Measurement of the internal dose to families of outpatients treated with 131I for hyperthyroidism

Do Current Radiation Safety Guidelines allow the Safe Release of a Thyroid Cancer Patient after High-dose Radioiodine Therapy? An Indian Perspective

Aim:

Radionuclide therapy may produce a significant radiation exposure risk to the patient's caregivers. The study aims to assess the radiation exposure rate to caregivers after the patient's discharge from the isolation ward.

Materials and Methods:

Patients of the well-Differentiated thyroid cancer (DTC)were given high-dose radioiodine therapy as an inpatient. Their radiation exposure was measured daily, and they were discharged once the exposure rate falls as per standard guidelines. Detail counseling of the patient and caregiver about radiation safety was done before admission and at the time of discharge. Caregivers were given thermoluminescence dosimeter (TLD) to wear as a locket for 7 days. Radiation exposure received by the caregiver was measure after that.

Results:

A total of 22 patients (8 male and 14 female) of DTC were recruited in the study. The mean age was 39.0 ± 14.5 years. Patients were treated with 3.79 ± 1.07 (102.4 ± 28.9 mCi) (1.85–5.55 (50–150 mCi) GBq of radioiodine. They were discharged from the isolation ward at a radiation level of 0.028 ± 0.015 mSv/h (3.193 ± 1.71 mR). The mean effective dose received by the caregiver was 14.60 ± 3.43 mSv (1460 ± 343 mR) (9.73–24.25 (973–2765 mR) mSv.

Conclusion:

Our study denotes that the caregivers of DTC patients receive a significant radiation dose. It was well above the caregiver's annual dose-limit constraints regarding the rationales well as international guidelines of 5 mSv/yr. These could be related to the long travel in public transport and housing conditions. There is a need for patient-specific discharge criteria rather than following standard guidelines to minimize radiation exposure to caregivers.

Assessment of the radiation exposure of relatives and caregivers of patients treated with Ra-223 - Results of a German multicenter study

A multicenter study was conducted to assess the radiation exposure of relatives and caregivers of patients suffering from castration resistant prostate cancer with bone metastases and treated with Ra-223 dichloride in an outpatient setting. As Ra-223 and most of its progeny emit alpha particles, especially the internal exposure of persons in the patient's vicinity had to be evaluated.

METHODS

The external radiation was measured in distances of 1 m and 2 m. Wipe-tests were taken in the patients' homes to identify significant contaminations and evaluated by liquid scintillation counting. Samples of saliva and sweat were taken and measured using gamma spectrometry.

RESULTS

The external exposure from the patients measured 10-20min post injection (p. i.) was<0.080μSv/h in median in 1 m distance (range: below decision threshold (

CONCLUSIONS

The potential exposure of relatives by external irradiation and incorporation of Ra-223 excreted by the patient with saliva or sweat is estimated to be well below 1 mSv. No objections are seen regarding outpatient treatment.

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Key Words

• Ra-223
• Radiation exposure
• caregivers
• outpatient treatment
• relatives

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MESH Headings

• Humans
• Radium/therapeutic use
• Male
• Caregivers
• Germany
• Radiation Exposure
• Family
• Aged
• Middle Aged
• Bone Neoplasms/secondary
• Bone Neoplasms/radiotherapy
• Radioisotopes/therapeutic use
• Prostatic Neoplasms, Castration-Resistant/radiotherapy
• Saliva/chemistry
• Saliva/radiation effects

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Affiliation(s)

Carsten Wanke Department for Radiation Protection and Medical Physics, Hannover Medical School, Hannover, Germany.
Joerg Pinkert Bayer AG, Berlin, Germany
Bastian Szermerski Department for Radiation Protection and Medical Physics, Hannover Medical School, Hannover, Germany
Lilli Geworski Department for Radiation Protection and Medical Physics, Hannover Medical School, Hannover, Germany

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Prediction of dose to the relatives of patients treated with radioiodine-131 using neural networks

