Abstract
This study aimed to evaluate the feasibility of quantifying iodine-131 (131I) accumulation in scintigraphy images and compare planar and single-photon emission computed tomography (SPECT) images to estimate 131I radioactivity in patients receiving radioactive iodine therapy for thyroid cancer. We evaluated 72 sets of planar and SPECT images acquired between February 2017 and December 2018. Simultaneously, we placed a reference 131I capsule next to the patient during image acquisition. We evaluated the correlation between the intensity of the capsule in the images and the capsule dose and estimated the radiation dose at the thyroid bed. The mean capsule dose was 2.14 MBq (range, 0.63–4.31 MBq). The correlation coefficients (p-value) between capsule dose and maximum and mean intensities in both planar and SPECT images were 0.93 (p < 0.01), 0.96 (p < 0.01), 0.60 (p < 0.01), and 0.47 (p < 0.01), respectively. The mean intensities of planar images show the highest correlation coefficients. Based on a regression equation, the average radiation dose in the thyroid bed was 5.9 MBq. In conclusion, planar images reflected the radiation dose more accurately than SPECT images. The regression equation allows to determine the dose in other regions, such as the thyroid bed or sites of distant metastasis.
Highlights
This study aimed to evaluate the feasibility of quantifying iodine-131 (131I) accumulation in scintigraphy images and compare planar and single-photon emission computed tomography (SPECT) images to estimate 131I radioactivity in patients receiving radioactive iodine therapy for thyroid cancer
The aims of radioactive iodine (RAI) therapy are divided into three categories[3]: ablation of the remnant thyroid tissue to simplify follow-up, adjuvant therapy for microscopic lesions to decrease the risk of recurrence or distant metastasis, and treatment for tangible residual or metastatic diseases
Based on the mean intensities in planar images, the regression equation can be expressed as y(dose) = 0.0845 ×
Summary
This study aimed to evaluate the feasibility of quantifying iodine-131 (131I) accumulation in scintigraphy images and compare planar and single-photon emission computed tomography (SPECT) images to estimate 131I radioactivity in patients receiving radioactive iodine therapy for thyroid cancer. Planar imaging or single-photon emission computed tomography (SPECT) has been used for qualitative evaluation of radioisotope distributions, with some reports focusing on the quantitative analysis of several low-energy radioisotopes, such as 99mTc, 123I, etc.[6,7,8]. These quantitative values are used to evaluate treatment response or predictive factors in the oncology field. Far, there has been no quantitative analysis or direct comparison between planar and SPECT images of 131I scintigraphy
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