Time-spatial Labeling Inversion Pulse Research Articles

Physiological variability in CSF motion using magnetic resonance time spatial labeling inversion pulse (Time-SLIP) - real time imaging

The ideal tracer for studying CSF dynamics is CSF itself. In time spatial labeling inversion pulse (Time-SLIP), MR radiofrequency pulses convert specific volumes of CSF into an endogenous tracer. CSF dynamics can then be observed under physiological and pathophysiological conditions. A gate-free and fast image acquisition technique like Time-SLIP is necessary to visualize natural CSF motion, whose behavior varies with cardiac pulsation and respiration.

Time-SLIP を用いた心電同期併用法3D True SSFP シーケンスによる骨盤部非造影MRA―移植腎動脈と吻合される右内腸骨動脈の描出評価のための基礎的検討―

To evaluate whether electrocardiography-gated is useful in non-contrast-enhanced MRA with time-spatial labeling inversion pulse (Time-SLIP) in renal transplantation patients compared with respiration-triggered free-breathing. Simulation-based analyses of black blood time interval (BBTI) values for spatial selective inversion-recovery pulse and electrocardiography rates were performed, and confirmed on human subjects using a three-dimensional (3D) coherent steady-state free precession (SSFP) sequence on a 1.5 tesla Toshiba MRI scanner. Signal acquisition interval and BBTI values in which signal of a water tissue becomes the null point showed a strong correlation, and successfully suppressed signals from the background and provided better contrast between the arteries and the background. Because electrocardiography-gated non-contrast MRA does not depend on the respiration interval, providing a contrast stable, it was suggested to be an effective screening tool for evaluation of pelvic arteries.

Non-contrast-enhanced MR portography and hepatic venography with time-spatial labeling inversion pulses: Comparison of imaging with the short tau inversion recovery method and the chemical shift selective method

PurposeTo compare and evaluate images of non-contrast enhanced magnetic resonance (MR) portography and hepatic venography acquired with two different fat suppression methods, the chemical shift selective (CHESS) method and short tau inversion recovery (STIR) method. Materials and methodsTwenty-two healthy volunteers were examined using respiratory-triggered three-dimensional true steady-state free-precession with two time-spatial labeling inversion pulses. The CHESS or STIR methods were used for fat suppression. The relative signal-to-noise ratio and contrast-to-noise ratio (CNR) were quantified, and the quality of visualization was scored. ResultsImage acquisition was successfully conducted in all volunteers. The STIR method significantly improved the CNRs of MR portography and hepatic venography. The image quality scores of main portal vein and right portal vein were higher with the STIR method, but there were no significant differences. The image quality scores of right hepatic vein, middle hepatic vein, and left hepatic vein (LHV) were all higher, and the visualization of LHV was significantly better (p<0.05). ConclusionThe STIR method contributes to further suppression of the background signal and improves visualization of the portal and hepatic veins. The results support using non-contrast-enhanced MR portography and hepatic venography in clinical practice.

Current and emerging MR imaging techniques for the diagnosis and management of CSF flow disorders: a review of phase-contrast and time-spatial labeling inversion pulse.

This article provides an overview of phase-contrast and time-spatial labeling inversion pulse MR imaging techniques to assess CSF movement in the CNS under normal and pathophysiologic situations. Phase-contrast can quantitatively measure stroke volume in selected regions, notably the aqueduct of Sylvius, synchronized to the heartbeat. Judicious fine-tuning of the technique is needed to achieve maximal temporal resolution, and it has limited visualization of CSF motion in many CNS regions. Phase-contrast is frequently used to evaluate those patients with suspected normal pressure hydrocephalus and a Chiari I malformation. Correlation with successful treatment outcome has been problematic. Time-spatial labeling inversion pulse, with a high signal-to-noise ratio, assesses linear and turbulent motion of CSF anywhere in the CNS. Time-spatial labeling inversion pulse can qualitatively visualize whether CSF flows between 2 compartments and determine whether there is flow through the aqueduct of Sylvius or a new surgically created stoma. Cine images reveal CSF linear and turbulent flow patterns.

