SU‐GG‐AUD‐03: The Development and Validation of An Image‐Based Dosimetry System for 90Y Microspheres Used to Treat Hepatic Tumors

• Published in: Medical physics (Lancaster) Vol. 34; no. 6; p. 2506
• Main Authors: Selwyn, R, Jaskowiak, C, Nickles, R, McDermott, J, Welsh, J, DeWerd, L, Thomadsen, B
• Format: Journal Article
• Language: English
• Published: American Association of Physicists in Medicine 01-06-2007
• Subjects: Cancer; Computed tomography; Computer software; Dosimetry; Gels; Germanium; Image scanners; Medical imaging; Positron emission tomography; Positrons
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.2761179

Purpose: To develop and experimentally validate an image‐based dosimetry system for determining the three‐dimensional (3D) dose distribution from
90
Y
microspheres used to treat hepatic tumors. Method and Materials: A rapid, efficient, and stable batch technique was used to label yttrium‐loaded microspheres with
18
F
. These
18
F
‐labeled microspheres served as surrogates for
90
Y
‐labeled microspheres.
18
F
and
90
Y
microspheres were coinjected into a gel‐based phantom and the
18
F
activity distribution was determined using a GE Discovery LS PET/CT scanner. The activity distribution was converted from
18
F
to
90
Y
by applying a precise activity ratio, which was determined using germanium detection and a low uncertainty
90
Y
positron branching ratio. To calculate the dose, the image data was convolved with a
90
Y
dose point kernel using 3D‐ID software. This dose was compared to the dose measured in the central plane using HD‐810 radiochromic film and a new film protocol. The film protocol and the gel‐based phantom were validated using a single
90
Sr
/
90
Y
source seed. The film was calibrated using two NIST‐traceable
90
Sr
ophthalmic applicators and was analyzed using a flatbed scanner in reflective mode. Additionally, the image‐based dose to the entire gel phantom was compared to a Monte Carlo‐derived dose. Results: The image‐based (3D‐ID) dose in the central plane was 90.20 Gy ± 6% and the film measured dose was 90.64 Gy ± 5%. A mean phantom dose of 74.30 Gy ± 6% and 74.70 Gy ± 2% was determined using 3D‐ID and Monte Carlo, respectively. Overall, these results agreed to within 0.5%. The image‐based in vivo dose volume histogram (DVH) for this study was in excellent agreement with the film measured DVH. Conclusion: Through the implementation of
18
F
‐labeled microspheres, a precise non‐destructive assay of
90
Y
, and a validated film protocol, a new image‐based dosimetry system for
90
Y
microspheres was experimentally validated.