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First-day iodine kinetics is useful for individualizing radiation safety precautions for thyroid carcinoma patients.

Tenhunen M, Lehtonen S, Heikkonen J, Halonen P, Mäenpää H - Nucl Med Commun (2013)

Bottom Line: We have developed a method to individualize radiation safety precautions.The TLD results were compared with the iodine kinetics.From these findings it is possible to individualize radiation safety precautions by taking into account the iodine pharmacokinetics and living conditions of a patient.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncology, Helsinki University Central Hospital, Helsinki, Finland.

ABSTRACT

Objective: There is considerable variation in the national regulations of different countries for the release of patients from hospitals after radioiodine therapy. Individual variations make these practices, when based on the worst case scenarios, too restrictive for the majority of patients. However, there are cases in which strict rules are needed to comply with the dose limits to other individuals, especially children. We have developed a method to individualize radiation safety precautions.

Materials and methods: Twenty-three patients with differentiated thyroid carcinoma were included in the study. Four weeks after thyroidectomy, 1.1-3.7 GBq of radioiodine was administered and iodine kinetics were followed with external measurements until hospital discharge. The absorbed dose at the wrist holder was measured with thermoluminescence dosimetry (TLD) during hospital stay and after hospital discharge for up to 1 week. The TLD results were compared with the iodine kinetics. The dose to other individuals was estimated with extra TLDs located both on the patient's bed and given to family members. The kinetics data were fitted in both monoexponential and biexponential models and both for the full measurement period (down to the residual activity level<400 MBq) and for the first 24 h after radioiodine administration.

Results: The biexponential model was capable of predicting the cumulated dose up to 1 week for both the longer and the shorter measured data set. The occupancy factors both for a person sleeping on the same bed and for a person living in the same apartment with the patient were in agreement with the recommended occupancy factor values of the American Thyroid Association. From these findings it is possible to individualize radiation safety precautions by taking into account the iodine pharmacokinetics and living conditions of a patient.

Conclusion: By measuring the activity content within the body for the first 24 h after radioiodine administration it is possible to individualize radiation safety precautions for thyroid carcinoma patients.

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Related in: MedlinePlus

Examples of the measurement setup for patients 14 (slower kinetics) and 17 (faster kinetics) who stayed 68 and 33 h in the hospital after iodine administration. The measured dose rates at 1-m distance (in logarithmic scale) during the hospital stay are presented with solid circles (#14) and open squares (#17) with two different model fits, monoexponential (solid line) and biexponential (dotted curve). The first thermoluminescence dosimetry holder was used during the hospital stay (solid arrow, Δt1) and the second holder was used after the hospital discharge up to 1 week from the administration of radioiodine (dashed arrow, Δt2). The parameters of the biexponential model are #14: k=0.013, T1=16.7 h (monoexponential: 17.1 h), and #17: k=0.006, T1=10.4 h (monexponential: 10.5 h).
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Figure 1: Examples of the measurement setup for patients 14 (slower kinetics) and 17 (faster kinetics) who stayed 68 and 33 h in the hospital after iodine administration. The measured dose rates at 1-m distance (in logarithmic scale) during the hospital stay are presented with solid circles (#14) and open squares (#17) with two different model fits, monoexponential (solid line) and biexponential (dotted curve). The first thermoluminescence dosimetry holder was used during the hospital stay (solid arrow, Δt1) and the second holder was used after the hospital discharge up to 1 week from the administration of radioiodine (dashed arrow, Δt2). The parameters of the biexponential model are #14: k=0.013, T1=16.7 h (monoexponential: 17.1 h), and #17: k=0.006, T1=10.4 h (monexponential: 10.5 h).

Mentions: Both models were tested against TLD measurements using the first wrist measurement (while the patient was in the hospital, Δt1) for normalization and an attempt was made to forecast the values of (a) the sum of the first and second measurements – that is, wrist dose from the time of iodine administration up to 1 week, Δt1+Δt2 – and (b) the second measurement alone – that is, wrist dose from the time of hospital discharge up to 1 week from iodine administration, Δt2. The values for the effective half-life T1 and, for the biexponential model additionally, the proportion of the slower component k were calculated. The examples of data collection timeline for two patients are presented in Fig. 1.


