Chun-Shan Yam

Coronary plaque quantification by voxel analysis: dual-source MDCT angiography versus intravascular sonography.

OBJECTIVE The purpose of this study was to evaluate a voxel-based analytic technique for quantification of noncalcified coronary artery plaque with intravascular sonography as a standard of reference. SUBJECTS AND METHODS Intravascular sonography and dual-source MDCT angiography prospectively performed on 12 patients resulted in identification of 20 segments containing noncalcified plaque. Four of these segments were used to establish reference measurements of 0.6-mm proximal wall thickness with a 0-HU cutoff between the epicardial fat and outer wall and an individually adjusted threshold for the interface between the wall and lumen. With these data, consecutive circular layers of the outer wall were subtracted from a 3D volume to determine the plaque plus medial layer and the actual plaque volume in the other 16 segments. Accuracy of the voxel technique was assessed by comparing the results with intravascular sonographic findings. RESULTS Both the total plaque burden (plaque plus medial layer) and the actual plaque volume had good concordance with intravascular sonographic findings (49.6 +/- 20 mm (3) vs 56.7 +/- 23.6 mm (3), p = 0.076; 26.5 +/- 14.8 mm (3) vs 30.9 +/- 15.3 mm (3), p = 0.09). Corresponding correlation coefficients were r = 0.76 and r = 0.79. The method had good reproducibility, the an intraclass correlation coefficients being 0.93 for total plaque burden and 0.90 for actual plaque volume. CONCLUSION Voxel analysis can be used for accurate and reproducible quantification not only of plaque burden but also of actual plaque volume.

Measuring Noncalcified Coronary Atherosclerotic Plaque Using Voxel Analysis with MDCT Angiography: A Pilot Clinical Study

OBJECTIVE The purpose of our study was to evaluate a new method using voxel analysis for quantifying noncalcified plaque in coronary arteries using MDCT angiography (MDCTA) compared with luminal stenosis by catheter coronary arteriography. MATERIALS AND METHODS Forty-one normal and eight abnormal arterial cross sections with noncalcified plaque selected from 40 patients undergoing MDCTA were analyzed for percentage of stenosis and plaque volume using a voxel analysis technique. RESULTS Using voxel analysis, the normal arterial wall thickness was determined to be 0.8 +/- 0.4 mm. Attenuation values (in Hounsfield units) for normal segments ranged between 30 and 175 H and for abnormal (plaque-containing) segments ranged from -49 to 139 H (p < 0.05). Plaque volume measurements varied from 0.90 to 156 mm(3) with good interobserver correlation (R(2) = 0.9671). Percentage of stenosis correlated with quantitative coronary arteriography measurement (R(2) = 0.55). Voxel analysis underestimated the percentage of stenosis (Pearsons correlation coefficient, 1.2; p = 0.03). CONCLUSION The study shows that the voxel analysis technique appears to be an accurate and reproducible method to measure arterial wall thickness, noncalcified plaque, and degree of arterial stenosis using density values measured in Hounsfield units. The technique may be useful on further correlative studies.

Absorbed Radiation Dose in Radiosensitive Organs During Coronary CT Angiography Using 320-MDCT: Effect of Maximum Tube Voltage and Heart Rate Variations

OBJECTIVE The purpose of this article is to estimate the absorbed radiation dose in radiosensitive organs during coronary MDCT angiography using 320-MDCT and to determine the effects of tube voltage variation and heart rate (HR) control on absorbed radiation dose. MATERIALS AND METHODS Semiconductor field effect transistor detectors were used to measure absorbed radiation doses for the thyroid, midbreast, breast, and midlung in an anthropomorphic phantom at 100, 120, and 135 kVp at two different HRs of 60 and 75 beats per minute (bpm) with a scan field of view of 320 mm, 400 mA, 320 × 0.5 mm detectors, and 160 mm collimator width (160 mm range). The paired Students t test was used for data evaluation. RESULTS At 60 bpm, absorbed radiation doses for 100, 120, and 135 kVp were 13.41 ± 3.59, 21.7 ± 4.12, and 29.28 ± 5.17 mGy, respectively, for midbreast; 11.76 ± 0.58, 18.86 ± 1.06, and 24.82 ± 1.45 mGy, respectively, for breast; 12.19 ± 2.59, 19.09 ± 3.12, and 26.48 ± 5.0 mGy, respectively, for lung; and 0.37 ± 0.14, 0.69 ± 0.14, and 0.92 ± 0.2 mGy, respectively, for thyroid. Corresponding absorbed radiation doses for 75 bpm were 38.34 ± 2.02, 59.72 ± 3.13, and 77.8 ± 3.67 mGy for midbreast; 26.2 ± 1.74, 44 ± 1.11, and 52.84 ± 4.07 mGy for breast; 38.02 ± 1.58, 58.89 ± 1.68, and 78 ± 2.93 mGy for lung; and 0.79 ± 0.233, 1.04 ± 0.18, and 2.24 ± 0.52 mGy for thyroid. Absorbed radiation dose changes were significant for all organs for both tube voltage reductions as well as for HR control from 75 to 60 bpm at all tube voltage settings (p < 0.05). The absorbed radiation doses for the calcium score protocol were 11.2 ± 1.4 mGy for midbreast, 9.12 ± 0.48 mGy for breast, 10.36 ± 1.3 mGy for lung, and 0.4 ± 0.05 mGy for thyroid. CONCLUSION CT angiography with 320-MDCT scanners results in absorbed radiation doses in radiosensitive organs that compare favorably to those previously reported. Significant dose reductions can be achieved by tube voltage reductions and HR control.

