Biomedical subjects

Andrew P Jones

Publications and source records attributed to Andrew P Jones.

6 recordsLinked to original sources

PubMed2006

Validation of travel times to hospital estimated by GIS.

BACKGROUND: An increasing number of studies use GIS estimates of car travel times to health services, without presenting any evidence that the estimates are representative of real travel times. This investigation compared GIS estimates of travel times with the actual times reported by a sample of 475 cancer patients who had travelled by car to attend clinics at eight hospitals in the North of England. METHODS: Car travel times were estimated by GIS using the shortest road route between home address and hospital and average speed assumptions. These estimates were compared with reported journey times and straight line distances using graphical, correlation and regression techniques. RESULTS: There was a moderately strong association between reported times and estimated travel times (r = 0.856). Reported travel times were similarly related to straight line distances. Altogether, 50% of travel time estimates were within five minutes of the time reported by respondents, 77% were within ten minutes and 90% were within fifteen minutes. The distribution of over- and under-estimates was symmetrical, but estimated times tended to be longer than reported times with increasing distance from hospital. Almost all respondents rounded their travel time to the nearest five or ten minutes. The reason for many cases of reported journey times exceeding the estimated times was confirmed by respondents' comments as traffic congestion. CONCLUSION: GIS estimates of car travel times were moderately close approximations to reported times. GIS travel time estimates may be superior to reported travel times for modelling purposes because reported times contain errors and can reflect unusual circumstances. Comparison with reported times did not suggest that estimated times were a more sensitive measure than straight line distance.

Adult↗

PubMed2006

Understanding diabetes population dynamics through simulation modeling and experimentation.

Health planners in the Division of Diabetes Translation and others from the National Center for Chronic Disease Prevention and Health Promotion of the Centers for Disease Control and Prevention used system dynamics simulation modeling to gain a better understanding of diabetes population dynamics and to explore implications for public health strategy. A model was developed to explain the growth of diabetes since 1980 and portray possible futures through 2050. The model simulations suggest characteristic dynamics of the diabetes population, including unintended increases in diabetes prevalence due to diabetes control, the inability of diabetes control efforts alone to reduce diabetes-related deaths in the long term, and significant delays between primary prevention efforts and downstream improvements in diabetes outcomes.

Diabetes Complications↗

PubMed2006

Measurement of single kidney function using dynamic contrast-enhanced MRI: comparison of two models in human subjects.

PURPOSE: To compare two methods for assessing the single kidney glomerular filtration rate (SK-GFR) in humans using dynamic contrast-enhanced (DCE)-MRI. MATERIALS AND METHODS: Images were acquired from 39 separate MR studies of patients with atherosclerotic renovascular disease (ARVD). Data from the kidneys and descending aorta were analyzed using both a Rutland-Patlak plot and a compartmental model. MR estimates of the SK-GFR were compared with standard radioisotope measures in a total of 75 kidneys. RESULTS: Estimates of renal function using both techniques correlated well with radioisotope-assessed SK-GFR (Spearman's rho=0.81, Rutland-Patlak; rho=0.71, compartmental model). The Rutland-Patlak approach provided a near one-to-one correspondence, while the compartmental method tended to overestimate SK-GFR. However, the compartmental model fits to the experimental data were significantly better than those obtained using the Rutland-Patlak approach. CONCLUSION: DCE-MRI of the kidneys provides data that correlate well with reference measures of SK-GFR. However, further work, including image registration, is needed to isolate measurement of glomerular filtration to the level of the renal cortex.

Aged↗

PubMed2005

Speeding drivers' attitudes and perceptions of speed cameras in rural England.

