Initial Results of 68Ga-FAPI-46 PET/MRI to Assess Response to Neoadjuvant Chemotherapy in Breast Cancer.

Improving imaging-based response after neoadjuvant chemotherapy (NAC) in breast cancer assessment could obviate histologic confirmation of pathologic complete response (pCR) and facilitate deescalation of chemotherapy or surgery. Fibroblast activation protein inhibitor (FAPI) PET/MRI is a promising novel molecular imaging agent for the tumor microenvironment with intense uptake in breast cancer. We assessed the diagnostic performance of follow-up breast 68Ga-FAPI-46 (68Ga-FAPI) PET/MRI in classifying the response status of local breast cancer and lymph node metastases after completion of NAC and validated this approach immunohistochemically. Methods: In women who completed NAC for invasive breast cancer, follow-up 68Ga-FAPI PET/MRI and corresponding fibroblast activation protein (FAP) immunostainings were retrospectively analyzed. Metrics of 68Ga-FAPI uptake and FAP immunoreactivity in women with or without pCR were compared using the Mann-Whitney U test. Diagnostic performance to detect remnant invasive cancer was calculated for tracer uptake metrics using receiver-operating-characteristic curves and for masked readers' visual assessment categories of PET/MRI and MRI alone. Results: Thirteen women (mean age ± SD, 47 ± 9 y) were evaluated. Seven of the 13 achieved pCR in the breast and 6 in the axilla. FAP immunoreactivity was significantly associated with response status. The 68Ga-FAPI PET/MRI mean breast tumor-to-background ratio was 0.9 (range, 0.6-1.2) for pCR and 2.1 (range, 1.4-3.1) for no pCR (P = 0.001). Integrated PET/MRI could classify breast response correctly in all 13 women based on readers' visual assessment or tumor-to-background ratio. Evaluation of MRI alone resulted in at least 2 false-positives. For lymph nodes, PET/MRI readers had at least 2 false-negative classifications, whereas MRI alone resulted in 2 false-negatives and 1 false-positive. Conclusion: To our knowledge, this was the first analysis of 68Ga-FAPI PET/MRI for response assessment after NAC for breast cancer. The diagnostic performance of PET/MRI in a small study sample trended toward a gain over MRI alone, clearly supporting future prospective studies.

Simultaneous FAPI PET/MRI Targeting the Fibroblast-Activation Protein for Breast Cancer.

Background Integrated PET/MRI is a promising modality for breast assessment. The most frequently used tracer, fluorine 18 (18F) fluorodeoxyglucose (FDG), is applied for whole-body staging in advanced breast cancer but has limited accuracy in evaluating primary breast lesions. The fibroblast-activation protein (FAP) is abundantly expressed in invasive breast cancer. FAP-directed PET tracers have recently become available, but results in primary breast tumors remain lacking. Purpose To evaluate the use of FAP inhibitor (FAPI) breast PET/MRI in assessing breast lesions and of FAPI whole-body scanning for lymph node (LN) and distant staging using the ligand gallium 68 (68Ga)-FAPI-46. Materials and Methods In women with histologically confirmed invasive breast cancer, all primary 68Ga-FAPI-46 breast and whole-body PET/MRI and PET/CT examinations conducted at the authors' center between October 2019 and December 2020 were retrospectively analyzed. MRI lesion characteristics and standardized uptake values (SUVs) were quantified with dedicated software. Mann-Whitney U tests were used to compare tumor SUVs across different tumor types. The Pearson correlation coefficient was calculated between SUV and measures of MRI morphologic characteristics. Results Nineteen women (mean age, 49 years ± 9 [standard deviation]) were evaluated-18 to complement initial staging and one for restaging after therapy for distant metastases. Strong tracer accumulation was observed in all 18 untreated primary breast malignancies (mean maximum SUV [SUVmax] = 13.9 [range, 7.9-29.9]; median lesion diameter = 26 mm [range, 9-155 mm]), resulting in clear tumor delineation across different gradings, receptors, and histologic types. All preoperatively verified LN metastases in 13 women showed strong tracer accumulation (mean SUVmax= 12.2 [range, 3.3-22.4]; mean diameter = 21 mm [range, 14-35 mm]). Tracer uptake established or supported extra-axillary LN involvement in seven women and affected therapy decisions in three women. Conclusion This retrospective analysis indicates use of 68Ga fibroblast-activation protein inhibitor tracers for breast cancer diagnosis and staging. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Mankoff and Sellmyer in this issue.

