High Sensitivity, Low Activity NeuroPET™ Proton Beam¹ Images

The feasibility of PET verification of 3D proton beam therapy is under investigation at Massachusetts General Hospital². The rectangular phantom shown in the photograph (9x9cmx20cm, PMMA plastic) was exposed to 8 Gy for 3 minutes with a proton beam diameter of 5cm and maximum range of 13cm. Following irradiation, the phantom was scanned for 30 minutes in the NeuroPET starting 9.5 minutes post exposure (upper images). The second scan was acquired for 60 seconds following the attachment of the PET markers seen in the lower images. The second scan started 40 minutes post exposure. It is estimated that at the start of scanning, 90% of the signal was due to C11 decay (20 minute half-life), and 10% O15 (2 minute half-life).

The proton dose distribution is well visualized with both the 30 minute and one minute NeuroPET scans 40 minutes post exposure.

1. Experiment reported by X. Zhu, PhD, MGH
2. PET/CT Imaging for treatment verification after proton therapy…,
Parodi, et. al., Medical Physics, PMC 2008, April 11