Ultra-Low-Dose Intra-Arterial Contrast Injection for Iliofemoral Computed Tomographic Angiography

Exploring Intra-arterial Contrast Administration for Intraoperative Imaging Using a Swine Model

Intraoperative computed tomography (CT) imaging with endovascular delivery of intra-arterial (IA) contrast could potentially provide higher attenuation with lower contrast volumes than intravenous (IV) administration. We aimed to compare IA and IV contrast use for organ-specific CT abdominal imaging. Five anesthetized swine had external jugular and brachial artery access with ascending aortic pigtail placement. An IV protocol was 100 mL at 5 mL/sec over 20 sec vs 50 mL of IA contrast at 5 mL/sec over 10 sec. Region-of-interest markers were applied to anatomical regions to measure attenuation (HU) over time. IA and IV contrast protocols achieved adequate aortic opacification (IA, 455 ± 289 vs IV, 450 ± 114 HU). The IA contrast aortic attenuation curve reached peak attenuation compared with IV contrast (IA, 8 vs 23 sec; P < .001). Time to peak attenuation was similar between IA and IV contrast in the portal vein (IA, 38 vs IV, 42 sec, P = .25). IA administration achieved a superior contrast-to-noise ratio (CNR) in less time compared with IV (R2 = .94; P < .001). IA contrast achieved adequate opacification with less bolus broadening and a superior CNR compared with IV contrast while using a smaller contrast volume for directed organ-directed imaging.

Systemic-pulmonary collateral supply associated with clinical severity of chronic thromboembolic pulmonary hypertension: a study using intra-aortic computed tomography angiography

OBJECTIVES

To assess whether systemic-pulmonary collaterals are associated with clinical severity and extent of pulmonary perfusion defects in chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

This prospective study was approved by a local ethics committee. Twenty-four patients diagnosed with inoperable CTEPH were enrolled between July 2014 and February 2017. Systemic-pulmonary collaterals were detected using pulmonary vascular enhancement on intra-aortic computed tomography (CT) angiography. The pulmonary enhancement parameters were calculated, including (1) Hounsfield unit differences (HUdiff) between pulmonary trunks and pulmonary arteries (PAs) or veins (PVs), namely HUdiff-PA and HUdiff-PV, on the segmental base; (2) the mean HUdiff-PA, mean HUdiff-PV, numbers of significantly enhanced PAs and PVs, on the patient base. Pulmonary perfusion defects were recorded and scored using the lung perfused blood volume (PBV) based on intravenous dual-energy CT (DECT) angiography. Pearson's or Spearman's correlation coefficients were used to evaluate correlations between the following: (1) segment-based intra-aortic CT and intravenous DECT parameters (2) patient-based intra-aortic CT parameters and clinical severity parameters or lung PBV scores. Statistical significance was set at p < 0.05.

RESULTS

Segmental HUdiff-PV was correlated with the segmental perfusion defect score (r = 0.45, p < 0.01). The mean HUdiff-PV was correlated with the mean pulmonary arterial pressure (PAP) (r = 0.52, p < 0.01), cardiac output (rho = - 0.41, p = 0.05), and lung PBV score (rho = 0.43, p = 0.04). And the number of significantly enhanced PVs was correlated with the mean PAP (r = 0.54, p < 0.01), pulmonary vascular resistance (r = 0.54, p < 0.01), and lung PBV score (rho = 0.50, p = 0.01).

CONCLUSIONS

PV enhancement measured by intra-aortic CT angiography reflects clinical severity and pulmonary perfusion defects in CTEPH.

KEY POINTS

• Intra-aortic CT angiography demonstrated heterogeneous enhancement within the pulmonary vasculature, showing collaterals from the systemic arteries to the pulmonary circulation in CTEPH. • The degree of systemic-pulmonary collateral development was significantly correlated with the clinical severity of CTEPH and may be used to evaluate disease progression. • The distribution of systemic-pulmonary collaterals is positively correlated with perfusion defects in the lung segments in CTEPH.

Computed Tomography Angiography Combined With Knowledge-Based Iterative Algorithm for Transcatheter Aortic Valve Implantation Planning: Image Quality and Radiation Dose Exposure With Low-kV and Low-Contrast-Medium Protocol

OBJECTIVE

To evaluate image quality and radiation dose exposure of low-kV setting and low-volume contrast medium (CM) computed tomography angiography (CTA) protocol for transcatheter aortic valve implantation (TAVI) planning in comparison with standard CTA protocol.

METHODS

Sixty-patients were examined with 256-row MDCT for TAVI planning: 32 patients (study group) were evaluated using 80-kV electrocardiogram-gated protocol with 60 mL of CM and IMR reconstruction; 28 patients underwent a standard electrocardiogram-gated CTA study (100 kV; 80 mL of CM; iDose4 reconstruction). Subjective and objective image quality was evaluated in each patient at different aortic levels. Finally, we collected radiation dose exposure data (CT dose index and dose-length product) of both groups.

