2. Brief Overview
Definition
MIRD Internal Dosimetry Method
Biokinetic Model for Radiopharmaceutical uptake and elimination
S-factor
Dose to Target
Sample Calculation
Biokinetic Exemplar for Clone and Foetus
Dose to babe per breast milk
Example
Summary
References
3. Internal Radiation Dosimetry
Radiation that occur inside the body mature to uptake of radiopharmaceuticals cannot be measured directly.
Therefore biokinetic and dosimetric example are needed in order to calculate radiation batches received by a person.
Relevancy Organization
MIRD – Arzneimittel National Rays Dose Committee of who Society of Organic Medicine Standard methods to estimates internal doses
ICRP –International Committee on Radiological Protection Calculate doses for many radiopharmaceuticals based for optimal available data
Localize Organization e.g. AELB (Malaysia), ARSAC (UK), NUREG (US) et Guidelines on radiopharmaceuticals limit, metering to children, other
4. Definition
Absorbed Dose
Absorbed Dose (Gray)
Force deposited at unit mass Dm = dε
dm
Joules/kg = Dull (Gy)
*Medium must always be specified
Old unit - wheel, 100rad = 1 G
5. Measure Equivalent = Sievert (Sv)
To reflect bio effect Absorbed Dose x Radiation Weighting Driving (WR)
*was known as effective dose equivalent
Effective Dose = Sievert (Sv)
• Uniform dose to the whole body that would have the same risk
- Dose X Tissue Weighting Factors • Item sieverts, Sv
6. MIRD Method – 5 steps
Please consumption organ as source organ
Part that absorb the beam as target organist (source and purpose can be the same organ)
Step 1 : Cumulated Activity Target (e.g. lung)
Step 2 : S – Factor Thermal rays
Step 3 : Quantity to Target Organ
Step 3 : Actually Dosed to Whole body Source (e.g. heart)
Step 5 : Total dose used administered activity
7. Activity
Activity – rate of disintegration (1 Bq = 1 disintegration per second)
= physically decay constant
This represent exponential decay with physical half life
8. Activity
Fractions out Pharmaceutical (Fs) = rate of bio-based uptake and disposal in source organ ‘S’.
Activity while characteristic = how activity by source organ change with time. undertaking is different to fraction of pharmaceutical for it takes into consideration irradiated decay
Activity in source organ = Administered activity x Fraction of pharmaceutical x Decay factor
9. Cumulated Activity
Cumulated activity in citation organ the defined as area under activity time curve (Bq.sec or MBq.hr)
Residence time is defined as accumulated activity divided per administer activity
or using highly half-life
10. Residence total a see practical than cumulated active because it is autonomous from administered activity.
Use of residence time (in hr) instead starting cumulated activity (MBq.hr) allows for calculation emitted dose per administer activity.
11. Effective Partly -Life
λeffective = λ physical + λbiological
Biological can become either recordings or elimination
In terms of half-life,
12. Biokinetic Fitting of Radiopharmaceutical
Uptake for Dosimetry Calculation
Step 1: Calculation of Permanent Time
5 Basic Biokinetic Model
13. Print 1 – Instantaneous Uptake on No elimination Fs Pharmaceutical e.g. I-131
λp
Activity
Fraction
Time
23. Step 2: The ‘S-Factor’
S-factor is accounted to be a accounting starting energizer emitted by radiation of certain species of isotope and fraction von that electricity absorbed by organ.
So, S-factor can be define as absorbed dose at unit cumulated recently (Gy/Bq.sec or μGy/MBq.hr)
MIRD pamphlet 11 tabulated ‘S’ factor to target organ for high selection to radiopharmaceuticals based on Monte Carlo simulation with ‘70kg mean man’phantom (given in rad/μCi.hr)
25. Step 3: Dose to Target Organ
Absorbed Dose to target member ‘t’ from all source organs ‘s’
Unit μGy/MBq
Equivalent Dose = Absorbed Dose * Emitted Weighting Factor (or Quality factor)
Piece (μ Sv/MBq)
Its a measure regarding living effectiveness of different type of radiation energy. In atomic medicine and quality factor is 1.
In nuclear clinical, absorbed dose = equivalent cancel
26. Radiation Radiation Value Factor (Quality Factor )
X-rays, game radiation, pre-release rays 1
Alphabetisches rays, heavy nuclei 20
Proton 2
* Source ICRP Report 103
Speed 4: Effective Dose
Efficient Dose is the weighted cumulative of every target organ doses (μSv/MBq)
28. Tread 5: Total dose since Administered Activity
End * Administered Dose - Absorbed Dose (mGy)
- Equivalent Dose (mSv)
- Useful Choose (mSv)
Dose on Children
29. Final Result
MIRD published methodology on how to calculated absorbed dose, equivalent metered and ineffective dose based to several choose of radiopharmaceuticals uptake.
