Stent grafting of abdominal aortic aneurysms: pre-and postoperative evaluation with multislice helical CT

The added value of CT virtual angioscopy to MDCT angiography in the evaluation of aortic diseases

PURPOSE

Incorporation of virtual angioscopy (VA) in the diagnostic work-up of aortic diseases could improve the clinical value and efficiency of multidetector computed tomography angiography (MDCTA). We aim to evaluate the clinical usefulness of virtual aortic navigation by CT angiography in various aortic diseases as a complement to standard MDCTA.

MATERIALS AND METHODS

We retrospectively selected 211 patients who performed MDCTA for suspected or operated aortic diseases. VA endoluminal images of the aorta were obtained by a fly-through technique. Two senior vascular radiologists independently evaluated all MDCTA images. After 1 month, the same two radiologists independently reviewed the MDCTA images combined with CTVA images. The respective accuracy of CTVA in delineating aortic abnormalities was compared to that of MDCTA using Fisher's exact test. The Fleiss kappa (κ) statistic was used to assess the inter-reader agreement (IRA).

RESULTS

We detected 229 abnormalities in 203 patients on MDCTA and 231 abnormalities in 205 patients on CTVA. CTVA provided significant additional findings in 63.8% (146/229) of all abnormalities diagnosed by MDCTA (p < 0.001, odd ratio [OR] = 42). Although CTVA diagnosed two abnormalities overlooked by MDCTA, the value was statistically insignificant (p = 0.787, OR = 1.3). Regarding postoperative abnormalities, the CTVA added significant additional findings over MDCTA (p = 0.006, OR = 87.4). The overall IRA for the performance of CTVA was good (κ = 0.699).

CONCLUSIONS

CTVA yields extra findings and improves diagnostic efficiency of MDCTA, especially in postoperative patients.

Use of Synchrotron Radiation to Accurately Assess Cross-Sectional Area Reduction of the Aortic Branch Ostia Caused by Suprarenal Stent Wires

PURPOSE

To compare in vivo the use of synchrotron radiation to computed tomography angiography (CTA) for the measurement of cross-sectional area (CSA) reduction of the aortic branch ostia caused by suprarenal stent-graft wires.

METHODS

This study was performed with a Zenith stent-graft placed in a phantom of the human aorta to simulate treatment of abdominal aortic aneurysm. Synchrotron radiation scans were performed using beam energies between 40 and 100 keV and spatial resolution of 19.88 μm per pixel. CSA reduction of the aortic branch ostia by suprarenal stent wires was calculated based on these exposure factors and compared with measurements from CTA images acquired on a 64-row scanner with slice thicknesses of 1.0, 1.5, and 2.0 mm.

RESULTS

Images acquired with synchrotron radiation showed <10% of the CSA occupied by stent wires when a single wire crossed a renal artery ostium and <20% for 2 wires crossing a renovisceral branch ostium. The corresponding areas ranged from 24% to 25% for a single wire and from 40% to 48% for double wires crossing the branch ostia when measured on CT images. The stent wire was accurately assessed on synchrotron radiation with a diameter between 0.38±0.01 and 0.53±0.03 mm, which is close to the actual size of 0.47±0.01 mm. The wire diameter measured on CT images was greatly overestimated (1.15±0.01 to 1.57±0.02 mm).

CONCLUSION

CTA has inferior spatial resolution that hinders accurate assessment of CSA reduction. This experiment demonstrated the superiority of synchrotron radiation over CTA for more accurate assessment of aortic stent wires and CSA reduction of the aortic branch ostia.

CT angiography in the diagnosis of cardiovascular disease: a transformation in cardiovascular CT practice

Computed tomography (CT) angiography represents the most important technical development in CT imaging and it has challenged invasive angiography in the diagnostic evaluation of cardiovascular abnormalities. Over the last decades, technological evolution in CT imaging has enabled CT angiography to become a first-line imaging modality in the diagnosis of cardiovascular disease. This review provides an overview of the diagnostic applications of CT angiography (CTA) in cardiovascular disease, with a focus on selected clinical challenges in some common cardiovascular abnormalities, which include abdominal aortic aneurysm (AAA), aortic dissection, pulmonary embolism (PE) and coronary artery disease. An evidence-based review is conducted to demonstrate how CT angiography has changed our approach in the diagnosis and management of cardiovascular disease. Radiation dose reduction strategies are also discussed to show how CT angiography can be performed in a low-dose protocol in the current clinical practice.

