Mm For Observer Research Articles

Accuracy of electroanatomical mapping-guided cardiac radiotherapy for ventricular tachycardia: pitfalls and solutions.

To analyse and optimize the interobserver agreement for gross target volume (GTV) delineation on cardiac computed tomography (CCT) based on electroanatomical mapping (EAM) data acquired to guide radiotherapy for ventricular tachycardia (VT). Electroanatomical mapping data were exported and merged with the segmented CCT using manual registration by two observers. A GTV was created by both observers for predefined left ventricular (LV) areas based on preselected endocardial EAM points indicating a two-dimensional (2D) surface area of interest. The influence of (interobserver) registration accuracy and availability of EAM data on the final GTV and 2D surface location within each LV area was evaluated. The median distance between the CCT and EAM after registration was 2.7 mm, 95th percentile 6.2 mm for observer #1 and 3.0 mm, 95th percentile 7.6 mm for observer #2 (P = 0.9). Created GTVs were significantly different (8 vs. 19 mL) with lowest GTV overlap (35%) for lateral wall target areas. Similarly, the highest shift between 2D surfaces was observed for the septal LV (6.4 mm). The optimal surface registration accuracy (2.6 mm) and interobserver agreement (Δ interobserver EAM surface registration 1.3 mm) was achieved if at least three cardiac chambers were mapped, including high-quality endocardial LV EAM. Detailed EAM of at least three chambers allows for accurate co-registration of EAM data with CCT and high interobserver agreement to guide radiotherapy of VT. However, the substrate location should be taken in consideration when creating a treatment volume margin.

Accuracy of electroanatomical mapping guided cardiac radiotherapy for ventricular arrhytmias: pitfalls and solutions

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was partially supported by the grant AZV NU20-02-00244 from the Ministry of Health of the Czech Republic OnBehalf WECAM Background One of the main limitations of Radiofrequency catheter ablation (RFCA) is the difficulty in targeting specific VT substrate locations when they are deep intramural, covered by epicardial fat or in the proximity of a coronary artery. Stereotactic body radiotherapy (SBRT) has emerged as an alternative treatment for VT after RFCA failure. However, the accuracy of substrate volume delineation, the gross target volume (GTV), based on electroanatomical mapping (EAM) and interobserver agreement are still unknown. Aim To analyze and optimize the interobserver agreement for GTV delineation on cardiac CT (CCT) based on EAM data acquired to guide radiotherapy for ventricular arrhythmias. Method Available EAM data was exported and merged with the segmented CCT using manual registration by two observers. A GTV was created by the observers for predefined left ventricular (LV) areas based on preselected endocardial EAM points, indicating the 2D-surface area of interest. The interobserver (non)overlapping GTV volumes were analyzed. The influence of (interobserver) registration accuracy and availability of EAM data on the final GTV and 2D-surface location within each LV area was evaluated. Results The median distance between the CCT and EAM after registration was 2.7 mm, 95%th percentile 6.2 mm for observer #1 and 3.0 mm, 95%th percentile 7.6 mm for observer #2 (p = 0.9). Created GTVs were significantly different (8 vs 19 ml) with lowest GTV overlap (35%) for lateral wall target areas. Similar, the highest shift between 2D-surfaces was observed for the lateral LV (6.4mm (3.0-9.9)). The same trend is seen in the (non) overlapping volume for lateral area (P = 0.004). The optimal surface registration accuracy (2.6 mm) and interobserver agreement (Δ interobserver EAM surface registration accuracy 1.32 mm) on final GTVs could be achieved if at least three cardiac chambers were mapped, including high-density LV EAM. Conclusion Detailed EAM of at least three chambers allows for accurate co-registration of EAM data with CCT and high interobserver agreement on GTVs to guide radiotherapy of ventricular arrythmias. However, the substrate location should be taken in consideration when creating a treatment volume margin. Gross target volume (GTV) and InterobserGTV volume Observer #1 (cc)GTV volume Observer #2 (cc)Surface shift (mm)Basal anterior, (IQR)7.6 (6.2-11.5)9.3 (5.3-10)3.8 (2.2-4.5)Lateral, (IQR)8.0 (6.9-12.7)19.1 (15.7-21.4)6.2 (5.3-6.4)Septal, (IQR)10.1 (6.2-12.8)13.9 (7.7-14.6)6.4 (3.0-9.9)Abstract Figure. Graphical abstract

Accuracy and reliability of 3D stereophotogrammetry: A comparison to direct anthropometry and 2D photogrammetry.

