Arrival Of Contrast Agent Research Articles

Myocardial Transit Time Mapping by CMR: A Novel Indicator of Microcirculatory Dysfunction in Cardiac Amyloidosis.

Cardiac amyloidosis (CA) is characterized by the deposition of amyloid fibrils within the myocardium, resulting in a restrictive physiology. Although microvascular dysfunction is a common feature, it is difficult to assess. This study aimed to explore myocardial transit time (MyoTT) by cardiovascular magnetic resonance (CMR) as a potential novel parameter of microcirculatory dysfunction in CA. This prospective study enrolled 20 CA patients and 20 control subjects. CMR acquisition included cine imaging, pre- and post-contrast T1 mapping, and MyoTT assessment, which was calculated from the time delay in contrast agent arrival between the aortic root and coronary sinus (CS). Compared to the control group, patients with CA exhibited significantly reduced left ventricular (LV) ejection fraction and myocardial strain, an increase in LV global peak wall thickness (LVGPWT), extracellular volume fraction (ECV), and prolonged MyoTT (14.4 ± 3.8s vs. 7.7 ± 1.5s, p < 0.001). Moreover, patients at Mayo stage III had a significantly longer MyoTT compared to those at stage I/II. MyoTT showed a positive correlation with the ECV, LVGPWT, and LV global longitudinal strain (LV-GLS) (p < 0.05). The area under the curve (AUC) for MyoTT was 0.962, demonstrating diagnostic performance comparable to that of the ECV (AUC 0.995) and LV-GLS (AUC 0.950) in identifying CA. MyoTT is significantly prolonged in patients with CA, correlating with fibrosis markers, remodeling, and dysfunction. As a novel parameter of coronary microvascular dysfunction (CMD), MyoTT has the potential to be an integral biomarker in multiparametric CMR assessment of CA.

Correlations of tumour permeability parameters with apparent diffusion coefficient in nasopharyngeal carcinoma.

Functional imaging has an established role in therapeutic monitoring of cancer treatments. This study evaluated the correlations of tumour permeability parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and tumour cellularity derived from apparent diffusion coefficient (ADC) in nasopharyngeal carcinoma (NPC). Twenty NPC patients were examined with DCE-MRI and RESOLVE diffusion-weighted MRI (DW-MRI). Tumour permeability parameters were quantitatively measured with Tofts compartment model. Volume transfer constant (Ktrans), volume of extravascular extracellular space (EES) per unit volume of tissue (Ve), and the flux rate constant between EES and plasma (Kep) from DCE-MRI scan were measured. The time-intensity curve was plotted from the 60 dynamic phases of DCE-MRI. The initial area under the curve for the first 60s of the contrast agent arrival (iAUC60) was also calculated. They were compared with the ADC value derived from DW-MRI with Pearson correlation analyses. Among the DCE-MRI permeability parameters, Kep had higher linearity in inverse correlation with ADC value (r=-0.69, p=<0.05). Ktrans (r=-0.60, p=<0.05) and iAUC60 (r=-0.64, p=<0.05) also had significant inverse correlations with ADC. Ve showed a significant positive correlation with ADC (r=0.63, p=<0.05). Nasopharyngeal tumour vascular permeability parameters derived from DCE-MRI scan were correlated linearly with tumour cellularity measured by free water diffusability with ADC. The clinical implementations of these linear correlations in the quantitative assessments of therapeutic response for NPC patients may be worth to further explore.

Bolus arrival time estimation in dynamic contrast-enhanced magnetic resonance imaging of small animals based on spline models

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is used to quantify perfusion and vascular permeability. In most cases a bolus arrival time (BAT) delay exists between the arterial input function (AIF) and the contrast agent arrival in the tissue of interest which needs to be estimated. Existing methods for BAT estimation are tailored to tissue concentration curves, which have a fast upslope to the peak as frequently observed in patient data. However, they may give poor results for curves that do not have this characteristic shape such as tissue concentration curves of small animals. In this paper, we propose a method for BAT estimation of signals that do not have a fast upslope to their peak. The model is based on splines which are able to adapt to a large variety of concentration curves. Furthermore, the method estimates BATs on a continuous time scale. All relevant model parameters are automatically determined by generalized cross validation. We use simulated concentration curves of small animal and patient settings to assess the accuracy and robustness of our approach. The proposed method outperforms a state-of-the-art method for small animal data and it gives competitive results for patient data. Finally, it is tested on in vivo acquired rat data where accuracy of BAT estimation was also improved upon the state-of-the-art method. The results indicate that the proposed method is suitable for accurate BAT estimation of DCE-MRI data, especially for small animals.

