Indoor 222Rn measurements using an activated charcoal detector

A commercially available activated charcoal detector for measuring ²²²Rn activity concentrations in air was calibrated with known amounts of ²²²Rn and examined in terms of air luminescence counts and interferences from ²²⁰Rn and ²¹⁹Rn. The results for conditions normally encountered indoor indicate that the detector is simple and reliable. The method has been applied to assay indoor ²²²Rn activity concentrations in 387 homes in Tokyo and the adjacent four prefectures, which ranged from 0.7 to 140 Bq/m³ and averaged 22.7 Bq/m³.     

238U, 235U, 137Cs and 133Xe in soils from two campuses in University of Douala—Cameroon

An evaluation of ²³⁸U, ²³⁵U, ¹³⁷Cs and ¹³³Xe in soils from two campuses in University of Douala—Cameroon using gamma spectroscopy based Broad Energy Germanium Detector (BEGe6530) has been performed. The mean activities in soils from Campuse 1 were 40.16±8.98 Bq/kg for ²³⁸U, 3.39±0.33 Bq/kg for ²³⁵U, 0.46±0.33 Bq/kg for ¹³⁷Cs and 0.14±0.16 Bq/kg for ¹³³Xe. In Campus 2, the mean activities in soils were 31.45±12.24 Bq/kg, 3.02±1.00 Bq/kg, 0.30±0.26 Bq/kg and 0.35±0.24 Bq/kg for ²³⁸U, ²³⁵U, ¹³⁷Cs and ¹³³Xe, respectively. Using the in situ survey meter, the mean values of the absorbed dose rate measured was 71.43 nGy/h for Campus 1 and 62.72 nGy/h for Campus 2. The evaluated average outdoor effective dose for Campus 1 and 2 were 87.60 µSv/yr and 76.93 µSv/yr, respectively. The overall results obtained in this work were generally low compared to that of UNSCEAR.     

Distribution of naturally occurring radionuclides activity concentration in East Malaysian marine sediment

Studies of naturally occurring radioactive materials (NORM) distribution of ²²⁶Ra, ²²⁸Ra and ⁴⁰K in East Malaysia were carried out as part of a marine coastal environment project. The results of measurements will serve as baseline data and background reference level for Malaysia coastlines. Sediments from 21 coastal locations and 10 near shore locations were collected for analyses. The samples were dried, finely ground, sealed in a container and stored for a minimum of 30 days to establish secular equilibrium between ²²⁶Ra and ²²⁸Ra and their respective radioactive progenies. They were counted using a high-purity germanium (HPGe) spectrometer covering the respective progeny energy peak. For ⁴⁰K, the presence of this was measured directly via its 1460 keV energy peak. The concentration of ²²⁶Ra, ²²⁸Ra and ⁴⁰K in samples obtained from coastal Sarawak ranged between 23 and 41 (mean 30±2) Bq/kg, 27 and 45 (mean 39±4) Bq/kg and 142 and 680 (mean 462±59) Bq/kg, respectively. Meanwhile, the concentration of ²²⁶Ra, ²²⁸Ra and ⁴⁰K for samples obtained from coastal Sabah ranged between 16 and 30 (mean 23±2) Bq/kg, 23 and 45 (mean 35±4) Bq/kg and 402 and 842 (mean 577±75) Bq/kg, respectively. For the Sarawak near shore stations, the concentration of ²²⁶Ra, ²²⁸Ra and ⁴⁰K ranged between 11 and 36 (mean 22±2) Bq/kg, 21 and 65 (mean 39±5) Bq/kg and 149 and 517 (mean 309±41) Bq/kg, respectively. Meanwhile, the concentration of ²²⁶Ra, ²²⁸Ra and ⁴⁰K for samples obtained from Sabah ranged between 9 and 31 (mean 14±2) Bq/kg, 10 and 48 (mean 21±3) Bq/kg and 140 and 580 (mean 269±36) Bq/kg, respectively. The calculated external hazard values of between 0.17 and 0.33 (less than unity) showed that there is little risk of external hazard to the workers handling the sediments.     

