Oblique Angulation Research Articles

Two‐dimensional quantitative coronary angiographic models for bifurcation segmental analysis

Quantitative coronary angiography (QCA) analysis for bifurcation lesions needs to be standardized. In vitro validation of two models for bifurcation QCA segmental analysis. In the latest edition of the Cardiovascular angiography analysis system (CAAS 5v8, Pie Medical Imaging, Maastricht, The Netherlands) a 6-segment model for two-dimensional coronary bifurcation analysis was implemented next to the currently available 11-segment model. Both models were validated against 6 precision manufactured plexiglas phantoms, each of them mimicking a vessel with three successive bifurcation lesions with variable anatomy and Medina class. The phantoms were filled with 100% contrast agent and imaged with a biplane gantry. Images acquired in antero-posterior (AP) direction by either C-arm and at 30° right and left anterior oblique angulation were analyzed by two independent analysts, blinded to the actual dimensions. Manual correction of the contours was not allowed. Measurements for minimal lumen diameter (MLD), reference vessel diameter (RVD), percent diameter stenosis (DS) and bifurcation angle (BA) were compared with the true phantom dimensions. In AP views the accuracy and precision (mean difference ± SD) of 11- and 6-segment model for MLD, RVD, and DS were 0.065 ± 0.128 mm vs. 0.058 ± 0.142 mm, -0.021 ± 0.032 mm vs. -0.022 ± 0.030 mm, and -2.45% ± 5.07% vs. -2.28% ± 5.29%, respectively. Phantom MLD values ≤ 0.7 mm were systematically overestimated; if excluded, MLD accuracy and precision became 0.015 ± 0.106 mm and 0.004 ± 0.125 mm for the 11- and 6-segment model, respectively. Accuracy and precision for BA were -2.2° ± 3.3°. Interobserver variability for MLD, RVD, DS, and BA for either model was ≤ 0.049 mm, ≤ 0.056 mm, ≤ 2.77%, and 1.6°, respectively. Agreement between models for MLD, RVD, and DS was ± 0.079 mm, ± 0.011 mm, and ± 2.07%. Accuracy and precision for diameter-derived parameters were slightly decreased in angulated projections; precision for BA measurements dropped to 6.1°. The results of both models are highly reproducible and for phantom MLD values >0.7 mm in excellent agreement with the true dimensions.

Qualitative and quantitative evaluation of root injury risk potentially burdening insertion of miniscrew implants

Objective: Microscrew implants (MSIs) offer many advantages, but some complications are known to occur during their insertion. One of the most commonly reported complications is root injury. Our aim was to identify factors associated with root injury and to evaluate their qualitative and quantitative values. Methods: Thirty-five orthodontists placed MSIs (AbsoAnchor ⓡ , Dentos Co. Ltd, Daegu, Korea) in the upper jaw of typodonts, labially between the second premolar and the first molar, in low and high vertical positions. Root contacts were counted, and distances between MSI apices and roots were measured. Fear level of the orthodontists was surveyed before and after the experiment. Wilcoxon’s test, chi-square test, and Mann-Whitney test were used for statistical analysis. Results: Overall root contact rate of MSI insertion was 23.57%. The root contact rate was significantly higher in MSIs inserted at 90° (45.71%) than at 30° (1.43%). The distance between the dental root and MSI also increased significantly in MSIs inserted at 30°. Mean fear level before MSI insertion (4.6) significantly decreased after insertion (3.2); the causative factors were risk of injury to dental root and maxillary sinus or mandibular canal. Conclusions: Root injury is relatively rare, and oblique angulation reduces the risk of root and MSI contact.

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.

