Time-resolved Imaging Of Contrast Kinetics Research Articles

4차원 TRICKS 자기공명혈관조영술과 기존 TOF 자기공명혈관조영술의 비교 및 유용성

Time Resolved Imaging of Contrast Kinetics 기법을 이용한 4차원 자기공명혈관조영술 (TRICKS-MRA)영상과 기존 TOF-MRA영상을 비교하여 임상적 유용성에 대해 알아보고자 하였다. 총17명 중 뇌혈관 질환이 의심되는 11명과 뇌종양을 의심하는 6명을 대상으로 TOF-MRA와 TRICKS-MRA을 시행한 후 17 대상자 중 11명에서 DSA를 추가적으로 시행하였다. TOF-MRA는 공간해상력보다 시간해상력이 부족하였고, TRICKS-MRA에서는 TOF-MRA보다 공간분해능은 부족한 점이 많지만 영상판독에 큰 영향은 없었고 모든 대상자에서 동맥과 정맥의 구별이 가능하여 시간분해능이 우수한 것을 나타났다. 또한 종양과 혈관과의 관계성 평가에서 TOF-MRA보다 좋은 것으로 나타났다. TRICKS-MRA방법은 시간대별로 동맥, 모세혈관, 정맥기를 신속하면서 쉽게 4차원적으로 영상화가 가능하여 앞으로 임상에서 이용도가 더욱 증가 할 것으로 사료된다. To assess the clinical value of time resolved imaging of contrast kinetics(TRICKS) MRA by comparison with conventional time of flight(TOF) MR angiography. Both TOF-MRA and TRICKS-MRA were performed in 17 patients with cerebrovascular disease and in 6 patients with brain tumor. Among 17 cerebraovascular patients, digital subtraction angiography(DSA) data were also obtained in 11 patients. TOF-MRA showed good spatial resolution but short in temporal resolution. Although TRICKS-MRA showed somewhat low spatial resolution, it showed superior temporal resolution by distinguishing vessel and tumor in all patients. Also, from the analysis of vessel-tumor relationship, TRICKS-MRA showed better performance than TOF-MRA. TRICKS-MRA makes it possible to image arterial, capillary and venous phase sequentially with very speedy manner and therefore, the clinical use of this method is highly suggestive for future use.

Cranial Dural Arteriovenous Fistula: Diagnosis and Classification with Time-Resolved MR Angiography at 3T

The diagnosis of dural arteriovenous fistula (DAVF) remains one of the few uncontested indications for catheter based cerebral angiography. We report our experience of using a commercially available form of time-resolved MR angiography (trMRA) at 3T for the diagnosis and classification of a cranial DAVF compared with the reference standard of digital subtraction angiography (DSA). A retrospective review of our patient records identified patients who had undergone trMRA at 3T and DSA for the evaluation of DAVF. The trMRA consisted of whole-head, contrast-enhanced "time-resolved imaging of contrast kinetics" (TRICKS) MRA. Image sets were independently reviewed by 3 readers for the presence, location, and classification of a DAVF. The reported result of the DSA was used as the gold standard against which the performance of the trMRA was measured. Forty patients were identified who had undergone DSA and trMRA for evaluation of DAVF, yielding a total of 42 cases. On DSA, the results of 7 cases were normal, 15 cases were performed for surveillance of a previously cured fistula, and a new fistula (14) or persistent (6) fistula was found in 20 cases. Of these 20 fistulas, on DSA, 13 were Borden I, 2 were Borden II, and 5 were Borden III. In 93% (39/42) of DAVF cases, the 3 readers were unanimous and correct in their independent interpretation of the trMRA, correctly identifying (or excluding) all fistulas and accurately classifying them when encountered. In this small series, trMRA at 3T seems be a reliable technique in the screening and surveillance of DAVF in specific clinical situations.

