PET/CT for the characterization of adrenal masses in patients with cancer: qualitative versus quantitative accuracy in 150 consecutive patients. AJR Am J Roentgenol. 2009;192:956-962. [PMID: 19304700 DOI: 10.2214/ajr.08.1431]

The Diagnostic Value of 18F-FDG PET/CT Scan in Characterizing Adrenal Tumors

CONTEXT

Imaging plays an important role in the characterization of adrenal tumors, but findings might be inconclusive. The clinical question is whether 18F fluodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) is of diagnostic value in this setting.

OBJECTIVE

This meta-analysis was aimed at the diagnostic value of 18F-FDG PET/CT in differentiating benign from malignant adrenal tumors discovered either as adrenal incidentaloma or during staging or follow-up of oncologic patients.

DATA SOURCES

PubMed, EMBASE, Web of Science, and Cochrane Library were searched to select articles between 2000 and 2021.

STUDY SELECTION

We included studies describing the diagnostic value of 18F-FDG PET/CT in adult patients with an adrenal tumor. Exclusion criteria were 10 or fewer participants, insufficient data on histopathology, clinical follow-up, or PET results. After screening of title and abstract by 2 independent reviewers, 79 studies were retrieved, of which 17 studies met the selection criteria.

DATA EXTRACTION

Data extraction using a protocol and quality assessment according to QUADAS-2 was performed independently by at least 2 authors.

DATA SYNTHESIS

A bivariate random-effects model was applied using R (version 3.6.2.). Pooled sensitivity and specificity of 18F-FDG PET/CT for identifying malignant adrenal tumors was 87.3% (95% CI, 82.5%-90.9%) and 84.7% (95% CI, 79.3%-88.9%), respectively. The pooled diagnostic odds ratio was 9.20 (95% CI, 5.27-16.08; P < .01). Major sources of heterogeneity (I2, 57.1% [95% CI, 27.5%-74.6%]) were in population characteristics, reference standard, and interpretation criteria of imaging results.

CONCLUSIONS

18F-FDG PET/CT had good diagnostic accuracy for characterization of adrenal tumors. The literature, however, is limited, in particular regarding adrenal incidentalomas. Large prospective studies in well-defined patient populations with application of validated cutoff values are needed.

Adrenal findings in FDG-PET: analysis of a cohort of 1021 patients from a cancer center

PURPOSE

The use of FDG-PET for cancer staging has led to the increasing incidence of adrenal lesions, which are usually a clinical challenge. We aimed to characterize the adrenal lesions found in FDG-PET of patients followed in a cancer center.

METHODS

Retrospective analysis was conducted of all FDG-PET studies performed in our center in the last 10 years. Exams reporting adrenal lesions in the CT component and/or anomalous adrenal FDG uptake were selected. Cases were characterized by the clinical, laboratory, imaging, and pathological findings.

RESULTS

We identified 27,427 FDG-PET studies. Of those, 7.6% reported adrenal findings. We included 1364 exams corresponding to 1021 patients. Only 15.6% of the patients were referred to the Endocrinology Department and 38% of the lesions were not studied. In 38.9% of the studied patients, malignant lesions were present, including metastases in 37.5%, carcinoma in 1.2%, and other malignant tumors in 0.4%. The median SUVmax of malignant lesions was significantly higher than the SUVmax of the benign findings (p < 0.05). We also observed a higher median SUVmax in adrenal metastases than in adenomas (p < 0.05). There was a tendency for higher SUVmax of adrenal carcinomas when compared with other malignant lesions (p = 0.066). The median SUVmax was not different between pheochromocytomas and other tumors (p > 0.05).

CONCLUSION

Occult adrenal lesions discovered during FDG-PET/CT are common in the cancer context and are frequently benign. SUVmax may be a useful tool in the workup of adrenal lesions but with several important caveats.

Imaging incidental adrenal lesions

Incidental adrenal masses are among the most common incidental lesions detected on cross-sectional imaging. The majority are benign lesions, adenomas and myelolipomas being the most common. Simple cross-sectional imaging techniques using CT and MRI permit the characterization of over 80%, thereby requiring no further imaging. The remaining lesions are considered indeterminate. These lesions consist of benign and malignant lesions sharing imaging features. Further imaging and management of these indeterminate lesions should be guided by close collaboration between different specialists in an MDT setting. Advanced imaging options include dedicated adrenal scintigraphy, positron emission tomography CT, biopsy and surveillance. Biochemical and hormonal evaluation is also important to identify hyperfunctioning adrenal lesions. This review focuses on imaging features of benign and malignant adrenal masses used for characterization and suggests an imaging pathway for indeterminate adrenal masses.

Fluoro-2-Deoxyglucose-Positron Emission Tomography/Computed Tomography in the Diagnosis and Management of Adrenocortical Carcinoma: A 10-Year Experience from a Tertiary Care Institute

Purpose

Adrenocortical carcinoma (ACC) is a rare primary malignancy of the adrenal gland. The present study was aimed to compare the performance of fluoro-2-deoxyglucose-positron emission tomography-computed tomography (FDG-PET-CT) compared to contrast-enhanced computed tomography (CECT) in diagnosis and management of ACC.

Materials and Methods

A retrospective analysis of the PET-CT studies from January 2010 to October 2020 was performed. Patients with adrenal lesions suspicious of ACC and diagnosed cases of ACC who underwent PET-CT for staging, restaging, and surveillance were reanalyzed. The PET-CT parameters were compared with the clinical, biochemical, histopathological, and CECT parameters.

Results

The study included 96 scans performed in 77 patients (36 males, aged 40.4 ± 17.9 years). Of these, 55 scans were performed to diagnose and stage suspected ACC (30 of them diagnosed as ACC), 31 for restaging, and 10 scans for surveillance of ACC. PET/CT revealed metastases from an extra-adrenal primary in 5/55 patients. FDG-PET-CT had a sensitivity and specificity of 100% and 70% to diagnose ACC. Standardized uptake value-peak more than 5.4 had a sensitivity of 90.9% and specificity of 91.7% for differentiating ACC from non-ACC lesions, while tumor-to-liver ratio peak (TLRpeak) of 3.3 was most specific. PET-CT changed the staging in 23.3% of the patients with an accuracy of 100%. PET-CT changed the management plan in 25.8% of the patients during restaging with a sensitivity and specificity of 95.6% and 100%, respectively. For surveillance, CECT was as sensitive as PET-CT; however, PET-CT was more specific (100% vs. 97.9%).

Conclusion

FDG-PET-CT performs better than CECT in the diagnosis, staging, restaging, and surveillance of ACC.

18F-FDG PET/CT image findings of a dog with adrenocortical carcinoma

Background

In human medicine, 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has been used to differentiate between benign and malignant adrenal tumors and to identify metastases. However, canine adrenocortical carcinomas identified by 18F-FDG PET/computed tomography (CT) have not been reported.

