Do we need high temporal resolution modelling of exposure in urban areas? A test case.

Roadside concentrations of harmful pollutants such as NOx are highly variable in both space and time. This is rarely considered when assessing pedestrian and cyclist exposures. We aim to fully describe the spatio-temporal variability of exposures of pedestrians and cyclists travelling along a road at high resolution. We evaluate the value added of high spatio-temporal resolution compared to high spatial resolution only. We also compare high resolution vehicle emissions modelling to using a constant volume source. We highlight conditions of peak exposures, and discuss implications for health impact assessments. Using the large eddy simulation code Fluidity we simulate NOx concentrations at a resolution of 2 m and 1 s along a 350 m road segment in a complex real-world street geometry including an intersection and bus stops. We then simulate pedestrian and cyclist journeys for different routes and departure times. For the high spatio-temporal method, the standard deviation in 1 s concentration experienced by pedestrians (50.9 µg.m-3) is nearly three times greater than that predicted by the high-spatial only (17.5 µg.m-3) or constant volume source (17.6 µg.m-3) methods. This exposure is characterised by low concentrations punctuated by short duration, peak exposures which elevate the mean exposure and are not captured by the other two methods. We also find that the mean exposure of cyclists on the road (31.8 µg.m-3) is significantly greater than that of cyclists on a roadside path (25.6 µg.m-3) and that of pedestrians on a sidewalk (17.6 µg.m-3). We conclude that ignoring high resolution temporal air pollution variability experienced at the breathing time scale can lead to a mischaracterization of pedestrian and cyclist exposures, and therefore also potentially the harm caused. High resolution methods reveal that peaks, and hence mean exposures, can be meaningfully reduced by avoiding hyper-local hotspots such as bus stops and junctions.

Mitigating diffuse phosphorus transfer from agriculture according to cost and efficiency.

Potential options for mitigating phosphorus (P) transfer from agriculture to water in England and Wales (E&W) were collated across a range of farm systems to assess their potential effectiveness in reducing mass of P transferred and potential cost (pounds sterling [ pound]) to the farming industry. A simple model framework (called PEASE) incorporating a number of assumptions was used to identify 15 methods for mitigating inputs of P to agricultural systems, 19 methods for preventing mobilization of P, and six methods for controlling the transport of P to streams. The scope for largest reductions in P inputs was to grassland and horticulture. Potential reductions in P mobilization were up to 1.2 kg P ha(-1). Reductions in P transfer associated with transport mitigation were larger than those associated with input and mobilization methods (up to 2.2 kg P ha(-1)). The largest estimated reductions were achieved by installing buffer zones and constructed wetlands, the former being very cost effective ( pound3-5 kg(-1) P saved). Plots of cost curves helped identify where the combined and cumulative P transfer reductions were attainable; these were approximately 0.2 kg ha(-1) for uplands, 0.6 kg ha(-1) for outdoor pigs, 0.9 kg ha(-1) for intensive dairy, and 2.2 kg ha(-1) for arable examples. We concluded that established catchment-scale evidence for mitigation is sparse, especially for specific farm systems in E&W. Sensitivities and uncertainties in the approach, especially associated with expert coefficients, are noted. This approach is nonetheless considered useful for prioritizing where and how best options might be most effectively targeted for least cost but greatest benefit.

Introduction to the DAPPLE Air Pollution Project.

The Dispersion of Air Pollution and its Penetration into the Local Environment (DAPPLE) project brings together a multidisciplinary research group that is undertaking field measurements, wind tunnel modelling and computer simulations in order to provide better understanding of the physical processes affecting street and neighbourhood-scale flow of air, traffic and people, and their corresponding interactions with the dispersion of pollutants at street canyon intersections. The street canyon intersection is of interest as it provides the basic case study to demonstrate most of the factors that will apply in a wide range of urban situations. The aims of this paper are to introduce the background of the DAPPLE project, the study design and methodology for data collection, some preliminary results from the first field campaign in central London (28 April-24 May 2003) and the future for this work. Updated information and contact details are available on the web site at http://www.dapple.org.uk.

