Which of the following does not increase image contrast?

• A. Increasing the amount of irradiated tissue
• B. Increasing grid ratio
• C. Decreasing filtration
• D. Decreasing kVp

Answer: (A)

In radiography, image contrast is shaped by how differently tissues attenuate X-rays and how much scatter reaches the film or detector. Scatter lowers contrast because it adds a uniform fog over the image, reducing the visibility of differences between tissues.

• Irradiating more tissue increases scatter, which tends to blur and reduce contrast. So this choice does not improve contrast.

• Increasing grid ratio absorbs more scattered photons before they reach the detector, so the image is formed mainly from primary photons. That sharpens edges and increases contrast.

• Decreasing filtration leaves more low-energy photons in the beam. Those low-energy photons interact more strongly with tissues, enhancing differential attenuation and boosting subject contrast, though at the cost of higher patient dose.

• Decreasing kVp lowers the beam energy, which also increases the difference in attenuation between tissues, improving contrast (again with a trade-off in exposure and dose).

Thus, the factor that does not increase image contrast is the increase in irradiated tissue, since it raises scatter and reduces contrast.