Timing bolus dynamic contrast‐enhanced (DCE) MRI assessment of hepatic perfusion: Initial experience

Purpose

To assess whether dynamic contrast‐enhanced (DCE) MRI timing bolus data from routine clinical examinations can be postprocessed to obtain hepatic perfusion parameters for diagnosing cirrhosis.

Materials and Methods

We retrospectively identified 57 patients (22 with cirrhosis and 35 without cirrhosis) who underwent abdominal MRI, which included a low‐dose (2 mL gadodiamide) timing bolus using a volumetric spoiled gradient echo T1‐weighted sequence through the abdomen. Using a dual‐input single‐compartment model, the following perfusion parameters were measured: arterial, portal, and total blood flow; arterial fraction; mean transit time; and distribution volume. Those parameters were compared between patients with and without cirrhosis using t‐tests. Receiver operating characteristic (ROC) curve analysis was used to identify the perfusion parameters that can best predict the presence of cirrhosis.

Results

The hepatic arterial fraction, arterial flow, and distribution volume in patients with cirrhosis (27.7 ± 8.3%, 44.8 ± 14.1 mL/minute/100 g, and 16.3 ± 4.5%, respectively) were significantly higher than those without cirrhosis (18.7 ± 4.4%, 28.5 ± 11.7 mL/minute/100 g, and 14.0 ± 4.2%, respectively; P < 0.05 for all). ROC analysis showed arterial fraction as the best predictor of cirrhosis, with sensitivity of 73% and specificity of 86%.

Conclusion

Timing bolus DCE MR images from routine examinations can be postprocessed to yield potentially useful hepatic perfusion parameters. J. Magn. Reson. Imaging 2009;29:1317–1322. © 2009 Wiley‐Liss, Inc.     

Dilution method of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd‐EOB‐DTPA)‐enhanced magnetic resonance imaging (MRI)

Purpose

To elucidate whether a contrast agent dilution method (dilution method), in which gadoxetate disodium (Gd‐EOB‐DTPA) is diluted with saline, is useful for good‐quality arterial‐phase images.

Materials and Methods

In this study we observed 494 hypervascular hepatocellular carcinomas (HCCs) in 327 patients with chronic liver disease. Three Gd‐EOB‐DTPA injection methods were adopted for comparison: 1) test injection method (undiluted Gd‐EOB‐DTPA and modified scan delay), in which a test dose of 0.5 mL of Gd‐EOB‐DTPA was injected to determine scan delay; 2) conventional method (undiluted Gd‐EOB‐DTPA and fixed scan delay); and ( 3 ) dilution method (diluted Gd‐EOB‐DTPA and fixed scan delay), in which Gd‐EOB‐DTPA was diluted to 20 mL with saline. Lesion‐liver contrast was calculated. Image quality and lesion detectability were evaluated by two radiologists blinded to the injection methods.

Results

The lesion‐liver contrast of the dilution method was significantly higher than that of the other two methods. Lesion detectability of the conventional method (64%) was significantly lower than that of the other two methods (contrast agent dilution method, 95%; test injection method, 93%). The image quality of the contrast agent dilution method was significantly better than that of the other two methods.

Conclusion

The dilution method contributed to improved image quality, high lesion‐liver contrast, and high lesion detectability in the arterial‐phase images of GD‐EOB‐DTPA‐enhanced MRI. J. Magn. Reson. Imaging 2009;30:849–854. © 2009 Wiley‐Liss, Inc.     

Assessing liver function using dynamic Gd‐EOB‐DTPA‐enhanced MRI with a standard 5‐phase imaging protocol

Purpose:

To evaluate liver function obtained by tracer‐kinetic modeling of dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) data acquired with a routine gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd‐EOB‐DTPA)‐enhanced protocol.

Materials and Methods:

Data were acquired from 25 cases of nonchronic liver disease and 94 cases of cirrhosis. DCE‐MRI was performed with a dose of 0.025 mmol/kg Gd‐EOB‐DTPA injected at 2 mL/sec. A 3D breath‐hold sequence acquired 5 volumes of 72 slices each: precontrast, double arterial phase, portal phase, and 4‐minute postcontrast. Regions of interest (ROIs) were selected semiautomatically in the aorta, portal vein, and whole liver on a middle slice. A constrained dual‐inlet two‐compartment uptake model was fitted to the ROI curves, producing three parameters: intracellular uptake rate (UR), extracellular volume (Ve), and arterial flow fraction (AFF).