Abstract No. 119: Clinical Utility of Time-Resolved Imaging of Contrast Kinetics (TRICKS) Magnetic Resonance Angiography (MRA) for Periprocedural Assessment of Central Venous Catheters

Abstract No. 119: Clinical Utility of Time-Resolved Imaging of Contrast Kinetics (TRICKS) Magnetic Resonance Angiography (MRA) for Periprocedural Assessment of Central Venous Catheters

Three‐dimensional dynamic time‐resolved contrast‐enhanced MRA using parallel imaging and a variable rate k‐space sampling strategy in intracranial arteriovenous malformations

To evaluate the effectiveness of three-dimensional (3D) dynamic time-resolved contrast-enhanced MRA (TR-CE-MRA) using a combination of a parallel imaging technique (ASSET: array spatial sensitivity encoding technique) and a time-resolved method (TRICKS: time-resolved imaging of contrast kinetics) and to compare it with 3D dynamic TR-CE-MRA using ASSET alone in the assessment of intracranial arteriovenous malformations (AVMs). Twenty consecutive patients with angiographically confirmed AVMs were investigated using both 3D dynamic TR-CE-MRA techniques. Examinations were compared with respect to image quality, spatial resolution, number and type of feeders and drainers, nidus size, presence of early venous filling and temporal resolution. Digital subtraction angiography was used as standard of reference. The higher temporal and spatial resolution of 3D dynamic TR-CE-MRA TRICKS ASSET allowed a better assessment of intracranial vascular malformations, namely better depiction of feeders, drainers and better detection of early venous drainage. There was no significant difference between them in terms of nidus size. 3D dynamic TR-CE-MRA combining parallel imaging and a time-resolved method with subsecond and submillimeter resolution could become the first-line investigation technique in both diagnosis and follow-up of intracranial AVMs.

Low Dose Pedal Magnetic Resonance Angiography at 3 Tesla With Time-Resolved Imaging of Contrast Kinetics

To assess the feasibility of low-dose time-resolved imaging of contrast kinetics (TRICKS) magnetic resonance (MR) angiography of the pedal vasculature at 3.0 Tesla (T) using a head coil. Eleven healthy volunteers were imaged using TRICKS MR angiography at 3.0 T with both feet positioned in a head coil. A dose of 7 mL was used for each of 3 acquisitions: images were obtained of each foot in the sagittal plane, and then both feet were imaged simultaneously in the transverse plane. The following parameters were used for acquisition: (TR/TE 4.7 milliseconds/ 1.3 milliseconds, field of view = 28 cm, Flip angle = 30 degrees, 384 x 256 matrix, section thickness = 1.6 mm, Bandwidth = 19.23). The dorsalis pedis, plantar arch, distal posterior tibial, lateral tarsal, and medial plantar arteries were graded for visualization, artifact, and overall image quality on a 4-point scale (1 = worst; 4 = best). Superior visualization trended towards separate sagittal acquisitions when compared with that of bilateral transverse acquisitions for most of the individual vessels of the foot. Overall, separate sagittal acquisitions (average score = 2.9) were superior to bilateral transverse acquisitions (average score = 2.6). The average image quality score reflecting the amount of artifact was 2.6 for studies obtained using bilateral transverse acquisitions and 3.1 for studies obtained using separate sagittal acquisitions. Low-dose gadolinium multi-injection TRICKS and bolus-chase MR angiography at 3.0 T provides an effective and easily reproducible technique for imaging of the pedal vasculature in volunteers and has great potential for clinical application.

Simulation of relative temporal resolution of time‐resolved MRA sequences

Time-resolved MRA sequences are typically characterized by the display frame rate. However, true temporal resolution should be defined in a manner analogous to spatial resolution; it is not the ability of a sequence to update rapidly but rather the ability to discern changes that occur within a small time that should characterize temporal resolution. For view-shared methods like Keyhole and time-resolved imaging of contrast kinetics (TRICKS), regions of k-space from multiple time frames are combined to form a single reconstructed time frame. This often causes the time needed to acquire all k-space data points to be significantly longer than the displayed frame time, resulting in a poor frequency response. Simulated here are the temporal impulse response and temporal frequency response (TFR) curves of three time-resolved MRA methods, including the recently introduced highly-constrained backprojection local reconstruction (HYPR LR) method. It is found that the HYPR LR reconstruction method exhibits a better TFR for a larger spectrum of temporal and spatial frequencies than the Keyhole and TRICKS methods.

