Diagnostic performance of magnetic resonance imaging features to differentiate adrenal pheochromocytoma from adrenal tumors with positive biochemical testing results

BACKGROUND

It is extremely essential to accurately differentiate pheochromocytoma from Adrenal incidentalomas (AIs) before operation, especially biochemical tests were inconclusive. We aimed to evaluate the value of magnetic resonance imaging (MRI) features to differentiate pheochromocytomas among adrenal tumors, among which the consequences of biochemical screening tests of catecholamines and/or catecholamine metabolites are positive.

METHODS

With institutional review board approval, this study retrospectively compared 35 pheochromocytoma (PHEO) patients with 27 non-pheochromocytoma(non-PHEO) patients between January 2022 to September 2023, among which the consequences of biochemical screening tests of catecholamines and/or catecholamine metabolites are positive. T test was used for the independent continuous data and the chi-square test was used for categorical variables. Univariate and multivariate logistic regression were applied to find the independent variate of the features to differentiate PHEO from non-PHEO and ROC analysis was applied to evaluate the diagnostic value of the independent variate.

RESULTS

We found that the T2-weighted (T2W) signal intensity in patients with pheochromocytoma was higher than other adrenal tumors, with greatly significant (p < 0.001). T2W signal intensity ratio (T2W nodule-to-muscle SI ratio) was an independent risk factor for the differential diagnosis of adrenal PHEOs from non-PHEOs. This feature alone had 91.4% sensitivity and 81.5% specificity to rule out pheochromocytoma based on optimal threshold, with an area under the receiver operating characteristics curve (AUC‑ROC) of 0.910(95% C I: 0.833-0.987).

CONCLUSION

Our study confirms that T2W signal intensity ratio can differentiate PHEO from non-PHEO, among which the consequences of biochemical screening tests of catecholamines and/or catecholamine metabolites are positive.

Adrenal washout CT in patients with no history of cancer: a waste of time?

PURPOSE

To validate the diagnostic performance of adrenal washout CT in patients without known malignancy in a Western Australian population.

METHODS

A radiology information system (RIS) search for CT reports containing "adrenal" and "washout" across six networked metropolitan public hospitals between January 2005 and November 2021. Homogenous nodules ≥ 1 cm, ≥ 10 HU without a suspected functional component in patients without a history of malignancy were included. Reported absolute and relative washout percentages were recorded and re-measured from unenhanced, 60-s portal venous and 15-min delayed phase imaging and compared to either histopathological or CT follow up for growth (≥ 12 months) reference standards.

RESULTS

2653 studies were screened with 191 meeting inclusion criteria. 105 nodules underwent washout CT and then had either histopathological (12 patients) or CT follow up (93 patients) reference standards available. Reported absolute washout (aWO) estimated sensitivity and specificity for malignant/indeterminate nodules was low at 33% (95% CI 25-43%) and 77% (95% CI 68-84%) respectively. Reported relative washout (rWO) sensitivity and specificity were 56% (95% CI 46-65%) and 69% (95% CI 60-77%) respectively. Negative predictive values for both aWO and rWO were reassuring at 92% (95% CI 86-96%) and 94% (95%CI 88-97%).

CONCLUSION

Our study validates a recent report suggesting that adrenal washout has poor sensitivity for and consequent limited utility to exclude malignancy in patients with no cancer history. However, patients with incidental adrenal nodules < 4 cm in size with benign washout can be reassured by the high negative predictive value and worked up to exclude functional adenoma and re-imaged in a year to confirm no growth.

Imaging of Pheochromocytomas and Paragangliomas

Pheochromocytomas/paragangliomas are unique in their highly variable molecular landscape driven by genetic alterations, either germline or somatic. These mutations translate into different clusters with distinct tumor locations, biochemical/metabolomic features, tumor cell characteristics (eg, receptors, transporters), and disease course. Such tumor heterogeneity calls for different imaging strategies in order to provide proper diagnosis and follow-up. This also warrants selection of the most appropriate and locally available imaging modalities tailored to an individual patient based on consideration of many relevant factors including age, (anticipated) tumor location(s), size, and multifocality, underlying genotype, biochemical phenotype, chance of metastases, as well as the patient's personal preference and treatment goals. Anatomical imaging using computed tomography and magnetic resonance imaging and functional imaging using positron emission tomography and single photon emission computed tomography are currently a cornerstone in the evaluation of patients with pheochromocytomas/paragangliomas. In modern nuclear medicine practice, a multitude of radionuclides with relevance to diagnostic work-up and treatment planning (theranostics) is available, including radiolabeled metaiodobenzylguanidine, fluorodeoxyglucose, fluorodihydroxyphenylalanine, and somatostatin analogues. This review amalgamates up-to-date imaging guidelines, expert opinions, and recent discoveries. Based on the rich toolbox for anatomical and functional imaging that is currently available, we aim to define a customized approach in patients with (suspected) pheochromocytomas/paragangliomas from a practical clinical perspective. We provide imaging algorithms for different starting points for initial diagnostic work-up and course of the disease, including adrenal incidentaloma, established biochemical diagnosis, postsurgical follow-up, tumor screening in pathogenic variant carriers, staging and restaging of metastatic disease, theranostics, and response monitoring.

Validation of the modified CT criteria for identifying non-adenomas

PURPOSE

Although adrenal computed tomography (CT) percentage washout is a potentially powerful imaging technique for differentiating adrenal adenomas from non-adenomas, its application to non-adenomas can be problematic. Recently, modified criteria for diagnosing pheochromocytomas using adrenal CT were developed based on data from 199 patients with surgically proven pheochromocytomas and adenomas. However, these criteria have not been thoroughly validated. The purpose of this study was to validate the performance of the modified criteria for diagnosing non-adenomas including pheochromocytomas.

METHODS

The conventional and modified criteria were applied to 266 patients from two cohorts who had surgically proven lipid-poor adenomas (155/266, 58.3%) and non-adenomas (111/266, 41.7%) and underwent adrenal CT. Two radiologists calculated the attenuation on each dynamic phase and percentage washout of adrenal masses. The final assessments based on the conventional and modified criteria were categorized into adenomas or non-adenomas. The diagnostic performance of each criterion for diagnosing non-adenomas was evaluated using the area under the receiver operating characteristic curve (AUC). False negatives and positives were also compared.

RESULTS

The AUC for the diagnosis of non-adenomas was 0.806 for conventional criteria and 0.858 for modified criteria (p = 0.047). The false-negative rate of conventional criteria for the diagnosis of non-adenomas was 29.7%. Use of modified criteria could have reduced the false-negative rate by to 7.2%. The false-positive rate increased from 9% to 21.3% when using the modified criteria.

CONCLUSION

The utilization of modified criteria has the potential to identify additional non-adenomas that would otherwise be misdiagnosed as adenomas using conventional criteria alone.

Performance of CT With Adrenal-Washout Protocol in Heterogeneous Adrenal Nodules: A Multiinstitutional Study

BACKGROUND. CT with adrenal-washout protocol (hereafter, adrenal-protocol CT) is commonly performed to distinguish adrenal adenomas from other adrenal tumors. However, the technique's utility among heterogeneous nodules is not well established, and the optimal method for placing ROIs in heterogeneous nodules is not clearly defined. OBJECTIVE. The purpose of our study was to determine the diagnostic performance of adrenal-protocol CT to distinguish adenomas from nonadenomas among heterogeneous adrenal nodules and to compare this performance among different methods for ROI placement. METHODS. This retrospective study included 164 patients (mean age, 59.1 years; 61 men, 103 women) with a total of 164 heterogeneous adrenal nodules evaluated using adrenal-protocol CT at seven institutions. All nodules had an available pathologic reference standard. A single investigator at each institution evaluated the CT images. ROIs were placed on portal venous phase images using four ROI methods: standard ROI, which refers to a single large ROI in the nodule's center; high ROI, a single ROI on the nodule's highest-attenuation area; low ROI, a single ROI the on nodule's lowest-attenuation area; and average ROI, the mean of the three ROIs on the nodule's superior, middle, and inferior thirds using the approach for the standard ROI. ROIs were then placed in identical locations on unenhanced and delayed phase images. Absolute washout was determined for all methods. RESULTS. The nodules comprised 82 adenomas and 82 nonadenomas (36 pheochromocytomas, 20 metastases, 12 adrenocortical carcinomas, and 14 nodules with other pathologies). The mean nodule size was 4.5 ± 2.8 (SD) cm (range, 1.6-23.0 cm). Unenhanced CT attenuation of 10 HU or less exhibited sensitivity and specificity for adenoma of 22.0% and 96.3% for standard-ROI, 11.0% and 98.8% for high-ROI, 58.5% and 84.1% for low-ROI, and 30.5% and 97.6% for average-ROI methods. Adrenal-protocol CT overall (unenhanced attenuation ≤ 10 HU or absolute washout of ≥ 60%) exhibited sensitivity and specificity for adenoma of 57.3% and 84.1% for the standard-ROI method, 63.4% and 51.2% for the high-ROI method, 68.3% and 62.2% for the low-ROI method, and 59.8% and 85.4% for the average-ROI method. CONCLUSION. Adrenal-protocol CT has poor diagnostic performance for distinguishing adenomas from nonadenomas among heterogeneous adrenal nodules regardless of the method used for ROI placement. CLINICAL IMPACT. Adrenal-protocol CT has limited utility in the evaluation of heterogeneous adrenal nodules.