Added value of multiphase CTA imaging for thrombus perviousness assessment

PurposeThrombus perviousness has been associated with favorable functional outcome in acute ischemic stroke (AIS) patients. Measuring thrombus perviousness on CTA may be suboptimal due to potential delay in contrast agent arrival in occluded arteries at the moment of imaging. Dynamic sequences acquired over time can potentially overcome this issue. We investigate if dynamic CTA has added value in assessing thrombus perviousness.MethodsProspectively collected image data of AIS patients with proven occlusion of the anterior or posterior circulation with thin-slice multi-phase CTA (MCTA) and non-contrast CT were co-registered (n = 221). Thrombus attenuation increase (TAI; a perviousness measure) was measured for the arterial, venous, and delayed phase of the MCTA and time-invariant CTAs (TiCTA). Associations with favorable clinical outcome (90-day mRS ≤ 2) were assessed using univariate and multivariable regressions and calculating areas under receiver operating curves (AUC).ResultsTAI determined from the arterial phase CTA was superior in the association with favorable outcome with OR = 1.21 per 10 HU increase (95%CI 1.04–1.41, AUC 0.62, p = 0.014) compared to any other phase (venous 1.14(95%CI 1.01–1.30, AUC 0.58, p = 0.033), delayed 1.046(95%CI 0.919–1.19, AUC 0.53, p = 0.50)), and TiCTA (1.15(95%CI 1.02–1.30, AUC 0.60, p = 0.022). In the multivariable model, only TAI on arterial phase was significantly associated with favorable outcome (aOR 1.59, 95%CI 1.04–2.43, p = 0.032).ConclusionAssociation between TAI with functional outcome was optimal on arterial-phase CTA such that dynamic CTA imaging has no additional benefits in current thrombus perviousness assessment, thereby suggesting that the delay of contrast arrival at the clot is a key variable for patient functional outcome.

Contrast-Enhanced Ultrasound Using Perfluorobutane-Containing Microbubbles in the Assessment of Liver Allograft Damage: An Exploratory Prospective Study

This prospective study investigated the usefulness of contrast (perfluorobutane-containing microbubbles)-enhanced ultrasound in the non-invasive assessment of liver allograft damage. Forty-one liver recipients underwent contrast-enhanced ultrasound followed by a liver biopsy. The hepatic filling rate (time between the arrival of contrast agent in the right hepatic artery and the maximum intensity of hepatic parenchyma) and parenchymal intensity difference before and after instantaneous high-power emission in the Kupffer phase were measured. Patients with allograft damage had higher hepatic filling rates and lower parenchymal intensity differences than those without damage (42.0 ± 16.9 vs. 30.5 ± 7.7 s, p = 0.005; 6.1 ± 7.4 vs. 16.6 ± 16.1 dB, p = 0.047, respectively). In the diagnosis of liver allograft damage, hepatic filling rate and parenchymal intensity difference had sensitivities of 61.5% and 90.9% and specificities of 92.6% and 63.6% using cutoffs of >38.5 s and ≤10.3 dB, respectively. In conclusion, contrast-enhanced ultrasound may be a promising tool in the detection of liver allograft damage.

CT Perfusion Mismatch in Subacute Stroke: Oligemia or Luxury Perfusion? Response to Persistent Benign Oligemia Causes CT Perfusion Mismatch in Patients with Intracranial Large Artery Occlusive Disease during Subacute Stroke

