Multivoxel MR Spectroscopy Research Articles

Evaluation of Key Molecular Markers in Adult Diffuse Gliomas Based on a Novel Combination of Diffusion and Perfusion MRI and MR Spectroscopy.

Preoperative identification of isocitrate dehydrogenase (IDH) mutation and 1p/19q codeletion status could help clinicians select the optimal therapy in patients with diffuse glioma. Although, the value of multimodal intersection was underutilized. To evaluate the value of quantitative MRI biomarkers for the identification of IDH mutation and 1p/19q codeletion in adult patients with diffuse glioma. Retrospective. Two hundred sixteen adult diffuse gliomas with known genetic test results, divided into training (N = 130), test (N = 43), and validation (N = 43) groups. Diffusion/perfusion-weighted-imaging sequences and multivoxel MR spectroscopy (MRS), all 3.0 T using three different scanners. The apparent diffusion coefficient (ADC) and cerebral blood volume (CBV) of the core tumor were calculated to identify IDH-mutant and 1p/19q-codeleted statuses and to determine cut-off values. ADC models were built based on the 30th percentile and lower, CBV models were built based on the 75th centile and higher (both in five centile steps). The optimal tumor region was defined and the metabolite concentrations of MRS voxels that overlapped with the ADC/CBV optimal region were calculated and added to the best-performing diagnostic models. DeLong's test, diagnostic test, and decision curve analysis were performed. A P value <0.05 was considered to be statistically significant. Almost all ADC models achieved good performance in identifying IDH mutation status, among which ADC_15th was the most valuable parameter (threshold = 1.186; Youden index = 0.734; AUC_train = 0.896). The differential power of CBV histogram metrics for predicting 1p/19q codeletion outperformed ADC histogram metrics, and the CBV_80th-related model performed best (threshold = 1.435; Youden index = 0.458; AUC_train = 0.724). The AUCs of ADC_15th and CBV_80th models in the validation set were 0.857 and 0.733. These models tended to improve after incorporation of N-acetylaspartate/total_creatine and glutamate-plus-glutamine/total_creatine, respectively. The intersection of ADC-, CBV-based histogram and MRS provide a reliable paradigm for identifying the key molecular markers in adult diffuse gliomas. 3 TECHNICAL EFFICACY: Stage 3.

Could thalamic biochemical changes correlate to cognitive impairment in idiopathic generalized epilepsy?

BackgroundThe thalamus is crucial in the development of idiopathic generalized epilepsy (IGE), which could lead to cognitive dysfunctions, according to data from neuropsychology and advanced neuroimaging investigations. This research aimed to measure the metabolic changes in the thalamus and to assess if could be contributed to cognitive impairment in IGE patients. Thirty IGE patients and thirty healthy volunteers with matched ages, genders, and educational levels participated in this cross-sectional case–control research. The IGE patients and controls were evaluated neuropsychologically using Intelligence Quotient (IQ) to assess general cognitive ability, Digit span for attention, Wechsler memory scale (WMS) for verbal memory, cube drawing test for visuospatial memory, Trail making test for executive functions, and Controlled Oral Word Association test (COWAT) for verbal fluency and quantitative multi-voxel MR spectroscopy (MRS) measurements of N-acetyl aspartate (NAA), choline (Cho), creatine (Cr), NAA/Cr, NAA/Cho and Cho/Cr ratios at 1.5 T scanner. The voxels were located over the right and left thalamus.ResultsThe IGE patients showed worse cognitive performance in IQ, attention, executive function, and verbal and visuospatial memory domains compared to the controls. The IGE patients exhibited a significantly decrease NAA in the right thalamus (p = 0.004) and a lower NAA/Cr ratio in the left thalamus (p = 0.01). the mean thalamus NAA level exhibited a positive correlation with CDT (r = 0.45, p = P = 0.01), and WMS-R (r = 0.39, p = 0.03) and a negative correlation with trail-making A test (r = 0.42, P = 0.01).Conclusionsit was concluded that IGE patients exhibited poor cognition which could be attributed to thalamic neurometabolic changes due to impaired thalamic cortical circuits.

Magnetic resonance spectroscopic imaging for detecting metabolic changes in glioblastoma after anti-angiogenic therapy-a systematic literature review.

