Diagnostic accuracy of 64 multislice CT angiography in the assessment of coronary in-stent restenosis: A meta-analysis

Purpose

The aim of this study was to perform a meta-analysis of the diagnostic accuracy of 64-slice CT angiography for the detection of coronary in-stent restenosis in patients treated with coronary stents when compared to conventional coronary angiography.

Materials and methods

A search of PUBMED/MEDLINE, ProQuest and Cochrane library databases for English literature was performed. Only studies comparing 64-slice CT angiography with conventional coronary angiography for the detection of coronary in-stent restenosis (more than 50% stenosis) were included for analysis. Sensitivity and specificity estimates pooled across studies were tested using a fixed effects model.

Results

Fourteen studies met selection criteria for inclusion in the analysis. The mean value of assessable stents was 89%. Prevalence of in-stent restenosis following coronary stenting was 20% among these studies. Pooled estimates of the sensitivity and specificity of overall 64-slice CT angiography for the detection of coronary in-stent restenosis was 90% (95% CI: 86%, 94%) and 91% (95% CI: 90%, 93%), respectively, based on the evaluation of assessable stents. Diagnostic value of 64-slice CT angiography was found to decrease significantly when the analysis was performed with inclusion of nonassessable segments in five studies, with pooled sensitivity and specificity being 79% (95% CI: 68%, 88%) and 81% (95% CI: 77%, 84%). Stent diameter is the main factor affecting the diagnostic value of 64-slice CT angiography.

Conclusion

Our results showed that 64-slice CT angiography has high diagnostic value (both sensitivity and specificity) for detection of coronary in-stent restenosis based on assessable segments when compared to conventional coronary angiography.     

Evaluation of patients with previous coronary stent implantation with 64-section CT

PURPOSE: To prospectively evaluate the diagnostic accuracy of 64-section computed tomography (CT) for the assessment of in-stent or peristent restenosis, with conventional coronary angiography as the reference standard. MATERIALS AND METHODS: The study was approved by the medical ethics committee, and informed consent was obtained in all 50 enrolled patients (40 men, 10 women; mean age, 60 years +/- 11 [standard deviation]). In addition to conventional coronary angiography with quantitative coronary angiography, 64-section CT was performed. For each stent, assessability was determined and was related to stent characteristics and heart rate by using a chi(2) test. On the interpretable images of stents and peristent lumina (5.00 mm proximal and distal to the stent), the presence of significant (> or =50%) restenosis was determined. For this analysis, partially overlapping stents were considered to represent a single stent. RESULTS: Of 76 stents, 65 (86%) were determined to be assessable. Increased heart rate and overlapping positioning were associated with increased uninterpretability of the images of stents (P < .05), whereas location of the stent and thickness of the strut were not. In seven patients, stents were placed in an overlapping manner, resulting in 58 stents available for the evaluation of significant (> or =50%) in-stent restenosis. All six significant (> or =50%) in-stent restenoses were detected, and the absence of significant (> or =50%) restenosis was correctly identified in the 52 remaining stents, resulting in sensitivity and specificity of 100%. Sensitivity and specificity for the detection of significant (> or =50%) peristent stenosis were 100% and 98%, respectively. CONCLUSION: In selected patients with previous stent implantation, 64-section CT can be used to evaluate in-stent restenosis with high accuracy. Accordingly, the technique may be useful for noninvasive exclusion of in-stent or peristent restenosis, thereby avoiding invasive imaging in a considerable number of patients.     

MDCT angiography assessment of renal artery in-stent restenosis: Can we reduce the radiation exposure burden? A feasibility study

Aim

We explored the feasibility of renal artery multidetector computed tomography (MDCT) and detection of in-stent restenosis at low exposure settings.

Patients/methods

Sixteen patients with 19 renal artery stents underwent CT angiography. A biphasic protocol was performed including arteriographic acquisition at standard 120 kVp and a late-arterial scan at 100 kVp (n = 9) or 80 kVp (n = 7). Images were reconstructed under various algorithms. Signal-to-noise and contrast-to-noise ratios (SNR, CNR) were determined within stent, aorta and renal arteries. Image quality and the presence of restenosis were assessed. Volume CT dose-index was recorded and dose reduction (DR%) between phases was calculated.

