July 2017
Proper Use of a Neck Phantom for Thyroid Uptakes

The use of a phantom mimicking a thyroid in a neck is recommended to determine the sensitivity of the measuring device during in-vivo thyroid uptake assessments. Several sources of inaccuracy and inconsistency have been recognized over the years with this procedure. Construction of the thyroid neck phantom to simulate the absorption and scatter characteristics of a human neck was one of the first steps towards adequate standardization of the thyroid uptake test. For a realistic representation, the phantom material should have radiation absorption and scatter characteristics similar to those of human soft tissue, and the calibration depth should be about 2 to 2.5 cm.>>

November 2016
New NIST Primary Standardization of F-18

In 2015 the National Institute of Standards and Technology (NIST) published an article in the Journal of Nuclear Medicine revising the activity standard for the positron emitter F-18. They reported a change of - 4% in its radioactivity standard for F-18. In addition to the obvious change that this brings to the direct measurement of this radionuclide in dose calibrators, it has an influence on the relative response ratio that allows Ge-68 based solid mock syringe sources to be used as a long-lived calibration reference source. It is important to make sure dose calibrator calibration factors (dial settings) are representing the true activity, thereby affecting the accuracy of the calculation of standard uptake values, scanner-reported activities and true-injected activities. The use of a direct traceable NIST standard can overcome any errors by adjusting the F-18 dial settings on your dose calibrator. >>

June 2016
Wipe Testing for Ra-223 Contamination

This is the third and final discussion in a series of three Hot Tips. In the preceding Hot Tips for the Technologist I gave you some interesting facts about the activated charcoal and Drierite used in xenon delivery systems. In this Hot Tip I would like to conclude this theme and talk about the use of Soda-Lime in xenon delivery systems.

In order to comply with regulatory requirements, wipe testing must be performed upon receipt of Ra-223 shipments and in restricted areas following Ra-223 administration.

Two important steps that must be checked on your NaI(Tl) well detector and multichannel analyzer well to insure accurate counting of your wipes are:

1. Obtain the Ra-223 detector efficiency for specific wipe smear sample/method.  
2. Calculate the Minimal Detectable Activity (MDA) of the well counter and appropriate trigger levels for NRC and DOT regulations. >>

October 2015
Interesting facts about Soda-Lime used in Xenon Delivery Systems

This is the third and final discussion in a series of three Hot Tips. In the preceding Hot Tips for the Technologist I gave you some interesting facts about the activated charcoal and Drierite used in xenon delivery systems. In this Hot Tip I would like to conclude this theme and talk about the use of Soda-Lime in xenon delivery systems.

Soda-Lime is a mixture of chemicals, used in granular form in closed breathing environments, such as general anesthesia, submarines, rebreathers, recompression chambers, respiratory therapy departments and xenon delivery systems, to remove carbon dioxide from breathing gases to prevent CO₂ retention and carbon dioxide poisoning. >>

August 2015
Interesting facts about Drierite and Soda Lime used in Xenon Delivery Systems

This is a second discussion in a series of three Hot Tips. In the preceding Hot Tip for the Technologist I gave you some interesting facts about the Activated Charcoal used in xenon delivery systems. In this Hot Tip I would like to continue the theme and talk about the use of Drierite in xenon delivery systems.

Water and moisture probably cause more damage than any other contaminant, either by direct attack or by indirect means. Dampness can promote the growth of mildew or fungus. Water molecules on the surface of metals can cause rust, tarnish or corrosion. >>

May 2015
Interesting facts about Activated Charcoal used in Xenon Delivery Systems

Activated charcoal has been used for a number of years by both the nuclear industry to trap exhaust gases and in nuclear medicine laboratories to trap effluent from Xe-133 used in lung ventilation studies.

The effect of the activated charcoal is to selectively slow down the migration or net flow rate of xenon through a trap or traps so that when it leaves the equipment through an exhaust port it will no longer be a radioactive gas. >>

January 2015
'Hot Spots' on the Radioaerosol Lung Ventilation Scan

Historically, one of the overriding problems with performance and interpretation of the Radioaerosol Lung Ventilation scan has been ‘hot spots’.

