Additional Value of Post-Therapy 131i Spect/Ct in Patients With Differentiated Thyroid Cancer

Abstract

BACKGROUND Generally, it is seen that SPECT/CT images are more useful than the planar images. We compared post-therapy 131 I imaging findings on planar and SPECT/CT scans to assess the clinical utility of SPECT/CT in management of patients with differentiated thyroid cancer. MATERIALS AND METHODS Post-therapy imaging was performed at 4-7 (when 5mR/hrs. exposure rate were observed by the survey meter) days after 131 I administration and all patients underwent whole-body scintigraphy and SPECT/CT scanning on the same day. A generalised McNemar 1 was used to determine to establish the agreement between planar whole-body imaging and SPECT/CT for the assignment of benign, equivocal and malignant findings. RESULTS In 44 patients, 32 of the 44 patients underwent postsurgical 131 I ablation of residual thyroid tissue and 12 of 44 patients, 2 patients were treated twice. Hence, a total of 46 scans were analysed. SPECT/CT helped to localise focal iodine uptake and characterise it as either normal or abnormal thereby reducing the need for additional imaging studies. In post-thyroidectomy patients, SPECT/CT findings affected the ATA risk classification with implications for management by changing the interval for clinical followup and the need for additional imaging and laboratory tests. Our study found an 11% change in nodal status in the postsurgical group. Change in patient management was observed in 18%. CONCLUSION SPECT/CT enabled more accurate characterisation of focal iodine accumulation in patients.