Improved visualization of choledocholithiasis by sonography

During a 20 month period, real-time sonography performed on 26 patients achieved an overall sensitivity of 75% for detecting choledocholithiasis. Although previous publications have stressed very low sensitivities for diagnosing choledocholithiasis (13%-55%), it was postulated that the reasons for these disappointing results are primarily related to technique. Most laboratories evaluate the distal common bile duct (where most calculi are located) by obtaining parasagittal scans. Detection of choledocholithiasis can be substantially improved by scanning the intrapancreatic part of the bile duct in a transverse fashion with the patient in an erect position. Advantages of the transverse view include the ability to demonstrate the distal common bile duct in a high percentage of patients and to differentiate shadowing caused by duodenal gas from ductal calculi. The proximal duct is best imaged by obtaining parasagittal scans with the patient in a supine left posterior oblique position. Using these scanning techniques, eight (89%) of nine proximal and 16 (70%) of 23 distal calculi were visualized.     

Direct visualization of intracranial aneurysms by computed tomography

Twenty seven aneurysms in 25 patients were directly visualized by CT. Thin-walled non-thrombosed aneurysms showed homogeneous sharply-marginated intraluminal enhancement. Partially thromhosed aneurysms had a thickened high-density peripheral rim which was sometimes calcified and enhanced; the intraluminal portion also enhanced but the thrombosed region was isodense and non-enhancing. Completely thrombosed aneurysms showed dense calcification in the peripheral wall with sometimes peripheral but no intraluminal enhancement.     

Direct visualization of intracranial aneurysms by multiplane dynamic CT

Using an intravenous injection of 100-150 ml contrast medium (flow, 1-1.5 ml/sec) adjacent 2-mm-thick cuts are scanned at the level of the circle of Willis. After highlighting and multilevel image summation a complete picture of the vascular anatomy of the base of the brain is obtained. In this way aneurysms as small as 2-3 mm in diameter can be detected. The method has high reliability, as indicated by the results in 31 cases.     

Contrast-enhanced coronary artery visualization by dual-source computed tomography--initial experience

Multi-detector computed tomography (CT) scanners, by virtue of their high temporal and spatial resolution, permit imaging of the coronary arteries. However, motion artifacts, especially in patients with higher heart rates, can impair image quality. We thus evaluated the performance of a new dual-source CT (DSCT) with a heart rate independent temporal resolution of 83 ms for the visualization of the coronary arteries in 14 consecutive patients. METHODS: Fourteen patients (mean age 61 years, mean heart rate 71 min(-1)) were studied by DSCT. The system combines two arrays of an X-ray tube plus detector (64 slices) mounted on a single gantry at an angle of 90 degrees With a rotation speed of 330 ms, a temporal resolution of 83 ms (one-quarter rotation) can be achieved independent of heart rate. For data acquisition, intraveous contrast agent was injected at a rate of 5 ml/s. Images were reconstructed with 0.75 slice thickness and 0.5 mm increment. The data sets were evaluated concerning visibility of the coronary arteries and occurrence of motion artifact. RESULTS: Visualization of the coronary arteries was successful in all patients. Most frequently, image reconstruction at 70% of the cardiac cycle provided for optimal image quality (50% of patients). Of a total of 226 coronary artery segments, 222 (98%) were visualized free of motion artifact. In summary, DSCT constitutes a promising new concept for cardiac CT. High and heart rate independent temporal resolution permits imaging of the coronary arteries without motion artifacts in a substantially increased number of patients as compared to earlier scanner generations. Larger and appropriately designed studies will need to determine the method's accuracy for detection of coronary artery stenoses.     

