ESTRO 2024 - Abstract Book

S4769

Physics - Quality assurance and auditing

ESTRO 2024

Under Institutional Review Board (IRB) exempt status, 425 patients were sequentially chosen from a larger study that was just published on the variation of dosimetry and prescription for SBRT (5). Fourier transform (FT) is used in most medical application but mainly in MRI for imaging. The unique aspect of FT is that a step function in frequency domain gives Sinc function ((sin(x)/x) that can be analyzed for its eigenvalue. An ideal DVH is like a step function and its FT should provide a Sinc value. The FT of DVH is used, the harmonic of Sinc function could be used as a quality matrix. It is found that there is a point of inflection where the Sinc function of DVH loses its harmonic as DVH gets slowly flat, as shown in Figure 1. At this value, it was analyzed with HI for these patients.

Results:

The FT of 425 patients DVH where harmonics of the Sinc function start disappearing as shown in figure 1 is analyzed. The HI was binned with respect to FT harmonics when it disappears. The magnitude of the peak to disappearance of the first harmonic and the magnitude are plotted in Figure 2.

Figure 1. DVH and associated Fourier Transform of 425 patients.

Figure 2. For three different HI values, the ratio of peak of the sinc function to the magnitude of the first harmonic (left) and the peak of the sinc function (right) are plotted.