Dual-source parallel radiofrequency transmission for magnetic resonance breast imaging at 3 T: Any added clinical value?

Purpose

To investigate the influence of dual-source parallel radiofrequency (RF) excitation on clinical breast MR images.

Methods

A 3 T MR system with both dual-source and conventional single-source RF excitations was used to examine 22 patients. Axial TSE-T₂WI with fat suppression, TSE-T₁WI without fat suppression, THRIVE (3D field echo) and DWI (SE-EPI) were obtained by using both excitation techniques. Image homogeneity, image contrast and lesion conspicuity were measured or independently scored by two radiologists and were compared by paired-sample t test or Wilcoxon test.

Results

Both excitations revealed 24 lesions. For SE sequences using dual-source mode, image homogeneity was improved (P = 0.00), scan time was reduced, and ghost artifacts on DWI were significantly reduced (P = 0.00). However, image contrast was not increased and lesion conspicuity had no significant difference between two modes, except DWI on which lesion conspicuity was significantly improved (P = 0.00), due to less ghost artifacts. For field-echo sequence, image homogeneity, acquisition time, image contrast and lesion conspicuity had no significant difference between the two modes.

Conclusions

Dual-source parallel RF transmission has some added value for improving breast image quality. However, its value is limited in terms of improving lesion detection and characterization.     

Optimization of MR diffusion-weighted imaging acquisitions for pancreatic cancer at 3.0 T

Objectives

To investigate and optimize diffusion-weighted imaging (DWI) acquisitions for pancreatic cancer at 3.0 T.

Methods

Forty-five patients with pancreatic cancer were examined by four DWI acquisitions with b values = 0 and 600 s/mm² at 3.0 T, including breath-holding DWI (BH-DWI), respiratory-triggered DWI (TRIG-DWI), respiratory-triggered DWI with inversion–recovery technique (TRIGIR-DWI), and free-breathing DWI with inversion–recovery technique (FBIR-DWI). Artifacts, contrast ratio (CR), contrast-to-noise ratio (CNR) and apparent diffusion coefficient (ADC) of pancreatic cancer were statistically compared among DWI acquisitions.

Results

TRIGIR-DWI displayed the lowest artifacts and highest CR compared to other DWI acquisitions. CNRs of pancreatic cancer in TRIG-DWI and TRIGIR-DWI were statistically higher than that in FBIR-DWI and BH-DWI. Different ADCs between pancreatic cancer and noncancerous pancreatic tissues were noticed by a paired-samples T test in TRIG-DWI (p = 0.017), TRIGIR-DWI (p = 0.00001) and FBIR-DWI (p = 0.000041).

Conclusions

TRIGIR-DWI may be the optimal acquisition of DWI for pancreatic cancer at 3.0 T.     

Diagnostic value of breast MRI for predicting metastatic axillary lymph nodes in breast cancer patients: diffusion-weighted MRI and conventional MRI

Purposes

To evaluate the diagnostic value of diffusion-weighted MRI (DWI) and combination of conventional MRI and DWI to predict metastatic axillary lymph nodes in breast cancer.

Materials and methods

Two hundred fifty-two breast cancer patients with 253 axillae were included. The morphological parameters on axial T2-weighted images without fat saturation and apparent diffusion coefficient (ADC) values were retrospectively analyzed. An independent t-test/chi-square test and receiver operating characteristics (ROC) curve analysis were used.

Results

On conventional MRI, short and long axis length, maximal cortical thickness, relative T2 value, loss of fatty hilum (p < 0.001 for each), and eccentric cortical thickening (p < 0.003) were statistically significantly different between the metastatic and nonmetastatic groups. The short axis to long axis ratio was not a statistically significant parameter. The ADC value was significantly different between the 2 groups, with an AUC that was higher than that of conventional MR parameters (AUC, 0.815; threshold, ≤ 0.986 × 10–3 mm²/sec; sensitivity, 75.8%; specificity, 83.9%). Using the adopted thresholds for each parameter, a total number of findings suggesting malignancy of 4 or higher was determined as the threshold, with high specificity (90.1%).

