Is diffusion-weighted imaging useful in grading and differentiating histopathological subtypes of meningiomas?

Purpose

Meningiomas are mostly benign, however atypical or malignant subtypes with more aggressive clinical course and higher recurrence rates can also be seen. The purpose of this study was to determine whether histopathological subtypes of meningiomas could be assessed preoperatively using apparent diffusion coefficient (ADC) values.

Materials and methods

Conventional magnetic resonance (MR) and diffusion-weighted (DW) imaging of 177 adult patients with pathologically proven meningiomas were retrospectively evaluated. Tumor size and the degree of associated edema were noted. The signal intensity of the lesions on DW imaging was evaluated and graded. Mean ADC values were obtained as the mean of measurements from three regions of interests within the mass. ADC ratios of meningioma/contralateral normal appearing subcortical parietal white matter were also calculated.

Results

The histopathological analysis revealed 135 benign, 37 atypical and 5 malignant lesions. With classification according to the subtype, the mean ADC values and ratios of benign meningiomas were as 0.99 ± 0.12 × 10⁻³ mm²/s and 1.22 ± 0.07, respectively. ADC values for atypical and malignant groups were both 0.84 ± 0.1 × 10⁻³ mm²/s. The ADC ratios were 1.05 ± 0.1 and 0.96 ± 0.2 for atypical and malignant subtypes, respectively. There was no statistically significant difference between the mean ADC ratios of the three subtypes (ANOVA test; P ≥ 0.05). Gender, age of the patients and tumor size showed no statistically significant difference between the different histological groups.

Conclusion

DW MR imaging was not found to have any additional value in determining histological behaviour nor in differentiating histopathological subtypes of meningiomas.     

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.     

Correlating apparent diffusion coefficients with histopathologic findings on meningiomas

Purpose

To determine whether the apparent diffusion coefficient (ADC) correlates with histopathologic findings and whether ADC values can be used to differentiate benign from atypical/malignant meningiomas.

Materials and methods

MR images were reviewed retrospectively in 138 patients with meningiomas treated between September 1997 and July 2003. The ADC values were measured in the lesions and peritumoral edema, and the normalized ADC (NADC) ratios were calculated using the formula NADC = ADC of the tumor/ADC of the normal white matter. The ADC findings were compared with the histopathologic findings after resection using the World Health Organization criteria (2007).

Results

Meningiomas were histologically graded as malignant (9%), atypical (14%) and benign (77%). Of the 138 meningiomas, 32 (23%) were atypical (n = 19) or malignant (n = 13), whereas 106 (77%) were typical. The mean ADC values were statistically different between typical and atypical/malignant meningiomas (0.97 ± 0.21 × 10⁻³ mm²/s vs 0.85 ± 0.17 × 10⁻³ mm²/s). The mean NADC ratios were also significantly lower in the atypical/malignant group (1.09 ± 0.23) than in the benign group (1.24 ± 0.25; P = 0.002 < 0.05). The mean ADC values and NADC ratios did not differ significantly among fibrous, meningothelial, transitional and atypical tumors (P > 0.05). The mean ADC values and NADC ratios were higher in the angiomatous and secretory subgroups than in the fibrous, meningothelial, transitional, atypical and malignant subgroups (P < 0.05). The ADC values and NADC ratios were the lowest in the malignant subgroup, and the difference between atypical and malignant meningiomas was statistically significant (P < 0.05).

Conclusions

Meningioma subgroups displayed different ADC values from each other. Thus, ADC values may provide a useful supplement to the information obtained from conventional contrast-enhanced MR imaging, enhancing the ability of medical professionals to differentiate among the subgroups of meningiomas.     

Usefulness of perfusion weighted magnetic resonance imaging with signal-intensity curves analysis in the differential diagnosis of sellar and parasellar tumors: Preliminary report

Purpose

The most common pituitary tumors are adenomas, which however may be mimicked by other tumors that can show a very similar appearance in plain MRI. The aim of our study was to evaluate the usefulness of perfusion weighted MR imaging (PWI), including signal-intensity curves analysis in the differential diagnosis of sellar/parasellar tumors.