In this study, the effective dose received by the family members and caregivers of 52 thyroid cancer patients, who had been treated with radioiodine I-131, was measured to investigate the ability of the neural network to predict the doses to the relatives. The effectiveness of this method to predict the relatives who will receive doses of more than 1 mSv was evaluated. The effective doses were measured by TLD. The inputs of the neural network include 13 different parameters that can potentially affect the dose, and the output was the dose to the family members. The neural networks in this study were feed-forward with a sigmoid activation function and one hidden layer. The mean and median of the measured doses were 0.45 and 0.28 mSv and its range was 0.1-3.64 mSv. The mean square error of the predicted doses by the neural network and the measured doses by TLD (mean squared error) for 99 individuals was 0.142. The optimum neural network was able to predict all the relatives who received doses of more than 1 mSv. The area under the receiver operating characteristic curve for the trained neural network was 0.957, showing its ability to distinguish these groups. Predicting the dose to a patient's relatives before release is a helpful strategy for future optimisation. Using neural networks is a promising method for predicting the dose to the family members and defining high-risk patients and relatives. Patient-specific criteria for release and patient-specific advice and consultation can be used to reduce the dose to each family member.

Exhalation of 131I after radioiodine therapy: Dosimetric considerations based on measurements in exhaled air

It is well known that a considerable amount of radioiodine is exhaled after radioiodine therapy (RIT) leading to unwanted radiation exposure through inhalation for non-involved persons. This study focuses on the amount of exhalation in the breath-out air of RIT-patients and the dosimetric consequences. Furthermore, the correlation between radioiodine uptake and exhalation was investigated. The radioiodine species were collected in a filter system and quantified over time by measurements with a scintillation counter. The dosimetric implications were then studied for different exposure scenarios. Of the activity administered to the patient, approximately 10^-3% (50-110 ppm) is exhaled. The radioiodine inhalation taking place following exhalation in the vicinity yields doses of up to 500 μSv (children, staying with the patient immediately after application and for the next 8 h). Three days after administration the doses are significantly reduced. This study lays emphasis on previous assumptions that exhalation depends on thyroid storage. Regardless of the type of thyroid disease, the predominant form exhaled is organic radioiodine. The amount of exhaled radioiodine is small but from the point of view of radiation protection, by no means negligible immediately after administration. Radiation doses received by incorporation of exhaled radioiodine can easily exceed 100 μSv soon after administration of radioiodine. Three days after RIT the radioactivity can still be measured in the exhaled air but even at maximum, the annual doses lie far below 10 μSv and are thus comparatively low.

Radiation Safety Precautions in (131)I Therapy of Graves' Disease Based on Actual Biokinetic Measurements

CONTEXT

Radiation protection is an integral part of targeted radionuclide therapy. How to offer rational radiation precautions to patients with Graves' disease (GD) undergoing (131)I therapy is still a matter of ongoing discussions.

OBJECTIVE

The objective of the study was to formulate radiation precautions for GD patients undergoing (131)I therapy through actual biokinetic measurements for a particular population of patients.

DESIGN

This was a prospective study.

SETTING

The study was conducted at a university hospital.

PATIENTS

From January 2009 through January 2012, consecutive GD patients prepared for (131)I therapy were prospectively recruited.

MAIN OUTCOME MEASURES

Pretherapy thyroid radioiodine uptake and uptake ratio (4 to 24 h radioiodine uptake) were measured. Serial whole-body dose-rate measurements after therapy were performed to deduce (131)I whole-body retention. Calculations based on deduced whole-body retention and measured thyroid radioiodine biokinetics were derived to determine the thyroidal and extrathyroidal compartment uptake fractions and effective half-lives. Precaution times necessary to avoid close contact with family members and the general public were derived from these parameters and regulatory dose limits.

RESULTS

A total of 72 patients were eligible for the analysis. A high interpatient variability in (131)I biokinetics was observed: the mean peaking (131)I uptake (±1 SD) in the thyroid was 68% (±19%), and the range was 18%-89%; the mean effective (131)I half-life (±1 SD) in the remainder of the body was 5.1 (±0.9) hours (range 3.5-7.2 h). The mean measured initial dose rate (±1 SD) at 1.0 m after (131)I administration was 0.039 (±0.003) μSv·h(-1) · MBq(-1) (range 0.017-0.055 μSv·h(-1) · MBq(-1)). The 0.3:1.0 m initial dose rate ranged from 2.9 to 7.1, which was greatly lower than the projected ratio of 11.1 by the inverse square law approximation. On the basis of the measured radioiodine biokinetics and dose rates, detailed instructions were provided to limit nearby individuals' exposure.

