Perbandingan Jarak Kolimator Terhadap Nilai Thyroid Uptake Pada Pemeriksaan Uji Tangkap Thyroid Menggunakan Kamera Gamma

  • Rifa Afifah Akademi Teknik Radiodiagnostik dan Radioterapi Bali, Indonesia, 4 Rumah Sakit Santosa Kopo Bandung
  • I Putu Pande Wahyu Gitawiarsa Akademi Teknik Radiodiagnostik dan Radioterapi Bali, Indonesia, 4 Rumah Sakit Santosa Kopo Bandung
  • Widia Putri Akademi Teknik Radiodiagnostik dan Radioterapi Bali, Indonesia, 4 Rumah Sakit Santosa Kopo Bandung

Keywords

Gamma Camera, LEHR Collimator, Collimator Distance, Thyroid Uptake Test, Thyroid Uptake, Tc-99m Pertechnetate

Abstract

The accuracy of thyroid uptake quantification using a gamma camera with Tc-99m pertechnetate is influenced by acquisition geometry parameters, particularly the distance between the collimator and the patient. This study aimed to evaluate the effect of collimator distances of 5 cm and 20 cm on thyroid uptake percentage values in patients with normal thyroid function. A quantitative analytical study with a within-subject paired design was conducted among 12 patients with normal thyroid function at Santosa Kopo Hospital, Bandung, during June–August 2026. Each patient was scanned at collimator distances of 5 cm and 20 cm using a planar anterior acquisition with an LEHR collimator (128 × 128 matrix, zoom 4, 10-minute acquisition). Differences in uptake values were analyzed using a paired t-test (α = 0.05), Bland–Altman bias analysis, and Spearman rank correlation. All subjects demonstrated higher thyroid uptake values at a 5 cm distance (* ) compared with 20 cm ( ). Increasing the collimator distance reduced the uptake value by a mean difference of * * percentage points, corresponding to a relative reduction of 36.46% ( *; * *; Cohen’s * ). Bland–Altman analysis confirmed a positive mean bias of 0.32% (95% LoA: 0.10–0.54%). Patient characteristics, including age, body weight, and radiopharmaceutical dose, were not significantly correlated with the reduction in uptake ( *). Variation in collimator distance significantly affects the percentage thyroid uptake values obtained during thyroid uptake examinations. Increasing the scanning distance reduces the measured uptake due to degradation of spatial resolution and count loss outside the ROI. Standardization of the collimator distance as close as possible to the patient’s neck (5 cm) is recommended for clinical protocols

References

Agency, I. A. E. (2018). Quality Assurance for Radioactivity Measurement in Nuclear Medicine. In Technical Reports Series No. 454. International Atomic Energy Agency. https://www-pub.iaea.org/MTCD/Publications/PDF/TRS454_web.pdf

Bushberg, J. T., Seibert, J. A., Leidholdt, E. M., & Boone, J. M. (2020). The Essential Physics of Medical Imaging (4th ed.). Wolters Kluwer Health.

Cherry, S. R., Sorenson, J. A., & Phelps, M. E. (2018). Physics in Nuclear Medicine. Elsevier.

Dahlan, M. S. (2018). Statistik untuk Kedokteran dan Kesehatan: Deskriptif, Bivariat, dan Multivariat (6th ed.). Epidemiologi Indonesia.

Giovanella, L., Avram, A. M., Iakovou, I., Kwak, J., Lawson, S. A., Lulaj, E., Luster, M., Piccardo, A., Schmidt, M., Tulchinsky, M., Verburg, F. A., & Wolin, E. (2019). EANM practice guideline/SNMMI procedure standard for RAIU and thyroid scintigraphy. European Journal of Nuclear Medicine and Molecular Imaging, 46(12), 2514–2525. https://doi.org/10.1007/s00259-019-04472-8

Karakatsanis, N. A., Casey, M. E., Lodge, M. A., Rahmim, A., & Zaidi, H. (2020). Quantification accuracy results of gamma camera using LEHR collimators and distance degradation. EJNMMI Physics, 7(1), 22. https://doi.org/10.1186/s40658-020-0275-6

Kim, H., Kim, S. J., Pak, K., & Kim, I. J. (2022). Quantitative thyroid uptake measurements using gamma camera: Comparative evaluation with thyroid uptake probe system. Journal of Nuclear Medicine Technology, 50(2), 145–151. https://doi.org/10.2967/jnmt.121.263152

Mourik, J. E. M. (2023). Gamma camera-specific reference standards for radioactive iodine uptake measurements. EJNMMI Physics, 10(1), 55. https://doi.org/10.1186/s40658-023-00575-2

Prekeges, J. (2022). Nuclear Medicine Instrumentation (3rd ed.). Jones & Bartlett Learning.

Serrano, J. (2023). Quantitative analysis of 99mTc-pertechnetate thyroid uptake with a large-field CZT gamma camera: Feasibility and comparison between SPECT/CT and planar acquisitions. EJNMMI Physics, 10(1), 45. https://doi.org/10.1186/s40658-023-00566-3

Soret, M., Bacharach, S. L., & Buvat, I. (2017). Partial-volume effect in PET and SPECT imaging. Annals of Nuclear Medicine, 31(8), 589–601. https://doi.org/10.1007/s12149-017-1186-0

Yousif, Z. T., Mohamed, I. A., Fadlalla, S. A., Alghamdi, S. S., Bushara, L., Mahmoud, M. Z., Yousef, M., Osman, H., & Osman, H. E. (2022). Evaluation of thyroid uptake of 99mTc pertechnetate using gamma camera and dose calibrator methods in the Sudanese population. International Journal of Biomedicine, 12(3), 380–384. https://doi.org/10.21103/Article12(3)_OA5

Ziessman, H. A., O’Malley, J. P., & Thrall, J. H. (2020). Nuclear medicine: The requisites (5th ed.). Elsevier.

2026-10-03