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991.
The optimal temporal window of intravenous (IV) computed tomography (CT) cholangiography was prospectively determined. Fifteen
volunteers (eight women, seven men; mean age, 38 years) underwent dynamic CT cholangiography. Two unenhanced images were acquired
at the porta hepatis. Starting 5 min after initiation of IV contrast infusion (20 ml iodipamide meglumine 52%), 15 pairs of
images at 5-min intervals were obtained. Attenuation of the extrahepatic bile duct (EBD) and the liver parenchyma was measured.
Two readers graded visualization of the higher-order biliary branches. The first biliary opacification in the EBD occurred
between 15 and 25 min (mean, 22.3 min ± 3.2) after initiation of the contrast agent. Biliary attenuation plateaued between
the 35- and the 75-min time points. Maximum hepatic parenchymal enhancement was 18.5 HU ± 2.7. Twelve subjects demonstrated
poor or non-visualization of higher-order biliary branches; three showed good or excellent visualization. Body weight and
both biliary attenuation and visualization of the higher-order biliary branches correlated significantly (P<0.05). For peak enhancement of the biliary tree, CT cholangiography should be performed no earlier than 35 min after initiation
of IV infusion. For a fixed contrast dose, superior visualization of the biliary system is achieved in subjects with lower
body weight. 相似文献
992.
Schindera ST Nelson RC Lee ER Delong DM Ngyen G Toncheva G Yoshizumi TT 《Academic radiology》2007,14(4):486-494
RATIONALE AND OBJECTIVES: To evaluate the effect of a modified abdominal multislice computed tomography (CT) protocol for obese patients on image quality and radiation dose. MATERIALS AND METHODS: An adult female anthropomorphic phantom was used to simulate obese patients by adding one or two 4-cm circumferential layers of fat-equivalent material to the abdominal portion. The phantom was scanned with a subcutaneous fat thickness of 0, 4, and 8 cm using the following parameters (detector configuration/beam pitch/table feed per rotation/gantry rotation time/kV/mA): standard protocol A: 16 x 0.625 mm/1.75/17.5 mm/0.5 seconds/140/380, and modified protocol B: 16 x 1.25 mm/1.375/27.5 mm/1.0 seconds/140/380. Radiation doses to six abdominal organs and the skin, image noise values, and contrast-to-noise ratios (CNRs) were analyzed. Statistical analysis included analysis of variance, Wilcoxon rank sum, and Student's t-test (P < .05). RESULTS: Applying the modified protocol B with one or two fat rings, the image noise decreased significantly (P < .05), and simultaneously, the CNR increased significantly compared with protocol A (P < .05). Organ doses significantly increased, up to 54.7%, comparing modified protocol B with one fat ring to the routine protocol A with no fat rings (P < .05). However, no significant change in organ dose was seen for protocol B with two fat rings compared with protocol A without fat rings (range -2.1% to 8.1%) (P > .05). CONCLUSIONS: Using a modified abdominal multislice CT protocol for obese patients with 8 cm or more of subcutaneous fat, image quality can be substantially improved without a significant increase in radiation dose to the abdominal organs. 相似文献
993.
Accuracy of 64-slice CT angiography for the detection of functionally relevant coronary stenoses as assessed with myocardial perfusion SPECT 总被引:3,自引:0,他引:3
Gaemperli O Schepis T Koepfli P Valenta I Soyka J Leschka S Desbiolles L Husmann L Alkadhi H Kaufmann PA 《European journal of nuclear medicine and molecular imaging》2007,34(8):1162-1171
Purpose CT angiography (CTA) offers a valuable alternative for the diagnosis of CAD but its value in the detection of functionally
relevant coronary stenoses remains uncertain. We prospectively compared the accuracy of 64-slice CTA with that of myocardial
perfusion imaging (MPI) using 99mTc-tetrofosmin-SPECT as the gold standard for the detection of functionally relevant coronary artery disease (CAD).
Methods MPI and 64-slice CT were performed in 100 consecutive patients. CTA lesions were analysed quantitatively and area stenoses
≥50% and ≥75% were compared with the MPI findings.
