Dynamic Contrast-enhanced MRI Technique Research Articles

Screening Breast MRI Primer: Indications, Current Protocols, and Emerging Techniques.

Breast dynamic contrast-enhanced MRI (DCE-MRI) is the most sensitive imaging modality for the detection of breast cancer. Screening MRI is currently performed predominantly in patients at high risk for breast cancer, but it could be of benefit in patients at intermediate risk for breast cancer and patients with dense breasts. Decreasing scan time and image interpretation time could increase cost-effectiveness, making screening MRI accessible to a larger group of patients. Abbreviated breast MRI (Ab-MRI) reduces scan time by decreasing the number of sequences obtained, but as multiple delayed contrast enhanced sequences are not obtained, no kinetic information is available. Ultrafast techniques rapidly acquire multiple sequences during the first minute of gadolinium contrast injection and provide information about both lesion morphology and vascular kinetics. Diffusion-weighted imaging is a noncontrast MRI technique with the potential to detect mammographically occult cancers. This review article aims to discuss the current indications of breast MRI as a screening tool, examine the standard breast DCE-MRI technique, and explore alternate screening MRI protocols, including Ab-MRI, ultrafast MRI, and noncontrast diffusion-weighted MRI, which can decrease scan time and interpretation time.

Measurement of murine kidney functional biomarkers using DCE-MRI: A multi-slice TRICKS technique and semi-automated image processing algorithm

PurposeTo propose a rapid multi-slice T1 measurement method using time-resolved imaging of contrast kinetics (TRICKS) and a semi-automated image processing algorithm for comprehensive assessment murine kidney function using dynamic contrast-enhanced MRI (DCE-MRI). MethodsA multi-slice TRICKS sampling scheme was implemented in an established rapid T1 measurement method. A semi-automated image-processing scheme employing basic image processing techniques and machine learning was developed to facilitate image analysis. Reliability of the multi-slice technique in measuring renal perfusion and glomerular filtration rate (GFR) was tested in normal mice (n = 7 for both techniques) by comparing to the validated single-slice technique. Utility of this method was demonstrated on mice after either sham surgery (n = 7) or induction of unilateral renal artery stenosis (RAS, n = 8). Renal functional parameters were extracted using a validated bi-compartment model. ResultsThe TRICKS sampling scheme achieved an acceleration factor of 2.7, allowing imaging of eight axial slices at 1.23 s/scan. With the aid of the semi-automated scheme, image analysis required under 15-min for both kidneys per mouse. The multi-slice technique yielded renal perfusion and GFR values comparable to the single-slice technique. Model-fitted renal parameters successfully differentiated control and stenotic mouse kidneys, including renal perfusion (706.5 ± 164.0 vs. 375.9 ± 277.9 mL/100 g/min, P = 0.002), blood flow (1.6 ± 0.4 vs. 0.7 ± 0.7 mL/min, P < 0.001), and GFR (142.9 ± 17.9 vs. 58.0 ± 42.8 μL/min, P < 0.001). ConclusionThe multi-slice TRICKS-based DCE-MRI technique, with a semi-automated image processing scheme, allows rapid and comprehensive measurement of murine kidney function.

The Utility of Diffusion Weighted Imaging and Dynamic Contrast Enhanced MRI Techniques in Differentiation Between Benign and Malignant Uterine Masses

