Performance of dual source versus 256-slice multi-slice CT in the evaluation of 16 coronary artery stents

Introduction

Invasive coronary angiography is the reference method for identification of in-stent restenosis (ISR) bearing the disadvantages of high costs and invasiveness. New approaches like dual-source CT (DSCT) and 256-multi-slice CT (256-MSCT) may potentially be the future methods of choice to reliably exclude ISR in patients with low or intermediate risk of restenosis.We sought to compare the performance of DSCT and 256-MSCT for the in vitro assessment of stent lumen diameter and basic scan parameters in stents of various diameters and designs.

Materials and Methods

In 16 coronary artery stents we evaluated relative in-stent lumen diameter, attenuation, noise, attenuation-/signal-to-noise ratio (ANR/SNR) and radiation dose (CTDI_vol) in an acknowledged coronary vessel in vitro phantom (iodine-filled plastic tubes) with DSCT (Siemens, SOMATOM Definition, collimation = 2 × 64 × 0.6 mm, pitch = 0.26, current = 400 mAs/rot, voltage = 120 kV, tube-rotation-time = 330 ms) and 256-MSCT (Philips Brilliance, iCT, tube collimation = 2 × 128 × 0.625 mm, pitch = 0.18, current = 800 mAs_eff, voltage = 120 kV, tube-rotation-time = 270 ms). Diameter analysis was conducted with the observer-independent full-width-at-half-maximum (FWHM) technique.

Results

DSCT and 256-MSCT revealed similar stent lumen diameters (50.7 ± 7.2% vs. 50.8 ± 7.4%, p = 0.98). Attenuation (−19 ± 25 HU vs. 54 ± 29 HU), ANR (−0.9 ± 1.2 vs. 2.9 ± 1.8) and SNR (12.1 ± 2.4 vs. 17.4 ± 1.9) were better in the DSCT (all p < 0.001) at the expense of significantly higher radiation doses (CTDI_vol = 87 vs. 51 mGy, p < 0.01). Noise was comparable (21 ± 2 HU vs. 20 ± 2 HU, p = n.s.). Only stents with a diameter >3 mm allowed sufficient stent lumen assessment in both scanners and showed a relative lumen diameter of 60–66%.

Conclusions

The measured stent lumen diameter and image noise were similar in both scanners. Yet the DSCT offered a more truthful stent lumen visualization at the cost of higher radiation dose.Applying the FWHM approach only stents with a diameter >3 mm offered sufficient stent lumen assessment.     

Diagnostic accuracy of 64-slice computed tomography coronary angiography for the detection of in-stent restenosis: A meta-analysis

Background

We sought to evaluate the diagnostic accuracy of 64-slice multi-detector row computed tomography (MDCT) compared with invasive coronary angiography for in-stent restenosis (ISR) detection.

Methods

MEDLINE, Cochrane library, and BioMed Central database searches were performed until April 2009 for original articles. Inclusion criteria were (1) 64-MDCT was used as a diagnostic test for ISR, with >50% diameter stenosis selected as the cut-off criterion for significant ISR, using invasive coronary angiography and quantitative coronary angiography as the standard of reference; (2) absolute numbers of true positive, false positive, true negative, and false negative results could be derived. Standard meta-analytic methods were applied.

Results

Nine studies with a total of 598 patients with 978 stents included were considered eligible. On average, 9% of stents were unassessable (range 0-42%). Accuracy tests with 95% confidence intervals (CIs) comparing 64-MDCT vs invasive coronary angiography showed that pooled sensitivity, specificity, positive and negative likelihood ratio (random effect model) values were: 86% (95% CI 80-91%), 93% (95% CI 91-95%), 12.32 (95% CI 7.26-20.92), 0.18 (95% CI 0.12-0.28) for binary ISR detection. The symmetric area under the curve value was 0.94, indicating good agreement between 64-MDCT and invasive coronary angiography.