Differentiating adrenal metastases from benign lesions with multiphase CT imaging: Deep learning could play an active role in assisting radiologists

OBJECTIVES

To develop and externally validate multiphase CT-based deep learning (DL) models for differentiating adrenal metastases from benign lesions.

MATERIALS AND METHODS

This retrospective two-center study included 1146 adrenal lesions from 1059 patients who underwent multiphase CT scanning between January 2008 and March 2021. The study encompassed 564 surgically confirmed adenomas, along with 135 benign lesions and 447 metastases confirmed by observation. DL models based on multiphase CT images were developed, validated and tested. The diagnostic performance of the classification models, imaging phases and radiologists with or without DL were compared using accuracy (ACC) and receiver operating characteristic (ROC) curves. Integrated discrimination improvement (IDI) analysis and the DeLong test were used to compare the area under the curve (AUC) among models. Decision curve analysis (DCA) was used to assess the clinical usefulness of the predictive models.

RESULTS

The DL signature based on LASSO (DLSL) had a higher AUC than that of the other classification models (IDI > 0, P < 0.05). Furthermore, the precontrast phase (PCP)-based DLSL performed best in the independent external validation (AUC = 0.881, ACC = 82.9 %) and clinical test cohorts (AUC = 0.790, ACC = 70.4 %), outperforming DLSL based on the other single-phase or three-phase images (IDI > 0, P < 0.05). DCA demonstrated that PCP-based DLSL provided a higher net benefit (0.01-0.95). The diagnostic performance led to statistically significant improvements when radiologists incorporated the DL model, with the AUC improving by 0.056-0.159 and the ACC improving by 0.069-0.178 (P < 0.05).

CONCLUSION

The DL model based on PCP CT images performed acceptably in differentiating adrenal metastases from benign lesions, and it may assist radiologists in accurate tumor staging for patients with a history of extra-adrenal malignancy.

A Laboratory Medicine Perspective on the Investigation of Phaeochromocytoma and Paraganglioma

Phaeochromocytomas (PC) and sympathetic paragangliomas (PGL) are potentially malignant tumours arising from the adrenal medulla (PC) or elsewhere in the sympathetic nervous system (PGL). These tumours usually secrete catecholamines and are associated with significant morbidity and mortality, so accurate and timely diagnosis is essential. The initial diagnosis of phaeochromocytoma/paraganglioma (PPGL) is often dependent on biochemical testing. There is a range of pre-analytical, analytical and post-analytical factors influencing the analytical and diagnostic performance of biochemical tests for PPGL. Pre-analytical factors include patient preparation, sample handling and choice of test. Analytical factors include choice of methodology and the potential for analytical interference from medications and other compounds. Important factors in the post-analytical phase include provision of appropriate reference ranges, an understanding of the potential effects of various medications on metanephrine concentrations in urine and plasma and a consideration of PPGL prevalence in the patient population being tested. This article reviews these pre-analytical, analytical and post-analytical factors that must be understood in order to provide effective laboratory services for biochemical testing in the diagnosis of PPGL.

W, Barreto LO, Secaf A, Mermejo LM, Lucchesi FR, Tucci Jr. S, Elias Junior J, Molina CAF, Muglia VF. Histogram analysis in the differentiation between adrenal adenomas and pheochromocytomas: the value of a single measurement

Objective

To assess the diagnostic accuracy of histogram analysis on unenhanced computed tomography (CT) for differentiating between adrenal adenomas and pheochromocytomas (PCCs).

Materials and Methods

We retrospectively identified patients with proven PCCs who had undergone CT examinations between January 2009 and July 2019 at one of two institutions. For each PCC, we selected one or two adenomas diagnosed within two weeks of the date of diagnosis of the PCC. For each lesion, two readers scored the size, determined the mean attenuation, and generated a voxel histogram. The 10th percentile (P10) was obtained from the conventional histogram analysis, as well as being calculated with the following formula: P10 = mean attenuation - (1.282 × standard deviation). The mean attenuation threshold, histogram analysis (observed) P10, and calculated P10 (calcP10) were compared in terms of their diagnostic accuracy.

Results

We included 52 adenomas and 29 PCCs. The sensitivity, specificity, and accuracy of the mean attenuation threshold were 75.0%, 100.0%, and 82.5%, respectively, for reader 1, whereas they were 71.5%, 100.0%, and 81.5%, respectively, for reader 2. The sensitivity, specificity, and accuracy of the observed P10 and calcP10 were equal for both readers: 90.4%, 96.5%, and 92.6%, respectively, for reader 1; and 92.3%, 93.1%, and 92.6%, respectively, for reader 2. The increase in sensitivity was significant for both readers (p = 0.009 and p = 0.005, respectively).

Conclusion

For differentiating between adenomas and PCCs, the histogram analysis (observed P10 and calcP10) appears to outperform the mean attenuation threshold as a diagnostic criterion.

Can 3-Phase Computed Tomography Urography Be Used to Characterize Adrenal Nodules? Results in 145 Patients

OBJECTIVE

The aim of the study is to determine whether computed tomography (CT) urography (CTU) can characterize incidental adrenal nodules.

METHODS

This retrospective cohort study was performed at an academic medical center. Patients were identified by free text search of CTU reports that contained the terms "adrenal mass" "adrenal nodule" and "adrenal lesion." Computed tomography urography technique consisted of unenhanced images and postcontrast images obtained at 100 seconds and 15 minutes. The final cohort included 145 patients with 151 adrenal nodules. Nodules were considered lipid-rich adenomas or myelolipomas based on unenhanced imaging characteristics. Absolute and relative washout values were calculated for the remaining nodules, using a cutoff of 60% and 40%, respectively, to diagnose adenomas. Reference standard for lipid-poor adenomas and malignant nodules was histopathology or imaging/clinical follow-up. Mann-Whitney U test was used for comparison of continuous variables, and Fisher exact test was used for categorical variables.

RESULTS

One hundred nodules were lipid-rich adenomas and 3 were myelolipomas. Forty-eight nodules were indeterminate at unenhanced CT, corresponding to 39 lipid-poor adenomas and 9 malignant nodules based on reference standards. Both absolute and relative washout correctly characterized 71% of nodules (34/48), with a sensitivity of 67% and specificity of 89%. Overall, 91% of all adrenal nodules (137/151) were correctly characterized by CTU alone. Lipid-poor adenomas were smaller than malignant nodules (P < 0.01) and were lower in attenuation on unenhanced and delayed images (P < 0.01).

CONCLUSIONS

Adrenal nodules detected at 3-phase CTU can be accurately characterized, potentially eliminating the need for subsequent adrenal protocol CT or magnetic resonance imaging.

Incidental Adrenal Nodules in Patients Without Known Malignancy: Prevalence of Malignancy and Utility of Washout CT for Characterization-A Multiinstitutional Study

BACKGROUND. Washout CT is commonly used to evaluate indeterminate adrenal nodules, although its diagnostic performance is poorly established in true adrenal incidentalomas. OBJECTIVE. The purpose of this study was to compare, in patients without a known malignancy history, the prevalence of malignancy for incidental adrenal nodules with unenhanced attenuation more than 10 HU that do and do not show absolute washout of 60% or more, thereby determining the diagnostic performance of washout CT for differentiating benign from malignant incidental adrenal nodules. METHODS. This retrospective six-institution study included 299 patients (mean age, 57.3 years; 180 women, 119 men) without known malignancy or suspicion for functioning adrenal tumor who underwent washout CT, which showed a total of 336 adrenal nodules with a short-axis diameter of 1 cm or more, homogeneity, and unenhanced attenuation over 10 HU. The date of the first CT ranged across institutions from November 1, 2003, to January 1, 2017. Washout was determined for all nodules. Reference standard was pathology (n = 54), imaging follow-up (≥ 1 year) (n = 269), or clinical follow-up (≥ 5 years) (n = 13). RESULTS. Prevalence of malignancy among all nodules, nodules less than 4 cm, and nodules 4 cm or more was 1.5% (5/336; 95% CI, 0.5-3.4%), 0.3% (1/317; 95% CI, 0.0-1.7%), and 21.1% (4/19; 95% CI, 6.1-45.6%), respectively. Prevalence of malignancy was not significantly different for nodules smaller than 4 cm with (0% [0/241]; 95% CI, 0.0-1.2%) and without (1.3% [1/76]; 95% CI, 0.0-7.1%) washout of 60% or more (p = .08) or for nodules 4 cm or larger with (16.7% [1/6]; 95% CI, 0.4-64.1%) and without (23.1% [3/13]; 95% CI, 5.0-53.8%) washout of 60% or more (p = .75). Washout of 60% or more was observed in 75.5% (243/322; 95% CI, 70.4-80.1%) of benign nodules (excluding pheochromocytomas), 20.0% (1/5; 95% CI, 0.5-71.6%) of malignant nodules, and 33.3% (3/9; 95% CI, 7.5-70.1%) of pheochromocytomas. For differentiating benign nodules from malignant nodules and pheochromocytomas, washout of 60% or more had 77.5% sensitivity, 70.0% specificity, 98.8% PPV, and 9.2% NPV among nodules smaller than 4 cm. CONCLUSION. Prevalence of malignancy is low among incidental homogeneous adrenal nodules smaller than 4 cm with unenhanced attenuation more than 10 HU and does not significantly differ between those with and without washout of 60% or more; wash-out of 60% or more has suboptimal performance for characterizing nodules as benign. CLINICAL IMPACT. Washout CT has limited utility in evaluating incidental adrenal nodules in patients without known malignancy.