We read with great interest the study of Li et al. 1 which demonstrates the existence of a mismatched area with similar characteristics to penumbra in patients with intracranial large artery occlusive disease (ICAD) during the subacute phase of stroke. The authors suggest that this area may be the result of benign oligemia rather than penumbra. CBV ratio was significantly higher in the ICAD versus the acute stroke group, and there was a trend toward higher CBF values in the ICAD group as well. MTT values were >145% in both groups. However, the authors did not consider the possibility that these data may be the result of postischemic hyperperfusion (PH) rather than oligemia. PH refers to restoration of perfusion in a cerebrovascular territory affected by prior severe ischemia due to either spontaneous or therapeutic recanalization of the occluded vessels. This phenomenon has been termed “luxury perfusion” and may or may not progress to infarction. Luxury perfusion refers to a condition where CBF is in excess of oxygen demand. Luxury perfusion thus represents nonnutritive flow to infarcted tissue, resulting from a loss of cerebrovascular autoregulation. Luxury perfusion is reported to occur in up to one-third of patients by 48 h after ischemic stroke 2. With functional imaging (PET/SPECT) 2 in animal and human studies, the pattern of luxury perfusion is characterized by a near-normal or slight increase in CBV and CBF; however, limited data are available on this topic with respect to CT perfusion (CTP) imaging. Nagar et al. 3 reported elevated CBV, MTT, and variable CBF in patients with subacute infarcts, ascribing these changes to the reperfusion phenomenon masking acute/subacute hypoperfusion. The appearance of CTP data in the subacute stage of ischemic stroke can lead to misinterpretation of tissue as normal or simply oligemic 4. However, in this setting, the neurologist or radiologist should already suspect infarction either clinically, from areas of low attenuation on unenhanced CT images, or from similar findings on the source imaging data from the CT-angiography/CTP. Thus, careful patient history and physical examination as well as critical assessment of unenhanced CT and dynamic CT source data are critical prior to CTP interpretation. Software applications from different vendors also do not generate equivalent quantitative perfusion results. Caution should thus be exercised when interpreting quantitative CTP measures because these values may vary considerably depending on the postprocessing software. In the work of Li et al. 1, important methodological details concerning the CTP postprocessing data are missing. The major mathematical technique utilized for calculation of perfusion parameters is the deconvolution approach. Deconvolution can be performed by several methods. The classic deconvolution method is termed “standard singular value decomposition” (sSVD). This technique is robust and independent of the underlying vascular anatomy (i.e., intra/extracranial stenoses and/or leptomeningeal collaterals). However, the technique is sensitive to delayed arrival of contrast media. When such delays occur, MTT is overestimated and CBF is underestimated. The use of abnormal CBF/MTT values may lead to overestimation of the ischemic penumbra by including nonischemic brain regions with delayed contrast agent arrival into calculations. To overcome these difficulties, new deconvolution methods have been developed to minimize the effects of bolus delay and dispersion, including delay-corrected deconvolution (dSVD) and delay-insensitive technique named block-circulant deconvolution (bSVD) algorithms. As a general rule, the use of a delay-insensitive method is recommended when dealing with stroke patients, a population in whom arterial stenoses are common, because dSVD and bSVD methods yield more stable results than sSVD regardless of contrast agent delay. Kamalian et al. 5 reported that MTT maps optimally distinguish benign oligemia from true “at-risk” ischemic penumbra, but that thresholds vary depending upon the postprocessing technique (sSVD or dSVD). In light of these considerations to correctly interpret the work of Li et al., we must know which method the authors used. It is critical for radiologists using PCT for stroke imaging to be familiar with the postprocessing software used at their institution, including its advantages and limitations. This can be helpful to avoid misinterpretation of perfusion maps and to define the infarct core and penumbra more accurately. Also in the presence of MTT prolongation and near-normal CBV and CBF values, it is important to keep in mind the possibility of PH, although the presence of PH must be supported by findings on unenhanced CT, dynamic source data, and/or clinical data. The concepts of the penumbra, oligemia, and PH have not yet been fully resolved, and further studies must be performed to better understand the hemodynamic phenomena that occur in the acute and subacute phases of ischemic stroke. The authors declare no conflict of interest.