BackgroundThe impact of anti-angiogenic therapy (AAT) on patients with glioblastoma (GBM) is unclear due to a disconnect between radiographic findings and overall survivorship. MR spectroscopy (MRS) can provide clinically relevant information regarding tumor metabolism in response to AAT. This review explores the use of MRS to track metabolic changes in patients with GBM treated with AAT.MethodsWe conducted a systematic literature review in accordance with PRISMA guidelines to identify primary research articles that reported metabolic changes in GBMs treated with AAT. Collected variables included single or multi-voxel MRS acquisition parameters, metabolic markers, reported metabolic changes in response to AAT, and survivorship data.ResultsThirty-five articles were retrieved in the initial query. After applying inclusion and exclusion criteria, 11 studies with 262 patients were included for qualitative synthesis with all studies performed using multi-voxel 1H MRS. Two studies utilized 31P MRS. Post-AAT initiation, shorter-term survivors had increased choline (cellular proliferation marker), increased lactate (a hypoxia marker), and decreased levels of the short echo time (TE) marker, myo-inositol (an osmoregulator and gliosis marker). MRS detected metabolic changes as soon as 1-day after AAT, and throughout the course of AAT, to predict survival. There was substantial heterogeneity in the timing of scans, which ranged from 1-day to 6–9 months after AAT initiation.ConclusionsMulti-voxel MRS at intermediate and short TE can serve as a robust prognosticator of outcomes of patients with GBM who are treated with AAT.

Role of multi-parametric MRI in the differentiation between mucinous breast carcinoma and fibroadenoma

BackgroundThe purpose of this study was to evaluate diagnostic performance of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and functional MRI (diffusion and MR spectroscopy) using the latest MRI breast imaging reporting and data system (MRI-BIRADS) descriptors and non-BIRADS items for differentiation of mucinous breast carcinomas from fibroadenomas.MethodsWe included 19 cases of mucinous breast carcinoma and 37 cases of fibroadenoma. DCE-MRI, Diffusion-weighted MR imaging (DWI) and multi-voxel MR spectroscopy (MRS) were done, MRI-BIRADS (5th edition) analysis of the lesions was performed, and histopathological examination of all cases was done.ResultsAccording to univariate analysis, mucinous carcinoma was frequently detected in older age-group (COR = 1.4, 95% CI = 1.1–1.7 and p value < 0.001) and had more frequent irregular borders and non-circumscribed margins than fibroadenoma (COR = 11.6, 95% CI = 2–66.4 and p value = 0.002). All mucinous carcinoma had high T2 signal. Fibroadenomas had more frequent homogenous enhancement than mucinous carcinoma; none of the fibroadenomas had rim enhancement nor enhancing internal septations; mucinous carcinoma had more frequent rim enhancement and (n = 6, p value < 0.001) and enhancing internal septations (n = 7, p value < 0.001). Fibroadenoma had frequent dark non-enhancing internal septations than mucinous carcinoma (p value < 0.001). On multivariate analysis, mucinous carcinoma had significant combination of being common in older age, larger in size, with irregular shape, and non-circumscribed margins. On ADC map and MRS, mucinous carcinoma had higher ADC values and higher CHO.SNR than fibroadenoma. The mean ADC value of mucinous carcinoma was 1.3 ± 0.1 × 10−3mm2/s, which was significantly higher than that of fibroadenoma (1.1 ± 0.1 × 10−3mm2/s), with p = 0.002. Also, the mean CHO.SNR was significantly higher in mucinous carcinoma (3.1 ± 0.8) than fibroadenoma (0.8 ± 0.5) with p value < 0.001. According to our results, the presence of type 3 (washout curve), dark internal septations, non-circumscribed margins and irregular shape of the lesion showed the highest sensitivity and accuracy for differentiation of mucinous carcinomas and fibroadenomas (100, 78.6%), (89.4, 82%), (86.5, 80.3%) and (81, 71.4%), respectively.ConclusionThe combined use of DCE-MRI, DW-MRI and MRS with breast MRI-BIRADS descriptors and non-BIRADS items increases the diagnostic accuracy for differentiation of mucinous carcinomas from fibroadenomas.

Karakteristik Manyetik Rezonans Görüntüleme Bulguları ile Ortaya Çıkan Soliter Toksoplazmozis Olgusu

Toxoplasmosis is caused by an intracellular protozoan called Toxoplasma gondii, and is seen worldwide. In patients with acquired immunodeficiency syndrome (AIDS), it constitutes the most common opportunistic central nervous system (CNS) infection. Magnetic resonance imaging (MRI) is the modality of choice for the evaluation of CNS involvement in these patients. In our case report, we described a 53-year-old male patient presenting with a right side hemiparesis and sensorial loss, who also had a history of AIDS. He underwent computed tomography examination where a hypodense left thalamic mass lesion was found. For further characterization, an MRI examination was performed and on T1 weighted images, a hypointense mass with a peripheral incomplete hyperintense rim at the left thalamic region was found, exhibiting a lamellar appearance on T2 weighted images. The mass showed slight peripheral contrast enhancement. Multivoxel MR spectroscopy demonstrated a conspicuous lactate peak. A biopsy procedure was performed and the pathological evaluation revealed cerebral toxoplasmosis.