Results

Ten patients presented with Hounsfield values >250 HU in all segments, phases and reconstructions and were further evaluated. The 120 kVp protocol performed better in all vessels and reconstruction algorithms. SNR at 120 kVp (B31f) did not differ significantly compared to 100 kVp (B31f). CNR within stent was borderline compromised at 100 kVp (p = 0.042). All but two image sets (at 80 kVp) were considered diagnostic. Minor loss of subjective image quality was noticed at 100 kVp. No difference in assessment of restenosis was observed between 120 kVp and the diagnostic low-exposure scans. Mean DR% was estimated 45% at 100 kVp and 77% at 80 kVp.

Conclusions

Renal MDCT angiography and stent-restenosis assessment are feasible at 100 kVp with minor loss of image quality and almost half radiation exposure.     

Multi-detector row CT angiography in the assessment of coronary in-stent restenosis: a systematic review

Purpose

The aim of this study was to perform a systematic review of the diagnostic accuracy of multi-detector row computed tomography angiography (MDCT) for detection of coronary in-stent restenosis in patients treated with coronary stenting when compared to invasive catheter angiography.

Materials and methods

A search of PUBMED and MEDLINE databases for English literature was performed. Only studies with at least 10 patients comparing 16- or more detector rows MDCT angiography with invasive catheter angiography in the detection of coronary in-stent restenosis (more than 50% stenosis) were included for analysis. Sensitivity and specificity estimates pooled across studies were tested using a fixed effects model.

Results

15 studies met selection criteria for inclusion in the analysis. There were eight studies performed with 16-detector row CT scanners, and five studies with 64-detector row scanners and one study with a 40-detector scanner. The remaining study was performed with a mixture of 16-and 64-detector row scanners. Prevalence of in-stent restenosis following coronary stenting was 18% (95% CI: 13, 24%). Pooled estimates of the sensitivity and specificity of overall MDCT angiography for the detection of coronary in-stent restenosis was 85% (95% CI: 78, 90%) and 97% (95% CI: 95, 98%), respectively. No significant difference was found between 16- and 64-detector row scanners regarding the sensitivity and specificity of MDCT for assessment of in-stent restenosis (p > 0.05).

Conclusion

The results showed that MDCT angiography (with 16 or more detector rows) has moderate sensitivity and high specificity for the detection of coronary in-stent restenosis when compared to invasive catheter angiography. A high specificity value of MDCT may be most valuable as a non-invasive technique of excluding coronary stent restenosis or occlusion. The main factors affecting visualization are stent diameters and stent materials.     

Assessment of vertebral artery stents using 16-slice multi-detector row CT angiography in vivo evaluation: comparison of a medium-smooth kernel and a sharp kernel

Objectives

To assess the lumen visibility of extracranial vertebral artery stents examined with 16-slice multi-detector row computed tomography (MDCT) angiography in vivo using a medium-smooth kernel (B30s) and a sharp kernel (B60s), and to compare these with digital subtraction angiography (DSA) after stent placement.

Methods

Twenty stents from 20 patients (14 men, 6 women; mean age, 62.7 ± 10.1 years) who underwent CT angiography (CTA) with 16-slice MDCT were retrospectively analyzed. In CT angiograms using a B30s and a B60s, the lumen diameters and CT attenuations of the stented vessels were measured three times by three observers, and artificial luminal narrowing (ALN) was calculated. To assess measurement reliability on CT angiograms, the intraclass correlation coefficient (ICC) was used. DSA served as the reference standard for the in-stent luminal measurements on CT angiography. The median interval between CT angiography and DSA was 1 day (range 1–10).

Results

For interobserver reliability, intraclass correlation coefficients for the lumen diameters on CT angiograms with a B30s and a B60s were 0.90 and 0.96, respectively. The lumen diameters on CT angiograms using a B30s were consistently smaller than that on CT angiograms using a B60s (p < 0.01). The mean ALN was 37 ± 7% on CT angiograms using a B30s and 25 ± 9% on CT angiograms using a B60s. The mean CT attenuation in in-stent lumen was 347 ± 55 HU on CT angiograms using a B30s and 295 ± 46 HU on CT angiograms using a B60s. The ALN and CT attenuation within the stented vessels between CT angiograms using a B30s and a B60s was significant (p < 0.01).

Conclusions

16-slice MDCT using a sharp kernel allows good visualization of the stented vessels and is useful in the assessment of vertebral artery stent patency after stent placement.     

