First-pass Imaging Research Articles

Thoracic central venous evaluation: comparison of first-pass direct versus delayed-phase indirect multidetector CT venography

PurposeThe purpose was to compare first-pass and delayed-phase thoracic computed tomography (CT) venography for the evaluation of suspected central thoracic venous pathology. Material and methodsCT images and medical records of all patients who underwent thoracic CT venography over a 5-year period were retrospectively reviewed. Both first-pass (18s) and delayed-phase (60s) venous images were obtained in all patients. The images were reviewed in random order by three readers using a semiquantitative visual grading scheme for image quality, including artifacts and the uniformity of venous enhancement. In addition, enhancement was quantitatively evaluated. The presence and type of venous pathology, and overall diagnostic confidence were recorded and compared. Reference verification was performed when available. ResultsEighteen patients formed the study group, mean age 49.5years and 28% male. Dual-arm injection was successful in 72% of exams. All readers reported more streak artifacts on first-pass imaging than delayed imaging (72%–94% vs. 27%–44%, respectively; P<.05). First-pass imaging had significantly higher measured enhancement across all central venous segments than delayed imaging (mean HU range 212–906 HU vs. 173–414 HU; P<.05) but also had significantly more heterogeneous enhancement (mean S.D. range 75–1058 HU vs. 67–378 HU; P<.05). For overall diagnosis, reader agreement, accuracy, and confidence levels were higher for delayed-phase images (P<.05). ConclusionIndirect thoracic CT venography using delayed-phase imaging alone may be sufficient for evaluating clinically suspected central venous abnormality.

First-pass stress perfusion MR Imaging findings of apical hypertrophic cardiomyopathy: with relation to LV wall thickness and late Gadolinium-enhancement

Hypertrophic cardiomyopathy (HCM) is a complex and common genetic cardiac disease and it is a primary disease of the cardiac muscle that typically displays a marked and diffuse pattern of ventricular wall thickening (1). A variant apical form of HCM is characterized by wall thickening confined to the ventricular apex, with a typical ‘ace of spade’ configuration (2, 3). Although apical hypertrophic cardiomyINTRODUCTION �Received; January 12, 2014�Revised; February 14, 2014 �Accepted; March 5, 2014 Corresponding author : Eun Ju Chun, M.D., Ph.D. Divison of Cardiovascular Imaging, Department of Radiology, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707, Korea. Tel. 82-31-787-7618, Fax. 82-31-787-4011 E-mail : drejchun@hanmail.net This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. First-pass Stress Perfusion MR Imaging Findings of Apical Hypertrophic Cardiomyopathy: with Relation to LV Wall Thickness and Late Gadolinium-enhancement

Breathing maneuvers as a metabolic coronary vasodilator for first-pass perfusion MR imaging

Methods We studied 24 healthy volunteers (37 ± 12 years; 62.5% men) in a clinical 3T MRI system. Each exam included three sets of first pass perfusion images, (1) at rest and, after 1 minute of hyperventilation during (2) a short breath-hold (SBH) or (3) a long breath-hold (LBH), performed in random order. A reader blinded to the maneuver applied, analyzed signal intensity upslope, upslope index and time between 20 and 80% of maximal signal. For inter-observer variability, a different, blinded, reader repeated the analysis in 4 volunteers.

Free breathing myocardial perfusion data sets for performance analysis of motion compensation algorithms.