The aim of the present study was to evaluate the role of diffusion weighted imaging (DWI) and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) in the differentiation between benign and malignant endometrial, uterine and cervical masses. The study included 78 patients. All patients had uterine or cervical masses on ultrasound examination. All patients had conventional MRI, DWI, and DCE-MRI. The patients were classified into three groups: patients with endometrial masses, myometrial lesions and cervical masses. The mean ADC value of benign endometrial and myometrial lesions was higher significantly from malignant lesions (P value <0.001 and <0.001). The cut off value of ≤1.1×10^-3mm²/sec as a predictor of malignant lesions yielded a sensitivity, specificity, PPV, NPV and accuracy of 89.65%, 91.54%, 88.67%, 92.41% and 95.21% respectively. The semi-quanitative parameters of DCE-MRI including the enhancement amplitude (EA), maximum slope (MS) and time of half rising (THR), all showed significant difference between the benign and malignant lesion in endometrial, myometrial and cervical lesions. In clinically and sonographically indeterminate endometrial, myometrial or cervical masses, DWI and DCE-MRI proved to be more accurate than conventional MRI in differentiation between benign and malignant masses, with the DWI and ADC value had more sensitivity and specificity especially in endometrial masses and should be included in the routine pelvic MRI. DCE-MRI should be reserved for still questionable cases after DWI and to study the vascularity of the lesions.

Pulmonary perfusion quantification with flow-sensitive inversion recovery (FAIR) UTE MRI in small animal imaging.

Blood perfusion in lung parenchyma is an important property for assessing lung function. In small animals, its quantitation is limited even with radioactive isotopes or dynamic contrast-enhanced MRI techniques. In this study, the feasibility flow-sensitive alternating inversion recovery (FAIR) for the quantification of blood flow in lung parenchyma in free breathing rats at 7T has been investigated. In order to obtain sufficient signal from the short T2 * lung parenchyma, a 2D ultra-short echo time (UTE) Look-Locker read-out has been implemented. Acquisitions were segmented to maintain acquisition time within an acceptable range. A method to perform retrospective respiratory gating (DC-SG) has been applied to investigate the impact of respiratory movement. Reproducibilities within and between sessions were estimated, and the ability of FAIR-UTE to identify the decrease of lung perfusion under hyperoxic conditions was tested. The implemented technique allowed for the visualization of lung parenchyma with excellent SNR and no respiratory artifact even in ungated acquisitions. Lung parenchyma perfusion was obtained as 32.54±2.26mL/g/min in the left lung, and 34.09±2.75mL/g/min in the right lung. Application of retrospective gating significantly but minimally changes the perfusion values, implying that respiratory gating may not be necessary with this center-our acquisition method. A decrease of 10% in lung perfusion was found between normoxic and hyperoxic conditions, proving the feasibility of the FAIR-UTE approach to quantify lung perfusion changes.

Assessment of blood-brain barrier disruption using dynamic contrast-enhanced MRI. A systematic review.

There is increasing recognition of the importance of blood–brain barrier (BBB) disruption in aging, dementia, stroke and multiple sclerosis in addition to more commonly-studied pathologies such as tumors. Dynamic contrast-enhanced MRI (DCE-MRI) is a method for studying BBB disruption in vivo. We review pathologies studied, scanning protocols and data analysis procedures to determine the range of available methods and their suitability to different pathologies. We systematically review the existing literature up to February 2014, seeking studies that assessed BBB integrity using T1-weighted DCE-MRI techniques in animals and humans in normal or abnormal brain tissues. The literature search provided 70 studies that were eligible for inclusion, involving 417 animals and 1564 human subjects in total. The pathologies most studied are intracranial neoplasms and acute ischemic strokes. There are large variations in the type of DCE-MRI sequence, the imaging protocols and the contrast agents used. Moreover, studies use a variety of different methods for data analysis, mainly based on model-free measurements and on the Patlak and Tofts models. Consequently, estimated KTrans values varied widely. In conclusion, DCE-MRI is shown to provide valuable information in a large variety of applications, ranging from common applications, such as grading of primary brain tumors, to more recent applications, such as assessment of subtle BBB dysfunction in Alzheimer's disease. Further research is required in order to establish consensus-based recommendations for data acquisition and analysis and, hence, improve inter-study comparability and promote wider use of DCE-MRI.