Results In 23 patients, MPI perfusion defects were found (12 reversible, 13 fixed). A total of 399 coronary arteries and 1,386 segments
was analysed. Eighty-four segments (6.1%) in 23 coronary arteries (5.8%) of nine patients (9.0%) were excluded owing to insufficient
image quality. In the remaining 1,302 segments, quantitative CTA revealed stenoses ≥50% in 57 of 376 coronary arteries (15.2%)
and stenoses ≥75% in 32 (8.5%) coronary arteries. Using a cut-off at ≥75% area stenosis, CTA yielded the following sensitivity,
specificity, negative (NPV) and positive predictive value (PPV), and accuracy for the detection of any (fixed and reversible)
MPI defect: by patient, 75%, 90%, 93%, 68% and 87%, respectively; by artery, 76%, 95%, 99%, 50% and 94%, respectively.
Conclusion Sixty-four-slice CTA is a reliable tool to rule out functionally relevant CAD in a non-selected population with an intermediate
pretest likelihood of disease. However, an abnormal CTA is a poor predictor of ischaemia. 相似文献
994.
Gaemperli O Schepis T Kalff V Namdar M Valenta I Stefani L Desbiolles L Leschka S Husmann L Alkadhi H Kaufmann PA 《European journal of nuclear medicine and molecular imaging》2007,34(7):1097-1106
Purpose Combining the functional information of SPECT myocardial perfusion imaging (SPECT-MPI) and the morphological information of
coronary CT angiography (CTA) may allow easier evaluation of the spatial relationship between coronary stenoses and perfusion
defects. The aim of the present study was the validation of a novel software solution for three-dimensional (3D) image fusion
of SPECT-MPI and CTA.
Methods SPECT-MPI with adenosine stress/rest 99mTc-tetrofosmin was fused with 64-slice CTA in 15 consecutive patients with a single perfusion defect and a single significant
coronary artery stenosis (≥50% diameter stenosis). 3D fused SPECT/CT images were analysed by two independent observers with
regard to superposition of the stenosed vessel onto the myocardial perfusion defect. Interobserver variability was assessed
by recording the X, Y, Z coordinates for the origin of the stenosed coronary artery and the centre of the perfusion defect
and measuring the distance between the two landmarks.
Results SPECT-MPI revealed a fixed defect in seven patients, a reversible defect in five patients and a mixed defect in three patients
and CTA documented a significant stenosis in the respective subtending coronary artery. 3D fused SPECT/CT images showed a
match of coronary lesion and perfusion defect in each patient and the fusion process took less than 15 min. Interobserver
variability was excellent for landmark detection (r = 1.00 and r = 0.99, p < 0.0001) and very good for the 3D distance between the two landmarks (r = 0.94, p < 0.001).
Conclusion 3D SPECT/CT image fusion is feasible, reproducible and allows correct superposition of SPECT segments onto cardiac CT anatomy. 相似文献
995.
Use of coronary calcium score scans from stand-alone multislice computed tomography for attenuation correction of myocardial perfusion SPECT 总被引:1,自引:1,他引:0
Schepis T Gaemperli O Koepfli P Rüegg C Burger C Leschka S Desbiolles L Husmann L Alkadhi H Kaufmann PA 《European journal of nuclear medicine and molecular imaging》2007,34(1):11-19
Purpose To evaluate the use of CT attenuation maps, generated from coronary calcium scoring (CCS) scans at in- and expiration with
a 64-slice CT scanner, for attenuation correction (AC) of myocardial perfusion SPECT images.
Methods Thirty-two consecutive patients underwent 99mTc-tetrofosmin gated adenosine stress/rest SPECT scan on an Infinia Hawkeye SPECT-CT device (GE Medical Systems) followed
by CCS and CT angiography on a 64-slice CT. AC of the iteratively reconstructed images was performed with AC maps obtained:
(a) from the “Hawkeye” low-resolution X-ray CT facility attached to the Infinia camera (IRAC); (b) from the CCS scan acquired
on a 64-slice CT scanner during maximal inspiration (ACINSP) and (c) during normal expiration (ACEXP). Automatically determined uptake values of stress scans (QPS, Cedars Medical Sinai) from ACINSP and ACEXP were compared with IRAC. Agatston score (AS) values using ACINSPversus ACEXP were also compared.
Results ACINSP and ACEXP resulted in identical findings versus IRAC by visual analysis. A good correlation for uptake values between IRAC and ACINSP was found (apex, r=0.92; anterior, r=0.85; septal, r=0.91; lateral, r=0.86; inferior, r=0.90; all p<0.0001). The correlation was even closer between IRAC and ACEXP (apex, r=0.97; anterior, r=0.91; septal, r=0.94; lateral, r=0.92; inferior, r=0.97; all p<0.0001). The mean AS during inspiration (319±737) and expiration(317±778) was comparable (p=NS).