Abdominal aortic aneurysm: Treatment options, image visualizations and follow-up procedures

Abdominal aortic aneurysm is a common vascular disease that affects elderly population. Open surgical repair is regarded as the gold standard technique for treatment of abdominal aortic aneurysm, however, endovascular aneurysm repair has rapidly expanded since its first introduction in 1990s. As a less invasive technique, endovascular aneurysm repair has been confirmed to be an effective alternative to open surgical repair, especially in patients with co-morbid conditions. Computed tomography (CT) angiography is currently the preferred imaging modality for both preoperative planning and post-operative follow-up. 2D CT images are complemented by a number of 3D reconstructions which enhance the diagnostic applications of CT angiography in both planning and follow-up of endovascular repair. CT has the disadvantage of high cummulative radiation dose, of particular concern in younger patients, since patients require regular imaging follow-ups after endovascular repair, thus, exposing patients to repeated radiation exposure for life. There is a trend to change from CT to ultrasound surveillance of endovascular aneurysm repair. Medical image visualizations demonstrate excellent morphological assessment of aneurysm and stent-grafts, but fail to provide hemodynamic changes caused by the complex stent-graft device that is implanted into the aorta. This article reviews the treatment options of abdominal aortic aneurysm, various image visualization tools, and follow-up procedures with use of different modalities including both imaging and computational fluid dynamics methods. Future directions to improve treatment outcomes in the follow-up of endovascular aneurysm repair are outlined.

Multi-detector CT angiographic imaging in the follow-up of patients after endovascular abdominal aortic aneurysm repair (EVAR)

BACKGROUND

Multidetector computed tomography (MDCT) angiography represents the standard of reference in the follow-up of patients after endovascular abdominal aortic aneurysm repair (EVAR), being effective in the detection of the full spectrum of possible complications on both axial and 3D images.

METHODS

The purpose of this article is to review the normal CT angiography findings of the different types of stent-grafts and to describe the radiological findings of early and late complications after EVAR on axial and reconstructed images. A selection of cases of post-EVAR MDCT angiography is presented to learn the techniques most commonly used for endovascular treatment, the correct CT scanning technique to acquire the data, the full gamut of possible procedure-related complications and how these complications usually appear on CT images.

CONCLUSION

MDCT angiography is an effective and specific technique in both the pre- and postoperative settings of EVAR procedures. A better understanding of the procedure, the devices, the normal postoperative imaging features and the possible procedure-related complications ensures optimal planning and follow-up of patients undergoing an EVAR procedure.

Dual-source CT angiography in aortic stent grafting: An in vitro aorta phantom study of image noise and radiation dose

RATIONALE AND OBJECTIVES

The aim of the study was to investigate the optimal protocols of dual-source computed tomography (CT) angiography in aortic stent grafting in terms of image noise and radiation dose, based on an in vitro phantom study.

MATERIALS AND METHODS

A series of helical CT cans were performed on a human aorta phantom using a dual-source CT scanner with kVp of 100, 120, and 140, corresponding mAs of 180, 150, and 100; slice thickness of 1.0, 1.5, and 2.0 mm; and pitch value of 0.5, 1.0, and 1.5, respectively. Image quality was determined by measuring the standard deviation (SD) on three-dimensional virtual intravascular endoscopy (VIE) images. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured on two-dimensional (2D) axial images at superior mesenteric artery (SMA), renal arteries, and aneurysm. Effective dose was determined based on dose-length product.

