Excitation functions of proton-induced reactions on natFe and enriched 57Fe with particular reference to the production of 57Co

Excitation functions of the reactions ^natFe(p,xn)^55,56,57,58Co, ^natFe(p,x)⁵¹Cr, ^natFe(p,x)⁵⁴Mn, ⁵⁷Fe(p,n)⁵⁷Co and ⁵⁷Fe(p,α)⁵⁴Mn were measured from their respective thresholds up to 18.5 MeV, with particular emphasis on data for the production of the radionuclide ⁵⁷Co (T_1/2=271.8 d). The conventional stacked-foil technique was used, and the samples for irradiation were prepared by an electroplating or sedimentation process. The measured excitation curves were compared with the data available in the literature as well as with results of nuclear model calculations. From the experimental data, the theoretical yields of the investigated radionuclides were calculated as a function of the proton energy. Over the energy range E_p=15→5 MeV the calculated yield of ⁵⁷Co from the ⁵⁷Fe(p,n)⁵⁷Co process amounts to 1.2 MBq/μA h and from the ^natFe(p,xn)⁵⁷Co reaction to 0.025 MBq/μA h. The radionuclidic impurity levels are discussed. Use of highly enriched ⁵⁷Fe as target material would lead to formation of high-purity ⁵⁷Co.     

Production of the mercury-197 through proton induced reaction on gold

The excitation function of the proton exchange reactions on gold was investigated in the energy range from threshold up to 20 MeV. We presented our experimental results upto 14 MeV stacked-foil technique was used, the target was of high purity gold foils (99.99%.) Reactions cross-sections and excitation functions were studied. Both isomeric level cross sections of ¹⁹⁷Hg were measured and calculated theoretically using the DDHMS routine of the EMPIRE-II (v2.19) code. Isomeric cross-section ratios for the pair ^197m,gHg were calculated and presented as a function of proton energy.     

Yield and purity of 82Sr produced via the natRb(p,xn)82Sr process

The recently reported cross-section data for the production of ⁸²Sr via the ^natRb(p,xn)⁸²Sr process were evaluated. For the ^natRb(p,xn)⁸⁵Sr process, cross-sections were measured experimentally over the proton energy range of 25–45 MeV, a region where very few data existed. An evaluation of the recently published data on the formation of ⁸⁵Sr was then also performed. From the recommended data curves, the integral yields of the desired radionuclide ⁸²Sr and the impurity ⁸⁵Sr were calculated. Yields were also determined experimentally over several energy ranges using thick ^natRbCl targets. The experimental and calculated yields were found to be in agreement within 15%. These integral tests add confidence to the evaluated cross-section data. For the production of ⁸²Sr, an incident proton energy of 60 MeV or above is recommended; the ⁸⁵Sr impurity then corresponds to <20%.     

The production of radionuclides for nuclear medicine from a compact,low-energy accelerator system

IntroductionThe field of nuclear medicine is reliant on radionuclides for medical imaging procedures and radioimmunotherapy (RIT). The recent shut-downs of key radionuclide producers have highlighted the fragility of the current radionuclide supply network, however. To ensure that nuclear medicine can continue to grow, adding new diagnostic and therapy options to healthcare, novel and reliable production methods are required. Siemens are developing a low-energy, high-current – up to 10 MeV and 1 mA respectively – accelerator. The capability of this low-cost, compact system for radionuclide production, for use in nuclear medicine procedures, has been considered.MethodologyThe production of three medically important radionuclides – ⁸⁹Zr, ⁶⁴Cu, and ¹⁰³Pd – has been considered, via the ⁸⁹Y(p,n), ⁶⁴Ni(p,n) and ¹⁰³Rh(p,n) reactions, respectively. Theoretical cross-sections were generated using TALYS and compared to experimental data available from EXFOR. Stopping power values generated by SRIM have been used, with the TALYS-generated excitation functions, to calculate potential yields and isotopic purity in different irradiation regimes.ResultsThe TALYS excitation functions were found to have a good agreement with the experimental data available from the EXFOR database. It was found that both ⁸⁹Zr and ⁶⁴Cu could be produced with high isotopic purity (over 99%), with activity yields suitable for medical diagnostics and therapy, at a proton energy of 10 MeV. At 10 MeV, the irradiation of ¹⁰³Rh produced appreciable quantities of ¹⁰²Pd, reducing the isotopic purity. A reduction in beam energy to 9.5 MeV increased the radioisotopic purity to 99% with only a small reduction in activity yield.ConclusionThis work demonstrates that the low-energy, compact accelerator system under development by Siemens would be capable of providing sufficient quantities of ⁸⁹Zr, ⁶⁴Cu, and ¹⁰³Pd for use in medical diagnostics and therapy. It is suggested that the system could be used to produce many other isotopes currently useful to nuclear medicine.     

