LINE FOCUS PRINCIPLE

#### Physics

LINE FOCUS PRINCIPLE

1. Foreshortening of the focal spot length at the central ray is called the line focus principle, as described by: $Effective.Focal.Length=Actual.Focal.Length*Sin\theta$

2. Example 1: The actual anode focal area for a 20-degree anode angle is 4 mm (length) by 1.2 mm (width). What is the projected focal spot size at the central axis position?

3. Answer: Effective length = actual length  sin  = 4 mm  sin 20 degrees = 4 mm  0.34 =
1.36 mm; therefore, the projected focal spot size is 1.36 mm (length) by 1.2 mm (width).

##### REFERENCES

1. Bushberg, J. T. (2012). The essential physics of medical imaging. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. Find it at Amazon
2. Heggie, J. C., Liddell, N. A., & Maher, K. P. (1997). Applied imaging technology. Melbourne: St. Vincents Hospital.

Ⓒ A. Manickam 2018