Evaluation of metabolic changes within the normal appearing gray and white matters in neurologically asymptomatic HIV-1-positive and HCV-positive patients: Magnetic resonance spectroscopy and immunologic correlation

Objective

The aim of the study was to evaluate early metabolic changes using proton MR spectroscopy (MRS) in asymptomatic HIV-1-positive and HCV-positive patients without abnormalities in the structural MR examination.

Methods

Sixty-five asymptomatic patients: 21 HIV-1-positive naive, 20 HIV-1-positive with combination antiretroviral therapy (cART), 9 HIV-1/HCV-positive naive, 15 HCV-positive naive and 18 normal subjects were enrolled in the study. The MRS examinations were performed with a 1.5 T MR scanner. Voxels were located in the following regions: posterior cingulate gyrus (PCG), anterior cingulate gyrus (ACG), parietal white matter (PWM), left basal ganglia (BG) and frontal white matter (FWM). The NAA/Cr, Cho/Cr, mI/Cr ratios and correlations of MRS measurements with the immunologic data were analyzed.

Results

There was a significant decrease (p < 0.05) of the NAA/Cr ratios in PCG, ACG and PWM regions in HIV-1-positive cART treated patients compared to the normal subjects. The significantly decreased NAA/Cr ratios in PWM and FWM were observed in HCV infected patients. The subjects with HIV-1/HCV co-infection revealed significantly lower NAA/Cr ratios in the ACG area. Other metabolite ratios in all analyzed regions, as well as the NAA/Cr ratios in BG showed no significant differences. The decrease of CD4n T cell count was associated with the decease of the NAA/Cr ratio in the PCG area and the increase of Cho/Cr ratio in the FWM region.

Conclusions

The metabolic changes – reduction of NAA/Cr ratios are most pronounced in HIV-1-positive patients using cART. The low CD4n T cell count is a risk factor for neurocognitive impairment in HIV-1-positive patients.     

Diagnostic yield of combined magnetic resonance spectroscopy and diffusion weighted imaging in intracranial neoplasms

Purpose

Our intention was to evaluate the role of combined diffusion magnetic resonance imaging and spectroscopy in diagnosis and grading of brain tumors.

Materials and methods

Ninety-three included cases underwent magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) of the brain lesion, stereotactic or open biopsies and histopathological examination. MRI protocol included DWI and calculated ADC values. Multivoxel MRS spectroscopic technique (MVS) was used and all MRS metabolic parameters were obtained.

Results

High grade tumors had significantly lower ADC values than low grade tumors (P < 0.001). ADC values were the lowest in lymphoma (0.54 × 10⁻³ mm²/s) and the highest in craniopharyngioma (1.9 × 10⁻³ mm²/s). MRS revealed a statistically significant difference in CHO/NAA and CHO/Cr ratios between low and high grade tumors with P < 0.01 and P < 0.001, respectively. The mI/Cr ratio and presence of lactate, lipid and taurine also aided in differentiation and grading of brain tumors. The overall MRI/MRS sensitivity and specificity were 91%, 90.5%, respectively.

Conclusion

MRS has a robust diagnostic accuracy in cases of well defined high or low grade brain neoplasms. ADC value had the ability to confirm and differentiate low from high grade tumors in many situations where there were diagnostic confusions with MRS due to borderline values.     

Feasibility of H-MR Spectroscopy in evaluation of cervical spondylotic myelopathy

Purpose

To assess the diagnostic value of magnetic resonance spectroscopy (MRS) in the evaluation of cervical spinal cord biochemical changes in patients with cervical spondylotic myelopathy (CSM).

Materials and methods

Twenty-four patients with cervical spondylotic myelopathy (patient group) and eleven age matched neurologically free volunteers (control group) underwent magnetic resonance imaging. MRS was assessed for the main metabolites including N-acetylaspartate (NAA), Choline (Cho), Creatine (Cr) and Lactate (Lac). The MRS findings of both groups were compared.

