title: Usefulness of SPECT/CT in Parathyroid Lesion Detection in Patients with Thyroid Parenchymal99mTc-Sestamibi Retention.
abstract: OBJECTIVE
  Parathyroid adenoma detection with dual-phase99mTc-sestamibi (MIBI) scintigraphy depends on differential MIBI washout from thyroid. However, autoimmune thyroid disease (AITD) may cause MIBI to be retained in the thyroid gland and reduce parathyroid detection. We evaluated the impact of AITD on MIBI thyroid retention and additional benefit of SPECT/CT in these patients.
  
  
  METHODS
  Dual phase planar MIBI and SPECT/CT was performed on 82 patients. SPECT/CT was performed immediately after delayed planar scan. Thyroid density (Hounsfield unit, CT-HU) and size were measured on CT component of SPECT/CT. MIBI uptake in early scans and retention in delayed scans were visually graded and correlated with clinical factors and CT findings. Finally, planar and SPECT/CT findings were compared for parathyroid lesion visualization according to thyroid MIBI retention.
  
  
  RESULTS
  In early scan, multivariate analysis showed only thyroid size predicted early uptake. In delayed scan, multivariate analysis showed higher visual grade in early scan, lower CT-HU or AITD were significant predictors for delayed thyroid parenchymal retention. Overall, ten more parathyroid lesions were visualized on SPECT/CT compared to planar scans (57 vs. 47,p= 0.002). SPECT/CT was especially more useful in patients with thyroidal MIBI retention, as eight out of the ten additional lesions detected were found in patients with thyroid MIBI retention.
  
  
  CONCLUSIONS
  AITD is an important factor for MIBI thyroid parenchymal retention on delayed scans, and may impede parathyroid lesion detection. Patients with MIBI retention in the thyroid parenchyma on delayed scans are likely to benefit from an additional SPECT/CT.
authors.affiliation: Department of Nuclear Medicine, Severance Hospital, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722 South Korea.
authors.forename: Sang Hyun
authors.initials: SH
authors.lastname: Hwang
authors.affiliation: Department of Internal Medicine, Severance Hospital, Endocrine Research Institute, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722 South Korea.
authors.forename: Yumie
authors.initials: Y
authors.lastname: Rhee
authors.affiliation: Department of Nuclear Medicine, Severance Hospital, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722 South Korea.
authors.forename: Mijin
authors.initials: M
authors.lastname: Yun
authors.affiliation: Department of Radiology, Severance Hospital, Research Institute of Radiological Science, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722 South Korea.
authors.forename: Jung Hyun
authors.initials: JH
authors.lastname: Yoon
authors.affiliation: Department of Nuclear Medicine, International St. Mary's Hospital, Catholic Kwandong University College of Medicine, 25, Simgok-ro 100 Beon-gil, Seo-gu, Incheon, 22711 South Korea.
authors.forename: Jeong Won
authors.initials: JW
authors.lastname: Lee
authors.affiliation: Department of Nuclear Medicine, Severance Hospital, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722 South Korea.
authors.forename: Arthur
authors.initials: A
authors.lastname: Cho
keywords: 99mTc-sestamibi scintigraphy; Autoimmune thyroid disease; Parathyroid; SPECT/CT