CT angiography in complex upper extremity reconstruction.

Computed tomography angiography is a new technique that provides high-resolution, three-dimensional vascular imaging as well as excellent bone and soft tissue spatial relationships. The purpose of this study was to examine the use of computed tomography angiography in planning upper extremity reconstruction. Seventeen computed tomography angiograms were obtained in 14 patients over a 20-month period. All studies were obtained on an outpatient basis with contrast administered through a peripheral vein. All the studies demonstrated the pertinent anatomy and the intraoperative findings were as demonstrated in all cases. Information from two studies significantly altered pre-operative planning. The average charge for computed tomography angiography was 1,140 dollars, compared to 3,900 dollars for traditional angiography.

Three-dimensional CT evaluation for endovascular abdominal aortic aneurysm repair. Quantitative assessment of the infrarenal aortic neck.

Endovascular grafting of abdominal aortic aneurysms should be offered only to those patients with suitable anatomy. This is especially true at the level of the proximal aortic neck in order to secure long-term proximal fixation. Aortoiliac anatomy is easy to understand conceptually, however, it is difficult to define and measure quantitatively. In this article, we discuss the use of three dimensional computed tomographic angiography to determine aneurysm morphology and select patients for endovascular repair. Specifically, we apply our methods to define and measure angulation of the aorta and iliac arteries. The anatomic definition of the angulation of the proximal aortic neck is emphasized.

Aortoiliac angulation and the need for secondary procedures to secure stent graft fixation: which angle is important?

BACKGROUND: The purpose of this study was to quantify the degree of aortoiliac tortuosity and determine the relationship between aortoiliac angulation and the need for a secondary procedure following endovascular repair. METHODS: Among 206 patients treated with the AneuRx stent graft, 3-year follow up data were available in 71 patients. Twenty eight patients without duplex and CT angiograms (CT angiography) on follow-up were excluded. The anatomy of the preoperative proximal aortic neck was evaluated using 3D-CT angiography reconstructed images in: a) Group I: 15 patients who required secondary procedures and b) Group II: 18 patients without any endovascular leak during follow up. The groups did not differ in age (72.9+/-6.1 versus 73.3+/-9.1) or aneurysm diameter (60.1+/-9.1 versus 60.5+/-10.1). In order to determine the aortoiliac tortuosity, we measured: a) the suprarenal aorta-infrarenal aortic neck angle: angle of the aorta at the level of the renal arteries, b) infrarenal aortic neck-aneurysm angle: angle of the aorta at the start of aneurysm, c) right iliac angle, d) left iliac angle, e) aortic neck length, f) aortic neck diameter. RESULTS: Computer-based measurements on 3D-CT angiography reconstructed images were: a) suprarenal aorta-infrarenal aortic neck angle: group I: (22.6+/-16.2), group II: (11.9+/-6.9), p<0.05; b) infrarenal aortic neck-aneurysm angle: group I: 17.6+/-12.4, group II: 18.8+/-9.4, p=NS; c) right iliac angle: group I: 22.9+/-12.6, group II: 20.4+/-9.5, p=NS; d) left iliac angle: group I: 22.4+/-10.5, group II: 19.1+/-12.2, p=NS; e) aortic neck length: group I: 18.9+/-5.3 mm, group II: 20.4+/-5.3 mm, p=NS; f) aortic neck diameter: group I: 24.1+/-1.0 mm, group II: 23.3+/-1.6, p=NS. CONCLUSIONS: Aortoiliac angulation can be defined and quantified. In patients requiring secondary procedures, there is an increased angulation at the proximal aortic neck angle.

Type-II endoleaks following endovascular AAA repair: preoperative predictors and long-term effects.

PURPOSE: To determine the significance of persistent type-II endoleaks and whether they can be predicted preoperatively in patients with abdominal aortic aneurysms (AAA). METHODS: The charts of all AAA patients treated with the AneuRx stent-graft at a single center from 1996 to 1998 were reviewed. Patients with <12-month follow-up or type-I endoleaks were excluded. The presence or absence of type-II endoleaks was determined from duplex imaging and computed tomographic angiography. Three groups were identified and compared: 16 patients with persistent type-II endoleaks (PE), 14 patients with transient type-II endoleaks (TE), and 16 patients with no endoleak (NE). RESULTS: The groups did not differ with regard to age, preoperative comorbidities, follow-up time, and AAA neck diameter and length. AAA diameters were 57.1 +/- 9.0 mm for NE, 63.4 +/- 11.4 mm for TE, and 55.6 +/- 4.2 mm for PE. The inferior mesenteric artery (IMA) was patent in 5 (31%) NE patients, 6 (43%) TE patients, and 13 (81%) PE patients (p < 0.01). The number of patent lumbar arteries visualized preoperatively was 0.5 +/- 1.0 in NE, 1.3 +/- 0.8 in TE, and 2.4 +/- 0.6 in PE (p < 0.0001). Patent IMAs (RR 0.82, p < 0.01) and >2 lumbar arteries (RR 0.40, p < 0.0001) were identified as independent preoperative risk factors for persistent endoleaks. There were no changes in mean diameter or volume in aneurysms with persistent endoleaks. CONCLUSIONS: No adverse clinical events were related to the presence of type-II endoleaks, but there was no decrease in aneurysm size in patients with persistent type-II leaks. Patients with a large, patent IMA, or >2 lumbar arteries on preoperative CT angiography are at higher risk for persistent type-II endoleaks.