RESULTS

In study protocol, significant higher mean attenuation values were achieved in all measurements compared with the standard protocol. There were no significant differences in the subjective image quality evaluation in both groups. Mean dose-length product of study group was 56% lower than in the control one (P < 0.0001).

CONCLUSION

Low-kV and low-CM volume CTA, combined with IMR, allows to correctly performing TAVI planning with high-quality images and significant radiation dose reduction compared with standard CTA protocol.

Diagnostic efficacy of model-based iterative reconstruction algorithm in an assessment of coronary artery in comparison with standard hybrid-Iterative reconstruction algorithm: dose reduction and image quality

PURPOSE

To evaluate the image quality and radiation dose exposure of low-dose coronary CTA (cCTA) study, reconstructed with the new model-based iterative reconstruction algorithm (IMR), compared with standard hybrid-iterative reconstruction (iDose⁴) cCTA in patients with suspected coronary artery disease.

MATERIALS AND METHODS

Ninety-eight patients with an indication for coronary CT study were prospectively enrolled. Fifty-two patients (study group) underwent 256-MDCT low-dose cCTA (80 kV; automated-mAs; 60 mL of CM, 350 mgL/mL) with prospective ECG-triggering acquisition and IMR. A control group of 46 patients underwent 256-MDCT standard prospective ECG-gated protocol (100 kV; automated-mAs; 70 mL of CM, 400 mgL/mL; iDose⁴). Subjective and objective image quality (attenuation value, SD, SNR and CNR) were evaluated by two radiologists subjectively. Radiation dose exposure was quantified as DLP, CTDIvol and ED.

RESULTS

Mean values of mAs were significantly lower for IMR-cCTA (167 ± 62 mAs) compared to iDose-cCTA (278 ± 55 mAs), p < 0.001. With a significant reduction of 38% in radiation dose exposure (DLP: IMR-cCTA 91.7 ± 26 mGy cm vs. iDose-cCTA 148.6 ± 35 mGy cm; p value < 0.001), despite the use of different CM, we found higher mean attenuation values of the coronary arteries in IMR group compared to iDose⁴ (mean density in LAD: 491HU IMR-cCTA vs. 443HU iDose-cCTA; p = 0.03). We observed a significant higher value of SNR and CNR in study group due to a lower noise level. Qualitative analysis did not reveal any significant differences between the two groups (p = 0.23).

CONCLUSIONS

Low-dose cCTA study combined with IMR reconstruction allows to correctly evaluate coronary arteries disease, offering high-quality images and significant radiation dose exposure reduction (38%), as compared to standard cCTA protocol.

Endovascular Therapy Using Diluted Contrast Medium for Critical Limb Ischemia in a Patient with Chronic Kidney Disease

A high percentage of patients with critical limb ischemia have concurrent chronic kidney disease (CKD). However, endovascular therapy (EVT) can be problematic in CKD patients. Thus, we developed a method of EVT using digital subtraction angiography (DSA) with diluted contrast medium (low-concentration DSA), wherein DSA parameters were adjusted for diluted contrast angiography (1:10 dilution). Herein, we report the case of an 88-year-old woman with a foot wound and severe CKD. Her estimated glomerular filtration rate was 7.9 mL/minute/1.73 m². Therefore, EVT was performed with low-concentration DSA. Control angiography revealed total occlusion of the anterotibial and posterotibial arteries as well as severe stenosis of the peroneal artery. EVT with ballooning of the below-the-knee (BTK) lesions resulted in sufficient flow to the wound. Angiographic images of sufficient quality and visible wound blush were obtained with 1:10 diluted contrast medium. Because only 20 mL of contrast medium was required, renal function was preserved. EVT using DSA with diluted contrast medium was shown to be an effective BTK intervention in this CKD patient.

Diagnostic value of iterative reconstruction algorithm in low kV CT angiography (CTA) with low contrast medium volume for transcatheter aortic valve implantation (TAVI) planning: image quality and radiation dose exposure

OBJECTIVE:

To evaluate image quality and radiation dose exposure of low-kV (100 kV) and low contrast medium (CM) volume CT angiography (CTA) in patients candidate to Transcatheter Aortic Valve Implantation (TAVI), in comparison with standard CTA protocol.

METHODS:

79 patients candidate for TAVI were prospectively enrolled in this study and examined with 256-MDCT. 42 patients were evaluated using study-group protocol (100 kV; whole-body retrospective ECG-gating; with 50 ml of CM; iterative reconstruction algorithm) while 37 patients underwent a standard CTA study (120 kV; ECG-gating for chest; 100 ml of CM; FBP reconstruction). Overall image quality was evaluated using a 4-point scale. Vascular enhancement (HU) was then assessed in each patient by manually drawing multiple ROIs in lumen of 7 segments of the whole aorta. The radiation dose exposure of both groups was calculated and all data were compared and statistically analyzed.

RESULTS:

On low-kV protocol, higher mean attenuation values were achieved in all the measurements as compared to standard protocol. There were no significant differences in the image quality evaluation in both groups. Mean radiation dose value of study group was significantly lower than in control group (reduction of 20%).