Radiomics approach based on biphasic CT images well differentiate "early stage" of adrenal metastases from lipid-poor adenomas: A STARD compliant article

The aim of the study was to develop an optimal radiomics model based on abdominal contrast-enhanced computed tomography (CECT) for pre-operative differentiation of "early stage" adrenal metastases from lipid-poor adenomas (LPAs). This retrospective study included 188 patients who underwent abdominal CECT (training cohort: LPAs, 68; metastases, 64; validation cohort: LPAs, 29; metastases, 27). Abdominal CECT included plain, arterial, portal, and venous imaging. Clinical and CECT radiological features were assessed and significant features were selected. Radiomic features of the adrenal lesions were extracted from four-phase CECT images. Significant radiomics features were selected using the least absolute shrinkage and selection operator (LASSO) and multivariable logistic regression. The clinical-radiological, unenhanced radiomics, arterial radiomics, portal radiomics, venous radiomics, combined radiomics, and clinical-radiological-radiomics models were established using a support vector machine (SVM). The DeLong test was used to compare the areas under the receiver operating characteristic curves (AUCs) of all models. The AUCs of the unenhanced (0.913), arterial (0.845), portal (0.803), and venous (0.905) radiomics models were all higher than those of the clinical-radiological model (0.788) in the testing dataset. The AUC of the combined radiomics model (incorporating plain and venous radiomics features) was further improved to 0.953, which was significantly higher than portal radiomics model (P = .033) and clinical-radiological model (P = .009), with the highest accuracy (89.13%) and a relatively stable sensitivity (91.67%) and specificity (86.36%). As the optimal model, the combined radiomics model based on biphasic CT images is effective enough to differentiate "early stage" adrenal metastases from LPAs by reducing the radiation dose.

Diagnostic value of the relative enhancement ratio of the portal venous phase to unenhanced CT in the identification of lipid-poor adrenal tumors

PURPOSE

Adrenal incidentalomas are common lesions found on abdominal imaging, most of which are lipid-rich adrenal adenomas. Imaging diagnoses differentiating lipid-poor adrenal adenomas (LPA) from non-adenomas (NA) are presently challenging to perform. The aim of the study was to investigate the diagnostic performance of the relative enhancement ratio parameter in identifying LPA from NA.

METHODS

We retrospectively evaluated consecutively presenting patients with lipid-poor adrenal lesions (January 2015 to August 2021). Lesions were divided into LPA and NA (including hyperenhancing and hypoenhancing NA). Kruskal-Wallis and Bonferroni tests were used to determine the differences in feature parameters between these three groups. Receiver operating characteristic curve analysis was performed to determine the sensitivity for diagnosing LPA and NA at 95% specificity; the parameters were compared using the McNemar test.

RESULTS

A total of 253 patients (mean age, 55 ± 12 years; 135 men), 121 with LPA and 132 with NA, were analyzed herein. The sensitivity (achieved at 95% specificity) of the relative enhancement ratio was higher than that of unenhanced attenuation in differentiating LPA from NA (60% vs. 52%, p = 0.064). The relative enhancement ratio yielded a higher sensitivity than unenhanced attenuation (79% vs. 59%, p < 0.001) in differentiating LPA from hypoenhancing NA, and a lower sensitivity (26% vs. 69%, p < 0.001) in differentiating LPA from hyperenhancing NA.

CONCLUSION

The relative enhancement ratio showed better diagnostic performance than unenhanced attenuation in differentiating LPA from hypoenhancing NA, while simultaneously showing poor diagnostic performance in identifying LPA from all NA.

Hereditary and Sporadic Pheochromocytoma: Comparison of Imaging, Clinical, and Laboratory Features

BACKGROUND. A considerable fraction of pheochromocytomas initially suspected to be sporadic, whether or not symptomatic, are a result of germline mutations. OBJECTIVE. The purpose of this article is to compare imaging features between hereditary and sporadic pheochromocytomas. METHODS. This retrospective study included 71 patients (39 women, 32 men; median age, 48 years) who underwent adrenal pheochromocytoma resection from January 2002 to October 2021 after preoperative CT or MRI. Two radiologists independently reviewed examinations to assess features of the largest resected pheochromocytoma. Interreader agreement was assessed by prevalence-adjusted bias-adjusted kappa coefficients; a third radiologist resolved discrepancies for further analysis. Genetic testing was used to classify pheochromocytomas as hereditary or sporadic and to classify hereditary pheochromocytomas by germline mutation clusters. Symptoms associated with pheochromocytomas and preoperative biochemical laboratory values were recorded. Groups were compared using Kruskal-Wallis, Fisher exact, and chi-square tests, and false-discovery rate-adjusted p values were computed to account for multiple comparisons. RESULTS. Hereditary pheochromocytoma (n = 32), compared with sporadic pheochromocytoma (n = 39), was associated with younger median age (38 vs 52 years, p = .001) and smaller median size (24 vs 40 mm, p < .001). Interreader agreement for CT and MRI features, expressed as kappa, ranged from 0.44 to 1.00. Hereditary and sporadic pheochromocytoma showed no difference in frequency of calcifications, hemorrhage, cystic change/necrosis, or macroscopic fat on CT, or in frequency of hemorrhage, cystic change/necrosis, macroscopic fat, or microscopic fat on MRI (p > .05). When combining CT and MRI, cystic change/necrosis was observed in 35% of hereditary versus 67% of sporadic pheochromocytomas (p = .10). Hereditary pheochromocytoma, compared with sporadic, had lower frequency of symptoms (31% vs 74%; p = .004) and lower 24-hour urinary normetanephrines (1.1 vs 5.1 times upper limits of normal, p = .006). Among hereditary pheochromocytomas, cystic change/necrosis (when assessable on imaging) was present in 18% and 45% of those with cluster 1 (n = 11) and cluster 2 (n = 21) germ-line mutations, respectively. CONCLUSION. Hereditary pheochromocytomas, compared with sporadic, are detected at a younger age and smaller size, produce lower 24-hour urinary normetanephrines, are less often symptomatic, and may less frequently show cystic change/necrosis. CLINICAL IMPACT. Imaging findings may complement clinical and biochemical features in raising suspicion for a previously unsuspected germline mutation in patients with pheochromocytoma.

Evaluation of the T2-weighted (T2W) adrenal MRI calculator to differentiate adrenal pheochromocytoma from lipid-poor adrenal adenoma

OBJECTIVES

To evaluate the T2-weighted (T2W) MRI calculator to differentiate adrenal pheochromocytoma from lipid-poor adrenal adenoma.

METHODS

Twenty-nine consecutive pheochromocytomas resected between 2010 and 2019 were compared to 23 consecutive lipid-poor adrenal adenomas. Three blinded radiologists (R1, R2, R3) subjectively evaluated T2W signal intensity and heterogeneity and extracted T2W signal intensity ratio (SIR) and entropy. These values were imputed into a quantitative and qualitative T2W adrenal MRI calculator (logistic regression model encompassing T2W SIR + entropy and subjective SI [relative to renal cortex] and heterogeneity) using a predefined threshold to differentiate metastases from adenoma and accuracy derived by a 2 × 2 table analysis.

RESULTS

Subjectively, pheochromocytomas were brighter (p < 0.001) and more heterogeneous (p < 0.001) for all three radiologists. Inter-observer agreement was fair-to-moderate for T2W signal intensity (K = 0.37-0.46) and fair for heterogeneity (K = 0.24-0.32). Pheochromocytoma had higher T2W-SI-ratio (p < 0.001) and entropy (p < 0.001) for all three readers. The quantitative calculator differentiated pheochromocytoma from adenoma with high sensitivity, specificity, and accuracy (100% [95% confidence intervals 88-100%], 87% [66-97%], and 94% [86-100%] R1; 93% [77-99%], 96% [78-100%], and 94% [88-100%] R2; 97% [82-100%], 96% [78-100%], and 96% [91-100% R3]). The qualitative calculator was specific with lower sensitivity and overall accuracy (48% [29-68%], 100% [85-100%], and 74% [65-83%] R1; 45% [26-64%], 100% [85-100%], and 72% [63-82%] R2; 59% [39-77%], 100% [85-100%], and 79% [70-88% R3]).

CONCLUSIONS

T2W signal intensity and heterogeneity differ, subjectively and quantitatively, in pheochromocytoma compared to adenoma. Use of a quantitative T2W adrenal calculator which combines T2W signal intensity ratio and entropy was highly accurate to diagnose pheochromocytoma outperforming subjective analysis.

KEY POINTS

• Pheochromocytomas have higher T2-weighted signal intensity and are more heterogeneous compared to lipid-poor adrenal adenomas evaluated subjectively and quantitatively. • The quantitative T2-weighted adrenal MRI calculator, a logistic regression model combining T2-weighted signal intensity ratio and entropy, is highly accurate for diagnosis of pheochromocytoma. • The qualitative T2-weighed adrenal MRI calculator had high specificity but lower sensitivity and overall accuracy compared to quantitative assessment and agreement was only fair-to-moderate.