Basilar trunk occlusion during endovascular treatment of giant and fusiform aneurysms of the basilar artery.

Giant and fusiform aneurysms of the basilar artery (BA) are difficult to manage surgically, and they still present a challenge for the neurosurgeon despite progress in posterior fossa surgery. Guglielmi detachable coils have provided an alternative approach to treatment, but they have their own difficulties. We present a series of three patients with BA aneurysms treated with endovascular occlusion of the aneurysm and basilar trunk. Our experience suggests that, in select cases, BA occlusion may be not only safe but also necessary for the effective treatment of these aneurysms.

A population-based study of brain arteriovenous malformation: long-term treatment outcomes.

BACKGROUND AND PURPOSE: By undertaking long-term follow-up of a functionally isolated population study group, we sought to achieve a true picture of intrinsic brain arteriovenous malformation (BAVM). We sought to assess the validity of earlier population-based series and to determine the effects of newer treatment methods on the overall morbidity and mortality of BAVM. METHODS: We excluded other intracranial vascular pathologies by defining criteria. By retrospective and prospective study, 240 patients with BAVM were followed for a mean of 10.11 years from first diagnosis. RESULTS: Death rates were as follows: all causes, 12.9%; all BAVM related, 8.75%; BAVM related during conservative management, 24.6%; and BAVM related during active management, 3.9% (P=0.031). Mean diagnosis-to-death interval was 10.6 years. Oxford neurological disability scale grades of 209 survivors (July 2001) were as follows: grades 0 to 2, 74.1%; grade 3, 17.2%; and grades 4 to 5, 9.5%. Death rates were higher for patients who had bled or suffered nonhemorrhagic neurological deficit at original presentation. Incidence of first-ever hemorrhage in untreated patients was as follows: 0 to 9 years, 4.6% (P=0.0035); 30 to 39 years, 21% (P=0.02); and 60 to 69 years, 40.0% (P=0.045). The first bleed was fatal in 4.6%. CONCLUSIONS: We find no evidence of a substantial undiagnosed reservoir of nonsymptomatic BAVM. All BAVM are potentially hazardous. The great majority of BAVM patients become symptomatic during the patient's lifetime, and the majority will bleed. The risk of first hemorrhage is lifelong and rises with age. Compared with earlier population-based series, our low overall patient mortality is predominantly due to higher proportions of active treatment in the 1980s and 1990s.

Ammonia emission, deposition and impact assessment at the field scale: a case study of sub-grid spatial variability.

A local ammonia (NH3) inventory for a 5x5 km area in central England was developed, to investigate the variability of emissions, deposition and impacts of NH3 at a field scale, as well as to assess the validity of the UK 5-km grid inventory. Input data were available for the study area for 1993 and 1996 on a field by field basis, allowing NH3 emissions to be calculated for each individual field, separately for livestock grazing, livestock housing and manure storage, landspreading of manures and fertiliser N application to crops and grassland. An existing atmospheric transport model was modified and applied to model air concentrations and deposition of NH3 at a fine spatial resolution (50 m grid). From the mapped deposition estimates and land cover information, critical loads and exceedances were derived. to study the implications of local variability for regional NH3 impacts assessments. The results show that the most extreme local variability in NH3 emissions, deposition and impacts is linked to housing and storage losses. However, landspreading of manures and intensive cattle grazing are other important area sources, which vary substantially in the landscape. Overall, the range of predicted emissions from agricultural land within the study area is 0-2000 kg N ha(-1) year(-1) in 1993 and 0-8000 kg N ha(-1) year(-1) in 1996, respectively, with the peak at a poultry farm located in the study area. On average, the estimated field level NH3 emissions over the study area closely match the emission for the equivalent 5-km grid square in the national inventory for 1996. Deposition and expected impacts are highly spatially variable, with the edges of woodland and small "islands" of semi-natural vegetation in intensive agricultural areas being most at risk from enhanced deposition. Conversely the centres of larger nature reserves receive less deposition than average. As a consequence of this local variability it is concluded that national assessments at the 5 km grid level underestimate the occurrence of critical loads exceedances due to NH3 in agricultural landscapes.

