Fading characteristics of an alanine-polystyrene dosimeter

Alanine dosimetry is useful for transfer dosimetry by long distance mailing, because of its stability. It has the advantage that the measurement of electron spin resonance (ESR) spectral signal is non-destructive to the dosimeter, with the promise that the method may supply archival dosimetry data, depending on the degree of post-irradiation stability of the signal. The effects of temperature during irradiation and storage on fading of the ESR signal were studied using an alanine dosimeter molded with polystyrene (alanine-PS dosimeter). This investigation covered a long range of storage time (up to 160 days) after irradiation to absorbed doses in the range 1 to 100 kGy, for application to transfer dosimetry between Japan and neighboring Asian countries.Dose response of an alanine-PS dosimeter depends on the temperature during irradiation. The same temperature coefficient of +0.24%/°C was measured at different dose levels of 1, 10 and 100 kGy administered at a constant dose rate of 7 kGy/h. Fading of the dose response was measured under storage at various temperatures (5–40°C). The fading curve generally has two phases with fast and slow fading rates. The response of an alanine dosimeter is relatively stable for doses of 1.4 and 14 kGy, when stored at temperatures below 25°C. However, the degree of fading was roughly 3 and 5% under a storage temperature of 40°C for 5 and 100 days, respectively, after irradiation to 14 kGy. The fading percentages at 100 kGy were 2 and 4% (after 5 days) and 6 and 15% (after 100 days) under the storage temperature of 25 and 40°C, respectively. The fading rates have a relatively small dependence on irradiation temperature. This is observed even when irradiation are made at high temperatures (60°C) and for the doses 100 kGy and above. The mechanism of decay of radicals is discussed to explain the fading characteristics of the two phases of fading. The alanine-PS dosimeter is useful for transfer standard dosimetry up to a dose level of 10 kGy when stored after irradiation at temperature below 40°C. However, consideration of temperature effects during and after irradiation is vital for accurate transfer dosimetry of high doses, especially in the southern Asian countries.     

Effects of temperature,relative humidity,and dose rate on the sensitivity of cellulose triacetate dosimeters to electrons and γ-rays

Cellulose triacetate (CTA) films are useful dosimeters for radiation processing with γ rays and electron beams, and are usually analyzed by u.v. spectrophotometry. The radiation sensitivity of CTA film material increases linearly with both temperature (around room temperature) and relative humidity (between 20 and 80% r.h.) when irradiated at lower dose rates typical for ⁶⁰Co γ-ray irradiation (< 100 kGy h⁻¹). On the other hand, the response depends neither on temperature up to 45°C nor on relative humidity of the surrounding atmosphere during irradiation at high dose rates above 1 MGy h⁻¹, which are typical for electron irradiation. In fact, the extent of temperature dependence and humidity of response are markedly influenced by dose rate. There are also appreciable influences of temperature and relative humidity changes during the post-irradiation storage, but in this case there is no difference of storage effect for different dose levels. The thickness of CTA film influences the dose-rate dependence in the range between 10 kGy h⁻¹ and 1 MGy h⁻¹, but not the dependence on temperature during irradiation. Other environmental influences on the sensitivity were also examined, for the purpose of evaluating systematic uncertainties due to these effects in practical dosimetry.     

Thermal Radiosensitization in CHO Cells by Prior Heating at 41–46°C

Summary

CHO cells were exposed to heat at temperatures ranging from 41°C to 46°C followed by irradiation on ice with graded doses of X-rays. The dose–response curves obtained were analysed in terms of D_10%, D₀ and Dq and thermal enhancement was expressed by the corresponding values TER_10%, TEF and TEQ, respectively. TER_10% and TEF were shown to increase linearly with heating time, the increase being steeper at higher temperatures. The dose–response curves were also analysed using the equation ? ln(S/S₀) = αD + βD²; the values of α and β obtained from curve-fitting were found to increase with heating time. For temperatures below 43°C the relative increase in α was greater than that in β; the Arrhenius activation energies were E_a = 890 kJ mol^?1 for α and E_a = 1830 kJ mol^?1 for β. At temperatures exceeding 43°C the relative increase of α and β was similar and the corresponding activation energies were about the same (E_a ≈ 700 kJ mol^?1). The increase in the α-term was attributed to a depressed repair of double-strand breaks, whereas the increase of β was assumed to be a consequence of an insufficient repair of base damage.     