Conclusion

Using conventional MRI and DWI, we can evaluate the axilla in breast cancer with high specificity.     

Neuroprotective effect of agmatine in rats with transient cerebral ischemia using MR imaging and histopathologic evaluation

Purpose

This study aimed to further investigate the effects of agmatine on brain edema in the rats with middle cerebral artery occlusion (MCAO) injury using magnetic resonance imaging (MRI) monitoring and biochemical and histopathologic evaluation.

Materials and methods

Following surgical induction of MCAO for 90 min, agmatine was injected 5 min after beginning of reperfusion and again once daily for the next 3 post-operative days. The events during ischemia and reperfusion were investigated by T2-weighted images (T2WI), serial diffusion-weighted images (DWI), calculated apparent diffusion coefficient (ADC) maps and contrast-enhanced T1-weighted images (CE-T1WI) during 3 h–72 h in a 1.5 T Siemens MAGNETON Avanto Scanner. Lesion volumes were analyzed in a blinded and randomized manner. Triphenyltetrazolium chloride (TTC), Nissl, and Evans Blue stainings were performed at the corresponding sections.

Results

Increased lesion volumes derived from T2WI, DWI, ADC, CE-T1WI, and TTC all were noted at 3 h and peaked at 24 h–48 h after MCAO injury. TTC-derived infarct volumes were not significantly different from the T2WI, DWI-, and CE-T1WI-derived lesion volumes at the last imaging time (72 h) point except for significantly smaller ADC lesions in the MCAO model (P < 0.05). Volumetric calculation based on TTC-derived infarct also correlated significantly stronger to volumetric calculation based on last imaging time point derived on T2WI, DWI or CE-T1WI than ADC (P < 0.05). At the last imaging time point, a significant increase in Evans Blue extravasation and a significant decrease in Nissl-positive cells numbers were noted in the vehicle-treated MCAO injured animals. The lesion volumes derived from T2WI, DWI, CE-T1WI, and Evans blue extravasation as well as the reduced numbers of Nissl-positive cells were all significantly attenuated in the agmatine-treated rats compared with the control ischemia rats (P < 0.05).

Conclusion

Our results suggest that agmatine has neuroprotective effects against brain edema on a reperfusion model after transient cerebral ischemia.     

Usefulness of slice encoding for metal artifact correction (SEMAC) for reducing metallic artifacts in 3-T MRI

Purpose

The purpose of the study was to assess the usefulness of slice encoding for metal artifact correction (SEMAC) in 3.0-T magnetic resonance (MR) in minimizing metallic artifacts in patients with spinal prostheses.

Materials and Methods

Institutional review board approval and informed consent were obtained for this study. Twenty-seven spine MR scans were performed with metal artifact reduction SEMAC between May 2011 and July 2012 in patients with metallic devices. The MR scans were performed on a 3-T MR system (Achieva; Philips Healthcare, Best, the Netherlands) including SEMAC-corrected T2-weighted axial/sagittal images and two-dimensional fast spin echo (FSE) axial/sagittal images. The SEMAC-corrected images were compared to conventional T2-weighted FSE images. Two musculoskeletal radiologists qualitatively analyzed the images in terms of visualization of the pedicle, vertebral body, dural sac, intervertebral disc, intervertebral neural foramina, screws and metallic artifacts. The paired images were rated using a 5-point scale. P values less than .05 were considered to indicate statistically significant differences.

Results

The SEMAC-corrected MR images significantly reduced the metal-related artifacts. The T2-weighted images with SEMAC sequences enabled significantly improved periprosthetic visualizations of the pedicle, vertebral body, dural sac and neural foramina, with the exception of the intervertebral disc (P < .05). In addition, there was significant improvement in prosthesis visualization (P < .05).

Conclusion

MR images with SEMAC can reduce metal-related artifacts, providing improved delineation of the prosthesis and periprosthetic region. However, for the evaluation of the intervertebral disc, the SEMAC-corrected MR images showed no significant benefits.     

Delayed gadolinium-enhanced MRI of the fibrocartilage disc of the temporomandibular joint – a feasibility study

Objective

To 1) test the feasibility of delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) at 3 T in the temporomandibular joint (TMJ) and 2) to determine the optimal delay for measurements of the TMJ disc after i.v. contrast agent (CA) administration.