Comparison of 16-row multislice CT angiography with conventional angiography for detection and evaluation of intracranial aneurysms

Purpose

The aim of this study is to compare the diagnostic performance of 16-row computed tomographic angiography (MDCTA) with digital subtraction angiography (DSA) for the detection and characterization of intracranial aneurysms in patients with nontraumatic subarachnoid hemorrhages (SAH).

Materials and methods

One-hundred and twelve consecutive patients with suspected intracranial aneurysm underwent both 16-row MDCTA and DSA. The MDCT angiograms were interpreted in a blinded fashion by using combination with VRI, MIP and MPR techniques. Sensitivity specificity and accuracy were calculated for the CTA and DSA. The results were compared with each other. The DSA reader's interpretation was accepted as the reference standard.

Results

A total of 164 aneurysms were detected at DSA in 112 patients, no aneurysms were detected by DSA and MDCTA in 16 patients. Eight aneurysms were missed by MDCTA. The overall sensitivity, specificity, and accuracy of MDCTA on a per-aneurysm basis were 95.1%, 94.1%, and 95%, respectively. According to the size of the aneurysm less than 3 mm; sensitivity, specificity and diagnostic accuracy of MDCTA were 86.1%, 94.1%, 88.6%, respectively.

Conclusion

This study suggests that MDCTA is equally as sensitive as DSA in the detection of intracranial aneurysms of greater than 3 mm, and it also reveals 100% detection rate for ruptured aneurysms.     

Evaluation of various image reconstruction parameters in lower extremity stents using multidetector-row CT angiography: initial findings

Image quality, visible lumen and patency of lower limb stents was assessed by multidetector-row computed tomography (MDCT) angiography using various reconstruction parameters and the results compared with conventional angiography. Fourteen patients (25 stents) were evaluated. From MDCT datasets, axial and coronal oblique reformations were reconstructed using differing reconstruction parameters (slice thickness, kernel, views). Artifacts and image quality were assessed using a five-degree scale (1=excellent, 5=poor). Visible stent diameter was measured. Stenosis severity was compared with calibrated catheter angiography. The image quality of medium and sharp image kernels were good/fair (1.9-2.4), while smooth kernel provided only acceptable/poor image quality (3.9-4.4). Coronal oblique images were rated superior to assess in-stent lumen rather than axial. Using medium and sharp kernels, the visible stent lumen was significantly greater than using smooth kernel (P<0.001). thirteen out of fourteen patients (24/25 stents) were correctly classified as patent. In one patient, in-stent stenosis (> or =50%) was falsely diagnosed using CT angiography (CTA) with smooth kernel and was, therefore, rated as false positive. Coronal oblique views, as well as medium and sharp kernels, have shown the best results regarding image quality to assess stent patency in the lower limb. Therefore, MDCT could be a valuable non-invasive modality for stent imaging in the peripheral vasculature.     

Diagnostic accuracy of 64-slice multidetector CT for detection of in-stent restenosis in an unselected, consecutive patient population

Objectives

To investigate the diagnostic accuracy of 64-slice multidetector computed tomography (64-CT) for detection of in-stent restenosis (ISR) in an unselected, consecutive patient population.

Background

Detection of in-stent restenosis by cardiac CT would be a major advance for the evaluation of patients suspected of having ISR. However, the diagnostic accuracy of current generation 64-CT in this context is not fully established.

Methods

We conducted a prospective study on patients with stable angina or acute coronary syndrome with no prior history of coronary artery disease. Six months after percutaneous coronary intervention (PCI) with stent placement they underwent a 64-CT scan (Toshiba Multi-Slice Aquilion 64) and consequently a repeat coronary angiography for comparison. Cardiac CT data sets were analyzed for the presence of in-stent restenosis by two independent expert readers blinded to the coronary angiographic data.

Results

Ninety-three patients with a total of 140 stents were evaluated. Males comprised 82% of the study group and the mean age was 63 ± 10 years. The mean time from PCI to the repeat coronary angiography was 208 ± 37 days and the mean time from 64-CT to repeat coronary angiography was 3.7 ± 4.9 days. The restenosis rate according to coronary angiography was 26%. Stent diameter, strut thickness, heart rate and body mass index (BMI) significantly affected image quality. The sensitivity, specificity, positive and negative predictive values of 64-CT for detection of in-stent restenosis were 27%, 95%, 67% and 78%, respectively.