RESULTS

SD measured on VIE images was independent of kVp and pitch values but was determined by the slice thickness (P < .05) at the SMA and renal arteries. SNR and CNR measured on 2D images showed significant differences between variable kVp values and slice thicknesses (P < .05), but were independent of pitch values. The mean estimated effective dose for 120 kVp and 140 kVp protocols were 2.66 +/- 0.21 mSv and 2.68 +/- 0.18 mSv, respectively. The mean estimated effective dose for 100 kVp protocol was significantly lower (1.97 +/- 0.07 mSv, P < .0001). This indicates a reduction of 26.5% radiation dose when the kVp was lowered from 140 to 100.

CONCLUSION

A scanning protocol of 1.5-mm slice thickness, pitch 1.5 with 100 kVp, and 180 mAs is recommended for a dual-source CT angiography in aortic stent grafting as it leads to significant reduction of radiation dose while achieving diagnostic images.

3D stereoscopic visualization of fenestrated stent grafts

The purpose of this study was to present a technique of stereoscopic visualization in the evaluation of patients with abdominal aortic aneurysm treated with fenestrated stent grafts compared with conventional 2D visualizations. Two patients with abdominal aortic aneurysm undergoing fenestrated stent grafting were selected for inclusion in the study. Conventional 2D views including axial, multiplanar reformation, maximum-intensity projection, and volume rendering and 3D stereoscopic visualizations were assessed by two experienced reviewers independently with regard to the treatment outcomes of fenestrated repair. Interobserver agreement was assessed with Kendall's W statistic. Multiplanar reformation and maximum-intensity projection visualizations were scored the highest in the evaluation of parameters related to the fenestrated stent grafting, while 3D stereoscopic visualization was scored as valuable in the evaluation of appearance (any distortions) of the fenestrated stent. Volume rendering was found to play a limited role in the follow-up of fenestrated stent grafting. 3D stereoscopic visualization adds additional information that assists endovascular specialists to identify any distortions of the fenestrated stents when compared with 2D visualizations.

Multislice CT angiography in the follow-up of fenestrated endovascular grafts: effect of slice thickness on 2D and 3D visualization of the fenestration stents

PURPOSE

To investigate the effect of multislice computed tomography (CT) protocols on the visualization of target vessel stents in patients with abdominal aortic aneurysm (AAA) treated with fenestrated endovascular grafts.

METHODS

Twenty-one patients (19 men; mean age 75 years, range 63-86) undergoing fenestrated endovascular repair of AAA were retrospectively studied. Multislice CT angiography was performed with several protocols, and the section thicknesses used in each were compared to identify any relationship between slice thickness and target vessel stents visualized on 2-dimensional (2D) axial, multiplanar reformatted (MPR), and 3-dimensional (3D) virtual intravascular endoscopy (VIE) images. Image quality was assessed based on the degree of artifacts and their effect on the ability to visualize the configuration, intra-aortic location, and intraluminal appearance of the target vessel stents and measure their protrusion into the aortic lumen.

RESULTS

There were 7 different multislice CT scanning protocols employed in the 21 patients (25 datasets, with 2 sets of follow-up images in 4 patients). The slice thicknesses and numbers (n) of studies included were 0.5 (n=3), 0.625 (n=6), 1.0 (n=1), 1.25 (n=9), 2.5 (n=3), 3.0 (n=1), and 5.0 mm (n=2). Of these CT protocols, images (especially 2D/3D reconstructions) acquired at 2.5, 3.0, and 5.0 mm were significantly compromised by interference from artifacts. Images acquired with a slice thickness of 1.0 or 1.25 mm were scored equal to or lower than those acquired with a submillimeter section thickness (0.5 or 0.625 mm), with minor degrees of artifacts resulting in acceptable image quality.

CONCLUSION

Visualization of the target vessel stents depends on the appropriate selection of multislice CT scanning protocols. Our results showed that studies performed with a slice thickness of 1.0 or 1.25 mm produced similar image quality to those with a thickness of 0.5 or 0.625 mm. Submillimeter slices are not recommended in imaging patients treated with fenestrated stent-grafts, as they did not add additional information to the visualization.