Results

Significant reduction in NAA/Cr ratio of patients with CSM (mean = 1.34 ± 0.09) in comparison to controls (mean = 1.82 ± 0.08). No significant differences in Cho/Cr ratio between both groups. Lactate peak was detected in nine patients while it was not detected in any of the controls. The difference in NAA/Cr ratio between patients with Lac peak and those without Lac peak was insignificant.

Conclusion

MRS is a promising non invasive technique that can help to evaluate metabolic changes of the cervical cord in cervical spondylotic myelopathy even in normally looking-areas.     

Metabolic Alterations in Parkinson's Disease after Thalamotomy, as Revealed by 1H MR Spectroscopy

Objective

To determine, using proton magnetic resonance spectroscopy (¹H MRS) whether thalamotomy in patients with Parkinson''s disease gives rise to significant changes in regional brain metabolism.

Materials and Methods

Fifteen patients each underwent stereotactic thalamotomy for the control of medically refractory parkinsonian tremor. Single-voxel ¹H MRS was performed on a 1.5T unit using a STEAM sequence (TR/TM/TE, 2000/14/20 msec), and spectra were obtained from substantia nigra, thalamus and putamen areas, with volumes of interest of 7-8ml, before and after thalamotomy. NAA/Cho, NAA/Cr and Cho/Cr metabolite ratios were calculated from relative peak area measurements, and any changes were recorded and assessed.

Results

In the substantia nigra and thalamus, NAA/Cho ratios were generally low. In the substantia nigra of 80% of patients (12/15) who showed clinical improvement, decreased NAA/Cho ratios were observed in selected voxels after thalamic surgery (p < 0.05). In the thalamus of 67% of such patients (10/15), significant decreases were also noted (p < 0.05).

Conclusion

Our results suggest that the NAA/Cho ratio may be a valuable criterion for the evaluation of Parkinson''s disease patients who show clinical improvement following surgery. By highlighting variations in this ratio, ¹H MRS may help lead to a better understanding of the pathophysiologic processes occurring in those with Parkinson''s disease.     

Malignant focal brain lesions. Value of MRS tumour biomarkers in preoperative prediction of grades of malignancy

Purpose

Our aim is to describe the spectrum of proton-MR spectroscopy in malignant focal brain lesions and to detect grade of malignancy using MRS tumor biomarkers.

Materials and methods

87 patients (63 males and 24 females) with focal brain lesion(s) are included in this study. All had a brain tumor recently diagnosed by MRI and had received no previous treatment. They were referred to MRS examination before surgical biopsy and/or resection or radiotherapy.

Results

In malignant brain tumors, average Cho/NAA ratio was 3.3 ± 0.22, Cho/Cr ratio was 2.95 ± 0.21, MI/NAA ratio was 1.5 ± 0.12, MI/Cr was 0.53 ± 0.11 with lower MI levels and higher choline levels in more malignant tumours, lipid/lactate peak was detected in brain metastasis and high grade malignant brain tumors.

Conclusion

Higher Cho/NAA, Cho/Cr and MI/NAA ratios with lower MI/Cr, and high lipid/lactate peak, were most likely to be in high grade malignant brain tumors.     

MR spectroscopy and diffusion MR imaging in characterization of common sellar and supra-sellar neoplastic lesions

Background

MR spectroscopy and diffusion-weighted imaging are useful non invasive imaging modalities used for characterization of different sellar and suprasellar lesions.

Patient and methods

We studied 30 cases of suprasellar SOLs (as proved by conventional MRI), MRS and DWI. Our findings were correlated with histopathological analysis after surgical resection.