Impact of aortoiliac tortuosity on endovascular repair of abdominal aortic aneurysms: evaluation of 3D computer-based assessment.

OBJECTIVE: The purpose of this study was to examine the effect of aortoiliac tortuosity, as assessed by observers and 3-dimensional (3D) computer-based methods, on the conduct and outcome of endovascular repair of abdominal aortic aneurysms. METHODS: Infrarenal aortoiliac tortuosity was measured in 75 patients (mean follow-up, 14.8 +/- 10.4 months) who underwent endovascular repair of abdominal aortic aneurysms by using the following four methods: (1) grading by 2 experienced observers; (2) tortuosity index measured as the inverse radius of curvature (cm(-1)) at 1-mm intervals along the median luminal centerline (MLC) on 3D reconstructions of computed tomography (CT) angiograms and was calculated as the sum of values greater than 0.3 cm(-1); (3) MLC-straight line length ratio from renal to hypogastric arteries; (4) manual measurement of angles at points of angulation on anteroposterior and lateral projections of 3D CT reconstructions. In evaluating association between these measures, correlation between human observers was accepted as the gold standard. RESULTS: For rating of overall aortoiliac tortuosity, interobserver correlation (r = 0.67) was comparable with correlation of observers with tortuosity index (r = 0.67 and 0.56), whereas correlations of each observer with MLC-straight line ratio (r = 0.50 and 0.56) and cumulative angulation (r = 0.44 and 0.44) were significant but weaker. For determining the relative tortuosity of right and left aortoiliac access, agreement between observers and tortuosity index (54% and 58%; P < .05; kappa, 0.33 and 0.38) was not as good as between observers (68%; P < .001; kappa, 0.53). This difference was primarily related to evaluation of the aorta, where interobserver correlation (r = 0.71) was better than that between each observer and tortuosity index (r = 0.47 and 0.55), whereas correlations in the iliac arteries were comparable (r = 0.64 and 0.67) (all coefficients P < .01). Increased tortuosity was associated with a more complex endovascular repair, as reflected by longer fluoroscopy time (P = .05), use of more contrast material (P = .03), use of extender modules (P = .04), and more frequent use of arterial reconstruction (P = .01), but was not associated with a higher overall complication rate. Increased tortuosity, when it occurred in the aortic neck, was associated with predischarge endoleak (P = .03) but not with late endoleak, intervention, or aneurysm-related adverse events. CONCLUSION: Aortoiliac tortuosity is associated with increased complexity of endovascular aneurysm repair and with predischarge endoleak but does not appear to affect intermediate-term results. Computer-based 3D measurement of aortoiliac tortuosity is feasible and clinically meaningful. Its ultimate role in relation to human assessment must be further defined in future studies.

Multi-detector row CT angiography of lower extremity arterial inflow and runoff: initial experience.

PURPOSE: To assess the patterns of lower extremity arterial inflow and runoff opacification with four-channel multi-detector row computed tomographic (CT) angiography in a cohort of patients with disease warranting imaging of the lower extremity arterial system. MATERIALS AND METHODS: Twenty-four patients with symptomatic lower extremity arterial occlusive or aneurysmal disease underwent imaging with four-channel multi-detector row CT from the supraceliac abdominal aorta through the feet. Transverse sections were acquired with a 2.5-mm nominal detector width and pitch of 6.0 (3.2-mm effective section thickness) following intravenous injection of 174-185 mL of iodinated contrast medium (300 mg iodine per milliliter). In each patient, attenuation measurements were recorded in 16 arterial and 16 venous locations. In 18 patients, two radiologists assessed the detectability and stenosis degree of 21 arterial segments per patient relative to these features at conventional angiography. RESULTS: A mean scanning time of 66 seconds was required to cover a mean of 1,233 mm, resulting in a mean of 908 transverse reconstructions. All 504 arterial segments were depicted and analyzable. Mean arterial attenuation ranged from 253 HU in the midabdominal aorta to 357 HU in the popliteal artery and 253 HU in the dorsalis pedis or posterior tibial artery measured inferior to the tibiotalar joint. Maximum mean venous enhancement (99 HU) was observed in the saphenous vein at the ankle, with all other venous stations measuring less than 74 HU. CONCLUSION: The arteries of lower extremity inflow and runoff can be reliably depicted with minimal venous enhancement by using multi-detector row CT.

