All of the following are examples of INTRINSIC contrast parameters in tissues EXCEPT:

Intrinsic contrast parameters refer to the inherent properties of tissues that influence the appearance of images during magnetic resonance imaging. These parameters reflect how tissues respond to the magnetic field and radiofrequency pulses used in MRI.

Proton density indicates the concentration of hydrogen protons in tissue, which directly affects the amount of signal generated during an MRI scan. Higher proton density typically results in a stronger signal and clearer images.

The apparent diffusion coefficient (ADC) is a measure of the diffusion of water molecules within tissue. Changes in the ADC value can provide valuable information about tissue composition, cellularity, and integrity, making it an intrinsic parameter influenced by the microscopic structure of the tissue.

T2 time, or T2 relaxation time, refers to the time it takes for protons in tissue to lose coherence after being excited by a radiofrequency pulse. It is another fundamental property of tissues that impacts the contrast and quality of MRI images, particularly in differentiating between different types of tissues or pathological conditions.

In contrast, the repetition time (TR) is an extrinsic parameter that relates to the timing of the radiofrequency pulses and governs the timing of the imaging sequence rather than being a property of the tissue itself. TR influences the overall image contrast by affecting the signal-to-noise ratio and