Case presentation

A 13-year-old, castrated male, Cocker Spaniel dog with severe systolic hypertension exhibited an adrenal mass approximately 3.6 cm in diameter on ultrasonography. There was no evidence of pulmonary metastasis or vascular invasion on thoracic radiography and abdominal ultrasonography, respectively. 18F-FDG PET/CT was performed to identify the characteristics of the adrenal mass and the state of metastasis. One hour after injection of 5.46 MBq/kg 18F-FDG intravenously, the peripheral region of the adrenal mass visually revealed an increased 18F-FDG uptake, which was higher than that of the liver, and the central region of the mass exhibited necrosis. The maximal standardized uptake value (SUV) of the adrenal mass was 3.24; and relative SUV, calculated by dividing the maximal SUV of the adrenal tumor by the mean SUV of the normal liver, was 5.23. Adrenocortical carcinoma was tentatively diagnosed and surgical adrenalectomy was performed. Histopathologic examination of the resected adrenal mass revealed the characteristics of an adrenocortical carcinoma. After adrenalectomy, systolic blood pressure reduced to below 150 mmHg without any medication.

Conclusion

This is the first case report of 18F-FDG PET/CT findings in a dog with suspected adrenocortical carcinoma and may provide valuable diagnostic information for adrenocortical carcinoma in dogs.

ACR Appropriateness Criteria® Adrenal Mass Evaluation: 2021 Update

The appropriate evaluation of adrenal masses is strongly dependent on the clinical circumstances in which it is discovered. Adrenal incidentalomas are masses that are discovered on imaging studies that have been obtained for purposes other than adrenal disease. Although the vast majority of adrenal incidentalomas are benign, further radiological and biochemical evaluation of these lesions is important to arrive at a specific diagnosis. Patients with a history of malignancy or symptoms of excess hormone require different imaging evaluations than patients with incidentalomas. This document reviews imaging approaches to adrenal masses and the various modalities utilized in evaluation of adrenal lesions. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Quantitative accuracy in total-body imaging using the uEXPLORER PET/CT scanner

Absolute quantification of regional tissue concentration of radioactivity in positron emission tomography (PET) is a critical parameter-of-interest across various clinical and research applications and is affected by a complex interplay of factors including scanner calibration, data corrections, and image reconstruction. The emergence of long axial field-of-view (FOV) PET systems widens the dynamic range accessible to PET and creates new opportunities in reducing scan time and radiation dose, delayed or low radioactivity imaging, as well as kinetic modeling of the entire human. However, these imaging regimes impose challenging conditions for accurate quantification due to constraints from image reconstruction, low count conditions, as well as large and rapidly changing radioactivity distribution across a large axial FOV. We comprehensively evaluated the quantitative accuracy of the uEXPLORER total-body scanner in conditions that encompass existing and potential imaging applications (such as dynamic imaging and ultralow-dose imaging) using a set of total-body specific phantom and human measurements. Through these evaluations we demonstrated a relative count rate accuracy of ±3%-4% using the NEMA NU 2-2018 protocol, an axial uniformity spread of ±3% across the central 90% axial FOV, and a 3% activity bias spread from 17 to 474 MBq¹⁸F-FDG in a 210 cm long cylindrical phantom. Region-of-interest quantification spread of 1% was found by simultaneously scanning three NEMA NU 2 image quality phantoms, as well as relatively stable volume-of-interest quantification across 0.2%-100% of total counts through re-sampled datasets. In addition, an activity bias spread of -2% to +1% post-bolus injections in human subjects was found. Larger bias changes during the bolus injection phase in humans indicated the difficulty in providing accurate PET data corrections for complex activity distributions across a large dynamic range. Our results overall indicated that the quantitative performance achieved with the uEXPLORER scanner was uniform across the axial FOV and provided the accuracy necessary to support a wide range of imaging applications.

Evaluation of accuracy for 18 F-FDG positron emission tomography and computed tomography for detection of lymph node metastasis in canine oral malignant melanoma

Tumour stage has been demonstrated to have prognostic significance in canine oral malignant melanoma (OMM). Various evaluation techniques of positron emission tomography/computed tomography (PET/CT) have been reported for staging of head-and-neck tumours in people, but canine-specific data are limited, and reports for CT accuracy have been variable. In this prospective study, the head/neck of client-owned dogs with cytologically or histologically diagnosed OMM were imaged with 18 Fluorine-fluorodeoxyglucose (18 F-FDG) PET/ CT. Bilateral mandibular lymphadenectomy was performed for histopathologic assessment. Two evaluation techniques for CT and PET were applied by four independent observers. CT evaluation utilized both a standardized grading scheme and a subjective clinical interpretation. PET evaluation was first performed solely on 18 F-FDG-uptake in lymph nodes compared to background on a truncated scan excluding the oral cavity. Subsequently, the entire head/neck scan and standardized uptake value (SUV) measurements were available. Receiver operating characteristic analysis was performed with histopathology as gold standard. Twelve dogs completed the study and metastatic OMM was identified in six mandibular lymph nodes from five dogs. Of the CT-interpretation techniques, use of clinical grading performed best (sensitivity = 83% and specificity = 94%). Both PET techniques resulted in 100% sensitivity, but primary tumour site evaluation and use of SUV increased specificity from 78% to 94%. The SUVmax cut-point, 3.3, led to 100% sensitivity and 83% specificity. In this population of dogs, PET appeared to be highly sensitive but at risk of being less specific without use of appropriate parameters and thresholds.

Update on primary bilateral macronodular adrenal hyperplasia (PBMAH)

Primary bilateral macronodular adrenal hyperplasia (PBMAH), characterized by bilateral benign adrenal macronodules (>1 cm) potentially responsible for variable levels of cortisol excess, is a rare and heterogeneous disease. However, its frequency increases due to incidentally diagnosed cases on abdominal imaging carried out for reasons other than suspected adrenal disease. Mostly isolated, it can also be associated with dominantly inherited genetic conditions in rare cases. Considering the bilateral nature of adrenal involvement and the description of familial cases, the search of a genetic predisposition has led to the identification of germline heterozygous inactivating mutations of the putative tumor suppressor gene ARMC5, causing around 25% of the apparent sporadic cases. Rigorous biochemical and imaging assessment are key elements in the management of this challenging disease in terms of diagnosis. Treatment is reserved for symptomatic patients with overt or subclinical Cushing syndrome, and was historically based on bilateral adrenalectomy, which nowadays tends to be replaced by unilateral adrenalectomy or lifelong treatment with cortisol synthesis inhibitors.

The value of 18F-FDG PET-CT and 131I-norcholesterol scintigraphy in the characterization of high-risk adrenal masses

PURPOSE

To assess the value of F-FDG PET-computed tomography (CT) and I-norcholesterol scintigraphy in noninvasive characterization of high-risk adrenal lesions using surgical pathology as the gold standard.

METHODS

We retrospectively reviewed clinical cases referred to the adrenal multidisciplinary team in a tertiary centre over the last 6 years. Inclusion criteria were the presence of indeterminate adrenal lesions and performance of combined imaging with 2-deoxy-2-[fluorine-18] fluoro- D-glucose Positron emission tomography/ computed tomography and I-norcholesterol scans. The accuracy of CT, PET-CT and I-norcholesterol findings was assessed by comparison with the postoperative histopathological outcome.

