Monthly Archives: November 2011

Prenatal Radiation Exposure Limits

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The Nuclear Regulatory Commission (NRC) publishes guides that provide advice to licensees on how best to satisfy regulatory requirements.  Regulatory Guide (RG) 8.13 discusses the limits on prenatal radiation exposure.

For Illinois, dose to the fetus/embryo is governed by 32 Ill. Adm. Code 340.280.  Section 340.280 states, “[Licensees] shall ensure that the dose equivalent to an embryo/fetus during the entire pregnancy, due to occupational exposure of a declared pregnant woman, does not exceed 5 mSv (0.5 rem).  In addition, if a woman does not notify the administration of the estimated date of conception, Section 340.280 (d) states that, “…the licensee or registrant shall ensure that the dose equivalent to an embryo/fetus, as specified in subsection (b) of this Section, due to occupational exposure of the declared pregnant woman does not exceed 0.5 mSv (0.05 rem) per month, during the remainder of the pregnancy.”

It’s interesting to note that if a woman does not declare her pregnancy in writing, the standard occupational dose limits are applied to her, and not the more restrictive dose limits assigned to a woman with a declared pregnancy. So, if you’re pregnant and you don’t declare, a male member of the public has a lower limit placed on him than that of the effective limit placed on your unborn child – by a factor of 50. (5000 mrem for pregnant undeclared worker versus 100 mrem for a male member of the public).  Dr. Michael Stabin, Ph.D. of Vanderbilt wrote an excellent article about radiation as a carcinogen, and the regulatory contradictions surrounding dose equivalent limits for radiation workers and members of the public.  Be sure to take the test at the bottom of his article.

 

DaTscan (Ioflupane Iodine-123) Nuclear Medicine Scan

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Midbrain slice of a SPECT DaTSCAN image showing normal striatal morphology

Darius Rubas, CNMT, lead nuclear medicine technologist at St. Alexius Medical Center in Hoffman Estates, IL, introduced us to DaTscan,  the GE trademark name for Ioflupane Iodine-123 injection.  DaTscan is the first FDA-approved radiopharmaceutical adjunct imaging agent to help physicians evaluate patients with suspected parkinsonian syndromes (PS), such as Parkinson’s disease (PD).  St. Alexius Medical Center is among the first hospitals in the Chicagoland area to offer DaTscan in a routine nuclear medicine imaging procedure.

DaTscan is a radiopharmaceutical imaging agent that works by binding to dopamine transporters (DaT) in the brain, and gives physicians adjunctive diagnostic capability that may help lead to timely and appropriate diagnosis and treatment.

PS occurs when the brain does not get enough dopamine to perform certain functions. This affects the ability of the brain to control movement and other muscle functions.  According to GE Healthcare, DaTscan is an adjunct to other diagnostic evaluations that help differentiate essential tremor (ET) – a common movement disorder – from tremors due to PS.  The effectiveness of DaTscan as a screening or confirmatory test for monitoring disease progression or response to therapy hasn’t been established, however.  WGN Chicago recently aired a three minute video describing the new DaTscan benefits.

Geiger Fukushima: iPhone Geiger Counter

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Fukushima Geiger Counters. Sanwa Corporation's President Yuichiro Saito shows the newly developed Geiger counter models. (Mainichi)

Sanwa Corporation of Japan recently developed a small Geiger-Muller tube for use with the iPhone Geiger Bot app.  The Geiger Bot app counts the audible clicks from the output speaker of a Geiger counter setup.  Although the Geiger Bot app could previously be used to provide a digital readout from older, analog Geiger counters, Sanwa has developed their own Geiger tube for use with the app.  There’s no confirmation yet on the accuracy of readings or if they’re sold pre-calibrated.

The Sanwa team started developing the tube in June, after the March tsunami and subsequent radiation disaster created high demand for radiation survey meters.  According to the Daily Yomiuri, a leading Japanese newspaper, as of November 16 nearly 3,000 reserved orders had been placed for the iPhone compatible Geiger tube and another, self contained Geiger counter developed by the company.  More info can be found at the Mainichi Daily News.

California Department of Public Health and the Implementation of SB 1237

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In late August, 2011 The Joint Commission issued a sentinel alert concerning the radiation risks of diagnostic imaging.  This follows California passing a dose reporting law last year, known as SB 1237, that will require providers to record radiation dose on both the diagnostic image and in a patient’s medical record.  In addition, the law stipulates that all radiation overexposures will have to be reported to patients, treating physicians, and the California Department of Health.  This law will effectively bring the dose reporting requirements and monitoring to roughly the same standard as that currently in place for radiation therapy.

Much debate surrounds the successful implementation of this law and the burdens it will place on hospital administrators and medical staff.  The California Department of Public Health has produced, and is currently modifying, a question-and-answer document that will help providers meet the requirements of SB 1237.  This question-and-answer document may help in your preparation for answering questions stemming from The Joint Commission’s Sentinel Alert concerning radiation risks and reporting in radiology.

Blood Sampling of Patients Treated with Iodine-131

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Patients with thyroid diseases who are treated with I-131 may be released if the total effective dose equivalent to any other individual from exposure to the released individual is not likely to exceed 5 mSv (0.5 rem) following assessment of the patient’s medical, living and working conditions (32 IL Adm. Code 335.2110).  Occasionally, these individuals will need to have blood drawn for unrelated issues several hours to a few days after the administration of I-131.  This could present a radiation safety or regulatory issue if protocol is not established for the phlebotomy or laboratory staff.  An article discussing the radioactivity of blood in patients treated with I-131 describes measuring methods and the relative radioactivity of blood depending on activity administered, sample volume, and time elapsed.  In most cases, for adults with normal kidney function, a 3 ml sample of blood from a patient given a normal therapy dose of I-131 presents little danger to laboratory staff.

Still, in keeping with ALARA, it is recommended to include requirements for monitoring all blood samples drawn from hospitalized patients undergoing treatment with I-131 NaI.  Hospital laboratory staff should be advised to contact nuclear medicine personnel in a timely manner prior to performing phlebotomy on treated patients to ensure that blood samples are monitored for elevated radiation levels.  Policies should state that if the survey meter reading from a blood sample, or the gloves or lab coat of the phlebotomist, are indistinguishable from background radiation as measured with a survey instrument specified in a license application, no further action will be taken.  If a blood sample is above background radiation, further monitoring of laboratory personnel and the area and equipment where the blood sample will be processed should be conducted.