Diffusion-weighted Magnetic Resonance Spectroscopy Research Articles

Validity of dynamic contrast-enhanced magnetic resonance imaging of the breast versus diffusion-weighted imaging and magnetic resonance spectroscopy in predicting the malignant nature of non-mass enhancement lesions

BackgroundBreast cancer is the commonest cancer affecting women worldwide. So, it is important to accurately detect and classify different breast lesions. Noninvasive methods for tissue characterization have increased interest, particularly for early diagnosis. Non-mass enhancement (NME) breast lesions are described in magnetic resonance imaging (MRI) as the presence of enhancement without space-occupying lesions. Several studies have described that certain characteristics can be used as new indicators of malignancy in breast NME lesions. We aimed to study the role of multiparametric-MRI (Mp-MRI) as diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) in assessment of NME lesions and to suggest which one offers the greatest diagnostic accuracy.MethodsThis retrospective study was conducted from March 2017 to December 2023 on 220 NME breast lesions. All lesions were analyzed to study the features of benign and malignant NME lesions using different MRI techniques including dynamic contrast-enhanced MRI (DCE-MRI), DWI, and MRS. Breast MRI was performed at 1.5 Tesla, findings were correlated with histopathological results of all cases.ResultsPatients’ mean age was 46.56 years with 220 NME breast lesions (54 were benign and 166 were malignant). Invasive ductal carcinoma with ductal carcinoma in situ was the most malignant type representing 93 cases. We found that segmental distribution, heterogeneous enhancement, type III curve, restricted diffusion, lower apparent diffusion coefficient, and positive choline peak were more with malignancy (P = 0.008, 0.02, 0.004, 0.001, and < 0.001). We detected that Mp-MRI has higher diagnostic accuracy than DCE-MRI and combined other functional sequences (DWI, MRS), it was 91.2% with sensitivity 89.9%, specificity 87.8%, positive predictive value 89.2%, and negative predictive value 82.2%.ConclusionsFunctional MRI techniques, such as DWI and MRS, can provide helpful information in assessment of NME lesions. They have high diagnostic accuracy, sensitivity, and specificity in characterizing NME breast lesions as benign or malignant. However, DCE-MRI is mandatory for lesion characterization and delineation of its nature and cannot be replaced by them alone in cases of lesion visualization. So, multiparametric-MRI can improve the diagnostic accuracy of NME breast lesions when combined with dynamic contrast-enhanced MRI and can help in reducing negative biopsy rates.

Diffusion of brain metabolites highlights altered brain microstructure in type C hepatic encephalopathy: a 9.4 T preliminary study.

Type C hepatic encephalopathy (HE) is a decompensating event of chronic liver disease leading to severe motor and cognitive impairment. The progression of type C HE is associated with changes in brain metabolite concentrations measured by 1H magnetic resonance spectroscopy (MRS), most noticeably a strong increase in glutamine to detoxify brain ammonia. In addition, alterations of brain cellular architecture have been measured ex vivo by histology in a rat model of type C HE. The aim of this study was to assess the potential of diffusion-weighted MRS (dMRS) for probing these cellular shape alterations in vivo by monitoring the diffusion properties of the major brain metabolites. The bile duct-ligated (BDL) rat model of type C HE was used. Five animals were scanned before surgery and 6- to 7-week post-BDL surgery, with each animal being used as its own control. 1H-MRS was performed in the hippocampus (SPECIAL, TE = 2.8 ms) and dMRS in a voxel encompassing the entire brain (DW-STEAM, TE = 15 ms, diffusion time = 120 ms, maximum b-value = 25 ms/μm2) on a 9.4 T scanner. The in vivo MRS acquisitions were further validated with histological measures (immunohistochemistry, Golgi-Cox, electron microscopy). The characteristic 1H-MRS pattern of type C HE, i.e., a gradual increase of brain glutamine and a decrease of the main organic osmolytes, was observed in the hippocampus of BDL rats. Overall increased metabolite diffusivities (apparent diffusion coefficient and intra-stick diffusivity-Callaghan's model, significant for glutamine, myo-inositol, and taurine) and decreased kurtosis coefficients were observed in BDL rats compared to control, highlighting the presence of osmotic stress and possibly of astrocytic and neuronal alterations. These results were consistent with the microstructure depicted by histology and represented by a decline in dendritic spines density in neurons, a shortening and decreased number of astrocytic processes, and extracellular edema. dMRS enables non-invasive and longitudinal monitoring of the diffusion behavior of brain metabolites, reflecting in the present study the globally altered brain microstructure in BDL rats, as confirmed ex vivo by histology. These findings give new insights into metabolic and microstructural abnormalities associated with high brain glutamine and its consequences in type C HE.