Design

MRI of the right and left TMJ of six asymptomatic volunteers was performed at 3 T using a dedicated coil. 2D inversion recovery (2D-IR) sequences were performed at 4 time points covering 120 minutes and 3D gradient-echo (3D GRE) dual flip-angle sequences were performed at 14 time points covering 130 minutes after the administration of 0.2 mmol/kg of Gd-diethylenetriamine pentaacetic acid ion (Gd-DTPA)^2-, i.e., 0.4 mL of Magnevist™ per kg body weight. Pair-wise tests were used to assess differences between pre-and post-contrast T1 values.

Results

2D-IR sequences showed a statistically significant drop (p < 0.001) in T1 values after i.v. CA administration. The T1 drop of 50% was reached 60 minutes after bolus injection in the TMJ disc. The 3D GRE dual flip-angle sequences confirmed these results and show plateau of T1 after 60 minutes.

Conclusions

T1(Gd) maps calculated from dGEMRIC data allow in vivo assessment of the fibrocartilage disc of the TMJ. The recommended measurement time for dGEMRIC in the TMJ after i.v. CA administration is from 60 to 120 minutes.     

Noncontrast MRI with diffusion-weighted imaging as the sole imaging modality for detecting liver malignancy in patients with high risk for hepatocellular carcinoma

Purpose

To compare the diagnostic performance of the noncontrast MRI including DWI to the standard MRI for detecting hepatic malignancies in patients with chronic liver disease.

Materials and methods

We included 135 patients with 136 histologically-confirmed hepatocellular carcinomas (HCCs), 12 cholangiocarcinomas, and 34 benign lesions (≤ 2.0 cm), and 22 patients with cirrhosis but no focal liver lesion who underwent 3.0 T liver MRI. Noncontrast MRI set (T1- and T2-weighted images and DWI) and standard MRI set (gadoxetic acid-enhanced and noncontrast MRI) were analyzed independently by three observers to detect liver malignancies using receiver operating characteristic analysis.

Results

The Az value of the noncontrast MRI (mean, 0.906) was not inferior to that of the combined MRI (mean, 0.924) for detecting malignancies by all observers (P > 0.05). For each observer, no significant difference was found in the sensitivity and specificity between the two MRI sets for detecting liver malignancies and distinguishing them from benign lesions (P > 0.05), whereas negative predictive value was higher with the combined MRI than with the noncontrast MRI (P = 0.0001). When using pooled data, the sensitivity of the combined MRI (mean 94.8%) was higher than that of the noncontrast MRI (mean, 91.7%) (P = 0.001), whereas specificity was equivalent (78.6% vs 77.5%).

Conclusion

Noncontrast MRI including DWI showed reasonable performance compared to the combined gadoxetic acid-enhanced and noncontrast MRI set for detecting HCC and cholangiocarcinoma and differentiating them from benign lesions in patients with chronic liver disease.     

Measurements of RF heating during 3.0-T MRI of a pig implanted with deep brain stimulator

Purpose

To present preliminary, in vivo temperature measurements during MRI of a pig implanted with a deep brain stimulation (DBS) system.

Materials and Methods

DBS system (Medtronic Inc., Minneapolis, MN) was implanted in the brain of an anesthetized pig. 3.0-T MRI was performed with a T/R head coil using the low-SAR GRE EPI and IR-prepped GRE sequences (SAR: 0.42 and 0.39 W/kg, respectively), and the high-SAR 4-echo RF spin echo (SAR: 2.9 W/kg). Fluoroptic thermometry was used to directly measure RF-related heating at the DBS electrodes, and at the implantable pulse generator (IPG). For reference the measurements were repeated in the same pig at 1.5 T and, at both field strengths, in a phantom.

Results

At 3.0 T, the maximal temperature elevations at DBS electrodes were 0.46 °C and 2.3 °C, for the low- and high-SAR sequences, respectively. No heating was observed on the implanted IPG during any of the measurements. Measurements of in vivo heating differed from those obtained in the phantom.

