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11C-metomidate positron emission tomography after dexamethasone suppression for detection of small adrenocortical adenomas in primary aldosteronism
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Endocrine Surgery. (Hellman/Endokrinkirurgi)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Radiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Endocrine Surgery.
2010 (English)In: Langenbeck's archives of surgery (Print), ISSN 1435-2443, E-ISSN 1435-2451, Vol. 395, no 7, 963-967 p.Article in journal (Refereed) Published
Abstract [en]

Purpose: To evaluate whether dexamethasone suppression treatment can improve 11 C-metomidate positron emission tomography (MTO-PET) detection of small adrenocortical adenomas in primary aldosteronism (PA).

Materials and Methods: Eleven patients with proven PA and two patients with non-hyperfunctioning adrenocortical incidentalomas and small adrenocortical tumours observed on CT underwent MTO-PET before and 3 days after administration of oral dexamethasone suppression treatment. Small “hot-spot” regions of interest (ROIs) comprising 4-pixels (SUVhs) and 1-pixel  (SUVmax) were placed in the tumour area with the highest radioactivity concentration and their respective standardised uptake values (SUV) were recorded.

Results: All tumours were detected and categorised as adrenocortical by MTO-PET. SUVhs as well as SUVmax were higher in PA compared to non-functional adenomas. Normal adrenal cortex was suppressed after dexamethasone (p<0.05) but tumour SUV was not significantly decreased after suppression in either PA or non-functional tumours (p>0.05).  However, these changes caused no significant increase in the tumour-to-normal adrenal ratio (p>0.05).

Conclusion: MTO-PET is a highly sensitive method for detecting and categorising even small adrenocortical tumours in PA. In this series dexamethasone-suppressed MTO-PET was ubable to increase the tumour-to-normal-adrenal ratio to further facilitate detection of small adenomas in PA as an alternative to adrenal venous sampling.

Place, publisher, year, edition, pages
2010. Vol. 395, no 7, 963-967 p.
Keyword [en]
Metomidate, PET, Primary aldosteronism, Dexamethasone, Adrenal, Suppression
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-108798DOI: 10.1007/s00423-010-0681-7ISI: 000283474100020PubMedID: 20644954OAI: oai:DiVA.org:uu-108798DiVA: diva2:240803
Available from: 2009-09-29 Created: 2009-09-29 Last updated: 2012-03-20Bibliographically 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.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 486
National Category
Research subject
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)
Available from: 2009-10-23 Created: 2009-09-29 Last updated: 2009-10-23Bibliographically approved

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