It has long been thought that ‘hot spots’ were the result of clumping of particles, which were either too large or were sticking together. ‘Hot spots’, rather than being related to particle size, are almost entirely a function of velocity. >>

June 2014
Dose Calibrator Linearity Testing

Linearity testing assesses the ability of the dose calibrator to indicate the correct activity over the range of use of the calibrator. This test is usually performed using a vial or syringe of Tc-99m whose activity is at least as large as the maximum activity normally measured in a prepared radiopharmaceutical kit, in a unit dosage syringe given to a patient, or in a radiopharmaceutical therapy, whichever is largest. For users of Mo-99/Tc-99m generators this activity may be the total eluate from a fresh generator. Other isotopes can be used to perform linearity such as F-18.

The NRC requires that linearity be tested upon installation and at least quarterly thereafter as well as after repair. There are two methods for testing the linearity of a dose calibrator: the decay method and the attenuation tube or shielding method. >>

March 2014
Dispensing Xenon Xe-133 Gas

Xenon Xe-133 Gas is supplied in a mixture of xenon gas (5%) in carbon dioxide (95%). It is contained within septum sealed glass vials and has been proven valuable in the diagnostic evaluation of pulmonary function and imaging of the lungs, as well as assessment of cerebral blood flow.

It is reactor-produced as a by-product of Uranium U235 fission. The contents of the vial are in gaseous form, contain no preservatives, and are ready for use. Xenon Xe-133 is chemically and physiologically related to elemental Xenon, a non-radioactive monoatomic gas, which is physiologically inert except for anesthetic properties at high doses. The vial stopper contains dry natural rubber latex and may cause allergic reactions in providers or patients who are sensitive to latex. >>

February 2014
Simple Solution to Reduce Exposure from Patient to Technologist

There is a lot of concern about diagnostic testing and the use of radiation in the medical field. 
The concern is equally justifiable for both the patient and health care professional during the procedure. Many reports have been published listing recommendations on how to reduce exposure to both parties. >>

January 2014
Exposure Filters on a Geiger-Müller (GM) Counters for Alpha Particles

The survey meter is an essential resource a technologist has to determine the presence of radiation contamination in typical surveys such as during routine area surveys, checking incoming packages, testing after spills or other radiation incidents and measurement of waste held for decay-in-storage prior to disposal. A literature review of incident and overexposure reports indicate that a majority of these events occurred because a radiation worker did not have or did not use a survey meter. With the development of new radiotracers for therapy using alpha and beta emitters, it is important that the proper equipment is used to survey for contamination. >>

December 2013
Radioaerosol Studies in Ventilator Assisted Patients

Radioaerosol inhalation lung scanning in ventilator assisted patients is not only feasible but a valuable tool that can lead to important changes in patient management. However, in these patients, radioaerosols have been less readily accepted. It generally has been felt that the central bronchial deposition and poor peripheral penetration tendencies of radioaerosols are likely to be accentuated in this patient group. With technical improvements in current delivery systems, this appears to be less of a problem and has resulted in substantially increased clinical utilization in this patient population. >>

November 2013
USP<797> Requirements for Radiopharmaceuticals

The section in USP <797> addressing the requirements for radiopharmaceuticals as Compounded Sterile Preparations (CSPs) is based on specific and detailed recommendations from an advisory panel of nuclear pharmacists. This section clarifies details and exemptions for radiopharmaceutical compounding, especially in regards to microbial contamination risk levels.

Determining the risk level of CSPs prepared in a nuclear pharmacy is one of the most important aspects of the section. Keep in mind that both radionuclides and non-radioactive medications are handled, prepared, and stored in nuclear pharmacies. Table 1 provides a list of common radionuclides and traditional drugs that are prepared and dispensed with their corresponding risk levels. >>

October 2013
Spilled Gas Clearance Time

Noble gases such as Xenon in the air present an external source of radiation exposure that must be calculated. Many commercially available dosimeters and survey instruments are not capable of accurately measuring worker doses from immersion in noble gases.

