In the case of 192Ir HDR source, what is the essential input for the treatment planning system (TPS)?

The essential input for a treatment planning system (TPS) when using a 192Ir HDR source is the measured value of AKS, which stands for "air kerma strength." AKS is a critical parameter in dosimetry as it quantifies the intensity of radiation emitted from the radioactive source at a certain distance. This value is crucial for accurately calculating the dose delivered to the patient, as it directly impacts the treatment plan and ensures that the prescribed dose is achieved safely and effectively.

In HDR brachytherapy, the use of 192Ir sources necessitates precise measurements of AKS to inform the TPS of how much radiation the source emits, thus allowing the system to compute appropriate treatment times and distances for delivering the necessary radiation dose to the target area while minimizing exposure to surrounding healthy tissues. This ensures the effective targeting of tumors with optimized safety measures in place.

Other parameters, such as the calculated dose rate, time of exposure, and distance from the source, are important in the overall treatment planning process but rely on the accuracy of the AKS measurement to provide a comprehensive and effective treatment plan. Without the correct AKS value, the calculation of the dose distribution and treatment delivery would be flawed, putting patient safety and treatment efficacy at risk.