Radiofrequency-induced thermal inactivation of Toxoplasma gondii oocysts in water.

Toxoplasma gondii, a ubiquitous parasitic protozoan, is emerging as an aquatic biological pollutant. Infections can result from drinking water contaminated with environmentally resistant oocysts. However, recommendations regarding water treatment for oocyst inactivation have not been established. In this study, the physical method of radiofrequency (RF) power was evaluated for its ability to inactivate T. gondii oocysts in water. Oocysts were exposed to various RF energy levels to induce 50, 55, 60, 70 and 80 degrees C temperatures maintained for 1 min. Post-treatment oocyst viability was determined by mouse bioassay with serology, immunohistochemistry and in vitro parasite isolation to confirm T. gondii infections in mice. None of the mice inoculated with oocysts treated with RF-induced temperatures of > or =60 degrees C in an initial experiment became infected; however, there was incomplete oocyst activation in subsequent experiments conducted under similar conditions. These results indicate that T. gondii oocysts may not always be inactivated when exposed to a minimum of 60 degrees C for 1 min. The impact of factors such as water heating time, cooling time and the volume of water treated must be considered when evaluating the efficacy of RF power for oocyst inactivation.

Disinfection of dairy and animal farm wastewater with radiofrequency power.

Radiofrequency (RF) power was investigated as a new, physical (nonchemical), thermal process to disinfect wastewater from dairy and animal facilities. Samples (n = 38) from 8 dairy, 2 calf, and 3 swine facilities in California were collected over a 3-yr period and characterized for their dielectric properties, chemical composition, and suitability for thermal processing using RF power. To establish efficacy for disinfection, selected samples were inoculated with high levels (10(6) to 10(9) cfu/mL) of bacterial pathogens such as Salmonella sp., Escherichia coli O157:H7, and Mycobacterium avium ssp. paratuberculosis and processed with an RF prototype system. The capabilities of RF power as a method for thermal disinfection of wastewater were demonstrated when bacteria pathogens were completely and rapidly (<1 min) inactivated when temperatures of 60 to 65 degrees C were achieved. Furthermore, RF technology can be used for large-scale, batch or continuous and portable applications, allowing significant improvements in energy-use efficiencies compared with conventional thermal (surface heating) technologies. Therefore, RF power has potential as an alternative to disinfect dairy/animal farm wastewater before recycling.

Radionuclides in fishes and mussels from the Farallon Islands Nuclear Waste Dump Site, California.

The Farallon Islands Nuclear Waste Dump Site (FINWDS), approximately 30 miles west of San Francisco, California, received at least 500 TBq encapsulated in more than 47,500 containers from approximately 1945 to 1970. During several seasons in 1986/87 deep-sea bottom feeding fishes (Dover sole = Microstomus pacificus; sablefish = Anoplopoma fimbria; thornyheads = Sebastolobus spp.) and intertidal mussels (Mytilus californianus) were collected from the vicinity of the FINWDS and from comparable depths at a reference site near Point Arena, CA. Tissues were analyzed for several radionuclides (137Cs, 238Pu, 239+240Pu, and 241Am). Radionuclide concentrations for fish mussel tissue ranged from non-detectable to 4,340 mBq kg(-1) wet weight, with the following means for Farallon fishes: 137Cs = 1,110 mBq kg(-1); 238Pu = 390 mBq kg(-1); 239+240Pu = 130 mBq kg(-1); and 241Am = 1,350 mBq kg(-1). There were no statistically significant differences in the radionuclide concentrations observed in samples from the Farallon Islands compared to reference samples from Point Arena, CA. Concentrations of both 238Pu and 241Am in fish tissues (from both sites) were notably higher than those reported in literature from any other sites world-wide, including potentially contaminated sites. Concentrations of 239+24OPu from both sites were typical of low values found at some contaminated sites worldwide. These results show approximately 10 times higher concentrations of 239+240Pu and approximately 40-50 times higher concentrations of 238Pu than those values reported for identical fish species from 1977 collections at the FINWDS. Radionuclide concentrations were converted to a hypothetical per capita annual radionuclide intake for adults, yielding the following values of annual Committed Effective Dose Equivalent (CEDE) from ionizing radiation emitted from these radionuclides: 0.000 mSv y(-1) for 137Cs, 0.009 mSv Y(-1) for 228Pu, and 0.003 mSv y(-1) for 239+240Pu. For 241Am, projected CEDE for Dover sole, sablefish, and thornyheads were higher, averaging 0.03 mSv y(-1). The observed isotopic ratio of 238Pu/239+240Pu was about 4 (which is two orders of magnitude higher than the ratio of 0.03 associated with fallout from weapons tests and accidental releases in the north temperate zone of the earth), indicating a considerably higher environmental mobilization for 238Pu compared to 239+240Pu. Likewise, the observed ratio of 241Am/239+240Pu of about 30 was nearly two orders of magnitude higher than the fallout ratio of 0.43 in the north temperate zone of the earth. The projected ionizing radiation CEDE to people from the ingestion of fish with fallout radionuclides was three times higher for 241Am than from the plutonium isotopes.

