Use of radioactive iodine is an essential adjuvant treatment strategy after thyroidectomy in patients with differentiated thyroid carcinoma. Although generally safe, radioiodine therapy has some potential side effects, classified as early and late complications, which we have reviewed in this paper. Early complications include gastrointestinal symptoms, radiation thyroiditis, sialadenitis/xerostomia, bone marrow suppression, gonadal damage, dry eye, and nasolacrimal duct obstruction. The late complications include secondary cancers, pulmonary fibrosis, permanent bone marrow suppression, and genetic effects. As I is an efficacious form of treatment that can significantly decrease the rate of mortality, recurrence, and metastasis, and as the side effects are often minor and well tolerated, radioiodine therapy remains the principal mode of treatment for patients with differentiated thyroid carcinoma.

Radioiodine ablation of thyroid tissue remains the cornerstone of treatment for patients with differentiated thyroid carcinoma after thyroidectomy. Selecting an optimal dose of radioiodine for successful ablation is a continuous challenge in these patients. We compared the treatment response of 341 patients with thyroidectomy randomly allocated to the high-dose group, 3700 MBq (170 patients), versus the low-dose group, 1110 MBq (171 patients), for radioiodine ablation therapy in a double-blind randomized clinical trial. The response to treatment was defined as successful or unsuccessful according to post-therapy ultrasonography of the neck, serum thyroglobulin (Tg), anti-Tg, and functioning residual tissue after 6-month and 12-month intervals. The major criteria of successful ablation were Tg<2 ng/ml, anti-Tg<100 IU/ml, and absent remnant in the off-levothyroxine state. Additional radioiodine doses were administered in cases showing no significant response to the first therapy. Finally, the initial outcome, the total hospitalization time, and the cumulative I-131 doses during the 12-month course of the study were compared between the subgroups. The rate of initial successful ablation was 51.6% in all patients, 39.2% in the low-dose group, and 64.1% in the high-dose group. The corresponding success rates at the end of the 12-month follow-up without additional treatment were 55.1, 41.5, and 68.8%, respectively. The relative risk (RR) of unsuccessful ablation for the low-dose versus the high-dose group was 1.695 [95% confidence interval (CI), 1.34-2.14]. In the low-dose group, more patients needed a second dose of I-131, resulting in a higher cumulative activity (median, 4810 vs. 3700 MBq, P<0.0001) and more inpatient time (median 4 vs. 3 days) in comparison with the high-dose group. The covariate factors predicting the treatment response, in order of significance, were radioiodine dose, baseline Tg, baseline thyroid stimulating hormone (TSH) level, efficiency of TSH suppressive therapy, and sex. The higher dose of I-131 (3700 MBq) resulted in successful ablation more often than the low dose (1110 MBq).

Background: ^99mTc–prostate-specific membrane antigen (PSMA) SPECT/CT is less expensive and readily available modality compared with ⁶⁸Ga-PSMA PET/CT for imaging prostate cancer (PC). The aim of this study is to compare the value of these 2 modalities in patients confirmed or suspicious to have metastatic prostate cancer. Patients and Methods: Twenty-two patients with the mean age of 66.6 ± 10.1 years were studied using ^99mTc-PSMA SPECT/CT and ⁶⁸Ga-PSMA PET/CT, with less than 7 days interval between the 2 imaging procedures. Whole-body PET/CT was done 60 minutes after IV injection of 185 MBq (5 mCi) of ⁶⁸Ga-PSMA. ^99mTc-PSMA SPECT/CT was performed 3 hours after IV injection of 555 to 740 MBq (15–20 mCi) of ^99mTc-PSMA. The images of each modality were interpreted independently, and the results were compared according to patient-based as well as region-based analyses. Results: In patient-based evaluation, both ^99mTc-PSMA SPECT/CT and ⁶⁸Ga-PSMA PET/CT scans were positive in 95.45% (21/22). In region-based evaluation, ⁶⁸Ga-PSMA PET/CT detected 53 regions (median of 2 regions per patient; range, 0–5), whereas 43 (median of 2 regions per patient; range, 0–5) were detected by ^99mTc-PSMA SPECT/CT. Most of these differences could be explained by lower detection rate of ^99mTc-PSMA SPECT/CT in prostate bed (n = 6). PET/CT detected more involved regions than SPECT/CT (P = 0.007), whereas similar frequency of extraprostatic lesions were diagnosed in both modalities (P = 0.102). Significant correlation was also demonstrated between serum prostate-specific antigen level and imaging parameters of disease extension detected by 2 modalities. Conclusions: ^99mTc-PSMA SPECT/CT could be a potential substitute for ⁶⁸Ga-PSMA PET/CT in high-risk patients, except when evaluation of prostate bed is of major concern.

Introduction: Nowadays, nanoparticles (NPs) have attracted much attention in biomedical imaging due to their unique magnetic and optical characteristics. Superparamagnetic iron oxide nanoparticles (SPIONs) are the prosperous group of NPs with the capability to apply as magnetic resonance imaging (MRI) contrast agents. Radiolabeling of targeted SPIONs with positron emitters can develop dual positron emission tomography (PET)/MRI agents to achieve better diagnosis of clinical conditions. Methods: In this work, N,N,N-trimethyl chitosan (TMC)-coated magnetic nanoparticles (MNPs) conjugated to S-2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (DOTA) as a radioisotope chelator and bombesin (BN) as a targeting peptide (DOTA–BN–TMC–MNPs) were prepared and validated using fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and powder X-ray diffraction (PXRD) tests. Final NPs were radiolabeled with gallium-68 (⁶⁸Ga) and evaluated in vitro and in vivo as a potential PET/MRI probe for breast cancer (BC) detection. Results: The DOTA–BN–TMC–MNPs with a particle size between 20 and 30 nm were efficiently labeled with ⁶⁸Ga (radiochemical purity higher than 98% using thin layer chromatography (TLC)). The radiolabeled NPs showed insignificant toxicity (>74% cell viability) and high affinity (IC₅₀=8.79 µg/mL) for the gastrin-releasing peptide (GRP)-avid BC T-47D cells using competitive binding assay against ^99mTc–hydrazinonicotinamide (HYNIC)–gamma-aminobutyric acid (GABA)–BN (7–14). PET and MRI showed visible uptake of NPs by T-47D tumors in xenograft mouse models. Conclusion: ⁶⁸Ga–DOTA–BN–TMC–MNPs could be a potential diagnostic probe to detect BC using PET/MRI technique.