Endovascular treatment of intracranial aneurysms with Guglielmi detachable coils: analysis of midterm angiographic and clinical outcomes.

BACKGROUND AND PURPOSE: The previous decade has witnessed increasing application of Guglielmi detachable coils (GDCs) for the treatment of intracranial aneurysms. However, the midterm angiographic and clinical outcomes are not well documented. We report here the angiographic and clinical outcomes of patients treated with GDCs over an 8-year period. METHODS: Between 1992 and 1998, 144 patients with 160 intracranial aneurysms were treated with GDCs. Clinical follow-up data were obtained from medical records, questionnaires, and telephone interviews. Angiographic studies were reviewed by 2 neuroradiologists to obtain consensus regarding the degree of aneurysm occlusion. RESULTS: Eighty-one patients had ruptured aneurysms; 63 had unruptured aneurysms. Technical success was achieved in 91% of patients, with complete aneurysm occlusion in 46%, neck remnants in 16%, and residual body filling in 38%. Angiographic follow-up revealed that residual body filling in some aneurysms was resolved, small neck remnants were stable, and the recanalization rate decreased with time. All 63 patients with unruptured aneurysms were discharged from hospital with independent clinical status (Glasgow Outcome Score, 1 or 2). For patients with ruptured aneurysms, discharge clinical status correlated with the Hunt & Hess clinical grade at the time of treatment. Clinical follow-up for a minimum of 2 years was available in 98.5% of patients. Ninety-four percent of patients treated for unruptured aneurysms were independent at 2 years, and 82% of Hunt & Hess grade I to II patients were independent. CONCLUSIONS: Coil embolization is a safe and effective treatment for both ruptured and unruptured aneurysms. Increasing angiographic stability is demonstrated in treated aneurysms up to 3 years from coil embolization. Therefore, follow-up angiography until this time is advisable.

Endovascular management of acute subarachnoid haemorrhage in the elderly.

The objective of this study was to analyse the technical and clinical outcome in elderly patients receiving endovascular treatment for acutely ruptured intracranial aneurysms. The case notes and angiograms of 14 patients over the age of 69 years undergoing endovascular treatment for subarachnoid haemorrhage within the Interventional Neuroradiology Unit, Royal Perth Hospital over a period of 6 years were retrospectively reviewed. The degree of angiographic occlusion achieved, and periprocedural, short-term and long-term clinical outcome were retrospectively assessed. Greater than 90% occlusion was obtained in 92% of cases. 82% of patients with Hunt and Hess grade I and II had an excellent clinical outcome. We conclude that endovascular coiling is an effective means of treating acute subarachnoid haemorrhage in grade I and II elderly patients.

Endovascular treatment of posterior circulation aneurysms.

The objective of this paper was to analyse the technical and clinical outcome in patients receiving endovascular treatment for posterior circulation intracranial aneurysms at Royal Perth Hospital. The case notes and angiograms of 35 patients with ruptured and unruptured posterior circulation aneurysms treated by endovascular coil occlusion between 1992 and 1998 were included in the study. The degree of angiographic occlusion achieved, and periprocedural, short and long-term clinical outcome were retrospectively analysed. Total aneurysm occlusion was achieved at initial treatment in 46% of cases, with 90% or greater occlusion achieved in 97% of cases. For aneurysms 12 mm or less in diameter, 100% of patients treated electively, and 100% of patients with grade I or II subarachnoid haemorrhage treated in the acute postictal phase had a good clinical outcome (Rankin Disability Score 1 and 2), with no serious morbidity or associated mortality. Excluding patients with grade V subarachnoid haemorrhage, the treatment-related serious morbidity rate was 3.4% and procedure-related mortality rate was 0%. We conclude that endovascular management provides an effective means of treatment for selected cases of posterior circulation aneurysms.

Visual symptoms with dural arteriovenous malformations draining into occipital veins.