A polymer-alanine film for measurements of radiation dose distributions

A film dosimeter (0.35 mm thick) composed of polyethylene-vinyl acetate and microcrystalline l-α-alanine has been prepared and investigated with respect to dosimetric properties using electron spin resonance spectroscopy. The useful absorbed dose range is ∼ 25 to 10⁵ Gy and no dose-rate dependence of the response is observed between 1 and 10⁷ Gy s⁻¹ within the dose range up to 50 kGy. With irradiation temperature increasing from 25 to 80°C, the response increases at most by 10%. The response is stable, within experimental uncertainty, at least up to 2500 h after irradiation. The suitability of the polymer-alanine film for measurements of ionizing photon and electron dose distributions is demonstrated.     

Investigation of cobalt-60-labelled cobalt pyrrolidinedithiocarbamate as a chemical dosimeter

A ground-stoppered glass tube filled with 5.00 ml of 1.0 × 10⁻⁴ M ⁶⁰Co(PDC)₃/CHCl₃ layered with 3.00 ml of pure water was used as a γ dosimeter. The G(Co²⁺) value was found to be 1.60 ± 0.09. The effective working range was from approx. 50 to approx. 40,000 rad.     

A search for novel thermoluminescent radiation dosimeter media

We describe two example pilot efforts to help define new thermoluminescent dosimeter media. The first concerns ZnS:Mn nanophosphors, prepared by chemical precipitation using zinc and sodium sulfate, doped with manganese sulfate at concentrations varying from 1 to 3 mol. The second concerns chemical vapor deposited diamond, produced as a thin film or as amorphous carbon on a single-crystal silicon substrate, each deposited under the same conditions, use being made of the hot filament-chemical vapor deposition (HFCVD) technique. The gas concentrations used were 1% CH₄ in 99% H₂ and 25% CH₄ in 75% H₂. Characterization of formations used FESEM, XRD and EDX. The nanophosphors consisted of particles of sizes in the range 85–150 nm, the thermoluminescence (TL)-based radiation detection medium giving rise to a single peaked glow curve of maximum yield at a temperature of 250 °C at a heating rate of 5 °C/s. The TL response increased linearly with radiation dose, ZnS doped to 2 mol of Mn being found the most sensitive. Regarding chemical vapor deposited (CVD) carbon, inappreciable TL was found for the resultant ball-like amorphous carbon films, graphite, and the silicon substrate, whereas CVD diamond films showed a promising degree of linearity with dose. For both the ZnS and diamond samples, TL signal fading was appreciable, being some 40% per day for ZnS and>50% per day for CVD films even under storage in the dark at room temperature, making it apparent that there is need to adjust parameters such as the size of nanoparticles.     

The gamma-ray response of clear polymethylmethacrylate dosimeter radix RN15®

Basic characteristics of different batches of Radix RN15® dosimeter, a commercially available undyed polymethylmethacrylate dosimeter, was studied for its application to process control of radiation sterilization. Radix has relatively small deviation of thickness, optical absorption spectrum, and optical density values before irradiation. The response curves, in terms of net optical density per unit thickness (ΔOD/mm) as a function of absorbed dose, D_PMMA, are nearly linear up to 15 kGy and become sublinear at higher doses. Scattering of dose response in 5 dosimeter replicates is ± 1% (1 σ). The dose-response slope at 25 kGy while held at irradiation temperatures in the range 0–60°C, relative to those under 25°C, increases with temperature up to 40°C, the maximum point, and decreases at higher temperatures. Over the temperature range of 10–50°C, the variation with temperature of evaluated dose derived from the calibration curve at 25°C is less than 5% when using a dose rate of 6 kGy/h. At lower dose rates (e.g. 0.7 kGy/h) the irradiation temperature dependence is negligible over this temperature range. The temperature dependence at 40 kGy is less severe than that at 25 kGy. The post-irradiation stability of dose response is less than 5% for more than 100 h after 25 kGy irradiation and storage at 0–35°C. The change in optical density of unirradiated dosimeters 3 years after manufacturing is negligible when the dosimeters are stored at controlled laboratory conditions of temperature (25°C) and relative humidity (40%). The 3-year-old dosimeters by irradiation to a dose of 25 kGy show about 2% lower response than that at 25 kGy at the beginning of the 3-year period.     

