We present a new algorithm, called marching cubes, that creates triangle models of constant density surfaces from 3D medical data. Using a divide-and-conquer approach to generate inter-slice connectivity, we create a case table that defines triangle topology. The algorithm processes the 3D medical data in scan-line order and calculates triangle vertices using linear interpolation. We find the gradient of the original data, normalize it, and use it as a basis for shading the models. The detail in images produced from the generated surface models is the result of maintaining the inter-slice connectivity, surface data, and gradient information present in the original 3D data. Results from computed tomography (CT), magnetic resonance (MR), and single-photon emission computed tomography (SPECT) illustrate the quality and functionality of marching cubes. We also discuss improvements that decrease processing time and add solid modeling capabilities.

/pdf/marching-cubes-a-high-resolution-3d-surface-construction-3ealswkmtb.pdf

Marching cubes: A high resolution 3D surface construction algorithm

Co-Planar Stereotaxic Atlas of the Human Brain—3-Dimensional Proportional System: An Approach to Cerebral Imaging, J. Talairach, P. Tournoux. Georg Thieme Verlag, New York (1988), 122 pp., 130 figs. DM 268

https://users.fmrib.ox.ac.uk/~jesper/papers/readgroup_071009/Ashburner07.pdf

A fast diffeomorphic image registration algorithm

http://midag.cs.unc.edu/pubs/papers/Neuroimage06_Yushkevich.pdf

User-guided 3D active contour segmentation of anatomical structures: Significantly improved efficiency and reliability

A novel approach to correcting for intensity nonuniformity in magnetic resonance (MR) data is described that achieves high performance without requiring a model of the tissue classes present. The method has the advantage that it can be applied at an early stage in an automated data analysis, before a tissue model is available. Described as nonparametric nonuniform intensity normalization (N3), the method is independent of pulse sequence and insensitive to pathological data that might otherwise violate model assumptions. To eliminate the dependence of the field estimate on anatomy, an iterative approach is employed to estimate both the multiplicative bias field and the distribution of the true tissue intensities. The performance of this method is evaluated using both real and simulated MR data.

/pdf/a-nonparametric-method-for-automatic-correction-of-intensity-4smqm7oz20.pdf

A nonparametric method for automatic correction of intensity nonuniformity in MRI data

Existing methods for evaluating in vivo placental function fail to reliably detect pregnancies at-risk for adverse outcomes prior to maternal and/or fetal morbidity. Here we report the results of a prospective dual-site longitudinal clinical study of quantitative placental T2* as measured by blood oxygen-level dependent magnetic resonance imaging (BOLD-MRI). The objectives of this study were: 1) to quantify placental T2* at multiple time points across gestation, and its consistency across sites, and 2) to investigate the association between placental T2* and adverse outcomes. 797 successful imaging studies, at up to three time points between 11 and 38 weeks of gestation, were completed in 316 pregnancies. Outcomes were stratified into three groups: (UN) uncomplicated/normal pregnancy, (PA) primary adverse pregnancy, which included hypertensive disorders of pregnancy, birthweight <5th percentile, and/or stillbirth or fetal death, and (SA) secondary abnormal pregnancy, which included abnormal prenatal conditions not included in the PA group such as spontaneous preterm birth or fetal anomalies. Of the 316 pregnancies, 198 (62.6%) were UN, 70 (22.2%) PA, and 48 (15.2%) SA outcomes. We found that the evolution of placental T2* across gestation was well described by a sigmoid model, with T2* decreasing continuously from a high plateau level early in gestation, through an inflection point around 30 weeks, and finally approaching a second, lower plateau in late gestation. Model regression revealed significantly lower T2* in the PA group than in UN pregnancies starting at 15 weeks and continuing through 33 weeks. T2* percentiles were computed for individual scans relative to UN group regression, and z-scores and receiver operating characteristic (ROC) curves calculated for association of T2* with pregnancy outcome. Overall, differences between UN and PA groups were statistically significant across gestation, with large effect sizes in mid- and late- pregnancy. The area under the curve (AUC) for placental T2* percentile and PA pregnancy outcome was 0.71, with the strongest predictive power (AUC of 0.76) at the mid-gestation time period (20–30 weeks). Our data demonstrate that placental T2* measurements are strongly associated with pregnancy outcomes often attributed to placental insufficiency. Trial registration: ClinicalTrials.gov: NCT02749851.