Direct visualization of pancreatic juice flow using unenhanced MRI with spin labeling can be aid in diagnosing chronic pancreatitis.

The purpose of this study is to prospectively assess whether direct visualization of pancreatic juice flow using an unenhanced MRI technique with spin labeling can aid in the diagnosis of chronic pancreatitis. Ten healthy volunteers and 50 patients who were categorized as having no chronic pancreatitis (n = 11), early chronic pancreatitis (n = 7), or established chronic pancreatitis (n = 32) underwent MRI, including direct pancreatic juice visualization using a flow-out technique with a time-spatial labeling inversion pulse, comprising a nonselective inversion recovery pulse immediately followed by a spatially selective inversion labeling pulse. The mean velocities and volumes of pancreatic juice excretion were also obtained. Variance tests were used to evaluate the clinical groups with respect to the appearance rate and mean velocity; the Kruskal-Wallis test was used for volume. There were no significant differences between healthy volunteers and patients with no chronic pancreatitis. The appearance rate, mean velocity, and volume of pancreatic juice excretion tended to decrease with the degree of chronic pancreatitis. Although the difference in these values was statistically significant between the healthy group and the established chronic pancreatitis group, the values of the early group and other groups were not statistically significant. There was a significant correlation between the appearance rate of pancreatic juice and the clinical groups (τ = -0.4376, p = 0.0015). The measurement of directly visualized pancreatic juice flow may aid in establishing the diagnosis of chronic pancreatitis.

Nonenhanced renal MR angiography using steady-state free precession (SSFP) and time-spatial labeling inversion pulse (Time-SLIP): repeatability and comparison of different tagging location

To prospectively determine the repeatability of noncontrast-enhanced renal arterial angiography with steady-state free precession (SSFP) and time-spatial labeling inversion pulse (Time-SLIP), and to compare the visibility of renal artery and its branches when different locations of tagging pulse were placed. Thirty-six young healthy volunteers were enrolled in this study and were twice examined by noncontrast-enhanced renal arterial angiography with SSFP and Time-SLIP in 1.5T MR scanner. Measurement error and repeatability were assessed for each of the five major parameters [vessel-to-kidney ratio (VKR), grade of renal arterial branching, grading of image quality, diameter and area of the main renal artery] using the Bland-Altman plot. Two independent observers recorded the values of the parameters; Inter- and intra-observer agreement was assessed using the intraclass correlation coefficients (ICCs). The same parameters, acquired at the tagging pulse placed just above the superior poles of both kidneys or closer to the main renal arteries, were compared using the Wilcoxon signed-rank test. Grading of arterial branching by the Time-SLIP SSFP was satisfactorily reproducible with the mean score of greater 3.83 indicating the visibility of branches within the renal parenchyma. The image quality was excellent for Segment I (the main trunk of renal artery) and good for Segment II (segmental branches pre renal parenchyma) and III (vessels within the renal parenchyma) with a satisfying repeatability between two examinations and a good inter- and intra-observer agreement. The ICCs for the inter- and intra-observer measurements of both diameter and area of the main arteries ranged from 0.781 to 0.934, indicating very good agreement. The repeatability of VKR was poor between the two examinations and at the two different tagging pulse locations. The position of tagging pulse in the origination of the main renal arteries was better than in the superior poles of kidneys as it provided a better visualization of arterial branches. Noncontrast-enhanced renal artery angiography with SSFP and Time-SLIP yields reliable and reproducible visualization of normal renal arteries. Localization of the tagging pulse closer to the main renal arteries provides better visibility of renal artery and its branches than the tag placement just above the superior poles of both kidneys.