RESULTS

Sixteen patients fulfilled the inclusion criteria. Ten underwent unilateral adrenalectomy, and six had clinical follow-up. The number of cases categorized as concerning on the basis of unenhanced CT, F-FDG PET-CT and I-norcholesterol was 11, 9 and 2, respectively. The mean diameter of adrenal lesions was 4.5 ± 1.9 cm. Average SUVmax of the FDG-avid adrenal lesions was 5.0 ± 2.0 (range 3.5-9.7). Fourteen adrenal masses showed I-norcholesterol uptake. All adrenal masses turned out to be benign lesions.

CONCLUSION

Conventional CT and FDG PET parameters are not adequately specific for determination of a benign lesion in this selected cohort of high-risk patients. Use of I-norcholesterol in this patient cohort may provide additional value.

Management of adrenocortical carcinoma in Western Australia: a perspective over 14 years

BACKGROUND

Adrenocortical carcinoma is a rare but aggressive form of endocrine neoplasm that confers a poor prognosis. To date, the only Australian data published is from New South Wales. This paper describes our experience in Western Australia with a focus on surgical approach and outcomes.

METHODS

A retrospective study of patients treated for adrenocortical carcinoma in Western Australia over 14 years was performed.

RESULTS

Over the 14-year period, a total of 33 patients underwent surgery for adrenocortical carcinoma. Resection outcomes were superior in an open en bloc approach with an 85% R0 margin (P = 0.007). Local recurrence rates were lowest in an open en bloc approach (11%) compared to laparoscopic (75%). Multivariate analysis showed that an en bloc resection is highly correlated with an R0 resection (P < 0.05) and significantly associated with lower (odds ratio = 0.06) local recurrence (P = 0.009). Higher volume surgeons (>5 cases) had lower operative times and blood loss. Compliance with mitotane was significantly improved with close monitoring of levels. The European Network for the Study of Adrenal Tumours (ENSAT) stage at presentation was most predictive of long-term survival with 100% of stage I patients alive compared to 53% of stage II, 25% of stage III and 17% of stage IV patients at the end of the follow-up period.

CONCLUSION

An open en bloc approach with a low threshold for multi-visceral resection performed by high volume surgeons have improved outcomes in local recurrence, operative times and blood loss.

Metabolic active peritoneal sites affect tumor debulking in ovarian and peritoneal cancers

Rationale and objectives

To evaluate the impact of metabolic parameters in the peritoneal cavity on the likelihood of achieving complete tumor debulking in patients with ovarian and peritoneal cancers.

Materials and methods

Forty-nine patients with ovarian and peritoneal cancers were included, who underwent pre-operative ¹⁸F-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (¹⁸F-FDG PET/CT). The immediate surgical outcome was dichotomized into complete and incomplete tumor debulking. ¹⁸F-FDG PET/CT was qualitatively and quantitatively assessed by scrutinizing 15 anatomical sites for the presence of peritoneal carcinomatosis (PC). Patient-based and site-based diagnostic characteristics were described. Metabolic parameters (SUVmax, metabolic tumor volume and total lesion glycolysis) and the number of ¹⁸F-FDG avid peritoneal sites were evaluated between the two groups. Receiver operating curve (ROC) analysis was performed to determine the optimal cut-off value in predicting incomplete tumor debulking.

Results

Twenty-seven out of the 49 patients had PC and 11 had incomplete debulking. Patient-based and site-based accuracies for detection of PC were 87.8 and 97.6%, respectively. The number of ¹⁸F-FDG avid peritoneal sites was significantly different between complete and incomplete debulking groups (0.6 ± 0.8 versus 2.3 ± 1.7 sites respectively, p = 0.001), and the only independent significant risk factor among other metabolic parameters tested (odd ratio = 2.983, 95% CI 1.104–8.062) for incomplete tumor debulking with an optimal cut-off value of ≥4 (AUC = 0.816).

Conclusion

The number of ¹⁸F-FDG avid peritoneal sites increased the risk of incomplete tumor debulking after surgery and potentially useful in assisting treatment stratification in patients with ovarian and peritoneal cancers.

Adrenal cortical adenoma: current update, imaging features, atypical findings, and mimics

Adrenal adenoma is the most common adrenal lesion. Due to its wide prevalence, adrenal adenomas may demonstrate various imaging features. Thus, it is important to identify typical and atypical imaging features of adrenal adenomas and to be able to differentiate atypical adrenal adenomas from potentially malignant lesions. In this article, we will discuss the diagnostic approach, typical and atypical imaging features of adrenal adenomas, as well as other lesions that mimic adrenal adenomas.

CT and 18F- FDG-PET-CT Findings in Secondary Adrenal Lymphoma with Pathologic Correlation

RATIONALE AND OBJECTIVE

To evaluate computed tomography (CT) and positron emission tomography-computed tomography (PET-CT) imaging manifestations of lymphomas secondarily involving the adrenal gland.

MATERIALS AND METHODS

Seven patients (Five men, two women; median age [range], 66 years [34-75 years]) with pathologically proven adrenal lymphoma were assessed retrospectively. Clinical findings, prior history of lymphoproliferative malignancy, CT (n = 7) and fludeoxyglucose positron emission tomography-computed tomography (¹⁸F-FDG-PET-CT) (n = 6) features were analyzed.

RESULTS

Six cases were diffuse large B-cell lymphoma, and one case was peripheral T-cell lymphoma. The longest diameter of the lesions ranged from 3.2 to 6.6 cm (median 4.3 cm). Six lesions were well-defined and one lesion was ill-defined. In five cases, an adreniform shape was preserved. No lesions contained fat, calcification or hemorrhage. Two lesions had necrosis on CT. Median (range) unenhanced CT density of six lesions was 31.8 (29.2-35.2) Hounsfield units. Following administration of IV contrast media (n = 6), three lesions enhanced homogenously whereas three enhanced heterogeneously. The median increase in attenuation was 35.1 Hounsfield units. Two patients had 15-minute delayed CT and they both demonstrated limited wash-out consistent with nonadenoma. Six patients had fludeoxyglucose positron emission tomography-computed tomography(^18-F-FDG-PET-CT) and all lesions were fludeoxyglucose (FDG) avid with a median SUV_max of 18.6 (range: 10.3-49.2).

CONCLUSION

Secondary adrenal lymphomas usually manifest as, large (>3 cm), well-defined, homogenously or slightly heterogeneously enhancing masses on CT with preserved adreniform shape. These lesions tend to show limited wash-out and high fludeoxyglucose (FDG) uptake.

Bilateral adrenal abnormalities: imaging review of different entities

Bilateral adrenal abnormalities are not infrequently encountered during routine daily radiology practice. The differential diagnoses of bilateral adrenal abnormalities include neoplastic and non-neoplastic entities. The bilateral adrenal tumors include metastasis, lymphoma, neuroblastoma, pheochromocytoma, adenoma, and myelolipoma. Non-neoplastic bilateral adrenal masses include infectious processes and haematomas. There are different diffuse bilateral adrenal changes such as adrenal atrophy, adrenal enlargement, adrenal calcifications, and altered adrenal enhancement. In this pictorial review article, we will discuss the imaging features of these entities with emphasis on their clinical implications.

Characterization of adrenocortical tumors by 18F-FDG PET/CT: Does steroid hormone hypersecretion status modify the uptake pattern?