Prediction of aortoiliac stent-graft length: comparison of measurement methods.

PURPOSE: To determine the accuracy of helical computed tomography (CT), projectional angiography derived from CT angiography, and intravascular ultrasonographic withdrawal (IUW) length measurements for predicting appropriate aortoiliac stent-graft length. MATERIALS AND METHODS: Helical CT data from 33 patients were analyzed before and after endovascular repair of abdominal aortic aneurysm (Aneuryx graft, n = 31; Excluder graft, n = 2). The aortoiliac length of the median luminal centerline (MLC) and the shortest path (SP) that remained at least one common iliac arterial radius away from the vessel wall were calculated. Conventional angiographic measurements were simulated from CT data as the length of the three-dimensional MLC projected onto four standard viewing planes. These predeployment lengths and IUW length, available in 24 patients, were compared with the aortoiliac arterial length after stent-graft deployment. RESULTS: The mean error values of SP, MLC, the maximum projected MLC, and IUW were -2.1 mm +/- 4.6 (SD) (P =.013), 9.8 mm +/- 6.8 (P <.001), -5.2 mm +/- 7.8 (P <.001), and -14.1 mm +/- 9.3 (P <.001), respectively. The preprocedural prediction of the postprocedural aortoiliac length with the SP was significantly more accurate than that with the MLC (P <.001), maximum projected MLC (P <.001), and IUW (P <.001). CONCLUSION: The shortest aortoiliac path length maintaining at least one radius distance from the vessel wall most accurately enabled stent-graft length prediction for 31 AneuRx and two Excluder stent-grafts.

Utility of three-dimensional volume rendering images using electron-beam computed tomography to evaluate possible causes of ischemia from an anomalous origin of the right coronary artery from the left sinus of valsalva.

The present study evaluated the usefulness of 3-dimensional volume rendering (VR) images using electron-beam computed tomography (EBCT) in determining the possible causes of ischemia resulting from the anomalous origin of the right coronary artery (RCA) from the left sinus of Valsalva, which coursed between the ascending aorta and pulmonary trunk. Such anomalies could cause ischemia or sudden death without obstructive coronary artery disease. The suggested mechanism is either compression causing closure of the slit-like orifice of the anomalous artery as the aorta dilates with exertion or compression of the anomalous artery by the aorta and pulmonary trunk as it courses between these 2 arteries, which dilate with exercise. A 17-year-old male underwent EBCT coupled with a 100-ml intravenous injection of iodinated contrast medium. Data were reconstructed into 3-dimensional images through VR to evaluate the shape of the orifice and the spatial relationship of the RCA, ascending aorta and pulmonary trunk. Perspective VR showed the shape of the orifice of the left main trunk, which was not slit-like, and cut-plane VR showed the spatial relationship of both the lumen and the surface of the RCA, ascending aorta and pulmonary trunk, providing information on whether the ascending aorta or pulmonary trunk would compress the RCA and cause ischemia.

Direct identification of patency achieved by a bi-directional Glenn shunt procedure: images by volume rendering using electron-beam computed tomography.

The present study aimed to identify the patency achieved by a bi-directional Glenn shunt procedure by shaded volume rendering (VR) images using electron-beam computed tomography (EBCT). A Damus Kay-Stanzel type procedure was performed on a female with hypoplastic left heart syndrome who later received a bi-directional Glenn shunt to increase pulmonary blood flow. In considering the characteristics of the bi-directional Glenn shunt procedure, in which the superior vena cava is connected to the right pulmonary artery, an early phase acquisition protocol with injection of contrast material from the right cubital vein using the step volume scan mode of EBCT was planned to acquire blood flow information. Excellent spatial resolution volume data of the heart and great vessels was obtained from which 3-dimensional images were made. Bi-directional Glenn shunt flow could be observed directly and the complex morphology and relationships between adjacent structures were revealed by 3-dimensional VR imaging. The combination of EBCT and VR can provide useful information to evaluate congenital heart diseases.

Acute aortic abnormalities.