Avaliação pós-operatória do tratamento endovascular de aneurismas da aorta abdominal por angiotomografia com multidetectores

OBJETIVO: Este estudo tem como objetivo a avaliação pós-operatória do tratamento endovascular de aneurismas da aorta abdominal por angiotomografia com multidetectores. MATERIAIS E MÉTODOS: Foram analisadas, retrospectivamente, angiotomografias de 166 pacientes (137 homens e 29 mulheres) com idade média de 73 anos portadores de aneurisma da aorta abdominal submetidos a terapêutica endovascular, no período de junho de 2005 a agosto de 2006. Os exames foram feitos em tomógrafo multidetector de 64 canais e os parâmetros adotados foram: colimação, 0,625 mm; pitch, 0,6-1; mAs, 300-400; kV, 120. Em todos os casos foi utilizado meio de contraste iodado não-iônico (350 mg/ml) administrado por meio de bomba infusora, com fluxo de 4 ml/s a 5 ml/s e com volume variável de 70 ml a 100 ml. Os exames foram avaliados quanto à presença de complicações. RESULTADOS: Dos 166 exames realizados, 93 pacientes não apresentaram complicações e 73 apresentaram os seguintes achados: endoleak (n=37), trombose circunferencial da endoprótese (n=29), angulação (n=17), coleção no sítio de punção (n=10), migração da prótese (n=7), dissecção dos vasos de acesso (n=7) e oclusão (n=6). CONCLUSÃO: O endoleak foi a complicação mais prevalente em nosso estudo, sendo o tipo II o mais comum.

Multislice CT angiography in abdominal aortic aneurysm treated with endovascular stent grafts: evaluation of 2D and 3D visualisations

Endovascular repair of abdominal aortic aneurysms has been introduced into the clinical practice for more than a decade and has been confirmed to be an effective alternative to conventional open surgery, especially in patients with co-morbid medical conditions. Helical CT angiography is the preferred imaging method in the follow-up of endovascular repair. Recent introduction of multislice CT scanners has augmented its diagnostic role in this area. Diagnostic value of multlislice CT has been complemented by a series of 3D post-processings, which assist vascular surgeons in accurately assessing the effect of endovascular repair by providing additional information when compared to conventional 2D axial images. These reconstructions include multiplanar reformation, curved multiplanar reconstruction, shaded surface display, maximum intensity projection, volume rendering and virtual endoscopy. This article aims to demonstrate the generation of these 2D/3D reconstructions based on multislice CT data acquired from a group of patients with abdominal aortic aneurysm following endovascular repair. A brief introduction of generating each reconstruction was provided; potential clinical applications of each reconstruction were briefly discussed. Images were presented in a dynamic format with the aim of allowing the reader to easily understand the post-processing of these reconstructions.

Multislice CT angiography in aortic stent grafting: Relationship between image noise and body mass index

PURPOSE

To investigate the correlation between image noise and body mass index (BMI) in multislice CT angiography (MSCT) for patients with abdominal aortic aneurysm (AAA) treated with endovascular stent grafts.

MATERIALS AND METHODS

Seventeen patients who underwent MSCT following endovascular repair of AAA were included in the study. Image noise (standard deviation of the CT attenuation: S.D.) and signal to noise ratio (SNR) were plotted against BMI to demonstrate the correlation using a linear regression method. Image quality of 3D reconstructions was correlated to the SNR and BMI.

RESULTS

The r-value of linear regression between S.D. and BMI was 0.578 (p<0.05), 0.835 and 0.802 (p<0.001), respectively, at the level of renal artery, aortic aneurysm and common iliac artery. The r-value of linear regression between SNR and BMI was 0.332, 0.516 and 0.552 (p<0.05), respectively, at above three levels. Image quality of 3D reconstructions was compromised in five patients and diagnosis was affected in two patients with BMI more than 30.

CONCLUSION

A significant correlation was observed between image noise and BMI in MSCT angiography of endovascular repair of AAA. Our findings are valuable for optimisation of MSCT angiography scanning protocols and reduction of radiation dose in MSCT examinations.