OCT-Angiography reveals reduced vessel density in the deep retinal plexus of CADASIL patients.

Optical coherence tomography angiography (OCT-A) represents the most recent tool in ophthalmic imaging. It allows for a non-invasive, depth-selective and quantitative visualization of blood flow in central retinal vessels and it has an enormous diagnostic potential not only in ophthalmology but also with regards to neurologic and systemic diseases. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary vascular small-vessel disease caused by Notch3 mutations and represents the most common form of hereditary stroke disorder. In this study, CADASIL patients prospectively underwent OCT-A imaging to evaluate retinal and choriocapillaris blood flow as well as blood flow at the optic nerve head. The vessel density of the macular region and the size of the foveal avascular zone in the superficial and deep retinal plexus were determined as well as the vessel density at the optic nerve head and in the choriocapillaris. Additionally, cerebral magnetic resonance images were evaluated. The main finding was that vessel density of the deep retinal plexus was significantly decreased in CADASIL patients compared to healthy controls which may reflect pericyte dysfunction in retinal capillaries.

Impact of helmet use in equestrian-related traumatic brain injury: a matched-pairs analysis.

PURPOSE: Traumatic brain injury is an important health concern in equestrian sports. Nevertheless, the use of safety helmets, especially in recreational riding, is reported to be rare. The purpose of this study was to perform the first matched-pairs analysis of traumatic brain injury with regard to the use of helmets. MATERIALS AND METHODS: In a multicenter retrospective database analysis 40 patients (mean age: 35 ± 17.13 years; 34 female & 6 male) were combined in 20 matched pairs based on age group, gender and trauma mechanism. Admission trauma computed tomography was qualitatively analyzed for the presence or absence of fractures or intracranial hemorrhage. Quantitatively, in patients with intracranial hemorrhage dedicated volumetry of the blood volume was performed. Odds ratio and relative risk were calculated for the endpoints fractures and intracranial hemorrhage. Crude risk ratio and lesion volume differences between helmeted and unhelmeted riders were compared. RESULTS: Concerning skull fractures, in this cohort 6 patients (85.7% of all patients with fractures) did not wear a helmet and only one (14.3%) wore a helmet (p = .068).and fractures were considered more complex in the unhelmeted subgroup. Intracranial hemorrhage occurred significantly more often in the unhelmeted subgroup (10 vs. 2; p = .008). Moreover, the total lesion volume with 19.31 ± 23.93ml in the unhelmeted subgroup, presenting with intracranial hemorrhage, was significantly higher than in the control group (0.65 ± 0.35ml; p = .002). Odds ratios were 9 for intracranial hemorrhage (p = .014) and 8.14 for skull fractures without helmet (p = .09). Altogether, the relative risk for intracranial bleeding for unhelmeted riders was 5-fold higher and the relative risk reduction was 96% by wearing a safety helmet. CONCLUSIONS: Under consideration of comparable trauma mechanisms, horseback riders that do not wear a safety helmet are at risk to suffer significantly more severe brain injury than helmeted riders. Therefore, safety helmets are recommendable for all horseback riders.

Multispectral optoacoustic tomography of the human breast: characterisation of healthy tissue and malignant lesions using a hybrid ultrasound-optoacoustic approach.

