ESTRO 2024 - Abstract Book

S3846

Physics - Image acquisition and processing

ESTRO 2024

PET acquisition . The PET acquisition in list-mode was initiated 60 s prior to each irradiation and lasted 600 s. List-mode files comprised the crystal IDs necessary for the image reconstruction and the time event tag, which was used for evaluating the time image evolution. Data analysis . The data analysis consisted of the PET reconstruction [4] at different time stages: during the beam-off periods in-between the energy layers, during the irradiation (60-78 s, treatment stage), and after the irradiation (decay stage, 80-300 s). From these images, the range was determined using a sigmoid fit on the distal beam-direction profile giving the depth for which the intensity of the profile is 50% of the value reached on the CTV

Figure 1 . Experimental setup used for range measurements: 1. Proteus Plus, IBA gantry at 90°, 2. Upright CIRS-731 HN phantom, 3a and 3b. PET scanner panels.

Results:

The PET images are shown in figure 2 and the measured ranges are presented in table 1. It proves the feasibility of detecting range shifts at any PET acquisition stage with an uncertainty from 0.6 mm (for the decay stage) to 3 mm (for the 1st energy layer stage).

Plan 1

Stage\ Irradiation

Nominal

2 mm shift

5 mm shift

1st energy layer (146.5 MeV)

141.4±3.0

140.0±2.3

135.9±2.5

Treatment

128.8± 1.0

126.8±1.1

123.3±0.9

Decay

124.8±0.8

123.0±0.7

120.1±0.6

Plan 2