Effect of co-ligands on chemical and biological properties of 99mTc(III) complexes [99mTc(L)(CDO)(CDOH)2BMe] (L = Cl,F, SCN and N3; CDOH2 = cyclohexanedione dioxime)

Introduction^99mTc-Teboroxime ([^99mTcCl(CDO)(CDOH)₂BMe]) is a member of the BATO (boronic acid adducts of technetium dioximes) class of ^99mTc(III) complexes. This study sought to explore the impact of co-ligands on solution stability, heart uptake and myocardial retention of [^99mTc(L)(CDO)(CDOH)₂BMe] (^99mTc-Teboroxime: L = Cl; ^99mTc-Teboroxime(F): L = F; ^99mTc-Teboroxime(SCN): L = SCN; and ^99mTc-Teboroxime(N₃): L = N₃).MethodsRadiotracers ^99mTc-Teboroxime(L) (L = F, SCN and N₃) were prepared by reacting ^99mTc-Teboroxime with NaF, NaSCN and NaN₃, respectively. Biodistribution and imaging studies were carried out in Sprague–Dawley rats. Image quantification was performed to compare their heart retention and liver clearance kinetics.ResultsComplexes ^99mTc-Teboroxime(L) (L = F, SCN and N₃) were prepared in high yield with high radiochemical purity. All new radiotracers were stable for > 6 h in the kit matrix. In its HPLC chromatogram, ^99mTc-Teboroxime showed one peak at ~ 15.5 min, which was shorter than that of ^99mTc-Teboroxime(F) (~ 16.4 min). There were two peaks for ^99mTc-Teboroxime(SCN) at 16.5 and 18.3 min. ^99mTc-Teboroxime(N₃) appeared as a single peak at 18.4 min. Their heart retention and liver clearance curves were best fitted to the bi-exponential decay function. The half-times of fast/slow components were 1.6 ± 0.4/60.7 ± 8.9 min for ^99mTc-Teboroxime, 0.8 ± 0.2/101.7 ± 20.7 min for ^99mTc-Teboroxime(F), 1.2 ± 0.3/84.8 ± 16.6 min for ^99mTc-Teboroxime(SCN), and 2.9 ± 0.9/51.6 ± 5.0 min for ^99mTc-Teboroxime(N₃). The 2-min heart uptake followed the order of ^99mTc-Teboroxime (3.00 ± 0.37%ID/g) > ^99mTc-Teboroxime(N₃) (2.66 ± 0.01 %ID/g) ≈ ^99mTc-Sestamibi (2.55 ± 0.46 %ID/g) > ^99mTcN-MPO (2.38 ± 0.15 %ID/g). ^99mTc-Teboroxime remains the best in first-pass extraction. The best image acquisition window is 0–5 min for ^99mTc-Teboroximine and 0–15 min for ^99mTc-Teboroximine(N₃).ConclusionCo-ligands had significant impact on the heart uptake and myocardial retention of complexes [^99mTc(L)(CDO)(CDOH)₂BMe] (L = Cl, F, SCN and N₃). Future studies should be directed towards minimizing the liver uptake and radioactivity accumulation in the blood vessels while maintaining their high heart uptake.     

Separation of 90Sr from radioactive waste matrices—Microwave versus fusion decomposition