BACKGROUND

adrenal tumor-to-liver uptake value (Tmx:Lmx) on ¹⁸F-FDG PET/CT is an accurate and reproducible PET parameter in the distinction between benign and malignant adrenal masses. The potential impact of steroid hormone secretion on ¹⁸F-FDG uptake is still debatable. The aim of this study was to evaluate this relationship.

METHODS

2010-2015: 73 patients who underwent adrenalectomy for adrenocortical tumors [49 secreting/(SA) and 24 non-secreting/(NSA)] were retrospectively included in the study. Fourteen were malignant. All patients underwent hormonal evaluation, functional and anatomical imaging, Weiss scoring and Ki 67 evaluation.

RESULTS

malignant tumors exhibit higher SUVmax than benign tumors (median 7.75 vs 3.06 respectively, p < 0.001) and Tmx:Lmx was 2.7 vs 1.17 for benign tumors, p < 0.001. Tmx:Lmx was positively correlated to Weiss score (p < 0.001). No significant difference was observed for Tmx:Lmx between SA and NSA overall (p = 0.851), regardless of the subgroup of tumors analyzed. Tmx:Lmx was not correlated to tumor size (p < 0.508) or 24 h free urinary cortisol level (p < 0.522).

CONCLUSIONS

no correlation was observed between Tmx:Lmx and hormonal status, however the correlation between ratio, malignancy and Weiss score confirm the utility of ¹⁸F-FDG PET/CT for the differentiation of benign from malignant adrenal lesions, irrespective of the hormone secretory status of the tumor. ¹⁸F-FDG PET/CT is a useful biomarker in the diagnosis of adrenal tumors, regardless of the secretion status.

Diagnostic accuracy of 18F-FDG PET or PET/CT for the characterization of adrenal masses: a systematic review and meta-analysis

OBJECTIVE

We aimed to explore the role of the diagnostic accuracy of ¹⁸F fluodeoxyglucose PET (¹⁸F-FDG PET) or PET/CT for characterization of adrenal lesions through a systematic review and meta-analysis.

METHODS

The MEDLINE, EMBASE, and Cochrane Library database, from the earliest available date of indexing through 30 April 2017, were searched for studies evaluating the diagnostic performance of ¹⁸F-FDG PET or PET/CT for characterization of adrenal lesions. We determined the sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LR + and LR-), and constructed summary receiver operating characteristic curves.

RESULTS

Across 29 studies (2421 patients), the pooled sensitivity for ¹⁸F-FDG PET or PET/CT was 0.91 [95% CI (0.88-0.94)] with heterogeneity (χ² = 141.8, p = 0.00) and a pooled specificity of 0.91 [95% CI (0.87-0.93)] with heterogeneity (χ² = 113.7, p = 0.00). Likelihood ratio (LR) syntheses gave an overall positive likelihood ratio (LR+) of 9.9 [95% CI (7.1-13.7)] and negative likelihood ratio (LR-) of 0.09 [95% CI (0.07-0.13)]. The pooled diagnostic odds ratio was 105 [95% CI (63-176)]. In metaregression analysis, study design, publication year, study location (western vs others), interpretation criteria of PET or PET/CT images, quantification of PET or PET/CT [SUV_max (maximum standardized uptake value) vs SUV (standardized uptake value) ratio], patient group, and analysis method (patient-based vs lesion-based) were the sources of the study heterogeneity. However, in multivariate metaregression, no definite variable was the source of the study heterogeneity.

CONCLUSION

¹⁸F-FDG PET or PET/CT demonstrated good sensitivity and specificity for the characterization of adrenal masses. At present, the literature regarding the use of ¹⁸F-FDG PET or PET/CT for the characterization of adrenal masses remains still limited; thus, further large multicenter studies would be necessary to substantiate the diagnostic accuracy of ¹⁸F-FDG PET or PET/CT characterization of adrenal masses. Advances in knowledge: ¹⁸F- FDG PET or PET/CT showed good sensitivity and specificity for the characterization of adrenal masses and could provide additional information for that purpose.

Evidence-based management of incidental focal uptake of fluorodeoxyglucose on PET-CT

Focal incidental uptake, with or without CT abnormalities, is a common finding on fluorodeoxyglucose PET/CT and evidence-based management for this type of uptake is lacking. This article reviews the evidence on focal incidental uptake including the incidence of malignancy, differential diagnosis and imaging criteria which can be used to further characterize it. The article focusses on PET rather than CT criteria. The strength of the evidence base is highly variable ranging from systematic reviews and meta-analyses to a virtual absence of evidence. Caution needs to be used when using standardized uptake values (SUVs) reported in other studies due to interpatient and institution observed variation in SUVs. There is sufficient evidence to permit specific suggestions on how to interpret the foci and recommend further management in the: pituitary (investigate when SUVmax >4.1), thyroid (investigate all), breast (investigate all), lung parenchyma (if focus of fluorodeoxyglucose without a CT nodule, no further investigations), colon (investigate all foci with SUVmax >5.9, urgently if SUVmax >11.4), adrenals (criteria depend on if patient has cancer) and prostate gland (investigate in males aged >50 years or >40 years if peripheral uptake or patient has other risk factors). There is some evidence to guide further management for the parotid gland, naso-orophaynx, oesophagus, pancreas, uterus and ovaries. There is insufficient evidence to guide management for the liver, spleen, kidneys, gallbladder, testis and bone, for these organs patient characteristics and other guidelines will likely be of more use in determining further management.

Role of PET/CT in the Clinical Management of Locally Advanced Pancreatic Cancer

Aim

To evaluate the role of 18F-fluorodeoxyglucose (FDG) PET/CT in: a) the selection of patients with locally advanced pancreatic cancer for helical tomotherapy with concurrent chemotherapy (HTT-ChT); b) monitoring HTT-ChT treatment efficacy in comparison with contrast-enhanced CT (c.e.CT).

Methods

Forty-two consecutive patients with unresectable locally advanced pancreatic cancer referred for HTT-ChT were enrolled in the study. All patients were pretreated with induction ChT. Before the beginning of HTT-ChT treatment patients underwent diagnostic c.e.CT (CT0) and FDG PET/CT (PET/CT0) for staging. After staging, patients received HTT-ChT. Three months after the end of HTT-ChT a control c.e.CT (CT1) was done. FDG PET/CT (PET/CT1) was repeated only in patients with positive PET/CT0. PET/CT1 and CT1 were compared with baseline imaging results to assess treatment efficacy.

Results

In 31/42 cases (74%) PET/CT0 documented pathological uptake in pancreatic lesions, while in the remaining 11/42 cases it showed no uptake. In 7/42 (17%) patients, PET/CT0 also detected distant metastases, prompting a change in the therapeutic approach. Compared to PET/CT0, PET/CT1 (n = 18) documented 3 complete metabolic responses, 9 partial metabolic responses, 2 instances of stable metabolic disease, and 4 instances of progressive metabolic disease. In the same group of 18 patients, CT1 showed 0 complete responses, 3 partial responses, 8 instances of stable disease, and 7 instances of progressive disease compared to CT0. Concordance between PET/CT and CT response was seen in 33% of cases. In 50% of cases, PET/CT1 documented a response to therapy that was not evident on CT.

