Diffusion-weighted and dynamic contrast-enhanced MRI in evaluation of early treatment effects during neoadjuvant chemotherapy in breast cancer patients

Purpose:

To use dynamic contrast‐enhanced (DCE) and diffusion‐weighted (DW) MRI at 3 Tesla (T) for early evaluation of treatment effects in breast cancer patients undergoing neoadjuvant chemotherapy (NAC), and assess the reliability of DW‐MRI.

Materials and Methods:

DW‐ and DCE‐MRI acquisitions of 15 breast cancer patients were performed before and after one cycle of NAC. MRI tumor diameter and volume, apparent diffusion coefficient (ADC) and kinetic parameters (K^trans, v_e) were derived. The reliability of ADC before NAC was assessed. Changes in MRI parameters after NAC were analyzed, and logistic regression analysis was used to find the best predictors for pathologic response.

Results:

The reliability for ADC values was high, with intraclass correlation coefficient of 0.84 (P = 0.001). After one cycle of NAC, MRI tumor diameter (8%, P = 0.005) and tumor volume (30%, P = 0.008) was reduced for all patients, while ADC mean values increased (0.12 mm²/s, P = 0.008). The best predictor for treatment response was a change in MRI tumor diameter with mean error rate of 0.167 (13% for responders, 5% for nonresponders, P = 0.291).

Conclusion:

Changes in MRI derived tumor diameter and ADC after only one cycle of NAC could provide a valuable tool for early evaluation of treatment effects in breast cancer patients. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.     

Multiparametric MRI for prostate cancer localization in correlation to whole‐mount histopathology

Purpose:

To prospectively evaluate multiparametric magnetic resonance imaging (MRI) for accurate localization of intraprostatic tumor nodules, with whole‐mount histopathology as the gold standard.

Materials and Methods:

Seventy‐five patients with biopsy‐proven, intermediate, and high‐risk prostate cancer underwent preoperative T2‐weighted (T2w), dynamic contrast‐enhanced (DCE) and diffusion‐weighted (DW) MRI at 1.5T. Localization of suspicious lesions was recorded for each of 24 standardized regions of interest on the different MR images and correlated with the pathologic findings. Generalized estimating equations (GEE) were used to estimate the sensitivity, specificity, accuracy, positive, and negative predictive value for every MRI modality, as well as to evaluate the influence of Gleason score and pT‐stage. Tumor volume measurements on histopathological specimens were correlated with those on the different MR modalities (Pearson correlation).

Results:

DW MRI had the highest sensitivity for tumor localization (31.1% vs. 27.4% vs. 44.5% for T2w, DCE, and DW MRI, respectively; P < 0.005), with more aggressive or more advanced tumors being more easily detected with this imaging modality. Significantly higher sensitivity values were obtained for the combination of T2w, DCE, and DW MRI (58.8%) as compared to each modality alone or any combination of two modalities (P < 0.0001). Tumor volume can most accurately be assessed by means of DW MRI (r = 0.75; P < 0.0001).

Conclusion:

Combining T2w, DCE, and DW imaging significantly improves prostate cancer localization. J. Magn. Reson. Imaging 2013;37:1392–1401. © 2012 Wiley Periodicals, Inc.     

Time course study on the effects of iodinated contrast medium on intrarenal water transport function using diffusion-weighted MRI

Purpose:

To assess the effects of intravenous‐injected iodinated contrast medium (CM) on intrarenal water diffusion using noninvasive diffusion‐weighted MRI (DW‐MRI).

Materials and Methods:

Ten New Zealand White rabbits were randomized to receive a 6 mL/kg body weight intravenous injection of clinically used iopamidol‐370 (n = 7) or an equivalent amount of 0.9% physiological saline (n = 3). A sequential DW‐MRI was performed to estimate the intrarenal apparent diffusion coefficient (ADC) at 24 h before and 1 h, 24 h, 48 h, and 72 h after administration.

