Visualizing Bioabsorbable Spacer Effectiveness by Confirming the Distal-Tail of Carbon-Ion Beams: First-In-Human Report

• Published in: Tomography (Ann Arbor) Vol. 8; no. 5; pp. 2339 - 2346
• Main Authors: Shiba, Shintaro, Okamoto, Masahiko, Sakai, Makoto, Ohno, Tatsuya
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 21.09.2022; MDPI
• Subjects: Absorbable Implants; auto-activation positron emission tomography; bioabsorbable polyglycolic acid spacer; Bragg peak; Carbon - therapeutic use; carbon-ion radiotherapy; Gastrointestinal system; Humans; Ions; Middle Aged; PET imaging; Polyglycolic Acid; positron emission tomography; Tomography, X-Ray Computed; Japan; Bragg peak; bioabsorbable polyglycolic acid spacer; carbon-ion radiotherapy; positron emission tomography; auto-activation positron emission tomography
• DOI: 10.3390/tomography8050195
• ISSN: 2379-139X; 2379-1381

In particle therapy, bioabsorbable polyglycolic acid (PGA) spacer was developed to reduce the healthy organ irradiation dose, especially in the gastrointestinal tract. The PGA spacer is safe and effective; however, there are no reports that have confirmed whether the PGA spacer which inserted in the body actually stops the carbon-ion (C-ion) beams. Here, we visualized and confirmed that the PGA spacer stops the C-ion beams in the body based on the dose distribution using auto-activation positron emission tomography (AAPET). A 59-year-old dedifferentiated retroperitoneal liposarcoma patient underwent C-ion radiotherapy (C-ion RT) on referral. A month before C-ion RT initiation, the patient underwent PGA spacer placement. Postoperatively, the patient received 4.4 Gy (RBE) per fraction of C-ion RT, followed by AAPET. AAPET revealed lower positron emitter concentrations at the distal tissue ventral to the PGA spacer than in the planning target volume. In observing the efficacy of the PGA spacer, the AAPET images and the average count per second of the positron emitter suggested that the PGA spacer stopped the C-ion beams in the body in accordance with the dose distribution. Therefore, AAPET was useful in confirming the PGA spacer's effectiveness in this study, and the PGA spacer stopped the C-ion beams.