Conclusions

PET/CT influenced the treatment strategy by detecting distant metastases not documented by CT, thus accurately selecting patients for HTT-ChT after induction ChT. In monitoring treatment efficacy, PET/CT can detect a metabolic response to treatment not identified by CT.

Diagnostic performance of unenhanced computed tomography and 18 F-fluorodeoxyglucose positron emission tomography in indeterminate adrenal tumours

OBJECTIVE

Evidence on the diagnostic performance of adrenal imaging is limited. We aimed to assess the diagnostic performance of unenhanced computed tomography (CT) and ¹⁸ F-fluorodeoxyglucose (¹⁸ FDG) positron emission tomography (PET)/CT imaging in a high-risk population for adrenal malignancy using an optimal reference standard.

DESIGN

Retrospective cohort study.

METHODS

Imaging studies of patients with adrenal nodules who underwent adrenal biopsy and/or adrenalectomy between 1994 and 2014 were reviewed and compared to the reference standard of histology. Eighty % of patients presented with known or suspected extra-adrenal malignancy.

RESULTS

Unenhanced abdominal CT was performed in 353 patients with adrenal lesions; median size was 3 (0.7-15) cm and median radiodensity was 33 (-21-78) Hounsfield units (HU). Radiodensity of >10 HU diagnosed malignancy with a sensitivity of 100%, specificity of 33%, positive predictive value (PPV) of 72% and negative predictive value (NPV) of 100%. ¹⁸ FDG-PET/CT was performed in 89 patients; median tumour size was 2.1 (0.7-9.2) cm. Maximum standardized uptake (SUV max) was higher in malignant lesions when compared to benign lesions (median=10 [2.3-29.4] vs 3.7 [1.4-24.5], respectively, P<.0001). Similarly, median SUV max lesion to SUV max liver ratio (ALR) in malignant lesions was higher than in benign lesions (median=3 [0.74-13.4] vs 1.2 [0.5-6.6], respectively, P<.0001). ¹⁸ FDG-PET/CT ALR >1.8 diagnosed malignancy with a sensitivity of 87%, specificity of 84%, PPV of 85% and NPV of 86%.

CONCLUSION

Noncontract CT radiodensity of ≤10 HU excludes malignancy even in a high-risk population. For indeterminate adrenal lesions, given a superior specificity, ¹⁸ FDG-PET/CT could be considered as a second stage imaging study.

PET-CT and PET-MR in urological cancers other than prostate cancer: An update on state of the art

Hybrid positron emission tomography with computed tomography (PET/CT) and magnetic resonance imaging (PET/MRI) have enabled the combination of morphologic and functional imaging with the promise of providing better information in guiding therapy. Further advance has been made in the past decade with the development of newer radiotracers and optimization of the technical aspects. We performed a search in PubMed, Scopus, and Google Scholar for peer-reviewed literature concerning the advances and newer developments in the imaging of nonprostate urologic cancers between 2005 and 2017. This review aims at summarizing the current evidence on PET imaging in nonprostate urologic cancers and their impact on the diagnosis, staging, prognostication, response assessment, and restaging of these malignancies. However, much of the evidence is still in infancy and has not been incorporated into routine management or the practice guidelines of National Comprehensive Cancer Network or European Society for Medical Oncology (ESMO).

Texture analysis of FDG PET/CT for differentiating between FDG-avid benign and metastatic adrenal tumors: efficacy of combining SUV and texture parameters

PURPOSE

To retrospectively investigate the SUV-related and texture parameters individually and in combination for differentiating between F-18-fluorodeoxyglucose (FDG)-avid benign and metastatic adrenal tumors with PET/CT.

METHODS

Thirteen benign adrenal tumors (BATs) and 22 metastatic adrenal tumors (MATs) with a metabolic tumor volume (MTV) > 10.0 cm³ and SUV ≥ 2.5 were included. SUVmax, MTV, total lesion glycolysis, and four textural parameters [entropy, homogeneity, intensity variability (IV), and size-zone variability] were obtained. These parameters were compared between BATs and MATs using Mann-Whitney U test, and the diagnostic performance was evaluated by the area under the curve (AUC) values derived from the receiver operating characteristic analysis. The diagnostic value of combining SUV and texture parameters was examined using a scoring system.

RESULTS

MATs showed significantly higher SUV_max (p = 0.004), entropy (p = 0.013), IV (p = 0.006), and lower homogeneity (p = 0.019) than BATs. The accuracies for diagnosing MATs were 82.9, 82.9, 85.7, and 71.4% for SUV_max, entropy, IV, and homogeneity, respectively. No significant differences in AUC were found among these parameters (p > 0.05 each). When each parameter was scored as 0 (negative for malignancy) and 1 (positive for malignancy) according to each threshold criterion and the four parameter summed scores 0, 1, and 2 were defined as benignity and 3 and 4 as malignancy, the sensitivity and specificity and accuracy to predict MATs were 100% (22/22), 84.6% (11/13), and 94.3% (33/35), respectively, with 0.97 of the AUC.

CONCLUSION

The combined use of SUV_max and texture parameters has a potential to significantly increase the diagnostic performance to differentiate between large FDG-avid BATs and MATs.

Adrenal Imaging

Cross-sectional imaging can make a specific diagnosis in lesions, such as myelolipomas, cysts, and hemorrhage, and is often sufficient to distinguish benign from malignant adrenal processes. CT and MRI are useful studies to identify pheochromocytomas and cortisol-secreting or androgen-secreting tumors. In patients with primary aldosteronism, adrenal venous sampling remains the most accurate localizing study and should be performed in all patients older than 35. Radiolabeled isotope studies serve as second-line diagnostic tests for malignant adrenal tumors, primary or metastatic, as well as for pheochromocytoma. Nuclear imaging studies should follow a robust hormonal diagnosis and be correlated with findings on cross-sectional imaging.

A case of long-term survival after surgical resection for solitary adrenal recurrence of esophageal squamous carcinoma

Background

Esophageal carcinomas are highly malignant tumors with a high frequency of lymph node and distant organ metastasis. Treatment for recurrent tumors is generally decided on an individual basis. Although multidisciplinary treatments involving chemotherapy, surgical resection, and radiation are performed, the prognosis remains poor. Here, we report a case of prolonged recurrence-free survival (38 months) after esophageal carcinoma surgery and subsequent laparoscopic adrenalectomy for right adrenal metastasis.

Case presentation

An 83-year-old man was diagnosed with type 3 esophageal squamous cell carcinoma (T3N1M0, cStage IIIA, UICC-7), spreading from the lower thoracic esophagus to the abdominal esophagus. He underwent thoracoscopic esophagectomy with a two-field lymph node dissection followed by substernal gastric tube reconstruction. The final diagnosis was moderately differentiated squamous cell carcinoma (T3N2M0, fStage IIIB). Adjuvant chemotherapy was not administered because of the advanced age and postoperative condition of the patient. Computed tomography (CT) at 14 months postoperatively showed a mass with a 2-cm diameter at the right adrenal gland. Positron emission tomography (PET)/CT revealed a high fluorodeoxyglucose (FDG) uptake in the mass. It was suspected that the mass was a metastatic lesion secondary to the primary esophageal carcinoma. No metastases to lymph nodes or other distant organs were identified. The patient underwent laparoscopic right adrenalectomy. The histopathological examination revealed moderately differentiated squamous cell carcinoma, suggesting metastasis from the primary esophageal carcinoma. He has survived without recurrence for 38 months since laparoscopic adrenalectomy to remove the right adrenal metastastic mass after the esophageal carcinoma surgery.