CONCLUSION:

Low kV and low CM volume CTA protocols allow TAVI planning to be carried out with high quality images and a significant reduction in the radiation dose as compared to the standard CTA protocol.

ADVANCES IN KNOWLEDGE:

Low-kV CTA for pre-operative assessment of patients candidates for TAVI, permits to achieve a significant reduction of radiation dose exposure and contrast medium volume, reducing the risk of contrast induced nephropathy.

Noninvasive aortic imaging

Non-invasive imaging of the aorta has undergone considerable advancements in recent times; largely driven by the technological advances in computed tomography (CT) and magnetic resonance imaging (MRI). This review article highlights these recent advancements and discusses the current role of different imaging tools in the management of aortic diseases.

Multidetector computed tomography evaluation of candidates for transcatheter aortic valve implantation

In transcatheter aortic valve implantation (TAVI), a biologic valve mounted in a stent is implanted without removing the native valve. This procedure was first done in humans by Alain Cribier in 2002 and was included in clinical guidelines after the multicenter PARTNER (Placement of AoRtic TraNscathetER) randomized clinical trial, which showed that TAVI obtained better outcomes than conservative medical treatment and is an alternative to surgery in patients with high surgical risk. Candidates for TAVI must be assessed to determine whether the procedure is feasible, because TAVI is not ideal for all patients who are considered inoperable. Multidetector computed tomography plays an important role in the anatomic evaluation of candidates and in guiding the procedure in those who are finally selected.

Spectral detector CT for cardiovascular applications

Spectral detector computed tomography (SDCT) is a novel technology that uses two layers of detectors to simultaneously collect low and high energy data. Spectral data is used to generate conventional polyenergetic images as well as dedicated spectral images including virtual monoenergetic and material composition (iodine-only, virtual unenhanced, effective atomic number) images. This paper provides an overview of SDCT technology and a description of some spectral image types. The potential utility of SDCT for cardiovascular imaging and the impact of this new technology on radiation and contrast dose are discussed through presentation of initial patient studies performed on a SDCT scanner. The value of SDCT for salvaging suboptimal studies including those with poor contrast-enhancement or beam hardening artifacts through retrospective reconstruction of spectral data is discussed. Additionally, examples of specific benefits for the evaluation of aortic disease, imaging before transcatheter aortic valve implantation, evaluation of pulmonary veins pre- and post-pulmonary radiofrequency ablation, evaluation of coronary artery lumen, assessment of myocardial perfusion, detection of pulmonary embolism, and characterization of incidental findings are presented.

Imaging for surveillance and operative management for endovascular aortic aneurysm repairs

Endovascular aortic aneurysm repairs rely heavily on radiologic imaging modalities for preoperative surveillance, intraoperative management, and postoperative follow-up. Ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI) and angiography all have utility at different stages of management. Often one imaging modality compliments another by providing supplementary information. Data from the imaging exams must be synthesized into one coherent plan for managing patients with aortic aneurysms.

Computerized tomography angiography by direct intra-aortic low volume contrast injection in patients being evaluated for EVAR

Background Computerized tomography angiography is an important tool for endovascular repair of abdominal aortic aneurysm planning. This study aimed to evaluate the utility of computerized tomography angiography using direct intra-aortic injection of low volume of iodinated contrast in patients being considered for endovascular repair of abdominal aortic aneurysm. Design A 5F high-flow angiographic catheter was positioned in the mid-thoracic aorta through femoral percutaneous access. Computerized tomography angiography was performed with image acquisition starting simultaneously with power injection of 10 mL of iopamidol 76% diluted with normal saline to 50 mL, at 6 mL/s through the angiographic catheter. Aortic enhancement was assessed with a circular region-of-interest within the aorta. Values ≥150 HU were considered adequate. Results Nine patients with abdominal aortic aneurysm and chronic renal dysfunction underwent computerized tomography angiography with intra-arterial contrast injection for endovascular repair of abdominal aortic aneurysm planning. Mean age 78.8 ± 5.0 years, mean baseline creatinine 1.8 ± 0.4 mg/dL and mean glomerular filtration rate 36.8 ± 4.2 mL/min. Adequate computerized tomography angiography aortic enhancement was obtained in all cases (mean intra-aortic density: 300.4 ± 72.8 HU). The total contrast volume used for the computerized tomography angiography and the endovascular repair of abdominal aortic aneurysm combined was 30.0 ± 21.4 mL. Seventy-five percent of the patients received ≤30 mL of contrast. No significant renal function deterioration occurred (creatinine clearance pre- and post-procedure 36.8 ± 4.2 mL/min versus 38.6 ± 6.1 mL/min, p = 0.32). Successful endovascular repair of abdominal aortic aneurysm was achieved in eight patients. One patient underwent open treatment based on computerized tomography angiography information. No endoleak or aneurysm growth occurred (median follow-up: 121 days (range 36-1242)). Conclusion Direct intra-aortic injection of low volume of iodinated contrast provides adequate and reproducible pattern of aortic enhancement on computerized tomography angiography. The computerized tomography angiography so acquired can be used for endovascular repair of abdominal aortic aneurysm limiting the total volume of iodinated contrast required.

