Directionally-Sensitive Personal Wearable Radiation Dosimeter Hai Huu Le, Paul Junor, Moshi Geso, Graeme O’Keefe Abstract—In this paper, the authors propose a personal wearable directionally-sensitive radiation dosimeter using multiple semiconductor CdZnTe detectors. The proposed dosimeter not only measures the real-time dose rate but also provide the direction of the radioactive source. A linear relationship between radioactive source direction and the radiation intensity measured by each detectors is established and an equation to determine the source direction is derived by the authors. The efficiency and accuracy of the proposed dosimeter is verified by simulation using Geant4 package. Results have indicated that in a measurement duration of about 7 seconds, the proposed dosimeter was able to estimate the direction of a 10μCi 137 55 Cs radioactive source to within 2 degrees. Keywords—Dose rate, Geant4 package, radiation detectors, radioactive source direction. I. I NTRODUCTION T HE increasing worldwide use of radioactive sources has necessitates a dosemeter which not only detect their presence but also indicate their direction. An example of these attempts is a self-collimating BGO detector system [1] which is able to determine the direction of a 1mCi source placed 5m away from the detectors, with 10 degrees angular resolution using a 300 second measurement duration. Another approach was proposed in [2], using pixelated CZT arrays and coded mask apertures to detect and provide orientation information of radioactive sources. The result showed that a 2mCi source at 5m can be detected and localized with the accuracy of less than 3 degrees. In [3], a directional radiation detector based on an array of semiconductor detectors was presented, which can derive the source direction with the precision of 9 degrees by comparing the count rates measured at different detectors. Other systems using four scintillation detectors placed in a four-quadrant formation to localized radioactive source was proposed by Willis et al [4]. A fuzzy logic algorithm has been constructed to calculate the source position based on the relative measured signal intensity in the arrays of detectors. Simulation results have shown that the position of a radioactive source, placed 50cm away, can be determined with accuracy of less than 1 degree. In this work we aim at designing and fabricating a personal wearable directionally-sensitive radiation dosimeter using multiple semiconductor detectors which not only measure the dose rate but also indicate direction of the radioactive source based on the radiation intensity measured by each detector in H. H.Le and P. Junor are with the Department of Electronic Engineering, La Trobe University, Bundoora, VIC 3083, Australia (e-mail: h10le@students.latrobe.edu.au). M. Geso is with School of Health and Biomedical Sciences, RMIT University, Bundoora, VIC 3083, Australia. G. O’Keefe is with Centre for PET, Austin Health, Heidelberg, VIC 3084, Australia. the dosimeter. The configuration of proposed dosimeter, which includes 8 detectors (D1 to D8) placed in a circle at the angle of 45 degrees, can be seen on Fig. 1. The process of radioactive source direction estimation in our proposed dosimeter includes two steps: • Determining the four detectors closest to the radioactive source in the detectors array. • Calculating the direction of the radioactive source as the angle between source and the centre of the dosimeter. In the proposed system, radioactive source direction is calculated directly from the measurement results using a simple and compact computational algorithm, easy to implement on small micro-controller which is best suited for personal wearable real-time dosimeter. Simulation has suggested that over a measurement duration of about 7 seconds, the proposed dosimeter can estimate the direction of a 10μCi 137 55 Cs radioactive source to within 2 degrees. Fig. 1 Layout of the proposed dosimeter II. DETERMINING FOUR CLOSEST DETECTORS TO THE SOURCE IN THE DETECTORS ARRAY The four detectors closest to the source can be identified based on the number of interacting photons recorded in each detector in the array. After completing the measurement, the recorded number of interacting particles in each detector will be compared and the four detectors of highest reading are selected to be the closest detectors to the source. This can be explained further by an illustrative example shown in Fig. 1, with eight detectors from D1 to D8 of the array, the number of interacted particles from the sources S will be different. In this example detector D1, D2, D3 and D8 will record the highest number of interacted particles due to the closer distance from World Academy of Science, Engineering and Technology International Journal of Physical and Mathematical Sciences Vol:11, No:5, 2017 202 International Scholarly and Scientific Research & Innovation 11(5) 2017 scholar.waset.org/1307-6892/10007110 International Science Index, Physical and Mathematical Sciences Vol:11, No:5, 2017 waset.org/Publication/10007110