Results

Three false positive cases in which cMRI give diagnosis mismatched with that obtained after adding the MRS findings and ADC values. MR spectrum type IIC is found in macroadenoma, craniopharyngioma, meningioma and germinoma with characteristic broad lipid peak in the second and forth types and elevated alanine peak in meningioma. Glioma had MRS appearance of type IIB. Simple differentiation between tumor types were achieved by the mean ADC values which were statistically significant (p < 0.001) when correlated to the histological diagnosis. When the ADC value of 0.6 × 10⁻³ mm²/s this strongly points to macroadenoma, ADC value of 1.05 × 10⁻³ mm²/s in meningiomas, ADC value 1.88 8 × 10⁻³ mm²/s strongly points to craniopharyngioma, while gliomas and germinoma had ADC values 1.6 × 10⁻³ mm²/s and 1.0 × 10⁻³ mm²/s respectively.

Conclusion

MR spectroscopy and DWMRI are considered important diagnostic tools complementary to cMRI in pre-surgical evaluation and discrimination between different sellar and suprasellar lesions.     

Clinical use of H MR spectroscopy in assessment of relapsing remitting and secondary progressive multiple sclerosis

Background

Conventional MRI has a limited ability to provide specific information about axonal pathology in MS, recently, MRI spectroscopy used for assessment of the axonal loss even in normal appearing white matter.

Objective

To assess the axonal degeneration in plaques and normal appearing white matter in patients with relapsing remitting MS and secondary progressive MS, and correlate their clinical disability using expanded disability status scale (EDSS) score with H¹ MRS abnormalities.

Patients and methods

Thirty-two MS patients (20 RRMS, 12 SPMS) and 20 controls were subjected to thorough history taking, clinical examination with special attention to: age at first symptoms, disease duration and the EDSS score. MRS was performed in order to map N-acetylaspartate (NAA), choline (Cho) and creatine (Cr).

Results

In SPMS, the NAA/Cr ratio and absolute concentrations for NAA in MS plaques and NAWM were significantly reduced compared to RRMS and to controls, also, significant relation with this metabolite values and clinical disability using EDSS score.

Conclusion

In SPMS patients group there were significant reduction in the levels of NAA in both plaques and NAWM compared to RRMS and control groups, moreover significant correlation of NAA reduction in the plaques of both groups related to clinical disability and disease progression.     

An experimental study on acute brain radiation injury: Dynamic changes in proton magnetic resonance spectroscopy and the correlation with histopathology

Purpose

To investigate the correlation between the alterations of single-voxel ¹H MRS and the histopathological characteristics of radiation brain injury following radiation.

Materials and methods

Twenty-seven rabbits were randomized into nine groups to receive radiation with a single dose of 25 Gy. The observation time points included a pre-radiation and 1, 2, 3, 4, 5, 6, 7, and 8 wk following radiation. Each treatment group underwent conventional MRI and single-voxel ¹H MRS, N-acetyl aspartate (NAA), choline (Cho), and creatine (Cr) were observed over the region of interest, and the presence or absence of lactate (Lac) and lipid (Lip) was detected. Histological specimens of each group were obtained after image acquisition.

Results

The values of Cho were significantly increased in the first 3 wk, and decreased over the following 5 wk after radiation. Levels of NAA showed a trend toward a decrease 5 wk after radiation. The levels of Cr were not changed between before and after radiation. The Cho/NAA metabolic ratio was significantly increased in weeks 6, 7, and 8 following irradiation, compared to pre-radiation values. Vascular and glial injury appeared on 2 wk after RT in the histology samples, until 4 wk after RT, necrosis of the oligodendrocytes, neuronal degeneration and demyelination could be observed.

Conclusions

MRS is sensitive to detect metabolic changes following radiation, and can be used in the early diagnosis of radiation brain injury.     

Necrotic cervical nodes: Usefulness of diffusion-weighted MR imaging in the differentiation of suppurative lymphadenitis from malignancy

Purpose

The purpose of this study was to assess the efficacy of diffusion-weighted (DW) MR imaging for the differentiation between suppurative lymphadenitis and malignancy in necrotic cervical lymph nodes.