Conclusions

We describe a very elderly male who survived laparoadrenalectomy for right adrenal metastasis following esophageal cancer surgery without recurrence for 38 months postoperatively. Therefore, surgical resection might be an option for solitary adrenal recurrence.

C-arm cone-beam computed tomography with stereotactic needle guidance for percutaneous adrenal biopsy: initial experience

Background Metastasis to the adrenal glands is frequent in patients with various cancers and adrenal gland biopsy is routinely performed using ultrasound or computed tomographic (CT) guidance. However, this method is technically challenging, especially in the case of small masses. Purpose To determine whether the new real-time stereotactic needle guidance technique C-arm cone-beam CT (CBCT) allows safe and accurate biopsy of adrenal gland masses, especially those in hard-to-reach anatomical locations. Material and Methods CBCT guidance was used to perform 60 stereotactic biopsy procedures of lesions that were inaccessible with ultrasound or CT guidance. The needle path was carefully planned and calculated on the CBCT virtual navigation guidance system, which acquired 3D CT-like cross-sectional images. The adrenal biopsy procedures were performed with fluoroscopic feedback. Technical success rate, sensitivity, specificity, accuracy, and complications were investigated. Results The technical success rate of adrenal biopsy under CBCT virtual navigation was 100%, with a mean total procedure time of 14.6 ± 3.6 min. Of the 60 lesions, 46 were malignant, 11 were benign, and three were non-diagnostic. The three non-diagnostic lesions proved to be malignant. Thus, the sensitivity, specificity, and accuracy were 93.8%, 100%, and 95.0%, respectively. Minor bleeding occurred in two (3.3%) cases. Conclusion CBCT guidance allows safe and accurate biopsy of adrenal gland masses and may be especially useful for hard-to-reach anatomical locations.

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.

Diagnostic performance of 18-F-FDG-PET-CT in adrenal lesions using histopathology as reference standard

PURPOSE

To determine the diagnostic performance of PET-CT in differentiating benign and malignant adrenal lesions when evaluating PET parameters individually as well as in combination with CT parameters, using histopathology as the reference standard.

METHODS

¹⁸F-FDG-PET-CT scans of patients undertaken within 6 months prior to pathologic evaluation of their adrenal lesion(s) were evaluated. PET assessments consisted individually of maximum standardized uptake value of the adrenal lesion (A-SUV_max) and its ("normalized") ratio to the liver (R-SUV_max). The diagnostic performances of these two PET parameters were also assessed when combined with the Hounsfield density from the non-contrast CT component of the PET-CT (A-HU). Diagnostic performance was assessed by area under the curve (AUC) of the receiver operating characteristics. Multiple logistic regression analysis was used to evaluate the individual and combined parameters.

RESULTS

The study cohort consisted of 61 adrenal lesions (59 patients). Malignant lesions (n = 52) had significantly higher median PET and CT parameters than benign lesions: A-SUV_max (11.4 vs. 6.1), R-SUV_max (3.3 vs. 1.7), and A-HU (37 vs. 24) [all p < 0.023]. AUC for the PET parameters individually was almost identical: 0.75 for A-SUV_max and 0.74 for R-SUV_max. On univariate analysis, thresholds of A-SUV_max >3.47 and R-SUV_max >0.83 yielded maximum accuracy (both 87%). The combination of these PET parameters individually with A-HU improved both AUC and accuracy (0.81% and 93%, respectively).

CONCLUSIONS

The individual PET parameters A-SUV_max and R-SUV_max have similar diagnostic performance for differentiating malignant and benign adrenal lesions; their performance and accuracy improve when combined with the CT component (A-HU).

Contemporary imaging of incidentally discovered adrenal masses

Adrenal lesions are routinely encountered incidentally in clinical practice. Although most of these lesions are benign, malignancy needs to be excluded. Therefore, the initial clinical workup is to exclude aggressive characteristics suggesting malignancy and to identify characteristics predictive of the most common benign lesion, an adrenal adenoma. Predicting a benign adenoma using a variety of imaging modalities has been widely studied using unenhanced computed tomography (CT), contrast enhanced CT, and magnetic resonance (MR) imaging. This review article describes the currently used imaging protocols and clinical interpretation criteria of common adrenal lesions. An adenoma can be predicted if a homogenous soft tissue adrenal mass demonstrates low attenuation (upper threshold value of 10 Hounsfield Units) on unenhanced CT, demonstrates an absolute enhancement washout of ≥ 60% and/or relative enhancement washout of ≥ 40% on adrenal washout contrast enhanced CT, or demonstrates signal loss in opposed-phased MR imaging. If an adrenal adenoma cannot be predicted based upon these criteria, the lesion should be evaluated for other imaging characteristics that suggest a specific pathology, such as an adrenal cyst or myelolipoma. Although nonspecific and with limitations, 18F-fluorodeoxyglucose (FDG) PET/CT has a potential role for differentiating benign from malignant lesions based upon the amount of radiopharmaceutical uptake with malignant lesions generally having greater uptake. If clinical and/or hormonal screening suggests a pheochromocytoma, consideration can be given to 18F-dihydroxyphenylalanine (DOPA) or 123I-metaiodobenzylguanidine (MIBG) in addition to CT and MR. Finally, this review proposes a diagnostic work-up strategy for routine use in clinical practice.

Fat-Containing Hypermetabolic Masses on FDG PET/CT: A Spectrum of Benign and Malignant Conditions

OBJECTIVE

This article focuses on identifying the imaging appearances of hypermetabolic fatty masses and masslike lesions on PET/CT and understanding the diagnostic challenges radiologists may face while interpreting findings of these lesions on PET/CT. This article provides an approach to aid in the diagnosis of these lesions and the appropriate management of patients.

CONCLUSION

Both malignant and benign fat-containing masses and masslike lesions can show hypermetabolic activity on PET/CT. Although the differential diagnosis is broad, clinical history, anatomic location, and knowledge of anatomic variants and imaging features can help radiologists avoid misinterpretation of benign fatty lesions as malignancy.

Review of primary extra-adrenal myelolipoma of the thorax

Extra-adrenal myelolipoma happens in adrenal glands, and the thoracic location is extremely unusual. This is the first study involving 36 of patients with thoracic myelolipoma of English literature by investigating the clinical data, pathologic findings, radiological manifestation, and treatment strategy of all patients. Imageologic diagnosis including computed tomography, magnetic resonance imaging, and positron emission tomography/computed tomography scans is useful to identify the feature of extra-adrenal myelolipoma. Pathologic analysis is an effective method to clarify the diagnosis. In view of the potential progressive enlargement of the lesion, most myelolipomas are removed by surgery, and this operation has frequently been accomplished by using video-assisted thoracic surgery.

