aapm task group #108 on pet and pet/ct shielding ... · pdf fileanswer 2: 5 mm lead reference...

Site Planning and Design of PET/CT FacilitiesSite Planning and Design of PET/CT Facilities
Melissa C. Martin, M.S., FACR, FAAPMMelissa C. Martin, M.S., FACR, FAAPM
AAPM Annual Meeting, Minneapolis, MNAAPM Annual Meeting, Minneapolis, MN
July 26, 2007July 26, 2007
Acknowledgements:Acknowledgements:
AAPM Task Group #108 on PET and PET/CTAAPM Task Group #108 on PET and PET/CTShielding RequirementsShielding Requirements
Report published inReport published in Medical PhysicsMedical Physics 33:1,33:1,January 2006, pages 4January 2006, pages 4--1515 Mark Madsen,Mark Madsen,Ph.D., Chair, University of Iowa Medical CenterPh.D., Chair, University of Iowa Medical Center
Jon Anderson, Ph.D.Jon Anderson, Ph.D. UT Southwestern MedicalUT Southwestern MedicalCenter, DallasCenter, Dallas
GE AdvanceGE Advance NXiNXiSiemens Biograph
(CTI, CPS)
LSO Hi-Rez Resolution
70 cm Patient Port
450 pound table

Site Planning and Radiation SafetySite Planning and Radiation SafetyWhat Is Different When PET is brought into a department?What Is Different When PET is brought into a department?
1) Requirements for patient handling during injection and1) Requirements for patient handling during injection anduptake phaseuptake phase
2) 5112) 511 keVkeV energyenergy
--increases exposure rate from doses, patientsincreases exposure rate from doses, patients
--greatly increases thickness of required shieldinggreatly increases thickness of required shielding(hence, use time and distance when possible)(hence, use time and distance when possible)
3) Combined modality scanners (PET/CT) require3) Combined modality scanners (PET/CT) requireconsideration of both gammaconsideration of both gamma--ray and xray and x--ray hazardray hazard
Factors Affecting Radiation ProtectionFactors Affecting Radiation Protection
Number of Patients ImagedNumber of Patients Imaged
Amount of Isotope Administered per PatientAmount of Isotope Administered per Patient
Length of Time each Patient Remains in theLength of Time each Patient Remains in theFacilityFacility
Location of the FacilityLocation of the Facility
General Environs of the FacilityGeneral Environs of the Facility
Typical PET FacilityTypical PET FacilityRoom LayoutRoom Layout
PETTomograph
PETUptakeRoom
PETControlRoom
Controlled Corridor
GammaCamera
GammaCamera
GammaCamera
CardiacStressRoom
Supplies
Bathroom
WorkArea
Bathroom
GammaCamera
UptakeProbe
OfficeOffice
Office
Office
Office
Office
Office
Office
Office
Office
Office
Office
ElectricalUtility
10 m3 m
PETTomograph
PETUptakeRoom
PETControlRoom
Controlled Corridor
GammaCamera
GammaCamera
GammaCamera
CardiacStressRoom
Supplies
Bathroom
WorkArea
Bathroom
GammaCamera
UptakeProbe
OfficeOffice
Office
Office
Office
Office
Office
Office
Office
Office
Office
Office
ElectricalUtility
PETTomograph
PETUptakeRoom
PETControlRoom
Controlled Corridor
GammaCamera
GammaCamera
GammaCamera
CardiacStressRoom
Supplies
Bathroom
WorkArea
Bathroom
GammaCamera
UptakeProbe
OfficeOffice
Office
Office
Office
Office
Office
Office
Office
Office
Office
Office
ElectricalUtility
10 m3 m
The approximate halfThe approximate half--value layer to be usedvalue layer to be usedfor PET Shielding calculations is:for PET Shielding calculations is:
25%
25%
25%
25%
10
1.1. 2 mm lead2 mm lead

