nuclear medicine physics jerry allison, ph.d. department of radiology medical college of georgia...
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Nuclear Medicine Physics
Jerry Allison, Ph.D.
Department of Radiology
Medical College of Georgia
Radioiodine Therapy
A note of thanks to
Z. J. Cao, Ph.D.
Medical College of Georgia
And
Sameer Tipnis, Ph.D.
G. Donald Frey, Ph.D.
Medical University of South Carolina
for
Sharing nuclear medicine presentation content
http://www.hpschapters.org/northcarolina/fall2008/TPM.3.pdf
http://www.hpschapters.org/northcarolina/fall2008/TPM.3.pdf
Thyroid Uptake/Imaging
• I-123: 100 – 200 mCi (g only) T1/2 = 13.2 h
• 1-131: 15 – 100 mCi (g & b) T1/2 = 8 d
Thyroid probe
Measure thyroid uptake of I-131 in-vivo
5×5 cm NaI(Tl) with 15 cm long conical collimator
pointing to neck and thigh (bkg)
calibration phantom with known activity for calculating
uptake (pt capsule)
1 – 2 cm difference in depth 10 – 40% difference in count rate
Thyroid uptake neck phantom
For use with thyroid uptake probe.
Used to estimate atteuation and scatter for soft tissue overlying thyroid glad.
Approximates typical patient neck geometry.
http://www.biodex.com/nuclear-medicine/products/thyroid-uptake-system/thyroid-uptake-system-accessories/thyroid-uptake-nec
Thyroid
http://www.hpschapters.org/northcarolina/fall2008/TPM.3.pdf
- Emitters
• - (beta) - 131I, 90Y, 153Sm
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABR
b- decay
• A neutron decays to a proton, electron and anti- neutrino: n p + e- +.
• e- and created inside the nucleus at the moment of decay and ejected instantaneously
• AXz AYz+1 • e.g. 131I53 131Xe54 + e- +
e-
Applications
• - emitters – used for therapy - cannot escape pt, localized energy deposition 90Y (pure -) 131I , 153Sm (- and )
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABR
131I Production
• Reactor produced as fission product
131I Decay
© Physics in Nuclear Medicine: Cherry, Sorenson and Phelps
131I Decay
https://en.wikipedia.org/wiki/File:Iodine-131-decay-scheme-simplified.svg
I-131 Absorbed Dose
http://www.nuclearonline.org/PIbyGeneric2.htm
90% of pt dose is b; 10% by g
Written directive• Required for I-131 dose exceeding 30
μCi
• Pregnancy test results
• Order for the radiopharmaceutical is written twice Once to order the drug The second dosage usually represents the
actual amount given Route of administration
• Must be signed by an authorized user
NM Written Directive for I-131 Therapy
http://www.gru.edu/services/ehs/radsafe/
Authorized User
• A physician licensed to practice and who meets specific requirements (NRC) and identified as an AU on the institution’s license or permit Board Certified (by appropriate Board)
• Other physicians and technologists may work with byproduct material under the supervision of an AU
• All radiopharmaceuticals dispensed or administered must be pursuant to an order (e.g. prescription) of an AU
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABR
• Authorized User
10CFR35.290 Training for imaging and localization studies Has completed 700 hours of training and experience, including a minimum of 80 hours of classroom and laboratory training http://www.nrc.gov/reading-rm/doc-collections/cfr/part035/part035-0290.html
• Authorized User 10CFR35.390 Training for use of unsealed byproduct material for which a written directive is required Has completed 700 hours of training and experience, including a minimum of 200 hours of classroom and laboratory training
http://www.nrc.gov/reading-rm/doc-collections/cfr/part035/part035-0390.html
• Authorized User
10CFR35.392 Training for the oral administration of sodium iodide I-131 requiring a written directive in quantities less than or equal to 1.22 gigabecquerels (33 millicuries) Administering dosages to patients …, that includes at least 3 cases involving the oral administration of less than or equal to 1.22 gigabecquerels (33 millicuries) of sodium iodide I-131
http://www.nrc.gov/reading-rm/doc-collections/cfr/part035/part035-0392.html
• Authorized User
35.394 Training for the oral administration of sodium iodide I-131 requiring a written directive in quantities greater than 1.22 gigabecquerels (33 millicuries) Administering dosages to patients …, that includes at least 3 cases involving the oral administration of greater than 1.22 gigabecquerels (33 millicuries) of sodium iodide I-131
http://www.nrc.gov/reading-rm/doc-collections/cfr/part035/part035-0392.html
131I studiesFor 131I doses > 30 µCi a “written directive” which may only be issued by an AU is required for each treatment
Radiology residents (under AU supervision) need to direct 3 treatments < 33 mCi and 3 > 33 mCi to be “AU Eligible”
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABR
Getting “AU Eligible”Radiology Residents who • Complete the requirements during their
residency• Get “OK” from the residency director• Pass the RISE exam (part of core exam)
Radioisotope Safety Exam (~60 items)• ~15 NM physics items• ~15 NM safety items• ~20 NM clinical items• ~20 NM regulatory/administrative items
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABR
COMPLIANCE WITH NRC TRAINING AND EXPERIENCE REQUIREMENTS
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Release of I-131 therapy patients
• I-131 in patients may be excreted in their urine, perspiration and saliva and these body fluids can contaminate household surfaces.