Evaluation of Optimal Scan Delay for Gadoxetate Disodium–Enhanced Hepatic Arterial Phase MRI Using MR Fluoroscopic Triggering and Slow Injection Technique

The purpose of this article is to prospectively evaluate the optimal scan delay for gadoxetate disodium-enhanced hepatic arterial phase MRI of hypervascular hepatocellular carcinoma (HCC) using MR fluoroscopic triggering and a slow-injection technique. Sixty-three patients (37 men and 26 women; age range, 33-92 years; mean age, 68.2 years) underwent gadoxetate disodium-enhanced MRI; there were 33 hypervascular HCCs (size range, 8-57 mm; mean size, 19.8 mm) in 19 patients. The time from the start of contrast agent injection to its arrival in the abdominal aorta (time to arrival) and the time from contrast agent arrival to peak enhancement (time to peak) were determined using MR fluoroscopy using IV slow injection at 1 mL/s of contrast material and a saline chaser. All patients underwent four-phase whole-liver imaging with a 3D keyhole gradient-echo sequence during a single breath-hold immediately after confirmation of aortic peak enhancement. Delays from peak aortic enhancement to k-space filling were 5-9, 10-14, 15-19, and 20-28 seconds, respectively, in the four phases. Time to arrival, time to peak, and HCC-to-liver contrast were evaluated. The time to arrival (range, 11-24 seconds; mean, 16.2 seconds) and the time to peak (range, 3-10 seconds; mean, 6.8 seconds) showed considerable variation among patients. HCC-to-liver contrast peaked at the first phase in 58% of cases, at the second phase in 42% of cases, and at the third and fourth phases in 0% of cases. Mean HCC-to-liver contrast in the first and second phases was significantly higher than that in the third and fourth phases (p<0.01). Optimal scan delays for imaging hypervascular HCCs with gadoxetate disodium-enhanced hepatic arterial phase MRI was 7-12 seconds after the peak aortic enhancement using a slow-injection protocol.

The effect of motion correction on pharmacokinetic parameter estimation in dynamic-contrast-enhanced MRI

A dynamic-contrast-enhanced magnetic resonance imaging (DCE-MRI) dataset consists of many imaging frames, often acquired both before and after contrast injection. Due to the length of time spent acquiring images, patient motion is likely and image re-alignment or registration is required before further analysis such as pharmacokinetic model fitting. Non-rigid image registration procedures may be used to correct motion artefacts; however, a careful choice of registration strategy is required to reduce misregistration artefacts associated with enhancing features. This work investigates the effect of registration on the results of model-fitting algorithms for 52 DCE-MR mammography cases for 14 patients. Results are divided into two sections: a comparison of registration strategies in which a DCE-MRI-specific algorithm is preferred in 50% of cases, followed by an investigation of parameter changes with known applied deformations, inspecting the effect of magnitude and timing of motion artefacts. Increased motion magnitude correlates with increased model-fit residual and is seen to have a strong influence on the visibility of strongly enhancing features. Motion artefacts in images close to the contrast agent arrival have a disproportionate effect on discrepancies in parameter estimation. The choice of algorithm, magnitude of motion and timing of the motion are each shown to influence estimated pharmacokinetic parameters even when motion magnitude is small.

SU‐E‐I‐132: Whole‐Brain DCE Quantitative Perfusion Imaging

Purpose: To develop a whole‐brain acquisition protocol based on dynamic contrast enhanced (DCE) MR imaging that is able to provide absolute brain tissue perfusion estimates and to assess, evaluate and minimize the uncertainty in the estimates of contrast agent concentration. Methods: Preliminary in vivo data was collected using a 3D spoiled‐gradient recalled echo (SPGR) sequence with TR/TE/flip angle (FA) = 2.5 ms/1.15 ms/15°. The spatial resolution was 1.7×1.7×4.0 mm3. A variable rate k‐space sampling scheme and view sharing resulted in a temporal resolution of 2.4 s. The perfusion estimates were calculated using indicator‐dilution theory. Based on preliminary data, simulations estimating the uncertainty and sensitivity to misestimated parameters in the concentration measures were performed. Tissue parameters and contrast agent relaxivities were obtained from literature. The SNR before contrast injection was extracted from the preliminary data. Results: Absolute perfusion maps were successfully generated for the whole brain in all three subjects. As predicted, the low signal enhancement in cerebral tissue, especially in white matter, resulted in noisy perfusion maps. The range of the cerebral blood flow (CBF) and cerebral blood volume (CBV) maps corresponded to the range of the values reported in literature. The mean transit times (MTT) however were overestimated. The simulations showed that a FA of 9° minimizes the concentration coefficient of variation in white matter. However, the sensitivity to misestimated parameters was reduced with increasing FA: a FA &gt; 20° was beneficial. For realistic SNR levels, averaging 5 acquisitions of the signal before contrast agent arrival were sufficient. More baseline measurements did not significantly decrease the signal variance. Conclusion: It is possible to acquire qualitatively acceptable whole‐brain bolus tracking data using a DCE sequence. In addition, the FA influences the uncertainty and sensitivity in concentration estimates when using a SPGR sequence.Grant support from the Canadian Institutes for Health Research, Canada Research Chairs Program and Hopewell Professorship in Brain Imaging.