Dr Ganguli and colleauges respond

Dr Ganguli and colleauges respond

Anatomy of the Left Atrial Appendage

Anatomy of the Left Atrial Appendage

Radiation-reducing planning of cardiac catheterisation

Any radiation exposition for medical purposes should be kept as low as is reasonably achievable. Mean patient radiation exposure of diagnostic cardiac catheterisation is high (16-106 Gy x cm2) and for this reason the International Commission on Radiological Protection (ICRP) recommends credentialing radiation protection training programmes. Twenty cardiologists each documented various dose parameters of 10 cardiac catheterisations, before and after a 90-minute mini-course of the ELICIT study group ("Encourage to Less Irradiating Cardiologic Interventional Techniques"), and could achieve a reduction of the mean dose-area product by 15.9+/-9.0 Gy x cm2, equivalent to 47%. The presented radiation-reducing planning of invasive cardiac catheterisation for this reason is the first one validated in clinical routine and consists of 6 standard runs--one for the left ventricle, 3 and 2 for the left (LCA) and right coronary artery (RCA), respectively--depending on anatomy and findings supplemented by 1...4 special projections. The caudal posteroanterior (PA) view documents the left coronary main stem, proximal and distal left anterior descending artery (LAD), and proximal and mid circumflex segments. The cranial PA view however is suitable for the left coronary orifice, circumflex periphery, LAD, all diagonal bifurcations, and collateral pathways towards the RCA. LCA standard angiography is completed by lateral 90 degrees/0 degrees left anterior oblique (LAO) angulation. The 60 degrees/0 degrees LAO angulation visualises the right posterolateral artery (RPL) and the RCA to its bifurcation. The more proximal one finds the bifurcation, the more the second standard cranial PA view for RCA should vary towards the cranial right anterior oblique (RAO) and finally 30 degrees/0 degrees RAO view. The efficiency of these less-irradiating angulations are improved by radiation-reducing techniques as follows: restriction to essential radiographic frames and runs, consistent collimation to the region of interest--particularly during coronary intubation--, adequate instead of best possible image quality, short skin-to-image-intensifier distance, inspiration during radiography, preference for projections that rotate out the spine, optimisation of fluoroscopy time, well-experienced and well-rested interventionists.

A Novel Technique for Pudendal Nerve Block

Pudendal nerve block is performed to confirm the diagnosis of pudendal neuralgia. Many physicians and patients are hesitant to pursue diagnostic nerve blocks to confirm the diagnosis of pudendal neuralgia secondary to significant patient discomfort, the need for special equipment, and the risk in the traditionally described approach. To describe a novel technique for pudendal nerve block with minimal risk and decreased patient discomfort. With the patient in the prone position, the C-arm is projected in the anteroposterior position until the pelvic inlet is visualized. Subsequently, the ischial spine is highlighted by 5 to 15 degree ipsilateral oblique angulation of the fluoroscope. A 25-gauge 3.5 cm needle is advanced to the tip of the ischial spine where the pudendal nerve transiently leaves the pelvis. The pudendal nerve block is performed at this level. We described a new and novel technique to block pudendal nerve under fluoroscopic visualization safely with increased patient comfort.

Interactive selection of optimal section orientations using real-time MRI.

In applications where precise image section positioning is vital, the interactive section rotation and offset capabilities of interactive MRI should be valuable. However, due to the independent nature of these two adjustments, the desired structure may often not be visible in the image after a rotation. Valuable time is wasted during relocation. An algorithm is presented that automatically alters the section offset after a rotation to provide continuous viewing of a marked structure, greatly improving section orientation efficiency. The technique is illustrated in the determination of double oblique angulation for through-plane imaging of the portal vein. This algorithm is expected to prove useful in applications of interactive MRI requiring precise positioning.

Modifying fluoroscopic views reduces operator radiation exposure during coronary angioplasty

Objectives. This three-part study examined the feasibility of reducing operator radiation exposure during coronary angioplasty.Background. As case loads and complexity increase, some cardiologists are receiving increasing radiation scatter doses. Techniques to reduce this are therefore becoming more important.Methods. First, the determinants of the operator dose were assessed by measuring the differences in scatter dose with different camera views. The relative contribution of fluoroscopy as opposed to cine was then quantified. Finally, operators were provided with these data, and subsequent changes in technique were evaluated.Results. Left anterior oblique views resulted in 2.6 to 6.1 times the operator dose of equivalently angled right anterior oblique views. Increasing steepness of the left anterior oblique view also resulted in a progressive increase in operator dose, with left anterior oblique 90 ° causing eight times the dose of left anterior oblique 30 ° and three times that of left anterior oblique 60 °. In the 45 coronary angioplasly cases prospectively analyzed, fluoroscopy was found to be a greater source of total radiation than cine by a 6.3:1 ratio (range 1.1 to 15.8). Once operators were made aware of the importance of left anterior oblique fluoroscopy, there was a marked reduction in its use. When this was not feasible, there was a reduction in the steepness of the angulation. Left anterior oblique fluoroscopy during angioplasty of the left anterior descending and circumflex coronary arteries was reduced from 40% of total screening time to ~5%, and left anterior oblique angulation for fluoroscopy during angioplasty of the right coronary artery decreased from 43.6 ° (± 9.1 °) to 29.4 ° (± 2.2 °). Success rates (90% vs. 89%) and screening times (19.5 vs. 20.7 min) remained unchanged in 200 coronary angioplasties performed after the study. Average operator radiation dose (Measured by radiation badges worn under lead at waist level) was reduced from 32.6 to 14.3 J μSv/operator per week despite a slight increase in case load.Conclusions. Fluoroscopy is the major source of total radiation exposure during coronary angioplasty, with left anterior oblique views providing the highest dose. Modification of views is feasible and will result in significant reduction of operator radiation dose.