Production of LiF:Ti thermoluminescence dosimeter material

Titanium (Ti) doped LiF:Ti thermoluminescent crystals were prepared and their dosimetric properties were studied. They showed different thermoluminescence sensitivies with increasing amounts of Ti dopings, reaching maximum for 400 ppm in LiF. In the glow curves of all samples, two peaks at 140°C and 210°C were observed. The stability of the traps connected with these peaks were studied for a period of one month. Dose-response and energy dependence properties of the stable 210°C peak were investigated between dose ranges of 200 mR and 200 R and 50 mR and 100 R for ¹³⁷Cs γ rays and x-rays respectively. Dose-response curves were found to be linear in these ranges. The energy dependence was 1.7% between 33 and 662 keV when the thermoluminescent responses were normalized to ¹³⁷Cs γ rays. It is suggested that LiF:Ti (400 ppm) may be used as a personnel dosimeter.     

Men's lacrosse protective equipment increases strain during exercise in the heat

ObjectivesThe purpose of this study was to determine thermoregulatory and cardiovascular effects of wearing men's lacrosse protective equipment during simulated lacrosse activities in the heat.DesignWe conducted a randomized, controlled, crossover study.MethodsThirteen healthy men (22 ± 3 y, 76.2 ± 8.9 kg, 181 ± 6 cm, 16.06 ± 6.16% body fat) completed two matched exercise trials in the heat (WBGT: 25.5 ± 0.8 °C). In randomized order, participants donned full men's lacrosse equipment (helmet, shoulder/elbow pads, and gloves) in one trial while the other included no equipment. Participants completed a topography body scan to determine specific body surface area covered with equipment. Rectal temperature (T_re), heart rate (HR), and mean weighted skin temperature (T_sk) were measured throughout trials. Whole body sweat rate was assessed for trial comparisons.ResultsThe equipment covered 32.62 ± 2.53% body surface area in our participants. Post-exercise T_re was significantly greater with equipment (39.36 ± 0.04 °C) compared to control (38.98 ± 0.49 °C; p = .007). The overall rate of rise of T_re was significantly greater with equipment (0.043 ± 0.015 °C·min⁻¹) compared to control (0.031 ± 0.008 °Cmin⁻¹; p = .041). Regardless of time point, HR and T_sk were significantly elevated with equipment compared to control trial (p ≤ .026). Sweat rates were elevated with equipment (1.76 ± 0.74 L·h⁻¹) compared to shorts and t-shirt (1.13 ± 0.26 L·h⁻¹), but this difference was not significant (p = .058).ConclusionsOur data indicate impairments in heat dissipation and increased cardiovascular strain imposed by men's lacrosse equipment.     

Effect of Silver ions in dichromate dosimetry

Dichromate solutions containing silver ions have been investigated for use in dosimetry. The marked effect of hydrogen on the ⁶⁰Co γ radiation-induced reduction of potassium dichromate solutions is completely inhibited by 1 × 10⁻³ M silver nitrate. A silver nitrate concentration of 1 × 10⁻⁴ M significantly improves the linearity and precision of response of dichromate to radiation, probably by inhibiting impurity effects as well as the hydrogen effect. G(−Cr₂O⁻²₇) values are given for a number of solutions containing different concentrations of silver and dichromate ions and sulphuric acid, for the measurement of doses up to 10 Mrad. The G(−Cr₂O²⁻₇) value decreases with increasing silver ion concentration and increases with increasing dichromate ion concentration. No difference was found between the response of solutions prepared using singly distilled water and those using triply distilled water. Simple empirical equations are given for the calculation of dose from the absorbance of solutions. The mean error for doses in the range 0.3–4.2 Mrad, estimated with solutions containing 1 × 10⁻⁴ M silver nitrate, was ± 1.5%; for doses of 1–9 Mrad from solutions containing 1 × 10⁻³ M silver nitrate, the mean error was ± 0.9%. Spectrophotometry at 350 nm on an undiluted solution of 4 × 10⁻⁴ M K₂Cr₂O₇/1 × 10⁻⁴ M AgNO₃/0.4 M H₂SO₄ allows measurements in the range 0.08 to 0.80 Mrad; the G(−Cr₂O²⁻₇) value for this solution was 0.37 ± 0.001.     

A new dosimeter based on ferrous sulphate solution and agarose gel

A new dosimeter made of ferrous sulphate solution and agarose gel has been developed. Due to a chain reaction in the agarose gel the sensitivity of the ferrous sulphate dosimeter is increased substantially. A G(Fe³⁺)-value up to almost 180 (100 eV)⁻¹ can be achieved. The G(Fe³⁺)-value and the linear dose response are dependent on the initial ferrous ion concentration. This dosimeter also has a uniform sensitivity over large volumes. The concentration of sulphuric acid has only minor influence on the sensitivity.     