Characterizing tumor invasiveness of glioblastoma using multiparametric magnetic resonance imaging.

The objective of this study was to characterize the abnormalities revealed by diffusion tensor imaging (DTI) using MR spectroscopy (MRS) and perfusion imaging, and to evaluate the prognostic value of a proposed quantitative measure of tumor invasiveness by combining contrast-enhancing (CE) and DTI abnormalities in patients with glioblastoma. Eighty-four patients with glioblastoma were recruited preoperatively. DTI was decomposed into isotropic (p) and anisotropic (q) components. The relative cerebral blood volume (rCBV) was calculated from the dynamic susceptibility contrast imaging. Values of N-acetylaspartate, myoinositol, choline (Cho), lactate (Lac), and glutamate + glutamine (Glx) were measured from multivoxel MRS and normalized as ratios to creatine (Cr). Tumor regions of interest (ROIs) were manually segmented from the CE T1-weighted (CE-ROI) and DTI-q (q-ROI) maps. Perfusion and metabolic characteristics of these ROIs were measured and compared. The relative invasiveness coefficient (RIC) was calculated as a ratio of the characteristic radii of CE-ROI and q-ROI. The prognostic significance of RIC was tested using Kaplan-Meier and multivariate Cox regression analyses. The Cho/Cr, Lac/Cr, and Glx/Cr in q-ROI were significantly higher than CE-ROI (p = 0.004, p = 0.005, and p = 0.007, respectively). CE-ROI had significantly higher rCBV values than q-ROI (p < 0.001). A higher RIC was associated with worse survival in a multivariate overall survival (OS) model (hazard ratio [HR] 1.40, 95% confidence interval [CI] 1.06-1.85, p = 0.016) and progression-free survival (PFS) model (HR 1.55, 95% CI 1.16-2.07, p = 0.003). An RIC cutoff value of 0.89 significantly predicted shorter OS (median 384 vs 605 days, p = 0.002) and PFS (median 244 vs 406 days, p = 0.001). DTI-q abnormalities displayed higher tumor load and hypoxic signatures compared with CE abnormalities, whereas CE regions potentially represented the tumor proliferation edge. Integrating the extents of invasion visualized by DTI-q and CE images into clinical practice may lead to improved treatment efficacy.

Water suppression in the human brain with hypergeometric RF pulses for single-voxel and multi-voxel MR spectroscopy.

To develop and investigate a novel water suppression sequence with hypergeometric pulses at 3 T. Simulations were used to optimize the delays and amplitudes of 5 hypergeometric prepulses, to minimize the residual water over a range of T1 and B1 values. Single-voxel data with hypergeometric water suppression (HGWS) prepulses were acquired in the centrum semiovale, 2 parietal regions, and insula of 7 subjects, and compared with VAPOR water suppression. Magnetic resonance spectroscopic imaging (MRSI) data using both VAPOR and HGWS prepulses were also collected and compared. Water suppression performance was calculated as the residual water peak height relative to the unsuppressed water peak. MRSI voxel-by-voxel comparison was performed by calculating the ratio between HGWS and VAPOR residual water peaks. In simulations, HGWS and VAPOR are insensitive to B1 and water T1 variations, but with no B1 variation, HGWS has a lower average residual water fraction (0.0033) than that of VAPOR (0.0091). In single-voxel acquisitions, HGWS performs better than VAPOR in all regions with a 2.3-fold to 5.7-fold lower residual water. In MRSI acquisitions, HGWS performs on average 2.3-fold better than VAPOR in 98.9% of the voxels. HGWS provides better water suppression than VAPOR in both single-voxel and multivoxel acquisitions with a shorter sequence duration.

An MRS- and PET-guided biopsy tool for intraoperative neuronavigational systems.