End-on aortogram: improved identification of important coronary artery anomalies in tetralogy of Fallot.

To identify coronary artery anomalies in patients with tetralogy of Fallot with an aortogram taken with steep caudal and left oblique angulation ("end-on" aortogram). Prospective evaluation of end-on aortogram in the preoperative angiographic assessment of consecutive patients with tetralogy of Fallot. Regional paediatric cardiology centre. 34 patients, aged 3 months to 12 years (median age 9 months). An aortogram was performed with steep caudal (38 degrees-45 degrees) and left oblique (0 degrees-30 degrees) angulation under general anaesthetic as part of routine preoperative angiographic assessment. The origins and courses of the coronary arteries were visualised in all patients and important coronary artery anomalies were identified in four patients: single left coronary artery; single right coronary artery (two patients); separate high origin of left anterior descending. These anomalous coronary vessels crossed the right ventricular outflow tract. It is important to identify preoperatively coronary arteries that may interfere with right ventricular outflow tract reconstruction. An aortogram with steep caudal and left oblique angulation is useful in identifying anomalous coronary arteries and more importantly it defines the relation of these vessels to the right ventricular outflow tract.

Use of standard gradients with compound oblique angulation for optimal quantitative MR flow imaging in oblique vessels.

The earliest described phase-modulation techniques for flow quantification by MR imaging require a phase image obtained by modifying one of the imaging gradients and a reference phase image obtained without the modified gradient. However, by using the same gradients that are used for routine two-dimensional Fourier transform imaging, both anatomic and velocity-encoded images can be obtained in one scan. Although convenient, this technique is sensitive to flow both within and perpendicular to the imaging plane. Consequently, significant errors occur in the measurement of flow in vessels oblique to the image plane. To determine the relative accuracy and practicality of quantitatively measuring flow in oblique vessels, we used standard sequence gradients with routine orthogonal plane imaging and direct compound oblique plane imaging. Phantom studies of flow in a vessel aligned along the z axis showed a significant linear correlation (r = .999; p less than .05) between the spin phase and spin velocity. However, studies of flow at relatively low physiologic rates (12-17 cm/sec) in vessels angled 0-30 degrees off axis showed that obliquities of as little as 10 degrees result in significant quantification errors. This is due to a larger phase shift per unit velocity along the frequency-encoding direction vs along the slice-select direction and to a mixture of velocities within a voxel that is oblique to the flow direction. In most instances, resolution of these errors can be achieved satisfactorily only by electronic plane rotation with compound oblique angulation so that the image plane and vessel are perpendicular. When so used, this technique potentially might provide important adjunctive quantitative flow data in oblique vessels during routine clinical imaging.

Evaluation of peripheral vascular disease using digital subtraction angiography.

Intravenous digital subtraction angiography (DSA) facilitates imaging of peripheral arteries and bypass grafts on an outpatient basis. Forty-five patients underwent intravenous peripheral angiography, 16 following placement of bypass grafts. Complex oblique and sagittal angulations optimize visualization of bifurcations and overlapping vascular structures. Reprocessing techniques using integrated masks and contrast images allow for diagnostic delineation of fine vascular detail. This is a practical, noninvasive, well tolerated method for both diagnostic screening and follow-up evaluation of patients with peripheral vascular disease.

Assessment of patent ductus arteriosus in preterm infants by single lateral film aortography.

Differentiation of a hemodynamically significant cardiovascular abnormality from lung disease in the newborn infant may remain problematic after clinical, radiographic, and echocardiographic evaluation. Single-view aortography was performed in 38 preterm and one full term infant in the neonatal special care nursery. Special lateral views were obtained consisting of either a horizontal x-ray beam with oblique angulation of the supine patient or a vertical bean with 30 degree head-up angulation of the patient. These views projected the ductus caudal to the aortic arch and enabled visualization of the entire length of the ductus and focal constrictions of the ductus. The severity of patent ductus arteriosus was judged by anatomic (diameter of the ductus compared to the descending aorta) and physiologic (preferential opacification of the aortic arch or pulmonary circulation) criteria.

Specification of angulated projections in coronary arteriography.

In coronary arteriography cranial and caudal angulations are combined with oblique angulations to obtain additional views. The angulations are obtained with a variety of equipment rotating about different axes. The planes and axes in and about which the patient and equipment rotate are defined and the equipment is grouped according to the axes about which it rotates. It is shown that a simple definition of the angulation of a projection may be obtained using concepts and terminology consistent with current radiological practice. One group of equipment then gives directly from the rotation of its component parts the angles specifying the projection. For other equipment, the angles specifying the projection are calculated and tabulated for angles of rotation of the equipment from 0 to 90 degrees. Thus, equivalent projections for the different equipment may be found and compared.