More Peripheral Visualization of Hepatic Arteries by Using Respiratory-Triggered 3D True Steady-State Free-Precession Projection Magnetic Resonance Angiographic Sequences with Time-Spatial Labeling Inversion Pulse

Purpose: To evaluate respiratory-triggered three-dimensional (3D) true steady-state free-precession (SSFP) projection magnetic resonance angiographic sequences with time-spatial labeling inversion pulse (Time-SLIP) for visualizing the hepatic arteries and to optimize the image acquisition protocol. Materials and Methods: A 1.5-T clinical magnetic resonance imager was used to perform abdominal magnetic resonance angiography (MRA) in 25 consecutive patients before transcatheter arterial chemoembolization or surgery. We compared two selective space-labeling inversion pulse (tag pulse) patterns (Patterns I and II, oblique and parallel tag pulses, respectively). Two experienced radiologists evaluated the number of hepatic arterial branches visible on the acquired MRA images, and the results were referenced with those on images from intra-arterial digital subtraction angiography. Results: Images were acquired from all patients. The two radiologists clearly visualized branches of the left and right hepatic arteries. More peripheral hepatic arterial branches were identified in MRA images captured by using tag pulse Pattern I than in those acquired by using Pattern II (P P > 0.05). Conclusion: Non-contrast-enhanced Time-SLIP hepatic MRA with true SSFP allowed selective visualization of peripheral hepatic vessels.

Automated flow quantification for spin labeling MR imaging

The Time-Spatial Labeling Inversion Pulse (Time-SLIP) technique enables tracing of regional fluid flows without the use of contrast medium. The objective of this study is to quantify automatically slow and complex fluid flows using the Time-SLIP technique. Series images were acquired with a 1.5-T MRI scanner using the Time-SLIP technique with half-Fourier fast spin-echo (FSE) and balanced steady-state free precession (bSSFP) sequences. In this method, labeled fluid regions in images were automatically detected based on image processing techniques for a given point. The flow velocity of the labeled fluid region was calculated using regression fitting for the region's position. To evaluate our method, constant and non-constant laminar flows in a water phantom were studied. In addition, volunteer experiments were conducted to quantify the flow of cerebrospinal fluid. In the constant flow experiments the correlation factor r (2) between the flow velocity calculated from our method and the laminar peak velocity calculated from the volumetric flow rate was 0.9992 for the FSE sequence and 0.9982 for the bSSFP sequence. In the non-constant flow study, the flow velocity was calculated accurately for any period inversion time even when the flow velocity was changed, and the quantification error was negligible. In the volunteer experiments, r (2) between the flow velocity calculated by the proposed method and that obtained by manual annotation was 0.9383. The experimental results showed that our proposed method can quickly and accurately provide information on flow velocities especially for slower and complex flows. Our method is, therefore, expected to be useful in diagnostic support systems.

Influence of respiration on cerebrospinal fluid movement using magnetic resonance spin labeling

BackgroundMagnetic resonance imaging (MRI) cardiac gated phase contrast (PC) cine techniques have non-invasively shown the effect of the cardiac pulse on cerebrospinal fluid (CSF) movement. Echo planar imaging (EPI) has shown CSF movement as influenced by both cardiac pulsation and respiration. Previously, it has not been possible to visualize CSF movement in response to respiration non-invasively. The present study was undertaken to do so.MethodsThe effect of respiration on CSF movement was investigated using a non-contrast time-spatial labeling inversion pulse (Time-SLIP) with balanced steady-state free precession (bSSFP) readout. CSF movement was observed in the intracranial compartment in response to respirations in ten normal volunteers. To elucidate the respiration effect, the acquisition was triggered at the beginning of deep inhalation, deep exhalation and breath holding.ResultsBy employing this respiration-induced spin labeling bSSFP cine method, we were able to visualize CSF movement induced by respiratory excursions. CSF moved cephalad (16.4 ± 7.7 mm) during deep inhalation and caudad (11.6 ± 3.0 mm) during deep exhalation in the prepontine cisternal area. Small but rapid cephalad (3.0 ± 0.4 mm) and caudad (3.0 ± 0.5 mm) movement was observed in the same region during breath holding and is thought to reflect cardiac pulsations.ConclusionsThe Time-SLIP bSSFP cine technique allows for non-invasive visualization of CSF movement associated with respiration to a degree not previously reported.

