i-131 patient release criteria based on measured data patient release criteria based on measured...

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  • I-131 Patient Release I-131 Patient Release Criteria based on Criteria based on Measured DataMeasured Data

    Presentation by:Presentation by:Christopher B. Martel, CHPChristopher B. Martel, CHPDirector and Radiation Safety Director and Radiation Safety

    OfficerOfficerAssistant Professor of RadiologyAssistant Professor of RadiologyBoston University Medical CenterBoston University Medical Center

  • Study ObjectiveStudy ObjectiveDevelop a method to demonstrate Develop a method to demonstrate

    compliance with regulatory release compliance with regulatory release limits for outpatient radioiodine limits for outpatient radioiodine therapy that is:therapy that is: More accurate than current methodsMore accurate than current methods Easier to performEasier to perform Less expensiveLess expensive

  • OutlineOutlinePrimer on Radioiodine TherapyPrimer on Radioiodine TherapyApproach using Regulatory Guide 8.39Approach using Regulatory Guide 8.39Approach using NCRP Report No. 155Approach using NCRP Report No. 155Approach using Patient-Specific Approach using Patient-Specific

    Measured DataMeasured Data

  • Thyroid DiseasesThyroid Diseases Thyroid CancerThyroid Cancer

    Papillary and/or mixed papillary/follicular ~ 78% Follicular and/or Hurthle cell ~ 17% Medullary ~

    4% Anaplastic ~ 1% (Most aggressive) (Most aggressive)

    HyperthyroidismHyperthyroidism Diffuse Toxic GoiterDiffuse Toxic Goiter Toxic Nodular GoiterToxic Nodular Goiter Subacute ThyroiditisSubacute Thyroiditis

    HypothyroidismHypothyroidism

  • Thyroid Function Radioiodine is used Radioiodine is used

    to determine thyroid to determine thyroid uptake.uptake. Isotopes used include Isotopes used include

    I-123 and I-131.I-123 and I-131. Normal uptake Normal uptake

    15-25%15-25% Hypo 30%

  • Thyroid Uptake ValueThyroid Uptake ValueThyroid uptake of Thyroid uptake of

    radioiodine can be used radioiodine can be used to:to: Determine the therapeutic Determine the therapeutic

    dose.dose. Determine if the patient is Determine if the patient is

    releasable according to releasable according to regulatory limits.regulatory limits.

  • Thyroid Uptake Thyroid Uptake MeasurementsMeasurements

    Uptake measurements for Uptake measurements for thyroid thyroid cancercancer patients are performed by: patients are performed by: Counting pills (up to 2 millicuries of I-123) Counting pills (up to 2 millicuries of I-123)

    under gamma camera,under gamma camera, Administering pills to patient,Administering pills to patient, imaging the patients neck region using a imaging the patients neck region using a

    gamma camera at 24 hours post gamma camera at 24 hours post administration, andadministration, and

  • quantifying uptake byquantifying uptake by drawing a region of interest around the drawing a region of interest around the

    thyroid region, thyroid region, subtracting background, subtracting background, decay correcting to time of administration, decay correcting to time of administration,

    and and dividing by the measured pill counts dividing by the measured pill counts

    obtained prior to administration. obtained prior to administration.

    Thyroid Uptake Thyroid Uptake MeasurementsMeasurements

  • Iodine-131 TherapyIodine-131 TherapyUsed to ablate thyroid cancer Used to ablate thyroid cancer

    remnants including metastatic disease remnants including metastatic disease after surgical removal of the thyroid.after surgical removal of the thyroid.