Incidence of malignancy in adrenal nodules detected on staging CTs of patients with potentially resectable colorectal cancer

OBJECTIVE

To measure the prevalence of adrenal nodules detected on staging CT in patients with resectable colorectal cancer, and the proportion of patients with malignant nodules among them.

METHODS

This retrospective study included 6474 patients (median age, 65; interquartile range, 56-73; 3902 men) who underwent staging CT for colorectal cancer between May 2003 and December 2018. The patients had potentially resectable colorectal cancer, including resectable hepatic or pulmonary metastases. Through retrospective CT image review, patients with adrenal nodules were identified for the prevalence of adrenal nodule. Among patients with adrenal nodules, per-patient proportions of malignant nodules, adrenal metastasis from colorectal cancer, and additional adrenal examinations (biopsy or imaging tests) were measured. A secondary analysis was performed using data from the official CT reports.

RESULTS

The prevalence of adrenal nodules was 5.6% (363 of 6474; 95% CI: 5.1, 6.2). The proportions of malignant nodules and adrenal metastasis from colorectal cancer were 0.8% (3 of 363; 0.2, 2.4) and 0.3% (1 of 363; 0.0, 1.5), respectively. 6.1% (22 of 363; 3.8, 9.0) of the patients underwent additional adrenal examination. According to official CT reports, the prevalence of adrenal nodules and proportions of malignant nodules, adrenal metastasis from colorectal cancer, and additional adrenal examination were 1.9% (125 of 6474; 1.6, 2.3), 1.6% (2 of 125; 0.2, 5.7), 0% (0 of 125; 0.0, 2.9), and 10.4% (1 of 125; 5.7, 17.1), respectively.

CONCLUSION

Adrenal nodules detected in staging CTs in patients with otherwise resectable colorectal cancers are rarely malignant.

KEY POINTS

• Among 6474 patients who underwent staging CT and had potentially resectable colorectal cancer, 363 had adrenal nodules (≥ 10 mm) detected in retrospective CT image review. • Three out of the 363 patients with adrenal nodules detected on staging CT had malignant adrenal nodules, one of whom had metastasis from colorectal cancer.

Clinicoradiologic diagnosis of a rare type of congenital adrenal hyperplasia: A case report from Nepal

Congenital adrenal hyperplasia includes defects in the synthesis of steroid hormones in the adrenal cortex. The implications of this disorder manifest in other genitourinary organs, including ovaries and uterus. The diagnosis may be suspected based on the clinical and radiologic features.

Inter-individual comparison of diagnostic accuracy of adrenal washout CT compared to chemical shift MRI plus the T2-weighted (T2W) adrenal MRI calculator in indeterminate adrenal masses: a retrospective non-inferiority study

OBJECTIVE

To compare diagnostic accuracy of washout (WO)-CT to chemical shift (CS)-MRI + T2W adrenal MRI Calculator (T2W-Calculator) to diagnose adrenal adenoma in indeterminate adrenal masses.

METHODS

This retrospective, cross-sectional, non-inferiority study evaluated 40 consecutive indeterminate adrenal masses; each with WO-CT and MRI. Two blinded radiologists independently evaluated in mixed order: pre-contrast attenuation (Hounsfield Units, HU) and absolute WO ([Peak.HU-Delay.HU]/[Peak.HU-Pre.HU] × 100%), Chemical Shift Signal Intensity (CS-SI) Index, T2W SI ratio, and Entropy (which were imputed into the T2W-Calculator). Diagnostic accuracy for adrenal adenoma was tabulated using 2 × 2 tables. True -positive diagnoses of adenoma were CT = Pre-HU < 10 or absolute WO ≥ 60%, MRI = SI index ≥ 16.5% or T2W-Calculator < 0.631.

RESULTS

There were 73% (29/40) adenomas and 27% (11/40) other masses (5 pheochromocytoma, 3 solitary fibrous tumor, 1 metastasis, 1 cavernous hemangioma, and 1 adrenocortical carcinoma). Sensitivity, specificity, and accuracy for diagnosis of adenoma using CT-WO were 78% (95% confidence intervals [CI] 56-93%), 35% (14-62%), and 57% (42-71%) Reader 1 and 72% (53-87%), 46% (17-77%), and 59% (41-76%) Reader 2. Sensitivity, specificity, and accuracy for diagnosis of adenoma using MRI were 100% (88-100%), 64% (34-90%), and 82% (67-97%) Reader 1 and 86% (68-96%), 73% (39-94%), and 80% (64-95%) Reader 2. MRI had higher overall accuracy (p = 0.02 Reader 1, 0.05 Reader 2) compared to CT-WO.

CONCLUSION

Chemical shift MRI combined with the T2W adrenal MRI calculator is not inferior to CT Washout for diagnosis of adrenal adenoma among indeterminate adrenal masses.

Can Radiomics Provide Additional Diagnostic Value for Identifying Adrenal Lipid-Poor Adenomas From Non-Adenomas on Unenhanced CT?

Background

It is difficult for radiologists to differentiate adrenal lipid-poor adenomas from non-adenomas; nevertheless, this differentiation is important as the clinical interventions required are different for adrenal lipid-poor adenomas and non-adenomas.

Purpose

To develop an unenhanced computed tomography (CT)-based radiomics model for identifying adrenal lipid-poor adenomas to assist in clinical decision-making.

Materials and methods

Patients with adrenal lesions who underwent CT between January 2015 and August 2021 were retrospectively recruited from two independent institutions. Patients from institution 1 were randomly divided into training and test sets, while those from institution 2 were used as the external validation set. The unenhanced attenuation and tumor diameter were measured to build a conventional model. Radiomics features were extracted from unenhanced CT images, and selected features were used to build a radiomics model. A nomogram model combining the conventional and radiomic features was also constructed. All the models were developed in the training set and validated in the test and external validation sets. The diagnostic performance of the models for identifying adrenal lipid-poor adenomas was compared.

Results

A total of 292 patients with 141 adrenal lipid-poor adenomas and 151 non-adenomas were analyzed. Patients with adrenal lipid-poor adenomas tend to have lower unenhanced attenuation and smoother image textures. In the training set, the areas under the curve of the conventional, radiomic, and nomogram models were 0.94, 0.93, and 0.96, respectively. There was no difference in diagnostic performance between the conventional and nomogram models in all datasets (all p < 0.05).

Conclusions

Our unenhanced CT-based nomogram model could effectively distinguish adrenal lipid-poor adenomas. The diagnostic power of conventional unenhanced CT imaging features may be underestimated, and further exploration is worthy.

Management of incidental adrenal nodules: a survey of abdominal radiologists conducted by the Society of Abdominal Radiology Disease-Focused Panel on Adrenal Neoplasms

Adrenal incidentalomas are common findings discovered at abdominal CT and MRI, yet the most appropriate management remains controversial and guidelines vary. The Society of Abdominal Radiology (SAR) Disease-Focused Panel on Adrenal Neoplasms sought to determine the practice patterns of abdominal radiologists regarding the interpretation and management of adrenal incidentalomas. An electronic survey consisting of eleven multiple choice questions about adrenal incidentalomas was developed and distributed to the email list of current and past SAR members. The response rate was 11.8% (423/3581) and most respondents were academic radiologists (80.6%). The 2017 American College of Radiology White Paper was the most used guideline, yet the management of indeterminate adrenal incidentalomas was highly variable with no single management option reaching a majority. Hormonal evaluation and endocrinology consultation was most often rarely or never recommended. The results of the survey indicate wide variability in the interpretation of imaging findings and management recommendations for incidental adrenal nodules among surveyed radiologists. Further standardization of adrenal incidentaloma guidelines and education of radiologists is needed.

Machine intelligence in non-invasive endocrine cancer diagnostics

Artificial intelligence (AI) has illuminated a clear path towards an evolving health-care system replete with enhanced precision and computing capabilities. Medical imaging analysis can be strengthened by machine learning as the multidimensional data generated by imaging naturally lends itself to hierarchical classification. In this Review, we describe the role of machine intelligence in image-based endocrine cancer diagnostics. We first provide a brief overview of AI and consider its intuitive incorporation into the clinical workflow. We then discuss how AI can be applied for the characterization of adrenal, pancreatic, pituitary and thyroid masses in order to support clinicians in their diagnostic interpretations. This Review also puts forth a number of key evaluation criteria for machine learning in medicine that physicians can use in their appraisals of these algorithms. We identify mitigation strategies to address ongoing challenges around data availability and model interpretability in the context of endocrine cancer diagnosis. Finally, we delve into frontiers in systems integration for AI, discussing automated pipelines and evolving computing platforms that leverage distributed, decentralized and quantum techniques.

Computed Tomography-Based Machine Learning Differentiates Adrenal Pheochromocytoma From Lipid-Poor Adenoma

OBJECTIVES

To assess the accuracy of computed tomography (CT)-based machine learning models for differentiating subclinical pheochromocytoma (sPHEO) from lipid-poor adenoma (LPA) in patients with adrenal incidentalomas.

PATIENTS AND METHODS

The study included 188 tumors in the 183 patients with LPA and 92 tumors in 86 patients with sPHEO. Pre-enhanced CT imaging features of the tumors were evaluated. Machine learning prediction models and scoring systems for differentiating sPHEO from LPA were built using logistic regression (LR), support vector machine (SVM) and random forest (RF) approaches.

