The anatomical relationship of the aortic bifurcation to the lumbar vertebrae: a MRI study.

The objective of this study was to determine the level of the aortic bifurcation in relation to the lumbar spine by MRI and the effect of lumbosacral anomalies on the aortic bifurcation. A prospective study of 441 patients was performed. Sagittal MR images of the entire spine were obtained along with the standard protocol for imaging of the lumbar spine. The vertebrae were counted caudally from C2 instead of cranially from the presumed L5 vertebra. The aortic bifurcation in relation to the lumbar vertebrae was determined. The aorta bifurcated at the L4 vertebral body in 67% of cases. In patients with sacralization of L5 the aortic bifurcation was at the L3 vertebral body in 59%. In those patients with lumbarization of S1 the aorta bifurcated at the level of the L4 vertebral body in 40% and at the L4/5 disc space in 33%. There was no demographic variation of the aortic bifurcation in relation to age or sex. The aorta bifurcated at L4 in two-thirds of cases and was variably located in the remaining third. The stability of this as a landmark is disturbed by the significant high incidence of lumbosacral transitional segments.

Arterial pressure measurements using infrared photosensors: comparison with CW Doppler.

We evaluated the accuracy of modern infrared photosensors (IPs) from a photoplethysmography (PPG) machine as flow detector in determining the systolic arterial pressures and ankle/brachial indices (ABIs) in comparison to the traditional continuous wave Doppler (Doppler) method. Pressures were obtained by placing an appropriate pneumatic cuff above the elbow and ankle. The Doppler probe was placed at brachial artery, posterior tibial artery and dorsalis pedis artery, and the IP was placed on the pad of the index finger and great toe. The two techniques were compared in 181 limbs in our non-invasive vascular laboratory, 133 limbs with normal and 48 limbs with abnormal ABIs. The accuracy of absolute ankle pressure measurements was also compared by both methods. We found that IPs from PPG machine have a good correlation (linear regression r=0.96 for normal and r=0.95 for abnormal ankle pressures) with the Doppler method. There was no significant difference (P< or =0.0001) in the ABIs calculated by two methods in either normal or abnormal subjects. The PPG method was easier, quicker and automated as compared with the cumbersome Doppler method. While PPG method does not differentiate between occlusive disease of posterior tibial and anterior tibial/dorsalis pedis arteries, it is better suited for non-compliant patients and is superior to Doppler method in advanced occlusive arterial disease. We recommend that it be used on a routine basis.