Adrenal Gland Scintigraphy

Evaluation of standardized uptake value on 131I-6β-iodomethyl-19-norcholesterol scintigraphy for diagnosis of primary aldosteronism and correspondence with adrenal venous sampling

PURPOSE

Adrenal venous sampling (AVS) is a reliable method for lateralization of adrenal hormone secretion, which is important for discriminating between aldosterone-producing adenoma and bilateral adrenal hyperplasia, both of which cause primary aldosteronism (PA). The aim of this study was to evaluate the diagnostic accuracy of the maximum and mean standardized uptake values (SUV_max and SUV_mean, respectively) of ¹³¹I-6β-iodomethyl-19-norcholesterol (NP-59) single-photon emission computed tomography (SPECT) for PA and its correspondence with AVS.

METHODS

Adrenal NP-59 scintigraphy was performed in 14 patients with suspected PA, and AVS was also performed in 7 of them. SUV_max and SUV_mean of the adrenal lesions on the dominant side and their ratios to the values on the non-dominant side (SUVR_max and SUVR_mean, respectively) were calculated on SPECT images using ordered-subset conjugate gradient minimization (OSCGM) and three-dimensional ordered-subset expectation maximization (3D-OSEM) reconstruction algorithms.

RESULTS

SUV_max and SUV_mean on NP-59 SPECT images were significantly higher for aldosterone-producing adenoma than for bilateral adrenal hyperplasia or non-functioning adenoma and slightly superior to SUVR_max and SUVR_mean (P = 0.0475 and P = 0.0447 vs. P = 0.124 and P = 0.132, respectively, with OSCGM). The respective areas under the receiver-operating characteristic curve for SUV and SUVR were 0.933 and 0.725 with OSCGM and 0.844 and 0.750 with 3D-OSEM, while SUV_max and SUVR_max had exactly the same diagnostic accuracy as SUV_mean and SUVR_mean. SUV and SUVR were associated with the diagnostic features on AVS and consistent with lateralization by AVS in most patients.

CONCLUSION

In this study, SUV on NP-59 SPECT helped in the diagnosis of PA and was consistent with the results of AVS in nearly all cases.

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

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

ACTH-Independent Cushing’s Syndrome Caused by an Ectopic Adrenocortical Adenoma in the Renal Hilum

We report a rare case of Cushing’s syndrome induced by an ectopic adrenocortical adenoma. A 57-year-old woman was diagnosed with adrenocorticotropic hormone (ACTH)-independent Cushing’s syndrome based on clinical manifestation and laboratory information. She was found to have a mass in the left renal hilum via contrast-enhanced computed tomography (CT). The mass was negative, as seen in somatostatin receptor imaging with ^99mTc-hydrazinonicotinyl-Tyr3-octreotide (HYNIC-TOC), and showed mild fluorodeoxyglucose (FDG) activity via positron emission tomography (PET)/CT. The results of adrenal venous sampling suggested a left-side adrenal origin of hypercortisolism, possibly secreted by the mass in the renal hilum. Histopathology after surgical resection of the mass confirmed an ectopic adrenocortical adenoma, which was responsible for the patient’s Cushing’s syndrome. During the 8-month follow-up after surgery, no recurrence of Cushing’s syndrome was found.

Integration of molecular imaging in the personalized approach of patients with adrenal masses

Adrenal masses are a frequent finding in clinical practice. Many of them are incidentally discovered with a prevalence of 4% in patients undergoing abdominal anatomic imaging and require a differential diagnosis. Biochemical tests, evaluating hormonal production of both adrenal cortex and medulla (in particular, mineralocorticoids, glucocorticoids and catecholamines), have a primary importance in distinguishing functional or non-functional lesions. Conventional imaging techniques, in particular computerized tomography (CT) and magnetic resonance imaging (MRI), are required to differentiate between benign and malignant lesions according to their appearance (size stability, contrast enhanced CT and/or chemical shift on MRI). In selected patients, functional imaging is a non-invasive tool able to explore the metabolic pathways involved thus providing additional diagnostic information. Several single photon emission tomography (SPET) and positron emission tomography (PET) radiopharmaceuticals have been developed and are available, each of them suitable for studying specific pathological conditions. In functional masses causing hypersecreting diseases (mainly adrenal hypercortisolism, primary hyperaldosteronism and pheochromocytoma), functional imaging can lateralize the involvement and guide the therapeutic strategy in both unilateral and bilateral lesions. In non-functioning adrenal masses with inconclusive imaging findings at CT/MR, [¹⁸F]-FDG evaluation of tumor metabolism can be helpful to characterize them by distinguishing between benign nodules and primary malignant adrenal disease (mainly adrenocortical carcinoma), thus modulating the surgical approach. In oncologic patients, [¹⁸F]-FDG uptake can differentiate between benign nodule and adrenal metastasis from extra-adrenal primary malignancies.