OBJECTIVE Glioma heterogeneity and the limitations of conventional structural MRI for identifying aggressive tumor components can limit the reliability of stereotactic biopsy and, hence, tumor characterization, which is a hurdle for developing and selecting effective treatment strategies. In vivo MR spectroscopy (MRS) and PET enable noninvasive imaging of cellular metabolism relevant to proliferation and can detect regions of more highly active tumor. Here, the authors integrated presurgical PET and MRS with intraoperative neuronavigation to guide surgical biopsy and tumor sampling of brain gliomas with the aim of improving intraoperative tumor-tissue characterization and imaging biomarker validation. METHODS A novel intraoperative neuronavigation tool was developed as part of a study that aimed to sample high-choline tumor components identified by multivoxel MRS and 18F-methylcholine PET-CT. Spatially coregistered PET and MRS data were integrated into structural data sets and loaded onto an intraoperative neuronavigation system. High and low choline uptake/metabolite regions were represented as color-coded hollow spheres for targeted stereotactic biopsy and tumor sampling. RESULTS The neurosurgeons found the 3D spherical targets readily identifiable on the interactive neuronavigation system. In one case, areas of high mitotic activity were identified on the basis of high 18F-methylcholine uptake and elevated choline ratios found with MRS in an otherwise low-grade tumor, which revealed the possible use of this technique for tumor characterization. CONCLUSIONS These PET and MRI data can be combined and represented usefully for the surgeon in neuronavigation systems. This method enables neurosurgeons to sample tumor regions based on physiological and molecular imaging markers. The technique was applied for characterizing choline metabolism using MRS and 18F PET; however, this approach provides proof of principle for using different radionuclide tracers and other MRI methods, such as MR perfusion and diffusion.

Reliability of multiparametric prostatic MRI quantitative data in the evaluation of prostate cancer aggressiveness

PurposeTo compare the quantitative data of multiparametric prostatic MRI with Gleason scores of histopathological analysis. Materials and methodsOne hundred twenty-two patients performed Multiparametric MRI of the prostate. Functional MRI quantitative data (including diffusion with mean ADC value and spectroscopic metabolic ratio) where the DWI is employing b 50, 400, 800, 1000 and 2000sec/mm2 and multivoxel MR spectroscopy compared with of Gleason scores of histopathological results. Malignant cases are classified into three groups according to their Gleason score as group I with Gleason score ≤6, group II Gleason score 7, while Gleason score 8–10 stratified as Group III. ResultsThe histopathological analysis reveals 78 malignant cases and 44 benign Cases. The significant statistical difference between group I and the other two groups (p<0.001) regarding the quantitative mean ADC value and metabolic spectroscopic ratio. No significant statistical difference between group II and III with p=0.2 for mean ADC difference and p=0.8 for the metabolic spectroscopic ratio with a weak negative correlation between ADCand Gleason score [rs=−0.26] and significant positive correlation (p=0.02) for MRSI metabolic ratio [rs=0.2]. ConclusionThe quantitative data of functional imaging of the prostate is reliable in evaluating prostatic cancer aggressiveness and proper construction of therapeutic plan.

An MRS- and PET-guided biopsy tool for intraoperative neuronavigational systems.

OBJECTIVE Glioma heterogeneity and the limitations of conventional structural MRI for identifying aggressive tumor components can limit the reliability of stereotactic biopsy and, hence, tumor characterization, which is a hurdle for developing and selecting effective treatment strategies. In vivo MR spectroscopy (MRS) and PET enable noninvasive imaging of cellular metabolism relevant to proliferation and can detect regions of more highly active tumor. Here, the authors integrated presurgical PET and MRS with intraoperative neuronavigation to guide surgical biopsy and tumor sampling of brain gliomas with the aim of improving intraoperative tumor-tissue characterization and imaging biomarker validation. METHODS A novel intraoperative neuronavigation tool was developed as part of a study that aimed to sample high-choline tumor components identified by multivoxel MRS and 18F-methylcholine PET-CT. Spatially coregistered PET and MRS data were integrated into structural data sets and loaded onto an intraoperative neuronavigation system. High and low choline uptake/metabolite regions were represented as color-coded hollow spheres for targeted stereotactic biopsy and tumor sampling. RESULTS The neurosurgeons found the 3D spherical targets readily identifiable on the interactive neuronavigation system. In one case, areas of high mitotic activity were identified on the basis of high 18F-methylcholine uptake and elevated choline ratios found with MRS in an otherwise low-grade tumor, which revealed the possible use of this technique for tumor characterization. CONCLUSIONS These PET and MRI data can be combined and represented usefully for the surgeon in neuronavigation systems. This method enables neurosurgeons to sample tumor regions based on physiological and molecular imaging markers. The technique was applied for characterizing choline metabolism using MRS and 18F PET; however, this approach provides proof of principle for using different radionuclide tracers and other MRI methods, such as MR perfusion and diffusion.

HIV-associated neurodegeneration and neuroimmunity: multivoxel MR spectroscopy study in drug-naïve and treated patients.