Practical considerations for optimizing cardiac computed tomography protocols for comprehensive acquisition prior to transcatheter aortic valve replacement

Transcatheter aortic valve replacement (TAVR) is performed frequently in patients with severe, symptomatic aortic stenosis who are at high risk or inoperable for open surgical aortic valve replacement. Computed tomography angiography (CTA) has become the gold standard imaging modality for pre-TAVR cardiac anatomic and vascular access assessment. Traditionally, cardiac CTA has been most frequently used for assessment of coronary artery stenosis, and scanning protocols have generally been tailored for this purpose. Pre-TAVR CTA has different goals than coronary CTA and the high prevalence of chronic kidney disease in the TAVR patient population creates a particular need to optimize protocols for a reduction in iodinated contrast volume. This document reviews details which allow the physician to tailor CTA examinations to maximize image quality and minimize harm, while factoring in multiple patient and scanner variables which must be considered in customizing a pre-TAVR protocol.

Ultralow Iodine Dose Transarterial Catheter-Directed CT Angiography for Fenestrated Endovascular Aortic Repair Planning

BACKGROUND

Preoperative planning for fenestrated endovascular aortic repair (fEVAR) requires high-quality cross-sectional imaging, most commonly computed tomography angiography (CTA). However, in the setting of chronic kidney disease (CKD), the iodine load delivered during conventional CTA is associated with risk for acute kidney injury (AKI). In this report, we describe the feasibility of using transarterial catheter directed CT angiography (tcd-CTA) with ultralow-dose iodine as an alternative for fEVAR planning in patients with stage 3-4 CKD to lower the risk of AKI.

METHODS

Preserum and postserum creatinine levels were retrospectively evaluated from 8 patients with stage 3-4 CKD who underwent tcd-CTA with 20 mL of Iohexol for fEVAR planning for the treatment of pararenal abdominal aortic aneurysms. The tcd-CTA images were evaluated by two vascular surgeons for adequacy for fEVAR planning and progression to fEVAR completion was recorded.

RESULTS

The mean serum creatinine before tcd-CTA was 2.1 ± .32 mg/dL, and the mean estimated glomerular filtration rate was 29.7 ± 6.31 mL/min/1.73 m(2). After tcd-CTA, the mean serum creatinine was 1.9 ± .25 mg/dL and the mean estimated glomerular filtration rate was 32.9 ± 5.12 mL/min/1.73 m(2). All 8 of the studies were determined to be adequate for fEVAR planning independently by two vascular surgeons. Six of the patients underwent successful fEVAR and 2 opted for watchful waiting.

CONCLUSIONS

tcd-CTA with ultralow-dose iodine is a feasible option for pre-fEVAR planning in patients with stage 3-4 CKD.

Intra-arterial Ultra-low-Dose CT Angiography of Lower Extremity in Diabetic Patients

PURPOSE

To image lower extremity arteries by CT angiography using a very low-dose intra-arterial contrast medium in patients with high risk of developing contrast-induced nephropathy (CIN).

MATERIALS AND METHODS

Three cases with long-standing diabetes mellitus and signs of lower extremity atherosclerotic disease were evaluated by CT angiography using 0.1 ml/kg of the body weight of contrast medium given via 10-cm-long 4F introducer by puncturing the CFA. Images were evaluated by an interventional radiologist and a cardiovascular surgeon. Density values of the lower extremity arteries were also calculated. Findings in two cases were compared with digital subtraction angiography images performed for percutaneous revascularization. Blood creatinine levels were followed for possible CIN.

RESULTS

Intra-arterial CT angiography images were considered diagnostic in all patients and optimal in one patient. No patient developed CIN after intra-arterial CT angiography, while one patient developed CIN after percutaneous intervention.

CONCLUSION

Intra-arterial CT angiography of lower extremity might be performed in selected patients with high risk of developing CIN. Our limited experience suggests that as low as of 0.1 ml/kg of the body weight of contrast medium may result in adequate diagnostic imaging.

MRI evaluation prior to Transcatheter Aortic Valve Implantation (TAVI): When to acquire and how to interpret

Transcatheter Aortic Valve Implantation (TAVI) is increasingly being used in patients with severe aortic stenosis who are not candidates for surgery. ECG-gated CT angiography (CTA) plays an important role in the preoperative planning for these devices. As the number of patients undergoing these procedures increases, a subset of patients is being recognized who have contraindications to iodinated contrast medium, either due to a prior severe allergic type reaction or poor renal function. Another subgroup of patients with low flow and low gradient aortic stenosis is being recognized that are usually assessed for severity of aortic stenosis by stress echocardiography. There are contraindications to stress echocardiography and some of these patients may not be able to undergo this test. Non-contrast MRI can be a useful emerging modality for evaluating these patients. In this article, we discuss the emerging indications of non-contrast MRI in preoperative assessment for TAVI and describe the commonly used MRI sequences. A comparison of the most important measurements obtained for TAVI assessment on CTA and MRI from same subjects is included. Teaching Points • MRI can be used for preoperative assessment of aortic annulus. • MRI is an alternate to CTA when iodinated contrast is contraindicated. • Measurements obtained by non-contrast MRI are similar to contrast enhanced CTA. • MRI can be used to assess severity of aortic stenosis.