Materials and methods

Fifteen patients with suppurative lymphadenitis, 40 with squamous cell carcinoma (SCC), eight with lymphoma, and six with thyroid cancer were accompanied by necrotic cervical nodes. All 69 patients underwent 1.5-T MR imaging including DW and 58 underwent gadolinium-enhanced MR imaging. Necrotic area-to-spinal cord signal intensity ratios (SIR) on T1-, T2- and DW images and apparent diffusion coefficients (ADCs) [10⁻³ mm²/s] were correlated with the pathologies.

Results

Nineteen necrotic cervical nodes with suppurative lymphadenitis, 67 with SCC, 10 with lymphoma, and 12 with thyroid cancer were identified. SIR on DW images was higher in suppurative lymphadenitis (2.50 ± 1.21) than in malignancies (1.29 ± 0.67) (p < .01), and ADC value was lower in suppurative lymphadenitis (0.89 ± 0.21) than in malignancies (1.46 ± 0.46) (p < .01). SIR on T1-weighted images was higher in thyroid cancer (1.95 ± 0.53) than in suppurative lymphadenitis (0.87 ± 0.17), SCC (0.92 ± 0.13), and lymphoma (0.95 ± 0.09) (p < .01). No significant difference in SIR on T2-weighted images was found between suppurative lymphadenitis (1.46 ± 0.50) and malignancies (1.61 ± 0.56).

Conclusion

DW imaging with ADC measurements may play a supplementary role in the differentiation of necrotic cervical nodes between suppurative lymphadenitis and malignancy.     

Diagnostic value of proton MR spectroscopy and diffusion-weighted MR imaging in childhood inherited neurometabolic brain diseases and review of the literature

The purpose of this study is to evaluate parenchymal diffusion properties and metabolite ratios in affected brain tissues of inherited neurometabolic brain diseases with an overview of the current literature about the diagnostic data of both techniques in childhood inherited metabolic brain diseases. The study group was consisting, 19 patients (15 males, 4 females; mean age, 54 months (4.5 years); age range, 1-171 months (14.25 years)) diagnosed with inherited neurometabolic brain disease. Single- and multivoxel proton MRS was carried out and NAA/Cr, Cho/Cr, mI/Cr, Glx/Cr ratios were calculated. Presence of lactate peak and abnormal different peaks were noted. ADC values were calculated from brain lesions. Results are compared with age and sex matched normal subjects. Elevated NAA/Cr ratio (Canavan disease), galactitol peak (galactosemia) at 3.7 ppm, branched chain amino acids (Maple syrup urine disease—MSUD) at 0.9 ppm were seen on different diseases. In Leigh disease and MSUD restricted diffusion was detected. Different diffusion properties were seen only in one Glutaric aciduria lesions. NAA/Cr ratios and calculated ADC values were significantly different from normal subjects (p < 0.05). DWI combined with MRS are complementary methods to routine cranial MRI for evaluating neurometabolic diseases which can give detailed information about neurochemistry of affected brain areas.     

Molecular and metabolic pattern classification for detection of brain glioma progression

Objectives

The ability to differentiate between brain tumor progression and radiation therapy induced necrosis is critical for appropriate patient management. In order to improve the differential diagnosis, we combined fluorine-18 2-fluoro-deoxyglucose positron emission tomography (¹⁸F-FDG PET), proton magnetic resonance spectroscopy (¹H MRS) and histological data to develop a multi-parametric machine-learning model.

Methods

We enrolled twelve post-therapy patients with grade 2 and 3 gliomas that were suspicious of tumor progression. All patients underwent ¹⁸F-FDG PET and ¹H MRS. Maximal standardized uptake value (SUVmax) of the tumors and reference regions were obtained. Multiple 2D maps of choline (Cho), creatine (Cr), and N-acetylaspartate (NAA) of the tumors were generated. A support vector machine (SVM) learning model was established to take imaging biomarkers and histological data as input vectors. A combination of clinical follow-up and multiple sequential MRI studies served as the basis for assessing the clinical outcome. All vector combinations were evaluated for diagnostic accuracy and cross validation. The optimal cutoff value of individual parameters was calculated using Receiver operating characteristic (ROC) plots.

