Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

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

http://ee.sharif.edu/~miap/Files/A%20Survey%20of%20Medical%20Image%20Registration.pdf

A survey of medical image registration.

Mini Mental State

Bone density achieved in early adulthood is the major determinant of risk of osteoporotic fracture. Up to 60% of women suffer osteoporotic fractures as a result of low bone density, which is under strong genetic control acting through effects on bone turnover. Here we show that common allelic variants in the gene encoding the vitamin D receptor can be used to predict differences in bone density, accounting for up to 75% of the total genetic effect on bone density in healthy individuals. The genotype associated with lower bone density was overrepresented in postmenopausal women with bone densities more than 2 standard deviations below values in young normal women. The molecular mechanisms by which bone density is regulated by the vitamin D receptor gene are not certain, although allelic differences in the 3' untranslated region may alter messenger RNA levels. These findings could open new avenues to the development and targeting of prophylactic interventions. It follows that other pathophysiological processes considered to be subject to complex multifactorial genetic regulation may also be modulated by a single gene with pleiotropic transcriptional actions.

Prediction of Bone-Density from Vitamin-D Receptor Alleles

The relative importance of genetic factors in determining bone mass in different parts of the skeleton is poorly understood. Lumbar spine and proximal femur bone mineral density and forearm bone mineral content were measured by photon absorptiometry in 38 monozygotic and 27 dizygotic twin pairs. Bone mineral density was significantly more highly correlated in monozygotic than in dizygotic twins for the spine and proximal femur and in the forearm of premenopausal twin pairs, which is consistent with significant genetic contributions to bone mass at all these sites. The lesser genetic contribution to proximal femur and distal forearm bone mass compared with the spine suggests that environmental factors are of greater importance in the aetiology of osteopenia of the hip and wrist. This is the first demonstration of a genetic contribution to bone mass of the spine and proximal femur in adults and confirms similar findings of the forearm. Furthermore, bivariate analysis suggested that a single gene or set of genes determines bone mass at all sites.

/pdf/genetic-determinants-of-bone-mass-in-adults-a-twin-study-21jo4nayb2.pdf

Genetic determinants of bone mass in adults. A twin study.

The relationship between physical fitness and bone mass in the femoral neck, lumbar spine, and forearm was studied in 84 normal women. Femoral neck and lumbar spine bone mineral density and forearm bone mineral content were estimated by absorptiometry. Fitness was quantitated from predicted maximal oxygen uptake. Femoral neck and lumbar bone mineral density were significantly correlated with fitness as well as age and weight. In the 46 postmenopausal subjects, fitness was the only significant predictor of femoral neck bone mineral density, and both weight and fitness predicted the lumbar bone mineral density. These data represent the first demonstration of a correlation between physical fitness, and, by implication, habitual physical activity, and bone mass in the femoral neck; they also support the previous reported correlation between lumbar bone mass and physical activity. The data suggest that increased physical fitness may increase bone mass at the sites of clinically important fractures in osteoporosis.

/pdf/physical-fitness-is-a-major-determinant-of-femoral-neck-and-13w91pl864.pdf

Physical fitness is a major determinant of femoral neck and lumbar spine bone mineral density.

A scanning collimated line source for simultaneously acquiring emission and transmission data from a gamma camera has been developed. The line source is microprocessor-controlled and incorporates hardware to electronically window the spatial gamma camera signals in order to separate the emission signals of the subject from transmission signals from the line source. The device improves upon the previously described emission-transmission scanning technique using a flood source in three ways: (1) it overcomes the limitation that the transmission radionuclide must have a lower energy than the emission radionuclide; (2) it provides narrow-beam (scatter free) attenuation measurements of the subject being examined; and (3) it reduces the radiation exposure to staff. Attenuation coefficients for an elliptocal water-filled phantom were measured to be mu = 0.15 +/- 0.01 cm-1. The technique has been validated in phantom and human studies using a range of radionuclide combinations and imaging geometries and gives equivalent results using separate and simultaneous acquisitions.

https://jnm.snmjournals.org/content/jnumed/34/10/1752.full.pdf

A scanning line source for simultaneous emission and transmission measurements in SPECT.

To assess mechanisms that cause generalized osteoporosis in rheumatoid arthritis (RA), we measured bone mineral density (BMD) by dual photon absorptiometry in the lumbar spine and femoral neck of 111 patients with RA. BMD was significantly reduced at both sites in these patients. Physical activity correlated significantly with BMD in patients with RA, and was found, by multiple regression analysis, to be a significant predictor of femoral bone density in female patients. Multiparity exerted a protective effect on lumbar bone density. Prednisolone (mean dosage 8 mg/day) was not associated with significantly increased bone loss in women, whereas higher dosages in men (mean 10.3 mg/day) were associated with increased lumbar bone loss. Reduced physical activity leading to a form of disuse osteoporosis appears to be an important factor in axial bone loss in RA.

Determinants of axial bone loss in rheumatoid arthritis.

Methods capable of correcting for head motion in all six degrees of freedom have been proposed for positron emission tomography (PET) brain imaging but not yet demonstrated in human studies. These methods rely on the accurate measurement of head motion in relation to the reconstruction coordinate frame. We present methodology for the direct calibration of an optical motion-tracking system to the reconstruction coordinate frame using paired coordinate measurements obtained simultaneously from a PET scanner and tracking system. We also describe the implementation of motion correction, based on the multiple acquisition frame method originally described by Picard and Thompson (1997), using data provided by the motion tracking system. Effective compensation for multiple six-degree-of-freedom movements is demonstrated in dynamic PET scans of the Hoffman brain phantom and a normal volunteer. We conclude that reduced distortion and improved quantitative accuracy can be achieved with this method in PET brain studies degraded by head movements.

Stefan Eberl

Papers

Genetic determinants of bone mass in adults. A twin study.

Physical fitness is a major determinant of femoral neck and lumbar spine bone mineral density.

A scanning line source for simultaneous emission and transmission measurements in SPECT.

Determinants of axial bone loss in rheumatoid arthritis.

Correction for head movements in positron emission tomography using an optical motion tracking system