Angiographie par Résonance Magnétique dans l’artériopathie distale des membres inférieurs : peut-on se passer d’une séquence multiphase (TRICKS) ?

To demonstrate the added diagnostic value of time-resolved imaging of contrast kinetics (TRICKS) in the evaluation of lower limb arteries compared to standard 3 level MRA with stepping table method. Forty patients (30% diabetics) with lower extremity peripheral arterial disease (87.5% with chronic ischemia) underwent standard contrast MRA including TRICKS of the distal arteries. Five arterial segments were defined per leg, and 395 arterial segments were compared (one patient with amputation). Two reviewers evaluated the quality of arterial imaging, presence of venous return and degree of stenosis per segment. The degree of interobserver agreement for arterial stenosis measurement was calculated. More arterial segments could be analyzed on the TRICKS sequence (good or excellent analysis in 63.03%-66.32% of arterial segments compared to 41.51%-47.08% on routine MRA). There was less venous contamination on TRICKS images (25.57% to 27.60% gain). The degree of interobserver agreement was superior with TRICKS compared to standard MRA (kappa 0.85 vs 0.69). The TRICKS sequence can be added to standard MRA for pre-therapeutic evaluation of distal arteries in patients with peripheral arterial disease, especially with chronic ischemic with rest pain and/or trophic changes.

Removing undersampling artifacts in DCE-MRI studies using independent components analysis

In breast MRI mammography both high temporal resolution and high spatial resolution have been shown to be important in improving specificity. Adaptive methods such as projection reconstruction time-resolved imaging of contrast kinetics (PR-TRICKS) allow images to be reconstructed at various temporal and spatial resolutions from the same data set. The main disadvantage is that the undersampling, which is necessary to produce high temporal resolution images, leads to the presence of streak artifacts in the images. We present a novel method of removing these artifacts using independent components analysis (ICA) and demonstrate that this results in a significant improvement in image quality for both simulation studies and for patient dynamic contrast-enhanced (DCE)-MRI images. We also investigate the effect of artifacts on two quantitative measures of contrast enhancement. Using simulation studies we demonstrate that streak artifacts lead to pronounced periodic oscillations in pixel concentration curves which, in turn, lead to increased errors and introduce bias into heuristic measurements. ICA filtering significantly reduces this bias and improves accuracy. Pharmacokinetic modeling was more robust and there was no evidence of bias due to the presence of streak artifacts. ICA filtering did not significantly reduce the errors in the estimated pharmacokinetic parameters; however, the chi-squared error was greatly reduced after ICA filtering.

Time‐resolved contrast‐enhanced MR angiography of intracranial lesions

To determine if contrast-enhanced (CE) MRI of intracranial lesions benefits from time-resolved MR angiography (MRA) during contrast agent injection. For 126 patients with suspected intracranial lesions undergoing routine CE MRI at 3.0T (N = 88) or 1.5T (N = 38), time-resolved CE MRA (three-dimensional [3D] time-resolved imaging of contrast kinetics [TRICKS]) was performed during injection of the routine gadolinium (Gd) dose of 0.1 mmol/kg. Time to peak (TTP) enhancement of lesions as well as time to internal carotid artery (ICA), middle cerebral artery (MCA), superior sagittal sinus (SSS), and jugular vein enhancement were measured. Source and maximum intensity projection (MIP) images were reviewed to delineate the spatial relationship of lesions and the vasculature. In 61 patients (48%), additional important findings were detected on time-resolved MRA that were not seen on the routine CE protocol, including aneurysms (N = 6), arteriovenous malformations (N = 7), ICA stenoses (N = 2), vascular anomalies (N = 18), and relationships between lesions and vessels (N = 28). In addition, tumor TTP correlated with glioma grade (r = 0.87) and discriminated epithelial from nonepithelial meningiomas (P = 2.6 x 10(-5)). MRA added eight minutes to the total exam time. Time-resolved MRA performed during contrast agent injection adds information to the routine brain CE MRI examination of intracranial lesions with only a small time penalty and no additional risk to the patient.

