anode surface which receives the beam of electrons from the cathode
. It is the apparent source of x-rays.
What is the actual focal spot size?
The actual dimension of the focal spot shall be determined as the value related to the Line Spread Function,
measured at 15% of the peak value
. Figure 1. A scheme of the slit position in relation to the tube axis and the reference axis, evaluation of the effective focal spot length (Not drawn to scale).
What is focal film distance in radiology?
Focal-film distance (FFD) is
the the distance between the center of the anode of the x-ray tube (the focal spot) and the film (top of cassette)
. Also known as, Source-image distance (SID) which this measurement effects magnification, distortion, and x-ray beam intensity.
What is focus in radiology?
The line focus principle in radiography explains
the relationship between the actual focal spot on the anode surface and the effective focal spot size
.
What determines the focal spot?
Size and shape of the focal spot is determined by
the size and shape of the electron beam when it strikes the
anode
1
. Size and shape of the electron beam is determined by: dimensions of the filament tungsten coil. construction of the focusing cup.
What is the role of focal spot in image quality?
Purpose Focal spot size partially defines
spatial resolution of a
computed tomography (CT) system. Many CT tubes have two focal spot sizes, with the finer one allowing more detailed imaging at the cost of photon intensity and increased heat production.
How many types of focal spots are there?
Almost all medical x-ray tubes have
two focal spot sizes
.
What is the shape of focal spot?
The effective focal spot of the Varian X-ray tube was observed to be
rectangular
, significantly longer in the front-back direction (6 mm) than in the anode-cathode direction (3.5 mm) and quite non-uniform in emission intensity over its length, with pronounced hot-spots at each end.
What causes focal spot blur?
Due to the finite size of the focal spot,
when the object is further away from the detector, the edges in the image of the object get
blurred (Penumbra).
What does OFD mean in radiology?
OFD –
Object-to-Film Distance
– is the distance between the radiation side of the test object and the film surface, measured along the central axis of the radiation beam.
What does Sid mean in radiology?
The
source image receptor distance
(SID), is the distance of the tube from the image receptor, affecting magnification.
What does sod mean in radiology?
Three terms are used to describe positioning:
source-object distance
(SOD, where the object represents the patient); object-image distance (OID, where the image is the detector); and source-image distance (SID). The effects of moving the patient and detector can be seen by the method of similar triangles.
How bremsstrahlung radiation is produced?
Bremsstrahlung, (German: “braking radiation”), electromagnetic radiation produced by
a sudden slowing down or deflection of charged particles (especially electrons) passing through matter
in the vicinity of the strong electric fields of atomic nuclei.
What does line focus mean?
VERB noun preposition] 8. countable noun. The focus of a number of rays or lines is
the point at which they meet
.
What is TLD badge?
TLD Badge is
a radiation dose measuring device
. This enables us to know whether we are working within the safe dose limits prescribed by AERB.
