Dynamic effects of axial loading on the lumbar spine during magnetic resonance imaging in patients with suspected spinal stenosis.

BACKGROUND: Previous studies have shown that axial compression in extension (ACE) of the spine during magnetic resonance imaging (MRI) has revealed unexpected pathological features compared with the conventional psoas-relaxed position (PRP) used in imaging. The purpose of this study was to evaluate the dynamic effect of axial loading on lumbar spinal stenosis using MRI in patients with spinal stenosis. METHODS: A total of 14 women and 11 men with lumbar spinal stenosis were examined in both PRP and ACE positions. We calculated the dural-sac cross-sectional area (DCSA) to evaluate severity of spinal canal stenosis. DCSA, as well as the dural-sac anteroposterior diameter (DAPD) and dural-sac transverse diameter (DTD) in both positions were measured using a digital image view station. A paired t test determined the differences in DCSA, DAPD and DTD between the two positions at each intervertebral disc level. RESULTS: Axial loading increased severity of lumbar spinal stenosis during MRI, as demonstrated by a decrease in DCSA from 20.5% to 6.3% (mean, 11.40 +/- 3.66%) between the PRP and ACE positions (p less than 0.01). Significant differences were also noted in DAPD and DTD between the PRP and ACE positions (p less than 0.01). A significant correlation was found between the decrease in mean DCSA and that in DAPD and DTD. The decrease in mean DCSA, DAPD and DTD following axial compression was greatest at the L4/5 and L5/S1 levels. CONCLUSION: Axial loading increases severity of lumbar canal stenosis and the effect of axial loading on MRI examination is greatest at the L4/5 and L5/S1 levels.

Spiral biphasic contrast-enhanced computerized tomography in the diagnosis of hepatocellular carcinoma.

Advances in spiral computerized tomography (CT) have made rapid biphasic contrast-enhanced CT possible. This study evaluated the capability of biphasic contrast-enhanced spiral CT to detect hepatocellular carcinoma (HCC). A total of 125 patients (68 men and 57 women) with proven HCC underwent preliminary noncontrast (NC) scanning, followed by hepatic arterial phase (HAP) and portal venous phase (PVP) imaging. Contrast medium (80 mL, 300 mgI/mL) was administered routinely at a rate of 2 mL/second using an automated contrast injector under guidance software monitoring. Study of NC and PVP images without concurrent study of HAP images detected 131/171 (76.6%) cases of HCC. In contrast, combined study of NC, PVP, and HAP images detected 153/171 (89.5%) cases of HCC. Thus, combined study of NC and biphasic images was able to detect an additional 12.9% of HCC cases in comparison with conventional study of NC and PVP images only. All HCCs that were detectable only on HAP imaging were enhanced homogeneously with contrast medium during the arterial phase.