Intraindividual comparison of 123I-mIBG SPECT/MRI, 123I-mIBG SPECT/CT, and MRI for the detection of adrenal pheochromocytoma in patients with elevated urine or plasma catecholamines. Clin Nucl Med. 2013;38:e1-e6. [PMID: 22996238 DOI: 10.1097/rlu.0b013e318263923d]

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

KEY POINTS

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

Draft of the clinical practice guidelines “Adrenal incidentaloma”

The wider application and technical improvement of abdominal imaging procedures in recent years has led to an increasingly frequent detection of adrenal gland masses — adrenal incidentaloma, which have become a common clinical problem and need to be investigated for evidence of hormonal hypersecretion and/or malignancy. Clinical guidelines are the main working tool of a practicing physician. Laconic, structured information about a specific nosology, methods of its diagnosis and treatment, based on the principles of evidence-based medicine, make it possible to give answers to questions in a short time, to achieve maximum efficiency and personalization of treatment. These clinical guidelines include data on the prevalence, etiology, radiological features and assessment of hormonal status of adrenal incidentalomas. In addition, this clinical practice guideline provides information on indications for surgery, postoperative rehabilitation and follow-up.

Combined Diagnosis of Whole-Lesion Histogram Analysis of T1- and T2-Weighted Imaging for Differentiating Adrenal Adenoma and Pheochromocytoma: A Support Vector Machine-Based Study

PURPOSE

This study aimed to determine whether a combined diagnosis of whole-lesion histogram analysis of T1- and T2-weighted imaging based on support vector machine (SVM) can distinguish pheochromocytoma from adrenal adenoma.

METHODS

A pathology database was retrospectively appraised over a period of 7 years and we obtained 40 histopathologically proven adrenal adenomas and 20 pheochromocytomas with magnetic resonance images. The T1-weighted imaging (T₁WI, including both in phase and opposed phase) and T2-weighted imaging (T₂WI) images of each patients were analyzed using Mazda software. Nine parameters were selected as indicators of comparison: variance, skewness, kurtosis, mean, 1st percentile, 10th percentile, 50th percentile, 90th percentile, and 99th percentile. The parameters with differential-diagnosis significance were used to establish the combined diagnostic model of SVM.

RESULTS

Among the 9 parameters extracted using histogram analysis, the 1st percentile, 10th percentile, and 50th percentile of T₁WI (in phase) and the skewness of T₂WI and almost all parameters of T₁WI (opposed phase), except variance and 99th percentile, showed statistical significance between groups. Among the above parameters, the area under the curve (AUC) of 10th percentile of T₁WI (opposed phase) was the largest with the value of 0.909 (100.0% sensitivity and 80.0% specificity). After the analysis of combined diagnosis was performed, the AUC of SVM model in testing set showed the value of 0.917 (85.0% accuracy).

CONCLUSIONS

Whole-lesion histogram analysis of T₁WI and T₂WI may help differentiate adrenal adenomas from pheochromocytomas. Furthermore, the combined diagnosis of T₁WI and T₂WI histogram based on SVM was more effective than most of individual histogram parameters.

Two decades of SPECT/CT - the coming of age of a technology: An updated review of literature evidence

PURPOSE

Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) was introduced as a hybrid SPECT/CT imaging modality two decades ago. The main advantage of SPECT/CT is the increased specificity achieved through a more precise localization and characterization of functional findings. The improved diagnostic accuracy is also associated with greater diagnostic confidence and better inter-specialty communication.

METHODS

This review presents a critical assessment of the relevant literature published so far on the role of SPECT/CT in a variety of clinical conditions. It also includes an update on the established evidence demonstrating both the advantages and limitations of this modality.

CONCLUSIONS

For the majority of applications, SPECT/CT should be a routine imaging technique, fully integrated into the clinical decision-making process, including oncology, endocrinology, orthopaedics, paediatrics, and cardiology. Large-scale prospective studies are lacking, however, on the use of SPECT/CT in certain clinical domains such as neurology and lung disorders. The review also presents data on the complementary role of SPECT/CT with other imaging modalities and a comparative analysis, where available.

