Use of a dosimetry-based RAI protocol for treatment of benign hyperthyroidism optimises response while minimising exposure to ionising radiation.

BACKGROUND: The optimal treatment strategy for radioiodine (RAI) treatment protocols for benign hyperthyroidism remains elusive. Although individualised activities are recommended in European Law, many centres continue to provide fixed activities. Our institution implemented a dosimetry protocol in 2016 following years of fixed dosing which facilitates the calculation of individualised activities based on thyroid volume and radioiodine uptake. METHODS: This was a retrospective study comparing success rates using a dosimetry protocol targeting an absorbed dose of 150 Gy for Graves' disease (GD) and 125 Gy for Toxic Multinodular Goiter (TMNG) with fixed dosing (200MBq for GD and 400MBq for TMNG) among 204 patients with hyperthyroidism. Success was defined as a non-hyperthyroid state at 1 year for both disease states. Results were analysed for disease specific or patient specific modulators of response. RESULTS: This study included 204 patients; 74% (n = 151) received fixed activities and 26% (n = 53) of activities administered were calculated using dosimetry. A dosimetry-based protocol was successful in 80.5% of patients with GD and 100% of patients with TMNG. Differences in success rates and median activity administered between the fixed (204Mbq) and dosimetry (246MBq) cohort were not statistically significant (p = .64) however 44% of patients with GD and 70% of patients with TMNG received lower activities following treatment with dosimetry as opposed to fixed activities. Use of dosimetry resulted in successful treatment and reduced RAI exposure for 36% of patients with GD, 70% of patients with TMNG, and 44% of patients overall. CONCLUSION: This retrospective clinical study demonstrated that treatment with a dosimetry-based protocol for TMNG and GD achieved comparable success rates to fixed protocols while reducing RAI exposure for over a third of patients with GD and most patients with TMNG. This study also highlighted that RAI can successfully treat hyperthyroidism for some patients with activities lower than commonplace in clinical practise. No patient or disease specific modulators of treatment response were established in this study; however, the data supports a future prospective trial which further scrutinises the individual patient factors governing treatment response to RAI.

Gender differences in estimating I-131 thyroid uptake from Tc-99m thyroid uptake for benign thyroid disease.

OBJECTIVE: For radioactive Iodine-131 (131I) treatments of thyroid diseases, increased efficacy has been reported for personalized dosimetry treatments. The measurement of Iodine-131 thyroid uptake (131IU) is required in these cases. This study aims to investigate whether 99mTc thyroid uptake (99mTcU) may be used in place of 131IU for implementing personalised treatments. METHODS: A retrospective study of 152 benign thyroid disease 131I treatments was carried out during 2012-2020; 117 treatments were for female patients while 35 were for male patients diagnosed with either Graves' disease, multinodular goitre or toxic nodules. RESULTS: A statistically significant correlation was found between 131IU and 99mTcU data, with the data more correlated for male than female patients (r = 0.71 vs 0.38, p-value < 0.001). Patient age and time difference between the two respective uptake measurements significantly influenced the uptake correlation in females but not for the male cohort, although there was no significant difference between the parameters across gender. Thyroid diagnosis and hormone levels showed a significant correlation with uptakes in both genders. Estimating 131IU based on 99mTcU was shown to be predictive for male but not in female patients (R2 = 91% vs 16%). CONCLUSION: Estimating 131IU based on 99mTcU is not recommended for females at our centre. Males reported good correlation, but a larger sample would be needed for validation. ADVANCES IN KNOWLEDGE: The initial findings showed a significant gender difference in benign thyroid uptake parameters at our centre, highlighting the potential need for gender consideration when planning 131IU patient management and when reporting studies results.

RETROSPECTIVE ANALYSIS OF PATIENT RADIATION DOSES IN DIGITAL CORONARY ANGIOGRAPHY AND INTERVENTIONS.

This study sought to assess patient and operator eye lens doses in diagnostic coronary angiography (DCA) and percutaneous coronary interventions (PCI) in a University hospital in Oman. Kerma area product (PkA), cumulative air kerma (CAK) and fluoroscopic time (FT) were retrospectively recorded from the DICOM header for 264 patients. The median (interquartile range) of FT, PKA and CAK were: 5.3 min (2.6-10.5), 60.9 Gy cm2 (41.3-91.4) and 0.86 Gy (0.61-1.29), respectively, for DCA procedures, and they were 20.2 min (13.3-30.1), 174.0 Gy cm2 (113.7-253.3) and 2.6 Gy (1.8-3.9), respectively, for PCI procedures. The results revealed wide variability in patient doses among individual patients. Monitoring and recording patient dose data can be valuable for quality assurance and patient safety purposes. Feedback to the operator may help optimize radiation doses to patients and prompt further action, as needed.