BackgroundPerfusion quantification by using first-pass gadolinium-enhanced myocardial perfusion magnetic resonance imaging (MRI) has proved to be a reliable tool for the diagnosis of coronary artery disease that leads to reduced blood flow to the myocardium. The image series resulting from such acquisition usually exhibits a breathing motion that needs to be compensated for if a further automatic analysis of the perfusion is to be executed. Various algorithms have been presented to facilitate such a motion compensation, but the lack of publicly available data sets hinders a proper, reproducible comparison of these algorithms.MaterialFree breathing perfusion MRI series of ten patients considered clinically to have a stress perfusion defect were acquired; for each patient a rest and a stress study was executed. Manual segmentations of the left ventricle myocardium and the right-left ventricle insertion point are provided for all images in order to make a unified validation of the motion compensation algorithms and the perfusion analysis possible. In addition, all the scripts and the software required to run the experiments are provided alongside the data, and to enable interested parties to directly run the experiments themselves, the test bed is also provided as a virtual hard disk.FindingsTo illustrate the utility of the data set two motion compensation algorithms with publicly available implementations were applied to the data and earlier reported results about the performance of these algorithms could be confirmed.ConclusionThe data repository alongside the evaluation test bed provides the option to reliably compare motion compensation algorithms for myocardial perfusion MRI. In addition, we encourage that researchers add their own annotations to the data set, either to provide inter-observer comparisons of segmentations, or to make other applications possible, for example, the validation of segmentation algorithms.

Quantification of myocardial blood flow using non-ECG-triggered MR imaging.

MR myocardial perfusion imaging is dependent on reliable electrocardiogram (ECG) triggering for accurate measurement of myocardial blood flow (MBF). A non-ECG-triggered method for quantitative first-pass imaging may improve clinical feasibility in patients with poor ECG signal. The purpose of this study is to evaluate the feasibility of a non-ECG-triggered method for myocardial perfusion imaging in a single slice. The proposed non-ECG-triggered technique uses a saturation-recovery magnetization preparation and golden-angle radial acquisition for integrated arterial input function (AIF) measurement. Image based self-gating with a temporal resolution of 42.6 ms is used to generate a first-pass image series with consistent cardiac phase. The AIF is measured using beat-by-beat T1 estimation of the ventricular blood pool. The proposed technique was performed on 14 healthy volunteers and compared against a conventional ECG-triggered dual-bolus acquisition. The proposed method produced MBF with no significant difference compared with ECG-triggered technique (mean of 0.63 ± 0.22 mL/min/g to 0.73 ± 0.21 mL/min/g). We have developed a non-ECG-triggered perfusion imaging method with T1 based measurement of the AIF in a single slice. In this preliminary study, our results demonstrate that MBF measured using the proposed method is comparable to the conventional ECG-triggered method.

Myocardial perfusion defects in scleroderma detected by contrast-enhanced cardiovascular magnetic resonance.

The authors investigated whether contrast-enhanced cardiovascular magnetic resonance (CMR) imaging may be used to detect early cardiac involvement in patients with systemic sclerosis (SSc). Twenty-six SSc patients (nine with diffuse cutaneous SSc and 17 with limited cutaneous SSc) and 13 sex- and age-matched healthy controls (HC) were studied. Contrast-enhanced CMR allowed the analysis of first-pass images (areas of hypo-enhancement indicating perfusion defects) and delayed images (persistent hyper-enhancement indicating fibrosis). Clinical variables including disease duration and presence of major visceral complications of SSc were investigated in each patient. Perfusion defects were detected in 53.8% of SSc patients but in none of the HC. Perfusion abnormalities were detected in 28.6% of SSc patients with disease duration less than 2years and in 29.2% of asymptomatic SSc patients. Delayed contrast enhancement was present in 25% of SSc patients but not in HC. All patients with delayed contrast enhancement showed first-pass hypoperfusion. Right ventricular wall thickness was significantly increased in all SSc patients when compared to HC (p<0.001); a similar trend was observed when SSc patients without pulmonary arterial hypertension were analysed (p<0.04). A trend to lower end-diastolic and end-systolic right ventricular volumes in SSc versus HC was observed (p<0.05 and p<0.04, respectively). Myocardial hypoperfusion is common in SSc and occurs early in the course of the disease. Co-localisation of perfusion defects and delayed contrast enhancement indicative of fibrosis suggests that myocardial hypoxia may play a role in the pathogenesis of myocardial fibrosis.

In vivo spectral and fluorescence microscopy comparison of microvascular function after treatment with OXi4503, Sunitinib and their combination in Caki-2 tumors.