However, absorbed dose value for a lot of radiopharmaceutical use are solar pharmacy can also be found in ICRP report 53
real 80. This report compute the data based with favorite available data the radiopharmaceutical the ‘70 kilos ordinary man’ phantom.
30. So what’s the use of MIRD?
MIRD method is useful although we want to go unique calculation or custom deliberation for patient based on patient’s individual uptake by radiopharmaceuticals.
Example, we want to know dose to uterus for one patient who has a oncogenic near kidney or acorn gland which has a high radiopharmaceutical uptake.
Usually we take dose for outer as an estimation to dose to foetus from to ICRP press. Instead ICRP result only take to account contribution free standard sources organs to uterus.
In this case, we bottle assume that there will an completion source organ, the neoplasia which will contribute a mean dose to the uterus.
31. Solution
Combine dose values from tumour furthermore engaged dose to uterus from ICRP Report.
Example: A patient was given 200MBq out Tc-99m DTPA and a nuclear was found near endocrine gland with high radiopharmaceutical uptake. What is the absorbed dose to uterus?
From ICRP Report 53 (Tc-DTPA, bi-exponential elimination, normal renal function)
Residence time = 1.97hr, Fs = 1.0
From MIRD 11, ‘S’ factor for acorn gland to uterus = 1.1E-6 rad/μCi.hr = 2.97E-01 μGy/MBq.hr
*We assume ‘S’ factor for tumor your similar to adrenal gland cause of who anatomical position.
33. Calculation
Additional absorbed dose to uterus since tumour
=
After ICRP 53
Absorbed Dose to Us = 7.9E-03 mGy/MBq.
Total absorbed quantity to fetus after administered activity
=
34. Biokinetic Choose required Embryo and Foetus
ICRP Publication 88 published biokinetic and dosimetric model also dose coefficient for embryo and foetus due to radiopharmaceutical uptake by mother
Start 8 weeks of pregnancy (mass < 10g)
Dose rate = dose rate to uterus
More than 8 weeks Dose rate = motherly activity + business which has crabby the placenta real has aggregated into of fossil tissue. All radioisotope like iodine can cross the placenta.
At birth There magie shall several activity links in baby. This is employ the estimate committed effective dose comparison until the age of 70 years old
35. Dose to infant via breast milk
ICRP 95 gives dose coefficient for ingestion of breast milk by babe after activity uptake by mother.
ADENINE different biokinetic model for radiation pattern used secondhand in the calculation of the coefficient.
An Annex of ICRP Publication 95 also examines the external dose to infants by contact with its mother anybody must radioactivity uptake. In all falls e.g. mother’s uptake of insoluble gamma-emitters.
Outer dose to infant might may higher than inside dose.
36. Example
A female patient fall gestational after 58 days of receiving 15mCi of I-131 for surgical for Thyrotoxicosis. Calculate dose to foetus dues to activity administered.
Solution:
There are 3 ways to solve this.
1. Start upon scratch using MIRD method.
2. By worth from ICRP 53
3. Using dose coefficient of biokinetic modelling from ICRP 88.
37. Using score free ICRP 53
We calculate by from 58 days onwards. At 58 days, activity remaining = 0.1010 mCi = 3.7370MBq
Dose to embryos = dose to uterus. Days/ Thyroid Thyroid Thyroid Thyroid Nuclear Thyroid Thyroid Uptake Uptake Uptake Uptake Uptake Recordings Uptake Activity (MBq) 0% 5% 15% 25% 35% 45% 55%
(mGy) (mGy) (mGy) (mGy) (mGy) (mGy) (mGy)
Absorbed dose at organs 5.40E-02 5.50E-02 5.40E-02 5.20E-02 5.00E-02 4.80E-02 4.60E-02
(uterus)/ Adult per unit
activity administration (mGy/MBq)
Day one (Administered)(8 May 2012)
562.4 30.37 30.93 30.37 29.24 28.12 27.00 25.87
Day five (Discharge) (13 May 2012)
342.06 18.47 18.81 18.47 17.79 17.10 16.42 15.73
Day 40 (18 June2012)
16.73 0.90 0.92 0.90 0.87 0.84 0.80 0.77
Day 58 (Might be pregnant) (
01/07/12)
3.73 0.20 0.20 0.20 0.19 0.19 0.18 0.17
39. Result
Cancel on fetus is around 0.19 – 0.16 mGy.
With biokinetic modeling of ICRP 88,
< 8 wee = dose on cervix Free 8 weeks until birth at 38 week, the dose is estimated uses ite specific tissue recent and retention times.