Conclusions

Current generation, 64-slice CT, remains limited in its ability to accurately detect in-stent restenosis.     

Diagnostic accuracy of 16-slice multidetector-row CT for detection of in-stent restenosis vs detection of stenosis in nonstented coronary arteries

The purpose of this study was to assess the diagnostic accuracy of 16-slice multidetector-row computed tomography (MDCT) for detecting in-stent restenosis. Fifty patients with 69 previously implanted coronary stents underwent 16-slice MDCT before quantitative coronary angiography (QCA). Diagnostic accuracy of MDCT for detection of in-stent restenosis defined as >50% lumen diameter stenosis (DS) in stented and nonstented coronary segments >1.5-mm diameter was computed using QCA as reference. According to QCA, 18/69 (25%) stented segments had restenosis. In addition, 33/518 (6.4%) nonstented segments had >50% DS. In-stent restenosis was correctly identified on MDCT images in 12/18 stents, and absence of restenosis was correctly identified in 50/51 stents. Stenosis in native coronary arteries was correctly identified in 22/33 segments and correctly excluded in 482/485 segments. Thus, sensitivity (67% vs 67% p=1.0), specificity (98% vs 99%, p=0.96) and overall diagnostic accuracy (90% vs 97%, p=0.68) was similarly high for detecting in-stent restenosis as for detecting stenosis in nonstented coronary segments. MDCT has similarly high diagnostic accuracy for detecting in-stent restenosis as for detecting coronary artery disease in nonstented segments. This suggests that MDCT could be clinically useful for identification of restenosis in patients after coronary stenting. Grant Funding: Dr Gerber was supported by a grant from the Fondation Nationale de la Recherche Scientifique of the Belgian Government (FRSM 3.4557.02).     

Diagnosis of arterial sequestration using multidetector CT angiography

Background

Arterial sequestration is a rare congenital disorder. The diagnostic evaluation of this condition using multidetector computerized tomography (MDCT) has not been described previously. The purpose of this study was to describe the characteristic features of this disorder and to assess the use of MDCT in visualizing the characteristic anatomic features.

Methods

We retrospectively reviewed the records of seven patients with anomalous systemic blood supply to left lower lobe of the lung. All the patients had undergone MDCT angiography. To evaluate the lung parenchyma, bronchial branching pattern, and vascular anatomy, four series of images were systematically reconstructed as follows: contiguous transverse CT scans viewed at mediastinal and pulmonary window settings, oblique coronal and sagittal maximum intensity projections (MIP), multiplanar reconstruction (MPR), and three-dimensional volume-rendered images (VR) of airway and thoracic vascular structures.

Results

All 7 cases had isolated and tortuous arterial anatomy from the descending thoracic aorta to the basal segment of the left lower lobe; however, variable distribution of branches was observed. Characteristic findings of anomalous systemic arterial (ASA) supply were distinct from those seen in other pulmonary sequestration syndromes and were well visualized by the use of noninvasive MDCT.

Conclusion

Complex CT findings allow clear imaging of arterial sequestration and the ASA blood supply; MDCT angiography has demonstrated its value and accuracy in diagnosing this condition, obviating the use of digital subtraction angiography and magnetic resonance angiography for the diagnosis of arterial sequestration.     

Accuracy of multislice CT angiography for the assessment of in-stent restenoses in the iliac arteries at reduced dose: a phantom study

Objective

We investigated the potential of low-dose CT angiography for accurate assessment of in-stent restenoses (ISRs) of the iliac artery.

Method

A Rando anthropomorphic phantom (Alderson Research Labs, Stanford, CA), custom-made wax simulating hyperplastic tissue and a nitinol stent were used to simulate a patient with clinically relevant iliac artery ISRs. The cylindrical lumen was filled with a solution of iodine contrast medium diluted in saline, representing a patient''s blood during CT angiography. The phantom was subjected to standard- and low-dose angiographic exposures using a modern multidetector (MD) CT scanner. The percentage of ISR was determined using the profile along a line normal to the lumen axis on reconstructed images of 2 and 5 mm slice thickness. Percentage ISRs derived using the standard- and low-dose protocols were compared. In a preliminary study, seven patients with stents were subjected to standard- and low-dose MDCT angiography during follow-up. The resulting images were assessed and compared by two experienced radiologists.

