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Computed tomography, magnetic resonance imaging and 11C-metomidate positron emission tomography for evaluation of adrenal incidentalomas
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Endocrine Surgery.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Endocrine Surgery.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Radiology. (Ahlström)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Radiology. (Ahlström)
2009 (English)In: European Journal of Radiology, ISSN 0720-048X, E-ISSN 1872-7727, Vol. 69, no 2, 314-23 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Given the higher sensitivity of modern computed tomography (CT) scanners, adrenal incidentalomas are being discovered increasingly often. This implies a growing quantitative diagnostic and clinical problem. CT and/or magnetic resonance imaging (MRI) and usually thorough hormonal testing are routinely used to determine the origin of these lesions. Recently, positron emission tomography (PET) using the tracer (11)C-metomidate (MTO) has been established as an alternative diagnostic method with high sensitivity for identifying adrenocortical lesions. The aim of this study was to evaluate the clinical use and value of MTO-PET compared to CT and MRI in the characterisation and work-up of adrenal incidentalomas. METHODS: Initially, we retrospectively evaluated 20 adrenal incidentalomas in patients who had undergone CT, MRI and MTO-PET and from whom we had either histopathological diagnosis or clinical follow-up data. After this analysis we conducted a prospective study in order to compare the imaging modalities. In the latter study, 24 incidentalomas were imaged by CT, MRI and MTO-PET and the results were correlated to those from histopathology (n=8) and clinical diagnosis after follow-up (n=16). RESULTS: In the retrospective analysis, MRI and especially MTO-PET, correlated well to histopathology and clinical diagnosis after follow-up, whereas specificity with CT was low. This was possibly due to the presence of several haematomas/fibrosis which were misdiagnosed as adrenocortical adenomas. In the prospective cohort, sensitivity and specificity with CT were 0.71 and 1.0, respectively, and further characterisation by MRI increased these values to 0.86 and 1.0, whereas maximum sensitivity and specificity were reached when MTO-PET was added. CONCLUSION: The diagnosis of an adrenocortical adenoma may be established by CT in most patients and by MRI in an additional number. For the few remaining patients needing further characterisation, MTO-PET is advantageous as an additional imaging modality.

Place, publisher, year, edition, pages
2009. Vol. 69, no 2, 314-23 p.
Keyword [en]
adrenal, incidentalomas, metomidate, PET, MRI, CT
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Diagnostic Radiology
Identifiers
URN: urn:nbn:se:uu:diva-104627DOI: 10.1016/j.ejrad.2007.10.024ISI: 000264220600017PubMedID: 18082990OAI: oai:DiVA.org:uu-104627DiVA: diva2:220008
Available from: 2009-05-29 Created: 2009-05-29 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Clinical Studies on Adrenocortical Tumours using  [11C]-metomidate Positron Emission Tomography
Open this publication in new window or tab >>Clinical Studies on Adrenocortical Tumours using  [11C]-metomidate Positron Emission Tomography
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Adrenal tumours, discovered en passant in patients undergoing radiological examinations for non-adrenal disease, so-called adrenal incidentalomas, have increased dramatically in the recent era of more sophisticated diagnostic modalities such as high resolution multidetector computed tomography (CT) and magnetic resonance imaging (MRI). Furthermore, primary aldosteronism (PA) has been documented in several screening studies as being far more common than previously believed among hypertensive patients.

In this thesis, a long-term follow-up cohort of patients who had undergone surgery for PA revealed that there was an excellent effect on blood-pressure, reduction of anti-hypertensive medication and hypokalaemia after surgery, even though the majority of these patients still required some anti-hypertensive medication. This was also true, in the higher than expected number of dominant nodular hyperplasia (nIHA) found in the study, but was slightly less pronounced than in aldosterone producing adenomas (APA).  Surgery was thus effective in lateralized PA.

Metomidate positron emission tomography (MTO-PET) was explored in relation to histopathology in post-operative patients and found to be highly specific and sensitive in categorizing adrenocortical disease. Also, a higher standardized uptake value (SUV) ratio between tumours and normal adrenal cortex was found in hormonally hypersecreting adenomas as well as in adrenocortical cancer (ACC). The resolution limited the diagnosis of small tumours (<1-1.5 cm).

MTO-PET was compared to standard radiological modalities (CT and MRI) in the diagnostic work-up of adrenal incidentalomas. All three modalities categorized and characterized the lesions well, with MTO-PET showing the highest sensitivity and specificity.  However this method is currently recommended to be used as complementary to the others in unclear cases, due to high costs and less availability.

The resolution of MTO-PET was improved with respect to less noise and better delineation of small tumours when applying masked volume-wise principal component analysis (MVW-PCA), which will possibly enable future detection of small tumours in PA patients.

Dexamethasone suppression treatment prior to MTO-PET examinations in PA patients decreased SUV in normal adrenal cortex but could not be shown to increase the SUV ratio between adenoma and normal cortex enabling better detection of small tumours, even though all the tumours were readily categorized in the study. Heterogenic SUV reactions to dexamethasone treatment indicate a need for further studies and refinement of the suppression method.

In conclusion, long-term results of surgery for lateralized PA are good. MTO-PET is a highly sensitive and specific method for categorizing adrenocortical disease. Modulation of the method, e.g. by using MVW-PCA and refined dexamethasone suppression treatment, may improve the resolution of the method in delineating small tumours in PA, thus making MTO-PET a non-invasive and non-operator dependent future alternative to the currently recommended adrenal venous sampling (AVS) for lateralization diagnosis prior to surgery for PA.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 33 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 486
National Category
Surgery
Research subject
Surgery
Identifiers
urn:nbn:se:uu:diva-108797 (URN)978-91-554-7618-2 (ISBN)
Public defence
2009-11-14, Auditorium Minus, Museum Gustavianum, Uppsala, 09:15 (Swedish)
Opponent
Supervisors
Available from: 2009-10-23 Created: 2009-09-29 Last updated: 2009-10-23Bibliographically approved

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Hennings, JoakimHellman, PerAhlström, HåkanSundin, Anders

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