Results:

Iopamidol produced a progressive ADC reduction in inner stripes of the renal outer medulla (IS) by 13.92% (P = 0.05) at 1 h, 17.52% (P = 0.02) at 24 h, 20.23% (P = 0.01) at 48 h and 16.31% (P = 0.04) at 72 h after injection. Cortical ADC was decreased by 14.14% (P = 0.01) at 48 h and 14.12% (P = 0.01) at 72 h after injection. Iopamidol produced slight decrease of ADCs in outer stripes of the outer medulla (OS) and inner medulla (IM) of kidney but without statistical difference. In control group, no significant ADC changes was observed in each anatomic compartment due to saline injection (P > 0.05).

Conclusion:

As demonstrated by DW‐MRI, intravenous iopamidol injection resulted in a successive reduction of intrarenal water diffusion, particularly in IS of kidney. This MR technique may be used as a noninvasive tool to perform a time course study of the pathogenesis associated with contrast‐induced nephropathy (CIN). J. Magn. Reson. Imaging 2012;35:1139‐1144. © 2012 Wiley Periodicals, Inc.     

Evaluation of the tibial tunnel after intraoperatively administered platelet‐rich plasma gel during anterior cruciate ligament reconstruction using diffusion weighted and dynamic contrast‐enhanced MRI

Purpose:

To evaluate effect of platelet‐rich plasma gel (PRPG), locally administered during the anterior cruciate ligament (ACL) reconstruction, with two MRI methods. The proximal tibial tunnel was assessed with diffusion weighted imaging (DWI) and with dynamic contrast‐enhanced imaging (DCE‐MRI).

Materials and Methods:

In 50 patients, standard arthroscopic ACL reconstructions were performed. The patients in the PRPG group (n = 25) received a local application of PRPG. The proximal tibial tunnel was examined by DWI and DCE‐MRI, which were used to calculate apparent diffusion coefficient (ADC) values, as well as the contrast enhancement gradient (G_enh) and enhancement factor (F_enh) values.

Results:

At 1 month, the calculated average ADC value in the PRPG group was significantly lower than in the control group. At 2.5 and at 6 months, G_enh was significantly higher in the PRPG group. There were no significant differences in F_enh between the groups at any control examination.

Conclusion:

DWI and DCE‐MRI measurements indicate a reduced extent of edema during the first postoperative month as well as an increased vascular density and microvessel permeability in the proximal tibial tunnel at 1 and 2.5 postoperative months as the effect of the application of PRPG. J. Magn. Reson. Imaging 2013;37:928–935. © 2012 Wiley Periodicals, Inc.     

Diffusion‐weighted MRI for monitoring tumor response to photodynamic therapy

Purpose:

To examine diffusion‐weighted MRI (DW‐MRI) for assessing the early tumor response to photodynamic therapy (PDT).

Materials and Methods:

Subcutaneous tumor xenografts of human prostate cancer cells (CWR22) were initiated in athymic nude mice. A second‐generation photosensitizer, Pc 4, was delivered to each animal by a tail vein injection 48 h before laser illumination. A dedicated high‐field (9.4 Tesla) small animal MR scanner was used to acquire diffusion‐weighted MR images pre‐PDT and 24 h after the treatment. DW‐MRI and apparent diffusion coefficients (ADC) were analyzed for 24 treated and 5 control mice with photosensitizer only or laser light only. Tumor size, prostate specific antigen (PSA) level, and tumor histology were obtained at different time points to examine the treatment effect.

Results:

Treated mice showed significant tumor size shrinkage and decrease of PSA level within 7 days after the treatment. The average ADC of the 24 treated tumors increased 24 h after PDT (P < 0.001) comparing with pre‐PDT. The average ADC was 0.511 ± 0.119 × 10^?3 mm²/s pre‐PDT and 0.754 ± 0.181 × 10^?3 mm²/s 24 h after the PDT. There is no significant difference in ADC values pre‐PDT and 24 h after PDT in the control tumors (P = 0.20).

Conclusion:

The change of tumor ADC values measured by DW‐MRI may provide a noninvasive imaging marker for monitoring tumor response to Pc 4‐PDT as early as 24 h. J. Magn. Reson. Imaging 2010;32:409–417. © 2010 Wiley‐Liss, Inc.