Optoacoustic imaging in endocrinology and metabolism

Imaging is an essential tool in research, diagnostics and the management of endocrine disorders. Ultrasonography, nuclear medicine techniques, MRI, CT and optical methods are already used for applications in endocrinology. Optoacoustic imaging, also termed photoacoustic imaging, is emerging as a method for visualizing endocrine physiology and disease at different scales of detail: microscopic, mesoscopic and macroscopic. Optoacoustic contrast arises from endogenous light absorbers, such as oxygenated and deoxygenated haemoglobin, lipids and water, or exogenous contrast agents, and reveals tissue vasculature, perfusion, oxygenation, metabolic activity and inflammation. The development of high-performance optoacoustic scanners for use in humans has given rise to a variety of clinical investigations, which complement the use of the technology in preclinical research. Here, we review key progress with optoacoustic imaging technology as it relates to applications in endocrinology; for example, to visualize thyroid morphology and function, and the microvasculature in diabetes mellitus or adipose tissue metabolism, with particular focus on multispectral optoacoustic tomography and raster-scan optoacoustic mesoscopy. We explain the merits of optoacoustic microscopy and focus on mid-infrared optoacoustic microscopy, which enables label-free imaging of metabolites in cells and tissues. We showcase current optoacoustic applications within endocrinology and discuss the potential of these technologies to advance research and clinical practice.

Feasibility of Iodine-131 6β-Methyl-Iodo-19 Norcholesterol (NP-59) Scintigraphy to Complement Adrenal Venous Sampling in Management of Primary Aldosteronism: A Case Series

Purpose

Primary aldosteronism (PA) is mainly comprised of aldosterone-producing adenoma and bilateral idiopathic adrenal hyperplasia. Current guidelines recommend adrenal venous sampling (AVS) as a gold standard method to classify the subtypes. However, because of technical challenges in AVS including invasiveness of AVS and a wide range of success rate for cannulation, it is not uncommon that appropriate decisions could not be made depending on AVS. The aim of this study is to elucidate the proper role of I‑131‑6β‑iodomethyl‑norcholesterol (NP-59) scintigraphy in management of PA.

Patients and Methods

Between January 2009 and October 2018, patients with PA were retrospectively reviewed for the study. Five patients were included in the study who had NP-59 scintigraphy with non-conclusive AVS results or without AVS. We described the clinical outcome of patients in whom clinical decisions were made according to NP-59 scintigraphy results.

Results

Patients in the presenting cases were diagnosed for PA. AVS, the most reliable test to identify unilateral APA, were not applicable because of hypersensitivity to contrast dye (patient 1), and use of antiplatelet agents after acute cerebral infarction (patient 2). NP-59 scintigraphy was performed in patients 3 and 4 whose result of AVS and CT scan were inconsistent. In patient 5, who had bilateral adrenal adenomas (two in the left and one in the right adrenal gland), both unsuccessful catheterization and coexistence of cortisol overproduction made AVS results unreliable.

Conclusion

Based on clinical outcomes of these case series, it is noticeable that NP-59 scintigraphy could play a substantial role in management of PA in selected cases.

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.

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.

Application of adrenal maximum standardized uptake value to 131I-6β-iodomethyl-19-norcholesterol SPECT/CT for characterizing unilateral hyperfunctioning adrenocortical masses

PURPOSE

To evaluate the maximum standardized uptake value (SUVmax) by ¹³¹I-6β-iodomethyl-19-norcholesterol (NP-59) single-photon emission computed tomography (SPECT)/computed tomography (CT) for characterizing unilateral hyperfunctioning adrenocortical masses.

METHODS

Ten patients underwent NP-59 SPECT/CT to evaluate the following unilateral adrenocortical hyperfuncting masses: three with Cushing's syndrome (CS), three with subclinical CS, and four with primary aldosteronism (PA). Visual and quantitative or semiquantitative analyses (noncontrast CT HU [Hounsfield units], lesion SUVmax, contralateral SUVmax, and SUVmax ratio [lesion SUVmax/contralateral adrenal SUVmax]) were performed. The Mann-Whitney U test or Chi-squared test was used appropriately to assess differences between quantitative variables or compare categorical data. Diagnostic performance was evaluated by receiver operating characteristic (ROC) curve analysis.

RESULTS

All adrenal tumors were diagnosed as cortical adenomas. On visual analysis, unilateral uptake was noted in three patients with CS and one patient with subclinical CS, whereas bilateral uptake was noted in four patients with PA and two patients with subclinical CS (p = 0.046). No significant difference was observed in CT HU (p = 0.055). The lesion SUVmax and SUVmax ratio were significantly higher and the contralateral SUVmax was significantly lower in six patients with CS than in four patients with PA (each, p < 0.05). The area under the ROC curve and accuracy for differentiating between CS and PA were, respectively, 0.92 and 90.0 % for the lesion SUVmax, 1.00 and 100 % for the contralateral SUVmax, and 0.92 and 90.0 % for the SUVmax ratio.

CONCLUSIONS

Quantitative or semiquantitative analysis using the adrenal SUVmax in adrenocortical NP-59 SPECT/CT has potential for characterizing unilateral hyperfunctioning adrenocortical masses.

Adrenal Artery Ablation for the Treatment of Hypercortisolism Based on Adrenal Venous Sampling: A Potential Therapeutic Strategy

AIM

Hypercortisolism is characterized by metabolic disorders and high mortality rates. Adrenalectomy and medical therapies are considered major treatment options. However, some patients, especially young patients, are strongly against undergoing surgery in case of secondary hypocortisolism or relapses that require replacement supplements or pharmacological interventions. In such cases, alternative therapies are needed to treat hypercortisolism.

METHODS

We report a 27-year-old Chinese female with adrenal cortisol-producing adenoma. The patient's circadian rhythm and concentrations of cortisol were abnormal, accompanying with an increased 24-hour urinary cortisol level. Computed tomography (CT) revealed a nodular soft-tissue mass in the right adrenal gland.

