MR IMAGING OF THE THYROID AND PARATHYROID GLANDS

Detectability of 18F-choline PET/MR in primary hyperparathyroidism

PURPOSE

We aimed to evaluate the power of 18F-fluorocholine (FCH) positron emission tomography/magnetic resonance (PET/MR) imaging in unlocalized primary hyperparathyroidism.

METHODS

Thirty-four patients were included. In 17/34 patients, PET/MR was performed immediately after a negative 18F-FCH PET/CT. Sensitivity, specificity, positive and negative predictive values were calculated for MR only (blinded to PET data) and PET only (blinded to MR data) findings.

RESULTS

18F-FCH PET/MR was positive in 26/34 (76%) patients. PET/MR was also positive in 12/17 (71%) patients with a negative PET/CT. Among 11/34 (32%) patients where 18F-FCH PET-only and MR-only results were discordant, MR was false positive in 7/11 patients (3/7 of the lesions were not 18F-FCH avid and in 4/7 of them PET and MRI pointed different locations. Postoperative histopathology revealed that 18F-FCH-positive ones were true positives). Sensitivity, specificity, PPV, NPV and accuracy of neck MR evaluated blinded to PET data were 80%, 50%, 70%, 64% and 68%, respectively, and all were calculated as 100% for PET/MR.

CONCLUSION

18F-FCH PET/MR is very effective in preoperative localization of parathyroid adenomas even if 18F-FCH PET/CT is negative. Neck MR alone is insufficient in detecting parathyroid adenomas but PET/MR combination helps in precise localisation.

Preoperative Localization for Primary Hyperparathyroidism: A Clinical Review

With increasing use of minimally invasive parathyroidectomy (PTx) over traditional bilateral neck exploration in patients with primary hyperparathyroidism (PHPT), accurate preoperative localization has become more important to enable a successful surgical outcome. Traditional imaging techniques such as ultrasound (US) and sestamibi scintigraphy (MIBI) and newer techniques such as parathyroid four-dimension computed tomography (4D-CT), positron emission tomography (PET), and magnetic resonance imaging (MRI) are available for the clinician to detect the diseased gland(s) in the preoperative workup. Invasive parathyroid venous sampling may be useful in certain circumstances such as persistent or recurrent PHPT. We review the diagnostic performance of these imaging modalities in preoperative localization and discuss the advantages and weaknesses of these techniques. US and MIBI are established techniques commonly utilized as first-line modalities. 4D-CT has excellent diagnostic performance and is increasingly performed in first-line setting and as an adjunct to US and MIBI. PET and MRI are emerging adjunct modalities when localization has been equivocal or failed. Since no evidence-based guidelines are yet available for the optimal imaging strategy, clinicians should be familiar with the range and advancement of these techniques. Choice of imaging modality should be individualized to the patient with consideration for efficacy, expertise, and availability of such techniques in clinical practice.

The diagnostic value of 4D MRI at 3T for the localization of parathyroid adenomas

PURPOSE

The aim of this study was to assess the feasibility of four-dimensional magnetic resonance imaging (4D MRI) at 3 T for the localization of parathyroid adenomas.

MATERIALS AND METHODS

Preoperative 4D MRI scans, encompassing dynamic contrast-enhanced (DCE) sequences and non-contrast enhanced (non-CE) sequences, including a T2-weighted multipoint Dixon (T2-mDixon) sequence, with in-phase, out-phase, and water-only images, were evaluated retrospectively in 41 patients with surgically proven parathyroid lesions. Two readers who were blinded to the surgical findings independently reviewed the images in two sessions (non-CE sequences alone and non-CE + DCE sequences). The MRI localization of the suspected adenoma in each session and the consensus interpretation of the MRI images, were compared with the surgical results and interobserver agreement was assessed.