Practical considerations of diffusion-weighted MRS with ultra-strong diffusion gradients.

Diffusion-weighted magnetic resonance spectroscopy (DW-MRS) offers improved cellular specificity to microstructure-compared to water-based methods alone-but spatial resolution and SNR is severely reduced and slow-diffusing metabolites necessitate higher b-values to accurately characterize their diffusion properties. Ultra-strong gradients allow access to higher b-values per-unit time, higher SNR for a given b-value, and shorter diffusion times, but introduce additional challenges such as eddy-current artefacts, gradient non-uniformity, and mechanical vibrations. In this work, we present initial DW-MRS data acquired on a 3T Siemens Connectom scanner equipped with ultra-strong (300 mT/m) gradients. We explore the practical issues associated with this manner of acquisition, the steps that may be taken to mitigate their impact on the data, and the potential benefits of ultra-strong gradients for DW-MRS. An in-house DW-PRESS sequence and data processing pipeline were developed to mitigate the impact of these confounds. The interaction of TE, b-value, and maximum gradient amplitude was investigated using simulations and pilot data, whereby maximum gradient amplitude was restricted. Furthermore, two DW-MRS voxels in grey and white matter were acquired using ultra-strong gradients and high b-values. Simulations suggest T2-based SNR gains that are experimentally confirmed. Ultra-strong gradient acquisitions exhibit similar artefact profiles to those of lower gradient amplitude, suggesting adequate performance of artefact mitigation strategies. Gradient field non-uniformity influenced ADC estimates by up to 4% when left uncorrected. ADC and Kurtosis estimates for tNAA, tCho, and tCr align with previously published literature. In conclusion, we successfully implemented acquisition and data processing strategies for ultra-strong gradient DW-MRS and results indicate that confounding effects of the strong gradient system can be ameliorated, while achieving shorter diffusion times and improved metabolite SNR.

Advanced multiparametric magnetic resonance imaging of intra-axial posterior fossa tumors

Background: For early treatment planning, it is required that accurate diagnosis of intra-axial posterior fossa tumors can be done. However, imaging diagnosis can be challenging due to analogous magnetic resonance imaging (MRI) features. Aims and Objectives: The aim of the study was to determine the accuracy of advanced MRI sequences such as diffusion-weighted imaging and magnetic resonance spectroscopy (MRS) in diagnosis of intra-axial posterior fossa masses in a tertiary care center. Materials and Methods: This was a retrospective observational study including 43 patients with posterior fossa intra-axial space-occupying tumors. Mean of minimum apparent diffusion coefficient (ADC) values (mean ADCmin) was derived in tumor, and normal white matter regions and ADC ratio was estimated. On MRS, choline/creatinine (Cho/Cr) and Cho/N-acetyl aspartate (NAA) ratios were noted. Receiver operating characteristic (ROC) curve was used to determine cut-off values for mean tumor ADCmin, ADC ratio, Cho/Cr ratio, and Cho/NAA ratio. Results: The most common tumor was medulloblastoma (MB) (30.23%), followed by metastasis (25.58%), pilocytic astrocytoma (16.28%), brainstem glioma (9.3%), hemangioblastoma (6.98%), glioneuronal tumor (6.98%), and ependymoma (4.65%). MBs showed lowest mean tumor ADCmin (0.57±0.12×10-3 mm2/s) and ADC ratio (0.92±0.18) and highest Cho/Cr ratio (8.26±3.9) and Cho/NAA ratio (6.4±1.83) with significant difference from the group of remaining tumors. ROC curve analysis revealed cutoff values of ≤0.71×10-3mm2/s for ADCmin; ≤ 1.02 for ADC ratio; &gt;3.76 for Cho/Cr ratio, and &gt;3.2 for Cho/NAA ratio for the differentiation of MBs from other tumors. Conclusion: The combined use of ADCmin values, ADC ratio, Cho/Cr ratio, and Cho/NAA ratio can help in better non-invasive analysis of similarly appearing intra-axial posterior fossa tumors.

Clinical Presentation, MRI findings and Molecular insights in Diffuse Intrinsic Pontine Gliomas (DIPGs): A Comprehensive Review.

Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive and the most common brainstem tumor affecting pediatric patients, with a poor prognosis and limited treatment options. Despite extensive research, the median overall survival remains low, and current treatment mainly relies on radiotherapy. Recent discoveries of recurrent somatic mutations, particularly in histone 3 variants, have led to a reclassification of pediatric diffuse gliomas. However, the relationship between genetic alterations, imaging features, and prognosis is not yet fully understood. This review provides an overview of DIPG, including its clinical presentation, typical imaging findings (with a focus on MRI techniques), diagnostic challenges, treatment modalities, and recent advancements in molecular understanding. DIPG presents with characteristic neurological symptoms and often manifests as an expansile intra-axial mass in the pons, usually exhibiting typical MRI findings. Diffusion-weighted imaging and magnetic resonance spectroscopy can provide additional insights. Pathologically, most DIPGs are pediatric type of diffuse high-grade gliomas, with specific histological features and occasional leptomeningeal spread. Radiotherapy remains the mainstay treatment. However, clinical trials with new agents are ongoing, trying to improve outcomes for DIPG patients.

