Download Why Quantitative I-131

Why Quantitative I-131
http://www.med.harvard.edu/physics/WhyQuantitativeI-131_2.ppt
Robert E. Zimmerman
Joint Program in Nuclear Medicine
Harvard Medical School
Brigham & Women’s Hospital
Dana Farber Cancer Institute
The Children Hospital
Boston MA
Reason
I-131
• “Magic Bullet”
–
–
–
–
Very specific for thyroid or thyroid mets
Usually cleared rapidly with 2-3 day Teff
8 day T1/2 leaves time for  to deposit its energy
364 kev -ray allows imaging
Thyroid ablation
• Very effective
• Doses to 6000-20000 rads to the thyroid
• Minimal dose to other organs
But there are complications in
some cases
•
•
•
•
Mets in lung and resultant dose to lung tissue
Dose to blood marrow
Dose to salivary glands
Other?
– Complex distribution
Goals
• Limit dose to marrow to < 200 rads
• Limit dose to lungs to < 2000 rads
• Estimate dose to bladder, salivary glands,
other organs with significant uptake
Selected History
• Benua 1962 based on MSK experience
gives these guidelines to limit bone marrow
dose :
– < 200 rads to blood
– < 120 mCi retained at 48 hr (80 mCi with
diffuse lung mets)
I-131 can be imaged
quantitatively but..
–
–
–
–
–
scatter
penetration
sensitivity
attenuation
time
…all complicate the task of
getting meaningful numbers
Generally accepted procedure
• Dual-head planar gamma camera imaging
w/standard source
• ROI for selected organs
• Obtain geometric mean of Ant and Post counts
• Measure attenuation using gamma camera and
area source (e.g. Co-57 sheet source)
• Obtain blood samples to estimate marrow dose
• Follow long enough (e.g 4 days)
• Use MIRD dose calculation techniques
Resource intensive
• Imaging:
– ~3 hr first day
• Attenuation scan
• 2 hr pre void scan + blood
• 4 hr post void scan + blood
– 1 hr day 2, 3 and 4 + bloods
•
•
•
•
Blood samples to count
ROI to draw and calculate
Dosimetry calculation
Dose plan
Attenuation
scan w/ Co-57
sheet source
Blank scan
previously
acquired
2 hr & 24 hr
48 hr & 72 hr
Aids
• MIRD – tables, models, data
• MIRDOSE 1, 2, 3 by Stabin
• RADAR by Stabin
(http://www.doseinfo-radar.com/RADARHome.html)
• Olinda by Stabin
• NucliDose Erwin & Groch (includes MIRDOSE2)
• Gamma camera ROI tools
• Spreadsheets
MIRD
Medical Internal Radiation Dose
Subcommittee of the
Society of Nuclear Medicine
• MIRD Publication - MIRD Dose Estimate Report #19: Radiation
Absorbed Dose Estimates from 18F-FDG
• MIRD Publication - MIRD Supplement 1999: Foreword, MIRD
Perspective, Pamphlets 14 Revised, 15, 16, and 17
• MIRD Publication - MIRD Dose Estimate Report #13: Radiation
Absorbed Dose from Technetium-99m-labeled bone imaging agents
• MIRD Publication - MIRD Pamphlet #11: S, Absorbed Dose
per Unit Cumulated Activity for Selected Radionuclides and
Organs (PART 1)
• MIRD Publication - MIRD Pamphlet #11: S, Absorbed Dose
per Unit Cumulated Activity for Selected Radionuclides and
Organs (PART 2)
• MIRD Publication - MIRD Pamphlet #11: S, Absorbed Dose
per Unit Cumulated Activity for Selected Radionuclides and
Organs (PART 3)
•
MIRD Publication - MIRD Pamphlet #13: Specific Absorbed
Fractions for Photon Sources Uniformly Distributed in the Heart
Chambers and Heart Wall of Heterogeneous Phantom
•
MIRD Publication - MIRD Pamphlet #5 Revised: Estimates of
Absorbed Fractions for Monoenergetic Photon Sources
Uniformly Distributed in Various Organs of a Heterogeneous
Phantom
MIRDOSE
• A series (v1, v2, v3) of software programs
that ran on PCs circa 1985-1998 by Michael
Stabin then of Oak Ridge Associated
Universities and Oak Ridge National
Laboratories
• Eventually FDA stopped distribution of the
software since it was a medical device!
