Intravenous Application Of Contrast Agent Research Articles

Diagnostic Performance of Contrast-Enhanced Ultrasound (CEUS) in the Evaluation of Solid Renal Masses.

Background: The present study aims to evaluate the diagnostic performance of contrast-enhanced ultrasound (CEUS) for discriminating between benign and malignant solid renal masses. Methods: 18 patients with histopathologically confirmed benign solid renal masses (11 oncocytomas, seven angiomyolipomas) as well as 96 patients with confirmed renal cell carcinoma (RCC) who underwent CEUS followed by radical or partial nephrectomy were included in this single-center study. CEUS examinations were performed by an experienced radiologist (EFSUMB Level 3) and included the application of a second-generation contrast agent. Results: Renal angiomyolipomas, oncocytomas, and renal cell carcinomas showed varying sonomorphological characteristics in CEUS. Angiomyolipomas showed heterogeneous echogenicity (57% hypo-, 43% hyperechoic), while all lesions showed rapid contrast-enhancement with two lesions also showing venous wash-out (29%). Notably, 9/11 oncocytomas could be detected in conventional ultrasound (64% hypo-, 9% hyper-, 9% isoechoic) and 2/11 only demarcated upon intravenous application of contrast agent (18%). All oncocytomas showed hyperenhancement in CEUS, venous wash-out was registered in 7/11 lesions (64%). Conclusions: In line with the current state of knowledge, no specific sonomorphological characteristics allowing for accurate distinction between benign and malignant solid renal masses in CEUS could be detected in our study.

Evaluation of Gadopiclenol and P846, 2 High-Relaxivity Macrocyclic Magnetic Resonance Contrast Agents Without Protein Binding, in a Rodent Model of Hepatic Metastases: Potential Solutions for Improved Enhancement at Ultrahigh Field Strength.

The aim of this study was to evaluate in vitro and in vivo the enhancement properties of experimental gadolinium (Gd)-based contrast agents (GBCAs) with different molecular weights and hydration numbers (P846 and gadopiclenol) compared with clinically approved low-molecular, extracellular agents (gadopentetate and gadoterate) at 9.4 T and to discuss influencing factors on r1 relaxivities. All experiments were performed with a 9.4 T animal scanner (Bruker, Germany). We performed relaxometry measurements for all contrast agents in human plasma at 37°C using an IR-RARE sequence. In addition, we compared P846 with gadopentetate and gadopiclenol with gadoterate intraindividually in rats with hepatic colorectal cancer metastases (n = 10 each) acquiring T1-weighted FLASH sequences before and at 10 consecutive time points during 20 minutes. After intravenous contrast agent application, signal-to-noise ratios (SNRs), contrast-to-noise ratios (CNRs), and lesion enhancement (LE) for liver parenchyma and tumors were calculated based on region of interest measurements. Longitudinal relaxivities (r1) of the low-molecular agents were lower as compared with the experimental compounds. However, r1 of gadopentetate and gadoterate demonstrated only a moderate decrease of r1 at 9.4 T as compared with known data at lower field strengths (gadopentetate: r1 [at 9.4 T], 3.4 mM s/r1 [at 1.5 T], 4.1 mM s/gadoterate: r1 [at 9.4 T], 3.1 mM s/r1 [at 1.5 T], 3.6 mM s). In contrast, r1 of P846 showed a marked reduction at 9.4 T compared with 1.5 T (P846: r1 [at 9.4 T], 6.4 mM s/r1 [at 1.5 T], 32 mM s). Gadopiclenol provided the highest r1 in this study at 9.4 T and the drop of r1 as compared with lower field strength is less apparent (gadopiclenol: r1 [at 9.4 T], 8.7 mM s/r1 [at 1.5 T], 12.7 mM s).In vivo, P846 and gadopiclenol showed significantly higher SNR, CNR, and LE as compared with the low-molecular control agents (mean ± SD; SNRliver [gadopentetate, 18.1 ± 1.2; P846, 27.2 ± 1.5; P < 0.001]; SNRtumor [gadopentetate, 22.6 ± 1.9; P846, 40.1 ± 1.9; P < 0.001]; CNR [gadopentetate, 4.6 ± 1.0; P846, 12.9 ± 0.9; P < 0.001]; LE [gadopentetate, 7.2 ± 1.9; P846, 14.9 ± 1.9; P < 0.001]/SNRliver [gadoterate, 8.8 ± 0.5; gadopiclenol, 12.6 ± 1.3; P < 0.001]; SNRtumor [gadoterate, 11.3 ± 1.2; gadopiclenol, 20.9 ± 2.9; P < 0.001]; CNR [gadoterate, 2.5 ± 0.7; gadopiclenol, 8.3 ± 1.7; P < 0.001]; LE [gadoterate, 4.4 ± 1.2; gadopiclenol, 13.0 ± 2.9; P < 0.001]). Thus, for equal Gd doses, gadopiclenol and P846 increase the CNR of liver metastases by a factor of 2.5 to 3 at 9.4 T compared with gadoterate and gadopentetate. P846 and gadopiclenol provide superior enhancement at 9.4 T as compared with gadopentetate and gadoterate. However, the macromolecular agent P846 shows a marked decrease of r1 from 1.5 T to 9.4 T. This effect is less apparent for the low-molecular agents gadopiclenol, gadopentetate, and gadoterate. Yet, based on the higher hydration number, r1 of P846 and gadopiclenol are markedly higher as compared with the reference contrast agents. Thus, building compounds with moderately increased molecular size and hydration number, as implemented in gadopiclenol, seems to be a promising way to develop highly effective GBCAs.Advantages for gadopiclenol include a strong enhancement regardless of the external magnetic field strength, pharmacokinetics comparable to those of clinically approved extracellular GBCAs, and the potential to either improve sensitivity in diagnostic magnetic resonance imaging by improving lesion conspicuity or to perform studies with significantly reduced Gd-dose while at the same time providing comparable diagnostic accuracy. However, all this needs to be proven in clinical studies.

