Dose Estimates for Nuclear Medicine Scans

This document contains radiation dose estimates for a number of radiopharmaceuticals commonly used in nuclear medicine. This resource provides effective dose and organ doses for adults, and in some cases children, and can be used to estimate the radiation dosimetry information required for JRSC or RDRC approval for use of radiopharmaceuticals in research involving human subjects.

 

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PET/CT Doses

For PET/CT it is important that the investigator include effective dose and organ dose estimates for both the radiopharmaceutical and the CT component of the examination. Effective dose for the radiopharmaceutical is provided by selecting the appropriate radiopharmaceutical from the tables provided later in this document. Organ and effective dose estimates for the CT component of PET are given below. These estimates are based on typical scenarios of common use clinically. In unusual circumstances these dose estimates may not be appropriate. It is the principal investigator's responsibility to provide reasonable estimates of all radiation doses a patient may incur.

 

Estimate of CT Component of PET/CT at CUMC

Combined PET/CT - CT dose is approximately 20% less than the standard clinical CT dose. In some instances physicians may use a standard CT in addition to this combined PET/CT or adjust the CT dose to improve image quality.

Scan type

CTDIvol (mGy)

DLP (mGy-cm)

Effective dose (mrem)

Male Whole Body

11.2

1285

1175

Female Whole Body

11.2

1225 1255

Brain

64.37

1526

 

Babies (3 scan increments)

3.89

218

 

Pediatrics (4 scan increments)

5.33

351

 
       
PET with only attenuation CT - This technique considerably reduces dose by lowering mAs by generating an attenuation map from poorer quality CTs which are not suitable for clinical diagnostic reading. This option is infrequently used at CU PET center.

Scan type

CTDIvol (mGy)

DLP (mGy-cm)

Effective dose (mrem)

Male Whole Body

3.7 428

392

Female Whole Body

3.7 408 418

Brain

64.37

1526

 

Babies (3 scan increments)

3.89

218

 

Pediatrics (4 scan increments)

5.33

351

 

 

 

 

Whole body PET/CT Organ Doses
                            CT Examination Type
  Female Male Female Attenuation Male Attenuation
Organ Organ Dose (mrad) Organ Dose (mrad) Organ Dose (mrad) Organ Dose (mrad)
Gonads 1205 1409 402 470
Bone Marrow 1014 908 338 303
Colon 1172 1063 391 354
Lung 1343 1276 448 425
Stomach 1234 1163 411 388
Bladder 1419 1339 473 446
Breast 1070 0 356 0
Liver 1169 1128 390 376
Oesophagus 1268 1229 423 410
Thyroid 2045 2024 682 675
Skin 938 876 313 292
Bone Surface 2211 1932 737 644
Brain 1024 851 341 284
Adrenals 1261 1166 420 389
Small Intestine 1110 1031 370 344
Kidney 1293 1229 431 410
Pancreas 1227 1123 409 374
Spleen 1237 1126 412 375
Thymus 1529 1430 510 477
Uterus 1355 0 452 0
Eye lenses 1731 1396 577 465

 

Adult and Pediatric Dose Estimates from ICRP 106

The most up-to-date resource for radiation dosimetry of radiopharmaceuticals is ICRP 106, Annex C, which provides dose tables for adults, 1-, 5-, 10-, and 15- year olds for a number of radiopharmaceuticals. Please note that absorbed dose per unit activity administered is provided in mGy/MBq. The list below provides the dose table for each radiopharmaceutical found in this reference:

ICRP Publication 106, Annex C Biokinetic models and dose tables.  Ann. ICRP 38(1-2):51-162, 2008.

Additional Adult Dose Estimates

These useful, credible and free estimates are maintained by the Radiation Internal Dose Information Center (RIDIC) and by CDE, Inc. Dosimetry Services.

Effective dose equivalent and organ doses to adults for the following radiopharmaceuticals are available:

H-3 Water   Tc-99m Pyrophosphate
H-3 Inulin   Tc-99m Red Blood Cells - In vitro Labeling
C-11 Monoxide - 20 s breathhold   Tc-99m Red Blood Cells - In vivo Labeling
C-11 Monoxide - continuous inhalation (1 hr)   Tc-99m Sulfur Colloid (Normal Patients)
N-13 Ammonia   Tc-99m Sulfur Colloid (Intermediate-to-Advanced Diffuse Parenchymal Liver Disease)
C-14 Inulin   Tc-99m Teboroxime
O-15 O2   Tc-99m White Blood Cells
F-18 Sodium Fluoride   In-111 DTPA
Cr-51 Erythrocytes (RBCs)   In-111 Platelets
Co-57 Vitamin B-12 (Cyanocobalamin)   In-111 Red Blood Cells
Co-58 Vitamin B-12 (Cyanocobalamin)   In-111 White Blood Cells
Fe-59 Citrate   I-123 Hippuran
Co-60 Vitamin B-12 (Cyanocobalamin)   I-123 IMP
Ga-67 Citrate   I-123 mIBG
Ga-68 Citrate   I-123 Sodium Iodide
Se-75 Selenomethionine   I-124 Sodium Iodide
Kr-81m Inhalation   I-125 Fibrinogen
Kr-81m Injections   I-125 IMP
Oral Administration of Kr-81m   I-125 mIBG
Rb-82   I-125 Sodium Iodide
Sr-85 Nitrate   I-126 Sodium Iodide
Tc-99m Albumin Microspheres   I-130 Sodium Iodide
Tc-99m Disofenin, Lidofenin and Mebrofenin   I-131 Hippuran
Tc-99m DMSA   I-131 HSA
Tc-99m DTPA (injection)   I-131 MAA
Tc-99m DTPA (aerosol)   I-131 mIBG
Tc-99m Exametazime (HMPAO)   I-131 Rose Bengal
Tc-99m Glucoheptonate   I-131 Sodium Iodide
Tc-99m HEDP   Xe-127 (Breathhold)
Tc-99m HMDP   Xe-127 (5 minute rebreathing)
Tc-99m HSA   Xe-127 (10 minute rebreathing)
Tc-99m MAA   Xe-133 (Breathhold)
Tc-99m MAG3   Xe-133 (5 minute rebreathing)
Tc-99m MDP   Xe-133 (10 minute rebreathing)
Tc-99m Sestamibi*   Xe-133 Injections
Tc-99m Oral Administrations   Hg-197 Chlormerodrin
Tc-99m Pertechnetate   Au-198 Colloid