High level γ-dosimetry using CaSO4: Dy phosphor with high dy-concentration

It has been observed that the thermoluminescent traps in CaSO₄:Dy phosphor with a high concentration of activator (2.0 mol% Dy) compared to that of normal samples (containing 0.05 mol% Dy) show a better stability and a lesser tendency towards saturation to γ-radiation. This effect has been observed for the main dosimetric peak (∼225°C) as well as for the high temperature peak (∼390°C). Thus by using 390°C TL peak in CaSO₄:Dy (2.0 mol%) we were able to make high level γ dose measurements in the range from 2 × 10² to 3 × 10⁶ Gy. The 390°C TL peak in CaSO₄:Dy (2.0 mol%) samples increases non-linearly with dose and does not show any tendency towards saturation at least up to 3 × 10⁶ Gy— the dose level studied. However, the corresponding high temperature peak in the normal samples (0.05 mol% Dy) shows saturation in its TL response above a γ-dose of 1.18 × 10⁶ Gy. In addition, a high temperature TL peak at 572°C which is only observed for the high activator concentration sample (as reported in our earlier work⁽¹¹⁾ increases non-linearly with dose and does not show saturation up to the γ-dose of 3 × 10⁶ Gy. Investigations on photo-transferred TL of high temperature peaks as a function of γ-dose were also carried out for both the types of samples.     

Constant ambient temperature of 24°C significantly reduces FDG uptake by brown adipose tissue in children scanned during the winter

Purpose  The aim of this study was to determine if warming patients prior to and during ¹⁸F-FDG uptake by controlling the room temperature could decrease uptake by brown adipose tissue (BAT). Methods  A group of 40 children underwent ¹⁸F-FDG PET after being kept in the injection room at a constant temperature of 24°C for half an hour before and 1 hour after intravenous tracer administration. The rate of uptake by BAT in this group was compared to the uptake in a control group of 45 patients who underwent PET when the injection room temperature was 21°C. Results  Uptake by BAT occurred in 5% of studies in the temperature-controlled room compared to 31% of studies performed when the injection room temperature was 21°C (p<0.002). Conclusion  Maintaining room temperature at a constant 24°C, half an hour prior to and during the period of FDG uptake significantly decreases accumulation of FDG in BAT in children.     

Aerobic fitness as a parameter of importance for labour loss in the heat

ObjectivesTo derive an empirical model for the impact of aerobic fitness (maximal oxygen consumption; V̇O_2max in mL∙kg⁻¹∙min⁻¹) on physical work capacity (PWC) in the heat.DesignProspective, repeated measures.MethodsTotal work completed during 1 h of treadmill walking at a fixed heart rate of 130 b∙min⁻¹ was assessed in 19 young adult males across a variety of warm and hot climate types, characterised by wet-bulb globe temperatures (WBGT) ranging from 12 to 40 °C. For data presentation and obtaining initial parameter estimates for modelling, participants were grouped into low (n = 6, 74 trials), moderate (n = 8, 76 trials), and high (n = 5, 29 trials) fitness, with group mean V̇O_2max 42, 52, and 64 mL∙kg⁻¹∙min⁻¹_, respectively. For the heated conditions (WBGT 18 to 40 °C), we calculated PWC% by expressing total energy expenditure (kJ above resting) in each trial relative to that achieved in a cool reference condition (WBGT = 12 °C = 100% PWC).ResultsThe relative reduction in energy expenditure (PWC%) caused by heat was significantly smaller by up to 16% for the fit participants compared to those with lower aerobic capacity. V̇O_2max also modulated the relationship between sweat rate and body temperature changes to increasing WBGT. Including individual V̇O_2max data in the PWC prediction model increased the predicting power by 4%.ConclusionsIncorporating individual V̇O_2max improved the predictive power of the heat stress index WBGT for Physical Work Capacity in the heat. The largest impact of V̇O_2max on PWC was observed at a WBGT between 25 and 35 °C.     