Vascular targeting agents on their own have been shown to be insufficient for complete treatment of solid tumors, emphasizing the importance of studying the vascular effects of these drugs for their use with conventional therapies in the clinic. First-pass fluorescence imaging combined with hyperspectral imaging of hemoglobin saturation of microvessels in the murine dorsal window chamber model provides an easily implementable, low cost method to analyze tumor vascular response to these agents in real-time. In this study, the authors utilized these methods to spectroscopically demonstrate distinct vessel structure, blood flow and oxygenation changes in human Caki-2 renal cell carcinoma following treatment with OXi4503 alone, Sunitinib alone and both drugs together. We showed that treatment with OXi4503 plus Sunitinib destroyed existing tumor microvessels, inhibited blood vessel recovery and impaired Caki-2 tumor growth significantly more than either treatment alone.

Assessment of myocardial perfusion with MRI using a modified dual bolus method

Quantification of regional myocardial blood flow (rMBF) with first-pass magnetic resonance imaging (FP-MRI) requires two contrast agent injections (dual bolus technique), inducing error in the determined rMBF if the injections differ. We hypothesize that using input and residue curves of the same injection would be more reliable. We aim to introduce and evaluate a novel method to correct the high concentration arterial input function (AIF) for determination of rMBF. Sixteen patients with non-Hodgkin's lymphoma were examined before and after chemotherapy. The input function was solved by correcting initial high concentration AIF using the ratio of low and high contrast AIF areas, normalized by corresponding heart rates (modified dual bolus method). For comparison, the scaled low contrast AIF was used as an input function (dual bolus method). Unidirectional transfer coefficient Ktrans was calculated using both methods. Ktrans-values determined with the dual bolus (0.81 ± 0.32 ml g−1 min−1) and modified dual bolus (0.77 ± 0.42 ml g−1 min−1) methods were in agreement (p = 0.21). Mean Ktrans-values increased from 0.76 ± 0.43 to 0.89 ± 0.55 ml g−1 min−1 after chemotherapy (p = 0.17). The modified dual bolus technique agrees with the dual bolus technique (R2 = 0.899) when the low and high contrast injections are similar. However, when this is not the case, the modified dual bolus technique may be more reliable.

Thrombospondin-1 domain-containing peptide properdistatin improves vascular function in human melanoma xenografts

Properdistatin is a novel peptide derived from the thrombospondin-1 domain of the plasma protein properdin. The purpose of this study was to investigate the effect of properdistatin treatment on the morphology and function of tumor vasculature. A-07 human melanoma xenografts grown in dorsal window chambers were used as preclinical model. Tumors were treated with 80mg/kg/day properdistatin or vehicle for 4days. Morphologic parameters of tumor vascular networks were assessed from high-resolution transillumination images, and tumor blood supply time and plasma velocities were assessed from first-pass imaging movies recorded after a bolus of 155kDa tetramethylrhodamine isothiocyanate-labeled dextran had been administered intravenously. Properdistatin-treated tumors showed reduced density of small-diameter vessels, reduced blood supply time, and increased plasma velocities. In conclusion, properdistatin treatment inhibited angiogenesis and improved vascular function in A-07 tumors.

Functional Magnetic Resonance Imaging of the Lung

Beyond being a substitute for X-ray, computed tomography, and scintigraphy, magnetic resonance imaging (MRI) inherently combines morphologic and functional information more than any other technology. Lung perfusion: The most established method is first-pass contrast-enhanced imaging with bolus injection of gadolinium chelates and time-resolved gradient-echo (GRE) sequences covering the whole lung (1 volume/s). Images are evaluated visually or semiquantitatively, while absolute quantification remains challenging due to the nonlinear relation of T1-shortening and contrast material concentration. Noncontrast-enhanced perfusion imaging is still experimental, either based on arterial spin labeling or Fourier decomposition. The latter is used to separate high- and low-frequency oscillations of lung signal related to the effects of pulsatile blood flow. Lung ventilation: Using contrast-enhanced first-pass perfusion, lung ventilation deficits are indirectly identified by hypoxic vasoconstriction. More direct but still experimental approaches use either inhalation of pure oxygen, an aerosolized contrast agent, or hyperpolarized noble gases. Fourier decomposition MRI based on the low-frequency lung signal oscillation allows for visualization of ventilation without any contrast agent. Respiratory mechanics: Time-resolved series with high background signal such as GRE or steady-state free precession visualize the movement of chest wall, diaphragm, mediastinum, lung tissue, tracheal wall, and tumor. The assessment of volume changes allows drawing conclusions on regional ventilation. With this arsenal of functional imaging capabilities at high spatial and temporal resolution but without radiation burden, MRI will find its role in regional functional lung analysis and will therefore overcome the sensitivity of global lung function analysis for repeated short-term treatment monitoring.

