ABSTRACT
OBJECTIVE: In clinical trials, patients become available for treatment sequentially. Especially in trials with a small number of patients, loss of power may become an important issue, if treatments are not allocated equally or if prognostic factors differ between the treatment groups. We present a new algorithm for sequential allocation of two treatments in small clinical trials, which is concerned with the reduction of both selection bias and imbalance. STUDY DESIGN AND SETTING: With the algorithm, an element of chance is added to the treatment as allocated by minimization. The amount of chance depends on the actual amount of imbalance of treatment allocations of the patients already enrolled. The sensitivity to imbalance may be tuned. We performed trial simulations with different numbers of patients and prognostic factors, in which we quantified loss of power and selection bias. RESULTS: With our method, selection bias is smaller than with minimization, and loss of power is lower than with pure randomization or treatment allocation according to a biased coin principle. CONCLUSION: Our method combines the conflicting aims of reduction of bias by predictability and reduction of loss of power, as a result of imbalance. The method may be of use in small trials.
Subject(s)
Algorithms , Randomized Controlled Trials as Topic/methods , Selection Bias , Humans , Patient Selection , Prognosis , Random Allocation , Research DesignABSTRACT
PURPOSE: To investigate the feasibility of using a dual-energy X-ray absorphometry (DEXA) scan to predict long-term force-transmission patterns in wrists. MATERIAL AND METHODS: Both wrists of a man with morbid Kienböck stage IIIa disease of his left wrist (avascular necrosis of the lunate) were examined by a DEXA scan to determine the differences in bone density in the distal radius. RESULTS: In the distal radius of the injured wrist, a shift in bone density was seen toward the scaphoid fossa, which resembles the shift in force-transmission pattern described in force-transmission studies of the wrist. CONCLUSIONS: These differences can be interpreted as a result of an altered force-transmission pattern in the injured wrist.
Subject(s)
Osteochondritis/diagnostic imaging , Wrist Injuries/diagnostic imaging , Absorptiometry, Photon , Adult , Bone Density , Feasibility Studies , Humans , Lunate Bone/diagnostic imaging , Lunate Bone/physiopathology , Male , Osteochondritis/physiopathology , Radius/diagnostic imaging , Stress, Mechanical , Wrist Injuries/physiopathologyABSTRACT
At the department of nuclear medicine of the University Hospital Utrecht a single modality PACS has been operational since mid 1990. After 1 year of operation the functionality, the organizational and economical consequences and the acceptability of the PACS are evaluated. The functional aspects reviewed are: viewing facilities, patient data management, connectivity, reporting facilities, archiving, privacy and security. It is concluded that the improved quality of diagnostic viewing and the potential integration with diagnosis, reporting and archiving are highly appreciated. The many problems that have occurred during the transition period, however, greatly influence the appreciation and acceptability of the PACS. Overall, we feel that on the long term there will be a positive effect on the quality and efficiency of the work done in our department.
Subject(s)
Nuclear Medicine Department, Hospital , Radiology Information Systems , Computer Communication Networks , Computer Systems , Confidentiality , Costs and Cost Analysis , Database Management Systems , Hospitals, University , Netherlands , Nuclear Medicine Department, Hospital/economics , Nuclear Medicine Department, Hospital/organization & administration , Radiology Information Systems/economicsABSTRACT
Within the framework of a study on the merits of a frequency-dependent automatic gain control in hearing aids, the effect of varying the slope of the amplitude-frequency response on the speech-reception threshold (SRT) for sentences in noise was studied for normal-hearing listeners. Speech and noise were both subjected to the same amplitude-frequency response. In the first experiment, the effect of a constant slope was investigated (20 listeners). Over a range of about -7 to +10 dB/oct, the SRT in noise remained constant. In the second experiment, a single change in the slope of the amplitude-frequency response was introduced halfway through the sentence. The effect of varying the transition time over a range down to 0.125 s appeared to be very small. In the third experiment, the slope varied continuously with range and variation frequency (0.25-2 Hz) as the parameters. The masked SRT increased gradually with variation frequency. The results indicate that the masked SRT for sentences is remarkably resistant to dynamic variations in the slope of the amplitude-frequency response.