    Used to reduce thyroid function for Used to reduce thyroid function for hyperthyroid patientshyperthyroid patients

    Typical administered doses are:Typical administered doses are: Thyroid cancer 30 to 400 millicuriesThyroid cancer 30 to 400 millicuries Hyperthyroidism 5 to 20 millicuriesHyperthyroidism 5 to 20 millicuries

  • Patient Release CriteriaPatient Release CriteriaRegulatory Guide 8.39Regulatory Guide 8.39NUREG 1556 Vol. 9, Appendix UNUREG 1556 Vol. 9, Appendix U

    Patient release can be determined by one Patient release can be determined by one of four methods:of four methods:

    1.1.Administered activityAdministered activity2.2.Retained activityRetained activity3.3.Measured dose rateMeasured dose rate4.4.Patient-specific dose calculationPatient-specific dose calculation

  • Patient Release CriteriaPatient Release CriteriaRelease based on:Release based on:

    Administered activity (< 33 millicuries)Administered activity (< 33 millicuries) Retained activity (< 33 millicuries)Retained activity (< 33 millicuries) Measured dose rate (< 7 millirem/hr at 1 Measured dose rate (< 7 millirem/hr at 1

    meter)meter) Patient specific release criteria usingPatient specific release criteria using

    Effective half-lifeEffective half-lifePatient uptakePatient uptakePublic occupancy valuesPublic occupancy values

    Member of public must be < 500 Member of public must be < 500 milliremmillirem

  • NCRP Report No. 155NCRP Report No. 155 Appendix A, Equation A.11Appendix A, Equation A.11

    ( )( )( )

    =

    =

    =n

    i

    Tt

    ieaja

    m

    jr

    ie

    release

    ijeFTKErTE K

    1

    693.0

    1

    1lim

    lim

    0,6.34

  • Doses calculated for:Doses calculated for:

    0.10.331General Public

    0.50.5

    0.5

    0.250.25

    0.33

    11

    0.3

    Family memberNonsleeping partnerAll activities except sleeping with patientSleeping with patient

    Dose LimitcSv

    Occ. Facto

    rDistance (m)Group

  • This goes on forThis goes on forDose to pregnant woman as sleeping Dose to pregnant woman as sleeping

    partner and nonsleeping partnerpartner and nonsleeping partnerDose to pregnant coworkerDose to pregnant coworkerDose to Children, holding or not Dose to Children, holding or not

    holdingholding

    Each has its own distance, occupancy Each has its own distance, occupancy factor and dose limit.factor and dose limit.

  • Equations allow forEquations allow forEquations allow from one to three Equations allow from one to three

    exponential components.exponential components.HOWEVER, recommends the value for HOWEVER, recommends the value for

    residence time be taken from residence time be taken from literature.literature.

    Also, makes use of Zero-time Also, makes use of Zero-time Exposure Rates at:Exposure Rates at: one meter from an upright patient and one meter from an upright patient and one foot from a supine patientone foot from a supine patient

  • New ApproachNew ApproachUse the Siemens MK2 Electronic Use the Siemens MK2 Electronic

    Personal Dosimeter Personal Dosimeter

  • MK2 SpecificationsMK2 SpecificationsDose rate linearity

    Hp(10) 137Cs10%

  • Critical FeatureCritical FeatureDose profile history: settable interval

    from 2 seconds to 35 hours, stores transitions of Hp(10) and Hp(0.07) at a resolution of 1Sv (0.1mrem); will store up to 579 records for transitions up to 127Sv or less

  • Using Mk2Using Mk2Determine Determine patient-specificpatient-specific effective effective

    half-lifehalf-lifeMeasure dose rate for calculating dose Measure dose rate for calculating dose

    at other distances.at other distances.Use these values for precise Use these values for precise

    calculations of dose to individuals of calculations of dose to individuals of concern as specified in NCRP Report concern as specified in NCRP Report No. 155No. 155

  • Dose MeasurementDose Measurement I need to figure out:I need to figure out:

    Can I accurately determine the effective Can I accurately determine the effective half-life by measuring exposure rate using half-life by measuring exposure rate using the Mk2?the Mk2?

    Can I extrapolate the dose measured on Can I extrapolate the dose measured on contact with the patient using the Mk2 to contact with the patient using the Mk2 to distances of 1 foot and 1 meter?distances of 1 foot and 1 meter?