The regional myocardial microvascular dysfunction differences in hypertrophic cardiomyopathy patients with or without left ventricular outflow tract obstruction: Assessment with first-pass perfusion imaging using 3.0-T cardiac magnetic resonance

PurposeTo assess regional myocardial microvascular dysfunction differences in hypertrophic cardiomyopathy (HCM) patients with or without left ventricular outflow tract obstruction using 3.0-T cardiac magnetic resonance (CMR) first-pass perfusion imaging. Materials and methodsForty-two HCM patients, including 25 HCM patients with left ventricular outflow tract obstruction (HOCM), 17 HCM patients without left ventricular outflow tract obstruction (NOHCM), and 14 healthy subjects underwent CMR. The left ventricular (LV) function, left ventricular end-diastolic wall thickness (EDTH), and diameter of left ventricular outflow tract (LVOT) were measured and calculated. Based on the signal–time curve of the first-pass myocardium perfusion imaging, perfusion parameters including upslope, time to peak, and peak intensity, were assessed and compared by using one-way analysis of variance and independent t tests. ResultsOn the first-pass perfusion imaging, lower upslope and peak intensity and longer time to peak were found in HCM patients compared with normal subjects (all p<0.05). In contrast to the NOHCM group, the average time to peak of the HOCM group was increased (13.30±4.82s vs 16.28±4.90s, p<0.05), but first-pass perfusion upslope was reduced (4.96±2.55 vs 2.58±0.77, p<0.05). According to the bull's-eye model, the HOCM group's average thickness of basal segments was thicker than the NOHCM group, especially the anteroseptal, inferolateral, and anterior wall values, with a corresponding lower first-pass perfusion upslope than the NOHCM group (all p<0.05). A significant correlation was observed between first-pass perfusion upslope and LV EDTH (r=−0.551, p<0.001) and LVOT diameter (r=0.472, p<0.001). ConclusionsThe regional myocardial microvascular dysfunction differences in hypertrophic cardiomyopathy (HCM) patients with or without left ventricular outflow tract obstruction can be detected with first-pass perfusion CMR imaging.

Contrast Agent Bolus Dispersion in a Realistic Coronary Artery Geometry: Influence of Outlet Boundary Conditions

Myocardial blood flow (MBF) quantification using contrast-enhanced first-pass magnetic resonance imaging relies on the precise knowledge of the arterial input function (AIF). Due to vascular transport processes, however, the shape of the AIF may change from the left ventricle where the AIF is measured to the myocardium. We employed computational fluid dynamics simulations in a realistic model of the left circumflex artery to investigate the degree to which this effect corrupts MBF quantification. Different outlet boundary conditions were applied to examine their influence on the solution. Our results indicate that vascular transport processes in realistic coronary artery geometries give rise to non-negligible systematic errors in the MBF values. The magnitude of these errors differs considerably between the outlets of the 3D model. Moreover, outlet boundary conditions are shown to have a significant influence on the outflows at the outlets of the 3D model. In particular, the employed boundary conditions respond differently to an artificially inserted stenosis and to hyperemia condition. Finally, outlet boundary conditions are shown to have an influence on the resulting MBF value. Since MBF errors are different under rest and under hyperemia conditions, overestimation of myocardial perfusion reserve values may occur as well.