     

Optimization of b value in diffusion-weighted MRI for characterization of benign and malignant gynecological lesions

Purpose:

To explore the optimal b value in diffusion‐weighted (DW)‐MRI for differentiation of benign and malignant gynecological lesions.

Materials and Methods:

Consecutive 58 patients (66 lesions) with pathologically confirmed diagnosis of gynecological disease were included in the study. Routine pelvic MRI sequences were used for defining the lesions and reviewed independently for benignity/ malignity. Single‐shot echoplanar imaging (SH‐EPI) DW‐MRI with eight b values and nine apparent diffusion coefficient (ADC) maps were obtained. The lesions were analyzed qualitatively on DW‐MRI for benignity/malignity on a five‐point‐scale and quantitatively by measurement of apparent diffusion coefficient (ADC) values. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic accuracy of ADC values for differentiating between benign and malignant lesions. Pathology results were the reference standard.

Results:

Differentiation between benign and malignant gynecological lesions using visual scoring was found to be successful with b values of 600, 800, or 1000 s/mm². The mean ADC values of malignant lesions were significantly lower than those of benign lesions for all b value (P < 0.005). The ADCs with b = 0 and 600, 0 and 1000 s/mm², 0, 600, 800 and 1000 s/mm², and all b values were more effective for distinguishing malignant from benign gynecological lesions (Az = 0.851, 0.847, 0.848, 0.849, respectively). Using ADC with b = 0, 600, 800, and 1000 s/mm², a threshold value of 1.20 × 10^?3 mm²/s permitted this distinction with a sensitivity of 83%, a specificity of 81%.

Conclusion:

DW‐MRI is an important method, and the optimal b values are between 600 and 1000 s/mm² for differentiation between benign and malignant gynecological lesions. J. Magn. Reson. Imaging 2012;35:650‐659. © 2011 Wiley Periodicals, Inc.

     

Washout gradient in dynamic contrast-enhanced MRI is associated with tumor aggressiveness of prostate cancer

Purpose:

To investigate the associations between dynamic contrast‐enhanced magnetic resonance imaging (DCE MRI) parameters and the Gleason score (GS) for prostate cancer (PCA) with localization information provided by concurrent apparent diffusion coefficient (ADC) maps.

Materials and Methods:

Forty‐three male patients received MR scans, including diffusion tensor imaging (DTI) and DCE MRI, on a 1.5 T MR system. All patients were confirmed to have PCA in the following biopsy within 2 weeks. ADC maps calculated from DTI were used to colocalize cancerous and noncancerous regions on DCE MRI for perfusion analysis retrospectively. Semiquantitative parameters (peak enhancement, initial gradient, and washout gradient [WG] and quantitative parameters [K^trans, ν_e, and k_ep]) were calculated and correlated with the GS. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic performance of the perfusion parameters in assessing the aggressiveness of PCA.

Results:

A total of 41 PCA nodules were included in the analysis. Among all quantitative and semiquantitative parameters, only WG showed significant correlation with GS (r = ?0.75, P < 0.0001). By defining tumor aggressiveness as a GS >6, WG demonstrated a good diagnostic performance, with the area under the ROC curve being 0.88. Under a cutoff point of WG = 0.125 min^?1, the sensitivity and specificity were 0.87 and 0.78, respectively.

Conclusion:

WG shows a significant association with GS and good diagnostic performance in assessing tumor aggressiveness. Therefore, WG is a potential marker of GS. J. Magn. Reson. Imaging 2012;36:912–919. © 2012 Wiley Periodicals, Inc.

     

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.     

Diffusion-weighted MRI in rectal cancer: apparent diffusion coefficient as a potential noninvasive marker of tumor aggressiveness

Purpose:

To assess the value of diffusion‐weighted MR imaging (DWI) as a potential noninvasive marker of tumor aggressiveness in rectal cancer, by analyzing the relationship between tumoral apparent diffusion coefficient (ADC) values and MRI and histological prognostic parameters.