 

Additional Pediatric Dose Estimates
The links below again are free estimates maintained by the Radiation Internal Dose Information Center (RIDIC) and by CDE, Inc. Dosimetry Services. Effective dose equivalent and organ doses for newborn, 1-, 5-, 10-, and 15- year olds for a variety of nuclear medicine studies are provided.

 

Age-dependent Committed Effective Dose Coefficients

ICRP Publication 72, states that doses can be estimated by applying age-specific dose coefficients to the age ranges as given in the table below:

Age-Specific Dose Coefficient Age Range
3 months from 0 to 1 year of age
1 year from 1 year to 2 years
5 years more than 2 years to 7 years
10 years more than 7 years to 12 years
15 years more than 12 years to 17 years
Adult more than 17 y

The information above provides age-specific dose information for a variety of radiopharmaceuticals. For radionuclides not covered in the above material, the dose ratio relative to an adult can be calculated by using the tables provided in ICRP 72. Please consult the radiation safety office or a qualified medical physicist for further advise.

ICRP Publication 72. Age-dependent Doses to the Members of the Public from Intake of Radionuclides - Part 5 Compilation of Ingestion and Inhalation Coeffiicients. Ann. ICRP 26(1):1-91, 1995.

 

Example Using F-18 FDG

As an example, consider a patient injected with 10 mCi of F-18 FDG in a single study. Assume that the patient will also receive an abdominal CT examination as a part of the study.

First, the radiation dosimetry for the radiopharmaceutical only is calculated.

   Dose to Critical Organ

The first two rows in the Radiation Dosimetry of Radiopharmaceutical table below involve calculating the committed equivalent dose for potential critical organs. Organ doses can be obtained from the tables linked above, particularly ICRP 106. The critical organ is the organ most susceptible to radiation damage resulting from the specific exposure conditions under consideration, taking into account the dose the various parts of the body receive under the exposure conditions. In the case of two radiopharmaceuticals, determination of the critical organ can be more complex. To determine the critical organ, we ask that investigators consider the organ dose to what would be the critical organ from each radiopharmaceutical for both radiopharmaceuticals. If, for example, a study involved one radiopharmaceutical whose critical organ is the bladder and another whose critical organ is the spleen, we ask that investigators consider the dose to both the bladder and spleen for both radiopharmaceuticals in order to determine the critical organ. The organ that receives the highest dose from all radiopharmaceuticals combined is likely the critical organ. If there is uncertainty in determining the critical organ, please consult the radiation safety office or a qualified medical physicist for further advise.

    Whole Body Dose

 

Radiation Dosimetry of Radiopharmaceutical (RDRC Form 5a, page 4)

 

Critical Organ Name

Radiation Absorbed Dose/Unit Activity

Activity per Administration (mCi)

Radiation Absorbed Dose per Administration

Total No. of Administrations per Study/Year

Dose for Study

Committed Equivalent  Dose from this Study

(mrem)

Committed Effective Dose

 (mrem)

Critical Organ Dose

(for first radionuclide)

 bladder

481

(mrad/mCi)

10

 4810 mrad

 1

 4810

 

Critical Organ Dose

(for second radionuclide)

 n/a

 n/a

(mrad/mCi)

 n/a  n/a (mrad)  n/a  n/a

 

Whole Body Dose

 

 70.3 (mrem/mCi)

10

703 mrem 

1

 

703 mrem

 

These results would then be copied into the Summary Dose Table (below). In the example, the patients in the study also receive an abdominal CT examination as a part of the study. The radiation dose from CT examination needs to be added to the radiopharmaceutical dose. A separate page provides information for CT dose estimates. Since the CT scanner is not specified, we would use the Average CT scanner dose information. For an abdominal CT the effective dose would be ~.5 rem (525 mrem)

 

Summary Dose Table (RDRC Form 5a, page 6)

 

Critical Organ1

Total Critical Organ 1 Dose per Study
(mrad)

Critical Organ2
(if necessary)

Total Critical Organ 2 Dose per Study (mrad)
(if necessary)

Committed Equivalent Dose (rem)

Total Body Committed Effective Dose (rem)

Study: (specify) F-18 FDG

 Bladder

 4810

 n/a

n/a

 4.81

 0.7

Study: (specify) abdominal CT

Bladder

  negligible

 n/a

 n/a

negligible

 0.5

Total from all studies

 Bladder

4810

n/a

n/a

 4.8

1.2

Total annual from all studies

 Bladder

 4810

n/a

n/a

 4.8

 1.2