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Biomedical subjects

J H Reiber

Publications and source records attributed to J H Reiber.

At least 19 recordsLinked to original sources
PubMed2001

Predictors of coronary in-stent restenosis: importance of angiotensin-converting enzyme gene polymorphism and treatment with angiotensin-converting enzyme inhibitors.

OBJECTIVES: This study aimed to clarify the role of the angiotensin-converting enzyme (ACE) gene polymorphism in the development of in-stent restenosis. BACKGROUND: In-stent restenosis occurs after treatment of coronary artery stenosis in 12% to 32% of coronary interventions with stents. Experimental and clinical studies have suggested that the deletion/insertion (D/I) polymorphism of the ACE gene plays a role in this. METHODS: Quantitative coronary angiography before, immediately after and six months after stent implantation were compared in 369 patients, in whom D/I typing of the ACE gene was performed. RESULTS: At follow-up we found no differences between the three genotypes in minimal lumen diameter (homozygotes with two deletion alleles in the ACE gene [DD], 2.20 mm; heterozygotes with one deletion and one insertion allele in the ACE gene [DI], 2.19 mm; and homozygotes with two insertion alleles in the ACE gene [II], 2.25 mm). The corresponding diameter stenoses were: DD: 25%, DI: 27%, II: 27% (p = NS), and the frequency of restenosis (>50% diameter stenosis) was: DD: 15.7%, DI: 11.0% and II: 16.4% (p = NS). Logistic regression analysis identified diabetes (odds ratio [OR]: 3.0, 95% confidence interval [CI]: 1.0 to 8.7), lesion length (OR: 1.1, 95% CI: 1.01 to 1.30) and minimal lumen diameter immediately after the intervention (OR: 0.3, 95% CI: 0.14 to 0.85) as predictors of in-stent restenosis. In a post hoc analysis of patients treated versus those not treated with an ACE-inhibitor antagonist or an angiotensin receptor antagonist, we found an increased frequency of in-stent restenosis in the DD genotypes (40% vs. 12%, p = 0.006). CONCLUSIONS: The D/I polymorphism is not an independent predictor of coronary in-stent restenosis in general, but it may be of clinical importance in patients treated with ACE inhibitors or angiotensin receptor antagonists.

Adult↗
PubMed2001

Stent placement to prevent restenosis after angioplasty in small coronary arteries.

BACKGROUND: Lesions in small-diameter vessels (<3 mm) define a group with distinct clinical and morphological characteristics. There is an inverse relationship between vessel size and angiographic restenosis rate. This study assessed whether stents reduce angiographic restenosis in small coronary arteries compared with standard balloon angioplasty. METHODS AND RESULTS: We randomly assigned 351 symptomatic patients needing dilatation of 1 native coronary vessel between 2.3 and 2.9 mm in size to angioplasty alone (n=182) or stent implantation (n=169). The primary end point was angiographic restenosis at 6 months. Secondary end points included death, myocardial infarction, bypass surgery, and target vessel revascularization in hospital and at 6 months. There were no significant differences between groups in terms of major in-hospital complications. There was a trend toward fewer in-hospital events in the stent group (3% versus 7.1% in angioplasty group, P=0.076). Crossovers to stent occurred in 37 patients (20.3%). Repeat angiography at 6-month follow-up was performed in 85.3% of patients. Angiographic restenosis occurred in 28% of the stent group and 32.9% of the angioplasty group (P=0.36). Target vessel revascularization was required in 17.8% versus 20.3% of patients (P=0.54), respectively. CONCLUSIONS: Stenting and standard coronary angioplasty are associated with equal restenosis rate in small coronary arteries. With a lower in-hospital complication rate, stenting may be a superior strategy in small vessels.

Angioplasty, Balloon, Coronary↗
PubMed2001

Decreased coagulability has no clinically relevant effect on atherogenesis: observations in individuals with a hereditary bleeding tendency.