Role of DOTATATE-PET/CT in preoperative assessment of phaeochromocytoma and paragangliomas

CONTEXT

Diagnosis of paragangliomas (PGL) and phaeochromocytomas (PC) can be challenging particularly if the tumour is small. Detection of metastatic disease is important for comprehensive management of malignant PC/PGL. Somatostatin receptor imaging (SRI) agents have high sensitivity for these tumours, particularly the DOTA family of radiopharmaceuticals labelled with ⁶⁸ Gallium.

OBJECTIVE

To describe the utility of SRI in primary assessment (ie before surgery) for PC/PGL and whether measures of maximum standardized uptake (SUVmax) could be used to distinguish between adrenal adenomas and PCs.

DESIGN

Retrospective analysis of patients with PC and PGL between 2012 and 2017.

PATIENTS

Somatostatin receptor imaging (SRI) was performed for suspected PC (n = 46) or PGL (n = 27) of which 36 were during primary assessment and 37 during secondary assessment (follow-up after surgery). For comparison of adrenal SUVmax, scans from 30 patients without suspected PC/PGL (20 with normal adrenals; 10 with incidental adenomas) were evaluated.

MEASUREMENTS

Baseline description, sensitivity, specificity, Youden's index.

RESULTS

Sensitivity of DOTATATE-PET was 88% for PC and 100% for PGL. False-negative scans were seen in 2/10 PCs < 28 mm and in 1/14 PCs > 28 mm which had features of cystic degeneration. SUVmax of PCs and PGLs was more than double compared to adrenal adenomas (P > .001).

CONCLUSION

Somatostatin receptor imaging (SRI) has high sensitivity in primary assessment for PC and PGL. We recommend that SRI should be performed as part of primary assessment in all suspected PGLs (due to higher risk of multifocal lesions) and in PCs suspected to be associated with hereditary syndromes or metastases.

Falciform Ligament Artery Uptake on 99mTc MAA Planning Scan Before 90Y SIRT Confirmed by Retrospective SPECT/MRI Fusion

Selective internal radiation therapy using Y spheres is a treatment option for patients with primary or secondary liver cancer. To avoid complications, screening using Tc macroaggregated albumin is performed to identify lung shunting and extrahepatic depositions. For the latter, deposition after the anterior abdominal wall is frequently attributed to a patent falciform artery, although the vessel itself is rarely visible on SPECT/CT scans. We demonstrate that retrospective SPECT/MRI fusion clearly attributes the nuclide accumulation to a patent falciform artery. During selective internal radiation therapy, ice packs were placed on the anterior abdominal wall, resulting in a complication-free treatment.

Clinical Significance of Quantitative 123I-MIBG SPECT/CT Analysis of Pheochromocytoma and Paraganglioma

PURPOSE

This retrospective study compared the diagnostic performances of quantitative versus visual analyses of I-MIBG scintigraphy in patients with suspected pheochromocytoma and paraganglioma (PPGL).

MATERIALS AND METHODS

SPECT images were obtained 6 and/or 24 h after MIBG injection from 68 patients with clinically suspected PPGL, with attenuation correction by low-dose unenhanced CT. Planar images were also obtained at each time point. SUVs of retroperitoneal tumors, including PPGLs, and physiological uptake by normal organs were measured using the SPECT images. The diagnostic performance of the quantitative assessment in differentiating PPGLs from other lesions or normal adrenal glands was assessed using receiver operating characteristic analysis. The planar scans and 6-h and 24-h SPECT/CT images were also assessed visually.

RESULTS

PPGLs showed a significantly higher SUVmax (mean ± SD = 9.97 ± 3.86) than other retroperitoneal lesions (3.85 ± 1.51) or normal adrenal glands (3.91 ± 1.20). At an optimal cut-off of 6.57, the sensitivity, specificity, and accuracy of the quantitative assessment for 6-h SPECT/CT in differentiating PPGLs was 78.6%, 96.3%, and 92.6%, respectively; the area under the curve was 0.878. The diagnostic performance did not significantly differ between the quantitative and visual analyses, but the specificity of the former tended to be higher at 6 h (96.3% vs. 90.7%) and at 24 h (91.2% vs. 82.4%).

CONCLUSIONS

The specificity, but not the sensitivity, of the quantitative approach was higher than that of visual assessment in differentiating PPGLs from other retroperitoneal pathologies and from physiological uptake in the normal adrenal gland.