Adrenal imaging for adenoma characterization: imaging features, diagnostic accuracies and differential diagnoses

Adrenocortical adenoma is the most common adrenal tumour. This lesion is frequently encountered on cross-sectional imaging that has been performed for unrelated reasons. Adrenal adenoma manifests various imaging features on CT, MRI and positron emission tomography/CT. The learning objectives of this review are to describe the imaging findings of adrenocortical adenoma, to compare the sensitivities of different imaging modalities for adenoma characterization and to introduce differential diagnoses.

High 18F-FDG uptake in PMAH correlated with normal expression of Glut1, HK1, HK2, and HK3

BACKGROUND

Primary macronodular adrenal hyperplasia (PMAH) is a rare cause of Cushing's syndrome, characterized by functioning adrenal macronodules and variable cortisol production. Recently, we demonstrated a high 18F-FDG uptake in PMAH, an unexpected finding for a benign disorder.

PURPOSE

To investigate whether there is a correlation between 18F-FDG high uptake and the expression levels of the glycolytic pathway components GLUT1, HK1, HK2, and HK3 in PMAH.

MATERIAL AND METHODS

We selected 12 patients undergoing surgery for PMAH who had preoperatively undergone 18F-FDG PET/CT. mRNA and protein expression of the selected genes were evaluated in the adrenal nodules from patients who underwent surgery through quantitative RT-PCR and by immunohistochemistry, respectively.

RESULTS

SUVmax in PMAH was in the range of 3.3-8.9 and the adrenal size was in the range of 3.5-15 cm. A strong correlation between 18F-FDG uptake and largest adrenal diameter was observed in patients with PMAH. However, no correlation between 18F-FDG uptake and GLUT1, HK1, HK2, HK3 mRNA, and protein expression was observed.

CONCLUSION

High 18F-FDG uptake is observed in the majority of PMAH cases. However, 18F-FDG uptake in PMAH is independent of the expression levels of GLUT1, HK1, HK2, and HK3. Further investigation is required to elucidate the molecular mechanisms underlying increased 18F-FDG uptake in PMAH.

Current generation time-of-flight (18)F-FDG PET/CT provides higher SUVs for normal adrenal glands, while maintaining an accurate characterization of benign and malignant glands

OBJECTIVE

Modern PET/CT scanners have significantly improved detectors and fast time-of-flight (TOF) performance and this may improve clinical performance. The aim of this study was to analyze the impact of a current generation TOF PET/CT scanner on standardized uptake values (SUV), lesion-background contrast and characterization of the adrenal glands in patients with suspected lung cancer, in comparison with literature data and commonly used SUV cut-off levels.

METHODS

We included 149 adrenal glands from 88 patients with suspected lung cancer, who underwent (18)F-FDG PET/CT. We measured the SUVmax in the adrenal gland and compared this with liver SUVmean to calculate the adrenal-to-liver ratio (AL ratio). Results were compared with literature derived with older scanners, with SUVmax values of 1.0 and 1.8 for normal glands [1, 2]. Final diagnosis was based on histological proof or follow-up imaging. We proposed cut-off values for optimal separation of benign from malignant glands.

RESULTS

In 127 benign and 22 malignant adrenal glands, SUVmax values were 2.3 ± 0.7 (mean ± SD) and 7.8 ± 3.2 respectively (p < 0.01). Corresponding AL ratios were 1.0 ± 0.3 and 3.5 ± 1.4 respectively (p < 0.01). With a SUVmax cut-off value of 3.7, 96% sensitivity and 96% specificity was reached. An AL ratio cut-off value of 1.8 resulted in 91% sensitivity and 97% specificity. The ability of both SUVmax and AL ratio to separate benign from malignant glands was similar (AUC 0.989 vs. 0.993, p = 0.22).

CONCLUSIONS

Compared with literature based on the previous generation of PET scanners, current generation TOF (18)F-FDG PET/CT imaging provides higher SUVs for benign adrenal glands, while it maintains a highly accurate distinction between benign and malignant glands. Clinical implementation of current generation TOF PET/CT requires not only the use of higher cut-off levels but also visual adaptation by PET readers.

18F-FDG PET/CT in the post-operative monitoring of patients with adrenocortical carcinoma

CONTEXT

The role of (18)F-labeled 2-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET)/computed tomography (CT) in the post-operative monitoring of patients with adrenocortical carcinoma (ACC) is still unclear.

OBJECTIVE

To assess the accuracy of FDG PET/CT to diagnose ACC recurrence in a real world setting.

DESIGN AND METHODS

Retrospective evaluation of data of 57 patients with presumed ACC recurrence at CT scan who underwent FDG PET/CT within a median time of 20 days. We compared the results of either FDG PET/CT or CT with a gold standard confirmation of recurrence (positive histopathology report of removed/biopsied lesions or radiological progression of target lesions at follow-up) to assess their diagnostic performance at different body sites to correctly categorize target lesions. We also assessed whether FDG PET/CT findings may be useful to inform the management strategy.

RESULTS

In 48 patients with confirmed ACC recurrence, we found that FDG PET/CT had lower sensitivity than CT in diagnosing liver and lung recurrences of ACC. FDG PET/CT had higher specificity than CT in categorizing liver lesions. FDG PET/CT had a greater positive likelihood ratio than CT to identify liver and abdominal ACC recurrences. The management strategy was changed based on FDG PET/CT findings in 12 patients (21.1%).

CONCLUSIONS

The greater sensitivity of CT may be partly expected due the specific inclusion criteria of the study; however, the greater specificity of FDG PET/CT was particularly useful in ruling out suspected ACC recurrences found by CT. Thus, use of FDG PET/CT as a second-line test in the post-operative surveillance of ACC patients following CT finding of a potential recurrence may have a significant impact on patient management.

Adrenal Imaging and Intervention

The adrenal glands are a common site for primary benign and malignant tumors and metastatic disease. Computed tomography (CT), MR imaging, and fluorine-18 fluorodeoxyglucose PET combined with CT are the most common imaging modalities used to assess the adrenal glands. There are established morphologic criteria for both CT and MR imaging that can be used to assess whether an adrenal mass is benign or malignant, and whether follow-up, biopsy, or resection should be performed. In the setting of a known primary malignancy, CT, MR imaging, and PET can help differentiate most benign masses from metastasis.

Imaging Features of Various Adrenal Neoplastic Lesions on Radiologic and Nuclear Medicine Imaging

OBJECTIVE

The purpose of this review is to describe the features of diverse adrenal neoplastic lesions on radiologic and nuclear medicine imaging.

CONCLUSION

Various neoplastic lesions with or without malignant potential can occur in the adrenal gland. Knowledge of imaging features of adrenal lesions on radiologic and nuclear medicine imaging will facilitate differential diagnosis and assessment of malignant potential.

The Value of Nonenhanced Single-Source Dual-Energy CT for Differentiating Metastases From Adenoma in Adrenal Glands

RATIONALE AND OBJECTIVES

To evaluate the value of the nonenhanced single-source dual-energy computed tomography (ssDECT) in differentiating metastases from adenomas in adrenal glands.