Results

The accuracy in measuring the percentage ISR was found to be better than 12% for all simulated stenoses. The differences between percentage ISRs measured on images obtained at 120 kVp/160 mAs and 80 kVp/80 mAs were below 6%. Patient image sets acquired using low-exposure factors were judged to be of satisfactory diagnostic quality. The assessment of ISR did not differ significantly between image sets acquired using the standard factors and those acquired using the low-exposure factors, although the mean reduction in patient effective dose was 48%.

Conclusion

A reduction in exposure factors during MDCT angiography of the iliac artery is possible without affecting the accuracy in the determination of ISRs.Follow-up in patients treated with peripheral arterial stent implantation is usually performed with clinical examination, ankle–brachial index measurement, exercise testing and proof of patency using duplex ultrasonography. However, digital subtraction angiography (DSA) is still considered to be the best imaging technique for the assessment of in-stent restenosis (ISR) and stent patency in the iliac and proximal superficial femoral arteries following stent implantation as it offers the unique advantage of incorporating diagnostic confirmation and endovascular treatment in a single session. Apart from the relatively high patient radiation burden, the main disadvantage of DSA relates to its invasive nature. DSA is associated with a certain risk for potentially serious complications. Over the last few years, there has been a continuous effort to improve the safety and effectiveness of percutaneous revascularisation in peripheral arterial occlusive disease. A host of technological advances associated with endovascular treatment have been recently developed including novel angioplasty balloons and “shape memory” nitinol stents [1]. Currently, nitinol stents are considered to be the most modern solution for revascularisation of aortoiliac and lower extremity arteries [1]. In addition, the advent of multislice CT angiography during the last few years has provided a non-invasive alternative for the assessment of stented vessels. The use of modern 16- and 64-slice CT systems was recently proven to significantly improve spatial resolution and lumen visualisation, rendering multidetector CT (MDCT) angiography a powerful tool for ISR assessment [2-8].MDCT imaging is considered to be a high-dose diagnostic procedure resulting in absorbed doses to patient tissues of 10–100 mGy. The cumulative dose to patient tissues from multiple CT examinations may often approach or even exceed radiation dose levels known to significantly elevate the probability for cancer induction [9, 10]. MDCT systems are rather complicated systems, and appropriate adaptation of exposure factors to achieve optimisation of the examination is a complex task influenced strongly by the specific diagnostic demands [11]. Given that image quality in modern CT is often higher than that required to achieve diagnostic confidence [12], we felt that it would be interesting to study whether there is any potential for dose reduction in MDCT angiography imaging for ISR assessment. The purpose of the current study was to investigate the effect of reducing the exposure parameters during MDCT angiography on the assessment of clinically relevant ISR in patients with nitinol stents in the external iliac or proximal superficial femoral artery.     

Optimal scanning protocols of 64-slice CT angiography in coronary artery stents: An in vitro phantom study

Purpose

The purpose of the study was to investigate the optimal scanning protocol of 64-slice CT angiography for assessment of coronary artery stents based on a phantom study.

Materials and methods

Coronary stents with a diameter of 2.5 mm was implanted in thin plastic tubes with an inner diameter of 3.0 mm to simulate a coronary artery. The tubes were filled with iodinated contrast medium diluted to 178 HU, closed at both ends and positioned in a plastic container filled with vegetable oil (−70 to −100 HU). A series of scans were performed with a 64-slice CT scanner with the following protocols: section thickness: 0.67 mm, 1.0 mm, 1.5 mm, 2.0 mm, pitch value: 0.2, 0.3, 0.5 and reconstruction interval of 50% overlap of the section thickness. 2D axial and multiplanar reformatted images were generated to assess the visibility of stent lumen, while virtual intravascular endoscopy (VIE) was reconstructed to evaluate the artery wall and stent surface.

Results

Our results showed that a scanning protocol of 1.0 mm slice thickness with a pitch of 0.3 produced acceptable images with best demonstration of the intrastent lumen and stent surface with minimal image noise or artifacts. In contrast, submillimeter scans with 0.67 mm resulted in moderate artifacts which affected visualization of the coronary lumen, in addition to the increased noise. When the section thickness increased to 1.5 mm and 2.0 mm, visualization of the artery wall and stent surface was compromised, although the intrastent lumen was still visible.