Conclusions

64-MDCT has a good diagnostic accuracy for ISR detection with a particularly high negative predictive value. However, still a relatively large proportion of stents remains uninterpretable. Accordingly, only in selected patients, 64-MDCT may serve as a potential alternative noninvasive method to rule out ISR.     

Next generation coronary CT angiography: in vitro evaluation of 27 coronary stents

Objectives

To evaluate in-stent lumen visibility of 27 modern and commonly used coronary stents (16 individual stent types, two stents at six different sizes each) utilising a third-generation dual-source CT system.

Methods

Stents were implanted in a plastic tube filled with contrast. Examinations were performed parallel to the system's z-axis for all stents (i.e. 0°) and in an orientation of 90° for stents with a diameter of 3.0 mm. Two stents were evaluated in different diameters (2.25 to 4.0 mm). Examinations were acquired with a collimation of 96?×?0.6 mm, tube voltage of 120 kVp with 340 mAs tube current. Evaluation was performed using a medium-soft (Bv40), a medium-sharp (Bv49) and a sharp (Bv59) convolution kernel optimised for vascular imaging.

Results

Mean visible stent lumen of stents with 3.0 mm diameter ranged from 53.3 % (IQR 48.9???56.7 %) to 73.9 % (66.7???76.7 %), depending on the kernel used at 0°, and was highest at an orientation of 90° with 80.0 % (75.6???82.8 %) using the Bv59 kernel, strength 4. Visible stent lumen declined with decreasing stent size.

Conclusions

Use of third-generation dual-source CT enables stent lumen visibility of up to 80 % in metal stents and 100 % in bioresorbable stents.

Key Points

? Blooming artefacts impair in–stent lumen visibility of coronary stents in CT angiography. ? CT enables stent lumen visibility of up to 80 % in metal stents. ? Stent lumen visibility varies with stent orientation and size. ? CT angiography may be a valid alternative for detecting in-stent restenosis.     

Prevalence and prognosis of coronary stent gap detected by multi-detector CT: a follow-up study

Objectives

To evaluate the features of stent gap (SG) and the long-term impact of SG on in-stent restenosis (ISR) in patent stents.

Methods

A total of 347 consecutive patients with 781 stents who underwent MDCT were assessed for SG and ISR. Clinical and stent features were compared between the SG and non-SG groups. In the follow-up study, among 82 patients with 175 patent stents [26 assessed by conventional coronary angiography (CCA) including 6 contacted in a telephone survey, 46 assessed by computed tomography angiography (CTA) and 10 by both], the incidence of ISR was compared between stents with and without SG.

Results

Three patients and 13 stents were excluded. SG was observed in 12.5% of patients and 8.6% of stents. ISR detected by CTA was noted in 21.2% of SG, and SG accounted for 23.7% of ISR. Stent number, length, location, overlapping pattern, tortuosity and in-out angle were predisposing factors for SG. During a mean follow-up period of 15?months after detection of SG, the incidence of ISR was significantly higher in the SG group than in the non-SG group (43.8/14.9% by CCA, 33.3/10.1% by CTA and CCA).

Conclusion

Patent stents with SG detected by CTA had a higher incidence of late restenosis, indicating that long-term follow-up or further intervention is necessary.

Key Points

? Coronary artery computed tomographic angiography (CTA) is increasingly used following coronary intervention. ? Gaps within coronary stents detected by CTA correlate with in-stent restenosis. ? Patients with stent gaps have more late restenosis at follow-up. ? More attention should be given to patients with stent gaps.     

Angiographic patterns of in-stent restenosis classified by computed tomography in patients with drug-eluting stents: correlation with invasive coronary angiography

Objectives

To evaluate the diagnostic accuracy of Mehran??s in-stent restenosis (ISR) classification by coronary computed angiography (CCTA), with reference to invasive coronary angiography (ICA).

