A statistically significant decrease was seen in the ADC values of degenerated lumbar disks when compared with ADC values of normal disks. More caudal disks, even when normal, showed lower ADC values than more cephalic disks.

The authors reviewed 40 computed tomographic (CT) perfusion studies to determine the effect of arterial and venous input function properties on perfusion parameter values and tissue signal-to-noise ratio (SNR). A 10-subject subset was analyzed to evaluate the effect of varying venous region of interest (ROI) locations. Venous peak enhancement correlated significantly with mean tissue cerebral blood flow (CBF) and cerebral blood volume (CBV); venous and arterial peak enhancement correlated significantly with SNR of perfusion maps. Different ROI locations within the same vein resulted in significantly different CBV and CBF values. Perfusion map parameters are related to peak enhancement within user-selected ROIs. Optimal ROI selection should limit variability and increase quality of CT perfusion images.

Visceral interventional radiology catheters can be difficult to exchange or remove for a variety of reasons. These reasons include exit of the guide wire through the side holes of the catheter, blockage of the catheter, difficulty unlocking the pigtail, retention of the string after catheter removal, migration of the string ahead of the guide wire, catheter fracture, and snaring of an adjacent stent by the pigtail. Secure fixation of the catheter to the skin is important. A technique that allows secure fixation without direct puncture and suturing of the catheter to the skin is recommended. If a catheter falls out or is inadvertently removed, access can occasionally be regained and the catheter can be replaced without repuncture. The timing of catheter removal is based on the clinical condition of the patient and the daily output from the catheter. "Tractography" is a useful study before removal of any catheter that requires a mature tract for removal, particularly cholecystostomy catheters and transpleural catheters. In biliary catheter exchange, the most vital issue is the position of the side holes of the catheter. If an abscess cavity remains large after catheter drainage, the catheter can be repositioned or a second catheter can be placed.

We found a high correlation between degree of contrast enhancement on dynamic contrast-enhanced images and rCBV values in whole tumors and in regions having the highest degree of contrast enhancement in this small study. Our findings, which suggest that relative permeability and rCBV values may be correlated in high-grade glial neoplasms, deserve further study in a larger patient population.