Results

The SVM and ROC analyses both demonstrated that SUVmax of the lesion was the most significant single diagnostic parameter (75% accuracy) followed by Cho concentration (67% accuracy). SVM analysis of all paired parameters showed SUVmax and Cho concentration in combination could achieve 83% accuracy. SUVmax of the lesion paired with SUVmax of the white matter as well as the tumor Cho paired with the tumor Cr both showed 83% accuracy. These were the most significant paired diagnostic parameters of either modality. Combining all four parameters did not improve the results. However, addition of two more parameters, Cho and Cr of brain parenchyma contralateral to the tumor, increased the accuracy to 92%.

Conclusion

This study suggests that SVM models may improve detection of glioma progression more accurately than single parametric imaging methods.

Research support

National Cancer Institute, Cancer Center Support Grant Supplement Award, Imaging Response Assessment Teams.     

Detection of prostate cancer: Utility of diffusion-weighted MR imaging and 3D MR spectroscopic imaging

Purpose

To prospectively compare the mean ADC generated from DWI, the mean choline + creatine/citrate ratio generated from 3D MRS and the combined mean ADC and mean choline + creatine/citrate ratio in the detection of prostate cancer, and to correlate between the choline + creatine/citrate ratio and the aggressiveness of malignancy determined by Gleason score, with histopathological examination of the excised gland as the reference standard.

Patients and methods

Forty-six patients with biopsy-proved cancer underwent pre-operative MRI at 1.5 T. Axial T1, axial, coronal and sagittal T2-weighted, diffusion-weighted and 3D MRS using a point-resolved spectroscopic sequence (PRESS) were acquired. The mean ADC, mean choline + creatine/citrate ratio and combined parameters for malignant lesions are correlated with the pathological results. For each malignant lesion choline + creatine/citrate ratio was correlated with the aggressiveness of malignancy determined by Gleason score. Receiver operating characteristic (ROC) curves were used to determine sensitivity, and specificity of the studied parameters, and Kappa measures of agreement were calculated for prostate cancer detection.

Results

The mean ADC for tumor tissue was 1.0 ± 0.22 × 10⁻³ mm²/s (mean ± SD), and was significantly lower than that for non-tumor tissue 1.44 ± 0.28 × 10⁻³ mm²/s (p < 0.001). For MRS study the mean (choline + creatine)/citrate ratio in tumor tissue was 1.98 ± 1.0, and was significantly higher than that for non-tumor tissue, 0.72 ± 0.39 (p < 0.001). By combining both ADC values and (choline + creatine)/citrate ratio for differentiating malignant from non-malignant tissues a receiver operating characteristic analysis (ROC) curve showed Area under curve (AUC = 0.93) and was significantly higher than either (choline + creatine)/citrate ratio alone (AUC = 0.86) (p < 0.001) or ADC value alone (AUC = 0.89) (p < 0.001). There is an increasing (choline + creatine)/citrate ratio with increasing Gleason score, however, there is overlap between groups. A greater sensitivity of MRS for tumor detection 85% and 92% was present for tumors with Gleason score 4 + 3 and ?4 + 4, respectively, while for tumors with Gleason score 3 + 3 the sensitivity was 63%.

Conclusion

The combination of ADC and (choline + creatine)/citrate ratio is better than each parameter alone in differentiating between tumor and non-tumor prostatic tissue, also MR spectroscopic imaging findings of prostate tumor (Cho + Cr)/Cit ratio correlate with pathologic Gleason score. The combined parameters offer a promising non-invasive method for the diagnostic workup of prostate cancer.     

Hydrogen MR spectroscopy of neck masses

Purpose

The purpose of this study is to evaluate the role of MR spectroscopy in differentiation between benign and malignant neck masses.