Methods

Forty-one patients with sellar/parasellar tumors (23 macroadenomas, 10 meningiomas, 5 craniopharyngiomas, 1 intrasellar hemangioblastoma, 1 intrasellar prostate cancer metastasis, 1 suprasellar glioma), underwent plain MRI followed by PWI using a 1.5T unit. In each tumor, the mean and maximum values of relative cerebral blood volume (rCBV), as well as the relative peak height (rPH) and the relative percentage of signal intensity recovery (rPSR) were calculated.

Results

The high perfusion tumors were: macroadenomas, meningiomas, squamous-papillary type of craniopharyngiomas, hemangioblastoma, glioma and metastasis. The low perfusion neoplasms included adamantinomatous type of craniopharyngiomas. By comparing adenomas and meningiomas, we found statistically significant differences in the mean and maximum rCBV values (p = 0.026 and p = 0.019, respectively), but not in rPH and rPSR. The maximum rCBV values >7.14 and the mean rCBV values >5.74 with the typical perfusion curve were very suggestive of the diagnosis of meningioma. There were differences between adenomas and other high perfusion tumors in rPH and rPSR values.

Conclusions

PWI can provide additional information helpful in differential diagnosis of sellar/parasellar tumors. In our opinion PWI, as an easy to perform and fast technique should be incorporated into the MR protocol of all intracranial neoplasms including sellar/parasellar tumors.     

Diffusion-weighted MR imaging: diagnosing atypical or malignant meningiomas and detecting tumor dedifferentiation

BACKGROUND AND PURPOSE: Atypical and malignant meningiomas are uncommon tumors with aggressive behavior and higher mortality, morbidity, and recurrence compared with benign tumors. We investigated the utility of diffusion-weighted (DW) MR imaging to differentiate atypical/malignant from benign meningiomas and to detect histologic dedifferentiation to higher tumor grade.MATERIALS AND METHODS: We retrospectively compared conventional and DW MR images (b-value 1000 s/mm²) acquired on a 1.5T clinical scanner between 25 atypical/malignant and 23 benign meningiomas. The optimal cutoff for the absolute apparent diffusion coefficient (ADC) and normalized ADC (NADC) ratio to differentiate between the groups was determined by using receiver operating characteristic (ROC) analysis.RESULTS: Irregular tumor margins, peritumoral edema, and adjacent bone destruction occurred significantly more often in atypical/malignant than in benign meningiomas. The mean ADC of atypical/malignant meningiomas (0.66 ± 0.13 × 10⁻³ mm²/s) was significantly lower compared with benign meningiomas (0.88 ± 0.08 × 10⁻³ mm²/s; P < .0001). Mean NADC ratio in the atypical/malignant group (0.91 ± 0.18) was also significantly lower than the benign group (1.28 ± 0.11; P < .0001), without overlap between groups. ROC analysis showed that ADC and NADC thresholds of 0.80 × 10⁻³ mm²/s and 0.99, respectively, had the best accuracy: at the NADC threshold of 0.99, the sensitivity and specificity were 96% and 100%, respectively. Two patients had isointense benign tumors on initial DW MR imaging, and these became hyperintense with the decrease in ADC and NADC below these thresholds when they progressed to atypical and malignant meningiomas on recurrence.CONCLUSIONS: ADC and NADC ratios in atypical/malignant meningiomas are significantly lower than in benign tumors. Decrease in ADC and NADC on follow-up imaging may suggest dedifferentiation to higher tumor grade.