3D multislice CT angiography in post-aortic stent grafting: a pictorial essay

Helical CT angiography has been widely used in both pre- and post-aortic stent grafting and it has been confirmed to be the preferred modality when compared to conventional angiography. The recent development of multislice CT (MSCT) has further enhanced the applications of CT angiography for aortic stent grafting. One of the advantages of MSCT angiography over conventional angiography is that the 3D reconstructions, based on the volumetric CT data, provide additional information during follow-up of aortic stent grafting. While endovascular repair has been increasingly used in clinical practice, the use of 3D MSCT imaging in endovascular repair continues to play an important role. In this pictorial essay, we aimed to discuss the diagnostic performance of 3D MSCT angiography in post aortic stent grafting, including the most commonly used surface shaded display, curvilinear reformation, the maximum intensity projection, volume rendering and virtual endoscopy. The advantages and disadvantages of each 3D reconstruction are also explored.

Three-dimensional visualization of suprarenal aortic stent-grafts: evaluation of migration in midterm follow-up

PURPOSE

To investigate the midterm results of transrenal fixation of abdominal aortic stent-grafts with regard to device migration and encroachment of stent wires on the renal and visceral branches.

METHODS

Imaging data from 18 patients (15 men; mean age 75 years, range 63-84) undergoing transrenal stent-graft fixation for abdominal aortic aneurysm (AAA) were included in the study. Computed tomographic angiographic data acquired within 1 week of stent-graft implantation were compared to the latest follow-up images. Postprocessing methods generated 3-dimensional (3D) maximum intensity projections (MIP) and virtual intravascular endoscopy (VIE) for evaluation of the relationship between suprarenal stents and aortic branches. Aortic neck angulation was measured in each patient for correlation with the incidence of stent migration.

RESULTS

The mean follow-up period was 40 months. 3D image visualizations showed that the stent-graft moved caudally in all patients (range 2.6-14.2 mm), with migration (>10 mm) observed in 4 (22%) patients. Corresponding VIE images documented changes in stent wire encroachment on the aortic branch ostia in 11 patients, including the number and position of crossing stent wires. There was no close relationship between aortic neck angulation and stent migration.

CONCLUSION

The current study demonstrated that migration occurs at midterm follow-up in transrenally deployed stent-grafts. 3D images were valuable for the assessment of stent migration, as well as its relationship with aortic branch ostia. Long-term follow-up of transrenal fixation deserves to be investigated, especially after observing stent migration relative to aortic ostial encroachment.

Diagnostic Value of Color Duplex Ultrasonography in the Follow-up of Endovascular Repair of Abdominal Aortic Aneurysma

PURPOSE

To systematically review the findings of diagnostic value of color duplex ultrasound (US) in the follow-up of endovascular repair of abdominal aortic aneurysms (AAAs).

MATERIALS AND METHODS

A search of PubMed and Medline databases for English-language literature was performed to find studies published between 1991 and 2005. Studies comparing the diagnostic accuracy of color duplex US with that of computed tomographic (CT) angiography were included, and analysis was performed of the detection of endoleaks and measurement of aneurysm diameter.

RESULTS

Twenty-one studies (39 separate comparisons) met the criteria and were included for analysis. Pooled estimates of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of color duplex US compared with CT angiography (with 95% CIs) were 66% (52%-81%), 93% (89%-97%), 76% (65%-87%), 90% (86%-95%), and 91% (86%-97%), respectively, for unenhanced color duplex US; and 81% (52%-100%), 82% (68%-97%), 58% (26%-90%), 95% (87%-100%), and 98% (91%-100%), respectively, for enhanced color duplex US. The sensitivity in the detection of endoleak was significantly improved with contrast material-enhanced color duplex US compared with unenhanced color duplex US (P < .05); however, no significant difference was found regarding the specificity, PPV, NPV, and accuracy between unenhanced and enhanced color duplex US (P > .05). Color duplex US was insensitive in measurement of aneurysm diameter compared with CT angiography in most situations.