Conclusion

Our in vitro study suggested that a scanning protocol of 1.0 mm section thickness with pitch of 0.3 is the optimal protocol for evaluation of coronary artery stents as it allows generation of acceptable images with better visualization of stent lumen, stent surface and coronary artery wall.     

Diagnostic value of color Doppler ultrasonography and MDCT angiography in complications of hemodialysis fistulas and grafts

Purpose

The purpose of the study was to compare the diagnostic value of color Doppler ultrasonography (CDUS) and multidetector computed tomography (MDCT) angiography against that of digital subtraction angiography (DSA) or surgery in the evaluation of failing hemodialysis arteriovenous fistulas (AVFs).

Materials and methods

CDUS and MDCT angiography were performed with 41 patients (24 men, 17 women; mean age 55.8) with dysfunctional hemodialysis fistulas. The presence of stenosis, thrombosis, aneurysm, pseudoaneurysm and seroma were recorded. The sensitivity, specificity, positive and negative predictive values (PPV and NPV) and accuracy of CDUS and MDCT angiography were calculated both individually and in combination for the detection of vascular segments with significant stenosis, thrombosis, aneurysms, pseudoaneurysms, perivascular complications and stenosis subgroups.

Results

Sixty-four segmental lesions were diagnosed by DSA or surgery. Sensitivity, specificity, PPV, NPV and accuracy of CDUS for all vascular tree lesions were 85.9%, 99.2%, 96.4%, 96.7% and 94.5%, respectively. For MDCT angiography the figures were 96.8%, 99.6%, 98.4%, 99.2% and 98.5%, respectively. When both tests were used in combination, sensitivity, specificity, PPV, NPV and accuracy for all vascular tree lesions rose to 100%.

Conclusion

Combined use of MDCT and CDUS for diagnosis of AVF dysfunctions is of equivalent value to surgery or DSA, a gold standard technique.     

Role of high resolution contrast-enhanced magnetic resonance angiography (HR CeMRA) in management of arterial complications of the renal transplant

Introduction

Transplant renal artery (RA) stenosis (TRAS) is the most frequent posttransplantation vascular complication. Contrast enhanced magnetic resonance (CeMRA) angiography has been established as the preferred imaging technique for the evaluation of TRAS because it does not require the use of iodinated contrast material and does not expose the patient to ionizing radiation. Digital subtraction angiography (DSA) is the gold standard in the evaluation of arterial tree of the renal allograft.

Aim of the work

This study was carried out to assess the accuracy of CeMRA in the detection of arterial complications after renal transplantation.

Patients and methods

Thirty renal transplant patients with suspected arterial complications in which both CeMRA and DSA were performed were included in the study. The HR CeMRA shows 93.7% sensitivity, 80% specificity, 88.2% positive predictive value, 88.9% negative predictive value and 88.5% accuracy.

Conclusion

HR CeMRA is an accurate reliable tool in the assessment of arterial complications after renal transplantation. It may replace DSA as a diagnostic modality with reservation of interventional techniques for endovascular treatment of suitable cases.     

Feasibility of gadolinium-diethylene triamine pentaacetic acid enhanced multidetector computed tomography for the evaluation of coronary artery disease

Background

Multidetector computed tomography (MDCT) has been proposed as a noninvasive method for the diagnosis of obstructive coronary artery disease (CAD). In patients with high risk of iodinated contrast adverse effects such as acute allergic-type reactions, the use of gadolinium could be an alternative.

Objective

We sought to evaluate the feasibility of gadolinium-enhanced MDCT for the diagnosis of obstructive CAD.

Methods

Twenty patients (mean age, 61 years; range, 50-73 years) referred for X-ray coronary angiography were studied by both gadolinium and iodine-enhanced 16-row MDCT coronary angiography. The degree of enhancement and the accuracy for detection of obstructive CAD (>50% diameter reduction) were evaluated with X-ray coronary angiography as the standard. Renal nephrotoxicity was strictly monitored.

Results

Gadolinium- and iodine-enhanced MDCT showed adequate visualization of the coronary arteries in 310 of the 312 coronary artery segments that were available by X-ray angiography, respectively. The average density of the coronary arteries in both iodine and gadolinium CT scans was 253.65 Hounsfield unit (HU) and 135.20 HU, respectively. In a per-coronary segment analysis, gadolinium- and iodine-enhanced MDCT showed sensitivities of 89% vs 84%, specificities of 96% vs 95%, and negative predictive values of 97% vs 96%, respectively. In a per-patient analysis, both gadolinium- and iodine-enhanced MDCT showed sensitivities of 92.85% vs specificities of 83.33%. Intermethod agreement between gadolinium- and iodine-enhanced MDCT (κ) was 0.95 (P < 0.0001).

