Black-blood T2 Research Articles

3D Fast Spin-Echo T1 Black-Blood Imaging for the Diagnosis of Cervical Artery Dissection

We performed non-contrast-enhanced 3D fast spin-echo T1 imaging with variable flip angles (CUBE T1) at 3T in 11 patients with CAD. CUBE T1 allowed easy diagnosis of CAD, owing to its comprehensive neck coverage, high spatial resolution enabling multiplanar reformations, fat saturation, and BB effect, the latter also allowing lumen patency to be studied. This sequence may replace 2D axial T1WI for the diagnosis of CAD.

In Vivo Imaging of Macrophages during the Early-Stages of Abdominal Aortic Aneurysm Using High Resolution MRI in ApoE−/− Mice

BackgroundAngiotensin II (ANG II) promotes vascular inflammation and induces abdominal aortic aneurysm (AAA) in hyperlipidemic apolipoprotein E knock-out (apoE−/−) mice. The aim of the present study was to detect macrophage activities in an ANG II-induced early-stage AAA model using superparamagnetic iron oxide (SPIO) as a marker.Methodology/Principal FindingsTwenty-six male apoE−/− mice received saline or ANG II (1000 or 500 ng/kg/min) infusion for 14 days. All animals underwent MRI scanning following administration of SPIO with the exception of three mice in the 1000 ng ANG II group, which were scanned without SPIO administration. MR imaging was performed using black-blood T2 to proton density -weighted multi-spin multi-echo sequence. In vivo MRI measurement of SPIO uptake and abdominal aortic diameter were obtained. Prussian blue, CD68,α-SMC and MAC3 immunohistological stains were used for the detection of SPIO, macrophages and smooth muscle cells. ANG II infusion with 1000 ng/kg/min induced AAA in all of the apoE−/− mice. ANG II infusion exhibited significantly higher degrees of SPIO uptake, which was detected using MRI as a distinct loss of signal intensity. The contrast-to-noise ratio value decreased in proportion to an increase in the number of iron-laden macrophages in the aneurysm. The aneurysmal vessel wall in both groups of ANG II treated mice contained more iron-positive macrophages than saline-treated mice. However, the presence of cells capable of phagocytosing haemosiderin in mural thrombi also induced low-signal-intensities via MRI imaging.Conclusions/SignificanceSPIO is taken up by macrophages in the shoulder and the outer layer of AAA. This alters the MRI signaling properties and can be used in imaging inflammation associated with AAA. It is important to compare images of the aorta before and after SPIO injection.

Quantification of MRI signal of transgenic grafts overexpressing ferritin in murine myocardial infarcts

The noninvasive detection of transplanted cells in damaged organs and the longitudinal follow-up of cell fate and graft size are important for the evaluation of cell therapy. We have shown previously that the overexpression of the natural iron storage protein, ferritin, permits the detection of engrafted cells in mouse heart by MRI, but further imaging optimization is required. Here, we report a systematic evaluation of ferritin-based stem cell imaging in infarcted mouse hearts in vivo using three cardiac-gated pulse sequences in a 3-T scanner: black-blood proton-density-weighted turbo spin echo (PD TSE BB), bright-blood T(2) -weighted gradient echo (GRE) and black-blood T(2) -weighted GRE with improved motion-sensitized-driven equilibrium (iMSDE) preparation. Transgenic C2C12 myoblast grafts overexpressing ferritin did not change MRI contrast in the PD TSE BB images, but showed a 20% reduction in signal intensity ratio in black-blood T(2) -weighted iMSDE (p < 0.05) and a 30% reduction in bright-blood T(2) -weighted GRE (p < 0.0001). Graft size measurements by T(2) iMSDE and T(2) GRE were highly correlated with histological assessments (r = 0.79 and r = 0.89, respectively). Unlabeled wild-type C2C12 cells transplanted to mouse heart did not change the MRI signal intensity, although endogenous hemosiderin was seen in some infarcts. These data support the use of ferritin to track the survival, growth and migration of stem cells transplanted into the injured heart.