Aneurysm and type B dissections account for most acute abdominal aortic abnormalities. The postsurgical aorta deserves special attention owing to the risk of complications. Most aortic abnormalities presenting acutely are emergencies that carry a high risk of mortality, and imaging plays a critical role in patient evaluation. Modern helical CT scanners provide excellent spatial resolution, are readily available, and allow for rapid imaging. For these reasons, helical CT angiography is the imaging modality of choice for initial evaluation of the acute aorta.

Single- versus multi-detector row CT of the brain: quality assessment.

PURPOSE: To assess the quality of brain computed tomographic (CT) studies obtained with a four-channel multi-detector row CT scanner compared with those obtained with a single-detector row CT scanner. MATERIALS AND METHODS: Forty-seven patients referred for brain CT were imaged with both single- and multi-detector row scanners. Single-detector row CT images were acquired by using a 5-mm-collimated beam in the transverse mode. Multi-detector row CT images were acquired in four simultaneous 2.5-mm-thick sections, which were combined in projection space to create two contiguous 5-mm-thick sections. Two neuroradiologists blinded to the acquisition technique independently evaluated the CT image pairs, which were presented in a stacked mode on two adjacent monitors. Each study was graded by using a five-point scale for posterior fossa artifact, overall image quality, and overall preference. RESULTS: Multi-detector row CT studies were acquired 1.8 times faster than single-detector row CT studies (0.92 vs 0.52 section per second). Multi-detector row CT posterior fossa artifact was less than single-detector row CT posterior fossa artifact in 87 (93%) of 94 studies. Overall preference was expressed for multi-detector row CT in 84 (89%) of 94 studies. The differences in mean posterior fossa artifact scores (P <.001) and mean overall image quality scores (P =.001) were significant. CONCLUSION: Brain CT images obtained with multi-detector row CT resulted in significantly less posterior fossa artifact and were preferred to single-detector row CT images.

Iliac arterial injuries after endovascular repair of abdominal aortic aneurysms: correlation with iliac curvature and diameter.

PURPOSE: To determine the relationship between iliac arterial tortuosity and cross-sectional area and the occurrence of iliac arterial injuries following transfemoral delivery of endovascular prostheses for repair of abdominal aortic aneurysms. MATERIALS AND METHODS: Iliac arterial curvature values and orthogonal cross-sectional areas were determined from helical computed tomographic (CT) data acquired in 42 patients prior to transfemoral delivery of aortic stent-grafts. The curvature and luminal cross-sectional area orthogonal to the median centerline were quantified every millimeter along the median centerline of the iliac arteries. An indicator of global iliac tortuosity, the iliac tortuosity index, was defined as the sum of the curvature values for all points with a curvature of 0.3 cm(-1) or greater, and cross-sectional area (CSA) was indexed for all points as the mean cross-sectional diameter (D = 2 radical[CSA/pi]). Following stent-graft deployment, helical CT data were analyzed for the presence of iliac arterial dissections independently by two reviewers. RESULTS: Eighteen dissections were detected in 16 patients. The iliac tortuosity index was significantly larger in iliac arteries with dissections (35.5 +/- 20.8 [mean +/- SD]) when compared with both nondissected contralateral iliac arteries in the same patients (26.1 +/- 21.0, P =.001) and iliac arteries in patients without any iliac arterial injury (20 +/- 9, P =.009). The tortuosity index was higher ipsilateral to the primary component delivery in 10 of 11 iliac dissections that developed along the primary component delivery route. CONCLUSION: A high degree of iliac arterial tortuosity appears to impart greater risk for the development of iliac arterial injuries in patients undergoing transfemoral delivery of endovascular devices.

Digital storage phosphor chest radiography: an ROC study of the effect of 2K versus 4K matrix size on observer performance.

PURPOSE: To compare observer performance in the detection of abnormalities on 1,760 x 2,140 matrix (2K) and 3,520 x 4,280 matrix (4K) digital storage phosphor chest radiographs. MATERIALS AND METHODS: One hundred sixty patients who underwent dedicated computed tomography (CT) of the thorax were prospectively recruited into the study. Posteroanterior and lateral computed radiographs of the chest were acquired in each patient and printed in 2K and 4K formats. Six radiologists independently analyzed the hard-copy images and scored the presence of parenchymal (opacities 2 cm, and subtle interstitial), mediastinal, and pleural abnormalities on a five-point confidence scale. With CT as the reference standard, observer performance tests were carried out by using receiver operating characteristic (ROC) analysis. RESULTS: Analysis of averaged observer performance showed 2K and 4K images were equally effective in detection of all three groups of abnormalities. In the detection of the three subtypes of parenchymal abnormalities, there were no significant differences in averaged performance between the 2K and 4K formats (area below ROC curve [A(z)] values: opacities 2 cm, 0.86 +/-.025 and 0.85 +/- 0.030; subtle interstitial abnormalities, 0.73 +/- 0.041 and 0.72 +/- 0.041). Averaged performance in detection of mediastinal and pleural abnormalities was equivalent (A(z) values: mediastinal, 0.70 +/- 0.046 and 0.73 +/- 0.033; pleural, 0.85 +/- 0.032 and 0.86 +/- 0.033). CONCLUSION: Observer performance in detection of parenchymal, mediastinal, and pleural abnormalities was not significantly different on 2K and 4K storage phosphor chest radiographs.

