Optimizing Contrast Resolution in Digital Chest Radiography by Varying Copper Filtration and kVp.

PURPOSE: To measure the effect of increasing kilovoltage peak (kVp) and copper filtration thickness on entrance skin exposure and contrast resolution for chest radiography performed using digital flat-panel detectors. METHODS: A phantom-based experiment was conducted in which 24 radiographs of a quality control chest phantom were obtained at varying kVp levels and copper filtration thicknesses. The entrance skin exposure was measured and analyzed for each exposure. All radiographs were analyzed based on measured pixel values and contrast:noise ratio (CNR) and using subjective analysis, which focused on contrast resolution assessment performed by 4 radiologists. RESULTS: The results from the subjective image analysis showed that increasing copper filtration in increments of 0.1 mm resulted in less of a decrease in contrast resolution compared with increasing the kVp by 10 kVp, and that contrast resolution is more dependent on energy level than on filtration. The results from objective image analysis indicated that CNR decreased when kVp increased at all filtration thicknesses, but consistent dependency between CNR and filtration was not evident. Exposure data analysis showed an average 46% decrease in entrance skin exposure for each increase of 0.1 mm in copper filtration thickness. DISCUSSION: Although subjective and objective data analysis results indicated that increases of copper filtration are more beneficial to maintaining contrast resolution and reducing entrance skin exposure compared with increases of kVp, objective image data analysis showed a greater reduction in contrast resolution when kVp is increased. These results validate previous research that concluded that copper filtration should be considered as a dose-reduction and image-optimization strategy in digital radiography departments. CONCLUSION: Although entrance skin exposure reduction can be accomplished using higher kVp and copper filtration, increasing copper filtration thickness could be considered to minimize the loss of contrast resolution for routine chest imaging when digital flat-panel detectors are used.

Educating staff about digital radiography.

Radiation dose has been and continues to be the topic of mainstream media. Radiation accidents specific to ionizing radiation have prompted significant changes in legislation and prompted The Joint Commission to issue a Sentinel Event Alert, issue 47. Radiology professionals at every level have the opportunity to be better informed about the use of digital equipment in order to maximize image quality and minimize patient dose. Optimum kV's and lower mAs are discussed, as well as exposure index numbers and legal risk of post image digital processing. Overexposure of a patient is possible with no warning signs even with a diagnostic quality image. Exposure techniques, which were tested on anatomical phantoms provided by the Community Hospital of the Monterey Peninsula in California, established the foundation to develop universal digital technique charts.

Morbidity and mortality of patients with invasive group A streptococcal infections admitted to the ICU.

STUDY OBJECTIVES: To describe the clinical features and outcome of patients with invasive group A streptococcal (GAS) infections admitted to the ICU. DESIGN: Prospective, population-based surveillance for invasive GAS infections was conducted in Ontario from January 1992 until June 2002. All 62 patients meeting clinical and/or histopathologic criteria for invasive GAS who were admitted to the ICUs of four university-affiliated hospitals in Toronto, Canada were included. Demographic and clinical information were obtained retrospectively by chart review. ICU morbidity data included the occurrence of organ dysfunction (renal, hepatic, coagulation, ARDS), treatment, and interventions such as hemodialysis and mechanical ventilation. MEASUREMENTS AND RESULTS: ARDS developed in 34%, renal dysfunction developed in 55%, hepatic dysfunction developed in 64%, and coagulopathy developed in 69% of patients. A total of 56% of patients were treated with IV polyspecific IgG (IVIG), 81% were intubated and placed on mechanical ventilation, and 21% required renal replacement therapy. The median durations of ICU and hospital stay were 5.3 days and 15.0 days, respectively. The overall mortality was 40%. Mortality correlated directly with acute physiology and chronic health evaluation II score and the number of dysfunctional organs. Survivors were younger, had lower severity of illness scores, fewer dysfunctional organs, and were less likely to have shock or to receive treatment with vasopressors, mechanical ventilation, or pulmonary artery catheters. There was no association between the use of IVIG, surgical intervention, or clindamycin, and survival. Variables independently associated with mortality on multivariable analysis were the presence of coagulopathy (p = 0.0005) and liver dysfunction (p = 0.0123). CONCLUSIONS: Patients with invasive GAS infection admitted to the ICU have a high mortality rate. In this group of patients, coagulopathy and liver failure were independently associated with mortality. We did not observe any association between the use of IVIG, surgical intervention, or clindamycin, and survival.

Canadian survey of the use of sedatives, analgesics, and neuromuscular blocking agents in critically ill patients.