Conclusion

The 3.0-T MRI using GRE EPI and IR-prepped GRE sequences resulted in local temperature elevations at DBS electrodes of no more than 0.46 °C. Although no extrapolation should be made to human exams and much further study will be needed, these preliminary data are encouraging for the future use 3.0-T MRI in patients with DBS.     

Evaluation of image quality of DWIBS versus DWI sequences in thoracic MRI at 3 T

Purpose

To compare diffusion weighted imaging with background suppression (DWIBS) sequence with classic spectral diffusion sequence (DWI) with and without respiratory gating in mediastinal lymph node analysis at 3 T.

Materials and methods

26 patients scheduled for mediastinoscopic lymph node analysis, prospectively undergone a thoracic 3 T MRI with DWIBS (FatSat = STIR; TR/TE = 6674.1/44.7 ms; IR = 260 ms) and DWI sequences (FatSat = SPIR; TR/TE = 1291/59.6 ms) (b = 0-400-800 s/mm2) with and without (free breathing) respiratory gating.Images at b = 800 were analyzed by two radiologists. They performed qualitative analysis of fat-sat homogeneity and motion artifacts, rated from 0 to 4, and quantitative evaluation by studying signal to background (STB) of lymph nodes.

Results

Quality of fat suppression was significantly higher for DWIBS than for DWI both for free-breathing (score 3.48 ± 0.65 vs. 1.76 ± 0.96, p < 0.0001) and respiratory-gated scans (3.17 ± 0.77 vs. 1.72 ± 0.73, p = 0.0001). Similarly, artifacts were reduced with DWIBS (3.16 ± 0.47 vs. 1.76 ± 0.59, p < 0.0001; 3.0 ± 0.73 vs. 2.04 ± 0.53, p = 0.0001). Quantitative analysis showed higher STB with DWIBS (3.26 ± 1.83 vs. 0.98 ± 0.44, p < 0.0001; 3.56 ±, 2.09 vs. 0.92 ± 0.59, p < 0.0001). Gating did not improve image quality and STB on DWIBS (p > 0.05).

Conclusion

In thoracic MRI, ungated DWIBS sequence improves fat-sat homogeneity, reduces motion artifacts and increases STB of lymph nodes. Respiratory gating does not improve DWIBS image quality.     

Assessment of early response to concurrent chemoradiotherapy in cervical cancer: value of diffusion-weighted and dynamic contrast-enhanced MR imaging

Purpose

To investigate diffusion-weighted (DWI) and dynamic contrast-enhanced MR imaging (DCE-MRI) as early response predictors in cervical cancer patients who received concurrent chemoradiotherapy (CCRT).

Materials and methods

Sixteen patients with cervical cancer underwent DWI and DCE-MRI before CCRT (preTx), at 1 week (postT1) and 4 weeks (postT2) after initiating treatment, and 1 month after the end of treatment (postT3). At each point, apparent diffusion coefficient (ADC) and DCE-MRI parameters were measured in tumors and gluteus muscles (GM). Tumor response was correlated with imaging parameters or changes in imaging parameters at each point.

Results

At each point, ADC, K^trans and V_e in tumors showed significant changes (P < 0.05), as compared with those of GM (P > 0.05). PostT1 tumor ADCs showed a significant correlation with tumor size response at postT2 (P = 0.041), and changes in tumor ADCs at postT1 had a significant correlation with tumor size (P = 0.04) and volume response (P = 0.003) at postT2. In tumors, preTx K^trans and V_e showed significant correlations with tumor size at postT3 (P = 0.011) and tumor size response at postT2 (P = 0.019), respectively.

Conclusion

DWI and DCE-MRI, as early biomarkers, have the potential to evaluate therapeutic responses to CCRT in cervical cancers.     

Diffusion-weighted magnetic resonance imaging to evaluate microvascular density after transarterial embolization ablation in a rabbit VX2 liver tumor model

Objective

To evaluate the correlation between findings from diffusion weighted imaging (DWI) and microvascular density (MVD) measurements in VX2 liver tumors after transarterial embolization ablation (TEA).

