Eli Olaug Hole

• Sagstuen, Einar; Kugler, Veronika; Hole, Eli Olaug & Lund, Anders (2022). Radicals in ammonium tartrate at 295 K by X-radiation: Revised radical structures by EMR and DFT analyses. Radiation Physics and Chemistry. ISSN 0969-806X. 196. doi: 10.1016/j.radphyschem.2022.110097. Full text in Research Archive Show summary

  The simple amino acid l-α-alanine (ala) in polycrystalline form was among the first substances to be proposed and subsequently developed for Electron Paramagnetic Resonance (EPR)-based solid state radiation dosimetry. One disadvantage with ala is a relatively low sensitivity for doses below a few gray (Gy) which is a dose range of particular interest in medical, accident and environmental applications. A number of other compounds have been screened and some of these have shown a better sensitivity to radiation exposure than ala, in some cases up to a factor of 7–8. In particular ammonium tartrate (AT) and lithium formate (LiFo) have been taken into practical use. The present work was initially aimed to investigate the low-temperature radical products in AT, and the reactions leading to the product of dosimetric interest at room temperature. As a part of these studies, the previously characterized major room temperature radical product was re-investigated using single crystal electron magnetic resonance (EMR) techniques combined with periodic density functional theory (DFT) -type quantum chemical calculations. Surprisingly, this study showed that the molecular structure of the dominant radical at room temperature is somewhat different from that previously proposed. Furthermore, a second room temperature radical, previously not well characterized, was carefully investigated and three hyperfine coupling tensors were determined. These three tensors were sufficient to simulate all experimental observations for the second radical but not alone sufficient to permit an unambiguous molecular structure of the defect to be determined. It appears that the EPR resonance from this radical does not influence the dosimetric potential of AT.

• Jåstad, Eirik Ogner; Torheim, Turid K Gjerstad; Villeneuve, Kathleen; Kvaal, Knut; Hole, Eli Olaug & Sagstuen, Einar [Show all 8 contributors for this article] (2017). In Quest of the Alanine R3 Radical: Multivariate EPR Spectral Analyses of X‑Irradiated Alanine in the Solid State. Journal of Physical Chemistry A. ISSN 1089-5639. 121(38), p. 7139–7147. doi: 10.1021/acs.jpca.7b06447. Full text in Research Archive Show summary

  The amino acid L-α-alanine is the most commonly used material for solidstate electron paramagnetic resonance (EPR) dosimetry, due to the formation of highly stable radicals upon irradiation, with yields proportional to the radiation dose. Two major alanine radical components designated R1 and R2 have previously been uniquely characterized from EPR and electron−nuclear double resonance (ENDOR) studies as well as from quantum chemical calculations. There is also convincing experimental evidence of a third minor radical component R3, and a tentative radical structure has been suggested, even though no well-defined spectral signature has been observed experimentally. In the present study, temperature dependent EPR spectra of X-ray irradiated polycrystalline alanine were analyzed using five multivariate methods in further attempts to understand the composite nature of the alanine dosimeter EPR spectrum. Principal component analysis (PCA), maximum likelihood common factor analysis (MLCFA), independent component analysis (ICA), self-modeling mixture analysis (SMA), and multivariate curve resolution (MCR) were used to extract pure radical spectra and their fractional contributions from the experimental EPR spectra. All methods yielded spectral estimates resembling the established R1 spectrum. Furthermore, SMA and MCR consistently predicted both the established R2 spectrum and the shape of the R3 spectrum. The predicted shape of the R3 spectrum corresponded well with the proposed tentative spectrum derived from spectrum simulations. Thus, results from two independent multivariate data analysis techniques strongly support the previous evidence that three radicals are indeed present in irradiated alanine samples.

• Knudtsen, Ingerid Skjei; Svestad, Jørund Graadal; Sande, Erlend Peter Skaug; Rekstad, Bernt Louni; Rødal, Jan & Elmpt, Wouter van [Show all 9 contributors for this article] (2016). Validation of dose painting of lung tumours using alanine/EPR dosimetry. Physics in Medicine and Biology. ISSN 0031-9155. 61(6), p. 2243–2254. doi: 10.1088/0031-9155/61/6/2243. Full text in Research Archive
• Øyen, Live Furnes; Aalbergsjø, Siv Gundrosen; Knudtsen, Ingerid Skjei; Hole, Eli Olaug & Sagstuen, Einar (2015). Direct Radiation Effects to the Amino Acid Side-Chain: EMR and Periodic DFT of X-Irradiated L-Asparagine at 6 K. Journal of Physical Chemistry B. ISSN 1520-6106. 119(2), p. 491–502. doi: 10.1021/jp5115866. Full text in Research Archive Show summary

  Radical formation in single crystals of L-asparagine monohydrate following X-irradiation at 6 K has been investigated at 6 K and at elevated temperatures using various Electron Magnetic Resonance (EMR) techniques like Electron Paramagnetic Resonance (EPR), Electron Nuclear DOuble Resonance (ENDOR) and ENDOR-Induced EPR (EIE) spectroscopy. Molecular structures of the three free radicals stable at 6K were assessed by detailed analysis of the experimental data and Density Functional Theory (DFT) calculations in a periodic approach. Radical LI is assumed to result from one-electron reduction at the amide functional group in the asparagine side chain followed by protonation at the amide carbonyl oxygen by proton transfer from a neighboring molecule across a hydrogen bond. Radical LII is assigned to an one-electron reduction of the carboxyl group in amino acid backbone, followed by proton transfer across a hydrogen bond between a carboxylic oxygen and a neighboring asparagine molecule. Radical LIII is suggested formed by a net CO2 abstraction from an initial one-electron oxidized amino acid backbone. For the DFT modeling of LIII at 6 K, it was chosen to include the CO2 group stably embedded in the crystalline lattice. The assignments made are discussed in relation to previous work on L-asparagine. The relevance of these results to possible charge transfer processes in protein-DNA complexes is discussed.

