Alanine Dosimeters Research Articles

Measurement of gamma and neutron radiations inside spent fuel assemblies with passive detectors

Abstract During operation of a fission nuclear reactor, many radionuclides are generated in fuel by fission and activation of 235 U, 238 U and other nuclides present in the assembly. After removal of a fuel assembly from the core, these radionuclides are sources of different types of radiation. Gamma and neutron radiation emitted from an assembly can be non-destructively detected with different types of detectors. In this paper, a new method of measurement of radiation from a spent fuel assembly is presented. It is based on usage of passive detectors, such as alanine dosimeters for gamma radiation and track detectors for neutron radiation. Measurements are made on the IRT-2M spent fuel assemblies used in the LVR-15 research reactor. During irradiation of detectors, the fuel assembly is located in a water storage pool at a depth of 6 m. Detectors are inserted into central hole of the assembly, irradiated for a defined time interval, and after the detectors removed from the assembly, gamma dose or neutron fluence are evaluated. Measured profiles of gamma dose rate and neutron fluence rate inside of the spent fuel assembly are presented. This measurement can be used to evaluate relative fuel burn-up.

APPLICATION OF ALANINE/ESR SPECTRUM SHAPE CHANGE IN GAMMA DOSIMETRY

Alnine pellets were installed in a nuclear power plant for one or two operation cycles and measured by electron spin resonance (ESR) spectrometers for dosimetry. Dose and “x/y ratio”, i.e., satellite peak over main center peak ratio, were measured for the returned alanine dosimeters from the nuclear power plant and compared to the values of reference alanine dosimeters exposed only to gamma rays. The variation of the x/y ratio change depended on the population of radicals from each radiation component with different LET. The gamma dose in a mixed radiation field was estimated by an additive gamma ray irradiation experiment and the measured dose rate at specified locations in the containment building.

The energy dependence of lithium formate and alanine EPR dosimeters for medium energy x rays

To perform a systematic investigation of the energy dependence of alanine and lilthium formate EPR dosimeters for medium energy x rays. Lithium formate and alanine EPR dosimeters were exposed to eight different x-ray beam qualities, with nominal potentials ranging from 50 to 200 kV. Following ionometry based on standards of absorbed dose to water, the dosimeters were given two different doses of approximately 3 and 6 Gy for each radiation quality, with three dosimeters 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, the 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. The experimental energy response estimates ranged from 0.89 to 0.94 and from 0.68 to 0.90 for lithium formate and alanine, respectively. The 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 0.94 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 y-rays.

SU‐GG‐T‐279: Current Practice in Small Radiosurgery Field Dosimetry — Preliminary Results from 21 Centers Participating in the International Leksell Gamma Knife Calibration Survey

Purpose: To investigate current practice in calibration of small Leksell Gamma Knife (LGK) radiosurgery fields and measure output of the surveyed LGK units using alanine dosimeter. Methods and Materials: Each participant of the project received a LGK calibration questionnaire addressing following information: LGK model, calibration protocol used, phantom used, ion chamber used, LGK calibration personnel, independent verification of calibration and collimator relative output factor values. Alanine dosimeters evaluated with a Bruker ECS106 Electron Paramagnetic Resonance spectrometer using the protocol described in the NIST Ionizing Radiation Division Quality System Manual were used to measure the dose rate of the surveyed LGK units. Results: To date, 21 LGK units have participated in this project (North America 9, Europe 5 and Asia 7).The calibration protocols used for surveyed sites were: AAPM TG21 9 sites, IAEA TRS277 1 site and IAEA TRS398 11 sites. ELEKTA ABS spherical phantom was used in 18 cases and ELEKTA solid water phantom in 3 cases. Following ion chambers were used for LGK calibration: PTW 31010 (0.125 cm3) 9 times, Exradin A16 (0.070 cm3) 2 times, PTW 31006 (0.125 cm3) 1 times, Capintec A1SL1 (0.070 cm3) 2 times, Wellhoffer IC‐10 (0.125 cm3) 1 time, Exradin A1SL 1 time and Exradin A14SL 1 time. Calibration of LGK units was performed by an on‐site physicist in 15 cases and by ELEKTA physicist in 6 cases. Independent verification was done in 8 cases out of total 21 surveyed units. All LGK units surveyed are currently using the ELEKTA default values for collimator relative output factors. Conclusions: The range of dose planned to measured ratio was 0.972 – 1.030 demonstrating reasonably good LGK calibration consistency. Mean absolute value percentage deviation between planned and measured dose was 1.34 – 0.84 %. This project is ongoing and more information will be provided at its conclusion.

