Blood oxygenation level dependent magnetic resonance imaging and diffusion weighted MRI imaging for benign and malignant breast cancer discrimination

PurposeThe purpose of this study is to assess Blood oxygenation level dependent Magnetic Resonance Imaging (BOLD-MRI) and Diffusion Weighted Magnetic Resonance Imaging (DW-MRI) in the differentiation of benign and malignant breast lesions.MethodsFifty-nine breast lesions (26 benign and 33 malignant lesions) pathologically proven in 59 patients were included in this retrospective study. As BOLD parameters were estimated basal signal S₀ and the relaxation rate R2*, diffusion and perfusion parameters were derived by DWI (pseudo-diffusion coefficient (Dp), perfusion fraction (fp) and tissue diffusivity (Dt)). Wilcoxon-Mann-Whitney U test and Receiver operating characteristic (ROC) analyses were calculated and area under ROC curve (AUC) was obtained. Moreover, pattern recognition approaches (linear discrimination analysis (LDA), support vector machine, k-nearest neighbours, decision tree) with least absolute shrinkage and selection operator (LASSO) method and leave one out cross validation approach were considered.ResultsA significant discrimination was obtained by the standard deviation value of S0, as BOLD parameter, that reached an AUC of 0.76 with a sensitivity of 65%, a specificity of 85% and an accuracy of 76%. No significant discrimination was obtained considering diffusion and perfusion parameters. Considering LASSO results, the features to use as predictors were all extracted parameters except that the mean value of R2* and the best result was obtained by a LDA that obtained an AUC = 0.83, with a sensitivity of 88%, a specificity of 77% and an accuracy of 83%.ConclusionsGood performance to discriminate benign and malignant lesions could be obtained using BOLD and DWI derived parameters with a LDA classification approach. However, these findings should be proven on larger and several dataset with different MR scanners.     

Diagnostic accuracy of automatic normalization of CBV in glioma grading using T1- weighted DCE-MRI

PurposeAim of this retrospective study was to compare diagnostic accuracy of proposed automatic normalization method to quantify the relative cerebral blood volume (rCBV) with existing contra-lateral region of interest (ROI) based CBV normalization method for glioma grading using T1-weighted dynamic contrast enhanced MRI (DCE-MRI).Material and methodsSixty patients with histologically confirmed gliomas were included in this study retrospectively. CBV maps were generated using T1-weighted DCE-MRI and are normalized by contralateral ROI based method (rCBV_contra), unaffected white matter (rCBV_WM) and unaffected gray matter (rCBV_GM), the latter two of these were generated automatically. An expert radiologist with > 10 years of experience in DCE-MRI and a non-expert with one year experience were used independently to measure rCBVs. Cutoff values for glioma grading were decided from ROC analysis. Agreement of histology with rCBV_WM, rCBV_GM and rCBV_contra respectively was studied using Kappa statistics and intra-class correlation coefficient (ICC).ResultThe diagnostic accuracy of glioma grading using the measured rCBV_contra by expert radiologist was found to be high (sensitivity = 1.00, specificity = 0.96, p < 0.001) compared to the non-expert user (sensitivity = 0.65, specificity = 0.78, p < 0.001). On the other hand, both the expert and non-expert user showed similar diagnostic accuracy for automatic rCBV_WM (sensitivity = 0.89, specificity = 0.87, p = 0.001) and rCBV_GM (sensitivity = 0.81, specificity = 0.78, p = 0.001) measures. Further, it was also observed that, contralateral based method by expert user showed highest agreement with histological grading of tumor (kappa = 0.96, agreement 98.33%, p < 0.001), however; automatic normalization method showed same percentage of agreement for both expert and non-expert user. rCBV_WM showed an agreement of 88.33% (kappa = 0.76,p < 0.001) with histopathological grading.ConclusionIt was inferred from this study that, in the absence of expert user, automated normalization of CBV using the proposed method could provide better diagnostic accuracy compared to the manual contralateral based approach.     