Hyperintense Acute Reperfusion Marker on FLAIR in a Patient with Transient Ischemic Attack.

The hyperintense acute reperfusion marker (HARM) has initially been described in acute ischemic stroke. The phenomenon is caused by blood-brain barrier disruption following acute reperfusion and consecutive delayed gadolinium enhancement in the subarachnoid space on fluid attenuated inversion recovery (FLAIR) images. Here we report the case of an 80-year-old man who presented with transient paresis and sensory loss in the right arm. Initial routine stroke MRI including diffusion- and perfusion-weighted imaging demonstrated no acute pathology. Follow-up MRI after three hours demonstrated subarachnoid gadolinium enhancement in the left middle cerebral artery territory consistent with HARM that completely resolved on follow-up MRI three days later. This case illustrates that even in transient ischemic attack patients disturbances of the blood-brain barrier may be present which significantly exceed the extent of acute ischemic lesions on diffusion-weighted imaging. Inclusion of FLAIR images with delayed acquisition after intravenous contrast agent application in MRI stroke protocols might facilitate the diagnosis of a recent acute ischemic stroke.

Dynamic contrast enhanced-MRI in rectal cancer: Inter- and intraobserver reproducibility and the effect of slice selection on pharmacokinetic analysis

To assess inter- and intraobserver reproducibility of DCE-MRI measurements and possible differences between two directly adjacent slices. DCE-MRI measurements of 30 patients with histologically proven rectal carcinoma were performed on a 1.5 Tesla (T) MR system during intravenous contrast agent application before and after neoadjuvant radiochemotherapy with two directly adjacent slices used for calculation per patient. Images were analyzed semiquantitatively (parameters TTP and MITR) and quantitatively using the Brix compartment model (parameters kep and A) by two different observers and at two different time points. The concordance correlation coefficient was calculated for every parameter in intra-/interobserver comparison and slice comparison. Median relative differences below 10% for all parameters and high values of the concordance correlation coefficient (CCC) were found for most pharmacokinetic parameters in inter-/intraobserver comparison and slice comparison, with the exception of the parameter A before therapy in intra-/ interobserver comparison (CCC: 0.315/0.452) and kep before therapy in intraobserver comparison (CCC: 0.362). Our results indicate good inter- and intraobserver reproducibility for most pharmacokinetic parameters and for the two adjacent slices measured. However, as there were some parameters that demonstrated poor correlation, testing for reproducibility and a multiobserver approach might be considered whenever using pharmacokinetic parameters as biomarkers.

