Ectopic thyroid is an uncommon condition defined as the presence of thyroid tissue at a site other than the pretracheal area. When the process of embryologic migration is disturbed, aberrant thyroid tissue may appear. In most cases, ectopic thyroid is located along the embryologic descent path of migration as either a lingual thyroid or a thyroglossal duct cyst. In rare cases, aberrant migration can result in lateral ectopic thyroid tissue. Approximately 1 to 3% of all ectopic thyroids are located in the lateral neck. Ectopic tissue frequently represents the only presence of thyroid tissue; a second site of orthotopic or ectopic thyroid tissue is found in other cases. The presentation of ectopic thyroid as a lateral mass should be differentiated from metastatic thyroid cancer; other differential diagnoses include a submandibular tumor, branchial cleft cyst, carotid body tumor, and lymphadenopathy of various etiologies. In addition to the history and physical examination, the workup for a patient with a submandibular mass suspicious for ectopic thyroid should include (1) technetium-99m or iodine-131 scintigraphy, (2) ultrasonography and either computed tomography or magnetic resonance imaging, (3) fine-needle aspiration biopsy, and (4) thyroid function testing. No treatment is required for asymptomatic patients with normal thyroid function and cytology, but hypothyroid patients should be placed on thyroid hormone replacement therapy. Most cases are diagnosed postoperatively. Surgical treatment of ectopic thyroid should be considered when a malignancy is suspected or diagnosed, when the patient is symptomatic, or when thyroid suppression therapy fails.

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Objective: Interest in low-dose radiotherapy (LD-RT) for the symptomatic treatment of nonmalignant conditions, including inflammatory and degenerative disorders of the joints and para-articular soft tissues, has increased substantially in recent years. In the present document, we provide a CT-based contouring atlas to help identify and delineate the most common osteoarticular regions susceptible to LD-RT. Methods: The clinical efficacy of LD-RT is supported by a large body of evidence. However, there is no consensus on the parameters for contouring the planning target volume (PTV). Moreover, 3D simulation and planning should be the standard of care even for nonmalignant disorders. For this reason, the present guidelines were prepared to help guide PTV contouring based on CT images, with the same quality criteria for patient immobilization, treatment simulation, planning and delivery as those routinely applied for cancer radiotherapy. Results: PTV for radiotherapy requires precise identification of the target areas based on CT and other imaging techniques. Using a series of cases treated at our institution, we have defined the PTVs for each location on the simulation CT to establish the relationship between the image and the anatomical structures to be treated. We also specify the immobilization systems used to ensure treatment accuracy and reproducibility. Conclusions: This comprehensive atlas based on CT images may be of value to radiation oncologists who wish to use LD-RT for the symptomatic treatment of degenerative or inflammatory osteoarticular diseases. Advances in knowledge: The recommendations and contouring atlas described in this article provide an eminently practical tool for LD-RT in non-malignant conditions, based on the same quality criteria recommended for all modern radiotherapy treatments in Spain.

Aim: To assess the performance of the monitor unit (MU) Objective tool in Eclipse treatment planning system (TPS) utilizing volumetric modulated arc therapy (VMAT) for rectal cancer. Background: Eclipse VMAT planning module includes a tool to control the number of MUs delivered: the MU Objective tool. This tool could be utilized to reduce the total number of MUs in rectal cancer treatments. Materials and methods: 20 rectal cancer patients were retrospectively studied using VMAT and the MU Objective tool. The baseline plan for each patient was selected as the one with no usage of the MU Objective tool. The number of MUs of this plan was set to be the reference number of MUs (MU ref). Five plans were re-optimized for each patient only varying the Max MU parameter. The selected values were 30%, 60%, 90%, 120% and 150% of MU ref for each patient. Differences with respect to the baseline plan were evaluated regarding MU number and parameters for PTVs coverage evaluation, PTVs homogeneity and OARs doses assessment. A two-tailed, paired-samples t-test was used to quantify these differences. Results: Average relative differences in MU number obtained was 10% for Max MU values of 30% and 60% of MU ref , respectively (p < 0.03). PTVs coverage and homogeneity were not compromised and discrepancies obtained with respect to baseline plans were not significant. Furthermore, maximum OARs doses deviations were also not significant. Conclusions: A 10% reduction in the MU number could be obtained without an alteration of PTV coverage and OARs doses for rectal cancer.

Purpose: In the present study, the performance of four VMAT beam arrangements used for hippocampal-sparing whole-brain radiation therapy is addressed. Material and Methods: Data corresponding to 20 patients were utilized so as to generate plans for every beam configuration. A preliminary study was conducted to assess the optimal distance between optimization structures (PTVx) and hippocampi. V 25 , V 30 , D 50% , D 2% , D 98% , homogeneity index (HI) and Paddick conformity factor (CF) were evaluated for PTV. D 100% and D max were considered for hippocampi. All plans were required to perform at least as recommended in RTOG 0933 trial regarding organs at risk (OAR) sparing and PTV objectives. Results: Considerable hippocampi sparing alongside with a reasonably low decrease in PTV coverage was achieved using a 7 mm distance between hippocampi and PTV optimization structure. Beam setup 3 (comprised of two full arcs with 0° couch angle and two half arcs with 90° couch angle) achieved the best PTV coverage, HI and CF, while it performed the second-best sparing in hippocampi and lenses. Moreover, beam setup 3 was the second-fastest treatment, although it resulted in the highest number of delivered MU among all beam setups. Beam setup 1 (comprised of two full arcs with no couch angles) was the fastest and it delivered a significantly less amount of monitor units compared with the other beam setups evaluated. Furthermore, a higher robustness was obtained by using no couch angles. Although beam setup 1 was the least optimal considering OAR sparing, it still performed better than required in the RTOG 0933 trial. Conclusions: Overall, beam setup 3 was considered to be the best. It is worth mentioning that, apart from our results, the election of one of these beam arrangements might be dependent on the amount of patient workload at a specific institution.