A knowledge-driven feature learning and integration method for breast cancer diagnosis on multi-sequence MRI

BackgroundThe classification of benign versus malignant breast lesions on multi-sequence Magnetic Resonance Imaging (MRI) is a challenging task since breast lesions are heterogeneous and complex. Recently, deep learning methods have been used for breast lesion diagnosis with raw image input. However, without the guidance of domain knowledge, these data-driven methods cannot ensure that the features extracted from images are comprehensive for breast cancer diagnosis. Specifically, these features are difficult to relate to clinically relevant phenomena.PurposeInspired by the cognition process of radiologists, we propose a Knowledge-driven Feature Learning and Integration (KFLI) framework, to discriminate between benign and malignant breast lesions using Multi-sequences MRI.MethodsStarting from sequence division based on characteristics, we use domain knowledge to guide the feature learning process so that the feature vectors of sub-sequence are constrained to lie in characteristic-related semantic space. Then, different deep networks are designed to extract various sub-sequence features. Furthermore, a weighting module is employed for the integration of the features extracted from different sub-sequence images adaptively.ResultsThe KFLI is a domain knowledge and deep network ensemble, which can extract sufficient and effective features from each sub-sequence for a comprehensive diagnosis of breast cancer. Experiments on 100 MRI studies have demonstrated that the KFLI achieves sensitivity, specificity, and accuracy of 84.6%, 85.7% and 85.0%, respectively, which outperforms other state-of-the-art algorithms.     

The correlation of fractional anisotropy parameters with Ki-67 index,and the clinical implication in grading of non-enhancing gliomas and neuronal-glial tumors

PurposeTo investigate the correlation between the FA parameters and Ki-67 labeling index, and their diagnostic performance in grading supratentorial non-enhancing gliomas and neuronal-glial tumors (GNGT).MethodsThis institutional review board-approved, Health Insurance Portability and Accountability (HIPAA) compliant retrospective study enrolled 35 patients, including 19 with low grade GNGT and 16 with high grade GNGT. The mean FA, maximal FA and mean maximal FA values derived from diffusion tensor imaging were measured. The correlation between the FA parameters and the Ki-67 labeling index was assessed by Spearman rank test. The receiver operating characteristic curve analysis and multivariate logistic regression analysis were performed to detect the optimal imaging parameters in grading GNGT.ResultsThe three FA parameters of low grade GNGT were significantly lower than the high grade GNGT (p < 0.001). The mean FA, maximal FA and mean maximal FA had significant positive correlation with Ki-67 labeling index (p = 0.001, p < 0.001, p < 0.001 respectively). The maximal FA showed a higher sensitivity and specificity in grading of non-enhancing GNGT with specificity of 78.9%, sensitivity of 100.0%, respectively.ConclusionsThe FA parameters correlated with Ki-67 labeling index, and were useful surrogates in preoperative grading supratentorial non-enhancing GNGT.     

Diffusion-weighted MR imaging for assessing synovitis of wrist and hand in patients with rheumatoid arthritis: A feasibility study

The purpose of this study was to investigate the feasibility of diffusion-weighted imaging (DWI) in detecting synovitis of wrist and hand in patients with rheumatoid arthritis (RA) and evaluate its sensitivity, specificity and accuracy as compared to T₂-weighted imaging (T2WI) with short tau inversion recovery (STIR) with the reference standard contrast-enhanced magnetic resonance imaging (CE-MRI). Twenty-five patients with RA underwent MR examinations including DWI, T2WI with STIR and CE-MRI. MR images were reviewed for the presence and location of synovitis of wrist and hand. The sensitivity, specificity and accuracy of DWI and T2WI with STIR were calculated respectively and then compared. All patients included in this study completed MR examinations and yielded diagnostic image quality of DWI. For individual joint, there was good to excellent inter-observer agreement (k = 0.62–0.83) using DWI images, T2WI with STIR images and CE-MR images, respectively. There was a significance between DWI and T2WI with STIR in analyzing proximal interphalangeal joints II–V, respectively (P < 0.05). The k-values for the detection of synovitis indicated excellent overall inter-observer agreements using DWI images (k = 0.86), T2WI with STIR images (k = 0.85) and CE-MR images (k = 0.91), respectively. Overall, DWI demonstrated a sensitivity, specificity and accuracy of 75.6%, 89.3% and 84.6%, respectively, for detection of synovitis, while 43.0%, 95.7% and 77.6% for T2WI with STIR, respectively. DWI showed positive lesions much better and more than T2WI with STIR. Our results indicate that DWI presents a novel non-invasive approach to contrast-free imaging of synovitis. It may play a role as an addition to standard protocols.     