BACKGROUND: Hemostasis affects ischemic cardiovascular disease through its role in formation of occluding arterial thrombi. Several studies suggest that hemostasis also might play a role in atherogenesis. We investigated whether individuals with an inherited bleeding tendency are protected against development of atherosclerosis. METHODS AND RESULTS: A total of 76 individuals with an inherited bleeding tendency (hemophilia and von Willebrand disease) and 142 healthy controls were included in the present study. Early atherosclerotic vessel-wall changes were quantified by measurement of intima-media thickness in the carotid and femoral arteries by B-mode ultrasonography. To validate intima-media thickness measurements, measurements also were performed in 77 individuals with clinically proven atherosclerosis and in 34 healthy, age-matched controls. A large difference in intima-media thickness was found between individuals with proven atherosclerosis and healthy controls, in particular for the femoral artery (difference for carotid artery, 0.16 mm; femoral artery, 0.53 mm). Comparison between patients with a bleeding tendency and healthy controls showed only minimally reduced intima-media in femoral artery in individuals with a bleeding tendency (adjusted difference, -0.078 mm; 95% CI, -0.17 to 0.018 mm). Subgroup analysis revealed that in subjects with moderate to severe hemophilia, vessel walls were thinnest (adjusted difference, -0.10 mm; 95% CI, -0.27 to 0.061 mm). CONCLUSIONS: Hypocoagulability caused by hemophilia or von Willebrand disease has at most a limited effect on atherogenesis.

Adult↗
PubMed2001

Suitability of the Cordis Stabilizer marker guide wire for quantitative coronary angiography calibration: an in vitro and in vivo study.

Catheters usually are used for calibration purposes in quantitative coronary angiography (QCA). The systematic and random errors in these calibration factors (CFs) are dependent on the size and quality of the catheters and limited by out-of-plane magnification (OPM). Theoretically, a guide wire with evenly spaced marker bands would solve many of these potential problems. For this reason, we tested the Cordis Stabilizer marker wire, featuring 10 radiopaque platinum marker bands 15 mm apart, in in vitro and in vivo studies. To assess the effect of foreshortening, wires were positioned in a tube phantom; a centimeter grid was used as the gold standard. Radiographic images were acquired at 5-inch and 7-inch image-intensifier sizes, 512(2) and 1,024(2) matrix sizes and angulations from 0 degrees to 70 degrees in steps of 10 degrees. It was concluded that the relative errors in CFs are less than 7% if the foreshortening angles remain less than 20 degrees. In DICOM images of 15 patients, 65 measurements were taken after calibration on an 8F catheter and on a guide wire positioned in the coronary lesion. In all but two cases, the wire CFs were larger than the catheter CFs (relative difference, 24.7 +/- 19.6%). The measurements were divided into four groups: (I) no apparent OPM or foreshortening (n = 7), (II) only OPM (n = 4), (III) only foreshortening (n = 10), and (IV) the combination of both (n = 44). In group I (no OPM or foreshortening) the QCA results were similar using the guide wire or catheter as the calibration device (relative CF difference, 2.9% only). In group III the diameters were overestimated using the guide wire (obstruction diameter difference, 0.22 +/- 0.11 mm; reference diameter difference, 0.35 +/- 0.06 mm). For only OPM (group II) and the combination of OPM and foreshortening (group IV), the lesion length was underestimated on average by 2.4 mm using the catheter instead of the guide wire. In conclusion, if accurate assessment of the lesion length is important, the marker wire should be used for calibration purposes. For vessel diameter measurements, the conventional catheter calibration approach is the method of choice.

Angiography, Digital Subtraction↗
PubMed2001

A novel quantitative method for evaluating diffuse in-stent narrowing at follow-up angiography.

A new quantitative parameter, diffuse index (DI), was proposed to evaluate objectively whether in-stent restenosis is diffuse or focal in nature. A total of 343 patients (346 lesions) with Wiktor-GX, AVE MS-II, or JOMED stents were evaluated at follow-up angiography. According to the QCA-CMS definition, lesion length is derived from the 100% reference diameter function (RDF). By moving the RDF downward, the lesion length, LL(x), at each percentage x of the RDF can be calculated. We have defined the DI by the ratio of this calculated length LL(x) and the total stent length, SL, in other words, DI = [LL(x)/SL]. The percentage plaque area (% PA) was calculated by dividing the plaque area by the sum of the plaque area and luminal area within the stent. An excellent correlation was found between the DI at 88% RDF and the % PA in all three stents (r > 0.88). The individual correlation curves were nearly identical, independent of the type of stent. Furthermore, based on the overall data, the combination of a DI > 0.8 and % PA > 30% correlated with a high incidence of subsequent major adverse cardiac events (13/25 = 52%). From these data, it can be concluded that the diffuse index is a new objective quantitative parameter to describe whether in-stent restenosis is of focal or diffuse nature.

Coronary Angiography↗
PubMed2001

Tumor diameter and volume assessed by magnetic resonance imaging in the prediction of outcome for invasive cervical cancer.

