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Biomedical subjects

C Di Mario

Publications and source records attributed to C Di Mario.

At least 145 records · Page 8Linked to original sources
PubMed1995

In vivo measurement of regional large artery compliance by intravascular ultrasound under pentobarbital anesthesia.

BACKGROUND: The presence of smooth muscle fibers on the wall of large arteries would suggest that arterial compliance might change in response to vasoactive substances. The purpose of this study is to determine the basal level of vasomotor tone in these arteries in a commonly used animal preparation and to learn whether the compliance of large conductance arteries can be altered in vivo by vasoactive agents. METHODS: Proximal iliac arterial compliance was measured in 7 pentobarbital-anesthetized pigs, before and during local infusions of adenosine and norepinephrine. Luminal area was measured every forty milliseconds by means of a 30 MHz intravascular ultrasound catheter and an automatic edge detection program. Simultaneous high-fidelity pressure measurements were obtained by means of a catheter-tipped pressure microtransducer positioned at the origin of the iliac artery. Linear regression analysis of the area/pressure relationship in two consecutive cardiac cycles (systolic phase only) was performed before and during adenosine and norepinephrine infusions. The slope of the area/pressure regression line was defined as an index of arterial compliance. Measurements after three minutes of infusions of adenosine (5-5000 micrograms/minute) and norepinephrine (0.001-10 micrograms/minute) were compared with the control measurements. RESULTS: Even at the highest infusion rate, adenosine did not significantly increase arterial compliance as compared with baseline (25 +/- 7 vs 19 +/- 4 mm2/mmHg x 10(-3), respectively, P = ns). In contrast, norepinephrine decreased arterial compliance as compared with the second baseline control (13 +/- 3 vs 20 +/- 3 mm2/mmHg x 10(-3), respectively, P < 0.01). CONCLUSIONS: In this animal model with pentobarbital anesthesia, arterial compliance may be modified more by the acute infusion of norepinephrine than by adenosine in large conductance arteries such as the proximal iliac. Thus, in this preparation, smooth muscle tone tends to be minimal and arterial compliance near maximal (ie, mostly a passive phenomenon). However, in response to norepinephrine, arterial compliance can decrease significantly as smooth muscle tone increases. Intravascular ultrasound allows continuous and accurate monitoring of these changes of arterial dimensions, suggesting that this technique may be useful in the evaluation of pharmacologically induced changes in the compliance of large arteries by vasoactive agents.

Adenosine↗
PubMed1995

Three-dimensional reconstruction of coronary arteries with intravascular ultrasound.

Three-dimensional (3D-) reconstruction of intravascular ultrasound (IVUS) images is a recently introduced technical method which has rapidly grown in science and clinical practice. In the catheterization laboratory it is particularly important to obtain the 3D-reconstruction on-line, since the dimensions measured and the plaque attributes displayed may guide the therapeutic decision. Off-line reconstruction, however, provides very accurate and reproducible area and volume measurements of lumen and plaque and is thus exceptionally qualified for studying progression/regression of atherosclerosis or restenosis after catheter-based interventions. Complementary 3D-reconstruction methods, revealing specific advantages and limitations, meet the requirements by slightly different technical approaches, but each 3D-reconstruction of two-dimensional IVUS images requires some basic procedural steps. The IVUS images can be acquired during continuous or ECG-gated withdrawals of the IVUS imaging catheter. The latter permits even to visualize the cyclic pulsation of the reconstructed arteries. As an alternative approach a sensing device recognizes the insertion depth of the IVUS catheter and permits reliable measurements even during manual handling of the IVUS catheter. A discrimination between the blood-pool and structures of the vascular wall, performed in the digitized images, can be achieved by the application of different techniques. This processing step which is called segmentation and the image acquisition are particularly crucial with regards to the final quality of the 3D-reconstruction. Currently there are still limitations of 3D-IVUS, but a new approach combining data obtained from 3D-IVUS and biplane angiography offers a promising potential to solve most of the remaining problems in the future. Thus, three-dimensional IVUS offers a great clinical and scientific potential since it provides spatial visualization of vascular pathology, longitudinal and volumetric measurement of luminal and plaque dimensions, and facilitated guidance of catheter-based interventions. Assuming a technical development similar to the progress of the previous years. 3D-IVUS has a realistic chance to gain significant importance and to become a routine technique in the future.