Contrast-enhanced MR angiography utilizing parallel acquisition techniques in renal artery stenosis detection

Significant renal artery stenosis (RAS) is a potentially curable cause of renovascular hypertension and/or renal impairment. It is caused by either atherosclerosis or fibromuscular dysplasia. Correct and timely diagnosis remains a diagnostic challenge. MR angiography (MRA) as a minimally invasive method seems to be suitable for RAS detection, however, its diagnostic value widely differs in the literature (sensitivity 62–100% and specificity 75–100%). The aim of our prospective study was to compare the diagnostic value of contrast-enhanced MRA utilizing parallel acquisition techniques in the detection of significant RAS with digital subtraction angiography (DSA). A total of 78 hypertensive subjects with suspected renal artery stenosis were examined on a 1.5 Tesla MR system using a body array coil. Bolus tracking was used to monitor the arrival of contrast agent to the abdominal aorta. The MRA sequence parameters were as follows: TR 3.7 ms; TE 1.2 ms; flip angle 25°; acquisition time 18 s; voxel size 1.1 mm × 1.0 mm × 1.1 mm; centric k-space sampling; parallel acquisition technique with acceleration factor of 2 (GRAPPA). Renal artery stenosis of 60% and more was considered hemodynamically significant. The results of MRA were compared to digital subtraction angiography serving as a standard of reference. Sensitivity and specificity of MRA in the detection of hemodynamically significant renal artery stenosis were 90% and 96%, respectively. Prevalence of RAS was 39% in our study population. Contrast-enhanced MRA with high spatial resolution offers sufficient sensitivity and specificity for screening of RAS.

Can arterial spin labeling detect white matter perfusion signal?

Since the invention of arterial spin labeling (ASL) it has been acknowledged that ASL does not allow reliable detection of a white matter (WM) perfusion signal. However, recent developments such as pseudo-continuous labeling and background suppression have improved the quality. The goal of this research was to study the ability of these newer ASL sequences to detect WM perfusion signal. Background suppressed pseudo-continuous ASL was implemented at 3T with multislice 2D readout after 1525 ms. In five volunteers it was shown that 10 min scanning resulted in significant perfusion signal in 70% of WM voxels. Increasing the labeling and delay time did not lead to a higher percentage. In 27 normal volunteers it was found that 35 averages are necessary to detect significant WM signal, but 150 averages are needed to detect signal in the deep WM. Finally, it was shown in a patient with a cerebral arteriovenous malformation that pseudo-continuous ASL enabled the depiction of hypointense WM perfusion signal, although dynamic susceptibility contrast MRI showed that this region was merely showing delayed arrival of contrast agent than hypoperfusion. It can be concluded that, except within the deep WM, ASL is sensitive enough to detect WM perfusion signal and perfusion deficits.

Renal Contrast-enhanced MR Angiography: Timing Errors and Accurate Depiction of Renal Artery Origins

To investigate bolus timing artifacts that impair depiction of renal arteries at contrast material-enhanced magnetic resonance (MR) angiography and to determine the effect of contrast agent infusion rates on artifact generation. Renal contrast-enhanced MR angiography was simulated for a variety of infusion schemes, assuming both correct and incorrect timing between data acquisition and contrast agent injection. In addition, the ethics committee approved the retrospective evaluation of clinical breath-hold renal contrast-enhanced MR angiographic studies obtained with automated detection of contrast agent arrival. Twenty-two studies were evaluated for their ability to depict the origin of renal arteries in patent vessels and for any signs of timing errors. Simulations showed that a completely artifactual stenosis or an artifactual overestimation of an existing stenosis at the renal artery origin can be caused by timing errors of the order of 5 seconds in examinations performed with contrast agent infusion rates compatible with or higher than those of hand injections. Lower infusion rates make the studies more likely to accurately depict the origin of the renal arteries. In approximately one-third of all clinical examinations, different contrast agent uptake rates were detected on the left and right sides of the body, and thus allowed us to confirm that it is often impossible to optimize depiction of both renal arteries. In three renal arteries, a signal void was found at the origin in a patent vessel, and delayed contrast agent arrival was confirmed. Computer simulations and clinical examinations showed that timing errors impair the accurate depiction of renal artery origins.