Quantitative determination of age-related geometric changes in the normal abdominal aorta.

PURPOSE: We conducted a novel quantitative three-dimensional analysis of computed tomography (CT) angiograms to establish the relationship between aortic geometry and age, sex, and body surface area in healthy subjects. METHODS: Abdominal helical CT angiograms from 77 healthy potential renal donors (33 men/44 women; mean age, 44 years; age range, 19-67 years) were selected. In each dataset, orthonormal cross-sectional area and diameter measurements were obtained at 1-mm intervals along the automatically calculated central axis of the abdominal aorta. The aorta was subdivided into six consecutive anatomic segments (supraceliac, supramesenteric, suprarenal, inter-renal, proximal infrarenal, and distal infrarenal). The interrelated effects of anatomic segment, age, sex, and body surface area on cross-sectional dimensions were analyzed with linear mixed-effects and varying-coefficient statistical models. RESULTS: We found that significant effects of sex and of body surface area on aortic diameters were similar at all anatomic levels. The effect of age, however, was interrelated with anatomic position, and gradually decreasing slopes of significant diameter-versus-age relationships along the aorta, which ranged from 0.14 mm/y (P <.0001) proximally to 0.03 mm/y (P =.013) distally in the abdominal aorta, were shown. CONCLUSION: The abdominal aorta undergoes considerable geometric changes when a patient is between 19 and 67 years of age, leading to an increase of aortic taper with time. The hemodynamic consequences of this geometric evolution for the development of aortic disease still need to be established.

Techniques for performing multidetector-row computed tomographic angiography.

The introduction of multidetector-row computed tomography (CT) scanners has substantially improved the quality and ease of performing CT angiography. CT angiography is a robust method of volumetric vascular imaging that offers benefits over conventional angiography. As CT angiography has become a mainstream examination in many radiology departments, a discussion of techniques toward optimizing CT angiography performed with multidetector-row CT scanners is important. Key principles for optimizing spiral CT acquisition are discussed, and an explanation of multidetector-row CT principles germane to peripheral vascular imaging is presented. A discussion of contrast medium administration strategies ensues, with attention toward injection protocol and bolus timing. An overview of 3-dimensional visualization techniques is subsequently presented, followed by some general rules for CT angiographic interpretation. The article concludes with anatomically directed protocol considerations for the carotid and intracranial circulation, thoracic aorta, pulmonary arteries, abdominal aortoiliac system, renal arteries, and lower extremity arterial inflow and run-off.

Data explosion: the challenge of multidetector-row CT.

The development of multi detector-row CT has brought many exciting advancements to clinical CT scanning. While multi detector-row CT offers unparalleled speed of acquisition, spatial resolution, and anatomic coverage, a challenge presented by these advantages is the substantial increase on the number of reconstructed cross-sections that are rapidly created and in need of analysis. This manuscript discusses currently available alternative visualization tecvhniques for the assessment of volumetric data acquired with multi detector-row CT. Although the current capabilities of 3-D workstations offer many possibilities for alternative analysis of MCDT data, substantial improvements both in automated processing, processing speed and user interface will be necessary to realize the vision of replacing the primary analysis of transverse reconstruction's with alternative analyses. The direction that some of these future developments might take are discussed.

Qualitative blood flow differentiation: depiction of a left to right cardiac shunt across a ventricular septal defect using electron-beam computed tomography.

Three-dimensional imaging using electron-beam computed tomography (EBCT) has been used to assess static anatomical information in heart disease. With volume rendering, differences in objects can be distinguished through selection of the shape of opacity and color curves for CT values. If there is a difference between the CT values for arterial and venous blood, differences in opacity and color between them can be set. In a newborn baby with a left to right cardiac shunt across the ventricular septal defect (VSD), EBCT could depict arterial blood crossing the VSD into the right ventricle.