Selection of task-dependent diffusion filters for the post-processing of SPECT images

Iterative reconstruction from single photon emission computed tomography (SPECT) data requires regularization to avoid noise amplification and edge artefacts in the reconstructed image. This is often accomplished by stopping the iteration process at a relatively low number of iterations or by post-filtering the reconstructed image. The aim of this paper is to develop a method to automatically select an optimal combination of stopping iteration number and filters for a particular imaging situation. To this end different error measures between the distribution of a phantom and a corresponding filtered SPECT image are minimized for different iteration numbers. As a study example, simulated data representing a brain study are used. For post-reconstruction filtering, the performance of 3D linear diffusion (Gaussian filtering) and edge preserving 3D nonlinear diffusion (Catté scheme) is investigated. For reconstruction methods which model the image formation process accurately, error measures between the phantom and the filtered reconstruction are significantly reduced by performing a high number of iterations followed by optimal filtering compared with stopping the iterative process early. Furthermore, this error reduction can be obtained over a wide range of iteration numbers. Only a negligibly small additional reduction of the errors is obtained by including spatial variance in the filter kernel. Compared with Gaussian filtering, Catté diffusion can further reduce the error in some cases. For the examples considered, using accurate image formation models during iterative reconstruction is far more important than the choice of the filter.     

Torsional and stiffness properties of Canal Master U stainless steel and nitinol instruments

The purpose of this study was to compare stiffness and resistance to fracture of stainless steel and nickel titanium Canal Master U instruments. Instruments sizes 20 through 50 were tested according to ANSI/ADA Specification No. 28. Resistance to fracture was determined by twisting and measuring the maximum torque and angular deflection (rotation) at the failure point. Stiffness was determined by measuring the moment required to bend the instrument 45 degrees. Stainless steel and nickel titanium Canal Master U instruments satisfied and far exceeded specification standards for stiffness. They also satisfied and far exceeded the standards for angular deflection at the failure point. Stainless steel Canal Master U met or exceeded the maximum torque at failure standards in all sizes except 50, whereas the nickel titanium instruments met the standards in all sizes except 45 and 50. The mechanical properties of nickel titanium, especially its low bending moment and high angular rotation at failure, encourage further evaluation with clinical studies.     

Oral topotecan given once or twice daily for ten days: a phase I pharmacology study in adult patients with solid tumors

The development of a highly sensitive method for detection of telomerase activity, telomeric repeat amplification protocol (TRAP), has provided knowledge on telomerase activity in normal and cancer tissues. Subsequent several modifications have been achieved, including an introduction of the internal standard and hybridization protection technique that leads to simplicity and improvement of reproducibility and linearity of this method, and application of TRAP to in situ analysis to identify the cells responsible for telomerase activity. As for measurement of telomere length, fluorescence in situ hybridization technique appeared to give an information of telomere length on an individual chromosome in contrast to analysis of terminal restriction fragment, a conventional method which can express mean telomere length of all chromosomes. Further methodological improvement in this field is ongoing and showing a new sight on cell mortality and immortality.     

Asphyxiated bladder syndrome in a pediatric intensive care unit

Sixteen neonates and infants with asphyxiated bladder syndrome (ABS) were prospectively studied over a two-year period. Their transient urinary bladder distention had developed as a sequel of asphyxial events, and presented as delayed micturition in the absence of obstructive lesion. The incidence was 1.9 percent in this Pediatric Intensive Care Unit. Five cases occurred in the neonatal period. All patients were younger than three years of age (mean: 9.1 months), and the incidence of ABS was 2.8 percent within this age group. For intermittent decompression of the bladder, all responded successfully to the suprapubic bladder expression method (Crede's maneuver). Most (81.3%, 13/16) ABS cases coexisted with intestinal dysfunction as either paralytic ileus (62.5%, 10/16) or as gas-less abdomen (18.8%, 3/16). There was no evidence of association with either systemic or urinary bacterial infection. Normal spontaneous voiding and bowel function were regained in all cases except one, who died early. Mean (SD) duration of bladder dysfunction was 66.9 (40.3) hours. Sonography showed normal kidneys and collecting system in all patients both during and after ABS episodes. Half of the patients (8/16) died ultimately. No urinary tract abnormality was found in post-mortem examinations in five cases.     

Cerebral ischemic events associated with prolapsing mitral valve

Twelve patients who had no evidence of arteriosclerotic cerebral vascular disease, lacked hypertension or coagulation defect, and had not been receiving contraceptive therapy had recurrent transient cerebral ischemic attacks (TIAs) and partial nonprogressive strokes. All had prolapsing mitral valve proved by angiocardiography. The average age was 38 years, compared with 62 years in a larger series of patients with TIA associated with arteriosclerosis. We propose that the ischemic events are related to emboli emanating from the abnormal mitral valve with or without an associated paroxysmal cardiac arrhythmia.     

Analytical techniques for cell fractions. XXIII. A stable thermal gradient device for heat denaturation studies on proteins

The ISO-DALT two-dimensional electrophoretic system (1,2), based on the method of O'Farrell (3), is capable of performing large numbers of analysis on complex mixtures of proteins. However, both separations employed are carried out under dissociating or denaturing conditions and no enzyme activities are readily observable in the analyzed proteins. In order to identify the spots corresponding to particular enzymes, it is therefore necessary to employ some nondestructive resolving technique first and as a second step to perform both enzyme and two-dimensional electrophoretic analyses on the fractions generated. By correlating enzyme activity with intensity of various spots on the two-dimensional gels throughout the series of initial fractions, identifications, can be made. This approach, unlike the more direct immunoprecipitation methods (4), requires the running of large numbers of enzyme analyses and two-dimensional gels and some convenient initial resolving procedure. Convenient and rapid techniques for the analyses (5,6) and gels (1,2) have been described previously in this series and elsewhere. This paper deals with the use of selective denaturation in a temperature gradient as an initial resolving procedure and describes a simple thermal gradient device for generating such a gradient.