  • Measurement OneMeasurement OneMeasurement One: Determine the Measurement One: Determine the

    half-life of a radionuclide using the half-life of a radionuclide using the Mk2.Mk2. Obtained pills of Iodine-123Obtained pills of Iodine-123 Placed in a neck phantomPlaced in a neck phantom Placed the Mk2 on contact with the Placed the Mk2 on contact with the

    phantomphantom Collect total dose measurements for 24 Collect total dose measurements for 24

    hourshours Use the dose measurements to calculate Use the dose measurements to calculate

    the half-life of the radionuclidethe half-life of the radionuclide Compare to published value of I-123 half-Compare to published value of I-123 half-

    lifelife

  • Half-Life Determination Half-Life Determination ResultsResults

    Cumulative Dose versus Time Using the Mk2

    0

    100

    200

    300

    400

    500

    600

    0 50 100 150 200 250 300 350Time in 20 minute intervals

    Cumu

    lative

    Dos

    e (mi

    llirem

    )

  • Half-Life Determination Half-Life Determination ResultsResults

    Half-life of I-123 from PlotHalf-life of I-123 from Plot13.30 hours13.30 hours

    Published Half-life (BNL)Published Half-life (BNL)13.22 hours13.22 hours

    Difference 0.6%Difference 0.6%

  • Measurement TwoMeasurement TwoMeasurement Two: Extrapolating dose Measurement Two: Extrapolating dose

    measured on contact of patient with measured on contact of patient with Mk2 to one foot and 1 meterMk2 to one foot and 1 meter Used ion chamber to measure exposure Used ion chamber to measure exposure

    rate at 0.75 ft, 1.75 ft, and 4 ft from rate at 0.75 ft, 1.75 ft, and 4 ft from patient administered I-131patient administered I-131

    Measured dose rate on contact with Measured dose rate on contact with patient using the Mk2patient using the Mk2

    Extrapolate data from Mk2 to 1.75 ft and Extrapolate data from Mk2 to 1.75 ft and 4 ft4 ft

  • Important Factor!Important Factor! If thyroid cancer localized, dose to If thyroid cancer localized, dose to

    distance relationship followed inverse distance relationship followed inverse square rule.square rule.

    If thryoid cancer metastatic, dose to If thryoid cancer metastatic, dose to distance relationship followed inverse distance relationship followed inverse to 1.6 power, which shows body as a to 1.6 power, which shows body as a cylindrical source rather than point cylindrical source rather than point source.source.

  • Sample Dose to Distance Sample Dose to Distance Relationship for a patientRelationship for a patient

    Relationship between Time post administration and Distance/Exposure Rate

    0

    0.5

    1

    1.5

    2

    2.5

    0 10 20 30 40 50 60

    Time post administration (hrs)

    Dis

    tanc

    e/Ex

    posu

    re R

    ate

  • On Contact Dose Rate Multiplier On Contact Dose Rate Multiplier for Different Disease Typesfor Different Disease Types

    0.0570.028One meter

    0.3300.250One foot

    11On contact

    Metastatic DiseaseThyroid OnlyDistance

  • Dose Rate Extrapolation Dose Rate Extrapolation Measurement ResultsMeasurement Results

    Whole Body % of Inital Activity at Time Post Administration

    y = 0.9658e-0.0007x

    R2 = 0.9941

    0%10%20%30%40%50%60%70%80%90%

    100%

    0 1000 2000 3000 4000 5000 6000

    Time Post Administration (min)

    Perc

    ent R

    emai

    ning

    (%)

    Patient data based on gamma camera counts using I-131 diagnostic scan

    Effective Half-Life = 16.5 hours

  • Patient Effective Half Life using Mk2

    y = 708.81e-0.0403x

    R2 = 0.883

    0

    50

    100

    150

    200

    250

    20 30 40 50 60 70 80Hours post administration

    Cum

    ulat

    ive

    dose

    per

    Hou

    rDose Rate Extrapolation Dose Rate Extrapolation

    Measurement ResultsMeasurement Results

    Effective half-life = 17.20 hours

  • Effective Half-Life using Whole Body Effective Half-Life using Whole Body scan by dual head gamma camerascan by dual head gamma camera

    16.5 hours16.5 hoursEffective Half-Life using Mk2Effective Half-Life using Mk2

    17.20 hours17.20 hoursDifference 4%Difference 4%

    Dose Rate Extrapolation Dose Rate Extrapolation Measurement Measurement Sample ResultSample Result

  • Dose rate measurements on contact Dose rate measurements on contact with patient using Ion Chamber and with patient using Ion Chamber and compared to Mk2 results were within compared to Mk2 results were within 10%.10%.