Characterization of peri-infarct zone by cardiac magnetic resonance: validation compared to ex-vivo imaging and post-mortem histology

Methods Adult sheep (40kg) were subjected to ischemia reperfusion injury (LAD for 45 min). Six animals underwent invivo CMR 10 days after surgery and were euthanized on the next day for exvivo CMR and histopathological examination. Invivo CMR included: black blood T2 and 2D LGE (in-plane resolution 2mm). Animals were euthanized 10 min after injection of Gadolinium. Heart specimens were sliced and imaged exvivo using a high resolution 3D LGE (isotropic resolution of 0.6mm). Heart specimens were then fixed for histological analysis (HE and Masson trichrome).

O-003 Prediction of periprocedual ischemic complication in carotid artery stenting with filter embolic protection device: feasibility of MR plaque imaging

PurposeOur purpose is to investigate the feasibility of MR plaque imaging to predict the high risk lesion for ischemic complication during carotid artery stenting (CAS) using a filter embolic protection...

Magnetic resonance plaque imaging to predict the occurrence of the slow-flow phenomenon in carotid artery stenting procedures

The purpose is to investigate the feasibility of magnetic resonance (MR) plaque imaging in predicting the arterial flow impairment (slow-flow phenomenon) during carotid artery stenting (CAS) using a filter-type protection device. Thirty-one carotid artery stenotic lesions in 30 patients (28 men and two women; mean age, 71.8 years) were evaluated by MR plaque imaging with black blood T1- and T2-weighted and time-of-flight sequences before CAS. Main plaque components were classified as vulnerable (intraplaque hemorrhage and lipid-rich/necrotic core) or stable (fibrous tissue and dense calcification) from the signal pattern. The plaque classification was statistically compared with the occurrence of slow-flow phenomenon. The slow-flow phenomenon was observed in ten CAS procedures (five flow arrests and five flow reductions). Flow arrests consisted of four vulnerable and one stable plaque, and flow reductions consisted of four vulnerable and one stable plaque. The slow-flow phenomenon occurred significantly (P<0.01) more frequently in patients with vulnerable plaque. Vulnerable carotid plaques have a significantly higher risk of slow-flow phenomenon than stable plaques. The occurrence of the slow-flow phenomenon can be predicted by MR plaque imaging before CAS.

Black and bright-blood sequences magnetic resonance angiography and gross sections of the canine thorax: An anatomical study

In this study, images of the canine thorax in transverse, dorsal and sagittal planes were obtained by black-blood T1 spin-echo pulse sequence and bright-blood gradient-echo sequence magnetic resonance imaging. The images were correlated with macroscopic cryosections and anatomical dissection of cadavers with blood vessels containing latex. Non-contrast-enhanced magnetic resonance angiography was obtained from two mature Beagle breed dogs. Macroscopic sections and dissections were performed in three dogs. Black and bright-blood angiography diagnostic methods are complementary and provide an accurate depiction of the vascular canine thorax.

2076 Comparison between black and bright blood T2* measurements in thalassemia

2076 Comparison between black and bright blood T2* measurements in thalassemia

Abstract 2124: Accuracy of T2-weighted Cardiac Magnetic Resonance in Detecting Myocardial Edema in Acute Myocardial Infarction is Strongly Influenced by Microvascular Obstruction.