Methods

Consecutive symptomatic patients, who had clinically suspected ISR and implanted stent diameter ?? 3?mm, were prospectively enrolled in our study. Mehran??s classification was employed by CCTA and ICA to classify ISR lesions into four subtypes: focal, diffuse intrastent, diffuse proliferative and total occlusion. CCTA and ICA measurement of lesion length was further compared.

Results

Sixty-one patients with 101 implanted stents were included in our study. The overall sensitivity, specificity, PPV and NPV of CCTA diagnosis of binary ISR, as shown by patient-based analysis (n?=?61), were 100?% (49/49), 75?% (8/12), 92.45?% (49/53) and 100?% (8/8) respectively. Mehran??s classification of CCTA correlated well with ICA findings. The diagnostic accuracy of CCTA for class I, class II, class III and class IV lesions was 92.5?%, 91.67?%, 100?% and 100?% respectively. Lesion length was assessed to be significantly longer with CCTA than with ICA (11.03?±?5.89?mm versus 8.56?±?4.99?mm, P?<?0.001).

Conclusions

Angiographic patterns of in-stent restenosis can be accurately classified by coronary computed angiography. The lesion length measured by CCTA is longer than that assessed by invasive coronary angiography

Key Points

? Patterns of in-stent restenosis can be accurately classified by coronary computed angiography. ? Lesion length appears longer on CCTA than on invasive coronary angiography. ? Stent occlusion is better delineated by coronary computed angiography. ? Optimal treatment can be planned pre-operatively based on CCTA evaluation.     

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 performance of computed tomography angiography in the detection of coronary artery in-stent restenosis: evidence from an updated meta-analysis

Objectives

To evaluate the performance of computed tomography angiography (CTA) ≥64 slices for detecting coronary in-stent restenosis (ISR) and determine the influence of separate characteristics on diagnostic accuracy.

Methods

We searched the PubMed, EMBASE and Cochrane databases for studies of CTA ≥64 slices in diagnosing ISR. We pooled data on bivariate modelling, and subgroup analysis was also performed.

Results

A total of 35 studies involving 4131 stents were included. The pooled positive likelihood ratio (LR⁺) and the negative likelihood ratio (LR^–) were 14.0 and 0.10, for CTA in diagnosis-significant ISR ≥50%. LR⁺ and LR^– were similar between CTA >64 slices versus 64 slices (both P > 0.99). LR^– (0.10) was good for ruling out suspected ISR for <3-mm diameter. Time between CTA and stent implantation >6 months did not affect the ability of CTA for the high LR⁺ (12.3) and the LR^– (0.10). Thick-strut stents ≥100 μm or bifurcation stenting demonstrated inferior accuracy, which was unfavourable for stent imaging.

Conclusions

With the high LR⁺ and LR^– of CTA, patients with ISR may be appropriate for non-invasive angiographic follow-up. However, CTA imaging seems unsuitable for patients with characteristics unfavourable for stent imaging, such as thick-strut stents or bifurcation stenting.

Key points

? CTA may provide accurate information on characteristics of in-stent restenosis lesions. ? Using CTA, ISR patients may be appropriate for non-invasive angiographic follow-up. ? Stent diameter and the number of slices do not influence CTA. ? CTA seems unsuitable for patients with thick-strut stents or bifurcation stenting.

     

Monoenergetic reconstructions for imaging of coronary artery stents using spectral detector CT: In-vitro experience and comparison to conventional images

Purpose

Accurate assessment of coronary stents using non-invasive CT imaging remains challenging despite new stent materials and improvements in CT technology. Virtual monoenergetic (monoE) images reconstructed from dual energy CT acquisitions potentially decrease artifacts caused by coronary stents. A novel spectral detector technology provides monoE and conventional images simultaneously for all conducted scans. The purpose of our study was to systematically investigate the influence of different monoE reconstructions on the visualization of coronary stent lumen in comparison to conventional images.

Incidence and classification of neointimal proliferation and in-stent restenosis in post-stenting patients at 1-year interval: Findings from non-invasive coronary computed tomography angiography

Objectives

To evaluate the incidence of coronary in-stent restenosis (ISR) and neointimal proliferation by coronary CT angiography (CCTA) at 1-year follow-up in asymptomatic patients.