RESULTS

By interpreting the non-CE sequences alone, reader 1 correctly localized 34 parathyroid lesions (sensitivity 81.0%, positive predictive value (PPV) 87.2%), and reader 2 correctly localized 34 parathyroid lesions (sensitivity 81.0%, PPV 91.9%). With the addition of DCE sequences, reader 1 correctly identified 35 parathyroid lesions (sensitivity 83.3%, PPV 87.5%), while reader 2 correctly identified 36 parathyroid lesions (sensitivity 85.7%, PPV 92.3%). Overall, MRI detected 38 parathyroid lesions (sensitivity 90.5%, PPV 95.0%). Interobserver agreement was slightly superior in non-CE + DCE sequences compared to non-CE sequences alone (ĸ = 0.796 vs. ĸ = 0.738).

CONCLUSION

4D MRI with DCE sequencing is a reliable method for the localization of parathyroid adenomas.

Imaging Evaluation of the Head and Neck Oncology Patient

Imaging plays a multifaceted role in the diagnosis and characterization of head and neck oncological patients and is integral to their care. Given the complexity of treatment, a multimodality approach is often necessary. With the advent of new technologies, imaging can also be used to predict tumor behavior and treatment response. In this chapter, with selected case examples, we describe the various imaging modalities available and offer suggestions on their utilization.

MR appearance of parathyroid adenomas at 3 T in patients with primary hyperparathyroidism: what radiologists need to know for pre-operative localization

OBJECTIVES

To identify frequent MRI features of parathyroid adenomas (PTAs) in patients with primary hyperparathyroidism (PHPT) using a fast protocol with a 3 T magnet.

METHODS

Thirty-eight patients with PHPT underwent a 3 T-MR. All patients had positive US and Tc-99 sestamibi, for a total number of 46 PTAs. T2-weighted IDEAL-FSE and T1 IDEAL-sequences, before and after contrast, were performed. Five features of PTAs were recognised: hyperintensity, homogeneous or "marbled" appearance and elongated morphology on T2-sequences; cleavage plane from thyroid gland on T2-outphase; rapid enhancement in post-contrast T1. Image quality for T2-weighted IDEAL FSE and usefulness for IDEAL post-contrast T1-weighted and T2-outphase sequences were also graded.

RESULTS

PTAs were hyperintense in T2-sequences in 44/46 (95.7%), "marbled" in 30/46 (65.2%) and elongated in 38/46 (82.6%) patients. Cleavage plane was observed in 36/46 (78.3%), and rapid enhancement in 20/46 (43.5%) patients. T2-sequences showed both excellent fat suppression and image quality (average scores of 3.2 and 3.1). T2-outphase images demonstrated to be quite useful (score 2.8), whereas, post-contrast T1 images showed a lower degree of utility (score 2.4).

CONCLUSIONS

A fast protocol with 3.0-T MRI, recognising most common features of PTAs, may be used as a second-line method in the preoperative detection of PTAs.

KEY POINTS

3 T MRI protocol based on T2-weighted IDEAL FSE sequences was used. T2-hyperintensity and elongated morphology are common features of PTAs. 3 T MRI could be used in the preoperative detection of PTAs.

Dynamic CT for parathyroid disease: are multiple phases necessary?

BACKGROUND AND PURPOSE

A 4D CT protocol for detection of parathyroid lesions involves obtaining unenhanced, arterial, early, and delayed venous phase images. The aim of the study was to determine the ideal combination of phases that would minimize radiation dose without sacrificing diagnostic accuracy.

MATERIALS AND METHODS

With institutional review board approval, the records of 29 patients with primary hyperparathyroidism who had undergone surgical exploration were reviewed. Four neuroradiologists who were blinded to the surgical outcome reviewed the imaging studies in 5 combinations (unenhanced and arterial phase; unenhanced, arterial, and early venous; all 4 phases; arterial alone; arterial and early venous phases) with an interval of at least 7 days between each review. The accuracy of interpretation in lateralizing an abnormality to the side of the neck (right, left, ectopic) and localizing it to a quadrant in the neck (right or left upper, right or left lower) was evaluated.

RESULTS

The lateralization and localization accuracy (90.5% and 91.5%, respectively) of the arterial phase alone was comparable with the other combinations of phases. There was no statistically significant difference among the different combinations of phases in their ability to lateralize or localize adenomas to a quadrant (P = .976 and .996, respectively).

CONCLUSIONS

Assessment of a small group of patients shows that adequate diagnostic accuracy for parathyroid adenoma localization may be achievable by obtaining arterial phase images alone. If this outcome can be validated prospectively in a larger group of patients, then the radiation dose can potentially be reduced to one-fourth of what would otherwise be administered.