Materials and methods

Thirty-two patients having neck masses underwent routine MRI of the neck as well as Hydrogen 1 (¹H) MR spectroscopy with echo time of 270 ms at 1.5 T. Peak amplitudes of choline (Cho) & creatine (Cr) for each lesion as well as normal appearing muscle of the neck were obtained. Results were compared by using a nonparametric t test.

Results

Thirty-two lesions were included (14 benign) & (18 malignant). Mean value (±standard deviation) was 4.42 ± 0.83 for malignant tumors and 1.93 ± 0.74 for benign tumors. Also spectra were obtained from normal appearing muscles with average Cho/Cr ratio 1.59 ± 0.49. Differences were significant between benign & malignant tumors as well as between malignant tumors & normal appearing muscles (p value < 0.001). No significant difference could be detected between benign tumors & normal appearing muscles (p value = 0.91).

Conclusion

MR spectroscopy should be used in the future as a complementary method to routine MRI to differentiate between benign and malignant lesions.     

Role of diffusion MRI and proton magnetic resonance spectroscopy in characterization of ovarian neoplasms

Introduction

Adnexal masses are a common clinical problem and considered as the leading indication for gynecological surgery. The ovary and adnexal structures are relatively difficult to image with any technology. Magnetic resonance spectroscopy (MRS) can detect metabolic changes. As molecular changes often precede morphologic alterations, sensitivity is expected to improve by MRS. Diffusion weighted magnetic resonance imaging (DW-MRI) is sensitive to molecular diffusion which is due to random microscopic translational motion of molecules (known as Brownian motion). In the event of morphologic evaluation of cystic ovarian tumors, whether benign or malignant, DW-MR imaging and calculated apparent diffusion coefficient (ADC) values would be useful for evaluation.

Purpose

The aim of this study is to evaluate the role of diffusion MRI & proton magnetic resonance spectroscopy (H-MRS) in diagnosis of ovarian neoplasms.

Subjects and methods

This study included 20 patients, their ages ranged from 20 to 72 years. In all cases, diagnosis was proven by surgical and pathological examination. Trans-abdominal ultrasound (n = 20) and trans-vaginal ultrasound (n = 11) were included in our routine protocol to obtain baseline information preceding MR examination. The routine MR examination protocol included: T1WI, T2WI, and post contrast fat suppressed T1WI. Diffusion weighted imaging (DWI) was done to all patients at b0, b500, b1000 and ADC values were calculated. MRS was performed in all cases using multi-voxel point resolved surface coil spectroscopy (PRESS sequence) for volume localization.

Results

Fourteen cases (70%) had benign ovarian masses while the remaining six cases (30%) had malignant masses. High lipid peak was detected in all three cases of mature cystic teratoma. All cases of simple serous cysts showed choline and creatine signals that were higher than the average noise level but lower than the two fold higher noise level. Sharp choline peak was detected in all malignant ovarian masses (except a case of metastases under chemotherapy) as well as the case of fibroma. Creatine signal was detected in all benign and malignant masses except two cases of mature cystic teratoma and cases of endometrioma. Lactate signal was detected only in cases of hemorrhagic cysts, mature cyst teratoma and one case of endometrioma and not obtained in any of malignant lesions except dysgerminoma. High NAA signal was detected in dysgerminoma and all three cases of mature cystic teratomas. The mean Cho/Cr ratio was significantly higher in malignant than benign ovarian masses (<0.05), there was no significant difference in mean and lowest ADC values between malignant and benign lesions.

Conclusion

Proton MRS using Cho/Cr ratio added useful information for the diagnosis of different ovarian neoplasms. Direct visual assessment of DWI of ovarian lesions is not useful in differentiating benign from malignant ovarian lesions; determining the threshold of the ADC for diagnosing cystic ovarian tumors is difficult because of their large variance. Further experience with a larger and more biologically variable range of tumors is recommended.     