RESULTS

The LR model performed better than other models. The LR model (M1) including three CT features: CT_pre value, shape, and necrosis/cystic changes had an area under the receiver operating characteristic curve (AUC) of 0.917 and an accuracy of 0.864. The LR model (M2) including three CT features: CT_pre value, shape and homogeneity had an AUC of 0.888 and an accuracy of 0.832. The S2 scoring system (sensitivity: 0.859, specificity: 0.824) had comparable diagnostic value to S1 (sensitivity: 0.815; specificity: 0.910).

CONCLUSIONS

Our results indicated the potential of using a non-invasive imaging method such as CT-based machine learning models and scoring systems for predicting histology of adrenal incidentalomas. This approach may assist the diagnosis and personalized care of patients with adrenal tumors.

Risk prediction model establishment with tri-phasic CT image features for differential diagnosis of adrenal pheochromocytomas and lipid-poor adenomas: Grouping method

OBJECTIVES

The purpose of this study was to establish a risk prediction model for differential diagnosis of pheochromocytomas (PCCs) from lipid-poor adenomas (LPAs) using a grouping method based on tri-phasic CT image features.

METHODS

In this retrospective study, we enrolled patients that were assigned to a training set (136 PCCs and 183 LPAs) from two medical centers, along with an external independent validation set (30 PCCs and 54 LPAs) from another center. According to the attenuation values in unenhanced CT (CTu), the lesions were divided into three groups: group 1, 10 HU < CTu ≤ 25 HU; group 2, 25 HU < CTu ≤ 40 HU; and group 3, CTu > 40 HU. Quantitative and qualitative CT imaging features were calculated and evaluated. Univariate, ROC, and binary logistic regression analyses were applied to compare these features.

RESULTS

Cystic degeneration, CTu, and the peak value of enhancement in the arterial and venous phase (DEpeak) were independent risk factors for differential diagnosis of adrenal PCCs from LPAs. In all subjects (groups 1, 2, and 3), the model formula for the differentiation of PCCs was as follows: Y = -7.709 + 3.617*(cystic degeneration) + 0.175*(CTu ≥ 35.55 HU) + 0.068*(DEpeak ≥ 51.35 HU). ROC curves were drawn with an AUC of 0.95 (95% CI: 0.927-0.973) in the training set and 0.91 (95% CI: 0.860-0.929) in the external validation set.

CONCLUSION

A reliable and practical prediction model for differential diagnosis of adrenal PCCs and LPAs was established using a grouping method.

Are the washout values currently accepted for lesion characterization in dedicated adrenal CT adequate for diagnosis?

PURPOSE

We aimed to investigate the accuracy of density characteristics and washout values of lesions detected on computed tomography (CT) at the cutoff values obtained from the literature by taking the pathological results of adrenalectomy specimens as reference and to determine the cutoff values of parameters evaluated on CT for the differentiation of adenoma and nonadenoma lesions in the study group.

METHODS

Hospital records and standard CT imaging data (noncontrast early phase [65 s] and late phase [15 min] ) of 84 patients with 87 lesions who underwent adrenalectomy between January 2012 and December 2018 were retrospectively reevaluated by two radiologists in consensus. The patients were categorized as having adenoma and nonadenoma lesions according to the pathology results. The sensitivity, specificity and diagnostic accuracy of CT parameters (density values and washout percentages) were evaluated. Differences in the CT parameters (size, noncontrast and early-late enhancement density and absolute and relative washout values) were investigated. The optimal cutoff values of CT parameters were determined by ROC analysis.

RESULTS

Noncontrast CT had a specificity of 87.75% and 95.9%, sensitivity of 60% and 48.6%, diagnostic accuracy of 77.7% and 89.47% for adenomas, at the cutoff values of ≤10 HU and ≤0 HU, respectively. For absolute washout value ≥ 60%, the sensitivity, specificity and accuracy were 64.7%, 52.38% and 56.75%, respectively; while these rates were 76.47%, 56.52% and 62.16%, respectively, for relative washout value ≥40%. Adenomas and nonadenomas showed significant difference in terms of size (p < 0.0001), unenhanced attenuation (p < 0.0001), relative washout (p = 0.020) and delay enhancement (p < 0.001). But there were no differences in terms of absolute washout (p = 0.230) and early enhancement (p = 0.264). The cutoff values for the differentiation of adenomas and nonadenomas were as follows: size ≤44 mm, noncontrast density <20 HU, early-phase density ≥45 HU, delayed-phase density ≤44 HU, absolute washout 74.83% and relative washout 57.76%.

CONCLUSION

The current washout criteria used in the differentiation of adenoma and nonadenoma lesions in dynamic CT imaging can give false negative and positive results. According to the existing criteria, the most reliable parameter in adenoma-nonadenoma differentiation is ≤ 0 HU noncontrast CT density value.

Adrenal Nodules Detected at Staging CT in Patients with Resectable Gastric Cancers Have a Low Incidence of Malignancy

Background Guidelines recommending additional imaging for adrenal nodules lack relevant epidemiologic evidence. Purpose To measure the prevalence of adrenal nodules detected at staging CT in patients with potentially resectable gastric cancer and the proportion of patients with malignant nodules among them. Materials and Methods This retrospective study included 10 250 consecutive patients (median age, 63 years; interquartile range, 53-71 years; 6884 men) who underwent staging CT and had potentially resectable gastric cancer in a tertiary center (May 2003 to December 2018). All 10 250 CT studies were retrospectively reviewed, and patients with adrenal nodules (or thickening ≥10 mm) were identified to measure the prevalence of adrenal nodules. Among patients with adrenal nodules, the per-patient proportions of malignant nodules, adrenal metastasis from gastric cancer, and additional adrenal examinations were measured. A secondary analysis was performed by using data from the original CT reports. The same metrics that were used in the retrospective review were assessed. Results The prevalence of adrenal nodules was 4.5% (95% CI: 4.1, 4.9; 462 of 10 250). The proportions of malignant nodules and adrenal metastasis from gastric cancer were 0.4% ( 95% CI: 0.1, 1.6; two of 462) and 0% (95% CI: 0.0, 0.8; 0 of 462), respectively. A total of 27% of the patients (95% CI: 23, 31; 123 of 462) underwent additional adrenal examination. According to original CT reports, the prevalence of adrenal nodules and the proportions of malignant nodules, adrenal metastases from gastric cancer, and additional adrenal examination were 2.7% (95% CI: 2.4, 3.0; 272 of 10 250), 0.7% (95% CI: 0.1, 2.6; two of 272), 0% (95% CI: 0.0, 1.4; 0 of 272), and 42.6% (95% CI: 36.7, 48.8; 116 of 272), respectively. Conclusion Although adrenal nodules were detected frequently on staging CT images of patients with otherwise resectable gastric cancer, these nodules were rarely malignant. ©RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Baumgarten in this issue.

Comparison of MRI features in lipid-rich and lipid-poor adrenal adenomas using subjective and quantitative analysis

OBJECTIVE

To compare MR-imaging features in benign lipid-rich and lipid-poor adrenal adenomas.

MATERIALS AND METHODS

With institutional review board approval, we compared 23 consecutive lipid-poor adenomas (chemical shift [CS] signal intensity [SI] index < 16.5%) imaged with MRI to 29 consecutive lipid-rich adenomas (CS-SI index ≥ 16.5%) imaged during the same time period. A blinded radiologist measured T2-weighted (T2W) SI ratio (adrenal adenoma/psoas muscle), dynamic enhancement wash-in (WI) and wash-out (WO) indices, and T2W texture features. Two blinded Radiologists (R1/R2) assessed T2W-SI (relative to renal cortex) and T2W heterogeneity (using 5-Point Likert scales). Comparisons were performed between groups using independent t tests and Chi-square with Holm-Bonferroni correction.

RESULTS

There was no difference in age or gender between groups (p = 0.594, 0.051 respectively). Subjectively, all lipid-rich and lipid-poor adenomas were rated hypointense or isointense compared to renal cortex and T2W-SI did not differ between groups (p = 0.129, 0.124 for R1, R2). Agreement was substantial (Kappa = 0.67). There was no difference in T2W SI ratio (1.8 ± 0.9 [0.5-4.3] lipid rich versus 2.2 ± 1.0 [0.6-4.3] lipid poor, p = 0.139). Enhancement WI and WO did not differ comparing lipid-rich and lipid-poor adenomas (p = 0.759, 0.422 respectively). There was no difference comparing lipid-rich and lipid-poor adenomas T2W heterogeneity judged subjectively (p = 0.695, 0.139 for R1, R2; Kappa = 0.19) or by texture analysis (entropy, kurtosis, skewness; p = 0.134-0.191) with all adenomas except for one rated as mostly or completely homogeneous.

CONCLUSIONS

There is no difference in T2W signal intensity, enhancement pattern or T2W heterogeneity judged subjectively or by quantitative texture analysis comparing lipid-poor and lipid-rich adrenal adenomas.

Adrenal pheochromocytoma: is it all or the tip of the iceberg?

Adrenal pheochromocytoma is not always a simple retroperitoneal tumor but may be part of a more complicated condition. It often has a spectrum of complex and variable imaging features, may present as a collision tumor and composite tumor, and is associated with a variety of clinical syndromes. A comprehensive understanding of the clinical, pathological, and variable imaging manifestations of pheochromocytoma can help radiologists make an accurate diagnosis. This article reviews various special imaging features of pheochromocytoma and pheochromocytoma-related diseases.