Noninvasive Dynamic Magnetic Resonance Angiography With Time-Resolved Imaging of Contrast KineticS (TRICKS) in the Evaluation of Orbital Vascular Lesions

To evaluate the clinical utility of time-resolved contrast-enhanced magnetic resonance angiography (MRA) in the evaluation of vascular orbital tumors. Retrospective medical record review of patients with vascular orbital lesions imaged with Time-Resolved Imaging of Contrast KineticS (TRICKS; GE Healthcare [Chalfont St Giles, England]) MRA, a noninvasive dynamic imaging modality. Five patients with orbital vascular tumors were evaluated using TRICKS MRA. These included 1 patient with a cavernous hemangioma, 2 patients with orbital varices, 1 patient with an orbitocutaneous arteriovenous malformation, and 1 patient who had a solitary fibrous tumor with features of a hemangiopericytoma. In 2 patients, diagnoses were altered as a result of TRICKS MRA. In addition, a young patient with a large orbitocutaneous arteriovenous malformation involving the ophthalmic artery was followed perioperatively and noninvasively using TRICKS MRA, which produced exquisite images and added substantial value in the care of these patients. Dynamic MRA in the form of TRICKS is a newly available imaging modality with great potential for improving the evaluation and management of patients with complex orbital tumors.

Magnetic resonance angiographic demonstration of carotid-cavernous fistula using elliptical centric time resolved imaging of contrast kinetics (EC-TRICKS)

Magnetic resonance angiographic evaluation of the intracranial vasculature has been predominantly carried out using conventional angiographic techniques such as time of flight and phase contrast sequences. These techniques have good spatial resolution but lack temporal resolution. Newer faster angiographic techniques have been developed to circumvent this limitation. Elliptical centric time-resolved imaging of contrast kinetics (EC-TRICKS) is one such technique which has combined the use of elliptical centric ordering of the k-space with multiphase 3D digital subtraction MR angiogram (MRA) to achieve excellent temporal resolution of the arterial and venous circulations. Its applications have been mainly in the peripheral vasculature. We report the use of this technique in a case of a high-flow, direct carotid-cavernous fistula to demonstrate its potential in intracranial MR angiography.

CE-MR Angiography at 3.0 T Magnetic Field in the Study of Spinal Dural Arteriovenous Fistula

We report technical data and results in eight patients studied with spinal contrast-enhanced MR angiography (CE-MRA). We used a 3.0 Tesla device, dedicated phased array coil and time resolved imaging of contrast kinetics (TRICKS) sequences to visualize the feeder vessels in patients with vascular malformations. TRICKS is a method of 3D CE-MRA providing temporal information. Thanks to its high temporal and spatial resolution and high signal/noise ratio the TRICKS optimized sequence at 3.0 T yielded very encouraging results in disclosing the origin of arteriovenous malformations.