A comparison study of inhomogeneous magnetization transfer (ihMT) and magnetization transfer (MT) in multiple sclerosis based on whole brain acquisition at 3.0 T

IntroductionMultiple sclerosis (MS) is a central nervous system disorder that may eventually affect its function. The clinical standard for MS severity is based on a clinical scale, which lacks lesion specific information. Magnetic resonance imaging of MS faces the challenge of myelin specificity, and in this work a new method inhomogeneous magnetization transfer (ihMT) is investigated as new biomarker of demyelination in MS.MethodsLocal ethics committee approved this study and written informed consents were obtained. Between Oct 2017 to May 2018, eighteen patients with relapsing-remitting MS (RRMS) (6 males, 12 females, mean age 31.2) and sixteen healthy volunteers (6 males, 10 females, mean age 30.4 years) were enrolled in this prospective study. All subjects underwent MRI exams including MT and ihMT imaging as well as the Expanded Disability Status Scale (EDSS) assessments. Independent sample t-test were used to compare the difference of ihMT parameters between healthy white matter (HWM) and normal appearing white matter (NAWM) and between HWM and MS lesions, respectively. Spearman correlation were used to analyze the correlation between ihMT parameters of MS lesions and EDSS score.ResultsThe ihMTR and qihMT demonstrate significant differences between WHM and NAWM groups, while no significant differences are observed for MTR and qMT. All parameters show significant differences between HWM and MS groups (p < 0.05). There was moderate negative correlation between MTR, qMT and EDSS score (−0.440 and −0.572), while there was a strong negative correlation between ihMTR and qihMT and EDSS score (−0.704 and −0.739).ConclusionBased on whole brain analysis at 3.0 T, ihMT showed better correlation with EDSS compared to magnetization transfer imaging, and may be a potentially valuable biomarker for demyelination in MS.     

Visual estimation of the extent of myocardial hyperenhancement on late gadolinium-enhanced CMR in patients with hypertrophic cardiomyopathy

Aim

So far different approaches have been used to quantify late gadolinium enhancement (LGE) in patients with hypertrophic cardiomyopathy (HCM), but there is no general consensus on the gold standard, since histological data are scarce. The aim of our study was to investigate whether the determination of LGE in patients with HCM using a semiquantitative score based on the 17-segment model is feasible and has comparable accuracy to manual planimetry.

Methods

Forty-two patients with HCM underwent LGE cardiovascular magnetic resonance imaging. Determination of LGE by planimetry based on visual assessment was used as reference standard. Then the extent of LGE was assessed using a semiquantitative score based on the standard left ventricular 17-segment model. Each segment was scored for the distribution of LGE. The resulting summed score expressed as percentage of the maximum possible score was thereafter compared with the manual planimetric evaluation of LGE, expressed as a percentage of the left ventricular myocardial area.

Results

In 28 patients (66%), LGE was present. There was a good correlation between the semiquantitative score and the planimetric approach (r=0.89; y=0.819x+2.45; standard error of estimation=2.327; P<.0001). Additionally, the Bland–Altmann plot showed a high concordance between the two approaches (mean of the difference +1.7%). The inter- and intraobserver limits of agreement and the coefficients of repeatability based on measurements with the semiquantitative score of the extent of LGE were superior to planimetric measurements. Besides, the time requirement for the LGE determination using the semiquantitative score was found to be significantly reduced compared to manual planimetry (median 2 vs. 10 min).