CONCLUSION

The use of actual biokinetic measurements may remove the effect of variability errors associated with general default assumptions about the (131)I biokinetics in GD patients. The marked variability in (131)I biokinetics among GD patients reinforces the need for patient-specific iodine biokinetic measurements for radiation safety precautions.

Measurement and analysis of patient attenuation correction factor during radioiodine therapy

The calculated dose rate from the radioiodine therapy patient should normally include a factor accounting for the attenuation and scatter of patient body tissues. The attenuation factor is currently neglected, and not applied in operational radiation protection. Realistic estimation of radiation dose rate levels from radioiodine therapy patients when properly performed will reduce operational cost and optimise institutional radiation protection practice. In this work, the existence of a patient body tissue attenuation factor is verified by comparing the dose rates measured from the radioiodine capsules immediately before administration with those measured from the patient immediately after administration. The correlation between the factors suspected to influence the patient body tissue attenuation and the measured dose rates from the patient normalised per unit activity is statistically analysed. The calculated attenuation correction factor based on authors' measurements was (0.55 ± 0.17). The measured dose rate per unit of radioactivity from the patient showed a negative correlation with their body mass index.

Potential third-party radiation exposure from patients undergoing therapy with 131I for thyroid cancer or metastases

The purpose of this work is to evaluate the potential third-party radiation exposure from patients undergoing therapy with 131I for ablation of residual thyroid tumor or metastases, based in part on serial measurements of exposure rates. Exposure rate measurements were performed at 1 m and 5 cm from the surface of each treated patient until patient release. Dose estimates based on measured exposure rates were compared with those based on analytic point-source (PSM) and line-source (LSM) models. Effective doses D(∞) to travelers, co-workers and sleeping partners were estimated by using the standard gamma factor (Γ) and the physical half-life or the values derived from measured data. Seven hundred ten patients were studied until the exposure at 1 m was below the constraints of 0.010 mSv. The 131I activities administered ranged from 1.85 to 11.0 GBq (median: 3.7 GBq), according to the therapeutic requirements. Based on the PSM and an experimental Γ, the mean/maximum estimated D(∞) to sleeping partners, partners, travelers, and co-workers were 2.60/20.65, 0.32/2.53, 0.96/7.59, and 0.57/4.50 mSv, respectively. Using the LSM and an experimental Γ, the D(∞) values were 2.41/19.15, 0.32/2.50, 0.83/6.62, and 0.57/4.42 mSv, respectively, while they were almost double using the theoretical Γ. The results presented, based on measured data in a large cohort of 131I-treated thyroid cancer patients, will allow more accurate estimation of potential third-party D(∞) following patient release and thus may be used to better inform physicians and hospital staff on recommendations for patient release and post-release precautions following radioiodine therapies.

Radiation exposure to comforters and carers during paediatric molecular radiotherapy

BACKGROUND

To show whether the incidental radiation exposure received by comforters and carers of children undergoing molecular radiotherapy was kept as low as reasonably achievable and was within English national dose constraints.

PROCEDURE

The radiation exposure of adult comforters and carers was routinely monitored with a whole body personal dose meter while the child was in hospital. Data were collected on iodine-131 meta-iodobenzylguanidine (¹³¹ I-mIBG), lutetium-177 DOTATATE (¹⁷⁷ Lu-DOTATATE), and iodine-131 sodium iodide (¹³¹ I-NaI) treatments.