• Krivokapic, Andre; Sanderud, Audun; Aalbergsjø, Siv Gundrosen; Hole, Eli Olaug & Sagstuen, Einar (2015). Lithium formate for EPR dosimetry (2): secondary radicals in X-irradiated crystals. Radiation Research. ISSN 0033-7587. 183(6), p. 675–683. doi: 10.1667/RR14046.1. Full text in Research Archive
• Knudtsen, Ingerid Skjei; Aalbergsjø, Siv Gundrosen; Hole, Eli Olaug & Sagstuen, Einar (2015). Radiation effects on crystalline l-asparagine, revisited: Radical formation by EMR and periodic DFT after X-irradiation at 275K. Radiation Physics and Chemistry. ISSN 0969-806X. 106, p. 151–159. doi: 10.1016/j.radphyschem.2014.07.008. Full text in Research Archive
• Pauwels, Ewald; Cooman, Hendrik De; Waroquier, Michel; Hole, Eli Olaug & Sagstuen, Einar (2014). Solved? the reductive radiation chemistry of alanine. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 16(6), p. 2475–2482. doi: 10.1039/c3cp54441a. Full text in Research Archive
• Fattibene, Paola; Trompier, Francois; Wieser, Albrecht; Brai, Maria; Ciesielski, Bartlomej & Angelis, Cinzia De [Show all 21 contributors for this article] (2014). EPR dosimetry intercomparison using smartphone touch screen glass. Radiation and Environmental Biophysics. ISSN 0301-634X. 53(2), p. 311–320. doi: 10.1007/s00411-014-0533-x. Full text in Research Archive
• Hauge, Ingrid Helen Ryste; Pedersen, Kristin; Olerud, Hilde Merete; Hole, Eli Olaug & Hofvind, Solveig (2014). The risk of radiation-induced breast cancers due to biennial mammographic screening in women aged 50-69 years is minimal. Acta Radiologica. ISSN 0284-1851. 55(10), p. 1174–1179. doi: 10.1177/0284185113514051. Full text in Research Archive
• Krivokapic, Andre; Aalbergsjø, Siv Gundrosen; Cooman, Hendrik De; Hole, Eli Olaug; Nelson, William H. & Sagstuen, Einar (2014). Lithium formate for EPR dosimetry: Radiation-induced radical trapping at low temperatures. Radiation Research. ISSN 0033-7587. 181(5), p. 503–511. doi: 10.1667/RR13582.1. Full text in Research Archive
• Lelie, S.; Hole, Eli Olaug; Duchateau, M.; Schroyers, W.; Schreurs, S. & Verellen, D. (2013). The investigation of lithium formate hydrate, sodium dithionate and N-methyl taurine as clinical EPR dosimeters. Radiation Measurements. ISSN 1350-4487. 59, p. 218–224. doi: 10.1016/j.radmeas.2013.07.001. Full text in Research Archive
• Aalbergsjø, Siv Gundrosen; Pauwels, Ewald; Cooman, Hendrik De; Hole, Eli Olaug & Sagstuen, Einar (2013). Structural specificity of alkoxy radical formation in crystalline carbohydrates. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 15(24), p. 9615–9619. doi: 10.1039/c3cp50789k. Full text in Research Archive Show summary

  A DFT study of radiation induced alkoxy radical formation in crystalline a-L-rhamnose has been performed to better understand the processes leading to selective radical formation in carbohydrates upon exposure to ionizing radiation at low temperatures. The apparent specificity of radiation damage to carbohydrates is of great interest for understanding radiation damage processes in the ribose backbone of the DNA molecule. Alkoxy radicals are formed by deprotonation from hydroxyl groups in oxidized sugar molecules. In a-L-rhamnose only one alkoxy radical is observed experimentally even though there are four possible sites for alkoxy radical formation. In the present work, the origin of this apparently specific action of radiation damage is investigated by computationally examining all four possible deprotonation reactions from oxygen in the oxidized molecule. All calculations are performed in a periodic approach and include estimates of the energy barriers for the deprotonation reactions using the Nudged Elastic Band (NEB) method. One of the four possible radical sites is ruled out due to the lack of a suitable proton acceptor. For the other three possible sites, the reaction paths and energy profiles from primary cationic radicals to stable, neutral alkoxy radicals are compared. It is found that deprotonation from one site (corresponding to the experimentally observed radical) differs from the others in that the reaction path is less energy demanding. Hence, it is suggested that the alkoxy radical formation is not necessarily site specific, but that the observed radical is formed in much greater abundance than the others due to the different energetics of the processes and reaction products.