OBJECTIVE: The aim of this study was to evaluate the predictive value of pretherapeutic magnetic resonance imaging (MRI)-based measurements of tumor diameter and volume with regard to recurrent disease. METHODS: MRI on 0.5- or 1.5-T scanners was performed in 126 consecutive women with invasive carcinoma of the uterine cervix. Initial tumor diameter and volume were determined on T(2)-weighted images; volume was calculated by the standard technique of multiplying the sum of the areas by the slice thickness. Patients were treated by radical surgery, radiotherapy, or a combined approach based on clinical International Federation of Gynecology and Obstetrics (FIGO) stage and individual patient criteria. Clinical data (patient age and FIGO stage), MRI-derived tumor dimensions (diameter and volume), and histological findings (tumor invasion depth and lymph-node involvement) were associated and linked to patient outcome. RESULTS: MRI-based tumor diameter correlated strongly with histological tumor invasion depth and lymph-node status (P < 0.01 and P = 0.01) while tumor volume on MRI was significantly associated only with tumor invasion depth into adjacent tissues (P < 0.01). Univariate analysis demonstrated graphically that MRI-derived tumor diameter and volume and clinical FIGO stage are associated with progression-free survival. Correlation analysis showed a strong association between MRI-derived tumor diameter and volume on MRI (r = 68%, P < 0.01) and also demonstrated a correlation between tumor diameter on MRI and FIGO stage Ib (Ib1 versus Ib2) cervical tumors (r = 46.7%, P < 0.01). CONCLUSION: Tumor diameter and volume, determined by pretreatment MRI examinations, predict progression-free survival for patients with invasive cervical carcinoma. This study demonstrates the value of MRI as an adjunct to clinical evaluation of invasive cervical cancer, providing more complete assessment of morphological risk factors important in patient prognosis and treatment planning.

Adult↗
PubMed2001

Model-based Roentgen stereophotogrammetry of orthopaedic implants.

Attaching tantalum markers to prostheses for Roentgen stereophotogrammetry (RSA) may be difficult and is sometimes even impossible. In this study, a model-based RSA method that avoids the attachment of markers to prostheses is presented and validated. This model-based RSA method uses a triangulated surface model of the implant. A projected contour of this model is calculated and this calculated model contour is matched onto the detected contour of the actual implant in the RSA radiograph. The difference between the two contours is minimized by variation of the position and orientation of the model. When a minimal difference between the contours is found, an optimal position and orientation of the model has been obtained. The method was validated by means of a phantom experiment. Three prosthesis components were used in this experiment: the femoral and tibial component of an Interax total knee prosthesis (Stryker Howmedica Osteonics Corp., Rutherfort, USA) and the femoral component of a Profix total knee prosthesis (Smith & Nephew, Memphis, USA). For the prosthesis components used in this study, the accuracy of the model-based method is lower than the accuracy of traditional RSA. For the Interax femoral and tibial components, significant dimensional tolerances were found that were probably caused by the casting process and manual polishing of the components surfaces. The largest standard deviation for any translation was 0.19mm and for any rotation it was 0.52 degrees. For the Profix femoral component that had no large dimensional tolerances, the largest standard deviation for any translation was 0.22mm and for any rotation it was 0.22 degrees. From this study we may conclude that the accuracy of the current model-based RSA method is sensitive to dimensional tolerances of the implant. Research is now being conducted to make model-based RSA less sensitive to dimensional tolerances and thereby improving its accuracy.

Biomechanical Phenomena↗
PubMed2001

Repeatability of lung density measurements with low-dose computed tomography in subjects with alpha-1-antitrypsin deficiency-associated emphysema.

RATIONALE AND OBJECTIVES: Multislice computed tomography (MSCT) of the lungs provides a new opportunity for longitudinal assessment of lung densities because of shorter scan duration. The aim of the present study was to assess the intraindividual variation of lung densities measured by MSCT of patients with emphysema. METHODS: Ten patients with emphysema participated in a study in which MSCT was obtained on two occasions, approximately 2 weeks apart. Scanning parameters were 140 kV, 20 mAs, 4 x 2.5-mm collimation, and effective slice thickness of 2.5 mm. Lung density was measured as the 15th percentile point and the relative area below -910 Hounsfield units (HU) by using Pulmo-LKEB software. RESULTS: The mean difference of the 15th percentile point was -1.29 +/- 3.2 HU, and that for the relative area below the -910-HU parameter was -1.02% +/- 3.09%. Intraclass coefficients of variation were 0.96 (0.86-0.99) and 0.94 (0.8-0.98), respectively (95% confidence interval). CONCLUSIONS: Lung density parameters of emphysema derived by MSCT provide an opportunity for analysis of the treatment effects of new drugs on the progression of emphysema.