Reactions of OH Radicals with Poly(U) in Deoxygenated Solutions: Sites of OH Radical Attack and the Kinetics of Base Release

Summary

Pulse radiolysis of N₂O-saturated solutions of poly(U) in the presence of tetranitromethane showed that 81 per cent of the radicals formed are reducing in nature. Using data from other sources it has been estimated that 70 per cent of the OH radicals add to the base at C(5) and 23 per cent at C(6) while only 7 per cent abstract an H-atom from the sugar moiety. To a large extent the C(5) OH adduct radicals attack the sugar moiety of poly(U) thereby inducing strand breakage and base release. G (base release) = 2·9 can be subdivided into three components: (a) immediate (20 per cent), (b) fast (50 per cent) and (c) slow (30 per cent). The immediate base release must occur either during the free-radical stage or as a result of the rapid (t_½ < 4 min at 0°C) decomposition of a diamagnetic product. The fast and the slow processes are only readily observable at elevated temperatures, e.g. at 50°C the half lives are 83 min and 26 h, respectively (E_a (fast) = 68 kJ mol^?1, E_a (slow) = 89 kJ mol^?1, A (fast) = 1·5 × 10⁷ s^?1, A (slow) = 1·9 × 10⁹ s^?1. It is concluded that there are three different types of sugar lesions giving rise to base release, structures for which are tentatively proposed.     

Linear DNA Elution Dose Response Curves Obtained in CHO Cells with Non-unwinding Filter Elution after Appropriate Selection of the Lysis Conditions

Summary

The effect of detergent type, pH and temperature during lysis on the DNA elution dose response was studied under non-winding conditions in exponentially growing, plateau-phase and synchronous S-phase CHO cells. Lysis with sodium-N-laurylsarcosine (NLS) increased the DNA elution rate and resulted in higher DNA elution for the same absorbed radiation dose than lysis with sodium dodecyl sulphate (SDS). This increase in elution caused a reduction in the shoulder width of the DNA elution dose-response curve, but did not significantly affect the final slope. One hour incubation at elevated temperatures (60°C) during lysis either with NLS or SDS further increased DNA elution. Under these conditions DNA elution dose-response curves with a small or zero shoulder were obtained with exponentially growing, plateau-phase or synchronized S-phase cells. DNA elution was reduced to about 50 per cent of the controls when the pH of the SDS lysis solution was adjusted from 9·6 to 7·6. This effect was observed in cells that were lysed at room temperature, as well as in cells lysed at 60°C. When NLS was used for lysis, a similar reduction in pH did not alter the DNA elution dose-response curve at either lysis temperature. Based on these results it is suggested that the shoulder observed in the DNA elution dose-response curve reflects partial separation of DNA from associated proteins. A direct and unconditional correlation of the DNA filter elution behaviour, as observed under non-unwinding conditions, with the induction of DNA dsb may thus not always be justified. Caution is required when elution results are used to establish correlations between the level of induction of DNA dsb and cell killing.     

Absolute temperature MR imaging with thulium 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetramethyl‐1,4,7,10‐tetraacetic acid (TmDOTMA−)

MR thermometry based on the water ¹H signal provides high temporal and spatial resolution, but it has low temperature sensitivity (～0.01 ppm/°C) and requires monitoring of another weaker signal for absolute temperature measurements. The use of the paramagnetic lanthanide complex, thulium 1,4,7,10‐ tetraazacyclo‐dodecane‐1,4,7,10‐tetramethyl‐1,4,7,10‐tetraac‐ etate (TmDOTMA^?), which is ～60 times more sensitive to temperature than the water ¹H signal, is advanced to image absolute temperatures in vivo using water signal as a reference. The temperature imaging technique was developed using gradient echo and asymmetric spin echo imaging sequences on 9.4 Tesla (T) horizontal and vertical MR scanners. A comparison of regional temperatures measured with TmDOTMA^? and fiber‐optic probes showed that the accuracy of imaging temperature is <0.3°C. The temperature imaging technique was found to be insensitive to inhomogeneities in the main magnetic field. The feasibility of imaging temperature of intact rats at ～1.4 mmol/kg dose with ～1‐mm spatial resolution in only 3 min is demonstrated. TmDOTMA^? should prove useful for imaging absolute temperatures in deep‐seated organs in numerous biomedical applications. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Operation and methodology of an alanine ion-selective electrode dosimetric system: II. Dose-response