Materials and Methods:

Fifty rectal cancer patients underwent primary staging MRI including DWI before surgery and neo‐adjuvant therapy. In 47, surgery was preceded by short‐course radiation therapy (n = 28) or long‐course chemoradiation therapy (n = 19). Mean tumor ADC was measured and compared between subgroups based on pretreatment CEA levels, MRI parameters (mesorectal fascia ‐ MRF ‐ status; T‐stage; N‐stage) and histological parameters (differentiation grade: poorly differentiated, poorly moderately differentiated, moderately differentiated, moderately well differentiated, well‐differentiated; lymphangiovascular invasion).

Results:

Mean tumor ADCs differ between MRF‐free versus MRF‐invaded tumors (P = 0.013), the groups of cN0 versus cN+ cancers (P = 0.011), and between the several groups of histological differentiation grades (P = 0.025). There was no significant difference in mean ADCs between the various groups of CEA levels, the T stage, and the presence of lymphangiovascular invasion.

Conclusion:

Lower ADC values were associated with a more aggressive tumor profile. Significant correlations were found between mean ADC values and radiological MRF status, N stage and differentiation grade. ADC has the potential to become an imaging biomarker of tumor aggressiveness profile. J. Magn. Reson. Imaging 2012;35:1365–1371. © 2012 Wiley Periodicals, 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.

     

Multiple‐bolus dynamic contrast‐enhanced MRI in the pancreas during a glucose challenge

Purpose:

To assess the feasibility of multiple‐bolus dynamic contrast‐enhanced (DCE) magnetic resonance imaging (MRI) in the pancreas; to optimize the analysis; and to investigate application of the method to a glucose challenge in type 2 diabetes.

Materials and Methods:

A 4‐bolus DCE‐MRI protocol was performed on five patients with type 2 diabetes and 11 healthy volunteers during free‐breathing. Motion during the dynamic time series was corrected for using a model‐driven nonlinear registration. A glucose challenge was administered intravenously between the first and second DCE‐MRI acquisition in all patients and in seven of the healthy controls.

Results:

Image registration improved the reproducibility of the DCE‐MRI model parameters across the repeated bolus‐acquisitions in the healthy controls with no glucose challenge (eg, coefficient of variation for K^trans improved from 38% to 28%). Native tissue T₁ was significantly lower in patients (374 ± 68 msec) compared with volunteers (519 ± 41 msec) but there was no significant difference in any of the baseline DCE‐MRI parameters. No effect of glucose challenge was observed in either the patients or healthy volunteers.

Conclusion:

Multiple bolus DCE‐MRI is feasible in the pancreas and is improved by nonlinear image registration but is not sensitive to the effects of an intravenous glucose challenge. J. Magn. Reson. Imaging 2010;32:622–628. © 2010 Wiley‐Liss, Inc.     

Diffusion-weighted MRI of fatty liver

Purpose:

To investigate the effect of fat infiltration on the apparent diffusion coefficient (ADC) of liver, and assess the relationship between ADC and hepatic fat fraction (HFF).

Materials and Methods:

MRI scans of 120 consecutive patients were included in this retrospective study. Of these, 42 patients were included in the fatty liver group and 78 in the control group. ADC values were measured from a pair of diffusion‐weighted (DW) images (b = 0 mm²/s and 1000 mm²/s). HFFs were measured using T1W GRE dual‐echo images. The difference between the ADCs of the two groups was assessed with the t‐test. The relationship between HFF and ADC was determined using linear regression analysis and the Pearson correlation coefficient (r).

Results:

Mean HFFs were 0.85 ± 2.86 and 13.67 ± 8.62 in the control and fatty liver groups, respectively. The mean ADC of fatty liver group 1.20 ± 0.22 × 10^?3 mm²/s was significantly lower than that of the control group 1.32 ± 0.23 × 10^?3 mm²/s (P = 0.02). Linear regression analysis revealed an inverse relationship between ADC and HFF (r = ?0.39, P < 0.0001).

Conclusion:

ADC significantly decreases in patients with >5% HFF, and ADC and HFF exhibit an inverse relationship. J. Magn. Reson. Imaging 2012;35:1109‐1111. © 2011 Wiley Periodicals, Inc.