Disease Progression↗
PubMed2001

Multistage hybrid active appearance model matching: segmentation of left and right ventricles in cardiac MR images.

A fully automated approach to segmentation of the left and right cardiac ventricles from magnetic resonance (MR) images is reported. A novel multistage hybrid appearance model methodology is presented in which a hybrid active shape model/active appearance model (AAM) stage helps avoid local minima of the matching function. This yields an overall more favorable matching result. An automated initialization method is introduced making the approach fully automated. Our method was trained in a set of 102 MR images and tested in a separate set of 60 images. In all testing cases, the matching resulted in a visually plausible and accurate mapping of the model to the image data. Average signed border positioning errors did not exceed 0.3 mm in any of the three determined contours-left-ventricular (LV) epicardium, LV and right-ventricular (RV) endocardium. The area measurements derived from the three contours correlated well with the independent standard (r = 0.96, 0.96, 0.90), with slopes and intercepts of the regression lines close to one and zero, respectively. Testing the reproducibility of the method demonstrated an unbiased performance with small range of error as assessed via Bland-Altman statistic. In direct border positioning error comparison, the multistage method significantly outperformed the conventional AAM (p < 0.001). The developed method promises to facilitate fully automated quantitative analysis of LV and RV morphology and function in clinical setting.

Computer Simulation↗
PubMed2001

Neuro-fuzzy systems for computer-aided myocardial viability assessment.

This paper describes a multimodality framework for computer-aided myocardial viability assessment based on neuro-fuzzy techniques. The proposed approach distinguishes two main levels: the modality-independent inference level and the modality-dependent application level. This two-level distinction releases the hard constraint of multimodality image registration. An abstract description template is used to describe the different myocardial functions (contractile function, perfusion, metabolism). Parameters extracted from different image modalities are combined to derive a diagnostic image. The neuro-fuzzy techniques make our system transparent, adaptive and easily extendable. Its effectiveness and robustness are demonstrated in a positron emission tomography/magnetic resonance imaging data fusion application.

Artificial Intelligence↗
PubMed2001

Automated observer-independent acquisition of cardiac short-axis MR images: a pilot study.

The authors compared an automated observer-independent acquisition planning method for short-axis multisection multiphase cardiac magnetic resonance imaging studies with conventional manual image planning. Systematic and random differences and reproducibility of left ventricular function measurements and image geometry were evaluated in five healthy adult volunteers and 20 patient studies. Results with the automated planning method were as accurate and reproducible as those with the manual planning method.

Adult↗
PubMed2000

Heparin-coated Wiktor stents in human coronary arteries (MENTOR trial). MENTOR Trial Investigators.

The purpose of this study was to determine the feasibility, safety, and efficacy of elective stenting with heparin-coated Wiktor stents in patients with coronary artery disease. In experimental studies, heparin coating has been shown to prevent subacute thrombosis and restenosis. Recently, a new method of heparin coating was developed, resulting in a more stable and predictable heparin layer on stent devices. This trial constitutes the first in-human use of this coating procedure, applied on the well-known Wiktor stent device. Heparin-coated Wiktor stent implantation was performed in 132 consecutive patients (132 lesions) in a multicenter international trial from September 1996 to February 1997. Forty-three percent of patients had unstable angina, 33% had previous myocardial infarction, and 10% had diabetes mellitus. Patients were followed for 12 months for occurrence of major adverse cardiovascular events, and 96% of the eligible patients underwent quantitative angiographic control at 6 months. Stent deployment was successful in 95.5% of lesions. Minimal lumen diameter increased by 1.67 +/- 0.48 mm (from 1.02 +/- 0.38 mm before to 2.69 +/- 0.37 mm after the stent implantation). Mean percent diameter stenosis decreased from 67.4 +/- 11.3% before to 18.9 +/- 7.7% after the intervention. A successful intervention (<50% diameter stenosis and no major adverse cardiac events within 30 days) occurred in 97% of the patients. The subacute thrombosis rate was 0.8%, which compares favorably with historical controls of this stent, and a low incidence of postprocedural increase in creatine kinase-MB was noted. At 6 months, event-free survival was 85% and angiographic restenosis rate was 22% with late loss of 0.78 +/- 0.69 mm and a loss index of 0.48 +/- 0.44. Heparin-coated Wiktor stents appeared to be an efficacious device to treat Benestent-like lesions, yielding angiographic and clinical results comparable to a heparin-coated Palmaz-Schatz stent. Despite its use in more complex lesions, the incidence of subacute thrombosis appeared to be lower than historical controls with a similar noncoated stent.