The role of proton MR spectroscopy and apparent diffusion coefficient values in the diagnosis of malignant thyroid nodules: preliminary results

PURPOSE

Performance of proton magnetic resonance spectroscopy (H-MRS) and apparent diffusion coefficient (ADC) values in the diagnosis of malignant thyroid nodules.

METHOD

In a retrospective study with malignant nodules of 14 patients, H-MRS and diffusion-weighted MR imaging (DWI) were performed. Choline (Cho) peak, Cho/creatine (Cr) ratio, and ADC values of malignant nodules were correlated with the five benign nodules and four normal-appearing thyroid lobe parenchymata. The gold standard reference was fine needle aspiration biopsy and histopathology.

RESULTS

At echo time 40-144-ms acquisitions, average Cho/Cr ratio for the malignant nodules was 2.95±1.54-5.30±2.38, cutoff values were >0.805 and >1.225, and ADC values were 0.06±0.02.

CONCLUSION

H-MRS acquisitions, DWI, and ADC mapping give diagnostic data about the nature of the nodules.

Imaging of the thyroid and parathyroid glands

Current multimodal imaging techniques offer practicing providers the adequate framework to plan and accomplish care for patients with thyroid and parathyroid disorders. Available imaging modalities include ultrasonography (US), nuclear scintigraphy, computed tomography (CT), and magnetic resonance imaging (MRI). US remains the most cost-effective and the safest approach for the initial evaluation of the thyroid gland. Parathyroid subtraction scintigraphy provides localization of pathologic parathyroid glands with the greatest sensitivity. Localizing imaging studies allow for surgical planning with minimal risk and morbidity to the patient. CT scan and MRI play an adjunctive role in the further characterization of neck pathology.

MR imaging of the thoracic inlet

The thoracic inlet serves as the junction between the neck and the chest. As such, it is sometimes considered a sort of "no-man's-land" between the well-defined and comfortable territories of the thoracic radiologist and that of the head and neck radiologist. Crucial digestive, respiratory, vascular, lymphatic, and neural structures traverse the thoracic inlet. Endocrine structures also are in close proximity to, and sometimes extend into, the thoracic inlet. Familiarity with the normal anatomy of the thoracic inlet on routine chest or neck imaging, and on dedicated high-resolution examinations of such areas as the brachial plexus, is critical for detection and characterization of pathologic conditions.

Role of apparent diffusion coefficient values in differentiation between malignant and benign solitary thyroid nodules

BACKGROUND AND PURPOSE

Accurate imaging characterization of a solitary thyroid nodule has been clearly problematic. The purpose of this study was to evaluate the role of the apparent diffusion coefficient (ADC) values in the differentiation between malignant and benign solitary thyroid nodules.

MATERIALS AND METHODS

A prospective study was conducted in 67 consecutive patients with solitary thyroid nodules who underwent diffusion MR imaging of the thyroid gland. Diffusion-weighted MR images were acquired with b factors of 0, 250, and 500 s/mm(2) by using single-shot echo-planar imaging. ADC maps were reconstructed. The ADC values of the solitary thyroid nodules were calculated and correlated with the results of histopathologic examination. Statistical analysis was performed.

RESULTS

The mean ADC value of malignant solitary thyroid nodules was 0.73 +/- 0.19 x 10(-3) mm(2)/s and of benign nodules was 1.8 +/- 0.27 x 10(-3) mm(2)/s. The mean ADC values of malignant nodules were significantly lower than those of benign ones (P = .0001). There were no significant differences between the mean ADC values of various malignant thyroid nodules, but there were significant differences between the subtypes of benign thyroid nodules (P = .0001). An ADC value of 0.98 x 10(-3) mm(2)/s was proved as a cutoff value differentiating between benign and malignant nodules, with 97.5%, 91.7%, and 98.9% sensitivity, specificity, and accuracy, respectively.

CONCLUSION

The ADC value is a new promising noninvasive imaging approach used for differentiating malignant from benign solitary thyroid nodules.