Characterizing Various Posterior Fossa Tumors in Children and Adults With Diffusion-Weighted Imaging and Spectroscopy.

Background Theposterior fossa is situated between thetentorium cerebelli above and the foramen magnum below. Vital structures like the cerebellum, the pons, and the medulla are situated within it; hence, tumors within the posterior fossa are considered one of the most critical brain lesions. Children are more likely to develop posterior fossa tumors than adults. Diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) sequences along with the conventional MRI helpin providing additional information in the characterization of the various posterior fossa tumors. We hereby present a series of 30 patients with clinically suspected posterior fossa masses who underwent preoperative MRI. Objectives This study aims to differentiate the neoplastic from non-neoplastic posterior fossa mass by evaluating the diffusion restriction pattern on DWI, quantifying the apparent diffusion coefficient (ADC) map in various posterior fossa tumors, and comparing the different metabolites of various posterior fossa tumors on MRS. Results Out of the 30 patients with posterior fossa lesions, 18 were males and 12 were females. Eight of them were in the pediatric age group, while twenty-two of them were adults. Metastasis was the most common posterior fossa lesionin our study sample and was found in six patients (20%), followed by vestibular schwannomas (17%) and arachnoid cysts (13%), meningiomas, medulloblastoma, and pilocytic astrocytoma (10% each) and epidermoid, ependymoma, and hemangioblastoma (7% each). The mean ADC value of benign tumors was higher than that of malignant tumors, and this difference was found to be significant (p = 0.012). The cut-off ADC value 1.21x 10-3mm2/s had a sensitivity of 81.82% and specificity of 80.47%. MRS metabolites played an additional role in differentiating benign from malignant tumors. Conclusion A combination of conventional MRI, DWI,ADC values, and MRS metabolites showed good diagnostic accuracy to differentiate between the various posterior fossa neoplastic tumors both in adults and children.

Diffusion-weighted magnetic resonance imaging and magnetic resonance spectroscopy for non-invasive characterization of azoospermia: A prospective comparative single-center study.

Azoospermia affects about 15% of childless males. The differential diagnosis between subtypes of azoospermia is the initial step in its management. To investigate the role of diffusion-weighted magnetic resonance imaging and proton magnetic resonance spectroscopy in distinguishing obstructive azoospermia from non-obstructive azoospermia and predicting sperm retrieval together with histological alterations in men with non-obstructive azoospermia. This prospective comparative study involved 60 men with obstructive azoospermia (group A) and 60 men with non-obstructive azoospermia (group B). Scrotal proton magnetic resonance spectroscopy and diffusion-weighted magnetic resonance imaging were conducted for all participants to respectively evaluate testicular metabolites and normalized apparent diffusion coefficient 1 week before sperm retrieval. Apparent diffusion coefficient was significantly higher in group B as compared to group A (0.47±0.11vs. 0.29±0.05; and 0.46±0.14vs. 0.28±0.02) for the right and left testis, respectively. Conversely, testicular choline and lipids were significantly higher in group A as compared to group B. Normalized apparent diffusion coefficient, choline, and lipids at cut-off levels of 0.353, 0.31, and 0.725 could differentiate between obstructive azoospermia and non-obstructive azoospermia (area under the curve=0.963; confidence interval=0.939-0.986, area under the curve=0.985; confidence interval=0.974-0.997, and area under the curve=0.970; confidence interval=0.940-0.999, respectively). Regarding the prediction of sperm retrieval in the non-obstructive azoospermia group, choline levels had the highest area under the curve (0.923), and its cut-off level was 0.195. The normalized apparent diffusion coefficient was significantly lower in men with positive sperm retrieval as compared to men with unsuccessful retrieval. Finally, it was revealed that all magnetic resonance imaging parameters except creatine could independently predict testicular histology in men with non-obstructive azoospermia. The highest prediction was 95% in normal spermatogenesis, and the least prediction was 40% in spermatid arrest. Regression analysis was used to detect final predictors and extrapolate an equation that could be used to predict testicular pathology CONCLUSIONS: Normalized apparent diffusion coefficient and proton magnetic resonance spectroscopy are helpful in differentiating obstructive azoospermia from non-obstructive azoospermia and predicting sperm retrieval and related histological alterations in men with non-obstructive azoospermia.