Non-contrast-enhanced MR portography with balanced steady-state free-precession sequence and time-spatial labeling inversion pulses: Comparison of imaging with flow-in and flow-out methods

To compare and evaluate images of non-contrast-enhanced MR portography acquired with two different methods, the flow-in and flow-out methods. Twenty-five healthy volunteers were examined using respiratory-triggered three-dimensional balanced steady-state free-precession (SSFP) with two selective inversion recovery pulses (flow-in method) and one tagging pulse and one nonselective inversion recovery pulse (flow-out method). For quantitative analysis, vessel-to-liver contrast (Cv-l) ratios of the main portal vein (MPV), right portal vein (RPV), and left portal vein (LPV) were measured. The quality of portal vein visualization was scored using a four-point scale. The Cv-ls of the MPV, RPV, and LPV were all significantly higher with the flow-out than flow-in method (MPV = 0.834 ± 0.06 versus 0.711 ± 0.10; RPV = 0.861 ± 0.04 versus 0.729 ± 0.11; LPV = 0.786 ± 0.08 versus 0.545 ± 0.22; P < 0.0001). In all analyses of vessel visibility, non-contrast-enhanced MR portography with the flow-out method showed higher scores than with the flow-in method. With the flow-out method, visual scores of the MPV, RPV, portal vein branches of segments 4 (P4), and 8 (P8) were significantly better than with the flow-in method (MPV = 3.4 ± 0.7 versus 2.6 ± 0.9; RPV = 4.0 ± 0.0 versus 3.5 ± 0.9; P4 = 2.8 ± 1.3 versus 1.6 ± 1.0; P8 = 4.0 ± 0.0 versus 2.9 ± 1.1; P < 0.05). Non-contrast-enhanced MR portography with the flow-out method improves the visualization of the intrahepatic portal vein in comparison with the flow-in method. J. Magn. Reson. Imaging 2014;40:583-587. © 2013 Wiley Periodicals, Inc.

Identification of peripheral vessels in oral and maxillofacial regions on magnetic resonance angiography obtained using a balanced steady-state free-precession sequence with a time-spatial labeling inversion pulse and using fresh blood imaging

To elucidate the characteristics of visualizing thin main peripheral vessels in oral and maxillofacial regions of 3-dimensional magnetic resonance angiography (MRA) using a balanced steady-state free-precession (SSFP) sequence with a time-spatial labeling inversion pulse (time-SLIP) and using fresh blood imaging (FBI). The conspicuity of blood vessels and the characteristics on MRA using SSFP with a time-SLIP was compared with those on MRA using FBI in 20 healthy participants. The conspicuity of the main peripheral arteries was significantly higher on MRA using SSFP with a time-SLIP than on MRA using FBI. MRA scans using SSFP were obtained in all participants, and scans using FBI were obtained in 16 of 20 participants. An electrocardiogram was unnecessary when using SSFP but was necessary when using FBI. MRA obtained using SSFP with a time-SLIP is a useful technique to visualize thin main peripheral arteries in the oral and maxillofacial regions without contrast medium.

Time spatial labeling inversion pulse magnetic resonance angiography in pregnancy with adenomyosis

Time spatial labeling inversion pulse (Time-SLIP) is a non-contrast magnetic resonance angiography (MRA) technique. No cases in which this technique was used during pregnancy have been reported. We report herein two cases with adenomyosis of the same size and location that underwent Time-SLIP MRA during pregnancy. In case 1, the blood flow within the adenomyosis was poor, and the uterine blood flow toward the placenta was normal, resulting in no fetal growth restriction (FGR). In case 2, the blood flow within the adenomyosis was quite rich, and placental blood flow seemed decreased, resulting in severe FGR. As well as the Doppler ultrasonography, Time-SLIP MRA was useful for evaluating uterine blood flow during pregnancy. This is the first report of the use of Time-SLIP MRA during pregnancy.

