Hypoechoic thyroid nodules on ultrasound 4 years after prenatal exposure to radioiodine: resolution with thyroxine therapy

<p>We describe an infant inadvertently exposed to radioiodine at 17 weeks gestation. His mother had received 400 MBq of <sup>131</sup>I for hyperthyroidism (total T4 178 nmol/L, thyroid stimulating hormone (TSH) <0.1 mU/L, 4-h <sup>131</sup>I uptake 16%). Following cordocentesis at 27 weeks (free T4 12.7 pmol/L, TSH 35.4 mU/L) intra-amniotic thyroxine was withheld and a male infant was born at 39 weeks gestation, birthweight 3520 g. Cord TSH was low (0.1 mU/L), total T4 151 nmol/L on day 4, the mother having received no medication during pregnancy. Postnatal follow-up showed mild TSH elevation (11.0–19.4 mU/L) but normal free T4 (9–12.7 pmol/L) during the first 2 years of life following which the child was discharged still untreated. On recall at 4.3 years, TSH elevation persisted (15.4 mU/L) and ultrasound showed several hypoechoic thyroid nodules within the left lobe that disappeared after thyroxine treatment.</p> <p>Conclusion: In the event of inadvertent exposure to radioiodine in utero, the infant should receive thyroxine therapy from birth in order to protect the thyroid gland from TSH over-stimulation, however mild.</p&gt

Noninvasive Multimodality Imaging of the Tumor Microenvironment: Registered Dynamic MRI and PET Studies of a Preclinical Tumor Model of Tumor Hypoxia

In vivo knowledge of the spatial distribution of viable, necrotic, and hypoxic areas can provide prognostic information about the risk of developing metastases and regional radiation sensitivity and may be used potentially for localized dose escalation in radiation treatment. In this study, multimodality in vivo magnetic resonance imaging (MRI) and positron emission tomography (PET) imaging using stereotactic fiduciary markers in the Dunning R3327-AT prostate tumor were performed, focusing on the relationship between dynamic contrast-enhanced (DCE) MRI using Magnevist (Gd-DTPA) and dynamic (18)F-fluoromisonidazole ((18)F-Fmiso) PET. The noninvasive measurements were verified using tumor tissue sections stained for hematoxylin/eosin and pimonidazole. To further validate the relationship between (18)F-Fmiso and pimonidazole uptake, (18)F digital autoradiography was performed on a selected tumor and compared with the corresponding pimonidazole-stained slices. The comparison of Akep values (kep = rate constant of movement of Gd-DTPA between the interstitial space and plasma and A = amplitude in the two-compartment model (Hoffmann U, Brix G, Knopp MV, Hess T and Lorenz WJ (1995). Magn Reson Med 33, 506-514) derived from DCE-MRI studies and from early (18)F-Fmiso uptake PET studies showed that tumor vasculature is a major determinant of early (18)F-Fmiso uptake. A negative correlation between the spatial map of Akep and the slope map of late (last 1 hour of the dynamic PET scan) (18)F-Fmiso uptake was observed. The relationships between DCE-MRI and hematoxylin/eosin slices and between (18)F-Fmiso PET and pimonidazole slices confirm the validity of MRI/PET measurements to image the tumor microenvironment and to identify regions of tumor necrosis, hypoxia, and well-perfused tissue

Fluorine-18-Labeled Fluoromisonidazole Positron Emission and Computed Tomography-Guided Intensity-Modulated Radiotherapy for Head and Neck Cancer: A Feasibility Study

Hypoxia renders tumor cells radioresistant, limiting locoregional control from radiotherapy (RT). Intensity-modulated RT (IMRT) allows for targeting of the gross tumor volume (GTV) and can potentially deliver a greater dose to hypoxic subvolumes (GTV(h)) while sparing normal tissues. A Monte Carlo model has shown that boosting the GTV(h) increases the tumor control probability. This study examined the feasibility of fluorine-18-labeled fluoromisonidazole positron emission tomography/computed tomography ((18)F-FMISO PET/CT)-guided IMRT with the goal of maximally escalating the dose to radioresistant hypoxic zones in a cohort of head and neck cancer (HNC) patients. METHODS AND MATERIALS: (18)F-FMISO was administered intravenously for PET imaging. The CT simulation, fluorodeoxyglucose PET/CT, and (18)F-FMISO PET/CT scans were co-registered using the same immobilization methods. The tumor boundaries were defined by clinical examination and available imaging studies, including fluorodeoxyglucose PET/CT. Regions of elevated (18)F-FMISO uptake within the fluorodeoxyglucose PET/CT GTV were targeted for an IMRT boost. Additional targets and/or normal structures were contoured or transferred to treatment planning to generate (18)F-FMISO PET/CT-guided IMRT plans. RESULTS: The heterogeneous distribution of (18)F-FMISO within the GTV demonstrated variable levels of hypoxia within the tumor. Plans directed at performing (18)F-FMISO PET/CT-guided IMRT for 10 HNC patients achieved 84 Gy to the GTV(h) and 70 Gy to the GTV, without exceeding the normal tissue tolerance. We also attempted to deliver 105 Gy to the GTV(h) for 2 patients and were successful in 1, with normal tissue sparing. CONCLUSION: It was feasible to dose escalate the GTV(h) to 84 Gy in all 10 patients and in 1 patient to 105 Gy without exceeding the normal tissue tolerance. This information has provided important data for subsequent hypoxia-guided IMRT trials with the goal of further improving locoregional control in HNC patients