Role of MRI modalities in assessment of cystic brain Lesions: a prospective study

Background. Intracranial cystic lesions are unnatural cavities in which the continuity of the brain parenchyma is disrupted because of different pathologies such as infections and tumors containing proteinaceous fluid and/or cellular/necrotic materials.&#x0D; Purpose – to investigate the value of some MRI modalities, mostly DWI and MR spectroscopy, in differentiation of the common intracranial intra-axial cystic brain lesions to help these patients benefit from the best medical management and treatment.&#x0D; Materials and Methods. This is a prospective study, conducted from April 2019 till April 2021. It involved forty adult patients of both sexes with a cystic/necrotic intra-axial brain lesion with variable perifocal edema and rim enhancement on post-contrast study at MRI unit, radiology department, Ain Shams University (ASU) Hospital. All examinations were carried out after signing of the informed consent by the patients themselves or their guardian if the patient was incapacitated by any means.&#x0D; Results. The ADC values in the center of lesions were not uniform. We found the lowest ADC value in the center of the lesion at the abscess 0.4x10–3 mm2 /s, and the highest ADC value 3.2x10–3 mm2 /s was in cystic neoplastic lesion. There was a significant difference in the ADC values in the center of neoplastic necrotic lesions; mean ADC value was (1.95±1.08) x10–3 mm2 /s and (1.15±0.65) x10–3 mm2 /s in abscess lesions, with a cut-off value, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy value of: 1.55%, 92.9%, 91.7%, 96.3%, 84.6% and 92.5% respectively. MRS was performed in 40 cases, and the Cho/Cr, Cho/NAA and NAA/Cr mean ratios were calculated. These ratios were compared between the different categories. Statistically significant differences were found in the Cho/Cr, Cho/NAA ratios between both groups (p values&lt;0.001**), while no statistically significant difference was found in the NAA/Cr ratio.&#x0D; Conclusion. Diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) are useful as additional diagnostic modalities for differentiating brain abscesses from cystic or necrotic brain tumors. Furthermore, the following MR techniques may be helpful for discriminating brain abscess from cystic or necrotic tumors: diffusion tensor imaging (DTI), perfusion weighted imaging as well as positron emission tomography computed tomography (PET-CT). This will help to improve the accuracy of MR in differentiating brain abscess from cystic or necrotic tumors.

MP-PCA denoising for diffusion MRS data: promises and pitfalls

Diffusion-weighted (DW) magnetic resonance spectroscopy (MRS) suffers from a lower signal to noise ratio (SNR) compared to conventional MRS owing to the addition of diffusion attenuation. This technique can therefore strongly benefit from noise reduction strategies. In the present work, Marchenko-Pastur principal component analysis (MP-PCA) denoising is tested on Monte Carlo simulations and on in vivo DW-MRS data acquired at 9.4 T in rat brain and at 3 T in human brain. We provide a descriptive study of the effects observed following different MP-PCA denoising strategies (denoising the entire matrix versus using a sliding window), in terms of apparent SNR, rank selection, noise correlation within and across b-values and quantification of metabolite concentrations and fitted diffusion coefficients. MP-PCA denoising yielded an increased apparent SNR, a more accurate B0 drift correction between shots, and similar estimates of metabolite concentrations and diffusivities compared to the raw data. No spectral residuals on individual shots were observed but correlations in the noise level across shells were introduced, an effect which was mitigated using a sliding window, but which should be carefully considered.

A prospective study to evaluate the role of multiparametric magnetic resonance imaging in the grading of gliomas using magnetic resonance imaging perfusion and diffusion and multivoxel magnetic resonance spectroscopy

Abstract Background: The primary aim of this study was to evaluate the individual and combined efficacy of magnetic resonance imaging (MRI) parameters, which include MRI perfusion, MRI diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) in the grading of gliomas as low grade versus high grade. The pre-operative imaging-based grading of gliomas by multiparametric MRI was compared with the gold standard histopathological studies. Methods: A total of 22 patients referred to the radiology department for multiparametric MRI of the brain with presumptive diagnosis of glioma on computed tomography/MRI were included in the study. Conventional T1, T2 and fluid-attenuated inversion recovery images were obtained followed by perfusion MRI using gadopentetate dimeglumine (Magnevist) administration. This was followed by DWI and MRS. Results: Our statistical analysis demonstrated that a cut-off of apparent diffusion coefficient value of 954.085 (10–6 mm2/Sec) provides a sensitivity and specificity of 87.5% and 85.7%, respectively, in differentiating low-grade gliomas (LGGs) from high-grade gliomas (HGGs). A choline/creatine ratio cut-off value of 2 provides sensitivity and specificity of 100% and 92.9%, respectively, while a cut-off value of 1.45 of choline/N-acetylaspartate ratio provides both sensitivity and specificity of 100% in differentiating LGG from HGG. A cut-off of 1.9 for maximum relative cerebral blood volume (rCBV) value provides both sensitivity and specificity of 100% in differentiating LGGs from HGGs. Conclusions: We concluded that perfusion MRI (rCBV) was the best parameter among perfusion MRI, DWI and MRI spectroscopy in differentiating HGGs from LGGs. Combined multiparametric results showed a diagnostic accuracy, sensitivity, specificity, positive predictive value and negative predictive value of 86.4%, 82.4%, 100%, 100% and 62.5%, respectively, on comparison with gold standard histopathological grading.