There is evidence that excessive speed leads to an increased frequency and severity of road traffic accidents, but it is not clear how speeds may be reduced. To increase understanding of why drivers exceed the speed limits, the views of a sample of road users who had been prosecuted for exceeding the speed limit in the rural county of Norfolk England were sought. Respondents were categorised into a four group driver typology comprising conformers (those who report they never exceed limits) deterred drivers (those put off speeding by the presence of cameras), manipulators (those who slow only at camera locations) and defiers (those who exceed limits regardless of cameras), and the consistency of opinions was compared between the groups. Speeding was perceived as widespread and normal, and many drivers resented camera enforcement. Indeed, some respondents considered that cameras in themselves caused dangerous driving. For many drivers, the prosecution experience resulted in distress, anger and anti-camera sentiments, predominantly because they expressed the belief that they were more skilled than other drivers. It was also apparent that many respondents displayed a lack of awareness of the link between speed and collisions. Conformers were the least likely to state that the prosecution had deterred them from further speeding behaviour, possibly because they perceived themselves as already law-abiding. The deterred drivers were most likely to express intentions to avoid further speeding and their speeding incident was found to be most likely to be accidental. Manipulators and defiers tended to report that they had deliberately chosen to infringe the speed limits. Manipulators often acknowledged that their style of driving was dangerous; however, they failed to link this to their own behaviour. It was evident that many defiers and manipulators did not perceive speeding as a serious traffic law violation. Possible implications for road safety initiatives are discussed and recommendations are given for specifically targeting different driver types.

Accidents, Traffic↗

PubMed2003

The use of multilevel models for the prediction of road accident outcomes.

An important problem in road traffic accident research is the resolution of the magnitude by which individual accident characteristics affect the risk of fatality for each person involved. This article introduces the potential of a recently developed form of regression models, known as multilevel models, for quantifying the various influences on casualty outcomes. The application of multilevel models is illustrated by the analysis of the predictors of outcome amongst over 16,000 fatally and seriously injured casualties involved in accidents between 1985 and 1996 in Norway. Risk of fatality was found to be associated with casualty age and sex, as well as the type of vehicles involved, the characteristics of the impact, the attributes of the road section on which it took place, the time of day, and whether alcohol was suspected. After accounting for these factors, the multilevel analysis showed that 16% of unexplained variation in casualty outcomes was between accidents, whilst approximately 1% was associated with the area of Norway in which each incident occurred. The benefits of using multilevel models to analyse accident data are discussed along with the limitations of traditional regression modelling approaches.

Accidents, Traffic↗

PubMed2002

Prediction of radiotherapy outcome using dynamic contrast enhanced MRI of carcinoma of the cervix.

PURPOSE: To investigate whether analysis of MRI enhancement data using a pharmacokinetic model improved a previously found correlation between contrast enhancement and tumor oxygenation measured using PO2 histograph. To evaluate the prognostic value of gadolinium enhancement data for radiotherapy outcome, and to study the efficacy of combined enhancement and MRI volume data. METHODS AND MATERIALS: Fifty patients underwent dynamic gadolinium-enhanced MRI as part of their initial staging investigations before treatment. Gadolinium enhancement was analyzed using the Brix pharmacokinetic model to obtain the parameters amplitude and rate of contrast enhancement. Pretreatment tumor oxygen measurements (Eppendorf PO2 histograph) were available for 35 patients. RESULTS: Both standard and pharmacokinetic-derived enhancement data correlated with tumor oxygenation measurements, and poorly enhancing tumors had low tumor oxygen levels. However, only the pharmacokinetic-analyzed data correlated with patient outcome and patients with poorly (amplitude less than median) vs. well-enhancing tumors had significantly worse disease-specific survival (p = 0.024). For the 50 patients studied, no relationship was found between enhancement and volume data. Combining MRI volume and enhancement information highlighted large differences in outcome (p = 0.0054). At the time of analysis, only 55% of patients with large, poorly enhanced tumors were alive compared with 92% of patients with small, well-enhanced tumors. CONCLUSION: These preliminary results suggest that pharmacokinetic modeling of dynamic contrast-enhanced MRI provides data that reflect tumor oxygenation and yields useful prognostic information in patients with locally advanced carcinoma of the cervix. Combining MRI-derived enhancement and volume data delineates large differences in radiotherapy outcome.

Adenocarcinoma↗