RESULTS

Cortisol hypersecretion from the right adrenal gland was verified by adrenal venous sampling (AVS). Adrenal artery ablation was performed. After ablation, long-term follow-up showed that the patient's symptoms subsided and abnormal laboratory test results returned to normal without pharmacological treatment.

CONCLUSION

AVS might be a promising method to aid the diagnosis of cortisol-producing adenoma. Adrenal artery ablation is minimally invasive and may be useful for the treatment of adrenal adenoma or nodular diseases, especially in patients who cannot undergo surgery.

Clinical Usefulness of 99mTc-HYNIC-TOC and 131I-MIBG Scintigraphy in the Evaluation of Adrenal Tumors

Disorders and morphological abnormalities affecting the adrenal gland, could lead to profound clinical consequences, owing to its biochemical structure-activity and morphological characteristics.

The recent focus on theranostic approach has led to a need for tumors characterization and early diagnosis at the molecular level. Many radiotracers have been developed with specific imaging characteristics for the adrenal tumors, by exploiting different physiological mechanisms of uptake and metabolism.

The aim of present study is to provide a prospective confirmation of 131I-MIBG and 99mTc-HYNIC-TOC scintigraphy, for the evaluation of patients with known or suspected tumors of the adrenal region.

The research is designed as a cross-sectional observational study of the clinical correlates and diagnostic accuracy of radionuclide-based imaging methods in relation to in vitro analysis, clinical manifestations and morphological characteristics of these tumors. Furthermore, the present study also evaluates the usefulness and the clinical impact of each radiopharmaceutical for the detection and management of tumors, and functional imaging modality as well.

Visual scintigraphic appearance of an increased focal tracer uptake in the suspected tumor site revealed that 99mTc-HYNIC-TOC is highly sensitive and reliable tumor-seeking radiotracer for adrenal tumors, but does not distinguish between adenoma and pheochromocytoma, and the existence of hormone secreting adrenocortical tumor cells. However, 131IMIBG scintigraphy is highly sensitive and specific method only in differentiating catecholamine-secreting adrenal tumors.

Clinical significance of this research is in the accurate localization of adrenal tumors, and is of paramount importance for an algorithmic diagnostic approach and management, and provide the rationale to different therapeutic possibilities.

Adrenal venous sampling in patients with ACTH-independent hypercortisolism

PURPOSE

To study the usefulness of adrenal venous sampling (AVS) in distinguishing unilateral from bilateral cortisol production in patients with ACTH-independent hypercortisolism and bilateral adrenal lesions, or morphologically normal adrenal glands.

METHODS

A retrospective analysis of ten consecutive patients with ACTH-independent hypercortisolism who underwent AVS at our institution between 2009 and 2017. Unilateral dominant cortisol production was defined as a side-to-side cortisol/aldosterone lateralization ratio >2.

RESULTS

Four of ten patients had overt Cushing's syndrome. Of these, two had bilateral adrenal lesions on computed tomography and two had normal adrenal glands. One of the two patients with bilateral adrenal lesions had, based on the AVS, a unilateral dominant cortisol production. Following unilateral adrenalectomy the patient developed adrenal insufficiency. The other three patients were considered to have bilateral cortisol production and underwent bilateral adrenalectomy. Six patients had a mild autonomous cortisol secretion and bilateral adrenal lesions. Based on AVS, one patient was considered to have unilateral dominant cortisol production, underwent unilateral adrenalectomy and developed transient adrenal insufficiency postoperatively.

CONCLUSIONS

AVS may contribute to appropriate treatment in patients with ACTH-independent hypercortisolism and bilateral adrenal lesions. In our series, AVS was helpful in the decision-making of two out of ten patients, avoiding chronic treatment with steroidogenesis inhibitors, or inappropriate bilateral adrenalectomy.

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.

Factors predicting the duration of adrenal insufficiency in patients successfully treated for Cushing disease and nonmalignant primary adrenal Cushing syndrome

Successful treatment of Cushing syndrome causes transient or permanent adrenal insufficiency deriving from endogenous hypercortisolism-induced hypothalamus-pituitary-adrenal-axis suppression. We analyzed pre-treatment factors potentially affecting the duration of adrenal insufficiency. We conducted a retrospective analysis on patients successfully treated for Cushing disease (15 patients) who underwent transsphenoidal surgery, and nonmalignant primary adrenal Cushing syndrome (31 patients) who underwent unilateral adrenalectomy, divided into patients with overt primary adrenal Cushing syndrome (14 patients) and subclinical primary adrenal Cushing syndrome (17 patients). Epidemiological data, medical history, and hormonal parameters depending on the etiology of hypercortisolism were collected and compared to the duration of adrenal insufficiency. The median duration of follow-up after surgery for Cushing disease and primary adrenal Cushing syndrome was 70 and 48 months, respectively. In the Cushing disease group, the median duration of adrenal insufficiency after transsphenoidal surgery was 15 months: younger age at diagnosis and longer duration of signs and symptoms of hypercortisolism before diagnosis and surgery were associated with longer duration of adrenal insufficiency. The median duration of adrenal insufficiency was 6 months for subclinical primary adrenal Cushing syndrome and 18.5 months for overt primary adrenal Cushing syndrome. The biochemical severity of hypercortisolism, the grade of hypothalamus-pituitary-adrenal-axis suppression, and treatment with ketoconazole before surgery accounted for longer duration of adrenal insufficiency. In patients with Cushing disease, younger age and delayed diagnosis and treatment predict longer need for glucocorticoid replacement therapy after successful transsphenoidal surgery. In patients with primary adrenal Cushing syndrome, the severity of hypercortisolism plays a primary role in influencing the duration of adrenal insufficiency after unilateral adrenalectomy.