Dynamic Contrast-Enhanced MRI Evaluation of Cerebral Cavernous Malformations

The aim of this study is to quantitatively evaluate the behavior of CNS cavernous malformations (CCMs) using a dynamic contrast-enhanced MRI (DCEMRI) technique sensitive for slow transfer rates of gadolinium. The prospective study was approved by the institutional review board and was HIPPA compliant. Written informed consent was obtained from 14 subjects with familial CCMs (4 men and 10 women, ages 22-76years, mean 48.1years). Following routine anatomic MRI of the brain, DCEMRI was performed for six slices, using T1 mapping with partial inversion recovery (TAPIR) to calculate T1 values, following administration of 0.025mmol/kg gadolinium DTPA. The transfer rate (Ki) was calculated using the Patlak model, and Ki within CCMs was compared to normal-appearing white matter as well as to 17 normal control subjects previously studied. All subjects had typical MRI appearance of CCMs. Thirty-nine CCMs were studied using DCEMRI. Ki was low or normal in 12 lesions and elevated from 1.4 to 12 times higher than background in the remaining 27 lesions. Ki ranged from 2.1E-6 to 9.63E-4min(-1), mean 3.55E-4. Normal-appearing white matter in the CCM patients had a mean Ki of 1.57E-4, not statistically different from mean WM Ki of 1.47E-4 in controls. TAPIR-based DCEMRI technique permits quantifiable assessment of CCMs in vivo and reveals considerable differences not seen with conventional MRI. Potential applications include correlation with biologic behavior such as lesion growth or hemorrage, and measurement of drug effects.

Prostate Cancer: Comparison of Dynamic Contrast-Enhanced MRI Techniques for Localization of Peripheral Zone Tumor

The objective of this study was to compare the performance of different methodologies for interpretation of dynamic contrast-enhanced MRI (DCE-MRI) in localization of peripheral zone prostate cancer. Forty-three men (mean age, 59±8 years) with biopsy-proven prostate cancer who underwent prostate MRI including DCE-MRI before prostatectomy were included. Two observers independently reviewed DCE-MRI data using three methodologies: qualitative, in which kinetic curves of signal intensity versus time were generated for foci showing rapid enhancement on subtracted contrast-enhanced images; semiquantitative, in which a biexponential heuristic model was used to generate color-coded maps depicting maximum slope and washout of contrast enhancement; and quantitative, in which a Tofts model was used to generate color-coded influx rate transfer constant (Ktrans) and efflux rate transfer constant (Kep) maps. Findings were stratified by whether suspicious foci showed evidence of washout with each method and compared with histopathologic results in each sextant. There was similar accuracy for the semiquantitative and quantitative models for both observers irrespective of requiring evidence of washout. For the more experienced observer, requiring washout resulted in lower sensitivity and higher specificity for the qualitative and semiquantitative models. Also for the more experienced observer, use of either a semiquantitative or quantitative model provided greater sensitivity compared with a qualitative model when requiring washout. There was no association between tumor detection and Gleason score for any DCE-MRI methodology for either reader. For the experienced reader, sensitivity for peripheral zone tumor was increased by use of either a semiquantitative or quantitative model compared with a qualitative model and decreased by requiring washout. We failed to identify a difference in performance between semiquantitative and quantitative models.

Dynamic contrast-enhanced MRI for the detection of testicular ischemia in experimental induced testicular torsion of rabbits