Using spectrally-selective radiofrequency pulses to enhance lactate signal for diffusion-weighted MRS measurements in vivo

Measurement of lactate diffusion properties using diffusion-weighted magnetic resonance spectroscopy in vivo may allow elucidating brain lactate cellular compartmentation, which would be of great importance for neuroscience. However, measuring lactate signal is complicated by low signal-to-noise ratio due to low lactate concentration and J-modulation of its 1.3 ppm peak.In this work, we assess the benefits of using a diffusion-weighting spin echo block and spectrally selective refocusing pulses to suppress the effect of J-coupling on the 1.3 ppm lactate resonance, by not refocusing its coupling partner at 4.1 ppm. Two different kinds of spectrally selective pulses, either polychromatic or single-band, are evaluated in the mouse brain at 11.7 T. Almost complete suppression of J-modulation is shown, resulting in an approximately two-fold signal increase as compared to a reference STE-LASER sequence (for the specific diffusion times used in this work). Repeated measurements confirm that lactate diffusion-weighted signal attenuation is measured with an approximately two-fold precision.

Diffusion-weighted MR spectroscopy (DW-MRS) is sensitive to LPS-induced changes in human glial morphometry: A preliminary study

BackgroundLow-dose lipopolysaccharide (LPS) is a well-established experimental method for inducing systemic inflammation and shown by microscopy to activate microglia in rodents. Currently, techniques for in-vivo imaging of glia in humans are limited to TSPO (Translocator protein) PET, which is expensive, methodologically challenging, and has poor cellular specificity. Diffusion-weighted magnetic resonance spectroscopy (DW-MRS) sensitizes MR spectra to diffusion of intracellular metabolites, potentially providing cell-specific information about cellular morphology. In this preliminary study, we applied DW-MRS to measure changes in the apparent diffusion coefficients (ADC) of glial and neuronal metabolites to healthy participants who underwent an LPS administration protocol. We hypothesized that the ADC of glial metabolites will be selectively modulated by LPS-induced glial activation. MethodsSeven healthy male volunteers, (mean 25.3 ± 5.9 years) were each tested in two separate sessions once after LPS (1 ng/Kg intravenously) and once after placebo (saline). Physiological responses were monitored during each session and serial blood samples and Profile of Mood States (POMS) completed to quantify white blood cell (WBC), cytokine and mood responses. DW-MRS data were acquired 5-5½ hours after injection from two brain regions: grey matter in the left thalamus, and frontal white matter. ResultsBody temperature, heart rate, WBC and inflammatory cytokines were significantly higher in the LPS compared to the placebo condition (p < 0.001). The ADC of the glial metabolite choline (tCho) was also significantly increased after LPS administration compared to placebo (p = 0.008) in the thalamus which scaled with LPS-induced changes in POMS total and negative mood (Adj R2 = 0.83; p = 0.004). ConclusionsDW-MRS may be a powerful new tool sensitive to glial cytomorphological changes in grey matter induced by systemic inflammation.

Magnetic Resonance Spectroscopy for Risk Stratification of Sonographically Indeterminate Ovarian Neoplasms: Preliminary Study.

We aim to assess the additional value of diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) for the risk stratification of sonographically indeterminate ovarian neoplasms. A total of 21 patients with diagnosed adnexal masses between 2014 and 2017 were divided into malignant (four serous cystadenocarcinomas, four endometrioid carcinomas, three clear cell carcinomas, and one carcinosarcoma) and benign (four cystadenomas, two teratomas, one fibroma, one endometrioma, and one corpus luteal cyst) groups. An apparent diffusion coefficient (ADC) value of 1.27 × 10−3 mm2/s was considered as the optimal threshold in distinguishing malignant from benign ovarian tumors (sensitivity and specificity: 100% and 77.8%, respectively). Choline peaks were detected in six of seven O-RADS (Ovarian-Adnexal Imaging-Reporting Data System) 4 lesions and corrected all of the DWI false-negative clear cell carcinoma. Based on the presence of the choline peaks, the diagnostic performance of MRS showed a sensitivity of 77.8%, a specificity of 100%, and an accuracy of 85.7%, respectively. In conclusion, MRS could potentially play a complementary role for DWI in tumor characterization, particularly for O-RADS 4 tumors or clear cell carcinomas.

