Use of radiochromic film as a high-spatial resolution dosimeter by Raman spectroscopy Jamal Ahmad Mirza and Hyeonsuk Park Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 08826, South Korea So-Yeon Park Interdisciplinary Program in Radiation Applied Life Sciences, Seoul National University College of Medicine, Seoul 03080, South Korea Sung-Joon Ye a) Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 08826, South Korea; Interdisciplinary Program in Radiation Applied Life Sciences, Seoul National University College of Medicine, Seoul 03080, South Korea; and Center for Convergence Research on Robotics, Advance Institutes of Convergence Technology, Seoul National University, Suwon 16229, South Korea (Received 1 March 2016; revised 14 June 2016; accepted for publication 20 June 2016; published 14 July 2016) Purpose: Due to increasing demand for high-spatial resolution dosimetry, radiochromic films have been investigated as potential candidates but are often limited by the scanning system, e.g., flatbed optical scanner. In this study, Raman spectroscopy in conjunction with a microscope was selected as an alternative method for high-spatial resolution dosimetry of radiochromic film. Methods: Unlaminated Gafchromic™ EBT3 films were irradiated with doses between 0 and 50 Gy using 6 MV x-rays of a clinical linear accelerator. Depth profiling from the surface of unlaminated film was performed to acquire the maximum Raman intensity peaks of C≡≡C and C==C stretching bands of diacetylene polymer. The Raman mapping technique for a region of interest (200 × 200, 30 × 30 μm 2 ) was developed to reduce a large variation in a Raman spectrum produced with a sampling resolution of a few μm. The preprocessing of Raman spectra was carried out to determine a dosimetric relationship with the amount of diacetylene polymerization. Results: Due to partial diacetylene polymerization upon irradiation, two Raman peaks of C==C and C≡≡C stretching bands were observed around 1447 and 2060 cm −1 , respectively. The maximum intensities of the two peaks were obtained by positioning a focused laser spot on the surface of unlaminated film. For the dose range of 0–50 Gy, the band heights of both C≡≡C and C==C peaks increase asymptotically with increasing doses and can be fit with an exponential function of two components. The relative standard deviation in Raman mapping was found to be less than ±5%. By using this technique, dose uniformity was found to be within ±2%. Conclusions: The Raman intensity for C==C and C≡≡C peaks increases with an increase in the amount of diacetylene polymerization due to an increase in dose. This study shows the potential of Raman spectroscopy as an alternative for absolute dosimetry verifications with a high-spatial reso- lution of a few μm, but these findings need to be further validated for the purpose of microdosimetry. C 2016 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4955119] Key words: Raman spectroscopy, high-spatial resolution, microdosimetry, radiochromic film 1. INTRODUCTION Recent technological progress in radiological imaging and therapy instruments has greatly improved tumor localization and management. Such innovative instruments often require dosimetry systems to fulfill extraordinary treatment planning and in vivo needs, e.g., evaluating the dose in regions with high gradients, at buildup and interface regions, regions in close proximity to brachytherapy sources, and for small field dosimetry. 1,2 Conventional radiation detectors, like an ionization chamber or a semiconductor detector, have certain limitations, such as a relatively large sensitive volume or nonwater equivalence. Other unsuitable dosimeters include thermoluminescent detectors due to the time-consuming readout procedure and inability to archive their dosimetric data, and radiographic films that are nonwater equivalent, sensitive to light, and require wet chemical processing. 3 On the other hand, polymer gels and radiochromic films have been considered suitable for these clinical needs because of their high-spatial resolution and near water equivalence. 1 For radiobiological considerations, a very high-spatial resolution dosimeter, which is capable of giving information on spatial, temporal, and spectral distributions of energy imparted in cellular and subcellular structures, and the associated biological effects, is required. 4 Novel dosimeters have been developed for the space industry, such as microelectronic 4520 Med. Phys. 43 (8), August 2016 0094-2405/2016/43(8)/4520/9/$30.00 © 2016 Am. Assoc. Phys. Med. 4520