• Use separate bathroom• Shower/brush teeth frequently• Limit hugs, sleep alone• Limit visitors and co-workers• Limited length of stay time
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Release of I-131 therapy patients
• Avoid public transportation• Children, pregnant women and nursing mothers
must stay at least 6’ away.• Written instructions must be provided to the
patient to minimize radiation exposure to public if a member of the public could receive a dose greater than 1 mSv.
Radioiodine Safety Manuals at MCG
http://www.gru.edu/services/ehs/radsafe/
Radioiodine Procedures and Nursing Instructions
http://www.gru.edu/services/ehs/radsafe/
Signage• Radioactive Material• Entry Log• Instructions• No Housekeeping
Shoe covers, absorbent floor pads
Plastic sheeting, absorbent floor pad, furniture covers
Disposable trash container (hazardous)
Bed rails covered
Toilet cover
Sink cover
Vanity cover
Absorbent sink cover
Door handle covers
Release of I-131 therapy patients• A patient may be released if the total
effective dose to any other individual (family or caregiver) is not likely to > 5 mSv
• Patients receiving diagnostic nuclear medicine examinations can be released without any calculations
• 131I Therapy patients need special instructions
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABR
Radiation exposure rate around patient
Typical exposure rate at 1 m from the patient soon after injection:
• Most diagnostic radiopharmaceuticals: <1 mR/hr (maximum dose to public 1 mSv/yr)
• 18F-FDG: ~5 - ~30 mR/hr
• 131I: ~5 or ~30 mR/hr for Graves or cancer dose respectively
Breast feeding Guidelines (recommended / not regulated)
Radiopharmaceutical Recommendation
131I NaI Cessation
123I NaI Cessation
67Ga Citrate Cessation
201Tl Chloride 96 hrs
123I MIBG, 99mTc WBC 48 hrs
99mTc MAA, 99mTc RBC 12 hrs
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABR
Lactating 131I therapy pts
• Lactating breasts accumulate radioiodine Patient breast dose can be quite high Breast pump reduces breast dose
• Lactating completely ceases 4 wks post-partum with no breast feeding
• Ask pt to stop breastfeeding 15 days BEFORE therapy
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABR
44
Absorbed dose to fetus
99mTc MAA 0.35 (mSv/mCi)99mTc sulfur colloid 0.3599mTc RBC 0.6099mTc DTPA 0.3599mTc diphosphonate 0.4067Ga citrate 2.50111In leukocytest 4.00131I (15% uptake) 1.00123I (15% uptake) 0.35201Tl chloride 3.00133Xe 0.01
Fetal thyroid dose from 131I• 131I can rapidly cross the placenta• Fetal thyroid starts concentrating 131I
after 11 to 12th week post-conception• Ability rapidly increases after 22nd week• Can result in hypothyroidism / ablation• Critical to check pt for pregnancy before
131I therapy
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABR
46
Homeland security
• Extremely sensitive radiation detectors aredeployed in train stations, airports, tunnels, etc.
• I-131 patients may set off alarms up to 95 days following a therapy procedure.
• Give a letter containing radionuclide and hospital contact information.
What is major spill?
• Activity released at location or on people 100 mCi Tc-99m or Tl-201 10 mCi Ga-67 or In-111 1 mCi I-131
• Radiation safety officer must be present.
• Focus on containment, shielding, and decontaminating individuals