BACKGROUND AND AIM: Multispectral optoacoustic tomography (MSOT) represents a new in vivo imaging technique with high resolution (~250 µm) and tissue penetration (>1 cm) using the photoacoustic effect. While ultrasound contains anatomical information for lesion detection, MSOT provides functional information based on intrinsic tissue chromophores. We aimed to evaluate the feasibility of combined ultrasound/MSOT imaging of breast cancer in patients compared to healthy volunteers. METHODS: Imaging was performed using a handheld MSOT system for clinical use in healthy volunteers (n = 6) and representative patients with histologically confirmed invasive breast carcinoma (n = 5) and ductal carcinoma in situ (DCIS, n = 2). MSOT values for haemoglobin and oxygen saturation were assessed at 0.5, 1.0 and 1.5 cm depth and selected wavelengths between 700 and 850 nm. RESULTS: Reproducible signals were obtained in all wavelengths with consistent MSOT signals in superficial tissue in breasts of healthy individuals. In contrast, we found increased signals for haemoglobin in invasive carcinoma, suggesting a higher perfusion of the tumour and tumour environment. For DCIS, MSOT values showed only little variation compared to healthy tissue. CONCLUSIONS: This preliminary MSOT breast imaging study provided stable, reproducible data on tissue composition and physiological properties, potentially enabling differentiation of solid malignant and healthy tissue. KEY POINTS: • A handheld MSOT probe enables real-time molecular imaging of the breast. • MSOT of healthy controls provides a reproducible reference for pathology identification. • MSOT parameters allows for differentiation of invasive carcinoma and healthy tissue.

Extracorporeal Membrane Oxygenation in Adults - Variants, Complications during Therapy, and the Role of Radiological Imaging.

Background Extracorporeal membrane oxygenation (ECMO) and extracorporeal life support (ECLS) as respiratory and circulatory assist therapies are gaining in importance in the treatment of critically ill patients. Depending on the place of cannulation - veno-venous for ECMO and veno-arterial for ECLS - distinct changes in hemodynamics will occur. In this review we describe the different types of ECMO and ECLS systems, the typical cannula placement and frequent complications under therapy. The most suitable imaging modalities will be presented and typical hemodynamic pitfalls in contrast-enhanced computed tomography or angiography will be elucidated. Methods The review is based on a literature search in PubMed with the terms "ECMO" and/or "ECLS" and/or "extracorporeal life support" and/or "imaging" and/or "complications". Statistical data was taken from the ECMO register of the "Extracorporeal Life Support Organization (ELSO)". Results Critical illness- and therapy-associated complications are common so that imaging, particularly computed tomography, becomes increasingly important. Following veno-venous cannulation in ECMO, the normal sequential blood flow is preserved, so that no contrast enhancement irregularities should be expected when the right timing and an adequate amount of contrast agent are selected. After veno-arterial cannulation in ECLS, different artifacts like pseudo-filling defects, pseudomembranes and irregular/low contrast enhancement of heart and pulmonary vessels can be found, depending on the site of cannulation and the residual cardiac function. Key points · Cannula placement is usually documented by radiography.. · Computed tomography is appropriate in the face of inconclusive cannula placement and probable complications.. · In veno-venous ECMO, no contrast enhancement artifacts are to be expected.. · Veno-arterial ECLS leads to pseudo-filling defects, pseudomembranes and irregular contrast enhancement of heart and pulmonary vessels.. Citation Format · Beck L, Burg MC, Heindel W et al. Extracorporeal Membrane Oxygenation in Adults - Variants, Complications during Therapy, and the Role of Radiological Imaging. Fortschr Röntgenstr 2017; 189: 119 - 127.

[(68)Ga]DOTATATE PET/MRI and [(18)F]FDG PET/CT are complementary and superior to diffusion-weighted MR imaging for radioactive-iodine-refractory differentiated thyroid cancer.