On the implementation of a recently proposed dosimetric formalism to a robotic radiosurgery system

The aim of this work is to implement a recently proposed dosimetric formalism for nonstandard fields to the calibration and small field output factor measurement of a robotic stereotactic radiosurgery system. Reference dosimetry measurements were performed in the nonstandard, 60 mm diameter machine specific reference (msr) field using a Farmer ion chamber, five other cylindrical chambers with cavity lengths ranging from 16.25 down to 2.7 mm, and alanine dosimeters. Output factor measurements were performed for the 5, 7.5, 10, and 15 mm field sizes using microchambers, diode detectors, alanine dosimeters, TLD microcubes, and EBT Gafchromic films. Measurement correction factors as described in the proposed formalism were calculated for the ion chamber and diode detector output factor measurements based on published Monte Carlo data. Corresponding volume averaging correction factors were calculated for the alanine output factor measurements using 3D dose distributions, measured with polymer gel dosimeters. Farmer chamber and alanine reference dosimetry results were found in close agreement, yielding a correction factor of k(Q(msr),Q)(f(msr),f(ref)) = 0.999 +/- 0.016 for the chamber readings. These results were also found to be in agreement within experimental uncertainties with corresponding results obtained using the shorter cavity length ionization chambers. The mean measured dose values of the latter, however, were found to be consistently greater than that of the Farmer chamber. This finding, combined with an observed inverse relationship between the mean measured dose and chamber cavity length that follows the trend predicted by theoretical volume averaging calculations in the msr field, implies that the Farmer k(Q(msr),Q)(f(msr),f(ref)) correction is greater than unity. Regarding the output factor results, deviations as large as 33% were observed between the different dosimeters used. These deviations were substantially decreased when appropriate correction factors were applied to the measured microchamber, diode, and alanine values. After correction, all diode and microchamber measured output factors agreed within 1.6% with the corresponding alanine measurements, and within 3.1% with the TLD measurements. The weighted mean output factors were 0.681 +/- 0.001, 0.824 +/- 0.001, 0.875 +/- 0.001, and 0.954 +/- 0.001 for the 5, 7.5, 10, and 15 mm beams, respectively. The comparison of Farmer chamber measurements versus alanine reference dosimetry validates the use of the former for dosimetry in the msr field of this treatment delivery system. The corresponding results of this work obtained using chambers with different cavity lengths, combined with previous literature findings, suggest that a k(Q(msr),Q)(f(msr),f(ref)) Farmer chamber dose response correction factor of 1.01 may improve calibration measurement accuracy when using the proposed dosimetric formalism. The k(Q(msr),Q)(f(msr),f(ref)) correction factor is within 0.5% from unity for ion chambers with cavity lengths less than 10 mm. Substantial improvements in small field output factor measurement accuracy can be obtained when using microchambers and diodes by applying appropriately calculated correction factors to the detector measurements according to the proposed dosimetric formalism, and their routine use is therefore recommended.

Bilateral comparison of an alanine/ESR dosimetry system at radiotherapy dose levels

To improve the signal to noise ratio and to reduce the uncertainty for Electron Spin Resonance (ESR) readout of alanine dosimeters irradiated in the dose range of 2–10 Gy, new spectrometer settings have been proposed for microwave power, modulation amplitude, conversion time, sweeps of the spectrum and orientations of the alanine pellets ( Garcia et al., 2009 ). To check the reliability of the new spectrometer settings at radiotherapy dose levels, a bilateral dose comparison in terms of absorbed dose to water was performed between the CEA LIST Laboratoire National Henri Becquerel (LNHB) and the Radiometrology Center of the China Institute of Atomic Energy (RC-CIAE). Eighteen alanine dosimeters were irradiated with 2, 5 and 10 Gy. Each dosimeter was readout with the new spectrometer settings developed within the framework of the collaboration. The results of D meas / D nom at both laboratories in the dose range of 2–10 Gy are within the tolerance limits. The maximum deviations observed are within the extended uncertainties ( k = 2).

