Detection and Evaluation of Differentiated Thyroid Carcinoma by using Tc99m and Iodinei 131 Scanning

The aim of this study was to demonstrate the clinical usefulness of simultaneous co-registration of 99m Tc MDP bone scanning as an anatomical landmark with 1311 scanning in the evaluation of metastatic DTC. A total of Twenty-five patients [16 females and 9 males, mean age + SD = 52 + 13 years]with metastatic DTC, [17 papillary, 8 follicular], were included. Who had undergone surgical thyroidectomy for DTC were evaluated prospectively. All patients had undergone technetium and iodine scintigraphy [IS]. Occasionally, additional simultaneous co-registration of localized detailed images was also performed. The two planar images were fused with optional fusion of SPECT images. TS had uptake values total number of metastases was 48 lesions, was in the lungs, bones or both, with a frequency of 10 [21%], 8 [16%] and 22 [46%], respectively. Nodal 8 cases [16%]. Metastatic lesions were [56%] from papillary DTC and [44%] from follicular DTC Regional anatomical distribution of metastatic lesions showed that (42%) thoracic region, and head region [4%]. Variable anatomical distribution was seen in the neck. I-131 WBS There were 56 areas of focal. All metastatic lesions showed positive focal uptake However, an additional eight false positive focal areas were seen reducing the specificity to 86%. Findings in 131I-WBS were divided into two groups. Group A: Positive 1311 metastatic lesions that are well localized anatomically, which included 32 lesions [67%]. Group B: are the 1311 metastatic lesions that are anatomically indeterminate, which included 16/48 lesions [33%] and included 10 lesions in the thorax and 6 in the pelvis-abdominal region. Accordingly, these were considered false positive findings by 1311 WBS. The remaining 48 lesions were considered true positives, and, therefore, the specificity of the fusion scan was 100%. In group A, fusion scintigraphy confirmed the 1311 findings with concordant agreement between both 1311 and fusion scan of 100%. In group B, out of 16 anatomically indeterminate lesions, planner fusion scans localized 14 lesions accurately [87%]. The other two lesions were clearly identified by SPECT of fused 1311 and MDP scintigraphy and were in the thorax and pelvi-abdominal regions. Table 5 shows the effect of fused planner 1311/99mTc-MDP scans in the identification of indeterminate lesions by standard 1311 WBS. The results of this study demonstrate that the concordance of IS and TS depends on the IU level after suspension of replacement therapy. Measurements of IU and TS are of considerable value in evaluating patient response to therapy and will substantially reduce the need for repetitive radioiodine scans and unnecessary treatment doses in patients with undetectable Tg values. Fusion image were considered to improve image interpretation in comparison with standard 1311 scanning when they provided better localization of lesion.