Contrast-enhanced Imaging Modalities Research Articles

A comparative study between the diagnostic performance of contrast-enhanced digital mammography and dynamic contrast-enhanced MRI in invasive lobular carcinoma of the breast

BackgroundInvasive lobular carcinoma is the second most prevalent histological subtype of breast cancer after invasive duct carcinoma, with a reported increased incidence in the last two decades. It often presents with challenging imaging characteristics that lower the sensitivity of mammography in their detection and delineation of their extent. Moreover, an increased risk of having synchronous lesions in the same or opposite breast was reported in cases with invasive lobular carcinoma. This obviates the need for other imaging modalities, specifically contrast-enhanced imaging modalities, to improve early detection as well as allow precise determination of the extent of the disease. Our aim in this study was to compare the diagnostic performance of contrast-enhanced digital mammography and dynamic contrast-enhanced magnetic resonance imaging (MRI) in the local staging of invasive lobular carcinoma regarding the size, extensions, multiplicity and bilaterality.MethodsThis study included 46 female patients with pathologically proven invasive lobular carcinoma. They underwent full-field digital mammography with a complementary ultrasound examination, contrast-enhanced digital mammography, and dynamic contrast-enhanced MRI. The findings encountered by the three imaging modalities were evaluated independently, and the results were compared with final histopathology.ResultsIn the current study, dynamic contrast-enhanced MRI study was the most sensitive modality in the detection of the index lesion, synchronous ipsilateral and contralateral lesions and achieved a sensitivity of 100% in each analysis as compared to contrast-enhanced digital mammography, which achieved a sensitivity of 97.8%, 85.7% and 80%, respectively. Regarding the assessment of the lesion extent to the surroundings, there was a tendency to overestimation by MRI examination.ConclusionsAlthough dynamic contrast-enhanced MRI is the most sensitive imaging modality for detecting the index lesion, multiplicity and bilaterality, contrast-enhanced digital mammography achieved comparable overall accuracy. Regarding the locoregional staging of invasive lobular carcinoma, there was a tendency for relative overestimation by MRI examination.

Usefulness of triggered non-contrast-enhanced magnetic resonance angiography in assessing lower extremity venous disease.

Although venous duplex ultrasonography (USG) is reliable for diagnosing lower extremity venous disease (LEVD), cross-sectional imaging studies were usually required before intervention or surgery. Patients of LEVD with renal insufficiency usually restrict the use of contrast-enhanced imaging modalities. In seeking an alternative imaging solution for these patients, we explore the clinical utility of triggered angiography non-contrast-enhanced magnetic resonance imaging (TRANCE-MRI) in the assessment of LEVD.We collected data from patients presenting to a tertiary wound-care center with symptoms of LEVD from April 2017–November 2019. Each participant underwent baseline USG followed by TRANCE-MRI on a 1.5T MR scanner (Philips Ingenia, Philips Healthcare, Best, The Netherlands). Inter-rater reliability was measured using Cohen's kappa (κ).All 80 participants (mean age, 61.9 ± 14.8 years; 35 males, 45 females) were assessed and were classified into one of five disease groups, deep vein thrombosis (n = 38), venous static ulcer (n = 16), symptomatic varicose veins (n = 18), recurrent varicose veins (n = 3), and lymphoedema (n = 5). The inter-rater reliability between TRANCE-MRI and doppler USG showed substantial agreement (κ, 0.73). The sensitivity, specificity, and accuracy of TRANCE-MRI were 90.5%, 88.1%, and 88.8%, respectively. In 59 (73.8%) USG-negative patients, we were able to diagnose positive findings (deep venous thrombosis, n = 7; varicose veins, n = 15; lymphedema, n = 10; iliac vein compression with thrombosis, n = 6; external venous compression, n = 5; vena cava anomaly, n = 2; occult peripheral artery disease, n = 5; ccluded bypass graft, n = 1) by using TRANCE-MRI. Of these, 9 (15.3%) patients underwent additional vascular surgery based on positive TRANCE-MRI findings.TRANCE technique provides the limb's entire venous drainage in clear images without background contamination by associated arterial imaging. Additionally, simultaneous evaluation of bilateral lower extremities can help determine the lesion's exact site. Although TRANCE-MRI can provide MR arteriography and MR venography, we recommend performing only MR venography in symptomatic LEVD patients because the incidence of occult arterial disease is low.