Should an accidental release of Xenon-133 occur into either the imaging room or the hot lab, the nuclear medicine technologists would immediately remove themselves and the patient, if feasible or applicable, from the room. The door to the room should be immediately closed to minimize leakage to surrounding unrestricted areas. The room will remain vacant until such a time as the room ventilation would dilute the concentration of released Xenon-133 to levels below the Derived Air Concentration (DAC) for restricted areas, i.e., 1 x 10-4 microcuries/milliliter for Xenon as specified by the NRC in Table 1 of Appendix B to Part 20.

Because normal room ventilation is usually not sufficient to ensure timely clearance of spilled gas, the calculations described below should be done to determine the amount of time a room should be cleared in case of a gas spill. This clearance time should be posted in the room.  >>

September 2013
The Geometry Test

The geometry of the container (syringe or vial) that is used to measure a radioactive source can be a cause of assay errors in dose calibrators. Specifically, if there is a difference in the container used to obtain initial calibration settings and the container used to assay dosages in clinical practice. Ideally, the geometry of the standard source should be identical to the geometry of the source being measured. If the source geometry is not identical, the error in the measurement should be quantified and, if significant, either a new calibration setting determined or a correction factor applied.  >>

August 2013
Chi-Square Test Made Easy
A series of data obtained by counting a single radioactive sample repeatedly will always demonstrate variation. To determine if the variation is due to the natural randomness of radioactive decay or is due to inconsistency in instrument performance, a chi-square (x²) test is performed.

The chi-square test allows you to determine how close a series of counts would come to a true Poisson distribution (bell curve) and provides a measure of the precision of the counting instrument’s performance.

Since it is time consuming and inconvenient to count every patient’s thyroid or wipe sample multiple times in a row, you would want to be certain that the individual values given by the counting instrument can be used with confidence.  >>

July 2013
Radioiodine Bioassays

Radioiodinated compounds and solutions undergo decomposition that may result in the volatilization of radioiodine. If this occurs, individuals working with these materials have a potential for accidental ingestion or inhalation of radioactive iodine. Once inside the body, the iodine concentrates in the thyroid and irradiates that organ. A bioassay program will enable the Radiation Safety staff to monitor and determine the radioiodine burden in an individual’s thyroid.

Regulatory Guide 8.20 Application of Bioassay for I-125 and I-131(dated September 1979) and DRAFT Regulatory Guide DG-8050 (dated September 2011), provide criteria acceptable to the NRC staff for the development and implementation of a bioassay program. It provides guidance on the selection of workers who should participate in the program, frequencies of bioassay, actions to take based on bioassay results and the particular results that should initiate such actions.  >>

June 2013
Quality Assurance Programs for Uptake Probes and Well Counters
Quality Assurance Programs for Uptake Probes and Well CountersUptake probes and well counters are subject to various types of malfunctions that can lead to sudden or gradual changes in their performance characteristics. For example, electronic components and detectors can fail or experience a progressive deterioration of function leading to changes in detection efficiency, increased background, etc.
To ensure consistently accurate results quality assurance procedures should be employed on a regular basis for probe and well counter measurement systems.  >>

May 2013
Radioaerosol Tips
With the possible shortage of Xenon looming over our heads, many departments will be turning to radioaerosol imaging with Tc-99m DTPA for lung ventilation studies. If you are only performing these studies during a shortage, you may be a little rusty in remembering some important tips that are useful when performing this procedure.  >>

April 2013
Xenon Effluent Monitoring

Did you know State and Federal regulations require the routine monitoring of trap effluent gas?

Noble gases such as xenon in the air present an external source of radiation exposure that must be calculated.  >>

March 2013
Low-Energy Photon Emitters
The copper vial/syringe dipper was designed for use when measuring I-123 and In-111.
This dipper removes variation in readings caused by low-energy photon attenuation differences from different materials,
thicknesses and volumes used in syringes and vials.

Are you using one with your measurements?  >>