Methods

234 patients (mean age: 67 ± 10.2 years, range 39–88 years, 180 males and 54 females) with 379 stents were prospectively enrolled in this study. Binary ISR was classified by CCTA into 4 types using Mehran classification. Neointimal proliferation was similarly classified into focal and diffuse types. All patients with CCTA-revealed ISR or neointimal proliferation underwent further invasive coronary angiography (ICA) for validation. Fisher's exact test was used for comparison.

Results

ICA revealed patent stents with neointimal proliferation in 39 patients (16.7%, 39/234) and binary ISR in 23 patients (9.8%, 23/234). Lesion-based analysis showed 12 type I ISR lesions, 4 type II ISR lesions, 1 type III ISR lesion and 7 type IV ISR lesions. Among cases with neointimal proliferation, 27 lesions were classified as focal type whereas 13 lesions were classified as diffuse type. Patients with diabetes mellitus were associated with higher incidence of CCTA-revealed neointimal proliferation (21/77 vs. 18/157, p = 0.002) as well as ISR (12/77 vs. 11/157, p = 0.038), compared to patients without diabetes. CCTA was found to have good diagnostic performance for neointimal proliferation and ISR detection as well as classification, with an overall accuracy of 84.4% (54/64).

Conclusions

Silent ISR as well as neointimal proliferation is not uncommon findings in asymptomatic post-stenting patients at 1-year interval, as revealed by CCTA. Patients with diabetes are prone to have higher incidence of neointimal proliferation.     

High diagnostic accuracy of prospective ECG-gating 64-slice computed tomography coronary angiography for the detection of in-stent restenosis: in-stent restenosis assessment by low-dose MDCT

Objectives

The accuracy of computed tomography (CT) for assessment of coronary stents is as yet unproven and radiation exposure has been a concern. The aim of our study is to compare radiation dose and diagnostic performance of CT with prospective ECG-triggering versus retrospective ECG-triggering for the detection of in-stent restenosis (ISR).

Methods

We enrolled 168 consecutive patients with suspected ISR, 83 studied using CT with prospective ECG-triggering (group 1) and 85 using retrospective ECG-triggering (group 2).

Results

Prevalence of ISR according to catheter angiography was 24% in both groups. The overall evaluability was similar (93% in group 1 vs 95% in group 2). Artefact sub-analysis showed a significantly lower number of blooming and higher number of slice misalignment in group 1 vs group 2. In the stent-based analysis using only evaluable stents, specificity, positive predictive value and accuracy were significantly higher in group 1 (100%, 100% and 99%, respectively) than in group 2 (97%, 91% and 95%, respectively, p?<?0.05). Group 1 was exposed to a lower radiation dose compared with group 2 (4.3?±?1.4?mSv vs 18.5?±?5.5?mSv, p?<?00.1).

Conclusions

CT with prospective ECG-triggering can improve diagnostic accuracy of non-invasive imaging of coronary stents with a significant reduction in radiation exposure     

Non-invasive assessment of coronary artery stent patency with multislice CT: preliminary experience

