Radiography and Source-to-Image Distance (SID) Flashcard

Front

What is the inverse square law in radiography?

Back

The inverse square law states that the intensity of radiation exposure is inversely proportional to the square of the distance from the source. If the distance is halved, the exposure increases by a factor of four.

Front

How does changing the Source-to-Image Distance (SID) affect radiographic exposure?

Back

Changing the SID affects the intensity of the radiation reaching the image receptor. A greater distance results in lower exposure, while a shorter distance increases exposure.

Front

What happens to exposure if the distance is reduced to one-third of the original according to the inverse square law?

Back

The exposure is 9 times greater.

Front

What is a common rule of thumb for adjusting exposure when changing SID between 100 cm and 180 cm?

Back

Adjust technique to maintain image quality.

Front

Why is the inverse square law important in radiography?

Back

It describes how exposure changes with distance, which is crucial for accurate imaging.

Front

What is the new exposure if the SID is changed from 80 cm to 140 cm, given the initial exposure is 50 mGy?

Back

16.3 mGy.

Front

What is the primary purpose of using the square law in radiography?

Back

To compensate the mAs to maintain the original exposure level.

Front

Define Source-to-Image Distance (SID).

Back

SID is the distance from the radiation source (e.g., x-ray tube) to the image receptor (e.g., film or digital detector). It affects image quality and exposure.

Front

What is the relationship between SID and image sharpness?

Back

Increasing the SID generally improves image sharpness by reducing the penumbra effect.

Front

How does increasing kVp affect exposure?

Back

Increasing kVp increases the energy of the x-ray beam, resulting in greater penetration and higher exposure.