Preoperative visualization of the artery of Adamkiewicz by intra-arterial CT angiography

BACKGROUND AND PURPOSE: CT and MR angiographies have been reported to visualize the artery of Adamkiewicz (AKA) noninvasively to prevent spinal cord ischemia in surgery of thoracic descending aortic aneurysms. The purpose of this work was to compare the usefulness of CT angiography (CTA) with intra-arterial contrast injection (IACTA) with that of conventional CTA with intravenous contrast injection (IVCTA).MATERIALS AND METHODS: We enrolled 32 consecutive patients with thoracic or thoracoabdominal aortic aneurysms who were scheduled for surgical repair or endovascular stent-graft treatment. All of the CTA images were obtained using a 16-detector row CT scanner and 100 mL of contrast material (370 mg/mL) injected at a rate of 5 mL/s. Contrast was injected via the antecubital veins of 15 patients and via a pig-tail catheter placed at the proximal portion of the descending aorta in 17 patients who underwent IVCTA and IACTA, respectively. Two datasets were reconstructed from 2 consecutive scans. The AKA was identified as a characteristic hairpin curved vessel in the anterior midsagittal surface of the spine and by the absence of further enhancement in the second rather than in the first phase. Continuity between the AKA and aorta was confirmed when the vessel could be traced continuously by paging the oblique coronal multiplanar reconstruction or original axial images.RESULTS: Intra-arterial contrast injection was significantly more sensitive in identifying the AKA than IVCTA: 16 (94.1%) of 17 versus 9 (60.0%) of 15 (P = .033). Continuity between the AKA and aorta through intercostal or lumbar artery was confirmed in 14 (87.5%) of 16 and 5 (55.6%) of 9 of the IACTA and IVCTA groups, respectively.CONCLUSION: Intra-arterial contrast injection detected the AKA at a high rate and verified continuity from the aorta to the AKA.

Paraplegia and paraplesis secondary to spinal cord ischemia remain serious complications of surgical repair or of endovascular treatment for descending thoracic aortic aneurysm (TAA) or thoracoabdominal aortic aneurysm (TAAA). The incidence ranges between 5% and 11% of thoracoabdominal surgeries.^1–4 The great anterior radiculomedullary artery (the artery of Adamkiewicz [AKA]) is the dominant feeder of the spinal cord. One possible cause of spinal cord ischemia during surgery is failure to reestablish the spinal cord blood supply, and many reports have stressed the importance of reattaching the intercostal or lumbar arteries related to the AKA.^5,6 Preoperative AKA identification and display of intercostal and lumbar arteries help surgeons to determine the appropriate range of aortic lesions that require graft replacement and intercostal or lumbar arteries requiring reconstruction.⁷The most reliable way to visualize the AKA is selective intercostal arterial angiography, the detection rate of which is 43%–86%.^8–12 However, selective angiography is time consuming, and complications including spinal cord injury can develop.^10,11 Recently, MR angiography (MRA)^13–18 and CT angiography (CTA)^17–21 have been used to visualize the AKA less invasively with reported detection rates of 67%–93% and 68%–90%, respectively. However, these rates could be further improved.The AKA is a small vessel with a diameter of 0.5–1.5 mm^22,23 that is surrounded by osseous structures. In addition, intercostal or lumbar arteries and dorsal branches run very close to the osseous structures (Fig 1). Due to these anatomic features, the contrast-to-noise ratio (CNR) in the spinal canal is decreased, and the AKA and its continuity with the aorta can be obscured. Robust aortic contrast enhancement is necessary to detect small vessels, but CTA with intravenous contrast injection (IVCTA) has limitations with respect to elevating aortic enhancement, because contrast material is diluted in the circulation of the right side of the heart. Nojiri et al²⁴ showed that CTA with intra-arterial contrast injection (IACTA) could track the AKA to the aorta because of high contrast. The present study compares the abilities of IACTA and IVCTA to detect the AKA.Open in a separate windowFig 1.Anatomic course of the AKA. Right anterosuperior view of a 3D volume-rendered CT image of IACTA with semitransparent skeletal system. Intercostal and lumbar arteries (1) originate from the aorta, and divide into posterior (2) and anterior (3) branches. Anterior branches run through the intercostal groove. Posterior branches subdivide into the radiculomedullary artery (4) and muscular branch (5). Radiculomedullary artery courses to the spine and enters the vertebral foramen. The AKA (6) is the largest anterior radiculomedullary artery and joins the anterior spinal artery (7) in a characteristic hairpin curve.     