Conclusion

Our preliminary results indicate lower attenuation with gadolinium but similar diagnostic accuracy for the detection of obstructive CAD when compared with iodine-enhanced MDCT. Therefore, gadolinium is a feasible alternative contrast agent for patients with iodine contrast allergy referred for MDCT coronary angiography.     

In vivo evaluation of patency and in-stent stenoses after implantation of nitinol stents in iliac arteries using MR angiography

OBJECTIVE: Our study was a prospective in vivo study to evaluate whether MR angiography is suitable for assessing stent patency and grading in-stent stenoses and to examine whether the accuracy of MR angiography changes with time after stent implantation. SUBJECTS AND METHODS: In a prospective study, 34 iliac stenoses in 27 patients were treated by implantation of 35 nitinol stents. MR angiography was performed immediately after stent placement for 32 stents, and both digital subtraction angiography (DSA) and MR angiography were repeated at the 6-month follow-up for 23 stents. Three blinded observers assessed stent patency and the degree of in-stent stenoses on MR angiography and DSA (the standard of reference) images. The difference between the observers' grading of stenoses on DSA and on MR angiography was determined. Statistical analysis was performed using the Student's t test for paired samples. RESULTS: Stent patency was assessed correctly for all stents and both sets of MR angiography images. Evaluation of DSA 1 images (obtained at end of implantation procedure) revealed that 96.9% of in-stent stenoses were less than 50%. On DSA 2 images (obtained at follow-up), 95.7% of in-stent stenoses were graded as less than 50%. The difference between grading of stenoses on DSA and MR angiography images was 15.0% +/- 16.0% (minimum, 0.0%; maximum, 63.3%) for DSA 1 versus MR angiography 1 (statistically significant, p = 0.037) and 9.8% +/- 13.5% (minimum, 0.0%; maximum, 63.3%) for MR angiography 2 versus DSA 2 (not statistically significant, p = 0.355). CONCLUSION: Patency was correctly assessed for all stents on MR angiography. The quality of MR angiography regarding characterization of in-stent stenoses improved with time after stent placement. However, discrepancies of more than 60% between grading of lumen narrowing on DSA and MR angiography images occurred even at the 6-month follow-up. Thus, MR angiography is not yet a reliable technique for characterization of in-stent stenoses.     

320-Multidetector row whole-head dynamic subtracted CT angiography and whole-brain CT perfusion before and after carotid artery stenting: Technical note

Introduction

Multidetector CT (MDCT) is increasingly used for the investigation of neurovascular disorders, but restricted z-axis coverage (3.2 cm for 64-MDCT) currently limits perfusion to a small portion of the brain close to the circle of Willis, and precludes dynamic angiographic appreciation of the entire brain circulation. We illustrate the clinical potential of recently developed 320-MDCT extending the z-axis coverage to 16 cm in a patient with symptomatic carotid artery stenosis.

Methods

In a 74-year-old patient presenting with critical symptomatic stenosis of the left CCA, pre- and post-carotid artery stenting whole-head subtracted dynamic MDCT angiography and perfusion were obtained in addition to CT angiography of the supra-aortic trunks. Both whole-head subtracted MDCT angiography and perfusion demonstrated delayed left ICA circulation, which normalized after carotid stenting.

Discussion

320-MDCT offers unprecedented z-axis coverage allowing for whole-brain perfusion and subtracted dynamic angiography of the entire intracranial circulation. These innovations can consolidate the role of MDCT as a first intention imaging technique for cerebrovascular disorders, in particular for the acute management of stroke.     

