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PubMed1992

Imaging of the human torso using cone-beam transmission CT implemented on a rotating gamma camera.

Radionuclide transmission CT generated on a rotating gamma camera can improve SPECT imaging by providing attenuation maps for attenuation compensation and for anatomical correlation. This paper demonstrates the feasibility and high quality of cone-beam transmission CT (CB-CT) of human subjects, in comparison to conventional parallel-ray CT, and evaluates some possible imaging protocols. Two CB-CT implementation modes, with a cone-beam collimator and without any collimator, were evaluated. Three human subjects of different dimensions were imaged. For the two smaller subjects, the CB-CT images were dramatically superior, in terms of noise and resolution, to those obtained with a parallel-ray geometry. The image noise was less by a factor of 6. CB-CT linear attenuation coefficients were found to be in close agreement with published values for various tissues. For the largest subject, image truncation produced a ring artifact at the edge, but inside the artifact, the image quality was still very good. Cone-beam images obtained without any collimator were acceptable, but photon scatter degraded the image contrast.

Body Height↗
PubMed1975

A method for the preparation and quality control of 68Ga radiopharmaceuticals.

Gallium-68 (T 1/2 68 min) is a convenient label for radiopharmaceuticals designed for use with positron detection devices; the radionuclide is a generator produce obtained from its parent 68Ge (T 1/2 287 days). The labeling procedure itself is simple since gallium forms complexes without the use of reducing agents. However, 68Ga is present in the generator eluant as the gallium-EDTA chelate and must be separated from EDTA prior to its use as a label. A rapid and efficient method for achieving this separation and for preparing 68Ga-labeled compounds for human use has been developed. Paper chromatography is employed to determine the amount of each major gallium species present in preparations of two gallium complexes; 68Ga-adenosine triphosphate and 68Ga-citrate.

Adenosine Triphosphate↗
PubMed1993

Quantification of regional myocardial perfusion with generator-produced 62Cu-PTSM and positron emission tomography.

BACKGROUND: Noninvasive assessment of regional myocardial perfusion at rest and after stress is important for the objective evaluation of the effects of coronary artery disease and its response to therapy. Centers that do not have cyclotrons rely on generator-produced radioisotopes for assessment of regional myocardial perfusion with positron emission tomography (PET). The aim of the present study was to develop and implement an approach to quantify regional myocardial perfusion using copper(II) pyruvaldehyde bis-(N4-thiosemicarbazone) (PTSM) labeled with the generator-produced, positron-emitting radionuclide 62Cu (t1/2 = 9.7 minutes). METHODS AND RESULTS: Regional perfusion was estimated from dynamic PET scans after intravenous administration of 62Cu-PTSM in 21 studies in 13 intact dogs evaluated over a wide range of myocardial flow values. In 15 interventions in nine dogs, regional perfusion was also estimated with H2(15)O. Regional perfusion with 62Cu-PTSM was estimated from dynamic blood and tissue time-activity curves, along with the model parameter k1 (forward rate of transport) and the PET parameter FBM (fraction of blood pool activity observed in tissue), using a two-compartment kinetic model. Arterial blood activity was corrected for red blood cell-associated 62Cu. In 44 comparisons, estimates of regional perfusion with 62Cu-PTSM correlated well with estimates obtained with concomitantly administered radiolabeled microspheres (y = 0.90x +/- 0.15, r = 0.95, p < 0.05) over a flow range from 0.23 to 6.14 ml/g per minute. In five healthy human volunteers evaluated at rest with H2(15)O and 62Cu-PTSM, regional perfusion estimated with 62Cu-PTSM was not significantly different from that obtained with H2(15)O (1.05 +/- 0.36 versus 0.96 +/- 0.28 ml/g per minute). 62Cu-PTSM provided high-quality images of the heart. CONCLUSIONS: The results of this study demonstrate that quantification of regional myocardial perfusion is feasible using generator-produced 62Cu-PTSM. Since 62Cu-PTSM can be used to estimate perfusion in the brain, kidney, and tumors as well as in the heart, it is an attractive tracer for centers that rely on generator-produced tracers for the evaluation of perfusion with PET.

Animals↗
PubMedDate not supplied

[Biological effects in natural populations of small rodents in radiation-polluted territories. Description of sites. Dynamics of concentration of gamma-emitting radionuclides in populations of two species of small mammals].

It has been revealed that dynamics of gamma-emitting radionuclide concentration in consecutive generations of two species of wild rodents (European bank vole and yellow-necked mouse) is characterised by the phases of an increase, a maximum content (peaks) and a decrease over 10 years after the Chernobyl accident. The peaks of specific activity of gamma-emitting radionuclides in populations in the areas with different densities of radio-contamination falls not on the first year but on the next ones (1987-1989) after the catastrophe, i.e. are observed in the subsequent (3-8) generations of animals. The revealed shift of maximum of radionuclide concentration in comparison with the maximum of their fallout is likely caused by an increase in radionuclide biological availability.