The aim of this study was to test neurobiochemical changes in normal appearing brain tissue in HIV+ patients receiving and not receiving combined antiretroviral therapy (cART) and healthy controls, using multivoxel MR spectroscopy (mvMRS). We performed long- and short-echo 3D mvMRS in 110 neuroasymptomatic subjects (32 HIV+ subjects on cART, 28 HIV+ therapy-naïve subjects and 50 healthy controls) on a 3T MR scanner, targeting frontal and parietal supracallosal subcortical and deep white matter and cingulate gyrus (NAA/Cr, Cho/Cr and mI/Cr ratios were analysed). The statistical value was set at p < 0.05. Considering differences between HIV-infected and healthy subjects, there was a significant decrease in the NAA/Cr ratio in HIV+ subjects in all observed locations, an increase in mI/Cr levels in the anterior cingulate gyrus (ACG), and no significant differences in Cho/Cr ratios, except in ACG, where the increase showed trending towards significance in HIV+ patients. There were no significant differences between HIV+ patients on and without cART in all three ratios. Neuronal loss and dysfunction affects the whole brain volume in HIV-infected patients. Unfortunately, cART appears to be ineffective in halting accelerated neurodegenerative process induced by HIV but is partially effective in preventing glial proliferation. • This is the first multivoxel human brain 3T MRS study in HIV. • All observed areas of the brain are affected by neurodegenerative process. • Cingulate gyrus and subcortical white matter are most vulnerable to HIV-induced neurodegeneration. • cART is effective in control of inflammation but ineffective in preventing neurodegeneration.

Characterisation of musculoskeletal tumours by multivoxel proton MR spectroscopy.

The purpose of this study is to evaluate the role of multi-voxel proton MR spectroscopy in differentiating benign and malignant musculoskeletal tumours in a more objective way and to correlate the MRS data parameters with histopathology. A hospital-based prospective study was carried out comprising 42 patients who underwent MRI examinations from 1 July 2013 to 30 June 2014. After routine sequences, single-slice multi-voxel proton MR spectroscopy was included at TE-135 using the PRESS sequence. The voxel with the maximum choline/Cr ratio was used for analysis of data in 32 patients. The strength of association between the MR spectroscopy findings and the nature of tumour and histopathological grading were assessed. Of the 42 patients, the MR spectra were not of diagnostic quality in 10. In the remaining 32 patients, 12 (37.5%) had benign and 20 (62.5%) malignant tumours. The mean choline/Cr ratio was 6.97 ± 5.95 (SD) for benign tumours and 25.39 ± 17.72 (SD) for malignant tumours. In our study statistical significance was noted between the choline/Cr ratio and the histological nature of musculoskeletal tumours (p = 0.002) assessed by unpaired t-test. The choline/Cr ratio and histological grading were also found to be significant (p = 0.001) when assessed by one-way ANOVA test. Multi-voxel MR spectroscopy showed a higher choline/Cr ratio in malignant musculoskeletal tumours than in benign ones (p = 0.002). The choline/Cr ratio and histological grading of musculoskeletal tumours also showed statistical significance (p = 0.001).

Post-WBRT cognitive impairment and hippocampal neuronal depletion measured by in vivo metabolic MR spectroscopy: Results of prospective investigational study

Background and purposeThe aim of this prospective study is to evaluate post-whole brain radiotherapy (WBRT) changes in hippocampal concentration of N-acetylaspartate (h-tNAA) as a marker of neuronal loss and to correlate those changes to neurocognitive function. Material and methodsThirty-five patients with brain metastases underwent baseline single slice multi-voxel MR spectroscopy (MRS) examination for measurement of hippocampal h-tNAA together with baseline battery of neurocognitive tests focused on memory (Auditory Verbal Learning Test and Brief Visuospatial Memory Test – Revised) as well as quality of life questionnaires (EORTC QLQ-C30 a EORTC QLQ-BN20). Eighteen patients completed follow-up evaluation four months after standard WBRT (2 laterolateral fields, 10×3.0Gy, 6MV photons) and were included in this analysis. MRS and cognitive examinations were repeated and compared to baseline measurements. ResultsStatistically significant decreases in h-tNAA were observed in the right (8.52–7.42mM; −12.9%, 95%CI: −7.6 to −16.4%) as well as in the left hippocampus (8.64–7.60mM; −12%, 95%CI: −7.9 to −16.2%). Statistically significant decline was observed in all AVLT and BVMT-R subtests with exception of AVLT_Recognition. Quality of life declined after WBRT (mean Δ −14.1±20.3 points in transformed 0–100 point scale; p=0.018) with no correlation to changes in hippocampal metabolite concentrations. Moderate positive correlation was observed between left h-tNAA concentration decrease and AVLT_TR decline (r=+0.32; p=0.24) as well as with AVLT_DR (r=+0.33; p=0.22) decline. Changes in right h-tNAA/Cr negatively correlated with AVLT_DR (r=−0.48; p=0.061). No correlation between right hippocampus h-tNAA and memory decline (AVLT) was observed. ConclusionsOur results suggest hippocampal NAA concentrations decline after WBRT and MRS may be a useful biomarker for monitoring neuronal loss after radiotherapy.