Conclusions

Thus, a reliable global index of the size of the LGE is feasible and can easily be obtained from visual assessment with a semiquantitative score of the extent of the hyperenhancement.     

A Novel Laryngeal Palpatory Scale (LPS) in Patients with Muscle Tension Dysphonia

ObjectivesLaryngeal palpation is a routine clinical method for evaluation of patients with muscle tension dysphonia (MTD). The aim of this study was to develop a new comprehensive valid and reliable “laryngeal palpatory scale” (LPS), based on psychometric criteria.MethodsThe scale items were selected based on an in-depth analysis of the literature and an expert focus group. Scale item generation and item reduction were followed by a psychometric assessment. Qualitative and quantitative content validity (the content validity ratio (CVR), content validity index (CVI)), the qualitative face validity, and the inter-rater reliability were determined. For this purpose, 531 patients were assessed and finally 55 patients with primary MTD (26 women, mean age: 40.8 years, SD: 12.5; 29 male, mean age: 41.6 years, SD: 11.8) participated in the study. A weighted kappa (k*) statistic was used to examine the inter-rater reliability for each single item.ResultsBased on the CVR, three items were omitted because they had a score of less than 0.62. The CVI for all remaining items was greater than 0.79 and the scale CVI was equal to 0.96. The final 45 items were a result of the study. The inter-rater reliability for each single item ranged from 0.41 to 1, indicating moderate to almost perfect agreement.ConclusionsThe LPS is a reliable and valid instrument for assessing patients with MTD. However, future studies are needed to provide adequate data on sensitivity, specificity, concurrent validity, and cutoff scores.     

Idiopathic dilatation of the pulmonary artery: report of four cases.

Idiopathic dilatation of the pulmonary artery (IDPA) is a rare congenital disease which is usually detected fortuitously on chest x-ray, thus radiologists must be aware of this clinical entity. This report describes four cases to which Magnetic Resonance Imaging (MRI) played a major role in diagnosing IDPA and in detecting the concomitant findings observed in this disease. MRI is a non-invasive procedure with many advantages for the accurate and reproducible measurement of artery structures, which makes it the preferred option for combined use with echocardiography in the diagnosis and follow-up of patients with IDPA.     

Predicting the nodal status in gastric cancers: The role of apparent diffusion coefficient histogram characteristic analysis

PurposeTo explore the application of histogram analysis in preoperative T and N staging of gastric cancers, with a focus on characteristic parameters of apparent diffusion coefficient (ADC) maps.Materials and methodsEighty-seven patients with gastric cancers underwent diffusion weighted magnetic resonance imaging (b = 0, 1000 s/mm²), which generated ADC maps. Whole-volume histogram analysis was performed on ADC maps and 7 characteristic parameters were obtained. All those patients underwent surgery and postoperative pathologic T and N stages were determined.ResultsFour parameters, including skew, kurtosis, s-sD_av and sample number, showed significant differences among gastric cancers at different T and N stages. Most parameters correlated with T and N stages significantly and worked in differentiating gastric cancers at different T or N stages. Especially skew yielded a sensitivity of 0.758, a specificity of 0.810, and an area under the curve (AUC) of 0.802 for differentiating gastric cancers with and without lymph node metastasis (P < 0.001). All the parameters, except AUC_low, showed good or excellent inter-observer agreement with intra-class correlation coefficients ranging from 0.710 to 0.991.ConclusionCharacteristic parameters derived from whole-volume ADC histogram analysis could help assessing preoperative T and N stages of gastric cancers.     

Applications of Magnetic Resonance Imaging to Materials Research

Abstract

This review article deals with the applications of magnetic resonance imaging (MRI) to materials. The authors have attempted to perform a thorough review of the current literature. The articles examined span the period mainly from January 1989 to June 1993. The authors used CAS on-line and Science Citation Index on CD-ROM as their main sources of references using numerous key words for the searches. The authors also assume a basic knowledge on the part of the reader of NMR and h4R.I. For the novice reader or someone who would like more background on NMR theory, the authors suggest, T. C. Farrar's book Pulse h'MR (Farragut Press) and E. D. Becker's book High Resolution M R (Academic Press). For information regarding MRI and microscopy, the reader is referred to a book by F. W. Wehrli entitled Biomedical Magnetic Resonance Imaging (VCH) and a book by B. Blumich and W. Kuhn entitled Magnetic Resonance Microscopy (VCH). A book by Ernst, Bodenhausen, and Wokaun called Principles of Nuclear Magnetic Resonance in One- and Two-Dimensions is another valuable resource.     