Differentiation of lipid-poor adenoma from pheochromocytoma on biphasic contrast-enhanced CT

PURPOSE

To evaluate the diagnostic performance of biphasic contrast-enhanced CT in differentiation of lipid-poor adenomas from pheochromocytomas.

METHODS

129 patients with 132 lipid-poor adenomas and 93 patients with 97 pheochromocytomas confirmed by pathology were included in this retrospective study. Patients underwent unenhanced abdominal CT scan followed by arterial and venous phase. Quantitative and qualitative imaging features were compared between the two groups using univariate analysis. Risk factors for pheochromocytomas were evaluated by multivariate logistic regression analysis and a diagnostic scoring model was established based on odd ratio (OR) of the risk factors.

RESULTS

Pheochromocytomas were larger and showed cystic degeneration more frequently compared with lipid-poor adenomas (p < 0.01). No significant difference was found in peak enhancement phase between the two groups (p = 0.348). Attenuation values on unenhanced phase (CTU), arterial phase (CTA), and venous phase (CTV) of pheochromocytomas were significantly higher than that of lipid-poor adenomas while enhancement ratio on arterial and venous phase (ERA, ERV) of pheochromocytomas was significantly lower than that of lipid-poor adenomas (all p < 0.05). Multivariate analysis revealed lesion size > 29 mm (OR: 5.74; 95% CI 2.51-13.16; p < 0.001), CTA > 81 HU (OR: 2.54; 95% CI 1.04-6.17; p = 0.04), CTV > 97 HU (OR: 11.19; 95% CI 3.21-38.97; p < 0.001), ERV ≤ 1.5 (OR: 20.23; 95% CI 6.30-64.87; p < 0.001), and the presence of cystic degeneration (OR: 6.22, 95% CI 1.74-22.25; p = 0.005) were risk factors for pheochromocytomas. The diagnostic scoring model yielded an area under the curve (AUC) of 0.911.

CONCLUSIONS

Biphasic contrast-enhanced CT showed good diagnostic performance in differentiation of lipid-poor adenomas from pheochromocytomas.

Relative Enhancement Ratio of Portal Venous Phase to Unenhanced CT in the Diagnosis of Lipid-poor Adrenal Adenomas

Background The development of an accurate, practical, noninvasive, and widely available diagnostic approach to characterize lipid-poor adrenal lesions (greater than 10 HU at unenhanced CT) remains an ongoing demand. Purpose To investigate whether combined assessment of unenhanced and portal venous phase CT allows for the differentiation of lipid-poor adrenal adenomas from nonadenomas. Materials and Methods Patients with lipid-poor adrenal lesions who underwent unenhanced and portal venous phase CT with a single-energy scanner between January 2016 and March 2020 were identified retrospectively. For each lesion, the unenhanced and contrast-enhanced attenuation were measured; the absolute enhancement (contrast-enhanced minus unenhanced attenuation [HU]) and relative enhancement ratio ([absolute enhancement divided by unenhanced attenuation] × 100%) were calculated. The sensitivity achieved at 95% specificity to distinguish adenomas from nonadenomas was determined with receiver operating characteristic curve analysis and compared among parameters with use of the McNemar test. Results A total of 220 patients (mean age ± standard deviation, 66 years ± 12; 134 men) with 131 lipid-poor adenomas and 89 nonadenomas were analyzed. The sensitivity (achieved at 95% specificity) of the relative enhancement ratio (86% [113 of 131 adenomas; 95% CI: 79, 92] at a threshold of >210%) was higher than that of unenhanced attenuation (50% [66 of 131 adenomas; 95% CI: 42, 59] at a threshold of ≤21 HU), contrast-enhanced attenuation (3% [four of 131 adenomas; 95% CI: 1, 8] at a threshold of >120 HU), and absolute enhancement (24% [32 of 131 adenomas; 95% CI: 17, 33] at a threshold of >74 HU; all P < .001). The sensitivities of the relative enhancement ratio were 100% (58 of 58 adenomas; 95% CI: 94, 100), 83% (52 of 63 adenomas; 95% CI: 71, 91), and 30% (three of 10 adenomas; 95% CI: 7, 65) for adenomas measuring unenhanced attenuation of more than 10 HU up to 20 HU, 21-30 HU, and more than 30 HU, respectively. Conclusion A relative enhancement ratio threshold of greater than 210%, measured at unenhanced and portal venous phase CT, accurately differentiated lipid-poor adenomas from nonadenomas, particularly for lesions with unenhanced attenuation of 10-30 HU. © RSNA, 2021 Online supplemental material is available for this article.

Technical and Interpretive Pitfalls in Adrenal Imaging

The adrenal gland may exhibit a wide variety of pathologic conditions. A number of imaging techniques can be used to characterize these, although it is not always possible to attain a definitive diagnosis radiologically. Incorrect diagnoses may be made if radiologists are not attentive to technical parameters and interpretive factors associated with adrenal gland imaging. Hence, an appreciation of the intricacies of adrenal imaging strategies and characterization is required; this can be aided by understanding the pitfalls of adrenal imaging. Technical pitfalls at CT may relate to the imaging parameters, including region of interest characteristics, tube voltage selection, and the timing of contrast material-enhanced imaging. With MRI, imaging acquisition technique and evaluation of the reference tissues used in chemical shift MRI are important considerations that can directly influence image interpretation. Interpretive errors may occur when evaluating adrenal washout at CT without considering other radiologic features, including the size of adrenal nodules, the presence of fat or calcification, the attenuation of nodules, and atypical imaging features. The characterization of an incidental adrenal lesion as benign or malignant does not end the role of the radiologist; consideration as to whether an adrenal lesion is associated with endocrine dysfunction is required. While imaging may not be optimal for establishing endocrine activity, there are imaging features from which radiologists may infer function. In cases of known endocrine activity, imaging can guide clinical management, including further investigations such as venous sampling. ^©RSNA, 2020.

Incidental Adrenal Nodules

Incidentally detected adrenal nodules are common, and prevalence increases with patient age. Although most are benign, it is important for the radiologist to be able to accurately determine which nodules require further testing and which are safely left alone. The American College of Radiology incidental adrenal White Paper provides a structured algorithm based on expert consensus for management of incidental adrenal nodules. If further diagnostic testing is indicated, adrenal computed tomography is the most appropriate test in patients for nodules less than 4 cm. In addition to imaging, biochemical testing and endocrinology referral is warranted to exclude a functioning mass.

Multimodality Imaging Review of Multiple Endocrine Neoplasia

OBJECTIVE. The purpose of this article is to review the clinical manifestations, endocrine tumors types, and multimodality diagnostic tools available to physicians involved in the management of patients with multiple endocrine neoplasia (MEN) syndrome, in addition to discussing relevant imaging findings and appropriate imaging follow-up. CONCLUSION. Thorough knowledge of the spectrum of tumors associated with MEN gene mutations aids in the screening, diagnostic workup, and posttreatment monitoring of patients with MEN-related gene mutations.

The role of percutaneous CT-guided biopsy of an adrenal lesion in patients with known or suspected lung cancer

PURPOSE

To determine the sensitivity, specificity, and complication rate of percutaneous adrenal biopsy in patients with known or suspected lung cancer.

METHODS

This study was approved by the Institutional Review Board at our institution as a retrospective analysis; therefore, the need for informed consent was waived. All percutaneous adrenal biopsies performed between April 1993 and May 2019 were reviewed. 357 of 582 biopsies were performed on 343 patients with known or suspected lung cancer (M:F 164:179; mean age 66 years). The biopsy results were classified into malignant, benign, or non-diagnostic. The final diagnosis was established by pathology (biopsy and/or surgical resection) or imaging follow-up on CT for at least 12 months following the biopsy. Patients with less than 12 months follow-up were excluded (n = 44). Complications were recorded.

RESULTS

The final diagnosis was metastatic lung cancer in 235 cases (77.8%), metastasis from an extrapulmonary primary in 2 cases (0.7%), pheochromocytoma in 2 cases (0.7%), and benign lesions in 63 cases (20.9%). Percutaneous adrenal gland biopsy had a sensitivity of 97% and specificity of 100% for lung cancer metastases. The non-diagnostic rate was 0.6%. Larger lesions were more likely to be malignant (p = 0.0000) and to be correctly classified as a lung metastasis (p = 0.025). The incidence of minor complications was 1.1%. There were no major complications.

CONCLUSION

Over 20% of adrenal lesions in patients with known or suspected lung cancer were not related to lung cancer. Percutaneous adrenal gland biopsy is a safe procedure, with high sensitivity and specificity for lung cancer metastases.

Distinguishing pheochromocytoma from adrenal adenoma by using modified computed tomography criteria

PURPOSE

To investigate the performance of modified criteria to distinguish pheochromocytoma from adrenal adenoma by using adrenal protocol computed tomography (CT).