     

Prostate cancer detection with multi‐parametric MRI: Logistic regression analysis of quantitative T2, diffusion‐weighted imaging,and dynamic contrast‐enhanced MRI

Purpose

To develop a multi‐parametric model suitable for prospectively identifying prostate cancer in peripheral zone (PZ) using magnetic resonance imaging (MRI).

Materials and Methods

Twenty‐five radical prostatectomy patients (median age, 63 years; range, 44–72 years) had T2‐weighted, diffusion‐weighted imaging (DWI), T2‐mapping, and dynamic contrast‐enhanced (DCE) MRI at 1.5 Tesla (T) with endorectal coil to yield parameters apparent diffusion coefficient (ADC), T2, volume transfer constant (K^trans) and extravascular extracellular volume fraction (v_e). Whole‐mount histology was generated from surgical specimens and PZ tumors delineated. Thirty‐eight tumor outlines, one per tumor, and pathologically normal PZ regions were transferred to MR images. Receiver operating characteristic (ROC) curves were generated using all identified normal and tumor voxels. Step‐wise logistic‐regression modeling was performed, testing changes in deviance for significance. Areas under the ROC curves (A_z) were used to evaluate and compare performance.

Results

The best‐performing single‐parameter was ADC (mean A_z [95% confidence interval]: A_z,ADC: 0.689 [0.675, 0.702]; A_z,T2: 0.673 [0.659, 0.687]; A_z,Ktrans: 0.592 [0.578, 0.606]; A_z,ve: 0.543 [0.528, 0.557]). The optimal multi‐parametric model, LR‐3p, consisted of combining ADC, T2 and K^trans. Mean A_z,LR‐3p was 0.706 [0.692, 0.719], which was significantly higher than A_z,T2, A_z,Ktrans, and A_z,ve (P < 0.002). A_z,LR‐3p tended to be greater than A_z,ADC, however, this result was not statistically significant (P = 0.090).

Conclusion

Using logistic regression, an objective model capable of mapping PZ tumor with reasonable performance can be constructed. J. Magn. Reson. Imaging 2009;30:327–334. © 2009 Wiley‐Liss, Inc.     

Intravoxel incoherent motion MR imaging for breast lesions: comparison and correlation with pharmacokinetic evaluation from dynamic contrast-enhanced MR imaging

Objectives

To compare diagnostic performance for breast lesions by quantitative parameters derived from intravoxel incoherent motion (IVIM) and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and to explore whether correlations exist between these parameters.

Methods

IVIM and DCE MRI were performed on a 1.5-T MRI scanner in patients with suspicious breast lesions. Thirty-six breast cancers and 23 benign lesions were included in the study. Quantitative parameters from IVIM (D, f and D*) and DCE MRI (K^trans, K_ep, V_e and V_p) were calculated and compared between malignant and benign lesions. Spearman correlation test was used to evaluate correlations between them.

Results

D, f, D* from IVIM and K^trans, K_ep, V_p from DCE MRI were statistically different between breast cancers and benign lesions (p?<?0.05, respectively) and D demonstrated the largest area under the receiver-operating characteristic curve (AUC?=?0.917) and had the highest specificity (83 %). The f value was moderately statistically correlated with V_p (r?=?0.692) and had a poor correlation with K^trans (r?=?0.456).

Conclusions

IVIM MRI is useful in the differentiation of breast lesions. Significant correlations were found between perfusion-related parameters from IVIM and DCE MRI. IVIM may be a useful adjunctive tool to standard MRI in diagnosing breast cancer.

Key Points

? IVIM provided diffusion as well as perfusion information ? IVIM could help differential diagnosis of breast lesions ? Correlations were found between perfusion-related parameters from IVIM and DCE MRI

     

Active Crohn's disease in the small bowel: evaluation by diffusion weighted imaging and quantitative dynamic contrast enhanced MR imaging

Purpose

To determine relative diagnostic value of MR diffusion and perfusion parameters in detection of active small bowel inflammation in patients with Crohn's disease (CD).

