Module 1 - Learning Hub - Exposure Factors in Radiography — Q&A Flashcards

A set of Q&A flashcards covering how kVp, mAs, SID, and collimation affect dose, scatter, noise, contrast, detail, and penetrability in radiography.

What does increasing kVp do to beam penetrability?

Increases penetrability (harder beam).

When kVp increases, what typically happens to dose, scatter, noise, contrast, and detail?

Dose increases; Scatter increases; Noise decreases; Contrast shows no visible change within proper kVp range (may fall if far outside range or wrong algorithm); Detail shows no change (can drop if scatter becomes excessive).

Why does low kVp produce high contrast?

Lower-energy photons are attenuated more and differently by tissues, increasing attenuation differences.

Why does high kVp produce low contrast?

Attenuation differences between tissues compress at higher energies.

Does increasing kVp always visibly lower contrast?

Not necessarily—within the recommended range, processing algorithms keep contrast/brightness consistent; visible loss occurs if kVp is far outside the range or the wrong algorithm is used.

What single technical factor primarily controls beam quantity only?

mAs (mA × time).

Effects of increasing mAs on dose, scatter, noise, contrast, penetrability?

Dose increases; Scatter increases; Noise decreases; Contrast shows no appreciable change; Penetrability remains unchanged.

What happens to the x-ray spectrum when you increase mAs?

Same energy distribution, higher amplitude (more photons).

What happens to the spectrum when you increase kVp?

Curve shifts to higher energies and area increases (quality and quantity increase).

Why does more matter = more scatter?

Irradiating a larger volume increases probability of Compton interactions, adding non-informational exposure ('fog').

Define noise in radiography and its relationship to photon quantity.

Mottle from too few photons at the image receptor; noise is inversely related to photon quantity.

Increase SID (no compensation): what happens to dose, scatter, noise, contrast, detail?

Dose decreases; Scatter decreases; Noise increases; Contrast tends to increase (less scatter); Detail increases.

Which factor improves spatial resolution by lowering magnification—kVp, mAs, SID, or collimation?

SID (increasing SID lowers magnification and improves detail).

Does changing collimation alter beam energy or intrinsic output at the center?

No—it changes field size, not intrinsic quality or central beam output.

Tighter collimation (smaller field): what happens to dose, scatter, noise, contrast?

Dose decreases; Scatter decreases a lot; Noise may increase slightly; Contrast increases (less fog).

Which factor is the main lever for improving contrast at the receptor: kVp or collimation?

Collimation—reducing scatter is the strongest way to improve contrast.

If your EI is low and the image is noisy, what technical change directly fixes that?

Increase mAs (more photons → EI rises, noise drops).

With increased kVp, which interaction type’s proportion decreases more—photoelectric or Compton?

Photoelectric falls faster; Compton’s proportion decreases more slowly → relatively more Compton (more scatter) at higher kVp.

Which single factor determines penetrability: mAs, SID, collimation, or kVp?

kVp.

Tight collimation sometimes makes images look a bit noisier. Why?

Less scatter reaches the IR (less 'fog'), so quantum mottle can become more apparent.

You increased kVp within protocol and contrast looks unchanged. Is that expected?

Yes—processing algorithms standardize contrast/brightness unless kVp is far outside the recommended range.

As SID increases (no compensation), what happens to EI and perceived noise?

EI tends to drop (fewer photons), and noise increases.

What patient/material properties raise absorbed dose?

Higher density or atomic number (e.g., bone) → more absorption.

If you need more penetration through a thick part, which factor should you prioritize?

Raise kVp (penetrability), then manage scatter (e.g., collimation/grid).

Summarize the best single action to improve contrast without altering anatomy coverage.

Collimate in (smaller field) to reduce scatter/fog.