[A new method of measuring temporal resolution for computed tomography].

In this study, we proposed a new method of measuring temporal resolution using an impulse signal in the time domain in computed tomography (CT). We employed a metal ball with a diameter of 11 mm as the source of the impulse signal, which was shot to a slice plane at a very fast speed during scanning, along the perpendicular direction to the plane. A 4-slice multi detector-row CT (MDCT) system was employed to evaluate the new method, and images for region of interest (ROI) measurement were reconstructed with a z-increment corresponding to a very short time (< or = 0.03 sec). Temporal sensitivity profiles (TSPs) for various helical beam-pitches were obtained by plotting averaged CT values within the ROIs against the temporal axis. The accuracy of the method was examined by comparing the measured TSPs with theoretical TSPs corresponding to respective helical beam-pitches. As a result, the theoretical TSPs and measured TSPs demonstrated high coincidence in all beam-pitches. Since the TSPs indicated the profiles with sharp shapes faithful to the theoretical TSPs, it was proved that the new method had sufficient inherent temporal resolution. It was indicated that the new method we proposed would be an effective method for evaluating temporal resolution in CT.

Prophylaxis of post-endoscopic retrograde cholangiopancreatography pancreatitis by an endoscopic pancreatic spontaneous dislodgement stent.

BACKGROUND & AIMS: Pancreatitis after endoscopic retrograde cholangiopancreatography (ERCP) is the most common and potentially serious complication of ERCP. The frequency of post-ERCP pancreatitis generally is reported to be between 1% and 9%. One cause of pancreatitis is retention of pancreatic juice resulting from papilledema after the procedure. We conducted a randomized controlled multicenter study to evaluate whether placement of a temporary pancreatic stent designed for spontaneous dislodgement prevents post-ERCP pancreatitis. METHODS: The subjects were 201 consecutive patients who underwent ERCP. The patients were randomized into the stent placement group (S group = 98) or the nonstent placement group (nS group = 103). The stent used was 5F in diameter, 3 cm in length, straight, and unflanged inside. RESULTS: Stents were placed successfully in 96% of the S group, and spontaneous stent dislodgment was recognized in 95.7% of those. The mean duration to dislodgment was 2 days, and there were no severe complications. The overall frequency of post-ERCP pancreatitis was 8.5%. The frequency of post-ERCP pancreatitis in the S and nS groups was 3.2% and 13.6%, respectively, showing a significantly lower frequency in the S group (P = .019). The mean increase in amylase level in the pancreatitis patients was significantly higher in the nS group (P = .014). CONCLUSIONS: The randomized controlled multicenter trial showed that placement of a pancreatic spontaneous dislodgment stent significantly reduces post-ERCP pancreatitis.

[Basic and clinical studies of visualizing right inferior phrenic artery by multi detector row-CT].

To perform transcatheter arterial embolization (TAE) successfully, it is important to obtain information about parasitic arterial supply to the hepatocellular carcinoma (HCC). Among these extrahepatic collateral vessels, the right inferior phrenic artery (RIPA) is the most frequent and important extrahepatic collateral artery supplying the HCC. In the present study, we obtained multi-planar reformation (MPR) images of RIPA using multi detector row computed tomography (MDCT), assessed the ability of MDCT to demonstrate the origin of RIPA, and then analyzed the morphology of the origin. In a basic study using an original phantom simulating vessel origin, the origin was poorly visualized depending on the phantom diameter and angle of the origin to the scanned section. A clinical study was performed in 28 patients with HCC who underwent both MDCT and angiography within a short period. In 19 of 28 patients, RIPA originated at the celiac artery. In 3 patients, RIPA originated at the right renal artery, and in 6, directly at the abdominal aorta. The origin of RIPA was categorized into four patterns according to the inclination of the origin on transverse sections of MDCT. RIPA that originated at the right renal artery and showed an upward course perpendicular to the scan section of MDCT were most clearly visualized at the origin. In addition, RIPA could be observed in an optional direction on the workstation. Pre-angiographic visualization of the origin of RIPA may save angiographic time, curtail contrast medium, and reduce radiation exposure.

[Visualization of the lower cranial nerves by 3D-FIESTA].

MR cisternography has been introduced for use in neuroradiology. This method is capable of visualizing tiny structures such as blood vessels and cranial nerves in the cerebrospinal fluid (CSF) space because of its superior contrast resolution. The cranial nerves and small vessels are shown as structures of low intensity surrounded by marked hyperintensity of the CSF. In the present study, we evaluated visualization of the lower cranial nerves (glossopharyngeal, vagus, and accessory) by the three-dimensional fast imaging employing steady-state acquisition (3D-FIESTA) sequence and multiplanar reformation (MPR) technique. The subjects were 8 men and 3 women, ranging in age from 21 to 76 years (average, 54 years). We examined the visualization of a total of 66 nerves in 11 subjects by 3D-FIESTA. The results were classified into four categories ranging from good visualization to non-visualization. In all cases, all glossopharyngeal and vagus nerves were identified to some extent, while accessory nerves were visualized either partially or entirely in only 16 cases. The total visualization rate was about 91%. In conclusion, 3D-FIESTA may be a useful method for visualization of the lower cranial nerves.