Monitoring proton radiation therapy with in-room PET imaging

Abstract

Purpose We used a mobile PET scanner positioned within the proton therapy treatment room to study the feasibility of proton range verification with an in-room, stand-alone PET system, and compared with off-line equivalent studies. Methods and materials Two subjects with adenoid cystic carcinoma were enrolled into a pilot study in which in-room PET scans were acquired in list-mode after a routine fractionated treatment session. The list-mode PET data were reconstructed with different time schemes to generate in-room short, in-room long and off-line equivalent (by skipping coincidences from the first 15 minutes during the list-mode reconstruction) PET images for comparison in activity distribution patterns. A phantom study was followed to evaluate the accuracy of range verification for different reconstruction time schemes quantitatively. Results The in-room PET has a higher sensitivity compared to the off-line modality so that the PET acquisition time can be greatly reduced from 30 min to <5 min. Features in deep-site, soft-tissue regions were better retained with in-room short PET acquisitions because of the collection of 15O component and lower biological washout. For soft tissue-equivalent material, the distal fall-off edge of an in-room short acquisition is deeper compared to an off-line equivalent scan, indicating a better coverage of the high-dose end of the beam. Conclusions In-room PET is a promising low cost, high sensitivity modality for the in vivo verification of proton therapy. Better accuracy in Monte Carlo predictions, especially for biological decay modeling, is necessary.

Investigating the limits of PET/CT imaging at very low true count rates and high random fractions in ion‐beam therapy monitoring

“…At present, the only clinically implemented approach to monitor the delivery of single treatment fractions shortly after irradiation relies on the detection of irradiation-induced β + -emitters within the patient by means of positron emission tomography (PET) imaging. [5][6][7][8][9] At the Heidelberg Ion-Beam Therapy Center (HIT), 10,11 a commercial full-ring PET/x-ray computed tomography (CT) scanner [Biograph mCT, Siemens Molecular Imaging, Knoxville (Ref. 12)] has been installed next to the treatment rooms (offline) for this purpose.…”

Systematic analysis on the achievable accuracy of PT-PET through automated evaluation techniques

“…Shakirin et al [11] described three different techniques: inbeam PET (PET cameras with limited angle geometry, fully integrated into the treatment site) [12], off-line PET (the usage of a standard PET-CT scanner outside the treatment room) [13] and in-room PET (full ring PET scanner inside the treatment room). In-room PET may also utilize a portable PET scanner [14,15]. Regarding off-line PET the most important limitation is the extensive influence of the patient metabolism [13,16,17].…”

Comparison study of RPC and crystal based PET systems for hadron therapy monitoring

“…The in-room PET method is based on the measurement immediately after irradiation by a standalone PET or PET/ CT scanner that is installed inside the treatment room. In this method, the patient does not have to be repositioned in the bed, which is moved from the treatment position to inside the PET scanner in 1-3 minutes, which is still big compared to the half-life of 150 and washout effects are still present [10], [11]. The in-beam PET concept relies on the PET measurement performed during and right after the irradiation by means of a PET scanner, which is integrated in the beam line [12].…”