Role of MRI in Differentiating Various Posterior Cranial Fossa Space-Occupying Lesions Using Sensitivity and Specificity: A Prospective Study

Background: Any abnormal space-occupying posterior fossa lesion may directly involve the vital structures like the brain stem, cranial nerves, cerebellum, vertebrobasilar artery, and venous sinuses, which makes the surgical approach and total excision very difficult. Hence for these reasons, precise evaluation of posterior fossa lesion with MRI is a must to visualize the vital structures, which helps in planning and safe surgery. Objective: This study aimed to evaluate the added value of diffusion-weighted imaging and magnetic resonance spectroscopy in the localization, extension, characterization, differentiation of various posterior fossa space-occupying lesions, and correlating with the histopathological result.Materials and methods: This prospective study comprised of 40 patients who were suspected with posterior fossa space-occupying lesions on basis of clinical features or on CT scan. All patients were evaluated using conventional as well as newer MRI techniques using Siemens 1.5 Tesla MRI scanner (Siemens Medical System, Erlangen, Germany). Diffusion-weighted imaging (DWI) was done in all patients and magnetic resonance spectroscopy (MRS) was done in 27 patients. Based on the MRI findings, various posterior fossa lesions were classified as neoplastic or non-neoplastic. The neoplastic lesions were further classified as benign and malignant. The MRI findings were correlated with histopathological findings or follow-up.Statistical analysis: Independent sample t-test was used to compare the mean apparent diffusion coefficient (ADC) values of various posterior fossa space-occupying lesions. Receiver operating characteristic (ROC) curve analysis was done to determine the optimal cut-off mean ADC values and choline/creatinine (Cho/cr) ratios for various benign and malignant posterior fossa tumors.Results: Of 40 patients with posterior fossa lesions, 23 were males and 17 were females with a mean age of 34.67±1.93[SD] years. Metastases were the most common posterior fossa lesions in our study sample and found in seven patients (17.5%) followed by vestibular schwannomas and brainstem gliomas in five patients (12.5%) each, demyelinating lesion in four patients (10%), tubercular abscess in three patients (7.5%), hemangioblastoma, tuberculoma, arachnoid cyst, epidermoid cyst, pilocytic astrocytoma, low-grade glioma in two patients (5%) each, meningioma, medulloblastoma, pyogenic abscess and high-grade glioma in one patient (2.5%) each. The mean ADC value of benign tumors was higher than that of malignant tumors and this difference was found to be significant (p = 0.019). The cut-off ADC value 1.022 x 10-3mm2/s had a sensitivity of 78.6% and specificity of 66.7%. MRS played important role in differentiating neoplastic from non-neoplastic lesions and benign from malignant tumors. The cut-off Cho/cr ratio of 1.25 had a sensitivity of 66.7%, specificity of 85.7% to differentiate benign from malignant tumors.Conclusion: Conventional MRI sequences able to diagnose most of the benign-appearing lesions of posterior fossa, however, adding advanced MRI sequences like diffusion-weighted imaging and MR spectroscopy helps us to differentiate and diagnose various posterior fossa lesions even closer to the actual histopathological diagnosis.

Multiparametric characterization of white matter alterations in early stage Huntington disease

Huntington’s disease (HD) is a monogenic, fully penetrant neurodegenerative disorder. Widespread white matter damage affects the brain of patients with HD at very early stages of the disease. Fixel-based analysis (FBA) is a novel method to investigate the contribution of individual crossing fibers to the white matter damage and to detect possible alterations in both fiber density and fiber-bundle morphology. Diffusion-weighted magnetic resonance spectroscopy (DW-MRS), on the other hand, quantifies the motion of brain metabolites in vivo, thus enabling the investigation of microstructural alteration of specific cell populations. The aim of this study was to identify novel specific microstructural imaging markers of white matter degeneration in HD, by combining FBA and DW-MRS. Twenty patients at an early stage of HD and 20 healthy controls were recruited in a monocentric study. Using diffusion imaging we observed alterations to the brain microstructure and their morphology in patients with HD. Furthermore, FBA revealed specific fiber populations that were affected by the disease. Moreover, the mean diffusivity of the intra-axonal metabolite N-acetylaspartate, co-measured with N-acetylaspartylglutamate (tNAA), was significantly reduced in the corpus callosum of patients compared to controls. FBA and DW-MRS of tNAA provided more specific information about the biological mechanisms underlying HD and showed promise for early investigation of white matter degeneration in HD.

