Does clinical pretest probability influence image quality and diagnostic accuracy in dual-source coronary CT angiography?

RATIONALE AND OBJECTIVES

To prospectively evaluate the influence of the clinical pretest probability assessed by the Morise score onto image quality and diagnostic accuracy in coronary dual-source computed tomography angiography (DSCTA).

MATERIALS AND METHODS

In 61 patients, DSCTA and invasive coronary angiography were performed. Subjective image quality and accuracy for stenosis detection (>50%) of DSCTA with invasive coronary angiography as gold standard were evaluated. The influence of pretest probability onto image quality and accuracy was assessed by logistic regression and chi-square testing. Correlations of image quality and accuracy with the Morise score were determined using linear regression.

RESULTS

Thirty-eight patients were categorized into the high, 21 into the intermediate, and 2 into the low probability group. Accuracies for the detection of significant stenoses were 0.94, 0.97, and 1.00, respectively. Logistic regressions and chi-square tests showed statistically significant correlations between Morise score and image quality (P < .0001 and P < .001) and accuracy (P = .0049 and P = .027). Linear regression revealed a cutoff Morise score for a good image quality of 16 and a cutoff for a barely diagnostic image quality beyond the upper Morise scale.

CONCLUSION

Pretest probability is a weak predictor of image quality and diagnostic accuracy in coronary DSCTA. A sufficient image quality for diagnostic images can be reached with all pretest probabilities. Therefore, coronary DSCTA might be suitable also for patients with a high pretest probability.

Fatty acids as metabolic mediators in innate immunity

BACKGROUND

Increasing data support the hypothesis of a local and systemic crosstalk between adipocytes and monocytes mediated by fatty acids. The aim of this study was to characterize the immunomodulatory effects of a large panel of fatty acids on cytokines and chemokines in monocytic THP-1 cells and primary human monocytes. We tested whether anti-inflammatory fatty acids are able to inhibit the binding of lipopolysaccharide (LPS) to its receptor, toll-like receptor/MD-2 (TLR4/MD-2).

MATERIALS AND METHODS

Resistin, monocyte chemoattractant protein-1 (MCP-1) and tumour necrosis factor (TNF) were measured by enzyme-linked immunosorbent assay. Proteins were analysed by Western blot. A designed Flag-tagged TLR4/MD-2 fusion protein (LPS trap) was used to investigate the effect of fatty acids on binding of LPS to its receptor. In 30 patients with type 2 diabetes mellitus (T2D), the correlation of serum triglyceride levels with LPS-induced monocyte activation was analysed.

RESULTS

Eleven fatty acids investigated exerted differential effects on the monocytic release of cytokines and chemokines. Eicosapentaenoic acid had potent anti-inflammatory effects on human primary monocytes and THP-1 cells; 100 and 200 microM eicosapentaenoic acid dose-dependently inhibited LPS binding to the LPS trap. LPS-induced release of monocytic MCP-1 and TNF was significantly and positively correlated with serum triglyceride levels in 30 patients with T2D.

CONCLUSIONS

Monocytic activation is differentially regulated by fatty acids and depends on triglyceride levels in T2D. The main finding of the present study shows that eicosapentaenoic acid inhibits the specific binding of LPS to TLR4/MD-2. Eicosapentaenoic acid represents a new anti-inflammatory LPS-antagonist.

Adiponectin downregulates CD163 whose cellular and soluble forms are elevated in obesity

BACKGROUND

CD163 is a monocyte/macrophage specific receptor whose soluble form (sCD163) is elevated in inflammatory diseases. Obesity is associated with chronic inflammation and low adiponectin, an anti-inflammatory adipokine. Adiponectin, 5-aminoimidazole-4-carboxamide-1-4-ribofuranoside (AICAR) and metformin activate the AMP-kinase that exerts anti-inflammatory effects, and the influence of adiponectin and these drugs on monocytic CD163 was analysed, and cellular and sCD163 were determined in obesity and type 2 diabetes.

MATERIALS AND METHODS

Monocytes were incubated with adiponectin, AICAR or metformin. Furthermore, monocytes and serum were obtained from type 2 diabetic patients (T2D), overweight (defined as a body mass index > or = 25 kg m(-2)) and normal-weight (NW) controls. CD163 was analysed by immunoblot and sCD163 was measured by enzyme-linked immunosorbent assay in the supernatants of the monocytes and in serum.

