Feasibility of generalised diffusion kurtosis imaging approach for brain glioma grading

Purpose An accurate differentiation of brain glioma grade constitutes an important clinical issue. Powerful non-invasive approach based on diffusion MRI has already demonstrated its feasibility in glioma grade stratification. However, the conventional diffusion tensor (DTI) and kurtosis imaging (DKI) demonstrated moderate sensitivity and performance in glioma grading. In the present work, we apply generalised DKI (gDKI) approach in order to assess its diagnostic accuracy and potential application in glioma grading. Methods Diffusion scalar metrics were obtained from 50 patients with different glioma grades confirmed by histological tests following biopsy or surgery. All patients were divided into two groups with low- and high-grade gliomas as grade II versus grades III and IV, respectively. For a comparison, trained radiologists segmented the brain tissue into three regions with solid tumour, oedema, and normal appearing white matter. For each region, we estimated the conventional and gDKI metrics including DTI maps. Results We found high correlations between DKI and gDKI metrics in high-grade glioma. Further, gDKI metrics enabled introduction of a complementary measure for glioma differentiation based on correlations between the conventional and generalised approaches. Both conventional and generalised DKI metrics showed quantitative maps of tumour heterogeneity and oedema behaviour. gDKI approach demonstrated largely similar sensitivity and specificity in low-high glioma differentiation as in the case of conventional DKI method. Conclusion The generalised diffusion kurtosis imaging enables differentiation of low- and high-grade gliomas at the same level as the conventional DKI. Additionally, gDKI exhibited higher sensitivity to tumour heterogeneity and tissue contrast between tumour and healthy tissue and, thus, may contribute as a complementary source of information on tumour differentiation

Feasibility of generalised diffusion kurtosis imaging approach for brain glioma grading

Purpose An accurate differentiation of brain glioma grade constitutes an important clinical issue. Powerful non-invasive approach based on diffusion MRI has already demonstrated its feasibility in glioma grade stratification. However, the conventional diffusion tensor (DTI) and kurtosis imaging (DKI) demonstrated moderate sensitivity and performance in glioma grading. In the present work, we apply generalised DKI (gDKI) approach in order to assess its diagnostic accuracy and potential application in glioma grading. Methods Diffusion scalar metrics were obtained from 50 patients with different glioma grades confirmed by histological tests following biopsy or surgery. All patients were divided into two groups with low- and high-grade gliomas as grade II versus grades III and IV, respectively. For a comparison, trained radiologists segmented the brain tissue into three regions with solid tumour, oedema, and normal appearing white matter. For each region, we estimated the conventional and gDKI metrics including DTI maps. Results We found high correlations between DKI and gDKI metrics in high-grade glioma. Further, gDKI metrics enabled introduction of a complementary measure for glioma differentiation based on correlations between the conventional and generalised approaches. Both conventional and generalised DKI metrics showed quantitative maps of tumour heterogeneity and oedema behaviour. gDKI approach demonstrated largely similar sensitivity and specificity in low-high glioma differentiation as in the case of conventional DKI method. Conclusion The generalised diffusion kurtosis imaging enables differentiation of low- and high-grade gliomas at the same level as the conventional DKI. Additionally, gDKI exhibited higher sensitivity to tumour heterogeneity and tissue contrast between tumour and healthy tissue and, thus, may contribute as a complementary source of information on tumour differentiation

Магнитно-резонансная трактография на основе вероятностных алгоритмов разложения по сферическим функциям у пациентов с глиомами зрительных путей