Contrast-enhanced ultrasound features of hepatocellular carcinoma not detected during the screening procedure

Aim The aim of this retrospective study is to report on the characteristics of contrast-enhanced ultrasound (CEUS) of primarily not detected hepatocellular carcinoma (HCC) during the screening procedure of patients at risk. Methods Sixty-four patients with a finally solitary and histologically proven HCC not detected HCC during the screening procedure were retrospectively analyzed. Most of HCC lesions (90.6 %, 58/64) measured < 20 mm in diameter. All HCC lesions were not detected during the initial screening procedure but suspected using contrast-enhanced magnetic resonance imaging. The final gold standard was biopsy or surgery with histological examination. Results On CEUS, 62/64 (96.8 %) of HCC were characterized as an obviously hyperenhanced lesion in arterial phase, and 41/64 (64.1 %) of HCC were characterized as hypoenhancing lesions in the portal venous and late phases. During the arterial phase of CEUS, 96.8 % of HCC displayed homogeneous hyperenhancement. Knowing the CEUS and magnetic resonance imaging findings, 45/64 (70.3 %) could have been detected using B-mode ultrasound (BMUS). Conclusion BMUS as a screening procedure is generally accepted. Contrast-enhanced imaging modalities have improved detection and characterization of HCC. Homogeneous hyperenhancement during the arterial phase and mild washout are indicative for HCC in liver cirrhosis.

Role of Contrast-Enhanced Ultrasound in the Follow-up of Kidney Transplant Patients.

Contrast-enhanced ultrasound combines the advantages of native ultrasound and other contrast-enhanced imaging modalities. In selected cases it can be preferable to computerized tomographic scan among kidney transplant recipients. We performed a retrospective study involving patients of Semmelweis University Department of Transplantation and Surgery who underwent contrast-enhanced ultrasound examination from 2011 to 2015. During this period, 251 examinations were performed, including 45 on kidney transplant patients. A Toshiba Aplio XU ultrasound device was used, and 1-1.5 mL contrast agent (Sonovue) was administered intravenously for each patient. The indications of these evaluations can be divided into 3 groups: characterization of circumscribed kidney lesions, control after radiofrequency ablation therapy, and examination of graft perfusion. Fully 93% of the examinations were conclusive. In the 1st group of the 37 cases where tumor-suspect lesions were investigated, 13 examinations suggested the presence of a space-occupying lesion. Of those 13 cases, 2 patients had a negative biopsy, nephrectomy was performed in 11 cases, and histologic evaluation verified a tumor in 8 samples. In the 2nd group, the ablation control examination detected a residual tumor in none of the 6 cases. Finally, in 1 of the 2 grafts where the circulation was investigated, blood flow was satisfactory, and in the other it was low. The contrast-enhanced ultrasound examination was conclusive in most cases. The applied contrast material is not nephrotoxic, and the method uses nonionizing radiation. These features make contrast-enhanced ultrasound highly suitable for the examination of kidney transplant patients.

Time-efficient estimation of the magnetic resonance dispersion model parameters for quantitative assessment of angiogenesis

The limitations of the available imaging modalities for prostate cancer (PCa) localization result in suboptimal protocols for management of the disease. In response, several dynamic contrast-enhanced imaging modalities have been developed, which aim at cancer detection through the assessment of the changes occurring in the tumor microenvironment due to angiogenesis. In this context, novel magnetic resonance dispersion imaging (MRDI) enables the estimation of parameters related to the microvascular architecture and leakage, by describing the contrast agent kinetics with a dispersion model. Although a preliminary validation of MRDI on PCa has shown promising results, parameter estimation can become burdensome due the convolution integral present in the dispersion model. To overcome this limitation, in this work we provide analytical solutions of the dispersion model in the time and frequency domains, and we implement three numerical methods to increase the time-efficiency of parameter estimation. The proposed solutions are tested for PCa localization. A reduction by about 50% of computation time could be obtained, without significant changes in the estimation performance and in the clinical results. With the continuous development of new technological solutions to boost the spatiotemporal resolution of DCE-MRI, solutions to improve the computational efficiency of parameter estimation are highly required.