PURPOSE: To evaluate the diagnostic accuracy of multislice computed tomography coronary angiography (MSCT-CA) in the detection of in-stent restenosis. MATERIALS AND METHODS: Forty-two patients (33 male, 9 female, mean age 58+/-8 years) previously subjected to percutaneous implantation of coronary stent with suspected in-stent restenosis, underwent a 16-row MSCT (Sensation 16, Siemens) examination. The average time between stent implantation and MSCT-CA was 7.4+/-5.3 months. The following scan parameters were used: collimation 16x0.75 mm, rotation time 0.42 s, feed 3.0 mm/rot., kV 120, mAs 500. After administration of iodinated contrast material (Iomeprol 400 mgI/ml, 100 ml at 4 ml/s) and bolus chaser (40 ml of saline at 4 ml/s) the scan was completed in <20 s. All segments with a stent were assessed by two observers in consensus and were graded according to the following scheme: patent stent, in-stent intimal hyperplasia (IIH) (lumen reduction <50%), in-stent restenosis (ISR) (=/>50%), in-stent occlusion (ISO) (100%). Consensus reading was compared with coronary angiography. RESULTS: Forty-seven stents were assessed (16 in the right coronary artery; 4 in the left main; 22 in the left anterior descending; 5 in the circumflex). In 7 (17%) stents there was ISR (3) or ISO (4), and in 4 (10%) stents there was IIH. The sensitivity and negative predictive values for the detection of ISO were 80% and 98%, respectively, while for the detection of ISR+ISO they were 50% and 89%, respectively. CONCLUSIONS: Although the results are encouraging, the follow-up of stent patency with MSCT-CA does not show a diagnostic accuracy suitable for clinical implementation.     

In vitro imaging of coronary artery stents: Are there differences between 16- and 64-slice CT scanners?

Purpose

To compare the performance of 64-slice with 16-slice CT scanners for the in vitro evaluation of coronary artery stents.

Methods and materials

Twelve different coronary artery stents were placed in the drillings of a combined heart and chest phantom, which was scanned with a 16- and 64-slice CT scanner. Coronal reformations were evaluated for artificial lumen narrowing, intraluminal attenuation values, and false widening of the outer stent diameter as an indicator of artifacts outside the stent.

Results

Mean artificial lumen narrowing was not significantly different between the 16- and 64-slice CT scanner (44% versus 39%; p = 0.408). The differences between the Hounsfield Units (HU) measurements inside and outside the stents were significantly lower (p = 0.001) with 64- compared to 16-slice CT. The standard deviation of the HU measurements inside the stents was significantly (p = 0.002) lower with 64- than with 16-slice CT. Artifacts outside the stents were not significantly different between the scanners (p = 0.866).

Conclusion

Visualization of the in-stent lumen is improved with 64-slice CT when compared with 16-slice CT as quantified by significantly lesser intraluminal image noise and less artificial rise in intraluminal HU measurement, which is the most important parameter for the evaluation of stent patency in vivo.     

Temporary placement of covered retrievable expandable nitinol stents with barbs in high-risk surgical patients with benign prostatic hyperplasia: work in progress

Purpose

To report the use of a newly constructed, covered, retrievable, expandable nitinol stent with barbs to overcome the problem of stent migration associated with conventional covered prostatic expandable stents and to evaluate prospectively the technical feasibility and clinical effectiveness of the stents in patients with benign prostatic hyperplasia (BPH).

Materials and Methods

A covered retrievable expandable nitinol stent with four barbs was placed with use of an 18-F stent delivery system in seven consecutive patients with symptomatic BPH who had high operative risks. Age range of patients was 62–83 years (mean 74 years). In cases in which the stent migrated, it was replaced with a stent with eight barbs. The stents were routinely removed 4 months after placement using a 21-F stent removal set.

Results

Stent placement was technically successful and well tolerated in six of the seven patients. The remaining patient needed a second stent placement after removal of the first stent. The stent with four barbs migrated into the urinary bladder in four patients (57%); three of these patients received a second stent with eight barbs with good results, and the fourth patient did not need further treatment because his symptoms improved. Routine removal of the stent 4 months after placement was performed in three of the seven patients with good results.

Conclusions

Retrievable stents with eight barbs seem to overcome the problem of stent migration associated with conventional prostatic expandable stents. Preliminary results suggest that stents with barbs are both feasible and effective in patients with BPH.     

Evaluation of coronary artery in-stent restenosis with prospectively ECG-triggered axial CT angiography versus retrospective technique: a phantom study

Purpose

This study compared the performance of prospectively electrocardiographically (ECG)-triggered axial computed tomography (CT) angiography with retrospective technique in evaluating coronary artery stent restenosis by 64-slice CT.