• Gustafsson, Håkan; Lund, Anders; Hole, Eli Olaug & Sagstuen, Einar (2013). SO3-- radicals for EPR dosimetry: X- and Q band EPR study and LET dependency of crystalline potassium dithionate. Radiation Measurements. ISSN 1350-4487. 59, p. 123–128. doi: 10.1016/j.radmeas.2013.05.001. Full text in Research Archive
• Sanchez, Luis; Taxt-Lamolle, Sebastien Francis Michel; Hole, Eli Olaug; Krivokapic, Andre; Sagstuen, Einar & Haugen, Håvard Jostein (2013). TiO2 suspension exposed to H2O2 in ambient light or darkness: Degradation of methylene blue and EPR evidence for radical oxygen species. Applied Catalysis B: Environmental. ISSN 0926-3373. 142-143, p. 662–667. doi: 10.1016/j.apcatb.2013.05.017. Full text in Research Archive
• Sagstuen, Einar; Hole, Eli Olaug & Lund, Anders (2012). Free Radical Products in X-Irradiated Rochelle Salt: Low Temperature ENDOR and DFT Studies. Radiation Physics and Chemistry. ISSN 0969-806X. 81(2), p. 168–179. doi: 10.1016/j.radphyschem.2011.10.001. Full text in Research Archive
• Tarpan, Mihaela Adeluta; Cooman, Hendrik De; Hole, Eli Olaug; Waroquier, Michel & Callens, Freddy J. (2012). Radiation Products at 77 K in Trehalose Single Crystals: EMR and DFT Analysis. Journal of Physical Chemistry A. ISSN 1089-5639. 116(13), p. 3377–3387. doi: 10.1021/jp300979g. Full text in Research Archive
• Sande, Erlend Peter Skaug; Martinsen, Anne Catrine Trægde; Hole, Eli Olaug & Olerud, Hilde Merete (2010). Interphantom and interscanner variations for Hounsfield units-establishment of reference values for HU in a commercial QA phantom. Physics in Medicine and Biology. ISSN 0031-9155. 55(17), p. 5123–5135. doi: 10.1088/0031-9155/55/17/015. Full text in Research Archive
• Pauwels, Ewald; Cooman, Hendrik De; Waroquier, Michel; Hole, Eli Olaug & Sagstuen, Einar (2010). On the identity of the radiation-induced stable alanine radical. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 12(31), p. 8733–8736. doi: 10.1039/c004380j. Full text in Research Archive
• Waldeland, Einar; Hole, Eli Olaug; Stenerlöv, Bo; Grusell, Erik; Sagstuen, Einar & Malinen, Eirik (2010). Radical Formation in Lithium Formate EPA Dosimeters after Irradiation with Protons and Nitrogen Ions. Radiation Research. ISSN 0033-7587. 174(2), p. 251–257. doi: 10.1667/RR2035.1. Full text in Research Archive Show summary

  Radical formation in polycrystalline lithium formate monohydrate after irradiation with gamma rays, protons and nitrogen ions at room temperature was studied by continuous-wave electron paramagnetic resonance (EPR) spectroscopy. The linear energy transfer (LET) of the various radiation beams was 0.2, 0.7–3.9 and 110–164 keV/mm for gamma rays, protons and nitrogen ions, respectively. Doses between 5 and 20 Gy were given. The EPR reading (the area under the EPR absorption resonance) increased linearly with dose for all types of radiation. As the LET increased, the relative effectiveness (the EPR reading per dose relative to that for gamma rays) decreased, while the EPR line width increased. Track structure theory and modeling of detector effectiveness predicted the dosimeter response observed after proton and nitrogen-ion irradiation. A semi-empirical line broadening model including dipolar spin-spin interactions was developed that explained the dependence of the line width on LET. The findings indicate that the local radical density in lithium formate is increased after high-LET irradiation.

• Waldeland, Einar; Hole, Eli Olaug; Sagstuen, Einar & Malinen, Eirik (2010). The energy dependence of lithium formate and alanine EPR dosimeters for medium energy x rays. Medical Physics. ISSN 0094-2405. 37(7), p. 3569–3575. doi: 10.1118/1.3432567. Full text in Research Archive Show summary

  Litium formate and alanine EPR dosemeters were exposed to 8 different X-ray beam qualities, with nominal potentials ranging from 50 kV to 200 kV. Following ionometry based on standards of absorbed dose to water, the dosemeters were given two different doses of approximately 3 and 6 Gy for each radiation quality, with three dosemeters for each dose. A reference series was also irradiated to three different dose levels at a 60Co unit. The dose to water energy response, that is, dosimeter reading per absorbed dose to water relative to that for 60Co gamma-rays, was estimated for each beam quality. In addition, the energy response was calculated by Monte Carlo simulations and compared to the experimental energy response. Experimental energy response estimates ranged from 0.89 - 0.94 and 0.68 - 0.90 for lithium formate and alanine, respectively. Uncertainties in the experimental energy response estimates were typically 3 %. The relative effectiveness, that is, the ratio of the experimental energy response to that following Monte Carlo simulations was on average 0.96 and 0.93 for lithium formate and alanine, respectively. This work shows that lithium formate dosimeters are less dependent on X-ray energy than alanine. Furthermore, as the relative effectiveness for both lithium formate and alanine were systematically less than unity, the yield of radiation-induced radicals is decreased following X-irradiation compared to irradiation with 60Co gamma-rays.