Low Contrast Dose Catheter-Directed CT Angiography (CCTA)

PURPOSE

Catheter-directed computed tomography angiography (CCTA) has been shown to reduce the contrast volumes required in conventional CTA, thus minimizing the risk of contrast-induced nephropathy (CIN).

MATERIALS AND METHODS

A retrospective analysis was performed on cases where CCTA was used to assess access vessels prior to transfemoral aortic valve implantation (TAVI, n = 53), abdominal aortic aneurysm assessment for endovascular aneurysm repair (EVAR, n = 11), and peripheral vascular disease (PVD, n = 24).

RESULTS

We show that CCTA can image vasculature with adequate diagnostic detail to allow assessment of lower extremity disease, anatomic suitability for EVAR, as well as potential contraindications to TAVI. Average contrast volumes for pre-TAVI, pre-EVAR, and PVD cases were 7, 11, and 28 mL, respectively.

CONCLUSION

This study validates the use of CCTA in obtaining diagnostic images of the abdominal and pelvic vessels and in imaging lower extremity vasculature.

Intraarterial CT Angiography Using Ultra Low Volume of Iodine Contrast - Own Experiences

Background

High volume of intravenous contrast in CT-angiography may result in contrast-induced nephropathy. Intraarterial ultra-low volume of contrast medium results in its satisfactory blood concentration with potentially good image quality. The first main purpose was to assess the influence of the method on function of transplanted kidney in patients with impaired graft function. The second main purpose of the study was to evaluate the usefulness of this method for detection of gastrointestinal and head-and-neck haemorrhages.

Material/Methods

Between 2010 and 2013 intraarterial CT-angiography was performed in 56 patients, including 28 with chronic kidney disease (CKD). There were three main subgroups: 18 patients after kidney transplantation, 10 patients with gastrointestinal hemorrhage, 8 patients with head-and-neck hemorrhage. Contralateral or ipsilateral inguinal arterial approach was performed. The 4-French vascular sheaths and 4F-catheters were introduced under fluoroscopy. Intraarterial CT was performed using 64-slice scanner. The scanning protocol was as follows: slice thickness 0.625 mm, pitch 1.3, gantry rotation 0.6 sec., scanning delay 1–2 sec. The extent of the study was established on the basis of scout image. In patients with CKD 6–8 mL of Iodixanol (320 mg/mL) diluted with saline to 18–24 mL was administered at a speed of 4–5 mL/s.

Results

Vasculature was properly visualized in all patients. In patients with impaired renal function creatinine/eGFR levels remained stable in all but one case. Traditional arteriography failed and CT-angiography demonstrated the site of bleeding in 3 of 10 patients with symptoms of gastrointestinal bleeding (30%). In 8 patients with head-and-neck bleeding CT-angiography did not prove beneficial when compared to traditional arteriography.

Conclusions

1. Ultra-low contrast intraarterial CT-angiography does not deteriorate the function of transplanted kidneys in patients with impaired graft function. 2. 3D reconstructions allow for excellent visualization of vascular anatomy of renal transplants. 3. Intraarterial CT-angiography is useful for detection of the bleeding site.

Low kV settings CT angiography (CTA) with low dose contrast medium volume protocol in the assessment of thoracic and abdominal aorta disease: a feasibility study

OBJECTIVE

To assess the diagnostic quality of low dose (100 kV) CT angiography (CTA), by using ultra-low contrast medium volume (30 ml), for thoracic and abdominal aorta evaluation.

METHODS

67 patients with thoracic or abdominal vascular disease underwent multidetector CT study using a 256 slice scanner, with low dose radiation protocol (automated tube current modulation, 100 kV) and low contrast medium volume (30 ml; 4 ml s(-1)). Density measurements were performed on ascending, arch, descending thoracic aorta, anonymous branch, abdominal aorta, and renal and common iliac arteries. Radiation dose exposure [dose-length product (DLP)] was calculated. A control group of 35 patients with thoracic or abdominal vascular disease were evaluated with standard CTA protocol (automated tube current modulation, 120 kV; contrast medium, 80 ml).

RESULTS

In all patients, we correctly visualized and evaluated main branches of the thoracic and abdominal aorta. No difference in density measurements was achieved between low tube voltage protocol (mean attenuation value of thoracic aorta, 304 HU; abdominal, 343 HU; renal arteries, 331 HU) and control group (mean attenuation value of thoracic aorta, 320 HU; abdominal, 339; renal arteries, 303 HU). Radiation dose exposure in low tube voltage protocol was significantly different between thoracic and abdominal low tube voltage studies (490 and 324 DLP, respectively) and the control group (thoracic DLP, 1032; abdomen, DLP 1078).

