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Image Sets (image + set)

Distribution by Scientific Domains

Life Sciences	66%
Medical Sciences	33%

Selected Abstracts

Quantitative evaluation of automated skull-stripping methods applied to contemporary and legacy images: Effects of diagnosis, bias correction, and slice location

HUMAN BRAIN MAPPING, Issue 2 2006
Christine Fennema-Notestine
Abstract Performance of automated methods to isolate brain from nonbrain tissues in magnetic resonance (MR) structural images may be influenced by MR signal inhomogeneities, type of MR image set, regional anatomy, and age and diagnosis of subjects studied. The present study compared the performance of four methods: Brain Extraction Tool (BET; Smith [2002]: Hum Brain Mapp 17:143,155); 3dIntracranial (Ward [1999] Milwaukee: Biophysics Research Institute, Medical College of Wisconsin; in AFNI); a Hybrid Watershed algorithm (HWA, Segonne et al. [2004] Neuroimage 22:1060,1075; in FreeSurfer); and Brain Surface Extractor (BSE, Sandor and Leahy [1997] IEEE Trans Med Imag 16:41,54; Shattuck et al. [2001] Neuroimage 13:856,876) to manually stripped images. The methods were applied to uncorrected and bias-corrected datasets; Legacy and Contemporary T1 -weighted image sets; and four diagnostic groups (depressed, Alzheimer's, young and elderly control). To provide a criterion for outcome assessment, two experts manually stripped six sagittal sections for each dataset in locations where brain and nonbrain tissue are difficult to distinguish. Methods were compared on Jaccard similarity coefficients, Hausdorff distances, and an Expectation-Maximization algorithm. Methods tended to perform better on contemporary datasets; bias correction did not significantly improve method performance. Mesial sections were most difficult for all methods. Although AD image sets were most difficult to strip, HWA and BSE were more robust across diagnostic groups compared with 3dIntracranial and BET. With respect to specificity, BSE tended to perform best across all groups, whereas HWA was more sensitive than other methods. The results of this study may direct users towards a method appropriate to their T1 -weighted datasets and improve the efficiency of processing for large, multisite neuroimaging studies. Hum. Brain Mapping, 2005. © 2005 Wiley-Liss, Inc. [source]

Magnetic resonance histology of the adult zebrafish brain: optimization of fixation and gadolinium contrast enhancement

NMR IN BIOMEDICINE, Issue 4 2010
Jeremy F. P. Ullmann
Abstract Magnetic resonance histology (MRH) has become a widespread tool to examine brain morphology in situ or ex vivo. Samples are routinely fixed and stained to allow for longer scan times with increased contrast and resolution. Although the zebrafish is an important model for neuroscience, to date most MRH studies have focused almost exclusively on mice. In this paper, we examined, for the first time, the zebrafish brain using MRH. We compared a range of fixatives, contrast agents, and fixation/staining durations to determine optimal imaging of the zebrafish brain. By quantifying the T1, T2, and T2* relaxation values, we demonstrated that ethanol and potassium permanganate are unviable for imaging and significant differences exist between mono and di-aldehydes. Furthermore, we compared two commercially available gadolinium-based contrast agents, Magnevist® and Optimark®, at five different concentrations. For both contrast agents, a concentration of 0.5% was determined to be ideal as it significantly shortened the T1 but maintained a relatively long T2 and T2*. Subsequently, we analyzed the duration of fixation/staining and established a period of 12,h, which best minimized T1 values but maintained T2 and T2* values. Finally, using this optimized fixation and staining protocol, we performed a gradient-echo T2*-weighted imaging to obtain an image set of the adult zebrafish brain at an isotropic resolution of 10,µm. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Interobserver agreement between primary graders and an expert grader in the Bristol and Weston diabetic retinopathy screening programme: a quality assurance audit

DIABETIC MEDICINE, Issue 8 2009
S. Patra
Abstract Aims, To assess the quality and accuracy of primary grading in the Bristol and Weston diabetic retinopathy screening programme and to set standards for future interobserver agreement reports. Methods, A prospective audit of 213 image sets from six fully trained primary graders in the Bristol and Weston diabetic retinopathy screening programme was carried out over a 4-week period. All the images graded by the primary graders were regraded by an expert grader blinded to the primary grading results and the identity of the primary grader. The interobserver agreement between primary graders and the blinded expert grader and the corresponding Kappa coefficient was determined for overall grading, referable, non-referable and ungradable disease. The audit standard was set at 80% for interobserver agreement with a Kappa coefficient of 0.7. Results, The interobserver agreement bettered the audit standard of 80% in all the categories. The Kappa coefficient was substantial (0.7) for the overall grading results and ranged from moderate to substantial (0.59,0.65) for referable, non-referable and ungradable disease categories. The main recommendation of the audit was to provide refresher training for the primary graders with focus on ungradable disease. Conclusion, The audit demonstrated an acceptable level of quality and accuracy of primary grading in the Bristol and Weston diabetic retinopathy screening programme and provided a standard against which future interobserver agreement can be measured for quality assurance within a screening programme. [source]

Quantitative evaluation of automated skull-stripping methods applied to contemporary and legacy images: Effects of diagnosis, bias correction, and slice location

Longitudinal quantitative evaluation of lesion size change in femoral head osteonecrosis using three-dimensional magnetic resonance imaging and image registration

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2006
Masaki Takao
Abstract It remains controversial whether some lesions of femoral head osteonecrosis regress during the natural course of the disease. With image registration, accurately matched image sets of the same subject can be acquired at different times. We applied image registration to evaluate lesion size change and assessed accuracy and usefulness compared to volume measurements and a conventional method. We also investigated whether lesions regress with this technique and with volume measurements. Baseline and 1 year minimum follow-up scans were conducted on 25 patients (31 hips) without radiological evidence of collapse. A three-dimensional (3D) spoiled gradient recalled echo sequence was used in the coronal direction (slice thickness,=,2 mm; slice pitch,=,1 mm). Size change was evaluated on all contiguous pairs of matched images after image registration. As a conventional method, coronal images (slice thickness,=,5 mm) were reconstructed, and size change was evaluated on the five representative coronal slices. Evaluation with the conventional method identified eight lesions with apparent reduction; assessments using image registration and volume measurements identified three lesions, all within a year of initial steroid treatment and remaining at ARCO stage I at follow up. Evaluation of lesion size change using image registration was comparable to volume measurements. Inaccurate estimation of lesion size change due to mismatching of slice planes can be excluded. We demonstrated that some early lesions detected less than a year after initial steroid treatment can show size reduction with image registration as well as with volume measurements. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1231,1239, 2006 [source]