Evaluation and testing of computed radiography systems.

The implementation of film replacement digital radiographic imaging systems throughout Europe is now gathering momentum. Such systems create the foundations for totally digital departments of radiology, since radiographic examinations constitute the most prevalent modality. Although this type of development will lead to improvements in the delivery and management of radiological service, such widespread implementation of new technology must be carefully monitored. The implementation of effective QA tests on installation, at periodic intervals and as part of a routine programme will aid this process. This paper presents the results of commissioning tests undertaken on a number of computed radiography imaging systems provided by different manufacturers. The aim of these tests was not only to provide baseline performance measurements against which subsequent measurements can be compared but also to explore any differences in performance, which might exist between different units. Results of measurements will be presented for (1) monitor and laser printer set-up; (2) imaging plates, including sensitivity, consistency and uniformity; (3) resolution and contrast detectability; and (4) signal and noise performance. Results from the latter are analysed in relationship with both system and quantum noise components.

DNA fingerprinting of serial Candida albicans isolates obtained during itraconazole prophylaxis in patients with AIDS.

During a randomized double-blind placebo-controlled study testing the efficacy of itraconazole for prophylaxis of systemic and mucosal fungal infections in patients with acquired immune deficiency syndrome, 298 patients were enrolled with 295 evaluable. Of those, 46 patients were considered prophylaxis failures because of recurrent oral or esophageal candidiasis. Oropharyngeal fungal cultures were taken at the time of suspected thrush or Candida esophagitis, but not at baseline. All of the Candida spp. isolates were cultured on CHROMagar Candida medium then identified using API 20 AUX strips. Antifungal susceptibility testing was performed following the National Committee for Clinical Laboratory Standards M-27A guidelines. Sequential isolates were genotyped using randomly amplified polymorphic DNA. Polymerase chain reaction fingerprints were generated using two repetitive sequence primers, (GGA)7 and (GACA)4. The study group consisted of 23 patients, nine from the itraconazole arm and 14 from the placebo arm, who were prophylaxis failures and had more than two C. albicans isolates. Five of 23 had isolates showing a > or =4-fold reduction in susceptibility; four of these patients were in the itraconazole prophylaxis arm and one was in the placebo arm. Three of the five had yeast isolations showing changes in banding patterns over time. Such changes may indicate genetic changes in the same strain that could be linked to acquired resistance to itraconazole, or acquisition of a new strain, or emergence of a previously minor component of the original population.

Typing of Histoplasma capsulatum isolates based on nucleotide sequence variation in the internal transcribed spacer regions of rRNA genes.

The nucleotide sequences of internal transcribed spacer (ITS) regions of rRNA genes of 24 isolates of Histoplasma capsulatum were examined. The results indicate that the sequences of ITS regions in different isolates are not identical. Sequence variations were found at 20 positions in the 496 bp that were sequenced. Ten different sequence patterns, designated types A through H, were observed when the sequences from the 24 isolates were aligned. Twelve isolates from Indianapolis were classified into four different types. Two isolates from New York belonged to type G. Three isolates from different cities were type F. The remaining six isolates were of different types.

Comparison of radioimmunoassay and enzyme-linked immunoassay methods for detection of Histoplasma capsulatum var. capsulatum antigen.

The purpose of this study was to compare the conventional radioimmunoassay (RIA) to an enzyme-linked immunoassay (EIA) for the measurement of Histoplasma antigen in banked urine specimens. A correlation between the two methods would allow the EIA to be used as a nonradioactive alternative to the established 125I RIA. The study used stored urine from patients diagnosed with histoplasmosis during an outbreak in Indianapolis which began in 1988. Control specimens from healthy adults, patients with other fungal infections, urinary tract infections, or nonfungal pneumonia were also tested. Both the RIA and EIA were run concurrently. The RIA system measured antigen levels of 0.4 to 27.0 RIA units, while the EIA measured antigen levels of 0.6 to 20.1 units. Both the EIA and RIA detected measurable antigen levels in urine from 50 of 56 patients (89%) with disseminated disease and 11 of 30 patients (37%) with self-limiting disease. One of 96 control specimens, from a patient with paracoccidioidomycosis, was positive with both systems. Antigen levels measured by EIA correlated well with those measured by the established RIA method (correlation coefficient, 0.974). The EIA is an acceptable alternative to the RIA for measuring Histoplasma antigen levels in urine specimens.