    Sample Result: Dose rate measured on Sample Result: Dose rate measured on contact with patient using Ion contact with patient using Ion Chamber was 90 millirem/hr, and Chamber was 90 millirem/hr, and distance corrected Mk2 measured 92 distance corrected Mk2 measured 92 millirem/hr.millirem/hr.

    Dose Rate Extrapolation Dose Rate Extrapolation Measurement ResultsMeasurement Results

  • Summary of ResultsSummary of ResultsUsing the Mk2 we can accurately Using the Mk2 we can accurately

    measure:measure: Patient-specific effective half-life for Patient-specific effective half-life for

    radioiodineradioiodine Patient-specific biological removal rate Patient-specific biological removal rate

    constant for radioiodineconstant for radioiodine Dose rate (and cumulative dose) on Dose rate (and cumulative dose) on

    contact and at distances from the patientcontact and at distances from the patient

  • Direct Measurement MethodDirect Measurement Method1.1. Administer diagnostic activity to Administer diagnostic activity to

    patient patient If I-123, make correction to I-131If I-123, make correction to I-131 If I-131, measured values are normalized If I-131, measured values are normalized

    to one millicurieto one millicurie Obtain cumulative dose data over 24 Obtain cumulative dose data over 24

    hourshours DetermineDetermine ee and extrapolate and extrapolate

    cumulative dose data using cumulative dose data using prescribed therapeutic dose of I-131 prescribed therapeutic dose of I-131 to distances of one foot and one to distances of one foot and one meter applying different tmeter applying different t11

  • Cumulative DoseCumulative Dose

    DD00 is the expected dose cumulated in the is the expected dose cumulated in the first hour post administrationfirst hour post administration

    Where tWhere t11 and t and t22 are the beginning and are the beginning and ending time point post administration of ending time point post administration of the therapeutic dose. If infinity, first exp = the therapeutic dose. If infinity, first exp = 1, and second = 0.1, and second = 0.

    ( )210 tte

    ee eeDCumDose

    =

  • Results from one patientResults from one patient

    01019

    29177

    4252196

    11656495

    30171151304

    78450383413

    20411831008972

    538311326423581

    One MeterOne FootOne MeterOne footTime Post Administration t1 (days)

    Dose from t1 to day 9 for Metastatic Disease (millirem)Dose from t1 to day 9 for Thyroid Only (millirem)

    Occuapncy Factor of 1

  • LimitationsLimitations Regulatory Guide 8.39 Regulatory Guide 8.39

    Uses one size fits all approach with respect to Uses one size fits all approach with respect to biokineticsbiokinetics

    Requires nuclear medicine equipmentRequires nuclear medicine equipment NCRP Report No. 155NCRP Report No. 155

    Cumbersome equationsCumbersome equations Disease type not consideredDisease type not considered Requires nuclear medicine equipmentRequires nuclear medicine equipment

    Proposed MethodProposed Method Requires purchase of dosimeterRequires purchase of dosimeter

  • StrengthsStrengths Regulatory Guide 8.39Regulatory Guide 8.39

    Simple approach easy to calculateSimple approach easy to calculate NCRP Report No. 155NCRP Report No. 155

    Allows patient specific data to be usedAllows patient specific data to be used Promotes use of dose to multiple populationsPromotes use of dose to multiple populations

    Proposed MethodProposed Method Uses patient-specific measured dataUses patient-specific measured data Allows use of dose to multiple populationsAllows use of dose to multiple populations Easy to do with EPDEasy to do with EPD Does not require expensive gamma camera timeDoes not require expensive gamma camera time

  • Future ResearchFuture ResearchMk2 Method will be used and Mk2 Method will be used and

    compared against gold standard for compared against gold standard for effective half-life determinations, and effective half-life determinations, and

    Mk2 Method release/dose to public Mk2 Method release/dose to public results will be compared to Regulatory results will be compared to Regulatory Guide 8.39 and NCRP 155 release/dose Guide 8.39 and NCRP 155 release/dose to public estimatesto public estimates