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Radiation Safety Considerations for PET/CT. Robert E. Reiman, MD, ABNM Radiation Safety / OESO Duke University Medical Center. Radiation Safety? Who Cares!. Why We Have Radiation Protection Programs. December 1895: Roentgen discovers x-rays.

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radiation safety considerations for pet ct

Radiation Safety Considerations for PET/CT

Robert E. Reiman, MD, ABNM

Radiation Safety / OESO

Duke University Medical Center

why we have radiation protection programs
Why We Have Radiation Protection Programs
  • December 1895: Roentgen discovers x-rays.
  • 1/1896 – 12/1896: 23 cases of radiation dermatitis documented.
  • 1911 –1914: 252 radiation-induced cancer cases with 54 fatalities.
why we re regulated
Why We’re Regulated

In the early years of the Twentieth Century, radium was widely promoted as a cure for practically everything, from cancer to baldness. Radium was added to hundreds of “over-the-counter” commercial “beauty” and “health” products.

why we re regulated6
Why We’re Regulated

Eben Byers, socialite and U.S. Open champion, drank three bottles of “Radithor” a day for three years. He died a painful death from radionecrosis of the jaw and skull in 1932. After a Congressional inquiry, the FDA seized oversight of radium-containing products.

pet ct regulations
PET/CT Regulations
  • “10 CFR 20” – Title 10 (Energy), Code of Federal Regulations, Part 20
  • “10 CFR 35” – Title 10, Code of Federal Regulations, Part 35
  • 10 CFR 20 addresses general standards for radiation protection.
  • 10 CFR 35 addresses use of “by-product” materials in medicine.
pet ct regulators
PET/CT Regulators
  • NRC directly oversees 17 states.
  • 33 “Agreement States” implement NRC regulations...and then some.
  • FDA regulates production of PET radiopharmaceuticals, and manufacture and sale of CT scanners.
  • Individual states regulate operation of CT scanners.
helpful organizations
Helpful Organizations
  • International Commission on Radiological Protection (ICRP)
  • National Council on Radiation Protection and Measurements (NCRP)
  • Nuclear Regulatory Commission (NRC)
  • “Agreement State” Radiation Protection Agencies
principle of alara
Principle of “ALARA”






radiation warning signs
Radiation Warning Signs

PET/CT Scanner


“Hot” Lab

record retention
Record Retention
  • Shipping and Receiving (3 years)
  • Area Surveys and Trash Surveys (3 years)
  • Public Dose Limit Compliance (3 years)
  • Personnel Dosimetry (lifetime)
criteria for personnel monitoring
Criteria for Personnel Monitoring
  • 10 CFR 20: Personnel monitoring occupational dose is required if the sum of external and internal EDE could be expected to exceed 10 % of the annual whole-body occupational limit.
  • Licensees can monitor at lower exposure levels as part of an ALARA program.
survey meter quality assurance
Survey Meter Quality Assurance
  • Meters OFF when not in use
  • Operation check with each use
  • Regular battery and high-voltage checks
  • Annual calibration
hands in the beam
Hands in the Beam?
  • NO hands in the useful (primary) beam unless protected by 0.5 mm lead or equivalent shielding.
  • Mechanical patient restraint should be used whenever practical in lieu of human holders.

Health Physics, Aug 2003

medical events administrative criteria
Medical Events: Administrative Criteria
  • Administered to wrongpatientorresearchsubject.
  • Wrongradiopharmaceutical administered.
  • Wrongroute of administration.
  • Administered activity differs from that in the written directive by more than 20 percent.
medical events dose criteria
Medical Events: Dose Criteria
  • Effective Dose Equivalent > 5 rem (0.05 Sv).
  • Single organ / tissue dose > 50 rem (0.5 Sv).

Reporting Medical Events

  • Must notify NRC / Agreement State agency within one calendar day after discovery.
  • Must follow up with a written report within 15 days after discovery.
  • Must notify referring physician within 24 hours.
  • Must notify patient or guardian unless contraindicated by referring physician.




TWICE the Headaches


why is pet different
Why is PET Different?
  • PET radionuclides have higher Exposure Rate Constants than “traditional” nuclear medicine radionuclides.
  • Photon energies are higher.
  • Half-lives are shorter.
pet shielding tenth value layers
PET Shielding: Tenth Value Layers

* TVL = thickness of material required to absorb 90% of photons

shorter half life lower dose
Shorter Half-Life >> Lower Dose*

*Dose received by a bystander at 1 meter during 5 half-lives or more

pet ct sources of exposure to staff
PET/CT: Sources of Exposure to Staff
  • Cyclotron (?)
  • Radiopharmaceutical Production (?)
  • Dose Dispensing / Calibration
  • Dose Administration
  • Patients
  • X-rays From CT
what doses do people get
What Doses Do People Get?

Ref: Beyer T, Mueller SP, Brix G et al. Radiation exposure during combined whole-body FGD-PET/CT imaging. 51st Annual Meeting, Society of Nuclear Medicine, June 22, 2004. Abstract 1331.

measures to reduce personnel dose
Measures to Reduce Personnel Dose
  • Time, Distance and Shielding
  • Laboratory Technique
  • Administrative and Procedural Controls
good hot lab technique
Good Hot Lab Technique
  • Cover work surfaces
  • Protective gloves
  • Wash hands frequently
things not to do in the hot lab
Things NOT To Do in the Hot Lab
  • Don’t Drink
  • Don’t Eat
  • Don’t Smoke
  • No cosmetics
minimize time and maximize distance
Minimize Time and Maximize Distance!