Improved Detection of Intracerebral Hemorrhage with Transcranial Ultrasound Perfusion Imaging

Background: Ultrasound perfusion imaging (UPI) is a new approach for the assessment of brain perfusion. In contrast to the increasing experience with this method in patients with ischemic stroke, data on the value of UPI for the diagnosis of intracerebral hemorrhage (ICH) are lacking. Methods: We investigated 12 consecutive patients with sufficient temporal bone windows and a CT diagnosis of acute supratentorial ICH (basal ganglia n = 9 and lobar n = 3). Native transcranial B-mode ultrasound and UPI studies with echo contrast agents were performed on day 1 and on days 5–7 including volume measurements using the maximum extension on transverse and coronal ultrasound planes. Results: ICH was identified as hyperechogenic mass on B-mode ultrasound in 11/12 patients, but the correlation with CT volume measurements was poor (day 1: r = 0.4, 95% confidence interval, CI: –0.23–0.79; p = 0.1; follow-up: r = 0.58, 95% CI: 0.04–0.86; p = 0.21). Volume measurement was more precise using UPI with a significant correlation on day 1 (r = 0.8, 95% CI: 0.47–0.94; p < 0.001) and during the follow-up (r = 0.94, 95% CI: 0.81–0.98; p < 0.001). Using UPI the typical finding was a focal reduction of contrast agent arrival in the ICH core which led to better delineation of the lesion borders from adjacent tissue. Depiction of lobar ICH was difficult with ultrasound, and lesion sizes tended to be underestimated. Conclusions: This study supports earlier work demonstrating the usefulness of native transcranial ultrasound for the diagnosis of ICH. UPI further improves diagnostic reliability and allows very precise ICH volume measurements. If confirmed in larger studies, this approach may be useful for bedside monitoring of ICH progression and regression.

Cardiac involvement of Echinococcus granulosus evaluated by multi-contrast CMR imaging

Cardiac manifestations of hydatid cysts are rare and occur in about 0.2 to 3% of all cases of human hydatidosis. We report the case of a young man with a known 4-year old infection with Echinoccus granulosus. Cardiovascular magnetic resonance imaging (CMR) was performed and showed two cysts in the left ventricular wall. The smaller cyst had a thin, noncontinuous membrane to the left ventricle. The T1- and T2-weighted images showed an isointense signal of the cysts compared to blood; fat-suppressed images showed no fatty components. To highlight the potential small signal differences we assigned the contents of the gray images to red, green and blue channels of a conventional color image. Blood and the content of the cysts had the same color, making a connection between the cysts and the LV blood pool highly probable. This was confirmed by first pass perfusion imaging, which showed simultaneous contrast agent arrival in the left ventricular cavity and the cysts. Delayed enhancement (DE) revealed fibrotic tissue surrounding the cysts. MR seems to be the most complete method of diagnosing the disease, as anatomical structures, type of content of the cyst (liquid or solid) and its relation to the myocardium can be assessed within one study.

Dynamic Contrast-Enhanced MRI Before and After Transcatheter Occlusion of Patent Foramen Ovale