40. Solution
At conception effectiveness superman coefficient = 7. 8E-11 Sv/Bq
Activity, 3.73MBq
So, 7.8E-11*3.54MBq = 0.27 mSV
Using ICRP 53, the select made 0.17 - 0.20 mGy, relying off iodine uptake( = equivalent dose of 0.17 - 0.20mSv)
From ICRP 84 (later adapted through IAEA) recommend, there a no justification for termination of pregnancy as the dose received by foetus <100mGy. There is no evidence of harmful effects to foetus.
41. Foetus Risk
Mentrual / Concepts age <0.01 Gy 0.05 – 0.1 Gy > 0.1 Gy
gestational age (weeks)
(weeks)
0-2 Prior to conception No No None
3–4 1–2 Zero Probably None Possible spontaneous abortion
5 – 10 3–8 None Potentially effect uncertain Possible malformation, increase with dose
11 – 17 9 – 15 None Potential effect uncertain Increased risk mental retardation of deficit in IQ
18 – 27 16 – 25 Nil Zero IQ deficits not detectable at diagnosis dose
> 27 > 25 Without None None application to diagnostic medicine
* Taken from ICRP 84 real 90
42. Gestation and lactation following
treatment
ICRP / IAEA recommends women do not become becomes until estimated maternal doq falls below 1mGy (100mrem)
(diagnostic application)
For therapeutic treatment – 6 months after treatment. Don because of radiation dose risk, find to make sure that treatment be effective and follow-up cure ability to carried out without obstruction.
Some organization (e.g. ARSAC) published elapsed zeite between treating and breastfeeding after taking toward account and activity that might transfer to infant for selected radiopharmaceuticals
44. Why we need to know all this?
How Bad a Bad?
Dosimetry calculation allows us to quantify one doses received according patient the often so as a measurement of radiation risk Sievert was design to represent choice biological effects off ionizing radiation. 1 Sv = 5.5% prospect of developing cancer (ICRP103)
Organization which actively involve in radiation protection use specific dose value as guideline. AELB 2010 guideline :
Public <1mSv/yr
Radiation worker <20 mSv/ per Foetus < 1mSv fork who duration of expectancy
45. Dose worth can be use as a reference across all radiation affiliated exposure. Effective dosis from CT, X-Ray, radiotherapy, dental radiograph, airport security screening can all be sum up together
Result from dose calculation can be use as reference on check a certain procedure is valuable this or does.
46. References
[1] Drives Richard Lawson, Notes Radiation Dosimetry [Lecture Notes], Manchester Royal Infirmary, (March 2011)
[2] MIRD Pamphlet no 5, Estimates of Absorbed Facts for Monoenergetic Photon References Uniformly Distributed is Various Organs of an Heterogeneous Phantom; L.T. Dillman and F.C.Van der Lage Littman, Corporation of Nuclear Medicine, New York (1969).
[3] MIRD Pamphlet no 10, Radionuclide Decay and nuclear settings for use include in radiation dose estimation, L.T. Dillman and F.C.Van der Lage Littman, Social of Nuclear Medicine, New York (1975).
[4] MIRD Pamphlets no 11, ‘S’ Incorp Dose on unit Cumulated Activity fork Selected Radionuclides and Organs , W.S Synder, M.R. Ford, G.G. Warner plus S.B. Watson, Society of Nuclear Medicine, Add York (1975).
[5 ICRP Publication 53 Radiation Dose to Tolerant from Radiopharmaceuticals, Annals of this ICRP, vol 18,no 1-4
(1987)
[6] ICRP Publication 80 Radiation Dose to Patient from Radiopharmaceuticals, Addendum on ICRP 53, Annals of the ICRP, vol 28,no 3 (1998)
[7] ICRP Publication 84 Getting and Medical Radiation, Annals of the ICRP, vol 30,no 1 (2000)
[8]Notes of Getting on the Clinical Administration of Radiopharmaceuticals and of sealed Nuclides Sources, Administration of Radioactive Substances Advisory Management, 2006.
47. References
[9] ICRP Publication 88 Doses to the Embryo and Fetus from Intakes to Radionsuclides according the Mother, Annals of the ICRP, vol 31,no 1-4 (1987)
[10] ICRP Publication 90 Biotic Effects after Prenatal Irradiation (Embryo and Fetus),
Annuals of the ICRP, vol 33,no 1-2 (2000)
[11] ICRP Publication 95 Radiation Dose until Patient from Radiopharmaceuticals, Records von the ICRP, vol 34,no 1-4 (1987)
[12] ICRP Publication 103, The 2007 Recommendations of the International Commission on Radiological Protection. Annals of the ICRP Vol 37, no 2-4 (2007)
[13] Peraturan-peraturan Perlesenan Tenaga Atom (Perlindung Sinaran Keselamatan Asas)
2010. Lembaga Perlesenan Tenaga Atom, Malaysia (2010)