• Krivokapic, Andre; Øhman, Kjell Tage; Munthe, Morten; Nelson, William H.; Hole, Eli Olaug & Sagstuen, Einar (2010). Radicals in 5-Methylcytosine by Ionizing Radiation. Electron Magnetic Resonance for Structural and Mechanistic Analyses. Radiation Research. ISSN 0033-7587. 173(5), p. 689–702. Full text in Research Archive
• Waldeland, Einar; Hörling, Magnus; Hole, Eli Olaug; Sagstuen, Einar & Malinen, Eirik (2010). Dosimetry of stereotactic radiosurgery using lithium formate EPR dosimeters. Physics in Medicine and Biology. ISSN 0031-9155. 55(8), p. 2307–2316. doi: 10.1088/0031-9155/55/8/012. Full text in Research Archive
• Krivokapic, Andre; Øhman, Kjell Tage; Nelson, William H.; Hole, Eli Olaug & Sagstuen, Einar (2009). Primary Oxidation Products of 5-Methylcytosine: Methyl Dynamics and Environmental Influences. Journal of Physical Chemistry A. ISSN 1089-5639. 113(35), p. 9633–9640. doi: 10.1021/jp904747j. Full text in Research Archive
• Pettersen, Erik O; Bjørhovde, Ingunn; Søvik, Åste; Edin, Nina Frederike J; Zachar, V & Hole, Eli Olaug [Show all 8 contributors for this article] (2007). Response of chronic hypoxic cells to low dose-rate irradiation. International Journal of Radiation Biology. ISSN 0955-3002. 83. doi: 10.1080/09553000701287791. Full text in Research Archive
• Malinen, Eirik; Waldeland, Einar; Hole, Eli Olaug & Sagstuen, Einar (2007). The energy dependence of lithium formate EPR dosimeters for clinical electron beams. Physics in Medicine and Biology. ISSN 0031-9155. 52, p. 4361–4369. doi: 10.1088/0031-9155/52/14/022. Full text in Research Archive
• Øhman, Kjell Tage; Sanderud, Audun; Hole, Eli Olaug & Sagstuen, Einar (2006). Single Crystals of L-O-Serine Phosphate X-Irradiated at Low Temperatures: EPR,ENDOR, EIE, and DFT Studies. Journal of Physical Chemistry A. ISSN 1089-5639. 110, p. 9585–9596. doi: 10.1021/jp061265o. Full text in Research Archive
• Sagstuen, Einar; Close, David M.; Vågane, Randi; Hole, Eli Olaug & Nelson, William H. (2006). Electron Transfer in Amino Acid:Nucleic Acid Base Complexes:EPR, ENDOR and DFT Study of X-Irradiated N-Formylglycine:Cytosine Complex Crystals. Journal of Physical Chemistry A. ISSN 1089-5639. 110(28), p. 8653–8662. Full text in Research Archive
• Malinen, Eirik; Waldeland, Einar; Hole, Eli Olaug & Sagstuen, Einar (2006). LET effects following neutron irradiation of lithium formate EPR dosimeters. Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. ISSN 1386-1425. 63, p. 861–869. Full text in Research Archive
• Østerås, Bjørn Helge; Hole, Eli Olaug; Olsen, Dag Rune & Malinen, Eirik (2006). EPR dosimetry of radiotherapy photon beams in inhomogeneous media using alanine films. Physics in Medicine and Biology. ISSN 0031-9155. 51, p. 6315–6328. Full text in Research Archive Show summary

  In the current work, EPR (electron paramagnetic resonance) dosimetry using alanine films (134 μm thick) was utilized for dose measurements in inhomogeneous phantoms irradiated with radiotherapy photon beams. The main phantom material was PMMA, while either Styrofoam or aluminium was introduced as an inhomogeneity. The phantoms were irradiated to a maximum dose of about 30 Gy with 6 or 15 MV photons. The performance of the alanine film dosimeters was investigated and compared to results from ion chamber dosimetry, Monte Carlo simulations and radiotherapy treatment planning calculations. It was found that the alanine film dosimeters had a linear dose response above approximately 5 Gy, while a background signal obscured the response at lower dose levels. For doses between 5 and 60 Gy, the standard deviation of single alanine film dose estimates was about 2%. The alanine film dose estimates yielded results comparable to those from the Monte Carlo simulations and the ion chamber measurements, with absolute differences between estimates in the order of 1–15%. The treatment planning calculations exhibited limited applicability. The current work shows that alanine film dosimetry is a method suitable for estimating radiotherapeutical doses and for dose measurements in inhomogeneous media.

• Bergstrand, Eva Stabell; Bjerke, Hans Aleksander & Hole, Eli Olaug (2005). An experimental investigation of the electron energy dependence of the EPR alanine dosimetry system. Radiation Measurements. ISSN 1350-4487. 39, p. 21–28. Full text in Research Archive
• Lund, Eva; Gustafsson, Håkan; Danilczuk, Marek; Sastry, Medury D.; Lund, Anders & Vestad, Tor Arne [Show all 9 contributors for this article] (2005). Formates and dithionates: sensitive EPR-dosimeter materials for radiation therapy. Applied Radiation and Isotopes. ISSN 0969-8043. 62, p. 317–324. Full text in Research Archive Show summary

  Polycrystalline formates and dithionates are promising materials for EPR dosimetry, as large yields of radiation induced stable radicals are formed with a linear dose response. Rapid spin relaxation rates were detected in many of the substances, indicating that a high microwave power can be applied during EPR acquisition in order to improve sensitivity. Different techniques used to further improve the sensitivity, such as the replacement of 7Li with 6Li or exchange of protons with deuterons in the corresponding crystalline matrices and metal ion doping are discussed. It is concluded that formates and dithionates may be up to 10 times as sensitive as L-alpha-alanine.

• Vestad, Tor Arne; Malinen, Eirik; Olsen, Dag Rune; Hole, Eli Olaug & Sagstuen, Einar (2004). Electron paramagnetic resonance (EPR) dosimetry using lithium formate in radiotherapy: comparison with thermoluminescence (TL) dosimetry using lithium fluoride rods. Physics in Medicine and Biology. ISSN 0031-9155. 49, p. 4701–4715. Full text in Research Archive Show summary