CONCLUSION

Low-tube-voltage protocol may provide a diagnostic performance comparable with that of the standard protocol, decreasing radiation dose exposure and contrast material volume amount.

ADVANCES IN KNOWLEDGE

Low-tube-voltage-setting protocol combined with ultra-low contrast agent volume (30 ml), by using new multidetector-row CT scanners, represents a feasible diagnostic tool to significantly reduce the radiation dose delivered to patients and to preserve renal function, while also maintaining adequate diagnostic quality images in assessment of aorta.

Effectiveness of a low contrast load CT angiography protocol in octogenarians and nonagenarians being evaluated for transcatheter aortic valve replacement

INTRODUCTION

Transcatheter aortic valve replacement (TAVR) typically requires computed tomographic angiography (CTA) for aortoiliofemoral assessment to determine feasibility of a transfemoral approach, although many candidates being considered for TAVR are at increased risk of contrast-induced nephropathy (CIN).

OBJECTIVE

To determine the feasibility and safety of a load contrast load CTA protocol in octogenarians and nonagenarians at risk of CIN.

APPROACH

We evaluated 54 consecutive octogenarians and nonagenarians considered for TAVR who underwent CTA using a standard contrast protocol (n=21) versus a protocol incorporating low-dose contrast in patients at risk of CIN (n=33). We compared clinical characteristics, CTA image quality (score 1-4) and interpretability, and clinical outcomes, including CIN and vascular complications.

RESULTS

The mean age was 88.5±4.0 years, 37% were male, and chronic renal insufficiency was common in both the standard and low-dose contrast cohorts (57% vs. 70%, P=.39). The low-dose contrast protocol was associated with a significantly less contrast volume compared to standard contrast protocol (127±18 ml vs 76±55 ml, P<.001). Individuals imaged using low-dose (n=16) versus standard (n=17) contrast protocols received 80% less contrast volume (23±10 vs. 125±23 ml, P<.001). There was similar graded image quality (3.8±0.4 vs. 3.9±0.3, P=.76) and interpretability (100% for each, P=1.0) between standard and low-dose contrast protocol groups. There was no significant difference in rates of CIN after CTA between standard and low-dose contrast protocol groups (10% vs. 3%, P=.55), with no CIN events in those imaged by low-dose CTA. There were no major vascular injuries associated with TAVR or pigtail insertion, no major bleeding for CTA, and no noninterpretable studies in all patients.

CONCLUSION

In this proof-of-principle study, a low-dose contrast protocol appears feasible and safe in octogenarians and nonagenarians undergoing screening for TAVR, and results in significant reduction in contrast load as compared to a standard contrast protocol without observed differences in image quality or safety.

Multidimensional MDCT angiography in the context of transcatheter aortic valve implantation

OBJECTIVE

Transcatheter aortic valve implantation has emerged as a viable treatment alternative for patients with severe aortic stenosis who are not surgical candidates. Multidimensional (3D and 4D) MDCT angiography plays a critical role in the safety, success, and outcome of an institutional transcatheter aortic valve implantation program.

CONCLUSION

Given the increasing therapeutic role of this innovative technique, an understanding of essential imaging concepts in its context is critical for appropriate image acquisition and interpretation.

Ultra-low contrast computed tomographic angiography (CTA) with 20-mL total dose for transcatheter aortic valve implantation (TAVI) planning

Transcatheter aortic valve implantation workup includes assessment of the aorta and the iliofemoral arteries by computed tomographic angiography. An important group of transcatheter aortic valve implantation candidates have severe renal failure. We tested a novel computed tomographic angiography protocol (128-detector-row dual-source scanner, high-pitch helical mode) with ultralow contrast volume (20 mL) in 8 patients, compared with 8 controls. Contrast-to-noise ratio and subjective image quality, albeit lower than in the controls, were suitable for interpretation in the ultralow contrast volume group throughout all measured locations.

Patient evaluation and selection for transcatheter aortic valve replacement: the heart team approach

Transcatheter aortic valve replacement (TAVR) has been shown to significantly impact mortality and quality of life in patients with severe aortic stenosis (AS) who are deemed high risk for surgical aortic valve replacement (SAVR). Essential to these outcomes is proper patient selection. The multidisciplinary TAVR heart team was created to provide comprehensive patient evaluation and aid in proper selection. This review with outline the history and components of the heart team, and delineate the team's role in risk and frailty assessment, evaluation of common co-morbidities that impact outcomes, and the complex multi-modality imaging necessary for procedural planning and patient selection. The heart team is critical in determining patient eligibility and benefit and the optimal operative approach for TAVR. The future of structural heart disease will certainly require a team approach, and the TAVR heart team will serve as the successful model.

Intra-arterial ultra low iodine CT angiography of renal transplant arteries

PURPOSE

This study was designed to evaluate the technical feasibility and the image quality of intra-arterial 320-row CT angiography (ia-CTA) in the detection of transplant renal artery stenosis (TRAS) using a very low dose of contrast agent.