The purpose of this study was threefold: to evaluate the diagnostic accuracy of dynamic contrast-enhanced MRI compared with transesophageal echocardiography (TEE) in the detection of patent foramen ovale (PFO) and of residual shunts after occlusion of PFO, to define cutoff values for semiquantitative analysis of signal intensity-time curves, and to compare the diagnostic accuracy of visual detection with that of semiquantitative analysis. Forty-three patients (18 women, 25 men; mean age, 51 +/- 14 years) who underwent TEE for suspicion of PFO (n = 26, 19 patients with and seven without PFO) or for routine assessment for residual shunt after transcatheter PFO occlusion (n = 17, nine patients with and eight without residual shunt) were consecutively enrolled to undergo contrast-enhanced MRI (saturation recovery steady-state free precession sequence). The images were analyzed both visually and semiquantitatively for arrival of contrast agent in the left atrium before arrival in the pulmonary veins during a Valsalva maneuver. TEE results were used as the clinical reference. With an area under the signal intensity-time curve of 0.85, height of the first initial peak in signal intensity in the left atrium proved to be the best discriminator in right-to-left shunt detection. For a cutoff value of 129% (from baseline signal intensity) for this parameter, sensitivity and specificity were 90% (17/19) and 100% (7/7) in patients without PFO devices and 56% (5/9) and 88% (7/8) in patients with PFO devices. The diagnostic accuracy of both visual assessment and semiquantitative analysis was consistently superior before PFO device implantation than after device implantation. The diagnostic accuracy of visual shunt assessment was better than that of semiquantitative shunt assessment in patients with PFO occluders (sensitivity, 67% [6/9] correctly diagnosed; specificity, 88% [7/8]) and those without PFO occluders (sensitivity, 95% [18/19]; specificity, 100% [7/7]). At present, MRI cannot replace TEE for the exclusion of potential embolic sources, such as thrombus in the left atrial appendage. However, MRI can be an attractive alternative noninvasive technique if TEE is technically unfeasible or is declined by patients.

Effects of injection rate and dose on image quality in time-resolved magnetic resonance angiography (MRA) by using 1.0M contrast agents

In time-resolved MRA (TR MRA), injection parameters and contrast agent (CA) dose are important factors influencing image quality. In this study, three different injection schemes with different CA volumes were evaluated in 12 healthy volunteers. Injection rates between 0.2 and 0.8 ml/s were evaluated with CA volumes of 10 and 20 ml. To measure circulatory parameters, cine cardiac MRI was performed before each exam. Spatial resolution could be reduced to 2 x 1.4 x 2 mm3, temporal resolution was 2.25 s/frame. To exclude signal saturation at high CA concentrations, a phantom with fixed CA concentrations was placed in the field of view. SNR was measured, and the area under the curve of the arterial signal of the different injection schemes was calculated. Results showed the largest diagnostic window at a relatively slow injection rate of 0.4 ml/s and a CA volume of 10 ml. Circulatory parameters have an important impact on CA arrival, so delay times have to be set depending on these parameters.

T2* effects in the dual‐sequence method for high‐dose first‐pass myocardial perfusion

To examine whether T2* effects reduce the accuracy of arterial input function (AIF) measurement by the dual-sequence method. The dual-sequence method obtains a low-resolution AIF image and high-resolution myocardial images in each cycle, with suitable T1 weightings. It was modified to assess T2* effects in the low-resolution AIF image (4.8x4.8x10 mm voxels, TE=0.58 msec) by minimizing T1 weighting in that sequence, while the myocardial sequence remained T1-weighted. In 10 patients who underwent perfusion MRI scans (0.5 M Magnevist, 0.1 mmol/kg, 15-ml flush, 7 mL/second right antecubital) the blood signal in the left ventricle (LV) was measured at the bolus peak and compared with the first cycle's fresh magnetization signal. The bolus peak measured 98%+/-4% (mean+/-SD, N=20) of the value before contrast agent arrival. T2* causes insignificant error in the dual-sequence method at the stated parameters.