Role of diffusion-weighted imaging with ADC mapping and in vivo H-MR spectroscopy in thyroid nodules

Purpose

To evaluate the role of the combined techniques of apparent diffusion coefficient (ADC) generated from diffusion-weighted magnetic resonance (MR) imaging (DWI) and metabolite spectrum acquired by magnetic resonance spectroscopy (MRS) in differentiating benign from malignant thyroid nodules.

Materials and methods

Thirty-seven patients with 56 thyroid nodules were evaluated with conventional MRI (T1- & T2-WI), DWI (b value 0.500 s/mm²; ADC values were calculated for the thyroid nodules), and MRS (for the presence or absence of choline peak). The ADC values and MRS findings were correlated with the histopathological results.

Results

The mean ADC of the malignant thyroid nodules (0.89 ± 0.27 × 10⁻³ mm²/s) was significantly lower than that of the mean ADC of the benign thyroid nodules (1.85 ± 0.24 × 10⁻³ mm²/s) (p value <0.0001). ADC value of 1.5 × 10⁻³ mm²/s was used as a cut-off value for differentiation benign from malignant thyroid nodules. The sensitivity, specificity, PPV&NPV of DWI in differentiating benign from malignant thyroid nodules were 94%, 95%, 94% & 95%, respectively (Kappa test 0.84, p value <0.0001), whereas they were 94.7%, 89.2%, 81.8% & 97.1% (Kappa test 0.8, p value <0.0001) with MRS, and 96%, 100%, 100% & 97% (Kappa test 0.96, p value <0.0001) with both DWI and MRS.

Conclusion

Both DWI and MRS are useful diagnostic modalities for characterization and differentiation between benign and malignant thyroid nodules. Our preliminary results showed that combination of DWI with calculated ADC values and metabolite spectrum acquired by MRS add more information to MRI and should be considered as an additional and complementary tool to conventional MRI for differentiating benign from malignant thyroid nodules.     

Role of diffusion weighted MRI in differentiating typical from atypical meningiomas at 1.5 and 3T MRI

Purpose

Atypical and malignant meningiomas are considered to have a higher rate of recurrence and show aggressive behavior compared to benign variety. The purpose of our study was to study the role of diffusion weighted imaging and determination of apparent diffusion coefficient (ADC) values and ADC ratios to differentiate typical meningiomas from atypical/malignant variety at 1.5 and 3T MRI.

Materials and methods

A total of 94 adult patients (48 patients at 3T and 46 patients at 1.5T) with pathologically proven meningiomas were retrospectively evaluated on conventional and diffusion weighted MRI. The signal intensity of the lesions on DW imaging was evaluated. ADC values and ADC ratios were calculated from lesion and contralateral normal white matter.

Results

94 lesions comprising of 66 benign and 28 atypical meningiomas were evaluated. The mean ADC values at 3T MRI were 0.82 ± 0.12 × 10⁻³ in benign (typical) meningiomas and 0.68 ± 0.10 × 10⁻³ in atypical meningiomas. At 1.5T, the mean ADC values of benign meningiomas were 0.83 ± 0.11 × 10⁻³ and 0.70 ± 0.09 × 10⁻³ in atypical meningiomas. The mean ADC ratios were 1.08 ± 0.17 and 0.85 ± 0.15 for benign and atypical meningiomas respectively. There was a statistically significant difference between the mean ADC ratios and the mean ADC values of typical and atypical meningiomas (P < 0.001) at both 1.5T and 3T MRI.

Conclusion

DWI with calculation of apparent diffusion coefficient (ADC) values and ADC ratios has a potential role in differentiating benign from atypical meningiomas at both 1.5 and 3T MRI. The differences in mean ADC values between benign and atypical meningiomas were similar at both 1.5 and 3T MRI.     

Hepatic hemangiomas: Factors associated with T2 shine-through effect on diffusion-weighted MR sequences

Purpose

To determine the frequency and factors associated with the presence of T2 shine-through effect in hepatic hemangiomas on diffusion-weighted (DW) magnetic resonance (MR) sequences.