Computer Graphics↗
PubMed1995

Volumetric intracoronary ultrasound: a new maximum confidence approach for the quantitative assessment of progression-regression of atherosclerosis?

Quantitative assessment of atherosclerosis during its natural history and following therapeutic interventions is important, as cardiovascular disease remains the most significant cause of morbidity and mortality in industrial societies. While coronary angiography delineates the vessel lumen, permitting only the indirect determination of atherosclerotic wall changes encroaching upon the lumen, intracoronary ultrasound permits direct plaque assessment and quantification. The angiographic percent diameter stenosis, previously suggested as measure of a maximum confidence approach, is still commonly used to quantify stenosis severity, but the reference segments which are required for angiographic interpolation of the normal vessel dimensions are frequently involved in the general process of atherosclerosis, including progression or regression. Considering also the variability of vascular remodeling during the evolution of atherosclerosis, including compensatory enlargement and paradoxical arterial shrinkage, intracoronary ultrasound appears currently to be the only reliable technique to measure plaque burden and progression or regression of atherosclerosis. However, correct matching of the site of measurement at follow-up with the site of the initial ultrasound study is often difficult to achieve, but is significantly facilitated by the use of volumetric intracoronary ultrasound. This approach permits not only area measurement, but also measurement of plaque volume, which appears to be the ideal measure for quantifying the atherosclerotic plaque, as it is highly reproducible and directly reflects the changes of an entire arterial segment.

Animals↗
PubMed1994

Response of conductance and resistance coronary vessels to scalar concentrations of acetylcholine: assessment with quantitative angiography and intracoronary Doppler echography in 29 patients with coronary artery disease.

Abnormal vasoreactivity of the large conductance arteries has been observed in the presence of impaired endothelial function. More recently, experimental and clinical reports have shown that in early coronary atherosclerosis the impairment of the endothelium-mediated vasodilatation also involves the resistance arteries. The aim of this study is the correlation of endothelium-dependent vasodilatation of conductance and resistance vessels in coronary arteries without significant stenoses. In 29 patients (aged 57 +/- 9 years, 24 men and 5 women) undergoing coronary angioplasty, a Doppler guide wire and a perfusion catheter were introduced into the proximal segment of an artery with less than 30% diameter stenosis. Selective infusions of papaverine (bolus of 7 mg), acetylcholine (continuous infusion of 0.036, 0.36, and 3.6 micrograms/ml at a flow rate of 2 ml/min), and isosorbide dinitrate (bolus of 3 mg) were sequentially performed. Heart rate, aortic blood pressure, and blood flow velocity were continuously measured. Mean cross-sectional areas of a proximal and a distal arterial segment were measured in baseline conditions, at the end of each infusion of acetylcholine, and at the peak effect of isosorbide dinitrate with quantitative angiography (CAAS System; Pie Medical Data, Maastricht, The Netherlands). Coronary blood flow was calculated from the time-averaged flow velocity and the cross-sectional area at the site of the Doppler sample volume. Coronary flow resistance was calculated as mean aortic pressure divided by coronary flow. All of the concentrations of acetylcholine induced a significant vasoconstriction of the studied artery. At the maximal concentration of acetylcholine all but three patients (90%) showed a reduction of cross-sectional area (-24% +/- 20% and -22% +/- 20% for the proximal and distal segments, respectively, p < 0.00001). Flow velocity showed a significant increase only with the two highest concentrations of acetylcholine. The maximal concentration induced a 105% +/- 138% increase from the baseline flow velocity (p < 0.001). The coronary flow changes after acetylcholine showed a large interpatient variability, with a mean increase from baseline after the highest dose of +43% +/- 85% (range, -60% +/- 239%), with the presence of a flow reduction in 10 patients (35%). No clinical or angiographic variables showed a significant correlation with the cross-sectional area, flow velocity, and flow changes after infusion of acetylcholine.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1994

Intracoronary ultrasound and angioscopic imaging facilitating the understanding and treatment of post-infarction angina.

We report on the use of intravascular ultrasound, coronary angioscopy and on-line quantitative angiography in an unstable patient soon after myocardial infarction. Combined intracoronary imaging made it possible to solve the therapeutic problem posed by an unusual angiographic appearance secondary to intracoronary thrombolysis during coronary recanalization. The pathological validation of the observations performed with angioscopy and intravascular ultrasound was made possible with the concomitant use of directional atherectomy.