RESPONSE OF ALANINE AND BARIUM DITHIONATE EPR DOSIMETERS

The response of alanine and barium dithionate EPR dosimeters to proton irradiation with energies ranging from 6.6-25 MeV has been investigated. EPR dosimeters were calibrated using calibrated gamma sources. Alanine dosimeters show a value 29% higher than those obtained by a Markus chamber at the same energy, and barium dithionate shows a value 22% smaller. The response of the EPR dosimeters to irradiation at a mean dose of about 40 Gy depends on the proton energy. Using experimental data, the yield of the radicals in the tracks for the alanine pellets was calculated. The yield of the radicals was determined to be proportional to the linear energy transfer (LET) on the straight-line length of the proton track, and the proportional coefficient for alanine is equal to 0.109 eV-1. In the area of the Bragg peak, the probability of recombination of the ionized electrons with cations is increased. As a result, approximately 4.6 MeV of proton energy is used for ionization that results in electron-cation recombination instead of formation of radicals, and maximum LET does not coincide with the maximum concentration of the radicals.

Dose Rate Estimation Around a 60Co γ-ray Irradiation Source by Means of 115mIn Photoactivation

Photoactivation of nuclear isomer (115m)In with a halflife of 4.48 h occurs by (60)Co gamma-ray irradiation. This is because the resonance gamma-ray absorption occurs at 1078 keV level for stable (115)In, and that energy gamma-rays are produced by Compton scattering of (60)Co primary gamma-rays. In this work, photoactivation of (115m)In was applied to estimate the dose rate distribution around a (60)Co irradiation source utilizing a standard dose rate taken by alanine dosimeter. The (115m)In photoactivation was measured at 10 to 160 cm from the (60)Co source. The derived dose rate distribution shows a good agreement with both alanine dosimeter data and Monte Carlo simulation. It is found that angular distribution of the dose rate along a circumference at radius 2.8 cm from the central axis shows +/- 10% periodical variation reflecting the radioactive strength of the source rods, but less periodic distribution at radius 10 and 20 cm. The (115m)In photoactivation along the vertical direction in the central irradiation port strongly depends on the height and radius as indicated by Monte Carlo simulation. It is demonstrated that (115m)In photoactivation is a convenient method to estimate the dose rate distribution around a (60)Co source.

Characterization of a silicate glass as a high dose dosimeter

Commercial silicate glass has been investigated as a possible high dose dosimeter using an UV–vis spectrophotometer. Glass samples were irradiated by 60Co γ rays and the results compared with those obtained with 3.4 and 8.4 MeV electron beams. The irradiated samples showed rapid fading at room temperature immediately after irradiation. In order to improve the stability of absorbance, glass samples were submitted to post-irradiation thermal treatments (150 °C for 20 min). The influences of the dose, type and energy of the ionizing radiation on the fading characteristics and on the response of the irradiated and thermally treated glasses were studied. Dependence of the glass response on the temperature during gamma irradiation in the range −3 to 80 °C is reported. The reproducibility to reuse glass dosimeter by thermal bleaching the radiation induced colour centres at 300 °C for 30 min was also investigated. Calibration curves in the range 0.1–17 kGy were obtained by using in-plant calibration techniques against transfer standard alanine dosimeters in the Tunisian semi-industrial gamma irradiation facility.

An absolute dose determination of helical tomotherapy accelerator, TomoTherapy High-Art II

A helical tomotherapy accelerator presents a dosimetric challenge because, to this day, there is no internationally accepted protocol for the determination of the absolute dose. Because of this reality, we investigated the different alternatives for characterizing and measuring the absolute dose of such an accelerator. We tested several dosimetric techniques with various metrological traceabilities as well as using a number of phantoms in static and helical modes. Firstly, the relationship between the reading of ionization chambers and the absorbed dose is dependent on the beam quality value of the photon beam. For high energy photons, the beam quality is specified by the tissue phantom ratio (TPR20,10) and it is therefore necessary to know the TPR20,10 to calculate the dose delivered by a given accelerator. This parameter is obtained through the ratio of the absorbed dose at 20 and 10 cm depths in water and was measured in the particular conditions of the tomotherapy accelerator. Afterward, measurements were performed using the ionization chamber (model A1SL) delivered as a reference instrument by the vendor. This chamber is traceable in absorbed dose to water in a Co-60 beam to a water calorimeter of the American metrology institute (NIST). Similarly, in Switzerland, each radiotherapy department is directly traceable to the Swiss metrology institute (METAS) in absorbed dose to water based on a water calorimeter. For our research, this traceability was obtained by using an ionization chamber traceable to METAS (model NE 2611A), which is the secondary standard of our institute. Furthermore, in order to have another fully independent measurement method, we determined the dose using alanine dosimeters provided by and traceable to the British metrology institute (NPL); they are calibrated in absorbed dose to water using a graphite calorimeter. And finally, we wanted to take into account the type of chamber routinely used in clinical practice and therefore measured the dose using a Farmer-type instrument (model NE 2571) as well. We found the tomotherapy TPR20,10 value to be around 0.629, which is close to a 4 MV conventional linear accelerator value. During static irradiation, the secondary standard and the alanine dosimeters were compatible within 0.5%. The A1SL relative deviation to the secondary standard was 1.2% and the NE2571 relative deviation to the secondary standard was -1.7%. The measurement in dynamic helical mode found the different dosimeters compatible within 1.4% and the alanine dosimeters and the secondary standard were even found under 0.2%. We found that the different methods are all within uncertainties as well as globally coherent, and the specific limitations of the various dosimeters are discussed in order to help the medical physicist design an independent reference system. We demonstrated that, taking into account the particular reference conditions, one can use an ionization chamber calibrated for conventional linear accelerators to assert the absolute dose delivered by a tomotherapy accelerator.