Impact of a new metal artefact reduction algorithm in the noninvasive follow-up of intracranial clips, coils, and stents with flat-panel angiographic CTA: initial results

Flat-panel angiographic CT after intravenous contrast agent application (ivACT) is increasingly used as a follow-up examination after coiling, clipping, or stenting. The purpose of this study was to evaluate the feasibility of a new metal artefact reduction algorithm (MARA) in patients treated for intracranial aneurysms and stenosis. IvACT was performed on a flat-panel detector angiography system after intravenous application of 80 ml contrast media. The uncorrected raw images were transferred to a prototype reconstruction workstation where the MARA was applied. Two experienced neuroradiologists examined the corrected and uncorrected images on a commercially available workstation. Artefacts around the implants were detected in all 16 uncorrected cases, while eight cases showed remaining artefacts after correction with the MARA. In the cases without correction, there were 11 cases with "extensive" artefacts and five cases with "many" artefacts. After correction, seven cases showed "few" and only one case "many" artefacts (Wilcoxon test, P < 0.001). Parent vessels were characterized as "not identifiable" in 62% of uncorrected images, while the delineation of parent vessels were classified as "excellent" in 50% of the cases after correction (Wilcoxon test, P = 0.001). Use of the MARA in our study significantly reduced artefacts around metallic implants on ivACT images and allowed for the delineation of surrounding structures.

Evaluation of Noninvasive Follow-up Methods for the Detection of Intracranial In-Stent Restenosis

Intra-arterial digital subtraction angiography (IA-DSA), an invasive procedure, is the current reference examination after percutaneous transluminal angioplasty and stenting for the detection of in-stent restenosis (ISR). In this phantom study, we evaluated flat-panel angiographic computed tomography after intravenous contrast agent application (IV-ACT) and multidetector computed tomographic angiography (MDCTA) as potential noninvasive follow-up alternatives after intracranial percutaneous transluminal angioplasty and stenting. We simulated an intracranial vessel using a silicon tube placed inside a human skull. Three different stent systems were deployed inside the silicon tubes, each with diameters of 3 or 4 mm. Three grades of ISR (25%, 50%, and 75%) were simulated. The IA-DSA and IV-ACT examinations were performed on a flat-panel detector angiography system. The MDCTA images were acquired with a 128-slice computed tomographic scanner. The mean stenosis diameters, measured with each technique, were compared using the Bland-Altman plot. The difference between the known stenosis diameter and the measured stenosis diameter was calculated for each examination. Stenosis measurements on the IA-DSA images showed no statistically significant differences compared with the known stenosis diameters (P = 0.19). In the 3-mm stent category, when compared with the known stenosis diameter, mean (SD) differences of 0.01 (0.15) mm, 0.03 (0.24) mm and 0.16 (0.5) mm were calculated for the IA-DSA, IV-ACT, and MDCTA stenosis measurements, respectively. As for the 4-mm stents, IA-DSA and IV-ACT were again very accurate, with mean (SD) differences of -0.03 (0.11) mm and 0.07 (0.19) mm, respectively, compared with the known stenosis diameters, whereas MDCTA overestimated ISR, with a mean (SD) difference of 0.49 (0.53) mm. The Bland-Altman plots show a mean (SD) difference of 0.08 (0.2) mm between IA-DSA and IV-ACT (95% confidence interval, 0.05-0.11) and a mean (SD) difference of 0.34 (0.56) mm between IA-DSA and MDCTA measurements (95% confidence interval, 0.25-0.42). In our phantom study, IA-DSA was the only examination to predict accurately degrees of stenosis compared with the known stenosis diameters. The results of the IV-ACT measurements were comparable with those of IA-DSA. Multidetector computed tomographic angiography was less accurate in the quantification of stenosis, usually overestimating ISR.

