Thyroid Ultrasound Examination
Implementation status
Preliminary Baseline Survey (the first-round survey) As of March 31, 2018
- Implementation period: October 2011 - March 2014
- Eligible persons: 367,637
- Primary examination participants: 300,472
- Grade A1 or A2 cases: 298,178
- Grade B cases: 2,293
- Confirmatory examination participants: 2,130
- Participants with finalized results: 2,091
- FNAC participants: 547
Results
Results of Primary Examination
Results of Confirmatory Examination
Age distribution of 116 persons diagnosed through cytology, etc. as having nodule that is malignant or suspected to be malignant
Evaluation of the Preliminary Baseline Survey (PBLS) results
The Oversight Committee made the following evaluation of the results of PBLS.
Exposure doses due to the accident at the Fukushima Daiichi Nuclear Power Plant were generally lower than those caused by the Chernobyl accident; the period of time from the exposure to the detection of cancers is shorter among Fukushima children (one to four years in most cases); cancers have not been detected in those aged five and under at the time of the Fukushima accident; and there are no substantial regional differences within Fukushima in detection rates. Accordingly, it can be concluded that thyroid cancers found thus far through the Thyroid Ultrasound Examination (TUE) program cannot be attributed to radiation released by the Fukushima accident.
However unlikely, the possibility of radiation effects cannot be completely denied at this point in time. Additionally, it is necessary to accumulate information in the long term for accurate evaluation of any effects. Therefore, the TUE should be continued, while meticulously explaining the disadvantages of receiving thyroid examinations and obtaining informed consent from participants.
Source: March 2016 Prefectural Oversight Committee Meeting for the FHMS
First Full-Scale Survey (the second-round survey) As of March 31, 2021
- Implementation period: April 2014 - March 2016
- Eligible persons: 381,237
- Primary examination participants: 270,552
- Grade A1 or A2 cases: 268,322
- Grade B cases: 2,230
- Confirmatory examination participants: 1,877
- Participants with finalized results: 1,834
- FNAC participants: 207
Results
Results of Primary Examination
Results of Confirmatory Examination
Age distribution of 71 persons diagnosed through cytology, etc. as having nodule that is malignant or suspected to be malignant
Evaluation of the First Full-Scale Survey (the second-round survey) results
The Oversight Committee made the following evaluation of the results of the first FSS.
At present, no causal relationship between thyroid cancer detected during the FSS (the second-round survey) and radiation exposure can be identified.
Basis for evaluation:
- An analysis of the relationship between the estimated thyroid absorbed doses published by UNSCEAR and the detection rate of thyroid cancer showed no consistent dose-effect relationship.
- The detection rate of thyroid cancer and suspected thyroid cancer in the results of ultrasound examinations, etc., was higher in the older age group at the time of the accident, which was different from the age group in which thyroid cancer was frequently detected after the Chernobyl accident (mainly in younger children).
Source: October 2019 the 36th Prefectural Oversight Committee Meeting for the FHMS (Handouts 1-1 and 1-2)
Second Full-Scale Survey (the third-round survey) As of March 31, 2021
- Implementation period: May 2016 - March 2018
- Eligible persons: 336,667
- Primary examination participants: 217,922
- Grade A1 or A2 cases: 216,420
- Grade B cases: 1,502
- Confirmatory examination participants: 1,104
- Participants with finalized results: 1,068
- FNAC participants: 79
Results
Results of Primary Examination
Results of Confirmatory Examination
Age distribution of 31 persons diagnosed through cytology, etc. as having nodule that is malignant or suspected to be malignant
Third Full-Scale Survey (the fourth-round survey) As of June 30, 2022
- Implementation period: April 2018 - March 2020
- Eligible persons: 294,228
- Primary examination participants: 183,410
- Grade A1 or A2 cases: 182,016
- Grade B cases: 1,394
- Confirmatory examination participants: 1,036
- Participants with finalized results: 1,016
- FNAC participants: 91
Results
Results of Primary Examination
Results of Confirmatory Examination
Age distribution of 39 persons diagnosed through cytology, etc. as having nodule that is malignant or suspected to be malignant
Fourth Full-Scall Survey (the fifth-round survey) As of March 31, 2024
- Implementation period: April 2020 - March 2023
- Eligible persons: 252,938
- Primary examination participants: 113,959
- Those who completed the processes of preliminary examination and with finalized results: 113,950
- Grade A1 or A2 cases: 112,604
- Grade B cases: 1,346
- Confirmatory examination participants: 1,108
- Participants with finalized results: 1,079
