I'm not implying that there is no need to worry.
However high-resolution ultrasound does produce very high incidence rates of small thyroid nodules, which is why such nodules are commonly left alone. The high figure of 2/3rds came from Ezzat, 1994:
http://www.ncbi.nlm.nih.gov/pubmed/8053752
That's why I think they should use the same equipment to conduct screening on a non-exposed sample of Japanese kids of the same age. If they find a difference in the incidence of nodules, their current screening plan in not reasonable, and they need to pick up the pace on their screening plan, which seems to be based on data from follow up for cancer risks in pediatric populations treated for cancer. The theory seems reasonable, because most of the resultant cancers in that population occur after 5 years, but it may not be.
As far as I know, no one's ever used ultrasound high-res for this type of screening before. Smaller screening projects have been done on pediatric populations that had been exposed to much higher dosages for cancer treatment. But not a general survey. When I tried to find the Chernobyl data, it appeared that they weren't counting the small nodules.
What I was implying is that they are assuming too much, and that they needed to look further. Ultrasound is very safe. It's not as if picking up the screening pace would present a danger to the kids.
The second thing about their stated plan is that they want to cut screening intervals down to 5 years after the kids reach 20, and that seems questionable, since the Chernobyl data and the cancer data show that's when the incidence of actual cancer should start picking up.
Sorry if I was not clear.
High-resolution ultrasound is relatively new in this application, and its use has changed the incidence rate of thyroid nodules:
http://www.enttoday.org/details/article/526325/New_Guidelines_Developed_to_Manage_Thyroid_Nodules_and_Thyroid_Cancer.html
Thyroid nodules are common-present in about 5% in women and 1% in men living in iodine-sufficient parts of the world. However, the prevalence is likely higher because high-resolution ultrasound can detect thyroid nodules in 19% to 67% of randomly selected individuals. The clinical problem is to isolate the 5% to 10% of these nodules that are malignant.
Here's another ultrasound discussion from 2005. It's not Japanese, so it cannot be considered part of the Japanese plot to kill the Fukushima kids. Note that when they discuss micronodules, they start with 1/2 centimeter nodules, and only 26 of those were found in the Fukushima screening.
http://www.touchbriefings.com/pdf/1479/Baskin.pdf
Because micronodules (nodules 0.5–1cm) are so common in the population, the question arises when to perform
UG FNA.A nodule this size seldom presents a threat to life and they are so numerous that routine biopsy of all such nodules is not practical or cost-effective. However, several investigators have shown that the incidence of malignancy in small non-palpable nodules is the same as in palpable nodules. In addition, others have shown that cancers that present less than 1.5cm in size are often as aggressive as larger cancers.
I happen to know something about this topic because a few years ago my husband developed a medical problem that appeared to be generated by an endocrine-secreting tumoro, although some are nearly impossible to find. And sure enough, an ultrasound of the neck did show a thyroid nodule, and there was much agonized research on my part because I was not sure it could be safely dismissed as benign, especially since his thyroid hormone levels were fluctuating. We eventually found the problem elsewhere.
Here's another article which touches on the very small thyroid nodule, and notes that 40% of those screened have them:
http://www.slideshare.net/roger961/click-here-to-download-this-article-as-a-word-document-5513989
Incidentalomas is the term used:
http://www.medscape.org/viewarticle/744819_3
I don't think these recommendations hold for this population, but they'll have to figure it out, won't they?
The size of the depicted nodule is an important determinant of the need for further evaluation. Proceeding to fine-needle aspiration (FNA) cytology of lesions >1.0-1.5 cm is recommended, unless the ultrasound features are highly suggestive of benignity, such as isoechogenicity with a spongiform appearance.[53] The need for FNA in subcentimeter nodules relies mainly on the presence of suspicious clinical and ultrasonographic characteristics. Thyroid lesions <5 mm detected with high-resolution ultrasonography should not put the patient to the distress of further testing, except on the rare occasion when findings indicate extracapsular growth or metastatic cervical lymph nodes. For lesions ≥5 mm, decisions are based on careful review of the history, the imaging characteristics of the nodule and clinical examination.[56]
The closest relevant thing I can find is this information on incidence in Korea, but of course it is not pediatric:
http://www.medscape.com/viewarticle/466575_4
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