Dual-Source CT Angiography of Peripheral Arterial Stents: In Vitro Evaluation of 22 Different Stent Types

Utility of follow-up ultra-high-resolution CT angiography with model-based iterative reconstruction after flow diverter treatment for cerebral aneurysms

PURPOSE

Follow-up examinations after flow diverter (FD) treatment for cerebral aneurysms typically involve magnetic resonance imaging (MRI) or digital subtraction angiography (DSA). However, MRI is prone to vascular defects due to metal artifacts from FD, and DSA carries a risk of ischemic complications. In the context of computed tomography angiography (CTA), this study compares the efficacy of ultra-high-resolution CT (UHRCT) and novel reconstruction techniques, such as model-based iterative reconstruction (MBIR), against conventional methods such as filtered back projection (FBP) and hybrid iterative reconstruction (IR), to determine if they are a viable alternative to DSA in clinical settings.

MATERIALS AND METHODS

A phantom study was conducted with the full-width half-maximum considered as the FD thickness. This study compared three reconstruction methods: MBIR, FBP, and hybrid IR. A clinical study was also conducted with 21 patients who underwent follow-up CTA after FD treatment. The FD's visibility was assessed using a 4-point scale in FBP, hybrid IR, and MBIR compared to cone-beam CT (CBCT) with angiographic systems.

RESULTS

In the phantom study, FBP, hybrid IR, and MBIR visualized thinner FD thicknesses and improved detail rendering in that order. MBIR proved to be significantly superior in both the phantom and clinical study.

CONCLUSION

UHRCT with MBIR is highly effective for follow-up evaluations after FD treatment and may become the first-choice modality in the future.

Carotid computed tomography angiography after cobalt-based alloy carotid artery stenting using ultra-high-resolution computed tomography with model-based iterative reconstruction

In conventional carotid computed tomographic angiography, the artifacts of the stent vary depending on the structure and characteristics of the alloy type. Cobalt-based alloy stents have been reported to exhibit high artifacts, and accurate evaluation of the internal lumen can be difficult. Recently, ultra-high-resolution computed tomography scanner systems have become available for clinical practice. The primary features of this computed tomography scanner are a 0.25-mm detector row width and a 1024 × 1024 matrix. We report a case-series of carotid artery stenting using a cobalt-based alloy stent scanned by an ultra-high-resolution computed tomography scanner system and model-based iterative reconstruction. We also report that the combination of the ultra-high-resolution computed tomography scanner system with model-based iterative reconstruction would be useful to evaluate vessel patency after placement of a cobalt-based alloy stent.

Computed tomography evaluation of the periacetabular gap of a porous tantalum acetabular component

The periacetabular gap is an inherent consequence of the peripheral rim press-fit of the porous tantalum acetabular component. The circumference of the prosthesis is clearly depicted with computed tomography (CT) images that have been optimised to reduce metal artefacts. This case report highlights the utility of single-energy metal artefact reduction (SEMAR) for CT evaluation of the periacetabular gap by comparing CT images with and without SEMAR. A 70-year-old woman with a 5-year history of rheumatoid arthritis underwent total hip arthroplasty with a porous tantalum modular acetabular component. A periacetabular gap was suspected by plain radiography 2 weeks postoperatively. The metal artefacts rendered evaluation of the circumference of the acetabular component difficult in CT images acquired without SEMAR. In contrast, there were fewer metal artefacts, and a periacetabular gap (depth of 6.5 mm in DeLee and Charnley zone 2) was clearly depicted in CT images with SEMAR 2 weeks postoperatively. The porous surface of the acetabular component was in contact with the anterior and posterior rims of the acetabulum. Gap filling with bone and bone ingrowth into the porous surface were observed on CT images with SEMAR 24 weeks postoperatively. In conclusion, SEMAR reduces metal artefacts and improves CT image quality around the circumference of the acetabular component. The periacetabular gap and its filling with bone are clearly depicted in CT images with SEMAR, but not without SEMAR.

Contemporary follow-up imaging after endovascular repair of lower extremity atherosclerotic lesions

Atherosclerotic disease is currently one of the most important problems of modern medicine because it is a leading cause of increased morbidity, morbidity and mortality, and disability in the Western World. Atherosclerosis of the lower limbs (peripheral arterial disease - PAD) significantly affects the quality of life and in a considerable proportion of patients is a cause of disability. Radical treatment of PAD, both surgical and endovascular, aims at revascularisation of ischaemic tissues distal to obstructed arteries. Surveillance imaging is an important part of patient management after endovascular repair of PAD. Apart from availability and contraindications, challenges of imaging include calcifications, flow dynamics, and stent-related artefacts. The aim of this paper was to review the current literature on imaging methods for follow-up after endovascular repair of atherosclerotic lesions, with special attention paid to novel techniques. As a non-invasive modality, ultrasound is still the first-line examination, but computed tomography angiography remains a current state-of-the art technique for follow-up. However, since current imaging recommendations seem not to adhere to contemporary imaging possibilities, more attention should be paid to recent improvements in magnetic resonance angiography technology.

