Letters to the Editor
COMMENTS ON ACOUSTIC EMISSION
VISUALIZATION OF BONE CEMENT FATIGUE LOCATIONS Currently, there are not many techniques to monitor the accumulation of damage in biomaterials in real time. In this perspective, the attempt of Qi et al. 1 to utilize acoustic emission as a tool for monitoring damage accumulation is valuable, and has future clinical and biological prospective. However, there are several major concerns with regard to their methodology and results that need to be discussed further.
The authors state their purpose as "to demonstrate the accuracy of the source location software," which was not satisfactorily performed. Accuracy is the agreement between the measured and the actual coordinates of the source wherein the value of the actual coordinate can be confirmed by post-hoc inspection of the fracture surface. 2 Qi et al. do not determine the actual coordinates of the source, but assume it to be at the tip of the notch. Therefore, the reported 2.5-mm difference between the coordinates measured by acoustic emission and the location of the tip of the notch is not the accuracy by definition. Alternatively, the accuracy of the measurement system can be determined by breaking pencil lead at known coordinates so as to compare with the measured coordinates. Al-