Objective To evaluate the dynamic contrast-enhanced MRI (DCE-MRI)in detecting experimentally induced testicular ischemia. Methods Thirty healthy male New Zealand rabbits were randomly assigned into 6 groups. There were 5 rabbits in each of the following experimental groups: ( 1 ) Normal control, (2) Sham-operated, (3) ischemia of 3 h group, (4) ischemia of 6 h group, (5) ischemia of 12 h group, (6) ischemia of 24 h group. In all experiment groups, the right testis served as the internal control while the left testis served as the experimental side. DCE-MRI for each animal lasts about 10 minutes. Signal enhanced ratios (SERs) of ROI for both sides of each group were calculated by a computer, and parameters of SERs of 30 s, 75 s, 120 s and maximal SER were used for statistical analysis.Time intensity curves (TICs) were made for two sides of each group via Excel 2003 software and classified into 4 types. Statistical analysis was performed to compare the differences of SERs between left and right testis by two independent Kolmogorov-Smirnov test. Results In group I and 2, significant enhancement was observed on both testes of 10 rabbits. The enhancement decreased gradually with the elongation of ischemia in torsion groups. Three cases of type Ⅰ and 2 cases of type Ⅱ were observed in group 1,5 cases of type Ⅰ in group two, 2 cases of type Ⅰ and 3 cases of type Ⅱ b in group three, 2 cases of type Ⅰ and 2 cases of type Ⅱ b in group four, 5 cases of type Ⅱ b in group five and 5 cases of type Ⅲ in group six were noticed in the left testes. And in TICs of right testes, all cases showed TICs of type Ⅰ except 2 cases of type Ⅱ a in group six. In four torsion groups, the values for SER75 of the left side were 0. 084%, 0. 076%, 0.164% and 0.065%, while the right side were 0.255%, 0.410%, 0.586% and 0.302% (P ＜0.05). The values for SER120 in group three, five and six were 0.221% , 0.158% and 0.059% for the left side, and 0.405%,0.522% and 0.207% for the right side(P ＜0.05). The values for MSER in group three, five and six were 0.217% ,0.164% and 0.072% for the left side, and 0.405%, 0.586% and 0.302% for the right side(P ＜0.05). Conclusion DCE-MRI technique may be useful in the diagnosis of testicular torsion, which shows potential in the clinical application. Key words: Spermatic cord torsion; Magnetic resonance imaging; Comparative study

Quantification of viable tumor microvascular characteristics by multispectral analysis

Tumor heterogeneity complicates the quantification of tumor microvascular characteristics assessed by dynamic contrast-enhanced MRI (DCE-MRI). To address this issue a novel approach was developed that combines DCE-MRI with diffusion-based multispectral (MS) analysis to quantify the microvascular characteristics of specific tumor tissue populations. Diffusion-based MS segmentation (feature space: apparent diffusion coefficient, T(2) and proton density) was performed to identify tumor tissue populations and the DCE-MRI characteristics were determined for each tissue class. The ability of this MS DCE-MRI technique to detect microvascular changes due to treatment with an antibody (G6-31) to vascular endothelial growth factor-A (VEGF) was evaluated in a tumor xenograft mouse model. Anti-VEGF treatment resulted in a significant reduction in K(trans) for the MS viable tumor tissue class (-0.0034 +/- 0.0022 min(-1), P < 0.01) at 24 hr posttreatment that differ significantly from the change observed in the control group (0.0002 +/- 0.0025 min(-1)). Viable tumor K(trans) for the anti-VEGF group was also reduced 62% relative to the pretreatment values (P < 0.01). Necrotic tissue classes were found to add only noise to DCE-MRI estimates. This approach provides a means to measure physiological parameters within the viable tumor and address the issue of tumor heterogeneity that complicates DCE-MRI analysis.

Method for quantitation of dynamic MRI contrast agent uptake in colorectal liver metastases.

To investigate the reproducibility of dynamic contrast-enhanced MRI (DCE-MRI) in colorectal liver metastases using a vascular normalization function (VNF) from pixels in the spleen and to compare this with a technique using an arterial input function (AIF) from pixels in the aorta. DCE-MRI with gadolinium-DTPA (Gd-DTPA) was performed in patients with colorectal liver metastases. The VNF and AIF were determined using an automated algorithm. The average Gd-DTPA uptake rate (k(ep)) was calculated for the metastases using a physiological pharmacokinetic model. The protocol was repeated on a second day to calculate the repeatability coefficient of the measurements of k(ep). Using the VNF from the spleen the overall mean k(ep) of the two sessions for 11 patients was 0.033 per second and the repeatability coefficient was 0.009 per second. Using the AIF from the aorta these values were 0.031 per second and 0.028 per second, respectively. The mean Gd-DTPA uptake rate using a VNF taken from the spleen can be determined with adequate reproducibility in colorectal liver metastases. The use of a VNF from pixels in the spleen is better than an AIF from pixels in the aorta in terms of reproducibility, and is recommended when this DCE-MRI technique is used for prediction and monitoring of therapy outcome in colorectal liver metastases.