METHODS

We retrospectively included consecutive 199 patients who underwent adrenal CT and surgically proven pheochromocytoma (n = 66) or adenoma (n = 133). Two independent radiologists analyzed two CT criteria for pheochromocytoma. Conventional criteria were as follows: (a) lesion attenuation on unenhanced CT > 10 Hounsfield unit (HU); (b) absolute percentage washout < 60%; and (c) relative percentage washout < 40%. Modified criteria were as follows: (a) conventional criteria or (b) one of the following findings: (i) lesion attenuation on unenhanced CT ≥ 40 HU, (ii) 1-min enhanced CT ≥ 160 HU, (iii) 15-min enhanced CT ≥ 70 HU, , or (iv) intralesional cystic degeneration seen on both 1-min and 15-min enhanced CT. We analyzed area under the curve (AUC) and inter-reader agreement.

RESULTS

Proportion of pheochromocytoma was 33.2% (66/199). AUC of modified criteria was consistently higher than that of conventional criteria for distinguishing pheochromocytoma from adenoma (reader 1, 0.864 versus 0.746 for raw data set and 0.865 versus 0.746 for internal validation set; reader 2, 0.872 versus 0.758 for raw data set and 0.872 versus 0.757 for internal validation set) (p < 0.05 for all comparisons). Inter-reader agreement was excellent in interpreting any criteria (weighted kappa > 0.800).

CONCLUSION

Our modified criteria seem to improve diagnostic performance of adrenal CT in distinguishing pheochromocytoma from adrenal adenoma.

Virtual Noncontrast Images From Portal Venous Phase Spectral-Detector CT Acquisitions for Adrenal Lesion Characterization

OBJECTIVE

The aim of this study was to investigate if Hounsfield unit (HU) values from virtual noncontrast (VNC) images derived from portal venous phase spectral-detector computed tomography can help to differentiate adrenal adenomas and metastases.

METHODS

Spectral-detector computed tomography datasets of 33 patients with presence of adrenal lesions and standard of reference for lesion origin by follow-up/prior examinations or dedicated magnetic resonance imaging were included. Conventional and VNC images were reconstructed from the same scan. Region of interest-based image analysis was performed in adrenal lesions and contralateral healthy adrenal tissue.

RESULTS

The 33 lesions consisted of 23 adenomas and 10 metastases. Hounsfield unit values of all lesions in VNC images were significantly lower compared with conventional images (18.2 ± 12.6 HU vs 59.6 ± 21.7 HU, P < 0.001). Hounsfield unit values in adenomas were significantly lower in VNC images (11.3 ± 6.5 HU vs 34.1 ± 9.1 HU, P < 0.001).

CONCLUSIONS

Virtual noncontrast HU values differed significantly between adrenal adenomas and metastases and can therefore be used for improved characterization of incidental adrenal lesions and definition of adrenal adenomas.

Pitfalls and differential diagnosis on adrenal lesions: current concepts in CT/MR imaging: a narrative review

The purpose of this pictorial essay is to review the imaging findings of adrenal lesions. Adrenal lesions could be divided into functioning or non-functioning masses, primary or metastatic, and benign or malignant. Imaging techniques have undergone significant advances in recent years. The most significant objective of adrenal imaging is represented by the detection and, when possible, characterization of adrenal lesions in order to direct patient management correctly. The detection and management of adrenal lesions is based on cross-sectional imaging obtained with non-contrast CT (tumour density), contrast-enhanced CT including delayed washout (either absolute percentage washout or relative percentage one) and finally with MR chemical shift analysis (loss of signal intensity between in-phase and out-of-phase images including both qualitative and quantitative estimates of signal loss). The small incidental adrenal nodules are benign, in most of cases; some tumors such as lipid-rich adenoma and myelolipoma have characteristic features that can be diagnosed accurately in CT. On contrary, if the presenting contrast-enhanced CT shows an adrenal mass with uncertain or malignant morphologic features, particularly in patients with a known history of malignancy, further evaluations should be considered. The most significative implications for radiologists are represented by how to assess risk of malignancy on imaging and what follow-up to indicate if an adrenal incidentaloma is not surgically removed.

Adrenal Incidentaloma

An adrenal incidentaloma is now established as a common endocrine diagnosis that requires a multidisciplinary approach for effective management. The majority of patients can be reassured and discharged, but a personalized approach based upon image analysis, endocrine workup, and clinical symptoms and signs are required in every case. Adrenocortical carcinoma remains a real concern but is restricted to <2% of all cases. Functional adrenal incidentaloma lesions are commoner (but still probably <10% of total) and the greatest challenge remains the diagnosis and optimum management of autonomous cortisol secretion. Modern-day surgery has improved outcomes and novel radiological and urinary biomarkers will improve early detection and patient stratification in future years to come.

A Critical Analysis of Computed Tomography Washout in Lipid-Poor Adrenal Incidentalomas

BACKGROUND

Contrast-enhanced computed tomography (CT) with washout has emerged as an option to distinguish lipid-poor adenomas from non-adenomas.

OBJECTIVE

The aim of this study was to assess the utility of CT washout in characterizing indeterminate lipid-poor adrenal incidentalomas.

METHODS

From an Institutional Review Board-approved database, patients with adrenal incidentalomas who had adrenal protocol CT scans with a 15-min washout between 2003 and 2019 were identified. Non-contrast CT attenuation and washout patterns of different tumor types were compared.

RESULTS

Overall, 156 patients with 175 adrenal lesions were included. Average tumor size was 3.0 cm, non-contrast CT density was 24.7 Hounsfield units (HU), and absolute washout was 52.6%. In 102 lesions (58.3%), CT washout was ≥ 60%; 94 (92.2%) of these were benign adrenocortical adenomas, 7 (6.9%) were pheochromocytomas, and 1 (0.9%) was an adrenal hematoma. Furthermore, in 73 tumors (41.7%), CT washout was < 60%; diagnosis was benign adrenocortical adenoma in 45 (61.6%) lesions, pheochromocytoma in 8 (11%) lesions, metastasis in 9 (12.3%) lesions, adrenocortical cancer in 6 (8.2%) lesions, and 'others' in 5 (6.9%) lesions. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of  > 60% absolute CT washout for detecting an adrenal adenoma was 67.6%, 77.8%, 92.2%, 38.4%, and 69.7%, respectively.

CONCLUSION

CT washout should be incorporated into the management algorithm of indeterminate adrenal incidentalomas with a high non-contrast CT attenuation to 'rule-in' benign tumors. For small tumors with mild elevation of plasma metanephrines, it should be kept in mind that adenomas and pheochromocytomas may have similar imaging and washout characteristics.

Diagnostic performance of adrenal CT in the differentiation of adenoma and pheochromocytoma

BACKGROUND

Differentiation of adenoma and pheochromocytoma on computed tomography (CT) may be problematic.

PURPOSE

To investigate if adenoma and pheochromocytoma can be differentiated with adrenal CT.

MATERIAL AND METHODS

A total of 147 pathologically proven adrenal masses (119 adenomas, 28 pheochromocytomas) that had undergone adrenal CT were retrospectively evaluated. Lesion attenuation on unenhanced phase (UEP), portal phase (PP), 15-min delayed phase (DP), absolute/relative percentage enhancement wash-out (APEW/RPEW), and qualitative features were recorded. Student's t-test for parametric data, Mann-Whitney U test for non-parametric data, and Fisher's exact test for categorical data were used. Diagnostic performance of CT attenuation was assessed by area under the curve (AUC) of the receiver operating characteristics.

RESULTS

APEW of adenomas was not significantly different from pheochromocytomas; 68.4% and 59% (P = 0.284). Adenomas had significantly higher RPEW; 57.3% vs. 37.4% (P = 0.004). Of pheochromocytomas, 50% met APEW >60% or RPEW >40% criteria, and therefore were misclassified as adenoma on wash-out CT. Of those, 80% (4/5) were < 3 cm. UEP, PP, and DP attenuations of pheochromocytomas were significantly higher than adenomas; however, they were overlapping. AUC for UEP, PP, and DP was 0.906, 0.784, and 0.926, respectively. Larger pheochromocytomas were more likely to contain necrosis compared to smaller pheochromocytomas and adenomas; 41.6% vs. 12.5% vs. 3%. Homogeneous enhancement was seen in 25% of pheochromocytomas and 49% of adenomas (P = 0.018). No significant difference was found in terms of lesion borders and presence of fat/calcification (P > 0.05).

CONCLUSIONS

A considerable percentage of pheochromocytomas, especially smaller ones, demonstrate adenoma-like wash-out on CT. Heterogeneous enhancement, higher attenuation, and necrosis are more suggestive of pheochromocytoma.

Imaging Features of Succinate Dehydrogenase-deficient Pheochromocytoma-Paraganglioma Syndromes

Pheochromocytoma (PC) and paraganglioma (PGL) are rare neuroendocrine tumors that occur throughout the body from the base of the skull to the pelvis. Sympathetic catecholamine-secreting tumors may be associated with hyperadrenergic symptoms and long-term morbidity if they are untreated. Typically biochemically silent, head and neck PGLs may result in cranial nerve palsies and symptoms due to localized mass effect. Tumors can arise sporadically or as part of an inheritable PC-PGL syndrome. Up to 40% of tumors are recognized to be associated with germline mutations in an increasing array of susceptibility genes, including those that appear to arise sporadically. Most commonly, up to 25% of all PC-PGLs are associated with mutations in one of the succinate dehydrogenase (SDH) enzyme subunit genes. The resulting familial PC-PGL syndrome varies according to the affected enzyme subunit (most commonly SDHB and SDHD mutations) with respect to tumor prevalence, location, age of onset, and risk of malignancy. Patients with SDH enzyme mutations have increased lifetime risk of developing multifocal tumors and malignancy. Early recognition of individuals at high risk, genetic testing, screening of family members, and lifelong surveillance programs are recommended, but not without health, economic, and psychologic implications. Anatomic and functional imaging is key to diagnosis, staging, treatment planning, and lifelong surveillance of these individuals. Radiologists must be aware of the imaging appearance of these varied tumors.^©RSNA, 2019.