MR T1ρ quantification of cartilage focal lesions in acutely injured knees: correlation with arthroscopic evaluation

Objective

Quantitative T₁ρ MRI has been suggested as a promising tool to detect changes in cartilage composition that are characteristic of cartilage damage and degeneration. The objective of this study was to evaluate the capability of MR T₁ρ to detect cartilage lesions as evaluated by arthroscopy in acutely ACL-injured knees and to compare with the Whole-Organ Magnetic Resonance Imaging Score (WORMS) using clinical standard MRI.

Method

Ten healthy controls (mean age 35) with no ACL injury or history of osteoarthritis (OA) and 10 patients with acute ACL injuries (mean age 39) were scanned at 3 Tesla (3 T). ACL patients underwent ACL reconstruction, where focal lesions were graded according to an Outerbridge grading system during arthroscopic evaluation. Normalized MR T₁ρ values (T₁ρ z-scores normalized to control values in matched regions) in full thickness, and superficial and deep layers of cartilage were compared between defined sub-compartments with and without focal lesions. Intraclass (ICC) correlation and the root mean square coefficient of variation (RMS-CV) were performed to evaluate the inter-observer reproducibility of T₁ρ quantification. Sub-compartments of cartilage were also evaluated using WORMS scoring and compared to their Outerbridge score respectively.

Results

The inter-observer ICC and the RMS-CV of the sub-compartment T₁ρ quantification were 0.961 and 3.9%, respectively. The average T₁ρ z-scores were significantly increased in sub-compartments with focal lesions compared to those without focal lesions and to the control cohort (p < 0.05).

Conclusion

Our results indicate that T₁ρ provided a better diagnostic capability than clinical standard MRI grading in detecting focal cartilage abnormalities after acute injuries. Quantitative MRI may have great potential in detecting cartilage abnormalities and degeneration non-invasively, which are occult with standard morphological MRI.     

Structural and Metabolic Pattern Classification for Detection of Glioblastoma Recurrence and Treatment-Related Effects

Artificial neuronal network (ANN) in classification of glioblastoma multiforme (GBM) recurrence from treatment effects using advanced magnetic resonance imaging techniques was evaluated. In 56 patients with treated GBM, normalised minimal and mean apparent-diffusion coefficient (ADC) values, vessels number on susceptibility-weighted images (SWI) and Cho/Cr ratio were analysed statistically and by ANN. Significant correlation exists between normalised minimal and mean ADC values, and no correlation between ADC and Cho/Cr values. Cut-off values for tumour presence were: 1.14 for normalised minimal ADC (54% sensitivity, 71% specificity), 1.13 for normalised mean ADC (51% sensitivity, 71% specificity), 1.8 for Cho/Cr ratio (92% sensitivity, 82% specificity), grade 2 for SWI (87% sensitivity, 82% specificity). An accurate prediction of ANN to classify patients into GBM progression or treatment effects group was 99% during the training and 96.8% during the testing phase. Multi-parametric ANN allows distinction between GBM recurrence and treatment effects, and can be used in clinical practice.     