Parameter optimization for non-contrast-enhanced selective magnetic resonance portography imaging

To evaluate subtraction images acquired with 3D true steady-state free-precession(SSFP)sequence combined with time-spatial labeling inversion pulse(T-SLIP)for selective and non-contrast-enhanced(non-CE)visualization of the portal venous system,and explore the optimization of this protocol. Totally 13 healthy volunteers were recruited.Respiratory-triggered 3D true SSFP sequences on a 1.5T MRI system combined with T-SLIP placed on the spleen and mesenteric area were performed.The portographic images were generated from the subtraction between the pulse on and off images.According to the difference in inversion time(TI)of T-SLIP,four image groups group A(TI of 1300 ms),group B(TI of 1100 ms),group C(TI of 900 ms)and group D(TI of 700 ms),were assigned and compared to detect the optimal TI for portography.For quantitative analysis,the signal intensity(SI)of left and right liver lobe,the large vessels as main,right and left portal vein(MPV,RPV and LPV,respectively)and small vessels as branches of segments four(P4),six(P6)and eight(P8)were measured.The relative SI of MPV,RPV and LPV,as well as P4,P6 and P8 were also compared.For qualitative evaluation,the quality score of visualization was also evaluated using a 4-point scale.One-Way ANOVA and LSD test were used for comparison of quantitative data,and Friedman signed rank test was used for comparison of qualitative scores. In 52 sequences of 13 volunteers,the selective visualization of the portal vein was all successfully conducted.Quantitative evaluation showed significant increased SI at the left lobe between C and D groups and A and B groups(comparison of group C to group A and BP=0.004,0.011;comparison of group D to group A and BP=0.001,0.004),while relative SI of LPV of groups C and D were lower than groups A and B(comparison of group C to group A and BP=0.015,0.015;comparison of group D to group A and BP=0.000,0.000).The relative SI of MPV in group D were decreased than groups A(P=0.000),B(P=0.000),and C(P=0.019).There was no significant difference in relative SI of small vessels among four groups(P>0.05).The image score of portal vessels in four groups also showed no differences(P>0.05). 3D true SSFP scan with T-SLIP enabled selective non-CE visualization of the portal vein with digital subtraction method.A fixed TI of both 1300 and 1100 ms can be preferable.

Feasibility of MR perfusion-weighted imaging by use of a time-spatial labeling inversion pulse

Perfusion-weighted imaging (PWI) by use of arterial spin labeling (ASL) has been introduced to the clinical setting. However, it is not widely available because it requires specialized pulse sequences. Imaging using a time-spatial labeling inversion pulse (time-SLIP), which is a magnetic resonance angiography (MRA) technique that is based on ASL, can be used in various situations. In this study, we examined the feasibility of time-SLIP PWI. Two types of time-SLIP sequences were evaluated: (1) a single inversion recovery (IR) pulse sequence, which is the same as that used in conventional time-SLIP MRA except for the timing of data acquisition, and (2) a dual IR pulse sequence, where a second, non-selective, IR pulse was added during the inflow time to suppress background signals. Subtraction processing is performed between the "on" and "off" settings of the first IR pulse (time-SLIP tag) to obtain PWI. The average signal intensity was measured in a uniform phantom as the residual of the background, and in five healthy subjects as the perfusion signal. The average signal-to-noise ratio (SNR) was also measured in the five subjects. All imaging was performed with a 1.5-T MR scanner. Images using the dual IR method showed lower background signals and higher perfusion signals compared with images using the single IR method. However, the SNR was lower in images with the dual IR method. These results demonstrate that a time-SLIP, which is an MRA method, can be used for obtaining cerebral PWI simply by adjusting the imaging parameters.

Unenhanced Magnetic Resonance Angiography with Time-Spatial Labeling Inversion Pulse for Evaluating Visceral Artery Aneurysms after Endosaccular Packing with Detachable Coils: Preliminary Results

The aim of this brief report is to compare unenhanced magnetic resonance (MR) angiography with time-spatial labeling inversion pulse (Time-SLIP) with conventional digital subtraction angiography (DSA) in assessing degree of saccular visceral artery aneurysm (VAA) occlusion after endosaccular packing with detachable coils. Eight patients with VAAs (five renal and three splenic artery aneurysms) were enrolled in this study. VAA occlusion rates based on Time-SLIP MR angiography were complete occlusion in four patients, neck remnants in three patients, and body filling in one patient. These findings corresponded with the DSA findings.