METHODS

Evaluation of ia-CTA using a 4F catheter in ten patients with impaired renal transplant function and suspected TRAS. Average amount of contrast agent applied was 10 ± 3.7 ml standard deviation (SD). Patient serum creatinine levels had been monitored for 72 h. TRAS was detected and graded (1: less than 20 %; 2: 20-49 %; 3: 50-74 %; 4: 75-99 %; 5: total occlusion) and presence of kinking was recorded. Attenuation and vessel delineation were parameters for image quality analysis of the renal arterial supply, divided into four segments. Subjective image quality.

RESULTS

Ia-CTA of the renal transplant was technically successful in all patients, revealing relevant stenoses in 7 of 10 patients. Serum creatinine levels before and after ia-CTA were 2.71 ± 1.46 and 2.56 ± 1.39 mg/dl, respectively. None of the patients developed signs of contrast-induced nephropathy within 72 h. Subjective image quality was excellent in all four segments, rated by two separate readers. No segment was found to be nondiagnostic. Mean attenuation values in the arterial segments ranged between 754 and 987 Hounsfield units.

CONCLUSIONS

Wide detector ia-CTA for the diagnosis of TRAS is feasible using very low doses of contrast agent and results in high image quality.

Imaging in Transcatheter Aortic Valve Replacement (TAVR): role of the radiologist

BACKGROUND

Transcatheter aortic valve replacement (TAVR) is a novel technique developed in the last decade to treat severe aortic stenosis in patients who are non-surgical candidates because of multiple comorbidities.

METHODS

Since the technique is performed using a transvascular approach, pre-procedural assessment of the aortic valve apparatus, ascending aorta and vascular access is of paramount importance for both appropriate patient selection and correct device selection. This assessment is performed by a multi-disciplinary team with radiology being an integral and important part.

RESULTS

Among imaging modalities, there is growing scientific evidence supporting the crucial role of MDCT in the assessment of the aortic valve apparatus, suitability of the iliofemoral or alternative pathway, and determination of appropriate coaxial angles. MDCT also plays an important role in post-procedure imaging in the assessment of valve integrity and position.

CONCLUSION

This review outlines the principal aspects of TAVR, the multidisciplinary approach and utilisation of different imaging modalities, as well as a step-by-step approach to MDCT acquisition protocols, reconstruction techniques, pre-procedure measurements and post-procedure assessment.

TEACHING POINTS

• TAVR is a new technique to treat severe aortic stenosis in high-risk and nonsurgical candidates. • MDCT assessment of the aortic annulus is important for appropriate patient and device selection. • Multidisciplinary approach is required for patient selection, procedure planning and performance. • MDCT is required for assessment of the aortic root, iliofemoral or alternative vascular pathway.

ACR appropriateness criteria imaging for transcatheter aortic valve replacement

Although aortic valve replacement is the definitive therapy for severe aortic stenosis, almost half of patients with severe aortic stenosis are unable to undergo conventional aortic valve replacement because of advanced age, comorbidities, or prohibitive surgical risk. Treatment options have been recently expanded with the introduction of catheter-based implantation of a bioprosthetic aortic valve, referred to as transcatheter aortic valve replacement. Because this procedure is characterized by lack of exposure of the operative field, image guidance plays a critical role in preprocedural planning. This guideline document evaluates several preintervention imaging examinations that focus on both imaging at the aortic valve plane and planning in the supravalvular aorta and iliofemoral system. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Multi-modality imaging of the aortic valve in the era of transcatheter aortic valve replacement: a guide for patient selection, valve selection, and valve delivery

Aortic stenosis is a common condition traditionally treated surgically. Transcatheter aortic valve replacement (TAVR) is an exciting and new method allowing treatment of high risk and inoperable patients. Multimodality imaging is extremely important in the preprocedural evaluation, the performance of the procedure, and the post-procedural assessment and includes transthoracic echocardiography, transesophageal echocardiography, conventional angiography, multi-detector computed tomography, and cardiac magnetic resonance. This paper will review the role of various imaging modalities during the phases of the TAVR procedure with an emphasis on the advantages and limitations of each approach.

Transcatheter aortic valve repair, imaging, and electronic imaging health record

Degenerative aortic stenosis (AS) is a common valvular pathology in developed nations. Secondary to advanced age and often multiple co-morbidities, a significant percentage of patients are not considered surgical candidates. For these high-risk patients, transcatheter aortic valve replacement (TAVR) is a rapidly emerging less-invasive treatment alternative. Because of the lack of direct exposure and visualization of the operative field, pre-procedural planning and intra-procedural guidance relies on imaging. Large 3-dimensional data files are acquired, which are reconstructed on advanced workstations during review and interpretation. Optimally, the imaging data is organized into a comprehensive digital file as an integral part of the electronic health record (EHR) following the patient. This manuscript will discuss the role of image data management in the context of TAVR.

