In the Paris system, what characteristics do the 192Ir wires used in interstitial implants possess?

The Paris system is a widely used method in brachytherapy, particularly for interstitial implants utilizing 192Ir (Iridium-192) sources. In this system, the characteristics of the 192Ir wires are critical for achieving uniform dose distribution in the targeted treatment area.

The correct answer focuses on the concept of uniform linear exposure and equal length of the 192Ir wires. This uniformity is essential as it ensures that the radiation dose delivered to the tumor is consistent and predictable across the area being treated. The equal length of the wires allows for a standardized approach to their placement, making it easier to calculate the dose distribution based on their known geometry and positioning.

When wires have a uniform exposure, it helps in preserving the therapeutic ratio, maximizing tumor dose while minimizing exposure to surrounding healthy tissue. This precision is fundamental in improving patient outcomes and reducing side effects associated with radiation therapy.

In summary, uniform linear exposure and equal length are vital aspects of the 192Ir wires in the Paris system, as they facilitate calculated and consistent radiation delivery in interstitial brachytherapy.