Materials and Methods

Eighteen New Zealand white rabbits were used in this study. VX2 tumor cells were implanted in livers by percutaneous puncture under computed tomography (CT) guidance. Two weeks later, all rabbits underwent conventional magnetic resonance imaging (MRI) (T1 and T2 imaging), DWI, (b = 100, 600, and 1000 s/mm²) and TEA. MRI was performed again1 week after TEA. Liver tissue was then harvested and processed for hematoxylin and eosin (H&E) staining and immunohistochemical staining for CD31to determine MVD.

Results

VX2 liver tumors were successfully established in all 18 rabbits. Optimal contrast was achieved with a b value of 600 s/mm².The maximum pre-operative apparent diffusion coefficient (ADC)_difference value was 0.28 × 10^− 3 ± 0.10 × 10^− 3 mm²/s, and was significantly different (P < 0.001) from the maximum postoperative ADC_difference value of 0.47 × 10^− 3 ± 0.10 × 10^− 3 mm²/s. However, the mean ADC value for the entire tumor was not significantly correlated with MVD (r = 0.221, P = 0.379), nor was the ADC value for the regions of viable tumor (r = − 0.044, P = 0.862). However, the maximum postoperative ADC_difference value was positively correlated with MVD(r = 0.606, F = 12.247, P = 0.003).

Conclusion

DWI is effective to evaluate the therapeutic efficacy of TEA. The maximum ADC_difference offers a promising new method to noninvasively assess tumor angiogenesis.     

Feasibility of diffusional kurtosis tensor imaging in prostate MRI for the assessment of prostate cancer: Preliminary results

Purpose

To assess the feasibility of full diffusional kurtosis tensor imaging (DKI) in prostate MRI in clinical routine. Histopathological correlation was achieved by targeted biopsy.

Materials and Methods

Thirty-one men were prospectively included in the study. Twenty-one were referred to our hospital with increased prostate specific antigen (PSA) values (> 4 ng/ml) and suspicion of prostate cancer. The other 10 men were volunteers without any history of prostate disease. DKI applying diffusion gradients in 20 different spatial directions with four b-values (0, 300, 600, 1000 s/mm²) was performed additionally to standard functional prostate MRI. Region of interest (ROI)-based measurements were performed in all histopathologically verified lesions of every patient, as well as in the peripheral zone, and the central gland of each volunteer.

Results

DKI showed a substantially better fit to the diffusion-weighted signal than the monoexponential apparent diffusion coefficient (ADC). Altogether, 29 lesions were biopsied in 14 different patients with the following results: Gleason score 3 + 3 = 6 (n = 1), 3 + 4 = 7 (n = 7), 4 + 3 = 7 (n = 6), 4 + 4 = 8 (n = 1), and 4 + 5 = 9 (n = 2), and prostatitis (n = 12). Values of axial (K_ax) and mean kurtosis (K_mean) were significantly different in the tumor (K_ax 1.78 ± 0.39, K_mean 1.84 ± 0.43) compared with the normal peripheral zone (K_ax 1.09 ± 0.12, K_mean 1.16 ± 0.13; p < 0.001) or the central gland (K_ax 1.40 ± 0.12, K_mean 1.44 ± 0.17; p = 0.01 respectively). There was a minor correlation between axial kurtosis (r = 0.19) and the Gleason score.

Conclusion

Full DKI is feasible to utilize in a routine clinical setting. Although there is some overlap some DKI parameters can significantly distinguish prostate cancer from the central gland or the normal peripheral zone. Nevertheless, the additional value of DKI compared with conventional monoexponential ADC calculation remains questionable and requires further research.     

Gadoxetic acid-enhanced MRI compared with CT during angiography in the diagnosis of hepatocellular carcinoma

Purpose

To assess the value of gadoxetic acid-enhanced magnetic resonance imaging (MRI) for the pre-therapeutic detection of hepatocellular carcinoma (HCC) using receiver operating characteristic (ROC) analysis with the combination of computed tomography (CT) arterial portography and CT hepatic arteriography (CTAP/CTHA).