Not all adrenal incidentalomas require biochemical testing to exclude pheochromocytoma: Mayo clinic experience and a meta-analysis

Background

Excluding a pheochromocytoma is important when a patient presents with an incidentally discovered adrenal mass. However, biochemical testing for pheochromocytoma can be cumbersome, time consuming, or falsely positive. Our objective was to determine if unenhanced computed tomography (CT) imaging alone can be used to rule out pheochromocytoma.

Methods

We performed a retrospective study of all patients with a pathologically confirmed pheochromocytoma and unenhanced CT imaging who were treated at the Mayo Clinic between 1998 and 2016. Additionally, we performed a systematic review and meta-analysis of original studies published after 2005 with patients who had adrenal masses, more than 10 patients with pheochromocytomas, and reported attenuation on unenhanced CT imaging in Hounsfield units (HU).

Results

In the Mayo cohort, we identified 186 patients and 199 pheochromocytomas with unenhanced CT imaging. The mean unenhanced CT attenuation was 35±9 HU (range, 15-62), and only 15 tumors had attenuation ≤20 HU. The systematic review identified 26 studies (1,217 tumors), and 23 studies provided a mean unenhanced CT attenuation. The overall mean unenhanced CT attenuation across the studies was 35.6 HU (95% CI, 22.0-49.1 HU). A cutoff of >10 HU had a 100% sensitivity (95% CI, 1.00-1.00) for pheochromocytoma with low heterogeneity between the 21 qualified studies (I²=0%). Sensitivity for pheochromocytoma was 100% and 99% for an unenhanced CT attenuation cutoff of >15 and >20 HU.

Conclusions

Biochemical testing may not be required to exclude pheochromocytoma if an incidental adrenal mass has low attenuation (<10 HU) on unenhanced CT images.

Management of incidental adrenal masses: an update

OBJECTIVE

To review the current evidence and guidelines for diagnosis and management of incidental adrenal masses with a focus on the recent changes made by the American College of Radiology (ACR) Incidental Findings Committee.

CONCLUSION

Incidentally detected adrenal nodules are a commonly encountered finding estimated to occur in 5-7% of the adult population. By following current recommendations, radiologists can improve patient care by efficiently determining which masses require further diagnostic testing and which masses can be considered benign and not require further follow-up.

Genetics and imaging of pheochromocytomas and paragangliomas: current update

Pheochromocytomas (PCCs) and paragangliomas (PGLs) are rare, heterogeneous neuroendocrine neoplasms of the autonomous nervous system of chromaffin cell origin that may arise within the adrenal medulla (PCCs) or the sympathetic and parasympathetic paraganglia (PGLs). Currently referred to by the umbrella term pheochromocytomas-paragangliomas (PPGLs), these distinct tumors are characterized by specific histopathology as well as biological and clinical profiles. PPGLs may occur as part of hereditary syndromes (40% of cases) or as sporadic tumors. Currently, there are 12 different hereditary syndromes with characteristic genetic abnormalities, at least 15 well-characterized driver genes and distinct tumor metabolic pathways. Based on the Cancer Genome Atlas (TCGA) taxonomic schemata, PPGLs have been classified into three main clusters of specific genetic mutations and tumor pathways with clinical, biochemical, and prognostic implications. Imaging plays a pivotal role in the initial diagnosis, tumor characterization, evaluation of treatment response, and long-term surveillance. While MDCT and MRI help in the anatomic localization, SPECT, and PET using different radiotracers are crucial in the functional assessment of these tumors. Surgery, chemotherapy, and radiotherapy are currently available treatment options for PPGLs; antiangiogenic drugs are also being used in treating metastatic disease. Evolving knowledge regarding the different genetic abnormalities involved in the pathogenesis of PPGLs has identified potential therapeutic targets that may be utilized in the discovery of novel drugs.

Mimics, pitfalls, and misdiagnoses of adrenal masses on CT and MRI

Due to the widespread use of imaging, incidental adrenal masses are commonly encountered. A number of pitfalls can result in misdiagnosis of these lesions, including inappropriate choice of imaging technique, presence of pseudolesions, and overlap of imaging features of different adrenal lesions. This article explores the potential pitfalls in imaging of the adrenal glands, on computed tomography and magnetic resonance imaging, that can lead to misinterpretation. Clues to correct diagnoses are provided to evade potential misinterpretation.

Diagnostic Accuracy of Computed Tomography to Exclude Pheochromocytoma: A Systematic Review, Meta-analysis, and Cost Analysis

OBJECTIVES

To assess the diagnostic accuracy of unenhanced computed tomography (CT) attenuation values to exclude a pheochromocytoma in the diagnostic work-up of patients with an adrenal incidentaloma and to model the associated difference in diagnostic costs.

METHODS

The MEDLINE and Embase databases were searched from indexing to September 27, 2018, and studies reporting the proportion of pheochromocytomas on either side of the 10-Hounsfield unit (HU) threshold on unenhanced CT were included. The pooled proportion of pheochromocytomas with an attenuation value greater than 10 HU was determined, as were the modeled financial costs of the current and alternative diagnostic approaches.

RESULTS

Of 2957 studies identified, 31 were included (N=1167 pheochromocytomas). Overall risk of bias was low. Heterogeneity was not observed between studies (Q=11.5, P=.99, I²=0%). The pooled proportion of patients with attenuation values greater than 10 HU was 0.990 (95% CI, 0.984-0.995). The modeled financial costs using the new diagnostic approach were €55 (∼$63) lower per patient.

CONCLUSION

Pheochromocytomas can be reliably ruled out in the case of an adrenal lesion with an unenhanced CT attenuation value of 10 HU or less. Therefore, determination of metanephrine levels can be restricted to adrenal tumors with an unenhanced CT attenuation value greater than 10 HU. Implementing this novel diagnostic strategy is cost-saving.

Diagnostic efficacy of 18F-FDG PET/CT in patients with adrenal incidentaloma

BACKGROUND

The management of adrenal incidentaloma is still a challenge with respect to determining its functionality (hormone secretion) and malignancy. In this light, we performed 18F-FDG PET/CT scan to assess the SUVmax values in different adrenal masses including Cushing syndrome, pheochromocytoma, primary hyperaldosteronism and non-functional adrenal adenomas.

METHODS

Total 109 (73 F, 36 M) patients with adrenal mass (incidentaloma), mean age of 53.3 ± 10.2 years (range, 24-70) were screened by 18F-FDG PET/CT. Data of 18F-FDG PET/CT imaging of the patients were assessed by the same specialist. Adrenal masses were identified according to the calculated standardized uptake values (SUVs). Clinical examination, 24-h urine cortisol, catecholamine metabolites, 1-mg dexamethasone suppression test, aldosterone/renin ratio and serum electrolytes were analyzed.

RESULTS

Based on the clinical and hormonal evaluations, there were 100 patients with non-functional adrenal mass, four with cortisol-secreting, four with pheochromocytomas and one with aldosterone-secreting adenoma. Mean adrenal mass diameter of 109 patients was 2.1 ± 4.3 (range, 1-6.5 cm). The 18F-FDG PET/CT imaging of the patients revealed that lower SUVmax values were found in non-functional adrenal masses (SUVmax 3.2) when compared to the functional adrenal masses including four with cortisol-secreting adenoma (SUVmax 10.1); four with pheochromcytoma (SUVmax 8.7) and one with aldosterone-secreting adenomas (SUVmax 3.30). Cortisol-secreting (Cushing syndrome) adrenal masses showed the highest SUVmax value (10.1), and a cut-off SUVmax of 4.135 was found with an 84.6% sensitivity and 75.6% specificity cortisol-secreting adrenal adenoma.

CONCLUSIONS

Consistent with the similar studies, non-functional adrenal adenomas typically do not show increased FDG uptake and a certain form of functional adenoma could present various FDG uptake in FDG PET/CT. Especially functional adrenal adenomas (cortisol secreting was the highest) showed increased FDG uptake in comparison to the non-functional adrenal masses. Therefore, setting a specific SUVmax value in the differentiation of malignant adrenal lesion from the benign one is risky and further studies, including a high number of functional adrenal mass are needed.

Imaging features of adrenal masses

The widespread use of imaging examinations has increased the detection of incidental adrenal lesions, which are mostly benign and non-functioning adenomas. The differentiation of a benign from a malignant adrenal mass can be crucial especially in oncology patients since it would greatly affect treatment and prognosis. In this setting, imaging plays a key role in the detection and characterization of adrenal lesions, with several imaging tools which can be employed by radiologists. A thorough knowledge of the imaging features of adrenal masses is essential to better characterize these lesions, avoiding a misinterpretation of imaging findings, which frequently overlap between benign and malignant conditions, thus helping clinicians and surgeons in the management of patients. The purpose of this paper is to provide an overview of the main imaging features of adrenal masses and tumor-like conditions recalling the strengths and weaknesses of imaging modalities commonly used in adrenal imaging.