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Masked volume wise Principal Component Analysis of small adrenocortical tumours in dynamic [11C]-metomidate Positron Emission Tomography
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Centrum för bildanalys. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datoriserad bildanalys.
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för kirurgiska vetenskaper, Endokrinkirurgi.
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för onkologi, radiologi och klinisk immunologi, Enheten för onkologi.
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för kirurgiska vetenskaper, Endokrinkirurgi.
Vise andre og tillknytning
2009 (engelsk)Inngår i: BMC Medical Imaging, ISSN 1471-2342, E-ISSN 1471-2342, Vol. 9:6Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

BACKGROUND: In previous clinical Positron Emission Tomography (PET) studies novel approaches for application of Principal Component Analysis (PCA) on dynamic PET images such as Masked Volume Wise PCA (MVW-PCA) have been introduced. MVW-PCA was shown to be a feasible multivariate analysis technique, which, without modeling assumptions, could extract and separate organs and tissues with different kinetic behaviors into different principal components (MVW-PCs) and improve the image quality. METHODS: In this study, MVW-PCA was applied to 14 dynamic 11C-metomidate-PET (MTO-PET) examinations of 7 patients with small adrenocortical tumours. MTO-PET was performed before and 3 days after starting per oral cortisone treatment. The whole dataset, reconstructed by filtered back projection (FBP) 0-45 minutes after the tracer injection, was used to study the tracer pharmacokinetics. RESULTS: Early, intermediate and late pharmacokinetic phases could be isolated in this manner. The MVW-PC1 images correlated well to the conventionally summed image data (15-45 minutes) but the image noise in the former was considerably lower. PET measurements performed by defining "hot spot" regions of interest (ROIs) comprising 4 contiguous pixels with the highest radioactivity concentration showed a trend towards higher SUVs when the ROIs were outlined in the MVW-PC1 component than in the summed images. Time activity curves derived from "50% cut-off" ROIs based on an isocontour function whereby the pixels with SUVs between 50 to 100% of the highest radioactivity concentration were delineated, showed a significant decrease of the SUVs in normal adrenal glands and in adrenocortical adenomas after cortisone treatment. CONCLUSION: In addition to the clear decrease in image noise and the improved contrast between different structures with MVW-PCA, the results indicate that the definition of ROIs may be more accurate and precise in MVW-PC1 images than in conventional summed images. This might improve the precision of PET measurements, for instance in therapy monitoring as well as for delineation of the tumour in radiation therapy planning.

sted, utgiver, år, opplag, sider
2009. Vol. 9:6
HSV kategori
Forskningsprogram
Datoriserad bildanalys
Identifikatorer
URN: urn:nbn:se:uu:diva-104646DOI: 10.1186/1471-2342-9-6PubMedID: 19386097OAI: oai:DiVA.org:uu-104646DiVA, id: diva2:220026
Tilgjengelig fra: 2009-04-22 Laget: 2009-05-29 Sist oppdatert: 2017-12-13bibliografisk kontrollert
Inngår i avhandling
1. Clinical Studies on Adrenocortical Tumours using  [11C]-metomidate Positron Emission Tomography
Åpne denne publikasjonen i ny fane eller vindu >>Clinical Studies on Adrenocortical Tumours using  [11C]-metomidate Positron Emission Tomography
2009 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis, 2009. s. 33
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 486
HSV kategori
Forskningsprogram
kirurgi
Identifikatorer
urn:nbn:se:uu:diva-108797 (URN)978-91-554-7618-2 (ISBN)
Disputas
2009-11-14, Auditorium Minus, Museum Gustavianum, Uppsala, 09:15 (svensk)
Opponent
Veileder
Tilgjengelig fra: 2009-10-23 Laget: 2009-09-29 Sist oppdatert: 2009-10-23bibliografisk kontrollert

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