Groupwise Elastic Registration by a New Sparsity-Promoting Metric: Application to the Alignment of Cardiac Magnetic Resonance Perfusion Images

This paper proposes a methodology for the joint alignment of a sequence of images based on a groupwise registration procedure by using a new family of metrics that exploit the expected sparseness of the temporal intensity curves corresponding to the aligned points. Therefore, this methodology is able to tackle the alignment of temporal sequences of images in which the represented phenomenon varies in time. Specifically, we have applied it to the correction of motion in contrast-enhanced first-pass perfusion cardiac magnetic resonance images. The time sequence is elastically registered as a whole by using the aforementioned family of multi-image metrics and jointly optimizing the parameters of the transformations involved. The proposed metrics are able to cope with dynamic changes in the intensity content of corresponding points in the sequence guided by the assumption that these changes allow for a sparse representation in a properly selected frame. Results have shown the statistically significant improvement in the performance of the proposed metric with respect to previous groupwise registration metrics for the problem at hand, which is especially relevant to correct for elastic deformations.

Factor analysis-based approach for early uptake automatic quantification of breast cancer by 18F-FDG PET images sequence

Factor Analysis of Medical Image Sequences (FAMIS) is recognized as one pioneer successfully used approach for analyzing especially dynamic images’ sequence for estimating kinetics and associated compartments having a physiological meaning.Some studies tried to extend the exploring of this approach to analyze Positron Emission Tomography (PET) image modality for dynamic sequences. PET images with 18F-fluorodesoxyglucose (18F-FDG) is the gold standard for in vivo, evaluation of tumor glucose metabolism and is widely used in clinical oncology.In this paper, a novel approach is proposed to obtain an automated quantification method for early accumulation of 18F-FDG tracer in order to explore breast cancer, by applying FAMIS tool on dynamic first pass 18F-FDG PET dynamic sequences. This approach starts by an automated identification of a tumor Region of Interest (ROI) from PET dynamic images’ sequence. Then, a FAMIS approach is applied to separate two compartments: one compartment is associated to the vascular and a second one is associated to the purely tumor compartment. The latter allows the evaluation of the temporal evolution of the glucose tracer metabolism and therefore for pursuing cancer characterization.A new empiric parameter KFPQ (First Pass Quantification), computed from the evolution of the 18F-FDG radiotracer accumulation using the first 11min PET early images, is proposed. This parameter is found to be correlated to standardized uptake value maximal index (SUVmax) metabolism tumor.The proposed framework is tested using image sequences’ database for 25 different pathology cases, which is considered as largely sufficient by the clinical team. Among clinicians’ experience, using a large dataset permits the possibility to obtain accurate information and precise early diagnosis. Pearson correlation coefficient is computed to evaluate as well as to analyze the relationship between the proposed empiric parameter KFPQ and glucose tracer metabolism SUVmax for the overall pathology cases. KFPQ is successfully evaluated by the dynamic first-pass 18F-FDG PET image sequences for exploring early breast cancer diagnosis. Quantitative evaluations, as discussed and validated by clinicians, confirmed the efficiency of the modeling and the usefulness of the new empiric parameter KFPQ to predict tumor glucose metabolism for early uptake. This can be considered as a significant indication for quantification as well as evaluation of early relapse and disease progression during the therapy.

Development of a theory for generating regional cardiac perfusion images during coronary angiography in the coronary angiography lab

The purpose of this study was to develop a novel theory and method for generating regional myocardial perfusion images using fluoroscopy in the coronary angiography lab. We modified the Kety model to introduce the Patlak plot method for two-dimensional fluoroperfusion (FP) imaging. For evaluation, seven porcine models of myocardial ischemia with stenosis in the left coronary artery were prepared. Rest and stress FP imaging were performed using cardiovascular X-ray imaging equipment during the injection of iopamidol via the left main coronary artery. Images were acquired and retrospectively ECG gated at 80 % of the R-R interval. FP myocardial blood flow (MBF) was obtained using the Patlak plot method applied to time-intensity curve data of the proximal artery and myocardium. The results were compared to microsphere MBF measurements. Time-intensity curves were also used to generate color-coded FP maps. There was a moderate linear correlation between the calculated FP MBF and the microsphere MBF (y = 0.9758x + 0.5368, R² = 0.61). The color-coded FP maps were moderately correlated with the regional distribution of flow. This novel method of first-pass contrast-enhanced two-dimensional fluoroscopic imaging can quantify MBF and provide color coded FP maps representing regional myocardial perfusion.