Angina Pectoris↗
PubMed1994

Slope of the instantaneous hyperemic diastolic coronary flow velocity-pressure relation. A new index for assessment of the physiological significance of coronary stenosis in humans.

BACKGROUND: Coronary flow reserve (CFR), the functional index of stenosis severity more frequently used in the catheterization laboratory, is greatly affected by the hemodynamic conditions at the time of measurement and cannot be applied in the immediate assessment of the outcome of coronary interventions. The aim of the present study was to establish the feasibility and reproducibility of the assessment of the slope of the instantaneous diastolic relation between coronary flow velocity and aortic pressure during maximal hyperemia (IHDVPS) using a spectral analysis of the intracoronary Doppler signal, to assess the sensitivity and specificity of this index in the detection of flow-limiting coronary stenoses in comparison with CFR, and to study the possibility of determining the zero-flow pressure from the intercept of the velocity-pressure relation on the pressure axis during a controlled cardiac arrest. METHODS AND RESULTS: The instantaneous peak coronary flow velocity measured after intracoronary papaverine with a Doppler guidewire was plotted against the simultaneously measured aortic pressure, and the slope of the velocity-pressure relation in the phase of progressive diastolic velocity decrease was calculated during four consecutive beats. In nine normal arteries, a controlled diastolic cardiac arrest was induced by an intracoronary bolus injection of 3 mg adenosine. The IHDVPS could be assessed in 79 of 95 patients (83%), with a moderate intraobserver variability (0.4 +/- 11% after independent selection of different beats during maximal hyperemia). The IHDVPS showed no significant correlation with heart rate, mean diastolic aortic pressure, type of vessel studied, and cross-sectional area at the site of the velocity recording. The IHDVPS was significantly lower in arteries with > or = 30% diameter stenosis than in normal or near-normal arteries (0.71 +/- 0.48 versus 1.73 +/- 0.80 cm.s-1.mm Hg-1, P < .0000002). In the stenosis group, both IHDVPS and CFR were significantly correlated with the minimal luminal cross-sectional area (r = .46, P < .05 and r = .62, P < .002, respectively). The study of the velocity-pressure relation during long diastolic pauses showed a curvilinear relation between velocity and pressure in the lower pressure range, with an upward concavity to the velocity axis and no intercept with the pressure axis in most cases. CONCLUSIONS: The IHDVPS can distinguish between arteries with and without coronary stenoses and has a significant inverse correlation with the severity of the stenosis. Under the stable hemodynamic conditions of this study, the IHDVPS and CFR had similar sensitivities and specificities in distinguishing normal and stenotic vessels and demonstrated similar correlation with minimal luminal cross-sectional area. The curvilinearity of the velocity-pressure relation during long diastolic pauses, possibly due to a significant reduction of luminal cross-sectional area at low pressures, complicates the use of the flow velocity-pressure relation for the assessment of the zero-flow pressure.

Adult↗
PubMed1994

Vascular remodeling in coronary artery disease.

Traditionally, the diagnosis of significant coronary atherosclerotic disease has relied on angiographic techniques. Both histologic analyses and, more recently, intravascular ultrasonography techniques have revealed that a significant atherosclerotic plaque load may be present in epicardial coronary arteries without significant luminal narrowing, consistent with compensatory vessel enlargement or remodeling. In patients with coronary atherosclerosis, more limited structural changes are present in the smaller resistance arterioles, whereas a decrease in luminal area with an increase in wall thickness and perivascular fibrosis are the characteristic structural changes observed in resistance arteries in the presence of systemic hypertension. Further, functional changes, such as impairment of endothelium-mediated vasodilation, are present in epicardial and resistance vessels of patients with coronary atherosclerosis and may influence the progression of this disease and development of ischemic syndromes. The introduction of two-dimensional intravascular and Doppler ultrasonography enables us to study in vivo these morphologic and functional changes. In this article, the knowledge acquired in humans on the mechanisms and clinical relevance of vascular remodeling with the use of these two ultrasonography-based techniques is reviewed. The possibility of using pharmacologic interventions to improve or normalize the vascular response to endothelium-dependent and independent vascular interventions is discussed, with special attention to the efficacy of the inhibition of the angiotensin-converting enzyme.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1993

Intracoronary pressure and flow velocity with sensor-tip guidewires: a new methodologic approach for assessment of coronary hemodynamics before and after coronary interventions.

