Functionality and operation of fluoroscopic automatic brightness control/automatic dose rate control logic in modern cardiovascular and interventional angiography systems: a report of Task Group 125 Radiography/Fluoroscopy Subcommittee, Imaging Physics Committee, Science Council

Task Group 125 (TG 125) was charged with investigating the functionality of fluoroscopic automatic dose rate and image quality control logic in modern angiographic systems, paying specific attention to the spectral shaping filters and variations in the selected radiologic imaging parameters. The task group was also charged with describing the operational aspects of the imaging equipment for the purpose of assisting the clinical medical physicist with clinical set-up and performance evaluation. Although there are clear distinctions between the fluoroscopic operation of an angiographic system and its acquisition modes (digital cine, digital angiography, digital subtraction angiography, etc.), the scope of this work was limited to the fluoroscopic operation of the systems studied. The use of spectral shaping filters in cardiovascular and interventional angiography equipment has been shown to reduce patient dose. If the imaging control algorithm were programmed to work in conjunction with the selected spectral filter, and if the generator parameters were optimized for the selected filter, then image quality could also be improved. Although assessment of image quality was not included as part of this report, it was recognized that for fluoroscopic imaging the parameters that influence radiation output, differential absorption, and patient dose are also the same parameters that influence image quality. Therefore, this report will utilize the terminology "automatic dose rate and image quality" (ADRIQ) when describing the control logic in modern interventional angiographic systems and, where relevant, will describe the influence of controlled parameters on the subsequent image quality. A total of 22 angiography units were investigated by the task group and of these one each was chosen as representative of the equipment manufactured by GE Healthcare, Philips Medical Systems, Shimadzu Medical USA, and Siemens Medical Systems. All equipment, for which measurement data were included in this report, was manufactured within the three year period from 2006 to 2008. Using polymethylmethacrylate (PMMA) plastic to simulate patient attenuation, each angiographic imaging system was evaluated by recording the following parameters: tube potential in units of kilovolts peak (kVp), tube current in units of milliamperes (mA), pulse width (PW) in units of milliseconds (ms), spectral filtration setting, and patient air kerma rate (PAKR) as a function of the attenuator thickness. Data were graphically plotted to reveal the manner in which the ADRIQ control logic responded to changes in object attenuation. There were similarities in the manner in which the ADRIQ control logic operated that allowed the four chosen devices to be divided into two groups, with two of the systems in each group. There were also unique approaches to the ADRIQ control logic that were associated with some of the systems, and these are described in the report. The evaluation revealed relevant information about the testing procedure and also about the manner in which different manufacturers approach the utilization of spectral filtration, pulsed fluoroscopy, and maximum PAKR limitation. This information should be particularly valuable to the clinical medical physicist charged with acceptance testing and performance evaluation of modern angiographic systems.     

Sensitivity of computed tomography in detection of perirectal abscess

Most patients with anorectal abscess are diagnosed clinically based on pain, erythema, warmth, and fluctuance. Some patients, however, present with subtle or atypical signs. CT is easily accessible and is commonly used for diagnosis and delineation of anorectal abscess. The purpose of this study is to determine the sensitivity of CT scan in detecting perirectal abscesses and to see if immune status impacts the accuracy of CT. A retrospective study was conducted to identify patients from 2000 to 2009 with International Classification of Diseases, 9th Revision code 566 (anal or rectal abscess). Patients included had a CT scan less than 48 hours before drainage. Patients with CT-positive abscess were compared with patients with CT-negative abscess. Patients were categorized as either immunocompetent or immunosuppressed based on documentation of diabetes mellitus, cancer, human immunodeficiency virus, or end-stage renal disease. One hundred thirteen patients were included in this study. Seventy-four (65.5%) were male and the average age was 47 years. Eighty-seven of 113 (77%) patients were positive on CT for anorectal abscess. Sixty of 113 (53%) patients included in this study were immunocompromised. CT missed 26 of 113 (23%) patients with confirmed perirectal abscess. Eighteen (69%) of these patients were immunocompromised compared with CT-positive patients (42 [48%], P = 0.05). The overall sensitivity of CT in identifying abscess was 77 per cent. CT lacks sensitivity in detecting perirectal abscess, particularly in the immunocompromised patient.     

Detection of Yersinia pestis by pesticin fluorogenic probe-coupled PCR

The assay (PE Applied Biosystems) combines PCR with concomitant release of fluorogenic nucleotides for immediate product detection by fluorometry. Yersinia pestis, the etiological agent of bubonic plague, expresses species-specific genes known to be located on two unique plasmids (9.6-kb pPCP and 100.9-kb pMT). Pesticin (pst) is a unique gene located on pPCP which encodes for a bacteriocin. Using fluorogenic probe coupled PCR as few as three copies of pst targets were detected from total Y. pestis genomic DNA. The pst probe used in this report was positive only for pesticinogenic isolates and did not show complementarity with Yersiniae nor with other bacteria targeted in this study suggesting, that the pst probe is very specific for Y. pestis. Under optimal conditions of Mg(2+)concentration and thermal cycle number, addition of extraneous DNA to respective assay mixtures had no effect on detection.     

Nurses' perceptions of a mental health education programme for Australian nurses

In the present study, we present qualitative findings of study of nurses' perceptions of a mental health education programme for Australian nurses. Many nurses avoid disclosing their mental health problem/illness because of the stigmatization by health workers. Mental health education is a successful means to address workplace stigma; thus, it can be anticipated that such education can address workplace difficulties experienced by nurses with mental health problems. During 2008, a qualitative study was conducted to obtain nurses' perceptions of a short mental health education programme for nurses. The workshop purpose was to improve mental health literacy in order to improve support to colleagues with mental health problems. Semistructured, audio-taped interviews were conducted with 13 nurses and then transcribed. A framework analysis approach guided interpretation of the data. The education programme had limited effect on the participants' attitudes towards colleagues with mental health problems. This was likely due to their high level of mental health literacy and experiences prior to the workshop. Participants felt that a more focused nurse-specific programme might have been more efficacious. Implementing a nurse-specific education session is potentially an effective means to improve support to nurses who experience mental health problems.