RESULTS

Data were available for 50 treatments with high-administered activity double-infusion ¹³¹ I-mIBG and 12 single administrations; 15 ¹⁷⁷ Lu-DOTATATE treatments and 28 ¹³¹ I-NaI administrations. The median age was 7 years (1-18). The median administered activity of: ¹³¹ I-mIBG was 16.2 GBq (6.8-59 GBq) for double infusion patients and 8.1 GBq (5.26-16.25 GBq) for single administrations; ¹⁷⁷ Lu-DOTATATE was 7.2 GBq (2.5-7.5 GBq); and ¹³¹ I-NaI was 3 GBq for thyroid remnant ablation and 5.5 GBq for cancer therapy. The median number of comforters and carers for all administrations was 2 (range 1-9). The median exposure values for comforters and carers for high-administered activity ¹³¹ I-mIBG administrations was 302 µSv (0-5282 µSv); for single fraction ¹³¹ I-mIBG 163 µSv (3-3104 µSv); ¹⁷⁷ Lu-DOTATATE 6 µSv (1-79 µSv); and ¹³¹ I-NaI 37 µSv (0-274 µSv). Only one of the comforters and carers exceeded the dose constraint of 5 mSv.

CONCLUSIONS

Doses to comforters and carers were in all but one case within the dose constraint nationally recommended by the Health Protection Agency, now part of Public Health England. New evidence is presented which show that comforter and carer radiation exposure levels from paediatric molecular radiotherapy in routine clinical practice are acceptably low. Pediatr Blood Cancer 2015;62:235-239. © 2014 Wiley Periodicals, Inc.

[Incorporation monitoring of employees of a radioiodine therapy ward. Is incorporation monitoring required for routine?]

Aim of the study was to determine the annual incorporation of staff on a radioiodine therapy ward and the resulting annual effective dose (aed). Following the German incorporation guideline (gig), incorporation monitoring is not necessary for potential aed below 0.5 mSv/a. For aed > 0.5 mSv/a adherence to the 1 mSv dose limit must be verified. For doses > 1 mSv/a incorporation has to be monitored by the authority. Furthermore, the (131)I incorporation factor from the gig should be verified.

METHODS

To determine the actual work related incorporation, the (131)I activity concentration in urine samples (collection over 24 h) of 14 employees of different professions were examined over a period of 27 months.

RESULTS

Measured activity concentrations were related to the individual time of exposure. A constant activity supply for at least three days was assumed. The mean annual effective doses were 2.4 · 10⁻¹ mSv/a (nursing staff; n = 3), 5.6 · 10⁻² mSv/a (cleaning staff; n = 2), 2.8 · 10⁻³ mSv/a (technical staff; n = 2) and 5.2 · 10⁻³ mSv/a (physicians; n = 7). All aed were below the dose limits of the gig. The calculated mean incorporation factors ranged from 3.0 · 10⁻⁸ for the nursing staff to 3.6 · 10⁻¹⁰ for the technical staff (cleaning staff: 7 · 10⁻⁹; physicians: 6.5 · 10⁻¹⁰) and were therefore well below the (131)I incorporation factor defined by the gig.

CONCLUSIONS

To estimate the aed caused by incorporation of (131)I it has to be subdivided for the different requirements in the diverse fields of activity of the employees. Regarding those who spend most of their time nearby the patient an incorporation monitoring by the authority might be required. The (131)I incorporation factor from the guideline (10⁻⁶) can be reduced by a factor of 10. For (99m)Tc and (18)F an incorporation factor of 10⁻⁷ is accepted.

Restriction periods for carers, comforters and members of the public in the treatment of hyperthyroidism

People treated for hyperthyroidism are normally outpatients who pose a potential radiological risk to some members of the public. In this study, measurements of the uptake in 30 patients were used to estimate the values of the activity of ¹³¹I in the whole body of patients, AWB, by using a model of two compartments. Restriction periods to be followed by patients for different values of the administered activity of ¹³¹I were calculated. To perform calculations, the following were used: the curve obtained for AWB; the value of the dose rate at one metre from patients after the administration of the treatment; and the estimated time that carers, comforters and members of the public will spend at certain distances from patients. Results show that protection from radiation for carers, comforters and members of the public related to patients treated for hyperthyroidism can become a cumbersome matter as patients may have to follow very long restriction periods.