Radioactive waste (slurry) from a detention pond deriving from two research reactors and several inactive and active drain outlets at the Paul Scherrer Institute are the basis for the current ⁹⁰Sr investigation. For decomposition, a microwave method was applied, where 1 g of dry-ashed slurry was partially dissolved (HNO₃ (65%)/H₂O₂ (30%); v:v=8:2). In this slurry we obtained an ⁹⁰Sr activity of 5.3±0.2 Bq/g in solution. In a second run, we applied a borate-fusion (Li metaborate/Li tetraborate (80:20 w/w%) dissolving 1 g of dry-ashed “Si-free” slurry at 1100 °C in a muffle furnace. We achieved an ⁹⁰Sr activity of (7.8±0.3) Bq/g, yet observing BaSO₄ precipitation during the chromatographical separation of Sr. An alkali fusion using Na₂CO₃ was done using the Bunsen burner and the muffle furnace for 20 min at 1000 °C, in combination. During formation of the hot glass, the surplus of Na₂CO₃, produced Na₂SO₄ and BaCO₃ in solid form. The hot glass was dissolved in deionised water, removing thus the SO₄²⁻ ions. Dissolving the residue directly in HNO₃, solves Ba as Ba(NO₃)₂ and thus we achieved over 80% of the ¹³³Ba activity in the solution, as measured by γ-spectrometry. ⁸⁵Sr tracer of 88.0%±3.3% was recovered, yielding on average in (7.4±0.3) Bq/g of ⁹⁰Sr activity. The increase of 2.1–2.5 Bq/g of ⁹⁰Sr activity achieved with the alkali fusion, and the Li metaborate/Li tetraborate 80:20 w/w% fusion, respectively, clearly shows that some Sr must have been present as SrSO₄ in the slurry.     

Spatial distributions of 137Cs and 239+240Pu in surface seawater within the Exclusive Economic Zone of East Coast Peninsular Malaysia

The studies of ¹³⁷Cs and ^239+240Pu distributions in surface seawater at South China Sea within the Exclusive Economic Zone (EEZ) of Peninsular Malaysia were carried out in June 2008. The analysis results will serve as additional information to the expanded baseline data for Malaysia’s marine environment. Thirty locations from extended study area were identified in the EEZ from which large volumes of surface seawater samples were collected. Different co-precipitation techniques were employed to concentrate cesium and plutonium separately. A known amount of ¹³⁴Cs and ²⁴²Pu tracers were used as yield determinant. The precipitate slurry was collected and oven dried at 60 ^oC for 1–2 days. Cesium precipitate was fine-ground and counted using gamma-ray spectrometry system at 661.62 keV, while plutonium was separated from other radionuclides using anion exchange, electrodeposited and counted using alpha spectrometry. The activity concentrations of ¹³⁷Cs and ^239+240Pu were in the range of 3.40–5.89 Bq/m³ and 2.3–7.9 mBq/m³, respectively. The ^239+240Pu/¹³⁷Cs ratios indicate that there are no new inputs of these radionuclides into the area.     

Presence of a radioactive gas in archaeological excavations,determination and mitigation

During recent archaeological discovery and excavation of a tunnel build approximately 2000 years ago by the Teotihuacans under the feathered serpent temple, in Mexico, abnormal radon concentrations up to 700 Bq m⁻³ were measured at several excavation stages. The tunnel is at 15 m below the earth surface with a vertical rectangular entrance of 4×4 m², a semi cylindrical shape of 3 m in diameter, with a probable length of 100 m.This study supports the assumption that at the opening of the tunnel radon concentration was around 5500 Bq m⁻³; however, although natural convection in the tunnel atmosphere naturally pups radon out, it build up to a maximum concentration of 2000 Bq m⁻³. This paper presents the identification of the radon problem in this archaeological site, dose determination, and the mitigation actions that reduced the radon concentration down to 40 Bq m⁻³ that ensure a negligible radon risk for archaeologist.     

How to assess the sensitivity and related uncertainty of a new solid state passive thoron measuring device

To test the sensitivity of our CR-39 alpha-track detector thoron passive device (ATD-TnPD), a closed-circuit exposure facility, composed by a new thoron source, a small exposure chamber and a new absolute ²²⁰Rn active monitor (TnM), was set up. ²²⁰Rn exposure was evaluated by assessing the TnM response and its combined uncertainty. The ATD-TnPD's sensitivity was determined by three thoron exposures, tested at different etching times. A non-linear relationship on etching conditions was obtained, with values in the range 1.54–1.76 (tracks cm²)(kBq h m⁻³)⁻¹.     