Materials and methods

This retrospective study was approved by institutional review board with waiver of informed consent. One hundred forty-nine consecutive patients with 388 hepatic hemangiomas who underwent a liver MR between January 2010 and November 2011 were included. MR analysis evaluated the lesion characteristics (signal intensities and enhancement patterns (classical, rapidly filling, delayed filling)), the presence of T2 shine-through effect on DW sequences (b values of 0, 150, and 600 s/mm²), and apparent diffusion coefficient (ADC) values. Multivariate analysis was performed to study the factors associated with the T2 shine-through effect.

Results

T2 shine-through effect was observed in 204/388 (52.6%) of hepatic hemangiomas and in 100 (67.1%) patients. Mean ADC value of hemangiomas with T2 shine-through effect was significantly lower than hemangiomas without (2.0 ± 0.48 vs 2.38 ± 0.45, P < .0001). On multivariate analysis, high signal intensity on fat-suppressed T2-weighted fast spin-echo images, hemangiomas with classical or delayed enhancement, and the ADC of the liver were the only significant factors associated with T2 shine-through effect.

Conclusion

T2 shine-through effect is commonly observed in hepatic hemangiomas and is related to hemangiomas characteristics. Radiologists should be aware of this phenomenon which could lead to misdiagnosis. Its presence should not question the diagnosis of hemangiomas when typical MR findings are found.     

The diagnostic value of diffusion weighted imaging in patients with meningioma

Purpose

This study aims to determine the use of diffusion-weighted (DW) magnetic resonance imaging (MRI) in differentiating typical and atypical meningiomas.

Patients and methods

In total, 31 patients aged 37–77 years with meningiomas were included in this study. Using routine MRI sequences, the meningiomas were diagnosed and DW images were performed using factor of b-0 and b-1000. Apparent diffusion coefficient (ADC) values were measured in the lesion, in the normal area of brain parenchyma. Student t-test was used for statistical analysis. P < 0.05 was considered significant.

Results

Showed that the mean ADC of atypical/malignant meningiomas (0.42–0.69 × 10⁻³ mm²/s; P < .0001) was significantly lower compared with benign meningiomas (0.72–1.5 × 10⁻³ mm²/s). Mean NADC ratio in the atypical/malignant group (0.61) was also significantly lower than the benign group (1.21; P < .0001), without overlap between groups. The difference between the ADC values of the subtypes of typical meningiomas was insignificant.

In conclusion

Typical meningiomas have higher ADC values than atypical cases. DW MRI may be of help in differentiating typical and atypical meningiomas.     

The role of MR diffusion in differentiation of malignant and benign hepatic focal lesions

Aim

To determine if focal liver masses could be differentiated as benign or malignant by DWI and ADC maps.

Methods and materials

Sixty focal liver lesions were scanned using 1.5 T MRI. DWI was performed with b 0, b 500 and b 1000 gradients with ADC measurements. Comparison of mean ADC values between each benign and malignant lesion was done. Reference standard of diagnosis was obtained by correlating DWI with histopathologic findings and imaging follow-up. The accuracies of DWI and ADC values were assessed with the Student’s t test, and cut-off values were determined with receiver operating characteristic curve analysis.

Results

When ADC value of 1.0 × 10⁻³ mm²/s was used as a threshold value for differentiation of malignant tumors from benign lesions, sensitivity was 90.3%, specificity 78.57% and accuracy 86.7%. The best result was obtained with the use of ADC cut off value (at b 500) of 1.5 × 10⁻³ mm²/s and ADC cut off value (at b 1000) of 1.0 × 10⁻³ mm²/s, with 90.3% sensitivity, 92.86% specificity, 91.1% accuracy, 96.6% positive predictive value and 81.3% negative predictive value.

Conclusion

DWI and ADC map is a useful tool in differential diagnosis of malignant from benign liver lesions.