Angiographic CT with intravenous contrast agent application for monitoring of intracranial flow diverting stents

Intracranial flow diverting devices are increasingly used to treat cerebral aneurysms. A reliable, non-invasive follow-up modality would be desirable. Our aim was to compare intra-arterial digital subtraction angiography (ia DSA) to angiographic computed tomography with intravenous contrast agent application (iv ACT) in the visualisation of flow diverting devices and aneurysm lumina. Follow-up monitoring by iv ACT (n = 36) and ia DSA (n = 25) in 14 patients treated with flow diverting devices for intracranial aneurysms was evaluated retrospectively. Images were evaluated by two neuroradiologists in anonymous consensus reading regarding the device deployment, wall apposition, neck coverage of the aneurysm, opacification of the vessel and device lumen, as well as the degree of aneurysm occlusion. Corresponding ia DSA and iv ACT images were scored identically in all patients regarding the stent deployment, wall apposition and neck coverage, as well as the degree of aneurysm occlusion and patency status of the device and parent artery. Opacification of the parent vessel lumen and perfused parts of the aneurysm was considered slightly inferior for iv ACT in comparison with ia DSA (seven of 36 cases), without impact on diagnosis. We demonstrated the feasibility and diagnostic value of iv ACT in follow-up imaging of intracranial flow diverting devices. Due to its high spatial resolution and non-invasive character, this novel technique might become a valuable imaging modality in these patients.

Feasibility of Flat Panel Angiographic CT after Intravenous Contrast Agent Application in the Postoperative Evaluation of Patients with Clipped Aneurysms

Important findings, such as aneurysm remnants or major arterial occlusion, can be detected on intra- or postoperative angiography after surgical clipping of intracranial aneurysms. The purpose of this study was to evaluate the feasibility of IV-ACT for the postoperative detection of residual aneurysms and parent vessel patency compared with IA-DSA, which was selected as the standard reference method. Twenty-two patients with 27 aneurysms treated by surgical clipping were examined by using both IA-DSA and IV-ACT. Both diagnostic procedures were performed on an FPD-equipped angiography system. Postprocessing of IV-ACT acquisitions was performed on a dedicated workstation producing multiplanar reformations and maximum intensity projections of the clip region and other intracranial arteries. Three interventional neuroradiologists independently evaluated both procedures. A residual aneurysm was delineated in 10 cases with IA-DSA. Sufficient opacification of the intracranial vessels was assigned in 26 IV-ACT cases. Due to metal artifacts, IV-ACT images were tagged as "not diagnostic" on 8 occasions. In the other 19 aneurysms, a residual aneurysm was delineated in 6 cases-all 6 being true-positive compared with IA-DSA-and was excluded in the remaining 13 cases-all true-negative. Even small aneurysm remnants with a diameter of 1.5 mm were detected with IV-ACT. Currently IV-ACT cannot be recommended as a routine tool for postoperative evaluation of clipped aneurysms due to metal artifacts in 30% of the examinations. These artifacts appear with multiple normal-sized or large clips. In patients with single or multiple small clips, IV-ACT can reliably show aneurysm remnants.

Angiographic CT after Intravenous Contrast Agent Application: A Noninvasive Follow-Up Tool after Intracranial Angioplasty and Stenting

ICAS is one of the therapeutic options in symptomatic cerebral artery stenosis. iaDSA is the current criterion standard examination after ICAS for the detection of ISR. In this study, we evaluated ivACT as a potential noninvasive follow-up alternative. In 17 cases, ivACT and iaDSA were performed after ICAS. Both procedures were carried out on a flat-panel-detector-equipped angiography system. Postprocessing of ivACT acquisitions was performed on a dedicated workstation producing multiplanar reformations of the stent region and other intracranial arteries. Restenotic lesions were compared with iaDSA measurements. All studies were independently evaluated by 2 experienced neuroradiologists blinded to patients data. In 5 cases, ISR was diagnosed on iaDSA images. All restenotic lesions were reliably detected (sensitivity, 100%; 95%CI, 48%-100%) and could be correctly quantified on ivACT images in comparison with iaDSA. The neuroradiologists correctly excluded ISR in 11 of 12 lesions after viewing the ivACT examinations (specificity, 92%; 95%CI, 62%-100%). Measurements of ISR on ivACT were highly correlated to iaDSA (Pearson r = 0.94, P < .01). IvACT is a promising noninvasive follow-up examination after ICAS. With its high spatial resolution, it can reliably detect or exclude ISR. Contrary to iaDSA, there is no need for a recovery period after ivACT and the risk of neurologic complications is practically lowered to zero.