Corticomedullary differentiation of the kidney: Evaluation with noncontrast‐enhanced steady‐state free precession (SSFP) MRI with time‐spatial labeling inversion pulse (time‐SLIP)

To assess whether noncontrast-enhanced steady-state free precession (SSFP) magnetic resonance imaging (MRI) with time-spatial labeling inversion pulse (Time-SLIP) can improve the visibility of corticomedullary differentiation of the normal kidney. A series of noncontrast-enhanced SSFP MRI with Time-SLIP were performed in 20 patients by using various inversion times (TIs); 500-1800 msec in increments of 100 msec. In-phase (IP) and opposed-phase (OP) MR images were also obtained. The signal intensity (SI) of the renal cortex and medulla was measured to calculate corticomedullary contrast ratio (SI of cortex/medulla). Additionally, the visibility of corticomedullary differentiation was visually categorized using a four-point scale. In SSFP with Time-SLIP, corticomedullary contrast ratio was highest with TI of 1200 msec in eight subjects (40%), followed by 1100 msec in seven (35%) and 1000 msec in three (15%). The corticomedullary contrast ratio in SSFP with optimal Time-SLIP (4.93 ± 1.25) was significantly higher (P < 0.001) than those of IP (1.46 ± 0.12) and OP (1.43 ± 0.14). The visibility of corticomedullary differentiation was significantly better (P < 0.001) in SSFP images with Time-SLIP (averaged grade = 4.0) than in IP images (averaged grade = 2.63) and OP images (averaged grade = 2.05). SSFP MRI with Time-SLIP can improve the visibility of renal corticomedullary differentiation without using contrast agents.

Effective surgical intervention for schizophrenia‐like symptoms and low event‐related potentials caused by arachnoid cyst

ARACHNOID CYSTS CAN occur wherever there is arachnoid tissue, although nearly half of all arachnoid cysts arise in the temporal fossa–Sylvian fissure. In general, clinical manifestations of arachnoid cyst are often mild. Several articles have suggested that there is an etiological relationship between arachnoid cyst and psychiatric symptoms.1 A 24-year-old man first presented with compulsive checking at the age of 21 years. In addition, he had experienced delusions of persecution and auditory hallucinations. He had no neurological abnormality and was treated with antipsychotic medication. The antipsychotics, however, did not improve the psychotic symptoms. At that time, computed tomography showed an arachnoid cyst in his left middle cranial fossa. The basic rhythm on electroencephalogram (EEG) was posterior dominant alpha wave. The psychotic symptoms were considered to be caused by the arachnoid cyst because of the antipsychotics' low effectiveness. Magnetic resonance imaging (MRI) showed a large anteromedial left temporal fossa arachnoid cyst (80 mm in diameter) expanding into the left Sylvian fissure. Event-related potentials (ERP), such as P300, and mismatch negativity (MMN) were low in amplitude. Some reports have suggested that surgical intervention for arachnoid cyst improved psychotic symptoms.2 Therefore, endoscopic fenestration of the cyst was performed. The delusions and hallucinations improved postoperatively, and the patient was discharged. The delusions of persecution, however, later increased. MRI using time–spatial labeling inversion pulse showed inadequate flow of cerebrospinal fluid through the fenestra. Hence, another craniotomy was performed. Fenestra closure caused by arachnoid regeneration was found during this procedure. After partial removal of the cyst wall, the delusions remitted partially. The amplitude of P300 and MMN in the frontocentral region increased after each surgery. In contrast, MMN amplitude in the bilateral mastoid region showed no change. There was no difference between the basic rhythm and amplitudes of EEG before and after surgery. This patient provided written, informed consent. In some reports, left temporal arachnoid cysts were found to be associated with schizophrenia-like symptoms.2 Recent studies have demonstrated volume loss in the left superior temporal gyrus in schizophrenia.3 The temporal lobe is regarded as an important region for P300 and MMN, the amplitudes of which are reduced in schizophrenia and the other psychoses. This is one of the reproducible abnormal biological findings in schizophrenia. Therefore, small P300 and MMN amplitude, schizophrenia-like psychotic symptoms, and left temporal lobe volume loss are closely related.3 In the present case, the compressed and/or defective development of the temporal lobe due to the arachnoid cyst probably caused the low P300 and MMN amplitudes. If low ERP were of organic origin, the amplitudes would improve.