The use of miniaturized pressure and velocity sensors mounted on angioplasty guidewires allows the simultaneous measurement of coronary blood flow velocity and transstenotic pressure gradient, 2 parameters that, combined, should perfectly characterize stenosis hemodynamics. The aim of this article is assessment of the changes in coronary blood flow velocity observed with a Doppler-tipped angioplasty guidewire in 35 patients undergoing balloon angioplasty. We also report our initial experience in 16 patients with the combined use of sensor-tip pressure and Doppler guidewires, and we discuss the application of new methodologic approaches for the study of the coronary circulation allowed by these techniques, such as the instantaneous assessment of the flow velocity/pressure and pressure gradient/flow velocity relations. Before and after angioplasty, flow velocity measurements were obtained distal to the stenosis, both in baseline conditions and after intracoronary injection of 8-12.5 mg of papaverine. The Doppler guidewire was left in place during the dilation procedure and the Doppler signal was continuously recorded during balloon inflation and after deflation to monitor the development of collateral flow, the restoration of flow after balloon deflation, the phase of postocclusive reactive hyperemia, and, incidently, the development of flow-limiting complications. Merits and pitfalls of several flow velocity parameters (average peak velocity, coronary flow velocity reserve, diastolic/systolic velocity ratio), as well as of parameters derived from the combination of pressure and velocity measurements (transstenotic pressure gradient/flow velocity relation and instantaneous diastolic hyperemic flow velocity/pressure relation) were evaluated in 35 patients with, and 37 without, significant coronary stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Maximal blood flow velocity in severe coronary stenoses measured with a Doppler guidewire. Limitations for the application of the continuity equation in the assessment of stenosis severity.

In vitro and animal experiments have shown that the severity of coronary stenoses can be assessed using the continuity equation if the maximal blood flow velocity of the stenotic jet is measured. The large diameter and the low range of velocities measurable without frequency aliasing with the conventional intracoronary Doppler catheters precluded the clinical application of this method for hemodynamically significant coronary stenoses in humans. This article reports the results obtained using a 12 MHz steerable angioplasty guidewire in a consecutive series of 52 patients undergoing percutaneous coronary angioplasty (61 coronary stenoses). The ratio between coronary flow velocity in a reference segment and in the stenosis was used to estimate the percent cross-sectional area stenosis. A Doppler recording suitable for quantitation was obtained in the stenotic segment in only 10 of 61 arteries (16%). The time-averaged peak velocity increased from 15 +/- 5 to 115 +/- 26 cm/sec from the reference normal segment to the stenosis. Volumetric coronary flow calculated from the product of mean flow velocity and cross-sectional area was similar in the stenosis and in the reference segment (33.2 +/- 14.9 vs 33.5 +/- 17.0 mL/min, respectively, difference not significant). The percent cross-sectional area stenosis and minimal luminal cross-sectional area derived from the Doppler velocity measurements using the continuity equation and calculated with quantitative angiography were also similar (Doppler, 86.7 +/- 5.1% and 1.00 +/- 0.48 mm2; quantitative angiography, 85.9 +/- 7.9% and 1.02 +/- 0.50 mm2).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Limitations of the zero crossing detector in the analysis of intracoronary Doppler: a comparison with fast Fourier transform analysis of basal, hyperemic, and transstenotic blood flow velocity measurements in patients with coronary artery disease.

The current clinical standard for the analysis of intracoronary Doppler signals is the application of a zero-crossing (ZC) detector. However, the accuracy of the method is questionable, especially in areas of disturbed flow, as confirmed by in vitro studies, animal experiments, and intraoperative observations. The aim of this study is the comparison of a conventional ZC detector and a custom-designed spectral analyzer (fast Fourier transform, FFT) in the analysis of intracoronary Doppler signals obtained in 19 patients undergoing coronary angioplasty. A 3F catheter with an end-mounted Doppler ceramic crystal was placed over an 0.014" guidewire in a normal or near-normal segment proximal to the lesion to be dilated. The Doppler signal was recorded before and after intracoronary infusion of 12.5 mg of papaverine. In 9 patients high flow velocities could be recorded when the catheter was advanced across the stenosis. The blood flow velocity measurements obtained with ZC were significantly lower than the maximal FFT flow velocity measurements (16 +/- 12 cm/s vs. 29 +/- 18 cm/s, p < .001). In all the conditions of Doppler signal acquisition (baseline, hyperemia, stenosis) a large scattering of the signed differences between corresponding measurements was observed. The standard deviation of the difference ZC-FFT was +/- 11 cm/s and +/- 5 cm/s for the maximal and mean FFT flow velocity, corresponding in both cases to +/- 37% of the mean of the ZC and FFT measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1993

Digital geometric measurements in comparison to cinefilm analysis of coronary artery dimensions.