Investigation of the natZn(p,x)62Zn nuclear process up to 70 MeV: a new 62Zn/62Cu generator

The excitation function of the ^natZn(p,x)⁶²Zn nuclear process was measured by the stacked-foil technique up to a proton energy of 70 MeV to obtain accurate data for production of the ‘mother nuclide’ (⁶²Zn) of the PET related β⁺ emitting radioisotope ⁶²Cu. Investigations were also made on the ⁶⁶Zn(p,x)⁶²Zn and ^natZn(p,xn)⁶⁶Ga processes and on the ⁶⁶Zn(p,n)⁶⁶Ga reaction using ^natZn and highly enriched ⁶⁶Zn. The excitation functions were compared with the published data. Thick target yields for the ^natZn(p,x)⁶²Zn and ^natCu(p,xn)⁶²Zn processes were also calculated up to 70 MeV. On the basis of these calculations the ^natZn+p process results in higher yield for ⁶²Zn above 50 MeV than the ^natCu+p process. The latter process is presently used for practical production of ⁶²Zn. In an energy window from 70 to 30 MeV the available EOB yield of the ^natZn+p reactions is around 19 mCi/μA h (0.7 GBq/μAh) that makes the ^natZn(p,x)⁶²Zn process a good candidate for routine generator production.     

High-power electron beam tests of a liquid-lithium target and characterization study of 7Li(p,n) near-threshold neutrons for accelerator-based boron neutron capture therapy

A compact Liquid-Lithium Target (LiLiT) was built and tested with a high-power electron gun at Soreq Nuclear Research Center (SNRC). The target is intended to demonstrate liquid-lithium target capabilities to constitute an accelerator-based intense neutron source for Boron Neutron Capture Therapy (BNCT) in hospitals. The lithium target will produce neutrons through the ⁷Li(p,n)⁷Be reaction and it will overcome the major problem of removing the thermal power >5 kW generated by high-intensity proton beams, necessary for sufficient therapeutic neutron flux.In preliminary experiments liquid lithium was flown through the target loop and generated a stable jet on the concave supporting wall. Electron beam irradiation demonstrated that the liquid-lithium target can dissipate electron power densities of more than 4 kW/cm² and volumetric power density around 2 MW/cm³ at a lithium flow of ~4 m/s, while maintaining stable temperature and vacuum conditions. These power densities correspond to a narrow (σ=~2 mm) 1.91 MeV, 3 mA proton beam. A high-intensity proton beam irradiation (1.91–2.5 MeV, 2 mA) is being commissioned at the SARAF (Soreq Applied Research Accelerator Facility) superconducting linear accelerator.In order to determine the conditions of LiLiT proton irradiation for BNCT and to tailor the neutron energy spectrum, a characterization of near threshold (~1.91 MeV) ⁷Li(p,n) neutrons is in progress based on Monte-Carlo (MCNP and Geant4) simulation and on low-intensity experiments with solid LiF targets. In-phantom dosimetry measurements are performed using special designed dosimeters based on CR-39 track detectors.     

The natBr(p,x)73,75Se nuclear processes: a convenient route for the production of radioselenium tracers relevant to amino acid labelling

A possible route for the production of no-carrier-added (n.c.a.) ⁷³Se (T_1/2=7.1 h) and ⁷⁵Se (120 d) is introduced. d,l-2-Amino-4-([⁷³Se]methyl-seleno) butanoic acid (d,l-[⁷³Se]selenomethionine) with an overall radiochemical yield of >40% could be prepared via a 3-step polymer-supported synthesis after successful separation of ⁷³Se from KBr targets. Excitation functions for the ^natBr(p,x) ^72,73,75Se processes were measured from threshold up to 100 MeV utilizing pellets of pressed KBr. Targets were irradiated at the NAC cyclotron with proton beams having primary energies of 40.4, 66.8 and 100.9 MeV. The calculated ⁷³Se yield (EOB) for 1 h irradiation in 1 μA of beam at the optimum proton energy range of 62→42 MeV is 81.4 MBq (2.2 mCi), and the calculated ⁷⁵Se yield (EOB) for the overall range 62 MeV→threshold for the same irradiation conditions is 0.97 MBq (0.026 mCi).     