RESULTS

In monocytes, adiponectin reduced cellular and surface CD163, whereas sCD163 was not altered in the corresponding supernatants. Further, metformin and AICAR downregulated CD163. Monocytic CD163 was higher in T2D and obesity, whereas sCD163 in the supernatants was not elevated and neither correlated with serum sCD163 nor systemic adiponectin. There was a positive correlation of monocytic sCD163 with serum but not with monocytic IL-6. In the serum of obese controls and T2D patients, sCD163 was significantly higher compared to NW donors and was positively associated with systemic IL-6.

CONCLUSIONS

This study indicates that monocytic CD163 and systemic sCD163 are elevated in T2D and obesity. Adiponectin reduces CD163 in vitro, but additional factors related to obesity like IL-6 may be more relevant in vivo.

Accuracy of dual-source CT in the characterisation of non-calcified plaque: use of a colour-coded analysis compared with virtual histology intravascular ultrasound

Non-invasive assessment of plaque volume and composition is important for risk stratification and long-term studies of plaque stabilisation. Our aim was to evaluate dual-source computed tomography (DSCT) and colour-coded analysis in the quantification and classification of coronary atheroma. DSCT and virtual histology intravascular ultrasound (IVUS-VH) were prospectively performed in 14 patients. 22 lesions were compared in terms of plaque volume, maximal per cent vessel stenosis and percentages of fatty, fibrous or calcified components. Plaque characterisation was performed with software that automatically segments luminal or outer vessel boundaries and uses CT attenuation for a colour-coded plaque analysis. Good correlation was found for per cent vessel stenosis in DSCT (53+/-13%) and IVUS (51+/-14%; r(2) = 0.70). Mean volumes for entire plaque and non-calcified atheroma were 68.5+/-33 mm(3) and 56.7+/-30 mm(3), respectively, in DSCT and 60.8+/-29 mm(3) and 55.8+/-26 mm(3), respectively, in IVUS. Mean percentages of fatty, fibrous or calcified components were 28.2+/-6%, 53.2+/-9% and 18.7+/-13%, respectively, in DSCT and 29.9+/-5%, 55.3+/-12% and 14.4+/-9%, respectively, in IVUS-VH. Significant overestimation was present for the entire plaque and the volume of calcified plaque (p = 0.03; p = 0.0004). Although good correlation with IVUS was obtained for the entire plaque (r(2) = 0.76) and non-calcified plaque volume (r(2) = 0.84), correlation proved very poor and insignificant for percentage plaque composition. Interclass correlation coefficients for non-calcified plaque volume and percentages of fatty, fibrous or calcified components were 0.99, 0.99, 0.95 and 0.98, respectively, and intraclass coefficients were 0.98, 0.93, 0.98 and 0.99, respectively. We found that using Hounsfield unit-based analysis, DSCT allows for accurate quantification of non-calcified plaque. Although percentage plaque composition proves highly reproducible, it is not correlated with IVUS-VH.

Peritoneal fluid adipokines: ready for prime time?

BACKGROUND

Visceral adipose tissues secret a variety of adipokines; however, it is not known whether they are present in the peritoneal fluid. It was the aim of this study to investigate peritoneal fluid concentrations of novel (cartonectin, omentin) and classical adipokines (leptin, adiponectin, resistin, visfatin) in patients with ascites.

MATERIAL AND METHODS

Ninety-six patients (71 men and 25 women) undergoing paracentesis were included. Of these, 76 suffered from liver cirrhosis. Adipokines were measured by enzyme-linked immunosorbent assay or Western blot.

RESULTS

Each adipokine was detected in ascites with a broad range. Serum-ascites ratios (SAR) correlated with clinical and laboratory parameters. The main variables influencing peritoneal fluid adipokine concentrations were body mass index (BMI), local inflammation, systemic inflammation and serum adipokine concentrations. Resistin was significantly higher in patients with peritonitis and showed a positive correlation with peripheral leucocytes (white blood cell count). Leptin was correlated with the underlying disease. Visfatin correlated with peripheral white blood cell and C-reactive protein levels. Omentin expression was correlated with ascitic leucocyte count, ascitic albumin concentration and low albumin SAR. BMI was correlated positively with ascitic leptin levels and cartonectin protein levels.