Six months follow-up post-PTCA angiograms from 31 patients were acquired digitally and on cinefilm and used for a comparison of geometric coronary measurements at the site of the previous dilatation. On 70 images of 34 coronary segments quantitative analysis was performed both on-line, using the Automated Coronary Analysis package of the Philips Digital Cardiac Imaging System (DCI, pixel matrix 512 x 512) and off-line, using the Cardiovascular Angiography Analysis System (CAAS). With the CAAS a cine-video conversion is performed and a 6.9 x 6.9 mm region of interest from the 18 x 24 mm cineframe is digitized into a 512 x 512 pixel matrix. In both systems the vascular contours are assessed by means of operator-independent edge detection algorithms. The angiographic catheter was used for calibration. Best agreement between DCI and CAAS was found for obstruction diameter and minimal luminal diameter, respectively (r = 0.82; y = 0.12 + 0.97x; SEE = 0.29). The reconstructed reference diameter related to a computed reference contour yields lower correlation (r = 0.76; y = 0.27 + 0.91x; SEE = 0.37). Worst results were obtained from the relative measure of percent diameter stenosis as well as from the derived parameter of plaque area. The on-line digital approach of geometric coronary assessments provides good agreement with cinefilm analysis when direct measurements of coronary dimensions are applied.

Algorithms↗
PubMed1993

Intracoronary blood flow velocity and transstenotic pressure gradient using sensor-tip pressure and Doppler guidewires: a new technology for the assessment of stenosis severity in the catheterization laboratory.

In a patient undergoing percutaneous balloon angioplasty of a stenotic proximal right coronary artery the transstenotic pressure gradient was measured using a 0.018" guidewire with a distal optical microsensor. Blood flow velocity was measured proximal to the stenosis using a 0.018" Doppler guidewire. Transstenotic pressure gradient and blood flow velocity were measured in baseline conditions and after intracoronary injection of 12.5 mg of papaverine. Coronary blood flow was calculated from the measured blood flow velocity and the corresponding cross-sectional area. The measured pressure gradients were compared with the values derived from the stenosis geometry assessed with quantitative coronary angiography (automated edge detection measurements in two orthogonal views, assuming an elliptical cross-sectional area). The measured transstenotic pressure gradient was 15 mm Hg in baseline conditions and 42 mm Hg at the peak effect of the papaverine injection. A 50% flow velocity increase was observed at peak hyperemia (time-averaged maximal flow velocity = 30 cm/s before and 45 cm/s after papaverine). The transstenotic pressure gradient calculated from the measured stenosis geometry was 20 mm Hg and 42 mm Hg in baseline and hyperemic conditions, respectively. The combined use of a pressure and a Doppler guidewire provides a complete assessment of the transstenotic pressure/coronary flow velocity relation at rest and after pharmacologically induced hyperemia and allows the characterization of stenosis hemodynamics and functional severity.

Angioplasty, Balloon, Coronary↗
PubMed1993

The angle of incidence of the ultrasonic beam: a critical factor for the image quality in intravascular ultrasonography.

The effects of the angle of incidence of the ultrasound beam on the image quality were studied in 21 pressurized arterial specimens examined with a 30 MHz intravascular ultrasonographic catheter. When the ultrasonographic catheter was in an eccentric position in the vessel lumen, the videodensity of the segments of the vessel wall with the least favorable angle of interrogation (a shift of 49 +/- 6 degrees from the tangent to the tissue surface) was 27% +/- 19% lower than the videodensity measured with the catheter in the center of the lumen. When the catheter was placed in a position that was not parallel to the long axis of the vessel, a further decrease was observed, especially in the vessel wall opposite the position of the catheter. An artificial dissection was induced in eight specimens. Dropouts that involved the dissection plane and the underlying structures were produced with positions of the echographic catheter inducing a narrow angle between ultrasound beam and dissection plane. These experimentally induced artifacts were compared with similar findings from the in vivo evaluation of peripheral and coronary arteries. The angle of incidence of the ultrasound beam is a major determinant of the image quality in intravascular ultrasonography. Angle-dependent artifacts occur with eccentric and noncoaxial positions of the ultrasonographic catheter and, in particular, with imaging of large intraluminal dissections. Awareness of this problem may prevent image misinterpretation and has relevance for future improvement of catheter technology and design.