CONCLUSIONS

Color duplex US is not as accurate as CT angiography and cannot replace CT angiography in the follow-up of endovascular aortic repair of AAAs. However, the use of contrast material-enhanced color duplex US resulted in improvement of diagnostic accuracy in the detection of endoleak and warrants further study.

Optimal scanning protocol of multislice CT virtual intravascular endoscopy in pre-aortic stent grafting: In vitro phantom study

OBJECTIVE

To investigate the optimal scanning protocol for multislice computed tomography angiography (MSCT) in pre-aortic stent grafting observed with virtual intravascular endoscopy (VIE).

MATERIALS AND METHODS

The study was performed on a human abdominal aortic phantom which was housed in a perspex container, filled with contrast medium having CT attenuation similar to that used in the patient's abdominal CT scan. A series of scans were performed on a four-slice multislice CT scanner with the scanning protocols as follows: section thickness of 1.3, 3.2 and 6.5 mm, pitch value of 0.875, 1.25 and 1.75 with reconstruction intervals of 50% overlap. The degree of stair-step artifacts was measured at three different locations, superior mesenteric artery (SMA), renal ostium and the normal abdominal aorta. Standard deviation (S.D.) of the signal intensity measured on surface shaded images was used to determine the image quality. Radiation dose was also recorded in each scanning protocol.

RESULTS

The VIE images showed that image quality was not dependent on pitch and section thickness in the visualization of renal ostium and SMA, whereas it was dependent on these two factors at the level of the normal aorta (p<0.05). It was noticed that when section thickness reached 6.5 mm the SMA and renal ostia became distorted. Radiation dose measured in 1.3 mm protocols was significantly higher that those measured in other section thicknesses (p<0.05).

CONCLUSION

The scanning protocol of section thickness 3.2 mm, pitch 1.25 with a reconstruction interval of 1.6 mm was recommended as it allows optimal visualization of VIE images of aortic ostia, generation of fewer artifacts and less radiation dose.

Multidetector CT Angiography of the Abdomen

Multidetector CT angiography (MDCTA) is redefining traditional imaging strategies of the vascular structures of the abdomen. Angiographic depiction of normal and variant anatomy is becoming the standard for evaluation and has a significant impact in transplant and oncologic surgery. MDCTA is increasingly being used for assessing diseases affecting the vasculature of the abdominal organs, including the abdominal aorta for treatment planning and post therapy follow-up.

Multislice CT angiography: a practical guide to CT angiography in vascular imaging and intervention

The development of multidetector CT (MDCT) has revolutionized CT angiography (CTA). Not only are new techniques now in the remit of CTA, but all the studies previously performed on single slice or helical CT can now be done with better resolution. The advantage of MDCT relevant to CTA is the ability to acquire high resolution, near isotropic data sets in a shorter acquisition time. Also important is the ability to achieve a longer scanning range in the arterial phase, which has seen the introduction of CTA of the peripheral arterial system. Image processing techniques have also progressed rapidly, with simplification of a previously cumbersome process. The high spatial resolution and relatively non-invasive nature make MDCT angiography a strong and serious competitor to established vascular imaging techniques. The implication is that traditional diagnostic pathways for evaluation of the vascular system have changed.

Characterization of endoleaks by dynamic computed tomographic angiography

BACKGROUND

Current imaging modalities may not be able to detect endoleaks, differentiate between type II and type III, or localize inflow and outflow sources. We describe a new technique that can characterize endoleaks to guide secondary intervention.

METHODS

One hundred four patients with Zenith (Cook, Inc.) endograft repair of abdominal aortic aneurysms (AAAs) were monitored by serial computed tomographic angiography (CTA). Endoleaks were evaluated with a dynamic CTA using a stationary table position, 24-mm beam collimation, and continuous scanning over 30 to 40 seconds to create a cine.

RESULTS

Twelve patients (12%) had endoleaks that persisted or appeared more than 30 days post-deployment. Five patients in whom the standard CT surveillance protocol could not differentiate type II versus type III endoleaks underwent dynamic CTA. This technique accurately characterized the endoleaks and localized inflow and outflow branches to guide the subsequent successful secondary interventions.