Preliminary clinical application of contrast-enhanced MR angiography using 3D time-resolved imaging of contrast kinetics (3D-TRICKS)

Objective To introduce a new better contrast-enhanced MR angiographic method, named 3D time-resolved imaging of contrast kinetics (3D-TRICKS). Methods TRICKS is a high temporal resolution (2-6 s) MR angiographic technique using a short TR(4 ms) and TE(1.5 ms), partial echo sampling, in which central part of k-space is updated more frequently than the peripheral part. TRICKS pre-contrast mask 3D images are firstly scanned, and then the bolus injecting of Gd-DTPA, 15-20 sequential 3D images are acquired. The reconstructed 3D images, subtraction of contrast 3D images with mask images, are conceptually similar to a catheter-based intra-arterial digital subtraction angiographic series (DSA). Thirty patients underwent contrast-enhanced MR angiography using 3D-TRICKS. Results Totally 12 vertebral arteries were well displayed on TRICKS, in which 7 were normal, 1 demonstrated bilateral vertebral artery stenosis, 4 had unilateral vertebral artery stenosis and 1 was accompanied with the same lateral carotid artery bifurcation stenosis. Four cases of bilateral renal arteries were normal, 1 transplanted kidney artery showed as normal and 1 transplanted kidney artery showed stenosis. 2 cerebral arteries were normal, 1 had sagittal sinus thrombosis and 1 displayed intracranial arteriovenous malformation. 3 pulmonary arteries were normal, 1 showed pulmonary artery thrombosis and 1 revealed pulmonary sequestration's abnormal feeding artery and draining vein. One left lower limb fibrolipoma showed feeding artery. One displayed radial-ulnar artery artificial fistula stenosis. One revealed left antebrachium hemangioma. Conclusion It TRICKS can clearly delineate most body vascular system and reveal most vascular abnormality. It possesses convenience and high successful rate, which make it the first choice of displaying most vascular abnormality.

Clinical utility of time-resolved imaging of contrast kinetics (TRICKS) magnetic resonance angiography for infrageniculate arterial occlusive disease

The diagnostic accuracy of magnetic resonance angiography (MRA) in the infrapopliteal arterial segment is not well defined. This study evaluated the clinical utility and diagnostic accuracy of time-resolved imaging of contrast kinetics (TRICKS) MRA compared with digital subtraction contrast angiography (DSA) in planning for percutaneous interventions of popliteal and infrapopliteal arterial occlusive disease. Patients who underwent percutaneous lower extremity interventions for popliteal or tibial occlusive disease were identified for this study. Preprocedural TRICKS MRA was performed with 1.5 Tesla (GE Healthcare, Waukesha, Wis) magnetic resonance imaging scanners with a flexible peripheral vascular coil, using the TRICKS technique with gadodiamide injection. DSA was performed using standard techniques in angiography suite with a 15-inch image intensifier. DSA was considered the gold standard. The MRA and DSA were then evaluated in a blinded fashion by a radiologist and a vascular surgeon. The popliteal artery and tibioperoneal trunk were evaluated separately, and the tibial arteries were divided into proximal, mid, and distal segments. Each segment was interpreted as normal (0% to 49% stenosis), stenotic (50% to 99% stenosis), or occluded (100%). Lesion morphology was classified according to the TransAtlantic Inter-Society Consensus (TASC). We calculated concordance between the imaging studies and the sensitivity and specificity of MRA. The clinical utility of MRA was also assessed in terms of identifying arterial access site as well as predicting technical success of the percutaneous treatment. Comparisons were done on 150 arterial segments in 30 limbs of 27 patients. When evaluated by TASC classification, TRICKS MRA correlated with DSA in 83% of the popliteal and in 88% of the infrapopliteal segments. MRA correctly identified significant disease of the popliteal artery with a sensitivity of 94% and a specificity of 92%, and of the tibial arteries with a sensitivity of 100% and specificity of 84%. When used to evaluate for stenosis vs occlusion, MRA interpretation agreed with DSA 90% of the time. Disagreement occurred in 15 arterial segments, most commonly in distal tibioperoneal arteries. MRA misdiagnosed occlusion for stenosis in 11 of 15 segments, and stenosis for occlusion in four of 15 segments. Arterial access was accurately planned based on preprocedural MRA findings in 29 of 30 patients. MRA predicted technical success 83% of the time. Five technical failures were due to inability to cross arterial occlusions, all accurately identified by MRA. TRICKS MRA is an accurate method of evaluating patients for popliteal and infrapopliteal arterial occlusive disease and can be used for planning percutaneous interventions.