Near-threshold 7Li(p,n)7Be neutrons on the practical conditions using thick Li-target and Gaussian proton energies for BNCT

The near threshold ⁷Li(p,n)⁷Be neutrons generated by incident proton energy having Gaussian distribution with mean energies from 1.85 to 1.95 MeV, were studied as a practical neutron source for BNCT wherein an RFQ accelerator and a thick Li-target are used. Gaussian energy distributions with the standard deviation of 0, 10, 20 and 40 keV for mean proton energies from 1.85 to 1.95 MeV were surveyed in 0.01 MeV increments. A thick liquid Li-target whose dimensions were established in our previous experiments (i.e., 1 mm-thick with 50 mm width and 50 mm length) was considered in this study. The suitable incident proton energy and physical dimensions of Pb layer which serves as a gamma absorber and a Polyethylene layer which is used as a BDE were surveyed by means of the concepts of TPD. Dose distribution were calculated by using MCNP5. A proton beam with mean energy of 1.92 MeV and a Gaussian energy distribution with a standard deviation of 20 keV at a current of 10 mA was selected from the viewpoint of irradiation time and practically achievable proton current. The suitable thicknesses of Pb gamma absorber was estimated to be about 3 cm. The estimated thickness of the polyethylene BDE was about 24 mm for an ideal proton current of 13 mA, and was 18 mm for a practical proton current of 10 mA.     

Assessment of radionuclidic impurities in cyclotron produced 99mTc

IntroductionThe commercial viability of cyclotron-produced ^99mTc as an alternative to generator-produced ^99mTc depends on several factors. These include: production yield, ease of target processing and recycling of ¹⁰⁰Mo, radiochemical purity, specific activity as well as the presence of other radionuclides, particularly various Tc radioisotopes that cannot be separated chemically and will remain in the final clinical preparation. These Tc radionuclidic impurities are derived from nuclear interactions of the accelerated protons with other stable Mo isotopes present in the enriched ¹⁰⁰Mo target. The aim of our study was to determine experimentally the yields of Tc radioisotopes produced from these stable Mo isotopes as a function of incident beam energy in order to predict radionuclidic purity of ^99mTc produced in highly enriched ¹⁰⁰Mo targets of known isotopic composition.MethodsEnriched molybdenum targets of ⁹⁵Mo, ⁹⁶Mo, ⁹⁷Mo, ⁹⁸Mo and ¹⁰⁰Mo were prepared by pressing powdered metal into an aluminum target support. The thick targets were bombarded with 10 to 24 MeV protons using the external beam line of the U-120 M cyclotron of the Nuclear Physics Institute, ?e?. The thick target yields of ⁹⁴Tc, ^94mTc, ⁹⁵Tc, ^95mTc, ^96m + gTc and ^97mTc were derived from their activities measured by γ spectrometry using a high purity Ge detector. These data were then used to assess the effect of isotopic composition of highly enriched ¹⁰⁰Mo targets on the radionuclidic purity of ^99mTc as a function of proton beam energy. Estimates were validated by comparison to measured activities of Tc radioisotopes in proton irradiated, highly enriched ¹⁰⁰Mo targets of known isotopic composition.ResultsThe measured thick target yields of ⁹⁴Tc, ^94mTc, ⁹⁵Tc, ^95mTc, ^96m + gTc and ^97mTc correspond well with recently published values calculated via the EMPIRE-3 code. However, the measured yields are more favourable with regard to achievable radionuclidic purity of ^99mTc. Reliability of the measured thick target yields was demonstrated by comparison of the estimated and measured activities of ⁹⁴Tc, ⁹⁵Tc, ^95mTc, and ^96m + gTc in highly enriched ¹⁰⁰Mo (99%) targets that showed good agreement, with maximum differences within estimated uncertainties. Radioisotopes ^94mTc and ^97mTc were not detected in the irradiated ¹⁰⁰Mo targets due to their low activities and measurement conditions; on the other hand we detected small amounts of the short-lived positron emitter ⁹³Tc (T_½ = 2.75 h). In addition to ^99mTc and trace amounts of the various Tc isotopes, significant activities of ⁹⁶Nb, ⁹⁷Nb and ⁹⁹Mo were detected in the irradiated ¹⁰⁰Mo targets.ConclusionsRadioisotope formation during the proton irradiation of Mo targets prepared from different, enriched stable Mo isotopes provides a useful data base to predict the presence of Tc radionuclidic impurities in ^99mTc derived from proton irradiated ¹⁰⁰Mo targets of known isotopic composition. The longer-lived Tc isotopes including ⁹⁴Tc (T_½ = 4.883 h), ⁹⁵Tc (T_½ = 20.0 h), ^95mTc (T_½ = 61 d), ^96m + gTc (T_½ = 4.24 d) and ^97mTc (T_½ = 90 d) are of particular concern since they may affect the dosimetry in clinical applications. Our data demonstrate that cyclotron production of ^99mTc, using highly enriched ¹⁰⁰Mo targets and 19–24 MeV incident proton energy, will result in a product of acceptable radionuclidic purity for applications in nuclear medicine.     