The effects of irradiation dose on the stiffness of cartilage grafts.

Various centers report irradiated cartilage graft absorption rates that differ quite widely. We postulated that a major factor governing this phenomenon might be irradiation dose. Irradiation produces collagen cross-binding and increased resistance to absorption of such material when implanted. Since cross-binding produces stiffening of collagen, cartilage grafts were exposed to increasing doses of irradiation and their elastic modulus was measured. The postulate was that increasing radiation doses will produce grafts of increasing stiffness. Sternal cartilage, harvested from horses, was cut into blocks of a standard size and irradiated to 4, 6, 8, and 10 megarads. The elastic modulus of each specimen and matched control were measured on an Instron flexural testing machine (Instron Corp, Canton, MA). Irradiation at all four doses reduced the elastic modulus of the cartilage grafts, with the lowest dose producing a reduction of 50% and the highest dose one of 90%. High-dose irradiation appears to lessen greatly the stiffness of cartilage grafts and may be responsible for increasing absorption of grafts in centers in which high doses are used.

Cyclotron production of NCA 99mTc and 99Mo. An alternative non-reactor supply source of instant 99mTc and 99Mo----99mTc generators.

The direct production of no-carrier-added (NCA) 6.02 h 99mTc and of 66 h 99mMo using proton beams of natural Mo targets was investigated. The major objective of this work was to evaluate the potential of utilizing high-intensity proton accelerators as a supply source of 99mTc and 99Mo for use in diagnostic nuclear medicine. The excitation functions for the production of the directly-made 99mTc via the 100Mo(p, 2n)99mTc (Q = -7.85 MeV) reaction, and of its parent 99Mo via the 100Mo(p, pn) 99Mo (Q = -8.30 MeV) and 100Mo(p, 2p)99mNb(15 s)----99Mo (Q = -11.14 MeV) reactions, were measured in the 68-8 MeV energy range. Single and cumulative yields for 99mTc and 99Mo, and for other Tc, Mo, Zr, Nb and Y radiocontaminants were also determined. The prospects of integrating the use of enriched 100Mo targets with high-intensity, dual beam, H- accelerators was analyzed. The potential of this combined method to replace or complement the current reactor-based supply sources of 99Mo----99mTc generators, is also discussed. Finally, a brief analysis is made on the potential use of this combined technology to support the anticipated expansion of nuclear medicine in developing nations.

Iodine-123 metaiodobenzylguanidine imaging of the heart in idiopathic congestive cardiomyopathy and cardiac transplants.

Iodine-123 metaiodobenzylguanidine ([123I]MIBG) is a norepinephrine analog which can be used to image the sympathetic innervation of the heart. In this study, cardiac imaging with [123I]MIBG was performed in patients with idiopathic congestive cardiomyopathy and compared to normal controls. Initial uptake, half-time of tracer within the heart, and heart to lung ratios were all significantly reduced in patients compared to normals. Uptake in lungs, liver, salivary glands, and spleen was similar in controls and patients with cardiomyopathy indicating that decreased MIBG uptake was not a generalized abnormality in these patients. Iodine-123 MIBG imaging was also performed in cardiac transplant patients to determine cardiac nonneuronal uptake. Uptake in transplants was less than 10% of normals in the first 2 hr and nearly undetectable after 16 hr. The decreased uptake of MIBG suggests cardiac sympathetic nerve dysfunction while the rapid washout of MIBG from the heart suggests increased cardiac sympathetic nerve activity in idiopathic congestive cardiomyopathy.