MATERIALS AND METHODS

This retrospective study was approved by our Institutional Review Board, and written informed consent was waived. One hundred twelve patients (66 men:46 women; mean age, 58 years) with 63 adrenal metastases (AMs) and 64 adrenal adenomas (AAs) underwent a plain dual-energy spectral CT imaging from August 2011 to December 2013 were included. The fat (water) density (DFa [Wa]) from the material decomposition (MD) images and CT number and effective atomic number (eff-Z) from the virtual monochromatic spectral (VMS) image sets were measured for the AMs and AAs. The spectral Hounsfield unit (HU) curve (CT number as a function of photon energy from 40 to 140 keV) was generated, and its slope (K) was calculated. The difference of these parameters between AMs and AAs was statistically compared by the Wilcoxon rank sum test. Receiver operating characteristic curve (ROC) curves were used to compare the diagnostic efficacies of these measures in the identification of AAs and AMs. The distribution of spectral HU curve was analyzed using the chi-square test in terms of its slope K: ascending (K > 0.1), straight (-0.1 ≤ K ≤ 0.1), and descending (K < -0.1).

RESULTS

1) The CT number (medium, range) of metastases (50.47, 29.93 HU at 40 keV and 29.00, 9.36 HU at 140 keV) was significantly higher than that of adenomas (-0.76, 33.04 to 13.73, 18.96 HU) at each energy level from 40 to 140 keV (P < .05). 2) The fat concentration of metastases (-177.37, 296.38 mg/mL) was statistically lower than that of adenomas (126.73, 328.07 mg/mL; P < .05). 3) The eff-Z of metastases (7.76, 0.23) was significantly higher than that of adenomas (7.42, 0.32; P < .05). 4) With CT number of VMS image at 40 keV of 21.78 HU as a threshold, the sensitivity and specificity for differentiating metastases from adenomas was 92.1% and 76.6%, respectively, and the area under the ROC curve was 0.90. 5) The spectral curve types included 3.2% (2 of 63) ascending, 20.6% (13 of 63) straight, and 76.2% (48 of 63) descending for the metastases, whereas the corresponding numbers were 60.9% (39 of 64), 21.9% (14 of 64), and 17.2% (11 of 64) for the adenomas. The difference was statistically significant (X(2) = 56.63; P < .05).

CONCLUSIONS

The nonenhanced ssDECT enables a multiparametric approach to provide an excellent sensitivity for identifying AMs from AAs.

Adrenal incidentalomas: a disease of modern technology offering opportunities for improved patient care

Adrenal incidentalomas (AIs) are found in approximately 4% of patients undergoing abdominal imaging, with peak prevalence in the sixth and seventh decades of life. Detection of AI warrants clinical, biochemical, and radiological evaluation to establish its secretory status and risk of malignancy. Careful review of the lipid content, size, and imaging phenotype of an adrenal mass is needed to evaluate the risk for malignancy. Identification of an AI may be an opportunity to identify an underlying secretory tumor that may have been otherwise unrecognized. A practical approach to investigation and follow-up of AIs is presented in this article.

Metabolic and anatomic characteristics of benign and malignant adrenal masses on positron emission tomography/computed tomography: a review of literature

PET/CT with (18)F-fluorodeoxyglucose (FDG) or using different radiocompounds has proven accuracy for detection of adrenal metastases in patients undergoing cancer staging. It can assist the diagnostic work-up in oncology patients by identifying distant metastases to the adrenal(s) and defining oligometastatic disease that may benefit from targeted intervention. In patients with incidentally discovered adrenal nodules, so-called adrenal "incidentaloma" FDG PET/CT is emerging as a useful test to distinguish benign from malignant etiology. Current published evidence suggests a role for FDG PET/CT in assessing the malignant potential of an adrenal lesion that has been 'indeterminately' categorized with unenhanced CT, adrenal protocol contrast-enhanced CT, or chemical-shift MRI. FDG PET/CT could be used to stratify patients with higher risk of malignancy for surgical intervention, while recommending surveillance for adrenal masses with low malignant potential. There are caveats for interpretation of the metabolic activity of an adrenal nodule on PET/CT that may lead to false-positive and false-negative interpretation. Adrenal lesions represent a wide spectrum of etiologies, and the typical appearances on PET/CT are still being described, therefore our goal was to summarize the current diagnostic strategies for evaluation of adrenal lesions and present metabolic and anatomic appearances of common and uncommon adrenal lesions. In spite of the emerging role of PET/CT to differentiate benign from malignant adrenal mass, especially in difficult cases, it should be emphasized that PET/CT is not needed for most patients and that many diagnostic problems can be resolved by CT and/or MR imaging.

FDG-PET/CT and FLT-PET/CT for differentiating between lipid-poor benign and malignant adrenal tumours

OBJECTIVE

To compare F-18-fluorodeoxyglucose (FDG) and F-18-fluorothymidine (FLT) PET/CT examinations for differentiating between benign and malignant adrenal tumours.

METHODS

Thirty lipid-poor benign and 11 malignant tumours of 40 patients were included. FDG- and FLT-based indices including visual score, maximum standardized uptake value (SUVmax) and FDG adrenal lesion/liver SUVmax (A/L SUVmax) or FLT adrenal lesion/back muscle SUVmax (A/B SUVmax) ratio were compared between benign and malignant tumours using the Mann-Whitney's U or Wilcoxon signed-rank test, and their diagnostic performances were evaluated by means of the area under the curve (AUC) values derived from the receiver operating characteristic analysis.

RESULTS

All indices were significantly higher in malignant than benign tumours on both images (p < 0.05 each). On FDG-PET/CT, the sensitivity, specificity, and accuracy were 91 %, 63 % and 71 % for visual score, 91 %, 67 % and 73 % for SUVmax, and 100 %, 70 % and 78 % for A/L SUVmax ratio, respectively. On FLT-PET/CT, they were 100 %, 97 % and 98 % for visual score, SUVmax and A/B SUVmax ratio, respectively. All FLT indices were significantly higher than those of FDG in AUC (p < 0.05 each).

CONCLUSION

FLT-PET/CT may be superior to FDG-PET/CT in differentiating lipid-poor benign from malignant adrenal tumours because of higher specificity and accuracy.

KEY POINTS

• All FDG indices were significantly higher in malignant than in benign tumours. • All FLT indices were significantly higher in malignant than in benign tumours. • All FLT indices were significantly higher than those of FDG in AUC.

Value of 18-F-FDG PET/CT and CT in the Diagnosis of Indeterminate Adrenal Masses

The purpose of this paper was to study the value of 18-FDG PET/CT and reassess the value of CT for the characterization of indeterminate adrenal masses. 66 patients with 67 indeterminate adrenal masses were included in our study. CT/MRI images and 18F-FDG PET/CT data were evaluated blindly for tumor morphology, enhancement features, apparent diffusion coefficient values, maximum standardized uptake values, and adrenal-to-liver maxSUV ratio. The study population comprised pathologically confirmed 16 adenomas, 19 metastases, and 32 adrenocortical carcinomas. Macroscopic fat was observed in 62.5% of the atypical adenomas at CT but not in malignant masses. On 18F-FDG PET/CT, SUVmax and adrenal-to-liver maxSUV ratio were significantly lower in adenomas than in malignant tumors. An SUVmax value of less than 3.7 or an adrenal-to-liver maxSUV ratio of less than 1.29 is highly predictive of benignity.