OBJECTIVE: To determine the cause of the visual dysfunction and effect of treatment on dural arteriovenous malformations (DAVMs) that secondarily involve the occipital lobe. BACKGROUND: DAVMs are an infrequent cause of visual dysfunction that should be amenable to treatment if diagnosed before permanent visual field loss. METHODS: The records of seven patients with cerebral visual disturbances associated with DAVMs were analyzed with attention to visual symptoms, visual field testing, and vascular anatomy. RESULTS: Sudden visual loss occurred in five patients, two with a hemorrhage and one with a venous infarct in the occipital lobe. Fortification images occurred in three patients, two of whom had palinopsia (one with de novo formed visual hallucinations). Homonymous quadrantic or hemianoptic field defects, some fluctuating, were found in six patients. Angiography revealed each DAVM was supplied solely by dural arteries and drained into occipital pial veins due to retrograde blood flow through the sites near or in the wall or lumen of the dural venous channels that normally drain the occipital lobe. Unlike DAVMs in other locations, only two patients had occlusion of an adjacent venous sinus. These patients, particularly the two with posterior fossa DAVMs remote to the occipital lobe, clearly demonstrate the visual and neurologic dysfunction resulting from venous hypertension. In six patients, intra-arterial embolization of the arterial feeders and nidus (one patient required additional surgery) resulted in resumption of normal occipital venous emptying. No further visual episodes occurred in five of these six patients. The visual fields normalized in three patients and improved in one with venous infarct but were unchanged in both patients with a hemorrhage. CONCLUSIONS: DAVMs that drain into occipital veins cause field loss and other visual disturbances because of venous hypertension in the occipital lobe, which can be reversed by occluding the DAVM nidus. If a venous infarct or hemorrhage has not caused irreversible damage, visual recovery should be complete.

Transarterial platinum coil occlusion of ruptured intracranial aneurysms: results in 51 patients.

Fifty-one patients with subarachnoid haemorrhage (SAH) due to ruptured intracranial aneurysm have been treated by the Guglielmi detachable platinum coil (GDC) treatment method; 36 patients within 28 days of the ictus. There was total body occlusion in 64.8%, subtotal body occlusion in 24.1% and failed coil placement in 11.1%. Technical success rates were highest in aneurysms with neck sizes up to 4 mm (75% total occlusion) and aneurysms smaller than 10 mm largest diameter (72.5% total occlusion). At discharge from primary care, there were 62.7% without deficit rising to 74.5% at follow-up assessment. Four patients are dead and one disabled (9.8%). Patient clinical outcomes relate most closely to Hunt and Hess grade at time of definitive treatment. Higher initial grades and poorer clinical outcomes are concentrated in patients treated in the first 14 days. The incidence of procedure related thrombo-embolic events has fallen from 20% in the first 30 patients to 4.8% in the next 21. Rebleeding during GDC procedures occurred in 20.6% of patients treated 1-14 days post SAH.

Spontaneous polymerisation of cyanoacrylate/lipiodol mixtures causing failed embolisation. Laboratory studies.

SUMMARY: In vitro experiments to investigate spontaneous polymerisation of n-butyl-2-cyanoacrylate when mixed with non ionic oily contrast medium are reported. The results suggest an interaction between the mixture components which is unique to one particular batch of Lipiodol Ultrafluid and Histoacryl n butyl cyanoacrylate. The interaction cannot be reproduced with other batches of Lipiodol Ultrafluid nor with an alternative preparation of n-butyl-2-cyanoacrylate. Implications for the use of the materials in neuro-interventional practice are discussed.

Cranial dural arteriovenous malformation and fistula. Radiological diagnosis and management. Review of thirty four patients.