PURPOSE: The purpose of this study was to determine whether [(68)Ga]DOTATATE PET/MRI with diffusion-weighted imaging (DWI) can replace or complement [(18)F]FDG PET/CT in patients with radioactive-iodine (RAI)-refractory differentiated thyroid cancer (DTC). METHODS: The study population comprised 12 patients with elevated thyroglobulin and a negative RAI scan after thyroidectomy and RAI remnant ablation who underwent both [(18)F]FDG PET/CT and [(68)Ga]DOTATATE PET/MRI within 8 weeks of each other. The presence of recurrent cancer was evaluated on a per-patient, per-organ and per-lesion basis. Histology, and prior and follow-up examinations served as the standard of reference. RESULTS: Recurrent or metastatic tumour was confirmed in 11 of the 12 patients. [(68)Ga]DOTATATE PET(/MRI) correctly identified the tumour burden in all 11 patients, whereas in one patient local relapse was missed by [(18)F]FDG PET/CT. In the lesion-based analysis, overall lesion detection rates were 79/85 (93 %), 69/85 (81 %) and 27/82 (33 %) for [(18)F]FDG PET/CT, [(68)Ga]DOTATATE PET/MRI and DWI, respectively. [(18)F]FDG PET(/CT) was superior to [(68)Ga]DOTATATE PET(/MRI) in the overall evaluation and in the detection of pulmonary metastases. In the detection of extrapulmonary metastases, [(68)Ga]DOTATATE PET(/MRI) showed a higher sensitivity than [(18)F]FDG PET(/CT), at the cost of lower specificity. DWI achieved only poor sensitivity and was significantly inferior to [(18)F]FDG PET in the lesion-based evaluation in the detection of both extrapulmonary and pulmonary metastases. CONCLUSION: [(18)F]FDG PET/CT was more sensitive than [(68)Ga]DOTATATE PET/MRI in the evaluation of RAI-refractory DTC, mostly because of its excellent ability to detect lung metastases. In the evaluation of extrapulmonary lesions, [(68)Ga]DOTATATE PET(/MRI) was more sensitive and [(18)F]FDG PET(/CT) more specific. Furthermore, DWI did not provide additional information and cannot replace [(18)F]FDG PET for postoperative monitoring of patients with suspected RAI-refractory DTC.

[(18)F]FDG PET/CT outperforms [(18)F]FDG PET/MRI in differentiated thyroid cancer.

PURPOSE: To evaluate the diagnostic potential of PET/MRI with [(18)F]FDG in comparison to PET/CT in patients with differentiated thyroid cancer suspected or known to have dedifferentiated. METHODS: The study included 31 thyroidectomized and remnant-ablated patients who underwent a scheduled [(18)F]FDG PET/CT scan and were then enrolled for a PET/MRI scan of the neck and thorax. The datasets (PET/CT, PET/MRI) were rated regarding lesion count, conspicuity, diameter and characterization. Standardized uptake values were determined for all [(18)F]FDG-positive lesions. Histology, cytology, and examinations before and after treatment served as the standards of reference. RESULTS: Of 26 patients with a dedifferentiated tumour burden, 25 were correctly identified by both [(18)F]FDG PET/CT and PET/MRI. Detection rates by PET/CT and PET/MRI were 97 % (113 of 116 lesions) and 85 % (99 of 113 lesions) for malignant lesions, and 100 % (48 of 48 lesions) and 77 % (37 of 48 lesions) for benign lesions, respectively. Lesion conspicuity was higher on PET/CT for both malignant and benign pulmonary lesions and in the overall rating for malignant lesions (p < 0.001). There was a difference between PET/CT and PET/MRI in overall evaluation of malignant lesions (p < 0.01) and detection of pulmonary metastases (p < 0.001). Surgical evaluation revealed three malignant lesions missed by both modalities. PET/MRI additionally failed to detect 14 pulmonary metastases and 11 benign lesions. CONCLUSION: In patients with thyroid cancer and suspected or known dedifferentiation, [(18)F]FDG PET/MRI was inferior to low-dose [(18)F]FDG PET/CT for the assessment of pulmonary status. However, for the assessment of cervical status, [(18)F]FDG PET/MRI was equal to contrast-enhanced neck [(18)F]FDG PET/CT. Therefore, [(18)F]FDG PET/MRI combined with a low-dose CT scan of the thorax may provide an imaging solution when high-quality imaging is needed and high-energy CT is undesirable or the use of a contrast agent is contraindicated.