To evaluate the accuracy of three-dimensional (3D) stereophotogrammetry by comparing it with the direct anthropometry and digital photogrammetry methods. The reliability of 3D stereophotogrammetry was also examined. Six profile and four frontal parameters were directly measured on the faces of 80 participants. The same measurements were repeated using two-dimensional (2D) photogrammetry and 3D stereophotogrammetry (3dMDflex System, 3dMD, Atlanta, Ga) to obtain images of the subjects. Another observer made the same measurements for images obtained with 3D stereophotogrammetry, and interobserver reproducibility was evaluated for 3D images. Both observers remeasured the 3D images 1 month later, and intraobserver reproducibility was evaluated. Statistical analysis was conducted using the paired samples t-test, intraclass correlation coefficient, and Bland-Altman limits of agreement. The highest mean difference was 0.30 mm between direct measurement and photogrammetry, 0.21 mm between direct measurement and 3D stereophotogrammetry, and 0.5 mm between photogrammetry and 3D stereophotogrammetry. The lowest agreement value was 0.965 in the Sn-Pro parameter between the photogrammetry and 3D stereophotogrammetry methods. Agreement between the two observers varied from 0.90 (Ch-Ch) to 0.99 (Sn-Me) in linear measurements. For intraobserver agreement, the highest difference between means was 0.33 for observer 1 and 1.42 mm for observer 2. Measurements obtained using 3D stereophotogrammetry indicate that it may be an accurate and reliable imaging method for use in orthodontics.

Reproducibility of aortic annulus measurements by computed tomography.

To evaluate a systematic approach for measurement of aortic annulus dimensions by cardiac computed tomography. CT data sets of 64 patients were evaluated. An oblique cross-section aligned with the aortic root was created by systematically identifying the caudal insertion points of the three aortic cusps and sequentially aligning them in a double oblique plane. Aortic annulus dimensions, distances of coronary ostia and a suitable fluoroscopic projection angle were independently determined by two observers. Interobserver intraclass correlation coefficients (ICC) for aortic annulus diameters were excellent (ICC 0.89-0.93). Agreement for prosthesis size selection was excellent (ĸ = 0.86 for mean, ĸ = 0.84 for area-derived and ĸ = 0.91 for circumference-derived diameter). Mean distances of the left/right coronary ostium were 13.4 ± 2.4/14.4 ± 2.8 mm for observer 1 and 13.2 ± 2.7/13.5 ± 3.2 mm for observer 2 (p = 0.30 and p = 0.0001, respectively; ICC 0.76/0.77 for left/right coronary artery). A difference of less than 10° for fluoroscopic projection angle was achieved in 84.3% of patients. A systematic approach to generate a double oblique imaging plane exactly aligned with the aortic annulus demonstrates high interobserver and intraobserver agreements for derived measurements which are not influenced by aortic root calcification. • Systematic approach to generate a double oblique imaging plane for TAVI evaluation. • This method is straightforward and software independent. • An approach with high reproducibility, not influenced by aortic root calcification.

Optimal Technique for Imaging Iliac Segments During Endovascular Repair of Abdominal Aortic Aneurysms

To determine if oblique angulation of the image intensifier is adequate to image the entire length of the common iliac artery during endovascular aneurysm repair or if additional caudal tilt is necessary. Using a 3D workstation, the apparent level of the iliac bifurcation (distal limit of the stent-graft) was determined on computed tomographic angiography by profiling the common iliac segment in oblique angulation only and repeated with a combination of oblique angulation and caudal tilt. Two independent observers measured twice the apparent length of the iliac segment in both profiles for 50 patients according to a set protocol. Intra- and interobserver variability was calculated using the Bland and Altman method; the differences between the two different profiles were tested using paired t tests. Of the 50 CTA datasets reviewed, 2 datasets were excluded owing to extensive calcification of the iliac system that prevented accurate interpretation of the image. Of the 96 segments studied, the iliac segments appeared longer (better profiled) with a combination of caudal tilt and oblique angulation in 80%, with an average discrepancy of 9 mm for observer 1 (range -1 to +28) and 7 mm for observer 2 (0 to +26). The effect of caudal tilt was statistically significant for individual observers (p = 0.001 and 0.024, respectively). Forty-six percent of iliac segments measured by observer 1 and 35% by observer 2 showed that the addition of caudal tilt resulted in improved profiling by at least 10 mm. Although inter- and intraobserver variation was significant, the gain in apparent iliac length with the addition of caudal tilt was preserved. When profiled with oblique angulation alone, the location of the iliac bifurcation may appear higher than its true location, resulting in underutilization of the iliac segment by >10 mm in over a third of the patients. The problem is corrected by employing additional caudal tilt.