Identification of the Active Form of Endothelial Lipase, a Homodimer in a Head-to-Tail Conformation

Endothelial lipase (EL) is a member of a subfamily of lipases that act on triglycerides and phospholipids in plasma lipoproteins, which also includes lipoprotein lipase and hepatic lipase. EL has a tropism for high density lipoprotein, and its level of phospholipase activity is similar to its level of triglyceride lipase activity. Inhibition or loss-of-function of EL in mice results in an increase in high density lipoprotein cholesterol, making it a potential therapeutic target. Although hepatic lipase and lipoprotein lipase have been shown to function as homodimers, the active form of EL is not known. In these studies, the size and conformation of the active form of EL were determined. Immunoprecipitation experiments suggested oligomerization. Ultracentrifugation experiments showed that the active form of EL had a molecular weight higher than the molecular weight of a simple monomer but less than a dimer. A construct encoding a covalent head-to-tail homodimer of EL (EL-EL) was expressed and had similar lipolytic activity to EL. The functional molecular weights determined by radiation inactivation were similar for EL and the covalent homodimer EL-EL. We previously showed that EL could be cleaved by proprotein convertases, such as PC5, resulting in loss of activity. In cells overexpressing PC5, the covalent homodimeric EL-EL appeared to be more stable, with reduced cleavage and conserved lipolytic activity. A comparative model obtained using other lipase structures suggests a structure for the head-to-tail EL homodimer that is consistent with the experimental findings. These data confirm the hypothesis that EL is active as a homodimer in head-to-tail conformation.

SU‐FF‐T‐392: Alanine as a Small Field Dosimeter ‐ First Tests in Gamma Knife Radiosurgery Fields

Introduction and purpose: An international working group on reference dosimetry of small and nonstandard fields has published a new formalism for the dosimetry of small and composite fields (Med. Phys. 35, 2008). Ionization chambers, which are the backbones of radiotherapy dosimetry, are not always suitable for measurements in regions of high dose gradients or where non‐uniform beam distributions are encountered. It is important to identify and evaluate new dosimeters that are suitable for measurements of absolute dose in small and non‐standard fields. The purpose of this study was to investigate whether alanine can be used as an absolute dosimeter for small field dosimetry of the Leksell Gamma Knife (LGK). Methods and Materials: Alanine pellets (4.8 mm in diameter and 2.0 mm in height) were irradiated to 40, 100 and 150 Gy in the center of a LGK spherical polystyrene phantom (diameter 160 mm) using 16 mm collimator on the LGK Perfexion unit and 18 mm collimator on the LGK 4C unit. For each dose point three pellets were irradiated separately in three separate irradiations. The alanine dosimeters were measured with a Bruker ECS106 Electron Paramagnetic Resonance spectrometer using the protocol described in the NIST Division Quality System Manual. Results of alanine dosimetry were compared with ion chamber measurements performed with A16 Exradin ion chamber following AAPM TG21 protocol. Results and Conclusions: Very good agreement was observed between the results obtained by alanine dosimetry and ionization chamber dosimetry. Mean deviations between both dosimetric methods for the LGK Perfexion were found to be −0.6%, 1.2% and 1.7% for doses 40, 100 and 150 Gy, respectively. Similarly, mean observed deviations for the LGK 4C were −0.2%, 0.7% and 1.2% for doses 40, 100 and 150 Gy, respectively. Measurements for the 8 mm collimator and composite field dosimetry are in progress.