  Solid-state radiation dosimetry by electron paramagnetic resonance (EPR) spectroscopy and thermoluminescence (TL) was utilised for the determination of absorbed doses in the range of 0.5-2.5 Gy. The dosimeter materials used were lithium formate and lithium fluoride (TLD-100 rods) for EPR dosimetry and TL dosimetry, respectively. 60Co gamma-rays and 4, 6, 10 and 15 MV X-rays were employed. The main objectives were to compare the variation in dosimeter reading of the respective dosimetry systems and to determine the photon energy dependence of the two dosimeter materials. The EPR dosimeter sensitivity was constant over the dose range in question, while the TL sensitivity increased with more than 5 % from 0.5 to 2.5 Gy, thus displaying a supralinear dose response. The average relative standard deviation in the dosimeter reading per dose was 3.0 % and 1.2 % for the EPR and TL procedures, respectively. For EPR dosimeters, the relative standard deviation declined significantly from 4.3 % to 1.1 % over the dose range in question. The dose-to-water energy response for the megavoltage X-ray beams relative to 60Co gamma-rays was in the range of 0.990-0.979 and 0.984-0.962 for lithium formate and lithium fluoride, respectively. The results show that EPR dosimetry with lithium formate provides dose estimates with a precision comparable to that of TL dosimetry (using lithium fluoride) for doses above 2 Gy, and that lithium formate is slightly less dependent on megavoltage photon beam energy than lithium fluoride.

• Sagstuen, Einar; Sanderud, Audun & Hole, Eli Olaug (2004). The solid-state radiation chemistry of simple amino acids, revisited. Radiation Research. ISSN 0033-7587. 162, p. 112–119. doi: 10.1667/RR3215. Full text in Research Archive Show summary

  The solid state radiation-induced free radical formation in simple amino acids like alpha-glycine (gly) and l-alpha-alanine (ala) has been subject to investigations by EPR spectroscopy since the late 1950�s. The EPR spectra from crystals of gly and ala generally are very complex due to the simultaneous trapping of several free radicals regardless of irradiation and observation temperatures. Untangling these complex spectra is necessary for understanding the mechanisms for the solid state radiation chemistry of amino acids. Recently, radical formation in gly and ala after room temperature irradiation has been reinvestigated in our laboratories using X, K and Q-band EPR and ENDOR spectroscopy, combined with the ENDOR-Induced EPR (EIE) techniques as well as single crystal and powder EPR and ENDOR spectrum simulations. Several new radical products have been detected and characterized, most prominently the gly species H2N-CH-COOH and the ala species H3N+-C(CH3)-COO- and H2N-C(CH3)-COOH. A short description of these radicals will be given, and an overview of the solid state radiation chemistry of the simple amino acids will be presented, based on a review of the literature combined with these recent experimental results.

• Vestad, Tor Arne; Gustavsson, Håkan; Lund, Anders; Hole, Eli Olaug & Sagstuen, Einar (2004). Radiation-induced radicals in lithium formate monohydrate (LiHCO2 center dot H2O). EPR and ENDOR studies of X-irradiated crystal and polycrystalline samples. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 6, p. 3017–3022. Full text in Research Archive Show summary

  Single crystals and polycrystalline samples of lithium formate monohydrate (LiHCO₂^.H₂O) were X-irradiated at 295 K and studied using X-band EPR, ENDOR, and ENDOR-induced EPR (EIE) spectroscopy at 200 or 295 K. Two different radical species were observed. The overall dominating species is the ^.CO₂^- radical trapped in the crystal matrix at an orientation not very different from that of the parent CO₂ fragment in the unirradiated matrix. The g- and ¹³C hyperfine coupling tensors of the ^.CO₂^- radical were determined. The large line width (about 1.5 mT) of the polycrystalline EPR spectrum is due to extensive hyperfine couplings with lithium ions and protons in the environment. Four lithium couplings and four proton couplings associated with the ^.CO₂^- radical were measured, and all couplings were assigned to specific matrix nuclei. The spectra yield evidence for a second radical in low relative abundance. One small lithium hyperfine interaction detected was ascribed to this radical. Spectral simulations of the EPR and ENDOR spectra support the conclusions made.

• Malinen, Eirik; Vestad, Tor Arne; Hult, Elin Agathe; Hole, Eli Olaug & Sagstuen, Einar (2004). Estimation of X-ray beam quality by electron paramagnetic resonance (EPR) spectroscopy. Applied Radiation and Isotopes. ISSN 0969-8043. 60, p. 929–937. Full text in Research Archive Show summary

  A novel dosimetry system using EPR spectroscopy to determine X-ray beam quality is proposed. The composite dosimetry system is a mixture of two polycrystalline substances, where the two materials have different X-ray absorption properties. The composite dosimeters, consisting of polycrystalline lithium formate monohydrate and calcium formate, were prepared as pellets, X-irradiated and analyzed with EPR spectroscopy. Taking the ratio between the EPR intensities of the two substances constituting the dosimeter, a measure of the beam quality was obtained in terms of the equivalent photon energy. The intensity ratio was calculated by a simple EPR spectrum reconstruction method. Plotting the logarithm of the EPR intensity ratio against the logarithm of the equivalent photon energy, a linear relation was obtained. The linear relation may be used as a calibration formula for the estimation of photon energy from the composite EPR spectrum. The composite dosimeters were used to investigate the changes in equivalent photon energy with increasing depths in a Perspex phantom. Using a 220 kV X-ray beam with an equivalent photon energy of about 100 keV, a buildup of scattered photons was detected with increasing depths in the phantom, displayed by a change in the EPR intensity ratio. This could furthermore be related to the equivalent photon energy in the logarithmic calibration curve. It was found that the equivalent photon energy was significantly reduced by about 25% from the surface of the phantom to a depth of 13 cm. The composite dosimetry system may be used to estimate effective beam energy in both standardized and non-standardized situations, with the latter corresponding to beam setups where the use of filters and ion chambers are difficult or not possible. Also, the system can provide means of measuring beam quality in phantoms following X-ray exposure.

