"The line focus principle describes two focal spots; an actual focal spot, the area of the anode surface struck by the electron beam, and the effective focal spot, which is the area of the x-ray beam as it's directed towards the patient."
"Limitation of the principle "
"For a smaller target angle, the field of view covered by the x-ray beam will be smaller so it is not possible to cover large areas at smaller focus film distances (FFDs). Therefore, it can be appreciated that choice of target angle is a compromise between geometric unsharpness and desired field of view. For practical purpose, at 40" FFD the anode angle should be no smaller than 15 degrees. A decrease in angle below six degrees will result in anode heel effect."
Expected headings
"Basic concept"
"Limitation of the principle "
"The line focus principle describes two focal spots; an actual focal spot, the area of the anode surface struck by the electron beam, and the effective focal spot, which is the area of the x-ray beam as it's directed towards the patient."