57Co Point Sources Research Articles

Impact of Attenuation Correction on Quantification Accuracy in Preclinical Whole-Body PET Images

Background Whole-body PET images can be obtained by using the “step-and-shoot” (SaS) method (using multiple bed positions) or continuous bed motion (CBM). As transmission scans are not always feasible, an alternative method where attenuation data can be generated via emission-based attenuation correction (AC) maps is of interest. The aim of this preclinical study was to investigate the influence of the acquisition method and AC on the quantitation accuracy of [18F]FDG-PET. Methods [18F]FDG-PET phantom images were acquired using either SaS or CBM. Transmission scans were recorded for the SaS method using a 57Co-point source. Emission-based attenuation sinograms were obtained from the image after segmentation and inverse Fourier rebinning. PET images were reconstructed without AC, transmission based (TX-AC) and emission-based (EM-AC) attenuation correction. Moreover, [18F]FDG-PET scans of rats bearing mammary carcinomas acquired using either SaS or CBM were analyzed retrospectively and quantification in tissues was compared. Results Phantom recovery coefficients (RC) varied greatly, ranging from 0.49±0.01 to 1.15 ± 0.07, dependent on acquisition method, reconstruction algorithm and AC method. In CBM acquired images, EM-AC improved quantification accuracy when compared to no-AC images in the phantom studies (RC 0.79±0.02 vs 0.49±0.01, respectively) and in tumors of rats (DMBA model: 1.16±0.42 SUV vs 0.86±0.28 SUV, respectively). Conclusion The method of AC has a strong influence on the quantification of [18F]FDG. Our data indicates that EM-AC improves quantification in images obtained by CBM and SaS. However, the obtained values were still underestimated when compared to TX-AC corrected images.

A systematic study on the uptake of 57Co ions on amidoxime functionalized PAN-PVDF beads: preliminary studies towards fabrication of 57Co point sources

This study describes the fabrication of 57Co point sources utilizing the metal sorption properties of amidoxime functionalized PAN-PVDF beads. PAN-PVDF beads were synthesized by phase inversion, functionalized and characterized by FT-IR spectroscopy. Uptake of 57Co on amidoxime-PAN-PVDF beads was investigated by optimizing the experimental parameters. The optimized procedure was employed for fabrication of 57Co point sources. Distribution pattern of 57Co on the source core was confirmed by autoradiography. SEM and EDS analyses of inactive Co loaded beads were performed. A simple procedure for stable loading of 57Co onto PAN-PVDF beads could be standardized. The method could be of potential utility for fabrication of 57Co point for calibration purposes after extensive quality control studies.

Experimental Study of an Easily Controlled Ultra-High-Resolution Pixel-Matched Parallel-Hole Collimator with a Small Cadmium Zinc Telluride Pixelated Gamma Camera System

The aim of this study was to develop an easily controlled, ultra-high-resolution, tungsten parallel-hole collimator based on a small pixelated gamma camera system. A small cadmium zinc telluride (CZT) pixelated semiconductor detector (eValuator-2500 detector [eV product, Saxonburg, PA]) was evaluated. This detector is composed of an array of 51.2 × 0.8 × 3-mm3 individual CZT crystal elements. The ultra-high-resolution, pixel-matched, parallel-hole collimators consisted of six layers, with the same between the hole and pixel size. The basic characteristics of the imaging system, such as sensitivity and spatial resolution, was measured using a 57Co point source. The measured averages of sensitivity and spatial resolution varied depending on the septal heights of the ultra-high-resolution parallel-hole collimator and source-to-collimator distances. When the 30-mm septal height was at 1-cm source-to-collimator distance, the spatial resolution was approximately 0.85 mm. Using 5-mm septal height, over 0.3 cps/kBq sensitivity was achieved. One advantage of our system is the use of stacked collimators that can select the best combination of system sensitivity and spatial resolution. Our results demonstrated that the developed CZT–pixelated gamma camera system using an ultra-high-resolution parallel-hole collimator of various collimator geometric designs has potential as an effective instrument.

