 Hello! Thank you for learning more about our new publication entitled The Lifetime of a LENAC Monitor Unit ION Chamber. To imagine yourself on a Friday evening, you're getting ready to head home for the day and you get a call learning that the ION Chamber is no longer working for one of your LENACs. In our clinic, we found that many of our ION chambers were needing to be replaced around the same time, so this motivated us to study the lifetime of the captain ION chambers currently being used in the variant true beams. This study is a retrospective review of our nine clinically used variant true beams. We report trends from the adjusted gain values, daily and monthly QA results, clinical monitor units delivered during patient treatments, and additional data collected during preventative maintenance inspections. We have seen in the literature that it's suggested that the output change would follow a trend where there would be an initial large change and then it would potentially begin leveling off or stabilizing over time. For our clinical data, we reviewed the trends over time extending beyond the first five million monitor units delivered. This graph shows the uncorrected monitor chamber response and how that changes as monitor units are delivered to each chamber. We also reviewed the changes in gain for each chamber longitude mulling as adjustments were made during routine quality assurance. Trends for the chambers for each treatment vault are shown in this figure with a linear fit shown for each chamber. The change in output can be considered by the cumulative output adjustments over the course of a year. This figure shows large changes in output over the first six months of a monitor chamber lifetime. While the changes in output are shown to be predictable over the lifetime of the chamber, our experience has shown required output adjustments ranging between 2% and 6% per year. To aid in the visualization of the required changes to output in shorter periods, each adjustment to the output was divided by time by days since the chamber was installed. For instance, if the output was adjusted by 3% after 182 days, the annualized output change would be calculated as shown in this figure. In summary, our clinical experience has shown the greatest change in output at the beginning, but there is a need for continued adjustments over time. We report the average lifetime of our ion chambers has been approximately 14 million clinically delivered MU. Please check out our paper to learn more and review our tips for what to do to streamline your replacement process. Thank you.