Pharmacokinetic Alteration of 99mTc-MAG3 using Serum Protein Binding Displacement Method

IntroductionWhen a radiopharmaceutical is simultaneously administered with a medicine that has high affinity for the same plasma protein, the radiopharmaceutical is released at higher concentrations in blood, leading to enhanced transfer into target tissues. This is known as the serum protein binding displacement method. In this study, we investigated the pharmacokinetic alteration of technetium-99m-labeled mercaptoacetylglycylglycylglycine (^99mTc-MAG3) using the serum protein binding displacement method.MethodsRat and human serum protein binding rates of ^99mTc-MAG3 were measured by ultrafiltration with or without displacers of human serum albumin (HSA) binding sites I and II (200 μM and 400 μM loading). Male Wistar rats were injected with ^99mTc-MAG3 (740 kBq/0.3 mL saline) via the tail vein, and biodistribution was assessed at 2, 5, 10 and 15 min. Dynamic whole-body images were obtained for ^99mTc-MAG3 (11.1 MBq/0.3 mL saline)-injected rats, with or without HSA displacers.Results^99mTc-MAG3 strongly bound to HSA (87.37%±2.13%). Using HSA site I displacers, the free fraction of ^99mTc-MAG3 increased significantly (1.20 to 1.47 times) when compared with controls. For biodistribution and imaging, rapid blood clearance was observed with bucolome (BCL) loading, which is an HSA site I displacer. With BCL loading, peak times for rat renograms were respectively shifted from 240 s to 110 s, and from 170 s to 120 s.ConclusionsWe found that ^99mTc-MAG3 bound to the HSA binding site I. It was confirmed that pharmacokinetic distribution of ^99mTc-MAG3 is altered by presence of BCL, which leads to increases in the free fraction of ^99mTc-MAG3, and BCL produced rapid blood clearance and fast peak times on rat renograms. The serum protein binding displacement method using ^99mTc-MAG3 and BCL, a safe displacer for humans, may be applicable to clinical study and lead to better diagnostic images with shorter waiting times and lower radiation doses for patients.     

Specific uptake of 99mTc-NC100692, an αvβ3-targeted imaging probe,in subcutaneous and orthotopic tumors

IntroductionThe α_vβ₃ integrin, which is expressed by angiogenic epithelium and some tumor cells, is an attractive target for the development of both imaging agents and therapeutics. While optimal implementation of α_vβ₃-targeted therapeutics will require a priori identification of the presence of the target, the clinical evaluation of these compounds has typically not included parallel studies with α_vβ₃-targeted diagnostics. This is at least partly due to the relatively limited availability of PET radiopharmaceuticals in comparison to those labeled with ^99mTc. In an effort to begin to address this limitation, we evaluated the tumor uptake of ^99mTc-NC100692, a cyclic RGD peptide that binds to α_vβ₃ with ~ 1-nM affinity, in an α_vβ₃-positive tumor model as well as its in vivo specificity.MethodsMicroSPECT imaging was used to assess the ability of cilengitide, a therapeutic with high affinity for α_vβ₃, to block and displace ^99mTc-NC100692 in an orthotopic U87 glioma tumor. The specificity of ^99mTc-NC100692 was quantitatively evaluated in mice bearing subcutaneous U87MG tumors, by comparison of the biodistribution of ^99mTc-NC100692 with that of the non-specific structural analogue ^99mTc-AH-111744 and by blocking uptake of ^99mTc-NC100692 with excess unlabeled NC100692.ResultsMicroSPECT imaging studies demonstrated that uptake of ^99mTc-NC100692 in the intracranial tumor model was both blocked and displaced by the α_vβ₃-targeted therapeutic cilengitide. Biodistribution studies provided quantitative confirmation of these imaging results. Tumor uptake of ^99mTc-NC100692 at 1 h post-injection was 2.8 ± 0.7% ID/g compared to 0.38 ± 0.1% ID/g for ^99mTc-AH-111744 (p < 0.001). Blocking ^99mTc-NC100692 uptake by pre-injecting the mice with excess unlabeled NC100692 reduced tumor uptake by approximately five-fold, to 0.68 ± 0.3% ID/g (p = 0.01).ConclusionThese results confirm that ^99mTc-NC100692 does, in fact, target the α_vβ₃ integrin and may, therefore, be useful in identifying patients prior to anti-α_vβ₃ therapy as well as monitoring the response of these patients to therapy.     