Using Macromedia Flash for Electronic Presentations: A New Alternative

OBJECTIVE This article provides a step-by-step tutorial for creating electronic presentations using Macromedia Shockwave Flash, one of the recommended file formats for many radiologic society annual meetings, including the American Roentgen Ray Society (ARRS). CONCLUSION Although Flash and PowerPoint can be used for creating presentation slide shows, Flash is more appropriate for integrating and delivering animations for Internet applications such as radiologic electronic presentations. For this reason, detailed step-by-step instructions for creating Flash slide shows with common features such as text, images, arrows, buttons, movie loops, and transitions are provided. The approach used in this article is particularly appropriate for academic radiologists who have basic PowerPoint skills but lack programming experience.

Measuring Noncalcified Coronary Atherosclerotic Plaque Using Voxel Analysis with MDCT Angiography: Phantom Validation

OBJECTIVE This purpose of this study was to evaluate the accuracy and reproducibility of a voxel analysis technique for measuring noncalcified plaque in the coronary arteries. MATERIALS AND METHODS Polyethylene phantoms representing noncalcified plaque were scanned in both MDCT and micro-CT scanners and inter- and intrareader variability of volume calculation was performed. RESULTS Volume measurements by both MDCT and micro-CT were comparable to the true volume as measured by micrometry (< 3%, p = 0.05). CONCLUSION There appears to be no significant difference (< 3%) between MDCT and micro-CT measurements.

Using Movie Clips in PowerPoint Presentations: Part 1, Compatibility Issues

OBJECTIVE The purpose of this article is to discuss common compatibility issues relating to the use of movie clips in PowerPoint presentations. CONCLUSION Our investigations found that successful display of movie clips in PowerPoint depends on the following three factors: movie file format, codec selection, and cross-platform compatibility. These factors primarily result from the rapid change in todays computer operating systems. Based on a compatibility study of common movie clips used in radiology presentations, a general guideline for preparing movie clips is presented. Also, a simple method is described for converting movie clips into compatible movie formats and reducing large movie clips to manageable file sizes to ensure smooth presentation.

Simple Method for Inserting Flash Movies into PowerPoint Presentations

OBJECTIVE This article describes a simple method for inserting Shockwave Flash (Adobe) movies into PowerPoint (Microsoft) slides. CONCLUSION Shockwave Flash is the latest recommended file format for presenting dynamic data sets in PowerPoint at radiologic society meetings. Unfortunately, the standard method recommended by Microsoft for inserting Flash into PowerPoint is cumbersome and labor intensive. The procedure also can be intimidating for many radiologists. This article offers a solution that entails a simple PowerPoint macro.

A Solution for Using Dynamic Data Sets in Electronic Presentations

OBJECTIVE This article offers a solution for displaying dynamic data sets in PowerPoint for todays electronic presentations using Shockwave Flash software. CONCLUSION Shockwave Flash is the most recommended file format for presenting dynamic data sets at the annual meetings of radiology societies. Detailed instructions and examples are provided for first-time Flash users who wish to take advantage of this alternative solution for using dynamic data sets with PowerPoint in electronic presentations.

Preparation of Digital Movie Clips for Online Journal Publication

OBJECTIVE This article presents general guidelines for preparing movie clips for online journal publication. CONCLUSION As more and more radiology journals establish an online presence, radiologists wishing to submit journal articles with movie clips need to understand the electronic submission process. Viewing a movie clip via an online journal is different from viewing one with PowerPoint using a local desktop computer because the movie file must first be downloaded onto the client computer before it can be displayed. Users thus should be cautious in selecting movie format and compression when creating movie clips for online journals. This article provides step-by-step demonstrations and general guidelines for movie format and compression selections.

Using Movie Clips in PowerPoint Presentations: Part 2, Movie Editing

OBJECTIVE The purpose of this article is to describe a simple method for editing movie clips for PowerPoint presentations. CONCLUSION We describe a simple method for editing movie clips using Adobe Photoshop, a common software utility used by many radiologists for preparing digital images.