Choledocolithiasis: diagnostic accuracy of MR cholangiopancreatography. Three-year experience

The purpose of this study was to evaluate the diagnostic accuracy of MR cholangiopancreatography (MRCP) in the detection of common bile duct stones. A series of 286 consecutive patients were referred for MRCP, that was performed with a 1.5 T MR unit, through a non-breath-hold, respiratory-triggered, fat-suppressed, two-dimensional, heavily T2-weighted fast spin-echo sequence in the coronal plane. Axial T1 and T2-weighted sequences were first obtained. Axial, coronal, and Maximum Intensity Projection images were evaluated by three independent readers, who were asked to determine whether stones were present or not inside the biliary tract. The findings of MRCP images were compared with endoscopic retrograde cholangiopancreatography, percutaneous trans-hepatic cholangiography, intra-operative cholangiography, surgical, or imaging follow-up findings. Two-hundred and seventy-eight out of 286 MRCP examinations were judged diagnostic by the three reviewers. Among the 278 patients included in our study group, biliary tract lithiasis was proved in 76 cases (27%). On the basis of reviewers' reading, MRCP had sensitivity 92-93%, specificity 97-98%, positive predictive value 91-93%, negative predictive value 97-98%, and the diagnostic accuracy ranged between 95% and 96% in the detection of calculi. Interobserver agreement was excellent (K = 0.84, kappa statistic). MRCP showed a high diagnostic accuracy and an excellent inter-observer agreement in the detection of common bile duct stones.     

Evaluating renal arterial wall by non-enhanced 2D and 3D free-breathing black-blood techniques: Initial experience

ObjectivesTo evaluate the feasibility and reproducibility of 2D and 3D black-blood sequences in measuring morphology of renal arterial wall.MethodsThe 2D and 3D imaging sequences used variable-refocusing-flip-angle and constant-low-refocusing-flip-angle turbo spin echo (TSE) readout respectively, with delicately selected black-blood scheme and respiratory motion trigger for free-breathing imaging. Fourteen healthy subjects and three patients with Takayasu arteritis underwent renal artery wall imaging with 3D double inversion recovery (DIR) TSE and 2D Variable Flip Angle-TSE (VFA-TSE) black-blood sequences at 3.0 T. Four healthy subjects were randomly selected for scan-rescan reproducibility experiments. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and morphology of arterial wall were measured and compared using paired-t-test or Wilcoxon signed-rank test between 2D and 3D sequences. The inter-observer, intra-observer and scan-rescan agreements of above measurements were determined using intraclass correlation coefficient (ICC).ResultsThe 2D and 3D imaging sequences showed similar morphological measurements (lumen area, wall area, mean wall thickness and maximum wall thickness) of renal arterial wall (all P > 0.05) and excellent agreement (ICC: 0.853–0.954). Compared to 2D imaging, 3D imaging exhibited significantly lower SNR_lumen (P < 0.01) and SNR_wall (P = 0.037), similar contrast-to-noise ratio (CNR) (P = 0.285), and higher CNR efficiency (CNR_eff) (P < 0.01). Both 2D and 3D imaging showed good to excellent inter-observer (ICC: 0.723–0.997), intra-observer (ICC: 0.749–0.996) and scan-rescan (ICC: 0.710–0.992) reproducibility in measuring renal arterial wall morphology, SNR and CNR, respectively.ConclusionsBoth high-resolution free-breathing 2D VFA-TSE and 3D DIR TSE black-blood sequences are feasible and reproducible in high-resolution renal arterial wall imaging. The 2D imaging has high SNR, whereas 3D imaging has high imaging efficiency.     

Magnetic resonance spectroscopy and brain volumetry in mild cognitive impairment. A prospective study