CONCLUSIONS

Peritoneal fluid adipokine concentrations are characterized by individual SARs, depend on the presence of peritonitis, and correlate with underlying disease, BMI and systemic inflammation. The data open a new field of research on the role of the peritoneum and visceral adipokines in gastrointestinal diseases.

Hip fractures in users of first- vs. second-generation bisphosphonates

This study compared population hip fracture rates for women with a prior fragility fracture who were treated with first-generation versus second-generation bisphosphonate therapies. The observational study found that, relative to women treated with etidronate, a first-generation bisphosphonate, women treated with the second-generation therapies 'alendronate' or 'risedronate' were equally likely to be admitted to hospital for hip fracture. Our findings must be confirmed in large randomized head-to-head controlled trials.

INTRODUCTION

Few studies have examined hip fracture outcomes among users of first- versus second-generation bisphosphonates. We compared hip fracture rates among elderly women with a history of fracture dispensed first- and second-generation bisphosphonates, hypothesizing that hip fracture rates would be higher among users of first- versus second-generation bisphosphonates after adjusting for confounders.

METHODS

Administrative data from Ontario, Canada from 01 April 1998 to 31 March 2002 was used to identify population-based bisphosphonate-naïve cohorts of subjects age 66 years and older initiated on first- (etidronate plus calcium; n = 19,127) or second-generation (alendronate or risedronate; n = 1,460) bisphosphonates. Multivariate Cox proportional hazard models were used for analysis.

RESULTS

During over 23,000 person-years of follow-up, we observed 293 hospital admissions for first hip fracture. The unadjusted event rates yielded approximately 12.5 hospital admissions for hip fracture per 1,000 person-years of follow-up in each study group. Relative to the etidronate plus calcium group, females in the alendronate or risedronate group were equally likely to be admitted for hip fracture (adjusted rate ratio [aRR] = 1.0; 95% CI 0.6-1.6).

CONCLUSIONS

The findings of this study suggest similar rates of hip fracture between the first- and second-generation bisphosphonates when used continuously among elderly females with a prior history of fracture.

First performance evaluation of a dual-source CT (DSCT) system

We present a performance evaluation of a recently introduced dual-source computed tomography (DSCT) system equipped with two X-ray tubes and two corresponding detectors, mounted onto the rotating gantry with an angular offset of 90 degrees . We introduce the system concept and derive its consequences and potential benefits for electrocardiograph [corrected] (ECG)-controlled cardiac CT and for general radiology applications. We evaluate both temporal and spatial resolution by means of phantom scans. We present first patient scans to illustrate the performance of DSCT for ECG-gated cardiac imaging, and we demonstrate first results using a dual-energy acquisition mode. Using ECG-gated single-segment reconstruction, the DSCT system provides 83 ms temporal resolution independent of the patient's heart rate for coronary CT angiography (CTA) and evaluation of basic functional parameters. With dual-segment reconstruction, the mean temporal resolution is 60 ms (minimum temporal resolution 42 ms) for advanced functional evaluation. The z-flying focal spot technique implemented in the evaluated DSCT system allows 0.4 mm cylinders to be resolved at all heart rates. First clinical experience shows a considerably increased robustness for the imaging of patients with high heart rates. As a potential application of the dual-energy acquisition mode, the automatic separation of bones and iodine-filled vessels is demonstrated.

Clinical evaluation of a computer simulated prediction model of contrast enhancement of the liver in spiral CT

OBJECTIVE

A software program was developed simulating a compartmental model of blood circulation based on differential equations. The aim of this study was to compare software-simulated levels of hepatic enhancement with the true values in patients and to test how many patients reach the simulated hepatic enhancement level.

METHODS

As software program the CT application software carebolus 2 (Siemens, Forchheim, Germany) was used. Hepatic contrast-enhancement curves were simulated prior to CT examinations to evaluate a patient specific time delay after contrast application. At the time delay, when the simulation curve showed an enhancement threshold of 40 Hounsfield Units (HU), the CT spiral scan was started applying 120 ml contrast media with 2 ml/s. The simulated curves were compared with the empiric curves of each patient.