A case of adrenal Cushing's syndrome with bilateral adrenal masses

A functional lesion in corticotrophin (ACTH)-independent Cushing's syndrome is difficult to distinguish from lesions of bilateral adrenal masses. Methods for distinguishing these lesions include adrenal venous sampling and (131)I-6β-iodomethyl-19-norcholesterol ((131)I-NP-59) scintigraphy. We present a case of a 29-year-old Han Chinese female patient with a history of hypercholesterolaemia and polycystic ovary syndrome. She presented with a 6month history of an 8kg body weight gain and gradual rounding of the face. Serial examinations revealed loss of circadian rhythm of cortisol, elevated urinary free-cortisol level and undetectable ACTH level (<5pg/mL). No suppression was observed in both the low- and high-dose dexamethasone suppression tests. Adrenal computed tomography revealed bilateral adrenal masses. Adrenal venous sampling was performed, and the right-to-left lateralisation ratio was 14.29. The finding from adrenal scintigraphy with NP-59 was consistent with right adrenal adenoma. The patient underwent laparoscopic right adrenalectomy, and the pathology report showed adrenocortical adenoma. Her postoperative cortisol level was 3.2μg/dL, and her Cushingoid appearance improved. In sum, both adrenal venous sampling and (131)I-NP-59 scintigraphy are good diagnostic methods for Cushing's syndrome presenting with bilateral adrenal masses.

LEARNING POINTS

The clinical presentation of Cushing' syndrome includes symptoms and signs of fat redistribution and protein-wasting features.The diagnosis of patients with ACTH-independent Cushing's syndrome with bilateral adrenal masses is challenging for localisation of the lesion.Both adrenal venous sampling and (131)I-NP-59 scintigraphy are good methods to use in these patients with Cushing's syndrome presenting with bilateral adrenal masses.

Multi-modality imaging of pheochromocytoma

Pheochromocytoma, a rare neuroendocrine adrenal tumor, is often diagnosed by a combination of clinical, laboratory, and radiographic features. While the imaging features of this entity are variable, the use of complementary modalities often helps to target the diagnosis and assess the extent of the disease. We present a multi-modality evaluation of a pheochromocytoma, with CT, MR, MIBG, and pathologic findings, in an individual who initially presented to the Emergency Department with flank pain.

Testicular adrenal rest tumors in a patient with congenital adrenal hyperplasia

Congenital adrenal hyperplasia refers to a group of autosomal recessive disorders caused by a deficiency of an enzyme involved in the synthesis of glucocorticoids. The enzyme deficiency generally leads to a deficiency of cortisol and/or aldosterone production within the adrenal cortex. The lack of glucocorticoids generally leads to elevated levels of plasma corticotropin (ACTH), which often results in adrenal hyperplasia. Testicular adrenal rest tumors may develop in males with congenital adrenal hyperplasia due to overstimulation of aberrant adrenal cells within the testes. Recognition of this disease entity is essential when evaluating young males with testicular masses.

NP-59 SPECT/CT imaging in stage 1 hypertensive and atypical primary aldosteronism: a 5-year retrospective analysis of clinicolaboratory and imaging features

OBJECTIVE

We retrospectively analyzed all primary aldosteronism (PA) patients undergoing NP-59 SPECT/CT imaging with regard to their clinicolaboratory and imaging features, investigation, and outcomes.

MATERIAL AND METHODS

11 PA patients who presented to our hospital for NP-59 SPECT/CT imaging between April 2007 and March 2012 and managed here were analyzed.

RESULTS

Among 11 PA patients, eight (73%) had stage 1 hypertension, three (27%) stage 2 hypertension, four (36%) normal plasma aldosterone concentration, nine (82%) nonsuppressed plasma renin activity (PRA), six (55%) normal aldosterone-renin-ratio (ARR), eight (73%) serum potassium ≧3 mEq/L, seven (64%) subclinical presentation, seven (64%) negative confirmatory testing, and four (36%) inconclusive results on CT scan and seven (64%) on planar NP-59 scan. All 11 (100%) patients had positive results on NP-59 SPECT/CT scan. Two (18%) met typical triad and nine (82%) atypical triad. Among nine atypical PA patients, three (33%) had clinical presentation, six (67%) subclinical presentation, six (67%) negative confirmatory testing, and four (44%) inconclusive results on CT scan and six (67%) on planar NP-59 scan. All patients had improved outcomes. Significant differences between typical and atypical PA existed in PRA and ARR.

CONCLUSIONS

NP-59 SPECT/CT may provide diagnostic potential in stage 1 hypertensive and atypical PA.

Neuroendocrine tumours of the head and neck: anatomical, functional and molecular imaging and contemporary management

Neuroendocrine tumours (NETs) of the head and neck are rare neoplasms and can be of epithelial or non-epithelial differentiation. Although the natural history of NETs is variable, it is crucial to establish an early diagnosis of these tumours as they can be potentially curable. Conventional anatomical imaging and functional imaging using radionuclide scintigraphy and positron emission tomography/computed tomography can be complementary for the diagnosis, staging and monitoring of treatment response. This article describes and illustrates the imaging features of head and neck NETs, discusses the potential future role of novel positron-emitting tracers that are emerging into clinical practice and reviews contemporary management of these tumours. Familiarity with the choice of imaging techniques and the variety of imaging patterns and treatment options should help guide radiologists in the management of this rare but important subgroup of head and neck neoplasms.

