TMR is a special case of which ratio?

Tissue Maximum Ratio (TMR) is indeed a special case of Tissue Phantom Ratio (TPR). TMR is used in radiotherapy dosimetry to compare the dose delivered to a specific point in tissue at a given depth to the dose at a reference depth, typically measured in a water phantom. Because TMR accounts specifically for the maximum dose response in tissue, it serves a similar purpose to TPR, but focuses on a point within the tissue that holds particular clinical significance.

Both TMR and TPR are important for understanding how radiation behaves in different tissues, particularly with respect to depth. TMR tends to be applied when considering higher energies where the dose distribution becomes more complex due to factors such as tissue density variations and scattering. This relationship helps clinicians ensure accurate dosing in treatments, as variations in tissue can significantly impact treatment effectiveness and safety.

In contrast, the other options involve different concepts: OAR (Organ At Risk) pertains to the sensitivity of surrounding organs to radiation, Dmax refers to the depth at which the maximum dose occurs, and scattering ratio relates to how much radiation is scattered versus absorbed in different materials. Hence, while these options are relevant in radiation therapy, they do not describe the specific relationship that TMR has with T