Answer 2: 5 mm leadAnswer 2: 5 mm lead
ReferenceReference
AAPM Task Group 108 ReportAAPM Task Group 108 Report PET and PET/CTPET and PET/CTShielding.Shielding. Medical Physics 33(1), January 2006, Page 7Medical Physics 33(1), January 2006, Page 7
Answer 2: 5 mm leadAnswer 2: 5 mm lead
ExplanationExplanation
Monte CarloCalculatedTransmissionFactors
PET Exposure Factors: FPET Exposure Factors: F--1818
Half Life: 110 minutesHalf Life: 110 minutes
Major Radiation Emission: 511Major Radiation Emission: 511 KeVKeV GammasGammas
HalfHalf--Value Layer: Several publications list 4.1 mmValue Layer: Several publications list 4.1 mm PbPb andand3.4 cm for normal concrete for3.4 cm for normal concrete for narrow beamnarrow beam conditions.conditions.Use of these values willUse of these values will notnot provide sufficient shieldingprovide sufficient shieldingsince they neglect scatter buildup factors.since they neglect scatter buildup factors.
Tables of broad beam transmission for lead, concreteTables of broad beam transmission for lead, concreteand steel based on Monte Carlo calculations performed byand steel based on Monte Carlo calculations performed byDougDoug SimpkinSimpkin, Ph.D., are included in the AAPM task group, Ph.D., are included in the AAPM task group#108 report on PET Shielding#108 report on PET Shielding
Transmission Data for 511Transmission Data for 511 keVkeV photonsphotons[Douglas J.[Douglas J. SimpkinSimpkin, Ph.D.], Ph.D.]
Curve fit to Archer EquationCurve fit to Archer Equation
Calculated ConstantsCalculated Constants

TransmissionTransmissionin Leadin Lead
TransmissionTransmissionis lower thanis lower thanconstant TVLconstant TVL
TransmissionTransmissionin Concretein Concrete
TransmissionTransmissionin Steelin Steel
Other PET Isotope DataOther PET Isotope Data
NN--13: Half life = 10 minutes13: Half life = 10 minutes
OO--15: Half life = 2.07 minutes15: Half life = 2.07 minutes
CC--11: Half life = 20.4 minutes11: Half life = 20.4 minutes
RbRb--82: Half life = 1.3 minutes82: Half life = 1.3 minutes
GaGa--68: Half life = 68.3 minutes68: Half life = 68.3 minutes
These isotopes are dominated by the FThese isotopes are dominated by the F--18 requirements18 requirements

FF--18 FDG PET Studies18 FDG PET Studies
FF--18 FDG is a non18 FDG is a non--specific tracer for metabolic activity thatspecific tracer for metabolic activity thatis taken up normally in the brain, heart, bone marrow,is taken up normally in the brain, heart, bone marrow,bowel, kidneys and activated muscles, and concentrates inbowel, kidneys and activated muscles, and concentrates inmany metabolically active tumors.many metabolically active tumors.
To reduce uptake in skeletal muscles, patients are kept in aTo reduce uptake in skeletal muscles, patients are kept in aquiet state after the administration of the Fquiet state after the administration of the F--18 FDG in either18 FDG in eithera bed or chair for 30a bed or chair for 30--90 minutes depending on the type of90 minutes depending on the type ofscan and the practices of the institution.scan and the practices of the institution.
The patient preparation room is a requirement for any PETThe patient preparation room is a requirement for any PETfacility andfacility and mustmust be included in the radiation safetybe included in the radiation safetyplanning.planning.
A busy PET facility will often have more than 1 patient inA busy PET facility will often have more than 1 patient inthe uptake room. This must be considered whenthe uptake room. This must be considered whenperforming shielding calculations.performing shielding calculations.
Ideally, the busy PET facility will have more than 1 uptakeIdeally, the busy PET facility will have more than 1 uptakeroom.room.
After the uptake period, the patient should void to clear theAfter the uptake period, the patient should void to clear theradioactivity that has accumulated in the bladder.radioactivity that has accumulated in the bladder.
It is highly recommended that a bathroom be reserved forIt is highly recommended that a bathroom be reserved forPET patientsPET patients
The amount of administered activity that is collected in theThe amount of administered activity that is collected in thebladder and excreted prior to scanning is approximately:bladder and excreted prior to scanning is approximately:
10
25%
25%
25%
25% 1.1. 5%5%
2.2. 10%10%
3.3. 15%15%
4.4. 30%30%
Answer 3: 15 %Answer 3: 15 %
ReferenceReference
AAPM Task Group 108 ReportAAPM Task Group 108 Report PET and PET/CTPET and PET/CTShielding.Shielding. Medical Physics 33(1), January 2006,Medical Physics 33(1), January 2006,Pages 8 and 10Pages 8 and 10

Answer 3: 15%Answer 3: 15%
ExplanationExplanation
About 15-20% of administered activity is excreted withinthe first 2 hours after administration. In most cases, thepatient will void prior to imaging, removing approximately15% of the administered activity and thereby decreasingthe dose rate by 0.85 for the activity used in the imagingroom shielding calculations.
The patient is then positioned on the scanner for theThe patient is then positioned on the scanner for theprocedure and remains in the PET imaging room for 30procedure and remains in the PET imaging room for 30--6060minutesminutes
Patients may be released immediately following thePatients may be released immediately

aapm task group #108 on pet and pet/ct shielding ... · pdf fileanswer 2: 5 mm lead reference...

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