Materials and methods

A pulsing cardiac phantom with artificial coronary artery in-stent restenosis was examined by CT angiography with different types of scan modes. The visibility of in-stent restenosis was evaluated with a three-point score. Artificial lumen narrowing [(inner stent diameter-measured lumen diameter)/inner stent diameter], lumen attenuation increase ratio [(in-stent attenuation-coronary artery lumen attenuation)/coronary artery lumen attenuation], measurement error of restenosis percent [(known restenosis percent-measured restenosis percent)/known restenosis percent] and imaging noise were analysed.

Results

Prospective acquisition showed better visibility than retrospective acquisition (p<0.05): 61% of in-stent restenoses had good visibility on the prospective acquisition compared with 17% on the retrospective acquisition. Furthermore, the effective dose was 6.2±0.3 mSv for the prospective technique compared with 18.8±1.1 mSv for the retrospective technique. Artificial lumen narrowing (mean 40%), lumen attenuation increase ratio (mean 33%) and measurement error of restenosis percent were not different between types of CT acquisitions.

Conclusions

Compared with the traditional retrospective technique, prospective coronary CT angiography offers improved image quality and reduces effective radiation dose in evaluating in-stent restenosis.     

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.     

High-Definition Computed Tomography for Coronary Artery Stent Imaging: a Phantom Study

Objective

To assess the performance of a high-definition CT (HDCT) for imaging small caliber coronary stents (≤ 3 mm) by comparing different scan modes of a conventional 64-row standard-definition CT (SDCT).

Materials and Methods

A cardiac phantom with twelve stents (2.5 mm and 3.0 mm in diameter) was scanned by HDCT and SDCT. The scan modes were retrospective electrocardiography (ECG)-gated helical and prospective ECG-triggered axial with tube voltages of 120 kVp and 100 kVp, respectively. The inner stent diameters (ISD) and the in-stent attenuation value (AV_in-stent) and the in-vessel extra-stent attenuation value (AV_in-vessel) were measured by two observers. The artificial lumen narrowing (ALN = [ISD - ISD_measured]/ISD) and artificial attenuation increase between in-stent and in-vessel (AAI = AV_in-stent - AV_in-vessel) were calculated. All data was analyzed by intraclass correlation and ANOVA-test.

Results

The correlation coefficient of ISD, AV_in-vessel and AV_in-stent between the two observers was good. The ALNs of HDCT were statistically lower than that of SDCT (30 ± 5.7% versus 35 ± 5.4%, p < 0.05). HDCT had statistically lower AAI values than SDCT (15.7 ± 81.4 HU versus 71.4 ± 90.5 HU, p < 0.05). The prospective axial dataset demonstrated smaller ALN than the retrospective helical dataset on both HDCT and SDCT (p < 0.05). Additionally, there were no differences in ALN between the 120 kVp and 100 kVp tube voltages on HDCT (p = 0.05).

Conclusion

High-definition CT helps improve measurement accuracy for imaging coronary stents compared to SDCT. HDCT with 100 kVp and the prospective ECG-triggered axial technique, with a lower radiation dose than 120 kVp application, may be advantageous in evaluating coronary stents with smaller calibers (≤ 3 mm).     

Use of Self-Expanding Stents for the Treatment of Vertebral Artery Ostial Stenosis: a Single Center Experience

Objective

To evaluate our early experience using self-expanding stents to treat atherosclerotic vertebral artery ostial stenosis (VAOS), with respect to technical feasibility and clinical and imaging follow-up results.

Materials and Methods

A total of 20 lesions in 20 patients underwent stenting of the VAOS using a self-expanding stent (Precise RX; Cordis Neurovascular, Miami Lakes, FL). Two patients were asymptomatic. We analyzed the technical success rate, causes of technical failure, occurrence of any vascular or neurological event, and the occurrence of any neurological abnormality or in-stent restenosis (ISR) seen on follow-up. The imaging follow-up was performed with Doppler ultrasound (DUS) as a primary screening modality.