SPECT/CT and tumour imaging

Scintigraphic techniques are sensitive imaging modalities in the diagnosis and follow-up of cancer patients providing the functional and metabolic activity characteristics of the tumour. Hybrid SPECT/CT improves the diagnostic accuracy of these well-established imaging techniques by precise anatomical localization and characterization of morphological findings, differentiation between foci of physiological and pathological tracer uptake, resulting in a significant impact on patient management and more definitive interpretations. The use of SPECT/CT has been studied in a variety of applications in tumour imaging which are reviewed in this article. By combining functional and anatomical information in a single imaging session, SPECT/CT has become a one-stop cancer imaging modality.

Functional characterization of adrenal lesions using [123I]IMTO-SPECT/CT

CONTEXT

Adrenal tumors are highly prevalent and represent a wide range of different pathological entities. Conventional imaging often provides only limited information on the origin of these lesions. Novel specific imaging methods are, therefore, of great clinical interest.

OBJECTIVE

We evaluated [(123)I]iodometomidate ([(123)I]IMTO) imaging for noninvasive characterization of adrenal masses.

DESIGN/SETTING

This was a prospective monocentric diagnostic study in a tertiary care center.

PATIENTS AND INTERVENTION

A total of 51 patients with an adrenal lesion underwent [(123)I]IMTO imaging after injection of 185 MBq of [(123)I]IMTO. Sequential planar whole-body scans until 24 hours postinjection and single photon emission computed tomography (SPECT)/computed tomography imaging 4 to 6 hours postinjection were performed.

MAIN OUTCOME MEASURE

Sensitivity and specificity of [(123)I]IMTO imaging for the noninvasive characterization of adrenal lesions were measured.

RESULTS

Adrenocortical tissue showed high and specific tracer uptake with a short investigation time and low radiation exposure. Qualitative analysis of SPECT/computed tomography data resulted in a sensitivity of 89% and a specificity of 85% for differentiating adrenocortical tumors from lesions of nonadrenocortical origin. Receiver-operating characteristic analysis of semiquantitative data revealed a sensitivity of 83% and a specificity of 86% for identification of adrenocortical lesions at a cutoff value of tumor to liver ratio of 1.3.

CONCLUSIONS

[(123)I]IMTO is a highly specific radiotracer for imaging of adrenocortical tissue with a short investigation time and low radiation exposure. Because of the general availability of SPECT technology, [(123)I]IMTO scintigraphy has the potential to become a widely used tool to noninvasively characterize the biology of adrenal lesions.

Contemporary nuclear medicine imaging of neuroendocrine tumours

Neuroendocrine tumours (NETs) are rare, heterogeneous, and often hormonally active neoplasms. Nuclear medicine (NM) imaging using single photon- and positron-emitting radiopharmaceuticals allows sensitive and highly specific molecular imaging of NETs, complementary to anatomy-based techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI). Somatostatin-receptor scintigraphy is a whole-body imaging technique widely used for diagnosis, staging and restaging of NETs. The increasing availability of hybrid single-photon emission CT (SPECT)/CT cameras now offers superior accuracy for localization and functional characterization of NETs compared to traditional planar and SPECT imaging. The potential role of positron-emission tomography (PET) tracers in the functional imaging of NETs is also being increasingly recognized. In addition to 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG), newer positron-emitting radiopharmaceuticals such as (18)F-dihydroxyphenylalanine (DOPA) and (68)Ga-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) peptides, show promise for the future. This article will summarize the role of current and emerging radiopharmaceuticals in NM imaging of this rare but important group of tumours.

Adrenal nodules in patients with Cushing's disease: prevalence, clinical significance and follow-up

Adrenal glands in Cushing's disease (CD) range from normal to showing diffuse enlargement in most cases. The finding of nodular lesions has been reported, but information about prevalence and evolution is described in few reports.

AIM

To investigate the prevalence of nodular adrenal glands in patients with CD and assess its evolution after disease remission.

SUBJECTS AND METHODS

We assessed 41 CD patients' abdominal computed tomography (CT) scans obtained during the active phase of the disease and evaluated the dynamics of ACTH and cortisol secretion. CT was repeated after disease remission in patients with adrenal nodules.

RESULTS

Fifteen of 41 patients had nodular and the remaining 26 had normal or enlarged adrenal glands. Patients with nodules were older (45.1 ± 8.8 vs 36.9 ± 12.7 yr; p=0.03) and had longer-standing disease (57.3 ± 56.9 vs 32.9 ± 29.1 months; p=0.05) than patients with normal/enlarged adrenal glands. ACTH (45.4 ± 21.3 vs 70.5 ± 39.1 pg/ml; p=0.04) and urinary free cortisol levels (606.1 ± 512.3 vs 301.0 ± 224.7 μg/day, p=0.01) were significantly lower in patients with adrenal nodules while there were no differences between the groups in terms of dynamic tests results. Post-operative follow-up showed regression or shrinkage of the nodules in 8 out of 10 patients in disease remission.