Reproducibility of quantitative dynamic MRI of normal human tissues.

The aim of the study was to establish the normal range and to evaluate the reproducibility of dynamic contrast enhanced MRI (DCE-MRI) parameter estimates in normal human pelvic tissues. Nineteen patients with prostate cancer, undergoing androgen deprivation treatment, had paired DCE-MRI examinations of the pelvis using spoiled gradient-echo sequences. Quantitative enhancement parameters were calculated for each examination: transfer constant (K(trans)), leakage space (v(e)) and maximum contrast medium accumulation (MCMA) of pelvic muscles, bone marrow and fat. Descriptive and reproducibility statistics were calculated: within-patient standard deviation (wSD), repeatability and within-patient coefficient of variation (wCV). The femoral head and ischiorectal fat showed large numbers of non-enhancing pixels (81 and 88%, respectively). The ischial bone marrow had the highest values of kinetic parameter estimates (K(trans) 0.554 min(-1), v(e) 18.5% and MCMA 0.164 mmol/kg). Muscle parameters values were lower (K(trans) 0.126-0.137 min(-1), v(e) 10.6-11.5% and MCMA 0.077-0.086 mmol/kg). The mean difference between paired examinations was not significantly different from zero for any parameter. v(e) and MCMA had the lowest wCV (between 19 and 29%). For individuals, a log(10) K(trans) change of approximately 0.90 in muscles and 0.52 in the ischium would be statistically significant. The corresponding absolute changes for v(e) are 6.7% in muscle and 13.6% in the ischium. For a group of 19 patients, small changes are statistically significant (muscle log(10) K(trans) 0.208 and v(e) 1.5% and ischium log(10) K(trans) 0.123 and v(e) 3.1%). Fat and the femoral head are unreliable tissues from which to obtain kinetic parameter estimates due to poor enhancement. v(e) and MCMA have smaller coefficient of variation than K(trans) in muscles and ischium. Reproducibility studies of normal and pathological tissues should be incorporated into clinical research protocols that measure treatment effects by DCE-MRI techniques.

Pharmacokinetic Mapping of the Breast: A New Method for Dynamic MR Mammography

A dynamic contrast-enhanced MRI technique for whole breast examinations is presented. The fast kinetics of tissue response during and after constant-rate intravenous infusion of gadolinium diethylenetriaminopentaacetic acid was resolved using a strongly T1-weighted saturation recovery TurboFLASH sequence that makes it possible to acquire signal-time courses sequentially from 15 adjacent slices with a temporal sampling rate of 21 s. On the basis of the mathematically established and experimentally verified linear relationship between the measured saturation recovery TurboFLASH signal variation and the gadolinium diethylenetriaminopentaacetic acid concentration in the tissue, the signal-time courses were analyzed within the framework of pharmacokinetic modeling. In our study, the tissue response was parameterized adequately using an open linear two-compartment model. With this approach, the tissue specific information contained in the signal-time course can be described using only two parameters: an amplitude A, reflecting the degree of MR signal enhancement, and an exchange parameter k21, characterizing vascular permeability and perfusion of the tissue. A clearly arranged representation of the large amount of data (480 saturation recovery TurboFLASH breast images/examination) was accomplished by means of color coding of the computed parameters, resulting in one color-coded pharmacokinetic parameter map/cross-section.