Results:

Median UR dropped from 4.46 10^?2 min^?1 in the noncirrhosis to 3.20 in Child–Pugh A (P = 0.001), and again to 1.92 in Child–Pugh B (P < 0.0001). Median Ve dropped from 6.64 mL 100 mL^?1 in the noncirrhosis to 5.80 in Child–Pugh A (P = 0.01). Other combinations of Ve and AFF changes were not significant for any group.

Conclusion:

UR obtained from tracer kinetic analysis of a routine DCE‐MRI has the potential to become a novel index of liver function. J. Magn. Reson. Imaging 2013;37:1109–1114. © 2012 Wiley Periodicals, Inc.

     

Feasibility of semiquantitative liver perfusion assessment by ferucarbotran bolus injection in double-contrast hepatic MRI

Purpose:

To evaluate the feasibility of semiquantitative measurement of liver perfusion from analysis of ferucarbotran induced signal‐dynamics in double‐contrast liver MR‐imaging (DC‐MRI).

Materials and Methods:

In total 31 patients (21 men; 58 ± 10 years) including 18 patients with biopsy proven liver cirrhosis prospectively underwent clinically indicated DC‐MRI at 1.5 Tesla (T) with dynamic T2*‐weighted gradient‐echo imaging after ferucarbotran bolus injection. Breathing artefacts in tissue and input time curves were reduced by Savitzky‐Golay‐filtering and semiquantitative perfusion maps were calculated using a model free approach. Hepatic blood flow index (HBFI) and splenic blood flow index (SBFI) were determined by normalization of arbitrary perfusion values to the perfusion of the erector spinae muscle resulting in a semiquantitative perfusion measure.

Results:

In 30 of 31 patients the evaluated protocol could successfully be applied. Mean HBF was 7.7 ± 2.46 (range, 4.6–12.8) and mean SBF was 13.20 ± 2.57 (range, 8.5–17.8). A significantly lower total HBF was seen in patients with cirrhotic livers as compared to patients with noncirrhotic livers (P < 0.05). In contrast, similar SBF was observed in cirrhotic and noncirrhotic patients (P = 0.11).

Conclusion:

Capturing the signal dynamics during bolus injection of ferucarbotran in DC‐MRI of the liver allows for semiquantitative assessment of hepatic perfusion that may be helpful for a more precise characterisation of liver cirrhosis and focal liver lesions. J. Magn. Reson. Imaging 2012;36:168–176. © 2012 Wiley Periodicals, Inc.     

Automated perfusion-weighted MRI using localized arterial input functions

PURPOSE: To investigate the utility of an automated perfusion-weighted MRI (PWI) method for estimating cerebral blood flow (CBF) based on localized arterial input functions (AIFs) as compared to the standard method of manual global AIF selection, which is prone to deconvolution errors due to the effects of delay and dispersion of the contrast bolus. MATERIALS AND METHODS: Analysis was performed on spin- and gradient-echo EPI images from 36 stroke patients. A local AIF algorithm created an AIF for every voxel in the brain by searching out voxels with the lowest delay and dispersion, and then interpolating and spatially smoothing them for continuity. A generalized linear model (GLM) for predicting tissue outcome, and MTT lesion volumes were used to quantify the performance of the localized AIF method in comparison with global methods using ipsilateral and contralateral AIFs. RESULTS: The algorithm found local AIFs in each case without error and generated a higher area under the receiver operating characteristic (ROC) curve compared to both global-AIF methods. Similarly, the local MTT lesion volumes had the least mean squared error (MSE). CONCLUSION: Automated CBF calculation using local AIFs is feasible and appears to produce more useful CBF maps.     

Reversible heterogeneous arterial phase liver perfusion associated with transient acute hepatitis: findings on gadolinium-enhanced MRI

PURPOSE: To assess a possible correlation between active acute hepatitis and the development of abnormal liver perfusion demonstrated as heterogeneous enhancement on arterial phase gadolinium-enhanced MRI. Dynamically-enhanced MRI of the liver can detect reversible perfusion abnormalities that correlate with acute hepatitis. MATERIALS AND METHODS: Six patients presenting with symptoms and clinical findings in keeping with transient acute hepatitis underwent serial MRI of the liver throughout the course of the disease. Serial liver enzyme analysis was performed for all six patients, and histopathology was assessed for three patients. Imaging included gadolinium-enhanced arterial and venous-phase gradient-echo sequences. RESULTS: Arterial phase gadolinium-enhanced MRI showed abnormal irregular liver perfusion in the setting of acute hepatitis, and the degree of irregularity, as well as the persistence of irregular enhancement into the venous phase, correlated with the clinical severity of the disease. CONCLUSION: Acute hepatitis can cause irregular enhancement of the liver on arterial-phase, gadolinium-enhanced, gradient-echo MRI, a reversible finding that improves with clinical improvement of the disease.     

