Comparison of indirect radiation dose estimates with directly measured radiation dose for patients and operators during complex endovascular procedures

BackgroundA great deal of attention has been directed at the necessity and potential for deleterious outcomes as a result of radiation exposure during diagnostic evaluations and interventional procedures. We embarked on this study in an attempt to accurately determine the amount of radiation exposure given to patients undergoing complex endovascular aortic repair. These measured doses were then correlated with radiation dose estimates provided by the imaging equipment manufacturers that are typically used for documentation and analysis of radiation-induced risk.MethodsConsecutive patients undergoing endovascular thoracoabdominal aneurysm (eTAAA) repair were prospectively studied with respect to radiation dose. Indirect parameters as cumulative air kerma (CAK), kerma area product (KAP), and fluoroscopy time (FT) were recorded concurrently with direct measurements of dose (peak skin dose [PSD]) and radiation exposure patterns using radiochromatic film placed in the back of the patient during the procedure. Simultaneously, operator exposure was determined using high-sensitivity electronic dosimeters. Correlation between the indirect and direct parameters was calculated. The observed radiation exposure pattern was reproduced in phantoms with over 200 dosimeters located in mock organs, and effective dose has been calculated in an in vitro study. Scatter plots were used to evaluate the relationship between continuous variables and Pearson coefficients.ResultseTAAA repair was performed in 54 patients over 5 months, of which 47 had the repair limited to the thoracoabdominal segment. Clinical follow-up was complete in 98% of the patients. No patients had evidence of radiation-induced skin injury. CAK exceeded 15 Gy in 3 patients (the Joint Commission on Accreditation of Healthcare Organizations [JCAHO] threshold for sentinel events); however, the direct measurements were well below 15 Gy in all patients. PSD was measured by quantifying the exposure of the radiochromatic film. PSD correlated weakly with FT but better with CAK and KAP (r = 0.55, 0.80, and 0.76, respectively). The following formula provides the best estimate of actual PSD = 0.677 + 0.257 CAK. The average effective dose was 119.68 mSv (for type II or III eTAAA) and 76.46 mSv (type IV eTAAA). The operator effective dose averaged 0.17 mSv/case and correlated best with the KAP (r = 0.82, P < .0001).ConclusionFT cannot be used to estimate PSD, and CAK and KAP represent poor surrogate markers for JCAHO-defined sentinel events. Even when directly measured PSDs were used, there was a poor correlation with clinical event (no skin injuries with an average PSD >2 Gy). The effective radiation dose of an eTAAA is equivalent to two preoperative computed tomography scans. The maximal operator exposure is 50 mSv/year, thus, a single operator could perform up to 294 eTAAA procedures annually before reaching the recommended maximum operator dose

Butterflies and Continuous Conservation Reserve Program Filter Strips: Landscape Considerations

Filter strips or buffers are areas of grass or other perennial herbaceous vegetation established along waterways to remove contaminants and sediments from agricultural field runoff. In the heavily cultivated regions of the Midwestern United States, these buffer zones established under the Farm Bill provide important habitat for wildlife such as butterflies. The question of how the landscape context of these plantings influences their use has not been adequately researched. We used multiple regression and Akaike’s Information Criteria to determine how habitat width and several landscape-level factors (i.e., landscape composition [total herbaceous cover, amount of developed area, and amount of wooded cover] and configuration [herbaceous edge density]) influenced the abundance and diversity of the butterfly community using filter strips in southwestern Minnesota, USA. Habitatsensitive butterfly abundance and all richness and diversity measures were positively correlated with filter-strip width. Butterfly abundance was negatively associated with the amount of developed areas (cities, towns, and roads) within the area of a 1-km radius (3.14 km2) surrounding the sites. Percentage of wooded cover in the landscape was an important variable explaining individual species abundance, although the direction of the relationship varied. Our finding that landscape context influences butterfly use of filter strips highlights the importance of landscape-level approaches to wildlife conservation in agroecosystems.This article is from Wildlife Society Bulletin 34 (2006): 936, doi:10.2193/0091-7648(2006)34[936:BACCRP]2.0.CO;2.</p

Classical test theory versus RASCH analysis in reducing CPQ's items

Session - Oral-health-related Quality of Life: abstract no. 0676BACKGROUND: To reduce burden of response shortening (or reducing) OHQoL questionnaires is routinely conducted. To date, reducing OHQoL questionnaires has been based on classic test theory (CTT). It is now recognised that the CTT approach to item reduction has major conceptual limitations – the resultant short form produced lacks an explicit ordered continuum of items that represents a unidimensional construct. RASCH analysis provides an alternate method to reduce items in questionnaires and overcomes this major conceptual limitation of CTT. OBJECTIVES: This study aimed to develop a short form of the Child Perception Questionnaire (CPQ) using RASCH Analyses and compare its psychometric properties with short forms of the CPQ developed through CTT – CPQ-16 and CPQ-8. METHODS: Data on child OHQoL was collected using the original 37-item CPQ in an oral health survey among 506 12-year-olds in Hong Kong. RASCH analysis using Winsteps software was used to create a short form of CPQ. The three short forms were compared for CTT and RASCH requirements. RESULTS: RASCH analysis resulted in a 23-item short form of CPQ (RASCH-23). All short forms showed similar characteristics under CTT requirements: item-total correlation ranged from 0.29-0.87 for ISF-16, 0.25-0.63 for ISF-8 and 0.22-0.77 for RASCH-23, while reliability ranged 0.52-0.78, 0.39-0.63 and 0.53-0.79 respectively. However, the CPQ-16 and CPQ-8 failed to meet the goodness-of-fit criteria of RASH modelling. CONCLUSIONS: A short form of CPQ developed through RASCH analyses (RASCH-23) satisfied the criteria of classic test theory similar to CPQ-16 and better than CPQ-8. However, the CPQ-16 and CPQ-8 failed to meet the requirements of RASCH modelling.link_to_OA_fulltextThe 89th General Session and Exhibition of IADR/AADR/CADR, San Diego, CA., 16-19 March 2011