Role of magnetic resonance spectroscopy & diffusion weighted imaging in differentiation of supratentorial brain tumors

PurposeTo evaluate the role of magnetic resonance spectroscopy & diffusion weighted imaging (DWI) in differentiating between primary and secondary brain tumors. Patients & methodsThis prospective study was performed for 40 patients. Diffusion weighted image (DWI) and apparent diffusion co-efficient (ADC) maps were acquired by using b-values of 0 and 1000mm2/s. Standard mean ADC values were calculated automatically and expressed in 10−3mm2/s in both intra-lesional and peri-lesional regions. Multi voxel MR spectroscopy was performed using a spin-echo mode sequence.The metabolites were identified including the following: N-acetylaspartate (NAA) at 2.0ppm, creatine (Cr) at 3.0ppm, choline (Cho) at 3.2ppm, lipid at the range of 0.7–1.3ppm, lactate at 1.33ppm and myoinositol at 3.56ppm. The ratios that were calculated include the following: Cho/NAA and Cho/Cr in both intralesional and perilesional regions. ResultsIntralesional ADC values showed no difference between the metastases (0.6: 1×10−3mm2/s with mean 0.86) and high grade primary tumors (0.6: 1.1×10−3mm2/s with mean 0.73). Perilesional ADC value Findings in the study revealed that primary tumors have low ADC values (0.9: 1.1×10−3mm2/s with mean 0.95) in their peri-lesional voxels denoting peri-lesional infiltration, while higher ADC values in metastasis (1.3–1.6×10−3mm2/s mean 1.41) due to the absence of peri-lesional infiltration increase in CHO/Cr ratios (>1) in primary high grade tumors (indicating perilesional infiltration) while there was no increase in CHO/Cr ratio in cases of metastases. Low grade primary tumors showed low lactate and lipid, with increasing malignancy, and tumors showed increasing levels of lactate and lipid peaks (indicating necrosis) with remarkable difference in lipid peaks between low and high grade tumors. There was no significant difference between primary & metastatic brain tumors as regards lactate peak. ConclusionIntra-lesional ADC values are not useful in the differentiation between primary and metastatic tumors. Perilesional ADC values can differentiate between primary & metastatic brain tumors. Intralesional MRS values (CHO/Cr ratio) were able to grade the tumor and differentiate between high and low grade tumors, while Perilesional MRS values (CHO/Cr ratio) could be able to differentiate primary tumors from metastasis.

Parallel reconstruction in accelerated multivoxel MR spectroscopy.

To develop the simultaneous acquisition of multiple voxels in localized MR spectroscopy (MRS) using sensitivity encoding, allowing reduced total scan time compared to conventional sequential single voxel (SV) acquisition methods. Dual volume localization was used to simultaneously excite voxels in both hemispheres. Receiver coil sensitivity profiles were used to unfold the data. To demonstrate the method, MRS voxels in the left and right hippocampus were measured at 3 tesla (T) and the left and right motor cortices at 7T. Spectra were compared to conventional SV acquisitions. Spectra were also recorded from the lesion and contralateral hemisphere of a patient with a low-grade oligodendroglioma at 7T. It was possible to generate signal in two voxels simultaneously and separate the signal originating from the different locations, with spectral results almost identical to those observed using conventional single voxel methods. The method results in an increased chemical shift displacement artifact, which might be improved by advanced pulse designs, and a noise increase due to the unfolding g-factor, which was larger at 3T than 7T. The simultaneous acquisition of voxels for MRS is possible by using modulated slice-selective pulses and receive coil sensitivity profiles to unfold the resulting signals.

Development of a Low-Cost Phantom to Assess Absolute Quantification in Multi-Voxel MR Spectroscopy

