minimal instruction to obtain and record data in a consistent manner. Completed records should be reviewed for clarity, and consistency. Any missing information should be obtained if possible. Additionalservices will be required to validate the quality of medical data collected,(e.g,, referral to original records to verify pertinentitems of self-reported data). These data should be preserved and retained indefinitely. 7.46 Other Procedures Considered but not Recommended 7.4.6.1 Screening by High Resolution Ultrasonic Imaging Although most experts agree that high resolution ultrasonographyis useful at referral centers to evaluate palpable thyroid nodules, opinions differ about its usefulness as a screening tool in the field because of its high sensitivity and lack of specificity in identifying non-palpable lesions. For example, in the adult U.S. population the prevalence of palpable thyroid nodules is estimated to be about four percent; however, the true prevalence of nodules as indicated by autopsy studies or by high-resolution ultrasonographyis estimated to be about 40 to 50 percent. Theclinical significance of such non-palpable lesions is considered to be negligible. Should U.S. DOE decide to include its use in future medical evaluations of the Marshall Islands’ population, only palpable nodules should be biopsied; non-palpable nodules should remain under medical surveillance pending observation of any significant changes in their clinical status (39-41). 7.4.6.2 Chromosomestudies of cultured lymphocytes Chromosomestudies of cultured lymphocytes for radiation dose estimation are not recommended for this population. Long-term follow-up evaluations have been conducted in several populations having previous radiation exposures, including survivors of the atomic bomb at Hiroshima and Nagasaki. The CF ie CSF oS 47