In vivo visualization of myelin water in brain by magnetic resonance

We exploit the intrinsic difference in magnetic resonance spin-spin relaxation time, T₂, between water associated with myelin sheaths and water in other central nervous system tissue in order to measure myelin water content within any region of an image or to generate indirectly a myelin map of the brain. In normal volunteers, myelin water maps give the expected myelin distribution. In multiple sclerosis patients, lesions exhibit different myelin water contents providing insight into the de-myelination process unavailable from conventional magnetic resonance images. In vivo myelin measurement has important applications in the clinical management of multiple sclerosis and other white matter diseases.     

Quantitative flow visualization of fluidized-bed heat exchanger by neutron radiography.

Quantitative flow visualization of a gas-solid fluidized-bed installed vertical tube-bank has been successfully conducted using neutron radiography and image processing technique. The quantitative data of void fraction distribution as well as the fluctuation data are presented. The time-averaged void fraction is well correlated by the drift-flux model. The bubbles formed in the bed, rise along the vertical tubes and the observed bubble size is smaller than that in a free bubbling bed without tube-banks. The bubble diameter is well correlated by the modified Mori and Wen's correlation taking into account the pitch of tube arrangement. The bubble rise velocity is also well correlated by applying the drift-flux model. These results are consistent for both bed materials of Geldart's B- and A-particles, while the bubble size is significantly different between two kinds of particles.     

Spontaneous infarct of the omentum majus: visualization by computed tomography

In a case report, idiopathic segmental infarction of the greater omentum is demonstrated for the first time by means of computed tomography. This rare disease of unknown etiology can mimic the clinical presentation of acute appendicitis or cholecystitis.     

Variability in measurement of radiomorphometric indices by general dental practitioners

OBJECTIVES: To assess the variability of general dental practitioners (GDPs) in measurement of radiomorphometric indices on panoramic radiographs following basic instruction and to examine whether the variability could be reduced by more individualised instruction. METHODS: Nine GDPs measured Gonion Index (GI), Antegonion Index (AI), Mental Index (MI) and Mandibular Cortical Index (MCI) on copies of 10 panoramic radiographs following a lecture on osteoporosis and the use of radiomorphometric indices. Their measurements were related to expert-derived measurements of the same copy radiographs. Mean differences and limits of agreement (2x standard deviation of differences) were calculated for quantitative indices (GI, AI, MI) and agreement of GDPs with expert-derived MCI assessments was determined using weighted kappa. Following individualised feedback to GDPs, all measurements were repeated after 2 weeks and the statistical analysis repeated. RESULTS: There was extensive variation amongst GDPs in measurement of GI, AI and MI and in assessment of MCI. There was a general tendency of GDPs to record thicker mandibular cortices than did the experts. Limits of agreement were wide relative to the mean values of each quantitative index at both readings. Agreement of the GDPs with experts in assessment of MCI was moderate at both readings, but with a wide range in assessment. CONCLUSIONS: Variability in measuring radiomorphometric indices amongst the GDPs was high and was not predictably improved by individualised instruction. This study casts considerable doubt on the potential value of radiomorphometric indices given their lack of precision.     

Improved vessel visualization in MR angiography by nonlinear anisotropic filtering

This paper deals with a preprocessing technique of magnetic resonance angiography (MRA) images, applied before maximum-intensity-projection (MIP). The purpose was to recover small low-intensity vessels, visible in individual slices, but lost in MIP images that usually have higher background level than the individual slices. The authors have developed a nonlinear three-dimensional spatial filtering technique (called HD filter) based on anisotropic smoothing. The filter first searches for the local orientation of the vessel. It then performs a nonlinear smoothing in the vessel's local direction so as to avoid blurring its boundaries. Noise level reduction, contrast enhancement, and improved small vessel visibility achieved by this filter are illustrated on dynamic contrast-enhanced subtraction MRA images of the lower limbs.     

Falx ossification--MR visualization

While falx calcification is rarely demonstrated using magnetic resonance, falx ossification, when seen, is characteristic. On magnetic resonance images, falx ossification exhibits a typical appearance consisting of a central marrow-containing portion with signal intensity similar to fat, surrounded by low signal intensity representing cortical bone. Falx ossification was seen in 0.7% of patients and should not be confused with a falx lipoma, a rare congenital entity.