CONCLUSIONS

We found that adrenal nodular glands are a frequent finding in CD in particular in older patients and in those with a longerstanding disease. Nevertheless, a high percentage of nodules regression or shrinking was evidenced in our series after disease remission.

Diagnostic value of I-131 NP-59 SPECT/CT scintigraphy in patients with subclinical or atypical features of primary aldosteronism

Accumulating evidence has shown the adverse effect of long-term hyperaldosteronism on cardiovascular morbidity that is independent of blood pressure. However, the diagnosis of primary aldosteronism (PA) remains a challenge for patients who present with subtle or atypical features or have chronic kidney disease (CKD). SPECT/CT has proven valuable in the diagnosis of a number of conditions. The aim of this study was to determine the usefulness of I-131 NP-59 SPECT/CT in patients with atypical presentations of PA and in those with CKD. The records of 15 patients with PA were retrospectively analyzed. NP-59 SPECT/CT was able to identify adrenal lesion(s) in CKD patients with suspected PA. Patients using NP-59 SPECT/CT imaging, compared with those not performing this procedure, significantly featured nearly normal serum potassium levels, normal aldosterone-renin ratio, and smaller adrenal size on CT and pathological examination and tended to feature stage 1 hypertension and non-suppressed plasma renin activity. These findings show that noninvasive NP-59 SPECT/CT is a useful tool for diagnosis in patients with subclinical or atypical features of PA and those with CKD.

Adrenal cortical imaging with I-131 NP-59 SPECT-CT

PURPOSE

The purpose of this article is to present our initial experience with hypersecretory adrenal syndromes investigated with radioiodinated I-6-B-iodomethyl-19-norcholesterol (NP-59) and SPECT-CT.

MATERIALS AND METHODS

Illustrative cases are presented of patients being investigated for adrenal hypersecretory syndromes, with or without adrenal nodules, using NP-59 scintigraphy with SPECT-CT imaging, representing a spectrum of diagnoses. Clinical and imaging data are reviewed to evaluate whether additional information derived from near-simultaneous anatomic localization aids study interpretation.

RESULTS

The final diagnoses reached are hyperfunctional and nonfunctioning adrenal nodules, physiological bowel activity, and bilateral adrenal hyperplasia. SPECT-CT assisted study interpretation by localizing focal uptake to the adrenal glands, allowing direct assessment of function within adrenal nodules, and distinguishing physiological bowel activity from adrenal uptake. SPECT-CT provided additional information to planar and SPECT imaging, which improved confidence of study interpretation.

CONCLUSION

Utilization of SPECT-CT with NP-59 scintigraphy allows precise localization of the functional activity to anatomic structures improving diagnostic interpretation.

Corticotropin-independent Cushing's syndrome in patients with bilateral adrenal masses

OBJECTIVES

To present our institutional experience in the patients with ACTH-independent Cushing's syndrome treated for bilateral adrenal masses during the past 8 years. Bilateral adrenal masses are rare in patients with adrenocorticotropic hormone (ACTH)-independent Cushing's syndrome.

METHODS

A retrospective review of 11 patients with ACTH-independent Cushing's syndrome of bilateral adrenal masses was performed. Bilateral adrenalectomy or bilateral/unilateral partial adrenalectomy was made for these patients. The steroid replacement was discontinued after 6-12 months postoperatively, and the follow-up information was obtained to evaluate the disease outcome.

RESULTS

Combining ultrasonography and computed tomography scan with biochemical tests, 6 cases of bilateral adrenal adenomas and 5 cases of ACTH-independent macronodular adrenal hyperplasia (AIMAH) were diagnosed. The median follow-up time was 13 months (range, 9-22). For all patients, both systolic (181 ± 17 vs 145 ± 11 mm Hg; P <.001) and diastolic blood pressure levels (118 ± 13 vs 88 ± 11 mm Hg; P <.001) were significantly reduced postoperatively. The body mass index significantly decreased (28.0 ± 2.4 vs 24.6 ± 1.3 kg/m(2); P <.001). After bilateral adrenalectomy, glucocorticoid therapy was enough to maintain the balance of water and electrolytes metabolism, and the follow-up outcome showed no disorder of serum electrolytes metabolism.

CONCLUSIONS

Although a feasible method is still needed for determining the lateralization of cortisol secretion of bilateral adrenal masses, ultrasonography and computed tomography scan are useful for the diagnosis and differentiated diagnosis of AIMAH. Rational surgical treatment is important for bilateral adrenal masses, while glucocorticoid therapies could be effective alternation for steroid replacement.

Hybrid imaging (SPECT/CT and PET/CT)--improving the diagnostic accuracy of functional/metabolic and anatomic imaging

In-line combined systems, single-photon emission computed tomography (SPECT)/computed tomography (CT) and positron emission tomography (PET)/CT, allow an instant generation of fused images of scintigraphy and CT data. The accumulated clinical data on the use of these systems in various clinical scenarios indicate that this hybrid technology improves the diagnostic accuracy as compared to scintigraphy and CT alone and even to side-by-side interpretation of scintigraphy and CT, which were acquired separately. The improved diagnostic accuracy is reflected by improving image quality of SPECT and PET, detection of more clinically relevant lesions, better localization of disease and differentiation between physiologic and pathologic uptake, characterization of disease by its functional and morphologic appearance before and after therapy and accurate delineation of disease, optimizing biopsy and therapy planning.