Peripheral Arteries in Diabetic Patients: Standard Bolus-Chase and Time-resolved MR Angiography

To prospectively determine the diagnostic performance of a combination of standard bolus-chase magnetic resonance (MR) angiography and MR angiography with time-resolved imaging of contrast kinetics (TRICKS) for depicting severity of peripheral vascular disease of the lower extremity, including the pedal arteries, in diabetic patients with digital subtraction angiography (DSA) as the reference standard. An ethical committee approved this study; written informed consent was obtained from patients. Standard three-station and TRICKS MR angiography of the calf and foot were performed in 31 consecutive diabetic patients (23 men, eight women; mean age, 67 years; range, 43-81 years). Two readers separately assessed images of arterial segments as diagnostic or nondiagnostic and graded stenosis. Results were compared with those at DSA when the corresponding arterial segments were considered diagnostic at DSA. Wilcoxon signed rank test was used to determine if a significant difference between imaging techniques existed, and kappa statistics were used to determine interobserver agreement. The difference between standard MR angiography and DSA regarding the number of diagnostic segments in the thigh was not significant (P = .50). A significantly higher number of calf and foot segments was considered diagnostic at TRICKS MR angiography than at standard MR angiography (P < .025). Sixteen of 26 segments in the foot that were considered nondiagnostic at DSA were considered diagnostic at TRICKS MR angiography. Average sensitivity of standard MR angiography for depicting hemodynamically significant arterial stenosis was 84% (reader 1) and 83% (reader 2) in the thigh and 78% (reader 1) and 80% (reader 2) in the calf. For both readers, average specificity was 97% in the thigh and 90% in the calf. Sensitivity and specificity of TRICKS MR angiography in the calf and foot were improved compared with those at standard MR angiography. TRICKS MR angiography of the distal calf and pedal vessels is superior to standard MR angiography regarding the number of diagnostic segments and assessment of the degree of luminal narrowing.

Adaptive bilateral breast MRI using projection reconstruction time‐resolved imaging of contrast kinetics

To introduce a bilateral implementation of an adaptive imaging technique in which both dynamic and high resolution breast MR images are acquired simultaneously. Adaptive three-dimensional bilateral breast imaging in the sagittal plane was achieved by combining two elements: a projection reconstruction time-resolved imaging of contrast kinetics (PR-TRICKS) k-space trajectory and a slab interleaved sequence that imaged alternate breasts every TR. A pilot study was performed to evaluate image quality and contrast uptake behavior, using eight patients with previously identified benign lesions. Adaptive reconstruction demonstrated breast lesions in all eight women with similar image quality and signal-to-noise ratio (SNR) to Cartesian images with comparable imaging parameters. Contrast enhancement curves covering the entire postinjection time period were obtained from the dynamic images and in one case compared to previous enhancement profiles from a conventional Cartesian trajectory. Bilateral dynamic and high spatial resolution images with high SNR can be achieved in a clinically feasible manner, providing both kinetic and morphologic analysis with a single data set. This may obviate the need for multiple MRI examinations for a thorough breast MRI workup.

High‐resolution, time‐resolved MRA provides superior definition of lower‐extremity arterial segments compared to 2D time‐of‐flight imaging