分离团注单期成像技术在MSCT泌尿系成像中的应用价值

目的 探讨分离团注单期成像技术在MSCT泌尿系疾病检查中的可行性及临床应用价值.方法 选取我院临床资料完整的泌尿系疾病患者60例,按不同扫描方法分为A、B两组各30例,A组采用常规平扫、皮质期(20 ～ 30 s)、髓质期(55 ～60 s)、排泄期(5～15 min)扫描;B组采用平扫、分离团注一次扫描;应用VR、M...     

Simultaneous measurement of arterial input function and tumor pharmacokinetics in mice by dynamic contrast enhanced imaging: effects of transcytolemmal water exchange.

A noninvasive technique for simultaneous measurement of the arterial input function (AIF) for gadodiamide (Omniscan) and its uptake in tumor was demonstrated in mice. Implantation of a tumor at a suitable location enabled its visualization in a cardiac short axis image. Sets of gated, low-resolution saturation recovery images were acquired from each of five tumor-bearing mice following intravenous administration of a bolus of contrast agent (CA). The AIF was extracted from the signal intensity changes in left ventricular blood using literature values of the CA relaxivity and a precontrast T1 map. The time-dependent 1H2O relaxation rate constant (R1 = 1/T1) in the tumor was modeled using the BOLus Enhanced Relaxation Overview (BOLERO) method in two modes regarding the equilibrium transcytolemmal water exchange system: 1) constraining it exclusively to the fast exchange limit (FXL) (the conventional assumption), and 2) allowing its transient departure from FXL and access to the fast exchange regime (FXR), thus designated FXL/FXR. The FXL/FXR analysis yielded better fittings than the FXL-constrained analysis for data from the tumor rims, whereas the results based on the two modes were indistinguishable for data from the tumor cores. For the tumor rims, the values of Ktrans (the rate constant for CA transfer from the vasculature to the interstitium) and ve (volume fraction of the tissue extracellular and extravascular space) returned from FXL/FXR analysis are consistently greater than those from the FXL-constrained analysis by a factor of 1.5 or more corresponding to a CA dose of 0.05 mmole/kg.     

Per‐subject characterization of bolus width in pulsed arterial spin labeling using bolus turbo sampling

Quantification of cerebral blood flow using QUIPSSII pulsed arterial spin labeling requires that the QUIPSS saturation delay TI₁ is shorter than the natural temporal bolus width. Yet the duration of the bolus of tagged spins entering the region of interest varies during vasoactive stimuli such as gaseous challenges or across subjects due to differences in blood velocity or vessel geometry. A new technique, bolus turbo sampling, to rapidly measure the duration of the inflowing bolus is presented. It allows to optimize the arterial spin labeling acquisition to ensure reliable quantification of perfusion while maximizing the arterial spin labeling signal by avoiding the use of unnecessarily short label durations. The average bolus width measured in the right and left middle cerebral artery territories using the bolus turbo sampling technique has a repeatability coefficient of 75 ms and correlates significantly with the TI_1,max determined from a novel multi‐TI₁ protocol (R = 0.65, P < 0.05). The possibility to measure the bolus width under hypercapnia is demonstrated. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

Assessing arterial blood flow and vessel area variations using real-time zonal phase-contrast MRI

PURPOSE: To measure peripheral artery function using a real-time phase-contrast (PC)-MRI sequence with tailored image-processing algorithms for flow computation. MATERIALS AND METHODS: An approach to real-time flow measurements was developed based on two-dimensional spatially selective excitation pulses and consecutive tailored processing of the data to derive blood flow and vessel area variations. The data acquisition strategy allows for flow measurements at high spatial and temporal resolutions of 1 mm(2) and 50 msec, respectively. In postprocessing the vessel area is automatically extracted using correlation measures in conjunction with morphological image operators. By means of in vitro and in vivo validations, it is shown that the current methods provide accurate and reproducible measurements of flow and vessel area variations. RESULTS: In vitro the comparison between the lumen area measured with the presented method and the values obtained by caliper gauge measurement showed a difference of 3.4% +/- 3.4% (mean +/- 2 SD). Similarly, the comparison between the stroke volumes determined with the presented method and by stopwatch and bucket measurements yielded a difference of 6.1% +/- 2.1%. In vivo the results from the real-time measurements for lumen area and stroke volume were compared with those from a gated PC-MRI technique with differences of 4.8% +/- 14% and 3.0% +/- 24.7%, respectively. CONCLUSION: The presented method constitutes a reliable tool set for quantifying the variations of blood flow and lumen area in the superficial femoral artery during reactive hyperemia and for studying their correlation with cardiovascular risk factors.     