Materials and Methods

A total of 54 consecutive patients with 87 nodular HCCs were retrospectively analyzed. All HCC nodules were confirmed pathologically. Three blinded readers independently reviewed 432 hepatic segments, including 78 segments with 87 HCCs. Each reader read two sets of images: Set 1, CTAP/CTHA; Set 2, gadoxetic acid-enhanced MRI including a gradient dual-echo sequence and diffusion-weighted imaging (DWI). The ROC method was used to analyze the results. The sensitivity, specificity, positive predictive value, negative predictive value and sensitivity according to tumor size were evaluated.

Results

For each reader, the area under the curve was significantly higher for Set 2 than for Set 1. The mean area under the curve was also significantly greater for Set 2 than for Set 1 (area under the curve, 0.98 vs. 0.93; P = .0009). The sensitivity was significantly higher for Set 2 than for Set 1 for all three readers (P = .012, .013 and .039, respectively). The difference in the specificity, positive predictive values and negative predictive values of the two modalities for each reader was not significant (P > .05).

Conclusion

Gadoxetic acid-enhanced MRI including a gradient dual-echo sequence and DWI is recommended for the pre-therapeutic evaluation of patients with HCC.     

Is gadoxetic acid-enhanced MRI limited in tumor characterization for patients with chronic liver disease?

Purpose

There are pros and cons to the use of gadoxetic acid in hepatocellular carcinoma (HCC) workup due to the potential for high false positive diagnosis. This study was conducted to investigate the preoperative diagnostic performance of gadoxetic acid-enhanced MRI protocol including diffusion-weighted imaging (DWI) with emphasis on tumor characterization developed in high risk HCC patients.

Materials and methods

We included 144 patients (102 men, 42 women; age range 33–74 years) with chronic viral hepatitis or cirrhosis and 183 focal hepatic tumors (size range, 0.4–11.0 cm; mean, 3.2 cm), including 148 HCCs, 13 cholangiocarcinomas, 12 hemangiomas, three hepatocellular adenomas, two focal nodular hyperplasias, and five other tumors. All patients underwent gadoxetic acid-enhanced MRI protocol with DWI. MRIs were independently interpreted by three observers for the detection and characterization of hepatic tumors.

Results

Sensitivities for detecting all 183 liver tumors were 98.4%, 97.8%, and 96.2% for each observer, respectively, with a 97.5% for pooled data. Among 183 hepatic tumors, 91.3% (n = 167), 87.4% (n = 160), and 86.9% (n = 159) were correctly characterized according to their reference standard by each observer, respectively. In 13 cholangiocarcinomas, one to three were misinterpreted as HCC, and the remaining tumors were correctly characterized by each observer. The accuracies (Az) of MRI for HCC diagnosis were 0.952 for observer 1, 0.906 for observer 2, and 0.910 for observer 3, with 0.922 for pooled data. There was good inter-observer agreement.

Conclusion

The gadoxetic acid-enhanced MRI including DWI showed a reasonable performance for tumor characterization with high sensitivity for tumor detection in patients with chronic liver disease, despite concerns of high false positive diagnosis of hypervascular tumors.     

The value of diffusion-weighted MRI to evaluate the response to radiochemotherapy for cervical cancer

Purpose

To investigate the value of apparent diffusion coefficient (ADC) to predict and monitor the therapy response for cervical cancer patients receiving concurrent radiochemotherapy, and to analyze the influence of different b-value combinations on ADC-based evaluation of treatment response.

Material and Methods

Seventy-five cervical cancer patients treated with radiochemotherapy received conventional MRI and DWI prior to therapy, after 2 weeks of therapy, after four weeks of therapy and after therapy completion. Treatment response was classified as complete response (CR, n = 35), partial response (PR, n = 22) and stable disease (SD, n = 18), which was determined according to final tumor size after 6 months of therapy completion. Dynamic changes of apparent diffusion coefficients (ADC) and tumor size in the three tumor groups were observed and compared. All the ADCs were calculated from b = 0, 600 s/mm² and b = 0, 1000 s/mm².