CONCLUSIONS

Dynamic CTA is a useful technique to evaluate endoleaks for characterization and precise localization to guide secondary interventional therapy.

Multidetector CT Angiography Versus Digital Subtraction Angiography for Aortoiliac Length Measurements Prior to Endovascular AAA Repair

PURPOSE

To assess observer variation between calibrated-catheter digital subtraction angiography (DSA) and software-enhanced multidetector computed tomography angiography (CTA) in measuring vessel length prior to endovascular aortic aneurysm repair (EVAR).

METHODS

Thirty patients (25 men; mean age 65 years, range 61-85) scheduled for EVAR underwent CTA in 4x2-mm collimation using advanced vessel analysis software. CTA measurements were performed twice by 2 blinded readers in random order with at least a 4-week interval between readings. Nine patients were found unsuitable for endovascular repair after the CTA, so DSA was performed in 21 patients for morphometric evaluation of the abdominal aorta and the iliac arteries. The following segments were measured: H1 (aneurysm neck), H2 (lower renal artery to distal aspect of the aneurysm), H3 (lower renal artery to aortic bifurcation), and H4a/H4b (lower renal artery to iliac bifurcations). Length measurements on DSA were made by (1) following the catheter path in the aortic lumen and (2) dividing tortuous vessel anatomy into segments and measuring each segment along an idealized centerline. Addition of the various segments allowed comparison with data obtained from CTA measurements.

RESULTS

CTA was performed with good intraobserver agreement for all length parameters except H3 in reader 2 (p<0.05). While good interobserver agreement was demonstrated for CTA over long aortoiliac distances (H4a, H4b), higher interobserver agreement was obtained with DSA for shorter segments (H1, H2). Considerable differences were observed between CTA and DSA for the lengths H2 and H4b.

CONCLUSIONS

CTA produces better intra and interobserver correlations in measuring vessel length than DSA. It has the potential to replace DSA as an imaging method before EVAR.

Cross-sectional area reduction of the aortic ostium by suprarenal stent wires: in vitro phantom study by CT virtual angioscopy

The study aims to investigate the reduction of cross-sectional area of the aortic ostium by the presence of aortic stent wires observed using CT virtual angioscopy in an aorta phantom. A human aorta phantom was built with a commercial stent graft placed in situ to simulate a repaired aortic aneurysm. Virtual angioscopic images of the aortic ostium and stent wires were generated in the locations of renal arteries, superior mesenteric artery and corresponding cross-sectional area reduction caused by stent wires was measured by virtual angioscopy in various scanning parameters. Our study showed that cross-sectional area reduction of the aortic ostium was determined by the diameter of renal ostium and stent wires, as well as the number of stent wires crossing the aortic ostium.

Diagnostic value of CT virtual intravascular endoscopy in aortic stent-grafting

PURPOSE

To investigate the diagnostic value of postprocessing techniques for 3-dimensional (3D) computed tomography (CT), with emphasis on CT virtual intravascular endoscopy (VIE), in patients with abdominal aortic aneurysms (AAA) treated with suprarenal stent-grafts.

METHODS

The preprocedural and postprocedural CT datasets from 47 AAA patients (40 men; mean age 75 years, range 61-87) undergoing aortic stent-grafting with suprarenal fixation were examined. The CT datasets were processed to create various 3D reconstructions: shaded surface display (SSD), maximum intensity projection (MIP), and VIE. Three independent radiologists assessed various diagnostic parameters for each 3D reconstruction method and compared them to axial CT images.

RESULTS

Scores for VIE reconstructions were inferior to axial CT images in the visualization of normal arterial branches, measurement of the aneurysm diameter and neck length, as well as assessment of vessel patency and presence of endoleaks. VIE was rated superior to axial CT and other 3D imaging methods in visualizing the configuration of stent struts relative to the aortic branch ostia and the number of stent wires crossing the ostia in >80% of cases.