- FNAC participants: 93
Results
Results of Primary Examination
Results of Confirmatory Examination
Age distribution of 46 persons diagnosed through cytology, etc. as having nodule that is malignant or suspected to be malignant
Fifth Full-Scall Survey (the sixth-round survey) As of March 31, 2024
- Implementation period: April 2023 -
- Eligible persons: 211,892
- Primary examination participants: 42,416
- Those who completed the processes of preliminary examination and with finalized results: 40,791
- Grade A1 or A2 cases: 40,209
- Grade B cases: 582
- Confirmatory examination participants: 243
- Participants with finalized results: 171
- FNAC participants: 7
Results
Results of Primary Examination
Results of Confirmatory Examination
Survey for Age 25 As of March 31, 2024
- Implementation period: May 2017 -
- Eligible persons*: 149,843
- Primary examination participants: 12,603
- Those who completed the processes of preliminary examination and with finalized results: 12,286
- Grade A1 or A2 cases: 11,609
- Grade B cases: 677
- Confirmatory examination participants: 554
- Participants with finalized results: 546
- FNAC participants: 49
Results
Results of Primary Examination
Results of Confirmatory Examination
Age distribution of 23 persons diagnosed through cytology, etc. as having nodule that is malignant or suspected to be malignant
*Those who become 25 during each fiscal year (those born between FY1992 and FY1998）
Survey for Age 30 As of March 31, 2024
- Implementation period: April 2022 -
- Eligible persons*: 44,489
- Primary examination participants: 2,221
- Those who completed the processes of preliminary examination and with finalized results: 1,624
- Grade A1 or A2 cases: 1,481
- Grade B cases: 143
- Confirmatory examination participants: 118
- Participants with finalized results: 111
- FNAC participants: 16
Results
Results of Primary Examination
Results of Confirmatory Examination
*Those who become 30 during each fiscal year (those who were born in FY1992 and FY1993）
Outline of the Thyroid Ultrasound Examination (TUE)
Purpose
One of the health problems caused by the Chornobyl (Chernobyl) nuclear power plant accident was thyroid cancer in children caused by internal exposure from radioactive iodine. Although the exposure level in Fukushima Prefecture caused by the nuclear accident in 2011 is considered to be much lower than in Chornobyl, we launched a Thyroid Ultrasound Examination program to address long-term health concerns by understanding the condition of children's thyroid glands.
Eligible persons and Progress of the TUE
| Survey category | Implementation Period | Eligible persons |
|---|---|---|
| Preliminary Baseline Survey (the first-round survey) Aiming to check the baseline condition of participants thyroid glands |
From October 2011 through March 2014 | Fukushima Prefecture residents who were born between April 2, 1992 and April 1, 2011, i.e., in the range of 0 to 18 years old as of March 11, 2011. |
| First Full-Scale Survey (the second-round survey) For comparison with the Preliminary Baseline Survey |
From April 2014 through March 2016 | Fukushima Prefecture residents who were born between April 2, 1992 and April 1, 2012 |
| Second Full-Scale Survey (the third-round survey) and after | Eligible participants are invited to receive thyroid examinations every two years until the age of 20, and then every five years thereafter at the age of 25, 30, and so on.(The interval before the Age 25 Survey should not be more than 5 years.) | |
Due to the COVID-19 pandemic, the Fourth Full-Scale Survey (the fifth-round survey) will be conducted over 3 years from 2020 through 2022.
Method
| Primary examination | Ultrasonography |
|---|---|
| Confirmatory examination | Advanced ultrasonography, urine, and blood test Fine-needle aspiration cytology (FNAC) is conducted, if needed. |
Diagnostic criteria of Primary Examination
| Grade | Criteria | Next step | |
|---|---|---|---|
| A | No abnormal findings | ||
| A1 | No cysts or nodules | Undergo another primary examination 2 (or 5) years later | |
| A2 | Nodule(s) with a diameter of 5.0 mm or less* or cyst(s) with a diameter of 20.0 mm or less | ||
| B | Nodule(s) with a diameter of 5.1 mm or more or cyst(s) with a diameter of 20.1 mm or more | Undergo a confirmatory examination | |
| C | Cases considered as requiring detailed examination** | Undergo a confirmatory examination immediately | |
* Some nodules that are 5.0 mm or less in diameter may be judged as Grade B based on ultrasound images.
** Cases in which thyroid nodules are suspected to have infiltrated non-thyroidal tissues or a large lymph node metastasis (Large N) of 3 cm or more is observed
Implementation criteria of FNAC in Confirmatory Examination
Nodules are treated in accordance with the Guidebook on Thyroid Ultrasound Diagnosis (edited by the Japan Association of Breast and Thyroid Sonology).
*Nodule without cystic characteristics
** FNAC: Fine-needle aspiration cytology