A reliable and efficient method for cerebral ventricular volumetry in pediatric neuroimaging.

OBJECTIVES: Cerebral ventricular volume has the potential to become an important parameter in quantitative neurological diagnosis. However, no accepted methodology for routine clinical use exists to date. We sought a robust, reproducible, and fast technique to evaluate cerebral ventricular volume in young children. METHODS: We describe a novel volumetric methodology to segment and visualize intracerebral fluid spaces and to quantify ventricular volumes. The method is based on broadly available T1 weighted volumetric magnetic resonance (MR) imaging, an interactive watershed transform, and a fully automated histogram analysis. We evaluated this volumetric methodology with 34 clinical volumetric MR datasets from non-sedated children (age 6-7 y) with a history of prematurity and low birth weight (< or = 1500 g) obtained during a prospective study. RESULTS: The methodology, with adaptation for small ventricular size, was capable of evaluating all 34 of the pediatric datasets for cerebral ventricular volume. The method was a) robust for normal and pathological anatomy, b) reproducible, c) fast with less than five minutes for image analysis, and d) equally applicable to children and adults. CONCLUSIONS: Clinical brain ventricular volume calculations in non-sedated children can be performed using routine MR imaging besides efficient three-dimensional segmentation and histogram analysis with results that are robust and reproducible.

A stereotactic method for the three-dimensional registration of multi-modality biologic images in animals: NMR, PET, histology, and autoradiography.

The objective of this work was to develop and then validate a stereotactic fiduciary marker system for tumor xenografts in rodents which could be used to co-register magnetic resonance imaging (MRI), PET, tissue histology, autoradiography, and measurements from physiologic probes. A Teflon fiduciary template has been designed which allows the precise insertion of small hollow Teflon rods (0.71 mm diameter) into a tumor. These rods can be visualized by MRI and PET as well as by histology and autoradiography on tissue sections. The methodology has been applied and tested on a rigid phantom, on tissue phantom material, and finally on tumor bearing mice. Image registration has been performed between the MRI and PET images for the rigid Teflon phantom and among MRI, digitized microscopy images of tissue histology, and autoradiograms for both tissue phantom and tumor-bearing mice. A registration accuracy, expressed as the average Euclidean distance between the centers of three fiduciary markers among the registered image sets, of 0.2 +/- 0.06 mm was achieved between MRI and microPET image sets of a rigid Teflon phantom. The fiduciary template allows digitized tissue sections to be co-registered with three-dimensional MRI images with an average accuracy of 0.21 and 0.25 mm for the tissue phantoms and tumor xenografts, respectively. Between histology and autoradiograms, it was 0.19 and 0.21 mm for tissue phantoms and tumor xenografts, respectively. The fiduciary marker system provides a coordinate system with which to correlate information from multiple image types, on a voxel-by-voxel basis, with sub-millimeter accuracy--even among imaging modalities with widely disparate spatial resolution and in the absence of identifiable anatomic landmarks.

Linking molecular imaging terminology to the gene ontology (GO).

The rapidly developing domain of molecular imaging represents the merging of current advances in the fields of molecular biology and imaging research. Despite this merger, an information gap continues to exist between the scientists who discover new gene products and the imaging scientists who can exploit this information. The Gene Ontology (GO) Consortium seeks to provide a set of structured terminologies for the conceptual annotation of gene product function, process and location in databases. However, no such structured set of concept-oriented terminology exists for the molecular imaging domain. Since the purpose of GO is to capture the information about the role of gene products, we propose that the mapping of GO's established ontological concepts to a molecular imaging terminology will provide the necessary bridge to fill the information gap between the two fields. We have extracted terms and definitions from an already published molecular imaging glossary as well as molecular imaging research articles, and developed molecular imaging concepts. We then mapped our molecular imaging concepts to the existing gene ontology concepts as a method to comprehensively represent molecular imaging.

Quantitative assessment of bone marrow hematopoiesis using parametric magnetic resonance imaging.

Spatial maps of the percentage cellularity in pelvic bone marrow were calculated at a resolution of 15.6 mm3 from six volunteers and 10 patients treated for documented hematologic disease using a three-point Dixon MRI pulse sequence. The percentage cellularity calculation was aided by analyzing a two-dimensional feature space consisting of the apparent water fraction (Wa), and the T2 relaxation time of water (T2w). An extracellular water fraction was assigned to each voxel on the basis of a two-component T2w algorithm. In six cases, the method was compared to results obtained from core biopsies or aspirates of the posterior iliac crest. The results indicate that segmentation schemes that combine high-quality phase-contrast imaging with nuclear relaxation time measurements can potentially identify the true fractional marrow volume occupied by hematopoietic elements in a variety of clinical situations.

Sensitivity-enhanced echo-planar MRI at 1.5T using a 5 x 5 mesh dome resonator.

In this work a 5 x 5 mesh dome resonator that has been optimized for functional brain imaging is presented. The resonator was reduced in length and diameter compared with previous versions to reduce sample losses, thus enhancing the signal-to-noise ratio of the acquired data. In addition, a 5 x 5 mesh design was employed, which offered improved axial homogeneity over an earlier 3 x 3 mesh version. The new resonator exhibited high sensitivity and good homogeneity over the brain volume, permitting analysis of functional activation over large areas of the cerebral cortex. In a direct comparison with a standard clinical head-imaging resonator, the high sensitivity of the 5 x 5 mesh dome resonator resulted in greater statistical confidence in functional activation.