Animals↗
PubMed2005

Generation of dose-volume histograms using Monte Carlo simulations on a multicellular model in radionuclide therapy.

An accurate calculation of the absorbed dose at the cellular level can lead to the optimization of the administered activity and the best clinical response in radionuclide therapy. This paper describes the implementation of dose-volume histograms (DVHs) for dosimetry at the cellular level in radionuclide therapy. The FOTELP code, based on Monte Carlo simulations of photon and electron transport, was used on a three-dimensional multicellular tumor model, which includes tumor morphometry and cell-labeling parameters. Differential and cumulated DVHs were generated for different radionuclides (Cu-67, I-131, Sm-153, Y-90, and Re-188) and labeled cell densities (10, 20, 40, 80, and 100%). DVHs were generated as a percentage of tumor cells in the function of a relative absorbed dose, defined as a cell-absorbed dose divided by an average tumor-absorbed dose. DVHs for high-energy beta emitters, such as Re-188 and Y- 90, were very close to the average tumor-absorbed dose. For low-energy beta emitters, such as Cu-67 and I-131, spectra showed that many cells absorbed a much lower dose than the average tumor-absorbed dose. Nonhomogeneity of the radionuclide distribution in tumor, presented by labeled cell density, had a greater influence on DVHs for low-energy beta emitters. Radionuclide therapy plans can be optimized using DVHs.

Dose-Response Relationship, Radiation↗
PubMed1988

An improved generator for the production of 212Pb and 212Bi from 224Ra.

We have developed an improved generator for the production of the alpha emitting radionuclide 212Bi and its parent, 212Pb. These radionuclides are well suited to use as radiotherapeutic agents due to their relatively short half lives and appropriate particle particle emissions. The parent, 224Ra, is available from a long-lived parent and can be isolated on a generator which produces the daughters in good yield and low breakthrough. The 212Bi can be eluted by itself or in equilibrium with its parent.

Bismuth↗
PubMed1980

Iridium- 191 angiocardiography for the detection and quantitation of left-to-right shunting.

An osmium- 191 leads to iridium- 191 generator that can deliver multiple doses of Ir- 191m for first-pass radionuclide angiography has been developed. Iridium- 191m has a physical half-life of 4.96 sec and decays with emission of 65-keV and 129-keV photons in 58 and 30% abundance, respectively. Using a gamma camera, Ir- 191m radionuclide angiography was carried out, in dogs and ten patients, for the detection and quantitation of left-to-right shunting. In a one-year-old patients, 25 mCi of Ir- 191m results in a whole-body radiation absorbed dose of 35 mrad. Multiple Ir- 191m angiograms can be performed, seconds to minutes apart, without interference from background. The 15.4-day half-life of Os- 191 permits transportation of the generator to centers far from the production facility. With the low radiation dose, high information density, and the ability to repeat studies with Ir- 191m, clinical use of radionuclide angiography should be expanded.

Adolescent↗
PubMed1991

Development and clinical performance of an automated, portable tungsten-178/tantalum-178 generator.

An automated, portable 178W/178Ta generator system has been developed for use in first-pass radionuclide angiography studies with the multiwire gamma camera. Eluant (0.03N HCI, 0.1% H2O2) and buffer (0.13 N Na2HPO4) are delivered with a dual channel peristaltic pump. The generator column is a borosilicate glass tube with 30 microns fused glass frit containing 0.75 ml AG1X8 anion exchange resin. This column and associated plumbing are assembled, integrally autoclaved, and then connected to sterile eluant and buffer containers. Automatic push-button elution directly into an injection syringe is provided. Three such generators have been employed in the study of 78 patients in the catheterization laboratory utilizing a mobile, multiwire gamma camera. Over a 3-mo period, 301 sterile pyrogen-free doses ranging from 15 to 99.5 mCi were supplied with a mean breakthrough level of 2.1 +/- 3.6 microCi. This automated, portable, high-yield 178W/178Ta generator represents a major advancement that will significantly facilitate first-pass radionuclide angiography with 178Ta and the multiwire gamma camera.

Angioplasty, Balloon, Coronary↗
PubMed1999

Five pediatric head and brain mathematical models for use in internal dosimetry.