Development of a transfer standard for the measurement of low Rn-222 activity concentration in air

A large volume transfer standard has been developed to calibrate commercial radon measurement devices in a homogeneous Rn-222 reference atmosphere. The transfer standard serves for the realization, maintenance and dissemination of the unit Bq/m³ below 1 kBq/m³.The transfer standard consists of a multi-wire impulse ionization chamber, electronic measurement equipment and the corresponding software. The multi-wire impulse ionization chamber is composed of two parallel printed boards. Between the boards, 478 vertical electrode wires are soldered in to include a volume of 10 L. In the dependency of the energy, the α-particles of Rn-222 and the decay products are detected in the active volume of the multi-wire impulse ionization chamber. By means of the measurement software an α-energy spectrum is produced. Via different algorithms, the activity concentration of the Rn-222 reference atmosphere is determined.     

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.     

Temporal variations of 7Be, 210Pb and 137Cs in moss samples over 14 month period

Concentrations of ²¹⁰Pb, ⁷Be and ¹³⁷Cs in moss samples were continuously measured, using low-background HPGe spectrometer at Novi Sad, Serbia (45°14′45″N, 19°51′35″E). Weekly data collected over 14 month period from January 2007 to March 2008 are presented and discussed. Measured values of ⁷Be activity concentrations in dry moss samples are ranged from 201 to 920 Bq/kg showing prominent increase in summer and autumn season. Data for ²¹⁰Pb, ranged from 347 to 885 Bq/kg do not show such trend. The average concentration of ¹³⁷Cs is 8.9 Bq/kg. It is shown that yield of ⁷Be can be estimated using average values of activity concentrations. Precipitation amount and duration of precipitation are measured and their possible influence on activity concentrations measured in moss samples was considered.     

Radiation surveillance using an unmanned aerial vehicle

Radiation surveillance equipment was mounted in a small unmanned aerial vehicle. The equipment consists of a commercial CsI detector for count rate measurement and a specially designed sampling unit for airborne radioactive particles. Field and flight tests were performed for the CsI detector in the area where ¹³⁷Cs fallout from the Chernobyl accident is 23–45 kBq m⁻². A 3-GBq ¹³⁷Cs point source could be detected at the altitude of 50 m using a flight speed of 70 km h⁻¹ and data acquisition interval of 1 s. Respective response for ¹⁹²Ir point source is 1 GBq. During the flight, the detector reacts fast to ambient external dose rate rise of 0.1 μSv h⁻¹, which gives for the activity concentration of ¹³¹I less than 1 kBq m⁻³. Operation of the sampler equipped with different type of filters was investigated using wind-tunnel experiments and field tests with the aid of radon progeny. Air flow rate through the sampler is 0.2–0.7 m³ h⁻¹ at a flight speed of 70 km h⁻¹ depending on the filter type in question. The tests showed that the sampler is able to collect airborne radioactive particles. Minimum detectable concentration for transuranium nuclides, such as ²³⁹Pu, is of the order of 0.2 Bq m⁻³ or less when alpha spectrometry with no radiochemical sample processing is used for activity determination immediately after the flight. When a gamma-ray spectrometer is used, minimum detectable concentrations for several fission products such as ¹³⁷Cs and ¹³¹I are of the order of 1 Bq m⁻³.     

Preparation of 99mTc-TRODAT-1 with high labeling yield in boiling water bath: A new formulation

