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Quantitative coronary arteriography: efficient correction of catheter calibrated vessel measurement
F Fischer1, W Wunderlich, J Noring
1Division of Cardiology, Klinikum Benjamin Franklin, Hindenburgdamm 30, D-12200 Berlin, Germany.
Insights
Different magnification in coronary angiography causes vessel dimension errors up to 15%. A simple, measurement-free magnification correction method can significantly reduce these errors, improving diagnostic accuracy.
Area of Science:
- Medical Imaging
- Cardiovascular Imaging
- Radiology
Background:
- Coronary angiography uses catheters for scaling, but differential magnification (DM) causes significant errors in vessel dimension quantification.
- Biplane angiography offers correction but requires complex gantry systems, limiting its widespread use.
- This study investigates the impact of DM on catheter-calibrated vessel dimensions and develops efficient correction methods.
Purpose of the Study:
- To analyze the magnitude of differential magnification (DM) errors in coronary angiography.
- To develop and evaluate low-computational and low-measurement effort DM correction procedures.
- To assess the accuracy of catheter-calibrated vessel dimensions with and without DM correction.
Main Methods:
- Biplane imaging of vessel phantoms with known dimensions was performed to establish true pixel sizes.
- Phantoms were digitized and calibrated using differently located catheters to calculate calibration errors.
- Developed and applied approximated formulas and fixed pre-settings for distance and videochain to reduce computational and measurement effort for DM correction.
Main Results:
- Differential magnification (DM) introduces errors in absolute vessel dimensions, increasing with vessel size.
- DM correction significantly reduces calibration errors, with even measurement-free methods showing substantial improvement.
- A measurement-free procedure corrected 71% of DM-induced errors.
Conclusions:
- Differential magnification (DM) can lead to errors of up to 15% in measured coronary vessel diameters.
- Simple, low-effort DM correction techniques, including measurement-free approaches, are effective in mitigating these errors.
- Accepting the minimal additional effort of using biplane views and marking vessel/catheter locations is crucial for accurate coronary dimension quantification.
Abstract:
1. BACKGROUND. To quantify coronary dimensions from digitized angiograms, the coronary catheter is commonly used as a scaling device. However, significant errors may result due to different angiographic magnification (DM) of the vessel and of the catheter resulting from deviating locations in the X-ray field. These errors can be corrected by biplane angiography. Since this correction needs a gantry measurement system, DM correction is less widely used. We analyzed the magnitude of DM that affects the accuracy of catheter calibrated vessel dimensions and developed DM corrections requiring low computational and measurement effort. 2. MATERIAL AND METHODS. We filmed biplane a perspex bloc of vessel phantoms (0.3 - 4.5 mm) in the isocenter of the x-ray system to get the true pixel sizes before any calibration. The phantoms were detected in the digitized images using a cardiac workstation (Kontron Cardio 500) and calibrated with differently located catheters. The calibration error was then calculated for increasing distances phantom-catheter. For DM correction, we developed procedures decreasing: (i) the computational effort (E) by approximated (A) formulas, as well as (ii) the measurement effort; this decrease approximates measured gantry settings (M) through fixed pre-settings for distances (D) and videochain (V). The several DM corrections were applied on the phantom images to analyze their correction performance and remaining calibration error. 3. RESULTS. The calibration of correctly detected pixel dimensions by a differentially magnified catheter causes a deviation of the absolute vessel dimensions, increasing with the vessel size. However, as shown in Table 1, DM correction reduces this calibration error substantially. Table 1: Calibration errors of catheter calibration and performance of DM corrections with decreasing effort (50 mm location distance phantom-catheter) 4. CONCLUSIONS. DM causes errors of vessel diameters of up to 15%. Even a measurement-free procedure (fixed presettings) corrects 71% of DM. Thus, the only additional effort of selecting an angiogram from the opposite view and marking the vessel and catheter locations in both images should be accepted.