title: Ultrasonographic localization of the thyroid gland for its optimal shielding prior to lateral cephalometric radiography: a pilot study.
abstract: OBJECTIVE
  Lateral cephalometric radiography is a common radiographic examination technique in children. The exclusion of the thyroid gland from the primary X-ray beam is important especially with children. However, patient treatment might require displaying the four most cranial cervical vertebrae (C1-C4) for the assessment of cervical vertebral maturation. Our aim was to present a safe way to display C1-C4 and exclude the thyroid gland from the X-ray beam during lateral cephalometric radiography.
  
  
  METHODS
  The thyroid glands of 25, 7- to 12-year-old patients were localized by ultrasound examination and shielded prior to lateral cephalometric radiography. A roentgen-positive mark was taped on the patient's skin at the level of most cranial level of the thyroid gland in the midsagittal plane. After exposure, each lateral cephalometric radiograph (LCR) was analyzed for the visibility of the cervical vertebrae. The distance between the ear post and the highest edge of the thyroid shield (TS) at the lateral part of the neck was measured and compared with the distance between the centre of the radiological external auditory meatus, and a roentgen-positive mark was made on the LCR.
  
  
  RESULTS
  68% of the LCRs displayed C1-C4, and the rest of them displayed C1-C3. In all of the patients, the highest edge of the TS in the lateral parts of the neck was located in a higher position than the actual most cranial level of the thyroid gland.
  
  
  CONCLUSIONS
  Despite localizing the thyroid gland prior to lateral cephalometric radiography, simultaneous visualization of C1-C4 and exclusion of the thyroid gland from the primary X-ray beam during lateral cephalometric radiography might not be completely possible in children because of the design and poor fitness of the TS.
authors.affiliation: 1 Department of Radiology, University of Helsinki and HUS Radiology (Medical Imaging Center), Helsinki, Finland.|2 Oral Radiology, Department of Oral and Maxillofacial Diseases, University of Helsinki, Helsinki, Finland.
authors.forename: Elmira
authors.initials: E
authors.lastname: Pakbaznejad Esmaeili
authors.affiliation: 3 Cleft Palate and Craniofacial Centre, Helsinki University Hospital, Helsinki, Finland.
authors.forename: Kirsti
authors.initials: K
authors.lastname: Hurmerinta
authors.affiliation: 4 Orthodontics, Department of Oral and Maxillofacial Diseases, University of Helsinki, Helsinki, Finland.|5 Orthodontics, Department of Oral and Maxillofacial Diseases, Helsinki University Hospital, Helsinki, Finland.
authors.forename: David
authors.initials: D
authors.lastname: Rice
authors.affiliation: 1 Department of Radiology, University of Helsinki and HUS Radiology (Medical Imaging Center), Helsinki, Finland.
authors.forename: Anni
authors.initials: A
authors.lastname: Suomalainen
mesh_terms: D002508:Cephalometry / Q000379:methods*; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000254:growth & development; D002648:Child; D004424:Ear Canal / Q000000981:diagnostic imaging; D005260:Female; D057918:Fiducial Markers; D006801:Humans; D008297:Male; D010865:Pilot Projects; D000069079:Radiation Exposure / Q000517:prevention & control*; D011835:Radiation Protection / Q000295:instrumentation / Q000379:methods*; D011859:Radiography; D013961:Thyroid Gland / Q000000981:diagnostic imaging*; D014463:Ultrasonography
keywords: child; medical imaging; radiation protection; thyroid gland; ultrasonography