Excitation function of 122Te(d,n)123I nuclear reaction: production of 123I at a low energy cyclotron

The excitation function of the ¹²²Te(d, n)¹²³I nuclear reaction has been measured from threshold up to 21 MeV by the stacked foil irradiation technique. Good agreement was obtained with the results of the recent model calculations but an energy shift of 2 MeV to lower energy can be seen when comparing with cross section measured earlier. Integral yields have been deduced from the measured excitation function and have been compared with experimental thick target yields found in the literature. A comparison of the yields of the proton and deuteron induced reactions for production of ¹²³I is given.     

Evaluation of excitation functions of proton and deuteron induced reactions on enriched tellurium isotopes with special relevance to the production of iodine-124

Cross-section data for the production of medically important radionuclide ¹²⁴I via five proton and deuteron induced reactions on enriched tellurium isotopes were evaluated. The nuclear model codes, STAPRE, EMPIRE and TALYS, were used for consistency checks of the experimental data. Recommended excitation functions were derived using a well-defined statistical procedure. Therefrom integral yields were calculated. The various production routes of ¹²⁴I were compared. Presently the ¹²⁴Te(p,n)¹²⁴I reaction is the method of choice; however, the ¹²⁵Te(p,2n)¹²⁴I reaction also appears to have great potential.     

44gSc production using a water target on a 13 MeV cyclotron

IntroductionAccess to promising radiometals as isotopes for novel molecular imaging agents requires that they are routinely available and inexpensive to obtain. Proximity to a cyclotron center outfitted with solid target hardware, or to an isotope generator for the metal of interest is necessary, both of which can introduce significant hurdles in development of less common isotopes. Herein, we describe the production of ⁴⁴Sc (t_1/2 = 3.97 h, E_avg,β⁺ = 1.47 MeV, branching ratio = 94.27%) in a solution target and an automated loading system which allows a quick turn-around between different radiometallic isotopes and therefore greatly improves their availability for tracer development. Experimental yields are compared to theoretical calculations.MethodsSolutions containing a high concentration (1.44–1.55 g/mL) of natural-abundance calcium nitrate tetrahydrate (Ca(NO₃)₂ · 4 H₂O) were irradiated on a 13 MeV proton-beam cyclotron using a standard liquid target. ^44gSc was produced via the ⁴⁴Ca(p,n)^44gSc reaction.Results^44gSc was produced for the first time in a solution target with yields sufficient for early radiochemical studies. Saturation yields of up to 4.6 ± 0.3 MBq/μA were achieved using 7.6 ± 0.3 μA proton beams for 60.0 ± 0.2 minutes (number of runs n = 3). Experimental data and calculation results are in fair agreement. Scandium was isolated from the target mixture via solid-phase extraction with 88 ± 6% (n = 5) efficiency and successfully used for radiolabelling experiments. The demonstration of the production of ⁴⁴Sc in a liquid target greatly improves its availability for tracer development.     