Volume-rendered multidetector CT angiography: noninvasive follow-up of patients treated with renal artery stents

OBJECTIVE: The purpose of our study was to evaluate the role of multidetector CT (MDCT) angiography with volume rendering for estimating the patency of renal artery stents. SUBJECTS AND METHODS: In 16 patients, 16 renal artery stents were evaluated with MDCT renal angiography and digital subtraction angiography (DSA). CT data were evaluated using multiplanar volume reformations and the volume-rendering algorithm with three different volume-rendered parameter settings (low-to-high, high-to-low, and high-low-high opacity transfer functions: VR(LH), VR(HL), and VR(VE), respectively). Targeted images of each stent were rendered in paraaxial and paracoronal planes and were interactively interpreted. The overall restenosis severity was measured on postprocessed paraaxial and paracoronal images and compared with that obtained on DSA using linear regression analysis. Image quality and lumen delineation on rendered images were also compared using Wilcoxon's signed rank test. RESULTS: Eight restenoses were identified on DSA. Correlations between restenosis severity measured with DSA and those measured with MDCT were significant (p < 0.001). Volume rendering with VR(HL) allowed the best correlation with DSA (reviewer 1, r(2) = 0.86; reviewer 2, r(2) = 0.94) and was significantly better than multiplanar volume reformations (p = 0.028). Overall image quality was high with all rendering techniques and with no significant differences (p > 0.59, for all comparisons). Stent lumen was well delineated with volume-rendering modalities; however, VR(HL) was significantly better than VR(LH) (p = 0.033). CONCLUSION: Volume-rendered MDCT angiography enabled high-quality three-dimensional reproducible evaluation of the patency of implanted renal artery stents. Volume rendering with VR(HL) achieved the best performance.     

Improving the image quality of contrast-enhanced MR angiography by automated image registration: A prospective study in peripheral arterial disease of the lower extremities

Objective

If a patient has moved during digital subtraction angiography (DSA), manual pixel shift can improve the image quality. This study investigated whether such image registration can also improve the quality of contrast-enhanced magnetic resonance angiography (MRA) in patients with peripheral arterial disease of the lower extremities.

Materials and methods

404 leg MRAs of patients likely to have peripheral artery disease were included in this prospective study. The standard non-registered MRAs were compared to automatically linear, affine and warp registered MRAs by four image quality parameters, including the vessel detection probability (VDP) in maximum intensity projection (MIP) images and contrast-to-noise ratios (CNR). The different registration types were compared by analysis of variance.

Results

All studied image quality parameters showed similar trends. Generally, registration improved the leg MRA quality significantly (P < 0.05). The 12% of lower legs with a body shift of 1 mm or more showed the highest gain in image quality when using linear registration instead of no registration, with an average VDP gain of 20-49%. Warp registration improved the image quality slightly further.

Conclusion

Automated image registration can improve the MRA image quality especially in the lower legs, which is comparable to the effect of pixel shift in DSA.     

Coronary CT angiography with dual source computed tomography in 170 patients

Introduction

In preliminary studies DSCT provides robust image quality over a wide range of heart rates and excludes CAD with high accuracy.The aim of the present study was to evaluate the reproducibility of these results in a large, unselected and consecutive group of patients scheduled for invasive coronary angiography (ICA).

Material and methods

170 patients (124 men, 46 women; mean age: 64 ± 9 years) with known CAD (101 patients) or suspected CAD (69 patients) scheduled for ICA were examined by coronary CTA prior to ICA. All coronary segments were assessed for image quality (1: excellent; 5: non-diagnostic). The presence of significant vessel stenosis (>50%) was calculated using ICA as standard of reference.

Results

A total of 680 vessels were analyzed. Despite of 45 arrythmic patients all analyzed coronary segments were diagnostically evaluable. Mean Agatston score equivalent was 686 (range 0-4950). ICA revealed 364 lesions with ≥50% diameter stenosis. DSCT correctly identified 336 of these lesions. 115 lesions with a diameter stenosis ≤50% were overestimated by DSCT and thus considered as false-positive findings. On a per-segment basis, sensitivity was 92%, specificity 93%, positive predictive value (PPV) was 75% and negative predictive value (NPV) 98%. On a per-vessel basis DSCT revealed a sensitivity of 93%, a specificity of 88%, a PPV of 78% and a NPV of 97%. On a per-patient basis sensitivity was 94%, specificity 79%, PPV 88% and NPV 90%.

Conclusions

Initial results of preliminary studies showing robust image quality and high accuracy in DSCT cardiac imaging could be approved with the present study enclosing a large consecutive population. However severe coronary calcifications and irregular heart rate still remain limiting factors for coronary CTA.Despite improved image quality and high accuracy of coronary DSCT angiography, proof of indication is necessary, due to still remaining limiting factors.