Additional value of hybrid SPECT/CT systems in neuroendocrine tumors, adrenal tumors, pheochromocytomas and paragangliomas

The aim of this review was to evaluate the potential advantages of SPECT/CT hybrid imaging in the management of neuroendocrine tumors, adrenal tumors, pheochromocytomas and paragangliomas. From the collected data, the superiority of fused images was observed as providing both functional/molecular and morphological imaging compared to planar imaging. This provided an improvement in diagnostic imaging, with significant advantages as regards: (1) precise locating of the lesions; (2) an improvement in characterization of the findings, resulting higher specificity, improved sensitivity, and overall greater accuracy, (3) additional anatomical information derived from the CT component; (4) CT-based attenuation correction and potential for volumetric dosimetry calculations, and (5) improvement on the impact on patient management (e.g. in better defining treatment plans, in shortening surgical operating times). It can be concluded that SPECT/CT hybrid imaging provides the nuclear medicine physician with a powerful imaging modality in comparison to planar imaging, providing essential information about the location of lesions, and high quality homogeneous images.

Endocrine radionuclide scintigraphy with fusion single photon emission computed tomography/computed tomography

AIM: To review the benefits of single photon emission computed tomography (SPECT)/computed tomography (CT) hybrid imaging for diagnosis of various endocrine disorders.

METHODS: We performed MEDLINE and PubMed searches using the terms: “SPECT/CT”; “functional anatomic mapping”; “transmission emission tomography”; “parathyroid adenoma”; “thyroid cancer”; “neuroendocrine tumor”; “adrenal”; “pheochromocytoma”; “paraganglioma”; in order to identify relevant articles published in English during the years 2003 to 2015. Reference lists from the articles were reviewed to identify additional pertinent articles. Retrieved manuscripts (case reports, reviews, meta-analyses and abstracts) concerning the application of SPECT/CT to endocrine imaging were analyzed to provide a descriptive synthesis of the utility of this technology.

RESULTS: The emergence of hybrid SPECT/CT camera technology now allows simultaneous acquisition of combined multi-modality imaging, with seamless fusion of three-dimensional volume datasets. The usefulness of combining functional information to depict the bio-distribution of radiotracers that map cellular processes of the endocrine system and tumors of endocrine origin, with anatomy derived from CT, has improved the diagnostic capability of scintigraphy for a range of disorders of endocrine gland function. The literature describes benefits of SPECT/CT for ^99mTc-sestamibi parathyroid scintigraphy and ^99mTc-pertechnetate thyroid scintigraphy, ¹²³I- or ¹³¹I-radioiodine for staging of differentiated thyroid carcinoma, ¹¹¹In- and ^99mTc- labeled somatostatin receptor analogues for detection of neuroendocrine tumors, ¹³¹I-norcholesterol (NP-59) scans for assessment of adrenal cortical hyperfunction, and ¹²³I- or ¹³¹I-metaiodobenzylguanidine imaging for evaluation of pheochromocytoma and paraganglioma.

CONCLUSION: SPECT/CT exploits the synergism between the functional information from radiopharmaceutical imaging and anatomy from CT, translating to improved diagnostic accuracy and meaningful impact on patient care.

Comparison of Quantitative MRI and CT Washout Analysis for Differentiation of Adrenal Pheochromocytoma From Adrenal Adenoma

OBJECTIVE

The purpose of this study was to use quantitative analysis to assess MRI and washout CT in the diagnosis of pheochromocytoma versus adenoma.

MATERIALS AND METHODS

Thirty-four pheochromocytomas (washout CT, 5; MRI, 24; both MRI and CT, 5) resected between 2003 and 2014 were compared with 39 consecutive adenomas (washout CT, 9; MRI, 29; both MRI and CT, 1). A blinded radiologist measured unenhanced attenuation, 70-second peak CT enhancement, 15-minute relative and absolute percentage CT washout, chemical-shift signal intensity index, adrenal-to-spleen signal intensity ratio, T2-weighted signal intensity ratio, and AUC of the contrast-enhanced MRI curve. Comparisons between groups were performed with multivariate and ROC analyses.

