Computed tomographic histogram analysis in the diagnosis of lipid-poor adenomas: comparison to adrenal washout computed tomography

Artificial intelligence in adrenal imaging: A critical review of current applications

In the elective field of adrenal imaging, artificial intelligence (AI) can be used for adrenal lesion detection, characterization, hypersecreting syndrome management and patient follow-up. Although a perfect AI tool that includes all required steps from detection to analysis does not exist yet, multiple AI algorithms have been developed and tested with encouraging results. However, AI in this setting is still at an early stage. In this regard, most published studies about AI in adrenal gland imaging report preliminary results that do not have yet daily applications in clinical practice. In this review, recent developments and current results of AI in the field of adrenal imaging are presented. Limitations and future perspectives of AI are discussed.

Clinical, pathophysiologic, genetic and therapeutic progress in Primary Bilateral Macronodular Adrenal Hyperplasia

Patients with primary bilateral macronodular adrenal hyperplasia (PBMAH) usually present bilateral benign adrenocortical macronodules at imaging and variable levels of cortisol excess. PBMAH is a rare cause of primary overt Cushing's syndrome, but may represent up to one third of bilateral adrenal incidentalomas with evidence of cortisol excess. The increased steroidogenesis in PBMAH is often regulated by various G-protein coupled receptors aberrantly expressed in PBMAH tissues; some receptor ligands are ectopically produced in PBMAH tissues creating aberrant autocrine/paracrine regulation of steroidogenesis. The bilateral nature of PBMAH and familial aggregation, led to the identification of germline heterozygous inactivating mutations of the ARMC5 gene, in 20-25% of the apparent sporadic cases and more frequently in familial cases; ARMC5 mutations/pathogenic variants can be associated with meningiomas. More recently, combined germline mutations/pathogenic variants and somatic events inactivating the KDM1A gene were specifically identified in patients affected by GIP-dependent PBMAH. Functional studies demonstrated that inactivation of KDM1A leads to GIP-receptor (GIPR) overexpression and over or down-regulation of other GPCRs. Genetic analysis is now available for early detection of family members of index cases with PBMAH carrying identified germline pathogenic variants. Detailed biochemical, imaging, and co-morbidities assessment of the nature and severity of PBMAH is essential for its management. Treatment is reserved for patients with overt or mild cortisol/aldosterone or other steroid excesses taking in account co-morbidities. It previously relied on bilateral adrenalectomy; however recent studies tend to favor unilateral adrenalectomy, or less frequently, medical treatment with cortisol synthesis inhibitors or specific blockers of aberrant GPCR.

Adrenal Mass Characterization in the Era of Quantitative Imaging: State of the Art

Simple Summary

Non-invasive characterization of adrenal lesions requires a rigorous approach. Although CT is the cornerstone of adrenal lesion characterization, a multimodality multiparametric imaging approach helps improve confidence in adrenal lesion characterization.

Abstract

Detection and characterization of adrenal lesions have evolved during the past two decades. Although the role of imaging in adrenal lesions associated with hormonal secretion is usually straightforward, characterization of non-functioning adrenal lesions may be challenging to confidently identify those that need to be resected. Although many adrenal lesions can be readily diagnosed when they display typical imaging features, the diagnosis may be challenging for atypical lesions. Computed tomography (CT) remains the cornerstone of adrenal imaging, but other morphological or functional modalities can be used in combination to reach a diagnosis and avoid useless biopsy or surgery. Early- and delayed-phase contrast-enhanced CT images are essential for diagnosing lipid-poor adenoma. Ongoing studies are evaluating the capabilities of dual-energy CT to provide valid virtual non-contrast attenuation and iodine density measurements from contrast-enhanced examinations. Adrenal lesions with attenuation values between 10 and 30 Hounsfield units (HU) on unenhanced CT can be characterized by MRI when iodinated contrast material injection cannot be performed. ¹⁸F-FDG PET/CT helps differentiate between atypical benign and malignant adrenal lesions, with the adrenal-to-liver maximum standardized uptake value ratio being the most discriminative variable. Recent studies evaluating the capabilities of radiomics and artificial intelligence have shown encouraging results.