• Vestad, Tor Arne; Malinen, Eirik; Lund, Anders; Hole, Eli Olaug & Sagstuen, Einar (2003). EPR dosimetric properties of formates. Applied Radiation and Isotopes. ISSN 0969-8043. 59, p. 181–188. Full text in Research Archive

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• Sagstuen, Einar & Hole, Eli Olaug (2009). Radiation Induced Radicals. In: Electron Paramagnetic Resonance: A Practitioner’s Toolkit. John Wiley & Sons. ISBN 9780470258828. 57 p. Full text in Research Archive

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• Sagstuen, Einar; Malinen, Eirik; Futsæther, Cecilia Marie & Hole, Eli Olaug (2017). Solid state dosimetry using the amino acid alanine: in quest for the third alanine radical using multivariate analysis. Full text in Research Archive
• Hole, Eli Olaug; Edin, Nina Frederike J; Malinen, Eirik; Pettersen, Erik O & Sagstuen, Einar (2017). Biophysics and medical physics at UiO: Research and education. An incomplete overview. Full text in Research Archive
• Wieser, Albrecht; Fattibene, Paola; Trompier, Francois; Angelis, Cinzia De; Quattrini, Maria Cristina & Brai, Maria [Show all 22 contributors for this article] (2015). Analysis of the EPR spectrum of gamma exposed Gorilla Glass. Full text in Research Archive
• Angelis, Cinzia De; Fattibene, Paola; Quattrini, Maria Cristina; Monaca, Sara Della; Trompier, Francois & Wieser, Albrecht [Show all 22 contributors for this article] (2015). Variability of the dosimetric EPR response of Gorilla Glass touchscreen to dose and to light. Full text in Research Archive
• Fattibene, Paola; Anglais, Cinzia De; Quattrini, Maria Cristina; Trompier, Francois; Wieser, Albrecht & Brai, Maria [Show all 22 contributors for this article] (2015). Influence of environmental parameters on the dosimetric EPR response of Gorilla Glass touchscreen glass. Full text in Research Archive
• Krivokapic, Andre; Aalbergsjø, Siv Gundrosen; Sanderud, Audun; Hole, Eli Olaug & Sagstuen, Einar (2015). Radiation chemistry of the EPR dosimeter lithium formate monohydrate. Full text in Research Archive
• Hole, Eli Olaug (2014). A useful link between smashed smart phones, nuclear terror attack survival, and EPR dosimetry? Full text in Research Archive
• Fattibene, Paola; Trompier, Francois; Wieser, Albrecht; Brai, Maria; Ciesielski, Bartlomej & Angelis, Cinzia De [Show all 21 contributors for this article] (2014). EPR dosimetry intercomparison using smartphone touch screen. Full text in Research Archive
• Øyen, Live Furnes; Aalbergsjø, Siv Gundrosen; Knudtsen, Ingerid Skjei; Hole, Eli Olaug & Sagstuen, Einar (2014). Primary radiation-induced radicals in l-asparagine monohydrate at 6 K: EMR and DFT-PBC studies. Full text in Research Archive
• Krivokapic, Andre; Aalbergsjø, Siv Gundrosen; Hole, Eli Olaug; Nelson, William H. & Sagstuen, Einar (2014). Radiation physics of the EPR dosimeter lithium formate. Full text in Research Archive
• Aalbergsjø, Siv Gundrosen; Pauwels, Ewald; Cooman, Hendrik De; Hole, Eli Olaug & Sagstuen, Einar (2013). Understanding selective radical formation in biomolecules after irradiation. Full text in Research Archive
• Aalbergsjø, Siv Gundrosen; Pauwels, Ewald; Cooman, Hendrik De; Hole, Eli Olaug & Sagstuen, Einar (2013). Why are only certain radicals formed in sugars after irradiation? Full text in Research Archive
• Sagstuen, Einar; Gustafsson, Håkan; Waldeland, Einar; Lund, Anders; Hole, Eli Olaug & Malinen, Eirik (2013). Photon and hadron dosimetry by EPR methods: LET dependence of EPR response function. Full text in Research Archive
• Svestad, Jørund; Knudtsen, Ingerid Skjei; Sande, Erlend Peter Skaug; Rekstad, Bernt Louni; Rødal, Jan & Elmpt, Wouter van [Show all 9 contributors for this article] (2013). PET-guided simultaneous integrated boost of lung tumors: Alanine/EPR dosimetry in an anthropomorphic phantom. Radiotherapy and Oncology. ISSN 0167-8140. 106, p. 292–292. Full text in Research Archive
• Fattibene, Paola; Hole, Eli Olaug & et, al. (2012). How can the Eurados Network on Retrospective Dosimetry contribute to research in low doses? Full text in Research Archive
• Aalbergsjø, Siv Gundrosen; Pauwels, Ewald; Hole, Eli Olaug & Sagstuen, Einar (2012). "Seeing" the molecules - using DFT calculations and periodiv boundary conditions. Full text in Research Archive
• Krivokapic, Andre; Aalbergsjø, Siv Gundrosen; Malinen, Eirik; Cooman, Hendrik De; Hole, Eli Olaug & Sagstuen, Einar (2012). Lithium formate - a challenging low-dose radiation dosimeter. Full text in Research Archive
• Hole, Eli Olaug (2011). Om Uran i berggrunnen - Er det sunt med litt radon? [Radio]. Østlandssendingen. Full text in Research Archive
• Hole, Eli Olaug (2011). Er det sunt med litt radon? Full text in Research Archive
• Hole, Eli Olaug (2011). Er det sunt med litt radioaktivitet? Full text in Research Archive
• Hole, Eli Olaug (2011). Livet er strålende - om radon og helserisiko. [Journal]. Dagsavisen. Full text in Research Archive
• Aalbergsjø, Siv Gundrosen; Cooman, Hendrik De; Hole, Eli Olaug; Sagstuen, Einar & Pauwels, Ewald (2010). Deprotonering fra oksygen i rhamnose kationer studert ved DFT og TD-DFT metoder. Full text in Research Archive
• Waldeland, Einar; Hole, Eli Olaug; Sagstuen, Einar & Malinen, Eirik (2010). Energy response to medium-energy X-rays for alanine and lithium formate EPR dosimeters. Full text in Research Archive
• Gjøvik, Marie; Malinen, Eirik; Sagstuen, Einar & Hole, Eli Olaug (2010). Lithium formate in EPR dosimetry: The story continues. Full text in Research Archive