Conclusion Attenuation maps from CCS allow accurate AC of SPECT MPI images. ACEXP proved superior to ACINSP, suggesting that in hybrid scans CCS may be performed during normal expiration to allow its additional use for AC of SPECT
MPI. 相似文献
996.
997.
998.
Corine A.N. Broekhuizen Leonie de Boer Kim Schipper Christopher D. Jones Shan Quadir Robert G. Feldman Christina M.J.E. Vandenbroucke-Grauls Sebastian A.J. Zaat 《Biomaterials》2009,30(32):6444-6450
Biomaterial-associated infection (BAI) is a major problem in modern medicine, and is often caused by Staphylococcus epidermidis. We aimed to raise monoclonal antibodies (mAbs) against major surface protein antigens of S. epidermidis, and to assess their possible protective activity in experimental BAI. Mice were vaccinated with a cell wall protein preparation of S. epidermidis. A highly immunodominant antigen was identified as Accumulation-associated protein (Aap). mAbs against Aap and against surface-exposed lipoteichoic acid (LTA) were used for passive immunization of mice in experimental biomaterial-associated infection. Neither anti-Aap nor anti-LTA mAbs showed protection. Either with or without antibodies, tissue surrounding the implants was more often culture positive than the implants themselves, but bacterial adherence to the implants was significantly increased in mice injected with anti-LTA. In vitro, anti-Aap and anti-LTA did show binding to S. epidermidis, but no opsonic activity was observed. We conclude that antibodies against S. epidermidis LTA or Aap showed no opsonic activity and did not protect mice against BAI. Moreover, the increase in binding to implanted biomaterial suggests that passive immunization may increase the risk for BAI. 相似文献
999.
von Wilmowsky C Bauer S Lutz R Meisel M Neukam FW Toyoshima T Schmuki P Nkenke E Schlegel KA 《Journal of biomedical materials research. Part B, Applied biomaterials》2009,89(1):165-171
Because of their ability to mimic the dimensions of constituent components of natural bone and the possibility to serve as a gene and drug-delivery carrier, nanotubes seem to be a promising coating for medical implants. Aim of this study was to investigate the effects of a TiO(2) nanotube structured surface on periimplant bone formation in vivo when compared with an untreated standard titanium surface. Twenty-five titanium implants covered with an ordered TiO(2) nanotube layer with an individual tube diameter of 30 nm and 25 commercially pure titanium (cp-Ti) implants were placed in the frontal skull of 25 domestic pigs. To evaluate the effects of the nanotube structured implants on the periimplant bone formation, bone-implant contact (BIC), and immunohistochemistry analysis were performed at day 3, 7, 14, 30, and 90. Evaluating immunohistochemistry, a significantly higher collagen type- I expression occurred at day 7 (p = 0.003), day 14 (p = 0.016), and day 30 (p = 0.044), for the nanostructured implants in comparison with the control group. It could be found that a nanotube structured implant surface with a diameter of 30 nm does influence bone formation and bone development by enhancing osteoblast function. SEM evaluation of the specimen surfaces revealed that the nanotube coatings do resist shearing forces that evoked by implant insertion. Because of their simple, low cost, flexible manufacturing and the possibility for the usage as drug or growth factor delivery system, nanotubes seem to be a promising method for future medical implant coatings. 相似文献
1000.
Florence Faure Adriana Mantegazza Charlotte Sadaka Christine Sedlik Francine Jotereau Sebastian Amigorena 《European journal of immunology》2009,39(2):380-390
DC cross‐present exogenous antigens on MHC class I molecules, a process required for the onset of anti‐tumor immune responses. In order to study the cross‐presentation of tumor antigens by human DC, we compared the pathways of cross‐presentation of long peptides requiring internalization and intracellular processing with the direct presentation of short peptides, which does not require intracellular processing. We found that, after brief incubations with DC, short peptides were presented to CD8+ T cells with higher efficiencies than long peptides. After longer times of chase in the absence of peptide, however, the efficiency of presentation of the two types of peptides was reversed. After 2–3 days, DC pulsed with long peptides still activated T cells efficiently, while DC pulsed with short peptides failed to do so. Long‐lasting presentation of the long peptides was, at least in part, due to a stored persistent pool of antigen, which was still available for loading on MHC class I molecules after several days of chase. These results show that the use of long synthetic peptides allows the efficient, long‐lasting, presentation of tumor antigens, suggesting that long peptides represent an interesting approach for active anti‐tumor vaccination. 相似文献