Comparability and Intra-/Interobserver Reliability of Anterior Chamber Depth Measurements With the Pentacam and IOLMaster

Purpose To assess the comparability and intra-/interobsever reliability of central anterior chamber depth measurements obtained using the Pentacam and IOLMaster. Methods Anterior chamber depth was measured in 50 eyes (25 healthy volunteers)—three times on each eye by two independent observers with each method. A total of 12 measurements were performed on each eye. Analysis of variance was used to analyze the data. Mean values, standard deviations, and confidence limits (95% confidence interval) of the two modalities, two observers, and every observer/modality interaction were calculated. Results The mean anterior chamber depth values were 3.23±0.031 mm for the IOLMaster and 3.21±0.033 mm for the Pentacam. No statistically significant difference was noted in measurements between the two modalities ( P =.291) or between the two observers ( P =.903). Observer/modality interaction was not significant ( P =.643). The confidence limits for observer 1 were 3.223±0.03 mm and 3.226±0.03 mm for observer 2. The confidence limits were: observer 1/IOLMaster, 3.23±0.04 mm; observer 2/IOLMaster, 3.24±0.04 mm; observer 1/Pentacam, 3.21±0.04 mm; and observer 2/Pentacam, 3.20±0.04 mm. The differences in measurements ranged from −0.14 to +0.10 mm for the IOLMaster and from −0.08 to +0.12 mm for the Pentacam. The worst deviation from the average eye reading of 3.23 mm was only 0.14 (4.3%). Conclusions Good agreement exists between anterior chamber depth measurements by the IOLMaster and Pentacam in the assessment of normal eyes, and they offer observer-independent results. Therefore, the modalities are interchangeable. [ J Refract Surg . 2008;24:615–618.]

Comparison of scotopic pupil measurement with slitlamp-based cobalt blue light and infrared video-based system

Purpose To determine the accuracy and reproducibility of scotopic pupil measurements with a slitlamp-based cobalt blue light. Setting University of Texas Health Science Center−San Antonio, San Antonio, Texas, USA. Methods In a prospective experimental study, 2 independent observers measured 16 subjects’ pupils with a standard slitlamp-based cobalt blue light. In the same setting, the accuracy and reproducibility of the measurements were compared with those obtained with an infrared video-based system. Results Measurements of pupil size using the infrared video−computer system were highly reproducible. With the slitlamp-based cobalt blue light, the 2 measurements obtained by observer 2 (n = 16) were very close to each other (mean difference 0.09 mm ± 0.23 [SD]; P = .12), whereas those obtained by observer 1 (n = 16) were slightly different from each other (mean difference 0.18 ± 0.33 mm; P = .043). The mean pupil diameter measured with cobalt blue light was not significantly different between the 2 observers ( P > .05), and the measurements were highly correlated with each other ( r = 0.96, P < .01). The mean difference between the measurements using cobalt blue light and the infrared video−computer system was 0.21 ± 0.54 mm for observer 1 ( P = .47) and 0.06 ± 0.47 mm for observer 2 ( P = .85). Good correlation was noted between the measurements taken from each measuring device for both observers ( r = 0.87 and 0.90, P < .01). Conclusion Slitlamp-based cobalt blue light provided a reasonably good measurement of scotopic pupil size. It correlated well with the infrared video system when used at the lowest setting by experienced personnel. However, the observed difference between the measurements obtained by the 2 devices indicates that the cobalt blue light should be used cautiously in the refractive surgery preoperative evaluation of patients with large pupils.

Intra- and interobserver reproducibility of ultrasound measurements of cervical length and width in the second and third trimesters of pregnancy.