Untreated Tetralogy of Fallot With Pulmonary Atresia

HomeCirculationVol. 113, No. 8Untreated Tetralogy of Fallot With Pulmonary Atresia Free AccessReview ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissionsDownload Articles + Supplements ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toSupplementary MaterialsFree AccessReview ArticlePDF/EPUBUntreated Tetralogy of Fallot With Pulmonary AtresiaGiant Aneurysm of an Aortopulmonary Collateral Artery Demonstrated by Magnetic Resonance Imaging Clerio F. Azevedo, MD, Marcelo S. Hadlich, MD, Denilson C. Albuquerque, MD and Jorge N. Moll, MD Clerio F. AzevedoClerio F. Azevedo From the Department of Cardiovascular Magnetic Resonance Imaging, Labs/Rede D’Or Hospitals, Rio de Janeiro, Brazil. Search for more papers by this author , Marcelo S. HadlichMarcelo S. Hadlich From the Department of Cardiovascular Magnetic Resonance Imaging, Labs/Rede D’Or Hospitals, Rio de Janeiro, Brazil. Search for more papers by this author , Denilson C. AlbuquerqueDenilson C. Albuquerque From the Department of Cardiovascular Magnetic Resonance Imaging, Labs/Rede D’Or Hospitals, Rio de Janeiro, Brazil. Search for more papers by this author and Jorge N. MollJorge N. Moll From the Department of Cardiovascular Magnetic Resonance Imaging, Labs/Rede D’Or Hospitals, Rio de Janeiro, Brazil. Search for more papers by this author Originally published28 Feb 2006https://doi.org/10.1161/CIRCULATIONAHA.105.550582Circulation. 2006;113:e293–e294A 41-year-old man with untreated tetralogy of Fallot and pulmonary atresia was referred to our department for imaging. His diagnosis had been established in early infancy, but cardiac surgery was repeatedly refused over the years. In addition to central cyanosis and clubbing of the fingers, the patient started experiencing worsening exertional dyspnea, cough, and pain in the back and left shoulder within the last 2 years. A transthoracic echocardiogram revealed, in addition to the findings consistent with his congenital heart disease, a large paracardiac mass in the left hemithorax. To evaluate the cardiac morphology in greater detail and to better characterize the paracardiac mass, magnetic resonance imaging was performed (Figure 1 through Figure 3 and Data SupplementMovie I through Movie III). The typical features of tetralogy of Fallot, such as outlet ventricular septal defect, overriding aorta, right ventricular (RV) hypertrophy, and obstruction to the RV outflow, were readily identified. In addition, this patient displayed extensive aortopulmonary collateral circulation, with a large aneurysmatic dilatation of the left internal mammary artery (a major aortopulmonary collateral vessel in this case). Download figureDownload PowerPointFigure 1. Steady-state, free-precession cine magnetic resonance images depicting cardiac morphology. A, Four-chamber view demonstrates the ventricular septal defect with overriding aorta (arrowhead), RV hypertrophy (straight arrow), and moderate pericardial effusion (curved arrow). B, Coronal view showing the characteristic boot-shaped heart (coeur en sabot) of tetralogy of Fallot and the giant aneurysm of the aortopulmonary collateral artery positioned in the left hemithorax above the heart (*).Download figureDownload PowerPointFigure 2. Coronally targeted, maximum-intensity projection images of the contrast-enhanced 3-dimensional magnetic resonance angiograms. Note the significant dilatation of the proximal portion of the left subclavian artery (arrowhead) and left internal mammary artery (LIMA), which gives rise to the aneurysm (straight arrow). The left subclavian artery demonstrates a normal diameter after the origin of the LIMA (curved arrow). The site of aneurysmatic dilatation (*) is shown just before (A) and immediately after (B) contrast agent arrival at the aneurysm.Download figureDownload PowerPointFigure 3. Coronally targeted, volume-rendered images of the contrast-enhanced 3D magnetic resonance angiograms. A, Anterior view; B, posterior view. Note the absence of pulmonary arteries (pulmonary artery atresia) and the extensive aortopulmonary collateral circulation (arrow). From the posterior wall of the aneurysm, the distal portion of the left internal mammary artery progresses to connect with the pulmonary circulation (arrowhead).The online-only Data Supplement can be found at http://circ.ahajournals.org/cgi/content/full/113/8/e293/DC1.DisclosuresNone.FootnotesCorrespondence to Clerio F. Azevedo, MD, Department of Cardiovascular Magnetic Resonance Imaging, Labs/Rede D’Or Hospitals, Rua Homem de Melo 126/201, Rio de Janeiro, RJ, Brazil. E-mail [email protected] Previous Back to top Next FiguresReferencesRelatedDetailsCited By (2009) Tetralogy of Fallot Congenital Heart Defects, 10.1007/978-3-7985-1719-6_8, (56-67), . February 28, 2006Vol 113, Issue 8 Advertisement Article InformationMetrics https://doi.org/10.1161/CIRCULATIONAHA.105.550582PMID: 16505180 Originally publishedFebruary 28, 2006 PDF download Advertisement SubjectsComputerized Tomography (CT)Congenital Heart DiseaseImaging