• Aalbergsjø, Siv Gundrosen; Cooman, Hendrik De; Hole, Eli Olaug; Sagstuen, Einar & Pauwels, Ewald (2010). DFT and TD-DFT studies of deprotonation from oxygen in rhamnose cations. Full text in Research Archive
• Waldeland, Einar; Hole, Eli Olaug; Sagstuen, Einar & Malinen, Eirik (2010). Energy dependence of alanine and lithium formate EPR dosimeters and LiF TL-dosimeters. Full text in Research Archive
• Hole, Eli Olaug (2010). Utdanning av medisinske fysikere ved universitetet i Oslo. Full text in Research Archive
• Cooman, Hendrik De; Aalbergsjø, Siv Gundrosen; Pauwels, Ewald; Sagstuen, Einar; Hole, Eli Olaug & Callens, Freddy J. [Show all 7 contributors for this article] (2010). Which role do excited states play in radiation damage to organic solid-state compounds? Full text in Research Archive
• Pauwels, Ewald; Hole, Eli Olaug; Sagstuen, Einar & Waroquier, M (2009). Elucidation of radiation-induced processes using DFT calculations. Full text in Research Archive
• Krivokapic, Andre; Øhman, Kjell Tage; Hole, Eli Olaug; Nelson, William H. & Sagstuen, Einar (2009). Primary Oxidation Radical in X-irradiated 5-Methylcytosine; Hindered rotation of Methyl group. Full text in Research Archive
• Hole, Eli Olaug (2008). EPR-dosimetry for ionizing radiation. Full text in Research Archive
• Hole, Eli Olaug; Gjøvik, Marie E.; Grøvik, Endre; Paulsen, Kristin; Fetene, Deneke & Sagstuen, Einar (2008). Stabilisering av radikaler i litiumformat for lav-dose EPR spektroskopi. Full text in Research Archive
• Olsen, Bård; Sagstuen, Einar & Hole, Eli Olaug (2008). Strålingsinduserte radikaler i enkrystaller av L-arginine monofosfat monohydrat ved 295 K og 77 K. Full text in Research Archive
• Knudtsen, Ingerid Skjei; Hole, Eli Olaug & Sagstuen, Einar (2008). Strålingsindusert radikaldannelse i enkrystaller av l-asparagin monohydrat ved 295 K. Full text in Research Archive
• Pauwels, Ewald; Sagstuen, Einar; Hole, Eli Olaug & Waroquier, Michel (2008). Elucidation of radiation induced processes in alanine using DFT calculations. Full text in Research Archive
• Krivokapic, Andre; Øhman, Kjell Tage; Hole, Eli Olaug; Nelson, William H. & Sagstuen, Einar (2008). Primary oxidation radical in X-irradiated 5-methylcytosine, a mutational hotspot in DNA. Radioprotection - Revue de la Societé Francaise de Radioprotection. ISSN 0033-8451. 43(5), p. 133–133. Full text in Research Archive
• Sagstuen, Einar & Hole, Eli Olaug (2007). Radiation Physics and Chemistry in Oslo. Full text in Research Archive
• Østerås, Bjørn Helge; Hole, Eli Olaug; Olsen, Dag Rune & Malinen, Eirik (2006). ESR-dosimetri med alaninfilm i heterogene medier. Full text in Research Archive
• Øhman, Kjell Tage; Sanderud, Audun; Hole, Eli Olaug & Sagstuen, Einar (2006). Single crystals of l-o-Serine Phosphate X-irradiated at low temperatures: EOR, ENDOR, EIE and DFT studies. Full text in Research Archive
• Hole, Eli Olaug (2006). Er LiFo et alternativ til alanin ved lave doser? Full text in Research Archive
• Sagstuen, Einar; Hole, Eli Olaug; Close, David M.; Vågane, Randi & Nelson, William H. (2006). Stråleskader i DNA:proteinkomplekser. Full text in Research Archive
• Sagstuen, Einar; Malinen, Eirik; Vestad, Tor Arne; Waldeland, Einar & Hole, Eli Olaug (2006). Development of a solid state EPR dosimeter for low radiation doses. Full text in Research Archive
• Hole, Eli Olaug; Malinen, Eirik; Vestad, Tor Arne; Waldeland, Einar & Sagstuen, Einar (2006). Is Lithium Formate an Alternative to Alanine at Low Doses? Full text in Research Archive
• Sagstuen, Einar; Hole, Eli Olaug; Vågane, Randi & Nelson, William H. (2006). Radiation induced spin transfer in model DNA:protein complexes. Full text in Research Archive
• Eldevik, Kristine; Sagstuen, Einar & Hole, Eli Olaug (2006). Radikaldanning i røntgenbestrålte einkrystaller av N-acetyl-L-tyrosin. EPR, ENDOR, EIE of DFT studiar. Full text in Research Archive
• Sagstuen, Einar; Malinen, Eirik; Vestad, Tor Arne; Waldeland, Einar & Hole, Eli Olaug (2006). Lithium Formate as a Low-Dose EPR Radiation Dosimeter. Full text in Research Archive
• Hole, Eli Olaug (2005). Health effects of low doses of ionizing radiation. Full text in Research Archive
• Hole, Eli Olaug & Lund, Eva (2005). Supervising master students in Biophysics and Medical Physics – similarities and differences between the University of Oslo and the University of Linköping. Full text in Research Archive
• Hole, Eli Olaug (2005). Madame Curie; Mother of Radioactivity. Full text in Research Archive
• Waldeland, Einar; Hole, Eli Olaug; Sagstuen, Einar; Stenerlöv, Bo; Grusell, Erik & Malinen, Eirik (2005). Dosimetry of ion beams using lithium formate EPR dosimeters. Radiotherapy and Oncology. ISSN 0167-8140. 76, p. s122–s122. Full text in Research Archive
• Østerås, Bjørn Helge; Hole, Eli Olaug; Olsen, Dag Rune & Malinen, Eirik (2005). Dose measurements in heterogeneous media using alanine film dosimetry. Radiotherapy and Oncology. ISSN 0167-8140. 76, p. s205–s206. Full text in Research Archive
• Østerås, Bjørn Helge; Hole, Eli Olaug; Olsen, Dag Rune & Malinen, Eirik (2005). Dose measurements in heterogeneous media using alanine film dosimetry. Full text in Research Archive
• Henriksen, Ellen Karoline; Hole, Eli Olaug; Viefers, Susanne F & Kronstad, Ragna (2005). Einstine - er hun mulig? [Journal]. Teknisk ukeblad. Full text in Research Archive Show summary