Quantitative longitudinal T2* mapping for assessing placental function and association with adverse pregnancy outcomes across gestation

Automated Coronary Artery Calcium Scoring for Chest CT Scans.

Computed tomography (CT) and MRI are arguably the two most important imaging approaches in modern hospitals and clinics. CT offers fast scanning speed and high spatial resolution, but suffers from poor soft-tissue contrast and a substantial radiation dose. MRI, on the other hand, provides superior soft-tissue contrast, and functional and molecular imaging capabilities, but often suffers from long scan time and sub-optimal geometrical accuracy. MRI is also difficult to quantify in any absolute units, and has much greater sensitivity than specificity. In some clinical scenarios—such as guiding radiation therapy, analyzing atherosclerotic plaques, and assessing acute strokes and brain injuries—CT and magnetic resonance (MR) images can be synergistic when captured simultaneously. However, because clinicians typically collect CT and MR images independently at different times and retrospectively register them based on a number of approximated assumptions, residual errors can be introduced. These errors can originate from non-repeatable contrast dynamics, organ motion, patient posture, signal nonlinearity, and inconsistent contrast mechanisms between CT and MRI. A combined CT-MRI scanner would reduce residual errors, enable simultaneous anatomical and functional imaging, and minimize exposure to ionizing radiation. Although multimodal imaging systems have become increasingly popular, a combined CT-MRI system has not yet been attempted. Two major obstacles in designing such a system are the bulkiness of the imaging scanners and the conflict in imaging physics, namely CT’s rotating metallic parts and MRI’s magnetic fields. Overcoming these challenges, we recently created a design for a combined CT-MRI Figure 1. Rendering of the proposed design for a synchronized computed tomography (CT) and MRI scanner to guide radiation therapy in real-time. Shown are the coil blocks of the superconducting MRI magnet’s primary layer (purple) and shielding layer (blue), a cryostat of the superconducting MRI magnet (aqua), longitudinal (green) and transverse (yellow) gradient coils, x-ray sources (red), and x-ray detectors (orange). The coil blocks of the superconducting magnet provide a uniform static magnetic field over a small region of interest, while the gradient coils enable MRI spatial encoding. A multi-source interior tomography scheme is used for CT image reconstruction.

Design proposed for a combined MRI/computed-tomography scanner

Let's read! We will often find out this sentence everywhere. When still being a kid, mom used to order us to always read, so did the teacher. Some books are fully read in a week and we need the obligation to support reading. What about now? Do you still love reading? Is reading only for you who have obligation? Absolutely not! We here offer you a new book enPDFd medical imaging workstations what is missing and coming to read.

Medical imaging workstations: what is missing and what is coming?

Contiguous transaxial high resolution CT scans of more than 100 patients with craniofacial deformities and orthopedic disorders were obtained. The CT scan examinations were used diagnostically in determining the need for surgery and for planning therapy. The serial section data was reconstructed in a three-dimensional form with surface and transparent volumetric computer graphics processing techniques. Real time sequences showing the presence of internal abnormalities in these patients were produced and recorded on video tape. This study demonstrates the feasibility and technical requirements of three-dimensional volumetric visualization for diagnostic evaluation of patients with craniofacial and orthopedic disorders.

Michael W. Vannier

Papers

Quantitative longitudinal T2* mapping for assessing placental function and association with adverse pregnancy outcomes across gestation

Automated Coronary Artery Calcium Scoring for Chest CT Scans.

Design proposed for a combined MRI/computed-tomography scanner

Medical imaging workstations: what is missing and what is coming?

Volumetric 3-D imaging of computerized tomography scans.