RESULTS

25 of 28 patients (89%) achieved 40 HU. The mean enhancement of empiric patients curves was 46.32 +/- 11.9 HU, the mean simulated enhancement was 46.62 +/- 4.3 HU S.D. (P= 0.48). 4.4 values per patient liver could be compared with the simulation curve (122 points for 28 patients): 50% of the patient curves were within a range of 5 HU compared with the simulation curve.

CONCLUSION

Software simulation of contrast enhancement curves of the liver is a feasible and valuable method to predict individual liver enhancement curves. Improvements concerning the integration of cardiovascular parameters and preexisting liver parenchymal diseases into the simulation software have to be arranged.

Effects of tamoxifen on transcriptional level of transforming growth factor beta (TGF-beta) isoforms 1 and 2 in tumor tissue during primary treatment of patients with breast cancer

Tamoxifen action in breast cancer is believed to be mediated in part by regulation of transforming growth factor beta (TGF-beta) isoforms in tumor tissue. However, the pattern of this regulation and its relation ship to clinical data are not yet clearly understood. Tumor tissue was derived from 10 patients with breast cancer before and following primary treatment with tamoxifen over a period of 1-12 days, preceding tumor ectomy. Each tissue sample was processed for semiquantitative assessment of the mRNA expression levels of the TGF-beta isoforms 1 and 2 using competitive RT-PCR. The results of mRNA quantification were then related to the estrogen receptor-alpha (ER-alpha) and progesterone receptor (PR) status of the tumors as well as to the clinical course during the first 5-6 postoperative years in patients who additionally received adjuvant tamoxifen therapy. TGF-beta 1 mRNA and TGF-beta 2 mRNA expression was detectable in all examined samples. During treatment with tamoxifen, the TGF-beta 2 mRNA level changed in 8 cases, increasing seven times and decreasing once, whereas the TGF-beta 1 mRNA level changed in only two cases, increasing once and decreasing once. Our data do not provide evidence of a strong correlation between the occurrence of tamoxifen-related induction of TGF-beta 2 mRNA expression and the ER-alpha or PR status. The prediction sensitivity of the response to adjuvant therapy, to which relapse-free survival during post-operative follow-up over 5-6 years was attributed, increased when the tamoxifen-related up-regulation of the TGF-beta 2 mRNA level was considered to predict response, in addition to the ER-alpha- and/or PR-rich receptor status. We conclude that tamoxifen predominantly induces an up-regulation of TFG-beta 2 expression on the transcriptional level in breast cancer, which may predict clinical response independently of the ER-alpha/PR status in some cases.

Comparison of 18FDG-PET with CT scans in the evaluation of patients with residual and recurrent Hodgkin's lymphoma

The reliable assessment of residual masses after treatment as well as of new lesions suspected for relapse remains a diagnostic problem in patients with Hodgkin's disease (HD). The current study compares the results obtained by CT scan to FDG-PET imaging in a blind analysis with respect to the viability of residual masses and in case of suspected relapse. Between 1/94 and 10/99, 47 comparisons of PET and corresponding CT scans - 26 comparisons in 24 patients with residual tumors and 21 comparisons in 20 patients with suspected relapse of HD - were evaluated by independent reviewers blinded to he results of each other. Patients with primary diagnosis had been treated within trials of the German HD Trial study group. Relapsed patients received intensified salvage chemotherapy regimens. PET was assessed visually and by quantifying glucose uptake (SUV). Changes in size of tumor lesions as well as contrast medium enhancement served as criteria for assessment by CT scans. Results were validated either by histologic examination of a resected mass or biopsy (n=17) or by a clinical follow-up over 6 months following treatment (n=30). In 26 cases with residual lesions FDG-PET showed an increased tracer uptake in 8, 7 of which were true positive (TP) and 1 false positive (FP). Eighteen cases were classified as being negative (no viable HD), 17 true negative (TN) and 1 FN. In the blinded reading of the corresponding CT scans, 10 cases with residual lesions were considered to contain vital lymphoma (2 TP, 8 FP). Sixteen CT scans were classified as negative (10 TP, 6 FN). The resulting sensitivity and specificity of PET were 87.5% and 94.4% in contrast to only 25% and 56% for CT scans. The positive and negative predictive values of PET and CT scans were 87.5% and 94.4% and 20% and 62.5%, respectively. In patients with suspected relapse, sensitivity and positive predictive value for the diagnosis of the relapse were 100% and 86%, respectively, yielding the same results for both methods. FDG-PET performed in HD patients with residual masses appears to offer important additional information regarding the presence of viable HD in these residual lesions. In patients with suspected relapse of HD, FDG-PET seems not to offer any information over CT scans. Using SUVs is not superior to visual assessment of PET alone.

