Evaluation of peripheral artery stent with 64-slice multi-detector row CT angiography: prospective comparison with digital subtraction angiography

Evaluation of resistance to radial cyclic loads of poly(L-lactic acid) braided stents with different braiding angles

Poly(L-lactic acid) (PLLA) braided stents have superior biocompatibility and flexibility, substituting metal stents in peripheral blood vessels. However, the radial supporting capacity of PLLA braided stent should be improved to bear the dynamic load from the peripheral artery. This paper evaluated the radial support performance of PLLA braided stents with different braiding angles after the radial cyclic loads test. The results indicate that braiding angle of stents is an important parameter affecting its ability to resist radial cyclic loads. The stent with a smaller braiding angle has better initial radial support but insufficient durability, while the stent with a larger braiding angle could maintain adequate radial support and suitable ability to resist radial cyclic loads. The theoretical analysis, verified by observing the surface morphology of filament crossover points, found that filaments of the stents with smaller braiding angles have more significant axial displacement and axial rotation angle during radial compression, which made the friction phenomenon more intense and led to insufficient ability to resist radial cyclic loads. This study could provide a meaningful idea for preparing biodegradable braided stents with suitable ability to resist radial cyclic loads.

Comparison of the diagnostic accuracy of FBP, ASiR, and MBIR reconstruction during CT angiography in the evaluation of a vessel phantom with calcified stenosis in a distal superficial femoral artery in a cadaver extremity

PURPOSE

To investigate whether adaptive statistical iterative reconstruction (ASiR) or model-based iterative reconstruction (MBIR) improves the diagnostic performance of computed tomography angiography (CTA) for small-vessel calcified lesions relative to filtered back projection (FBP) using cadaver extremities and a calcified stenosis phantom.

METHODS

A cadaver was used in accordance with our institutional regulations, and a calcified stenosis phantom simulating 4 grades of stenosis was prepared. The phantom was inserted within the distal superficial femoral artery of the cadaver leg. Ten CT images per reconstruction type and stenosis grade were acquired using a 64-slice multidetector-row CTA.As an objective measurement, the first and second derivatives of the CT value function profiles were calculated. As a subjective measurement, 2 blinded reviewers measured the stenosis ratio using a quantitative scale. The Wilcoxon rank-sum test was used to evaluate the data.

RESULTS

Objective measurements of both 25% and 50% stenosis differed significantly (P < 0.01) between MBIR (25/50%: 25.80/50.30 ± 3.88/3.86%) and FBP (25/50%: 35.60/83.80 ± 3.44/26.10%), whereas significant differences were not observed between ASiR and FBP.Reviewer 2's subjective measurements of 25% stenosis differed significantly (P < 0.01) between MBIR (35.13 ± 3.25%) and ASiR (40.89 ± 3.14%), and the measurements of 50% stenosis differed significantly (P < 0.01) between MBIR (reviewers 1/2, 62.36/54.78 ± 2.78/4.96%) and FBP (reviewers 1/2, 62.36/74.84 ± 2.78/18.10%). Significant differences in the subjective measurements were not observed between ASiR and FBP.

CONCLUSION

MBIR improves the diagnostic performance of CTA for small-vessel calcified lesions relative to FBP.

Evaluation of middle cerebral artery stents using multidetector row CT angiography in vivo study: comparison of the three different kernels

BACKGROUND

There are very few reports assessing middle cerebral artery (MCA) stents using multidetector computed tomography (MDCT).

PURPOSE

To assess MCA stents using multidetector CT angiography (CTA) in vivo evaluation: the differences in the CTA results according to the three different kernels.

MATERIAL AND METHODS

We retrospectively evaluated 27 MCA stents from 26 patients who underwent CTA with 16- and 64-slice MDCT after percutaneous transluminal angioplasty and stenting (PTAS). By CTA, using medium-smooth kernel (B30), medium-sharp kernel (B50), and sharp kernel (B60), the lumen diameter, artificial luminal narrowing (ALN), and subjective visibility score of the stented vessels were evaluated. The subjective visibility score ranged from 1 (poor quality) to 5 (excellent) using a five-point scale.

RESULTS

There were excellent inter-observer agreements for the lumen diameter measurements (P < 0.001). The mean diameter of the stented vessels was 2.10 ± 0.31 mm on digital subtraction angiography (DSA), 0.93 ± 0.20 mm on CTA using B30, 1.18 ± 0.27 mm on CTA using B50, and 1.29 ± 0.29 mm on CTA using B60. The mean ALN was 55.7 ± 6.0% on CTA using B30, 43.8 ± 7.5% on CTA using B50, and 38.7 ± 8.3% on CTA using B60. CTA with higher kernels had a smaller ALN than images with smaller kernels. The median subjective visibility score on the CTA using B50 was 3, which was higher than for the other kernels. The differences in the lumen diameter, ALN, and the subjective visibility score of the stented vessels on CTA using the three different kernels was statistically significant (P < 0.001).

CONCLUSION

The sharp kernel was better to assess the lumen diameter and ALN, but was inferior to the medium-sharp kernel for in-stent evaluation due to high image-to-noise. CTA with medium-sharp kernel showed good lumen visibility and acceptable ALN for MCA stents. This could therefore be a non-invasive, readily applicable clinical method for assessing MCA stent patency after stent placement.

Improved detection of in-stent restenosis by blood pool agent-enhanced, high-resolution, steady-state magnetic resonance angiography

OBJECTIVE

The aim of this study was to assess whether visualisation of in-stent changes can be improved with high-resolution, steady-state, blood pool contrast-enhanced MR angiography compared with first-pass MR angiography. Intra-arterial digital subtraction angiography (DSA) served as the reference standard.

METHODS

Twenty patients after stent placement in the superficial femoral artery (SFA) underwent MRA prior to reintervention. MRA of the SFA includes first-pass MRA as well as 3D high-resolution MRA in the steady state (SS-MRA) after injection of Gadofosveset trisodium. Sensitivity and specificity values for the detection of significant in-stent lesions by means of SS-MRA were calculated at the proximal, middle and distal stent segments in comparison to DSA. Kappa statistics were used to determine agreement between the two techniques.

RESULTS

Sensitivity and specificity values for the detection of significant stenosis with SS-MRA reached 95% in the proximal, 100% in the middle and 100% in the distal stent segment. Kappa coefficients between SS-MRA and DSA were 0.789, 0.797 and 0.859 for the proximal, middle and distal segments, whereas the Kappa coefficients for FP-MRA were 0,211, 0,200 and 0,594 in these segments, respectively.

CONCLUSION

Detection of in stent stenosis is significantly improved using SS MRA, in comparison to state-of-the-art FP-MRA.

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.