Materials and Methods

We reviewed 18 patients with active CD of terminal ileum (TI) who underwent MR enterography (MRE; including dynamic contrast enhanced MRI and diffusion‐weighted MRI). Conventional MRI findings of TI were recorded. Regions of interest were drawn over TI and normal ileum to calculate apparent diffusion coefficient (ADC), the volume transfer constant (K^trans) and the contrast media distribution volume (v_e). Receiver operating characteristic analysis was used to determine their diagnostic performance.

Results

Among conventional MR findings, mural thickening and increased enhancement were present in all actively inflamed small bowel. K^trans, v_e, and ADC values differed significantly between actively inflamed TI and normal ileum (0.92 s^?1 versus 0.36 s^?1; 0.31 versus 0.15 ± 0.08; 0.00198 mm²/s versus 0.00311 mm²/s; P < 0.001). Area under the curve (AUC) for K^trans, v_e, and ADC values ranged from 0.88 to 0.92 for detection of active inflammation. Combining K^trans and ADC data provided an AUC value of 0.95.

Conclusion

Dynamic contrast‐enhanced MRI (DCE‐MRI) and diffusion‐weighted imaging (DWI) provide quantitative measures of small bowel inflammation that can differentiate actively inflamed small bowel segments from normal small bowel in CD. DWI provides better sensitivity compared with DCE‐MRI and combination of ADC and K^trans parameters for analysis can potentially improve specificity. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.

     

Intraprocedural diffusion‐weighted PROPELLER MRI to guide percutaneous biopsy needle placement within rabbit VX2 liver tumors

Purpose

To test the hypothesis that diffusion‐weighted (DW)‐PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) magnetic resonance imaging (MRI) can be used to guide biopsy needle placement during percutaneous interventional procedures to selectively target viable and necrotic tissues within VX2 rabbit liver tumors.

Materials and Methods

Our institutional Animal Care and Use Committee approved all experiments. In six rabbits implanted with 15 VX2 liver tumors, baseline DW‐PROPELLER images acquired prior to the interventional procedure were used for apparent diffusion coefficient (ADC) measurements. Next, intraprocedural DW‐PROPELLER scans were performed with needle position iteratively adjusted to target viable, necrotic, or intermediate border tissue regions. DW‐PROPELLER ADC measurements at the selected needle tip locations were compared with the percentage of tumor necrosis qualitatively assessed at histopathology.

Results

DW‐PROPELLER images demonstrated intratumoral tissue heterogeneity and clearly depicted the needle tip position within viable and necrotic tumor tissues. Mean ADC measurements within the region‐of‐interest encompassing the needle tip were highly correlated with histopathologic tumor necrotic tissue assessments.

Conclusion

DW‐PROPELLER is an effective method to selectively position the biopsy needle tip within viable and necrotic tumor tissues. The DW‐PROPELLER method may offer an important complementary tool for functional guidance during MR‐guided percutaneous procedures. J. Magn. Reson. Imaging 2009;30:366–373. © 2009 Wiley‐Liss, Inc.     

Intravoxel incoherent motion MR imaging for prostate cancer: An evaluation of perfusion fraction and diffusion coefficient derived from different b‐value combinations

There has been a resurgent interest in intravoxel incoherent motion (IVIM) MR imaging to obtain perfusion as well as diffusion information on lesions, in which the diffusion was modeled as Gaussian diffusion. However, it was observed that this diffusion deviated from expected monoexponential decay at high b‐values and the reported perfusion in prostate is contrary to the findings in dynamic contrast‐enhanced (DCE) MRI studies and angiogenesis. Thus, this work is to evaluate the effect of different b‐values on IVIM perfusion fractions (f) and diffusion coefficients (D) for prostate cancer detection. The results show that both parameters depended heavily on the b‐values, and those derived without the highest b‐value correlated best with the results from DCE‐MRI studies; specifically, f was significantly elevated (7.2% vs. 3.7%) in tumors when compared with normal tissues, in accordance with the volume transfer constant (K^trans; 0.39 vs. 0.18 min^?1) and plasma fractional volume (v_p; 8.4% vs. 3.4%). In conclusion, it is critical to choose an appropriate range of b‐values in studies or include the non‐Gaussian diffusion contribution to obtain unbiased IVIM measurements. These measurements could eliminate the need for DCE‐MRI, which is especially relevant in patients who cannot receive intravenous gadolinium‐based contrast media. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