Mutagenicity of diagnostic and therapeutical doses of radiopharmaceutical iodine-131 in Wistar rats

Iodine-131 ((131)I) is a radioisotope used for the diagnosis and treatment of thyroidal disorders such as hyperthyroidism and cancer. During its decay, (131)I emits beta particles and gamma rays; its physical half-life is 8 days, and it is accumulated preferentially in the thyroid tissue. This study aimed to evaluate the cytotoxicity and mutagenicity of diagnostic and therapeutic doses of (131)I using bone marrow cells of rats treated in vivo in a test system with a single dose by gavage. Concentrations of 5, 25, 50 and 250 μCi in 1 ml of water were used, and after 24 h, the animals were killed. Also, a concentration of 25 μCi/ml of water was used, and the animals were killed after 5 days. The results showed that no concentration of (131)I was cytotoxic and that all concentrations were mutagenic. As a result, there was no statistically significant difference detected by the χ(2) test in the induction of chromosomal aberrations between the different doses. Thus, the present study demonstrated a significant increase in chromosomal aberration in bone marrow cells exposed to (131)I regardless of the dose or the treatment time.

Current safety practices relating to I-131 administration for diseases of the thyroid: a survey of physicians and allied practitioners

BACKGROUND

There is little information about the individual safety instructions provided by healthcare professionals to patients receiving radioactive iodine (I-131) therapy for the treatment of benign and malignant thyroid disorders or about whether these instructions are consistent across medical specialties. Currently, no national guidelines exist to standardize safety instructions related to I-131 administration. Here, we examine the spectrum of I-131 safety practices in contemporary use.

METHODS

Members of major societies of physicians and allied specialists who treat patients with thyroid disorders were invited to complete a 27-question online survey about safety practices related to I-131 administration. Data from questionnaires were analyzed by type of safety recommendation and grouped according to provider specialty and geographic location.

RESULTS

A total of 311 endocrinologists, surgeons, nuclear medicine radiologists, and allied health professionals completed questionnaires. They indicated that patients often receive instruction from more than one treating specialist. The decision to hospitalize a patient for treatment and the length of stay were determined by the patient's social situation and the dose of I-131 administered. Starting at I-131 doses between 259 and 1073 MBq (7 and 29 mCi), over 60% of respondents advised avoiding contact with children, sexual activity, and breastfeeding, with the latter recommendation continuing beyond 48 hours after treatment. Personal hygiene, laundry, and meal preparation precautions varied across respondents. Over 90% of respondents used serum or urine testing to screen for pregnancy status. Precautions to delay parenthood were given more often to female than male patients (90% vs. 60%), with a minimum recommended delay of 6 months. About 20% of respondents considered insurance coverage as a factor in selecting outpatient versus inpatient I-131 therapy, and this consideration varied geographically.

CONCLUSION

A wide variety of safety recommendations are given to patients who receive I-131. To our knowledge, this survey represents the first organized inquiry into safety practices related to I-131 administration. The diversity of responses suggests an opportunity for multispecialty collaboration in defining more uniform recommendations for patient safety instructions during and after I-131 treatment.

The evaluation of the external dose measurement of the patients treated with radioiodine therapy

The aim of the study is to compare the results of the external exposure and the range of the dose spread by the patients, hospitalized in two different groups of 3-4 d receiving radioiodine therapy because of having hyperthyroidism (HT) and thyroid cancer (TC). A total of 1989 patients were evaluated retrospectively. Of the total 1517 patients had TC and 472 had HT. External exposure value was taken at hospital discharge and the distance for external measurement was 1 m at the abdominal level. External exposure values of 99.7 % patients were <30 µSv h(-1) and of 0.3 %, >30 µSv h(-1). The results between patient groups with TC and HT at third and fourth days, and the dissimilarity of measurement results within third and fourth days in total patients, without discriminating the day difference, are statistically meaningful. Although 3-d isolation period for 30 µSv h(-1) limit is generally enough, it can be insufficient for some patients. Besides hospitalisation, the radiation safety training must be emphasised by establishing good communication with patients in order to protect their relatives and other people against radiation risk.