Coronary stent imaging with dual-source CT: assessment of lumen visibility using different convolution kernels and postprocessing filters.

BACKGROUND: Assesment of the coronary arteries after stent placement using coronary computed tomography angiography (CCTA) currently requires reconstruction of images with soft kernels for the assessment of atherosclerotic plaques and dedicated edge enhancing kernels for the evaluation of the stent lumen. PURPOSE: To evaluate a two-dimensional filter tool that provides instant postprocessing of images reconstructed with soft kernels into edge-enhanced images and vice versa and thus may eliminate the need for two separate reconstrcutions for the assessment of coronary artery stents using CCTA. MATERIAL AND METHODS: Twenty stents with a diameter of 3.0 mm placed in a vascular phantom were scanned with a dual-source CT using standard parameters. Images were reconstructed with a soft B30f and an edge-enhancing B46f kernel and postprocessed with the corresponding filter algorithm (F30 for B30f images; F46 for B46f images). The resulting four data-sets were evaluated for lumen visibility, intraluminal attenuation, and image noise by two independent readers. Results were validated in vivo against invasive coronary angiography in data-sets from patients with coronary artery stents. RESULTS: Average intraluminal attenuation was 552.6 HU, 527.3 HU, 207.9 HU, and 267.5 HU for B30f, F30, B46f, and F46 images, respectively (P < 0.0001). Average image noise was 11.3, 10.6, 19.2, and 15.0 HU, respectively (P < 0.0001). The visible stent diameter was significantly higher in the B46f (59.6%) and F46 images (54%) compared to the B30f (48.3%) and F30 (51.5%) images (P < 0.0001). In the patient study, lumen assessability was significantly better in B46f images than in F46 images. Sensitivity for stenosis detection was best in the original B46f images with a sensitivity of 67% and a specificity of 94%. CONCLUSION: The postprocessing filter reduces image noise, however currently it does not offer an alternative to image reconstruction using the edge-enhancing kernels for the evaluation of the stent lumen.

Aortic regurgitation severity after transcatheter aortic valve implantation is underestimated by echocardiography compared with MRI.

OBJECTIVE: Aortic regurgitation (AR) after transcatheter aortic valve implantation (TAVI) is associated with a poor clinical outcome and its assessment therefore crucial. Quantification of AR by transthoracic echocardiography (TTE), however, remains challenging in this setting. The present study used quantitative flow measurement by cardiac MRI (CMR) with calculation of regurgitant fraction (RF) for the assessment of AR and compared the results with TTE. METHODS AND RESULTS: We included 65 patients with a mean age of 82.2±8.1 years (38 women) who underwent successful TAVI with Edwards SAPIEN valves (52 transfemoral, 13 transapical). The post-interventional degree of AR was assessed by CMR and by TTE. There was agreement between CMR and TTE with regards to the absence of severe AR. However, TTE significantly underestimated the presence of moderate AR classifying it to be mild in 38 and moderate in only 5 patients, whereas CMR found mild AR in 23 and moderate in 16 patients. Overall, there was only fair agreement between CMR and TTE regarding the grading of AR with a weighted κ of 0.33. The rate of detection of TTE for more than mild AR was only 19%. CONCLUSIONS: Using CMR for the quantification of AR in a sizeable group of TAVI patients, we demonstrate a strong tendency of TTE to underestimate AR compared with CMR. Since higher AR severity on echocardiography has been associated with worse patient outcome, the potential incremental prognostic value of CMR should be studied prospectively in this setting.