Background: Magnetic resonance spectroscopy (MRS) is a technique to measure chemical shift and can be used to analyze biochemical parameters in a region-of-interest (ROI) of the tissue through a procedure called Quantification. Evaluation of accuracy and robustness of a quantification method is extremely important to help validate it in practice. This is particularly important when the method deals with absolute quantification as there is no consensus regarding absolute values found in different ROIs. Usually, such evaluation procedures are initially tested on simulated signals and then on phantom signals in the next step. Most of MRS phantoms designed so far are not multi-purpose, in that they evaluate either quality assurance and reliability, or absolute quantification results. Objectives: Here, we designed a low-cost MRS phantom with flexibility to contain one single solution for quality assurance and reliability tests, as well as different combinations of metabolites with known concentrations for evaluation of (absolute) quantification algorithms. Patients and Methods: Phantom production: Phantom was designed in cylindrical-shape. Phantom can be filled with water or any other liquid. A detachable circular holder plate was designed for the interior of the cylinder of phantom. The holder contained 55 holes to hold 25 standard 10 mL vials with 15 mm diameters for holes. Another circular plate at the bottom with holes of 5mm diameter was used in order to fix the vials in their place. The cone-shape vials could be filled with pure metabolites or any combination of metabolites with desired concentrations. The resulting cylindrical phantom body had an outer diameter of 21 cm, an inner diameter of 14 cm and a height 15 cm. The body of the phantom was made of acrylic glass with removable top that allowed easy access to the interior chamber. An O-ring was used to watertight the lid of the phantom. All materials, laser-cut and production procedure cost less than 100$.Data acquisition: Proton MRS imaging experiments were performed on a 1.5T Siemens Avanto MRI/MRS system in the room temperature using Point REsolved Spectroscopy (PRESS) pulse sequence with manufactures built-in auto-shimming on the volume-of-interest, CHESS water suppression and 3D imaging parameters as follows: TE/TR = 30/1500 ms, voxel size = 888 mm3, NEX = 2, frequency bandwidth = 2000Hz and number of data points = 1024. Each vial was filled with a pure metabolite with known concentration as exists in human normal brain. All solutions of metabolites were calibrated in chemical laboratory with highly sophisticated instruments. : Processing: Signal quantification, residual water peak removal and phase corrections were carried out with the Java-based MRUI quantification package. Receiver coil inhomogeneity was compensated using, 3D T2-weighted images acquired from the pure water phantom. Results: Position of the voxels on the T1-weighted MR scout image was shown. One sample spectrum of Choline in built-in Siemens Syngo MRS Package was shown. Quantification for all metabolites in different slices of each vial, based on QUEST method in jMRUI software, and after being post-processed with the 3D receive coil inhomogeneity profile was depicted. The result was in linear relationship between volume and concentration. Conclusions: We developed a versatile and low-cost phantom for evaluation purposes in different MR imaging and spectroscopy studies, with special capabilities to be utilized for multi-voxel spectroscopy experiments with the goal of absolute quantification.

The added value of quantitative multi-voxel MR spectroscopy in breast magnetic resonance imaging

ObjectiveTo determine whether quantitative multivoxel MRS improves the accuracy of MRI in the assessment of breast lesions.MethodsTwenty-five consecutive patients with 26 breast lesions ≥1 cm assessed as BI-RADS 3 or 4 with mammography underwent quantitative multivoxel MRS and contrast-enhanced MRI. The choline (Cho) concentration was calculated using the unsuppressed water signal as a concentration reference. ROC analysis established the diagnostic accuracy of MRI and MRS in the assessment of breast lesions.ResultsRespective Cho concentrations in 26 breast lesions re-classified by MRI as BI-RADS 2 (n = 5), 3 (n = 8), 4 (n = 5) and 5 (n = 8) were 1.16 ± 0.43 (mean ± SD), 1.43 ± 0.47, 2.98 ± 2.15 and 4.94 ± 3.10 mM. Two BI-RADS 3 lesions and all BI-RADS 4 and 5 lesions were malignant on histopathology and had Cho concentrations between 1.7 and 11.8 mM (4.03 ± 2.72 SD), which were significantly higher (P = 0.01) than that in the 11 benign lesions (0.4–1.5 mM; 1.19 ± 0.33 SD). Furthermore, Cho concentrations in the benign and malignant breast lesions in BI-RADS 3 category differed (P = 0.01). The accuracy of combined multivoxel MRS/breast MRI BI-RADS re-classification (AUC = 1.00) exceeded that of MRI alone (AUC = 0.96 ± 0.03).ConclusionsThese preliminary data indicate that multivoxel MRS improves the accuracy of MRI when using a Cho concentration cut-off ≤1.5 mM for benign lesions. Key Points • Quantitative multivoxel MR spectroscopy can improve the accuracy of contrast-enhanced breast MRI. • Multivoxel-MRS can differentiate breast lesions by using the highest Cho-concentration. • Multivoxel-MRS can exclude patients with benign breast lesions from further invasive diagnostic procedures.

