Ga-68 for PET imaging is now available in a generator form from Eckert and Ziegler. As with all generators, there is always a possibility of some of the radionuclide held on the column (Ge-68) breaking through into the eluate (Ga-68) needed for imaging. A breakthrough test is needed with a limit of 0.001% or less of the Ge-68 parent in the Ga-68 eluate. We have recently developed an inexpensive test using high resolution gamma spectroscopy. Call for more details.
Long-lived contaminants are introduced into cyclotron produced radiopharmaceuticals from the activation and spallation of elements in the HAVAR target window into the target water. They are removed during the synthesis of the final imaging agent. Below, are a series of papers on the measurement of these contaminants, their retention in the body, and the dose delivered to the patient from them. The quantity of the contaminants is strictly controlled by the FDA which requires all drugs be 99.5% pure. The vast majority of prepared radiopharmaceuticals have only a tiny fraction of the allowed levels in them. The radiation dose these contaminants deliver to the patient, if present, is trivial.
They do, however, outlive the imaging isotope (typically F-18) and may alarm Homeland Security detectors found in many locations. The length of time these isotopes can alarm the detectors will be determined and published in the near future.
Keith Eckerman and Richard Leggett have provided uptake retention functions for soluble injected forms of each possible contaminating isotope and these tables are also presented in the link above.
Dr. Robert Metzger of Radiation Safety Engineering, Inc. is pleased to be presenting 3 papers at next weeks ICRS-13 / RSPD-2016 joint conference in Paris, France.
Below are links to each of the 3 papers.
- Uranium, radium and thorium in soils with high-resolution gamma spectroscopy, MCNP-generated efficiencies, and VRF non-linear full-spectrum nuclide shape fitting.
Spectra acquired on high resolution Germanium crystals are analyzed by standard software packages produced by Canberra (Genie), or Ortec (Gammavision). We have both software products and both identify gamma peaks in the spectrum and associate them with the gamma lines from known radionuclides in the gamma library. Spectra from natural sources that contain uranium, radium and other nuclides from the natural chains are difficult to analyze as the gamma peaks are heavily overlapped as shown above. The photopeaks shown above are from an expanded section of the 90 keV peak complex from natural uranium in soils. While the information on the uranium and radium concentrations in the soils is plainly there, the current software cannot deconvolute the overlapped peaks to provide the results. So Radium and Uranium concentrations in soils are normally determined by putting a small quantity of the soil into solution by a pyrosulfate or NaOH fusion, and then separating the uranium and thorium by extraction chromatography and counting. This is time consuming and expensive.
Recently, George Lasche and Bob Caldwell developed a new spectrum analysis package that takes a different approach to the analysis of a HPGE acquired gamma spectrum. In their approach, an isotope, once identified in the spectrum, is stripped from the spectrum with all of its known gamma peaks. This process continues interactively until all of the lines in the spectrum have been resolved and the residuals are structureless. Then the spectrum is rebuilt and the contribution of each isotope in the overlapped peaks can be easily determined (see above).
Then, using soil specific efficiency curves at the soil density being analyzed, the concentrations of the uranium and radium in the sample can be quantified. Testing we have been doing with known soil standards and intercomparisons with the separations lab on routine samples indicate excellent correlation for the new approach. The minimum detectable activity for U and Ra is comparable to or below traditional methods if sufficient volumes of soil are analyzed. Please look back for papers and presentations being developed on this method for the RPSD 2016 meeting.
The end result is a fast, inexpensive measurement of isotopic uranium and radium in soils at a fraction of the time and cost required for traditional techniques.
This technique has been used for analysis of soils for NORM concentrations in several states, but has not been approved for analysis of drinking water or radiopharmaceuticals.
A MCNP model of a PET/CT scanner with a dosed patient in the scanner.
The vast majority of shield designs are performed by simple point kernel methods using the bulk attenuation properties of the shielding material and a known source term. All of the NCRP manuals use this method. However, when the geometries are complex (see above), or the shields are layered, the point kernel techniques perform poorly and can result in significant overshielding at great cost for the construction, or undershielding, requiring shielding retrofits, also at great cost.
For these complex designs, Monte Carlo (e.g. MCNP)or discreet ordinate (e.g. 3DANT or Mercurad) methods are preferable. While desirable, the implementation of these methods can be difficult. The three dimensional geometry of the shielded room must be described to the code, and the run times for Monte Carlo methods can run days to weeks before the results converge. Previously we have rented time on one of several supercomputers for these designs.
Recently, we have acquired two supercomputers from Thinkmate and Kingstar computers and have installed MCNP on them. With the new installations of these dedicated supercomputers, we have been able to completely eliminate the computer charge for advanced designs and have reduced the time it takes to perform the analysis significantly. This makes these approaches to shield designs far more affordable, and usable for smaller projects.
Areas where the Monte Carlo or discreet ordinate methods can contribute include facilities where:
- There is significant potential for streaming of radiation around barriers.
- Layered shields (e.g. Concrete over lead)
- Mixed field sources (e.g. protons, and photons)
- Multiple sources impacting a single area.
- Complex geometries where the source term is hard to define for point kernel methods.
Please call us for more information if these new capabilities could be of use to you.
We’re pleased to announce that the Journal of Radioanalytical and Nuclear Chemistry has published our article A Monte Carlo approach to food density corrections in gamma spectroscopy in their September, 2015 edition.
Dr. Robert Metzger’s Powerpoint presentation for the upcoming Methods of Analytical Radiochemistry Conference in Hawaii is now available online for download and review. In his presentation, Dr Metzger details a new approach to accurately measuring the radionuclides in food samples of different densities. This new approach is robust and less expensive than the normal method of using many standards of different densities.
Download the PDF version here:A Monte Carlo Approach to Food Density Corrections in Gamma Spectroscopy
Radiation Safety Engineering, Inc is pleased to present the first of our Radiation Safety Update courses available now online.
The first offering in this series is the always popular “Effects of Nuclear Weapons“. The program looks at Dmitry Kiselyov’s assertion that Russia could turn the US into radioactive ash. Mr.Kiselyov is a Kremlin backed journalist, and made his remarks during the Crimean crisis.
The course provides an overview of the Russian Nuclear arsenal and reviews all of the effects of nuclear weapons to include blast, thermal effects, radiation, fallout, and electromagnetic pulse. Students who complete the $35 program should have an understanding of the threat posed by a nuclear exchange.
For registration details please visit the Effects of Nuclear Weapons course page.
Radiation Safety Engineering is proud to announce that our class lectures for the one day Radiation Safety Short Course have been compiled into video and are now available online. The online course contains the same content as our classroom training, broken into convenient segments for viewing at your leisure using any popular web browser.
More details and registration information for the course are available here on the Radiation Safey Short Course page located under the Training & Classes section of our website. You can also contact our office at (480) 897-9459 or (800) 477-9691 if you have questions or prefer to register by phone.
Our one-day DOT Hazmat Class has also been converted to an online course and is available for completion.