Transient response harmonic imaging: an ultrasound technique related to brain perfusion.

Gray-scale harmonic imaging is the first method to visualize blood perfusion and capillary blood flow with ultrasound after intravenous contrast agent application. The purpose of the present study was to evaluate the potential of transient response second harmonic imaging (TRsHI) to assess normal echo contrast characteristics in different brain areas by transcranial ultrasound. In 18 patients without cerebrovascular diseases, TRsHI examinations were performed bilaterally with the use of the transtemporal approach after application of 6.5 mL of a galactose-based microbubble suspension (400 mg/mL). The transmission rate was once every 4 cardiac cycles. Regional cerebral contrast was visually assessed and then quantified off-line with the use of time-intensity curves. In 4 different regions of interest (ROI) (posterior part of the thalamus [ROIa], anterior part of the thalamus [ROIb], lentiform nucleus [ROIc], and white matter [ROId]), the following parameters were evaluated: peak intensity, area under the curve (AUC), and time to peak intensity. AUC ratios for ROIc/a, d/a, c/b, and d/b were calculated. In all patients parenchymal contrast enhancement was visually detectable. One hundred thirty-one characteristic time-intensity curves (baseline phase, peak contrast intensity, slow washout phase) were demonstrable in 144 ROIs. In ROIc and ROId, characteristic contrast curves could be observed most frequently (68/72 examinations), whereas time-intensity curves in ROIa and ROIb could not be evaluated because of inadequate contrast enhancement in 9 of 72 examinations. Time to peak intensity varied between 20 and 52 cardiac cycles; in 1 patient it was 88 cardiac cycles. In all individuals AUCs and in 16 of 18 subjects peak intensity in ROIc and ROId showed a 2- to 10-fold increase compared with ROIa and ROIb. In no examination did AUC ratios show a >2-fold side difference irrespective of the ROI. The present study demonstrates for the first time that TRsHI produces accurate contrast in different brain areas and represents an ultrasonic tool related to brain perfusion. Absolute values of quantitative parameters show high variations caused by different temporal bone thicknesses and a complex relationship between echo contrast concentrations and measurements of optic intensities. Ratios between different ROIs help to compare contrast enhancement in different brain areas. Furthermore, because of the fact that attenuation of contrast enhancement in TRsHI depends strictly on the insonation depth, harmonic imaging studies of brain perfusion cannot be compared directly with other imaging techniques such as positron emission tomography.

728-3 Contrast-enhanced Electron Beam Tomography for 3-D Reconstruction of Coronary Arteries: Detection of Stenoses and Documentation of Angioplasty Success

Non-invasive imaging of coronary arteries is complicated by their very fast movements. We evaluated the potential of contrast-enhanced Electron Beam Tomography (EBT, Ultrafast-CT) for the visualization of coronary artery stenoses. 24 patients with angiographically documented coronary artery disease were investigated. In 5 patients, EBT was repeated after angioplasty, Contrast agent was administered via a peripheral vein and ECG-triggered axial EBT scans were obtained during breathhold (acquisition time 100 ms/slice, table movement 2 mm/slice, slice thickness 3 mm). 3-D reconstruction of the coronary arteries was performed as shaded surface display with a density threshold chosen to consider only the vessels’ contrast enhanced inner lumen. By administration of contrast agent, the mean density within the coronary artery lumen was significantly increased from 18 ± 9.7 HU (mean value of native vessels) to 212 ± 78.3 HU (p &lt; 0.001). 3-D reconstruction with a threshold of 80 HU permitted selective visualization of the coronary arteries’ inner lumen in all cases. 9/11 hi9h grade stenoses and 5/5 occlusions of the proximal and mid LAD were clearly identified, as well as 3/4 high grade stenoses of the proximal and mid RCA (with decreased image quality due to rapid vessel movement). 2 high grade lesions of the LCX could not be identified. A followup investigation after angioplasty in 5 patients (4 pts. LAD, 1 pt. RCA) clearly visualized the increase in vessel lumen in all cases. Electron Beam Tomography with intravenous application of contrast agent permits the non-invasive imaging of high grade LAD stenoses. RCA and LCX stenoses can be visualized with limited success. The outcome of angioplasty can be documented.