Diagnosis and analysis of primary central nervous system lymphoma based on MRI segmentation algorithm.

Objective:This paper summarizes the MRI imaging findings of primary central nervous system lymphoma (PCNSL) in the posterior cranial fossa to improve the accuracy of PCNSL diagnosis in the posterior cranial fossa.Methods:This study retrospectively analyzed the MRI imaging manifestations of 15 PCNSL posterior cranial fossa cases confirmed by puncture or surgical pathology from June 2017 to May 2018, including their occurrence sites, the number of lesions, MRI plain and enhanced manifestations, and diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy. Imaging (MRS) performance.Results:A total of 15 cases were enrolled, including 10 cases of single lesion and five cases of multiple lesions. The total number of lesions was 25, which were in the cerebellar hemisphere and cerebellar vermis, midbrain, fourth ventricle, and pontine cerebellum. The lesions were round, irregular, nodular, patchy, with low or medium signals on T1WI, equal or slightly higher signals on T2WI, and enhanced with 25 meningiomas-like gray matter signals. All of them were significantly strengthened. “Acupoint sign” and “umbilical depression sign” were seen in eight lesions. There were 17 massive and nodular enhancements, four striped enhancements, three patchy enhancements, and one circular enhancement. five cases of DWI showed homogeneous high signal, two cases showed uneven high signal, and 3 cases showed medium signal. The ADC value of tumor parenchyma in 10 patients was (0.62±0.095)×10-3mm2/s. MRS examination showed obvious Lip peak in two cases.Conclusion:PCNSL in posterior cranial fossa has certain characteristics. DWI, ADC value and MRS are helpful to improve the correct diagnosis rate of PCNSL.

Thalamic energy dysfunction is associated with thalamo-cortical tract damage in multiple sclerosis: A diffusion spectroscopy study

Background: Diffusion-weighted 1H magnetic resonance spectroscopy (DW-MRS) allows to quantify creatine-phosphocreatine brain diffusivity (ADC(tCr)), whose reduction in multiple sclerosis (MS) has been proposed as a proxy of energy dysfunction. Objective: To investigate whether thalamic ADC(tCr) changes are associated with thalamo-cortical tract damage in MS. Methods: Twenty patients with MS and 13 healthy controls (HC) were enrolled in a DW-MRS and DW imaging (DWI) study. From DW-MRS, ADC(tCr) and total N-acetyl-aspartate diffusivity (ADC(tNAA)) were extracted in the thalami. Three thalamo-cortical tracts and one non-thalamic control tract were reconstructed from DWI. Fractional anisotropy (FA), mean (MD), axial (AD), and radial diffusivity (RD), reflecting microstructural integrity, were extracted for each tract. Associations between thalamic ADC(tCr) and tract metrics were assessed using linear regression models adjusting for age, sex, thalamic volume, thalamic ADC(tNAA), and tract-specific lesion load. Results: Lower thalamic ADC(tCr) was associated with higher MD and RD of thalamo-cortical projections in MS (MD: p = 0.029; RD: p = 0.017), but not in HC (MD: p = 0.625, interaction term between thalamic ADC(tCr) and group = 0.019; RD: p = 0.320, interaction term = 0.05). Thalamic ADC(tCr) was not associated with microstructural changes of the control tract. Conclusion: Reduced thalamic ADC(tCr) correlates with thalamo-cortical tract damage in MS, showing that pathologic changes in thalamic energy metabolism are associated with structural degeneration of connected fibers.

The value of Mr DWI and MRS imaging in the diagnosis of prostate cancer

Abstract: objective: to investigate the diagnostic value of combined diffusion-weighted magnetic resonance imaging (DWI) and magnetic resonance spectroscopy (MRS) in prostate cancer (PCa).Materials and methods: A total of 25 patients in group A, ranging in age from 67 to 85 years, had diffuse lesions in 3 of them and bone metastases (ilium, pubis, etc.) in 5 of them were confirmed by final examination. All the patients in group A had higher TPSA levels than the reference standard of 4ng/ml within 7 days before mri examination, and the lowest concentration in one patient was 5.02ng/ml. Results greater than 100ng/ml were measured in 5 patients. The sensitivity, specificity and accuracy of DWI, MRS and DWI combined with MRS for PCa diagnosis were analyzed.Results: the mean ADC values of PCa area, peripheral band and central gland in patients with BPH were (0.83±0.12)× 10-3mm /s, (1.82±0.26)× 10-3mm /s and (1.46±0.16)× 10-3mm /s(F=31.1, P &lt; 0.05), respectively.222The mean (Cho+Cr)/Cit values in PCa region, peripheral zone and central gland of BPH patients were 1.55±0.11, 0.53±0.16 and 0.64±0.13, respectively (F=18.2, P &lt; 0.05).There was a statistically significant difference between PCa and BPH patients' peripheral zone and central gland (Cho+Cr)/Cit (P &lt; 0.05), while there was no statistically significant difference between BPH patients' peripheral zone and central gland (Cho+Cr)/Cit (P &gt;, 0.05).The sensitivity, specificity and accuracy of PCa diagnosed by DWI were 79.17%, 80% and 79.63% respectively.The sensitivity, specificity and accuracy of PCa were 87.5%, 86.67% and 87.03% respectively.The sensitivity, specificity and accuracy of DWI combined with MRS in diagnosing PCa were 91.67%, 93.33% and 92.59%, respectively.Conclusion: DWI combined with MRS is better than DWI and MRS alone in the diagnosis of PCa.