4D phase contrast flow imaging for in-stent flow visualization and assessment of stent patency in peripheral vascular stents--a phantom study.

PURPOSE: 4D phase contrast flow imaging is increasingly used to study the hemodynamics in various vascular territories and pathologies. The aim of this study was to assess the feasibility and validity of MRI based 4D phase contrast flow imaging for the evaluation of in-stent blood flow in 17 commonly used peripheral stents. MATERIALS AND METHODS: 17 different peripheral stents were implanted into a MR compatible flow phantom. In-stent visibility, maximal velocity and flow visualization were assessed and estimates of in-stent patency obtained from 4D phase contrast flow data sets were compared to a conventional 3D contrast-enhanced magnetic resonance angiography (CE-MRA) as well as 2D PC flow measurements. RESULTS: In all but 3 of the tested stents time-resolved 3D particle traces could be visualized inside the stent lumen. Quality of 4D flow visualization and CE-MRA images depended on stent type and stent orientation relative to the magnetic field. Compared to the visible lumen area determined by 3D CE-MRA, estimates of lumen patency derived from 4D flow measurements were significantly higher and less dependent on stent type. A higher number of stents could be assessed for in-stent patency by 4D phase contrast flow imaging (n=14) than by 2D phase contrast flow imaging (n=10). CONCLUSIONS: 4D phase contrast flow imaging in peripheral vascular stents is feasible and appears advantageous over conventional 3D contrast-enhanced MR angiography and 2D phase contrast flow imaging. It allows for in-stent flow visualization and flow quantification with varying quality depending on stent type.

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

Purpose. To test different peripheral arterial stents using four image reconstruction approaches with respect to lumen visualization, lumen attenuation and image noise in dual-source multidetector row CT (DSCT) in vitro. Methods and Materials. 22 stents (nitinol, steel, cobalt-alloy, tantalum, platinum alloy) were examined in a vessel phantom. All stents were imaged in axial orientation with standard parameters. Image reconstructions were obtained with four different convolution kernels. To evaluate visualization characteristics of the stent, the lumen diameter, intraluminal density and noise were measured. Results. The mean percentage of the visible stent lumen diameter from the nominal stent diameter was 74.5% ± 5.7 for the medium-sharp kernel, 72.8% ± 6.4 for the medium, 70.8% ± 6.4 for the medium-smooth and 67.6% ± 6.6 for the smooth kernel. Mean values of lumen attenuation were 299.7HU ± 127 (medium-sharp), 273.9HU ± 68 (medium), 270.7HU ± 53 (medium-smooth) and 265.8HU ± 43. Mean image noise was: 54.6 ± 6.3, 20.5 ± 1.7, 16.3 ± 1.7, 14.0 ± 2 respectively. Conclusion. Visible stent lumen diameter varies depending on stent type and scan parameters. Lumen diameter visibility increases with the sharpness of the reconstruction kernel. Smoother kernels provide more realistic density measurements inside the stent lumen and less image noise.

MR Angiography of Peripheral Arterial Stents: In Vitro Evaluation of 22 Different Stent Types.

Purpose. To evaluate stent lumen visibility of a large sample of different peripheral arterial (iliac, renal, carotid) stents using magnetic resonance angiography in vitro. Materials and Methods. 21 different stents and one stentgraft (10 nitinol, 7 316L, 2 tantalum, 1 cobalt superalloy, 1 PET + cobalt superalloy, and 1 platinum alloy) were examined in a vessel phantom (vessel diameters ranging from 5 to 13 mm) filled with a solution of Gd-DTPA. Stents were imaged at 1.5 Tesla using a T1-weighted 3D spoiled gradient-echo sequence. Image analysis was performed measuring three categories: Signal intensity in the stent lumen, lumen visibility of the stented lumen, and homogeneity of the stented lumen. The results were classified using a 3-point scale (good, intermediate, and poor results). Results. 7 stents showed good MR lumen visibility (4x nitinol, 2x tantalum, and 1x cobalt superalloy). 9 stents showed intermediate results (5x nitinol, 2x 316L, 1x PET + cobalt superalloy, and 1x platinum alloy) and 6 stents showed poor results (1x nitinol, and 5x 316L). Conclusion. Stent lumen visibility varies depending on the stent material and type. Some products show good lumen visibility which may allow the detection of stenoses inside the lumen, while other products cause artifacts which prevent reliable evaluation of the stent lumen with this technique.

