Cavoatrial junction and central venous anatomy: implications for central venous access tip position.

PURPOSE: To quantify the anatomic relationships of the cavoatrial junction and propose a system for describing central venous access device tip location on the basis of structures visible on chest radiographs. MATERIALS AND METHODS: The authors performed a retrospective study of 100 consecutive computed tomographic (CT) studies from a predominantly pediatric population consisting of 52 male and 48 female patients aged 12-28 years (mean age, 16 years). With use of multiplanar and scout images, relevant mediastinal structures were marked, vertebral levels were noted, and measurements were made electronically. Catheter tip positions were recorded in the 26 children who had central catheters. RESULTS: A vertebral body unit was defined as the distance between the inferior endplate of one vertebra to the inferior endplate of the next, with the upper intervertebral disk included. The most reliable estimate of cavoatrial junction position is a point two vertebral body units below the carina; there was no association with patient age or other parameters. CONCLUSIONS: A more accurate understanding of the superior vena cava anatomy is essential for the correct interpretation of central venous access device position. The true cavoatrial junction is located more inferiorly than commonly believed and is not accurately estimated with commonly used imaging landmarks. A point two vertebral body units below the carina enables the reliable estimate of the position of the cavoatrial junction. Catheter tip position can be most reliably described in vertebral body units below the carina, with use of the thoracic spine as an internal ruler.

Early ischemia in growing piglet skeleton: MR diffusion and perfusion imaging.

PURPOSE: To determine whether diffusion changes with ischemia of increasing duration, whether diffusion magnetic resonance (MR) imaging provides different information than does gadolinium-enhanced imaging, and which structural and/or biochemical changes are potentially responsible for any changes in diffusion. MATERIALS AND METHODS: Ischemia was surgically induced in one hip of each piglet (n=8) after approval from the Subcommittee on Research Animal Care; the other hip served as a control. Piglets were imaged at approximately 48 hours and 1, 2, 4, and 8 weeks after surgery at 1.5 T by using line-scan diffusion and dynamic gadolinium-enhanced MR imaging. Apparent diffusion coefficients (ADCs) and enhancement ratios (ERs) were calculated. Significant differences in ADC and ER values over time were evaluated by using the Student t test (P<.05). At 8 weeks, piglets were sacrificed for histologic evaluation. RESULTS: MR images of ischemic hips showed essentially no flow 48 hours after surgery. Spontaneous partial reperfusion was observed 1-4 weeks after surgery (ischemic ER/control ER=66%+/-35 [standard deviation]), and the ER of the ischemic hips was well above that of the control hips at 8 weeks. The ADC of ischemic hips was elevated above that of control hips before reperfusion 1 week after surgery by 47%+/-12 and remained elevated despite flow restoration. Gross structural abnormalities on MR images appeared to coincide with reperfusion. Histologic findings revealed abnormal epiphyseal cartilage thickening, cartilaginous islands within ossified tissue, and less fatty marrow in ischemic hips than in control hips; all of these factors could explain elevated ADC. CONCLUSION: Diffusion is sensitive to early ischemia and follows a different time course than that of changes observed with gadolinium enhancement. ADC remained elevated in this model of severe, prolonged ischemia despite the spontaneous partial restoration of blood flow seen on gadolinium-enhanced images.

Multidetector row CT in pediatric musculoskeletal imaging.

The proliferation of multidetector row CT (MDRCT) has had a significant effect on imaging of the musculoskeletal system. An increasing number of such examinations is being performed in children. We reviewed our experience using such examinations in children during a period of 20 months. In this review, we discuss MDRCT techniques and issues regarding the radiation dose of these examinations. We present the effect of newer scanning techniques and their incorporation into our scanning protocols.