Technology and Health Care

Medical image registration is commonly required in order to combine the complementary information provided by different medical imaging modalities. In this paper, a new automatic registration scheme is proposed to register 3-D CT-MR head images and is currently tested on a clinical environment. The proposed scheme, after the preprocessing and the outer surface extraction of the data, is based on the use the rigid transformation method, in conjunction with a combination of global and local optimization techniques. Analytically, the paper exploits the optimization efficiency of three widely used optimization techniques, in obtaining the parameters of the rigid transformation model: the Downhill Simplex Method, the Genetic Algorithms and the Simulated Annealing. These optimization techniques are further combined by the sequential application of the Powell optimization method in order to refine the registration and increase its accuracy. A comparative study involving these optimization techniques in conjunction with the rigid transformation, and two other methods, the ICP and the manual methods, is also presented, for a sufficient number of clinical CT-MR brain images. Finally, quantitative and qualitative results are also presented to validate the performance of these automatic surface-based registration schemes, in terms of consistency and accuracy. Throughout of this study, the automatic registration scheme comprising of the rigid transformation in conjunction with the Simulated Annealing method sequentially combined with the Powell method has been performed superior regarding all the other compared registration schemes.

An experimental apparatus was developed to measure force production of a digit at various points of force application along the digit and in any direction within the transverse plane of the longitudinal axis of the digit. Eight normal subjects with asymptomatic hands were tested. Maximum voluntary isometric contraction forces were measured at the interphalangeal joint of the thumb in 16 directions that were evenly distributed within 360 degrees. Peak forces measured in all directions were used to create polar plots and to construct force envelopes using cubic spline interpolation. The areas of the force envelope and force quadrants were then calculated. The force produced by the thumb was dependent on the direction of force application. The highest force, 104.8 ± 14.2 N, was generated in flexion, while the lowest force was generated in extension. The forces in extension, abduction and adduction were 24.8%, 57.2%, and 46.2% of the flexion force, respectively. Relatively high forces were generated in the directions of flexion combined with abduction, and flexion combined with adduction. The area of the entire force envelope was found to be 12,142 ± 3,149 N-N. The percentage quadrant areas, relative to the total force envelope area, for extension-adduction, extension-abduction, flexion-abduction, and flexion-adduction were 7.8%, 11.4%, 39.3%, and 41.4%, respectively. The percentage quadrant areas for extension, abduction, flexion, and adduction were 4.9%, 23.6%, 52.7%, and 18.8%, respectively. The current study provides a more advanced and comprehensive method for quantification and investigation of the motor function of the thumb, which has potential in clinical applications for diagnosis of hand disorders, evaluation of deterioration or improvement of hand motor function, and guidance of therapeutic and surgical intervention.

The short- and long-term success of tibial cementless implants depend on the initial fixation stability often provided by posts and screws. Excessive relative interface motions are known to inhibit bone ingrowth and, hence, biologic fixation. In the present study, the stability of two cementless tibial implants under static and cyclic loading was studied. An apparatus was developed to perform compression tests on tibial components fixed by screws or posts onto resurfaced tibiae. Motion transducers were placed to record liftoff and subsidence displacements. A load of 1000 N was eccentrically applied on the medial plateau via the femoral component. The response was measured under static and repetitive loading up to 4000 cycles at 1 Hz.

Experimental results showed that the screw fixation yielded the stiffer response and, hence, provided greater initial stability. The tibial component fixed with posts demonstrated larger lift off displacements. Comparison of measured results of static tests before and after fatigue indicated that the load-displacement behavior was not significantly affected by the cyclic fatigue loading under 1000 N up to 4000 cycles at 1 Hz. Nevertheless, much larger permanent displacements were recorded for the post fixation systems. In contrast to screw fixation, posts fixation systems demonstrated marked deterioration under larger compression loads of ∼2000 N.