Cross section measurements of proton and deuteron induced reactions on natural europium and yields of SPECT-relevant radioisotopes of gadolinium

The existing cross section data of the ^natEu(d,x) and ^natEu(p,x) reactions relevant for the production of ^147,149Gd were expanded up to 70.9 MeV and 44.8 MeV, respectively. Integral yields of radiogadolinium were calculated, showing production rates higher than for the earlier proposed irradiation of highly enriched ¹⁴⁴Sm with α- or ³He-particles. The formation of radioisotopic impurities like ¹⁵¹Gd (T_1/2=124 d) and ¹⁵³Gd (T_1/2=240 d) was below 5%. Production of ^147,149Gd using enriched europium is also discussed.     

Physical optimization of production by deuteron irradiation of high specific activity 177gLu suitable for radioimmunotherapy

Deuteron-induced nuclear reactions for generation of no-carrier-added (NCA) Lu isotopes were investigated using the stacked-foil activation technique on natural Yb targets at energies up to E_d = 18.18 MeV.The decay curve of ¹⁷⁷Yb, the growth curve of the cumulative (direct and indirect) and the direct production of ^177gLu were determined. The analysis of these curves conducts to the evidence that the predominant route for the production of ^177gLu is the indirect reaction ¹⁷⁶Yb(d,p)¹⁷⁷Yb, which decays to ^177gLu. In the spectra acquired one year from the EOB the γ lines of ^177mLu are not evident.A comparison between the calculated activity of ^177gLu produced with a cyclotron and with a nuclear reactor is given.     

Experimental study of the excitation functions of proton induced nuclear reactions on 167Er for production of medically relevant 167Tm

¹⁶⁷Tm (T_1/2=9.25 d) is a candidate radioisotope for medical therapy and diagnostics due to its Auger-electron and low-energy X- and gamma-ray emission. Excitation functions of the ¹⁶⁷Er(p,n)¹⁶⁷Tm reaction and ¹⁶⁸Er(p,n)¹⁶⁸Tm, ¹⁶⁷Er(p,2n)¹⁶⁶Tm, ¹⁶⁶Er(p,2n)¹⁶⁵Tm disturbing reactions were measured up to 15 MeV by using the stacked foil irradiation technique and gamma-ray spectroscopy. The measured excitation functions agree well with the results of ALICE-IPPE, EMPIRE-II and TALYS nuclear reaction model codes. The thick target yield of ¹⁶⁷Tm in the 15–8 MeV energy range is 6.9 MBq/μAh. A short comparison of charged particle production routes of ¹⁶⁷Tm is given.     

Cross sections for 13.5–14.7 MeV neutron induced reactions on palladium isotopes

Cross sections for (n, p), (n, α) and (n, 2n) reactions have been measured on palladium isotopes at 13.5–14.7 MeV using the activation technique. Data are reported for the following reactions: ¹⁰²Pd(n, p)^102mRh, ¹⁰²Pd(n, p)^102gRh, ¹⁰⁵Pd(n, p)¹⁰⁵Rh, ¹⁰⁶Pd(n, p)¹⁰⁶Rh; ¹⁰⁶Pd(n, α)¹⁰³Ru, ¹⁰⁸Pd(n, α)¹⁰⁵Ru; ¹⁰²Pd(n, 2n)¹⁰¹Pd and ¹¹⁰Pd(n, 2n)¹⁰⁹Pd.     

Measurements of 186Re production cross section induced by deuterons on natW target at ARRONAX facility

IntroductionThe ARRONAX cyclotron, acronym for “Accelerator for Research in Radiochemistry and Oncology at Nantes Atlantique” is a new facility installed in Nantes, France. A dedicated program has been launched on production of innovative radioisotopes for PET imaging and for β − and α targeted radiotherapy using protons or α particles. Since the accelerator is also able to deliver deuteron beams up to 35 MeV, we have reconsidered the possibility of using them to produce medical isotopes. Indeed, in some cases, the use of deuterons allows higher production yield than protons.Methods¹⁸⁶Re is a β − emitter which has chemical properties close to the widely used ^99mTc and has been used in clinical trials for palliation of painful bone metastases resulting from prostate and breast cancer. ¹⁸⁶Re production cross section has been measured between 9 and 23 MeV using the ARRONAX deuteron beam and the stacked-foil technique.A novelty in our work is the use of a monitor foil behind each ^natW target foil in order to record efficiently the deuteron incident flux and energies all over the stack relying on the International Atomic Energy Agency (IAEA) recommended cross section of the ^natTi(d,x)⁴⁸V reaction. Since a good optimization process is supposed to find the best compromise between production yield and purity of the final product, isotope of interest and contaminants created during irradiation are measured using gamma spectrometry.ResultsOur new sets of data are presented and compared with the existing ones and with results given by the TALYS code calculations. The thick target yield (TTY) has been calculated after the fit of our experimental values and compared with the IAEA recommended ones.ConclusionsPresented values are in good agreement with existing data. The deuteron production route is clearly the best choice with a TTY of 7.8 MB/μAh at 30 MeV compared to 2.4 MBq/μAh for proton as projectile at the same energy. The TALYS code gives satisfactory results for ^183,186Re isotopes.     