Precision, signal-to-noise ratio, and dose optimization of magnitude and phase arterial input functions in dynamic susceptibility contrast MRI

PURPOSE: To determine optimal conditions for precise measurement of arterial input function (AIFs) in dynamic susceptibility contrast (DSC) perfusion MRI. MATERIALS AND METHODS: Magnitude-based (DeltaR(2)*) and phase-based (Deltaphi) AIFs were numerically simulated for several doses and baseline MRI noise levels [SNR(I(0))]. Random noise (1000 realizations) was added to real/imaginary MRI signals (derived from an internal carotid AIF), and AIF signal, noise, and signal-to-noise ratio (SNR) were determined. The optimal dose was defined as the dose that maximizes mean AIF SNR over the first-pass (SNR(mean)), rather than SNR at the AIF peak (SNR(peak)) because, compared to SNR(peak), doses predicted by SNR(mean) reduced the AIF-induced variability in cerebral blood flow (CBF) by 24% to 40%. RESULTS: The AIF SNR is most influenced by choice of AIF signal, then optimal dosing, each with little penalty. Compared to DeltaR(2)*, Deltaphi signal has 4 to 80 times the SNR over all doses and time points, and approximately 10-fold SNR(mean) at respective optimal doses. Optimal doses induce 85% to 90% signal drop for the DeltaR(2)* method, and 70% to 75% for Deltaphi, with two-fold dose errors causing approximately 1.7-fold loss in SNR(mean). Increases in SNR(I(0)) proportionally increase AIF SNR, but at a cost. CONCLUSION: AIF SNR is affected most by signal type, then dosing, and lastly, SNR(I(0)).     

Liver-vessel cancellation artifact on in-phase and out-of-phase MRI imaging: a sign of ultra-high liver fat content

Purpose:

To describe a new MRI sign, the liver‐vessel cancellation artifact, on In‐Phase and Out‐of‐Phase gradient‐echo sequences related to ultra‐high liver fat content (>90%) by qualitative histology.

Materials and Methods:

Institutional review board approval was obtained for this retrospective HIPAA‐compliant study with waived informed consent. Patients with liver steatosis were searched in MRI (n = 195) and pathology (n = 116) databases between January 1, 2008, and June 20, 2010. Two readers blindly reviewed all MR images for the presence of the liver‐vessel cancellation sign. Cross‐reference of patients with biopsy‐proven steatosis and MRI within one month was performed (n = 54; 25 males, 29 females; mean age 41.0 ± 18.9), with a population of 6 patients with ultra‐high liver fat content (1 male, 5 females; mean age 15.5 ± 11.2). Performance diagnostic tests, including sensitivity and specificity, were performed.

Results:

Liver‐vessel cancellation sign was present in all patients with ultra‐high liver fat content but in none of the remaining patients. Calculated sensitivity and specificity for the detection of ultra‐high liver fat content with this sign were 100% (95% confidence interval [CI]: 69.1–100%) and 100% (95% CI: 98.4–100%), respectively.

Conclusion:

The presence of liver‐vessel cancellation artifact around intra‐hepatic vessels is a feature of ultra‐high liver fat content. J. Magn. Reson. Imaging 2012;35:1112‐1118. © 2011 Wiley Periodicals, Inc.     

MR perfusion imaging using the arterial spin labeling technique for breast cancer

Purpose:

To investigate the feasibility of perfusion imaging using an arterial spin labeling (ASL) technique for breast cancer.

Materials and Methods:

Thirteen female patients with primary breast cancers were included in this study. All examinations were performed on 1.5 Tesla MRI systems. Visual evaluations of the colored perfusion map and MRI perfusion values were assessed. MRI and computed tomography (CT) perfusion values were compared.

Results:

Thirteen of 14 tumor lesions could be visualized on the colored perfusion map. CT perfusion examinations were performed in eight breasts, and the relationship between the blood flow values of CT perfusion and of MR perfusion showed a significant correlation.

Conclusion:

Nonenhanced MR imaging by an ASL technique is valid for depicting breast cancer, and the MR perfusion value is thought to be helpful for quantitative diagnosis of breast cancer. J. Magn. Reson. Imaging 2012;436‐440. © 2011 Wiley Periodicals, Inc.