RADAR
Web site
RAdiation Dose Assessment Resource
By Michael Stabin and colleagues
Difficult to use for individual dosimetry.
OLINDA/EXM
Organ Level INternal Dose
Assessment/EXponential Modeling
By Michael Stabin of Vanderbilt.
Has FDA 510(k) exemption
Summary of dose estimates for xxx
11/Mar/01
Administered dose
(mCi)
Organ
rad/mCi
100
120
140
160
180
200
220
240
260
280
300
320
340
360
Lungs
4
388
466
543
621
698
776
854
931
1009
1086
1164
1242
1319
1397
T.Body
0.34
34
41
47
54
61
68
75
81
88
95
102
108
115
122
Bladder
2.71
271
325
379
434
488
542
596
650
705
759
813
867
921
976
0.59
59
71
83
95
107
119
131
143
155
167
178
190
202
214
25
30
35
40
45
50
55
60
65
70
75
80
85
90
MIRD:
Benua:
Bld(Marrow)
48hr retain
(mCi)
The amount retained at 48 hr should be <80 mCi
Amount in lungs should be < 2000 rads
Brigham & Women's Hospital
Division of Nuclear Medicine
Whole Body Dosimetry Study with 131I
Indications: Quantitative estimate of 131I in metastases or thyroid remnants requiring
complete dosimetry to protect critical organs.
Patient Preparation: This exam should not be performed if the patient has had any
iodine
medications which will interfere with the study or any iodinated contrast media within
the last 6 weeks.
TSH level should be evaluated prior to radiopharmaceutical administration. Levels
should be greater than 50 uU/ml.
The patient should be fasting for 1 hour prior to ingestion of the radiopharmaceutical
and should not eat for at least 30 min. following.
Radiopharmaceutical: 131I solution
Dose: 3 mCi
Written directive form must be signed by Attending Physician prior to administration.
Route of Administration: oral
Imaging:
1. WB Blank scan with 57Co sheet source:
Use acquisition protocol BWH WB Co-57 Blank Scan. Prior to radiopharmaceutical administration a 57Co WB blank scan must be
performed. Mark the table for patient re-positioning for all imaging sessions by placing a piece of tape on the table corresponding to the
location of the top of the patient’s head. Place 57Co sheet source on detector 2 of e.cam or MS2 with high energy collimators in place. Use
both detectors and peak for 57Co. Do blank scan with no patient on table starting where top of head will be located to end of feet.
2. WB transmission scan is be performed next.
Use acquisition protocol BWH Co-57 Transmission Scan. Leave the 57 Co sheet source on detector 2. Place the patient on table at location
of tape. Do anterior WB sweep from head to toe for 20 min. (8 cm/min).
3. Administer the radiopharmaceutical. The patient must not void between administration and first imaging session.
4. Prepare standard of 50-100 Ci of I-131 in 250 ml tissue culture flask. Label flask with name, time, date and activity.
5. Use acquisition protocol BWH I131 WB scan. Perform WB sweep anterior/posterior 60-120 minutes post administration of I-131. Scan
for 20 min. (8 cm/min) and include standard in field of view (e.g. between feet or lower legs).
6. Repeat WB sweeps at 24, 48 and 72 hours post administration of 131I. Increase imaging time at later time points to 40 min (16 cm/min)
and include standard in all imaging sessions.
7. Spot views of head and neck may be required by Nuclear Med physician.
8. Draw 2 cc of blood at each imaging session, excluding transmission session. Record
name of patient, time and date of blood drawing on each tube and on patient jacket. All samples will be counted on the last day of imaging.
9. Processing using Nuclidose on ICON/IDL system will be done by the physicist. ROIs corresponding to each source organ will be drawn.
Time activity curves will be obtained. Dose calculations will be performed to obtain rads/mCi.
Adapted from CH protocol
REZ
5 Dec 2000