Verification Study of Residual Activity Measurements After Yttrium-90 Radioembolization with Glass Microspheres
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TECHNICAL NOTE
EMBOLISATION (ARTERIAL)
Verification Study of Residual Activity Measurements After Yttrium-90 Radioembolization with Glass Microspheres S. C. Ebbers1 • B. Kunnen1 • B. J. van Nierop1 • J. L. M. Bemelmans1 G. C. Krijger1 • M. G. E. H. Lam1 • A. J. A. T. Braat1
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Received: 6 January 2020 / Accepted: 23 April 2020 The Author(s) 2020
Abstract Objective After yttrium-90 (90Y) radioembolization, residual activity and its consequences for dosimetric calculations are often not reported. The manufacturer for glass microspheres prescribes standard residual activity measurements by a survey meter, but the validity lacks evidence. This study aims to verify the accuracy of the survey meter approach for measuring residual activity of glass microspheres after treatment with glass microspheres. Methods To validate the accuracy of the survey meter approach, the measured residual activity of glass microspheres by survey meter was compared with measurements by PET. A sample of these waste containers was also measured by dose calibrator to confirm the accuracy of the PET. Results Twenty-four waste containers from glass microsphere treatments were prospectively scanned with 90YPET/CT. Bland–Altman plots showed substantial disagreement in residual activity measured by survey meter versus the residual activity measured by PET and dose calibrator, whereas the correlation between PET and dose calibrator was excellent (q = 0.99). Conclusion This study found a significant disagreement between the residual activities measured by the survey meter, compared to measurements by PET and dose calibrator. If relatively high amounts of residual activity are encountered using the exposure rate measurement with a survey meter, additional quantification should be
& S. C. Ebbers [email protected] 1
Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands
considered using either PET/CT or a dose calibrator measurement. Keywords Yttrium-90 microsphere Radioembolization SIRT TheraSphere Residual activity Survey meter
Introduction Selective internal radiotherapy (SIRT), also known as radioembolization, has proved to be an effective and safe treatment for various primary and secondary liver tumors [1–5]. Yttrium-90 (90Y) is the most commonly used isotope and its decay is mainly b-radiation, but 32 out of every one million decays are accompanied by positron emission, allowing PET-based quantification [6–8]. Accurate dosimetry is important, as several studies suggest a dose– response relationship [9–14]. However, there is little reported on the amount of residual activity (RA) in the administration system after administration and its consequences on treatment dosimetry [15]. For glass microspheres (TheraSphere, Biocompatibles UK Ltd), the method of measuring RA recommended by the manufacturer is by exposure rate measurements (ERM) [16]. This method may be inaccurate, due to the differing geometry of the waste material. Two other widely avai
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