Adrenocortical neoplasms in adulthood and childhood: distinct presentation. Review of the clinical, pathological and imaging characteristics

Adrenocortical tumors (ACT) in adulthood and childhood vary in clinical, histopathological, molecular, prognostic, and imaging aspects. ACT are relatively common in adults, as adenomas are often found incidentally on imaging. ACT are rare in children, though they have a significantly higher prevalence in the south and southeast regions of Brazil. In clinical manifestation, adults with ACT present more frequently with glucocorticoid overproduction (Cushing syndrome), mineralocorticoid syndromes (Conn syndrome), or the excess of androgens in women. Subclinical tumors are frequently diagnosed late, associated with compression symptoms of abdominal mass. In children, the usual presentation is the virilizing syndrome or virilizing association and hypercortisolism. Histopathological grading and ACT classification in malignant and benign lesions are different for adults and children. In adults, the described criteria are the Hough, Weiss, modified Weiss, and Van Slooten. These scores are not valid for children; there are other criteria, such as proposed by Wieneke and colleagues. In molecular terms, there is also a difference related to genetic alterations found in these two populations. This review discusses the imaging findings of ACT, aiming to characterize the present differences between ACT found in adults and children. We listed several differences between magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography-computed (PET-CT) and also performed a literature review, which focuses on studied age groups of published articles in the last 10 years regarding cortical neoplasm and imaging techniques. Published studies on ACT imaging in children are rare. It is important to stress that the majority of publications related to the differentiation of malignant and benign tumors are based almost exclusively on studies in adults. A minority of articles, however, studied adults and children together, which may not be appropriate.

Cross-sectional imaging work-up of adrenal masses

Advances in medical imaging with current cross-section modalities enable non-invasive characterization of adrenal lesions. Computed tomography (CT) provides characterization with its non-contrast and wash-out features. Magnetic resonance imaging (MRI) is helpful in further characterization using chemical shift imaging (CSI) and MR spectroscopy. For differentiating between benign and malignant masses, positron emission tomography (PET) imaging is useful with its qualitative analysis, as well as its ability to detect the presence of extra-adrenal metastases in cancer patients. The work-up for an indeterminate adrenal mass includes evaluation with a non-contrast CT. If a lesion is less than 10 Hounsfield Units on a non-contrast CT, it is a benign lipid-rich adenoma and no further work-up is required. For the indeterminate adrenal masses, a lipid-poor adenoma can be differentiated from a metastasis utilizing CT wash-out features. Also, MRI is beneficial with CSI and MR spectroscopy. If a mass remains indeterminate, PET imaging may be of use, in which benign lesions demonstrate low or no fluorodeoxyglucose activity. In the few cases in which adrenal lesions remain indeterminate, surgical sampling such as percutaneous biopsy can be performed.

Adrenal mass imaging with multidetector CT: pathologic conditions, pearls, and pitfalls

The adrenal gland is involved by a range of neoplasms, including primary and metastatic malignant tumors; however, the most common tumor detected is the incidental benign adenoma. Although computed tomographic (CT) findings will not always yield a definitive diagnosis, attention to these findings provides a road map to guide image interpretation. Adenomas typically demonstrate rapid washout, which is defined as an absolute percentage washout (APW) of more than 60% and a relative percentage washout (RPW) of more than 40% on delayed images. Adrenocortical carcinoma typically has an RPW of less than 40%; however, large size and heterogeneity are more reliable indicators of the diagnosis than are washout values. Washout characteristics of pheochromocytoma are variable; in conjunction with high levels of dynamic enhancement, pheochromocytomas may mimic adenoma (ie, APW > 60%, RPW > 40%). Myelolipomas appear as well-defined masses with variable quantities of fat and soft tissue. After contrast material administration, metastases usually demonstrate slower washout on delayed images (APW < 60%, RPW < 40%) than do adenomas, although hypervascular metastases may enhance similarly to pheochromocytoma. Finally, a number of nonadrenal pathologic conditions have been reported to mimic adrenal masses at CT.

Adrenal imaging with multidetector CT: evidence-based protocol optimization and interpretative practice

Computed tomography (CT) is an integral tool in the assessment of adrenal masses. Dedicated adrenal CT is performed for a range of indications, including hormonal abnormalities suggestive of a functional adrenal mass and adrenal cancer staging. It is important to have an understanding of the published data that guide protocol design and image interpretation. Whether an adrenal mass is identified serendipitously or is being imaged for further characterization, there are several CT findings that contribute to the diagnosis, such as lesion size, precontrast attenuation, level of enhancement at 60 seconds and on delayed images, percentage washout on delayed images, histogram analysis, and extent (involvement of the inferior vena cava and bilaterality). In the past decade, a body of pertinent literature has evolved, addressing each of these measures individually.