A review on the clinical uses of SPECT/CT

In the era when positron emission tomography (PET) seems to constitute the most advanced application of nuclear medicine imaging, still the conventional procedure of single photon emission computed tomography (SPECT) is far from being obsolete, especially if combined with computed tomography (CT). In fact, this dual modality imaging technique (SPECT/CT) lends itself to a wide variety of useful diagnostic applications whose clinical impact is in most instances already well established, while the evidence is growing for newer applications. The increasing availability of new hybrid SPECT/CT devices with advanced technology offers the opportunity to shorten acquisition time and to provide accurate attenuation correction and fusion imaging. In this review we analyse and discuss the capabilities of SPECT/CT for improving sensitivity and specificity in the imaging of both oncological and non-oncological diseases. The main advantages of SPECT/CT are represented by better attenuation correction, increased specificity, and accurate depiction of the localization of disease and of possible involvement of adjacent tissues. Endocrine and neuroendocrine tumours are accurately localized and characterized by SPECT/CT, as also are solitary pulmonary nodules and lung cancers, brain tumours, lymphoma, prostate cancer, malignant and benign bone lesions, and infection. Furthermore, hybrid SPECT/CT imaging is especially suited to support the increasing applications of minimally invasive surgery, as well as to precisely define the diagnostic and prognostic profile of cardiovascular patients. Finally, the applications of SPECT/CT to other clinical disorders or malignant tumours is currently under extensive investigation, with encouraging results in terms of diagnostic accuracy.

6-Deoxy-6-[131I]iodo-L-ascorbic acid for the in vivo study of ascorbate: autoradiography, biodistribution in normal and hypolipidemic rats, and in tumor-bearing nude mice

Normal female rat distribution studies showed high and specific uptake of 6-deoxy-6-[(131)I]iodo-L-ascorbic acid (6-(131)IAsA) into the adrenal glands, known to highly express the ascorbate sodium-dependent vitamin C transporter-2 (SVCT-2), and the adrenal gland was clearly visualized by whole-body autoradiography. Preinjection of sulfinpyrazone, a known blocker of ascorbate transport, with 6-(131)IAsA resulted in decreased uptake of radioactivity in rat adrenal glands compared to the control group, seemingly illustrating the participation of the SVCT transporter (probably the SVCT-2 subtype) in the uptake process in vivo. 4-Aminopyrazolo[3,4-d]pyrimidine-induced hypolipidemic rats showed a 1.7-fold increase in adrenal uptake of radioactivity at 30 min postinjection of 6-(131)IAsA, compared to the control, with increased adrenal-to-liver and adrenal-to-kidney ratios. To further characterize 6-(131)IAsA for its tumor uptake properties, biodistribution studies were also performed using male nude mice implanted with either Y-1 adrenocortical tumor cells or adrenal medulla-derived PC12 cells. None of these tumors exhibited relevant uptake of 6-(131)IAsA while normal adrenal glands showed high uptake of radioactivity, suggesting that these tumors in this model have only a poor transport capacity for this agent. The present study demonstrates that the use of radioiodinated 6-IAsA may help to obtain information about functional alterations in diseased adrenal glands, but it does not exhibit desirable properties as a tumor-seeking agent for ascorbic acid bioactivity.

Usefulness of 123I-MIBG scintigraphy in the evaluation of patients with known or suspected primary or metastatic pheochromocytoma or paraganglioma: results from a prospective multicenter trial

Although (123)I-MIBG has been in clinical use for the imaging of pheochromocytoma for many years, a large multicenter evaluation of this agent has never been performed. The present study was designed to provide a prospective confirmation of the performance of (123)I-MIBG scintigraphy for the evaluation of patients with known or suspected primary or metastatic pheochromocytoma or paraganglioma.

METHODS

A total of 81 patients with a prior history of primary or metastatic pheochromocytoma or paraganglioma and 69 with suspected pheochromocytoma or paraganglioma based on symptoms of catecholamine excess, CT or MRI findings, or elevated catecholamine or metanephrine levels underwent whole-body planar and selected SPECT 24 h after the administration of (123)I-MIBG. Images were independently interpreted by 3 masked readers, with consensus requiring agreement of at least 2 readers. Final diagnoses were based on histopathology, correlative imaging, catecholamine or metanephrine measurements, and clinical follow-up.

RESULTS

Among 140 patients with definitive diagnoses (91, disease present; 49, disease absent), (123)I-MIBG planar scintigraphy had a sensitivity and specificity of 82%. For patients evaluated for suspected disease, sensitivity and specificity were 88% and 84%, respectively. For the subpopulations of adrenal (pheochromocytoma) and extraadrenal (paraganglioma) tumors, sensitivities were 88% and 67%, respectively. The addition of SPECT increased reader confidence but minimally affected sensitivity and specificity.

CONCLUSION

This prospective study demonstrated a sensitivity of 82%-88% and specificity of 82%-84% for (123)I-MIBG imaging used in the diagnostic assessment of primary or metastatic pheochromocytoma or paraganglioma.

Role of adrenal gland scintigraphy in patients with subclinical hypercortisolism and incidentally discovered adrenal mass

BACKGROUND

The role of adrenal scintigraphy (AS) in the diagnosis of subclinical hypercortisolism (SH) in adrenal incidentaloma (AI) is debated.

AIM

To evaluate the possible role of AS in identifying SH in AI patients.