CONCLUSIONS

VIE was not found to play a role in most preoperative situations compared to axial CT images. However, VIE provided additional postgrafting information on the 3D relationship of the suprarenal stent struts to the aortic branch ostia (in particular the renal and superior mesenteric arteries). VIE findings might aid clinicians in accurately assessing the effect of suprarenal stent-grafting on the renal arteries.

Multidetector row computed tomography of the aorta and peripheral arteries

MDCT represents a significant advance on SDCT and the advantages it brings are particularly clear in CTA applications. It allows cost effective assessment of longer segments of vascular territories to be imaged with higher spatial, contrast, and temporal resolution. It has replaced SDCT as the new CT standard and its technical abilities are rapidly approaching the temporal resolution of EBCT. With 3-D post processing tools its main benefit is in imaging studies customized to the patient's pathology, with greater measurement accuracy and reliable longitudinal assessment. MDCTA is increasingly applied not to individual vascular territories but to a complete assessment dictated by the pathology, such as the entire aorta and branch vessels in aneurysm evaluation and the aorta and the coronary arteries in dissection cases or the vascular and non-vascular chest in acute chest pain. Greater accuracy of vessel assessment will lead to a refinement of interventional and surgical techniques for an individual patient and facilitates conservative management of conditions that can be reliably monitored non-invasively and the development of intervention criteria. MDCTA will continue to increase its major role in peripheral vascular evaluation in the future though its reliability in assessing small vessels below the knee and in the foot remains to be conclusively proven to obviate the need for diagnostic catheter angiography.

Accuracy of computer-aided measurements in endovascular stent-graft planning: an experimental study with two phantoms

RATIONALE AND OBJECTIVES

The aim of this study was to evaluate the accuracy of the new measurement software, created for aortic stent-graft planning. The software finds semiautomatically the centerline of the vessel from computer tomographic angiography data and calculates semiautomatically diameters and lengths.

MATERIALS AND METHODS

Two phantoms were constructed, scanned by CT and measured with the measurement software. Results were compared with the known dimensions of the phantoms and mean fractional errors were calculated. Linear regression analysis was also made between measured and known diameters.

RESULTS

The mean fractional error (+/- SD) for all diameter measurements combined was 0.017 +/- 0.011. In the linear regression analysis, was 1.000. For length measurements, the mean fractional error (+/- SD) was 0.009 +/- 0.0006.

CONCLUSIONS

The software enables accurate measurements perpendicular or parallel to the semiautomatically created centerline path.

Dynamic multislice helical CT of ameloblastoma and odontogenic keratocyst: correlation between contrast enhancement and angiogenesis

PURPOSE

The purpose of this study was to assess whether the enhancement characteristics of dynamic multislice helical CT (MS-CT) could help in the differential diagnosis of ameloblastomas and odontogenic keratocysts. The correlation between enhancement characteristics and immunohistochemical findings, especially with regard to angiogenesis, was also evaluated.

METHOD

Dynamic MS-CT was performed in 13 consecutive patients (8 ameloblastoma cases and 5 odontogenic keratocyst cases). The percentage of density increase (Enh%) was measured in dynamic MS-CT images taken during the arterial phase, and microvessel density (MVD) was analyzed using immunohistochemical study with anti-CD31 antibody. The Mann-Whitney U test was used to evaluate the significance of the Enh% or the MVD values between lesion subtypes, and the Spearman correlation coefficient was used to evaluate the correlation between the Enh% and the MVD in ameloblastomas and odontogenic keratocysts.

RESULTS

The Enh% in ameloblastomas was significantly higher than that of odontogenic keratocysts (P < 0.005). The MVD of ameloblastomas was also significantly higher than that of odontogenic keratocysts (P < 0.005). The Enh% values for ameloblastomas and odontogenic keratocysts were positively correlated with the respective MVD values (r = 0.92, P < or = 0.000).

CONCLUSION

Dynamic MS-CT is useful tool for differentiating between ameloblastomas and odontogenic keratocysts on the basis of the contrast enhancement values of intratumoral vascularities during the arterial phase. Furthermore, the Enh% obtained by dynamic MS-CT is correlated with the MVD in ameloblastomas and odontogenic keratocysts.