Visualization of pancreatic juice movement using unenhanced MR imaging with spin labeling: Preliminary results in normal and pathophysiologic conditions

To visualize the movement of pancreatic juice noninvasively by using an unenhanced magnetic resonance (MR) imaging technique. Institutional review board approval and informed consent were obtained for this study. A flow-out technique of time-spatial labeling inversion pulse (SLIP) technique was applied using both nonselective and selective inversion pulses to label, or tag, pancreatic juice to move out of the region. Ten normal (eight men, two women; age range, 22-61 years; mean age, 35 years) and two pathologic conditions were examined on a commercially available 1.5 Tesla MR imager with quadrature-detected phased-array coils. All images were evaluated by two radiologists to assess depiction of the pancreatic juice movement or pancreatic juice reflux as compared to the pancreatic duct or the common bile duct on MRCP obtained before time-SLIP examination. The tagged pancreatic juice was satisfactory visualized after applying the pulse labeling. Noninvasive visualization of pancreatic juice movement, including normal pancreatic juice movement and reflux from the main pancreatic duct into the common bile duct, was possible by using the unenhanced time-SLIP technique. Noninvasive visualization of pancreatic juice movement is possible by using the unenhanced MR imaging time-SLIP technique.

Utility of time-resolved three-dimensional magnetic resonance digital subtraction angiography without contrast material for assessment of intracranial dural arterio-venous fistula

Intracranial dural arteriovenous fistula (DAVF) is an arteriovenous shunting disease of the dura. Magnetic resonance angiography (MRA) is expected to be a safer alternative method in evaluation of DAVF, compared with invasive intra-arterial digital subtraction angiography (IADSA). To evaluate the diagnostic use of time-spatial labeling inversion pulse (Time-SLIP) three-dimensional (3D) magnetic resonance digital subtraction angiography (MRDSA) without contrast material in six patients with DAVF. Images for 3D time-of-flight MRA, which has been a valuable tool for the diagnosis of DAVF but provide little or less hemodynamic information, and Time-SLIP 3D MRDSA, were acquired for each patient. The presence, side, and grade of the disease were evaluated according to IADSA. In all patients, the presence and side of the DAVF were correctly identified by both 3D time-of-flight MRA and Time-SLIP 3D MRDSA. Cortical reflux present in a patient with a grade 2b DAVF was not detected by Time-SLIP 3D MRDSA, when compared with IADSA findings. Time-SLIP 3D MRDSA provides hemodynamic information without contrast material and is a useful complementary tool for diagnosis of DAVF.

Time spatial labeling inversion pulse cerebral MR angiography without subtraction by use of dual inversion recovery background suppression

Time-spatial labeling inversion pulse (time-SLIP), which is a technique of nonenhanced magnetic resonance angiography (MRA) based on arterial spin labeling (ASL), is used in various situations. Although subtraction between the images obtained with and without ASL is usually employed in cerebral time-SLIP MRA, to reduce the imaging time, dual inversion recovery (IR) has been applied for suppression of the background signals in this study. Appropriate timings for the 1st IR, 2nd IR, and the interval of data acquisition were investigated using computer simulation and a phantom experiment. With a short interval of data acquisition, the visibility of the simulated vessel was inadequate because replacement of the suppressed flow was insufficient. With a long interval of data acquisition, the contrast between the vessel and background was reduced. The reasons for this appeared to be the following: the longitudinal magnetization of the replaced flow is reduced because of the prolonged 2nd inversion time, causing a mismatch of the null point between the calculated and the actual values to become prominent. As a result, 3-4 s seemed to be an appropriate interval for data acquisition. Sufficient angiographic information could be obtained by use of dual IR background suppression in a volunteer study. With this technique, cerebral time-SLIP MRA can be performed in half of the imaging time required with the conventional subtraction technique.