title: Size measurement of the thyroid gland on a magnified pinhole thyroid scan using an ultrasonic device measuring distance from the pinhole to the thyroid gland.
abstract: OBJECTIVE
  Pinhole has been used for magnification of gamma camera images and is valuable for imaging of small organs, such as thyroid; however, size of the organ cannot be measured on the image due to variable degree of magnification by distance between the pinhole and the organ. The aim of this study was to develop a true size measuring system (TSM system) on magnified pinhole thyroid scan using an ultrasonic sensor.
  
  
  METHODS
  An ultrasonic device capable of measuring the distance from the pinhole to the skin overlying the thyroid gland was manufactured using a ~40 kHz piezoelectric-transducer-based sensor, and its accuracy was tested. An interface program was developed and fused with the ultrasonic device for development of the TSM system. Accuracy of the TSM system for measuring size was tested with phantom images and 35 thyroid scans.
  
  
  RESULTS
  The ultrasonic device accurately measured the distance from the pinhole to the skin over the thyroid gland and the measured values were highly reproducible (6 cm; 6.02 ± 0.04 cm, 8 cm; 8.00 ± 0.05 cm, 10 cm; 10.00 ± 0.05 cm). Distance on the phantom image corrected by the TSM system was almost the same as the true distance. Size of the thyroid on the pinhole image was larger (+67.3 to 103.1 %) than the true thyroid size on the parallel-hole image and the magnification decreased by increase of the distance between the pinhole and the skin over the thyroid gland. However, size of the thyroid obtained using the TSM system was almost equal (-2.1 to +3.6 %) to the true thyroid size on the parallel-hole image.
  
  
  CONCLUSIONS
  We developed the TSM system for magnified pinhole images using a distance measuring ultrasonic sensor. Size of the thyroid on the magnified pinhole image obtained using the system was almost the same as the true thyroid size. The TSM system can be applied to obtain accurate size of the thyroid gland or lesions in the thyroid gland on pinhole thyroid scan.
authors.affiliation: Department of Nuclear Medicine, Kyungpook National University School of Medicine, 50 Samduk-dong 2-ga, Jung Gu, Daegu, 700-721, Republic of Korea, abc2000@knu.ac.kr.
authors.forename: Byeong-Cheol
authors.initials: BC
authors.lastname: Ahn
authors.forename: Gilhwan
authors.initials: G
authors.lastname: Ahn
authors.forename: Do-Hoon
authors.initials: DH
authors.lastname: Kim
authors.forename: Kyoung Dong
authors.initials: KD
authors.lastname: Kim
authors.forename: Shin Young
authors.initials: SY
authors.lastname: Jeong
authors.forename: Sang-Woo
authors.initials: SW
authors.lastname: Lee
authors.forename: Jaetae
authors.initials: J
authors.lastname: Lee
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted; D009929:Organ Size; D019047:Phantoms, Imaging; D013961:Thyroid Gland / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D014463:Ultrasonography / Q000295:instrumentation*