  Selv om likestillingen har kommet langt, er vitenskapen fortsatt en mannsverden. Har ikke kvinnehjernen det som skal til? Mange menn synes nok det er morsomt at de i gjennomsnitt har 10 prosent større hjerne enn kvinner. Men før våre mannlige lesere stolt proklamerer dette faktum videre til kjæreste, venninne, kollega eller kone, anbefaler vi: Les videre!

• Waldeland, Einar; Hole, Eli Olaug; Sagstuen, Einar; Stenerlöv, Bo; Grusell, Erik & Malinen, Eirik (2005). Dosimetry of hadron beams using lithium formate EPR dosimeters. Full text in Research Archive
• Malinen, Eirik; Waldeland, Einar; Hole, Eli Olaug & Sagstuen, Einar (2005). LET effects following neutron irradiation of lithium formate EPR dosimeters. Full text in Research Archive
• Hole, Eli Olaug (2004). Madame Marie S. Curie - Mennesket og Vitenskapskvinnen. Full text in Research Archive
• Vestad, Tor Arne; Malinen, Eirik; Lund, Anders; Hole, Eli Olaug & Sagstuen, Einar (2004). Properties of Formates for EPR Dosimetry Purposes. Full text in Research Archive
• Malinen, Eirik; Vestad, Tor Arne; Hult, Elin Agathe; Hole, Eli Olaug & Sagstuen, Einar (2004). Differensiell fotonabsorpsjon i faste stoffer - problemstillinger og anvendelser. Full text in Research Archive
• Sagstuen, Einar; Hole, Eli Olaug; Vågane, Randi; Close, David M. & Nelson, William H. (2004). Charge Transfer in Peptide�Nucleic Acid Base Complexes: An EPR, ENDOR and DFT Study. Full text in Research Archive
• Vestad, Tor Arne; Malinen, Eirik; Lund, Anders; Hole, Eli Olaug & Sagstuen, Einar (2003). EPR dosimetric properties of formates. Full text in Research Archive Show summary

  As a part of a program to develop an EPR dosimeter suited for clinical use (doses in the cGy range), polycrystalline samples of lithium formate monohydrate (HCO2Li�H2O), magnesium formate dihydrate (C2H2O4Mg�2H2O), and calcium formate (C2H2O4Ca) have been examined. L-alanine was included for comparison and reference. Samples were irradiated using 60Co -rays and 60 - 220 kV X-rays. The dosimeter response was assessed using the peak-to-peak intensity of the first-derivative EPR spectrum. Dose-response curves for 60Co -irradiated samples were constructed, and photon energy, microwave power and modulation amplitude dependencies of the EPR spectra as well as the stability of the irradiation products upon storage (fading characteristics) were investigated. Lithium formate monohydrate is by far the best candidate of the tested formates, suitable for measuring doses down to about 0.1 Gy. Lithium formate monohydrate is more sensitive than alanine by a factor 5.6-6.8 in the tested photon energy range, exhibits no zero-dose signal and shows a linear dose response in the dose range 0.5 to 1000 Gy. The EPR signal is unchanged in shape and intensity after one week following irradiation to a dose of 10 Gy. Various less favorable properties rendered the other formates generally unsuitable, although e.g. calcium formate exhibits some interesting EPR dosimetric properties.

• Hole, Eli Olaug; Bergstrand, Eva Stabell; Malinen, Eirik & Sagstuen, Einar (2003). Radiation quality dependency of the alanine dose response. Full text in Research Archive
• Malinen, Eirik; Vestad, Tor Arne; Lund, Anders; Hole, Eli Olaug & Sagstuen, Einar (2003). Formates � promising materials for EPR dosimetry at low doses. Full text in Research Archive
• Malinen, Eirik; Bergstrand, Eva Stabell; Vestad, Tor Arne; Hole, Eli Olaug & Sagstuen, Einar (2003). EPR-dosimetri. Full text in Research Archive

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