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      High-resolution fluorodeoxyglucose positron emission tomography and magnetic resonance imaging findings of a pituitary microtumor in a dog

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          Abstract

          A 16-year-old, castrated, male English cocker spaniel dog was presented due to generalized alopecia. Routine clinical pathology, endocrine and abdominal ultrasonography results were consistent with a diagnosis of pituitary-dependent hyperadrenocorticism. The adenohypophyseal lesion was clearly visualized on both 3 T and 7 T magnetic resonance imaging (MRI) of the pituitary gland. Although biochemical and MRI findings were consistent with a functional pituitary microtumor, a pituitary lesion was not detected using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET). This report firstly describes the application of high-resolution FDG-PET to a spontaneous pituitary microtumor in a dog.

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          Most cited references28

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          Correlation between impairment of glucocorticoid feedback and the size of the pituitary gland in dogs with pituitary-dependent hyperadrenocorticism.

          Under the assumption that the impaired inhibitory effect of glucocorticoids on cell division is an important determinant in the progression of corticotrophic adenomas, it is postulated that the magnitude of proliferation and the resistance to glucocorticoids are correlated. To test this hypothesis, 67 dogs with pituitary-dependent hyperadrenocorticism were studied to determine whether a correlation could be demonstrated between the effect of dexamethasone administration on the activity of the pituitary-adrenocortical axis and the size of the pituitary gland as estimated by computed tomography. The volumes of the pituitary glands as calculated from summations of subsequent images of pituitary areas, ranged from 11.8 to 3238.6 mm3. Among the three dimensions, the height of the pituitary was the most sensitive indicator of enlargement. Calculation of the pituitary height/brain area ratio (P/B ratio) allowed correction for the size of the dog. The P/B ratio had the highest discriminatory power in distinguishing enlarged (n = 41) from non-enlarged (n = 26) pituitaries. The effects of dexamethasone (0.1 mg/kg) on the plasma concentrations of cortisol and ACTH and on the urinary corticoid/creatinine (C/C) ratios were expressed as percentage changes from the initial values. For ACTH, cortisol and C/C ratios these figures for resistance to dexamethasone were significantly correlated with the dimensions of the pituitary, particularly the height, volume and P/B ratio. It is concluded that the magnitude of the expansion of pituitary corticotrophic adenomas is dependent upon the loss of restraint by glucocorticoids, i.e. the degree of insensitivity to glucocorticoid feedback.
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            Incidental focal 18F-FDG uptake in the pituitary gland: clinical significance and differential diagnostic criteria.

            The purpose of this study was to identify the incidence and clinical significance of incidental pituitary uptake on whole-body (18)F-FDG PET/CT. We evaluated 13,145 consecutive subjects who underwent (18)F-FDG PET/CT. The final diagnosis of pathologic or physiologic uptake was based on brain MRI and follow-up PET scanning. Receiver-operating-characteristic curve analysis was performed to determine an optimal cutoff for detecting pathologic uptake. We found that 107 (0.8%) subjects showed incidental pituitary uptake. In 29 of 71 subjects with the final diagnosis, the pituitary uptake was pathologic: macroadenomas (n = 21), microadenomas (n = 5), and malignancy (n = 3). When a maximum standardized uptake value of 4.1 was used as an optimal criterion for detecting pathologic uptake, the diagnostic sensitivity, specificity, and accuracy were 96.6%, 88.1%, and 91.5%, respectively. Although incidental pituitary uptake is an unusual finding, the degree of (18)F-FDG accumulation is helpful in identifying pathologic pituitary lesions that warrant further diagnostic evaluation.
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              Magnetic resonance imaging of pituitary adenomas.

              Today, MR is the only method needed for the morphological investigation of endocrine-active pituitary adenomas. In acromegaly and Cushing's syndrome, the therapeutic attitude is directly dictated by MR data. We present the MR aspect of pituitary adenomas according to size, sex, age, endocrine activity and a few particular conditions such as hemorrhagic pituitary adenomas, pituitary adenomas during pregnancy, cavernous sinus invasion and postsurgical changes. When an intrasellar mass extending out of the sella turcica is detected, the goal of the MR examination is to indicate precisely the origin of the tumor, its extension in relation to the various surrounding structures, its structure and its enhancement in order to help in the differential diagnosis. Demonstration of very small pituitary adenomas remains a challenge. When SE T1- and Turbo SE T2-weighted sequences are non-diagnostic, enhanced imaging becomes mandatory; half-dose gadolinium injection, delayed sequence, dynamic imaging can be of some help.
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                Author and article information

                Contributors
                ydson@gachon.ac.kr
                anna0106@naver.com
                jhkang@chungbuk.ac.kr
                dwchang@chungbuk.ac.kr
                ybjin@kribb.re.kr
                jungdi@gnu.ac.kr
                chulhyun@kbsi.re.kr
                mpyang@chungbuk.ac.kr
                +82-43-240-6322 , srlee@kribb.re.kr
                +82-43-261-3744 , kangbt@chungbuk.ac.kr
                Journal
                Ir Vet J
                Ir Vet J
                Irish Veterinary Journal
                BioMed Central (London )
                0368-0762
                2046-0481
                23 September 2015
                23 September 2015
                2015
                : 68
                : 1
                : 22
                Affiliations
                [ ]Neuroscience Research Institute, Gachon University, Incheon, South Korea
                [ ]Department of Biomedical Engineering, College of Health Science, Gachon University, Incheon, South Korea
                [ ]Laboratory of Veterinary Dermatology and Neurology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk South Korea
                [ ]Laboratory of Veterinary Internal Medicine, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk South Korea
                [ ]Laboratory of Veterinary Radiology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk South Korea
                [ ]The National Primate Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Ochang, Chungbuk Republic of Korea
                [ ]Institute of Animal Medicine, Gyeongsang National University, Jinju, South Korea
                [ ]Center of Magnetic Resonance Research, Korea Basic Science Institute, Ochang, Chungbuk Republic of Korea
                Article
                50
                10.1186/s13620-015-0050-5
                4581074
                eff6bc9f-37c8-407a-b033-46fd0e3ae14e
                © Son et al. 2015

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                History
                : 13 December 2014
                : 14 September 2015
                Categories
                Case Report
                Custom metadata
                © The Author(s) 2015

                Veterinary medicine
                dog,fluorodeoxyglucose positron emission tomography,magnetic resonance imaging,pituitary microtumor

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