ObjectiveTo assess the accuracy of magnetic resonance spectroscopy (1H-MRS) and brain volumetry in mild cognitive impairment (MCI) to predict conversion to probable Alzheimer's disease (AD).MethodsForty-eight patients fulfilling the criteria of amnestic MCI who underwent a conventional magnetic resonance imaging (MRI) followed by MRS, and T1-3D on 1.5 Tesla MR unit. At baseline the patients underwent neuropsychological examination. 1H-MRS of the brain was carried out by exploring the left medial occipital lobe and ventral posterior cingulated cortex (vPCC) using the LCModel software. A high resolution T1-3D sequence was acquired to carry out the volumetric measurement. A cortical and subcortical parcellation strategy was used to obtain the volumes of each area within the brain. The patients were followed up to detect conversion to probable AD.ResultsAfter a 3-year follow-up, 15 (31.2%) patients converted to AD. The myo-inositol in the occipital cortex and glutamate + glutamine (Glx) in the posterior cingulate cortex predicted conversion to probable AD at 46.1% sensitivity and 90.6% specificity. The positive predictive value was 66.7%, and the negative predictive value was 80.6%, with an overall cross-validated classification accuracy of 77.8%. The volume of the third ventricle, the total white matter and entorhinal cortex predict conversion to probable AD at 46.7% sensitivity and 90.9% specificity. The positive predictive value was 70%, and the negative predictive value was 78.9%, with an overall cross-validated classification accuracy of 77.1%. Combining volumetric measures in addition to the MRS measures the prediction to probable AD has a 38.5% sensitivity and 87.5% specificity, with a positive predictive value of 55.6%, a negative predictive value of 77.8% and an overall accuracy of 73.3%.ConclusionEither MRS or brain volumetric measures are markers separately of cognitive decline and may serve as a noninvasive tool to monitor cognitive changes and progression to dementia in patients with amnestic MCI, but the results do not support the routine use in the clinical settings.     

Non-contrast-enhanced MR-angiography (MRA) of lower extremity peripheral arterial disease at 3 tesla: Examination time and diagnostic performance of 2D quiescent-interval single-shot MRA vs. 3D fast spin-Echo MRA

PurposeNon-contrast enhanced MRA is a promising diagnostic alternative to contrast-enhanced (CE-) MRA or CT in patients with lower extremity peripheral arterial disease (PAD) but potentially associated with prolonged examination times and inferior diagnostic performance. We aimed to compare examination times and diagnostic performance of non-contrast enhanced quiescent-interval slice-selective (QISS)-MRA and fast-spin-echo (FSE)-MRA at 3.0 T.Materials and methodsForty-five patients with PAD were recruited for this IRB approved prospective study. Subjects underwent lower extremity MRA with 1) QISS-MRA, 2) FSE-MRA, and 3) CE-MRA (continuous table movement MRA and time-resolved MRA of the calf), which served as the standard of reference. Scan times for each examination step and total examination times for each of the three techniques was determined. Image quality and degree of stenosis were rated by two readers on a 5-point Likert scale. Sensitivity, specificity and diagnostic accuracy for relevant (>50%) stenosis were calculated.ResultsMedian total examination time was 27:02 min for QISS-MRA (IQR, 25:13–31:01 min), 28:37 min for FSE-MRA (IQR, 25:51–33:12 min), and 31:22 min for CE-MRA (IQR, 26:41–33:23 min). Acquisition time for QISS-MRA was significantly longer compared to FSE-MRA and CE-MRA (p ≤ 0.0001), while time for localizers, scouts and planning of the MRA sequence was significantly shorter for QISS-MRA compared to FSE-MRA and CE-MRA (p ≤ 0.0001). QISS-MRA had significantly better image quality compared to FSE-MRA with less segments classified as non-diagnostic (Reader 1: 3% vs. 35%; Reader 2: 3% vs. 50%, p ≤ 0.0001). Overall, QISS-MRA showed significantly better diagnostic performance than FSE-MRA (sensitivity, 85% vs. 54%; specificity, 90% vs. 47%, diagnostic accuracy, 89% vs. 48%; p ≤ 0.0001).ConclusionTotal examination time of QISS-MRA and FSE-MRA was comparable with a conventional CE-MRA protocol. QISS-MRA showed significantly higher diagnostic performance than FSE-MRA.     