Angioplasty, Balloon, Coronary↗
PubMed2000

Detection of areas with viable remnant tumor in postchemotherapy patients with Ewing's sarcoma by dynamic contrast-enhanced MRI using pharmacokinetic modeling.

An approach is presented for monitoring the effects of neoadjuvant chemotherapy in patients with Ewing's sarcoma using dynamic contrast-enhanced perfusion magnetic resonance (MR) images. For that purpose, we modify the three-compartment pharmacokinetic permeability model introduced by Tofts et al. (Magn Reson Med 1991;17:357-67) to a two-compartment model. Perfusion MR images acquired using an intravenous injection with Gadolinium (Gd-DTPA) are analyzed with this two-compartment pharmacokinetic model as well as the with an extended pharmacokinetic model that includes the (local) arrival time t(0) of the tracer as an endogenous (estimated) parameter. For each MR section, a wash-in parameter associated with each voxel is estimated twice by fitting each of the two pharmacokinetic models to the dynamic MR signal. A comparison of the two wash-in parametric images (global versus local arrival time) with matched histologic macroslices demonstrates a good correspondence between areas with viable remnant tumor and a high wash-in rate. This can be explained by the high number and permeability of the (leaking) capillaries in viable tumor tissue. The novel pharmacokinetic model based on a local arrival time of tracer results in the best fit of the wash-in rate, the most important factor discerning viable from nonviable tumor components. However, parameter estimates obtained with this model are also more sensitive to noise in the MR signal. The novel pharmacokinetic model resulted in a sensitivity between 0.22 and 0.60 and a specificity between 0.61 and 1. The model based on a global arrival time gave sensitivities between 0.33 and 0.77 and specificities between 0.58 and 0.99. Both statistics are computed as the fraction of correctly labeled voxels (viable or nonviable tumor) within a specified ROI, which delineates the tumor. We conclude that the added value of estimating the local arrival time of tracer first manifests itself for moderate noise levels in the MR signal. The novel pharmacokinetic model should moreover be preferred when pharmacokinetic modeling is applied on the average signal intensity within a ROI, where noise has less effect on the fitted parameters.

Adolescent↗
PubMed2000

Vessel diameter measurements in gadolinium contrast-enhanced three-dimensional MRA of peripheral arteries.

In this study, the possibilities for quantification of vessel diameters of peripheral arteries in gadolinium contrast-enhanced magnetic resonance angiography (Gd CE MRA) were evaluated. Absolute vessel diameter measurements were assessed objectively and semi-automatically in maximum intensity projections (MIPs) of contrast-enhanced T1-weighted 3D spoiled gradient-echo datasets, studied with digital subtraction techniques. In vivo, the complete peripheral arterial bed of six patients was studied, from the aorto-iliac bifurcation down to the distal run-off. By measuring the signal intensity (SI) over the lumen of a vessel in the MIP, an SI-plot was obtained. Next, the vessel boundaries were determined using a threshold algorithm; from these boundary points individual diameter values could be obtained along the trajectory of the vessel. In an in vitro study, an optimal threshold value of 30% of the range of SI-values between the background and the maximal SI in the vessel was obtained for accurate diameter measurement in Gd CE MRA (i.e., full-width 30%-maximum). Furthermore, the relationship between the accuracy of these measurements and the scan resolution was investigated. Accuracy was found to be acceptable (i.e., less than 10% over/underestimation) for vessel sizes covering at least 3 pixels. In six patients, diameters were measured in MIPs of the total datasets (i.e., D(T)) as well as in selective MIPs of the clipped datasets (i.e., D(S)) (n = 209). D(T) and D(S) were statistically significantly correlated (p < 0.01) with a Pearson correlation coefficient rP = 0.98. Measurements in the total MIPs yielded statistically significant (p < 0.01) smaller diameter values compared with measurements in selective MIPs, with a mean difference of 0.15 mm. Diameter values from the selective MIPs of the aorto-iliac arteries were also compared with diameter values measured at corresponding anatomic positions in X-ray angiograms of these patients (i.e., D(x)) (n = 70). D(X) and D(S) were statistically significantly correlated (p < 0.01) with a Pearson correlation coefficient rP = 0.92. Diameters measured in the selective MIPs were smaller than those measured in the X-ray angiograms (mean difference 0.49 mm) and this difference was statistically significant (p < 0.01). In conclusion, diameter values can be evaluated accurately in MIPs of vessels with at least 3 pixels in diameter, using the full-width 30%-maximum criterion.