Background: High signal intensity (SI) on T2-weighted Cardiac Magnetic Resonance (CMR) indicates infarct-associated myocardial edema in patients with acute myocardial infarction (MI). However, erythrocytes leaking from capillaries in infarct tissue may result in reduced signal on T2W CMR due to T2 shortening. The purpose of this study was to determine if detection of myocardial edema with T2-weighted CMR is influenced by microvascular obstruction (MO- ). Methods: Thirty-seven patients underwent black blood T2 weighted MRI with a spectral presaturation with inversion recovery fat saturation method, rest perfusion MRI and late gadolinium enhanced (LGE) MRI 5.4±3.1 days after onsets. The presence and transmural extent of LGE and MO were analyzed based on a 16-segment model. The relative SI compared with remote normal myocardium was determined in the infarction and peri-infarction zones on T2 weighted MRI, by using the mean + 2SD of the SI in normal segments as a threshold. Results: LGE was observed in 37 (100%) of 37 patients and MO in 19 (51%) of 37 patients. The SI in LGE segments without MO and the SI in periinfarct zones were significantly higher than those in normal segments (relative SI 1.84±0.5, p&lt;0.001 and 1.69±0.18, p&lt;0.001, respectively). However, no significant difference was found between the SI in MO segments and the SI in normal segments (relative SI 1.12±0.24, p=N.S.). The sensitivity of T2 weighted MRI for detecting edema in acute MI was 95% (73/77) in the LGE segments without MO, but was reduced to 30% (22/73) in the segments with MO. Myocardial edema was completely missed on T2 weighted MRI in 2 patients with severe MO. Conclusions: Although T2-weighted CMR is highly sensitive in detecting myocardial edema in the segments without MO, reduced T2 signal intensity in MO segments can be an important pitfall in characterizing the area of the acute event.

Black‐blood T2* technique for myocardial iron measurement in thalassemia

To compare the effectiveness and reproducibility of a new black-blood sequence vs. a conventional bright-blood gradient-echo T2* sequence for myocardial iron overload measurement in thalassemia. Twenty thalassemia patients were studied. Black-blood sequence images were acquired in diastole after a double inversion recovery (DIR) preparation pulse. Bright-blood sequence images were acquired in both early systole and late diastole. The data were randomized and the T2* analysis was performed blindly by two independent observers. The T2* values from the black-blood sequence were comparable to those of the conventional bright-blood sequence (25.7 +/- 12.9 msec vs. 26.4 +/- 14.2 msec in early systole, P = 0.44; and 25.2 +/- 13.1 msec in late diastole, P = 0.41). The coefficient of variation (CV) for black-blood image T2* analysis was 4.1% compared with 8.9% (early systole P = 0.03) and 7.8% (late diastole P = 0.05) for bright-blood image analysis. The black-blood T2* technique yields high-contrast myocardial images, provides clearly depicted myocardial borders, and avoids blood signal contamination of the myocardium while yielding improvements in interobserver variability.

Development of a novel optimized breathhold technique for myocardial T2 measurement in thalassemia

To develop a reproducible fast spin-echo (FSE) technique for accurate myocardial T2 measurement with application to iron overload assessment in thalassemia. An FSE sequence was developed to permit acquisition of multiple TE images in one breathhold (BH-FSE). A dynamic black-blood scheme was introduced to better cancel blood signal. A nonselective refocusing train was also adopted to suppress stimulated echoes. The optimized technique was tested on phantoms and then applied to 10 normal volunteers and 10 thalassemia patients. Interstudy reproducibility was measured on all the 20 subjects. The mean difference in T2 values was 1.7% from phantom experiments between BH-FSE and the conventional spin-echo (SE) technique. High contrast BH-FSE images were acquired from human subjects, with minimal stimulated echoes and effective blood suppression (P = 0.0005). The coefficient of variation for interstudy reproducibility was 4.3%. T2 values from thalassemia patients were substantially lower than those from the normal subjects (45.2 +/- 26.1 msec vs. 56.9 +/- 8.4 ms, P = 0.02). The dynamic black-blood T2 sequence is a fast reproducible acquisition that compares favorably with conventional techniques, is robust to motion artifacts, and yields high blood-myocardium contrast. This technique may provide a useful tool in thalassemia and other scenarios requiring myocardial T2 quantification.