Left main renal artery entrapment by diaphragmatic crura: spiral CT angiography.

Entrapment of renal artery by the diaphragmatic crus is a rare cause of renal artery stenosis. Spiral computed tomography angiography provides a definitive diagnosis and shows the precise relationship of the artery to the diaphragmatic crus. The authors present a case of hypertension developing in a young 20-year-old female due to entrapment of the left renal artery by the diaphragmatic crus. This condition should be considered in young hypertensive patients with renal artery stenosis without cardiovascular risk factors.

Diffuse panbronchiolitis: not just an Asian disease: Australian case series and review of the literature.

Diffuse panbronchiolitis is a disease of obscure aetiology that is traditionally associated with Asian ethnicity. We propose that this disease also occurs in Caucasians and the incidence in this population is greater than currently recognised. We further propose that high resolution computed tomography (HRCT) and response to macrolide therapy should be relied upon to make this diagnosis without verification by lung biopsy. In most circumstances, obtaining a biopsy for histopathology is not practical, and the disease may then be mistaken for other more common airway diseases. Accuracy of diagnosis is important as untreated disease is associated with a poor prognosis, and effective treatment is available. We report four out of a series of cases as evidence that DPB is in fact more common in the Western population than is currently understood.

Mesenteroaxial volvulus in an adult: time is of the essence in acute presentation.

Acute gastric volvulus is an uncommon condition with severe repercussions if untreated in the acute presentation. We describe such a case. We assert that computed tomography (CT) should be the first line of investigation.

Nociceptive and anaesthetic-induced changes in pulse transit time during general anaesthesia.

BACKGROUND: Pulse transit time (rPTT), the interval between ventricular electrical activity and arrival of a peripheral pulse waveform, has been used to detect changes in autonomic tone. The aim of this observational pilot study was to measure changes in rPTT in response to general anaesthesia and noxious stimuli. METHODS: Thirty-one healthy women undergoing gynaecological surgery were allocated to groups depending on the need for airway management with tracheal intubation (n=9), a laryngeal mask (LMA, n=17) or a facemask (n=5). During general anaesthesia, we measured changes in RR interval (RR-int) and rPTT after (i) induction of anaesthesia, (ii) airway manipulation and (iii) surgical stimulus. rPTT was estimated as the interval from the peak in the R-wave to detection of the pulse oximeter waveform in the periphery. RESULTS: Mean baseline rPTT was 245 (SD 27) ms. Upon induction of anaesthesia, rPTT increased (by 28.2 (20.4) ms, P<0.001) in all but two patients. rPTT decreased in response to endotracheal intubation (by 43.1 (24.6) ms, P=0.001) but did not vary in response to insertion of LMA or surgical stimulus. Mean baseline RR-int was 865 (141) ms. A mean reduction in RR-int after tracheal intubation did not reach statistical significance. RR-int was unchanged with induction of anaesthesia, LMA insertion or surgical stimulus. CONCLUSION: Variation in rPTT reflects autonomic responses to nociceptive stimulation and fluctuations in anaesthetic depth independently of heart rate.

Hybrid method in light scattering by an arbitrary particle.

A hybrid method for light scattering by an arbitrary particle using the scattering-order formulation of the coupled dipole method is described. An arbitrary particle is divided into two or more segments, and the field scattered by the particle is obtained from the fields scattered by each segment together with the field due to interactions among segments. An exact or approximate theory is used to calculate the scattered field from each segment, and interactions are included using the scattering-order formulation of the coupled dipole method. Calculations show that for certain particles, this hybrid approach can require fewer computations and give more accurate results than the scattering-order method.

Theoretical factors in modeling polarized light scattering by arbitrary particles.

The coupled dipole method has been used to model the S(34) scattering matrix element for particles of arbitrary shape. Comparison of the results of the approximate method with the exact theory for a sphere shows that the size of the units required for S(34) is much smaller than the size required for calculating S(11) with similar accuracy. Model calculations for chiral particles show that the S(34) matrix element depends sensitively on the exact shape, size and optical properties of the scatterer.

Light scattering by an arbitrary particle: the scattering-order formulation of the coupled-dipole method.

The field scattered by an arbitrary particle modeled as an array of coupled dipoles can be expressed as an infinite series in terms of scattering orders. The fields of a given scattering order can be calculated from those of the previous order. When the series converge, the approximate method agrees well with the exact theory for a sphere. The maximum size of the dipolar array that can be used with the method as well as the number of terms required for convergence depends on the relative refractive index and the shape of the particle.

Light scattering by an arbitrary particle: a physical reformulation of the coupled dipole method.

The coupled dipole model of scattering by an arbitrary particle has been reformulated in terms of internal scattering processes of all orders. This formalism readily permits physical interpretation of observables and provides a rational basis for making computations more efficient. The calculation of scattering parameters can be simplified by appropriately terminating the infinite series at any order as well as by restricting the summations over the dipolar interaction terms within each order. Large particles can be partitioned into segments so that the scattered field is a superposition of the fields from the segments together with fields due to interactions among dipoles in different segments.