Technologists should minimize the time spent in close proximity (less than two meters) from the patient.

maximize distance
Maximize Distance!
  • Inverse Square Law ( 1/r2 )
  • Dramatic reductions in exposure
  • Simulations of PET technologist’s interactions with patients show that 75% of dose is accumulated during time tech is within 2 meters of patient.

I’m Outta Here...

I Got 8 mrem!

I Got 2 mrem!

I Got 0.1 mrem!

I Got 0.5 mrem!

utilize shielding
Utilize Shielding

Positrons can be stopped by 2 - 5 mm Lucite. Gammas require a high-Z material. Neutrons require high hydrogen content (paraffin or the “waters of hydration” in concrete).

other shielding methods
Other Shielding Methods

Syringe Shields (Tungsten and Lead Glass)

Unit Dose Stations

x ray aprons no protection at 511 kev
X-ray Aprons -- No Protection at 511 KeV

The “lead” aprons used in diagnostic radiology have about 0.5 mm lead equivalent. These afford significant protection at energies under 120 KeV, but are nearly useless against annihilation photons.

100 KeV: Transmission = 4.3 %

511 KeV: Transmission = 91.0 %

measures to reduce dose other techniques
Measures to Reduce Dose: Other Techniques

Tongs to Maximize Distance

Syringe Shields (Tungsten and Lead Glass)

Mobile Shields

measures to reduce dose procedural controls
Measures to Reduce Dose: Procedural Controls
  • Automated dose dispensing and Calibration (“Unit” Dose)
  • Elimination or automation of “flush” during patient administration
  • Rotation of personnel
reducing pet ct patient dose
Reducing PET/CT Patient Dose
  • Optimize administered radioactivity.
  • Reduce CT mAs.
  • Increase “pitch”.
  • Technique charts to minimize CT exposure to pediatric patients and small adults.
reducing pet ct patient dose50
Reducing PET/CT Patient Dose

Ref: Beyer T, Mueller SP, Brix G et al. Radiation exposure during combined whole-body FGD-PET/CT imaging. 51st Annual Meeting, Society of Nuclear Medicine, June 22, 2004. Abstract 1331.

avoiding medical events
Avoiding “Medical Events”
  • Use Texas as an example (detailed information accessible).
  • Look at the “Root Causes” of radiopharmaceutical errors.
  • Look at corrective actions taken.
corrective actions
Corrective Actions
  • Increasing staff awareness and retraining.
  • Addition of policies or procedures.
  • Modification of existing policies and procedures.
  • Addition of engineering controls.
  • Termination of staff.
regulatory requirements
Regulatory Requirements
  • WrittenInstructions on minimizing exposure to others must be provided to patient if a member of the public could receive over 100 millirem.
  • Patient may be released if “public dose” is less than 500 millirem.
  • Reference: NRC Regulatory Guide 8.39
patient release guidelines
“Patient Release” Guidelines

*Calculated per USNRC Regulatory Guide 8.39, assuming occupancy factor of 0.75 at one meter

annual dose limit to non radiation workers
Annual Dose Limit to Non-Radiation Workers
  • Member of the “general public” is limited to 100 millirem per year.
  • Non-PET staff in adjacent areas are the same as the “general public”.
  • “General Public” will be the limiting consideration in shielding design.
principles of pet ct shielding calculations
Principles of PET/CT Shielding Calculations
  • Identify the potentially exposed population and determine a limiting weekly dose.
  • Characterize the x-ray equipment / PET doses.
  • Characterize the site.
  • Determine “Use” and “Occupancy” factors.
  • Choose a barrier material.
  • Calculate barrier thickness and location.

Scanner Room

Occupied Area

(< 100 mrem/yr)



(Photon Flux)

1 m




Do = D1 / d2

D1 = dose due to one patient at one meter from scanner

Do = dose due to one patient at point of occupancy


E = ( Ē x W x U x T ) / d2

X-ray Tube

(W, Ē)


(Primary Beam)




Us(= 1)

prevention of unintentional fetal exposure
Prevention of Unintentional Fetal Exposure
  • Good History(includes asking direct question “Are you pregnant?”)
  • Common-sense Assessment of Risk of Pregnancy(age, surgical hx, contraception)
  • Beta HCG
  • Cannot prevent all unintentional exposures.
fetal doses rads
Fetal Doses (rads)

Ref: Russell J, Sparks R, Stabin M, Toohey R. Radiation Dose Information Center, Oak Ridge Associated Universities.

if one of your staff becomes pregnant
If One of Your Staff Becomes Pregnant...
  • Confidential “Declaration of Pregnancy”.
  • Information regarding fetal effects.
  • Fetal dose monitoring during pregnancy.
internet resources
Internet Resources
  • U.S. Nuclear Regulatory Commission: www.nrc.gov
  • FDA: www.fda.gov/cdrh/index.html
  • Radiation Internal Dose Information Center: www.orau.gov/reacts/compendia.htm (Dose from internally-deposited radionuclides)
internet resources68
Internet Resources
  • Center for Disease Control: www.cdc.gov/other.htm (Web addresses of State Health Departments)
  • Health Physics Society: www.hps.org