SCCT expert consensus document on computed tomography imaging before transcatheter aortic valve implantation (TAVI)/transcatheter aortic valve replacement (TAVR)

Computed tomography (CT) plays an important role in the workup of patients who are candidates for implantation of a catheter-based aortic valve, a procedure referred to as transcatheter aortic valve implantation (TAVI) or transcatheter aortic valve replacement (TAVR). Contrast-enhanced CT imaging provides information on the suitability of the peripheral access vessels to accommodate the relatively large sheaths necessary to introduce the prosthesis. CT imaging also provides accurate dimensions of the ascending aorta, aortic root, and aortic annulus which are of importance for prosthesis sizing, and initial data indicate that compared with echocardiographic sizing, CT-based sizing of the prosthesis may lead to better results for postprocedural aortic valve regurgitation. Finally, CT permits one to predict appropriate fluoroscopic projections which are oriented orthogonal to the aortic valve plane. This consensus document provides recommendations about the use of CT imaging in patients scheduled for TAVR/TAVI, including data acquisition, interpretation, and reporting.

A practical guide to multimodality imaging of transcatheter aortic valve replacement

The advent of transcatheter aortic valve replacement (TAVR) is one of the most widely anticipated advances in the care of patients with severe aortic stenosis. This procedure is unique in many ways, one of which is the need for a multimodality imaging team-based approach throughout the continuum of the care of TAVR patients. Pre-procedural planning, intra-procedural implantation optimization, and long-term follow-up of patients undergoing TAVR require the expert use of various imaging modalities, each of which has its own strengths and limitations. Divided into 3 sections (pre-procedural, intraprocedural, and long-term follow-up), this review offers a single source for expert opinion and evidence-based guidance on how to incorporate the various modalities at each step in the care of a TAVR patient. Although much has been learned in the short span of time since TAVR was introduced, recommendations are offered for clinically relevant research that will lead to refinement of best practice strategies for incorporating multimodality imaging into TAVR patient care.

Incidence and predictors of acute kidney injury after transcatheter aortic valve replacement

BACKGROUND

Patients undergoing transcatheter aortic valve replacement (TAVR) are at increased risk for acute kidney injury (AKI). The Valve Academic Research Consortium (VARC) recently published criteria for AKI after TAVR. We aimed to identify predictors, assess the prognostic impact of AKI after TAVR, and compare various criteria for AKI.

METHODS

Patients with aortic stenosis undergoing TAVR were retrospectively analyzed for periprocedural AKI (<72 hours) according to the VARC definition (increase in serum creatinine ≥0.3 mg/dL or ≥1.5× baseline) or according to the modified Risk, Injury, Failure, Loss, and End-stage kidney disease (RIFLE) criteria (decrease of >25% in estimated glomerular filtration rate at 48 hours).

RESULTS

Acute kidney injury, according to the VARC definition, occurred in 24 (14.6%) of 165 patients after TAVR. Acute kidney injury, according to RIFLE criteria, occurred in 19 patients (11.5%). Men (63% vs 38%, P = .03) and patients receiving blood transfusion (63% vs 39%, P = .04) were more likely to develop AKI. In multivariable analysis, only blood transfusion emerged as a predictor for AKI (odds ratio 3.74, 95% CI 1.36-10.3). Patients who developed AKI had higher in-hospital (21% vs 4%, P = .007) and 30-day mortality (29% vs 7%, P = .004) as compared with patients without AKI.

CONCLUSION

Acute kidney injury is a frequent complication of TAVR. Even a small increase (0.3 mg/dL) in baseline creatinine post-TAVR is associated with worse outcome. The poor prognosis of these patients should encourage improvement in patient selection and careful management for prevention of this complication.

Computed tomography in the evaluation for transcatheter aortic valve implantation (TAVI)

If left untreated, symptomatic, severe aortic stenosis (AS) is associated with a dismal prognosis. Open-heart surgical valve replacement is the treatment of choice and is associated with excellent short and long-term outcome. However, many older patients with multiple co-morbidities and anticipated increased surgical risk are excluded from surgical intervention. For these patients, transcatheter aortic valve implantation (TAVI) is emerging as a viable treatment alternative. Transcatheter valvular heart procedures are characterized by lack of exposure and visualization of the operative field, therefore relying on image guidance, both for patient selection and preparation and the implantation procedure itself. This article describes the role of multi-detector row computed tomography (MDCT) for detailed assessment of the aortic valve, aortic root, and iliac arteries in the context of TAVI.

Computed tomography evaluation for transcatheter aortic valve implantation (TAVI): imaging of the aortic root and iliac arteries

For patients with severe aortic stenosis, open-heart surgical valve replacement remains the current clinical standard with documented, excellent long-term outcome. Over the past few years, transcatheter aortic valve implantation (TAVI) has developed into a treatment alternative for high-risk patients with severe aortic stenosis. Because transcatheter valvular procedures are characterized by lack of exposure of the operative field, image guidance is critical. This Pictorial Essay describes the role of 3-dimensional imaging with multidetector row computed tomography for detailed reconstructions of the aortic valve, aortic root, and iliac arteries in the context of TAVI.