Combined intravoxel incoherent motion diffusion-weighted MR imaging and magnetic resonance spectroscopy in differentiation between osteoporotic and metastatic vertebral compression fractures

PurposeOur purpose was to combine intravoxel incoherent motion diffusion-weighted MR imaging (IVIM-DWI) and magnetic resonance spectroscopy (MRS) to differentiate osteoporotic fractures from osteolytic metastatic vertebral compression fractures (VCFs).MethodsA total of 70 patients with VCFs were included and divided into two groups, according to their causes of fractures based on pathological findings or clinical follow-up. All patients underwent conventional sagittal T1WI, T2WI, STIR, IVIM-DWI, and single-voxel MRS. The diffusion coefficient (D), pseudo diffusion (D*), and perfusion fraction (f) parameters from IVIM-DWI and the lipid water ratio (LWR) and fat fraction (FF) parameters from MRS were obtained and compared among groups. Furthermore, the diagnostic performance of MRS, IVIM-DWI, and IVIM-DWI combined with MRS for differentiation between osteoporotic and osteolytic metastatic VCFs was assessed by using receiver operating characteristic (ROC) curve analysis.ResultsCompared with the osteoporotic group, the metastatic group had significantly lower values for f, D, and FF, but higher D* (all P < 0.05). The area under the receiver operating characteristic (ROC) curve of MRS, IVIM-DWI, and IVIM-DWI combined with MRS were 0.73, 0.88, and 0.94, respectively. Among these, the IVIM-DWI combined with MRS showed the highest sensitivity, specificity, and accuracy, which are 90.63% (29/32), 97.37 % (37/38), and 94.29% (66/70), respectively.ConclusionsIVIM-DWI combined with MRS can be more accurate and efficient for differentiation between osteoporotic and osteolytic metastatic VCFs than single MRS or IVIM-DWI.

Magnetic resonance spectroscopy extended by oscillating diffusion gradients: Cell-specific anomalous diffusion as a probe for tissue microstructure in human brain

PurposeTo demonstrate that oscillating gradient spin-echo sequences can be combined with diffusion-weighted magnetic resonance spectroscopy even on clinical MR systems to study human brain at short diffusion times to provide apparent diffusion coefficients (ADCs) sensitive to a narrower cellular length scale than pulsed gradient spin-echo sequences at long diffusion time. MethodsMeasurements were performed on a 3T MR system using a semiLaser sequence with diffusion-weighting realized by oscillating and pulsed gradient modules, encoding diffusion times <10 ms and >50 ms, respectively. Metabolite-cycling was included to measure metabolites and water simultaneously. The sequence was tested in a phantom and in a parieto-occipital cerebral region of interest with mixed gray/white matter content of 6 subjects. The water reference was used for phase, frequency, and eddy-current correction as well as motion compensation. ADCs were estimated by 1D sequential and 2D simultaneous fitting. ResultsMeasurements in the phantom established that both sequences yield equal ADCs, independent of diffusion time, as expected for free diffusion. In contrast, averaged metabolite diffusion in vivo was found to be 1.9 times faster at short (8.3 ms) than at long (155 ms) diffusion times. The difference in ADC was found to be statistically significant for the creatines, cholines, N-acetylaspartate, myo-inositol, and glutamate. The water ADC was measured to be 1.3 times larger at short than at long diffusion time. ConclusionIt is demonstrated that application of oscillating gradients in diffusion-weighted MRS is feasible on clinical MR systems to establish the dependence of ADCs on diffusion times in humans. The initial results largely confirm earlier reports for mice’ and rats’ brain at short and long diffusion times. ADCs representing diffusion at short and ultra-short diffusion times are of interest to probe cellular or subcellular changes in disease. The presented methodology may thus open the door for investigation of pathophysiological changes in cell-specific microstructures in human cohorts.