The prognostic value of multivoxel magnetic resonance spectroscopy determined metabolite levels in white and grey matter brain tissue for adverse outcome in term newborns following perinatal asphyxia

ObjectiveMagnetic resonance spectroscopy can identify brain metabolic changes in perinatal asphyxia by providing ratios of metabolites, such as choline (Cho), creatine (Cr), N-acetyl aspartate (NAA) and lactate (Lact) [Cho/Cr, Lact/NAA, etc.]. The purpose of this study was to quantify the separate white and grey matter metabolites in a slab cranial to the ventricles and relate these to the outcome.MethodsA standard 2D-chemical shift imaging protocol was used for measuring a transverse volume of interest located cranial to the ventricles allowing for direct comparison of the metabolites in white and grey matter brain tissue in 24 term asphyxiated newborns aged 3 to 16 days.ResultsCho, NAA and Lact showed significant differences between four subgroups of asphyxiated infants with more and less favourable outcomes. High levels of Cho and Lact in the grey matter differentiated non-survivors from survivors (P = 0.003 and P = 0.017, respectively).ConclusionIn perinatal asphyxia the levels of Cho, NAA and Lact in both white and grey matter brain tissue are affected. The levels of Cho and Lact measured in the grey matter are the most indicative of survival. It is therefore advised to include grey matter brain tissue in the region of interest examined by multivoxel MR spectroscopy.Key Points • Magnetic resonance spectroscopy can identify brain metabolic changes in perinatal asphyxia. • Choline and lactate levels in grey matter seem the best indicators of survival. • Both grey and white matter should be examined during spectroscopy for perinatal asphyxia.

Comparison of 3 Tesla proton MR spectroscopy, MR perfusion and MR diffusion for distinguishing glioma recurrence from posttreatment effects

To compare 3 Tesla (3T) multi-voxel and single-voxel proton MR spectroscopy (MRS), dynamic susceptibility contrast perfusion MRI (DSC), and diffusion-weighted MRI (DWI) for distinguishing recurrent glioma from postradiation injury. We reviewed all 3T MRS, DSC and DWI studies performed for suspicion of malignant glioma recurrence between October 2006 and December 2008. Maximum Cho/NAA and Cho/Cr peak-area and peak-height ratios were recorded for both multi-voxel and single-voxel MRS. Maximum cerebral blood volume (CBV) and minimum apparent diffusion coefficient (ADC) were normalized to white matter. Histopathology and clinical-radiologic follow-up served as reference standards. Receiver operating characteristic curves for each parameter were compared. Forty lesions were classified as glioma recurrence (n = 30) or posttreatment effect (n = 10). Diagnostic performance was similar for CBV ratio (AUC = 0.917, P < 0.001), multi-voxel Cho/Cr peak-area (AUC = 0.913, P = 0.002), and multi-voxel Cho/NAA peak-height (AUC = 0.913, P = 0.002), while ADC ratio (AUC = 0.726, P = 0.035) did not appear to perform as well. Single-voxel MRS parameters did not reliably distinguish tumor recurrence from posttreatment effects. A 3T DSC and multi-voxel MRS Cho/Cr peak-area and Cho/NAA peak-height appear to outperform DWI for distinguishing glioma recurrence from posttreatment effects. Single-voxel MRS parameters do not appear to distinguish glioma recurrence from posttreatment effects reliably, and therefore should not be used in place of multi-voxel MRS.

Evaluation of Normal Appearing White Matter in Multiple Sclerosis

The aim of this study was to determine diffusion magnetic resonance imaging (MRI), magnetization transfer (MT) imaging and multivoxel MR spectroscopy findings in plaques, periplaque white matter and normal appearing white matter (NAWM) regions in multiple sclerosis (MS) and to correlate the findings with the expanded disability status scale (EDSS). A total of 30 patients with MS and 30 healthy control subjects were studied and apparent diffusion coefficient (ADC) values, MT ratio (MTR), N-acetyl-aspartate/creatine (NAA/Cr) and choline/creatine (Cho/Cr) ratios were measured in plaques, periplaques and NAWM regions and compared with the control subjects. The MTR and NAA/Cr ratio were decreased more in plaques than periplaques and NAWM, in contrast ADC values and Cho/Cr ratios were highest in plaques and higher in periplaques than in NAWM. Decreased MTR and NAA/Cr in NAWM demonstrated moderate inverse correlations (r = - 0.604, p < 0.001 and r = - 0.494, p < 0.001, respectively) while Cho/Cr ratios and ADC of NAWM demonstrated weak linear correlations (r = 0.370, p = 0.004, r = 0.297, p = 0.021 respectively) with EDSS. The MS, MTR and MR spectroscopy findings were found to be useful for detecting subtle abnormalities in NAWM. Although ADC values were significantly altered in plaque and periplaque regions a significance difference was not found in NAWM.