A new formulation for preparation of ^99mTc-labeled tropane derivative, ^99mTc-TRODAT-1, which is useful as a potential CNS dopamine transporter imaging agent, was evaluated and characterized.Preparation of ^99mTc-TRODAT-1 was attained previously by a formulation in which vial has to be autoclaved at 121 °C for 30 min. It is highly desirable to further improve the preparation method by developing a simplified one vial formulation which will be labeled in boiling water bath (95 °C) for 15 min and a high labeling yield will be achieved. A formulation contained 10 μg of TRODAT-1, 20 μg tricine, 40 μg SnCl₂ and 20 mg manitol was prepared. Labeling was performed at 95 °C for 15 min and radiochemical analysis involved ITLC and HPLC methods. The stability of radioconjugate was checked in the presence of human serum at 37 °C up to 24 h.^99mTc-TRODAT-1 was prepared with a radiochemical purity of more than 95% and specific activity of 64.3 MBq/nmol. Biodistribution studies of this new formulation in rats revealed similar regional brain distribution as compared with those obtained with the previous preparation in which brain uptake was high in striatum and striatum to cerebellum ratio was high. Requiring no autoclave facility for labeling, this new formulation will significantly improve the using feasibility of this radiopharmaceutical in clinic.     

Improvements of low-level radioxenon detection sensitivity by a state-of-the art coincidence setup

The ability to quantify isotopic ratios of 135, 133 m, 133 and 131 m radioxenon is essential for the verification of the Comprehensive Nuclear-Test Ban Treaty (CTBT). In order to improve detection limits, CEA has developed a new on-site setup using photon/electron coincidence (Le Petit et al., 2013. J. Radioanal. Nucl. Chem., DOI : 10.1007/s 10697-013-2525-8.). Alternatively, the electron detection cell equipped with large silicon chips (PIPS) can be used with HPGe detector for laboratory analysis purpose. This setup allows the measurement of β/γ coincidences for the detection of ¹³³Xe and ¹³⁵Xe; and K-shell Conversion Electrons (K-CE)/X-ray coincidences for the detection of ^131mXe, ^133mXe and ¹³³Xe as well. Good energy resolution of 11 keV at 130 keV and low energy threshold of 29 keV for the electron detection were obtained. This provides direct discrimination between K-CE from ¹³³Xe, ^133mXe and ^131mXe. Estimation of Minimum Detectable Activity (MDA) for ^131mXe is in the order of 1 mBq over a 4 day measurement. An analysis of an environmental radioxenon sample using this method is shown.     

3T diffusion-weighted MRI in the response assessment of colorectal liver metastases after chemotherapy: Correlation between ADC value and histological tumour regression grading

PurposeThe purpose of the study was to correlate the apparent diffusion coefficient (ADC) values of diffusion-weighted MR imaging (DW-MRI) by 3T device with the histological tumour regression grading (TRG) analysis of colorectal liver metastases after preoperative chemotherapy.Materials and methodsOur study included thirty-five patients with colorectal liver metastases who had undergone MRI by 3T device (GE DISCOVERY MR750; GE Healthcare) after preoperative chemotherapy. DW-MRI was performed using a single-shot spin-echo echo-planar sequence with multiple b-values (0, 150, 500, 1000, 1500 s/mm²), thus obtaining an ADC map. For each liver lesion (more than 1 cm in diameter) the fitted ADC values were calculated by two radiologists in conference and three ROIs were drawn: around the entire tumour (ADC_e), at the tumour periphery (ADC_p) and at the tumour center (ADC_c). All ADC values were correlated with histopathological findings after surgery. Hepatic metastases were pathologically classified into five groups on the basis of TRG. Statistical analysis was performed on a per-lesion basis utilizing the one-way analysis of variance (ANOVA). This retrospective study was approved by our institutional review board; written informed consent was obtained from all patients.ResultsA total of 106 colorectal liver metastases were included for image analysis. TRG1, TRG2, TRG3, TRG4 and TRG5 were observed in 4, 14, 36, 35 and 17 lesions, respectively. ADC_e and ADC_p values were significantly higher in lesions classified as TRG1 (2.40 ± 0.12 × 10⁻⁹ m²/s and 2.28 ± 0.26 × 10⁻⁹ m²/s, respectively) and as TRG2 (1.40 ± 0.31 × 10⁻⁹ m²/s and 1.44 ± 0.35 × 10⁻⁹ m²/s), compared to TRG3 (1.16 ± 0.13 × 10⁻⁹ m²/s and 1.01 ± 0.18 × 10⁻⁹ m²/s), TRG4 (1.10 ± 0.26 × 10⁻⁹ m²/s and 0.97 ± 0.24 × 10⁻⁹ m²/s), and TRG5 (0.93 ± 0.17 × 10⁻⁹ m²/s and 0.82 ± 0.28 × 10⁻⁹ m²/s). ADC_e, ADC_p and ADC_c values were significantly different in TRG classes (p < 0.0001). Statistical correlations were found between the ADC_e, ADC_p, ADC_c values and the TRG classes (Spearman correlation coefficient were −0.568, −0.542 and −0.554, respectively).ConclusionOur study showed a significant correlation between ADC values of 3T DW-MRI and histological TRG of colorectal liver metastases after preoperative chemotherapy.     