Differentiation of malignant and benign breast lesions using magnetization transfer imaging and dynamic contrast‐enhanced MRI

Purpose:

To evaluate feasibility of using magnetization transfer ratio (MTR) in conjunction with dynamic contrast‐enhanced MRI (DCE‐MRI) for differentiation of benign and malignant breast lesions at 3 Tesla.

Materials and Methods:

This prospective study was IRB and HIPAA compliant. DCE‐MRI scans followed by MT imaging were performed on 41 patients. Regions of interest (ROIs) were drawn on co‐registered MTR and DCE postcontrast images for breast structures, including benign lesions (BL) and malignant lesions (ML). Initial enhancement ratio (IER) and delayed enhancement ratio (DER) were calculated, as were normalized MTR, DER, and IER (NMTR, NDER, NIER) values. Diagnostic accuracy analysis was performed.

Results:

Mean MTR in ML was lower than in BL (P < 0.05); mean DER and mean IER in ML were significantly higher than in BL (P < 0.01, P < 0.001). NMTR, NDER, and NIER were significantly lower in ML versus BL (P < 0.007, P < 0.001, P < 0.001). IER had highest diagnostic accuracy (77.6%), sensitivity (86.2%), and area under the ROC curve (.879). MTR specificity was 100%. Logistic regression modeling with NMTR and NIER yielded best results for BL versus ML (sensitivity 93.1%, specificity 80%, AUC 0.884, accuracy 83.7%).

Conclusion:

Isolated quantitative DCE analysis may increase specificity of breast MR for differentiating BL and ML. DCE‐MRI with NMTR may produce a robust means of evaluating breast lesions. J. Magn. Reson. Imaging 2013;37:138–145. © 2012 Wiley Periodicals, Inc.     

Differential diagnosis of mammographically and clinically occult breast lesions on diffusion‐weighted MRI

Purpose:

To investigate the diagnostic performance of diffusion‐weighted imaging (DWI) for mammographically and clinically occult breast lesions.

Materials and Methods:

The study included 91 women with 118 breast lesions (91 benign, 12 ductal carcinoma in situ [DCIS], 15 invasive carcinoma) initially detected on dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) and assigned BI‐RADS category 3, 4, or 5. DWI was acquired with b = 0 and 600 s/mm². Lesion visibility was assessed on DWI. Apparent diffusion coefficient (ADC) values were compared between malignancies, benign lesions, and normal (no abnormal enhancement on DCE‐MRI) breast tissue, and the diagnostic performance of DWI was assessed based on ADC thresholding.

Results:

Twenty‐four of 27 (89%) malignant and 74/91 (81%) benign lesions were hyperintense on the b = 600 s/mm² diffusion‐weighted images. Both DCIS (1.33 ± 0.19 × 10^?3 mm²/s) and invasive carcinomas (1.30 ± 0.27 × 10^?3mm²/s) were lower in ADC than benign lesions (1.71 ± 0.43 × 10^?3mm²/s; P < 0.001), and each lesion type was lower in ADC than normal tissue (1.90 ± 0.38 × 10^?3mm²/s, P ≤ 0.001). Receiver operating curve (ROC) analysis showed an area under the curve (AUC) of 0.77, and sensitivity = 96%, specificity = 55%, positive predictive value (PPV) = 39%, and negative predictive value (NPV) = 98% for an ADC threshold of 1.60 × 10^?3mm²/s.

Conclusion:

Many mammographically and clinically occult breast carcinomas were visibly hyperintense on diffusion‐weighted images, and ADC enabled differentiation from benign lesions. Further studies evaluating DWI while blinded to DCE‐MRI are necessary to assess the potential of DWI as a noncontrast breast screening technique. J. Magn. Reson. Imaging 2010;1:562–570. © 2010 Wiley‐Liss, Inc.