Application of a medium-energy collimator for I-131 imaging after ablation treatment of differentiated thyroid cancer
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ORIGINAL ARTICLE
Application of a medium-energy collimator for I-131 imaging after ablation treatment of differentiated thyroid cancer Masato Kobayashi • Hiroshi Wakabayashi • Daiki Kayano • Takahiro Konishi Hironori Kojima • Hiroto Yoneyama • Koichi Okuda • Hiroyuki Tsushima • Masahisa Onoguchi • Keiichi Kawai • Seigo Kinuya
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Received: 9 February 2014 / Accepted: 19 March 2014 Ó The Japanese Society of Nuclear Medicine 2014
Abstract Purpose High-energy (HE) collimators are usually applied for I-131 imaging after ablation treatment of differentiated thyroid cancer (DTC). However, purchase of HE collimators has been avoided in many nuclear medicine departments because the HE collimators are more expensive than other collimators. In this study, we compared the I-131 imaging using HE- and medium-energy (ME) collimators, which is more versatile than HE collimators. Materials and methods To simulate DTC patients with extra-thyroid beds, a phantom of acrylic containers containing I-131 was used. To simulate patients with thyroid beds, four phantoms representing extra-thyroid beds were arranged around the phantom representing normal thyroid tissues. Patients administered 1.11 or 3.70 GBq NaI-131 were also evaluated. Whole-body imaging and SPECT imaging of the phantoms and patients performed using HEgeneral-purpose (HEGP) and ME-low-penetration (MELP)
M. Kobayashi (&) M. Onoguchi K. Kawai School of Health Sciences, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa 920-0942, Japan e-mail: [email protected] H. Wakabayashi D. Kayano K. Okuda S. Kinuya Department of Biotracer Medicine, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan T. Konishi H. Kojima H. Yoneyama Department of Radiology, Kanazawa University Hospital, Kanazawa, Japan H. Tsushima Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, Ibaraki, Japan
collimators, and full-width at half maximum (FWHM) and percent coefficient of variation (%CV) were measured. Results In the extra-thyroid beds, FWHM and %CV with MELP were negligibly different from those with HEGP in whole-body imaging. Although FWHM with MELP was a little different from that with HEGP in SPECT imaging, %CV with MELP was significantly higher than that with HEGP. In the thyroid beds, only an extra-thyroid bed including higher radioactivity was identified in whole-body imaging with both collimators. Although SPECT images with MELP could not clarify extra-thyroid beds with low radioactivity, HEGP could identify them. In patients, although some whole-body images with MELP could not detect extra-thyroid beds, whole-body imaging with HEGP and SPECT imaging with both collimators could detect them. Conclusions Although HEGP is the best collimator for I-131 imaging, MELP is applicable for not only wholebody imaging but also SPECT imaging. Keywords NaI-131 Ablation Differentiated thyroid cancer Medium-energy collimator High-energy collimator
Introduction
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