Imaging the myocardium at risk with 99mTc-lactadherin administered after reperfusion in a porcine model

IntroductionPhosphatidylserine is translocated from the inner to the outer leaflet of the plasma membrane in the early stages of apoptosis and necrosis and in reversibly injured cells. In rabbit hearts, ischemia followed by reperfusion results in exposure of phosphatidylserine on myocytes unaffected by apoptosis or necrosis. Lactadherin was recently introduced as a highly sensitive phosphatidylserine ligand. We hypothesized that ischemic myocardial cell damage can be identified by radio-labeled lactadherin and that the ischemic area at risk (AAR) can be visualized retrospectively after reperfusion.MethodsLeft anterior descending coronary artery in pigs was occluded for 20 minutes, 45 minutes or 45 minutes preceded by ischemic preconditioning. In all three groups, ^99mTc-lactadherin was injected intravenously 30 minutes after reperfusion. The AAR was demarcated by Evans blue and the infarct size by 2,3,5,-triphenyltetrazodium chloride staining.ResultsThe regional myocardial uptake of ^99mTc-lactadherin closely correlated with the AAR (r = .83, P = .001). The area of ^99mTc–lactadherin uptake was unaltered by a shorter duration of ischemia and ischemic preconditioning (P = .23) despite significantly different infarct development (P = .001).ConclusionThe results suggest that ^99mTc–lactadherin can be used as a sensitive marker for AAR imaging when injected 30 minutes after reperfusion following acute ischemia.     

Biological evaluation of an ornithine-modified 99mTc-labeled RGD peptide as an angiogenesis imaging agent

IntroductionRadiolabeled RGD peptides that specifically target integrin α_νβ₃ have great potential in early tumor detection through noninvasive monitoring of tumor angiogenesis. Based on previous findings of our group on radiopeptides containing positively charged aminoacids, we developed a new cyclic cRGDfK derivative, c(RGDfK)-(Orn)₃-CGG. This new peptide availing the polar linker (Orn)₃ and the ^99mTc-chelating moiety CGG (Cys-Gly-Gly) is appropriately designed for ^99mTc-labeling, as well as consequent conjugation onto nanoparticles.MethodsA tumor imaging agent, c(RGDfK)-(Orn)₃-[CGG-^99mTc], is evaluated with regard to its radiochemical, radiobiological and imaging characteristics.ResultsThe complex c(RGDfK)-(Orn)₃-[CGG-^99mTc] was obtained in high radiochemical yield (> 98%) and was stable in vitro and ex vivo. It presented identical to the respective, fully analytically characterized ^185/187Re complex retention time in RP-HPLC. In contrary to other RGD derivatives, we showed that the new radiopeptide exhibits kidney uptake and urine excretion due to the ornithine linker. High tumor uptake (3.87 ± 0.48% ID/g at 60 min p.i.) was observed and was maintained relatively high even at 24 h p.i. (1.83 ± 0.05 % ID/g), thus providing well-defined scintigraphic imaging. Accumulation in other organs was negligible. Blocking experiments indicated target specificity for integrin receptors in U87MG glioblastoma cells.ConclusionDue to its relatively high tumor uptake, renal elimination and negligible abdominal localization, the new ^99mTc-RGD peptide is considered promising in the field of imaging α_νβ₃-positive tumors. However, the preparation of multifunctional SPECT/MRI contrast agents (RGD-conjugated nanoparticles) for dual modality imaging of integrin expressing tumors should be further investigated.