UNLABELLED: Mathematical models of the head and brain currently used in pediatric neuroimaging dosimetry lack the anatomic detail needed to provide the necessary physical data for suborgan brain dosimetry. To overcome this limitation, the Medical Internal Radiation Dose (MIRD) Committee of the Society of Nuclear Medicine recently adopted a detailed dosimetric model of the head and brain for the adult. METHODS: New head and brain models have been developed for a newborn, 1, 5, 10 and 15 y old for use in internal dosimetry. These models are based on the MIRD adult head and brain model and on published head and brain dimensions. They contain the same eight brain subregions and the same head regions as the adult model. These new models were coupled with the Monte Carlo transport code EGS4, and absorbed fractions of energy were calculated for 14 sources of monoenergetic photons and electrons in the energy range of 10 keV-4 MeV. These absorbed fractions were then used along with radionuclide decay data to generate S values for all ages for 99mTc, considering 12 source and 15 target regions. RESULTS: Explicit transport of positrons was also considered with separation of the annihilation photons component to the absorbed fraction of energy in the calculation of S values for positron-emitting radionuclides. No statistically significant differences were found when S values were calculated for positron-emitting radionuclides under explicit consideration of the annihilation event compared with the traditional assumption of a uniform distribution of 0.511-MeV photons. CONCLUSION: The need for electron transport within the suborgan brain regions of these pediatric phantoms was reflected by the relatively fast decrease of the self-absorbed fraction within many of the brain subregions, with increasing particle energy. This series of five dosimetric head and brain models will allow more precise dosimetry of radiopharmaceuticals in pediatric nuclear medicine brain procedures.

Adult↗
PubMed1985

Measurements of the rubidium isotopic activities and the elution parameters of 81mKr generators using a standardized 114mIn source.

A method is described for measuring a number of parameters associated with an inorganic ion-exchange krypton generator. These are the activities of rubidium isotopes in inorganic ion-exchange krypton generators, the 81mKr extraction rate, the 81mKr activity delivered to patients during ventilation studies, the elution efficiency, and the radionuclide purity of the eluted gas. The method is based on the calibration of detectors, Ge(Li) and NaI(Tl), with a standardized 114mIn source at matching photon energies. The average activities present in our generators at the end of bombardment (EOB) were 14.6 +/- 3.8 mCi (81Rb), 6.2 +/- 1.6 mCi (82mRb) and 53 +/- 9.4 microCi (83Rb). The 81mKr extraction rate 2 h post-EOB was 10.2 +/- 2.3 mCi/min at an air flowrate of 1 l/min. The 81mKr activity delivered to patients during a ventilation study was 91 +/- 16 mCi. The elution efficiency of the generators averaged 50% +/- 7% at an air flowrate of 1 l/min. The eluted gas contained Rb radioisotopic impurities in trace quantities of approximately 0.06 microCi/l.

Humans↗
PubMed1986

Comparison of ultrashort-lived iridium-191m with technetium-99m for first pass radionuclide angiocardiographic evaluation of right and left ventricular function in adults.

Ultrashort-lived iridium-191m (Ir-191m, physical half-life = 5.0 seconds) has been used in angiocardiography, primarily in pediatric patients. A theoretical obstacle to more widespread use of Ir-191m is the belief that its physical half-life is too short to permit evaluation of left ventricular function in adult patients. To evaluate its usefulness in adults, first pass ejection fractions of the left and right ventricles determined with use of Ir-191m and technetium-99m (Tc-99m) were compared in 33 adult patients. An osmium-191m----iridium-191m (Os-191----Ir-191m) generator was employed to deliver doses of 150 to 250 mCi (5.5 to 9.2 GBq) of Ir-191m for intravenous injection. The whole body radiation absorbed dose with Ir-191m was 15 to 25 mrad. High quality angiocardiograms were obtained with both Tc-99m and Ir-191m. Total counts per image for the right ventricle were 51,000 +/- 8,000 (mean +/- SD) for Ir-191m and 30,000 +/- 8,000 for Tc-99m. The left ventricular counts were comparable for both radiotracers (25,000 +/- 7,000 for Ir-191m and 25,000 +/- 8,000 for Tc-99m). Right ventricular ejection fractions were similar: 44 +/- 8% for Ir-191m and 47 +/- 9% for Tc-99m. The correlation coefficient was 0.93 with a standard deviation of the regression of 3.1% ejection fraction units. The left ventricular ejection fractions were also similar: 45 +/- 14% for Ir-191m and 46 +/- 13% for Tc-99m. The left ventricular ejection fraction correlation coefficient was 0.96 with a standard deviation of the regression of 3.7%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1980

Plutonium in [99mTc] Pertechnetate for clinical use: concise communication.

Pertechnetate from 31 different Tc-99m generators was analyzed to determine if alpha-emitting radionuclides were present. Significant amounts of Pu(239 + 240) were found in the pertechnetate eluted from neutron-activated molybdenum distributed by one manufacturer. The Pu(239 + 240)/Tc-99m activity ratio in the first eluate from these generators varied between 1.3 . 10(-12) and 1.4 . 10(-11). The Pu(239 + 240) contamination is believed to originate from uranium impurities in the molybdenum batch. The build-up of Am-241, the daughter decay product of Pu-241, has also been demonstrated. The estimated Pu-241/Pu(239 + 240) activity ratio at the reference time was 8:1. It is strongly recommended that upper limits for the plutonium content of eluates from nonfission-produced molybdenum should be included in the various pharmacopoeias and that restrictions be placed on the uranium content of molybdenum used for the production of Mo-99 by neutron activation.