Meningiomas comprise 14%–20% of all intracranial tumors, with a higher incidence of up to 35.2% among Asians and Africans.¹ Although they are generally benign tumors, up to 10% of meningiomas are atypical or malignant, characterized by nuclear disorganization, necrosis, prominent nucleoli, and increased mitoses on histology. Because of their aggressive behavior, atypical/malignant meningiomas are associated with high morbidity and mortality and may invade the adjacent bone and brain parenchyma. They are also more prone to recur in 29%–41% of patients than typical meningiomas, where the recurrence rate is between 7%–20%.² Although typical extra-axial benign meningiomas are easily diagnosed, distinction from more malignant histologic grades by CT or conventional MR imaging is difficult.³ Neuroimaging features, such as heterogeneous appearance, heterogeneous enhancement, marked perilesional edema, irregular cerebral surface, mushrooming on the outer edge of the lesion, and bone destruction, are not unique or reliable for diagnosing atypical/malignant meningiomas.^4–8 A diagnostic method that can differentiate between benign and atypical/ malignant meningiomas would, therefore, be desirable for surgical planning.Diffusion-weighted (DW) MR imaging has been used to study primary brain tumors, including histologic grading of gliomas and response to treatment.^9–16 Only a few studies have evaluated DW MR imaging for grading meningiomas, and although some have found that apparent diffusion coefficient (ADC) of atypical/malignant meningiomas was significantly lower than benign meningiomas,^2,17 others have not duplicated these results.¹⁶ Furthermore, the accuracy and threshold ADC to distinguish between benign and atypical/malignant meningiomas has not been established. There is also a paucity of literature on the DW MR imaging appearance of malignant transformation of benign meningiomas to higher grade tumors. In this study, we compared DW MR imaging between benign and atypical/malignant groups of meningiomas to estimate the cutoff ADC value for optimal tumor grading and describe imaging features of dedifferentiation of benign meningiomas.     

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.     

Role of diffusion-weighted MR imaging in discrimination between the intracranial cystic masses

Objective

Discriminating pyogenic brain abscesses from cystic or necrotic tumors is sometimes difficult with CT or conventional MR imaging. Diffusion MR imaging is a valuable diagnostic test in cases of intracranial cystic masses.

Methods

This work was conducted from July 2008 to June 2013 on 90 patients; 43 males and 47 females. Their ages range from 5 to 70 years. All patients were subjected to routine MRI examination and diffusion weighted imaging using 1.5 T MRI scanner. Gadolinium was given to some cases on routine MRI. Diffusion weighted imaging was performed with a single-shot spin-echo echo-planar pulse sequence (b = 0–1000 s/mm²). The apparent diffusion coefficient values and ratio were measured.

Results and conclusions

Patients in this study were categorized into three main groups; first group is brain abscesses (36 cases), 91.6% of them showed restricted diffusion, second group is malignant cystic or necrotic brain tumors, 28 cases of high grade necrotic glioma, 60.7% of them are free diffusion, and third group is benign cystic masses, arachnoid and epidermiod cysts (11 cases); all arachnoid cysts are free diffusion. From these results diffusion-weighted imaging is playing an important role in discrimination of cystic intracranial masses.     

Chordoid Meningioma: Differentiating a Rare World Health Organization Grade II Tumor from Other Meningioma Histologic Subtypes Using MRI

BACKGROUND AND PURPOSE:Meningiomas are very commonly diagnosed intracranial primary neoplasms, of which the chordoid subtype is seldom encountered. Our aim was to retrospectively review preoperative MR imaging of intracranial chordoid meningiomas, a rare WHO grade II variant, in an effort to determine if there exist distinguishing MR imaging characteristics that can aid in differentiating this atypical variety from other meningioma subtypes.MATERIALS AND METHODS:Ten cases of WHO grade II chordoid meningioma were diagnosed at our institution over an 11-year span, 8 of which had preoperative MR imaging available for review and were included in our analysis. Chordoid meningioma MR imaging characteristics, including ADC values and normalized ADC ratios, were compared with those of 80 consecutive cases of WHO grade I meningioma, 21 consecutive cases of nonchordoid WHO grade II meningioma, and 1 case of WHO grade III meningioma.RESULTS:Preoperative MR imaging revealed no significant differences in size, location, signal characteristics, or contrast enhancement between chordoid meningiomas and other meningiomas. There were, however, clear differences in the ADC values and normalized ADC ratios, with a mean absolute ADC value of 1.62 ± 0.33 × 10⁻³ mm²/s and a mean normalized ADC ratio of 2.22 ± 0.47 × 10⁻³ mm²/s in chordoid meningiomas compared with mean ADC and normalized ADC values, respectively, of 0.88 ± 0.13 × 10⁻³ mm²/s and 1.17 ± 0.16 × 10⁻³ mm²/s in benign WHO grade I meningiomas, 0.84 ± 0.11 × 10⁻³ mm²/s and 1.11 ± 0.15 × 10⁻³ mm²/s in nonchordoid WHO grade II meningiomas, and 0.57 × 10⁻³ mm²/s and 0.75 × 10⁻³ mm²/s in the 1 WHO grade III meningioma.CONCLUSIONS:Chordoid meningiomas have statistically significant elevations of ADC and normalized ADC values when compared with all other WHO grade I, II, and III subtypes, which enables reliable preoperative prediction of this atypical histopathologic diagnosis.