First-day iodine kinetics is useful for individualizing radiation safety precautions for thyroid carcinoma patients.

Tenhunen M, Lehtonen S, Heikkonen J, Halonen P, Mäenpää H - Nucl Med Commun (2013)

Examples of the measurement setup for patients 14 (slower kinetics) and 17 (faster kinetics) who stayed 68 and 33 h in the hospital after iodine administration. The measured dose rates at 1-m distance (in logarithmic scale) during the hospital stay are presented with solid circles (#14) and open squares (#17) with two different model fits, monoexponential (solid line) and biexponential (dotted curve). The first thermoluminescence dosimetry holder was used during the hospital stay (solid arrow, Δt1) and the second holder was used after the hospital discharge up to 1 week from the administration of radioiodine (dashed arrow, Δt2). The parameters of the biexponential model are #14: k=0.013, T1=16.7 h (monoexponential: 17.1 h), and #17: k=0.006, T1=10.4 h (monexponential: 10.5 h).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3815145&req=5

Figure 1: Examples of the measurement setup for patients 14 (slower kinetics) and 17 (faster kinetics) who stayed 68 and 33 h in the hospital after iodine administration. The measured dose rates at 1-m distance (in logarithmic scale) during the hospital stay are presented with solid circles (#14) and open squares (#17) with two different model fits, monoexponential (solid line) and biexponential (dotted curve). The first thermoluminescence dosimetry holder was used during the hospital stay (solid arrow, Δt1) and the second holder was used after the hospital discharge up to 1 week from the administration of radioiodine (dashed arrow, Δt2). The parameters of the biexponential model are #14: k=0.013, T1=16.7 h (monoexponential: 17.1 h), and #17: k=0.006, T1=10.4 h (monexponential: 10.5 h).
Mentions: Both models were tested against TLD measurements using the first wrist measurement (while the patient was in the hospital, Δt1) for normalization and an attempt was made to forecast the values of (a) the sum of the first and second measurements – that is, wrist dose from the time of iodine administration up to 1 week, Δt1+Δt2 – and (b) the second measurement alone – that is, wrist dose from the time of hospital discharge up to 1 week from iodine administration, Δt2. The values for the effective half-life T1 and, for the biexponential model additionally, the proportion of the slower component k were calculated. The examples of data collection timeline for two patients are presented in Fig. 1.

Bottom Line: We have developed a method to individualize radiation safety precautions.The TLD results were compared with the iodine kinetics.From these findings it is possible to individualize radiation safety precautions by taking into account the iodine pharmacokinetics and living conditions of a patient.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncology, Helsinki University Central Hospital, Helsinki, Finland.

ABSTRACT

Objective: There is considerable variation in the national regulations of different countries for the release of patients from hospitals after radioiodine therapy. Individual variations make these practices, when based on the worst case scenarios, too restrictive for the majority of patients. However, there are cases in which strict rules are needed to comply with the dose limits to other individuals, especially children. We have developed a method to individualize radiation safety precautions.

Materials and methods: Twenty-three patients with differentiated thyroid carcinoma were included in the study. Four weeks after thyroidectomy, 1.1-3.7 GBq of radioiodine was administered and iodine kinetics were followed with external measurements until hospital discharge. The absorbed dose at the wrist holder was measured with thermoluminescence dosimetry (TLD) during hospital stay and after hospital discharge for up to 1 week. The TLD results were compared with the iodine kinetics. The dose to other individuals was estimated with extra TLDs located both on the patient's bed and given to family members. The kinetics data were fitted in both monoexponential and biexponential models and both for the full measurement period (down to the residual activity level<400 MBq) and for the first 24 h after radioiodine administration.

Results: The biexponential model was capable of predicting the cumulated dose up to 1 week for both the longer and the shorter measured data set. The occupancy factors both for a person sleeping on the same bed and for a person living in the same apartment with the patient were in agreement with the recommended occupancy factor values of the American Thyroid Association. From these findings it is possible to individualize radiation safety precautions by taking into account the iodine pharmacokinetics and living conditions of a patient.

Conclusion: By measuring the activity content within the body for the first 24 h after radioiodine administration it is possible to individualize radiation safety precautions for thyroid carcinoma patients.

Show MeSH
Related in: MedlinePlus