Congress:
EuroSafe Imaging 2020
Keywords:
Not applicable, Quality assurance, Dosimetric comparison, Radiation therapy / Oncology, Physics, Dosimetry, Fluoroscopy, Experimental, Radiation physics, Oncology, Physics in Medical Imaging
Authors:
M. Komori, K. Senga, Y. Kitao, R. Horita, T. Toshito
DOI:
10.26044/esi2020/ESI-05838
Description of activity and work performed
Setup for luminescence imaging
The measurement was conducted in the spot-scanning treatment room at Nagoya Proton Therapy Center [3]. Figure 1 shows the experimental setup for luminescence imaging. The CCD camera was located 40 or 80 cm far from the water phantom to image the luminescence of water. Two types of lenses with a focal length of 8 and 12 mm were used for measurement at 40 and 80 cm distance, respectively. The images were measured during the irradiations of the uniform field at 12 cm range, 6 cm × 6 cm field width and 6 cm spread-out Bragg-peak (SOBP) width. We also measured the images during the irradiations of the pencil-like proton beam at 100 MeV. The size of the water phantom at 20 cm height × 20 cm width × 15 cm depth was enough larger than the field size. The acquisition time of the imaging was fixed to 3 min. Because the luminescence was very week, the experimental setup was shielded from environmental light by a black curtain. Furthermore, the blank image of 3 min. without proton-beam irradiation was also acquired for background subtraction.
Fig. 1: Experimental setup for luminescence imaging.
Results
Figure 2 shows the luminescence image measured from 80 cm distance from the water phantom during uniform-field irradiation. We can clearly find the field size from the image. Similarly, the luminescence image measured from the 40 cm distance clearly shows the field size. We derived depth profiles from the luminescence measured at each distance and compared them with the dose profile calculated by a treatment planning system as shown in figure 3. Distal fall off at 80 cm measurement was steeper than that of 40 cm measurement, because of the improvement of the distal fall off. For the pencil-beam irradiation, luminescence intensity in the Bragg-peak region at 80 cm measurement was 10% higher than that at 40 cm measurement.
Fig. 2: Luminescence image during uniform-field irradiation.
Fig. 3: Luminescence profiles compared with dose profile for uniform-field irradiation.