Results

The ADC increased percentage was higher in CR group than those in PR and SD groups after two weeks and four weeks of therapy, with significant differences in absolute ADCs between CR and PR, SD groups after therapy completion; the overall discriminatory capability for differentiation of CR and PR, SD groups was higher for high b-value combination (0, 1000 s/mm²) than for low b-value combination (0, 600 s/mm²).

Conclusion

DWI can be used as a predictive and monitoring biomarker of treatment response to radiochemotherapy in patients with cervical cancer. High b-value combination may be more reliable to evaluate the treatment response for cervical cancer.     

Histopathologically confirmed focal nodular hyperplasia of the liver: Gadoxetic acid-enhanced MRI characteristics

Purpose

The purpose of this study was to evaluate enhancement characteristics of histopathologically confirmed focal nodular hyperplasia (FNHs) with gadoxetic acid-enhanced MRI.

Materials and Methods

Twenty-seven patients with all histopathologically proven FNHs were retrospectively identified. MRI consisted of T₁- and T₂-weighted (w) sequences with and without fat saturation (FS), multiphase dynamic T₁-w images, and FS T₁-w images during the hepatobiliary phase. Standard of reference was surgical resection (n = 24) or biopsy (n = 3). Images were analyzed for morphology and contrast behavior including signal intensity (SI) measurement on T₁-w images normalized to the pre-contrast base line.

Results

In total 36 FNHs were evaluated. All FNHs showed enhancement in the arterial phase, significant reduction contrast enhancement (“wash-out”) in the late dynamic phases was not present. In the hepatobiliary phase, all FNHs (100%) showed enhancement (overall SI increase, 118% (± 91%), P < 0.001) with at least partial hyperintensity to the liver. Upon visual comparison, 3 of 36 FNHs appeared with heterogeneous/partial enhancement (8%) and 7 (19%) showed rim-accentuated enhancement.

Conclusion

The typical enhancement pattern of FNH with gadoxetic acid consists of arterial hyperperfusion, no wash-out during the venous phase, and at least partial hyperintensity compared to the liver in the hepatobiliary phase. Partial hypointensity or rim-accentuated enhancement rarely occurs.     

7 T versus 3 T contrast-enhanced breast Magnetic Resonance Imaging of invasive ductulolobular carcinoma: First clinical experience

Purpose

Here we describe our first experience with contrast-enhanced (CE) MRI of breast cancer at 7 tesla (T), compared to 3 T and histopathology.

Materials and Methods

A 52 year old female patient with a mammographically suspicious breast mass (BI-RADS V) underwent 7 T CE-MRI. Results were described according to the BI-RADS-MRI criteria and compared to 3 T and histopathology.

Results

After contrast administration, a homogeneously enhancing, irregular spiculated mass was depicted at both 3 T and 7 T; sizes were identical. The most malignant kinetic curve was characterized by a rapid initial rise followed by a wash-out pattern in the delayed phase, i.e. a type 3 curve, at both field strengths. Even though T1-effects of contrast agents are suggested to be reduced at higher fields, quantification of contrast enhancement-to-noise ratio showed a ratio of 4.6 at 7 T and 2.8 at 3 T when comparing contrast-to-noise of the mass before and after contrast administration. Both examinations, using a single dose of gadolinium-based contrast agent, achieved good image quality. Final histopathological evaluation showed an invasive ductulolobular carcinoma with an intraductal component.

Conclusion

This initial experience suggests that clinical contrast-enhanced 7 T MRI of the breast is technically feasible and may allow BI-RADS-conform analysis.     

Intravoxel incoherent motion (IVIM) imaging at different magnetic field strengths: What is feasible?

Background

Due to limited SNR the cerebral applications of the intravoxel incoherent motion (IVIM) concept have been sparse. MRI hardware developments have resulted in improved SNR and this may justify a reassessment of IVIM imaging for non-invasive quantification of the cerebral blood volume (CBV) as a first step toward determining the optimal field strength.

Purpose

To investigate intravoxel incoherent motion imaging for its potential to assess cerebral blood volume (CBV) at three different MRI field strengths.