Americium↗
PubMed2002

Development of a titanium tungstate-based 188W/188Re gel generator using tungsten of natural isotopic abundance.

The feasibility of developing titanium tungstate-based 188W/188Re gel generator using tungsten of natural isotopic abundance irradiated in a moderate flux reactor has been investigated. Influence of temperature, pH and eluent concentration on generator performance was studied. It was found that "post-formed" approach allows to construct gel generators with elution performance and 188Re elution yields very close to those of conventional alumina 188W/188Re generator. Curie-level 185W radionuclidic impurity presents a challenge during the processing of target material and subsequent elution of the generator. In the future use of semi-enriched with 186W target material (50-60% enrichment) would be beneficial in the development of titanium tungstate-based 188W/188Re gel generators.

Journal Article↗
PubMed1989

Sites of deposition of aqueous aerosols: a study of efficiency of delivery systems for lung ventilation imaging in man.

A study was made of the deposition of 99Tcm-DTPA aerosol in the components of a jet nebulizer-based aerosol production system. Three impaction devices were compared: a ball-bearing separator, a virtual impactor and a step separator. In addition a comparison was made of two types of tubing which carried aerosol from nebulizer to mouthpiece: corrugated and smooth-walled tubing. The retention of aerosol following inhalation was measured in five normal volunteers using different patterns of breathing. Using an aerosol production system which included a ball-bearing separator only a mean of 11% of the radioactivity loaded into the nebulizer was emitted as an aerosol. Some 18% remained in the ball-bearing separator. The ball-bearing and step separators produced similar total outputs (7% and 6% minimum), the step separator producing marginally higher mean output/min. The virtual impactor produced a lower output than the other two impactors studied, only 1%. A larger proportion of the aerosol output was deposited on corrugated tubing (7%) compared with smooth-walled tubing (1%). The retained fraction of the aerosol inhaled by subjects ranged from 16% to 43%. A higher fraction was retained when subjects inhaled deeply and held their breath for 10 s between each breath. The efficiency of radionuclide deposition from aerosol generator to patient ranged from 1.1% to 6% and was determined more by the retention in the subject than by choice of separator or tubing.

Aerosols↗
PubMed1995

An improved 191Os/191mIr generator using a hybrid anion exchanger.

Iridium-191m is an attractive radionuclide for first-pass radionuclide angiography, but development of an 191Os/191mIr generator with high 191mIr yield has proven difficult. The use of trans-dioxobisoxalatoosmate(VI) as a parent species results in a higher initial yield (20 to 25%/mL), but the yield decreases over time. Using an anion-exchange column of tridodecylmethylammonium chloride-treated silica gel and AG MP-1 resin, we have developed an improved 191Os/191mIr generator with higher initial yield (25 to 30%/mL) and a slower rate of decrease than the previous design.

Ion Exchange Resins↗
PubMed1989

Clinical usefulness of ultrashort-lived iridium-191m from a carbon-based generator system for the evaluation of the left ventricular function.

Ultrashort-lived 191mIr (4.96 sec; 63-74 and 129 keV photons) is potentially advantageous for first-pass radionuclide angiocardiography, offering the opportunity to perform repeat studies with very low absorbed radiation dose to the patient. Left ventricular (LV) first-pass studies were performed in 72 patients with 191mIr from a new bedside 1.3 Ci (48.1 GBq) 191Os/191mIr generator system using an activated carbon support that offers high 191mIr yields (15-18%) and consistent low 191Os breakthrough (2-4 x 10(-4)%/bolus). Using a single crystal digital gamma camera, uncorrected end-diastolic counts in the left ventricular representative cycle ranged from 10 up to 30 k counts. The reproducibility of repeated LV ejection fraction (LVEF) determination at 2-min intervals in 50 patients was r = 0.97, mean diff. = 2.08 +/- 1.55 EF units. Comparison between 191mIr (80-120 mCi; 2,960-4,400 MBq) and 99mTc (20-25 mCi; 750-925 MBq) LV count rates indicates a 3 wk useful shelf life of this new generator system for cardiac studies. Iridium-191m determined LVEF correlated closely with 99mTc determined LVEF in 32 patients (r = 0.96, mean diff. = 1.87 +/- 1.23 EF units). Parametric images for LV wall motion analysis were comparable with both isotopes. We conclude that rapid, repeat, and reproducible high count rate first-pass left ventricular studies can be obtained with 191mIr from this new 191Os/191mIr generator system using a single crystal digital gamma camera.

Adult↗