Serebral Hemisferdeki Yaşa Bağlı Değişikliklerin Bir Ölçüsü Olarak Silüet Manyetik Rezonans Beyin Görüntülerinin Fraktal Boyutu

Amaç: Bu çalışmanın amacı, manyetik rezonans beyin görüntülerinden elde edilen silüet görüntülerin fraktal analizini kullanarak serebral hemisferlerin uzaysal konfigürasyonundaki yaşa bağlı değişiklikleri (uzaysal karmaşıklık ve boşluk doldurma kapasitesindeki değişiklikler dahil) tanımlamaktır. Gereç ve Yöntemler: Yaşları 18-86 yıl arasında olan 100 (44 erkek, 56 kadın) katılımcının manyetik rezonans beyin görüntüleri incelenmiştir. Her bir beyin manyetik rezonans görüntülemeden, koronal düzlemde dört tomografik kesit ve aksiyal düzlemde bir kesit dahil olmak üzere beş manyetik rezonans görüntüsü seçildi. Serebral hemisfer silüetlerinin fraktal boyut değerleri, iki boyutlu kutu sayma algoritması kullanılarak ölçüldü. Öklid geometrisine dayalı morfometrik parametreler (çevre, alan ve bunlardan türetilen değerler) de belirlendi. Bulgular: Çalışılan beş tomografik kesitin ortalama fraktal boyut değeri 1,878±0,0009 ve dört koronal kesitin ortalama değeri ise 1,868±0,0010 idi. İncelenen tüm tomografi kesitleri ve dört koronal kesit için serebral silüetlerin fraktal boyut değerlerinin yaş ile birlikte anlamlı olarak azaldığı gösterildi (sırasıyla r=-0,512, p<0,001 ve r=-0,491, p<0,001). Erkeklerde ve kadınlarda yaşa bağlı değişikliklerin karakterindeki fark istatistiksel olarak anlamlı değildi. Çalışılan örneğin yaş ve fraktal boyut değerleri esas alınarak, serebral hemisfer silüetlerinin fraktal boyut değerleri için klinik nörogörüntülemede norm kriter olarak kullanılabilecek güven aralıkları belirlendi. Sonuç: Fraktal analiz ve elde edilen veriler, yaşa bağlı serebral atrofi derecesini değerlendirmek ve normal yaşlanma ile nörodejeneratif hastalıklar arasında ayrım yapmak için nörogörüntülemede kullanılabilir.

Anahtar Kelimeler:

Fraktal, beyin, yaşlanma, atrofi, nörogörüntüleme

Fractal Dimension of Silhouette Magnetic Resonance Brain Images as a Measure of Age-Associated Changes in Cerebral Hemispheres

Aim: The aim of the present study was to characterize age-associated changes in the spatial configuration of cerebral hemispheres (including changes in spatial complexity and space-filling capacity) using fractal analysis of silhouette magnetic resonance brain images. Material and Methods: Magnetic resonance brain images of 100 (44 male, 56 female) participants aged between 18-86 years were studied. Five magnetic resonance images were selected from the magnetic resonance imaging dataset of each brain, including four tomographic sections in the coronal plane and one in the axial plane. Fractal dimension values of the cerebral hemispheres silhouettes were measured using the two-dimensional box-counting algorithm. Morphometric parameters based on Euclidean geometry (perimeter, area, and their derivative values) were determined as well. Results: The average fractal dimension value of the five studied tomographic sections was 1.878±0.0009, the average value of four coronal sections was 1.868±0.0010. It was shown that fractal dimension values of cerebral silhouettes for all studied tomographic sections and four coronal sections significantly decrease with age (r=-0.512, p<0.001 and r=-0.491, p<0.001, respectively). The difference in the character of age-related changes in males and females was not statistically significant. Based on the age and the fractal dimension values of the studied sample, the confidence intervals of the fractal dimension values of cerebral hemispheres silhouettes were determined, which can be used as norm criteria in clinical neuroimaging. Conclusion: The fractal analysis and obtained data can be used in neuroimaging for assessing the degree of age-related cerebral atrophy and for differentiating between normal aging and neurodegenerative diseases.

Keywords:

Fractals, cerebrum, aging, atrophy, neuroimaging,

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