High-pitch 128-slice dual-source CT for the assessment of coronary stents in a phantom model.

RATIONALE AND OBJECTIVES: To evaluate the quality of stent lumen delineation using dual-source computed tomography (DSCT) in the standard-pitch mode (SP) as compared to the high-pitch mode (HP) in a phantom study. MATERIALS AND METHODS: Forty different coronary stents placed in plastic tubes filled with contrast agent were imaged with a second generation DSCT system in a SP (pitch 0.23) and HP (pitch 3.4) mode in orientations of 0°, 45°, and 90° relative to the z-axis. Two observers independently measured the in-stent lumen and the attenuation values in the center of the stents. The artificial lumen narrowing (ALN) was calculated using the measured in-stent lumen and the nominal diameter of the plastic tube. RESULTS: Interobserver correlation was excellent for in-stent lumen (0.86) and attenuation measurements (0.91). There was no significant difference neither for ALN (SP: 54.7-62.8%; HP: 55.8-64.0%) nor attenuation (SP: 356-395 Hounsfield units [HU]; HP: 352-384 HU) between SP and HP mode. For both modes, the orientation of the stent relative to the z-axis significantly affected ALN and attenuation (each P < .001). CT volume dose index was significantly lower using HP mode as compared to SP mode (P < .001). CONCLUSION: The HP mode in DSCT provides visualization of the coronary in-stent lumen comparable to that measured in SP mode while reducing applied radiation dose in a stationary phantom model.

Update on multidetector coronary CT angiography of coronary stents: in vitro evaluation of 29 different stent types with dual-source CT.

The aim of this study was to test a large sample of the latest coronary artery stents using four image reconstruction approaches with respect to lumen visualization, lumen attenuation, and image noise in dual-source multidetector row CT (DSCT) in vitro and to provide a CT catalogue of currently used coronary artery stents. Twenty-nine different coronary artery stents (19 steel, 6 cobalt-chromium, 2 tantalum, 1 iron, 1 magnesium) were examined in a coronary artery phantom (vessel diameter 3 mm, intravascular attenuation 250 HU, extravascular density -70 HU). Stents were imaged in axial orientation with standard parameters: 32 x 0.6 collimation, pitch 0.24, 400 mAs, 120 kV, rotation time 0.33 s. Image reconstructions were obtained with four different convolution kernels (soft, medium-soft, standard high-resolution, stent-dedicated). To evaluate visualization characteristics of the stent, the lumen diameter, intraluminal density, and noise were measured. The stent-dedicated kernel offered best average lumen visualization (54 +/- 8.3%) and most realistic lumen attenuation (222 +/- 44 HU) at the expense of increased noise (23.9 +/- 1.9 HU) compared with standard CTA protocols (p < 0.001 for all). The magnesium stent showed the least artifacts with a lumen visibility of 90%. The majority of stents (79%) exhibited a lumen visibility of 50-59%. Less than half of the stent lumen was visible in only six stents. Stent lumen visibility largely varies depending on the stent type. Magnesium is by far more favorable a stent material with regard to CT imaging when compared with the more common materials steel, cobalt-chromium, or tantalum. The magnesium stent exhibits a lumen visibility of 90%, whereas the majority of the other stents exhibit a lumen visibility of 50-59%.