Equilibrium-Phase High Spatial Resolution Contrast-Enhanced MR Angiography at 1.5T in Preoperative Imaging for Perforator Flap Breast Reconstruction

ObjectivesThe aim was (i) to evaluate the accuracy of equilibrium-phase high spatial resolution (EP) contrast-enhanced magnetic resonance angiography (CE-MRA) at 1.5T using a blood pool contrast agent for the preoperative evaluation of deep inferior epigastric artery perforator branches (DIEP), and (ii) to compare image quality with conventional first-pass CE-MRA.MethodsTwenty-three consecutive patients were included. All patients underwent preoperative CE-MRA to determine quality and location of DIEP. First-pass imaging after a single bolus injection of 10 mL gadofosveset trisodium was followed by EP imaging. MRA data were compared to intra-operative findings, which served as the reference standard.ResultsThere was 100% agreement between EP CE-MRA and surgical findings in identifying the single best perforator branch. All EP acquisitions were of diagnostic quality, whereas in 10 patients the quality of the first-pass acquisition was qualified as non-diagnostic. Both signal- and contrast-to-noise ratios were significantly higher for EP imaging in comparison with first-pass acquisitions (p<0.01).ConclusionsEP CE-MRA of DIEP in the preoperative evaluation of patients undergoing a breast reconstruction procedure is highly accurate in identifying the single best perforator branch at 1.5Tesla (T). Besides accuracy, image quality of EP imaging proved superior to conventional first-pass CE-MRA.

Assessment of coronary microvascular dysfunction in hypertrophic cardiomyopathy: First-pass myocardial perfusion cardiovascular magnetic resonance imaging at 1.5 T

To evaluate the integrity of the coronary microvasculature in patients with hypertrophic cardiomyopathy (HCM) using first-pass magnetic resonance perfusion imaging. Twenty-two patients with HCM and 13 healthy volunteers underwent cardiac magnetic resonance imaging (CMR) at rest. Imaging protocols included short axis cine, first-pass myocardial perfusion, and late-phase contrast-enhanced imaging. Left ventricular end-diastolic wall thickness (EDTH), myocardial thickening, maximal upslope of time-intensity curve (slopemax), and late myocardial gadolinium enhancement (LGE) were assessed for each myocardial segment. The differences in slopemax, myocardial thickening, and EDTH between healthy volunteers and HCM patients were evaluated as were differences among hypertrophic segments of different severities (mild, moderate, and severe hypertrophy) in a one-way analysis of variance analysis. The differences in slopemax, myocardial thickening, and EDTH between the segments with and without LGE were compared by independent-sample t-test. A Pearson correlation test was used to determine the relationships between slopemax, EDTH, and myocardial thickening. Slopemax was statistically significantly less in HCM patients; the degree of myocardial thickening was also significantly reduced (p < 0.001). Slopemax and the degree of thickening statistically significantly decreased with increasing degrees of myocardial hypertrophy (p < 0.05). Differences in slopemax, myocardial thickening, and EDTH were observed between segments with and without LGE (p < 0.05). Slopemax and myocardial thickening were negatively correlated with EDTH. First-pass myocardial perfusion CMR with slopemax measurements demonstrates microvascular coronary dysfunction in patients with HCM, a determination that may aid in risk stratification, therapeutic planning, and determination of prognosis for HCM.