The clinical features, imaging and angiographic findings of thirty four patients with cranial dural arteriovenous malformations and fistulae are presented in four groups. Group 1--Seven patients with anterior cavernous malformations, predominant superior ophthalmic vein drainage, and symptoms and signs of carotico-cavernous fistula. Group 2--Twelve patients with malformations of the superior petrosal, transverse and sigmoid sinus regions, presenting predominantly with bruit. Group 3--Seven patients with malformations of the basal sinuses and prominent cortical venous drainage, presenting with intracranial haemorrhage, headache and impaired cortical function. Intracranial haemorrhage never occurred in the absence of cortical venous drainage. Group 4--Eight patients with infrequent manifestations. Group 1 and 2 patients are readily recognized and diagnosed. Group 3 and 4 patients are often misdiagnosed. Treatment modalities comprised embolisation therapy, surgical excision, and carotid compression. Twenty patients were treated by one or more of these modalities with a successful outcome in thirteen patients. Group 1 patients are the most amenable to trans-arterial embolisation. Carotid compression as the sole modality of treatment was successful in four patients. Unless the fistula is successfully closed, Group 3 patients and patients who present with cervical or thoracic myelopathy carry a grave prognosis. There is need for greater radiologist awareness of Group 3 and the rarer presentations, particularly myelopathy. With the exception of one patient, the morphological features of our cases are consistent with the now-accepted view that these lesions are acquired arterio-venous fistulae and not congenital malformations.

Angiographically demonstrated arterial spasm in a case of benign sexual headache and benign exertional headache.

Benign headaches related to sexual activity and exertion are being recognised with increasing frequency. We wish to report a case of benign sexual headache (Type 2) and benign exertional headache, occurring sequentially in the same patient. Multiple areas of cerebral arterial spasm were demonstrable on angiography. This observation would support the concept that benign sexual headache (Type 2) and benign exertional headache may have a similar pathophysiology.

Validity and uncertainty in the calculation of an emission inventory for ammonia arising from agriculture in Great Britain.

Emissions of ammonia have received increasing attention recently, following concern about the environmental consequences, especially in The Netherlands where levels are high due to intensive livestock farming. Direct local effects and more widespread consequences for a range of ecosystems have been attributed to ammonia emissions. As the most prevalent alkaline gas in the atmosphere, ammonia interacts with acidic species, changing their characteristics, chemical and physical behaviour, and enhancing their potential for acidification of soils. Ammonia also forms an important component of the nitrogen cycle and of nitrogen deposition. In the UK, as in many other European countries, there has been a considerable increase in the emission of ammonia within the last 30 years, estimated at about 50%. This results mainly from increases in agricultural production based on the steadily rising number of livestock and increasing fertilizer consumption. This paper discusses the various sources to emissions of ammonia from agricultural sources in the United Kingdom, and some of the uncertainties involved in constructing a national emissions inventory.

Glomus intravagale tumour: aspects of management.

Glomus intravagale tumours are relatively rare tumours. A case is described and some aspects of its management are discussed with emphasis on the pre-operative investigation and diagnosis of this condition. Selective embolization of the lesion before operation is an important adjunct in treatment to reduce the vascularity of the tumour during operation. Intra-operative cardiac arrest due to traction of the vagus nerve was encountered. The methods to avoid this complication are discussed.

Improved technique of bucrylate embolisation in brain arteriovenous malformation. The use of additional temporary balloon occlusion.

Problems currently limiting the success and safety of calibrated leak balloon embolisation include suboptimal occlusion of malformation bed due to multiple or inaccessible pedicles and neural deficits due to paradoxical embolisation of normal brain. Analysis of preliminary calibrated leak balloon angiograms supported by temporary balloon occlusion of other pedicles yields insights into the dynamics of blood flow to anterior malformations. Strategies have been devised using temporary balloon occlusion to improve filling of malformation bed and reduce paradoxical embolisation of eloquent brain.

Valved latex balloons and water-soluble contrast opacified polymer. Simple detachable balloon system.

Latex balloons of different shapes, sizes and volume, incorporating a simple valve mechanism, were produced cheaply. These balloons are ethylene oxide sterilized and are available on 'the shelf' for use at any time. A contrast soluble polymer consisting of 2 hydroxy-ethyl-methacrylate, a cross linker, Iopamidol and water-soluble free radical curing system has been developed. The polymer sets in 10 minutes and there is no 'dead volume' problem. The balloons and polymer were evaluated in dog arteries, including histologic studies and have been subsequently used in 7 patients without any complications.