Aortic Dissection↗
PubMed1993

Quantitative angiography during coronary angioplasty with a single angiographic view: a comparison of automated edge detection and videodensitometric techniques.

Little information is available on the reliability of coronary luminal measurements obtained from quantitative analysis of a single angiographic view, an approach that is central to the practical use of on-line quantitative angiography. In the present study we investigated the contribution of two different techniques of quantitative angiography, edge detection (ED) and videodensitometry (VD), to the application of this concept during coronary angioplasty. Forty-six balloon angioplasty procedures were included in this study, all of them performed in a stenosis located in the mid right coronary segment. This coronary location was chosen to optimize data collection on luminal morphology and to minimize the number of factors that may adversely affect quantitative analysis with both techniques. In all cases two orthogonal angiographic projections were obtained before, after balloon dilatation, and at follow-up. Correlation coefficients and differences between orthogonal measurements obtained with each technique were used to evaluate the agreement between orthogonal readings at every stage of the procedure. The obtained correlation coefficients and mean differences (MD) between orthogonal measurements were as follows: before percutaneous transluminal coronary angiography (PTCA), 0.67 (MD 0.01 +/- 0.47 mm2) and 0.57 (MD 0.05 +/- 0.64 mm2) for ED and VD, respectively (Pitman's test for SD, p < 0.05); after balloon dilatation, 0.32 (MD -0.56 +/- 1.53 mm2) and 0.53 (MD -0.15 +/- 1.43 mm2) for ED and VD, respectively (paired t test for MD, p < 0.05); and at follow-up 0.79 (MD -0.15 +/- 0.97 mm2) and 0.73 (MD 0.17 +/- 1.16 mm2) for ED and VD, respectively (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1993

Can the same edge-detection algorithm be applied to on-line and off-line analysis systems? Validation of a new cinefilm-based geometric coronary measurement software.

In the Cardiovascular Measurement System (CMS) the edge-detection algorithm, which was primarily designed for the Philips digital cardiac imaging system (DCI), is applied to cinefilms. Comparative validation of CMS and DCI was performed in vitro and in vivo with intracoronary insertion of stenosis phantoms in anesthetized pigs. The "obstruction diameter" (OD) was measured at the artificial stenoses visualized by angiography with calibration at the isocenter (ISO) and catheter calibration (CATH) and compared with the true phantom diameters. A clinical comparison of OD, reference diameter (RD), and percentage diameter stenosis (DS) was performed on 70 corresponding images from post-PTCA angiograms. In vitro, OD (CMS) yielded an accuracy of 0.18 +/- 0.14 mm with 100% (correlation coefficient: r = 0.97, y = 0.06 + 0.75x, standard error of estimate [SEE] = 0.09) and 0.19 +/- 0.15 mm with 50% contrast (r = 0.94, y = 0.02 + 0.81 x). OD (DCI) yielded an accuracy of 0.11 +/- 0.06 mm with 100% (r = 0.99, y = -0.03 + 0.91 x, SEE = 0.05) and 0.24 +/- 0.13 mm with 50% contrast (r = 0.94, y = 0.29 + 6.69 x, SEE = 0.12). In vivo, OD (CMS) yielded an accuracy of 0.18 +/- 0.23 mm with ISO (r = 0.89, y = 0.02 + 0.83 x, SEE = 0.22) and 0.26 +/- 0.24 mm with CATH (r = 0.89, y = 0.06 + 0.72 x, SEE = 0.19). OD (DCI) yielded an accuracy of 0.08 +/- 0.15 mm with ISO (r = 0.96, y = 0.08 + 0.86 x, SEE = 0.14) and 0.18 +/- 0.21 mm with CATH (r = 0.92, y = 0.09 + 0.76 x, SEE = 0.17). The clinical comparison showed reasonable agreement for OD only (r = 0.81, y = 0.26 + 0.81 x, SEE = 0.29). Transformation of an edge-detection algorithm from a digital to a cinefilm-based system can lead to impairment of measurement reliability.

Algorithms↗