A methodology for choosing parameters for ESR readout of alanine dosimeters for radiotherapy

Spectrometer settings for ESR readout of alanine dosimeters for radiotherapy have been investigated. Several ESR parameters were studied and determined. The main reason for this work is to choose the suitable parameters to increase signal-to-noise ratio and to reduce the uncertainty on ESR readout, which is one of the main components of uncertainty of alanine/ESR dosimetry system for radiotherapy. The new spectrometer settings have been applied for ESR readout of alanine dosimeters irradiated from 1 to 10 Gy. A higher signal-to-noise ratio has been achieved compared to our old spectrometer settings. The extended uncertainty ( k=2) has been evaluated in the dose range 2–10 Gy (maximum uncertainty of 4.9% for 2 Gy, while minimum uncertainty of 1.4% for 10 Gy), which implies that the alanine/ESR dosimetry system can be applied to radiotherapy dose level that needs a global accuracy of 5%.

The impact of irradiation temperature estimations on the accuracy of dosimetry

Quality-control dosimetry is important to the routine operation of a radiation processing facility. For many applications this dosimetry must be traceable to a national primary standard. After irradiation at an industrial facility, National Institute of Standards and Technology (NIST)-supplied transfer dosimeters are certified by measurement and dose interpolation from the NIST calibration curve. However, prior to computing the absorbed dose the dosimeter response must be adjusted for the temperature difference between irradiation temperature for the alanine system calibration and the irradiation temperature for the industrial process. For most industrial applications, the temperature is not controlled and varies during the irradiation process. The alanine dosimeter response has a dependence on irradiation temperature, which is compensated for by applying a correction factor to the dosimeter response to compute the absorbed dose. Moreover, there is no consensus protocol to estimate the irradiation temperature and apply this correction. This work approximates industrial temperature profiles using a 60Co source with a temperature-controlled irradiation chamber, and then compares the relative effectiveness of commonly used industrial methods to correct for irradiation temperature influence on the alanine dosimeter response.

The behaviour of alanine dosimeters at temperatures between 100 and 300 K

A cryostat has been constructed to enable irradiations in a MDS Nordion Gammacell 220 irradiator to be carried out at selected temperatures between 100 and 300 K. The principle of operation and the performance of this cryostat are described and results are given of a study into the behaviour of alanine dosimeters at cryogenic temperatures. This work extends previously published data to the region between solid CO 2 and liquid N 2 temperatures and has demonstrated complex dose-dependent behaviour. A sharp discontinuity in the effect of temperature on alanine dosimeter response has been found in the region between 150 and 180 K, with no further influence of irradiation temperature on response observed below this point.

A study of the alanine dosimeter irradiation temperature coefficient from 25 to 80 °C

The response of high-dose-range chemical dosimeters is dependent on the dosimeter temperature during irradiation. Typically, irradiation temperatures are estimated by measurements, calculations, or some combination of the two. Then using the temperature coefficient for the dosimetry system, the dosimeter response is adjusted or corrected to be consistent with the irradiation temperature for the calibration curve. Consequently, the estimation of irradiation temperature and the response correction via the temperature coefficient are sources of uncertainty in industrial dosimetry. To date, studies of dosimetry system performance at high temperatures have been limited. The maximum irradiation temperature for temperature coefficient studies of commercial alanine dosimeter formulations has not exceeded 50 °C. However, high-energy electron-beam processing can expose dosimeters to temperatures as high as 70 °C. This study aims to examine the temperature coefficient above 50 °C and assess the accuracy of the dosimeter response corrections. The findings reveal small but significant deviations from linearity above 70 °C. The magnitude of this deviation and its implications to dosimetry measurements will be discussed.

The effect of irradiation temperatures between ambient and 80 °C on the response of alanine dosimeters

Published data on the effect of irradiation temperature on the response of alanine dosimeters does not extend to the temperatures that may be experienced in high-dose industrial irradiations, particularly in the case of electron beams. We describe here results of the irradiation of alanine dosimeters at temperatures up to 80 °C and doses up to 70 kGy. Data have been obtained for both 60Co and electron beam irradiations and the effect of temperature on the stability of the radiation-induced signal has also been investigated. At temperatures above 50 °C the irradiation temperature coefficient begins to deviate significantly from linearity and shows marked dose dependence. The effect of this behaviour under conditions typically experienced in industrial processing is evaluated and recommendations made concerning the use of alanine dosimeters at high doses and temperatures.