[Optimizing image reconstruction timing for the RR interval in imaging coronary arteries with multi-slice computerized tomography]

PURPOSE

Multislice spiral CT is a newly developed technology that allows the non-invasive detection of coronary stenoses and plaques. The acquired raw data are reconstructed at a given time point in the RR interval of the heart cycle. Thus, determination of this time point is a key factor for picture quality and for reliable diagnostic results. This study was performed to investigate the optimal time point for reconstruction within the RR interval.

MATERIALS AND METHODS

The coronary arteries of 13 patients were examined with CT. Raw data were reconstructed 250, 350, 450 and 550 ms before the following R wave (absolute reverse retrospective ECG gating) for each patient. Data were then analyzed with a volume rendering mode on a SIEMENS 3 D-Virtuoso workstation. A total of 91 segments (segments 1 and 2 of the RCA, segments 5, 6, 7 and proximal and distal parts of segment 11) were assessed and image quality was classified.

RESULTS

Visualization of the left main coronary artery was of a good quality at all time points, segments 6 and 7 of the LAD as well as the proximal and distal parts of segment 11 of the RCX had the best quality at 450 ms absolute reverse retrospective ECG gating. The segments 1 and 2 of the RCA were of best quality 550% ms absolute reverse to the R peak.

CONCLUSIONS

Classification of image quality of coronary artery CT scans after retrospectively ECG gated reconstruction is highly determined by the time point of reconstruction in the heart cycle. The optimization of this time point increases diagnostic accuracy and helps to avoid misinterpretation due to image artifacts.

Prophenoloxidase as a Reporter of Gene Expression in Drosophila

We have developed a novel reporter for the analysis of gene expression using a Drosophilaprophenoloxidase (proPO) gene. We have expressed proPO in transgenic flies using the GAL4-UAS system and characterized ectopic expression in imaginal discs. proPO staining is fast and robust, requiring only inexpensive reagents, and performs similarly to β-galactosidase (β-gal) staining. Double staining using UAS-proPO and β-gal reporters is straightforward and provides a convenient method for examining the expression of two genes simultaneously.

Waste gas exposure to sevoflurane and nitrous oxide during anaesthesia using the oesophageal-tracheal Combitube small adult

Exposure to sevoflurane (SEV) and nitrous oxide during ventilation using a Combitube (37Fr) small adult (SA) was compared with waste gas exposure using conventional endotracheal tubes. Trace concentrations of SEV and nitrous oxide were assessed using a direct reading spectrometer during 40 gynaecological laparoscopic procedures under general anaesthesia. Measurements were made at the patients' mouth and in the anaesthetists' breathing zone. Mean (SD) concentrations of SEV and nitrous oxide measured at the patients' mouth were comparable in the Combitube SA (SEV 0.6 (0.2) p.p.m.; nitrous oxide 9.7 (8.5) p.p.m.) and endotracheal tube group (SEV 1.2 (0.8) p.p.m.; nitrous oxide 17.2 (10.6) p.p.m.). These values caused comparable contamination of the anaesthetists' breathing zone (SEV 0.6 (0.2) p.p.m. and nitrous oxide 4.3 (3.7) p.p.m. for the Combitube SA group, compared with SEV 0.5 (0.2) p.p.m. and nitrous oxide 4.1 (1.8) p.p.m. for the endotracheal tube group). We conclude that the use of the Combitube SA during positive pressure ventilation is not necessarily associated with increased waste gas exposure, especially when air conditioning and scavenging devices are available.