Optimal slice thickness for object detection with longitudinal partial volume effects in computed tomography [JACMP, 18(1) 251-259, 2017]

Summary Objectives: Introduction of a new atlas-based method for analyzing functional data which takes into account the variability of individual human brains and the partial volume effects of functional emission computed tomography images in complex anatomical 3D regions, as well as describing the underlying multi-modal image processing principles. Methods: 3D atlas extraction is done directly by automated segmentation of individual magnetic resonance images of the patient’s head. This is done in two steps: voxel-based classification of T1-weighted images for tissue differentiation (low-level processing) is followed by knowledge-based analysis of the classified images for extraction of 3D anatomical regions (high-level processing). For atlas-based quantification of co-registered functional images, 3D anatomical regions can be convoluted with an idealized point spread function of the emission computed tomography system, after which a partial volume-dependent threshold can be determined. Results: Quantitative evaluation studies, based on 50 realistic software head phantoms and 24 image data sets obtained from healthy subjects and patients, show low misclassification rates and stable results for the neural network-based classification approach (mean ± SD 3.587 ± 0.466%, range 2.726-4.927%) as well as for the adjustable parameters of the knowledge-based approach. Computation time is <5 min for classification, <1 min for most of the extraction algorithms. The influence of the partial volume-dependent threshold is shown for an activation study. Conclusions: This new method allows 3D atlas generation without the need to warp individual image data to an anatomical or statistical brain atlas. Going beyond the purely tissue-oriented approach, partial volume effects of emission computed tomography images can be analyzed in complex anatomical 3D regions.

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3D MRI of the Ankle: A Concise State-of-the-Art Review

Seminars in Musculoskeletal Radiology ◽

10.1055/s-0041-1731332 ◽

2021 ◽

Vol 25 (03) ◽

pp. 514-526

Author(s):

Benjamin Fritz ◽

Jan Fritz ◽

Reto Sutter

Keyword(s):

Pulse Sequence ◽

Spin Echo ◽

Pulse Sequences ◽

Acquisition Time ◽

Slice Thickness ◽

3D Mri ◽

Partial Volume ◽

Partial Volume Effects ◽

Wide Range ◽

Volume Effects

AbstractMagnetic resonance imaging (MRI) is a powerful imaging modality for visualizing a wide range of ankle disorders that affect ligaments, tendons, and articular cartilage. Standard two-dimensional (2D) fast spin-echo (FSE) and turbo spin-echo (TSE) pulse sequences offer high signal-to-noise and contrast-to-noise ratios, but slice thickness limitations create partial volume effects. Modern three-dimensional (3D) FSE/TSE pulse sequences with isotropic voxel dimensions can achieve higher spatial resolution and similar contrast resolutions in ≤ 5 minutes of acquisition time. Advanced acceleration schemes have reduced the blurring effects of 3D FSE/TSE pulse sequences by affording shorter echo train lengths. The ability for thin-slice partitions and multiplanar reformation capabilities eliminate relevant partial volume effects and render modern 3D FSE/TSE pulse sequences excellently suited for MRI visualization of several oblique and curved structures around the ankle. Clinical efficiency gains can be achieved by replacing two or three 2D FSE/TSE sequences within an ankle protocol with a single isotropic 3D FSE/TSE pulse sequence. In this article, we review technical pulse sequence properties for 3D MRI of the ankle, discuss practical considerations for clinical implementation and achieving the highest image quality, compare diagnostic performance metrics of 2D and 3D MRI for major ankle structures, and illustrate a broad spectrum of ankle abnormalities.

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