Abstract No. 266 - Evaluation of the microcirculation and perfusion of a rat liver tumor model after transarterial embolization using contrast-enhanced ultrasonography and perfusion analysis

Purpose To evaluate the feasibility of contrast enhanced ultrasound in evaluation the changes of microcirculation and perfusion after transarterial embolization (TAE) in an N1-S1 model of hepatocellular carcinoma in rats. Materials and Methods This study was approved by the Institutional Animal Care and Use Committee at Case Western Reserve University. N1-S1 cells (5 × 10^6) were inoculated under the capsule of the median aspect of the left liver lobe of 10 Sprague-Dawley rats (6 weeks old, Charles River, Wilmington, MA) after a laparotomy. Two weeks later, the tumors were embolized by arterial injection of PVA particles (45-150 μm, Contour, Boston Scientific) after retrograde catheterization via gastroduodenal artery. Contrast enhanced ultrasound (CEUS) was performed before and 3 days after TAE. A prototype perfusion software (ImageLab, Toshiba Medical Systems Corp.) was used to analyze the first-pass enhancing images. Time-signal intensity-curves in the tumor and normal liver were first obtained, and then fitted with an S-shape function. The perfusion parameters [peak, mean transit time (MTT), flow] pre and 3 days after TAE were then calculated. Results Seven tumors (9.3 - 20.1 mm in maximum diameter) were established in the left lobes of rats. The other three animals without tumors were excluded from the study. On CEUS imaging, all liver tumors were enhanced before TAE. A significant filling defect and reduced blood flow in the whole tumor was noted on day 3 after TAE. The changes of parameters in normal liver and the MTT in tumor after TAE were not significant. The time to peak and flow in the tumors was significantly decreased after TAE (1.39 ± 1.05 vs 0.01 ± 0.03, 0.45 ± 0.40 vs 0.00 ± 0.01, respectively). The normalized tumor flow (flow in tumor / flow in liver) was 1.95 ± 1.71 vs 0.05 ± 0.08 pre and post TAE (P = 0.01), and the change rate was -96.47% ± 7.65. Conclusion CEUS and quantitative perfusion analysis is a useful and convenient tool to evaluate the microcirculation change after TAE, especially in hypervascular liver lesions.

Combination of spectral and fluorescence imaging microscopy for wide-field in vivo analysis of microvessel blood supply and oxygenation

Hyperspectral imaging of hemoglobin (Hb) saturation and first-pass fluorescence imaging of blood transit time were combined to analyze the oxygenation of and blood flow through microvessel networks. The combination imaging technique was demonstrated in a mouse dorsal window chamber model of a growing Caki-2 human renal cell carcinoma over time. Data from Hb saturation and blood supply time maps show the formation of arteriovenous malformations and shunting of blood directly from arteries to the tumor core and into veins in the periphery of the tumor. Images and data analysis show these malformations result in an oxygenated environment ideal for a tumor to proliferate.

First-pass myocardial perfusion imaging with whole ventricular coverage using L1-SPIRIT accelerated spiral trajectories

Background First-pass perfusion imaging using cardiac magnetic resonance (CMR) has become clinically applicable as an important tool for diagnosing coronary artery disease. We have recently demonstrated that high quality firstpass images can be acquired with an optimized spiral pulse sequence, but this sequence is only capable of imaging 3 short axis slices of the heart for a maximum heart rate of 110 bpm. In order to achieve whole ventricular coverage, we have developed an accelerated spiral sequence using the Paralle lI maging and Compressed Sensing technique L1-SPIRIT. Methods To evaluate and develop the accelerated reconstruction we retrospectively down-sampled data acquired from a fullysampled variable density (VD) spiral perfusion data set acquired on a 1.5T scanner. Pulse sequence parameters included: TE 1.0 ms, TR 11 ms, FOV 320 mm 2 ,i n-plane resolution 1.75 mm, 8 interleaves, readout duration 8.1ms per interleave, saturation time 8 ms. We then designed a 4x accelerated pulse sequence which prospectively collected only 2 of 8 interleaves, and collects two perfusion images after each saturation pulse. Resting perfusion imaging was performed after injection of 0.1 mmol/kg of