OBJECTIVES: To characterize the perceived utilization of sedative, analgesic, and neuromuscular blocking agents, the use of sedation scales, algorithms, and daily sedative interruption in mechanically ventilated adults, and to define clinical factors that influence these practices. DESIGN: Cross-sectional mail survey. PARTICIPANTS: Canadian critical care practitioners. MEASUREMENTS AND MAIN RESULTS: A total of 273 of 448 eligible physicians (60%) responded. Respondents were well distributed with regard to age, years of practice, specialist certification, size of intensive care unit and hospital, and location of practice. Twenty-nine percent responded that a protocol/care pathway/guideline for the use of sedatives or analgesics is currently in use in their intensive care unit. Daily interruption of continuous infusions of sedatives or analgesics is practiced by 40% of intensivists. A sedation scoring system is used by 49% of respondents. Of these, 67% use the Ramsay scale, 10% use the Sedation-Agitation Scale, 9% use the Glasgow Coma Scale, and 8% use the Motor Activity Assessment Scale. Only 3.7% of intensivists use a delirium scoring system in their intensive care units. Only 22% of respondents currently have a protocol for the use of neuromuscular blocking agents in their intensive care unit, and 84% of respondents use peripheral nerve stimulation for monitoring. In patients receiving neuromuscular blocking agents for >24 hrs, 63.7% of respondents discontinue the neuromuscular blocking agent daily. Intensivists working in university-affiliated hospitals are more likely to employ a sedation protocol and scale (p < .0001), as are intensivists working in larger intensive care units (>or=15 beds, p < .01). Intensivists with anesthesiology training (and no formal critical care training) are more likely to use a protocol and sedation scale, and critical care-trained intensivists are more likely to use daily interruption. Younger physicians (<40 yrs) are more likely to practice daily interruption (p = .0092). CONCLUSIONS: There is significant variation in critical care sedation, analgesia, and neuromuscular blockade practice. Given the potential effect of practices regarding these medications on patient outcome, future research and educational efforts related to evidence-based protocols for the use of these agents in mechanically ventilated patients might be worthwhile.

High-frequency oscillatory ventilation in adults: the Toronto experience.

STUDY OBJECTIVES: To review the clinical experience with high-frequency oscillatory ventilation (HFOV) in three medical-surgical ICUs in Toronto, ON, Canada, and to describe patient characteristics, HFOV strategies, and outcomes. DESIGN AND PATIENTS: Retrospective chart review of all patients treated with HFOV at three academic university-affiliated ICUs since 1998. The data extracted included patient demographics, etiology of respiratory failure, ventilator settings, and gas exchange and cardiovascular data from baseline to 72 h of treatment, as well as at the transition from HFOV to conventional ventilation (CV). Heart rate and BP were recorded at regular intervals in all patients, and hemodynamic data were recorded in 32 patients who had pulmonary artery catheters in place. Cointerventions and ICU mortality were also recorded. MEASUREMENTS AND RESULTS: A total of 156 adults (67 women and 89 men; mean [+/- SD] age, 48 +/- 18 years; mean acute physiology and chronic health evaluation [APACHE] II score, 23.8 +/- 7.5) with severe ARDS (ie, mean Pao(2)/fraction of inspired oxygen [Fio(2)] ratio, 91 +/- 48 mm Hg; mean oxygenation index [OI], 31 +/- 14) who had received CV for a duration of 5.6 +/- 7.6 days underwent 171 trials of HFOV. HFOV was discontinued within 4 h in 19 patients (12%) because of difficulties with oxygenation, ventilation, or hemodynamics. Pao(2)/Fio(2) ratios and OI ([Fio(2) x mean airway pressure x 100]/Pao(2)) improved significantly with the application of HFOV, and this benefit persisted for the 72-h study duration. Significant changes in hemodynamics following HFOV initiation included an increase in central venous pressure and a reduction in cardiac output (throughout the 72 h), and an increase in pulmonary artery occlusion pressure (at 3 and 6 h). Patients were treated with HFOV for 5.1 +/- 6.3 days. The 30-day mortality rate was 61.7%. Pneumothorax occurred in 21.8% of patients, 43.6% of patients were treated with inhaled nitric oxide, and 37.2% of patients were treated with steroids. Independent predictors of mortality on multivariate analysis were older age, higher APACHE II score, lower pH at the initiation of HFOV, and a greater number of days receiving CV prior to HFOV. CONCLUSIONS: HFOV has beneficial effects on Pao(2)/Fio(2) ratios and OI, and may be an effective rescue therapy for adults with severe oxygenation failure. The early institution of HFOV may be advantageous.

Patient care seeking barriers and tuberculosis programme reform: a qualitative study.

The patient's perspective, including his/her socio-economic and cultural environment, is an important consideration for tuberculosis control programmes. Through semi-structured interviews, this qualitative research studies the barriers to successful care seeking faced by 202 adult patients with pulmonary tuberculosis in urban Zambia. Three common, interdependent themes explain patient barriers to successful care seeking: (1) number of health care encounters and duration of illness prior to diagnosis; (2) existing financial constraints and additional unrecognized patient costs; and (3) travel distances. On average, patients have 6.7 health care encounters prior to being diagnosed with tuberculosis. Within a resource-poor setting, patients face financial constraints and unrecognized costs associated with their illness. Specifically, travel distances and related transportation costs create a significant burden on patients. In addition, 'special food' expenditures add to their financial constraints. The implications of these patient barriers from this study are then discussed in the context of three tuberculosis programme reforms occurring in sub-Saharan Africa: (1) decentralization of tuberculosis services; (2) integration of tuberculosis and other services; and (3) evaluation of diagnostic techniques. The patient's perspective and related care seeking barriers should be considered in reviewing existing tuberculosis programmes and policy, evaluating potential programme reform and assessing new tuberculosis interventions.