Results

One instance of technical failure was caused by failure of the guidewire passage. The stent diameter was 5 mm, and post-stenting balloon dilatations were necessary in all cases. Stent misplacement requiring placement of an additional stent occurred in four cases. Following a 14.8 month average clinical follow-up time, two patients showed anterior circulation ischemia, which was not attributed to the VAOS we treated. Following a 13.7 month average DUS follow-up, five patients showed a mild degree of diffuse or focal intimal thickening in the stent lumen; however, none of the stenosis showed luminal loss of more than 50% and no stent fracture was noted.

Conclusion

The use of self-expanding stents for treating VAOS was technically feasible and helped to improve artery patency during our limited follow-up interval.     

Prospective study comparing different indirect methods to measure portal pressure

Purpose

To compare the accuracy of wedged hepatic venous pressure (WHVP) measurement with use of an end-hole catheter or an occlusion-balloon catheter versus direct portal pressure (PP) measurement in patients with cirrhosis with sinusoidal portal hypertension and to investigate the factors that affect the results of these indirect measurements.

Materials and Methods

In a cohort of 174 patients with cirrhosis referred for transjugular intrahepatic portosystemic shunt creation, indirect PP was measured with an end-hole catheter and an occlusion-balloon catheter placed in the right hepatic vein. Direct PP was measured by a pigtail catheter in the main branch of the portal vein.

Results

PP was more accurately estimated by the occlusion-balloon technique: mean WHVP measurements were 25.5 mm Hg ± 7.9 and 30.6 mm Hg ± 13.9, respectively, for the occlusion-balloon and end-hole catheter techniques, and the direct PP measurement was 25.0 mm Hg ± 7.0. The median absolute differences between direct and the indirect methods were 6.0 mm Hg with the end-hole catheter and 2.0 mm Hg with the occlusion-balloon catheter (P < .0001, signed-rank test). Relative to direct PP measurements, the occlusion-balloon technique overestimated pressures in cases of higher Model for End-Stage Liver Disease (MELD) scores (Spearman ρ = −0.24; P = .0005).

Conclusions

Compared with direct PP measurements, agreement was clearly higher for indirect WHVP measurement with occlusion-balloon catheters versus end-hole catheters. However, in patients with a high MELD score, there was an overestimation of PP with the occlusion-balloon method.     

Coronary artery stent imaging with 128-slice dual-source CT using high-pitch spiral acquisition in a cardiac phantom: comparison with the sequential and low-pitch spiral mode

Objective

To evaluate coronary stents in vitro using 128-slice-dual-source computed tomography (CT).

Methods

Twelve different coronary stents placed in a non-moving cardiac/chest phantom were examined by 128-slice dual-source CT using three CT protocols [high-pitch spiral (HPS), sequential (SEQ) and conventional spiral (SPIR)]. Artificial in-stent lumen narrowing (ALN), visible inner stent area (VIA), artificial in-stent lumen attenuation (ALA) in percent, image noise inside/outside the stent and CTDIvol were measured.

Results

Mean ALN was 46% for HPS, 44% for SEQ and 47% for SPIR without significant difference. Mean VIA was similar with 31% for HPS, 30% for SEQ and 33% for SPIR. Mean ALA was, at 5% for HPS, significantly lower compared with ?11% for SPIR (p?=?0.024), but not different from SEQ with ?1%. Mean image noise was significantly higher for HPS compared with SEQ and SPIR inside and outside the stent (p?<?0.001). CTDIvol was lower for HPS (5.17 mGy), compared with SEQ (9.02 mGy) and SPIR (55.97 mGy), respectively.

Conclusion

The HPS mode of 128-slice dual-source CT yields fewer artefacts inside the stent lumen compared with SPIR and SEQ, but image noise is higher. ALN is still too high for routine stent evaluation in clinical practice. Radiation dose of the HPS mode is markedly (less than about tenfold) reduced.     

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.