Preparation of 57Co point sources for the performance evaluation of nuclear imaging instruments

This paper describes the utility of electrodeposition method to prepare 57Co point sources. A description of the electrolytic cell, the process of 57Co electrodeposition, encapsulation and quality control of the sealed 57Co sources is presented. Sources containing ∼3.7–4.81MBq (0.10–0.13mCi) of 57Co were prepared, encapsulated in miniature titanium capsules and subjected to quality control tests to ensure compliance with regulatory requirements. The encapsulated 57Co sources prepared by the reported procedure were found to be effective in routine performance evaluation of nuclear medicine instruments.

NORMAL THORACIC AND ABDOMINAL DISTRIBUTION OF 2‐DEOXY‐2‐[18F]FLUORO‐d‐GLUCOSE (18FDG) IN ADULT CATS

Positron emission tomography (PET) with 2-deoxy-2-[18sF]fluoro-D-glucose (18FDG) is an important imaging modality for diagnosis and staging of human neoplastic disease. The purpose of this study is to describe the normal is 18FDG uptake in adult cats. Six adult healthy female cats were used. Cats were sedated and then injected intravenously with 74.0 +/- 13.0 (mean +/- SD) MBq of 18FDG. General anesthesia was induced and cats were placed in ventral recumbancy on the PET scanner's bed. Static images using multiple bed positions were acquired approximately 60-90 min after injection. A transmission scan was acquired at each bed position utilizing a 57Co point source to perform attenuation and scatter correction. Regions of interest (ROIs) were drawn over the liver, right and left renal cortices, left ventricular wall, and wall of ascending and descending colonic segments. Standardized uptake values (SUV) were calculated using an established formula. Kidneys and intestinal tract had relatively intense uptake of 18FDG; liver activity was intermediate; the spleen was not identified in any of the cats. Cardiac activity was variable but intense activity was noted in the left ventricular myocardium in most cats. No appreciable lung uptake was noted. Mean +/- SD SUV values were calculated. This study established the normal pattern of uptake of 18FDG in adult cats and provided baseline data for comparison with future studies evaluating a variety of neoplastic and nonneoplastic diseases.

Measurement of the mass attenuation coefficients and electron densities for BiPbSrCaCuO superconductor at different energies

The mass attenuation coefficients for Bi, Pb, Sr, Ca, Cu metals, Bi2O3, PbO, SrCO3, CaO, CuO compounds and solid-state forms of Bi1.7Pb0.3Sr2Ca2Cu3O10 superconductor were determined at 57.5, 65.2, 77.1, 87.3, 94.6, 122 and 136keV energies. The samples were irradiated using a 57Co point source emitted 122 and 136keV γ-ray energies. The X-ray energies were obtained using secondary targets such as Ta, Bi2O3 and (CH3COO)2UO22H2O. The γ- and X-rays were counted by a Si(Li) detector with a resolution of 0.16keV at 5.9keV. The effect of absorption edges on electron density, effective atomic numbers and their variation with photon energy in composite superconductor samples was discussed. Obtained values were compared with theoretical values.

The development of strong 57Co Mössbauer sources for scattering experiments of 57Fe I. The production of large activities of 57Co at the compact cyclotron at Munich

Mössbauer scattering experiments on 57Fe need strong 57Co sources. This paper describes a new and efficient technique to produce 57Co activities of several Ci at the Munich compact cyclotron. Essential to this technique is the development of a rotating target device, which stands a 22 MeV proton beam with currents up to 500 μA. Typical production rates are I Ci 57Co in 10 days. A scattering experiment on a myoglobin crystal proves the advantage of the new strong 57Co point sources.

Radioisotopic X-ray analysis of uranium ores by K shell fluorescence

Uranium ores from various locations in Canada were analyzed by X-ray spectroscopy. A 10 mCi 57Co point source was employed and mounted on a one dimensional goniometer. This instrument was designed with adjustable scatter angle, primary and secondary collimation settings. The optimum geometrical conditions for analysis of uranium using partially thick powdered ore samples were found. Assumptions can be drawn for innate geological specimens which lead to the direct calculation of the matrix and thickness factors. This is accomplished by simultaneously and experimentally measuring the Compton scattering and transmitted peak intensities. These factors are then used to modify the U K αi peak intensity so that no comparative standards are required to maintain accuracy. As such, the technique is a prime candidate for application to on-stream industrial analysis.