Meningiomas are the second most common primary intracranial neoplasm, constituting approximately 13%–25% of such tumors.¹ There are 15 variants of meningioma according the 2007 World Health Organization (WHO) classification of tumors of the central nervous system.² Although 80%–90% of meningiomas are classified as benign WHO grade I tumors, WHO grade II and III varieties demonstrate a more aggressive clinical course and have a greater propensity for recurrence, and the grade and extent of original resection accounts for these differences.³ Ideally, preoperative imaging to identify the potentially more aggressive grade II and III varieties would be helpful for presurgical planning and subsequent imaging follow-up. One such rare variant is the WHO grade II chordoid meningioma. A little more than 100 cases of chordoid meningioma have been described in the English-language literature, the majority of which are in the pathology and neurosurgery literature.^4–9Attempts to distinguish benign from atypical and malignant meningiomas have been undertaken with variable results, and DWI and ADC values have provided the most reliable means of differentiation,^10,11 though no data analysis specifically examining the chordoid morphologic variant has been performed. To the best of our knowledge, only 3 case reports in which the MR imaging characteristics of chordoid meningiomas were described have been published in the radiology literature.^12–14We compared 8 cases of intracranial chordoid meningioma to 80 consecutive cases of WHO grade I meningioma, 21 consecutive cases of nonchordoid WHO grade II meningioma, and 1 WHO grade III meningioma in an effort to determine if there exist distinguishing MR imaging characteristics that can aid in differentiating this particular subtype.     

Atypical hemangioma and malignant lesions of spine: Can diffusion weighted Magnetic Resonance Imaging help to differentiate?

Objective

The aim of the work was directed to evaluate the value of diffusion weighted Magnetic Resonance Imaging in diagnosis, characterization and differentiation of atypical hemangioma and malignant lesions of spine.

Materials and methods

This study included three groups: group (A) 8 (33%) patients with metastatic bony lesions of spine, group (B) 6 (25%) patients with atypical hemangioma and group (C) 10 (42%) patients with typical hemangioma.All patients were presented with different degrees of back pain. MRI was done for all patients (including T1, T2, T2 fat suppression and DWI with IV contrast administration when needed). Complementary non contrast CT was also done.

Results

Atypical hemangioma and malignant lesions were low in T1 and high in T2 WI. Restricted diffusion and low ADC values were seen in metastasis compared with atypical hemangioma. Complementary CT revealed the lytic nature of malignant lesions while in hemangiomas, it showed their characteristic striated appearance.

Conclusion

Diffusion weighted Magnetic Resonance Imaging is a useful tool in diagnosis, characterization and differentiation of atypical hemangioma and metastasis of spine.     

Magnetic resonance spectroscopy and perfusion weighted imaging as predictors for tumor response to gamma knife radiosurgery: A single center experience

Objective

To test the hypothesis that hemodynamic and metabolic characteristics of intracranial neoplasms detected with magnetic resonance spectroscopy and perfusion weighted imaging are efficient predictors of tumor response to radiosurgery.

Methods

Fifty-four patients with 59 intracranial neoplasms, who underwent evaluation with echoplanar PW and MRS imaging prior to gamma knife radiosurgery were selected for this retrospective analysis. The mean irradiation dose was 13.76 Gy. The mean follow up after GNR constituted 24 months. Predictive diagnostic accuracy was calculated with standard formulas. The association of tumor response to radiosurgery with pretherapeutic MRI parameters was estimated using the Mann–Whitney U test.