To evaluate a novel time-resolved contrast-enhanced (CE) projection reconstruction (PR) magnetic resonance angiography (MRA) method for identifying potential bypass graft target vessels in patients with Class II-IV peripheral vascular disease. Twenty patients (M:F = 15:5, mean age = 58 years, range = 48-83 years), were recruited from routine MRA referrals. All imaging was performed on a 1.5 T MRI system with fast gradients (Signa LX; GE Healthcare, Waukesha, WI). Images were acquired with a novel technique that combined undersampled PR with a time-resolved acquisition to yield an MRA method with high temporal and spatial resolution. The method is called PR hyper time-resolved imaging of contrast kinetics (PR-hyperTRICKS). Quantitative and qualitative analyses were used to compare two-dimensional (2D) time-of-flight (TOF) and PR-hyperTRICKS in 13 arterial segments per lower extremity. Statistical analysis was performed with the Wilcoxon signed-rank test. Fifteen percent (77/517) of the vessels were scored as missing or nondiagnostic with 2D TOF, but were scored as diagnostic with PR-hyperTRICKS. Image quality was superior with PR-hyperTRICKS vs. 2D TOF (on a four-point scale, mean rank = 3.3 +/- 1.2 vs. 2.9 +/- 1.2, P < 0.0001). PR-hyperTRICKS produced images with high contrast-to-noise ratios (CNR) and high spatial and temporal resolution. 2D TOF images were of inferior quality due to moderate spatial resolution, inferior CNR, greater flow-related artifacts, and absence of temporal resolution. PR-hyperTRICKS provides superior preoperative assessment of lower limb ischemia compared to 2D TOF.

MR angiography of aberrant left subclavian artery arising from right-sided thoracic aortic arch

Right-sided thoracic aortic arch with aberrant left subclavian artery is an uncommon entity that is usually asymptomatic, but may present in adults with symptoms of dysphagia. Cross-sectional imaging such as CT or MR is often required to conclusively diagnose this condition, which may be suggested by chest radiograph or barium swallow. MRI including TRICKS (time-resolved imaging of contrast kinetics) magnetic resonance angiography (MRA) was utilized in the evaluation of a 40-year-old man presenting with dysphagia and abnormal barium swallow study. TRICKS MRA is a recently developed MRA technique, which can provide multiple high-resolution images of the thoracic vessels with a high temporal resolution without the need for timing doses of gadolinium contrast or multiple injections.

Time-resolved 3D MR angiography of the abdomen with a real-time system.

This study reports on the implementation of a real-time MR acquisition, reconstruction, and display system on standard hardware for 3D contrast-enhanced MR abdominal angiography. The system allows for dynamic imaging of the contrast passage with good spatial resolution in a single breathhold. It is capable of synchronously acquiring and processing multiple coil data. Bolus arrival can be detected confidently from the display of MIP images from sagittal 3D slabs with moderate spatial resolution. Upon detection of the contrast agent, the patient is asked to hold their breath and a novel 3D acquisition is started for a coronal volume. Temporal imaging within the breathhold is achieved through applying a modified time-resolved imaging of contrast kinetics (TRICKS) technique with elliptical centric view ordering. The technique displays contrast passage from the arterial phase through enhancement of the hepatic venous system. It also provides the ability to quantify motion of the diaphragm over a long breathhold.

Combined time‐resolved and high‐spatial‐resolution 3D MRA using an extended adaptive acquisition

To combine the benefits of time-resolved dynamic imaging and single elliptical centric acquisitions in a reasonable scan time. A time series of images with moderate spatial resolution was acquired using the 3D Time-Resolved Imaging of Contrast KineticS (3D TRICKS) technique with elliptical centric encoding during contrast arrival. Following venous opacification, a complete large centrically encoded k-space volume was acquired. The high-spatial-frequency portions of this volume were combined with a 3D TRICKS time frame to form a high-resolution image. An additional single image is formed by suppressing background and signal averaging all acquired data, including post-venous low-spatial-frequency data. For this image, 2D temporal correlation analysis is used to suppress low-spatial-frequency vein contributions. Arrival time and spatial correlations are used to suppress background. The 3D TRICKS time frame may be selected to ensure a combined high-resolution image that has optimal central k-space sampling for any vascular region. The single image formed by signal averaging all acquired data has increased contrast-to-noise (CNR) and signal-to-noise (SNR) ratios. The advantages of time-resolved and high-spatial-resolution imaging were combined using an extended dual-phase acquisition. Some SNR and CNR gain was achieved by signal averaging. This process is facilitated by background and vein suppression.