Proton beam range verification using off-site PET by imaging novel proton-activated markers

Jongmin Cho, Geoffrey Ibbott, Matthew Kerr, Richard Amos, Osama Mawlawi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Previously we showed that when 68Zn and Cu markers are placed along the distal end of the proton beam range, they result in higher PET signals than surrounding material such as Plastic Water® and balsa wood following proton treatment. In this work we investigated the use of PET signals from activated 68Zn and Cu markers for accurate proton range verification in two pseudo-clinical settings. 68Zn (>97%) and natural Cu ( 63Cu, 69%; 65Cu, 31%) markers (10 × 10 mm) of different thicknesses (0.1, 0.25, and 0.5 mm) were imbedded at 4 different distal fall-off depths in a balsa wood (simulating lung tissue) phantom. In a separate experiment, a rectangular block of raw beef (12 × 16 × 5 cm) simulating soft tissue was cut diagonally and imbedded with the same kind of 68Zn and Cu markers. Both phantoms were CT scanned for treatment planning and irradiated by a 160 MeV, 10-cm SOBP proton beam with 5 Gy and scanned for 5 hrs using an off-site PET scanner. Images were reconstructed using a 30 min interval without decay correction and using various post-irradiation delays to determine the image with the best visibility of activated markers. Treatment planned isodose lines of the phantom were overlaid on top of marker locations to correlate the isodose line level to marker activation. The best visibility of a 30 min PET scan was obtained after 1 and 2 hr delays for balsa wood and beef phantoms, respectively. Marker visibility increased with marker volume and scan time post irradiation until 1 hr (for balsa) and 2 hrs (for beef) before it decreased due to a decrease in accumulated coincidence events. 68Zn markers showed signals when located at ≥ 50% isodose line irrespective of different post-irradiation delays. However, Cu markers show signals in balsa phantom (1 hr delay) when located at ≥ 50% isodose line while in beef phantom (2 hrs delay) when located at ≥ 95% isodose line. This is due to the proton energy (and depth) dependency of different progeny radioisotopes from activated Cu. Markers located beyond those isodose lines were not activated. In both cases, markers of ≥ 25 mm3 were clearly visible. Activation of 68Zn and Cu markers and their correspondence with isodose lines suggest the possibility of using implanted markers for proton range verification.

Original languageEnglish (US)
Title of host publication2013 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2013
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Print)9781479905348
DOIs
StatePublished - 2013
Event2013 60th IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2013 - Seoul, Korea, Republic of
Duration: Oct 27 2013Nov 2 2013

Publication series

NameIEEE Nuclear Science Symposium Conference Record
ISSN (Print)1095-7863

Other

Other2013 60th IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2013
Country/TerritoryKorea, Republic of
CitySeoul
Period10/27/1311/2/13

ASJC Scopus subject areas

  • Radiation
  • Nuclear and High Energy Physics
  • Radiology Nuclear Medicine and imaging

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