Results

Significant association was found between the perfusion and hemodynamic parameters of intracranial neoplasms and the outcome of GKR. Diagnostic accuracy of multimodel MRI was 89% among low grade and 65% among high grade neoplasms. The overall accuracy was 81%. Normalized rCBV, choline, NAA and lipid contents and Chol/cr and NAA/cr were statistically different between low and high grade neoplasms (p < 0.001).

Conclusion

MR perfusion and spectroscopic results provided information that were predictive of the outcome of radiosurgery in this patient pool, increased the diagnostic accuracy of conventional MRI in defining tumor type and grade and may play an important role in pre-therapeutic planning for radiosurgery.     

MR imaging of hepatic metastasis in patients with malignant melanoma: evaluation of suspected lesions screened at contrast-enhanced CT

Purpose

To evaluate the magnetic resonance (MR) imaging feature of suspected hepatic metastasis in patients with malignant melanoma which showed intermediate findings on screened contrast-enhanced computed tomography (CECT).

Materials and methods

MR imaging was performed in 38 patients (22 men, 16 women; mean age, 58 years) whose CECT findings were intermediate. Hepatic metastases had been diagnosed on MR imaging in 23 of the 38 patients. Verification of hepatic metastasis was made by histological examination: ultrasonographic-guided needle biopsy (n = 3), autopsy (n = 3), and surgical resection (n = 1), or by an obvious progression in number and/or size of the lesions on follow-up MR imaging (n = 24). Two diagnostic radiologists reviewed MR images by consensus. The median follow-up duration was 14.2 months.

Results

Abnormal findings were detected in 31 patients on MR images, and undetected in the remaining seven patients resulting in false-positive on CECT. The mean size of the lesion was 11.0 mm. False-positive results were obtained in two lesions which disappeared on follow-up MR imaging. In six patients, lesions were considered as hepatic cysts on MR images. As a result, a total of 35 hepatic metastases were detected on MR images. Of these, 18 patients demonstrated typical melanotic appearance on MR images which showed shortened T1 and T2 relaxation times, and five patients demonstrated atypical melanotic appearance. In 16 patients, extra-hepatic metastases were also developed.

Conclusion

MR imaging could rule out hepatic metastasis in patients with malignant melanoma which showed intermediate findings on screened CECT, and could detect additional extra-hepatic metastases.     

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.     

Apparent diffusion coefficient and Magnetic resonance spectroscopy in grading of malignant brain neoplasms

Aim

This work aims to study the role of combined apparent diffusion coefficient (ADC) and Magnetic resonance spectroscopy (MRS) in grading malignant brain neoplasms.

Methods

A prospective study included 40 patients who were evaluated by standard contrast enhanced MRI, diffusion weighted imaging and multivoxel spectroscopy.

Results

Statistically significant difference was found between tumoral ADC values in low grade versus high grade tumors and metastasis and also between the peritumoral ADC values in metastasis versus low and high grade tumors. Statistically significant difference is noticed between tumoral Cho/Cr ratio values in low grade versus high grade tumors and metastasis, and also peritumoral Cho/Cr ratio values in low grade and metastasis versus high grade tumors. Statistically significant difference between tumoral Cho/NAA ratio in low grade versus high grade tumors and metastasis and lastly between peritumoral Cho/NAA ratio in low grade and metastasis versus high grade tumors was found. Lipid and lactate peaks were found frequently in high grade tumors and metastasis.

Conclusion

The combination of calculated ADC values and MR spectroscopy is useful in grading of malignant brain tumors and were more useful together than each on its own.     

Differentiation of intracranial tuberculomas and high grade gliomas using proton MR spectroscopy and diffusion MR imaging

Objective

The purpose of this study was to determine whether proton MR spectroscopy (¹H MRS) and diffusion-weighted (DW) imaging can be used to differentiate intracranial tuberculomas from high grade gliomas (HGGs).