Positron emission tomography assessment of effects of benzodiazepines on regional glucose metabolic rate in patients with anxiety disorder.

Patients with generalized anxiety disorder (n = 18) entered a 21-day, double-blind, placebo-controlled random assignment trial of clorazepate. Positron emission tomography with 18F-deoxyglucose was carried out before and after treatment. Decreases in glucose metabolic rate in visual cortex and relative increases in the basal ganglia and thalamus were found. A correlation between regional changes in metabolic rate and regional benzodiazepine receptor binding density from other human autopsy studies was observed; brain regions highest in receptor density showed the greatest decrease in rate.

Targetry and radiochemical methods for the simultaneous cyclotron production of no-carrier-added radiopharmaceutical-quality 100Pd, 97Ru and 101mRh.

Target-dissolution and radiochemical methods were investigated to optimize the simultaneous production of radiopharmaceutical-quality, no-carrier-added (NCA) 3.63-d 100Pd, 2.88-d 97Ru and 4.26-d 101mRh. These radionuclides have potential as radiotracer labels and/or as short-range dose emitters for use with specific-function radiopharmaceuticals being investigated for radioimmunotherapy applications. Metallic Rh (100% 103Rh) and RhCl3 X 3H2O were used as target materials. After bombardment with high energy protons these targets were subjected to a combination of procedures (i.e. electrolytic dissolution, ion-exchange, and solvent extraction) in order to separate the desired radionuclides. The use of a single cyclotron target in combination with several radiochemical processes were investigated to simultaneously produce these radionuclides in high-specific activities and radiochemical forms suitable for radiopharmaceutical syntheses.

Cyclotron production of no-carrier-added 206Bi (6.24 d) and 205Bi (15.31 d) as tracers for biological studies and for the development of alpha-emitting radiotherapeutic agents.

The production and radiochemical purification of no-carrier-added (NCA) bismuth isotopes (i.e. 6.24 d 206Bi and 15.31 d 205Bi) was studied. The Bi isotopes are intended for use as tracers in biodistribution studies and in the design and testing of alpha-emitting radiotherapeutic agents. The total cross sections and yields for the production of 206Bi and 205Bi from the proton bombardment of natural Pb targets were measured using the stacked-foils technique. A radiochemical method for the separation and purification of NCA Bi radioactivities from a multi-gram Pb target was also tested, modified, and improved to provide aqueous solutions of chemically and biologically useful amounts of NCA 206,205Bi for measuring tissue and subcellular-distributions, and for studies covering several chemical aspects of the development of Pb/Bi radiotherapeutic agents.

A 122Xe-122I generator for remote radio-iodinations.

A 122Xe-122I generator system is described that produces 122I extraction efficiencies of approximately 60%. Radiocontaminants were less than 0.1% at the time of 122I removal following a 10 min ingrowth period. The chemical form of 122I was identified as [122I]iodide, and the [122I]iodide was remotely incorporated into radiopharmaceuticals for PET studies with an overall efficiency of as much as 40%.

Iodine-123 assay using a radionuclide calibrator.

Iodine-123 (123I), an accelerator-produced radionuclide, gained wide acceptance recently in medical applications. Radionuclide dose calibrators are commonly used to assay radioactivities of radiopharmaceuticals, and should be maintained to read within +/- 5%, both for constancy and accuracy. Radionuclidic impurities present in commercial 123I preparations may produce an assay error larger than 10%. The type and quantity of impurities depend on the mode of production of 123I. The impurities can be reduced by either increasing the energy of the proton beam (over 60 MeV) and using the 127I (p,5n) 133Xe leads to 123I indirect reaction or using lower energies and highly enriched (better than 99%) 124Te (or 122Te) target for the direct production of 123I via 124Te (p, 2n) 123I or 122Te (d, n) 123I. A survey of radionuclide calibrators was undertaken to investigate the extent of the 123I assay error due to impurities present in commercially available preparations of 123I. Results from 24 calibrators indicate that the activity of a (p, 2n) 123I capsule is overestimated on average by 22% two half-lives after calibration time, while the activity of a (p, 5n) 123I capsule remains within the accuracy of the radionuclide calibrator of +/- 5%. The 124I fraction increases significantly with time during the useful life of a (p, 2n) 123I capsule introducing large 123I assay errors.