Hepatocellular carcinoma after ablation: The imaging follow-up scheme

Percutaneous ablation using thermal or chemical methods has been widely used in the treatment of hepatocellular carcinoma (HCC). Nowadays, contrast-enhanced imaging modalities such as computed tomography (CT), magnetic resonance imaging (MRI), and contrast-enhanced ultrasound (CEUS) are widely used to evaluate local treatment response after ablation therapies. CEUS is gaining increasing attention due to its characteristics including real-time scanning, easy performance, lack of radiation, wide availability, and lack of allergy reactions. Several studies have documented that CEUS is comparable to CT or MRI in evaluating local treatment efficacy within 1 mo of treatment. However, little information is available regarding the role of CEUS in the follow-up assessment after first successful ablation treatment. Zheng et al found that in comparison with contrast-enhanced computed tomography (CECT), the sensitivity, specificity, positive predictive value, negative predictive value and overall accuracy of CEUS in detecting local tumor progression (LTP) were 67.5%, 97.4%, 81.8%, 94.4% and 92.3%, respectively, and were 77.7%, 92.0%, 92.4%, 76.7% and 84.0%, respectively for the detection of new intrahepatic recurrence. They concluded that the sensitivity of CEUS in detecting LTP and new intrahepatic recurrence after ablation is relatively low in comparison with CECT, and CEUS cannot replace CECT in the follow-up assessment after percutaneous ablation for HCC. These results are meaningful and instructive, and indicated that in the follow-up period, the use of CEUS alone is not sufficient. In this commentary, we discuss the discordance between CT and CEUS, as well as the underlying mechanisms involved. We propose the combined use of CT and CEUS which will reduce false positive and negative results in both modalities. We also discuss future issues, such as an evidence-based ideal imaging follow-up scheme, and a cost-effectiveness analysis of this imaging follow-up scheme.

A review of 3D vessel lumen segmentation techniques: Models, features and extraction schemes

Vascular diseases are among the most important public health problems in developed countries. Given the size and complexity of modern angiographic acquisitions, segmentation is a key step toward the accurate visualization, diagnosis and quantification of vascular pathologies. Despite the tremendous amount of past and on-going dedicated research, vascular segmentation remains a challenging task. In this paper, we review state-of-the-art literature on vascular segmentation, with a particular focus on 3D contrast-enhanced imaging modalities (MRA and CTA). We structure our analysis along three axes: models, features and extraction schemes. We first detail model-based assumptions on the vessel appearance and geometry which can embedded in a segmentation approach. We then review the image features that can be extracted to evaluate these models. Finally, we discuss how existing extraction schemes combine model and feature information to perform the segmentation task. Each component (model, feature and extraction scheme) plays a crucial role toward the efficient, robust and accurate segmentation of vessels of interest. Along each axis of study, we discuss the theoretical and practical properties of recent approaches and highlight the most advanced and promising ones.

Numerical Simulation of Magnetic Resonance Angiographies of an Anatomically Realistic Stenotic Carotid Bifurcation

Magnetic Resonance Angiography (MRA) has become a routine imaging modality for the clinical evaluation of obstructive vascular disease. However, complex circulatory flow patterns, which redistribute the Magnetic Resonance (MR) signal in a complicated way, may generate flow artifacts and impair image quality. Numerical simulation of MRAs is a useful tool to study the mechanisms of artifactual signal production. The present study proposes a new approach to perform such simulations, applicable to complex anatomically realistic vascular geometries. Both the Navier-Stokes and the Bloch equations are solved on the same mesh to obtain the distribution of modulus and phase of the magnetization. The simulated angiography is subsequently constructed by a simple geometric procedure mapping the physical plane into the MRA image plane. Steady bidimensional numerical simulations of MRAs of an anatomically realistic severely stenotic carotid artery bifurcation are presented, for both time-of-flight and contrast-enhanced imaging modalities. These simulations are validated by qualitative comparison with flow phantom experiments performed under comparable conditions.