Fractures are not rare in male osteoporosis and bone mineral density (BMD) measurement is used in the diagnosis and monitoring, preventing and/or treating the disease. Muscle strength and BMD are highly related to each other. The distal radius is one of the most common sites of osteoporotic fractures. The relationship of quantitative muscle strength and BMD of the forearm has not yet been established. The objective of this study was to assess forearm muscle strength and grip strength in relation to BMD in 46 osteoporotic and randomly selected 45 healthy male participants. Forearm muscle strength and BMD were quantitatively measured using an isokinetic dynamometer and dual-energy-X-ray-absorptiometry (DEXA), respectively. Significant correlation was found among the muscle strength and dominant forearm BMD in 60 and 120 deg/s velocities. In the non-dominant arm, the 120 deg/s velocity was only significantly positively correlated to forearm BMD. Pearson's Product coefficient presented a moderate correlation between muscle strength and BMD at the dominant arms of both groups, whereas, the difference in the non-dominant forearm came from the difference of usage frequency. In conclusion, quantitative forearm muscle strength and BMD is moderately correlated and exercise can be advised to prevent distal radius fractures in male osteoporosis.

The effects of oxygen gas tensions and hydrostatic pressure on intracellular calcium, [Ca²⁺]_i, response to a flow stimulus in endothelial cells were investigated. Cultured bovine aortic endothelial cells (BAECs) were exposed to a hydrostatic pressure of 100 mmHg under low oxygen gas tensions and were subsequently subjected to a 1 minute mechanical stimulation of fluid shear stress of 20 dynes/cm². The [Ca²⁺]_i response in BAECs was measured using a fluorescent indicator, Calcium Green-1. The maximum intensity for low oxygen tension was significantly lower than that for normal oxygen tension, which provides evidence that low oxygen tension regulates cellular functions downward. Moreover, preloading of hydrostatic pressure also reduced the increases in [Ca²⁺]_i. These results suggest that BAECs in venous system, where oxygen tension and hydrostatic pressure are lower than those in arterial system, may be less sensitive to fluid flow. A separate observation showed that low oxygen tension did not significantly affect the cell morphology. In constrast, BAECs exposed to hydrostatic pressure showed marked elongation with no predominant orientation and the F-actin filament distributions were rearranged, indicating centrally located thick stress fibers. For better understanding of endothelial cell physiology, it is very important to elucidate the effect of oxygen gas tensions together with mechanical environment on endothelial cell responses.

The quality of the notifications issued within the European Medical Device Vigilance system were retrospectively reviewed and the adequacy of the recommended guidelines evaluated. The study material comprised all 589 vigilance notifications the Finnish competent authority received from manufacturers and other national competent authorities during 1997, 1999, and 2001. The number of vigilance reports, particularly the reports issued by national competent authorities, has increased from 82 in 1997 up 166 in 2001 while the proportion of reports with demonstrated bearing on health risk has decreased from about 40% down to 20% during the last five years. The number of manufacturers' reports has also increased from 28 in 1997 up to 98 in 2001 while the information given in the reports have become somewhat more incoherent. The time needed to close a device-related incident has increased, too. It is obvious that the present vigilance guidelines provide adequate guidance for both the manufacturers and competent authorities to manage vigilance cases efficiently and appropriately. It is crucial that all pertinent parties should adopt the recommended procedures and act accordingly. The vigilance system underpinned with high quality notifications only assures the continuous enhancement of patient safety, the bottom line.

Flatness and symmetry are main parameters determining the quality of a photon beam produced by linear accelerators. The quality assurance in routine clinical practice of radiotherapy and consequently the treatment-outcome depend definitely on the physical parameters of treatment-delivery. Several recommendations from national and international associations are reported. By reviewing the current literature and mainly according to the World Health Organization (WHO) report of quality assurance in radiotherapy, we may suggest that for flatness and symmetry, the optimal level of deviation should be within ± 3%. Flatness and symmetry should be checked monthly or once a year in accordance to the guidelines of national societies.