Before radioiodine therapy for Graves’ disease, the estimated thyroid-absorbed dose is calculated based on various clinical parameters. However, the actual accumulation of iodine in the thyroid during radioiodine therapy is not determined. We validated the feasibility of post-therapeutic image-based thyroid dosimetry through quantitative single-photon emission computed tomography (SPECT) imaging and thyroid biokinetics and expanding the Medical Internal Radiation Dose Committee’s (MIRD) voxel dosimetry guidelines. Forty-three patients with Graves’ disease who underwent radioiodine therapy were chosen as subjects for this retrospective analysis. We acquired patients’ SPECT images 24 h after oral administration. SPECT images were quantified using system volume sensitivity to calculate time-integrated activity coefficients on a voxel basis. Absorbed dose was obtained by convolving MIRD guideline voxel S values with time-integrated activity coefficients. To determine accuracy, we compared the results obtained using the post-therapeutic image-based absorbed-dose method (D̅image,PVC) with absorbed doses calculated using the method described by the European Association of Nuclear Medicine (pre-therapeutic method; DEANM). Using image-based dosimetry as post-therapeutic dosimetry, we visualized the local accumulation and absorbed dose distribution of iodine in the thyroid. Furthermore, we determined a strong correlation (Pearson’s correlation coefficient = 0.89) between both dosimetries, using the regression equation: D̅image,PVC = 0.94 × DEANM + 1.35. Post-therapeutic image-based doses absorbed in the thyroid resembled those of pre-therapeutic EANM method-based absorbed doses. Additionally, the post-therapeutic image-based method had the advantage of visualizing thyroid iodine distribution, thus determining local dose distributions at the time of treatment. From these points, we propose that post-therapeutic image-based dosimetry could provide an alternative to standard pre-therapeutic dosimetry to evaluate dose response.

中文翻译：

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使用定量SPECT / CT，碘生物动力学和MIRD的Graves病体素S值，对基于治疗后图像的甲状腺剂量测定进行研究。

在对格雷夫斯病进行放射性碘治疗之前，应根据各种临床参数计算出估计的甲状腺吸收剂量。但是，尚不确定放射性碘治疗期间甲状腺中碘的实际积累。我们通过定量单光子发射计算机断层扫描（SPECT）成像和甲状腺生物动力学验证了治疗后基于图像的甲状腺剂量测定的可行性，并扩大了医学内部辐射剂量委员会（MIRD）体素剂量测定指南。接受放射碘治疗的43例Graves病患者被选为该回顾性研究的对象。口服后24小时，我们获得了患者的SPECT图像。使用系统体积灵敏度对SPECT图像进行量化，以基于体素计算时间积分的活动系数。通过将MIRD准则体素S值与时间积分活动系数进行卷积获得吸收剂量。为了确定准确性，我们将使用基于治疗后图像的吸收剂量方法（D̅image，PVC）获得的结果与使用欧洲核医学协会描述的方法（治疗前方法； DEANM）计算的吸收剂量进行了比较。使用基于图像的剂量学作为治疗后的剂量学，我们观察了碘在甲状腺中的局部积累和吸收剂量分布。此外，我们使用回归方程确定了两个剂量之间的强相关性（Pearson相关系数= 0.89）：D̅image，PVC = 0.94×DEANM + 1.35。甲状腺中基于治疗后图像的剂量与基于EANM方法的基于治疗前的剂量相似。此外，基于治疗后图像的方法还具有可视化甲状腺碘分布的优势，因此可以确定治疗时的局部剂量分布。从这些观点出发，我们建议基于治疗后图像的剂量测定法可以替代标准的治疗前剂量测定法来评估剂量反应。