Thyroid nodules are a frequent finding on neck sonography. Most nodules are benign; therefore, many nodules are biopsied to identify the small number that are malignant or require surgery for a ...definitive diagnosis. Since 2009, many professional societies and investigators have proposed ultrasound-based risk stratification systems to identify nodules that warrant biopsy or sonographic follow-up. Because some of these systems were founded on the BI-RADS
classification that is widely used in breast imaging, their authors chose to apply the acronym TI-RADS, for Thyroid Imaging, Reporting and Data System. In 2012, the ACR convened committees to (1) provide recommendations for reporting incidental thyroid nodules, (2) develop a set of standard terms (lexicon) for ultrasound reporting, and (3) propose a TI-RADS on the basis of the lexicon. The committees published the results of the first two efforts in 2015. In this article, the authors present the ACR TI-RADS Committee's recommendations, which provide guidance regarding management of thyroid nodules on the basis of their ultrasound appearance. The authors also describe the committee's future directions.
The incidental thyroid nodule (ITN) is one of the most common incidental findings on imaging studies that include the neck. An ITN is defined as a nodule not previously detected or suspected ...clinically, but identified by an imaging study. The workup of ITNs has led to increased costs from additional procedures, and in some cases, to increased risk to the patient because physicians are naturally concerned about the risk of malignancy and a delayed cancer diagnosis. However, the majority of ITNs are benign, and small, incidental thyroid malignancies typically have indolent behavior. The ACR formed the Incidental Thyroid Findings Committee to derive a practical approach to managing ITNs on CT, MRI, nuclear medicine, and ultrasound studies. This white paper describes consensus recommendations representing this committee's review of the literature and their practice experience.
To identify an optimal margin about the gross target volume (GTV) for stereotactic radiosurgery (SRS) of brain metastases, minimizing toxicity and local recurrence.
Adult patients with 1 to 3 brain ...metastases less than 4 cm in greatest dimension, no previous brain radiation therapy, and Karnofsky performance status (KPS) above 70 were eligible for this institutional review board-approved trial. Individual lesions were randomized to 1- or 3- mm uniform expansion of the GTV defined on contrast-enhanced magnetic resonance imaging (MRI). The resulting planning target volume (PTV) was treated to 24, 18, or 15 Gy marginal dose for maximum PTV diameters less than 2, 2 to 2.9, and 3 to 3.9 cm, respectively, using a linear accelerator-based image-guided system. The primary endpoint was local recurrence (LR). Secondary endpoints included neurocognition Mini-Mental State Examination, Trail Making Test Parts A and B, quality of life (Functional Assessment of Cancer Therapy-Brain), radionecrosis (RN), need for salvage radiation therapy, distant failure (DF) in the brain, and overall survival (OS).
Between February 2010 and November 2012, 49 patients with 80 brain metastases were treated. The median age was 61 years, the median KPS was 90, and the predominant histologies were non-small cell lung cancer (25 patients) and melanoma (8). Fifty-five, 19, and 6 lesions were treated to 24, 18, and 15 Gy, respectively. The PTV/GTV ratio, volume receiving 12 Gy or more, and minimum dose to PTV were significantly higher in the 3-mm group (all P<.01), and GTV was similar (P=.76). At a median follow-up time of 32.2 months, 11 patients were alive, with median OS 10.6 months. LR was observed in only 3 lesions (2 in the 1 mm group, P=.51), with 6.7% LR 12 months after SRS. Biopsy-proven RN alone was observed in 6 lesions (5 in the 3-mm group, P=.10). The 12-month DF rate was 45.7%. Three months after SRS, no significant change in neurocognition or quality of life was observed.
SRS was well tolerated, with low rates of LR and RN in both cohorts. However, given the higher potential risk of RN with a 3-mm margin, a 1-mm GTV expansion is more appropriate.
The American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS) is an ultrasound-based risk stratification system (RSS) for thyroid nodules that was released in 2017. ...Since publication, research has shown that ACR TI-RADS has a higher specificity than other RSSs and reduces the number of unnecessary biopsies of benign nodules compared with other systems by 19.9-46.5%. The risk of missing significant cancers using ACR TI-RADS is mitigated by the follow-up recommendations for nodules that do not meet criteria for biopsy. In practice, after a nodule's ultrasound features have been enumerated, the ACR TI-RADS points-based approach leads to clear management recommendations. Practices seeking to implement ACR TI-RADS must engage their radiologists in understanding how the system addresses the problems of thyroid cancer overdiagnosis and unnecessary surgeries by reducing unnecessary biopsies. This review compares ACR TI-RADS to other RSSs and explores key clinical questions faced by practices considering its implementation. We also address the challenge of reducing interobserver variability in assigning ultrasound features. Finally, we highlight emerging imaging techniques and recognize the ongoing international effort to develop a system that harmonizes multiple RSSs, including ACR TI-RADS.
Parathyroid four-dimensional (4D) computed tomography (CT) is an imaging technique for preoperative localization of parathyroid adenomas that involves multidetector CT image acquisition during two or ...more contrast enhancement phases. Four-dimensional CT offers an alternative or additional tool in the evaluation of primary hyperparathyroidism. The purpose of this article is to describe the 4D CT technique and provide a practical guide to the radiologist for imaging interpretation. The article will discuss the rationale for imaging, approach to interpretation, imaging findings, and pitfalls.
To describe the prevalence of three relative enhancement patterns of parathyroid lesions on four-dimensional (4D) computed tomographic (CT) scans.
The institutional review board approved this ...HIPAA-compliant study and waived the need for informed consent. The authors retrospectively reviewed preoperative 4D CT scans obtained from November 2012 to June 2014 in 94 patients with pathologically proven parathyroid adenomas or hyperplasia. Lesions were classified into one of three relative enhancement patterns. All patterns required lesions to be lower in attenuation than the thyroid on non-contrast material-enhanced images, but patterns differed in the two contrast-enhanced phases. Type A lesions were higher in attenuation than the thyroid in the arterial phase, type B lesions were not higher in attenuation than the thyroid in the arterial phase but were lower in attenuation than the thyroid in the delayed phase, and type C lesions were neither higher in attenuation than the thyroid in the arterial phase nor lower in attenuation than the thyroid in the delayed phase. The prevalence of the relative enhancement patterns was compared. The t test was used to compare mean attenuation differences in Hounsfield units between the relative enhancement patterns.
Ninety-four patients had 110 parathyroid lesions, including 11 patients with multigland disease. The sensitivity for single-gland disease was 94% (78 of 83) and that for multigland disease was 59% (16 of 27). Type B enhancement was most common, with a prevalence of 57% (54 of 94), followed by type C (22% 21 of 94) and type A (20% 19 of 94). Five lesions were interpreted incorrectly as parathyroid adenoma (false-positive), and all lesions had the type C pattern. Relative to the thyroid, lesions categorized as type A by readers had mean attenuation difference (± standard deviation) of 39 HU ± 13 in the arterial phase, and type B lesions had a difference of -58 HU ± 26 in the delayed phase. These values differed from the mean attenuation difference of lesions not in these categories (P < .001).
Parathyroid adenomas and hyperplasia can be grouped into three relative enhancement patterns based on a protocol with a non-contrast-enhanced and two contrast-enhanced phases. The type B pattern is most common and could be diagnosed with two contrast-enhanced phases. However, almost one quarter of lesions have the type C pattern and thus could be missed without the non-contrast-enhanced phase.
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