No abstract available

[en] ^186gRe(T_1/2=89.2h) has theranostic decay properties that make it attractive for use in targeted radionuclide therapy of cancer. This radionuclide can be produced by irradiation of natural tungsten target in high flux research reactor. ¹⁸⁶Re has greater potential for development of theranostic radiopharmaceuticals compare to other radionuclide because of its emission of medium energy beta particle (E_β endpoint 1.07 and 0.93MeV) which can be used to treat a range of tumour sizes and its imaginable photon emission at 137 keV (9.5%). The drawback of ¹⁸⁶Re is its the low specific activity obtained from the (n,γ) production method. Despite high thermal and epithermal neutron cross sections of ¹⁸⁵Re (106b and 1632b respectively), research reactors are able to produce marginal specific activity of ∼ 111GBq/mg (∼ 3Ci/mg) which activate only 2% of ¹⁸⁵Re leaving 98% of the enriched ¹⁸⁵Re. An alternative to neutron activation for production of ^186gRe is accelerator production through (p,n) reaction using thick natural WO₃ target. This result in much higher specific activity as the ^186gRe can be chemically separated from the target. Earlier, cross section of ^181-184Re were measured and separation was carried out from proton irradiated tungsten target

[en] Published in summary form only

No abstract available

[en] Full text of publication follows. Aim: intravenous administration of Re-186 hydroxyethylidene-diphosphonate (HEDP) is used for metastatic bone pain palliation in hormone refractory prostate cancer patients. Dosimetry for bone seeking radionuclides is challenging due to the complex structure with osteoblastic, osteolytic and mixed lesions. The aim of this study was to perform image-based patient-specific 3D convolution dosimetry to obtain a distribution of the absorbed doses to each lesion and estimate inter- and intra-patient variations. Materials and methods: 28 patients received a fixed 5 GBq activity of Re-186 HEDP followed by peripheral blood stem cell rescue at 14 days in a phase II trial. A FORTE dual-headed gamma camera was used to acquire sequential Single-Photon-Emission Computed Tomography (SPECT) data of the thorax and pelvis area at 1, 4, 24, 48 and 72 hours following administration. The projection data were reconstructed using filtered-back projection and were corrected for attenuation and scatter. Voxelised cumulated activity distributions were obtained with two different methods. First, the scans were co-registered and the time-activity curves were obtained on a voxel-by-voxel basis. Second, the clearance curve was obtained from the mean number of counts in each individual lesion and used to scale the uptake distribution taken at 24 hours. The calibration factors required for image quantification were obtained from a phantom experiment. An in-house developed EGSnrc Monte Carlo code was used for the calculation of dose voxel kernels for soft-tissue and cortical/trabecular bone used to perform convolution dosimetry. Cumulative dose-volume histograms were produced and mean absorbed doses calculated for each spinal and pelvic lesion. Results: preliminary results show that the lesion mean absorbed doses ranged from 25 to 55 Gy when the medium was soft tissue and decreased by 40% if bone was considered. The use of the cumulated activity distribution obtained from the scan acquired at 24 hours following administration reduced the number of artefacts introduced by the registration and voxelised cumulated activity calculations. Conclusion: patient-specific convolution dosimetry calculations show that the absorbed dose to each lesion changes significantly depending on the medium density considered. This suggests that specific lesion and surrounding tissue compositions should be considered to overcome the limitations of convolution dosimetry, which could explain the range of absorbed doses observed. Future work will include the correlation of absorbed dose with patient outcome. (authors)

[en] We have developed a ¹⁸⁶Re-mercaptoacetylglycylglycylglycine complex-conjugated bisphosphonate (¹⁸⁶Re-MAG3-HBP) for the treatment of painful bone metastases. We assumed competitive inhibitors of protein binding to be useful for procuring a favorable biodistribution of ¹⁸⁶Re-MAG3-HBP for the palliation of bone pain because it has been reported that the concurrent administration of ^99mTc-MAG3 and drugs with high affinity for serum protein produced competitive displacement at specific binding sites and enhanced total clearance and tissue distribution. The displacement effects of several protein-binding inhibitors on the protein binding of ¹⁸⁶Re-MAG3-HBP were investigated. Biodistribution experiments were performed by intravenously administering ¹⁸⁶Re-MAG3-HBP into rats with ceftriaxone as a competitive protein-binding inhibitor or saline. The protein binding of ¹⁸⁶Re-MAG3-HBP in rat serum, human serum, and a human serum albumin solution was significantly decreased by the addition of ceftriaxone, which has high affinity for binding site I on serum albumin. In the biodistribution experiments, pretreatment with ceftriaxone enhanced the clearance of the radioactivity of ¹⁸⁶Re-MAG3-HBP in blood and nontarget tissues but had no effect on accumulation in bone. The findings suggested that the use of protein-binding competitive inhibitors would be effective in improving the pharmacokinetics of radiopharmaceuticals with high affinity for serum protein. (orig.)

No abstract available

[en] In 2006, the Physikalisch-Technische Bundesanstalt (PTB), Germany submitted a sample of known activity of ¹⁸⁶Re to the International Reference System (SIR). The value of the activity submitted was about 166 MBq. This comparison result is the first submission in the ongoing key comparison BIPM.RI(II)-K1.Re-186. The result agrees with that predicted from the efficiency curve for the SIR within a standard uncertainty. (authors)

[en] An improved generator was developed using a silica-based extraction chromatographic resin, Eichrom Silica Actinide Resin (Eichrom, Darien, IL), for the production of the α-emitting radionuclide ²¹³Bi and to minimize radiolysis of the ²²⁵Ac/²¹³Bi generator. Ac-225 was adsorbed and evenly distributed on the top two-thirds of the generator resin. Bi-213 was eluted quantitatively with 1.0 M HCl. Simultaneous elution of the generaor, subsequent dilution and re-adsorption of ²¹³Bi onto an MP-50 column to concentrate the activity was performed by assembling the columns in series. Breakthrough of ²²⁵Ac from the generator was <0.05%, and no ²²⁵Ac was found when ²¹³Bi was eluted from the second column. Bi-213 obtained can be easily used to radiolabel appropriate protein chelating agent conjugates. Hypothetically, resin damage by α-radiolysis should be obviated by employing such a silica-based resin and by broad distribution of the ²²⁵Ac on the column. (orig.)

[en] Pain palliation with bone-seeking radiopharmaceuticals is an effective treatment modality in patients with advanced metastatic bone cancer. Several studies have shown encouraging clinical results of palliative therapy using ¹⁸⁶Re-HEDP, with an overall reported response rate of ± 71% for painful osseous metastasize prostate and breast cancer patients. ¹⁸⁶Re-HEDP is a very potential isotope with numerous advantageous characteristics for this purpose. Myelosuppressive toxicity is limited and reversible, which makes repetitive treatment safe. However, individual studies are difficult to compare, and are hampered by the numerous and different methods used to assess clinical responses. Standardized clinical response assessment using the objective multi-dimensional pain evaluation model should therefore be implemented