Computed tomography image quality of aortic stents in patients with aortic coarctation: a multicentre evaluation

BACKGROUND

Stents are commonly used to treat aortic coarctation. The objective of this study was to evaluate the post-implantation computed tomography (CT) image quality of different stent types used to treat aortic coarctation.

METHODS

Adult and paediatric patients with stent-treated aortic coarctation who underwent contrast-enhanced CT were retrospectively included from three tertiary care centres. CT scans were subjectively scored for image quality using a 4-point scale (1 = unacceptable; 2 = poor; 3 = good; 4 = excellent). Furthermore, the amount of stent-induced blooming artefacts was measured as the percentage of the difference between outer and inner stent diameters over the outer stent diameter.

RESULTS

A total of 35 children and 34 adults implanted with 71 stents of six different types were included. The most commonly used stent type was the Cheatham Platinum stent (52 stents, 73%). The subjective image quality of the Cheatham Platinum stents was moderate with a score of 2.0±0.8 (mean ± standard deviation) in children and 2.3±0.6 in adults. The image quality in patients with Formula stents was 2.3±1.2. The Cheatham Platinum stents induced 34-48% blooming, the Formula stents 44-55%. The image quality in patients with the less commonly used Atrium Advanta V12, IntraStent, AndraStent and Palmaz stents was scored 3 (good) to 4 (excellent) with less blooming. The electrocardiographic gating and tube voltage (kVp) did not affect image quality.

CONCLUSIONS

There is a substantial variation in CT image quality and blooming artefacts for different stent types used to treat aortic coarctation.

Dual energy CT angiography in peripheral arterial stents: optimal scanning protocols with regard to image quality and radiation dose

Background

To determine the optimal scanning protocols of dual energy computed tomography angiography (DECTA) in terms of radiation dose and image quality assessment at different keV levels, and compare it with conventional computed tomography angiography (CTA) in patients treated with peripheral arterial stents.

Methods

Twenty-nine patients with previous stent placement in peripheral arteries were evaluated with DECTA. Images were reconstructed with virtual monochromatic spectral imaging (VMS) at 65, 68, 70 and 72 keV and adaptive statistical iterative reconstruction (ASIR) at 50% compared with CTA. Image quality comprising image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were assessed, and radiation dose was compared. Effects of different type of peripheral arterial stents on image quality were also evaluated. Fifty-six uniquely identified stents that were located in common iliac arteries (CIA), external iliac arteries (EIA) and superficial femoral arteries (SFA) were evaluated.

Results

Within subjects, the results showed that DECTA images (VMS) had less noise than the CTA images for CIA, EIA and SFA stents, with the lowest noise at 72 keV. Also, the VMS images had greater SNR than the CTA images for the EIA stents (P<0.05); and the VMS images had greater CNR than the CTA images for CIA, EIA, and SFA stents (P<0.001). Also, on CT attenuation, VMS continued to outperform CTA, but to a lesser extent. Between subjects, average VMS noise varied significantly with the type of the stent used (P=0.025) for CIA stents. Radiation dose was highly significant between DECTA and conventional CTA scans (6.98 vs. 7.40 mSv, P=0.047).

Conclusions

We conclude that an optimal scanning protocol consisting of 72 keV and 50% ASIR leads to better image quality for DECTA in peripheral arterial stenting when compared to conventional CTA.

Optimal Scanning Protocols for Dual-Energy CT Angiography in Peripheral Arterial Stents: An in Vitro Phantom Study

OBJECTIVE

To identify the optimal dual-energy computed tomography (DECT) scanning protocol for peripheral arterial stents while achieving a low radiation dose, while still maintaining diagnostic image quality, as determined by an in vitro phantom study.

METHODS

Dual-energy scans in monochromatic spectral imaging mode were performed on a peripheral arterial phantom with use of three gemstone spectral imaging (GSI) protocols, three pitch values, and four kiloelectron volts (keV) ranges. A total of 15 stents of different sizes, materials, and designs were deployed in the phantom. Image noise, the signal-to-noise ratio (SNR), different levels of adaptive statistical iterative reconstruction (ASIR), and the four levels of monochromatic energy for DECT imaging of peripheral arterial stents were measured and compared to determine the optimal protocols.

RESULTS

A total of 36 scans with 180 datasets were reconstructed from a combination of different protocols. There was a significant reduction of image noise with a higher SNR from monochromatic energy images between 65 and 70 keV in all investigated preset GSI protocols (p < 0.05). In addition, significant effects were found from the main effect analysis for these factors: GSI, pitch, and keV (p = 0.001). In contrast, there was significant interaction on the unstented area between GSI and ASIR (p = 0.015) and a very high significant difference between keV and ASIR (p < 0.001). A radiation dose reduction of 50% was achieved.

CONCLUSIONS

The optimal scanning protocol and energy level in the phantom study were GSI-48, pitch value 0.984, and 65 keV, which resulted in lower image noise and a lower radiation dose, but with acceptable diagnostic images.