Dissolution of irradiated α-alanine in an aqueous solution results in the liberation and formation of ammonia, which can be quantified for dosimetric purposes by means of an ion-selective gas sensing electrode. The operational principles, readout procedure as well as data analysis were presented and discussed in a preceding paper. Here the dose-response (0.5–1000 kGy) by direct concentration measurements is evaluated. A total ammonia yield decreasing from 6.5 (±0.3) × 10⁻⁷ mol J⁻¹ (i.e. 6.3 (±0.3) molecules per 100 eV) at 1 kGy, to 2.9 (±0.1) × 10⁻⁷ mol J⁻¹ (2.8 (±0.1) per 100 eV) at 1000 kGy is observed. No significant fading at ambient temperature is found during the first 2 months, even at 1000 kGy. Irradiation temperature coefficients of +0.34 to +0.47%°C⁻¹ were measured, dependent on dose level, The precision in concentration measurement for one calibration is within 1%; long-term precision varies from 2 to 4% (95% conf. lim.) for doses above 1 kGy.     

Thermoluminescent response of single crystal Al2O3:Fe

Thermoluminescence characteristics of iron doped aluminum oxide (Al₂O₃:Fe) single crystals were studied. The glow curve of x- and γ-ray irradiated Al₂O₃:Fe single crystals while being heated up to 375°C consisted essentially of an intense isolated single peak at 193°C and small peaks at 250° and 285°C. But the study was carried out on 193°C peak because of the accuracy of measurements and the possibility of using it a thermoluminescence dosimeter. The trap depth and escape frequency factor were calculated to be 1.156 eV and 3.1 × 10¹¹ s⁻¹ respectively. Dose-response was investigated between dose ranges of 5 × 10² mR and 10⁴R for ¹³⁷Cs γ-rays. Dose-response was found to be linear in this range. The energy dependence was 5% between 33 and 662 keV when the thermoluminescent responses were normalized to ¹³⁷Cs γ-rays. It is suggested that Al₂O₃:Fe may be used as a γ radiation dosimeter in high dose environments such as oncology hospitals, radiobiological centers, nuclear reactors.     

Preclinical and first-in-man studies of [<Superscript>11</Superscript>C]CB184 for imaging the 18-kDa translocator protein by positron emission tomography

Objective

We performed preclinical and first-in-man clinical positron emission tomography (PET) studies in human brain using N,N-di-n-propyl-2-[2-(4-[¹¹C]methoxyphenyl)-6,8-dichloroimidazol[1,2-a]pyridine-3-yl]acetamide ([¹¹C]CB184) to image the 18-kDa translocator protein (TSPO), which is overexpressed in activated microglia in neuroinflammatory conditions.

Methods

In vitro selectivity of CB184 was characterized. The radiation absorbed dose by [¹¹C]CB184 in humans was calculated from murine distribution data. Acute toxicity of CB184 hydrochloride in rats at a dose of 5.81 mg/kg body weight, which is >10,000-fold higher than the clinical equivalent dose of [¹¹C]CB184, was evaluated. Acute toxicity of [¹¹C]CB184 injection of a 400-fold dose to administer a postulated dose of 740 MBq [¹¹C]CB184 was also evaluated after the decay-out of ¹¹C. The mutagenicity of CB184 was studied with a reverse mutation test (Ames test). The pharmacological effect of CB184 injection in mice was studied with an open field test. The first PET imaging of TSPO with [¹¹C]CB184 in a normal human volunteer was performed.

Results

A suitable preparation method for [¹¹C]CB184 injection was established. CB184 showed low activity in a 28-standard receptor binding profile. The radiation absorbed dose by [¹¹C]CB184 in humans was sufficiently low for clinical use, and no acute toxicity of CB184 or [¹¹C]CB184 injection was found. No mutagenicity or apparent effect on locomotor activity or anxiety status was observed for CB184. We safely performed brain imaging with PET following administration of [¹¹C]CB184 in a normal human volunteer. A 90-min dynamic scan showed rapid initial uptake of radioactivity in the brain followed by prompt clearance. [¹¹C]CB184 was homogeneously distributed in the gray matter. The total distribution volume of [¹¹C]CB184 was highest in the thalamus followed by the cerebellar cortex and elsewhere. Although regional differences were small, the observed [¹¹C]CB184 binding pattern was consistent with the TSPO distribution in normal human brain. Peripherally, [¹¹C]CB184 was metabolized in humans: 30 % of the radioactivity in plasma was detected as the unchanged form after 60 min.

Conclusions

[¹¹C]CB184 is suitable for imaging TSPO in human brain and provides an acceptable radiation dose. Pharmacological safety was noted at the dose required for PET imaging.