Experimental studies and nuclear model calculations on proton induced reactions on manganese up to 45 MeV with reference to production of 55Fe, 54Mn and 51Cr

Excitation functions of the reactions ⁵⁵Mn(p,n)⁵⁵Fe, ⁵⁵Mn(p,x)⁵⁴Mn and ⁵⁵Mn(p,x)⁵¹Cr were measured from their respective thresholds up to 18 MeV in the first case and up to 45 MeV in the latter two cases, using the conventional stacked-foil technique. The radioactivity of ⁵⁵Fe was determined via high resolution X-ray spectrometry and of other radionuclides via high resolution γ-ray spectrometry. Nuclear model calculations were performed using the codes ALICE-IPPE, EMPIRE and TALYS. In some cases, good agreement was found between the experimental and theoretical data while in others considerable deviations were observed. From the experimental data the expected integral yields of the three investigated radionuclides were calculated.     

Radiochemical determination of cross sections of α-particle induced reactions on 192Os for the production of the therapeutic radionuclide 193mPt

For determination of cross sections of α-particle induced reactions on 99.65% enriched ¹⁹²Os, the methods for electrolytic preparation of thin samples and radiochemical separation of radioplatinum were optimized. The excitation functions of the ¹⁹²Os(α,n)^195mPt and ¹⁹²Os(α,3n) ^193mPt reactions were measured from 20 to 39 MeV. The cross section of the latter reaction reaches a maximum value of about 1.5 b at an energy around 36 MeV. The results of nuclear model calculations using the codes TALYS and STAPRE agreed well with the measured data. The optimum energy range for the production of no-carrier-added ^193mPt (T_1/2=4.33 d) was found to be E_α=40→30 MeV. The thick target yield amounts to 10 MBq/μA h and a possible batch yield of 2 GBq should be sufficient for Auger electron therapy on a wide scale.     

124I-Epidepride: A PET radiotracer for extended imaging of dopamine D2/D3 receptors

ObjectivesA new radiotracer, ¹²⁴I-epidepride, has been developed for the imaging of dopamine D2/3 receptors (D2/3Rs). ¹²⁴I-Epidepride (half-life of ¹²⁴I = 4.2 days) allows imaging over extended periods compared to ¹⁸ F-fallypride (half-life of ¹⁸ F = 0.076 days) and may maximize visualization of D2/3Rs in the brain and pancreas (allowing clearance from adjacent organs). D2/3Rs are also present in pancreatic islets where they co-localize with insulin to produce granules and may serve as a surrogate marker for imaging diabetes.Methods¹²⁴I-Epidepride was synthesized using N-[[(2S)-1-ethylpyrrolidin-2-yl]methyl]-5-tributyltin-2,3-dimethoxybenzamide and ¹²⁴I-iodide under no carrier added condition. Rats were used for in vitro and in vivo imaging. Brain slices were incubated with ¹²⁴I-epidepride (0.75 μCi/cc) and nonspecific binding measured with 10 μM haloperidol. Autoradiograms were analyzed by OptiQuant. ¹²⁴I-Epidepride (0.2 to 0.3 mCi, iv) was administered to rats and brain uptake at 3 hours, 24 hours, and 48 hours post injection was evaluated.Results¹²⁴I-Epidepride was obtained with 50% radiochemical yield and high radiochemical purity (> 95%). ¹²⁴I-Epidepride localized in the striatum with a striatum to cerebellum ratio of 10. Binding was displaced by dopamine and haloperidol. Brain slices demonstrated localization of ¹²⁴I-epidepride up until 48 hours in the striatum. However, the extent of binding was reduced significantly.Conclusions¹²⁴I-Epidepride is a new radiotracer suitable for extended imaging of dopamine D2/3 receptors and may have applications in imaging of receptors in the brain and monitoring pancreatic islet cell grafting.