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Keywords:
Dosimetric comparison, Dosimetry, SPECT, PET, Radioprotection / Radiation dose, Radiation physics
Authors:
H. Okino1, H. Hayashi1, K. Takegami1, N. Kimoto1, I. Maehata1, Y. Kanazawa1, T. Okazaki 2, T. Hashizume3, I. Kobayashi2; 1Tokushima/JP, 2Tsukuba, Ibaraki/JP, 3Tsukuba/JP
DOI:
10.1594/ecr2016/C-0024
Aims and objectives
Recently,
patient dose management has become an important topic in the X-ray based diagnosis.
This is because dose exposure has become increasingly precise during diagnosis. The relevance between the exposure dose and the quality of an obtained medical image should be managed through the measured exposure dose. In fact currently,
the exposure dose is estimated by the air-kerma measurement using an ionization chamber,
and the methodology to calculate the exposure dose has been established [1-3]. In this method,
the contribution of scattered X-rays is estimated by back scatter factor (BSF) which is functions of both quality of X-ray and size of irradiation field. The problem with this method is,
it does not consider the patients condition; there are large differences between patients. Therefore,
we plan to measure the exposure dose directly using a dosimeter that doesn’t interfere with the medical image.
Currently,
a small-type OSL (optically stimulated luminescence) dosimeter,
named nanoDot [4-8],
was commercially produced by Landauer Inc. Figure 1 illustrates nanoDot OSL dosimeter and its reader. Our research group focuses attention on its low detection properties which enables a measurement exposure dose without interfering with the medical image [9]. Currently,
we’re studying the basic properties of the nanoDot OSL dosimeter for direct measurement of patient dose in the general X-ray region [9-14]. In addition,
many reports have been published concerning measurements in the radiotherapeutic region [4-6].
Figure 2 indicates motivation for our study. In this investigation,
we focused attention on the nuclear medicine region. In this region,
we should be concerned with secondary electron equilibration,
because the range of secondary electrons is up to 10 m. This fact means that we should adopt an extremely large irradiation field. In reality,
the maximum size of the irradiation field may be limited,
also for the simulation study there is a restriction based on CPU power of the personal computer used. The aim of this study is to propose a new irradiation system,
which can establish a compact irradiation field for the nuclear medicine region. Using the Monte-Carlo simulation code,
we evaluated the accuracy of the proposed system.