The production of no-carrier-added radiopharmaceuticals with special reference to radionuclide impurities.

Charged-particle accelerators are being utilized extensively for the production of several neutron-deficient radionuclides for use in the synthesis of radiopharmaceuticals for diagnostic nuclear-medicine applications. The diversity of techniques being employed results in radionuclide preparations having significantly different radionuclidic composition. The choice of nuclear reaction, the knowledge of excitation functions, the proper timing and use of radiochemical methods, are all factors which will to some extent determine the quality of a radionuclide preparation. The different factors governing the production and quality of medical radionuclides will be discussed, with particular attention to the formation of radionuclidic impurities, and their effects in nuclear medicine practice.

An integrally shielded transportable generator system for thallium-201 production.

An integrally shielded transportable 201Pb leads to 201Tl generator system for the production of 201Tl has been developed at the Crocker Nuclear Laboratory, University of California, Davis. The present generator design allows for processing of up to 4 Ci of 201Pb parent radioactivity yielding approximately 400 mCi of 201Tl in a chemical form easily converted to radiopharmaceutical quality. Larger capacity generator systems can be constructed since the use of depleted uranium for shielding purposes is becoming readily available. While the parent 201Pb radioactivity decays to the daughter 201Tl, the combination depleted uranium-lead shielded system (approximately 33 kg) can be transported to distant locations for final processing. In this manner, decay losses (approximately 25%) associated with transportation of bulk 201Tl can be avoided since transportation would occur during the time (approximately 32 h) needed for the growth of 201Tl via 201Pb(9.4 h) leads to 201Tl (73.5 h). Single small-volume elutions (15-20 ml) provide more than 95% of the 201Tl radioactivity with no detectable radioactive Pb breakthrough and less than 20 micrograms/ml of carrier Tl.

Cyclotron production of 128Cs (3.62 min). A new positron-emitting radionuclide for medical applications.

The cyclotron production of the short-lived positron emitter 128Cs (3.62 min) from its longer-lived parent 128Ba (2.42 d), based upon the 133Cs(p, 6n) 128Ba leads to 128Cs reaction (Q = -43.98 MeV), has been studied. Cesium-128 has potential applications in positron tomography, particularly for imaging the myocardium and/or for the assessment of regional blood flow. Thick-target yields (mCi/muAh) and cross sections (mb) for 128Ba, 131Ba, 129Cs and 132Cs were measured in the 67-36 MeV proton-energy region. Cyclotron production of 128Ba-128Cs (transient equilibrium) was measured as 3.1 mCi/muAh at end of bombardment (EOB) with a 2.32 g cm-2 thick CsCl target with a proton entrance energy of 67 MeV and exit energy of 54 MeV. Target-radiochemistry using ion-exchange methods allow the preparation of a generator-type system from which high-radionuclidic purity, radiopharmaceutical quality, no-carrier-added 128Cs can be obtained for immediate administration. In addition, with proper radiochemical handling of the 128Ba-128Cs generator, no-carrier-added, high-purity 129Cs (32.35 h, 372 keV, 32%) can also be produced for use in research applications.

Renal clearance and extraction parameters of ortho-iodohippurate (I-123) compared with OIH(I-131) and PAH.

o-[131I] iodohippurate [OIH(I-131)] has been used for many years in the estimation of effective renal plasma flow. This compound suffers from low photon yield and poor images when the quantity used is limited to stay within a reasonable radiation dose. To test the validity of substituting I-123 for I-131, a series of experiments was performed in a surgically prepared dog model. The extraction ratios and clearance values OIH(I-123) prepared from radionuclidically pure I-123 were compared with those of commercial OIH(I-131) and PAH. The extraction ratios for OIH(I-123) and OIH(I-131) were 0.65 and 0.67, representing 0.86 and 0.88 that of PAH, respectively. The clearance values (cc/min/kg) for the I123 and I-123) can be used to estimate effective renal plasma flow; moreover, because of the high yield within an acceptable radiation dose range, images of good quality can be produced.