Adult↗
PubMed2000

American College of Cardiology/European Society of Cardiolgoy International Study of Angiographic Data Compression Phase II: the effects of varying JPEG data compression levels on the quantitative assessment of the degree of stenosis in digital coronary angiography. Joint Photographic Experts Group.

OBJECTIVES: This report describes whether lossy Joint Photographic Experts Group (UPEG) image compression/decompression has an effect on the quantitative assessment of vessel sizes by state-of-the-art quantitative coronary arteriography (QCA). BACKGROUND: The Digital Imaging and Communications in Medicine (DICOM) digital exchange standard for angiocardiography prescribes that images must be stored loss free, thereby limiting JPEG compression to a maximum ratio of 2:1. For practical purposes it would be desirable to increase the compression ratio (CR), which would lead to lossy image compression. METHODS: A series of 48 obstructed coronary segments were compressed/decompressed at CR 1:1 (uncompressed), 6:1, 10:1 and 16:1 and analyzed blindly and in random order using the QCA-CMS analytical software. Similar catheter and vessel start- and end-points were used within each image quartet, respectively. All measurements were repeated after several weeks using newly selected start- and end-points. Three different sub-analyses were carried out: the intra-observer, fixed inter-compression and variable inter-compression analyses, with increasing potential error sources, respectively. RESULTS: The intra-observer analysis showed significant systematic and random errors in the calibration factor at JPEG CR 10:1. The fixed inter-compression analysis demonstrated systematic errors in the calibration factor and recalculated vessel parameter results at CR 16:1 and for the random errors at CR 10:1 and 16:1. The variable inter-compression analysis presented systematic and random errors in the calibration factor and recalculated parameter results at CR 10:1 and 16:1. Any negative effect at CR 6:1 was found only for the calibration factor of the variable inter-compression analysis, which did not show up in the final vessel measurements. CONCLUSIONS: Compression ratios of 10:1 and 16:1 affected the QCA results negatively and therefore should not be used in clinical research studies.

Adult↗
PubMed2000

American College of Cardiology/ European Society of Cardiology international study of angiographic data compression phase II. The effects of varying JPEG data compression levels on the quantitative assessment of the degree of stenosis in digital coronary angiography.

OBJECTIVES: This report describes whether lossy Joint Photographic Experts Group (JPEG) image compression/decompression has an effect on the quantitative assessment of vessel sizes by state-of-the-art quantitative coronary arteriography (QCA). BACKGROUND: The Digital Imaging and Communications in Medicine (DICOM) digital exchange standard for angiocardiography prescribes that images must be stored loss free, thereby limiting JPEG compression to a maximum ratio of 2:1. For practical purposes it would be desirable to increase the compression ratio (CR), which would lead to lossy image compression. METHODS: A series of 48 obstructed coronary segments were compressed/decompressed at CR 1:1 (uncompressed), 6:1, 10:1 and 16:1 and analyzed blindly and in random order using the QCA-CMS analytical software. Similar catheter and vessel start- and end-points were used within each image quartet, respectively. All measurements were repeated after several weeks using newly selected start- and end-points. Three different sub-analyses were carried out: the intra-observer, fixed inter-compression and variable inter-compression analyses, with increasing potential error sources, respectively. RESULTS: The intra-observer analysis showed significant systematic and random errors in the calibration factor at JPEG CR 10:1. The fixed inter-compression analysis demonstrated systematic errors in the calibration factor and recalculated vessel parameter results at CR 16:1 and for the random errors at CR 10:1 and 16:1. The variable inter-compression analysis presented systematic and random errors in the calibration factor and recalculated parameter results at CR 10:1 and 16:1. Any negative effect at CR 6:1 was found only for the calibration factor of the variable inter-compression analysis, which did not show up in the final vessel measurements. CONCLUSIONS: Compression ratios of 10:1 and 16:1 affected the QCA results negatively and therefore should not be used in clinical research studies.

Cardiology↗