Monte Carlo simulation of the response of ESR dosimeters added with gadolinium exposed to thermal, epithermal and fast neutrons

Monte Carlo numerical calculations of the response of alanine and ammonium tartrate ESR (electron spin resonance) dosimeters exposed to neutron fields with different energy spectra are reported. Results have been obtained for various gadolinium concentrations inside the dosimeters. Furthermore, in order to simulate the in-phantom response we have carried out calculations by varying the depth of the dosimeter. We have found that a large enhancement is obtained for thermal neutrons, because of the very high capture cross section of gadolinium to thermal neutrons. A good enhancement was obtained for epithermal neutrons, whereas the sensitivity improvement in the case of fast neutron irradiation is poor. Furthermore, the simulations carried out by varying the depth suggests that an appreciable sensitivity to thermal and epithermal neutrons could be observed for in-phantom measurements in the 2–3 cm depth range. These results can provide useful insight for future experiments with epithermal neutron beams (such as those used in neutron capture therapy) and for future applications in neutron capture therapy dosimetry.

Elaboración de dosímetros de alanina y sus posibles aplicaciones en riesgos profesionales

Elaboration of alanine dosimeters and their possible applications in professional risks . Objective. To develop dosimeters of alanine and alanine/paraffin in order to meet the growing use of ionizing radiation at the technological level. Materials and methods. Free radicals produced by ionizing radiation in alanine are detected by electron spin resonance (ESR); paraffin is used as binder. The method ology of preparation includes: elaboration, irradiation, data collection and data analysis for the two types of dosimeters. The ESR spec tra studied correspond to alanine dosimeters with masses between 60 and 120 mg and irradiated with doses of 10 and 20 Gy, and alanine/paraf fin dosimeters with 160 mg and irradiated with different doses in a beam of photons 4 MV. Results. The intensity of the spectra (the characteristic five lines) depends on the doses received by the dosimeters and their relationship is linear. With pure alanine and a dose of 10 Gy, the minimum amount required was 120 mg; the achieved cylinder compaction was not sufficient to avoid the partial fragmentat ion of the dosimeter. Paraffin has no paramagnetic signal; in the alanine/paraffin dosimeters (cylinders of 13 mm in length and 3.5 mm of diameter, with a ratio 80:20, and good hardness) the response signal ESR-dose was studied in a range between 20 and 120 Gy. Conclusions. The cylinders of alanine/paraffin manufactured have an appropriate hardness to be handled as dosimeters of ionizing radiation; thei r reproducibility and effectiveness in the accumulation of dose is good.

Medical reference dosimetry using EPR measurements of alanine: Development of an improved method for clinical dose levels.

Background. Electron spin resonance (EPR) is used to determine the absorbed dose of alanine dosimeters exposed to clinical photon beams in a solid-water phantom. Alanine is potentially suitable for medical reference dosimetry, because of its near water equivalence over a wide energy spectrum, low signal fading, non-destructive measurement and small dosimeter size. Material and Methods. A Bruker EMX-micro EPR spectrometer with a rectangular cavity and a measurement time of two minutes per dosimeter was used for reading of irradiated alanine dosimeters. Under these conditions a new algorithm based on scaling of known spectra was developed to extract the alanine signal. Results. The dose accuracy, including calibration uncertainty, is less than 2% (k=1) above 4 Gy (n=4). The measurement uncertainty is fairly constant in absolute terms (∼30 mGy) and the relative uncertainty therefore rises for dose measurements below 4 Gy. Typical reproducibility is <1% (k=1) above 10 Gy and <2% between 4 and 10 Gy. Below 4 Gy the uncertainty is higher. A depth dose curve measurement was performed in a solid-water phantom irradiated to a dose of 20 Gy at the maximum dose point (dmax) in 6 and 18 MV photon beams. The typical difference between the dose measured with alanine in solid water and the dose measured with an ion chamber in a water tank was about 1%. A difference of 2% between 6 and 18 MV was found, possibly due to non-water equivalence of the applied phantom. Discussion. Compared to previously published methods the proposed algorithm can be applied without normalisation of phase shifts caused by changes in the g-value of the cavity. The study shows that alanine dosimetry is a suitable candidate for medical reference dosimetry especially for quality control applications.