RESULTS

There was no difference in age or sex between the groups (p > 0.05). For CT, pheochromocytomas were larger (4.2 ± 2.5 [SD] vs 2.3 ± 0.9 mm; p = 0.02) and had higher unenhanced attenuation (35.7 ± 6.8 HU [range, 24-48 HU] vs 14.0 ± 20.9 HU [range, -19 to 52 HU]; p = 0.002), greater 70-second peak CT enhancement (92.8 ± 31.1 HU [range, 41.0-143.1 HU] vs 82.6 ± 29.9 HU [range, 50.0-139.0 HU ]; p = 0.01), lower relative washout CT (21.7 ± 24.7 [range, -29.3 to 53.7] vs 65.3 ± 22.3 [range, 32.9-115.3]; p = 0.002), and lower absolute washout CT (31.9 ± 42.8 [range, -70.6 to 70.2] vs 76.9 ± 10.3 [range, 60.3-89.6]; p = 0.001). Thirty percent (3/10) of pheochromocytomas had absolute CT washout in the adenoma range (> 60%). For MRI, pheochromocytomas were larger (5.0 ± 4.2 vs 2.0 ± 0.7 mm; p = 0.003) and had a lower chemical-shift signal intensity index and higher adrenal-to-spleen signal intensity ratio (-3.5% ± 14.3% [range, -56.3% to 12.2%] and 1.1% ± 0.1% [range, 0.9-1.3%] vs 47.3% ± 27.8% [range, -9.4% to 86.0%] and 0.51% ± 0.27% [range, 0.13-1.1%]) (p < 0.001) and higher T2-weighted signal intensity ratio (4.4 ± 2.4 vs 1.8 ± 0.8; p < 0.001). There was no statistically significant difference in contrast-enhanced MRI AUC (288.9 ± 265.3 vs 276.2 ± 129.9 seconds; p = 0.96). The ROC AUC for T2-weighted signal intensity ratio was 0.91 with values greater than 3.8 diagnostic of pheochromocytoma.

CONCLUSION

In this study, the presence of intracellular lipid on unenhanced CT or chemical-shift MR images was diagnostic of adrenal adenoma. Elevated T2-weighted signal intensity ratio was specific for pheochromocytoma but lacked sensitivity. There was overlap in all other MRI and CT washout parameters.

Endocrine scintigraphy with hybrid SPECT/CT

Nuclear medicine imaging of endocrine disorders takes advantage of unique cellular properties of endocrine organs and tissues that can be depicted by targeted radiopharmaceuticals. Detailed functional maps of biodistributions of radiopharmaceutical uptake can be displayed in three-dimensional tomographic formats, using single photon emission computed tomography (CT) that can now be directly combined with simultaneously acquired cross-sectional anatomic maps derived from CT. The integration of function depicted by scintigraphy and anatomy with CT has synergistically improved the efficacy of nuclear medicine imaging across a broad spectrum of clinical applications, which include some of the oldest imaging studies of endocrine dysfunction.

Diagnosis and management of pheochromocytoma: a practical guide to clinicians

Pheochromocytomas (PCCs) are rare catecholamine producing neuroendocrine tumors. The majority of these tumors (85 %) arise from the adrenal medulla. Those arising from the extra-adrenal neural ganglia are called paragangliomas (PGLs). Paroxysmal hypertension with sweating, headaches and palpitation are the usual presenting features of PCCs/ PGLs. Gene mutations are reported in 32-79 % of cases, making genetic screening mandatory in all the cases. The malignancy rates are 10-15 % for PCCs and 20-50 % for PGLs. Measurement of plasma or 24-hour urinary fractionated metanephrines is the best biochemical diagnostic test. Computed tomography or magnetic resonance imaging has high sensitivity (90-100 %) and reasonable specificity (70-90 %) for the anatomical localization. The functionality is assessed by different radionuclide imaging modalities such as metaiodobenzylguanidine (MIBG) scintigraphy, positron emission tomography or single photon emission computed tomography. The only modality of curative treatment is tumor excision. Proper peri-operative management improves the surgical outcomes. Annual follow up with clinical and biochemical assessment is recommended in all the cases after treatment. Children, pregnant women and older people have higher morbidity and mortality risk. De-bulking surgery, chemotherapy, radiotherapy, molecular agents like sunitinib and everolimus, radionuclide agents and different ablation procedures may be useful in the palliation of inoperable/metastatic disease. An update on the diagnostic evaluation and management of PCCs and PGLs is presented here.