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. 2015 Winter;3(1):26-34.

Extremity Radioactive Iodine Uptake on Post-therapeutic Whole Body Scan in Patients with Differentiated Thyroid Cancer

Hiroshi Wakabayashi  1 , Junichi Taki  1 , Anri Inaki  1 , Ayane Toratani  1 , Daiki Kayano  1 , Seigo Kinuya  1
Affiliations

Extremity Radioactive Iodine Uptake on Post-therapeutic Whole Body Scan in Patients with Differentiated Thyroid Cancer

Hiroshi Wakabayashi et al. Asia Ocean J Nucl Med Biol. 2015 Winter.

Abstract

Objectives: We investigated a frequency of lower extremity uptake on the radioactive iodine (RAI) whole body scan (WBS) after RAI treatment in patients with differentiated thyroid cancer, in order to retrospectively examine whether or not the frequency was pathological.

Methods: This retrospective study included 170 patients with thyroid cancer, undergoing RAI treatment. Overall, 99(58%) and 71(42%) patients received single and multiple RAI treatments, respectively. Post-therapeutic WBS was acquired after 3 days of RAI administration. For patients with multiple RAI treatments, the WBS of their last RAI treatment was evaluated. Lower extremity uptake on post-therapeutic WBS was classified into 3 categories: bilateral femoral uptake (type A), bilateral femoral and tibia uptake (type B), and uptake in bilateral upper and lower extremities (type C). Then, the patients with RAI uptake in the lower extremities on WBS were analyzed with clinical parameters.

Results: Overall, 99 patients (58%) had the extremity uptake on their posttherapeutic RAI WBS. As the results indicated, 42, 53, and 4 patients had type A, type B, and type C uptakes, respectively. Lower extremity uptake was significantly associated with younger age, not only in subjects with multiple RAI treatments but also in all the patients (P<0.05). Accumulation in patients with multiple RAI treatments was more frequent than patients with single RAI treatment (P<0.05). Lower extremity uptake was not associated with counts of the white blood cell count, hemoglobin level, platelet count, estimated glomerular filtration rate, effective half-time of RAI, serum TSH level, and anti-Tg concentration.

Conclusion: About half of the patients had lower extremity uptake on the posttherapeutic RAI WBS, especially younger patients and those with multiple courses of RAI treatment. Bilateral lower extremity's RAI uptake on the posttherapeutic WBS should be considered as physiological RAI distribution in bone marrow.

Keywords: Lower Extremity; Physiological Uptake; Radioactive Iodine; Thyroid Cancer; Whole Body Scan.

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Figures

Figure 1
Figure 1
A 64-year-old female patient with type A uptake in the initial RAI therapy (3.7 GBq) (a). A 41-year-old female patient with type B uptake in the initial RAI therapy (3.7 GBq) (b). A 50-year-old male patient with type C uptake in the second RAI therapy (5.5 GBq) (c). Manual ROIs are delineated on images. A rectangular ROI was set manually on bilateral femur and tibia in both anterior and posterior views. As the background, a same-sized ROI was set on both sides (d)
Figure 2
Figure 2
A -41year-old female patient with type B uptake in the initial RAI therapy (3.7 GBq) (a). Axial CT (b) and fused SPECT/CT (c) images show an uptake, localized in the bilateral bone marrow of the femur.
See this image and copyright information in PMC

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