To determine intra- and interobserver reproducibility of ultrasound measurements of cervical length and width in the second and third trimesters of pregnancy. Twenty healthy women in the second or third trimester of pregnancy underwent transvaginal ultrasound examination of the cervix by two examiners. Three replicate meaurements of cervical length and width were taken by each observer for each woman. Intraobserver repeatability was expressed as the difference between the highest and lowest measurement value obtained by one observer, and as the repeatability coefficient and intraclass correlation coefficient. Interobserver reproducibility was expressed as the difference between the mean of the three measurements of each observer, limits of agreement, and interclass correlation coefficient. The repeatability coefficient/limits of agreement define the range within which 95% of the differences between two measurements by the same observer/two observers are likely to fall. Intra- and interobserver differences did not vary in any systematic way over the range of values measured. For cervical length measurements the repeatability coefficient was +/- 5.4 mm for Observer 1 and +/- 5.9 mm for Observer 2. The intraclass correlation coefficient for cervical length measurements was 0.93 for both observers. The corresponding coefficients for cervical width measurements were +/- 3.9 mm and +/- 7.3 mm, and 0.97 and 0.91. The interclass correlation coefficient for cervical length measurements was 0.76, the mean interobserver difference was 0.4 mm, and the limits of agreement were -10.0 mm to 10.8 mm. For cervical width measurements the interclass correlation coefficient was 0.74, the mean interobserver difference was -0.02 mm, and the limits of agreement were -12.4 mm to 12.4 mm. There was no systematic difference between the first, second and third cervical length measurements and no systematic bias between the two observers, and the results were not affected by which of the two examiners started the examination (three-way analysis of variance). The same was true of cervical width measurements. Our results do not support the contention that the first measurement of cervical length is the longest. There is substantial intra- and interobserver variability in the results of measurements of cervical length and width, even when experienced observers perform the measurements under standardized conditions. It is important to consider the possibility of 'measurement error' when ultrasound measurements of cervical length and width are used in clinical practice to monitor women at high risk of delivering preterm or to screen for preterm birth.

Automated edge-detection technique for measurement of brachial artery reactivity: a comparison of concordance with manual measurements

Concerns have been raised about the reproducibility of brachial artery reactivity (BAR), because subjective decisions regarding the location of interfaces may influence the measurement of very small changes in lumen diameter. We studied 120 consecutive patients with BAR to address if an automated technique could be applied, and if experience influenced reproducibility between two observers, one experienced and one inexperienced. Digital cineloops were measured automatically, using software that measures the leading edge of the endothelium and tracks this in sequential frames and also manually, where a set of three point-to-point measurements were averaged. There was a high correlation between automated and manual techniques for both observers, although less variability was present with expert readers. The limits of agreement overall for interobserver concordance were 0.13 ± 0.65 mm for the manual and 0.03 ± 0.74 mm for the automated measurement. For intraobserver concordance, the limits of agreement were − 0.07 ± 0.38 mm for observer 1 and − 0.16 ± 0.55 mm for observer 2. We concluded that BAR measurements were highly concordant between observers, although more concordant using the automated method, and that experience does affect concordance. Care must be taken to ensure that the same segments are measured between observers and serially. (E-mail: tmarwick@medicine.pa.uq.edu.au)

A simple and reproducible method for assessing intimal-medial thickness of the common carotid artery.

Intimal-medial thickness (IMT) of the inner arterial wall is a marker for early changes of atherosclerosis. In order to assess the IMT of the common carotid artery (CCA), two observers (A and B) examined the far wall of both CCAs of three groups of 10 healthy volunteers on two occasions, separated by a period of 2 weeks. Each observer examined one group, then both examined a third group (A, B and interobserver groups). The distance between the two echogenic lines representing the IMT of the arterial wall of the distal CCA was measured within 1 cm proximal to the carotid bulb. The maximal IMT at this site in the right and left CCAs was measured three times on each side and a mean value calculated. The mean of the absolute value of differences between both assessments was 0.027 mm for observer A, 0.027 mm for observer B and 0.0480 mm between observers. The calculated coefficient of variation was 5.02% for observer A, 5.70% for observer B and 8.98% between observers. The coefficient of repeatability was, 0.074 mm for observer A, 0.070 mm for observer B and 0.128 mm between observers. This method for estimating the IMT provides a reproducible and reliable measurement suitable for routine practice.

Sonographic measurement of renal length in children: does the position of the patient matter?

This prospective study was designed to determine the effect of patient positioning on sonographic measurements of renal length in children. Materials and methods. Two dedicated pediatric ultrasonographers (observers A and B) measured the sonographic lengths of 48 kidneys in 25 children (two had unilateral renal agenesis). Each observer obtained the two "longest possible" measurements for each kidney with the patient in three positions: supine, contralateral decubitus, and prone. Patients with myelomeningocele, hydronephrosis, and renal cysts were excluded. Both examiners obtained significantly higher values for renal lengths with the children lying supine (observer A P </= 0.0017; observer B P </= 0.0409) or in contralateral decubitus (observer A P </= 0.0001; observer B P </= 0.0419) than with them lying prone. There was no significant difference between the supine and decubitus measurements. The mean difference between the supine and prone measurements for the observers was 3.0 mm for observer A and 1.8 mm for observer B. The mean difference between the contralateral decubitus and prone measurements was 3.0 mm for observer A and 1.6 mm for observer B. Sonographic measurements of renal length made with the patient lying supine or in contralateral decubitus yield slightly higher values than those made with the patient prone.