Page 80 - ARNM-2-3

Advances in Radiotherapy
& Nuclear Medicine OrthoCT experimental proof of concept

lines of GSO scintillator crystals separated by 3-mm-thick between the lead slices was filled with pieces of extruded
slices of lead. Each GSO line consisted of 47 crystals polystyrene, each with a thickness of 4.6 mm. The distance
with a 4 mm × 4 mm cross-section and 30 mm length, between the centers of two consecutive GSO lines (i.e., the
individually wrapped with Teflon tape (Figure 4, top-left). detector pitch) was 7.6 mm. The scintillation light from
Each line of crystals was placed inside an aluminum box to the GSO lines was directed to the PMTs (specifically, the
maintain the crystals all together and aligned. In total, 188 model XP5602 from Photonis Imaging Sensors, France)
scintillator crystals were used. The aluminum box had a using custom-made acrylic light guides (Figure 4, bottom).
thickness of 1 mm at the radiation entrance region. The total
length of each scintillator line was approximately 200 mm. The prototype was mounted on a 10-mm-thick
The lead slices had dimensions of 200 mm × 200 mm. The aluminum base. In addition, it was enclosed by
collimator slices, along with the GSO lines, were enclosed 10-mm-thick polyvinyl chloride walls, with its top covered
inside a second aluminum box to ensure stability in the (Figure 3), to prevent it from being exposed to external
geometry (Figure 4, top-right). The thickness of this light. The total dimensions of the system are 1200 mm in
aluminum box at the radiation entrance region was 2 mm. length and 800 mm in width. It has a height of 320 mm and
To maintain the structure of the collimator, the space weighs approximately 75 kg.

Figure 3. Photographs of the prototype developed and tested in this work. The final prototype includes four lines of gadolinium orthosilicate crystals
separated by lead slices with a thickness of 3 mm. The scintillation light is directed to the photomultiplier tube by means of acrylic light guides
Abbreviation: PVC: Polyvinyl chloride.

Figure 4. Detector prototype parts. Top-left: gadolinium orthosilicate scintillator crystals; top-right: lead collimator inside the aluminum box; bottom:
custom-made acrylic light guides.

Volume 2 Issue 3 (2024) 3 doi: 10.36922/arnm.4099