Materials and methods

Four volunteers were scanned twice at 1.5 T, 3 T as well as 7 T. By correcting for field-strength-dependent effects of relaxation, estimates of corrected CBV (cCBV) were obtained in deep gray matter (DGM), frontal gray matter (FGM) and frontal white matter (FWM), using Bayesian analysis. In addition, simulations were performed to facilitate the interpretation of experimental data.

Results

In DGM, FGM and FWM we obtained cCBV estimates of 2.2 ml/100 ml, 2.7 ml/100 ml, 1.4 ml/100 ml at 1.5 T; 3.7 ml/100 ml, 5.0 ml/100 ml, 3.2 ml/100 ml at 3 T and 15.5 ml/100 ml, 20.3 ml/100 ml, 7.0 ml/100 ml at 7 T.

Conclusion

Quantitative cCBV values obtained at 1.5 T and 3 T corresponded better to physiological reference values, while 7 T showed the largest deviation from expected values. Simulations of synthetic tissue voxels indicated that the discrepancy at 7 T can partly be explained by SNR issues. Results were generally more repeatable at 7 T (intraclass correlation coefficient, ICC = 0.84) than at 1.5 T (ICC = 0.68) and 3 T (ICC = 0.46).     

Diagnostic performance of apparent diffusion coefficient and quantitative kinetic parameters for predicting additional malignancy in patients with newly diagnosed breast cancer

Purpose

To evaluate the diagnostic performance of an apparent diffusion coefficient (ADC) and quantitative kinetic parameters in patients with newly diagnosed breast cancer.

Materials and Methods

We enrolled 169 lesions in 89 patients with breast cancer who underwent dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI). Comparisons between benign and malignant lesions were performed for lesion type (mass or nonmass-like enhancement), size (≥ 1 cm or < 1 cm), ADC, kinetic parameters and the presence of a US correlate.

Results

There were 63 benign and 106 malignant lesions. The mean size and initial peak enhancement of the benign lesions were significantly lower than those of malignant lesions (P < 0.001 for both). The ADC of the benign lesions was significantly higher than that of malignant lesions (1.42 × 10^− 3 mm²/sec vs. 1.04 × 10^− 3 mm²/sec; P < 0.001). The area under the receiver operating characteristic curve (AUC) for predicting malignancy was 0.87 for the combined parameters of size, ADC, and initial peak enhancement, which was higher than those of each parameter.

Conclusions

Combination of quantitative kinetic parameters and ADC showed higher diagnostic performance for predicting malignancy than each parameter alone for the evaluation of patients with breast cancer.     

In vitro assessment of 3-T MRI issues for a bioabsorbable,coronary artery scaffold with metallic markers

Objective

Coronary artery stents are made from metallic mesh and, therefore, to ensure patient safety, these implants must be evaluated to determine risks associated with MRI. Recently, bioabsorbable scaffolds, which have metallic markers, have been developed for use in the coronary arteries. Because of the metallic materials, these implants may present issues for patients undergoing MRI. Therefore, the objective of this investigation was to assess MRI issues (i.e., magnetic field interactions, MRI-related heating, and artifacts at 3 T) for a new bioabsorbable, coronary artery scaffold with metallic markers.

Methods

A bioabsorbable, coronary artery scaffold (Mirage Microfiber Scaffold) underwent assessments for magnetic field interactions, MRI-related heating, and artifacts at 3-Tesla using standard techniques. MRI-related heating was evaluated with the scaffold placed in a gelled-saline-filled phantom and MRI was performed at an MR system reported, whole body averaged SAR of 2.9 W/kg for 15 minutes. Artifacts were characterized using T1-weighted spin echo and gradient echo, pulse sequences.

Results

There were no magnetic field interactions. The highest temperature rise was 1.6 °C (highest background temperature rise, 1.6 °C). Artifacts were relatively small in relation to the size and shape of this coronary artery scaffold. Notably, the lumen of the scaffold could be visualized on the GRE pulse sequence.

Conclusion

The results demonstrated that the coronary artery scaffold is acceptable (or “MR conditional,” using current MRI labeling terminology) for a patient undergoing an MRI procedure at 3 T or less. To our knowledge, this is the first bioabsorbable, coronary artery scaffold that has been evaluated for MRI issues.