SUBJECTS AND METHODS

In the retrospective phase (2000-2004), 102 AI patients [71 females (F)/31 males (M)] referred to our center were reevaluated for SH. In the prospective phase (2005-2006), 42 patients (32F/10M) with suspected SH were evaluated performing AS and biochemical assessment of cortisol secretion. We report data of the prospective phase of the study. In these patients AS was performed at baseline; the difference between the uptake of the affected and the controlateral gland [mean Delta uptake (MDeltau)] was calculated. Cortisol secretion was evaluated in 3 different occasions. Patients were considered affected with SH if they presented at least twice 2 of the following criteria: urinary free cortisol >193 nmol/l, cortisol after 1 mg dexamethasone suppression test >83 nmol/l, ACTH levels <2.2 pmol/l.

RESULTS

MDeltau was higher in patients with SH (no.=27, 5/22 M/F) than in patients without SH (83.7+/-12.5 vs 54.7+/-24.1%, p<0.001), and directly correlated with UFC (beta=0.387, p=0.015) and was predictive of SH (odds ratio 1.12, 95% confidence interval 1.03-1.22, p=0.009) regardless of age, body mass index, and diameter of the mass. A 75% MDeltau cut-off has 86.7% specificity and 81.5% sensitivity in diagnosing SH.

CONCLUSIONS

AS is not recommended as screening test in AI patients, but it can be useful to exclude the presence of a subtle cortisol excess in patients with unclear biochemical diagnosis of SH.

PET Imaging of Pheochromocytoma

Pheochromocytomas are tumors derived from chromaffin cells of the adrenal medulla that synthesize, store, metabolize, and usually, but not always, secrete catecholamines. Although pheochromocytomas are the cause of hypertension in only a small number of patients, they can precipitate life-threatening hypertension or cardiac arrhythmias caused by excessive and episodic catecholamine secretion. This article reviews the genetics, clinical presentation, and imaging of pheochromocytoma, with special emphasis on new positron emission tomographic radiopharmaceutical agents.

The Role of Adrenal Scintigraphy in the Preoperative Management of Primary Aldosteronism

Background and Aims:

Differentiation between the two major subgroups of primary aldosteronism, bilateral hyperplasia and aldosterone producing adenoma is essential since therapy in the former is medical and in the latter surgical. The aim of the present study was to evaluate the clinical utility of adrenocortical scintigraphy in the management of primary aldosteronism.

Material and Methods:

[131I] norcholesterol (NP-59) scintigraphy with dexamethasone suppression for subclassification and lateralization of primary aldosteronism was evaluated in 49 patients with long-term follow-up after diagnosis and treatment

Results:

Thirty-three patients with the diagnosis of aldosterone producing adenoma were operated with adrenalectomy. Preoperative scintigraphy showed lateralized isotope uptake in 27/33 patients while 6 showed no uptake. Twenty-two were cured and three significantly improved. Thus, in 25/33 (76%), scintigraphy showed the correct side as the patients benefited of surgery. Two patients did not improve. Fourteen patients with a probable diagnosis of bilateral hyperplasia had normal scintigraphies.

Conclusions:

In the present retrospective study we found limited sensitivity of NP-59 scintigraphy. However, when a lateralized scintigraphic uptake is achieved it has a high accuracy. Scintigraphy may be used as an adjunct in cases where adrenal venous sampling is inconclusive.

SPECT/CT

In view of the commercial success of integrated PET/CT scanners, there is an increasing interest in comparable SPECT/CT systems. SPECT in combination with CT enables a direct correlation of anatomic information and functional information, resulting in better localization and definition of scintigraphic findings. Besides anatomic referencing, the added value of CT coregistration is based on the attenuation correction capabilities of CT. The number of clinical studies is limited, but pilot studies have indicated a higher specificity and a significant reduction in indeterminate findings. The superiority of SPECT/CT over planar imaging or SPECT has been demonstrated in bone scintigraphy, somatostatin receptor scintigraphy, parathyroid scintigraphy, and adrenal gland scintigraphy. Also, rates of detection of sentinel nodes by biopsy can be increased with SPECT/CT. This review highlights recent technical developments in integrated SPECT/CT systems and summarizes the current literature on potential clinical uses and future directions for SPECT/CT in cardiac, neurologic, and oncologic applications.

Contemporary adrenal scintigraphy

INTRODUCTION

High-resolution computed tomography (CT) and magnetic resonance (MR) imaging have replaced scintigraphy as primary imaging modalities for the evaluation of adrenal diseases.

DISCUSSION

Thin-slice CT, CT contrast washout studies and MR pulse sequences specifically designed to identify adrenal lipid content have radically changed the approach to anatomic imaging and provide unique insight into the physical characteristics of the adrenals. With a confirmed biochemical diagnosis, further evaluation is often unnecessary, especially in diagnostic localization of diseases of the adrenal cortex. However, despite the exquisite detail afforded by anatomy-based imaging, there are not infrequently clinical situations in which the functional insight provided by scintigraphy is crucial to identify adrenal dysfunction and to assist in localization of adrenocortical and adrenomedullary disease. The introduction of hybrid PET/CT and SPECT/CT, modalities that directly integrate anatomic and functional information, redefine the radiotracer principle in the larger context of high-resolution anatomic imaging. Instead of becoming obsolete, scintigraphy is an element of a device that combines it with CT or MR to allow a direct correlation between function and anatomy, whereby the combination creates a more powerful diagnostic tool than the separate component modalities.