Parathyroid imaging: technique and role in the preoperative evaluation of primary hyperparathyroidism

OBJECTIVE

This article discusses the commonly used techniques for imaging the parathyroid glands and their role in the preoperative evaluation of patients with primary hyperparathyroidism.

CONCLUSION

The importance of sonography and sestamibi scintigraphy in the preoperative evaluation of patients with primary hyperthyroidism has increased with the adoption of minimally invasive parathyroidectomy techniques at most medical centers. When the results of these studies are concordant, the cure rates of minimally invasive surgery equal those of traditional bilateral neck exploration.

Parathyroid sonography: imaging and intervention

This article reviews the role of high-resolution sonography as an imaging modality for the diagnosis and treatment of patients with parathyroid disease. Included is a discussion of sonographic anatomy and technique, disease processes of the parathyroid glands and their sonographic appearances, preoperative imaging, and the use of sonography as a guide for diagnostic and therapeutic intervention in parathyroid disease.

Imaging for primary hyperparathyroidism--what beginners should know

For patients with primary hyperparathyroidism surgical removal of the hyperfunctioning parathyroid gland is curative. With advances in minimally invasive surgery, accurate pre-operative localization of the hyperfunctioning parathyroid tissue is essential to aid successful surgical treatment. The onus of identifying this hyperfunctioning parathyroid tissue therefore falls on imaging techniques such as high-resolution ultrasound, radionuclide imaging, computed tomography and magnetic resonance imaging. This article is not an exhaustive review, and its main aim is to familiarize the general radiologist, trainee radiologists and clinicians with the basics of various imaging techniques and their roles in practical management of patients with primary hyperparathyroidism.

MR imaging of the thyroid: correlation between apparent diffusion coefficient and thyroid gland scintigraphy

PURPOSE

To evaluate the usefulness of echo-planar MR imaging for assessing the thyroid function and confirm the clinical use of MR imaging for thyroid diseases.

MATERIALS AND METHODS

Thirty-four patients with a variety of thyroid disorders (24 Graves disease; five subacute thyroiditis; five Hashimoto thyroiditis) were examined using T1-, T2-, and diffusion-weighted magnetic resonance (MR) imaging and thyroid scintigraphy with Tc-99m pertechnetate.

RESULTS

The ADC values obtained from the diffusion-weighted images of the patients with Graves disease were significantly higher than those of patients with subacute hyroiditis and Hashimoto thyroiditis, though no difference among those disorders was observed on T1- and T2-weighted images. Based on the ADC value, anisotropy was not observed in the thyroid gland. An ADC value of 1.82 x 10(-3) mm(2)/second or higher indicated the presence of Graves disease (sensitivity 75%, specificity 80%).

CONCLUSION

Diffusion-weighted MR images may be of value for the diagnosis of thyroid diseases and could be clinically important in the evaluation of thyroid function.

Successful outcome after surgical management in two cases of the "painful variant" of Hashimoto's thyroiditis

OBJECTIVE

To describe two cases of the rare "painful variant" of Hashimoto's thyroiditis (HT) that were refractory to medical management and in which surgical intervention provided the definitive treatment.

METHODS

We thoroughly review the clinical history as well as the laboratory, imaging, and surgical pathology data in these cases, and follow-up of the clinical response over time is provided. The relevant literature is also discussed.

RESULTS

A 56-year-old woman, who had remotely undergone a left hemithyroidectomy and had been diagnosed with HT, sought further assessment because of neck pain and edema. Treatment with corticosteroids was partially successful but led to the development of Cushing's syndrome. A 32-year-old man had pain and swelling of the thyroid and was diagnosed with HT shortly thereafter. Levothyroxine treatment was unsuccessful. Both patients underwent thyroidectomy. Chronic lymphocytic thyroiditis (HT) with a variable degree of fibrosis was found on assessment of pathology specimens. The patients remained asymptomatic after the surgical procedure and did not require any further anti-inflammatory therapy.

CONCLUSION

In selected cases, surgical treatment may become necessary for effective and permanent control of symptoms and local signs in painful HT. Access to experienced endocrine surgeons is important in order to avoid postoperative complications because the thyroid gland may be small or fibrosed in this rare variant of HT.