Background: The use of magnetic resonance (MR) tractography in neurosurgery is becoming an increasingly common practice for noninvasive imaging of white matter pathways. The most common method of tract reconstruction is the deterministic algorithm of diffusion tensor magnetic resonance imaging (MRI). However, this method of reconstructing pathways has a  number of significant limitations. The most important of them are the lack of the possibility of visualizing the intersecting fibers, the complexity of building tracts in the area of perifocal edema and in the immediate vicinity of the tumor borders. The method of MR tractography, based on obtaining a  diffusion image with a  high angular resolution (High Angular Resolution Diffusion Imaging, HARDI), using the constrained spherical deconvolution (CSD) algorithm for post-processing of data, makes it possible to avoid these disadvantages. Relatively recently, a new algorithm, Single-Shell 3-Tissue CSD (SS3TCSD), has been proposed for processing HARDI data, which has the potential to improve the reconstructing of pathways in the area of perifocal edema or edema-infiltration.Aim: To evaluate the potential of the new SS3TCSD algorithm compared to ST-CSD (Single-Tissue CSD) in the imaging of the optic radiation and visual tracts in patients with gliomas.Materials and methods: Diffusion and routine brain MRI was performed in 10 patients with newly diagnosed cerebral gliomas, followed by reconstruction of the optic radiation and visual tracts. We compared new algorithms for postprocessing MR tractography (ST-CSD and SS3TCSD) in imaging of the optic tract and visual radiation in patients with brain gliomas affecting various parts of the visual system.Results: The SS3T-CSD method showed a  lower mean percentage of false positive tracts compared to the ST-CSD method: 19.75% for the SS3T-CSD method and 80.32% for the ST-CSD method in cases of proximity of the tumor to the tracts, 5.27% for the SS3T-CSD method and 25.27% for the STCSD method in cases of reconstructing tracts in healthy white matter.Conclusion: The SS3T-CSD method has a number of advantages over ST-CSD and allows for successful imaging of the optic pathways that have a complex structure and repeatedly change direction along their course.Обоснование. Использование магнитно-резонансной (МР)-трактографии в  нейрохирургии становится все более частой практикой благодаря возможности неинвазивно визуализировать проводящие пути белого вещества. Самый распространенный метод реконструкции трактов  – детерминистический алгоритм диффузионно-тензорной МР-томографии. Однако этот метод построения проводящих путей имеет целый ряд существенных ограничений. К  наиболее важным из них относятся отсутствие возможности визуализации пересекающихся между собой волокон, сложность построения трактов в  области перифокального отека и  в непосредственной близости к  границам опухоли. Этих недостатков помогает избежать метод МР-трактографии, основанный на получении диффузионного изображения с  высоким угловым разрешением (англ. high angulation reconstruction diffusion imaging, HARDI) с  использованием алгоритма разложения по сферическим функциям (англ. constrained spherical deconvolution, CSD) для постобработки данных. Относительно недавно был предложен новый алгоритм для обработки данных HARDI: разложение МР-сигнала нескольких типов ткани мозга по сферическим функциям с  использованием одного b-фактора  – SS3T-CSD (single-shell 3-tissue CSD). Предположительно, он позволит улучшить построение проводящих путей в  области перифокального отека или отека-инфильтрации.Цель  – исследовать возможности алгоритма SS3T-CSD по сравнению с  ST-CSD (single-tissue CSD – разложение МР-сигнала одного типа ткани мозга по сферическим функциям) при визуализации зрительной радиации и  зрительных трактов у пациентов с глиомами.Материал и  методы. Десяти пациентам с  впервые выявленными глиомами головного мозга выполняли диффузионную и  рутинную МР-томографию головного мозга с  последующей реконструкцией зрительной лучистости и зрительных трактов. Мы сравнили новые алгоритмы постобработки МР-трактографии STCSD и SS3T-CSD при визуализации зрительных трактов и зрительной лучистости у пациентов с  глиомами головного мозга, поражающими различные отделы зрительного анализатора.Результаты. Метод SS3T-CSD показал меньший средний процент ложноположительных трактов по сравнению с методом ST-CSD: 19,75 против 80,32% в случаях близкого расположения опухоли к  трактам и  5,27 против  25,27% в  случаях построения трактов в  нормальном белом веществе.Заключение. Метод SS3T-CSD имеет ряд преимуществ по сравнению с ST-CSD и позволяет успешно визуализировать зрительные проводящие пути, имеющие сложную структуру и  неоднократно меняющие направление по своему ходу