3D black blood MR angiography of the carotid arteries. A simple sequence for plaque hemorrhage and stenosis evaluation

ObjectivesTo evaluate the diagnostic performance of a new three-dimensional T1-weighted turbo-spin-echo sequence (3D T1-w TSE) compared to 3D contrast-enhanced angiography (CE-MRA) for stenosis measurement and compared to 2D T1-w TSE for intra-plaque hemorrhage (IPH) detection.MethodsEighty three patients underwent carotid MRI, using a new elliptic-centric phase encoding T1-weighted 3D TSE sequence in addition to the clinical protocol.Two observers evaluated image quality, presence of flow artifacts, and presence of intra-plaque hemorrhage, and computed the NASCET degree of stenosis for CE-MRA and for the new sequence. Inter-observer agreement and correlation between 3D TSE and CE-MRA for NASCET stenosis was estimated using Cohen's kappa, and correlation using linear regression and Bland-Altman plots.Histology was performed on endarterectomy samples for 18 patients. Sensitivity and specificity of 2D and 3D TSE for IPH diagnosis were computed.Results3D TSE showed better image quality than 2D TSE (p < 0.05). Interobserver agreement was good (kappa ≥ 0.86). Correlation between 3D TSE and CE-MRA was excellent (R = 0.95) for NASCET stenosis. Sensitivity and specificity for IPH diagnosis was 50% and 100% for 2D TSE and 100% and 83% for the 3D TSE.ConclusionsThe new 3D T1-w TSE allows both reliable measures of carotid stenosis, with a slight overestimation compared to CE-MRA (5%), and improved IPH identification, compared to 2D TSE.     

In vivo hypoxia characterization using blood oxygen level dependent magnetic resonance imaging in a preclinical glioblastoma mouse model

PurposeHypoxia measurements can provide crucial information regarding tumor aggressiveness, however current preclinical approaches are limited. Blood oxygen level dependent (BOLD) Magnetic Resonance Imaging (MRI) has the potential to continuously monitor tumor pathophysiology (including hypoxia). The aim of this preliminary work was to develop and evaluate BOLD MRI followed by post-image analysis to identify regions of hypoxia in a murine glioblastoma (GBM) model.MethodsA murine orthotopic GBM model (GL261-luc2) was used and independent images were generated from multiple slices in four different mice. Image slices were randomized and split into training and validation cohorts. A 7 T MRI was used to acquire anatomical images using a fast-spin-echo (FSE) T2-weighted sequence. BOLD images were taken with a T2*-weighted gradient echo (GRE) and an oxygen challenge. Thirteen images were evaluated in a training cohort to develop the MRI sequence and optimize post-image analysis. An in-house MATLAB code was used to evaluate MR images and generate hypoxia maps for a range of thresholding and ΔT2* values, which were compared against respective pimonidazole sections to optimize image processing parameters. The remaining (n = 6) images were used as a validation group. Following imaging, mice were injected with pimonidazole and collected for immunohistochemistry (IHC). A test of correlation (Pearson's coefficient) and agreement (Bland-Altman plot) were conducted to evaluate the respective MRI slices and pimonidazole IHC sections.ResultsFor the training cohort, the optimized parameters of “thresholding” (20 ≤ T2* ≤ 35 ms) and ΔT2* (±4 ms) yielded a Pearson's correlation of 0.697. These parameters were applied to the validation cohort confirming a strong Pearson's correlation (0.749) when comparing the respective analyzed MR and pimonidazole images.ConclusionOur preliminary study supports the hypothesis that BOLD MRI is correlated with pimonidazole measurements of hypoxia in an orthotopic GBM mouse model. This technique has further potential to monitor hypoxia during tumor development and therapy.     

Body Temperature Mapping by Magnetic Resonance Imaging

Abstract

There are numerous clinical situations, such as hyperthermia cancer therapy, under which body temperature has to be accurately evaluated. Magnetic Resonance Imaging presently offers the best set of non-invasive methods for body temperature mapping, including diffusion imaging, relaxation time measurement, magnetization transfer contrast and chemical shift spectroscopic imaging. The basic NMR parameters involved in each are first analyzed. The role of temperature in their physical variation is then presented and finally the different practical MRI methods are briefly discussed. In the present slate of available technology and for basic physical reasons, the T 1 method appears the best compromise at low and medium magnetic field in a limited temperature range. Chemical shift could be theoretically more promising but strictly depends from the homogeneity and stability of the magnet and will be available only at high or very high field.