Materials and methods

A total of 41 patients (19 with intracranial tuberculomas and 22 with HGGs) were examined in our study. ¹H MRS and DW imaging were performed at a 1.5T MR scanner before operation or treatment. Concentrations of N-acetylaspartate (NAA), creatine (Cr), choline (Cho), and lipid and lactate (LL) in the contrast-enhancing rim of each lesion were expressed as metabolite ratios and were normalized to the contralateral hemisphere. The apparent diffusion coefficient (ADC) was also calculated. The metabolite ratios and ADC values in the enhancing rim of intracranial tuberculomas and HGGs were compared using the Wilcoxon rank sum test. Diagnostic accuracy was compared using receiver operating characteristic (ROC) analysis.

Results

Significant differences were found in the maximum Cho/Cr (P = 0.015), Cho/NAA (P = 0.001) and Cho/Cho-n ratios (P = 0.002), and minimum ADC value (P < 0.001) between the intracranial tuberculomas and HGGs. Diagnostic accuracy was higher by minimum ADC value than maximum Cho/Cr, Cho/NAA and Cho/Cho-n ratios (93.8% versus 75.7%, 80.8% and 78.1%).

Conclusion

These results suggest a promising role for ¹H MRS and DW imaging in the differentiation between the intracranial tuberculomas and HGGs.     

Diagnostic value of gadolinium-enhanced dynamic MR imaging for parotid gland tumors

Objective

This study aimed to evaluate the value of gadolinium-enhanced dynamic MR imaging for differentiating benign and malignant parotid gland tumors, and for characterizing the various histological types.

Patients and methods

Non-enhanced T1-weighted (T1-W), fat-suppressed T2-weighted (T2-W), and gadolinium-enhanced fat-suppressed dynamic T1-weighted images were obtained preoperatively in 27 patients (28 parotid gland tumors), by using a 1.5 or 3 T MR imaging unit (GE, Signa Exite). The tumor margins and the enhancement curve patterns on dynamic MR imaging were analyzed. All patients underwent a parotidectomy with histopathologic analysis.

Results

Pleomorphic adenomas depict a gradual enhancement pattern. Warthin’s tumors depict an early peak of enhancement and a high washout pattern. Malignant tumors depict an early peak of enhancement and a low washout pattern.

Conclusion

Gadolinium-enhanced dynamic MR imaging improved the performance of MR imaging in differentiating benign from malignant parotid gland tumors and characterizing the different histological types of benign tumors.     

H proton MR spectroscopy and diffusion-weighted imaging in discrimination between pyogenic brain abscesses and necrotic brain tumors

Background

Differentiation between cerebral abscesses and necrotic brain tumors showing ring enhancement can be confusing at times by conventional MRI. The introduction of advanced imaging techniques, such as MR spectroscopy and diffusion WI, have contributed to the differentiation.The purpose of this study is to test the hypothesis that MR spectroscopy and diffusion weighted can be used to differentiate between necrotizing or cystic brain tumor and brain abscesses.

Methods

The study was conducted on 45 patients (necrotic or cystic tumor (30 cases); brain abscess (15 cases) showing ring-shaped contrast enhancement on conventional MRI. 1.5-T ¹H-MR Spectroscopy and diffusion WI were performed and the results were ensured by stereotactic biopsy or aspiration procedures in surgically indicated cases and/or follow up.

Results

14 patients (out of 15) with pyogenic abscess had lactate, amino acids, and acetate peaks; Succinate peak is seen as extra peak in three of these patients, and lipid peaks are also seen as extra peaks in 3 patients. One patient with brain stem abscess after 20 days treatment by antibiotics shows only lactate and lipid peaks. 2 of them show mild increase in choline with decrease in NAA (brain tissue contamination).17 out of 30 patients with cystic or necrotic tumor showed only lactate peak in MRS. While 13 patients show lactate and lipid peaks, four of them show additional high choline peak with low NAA and creatine peak (contamination with brain tissue).The results were confirmed by Sterotactic biopsy in 27 cases and aspiration in 13 cases and follow up for all cases.The sensitivity, specificity, PPV, NPV and overall accuracy of diffusion and MRS were 88%, 100%, 100%, 93.3% and 95.5% respectively.

Conclusion

¹H-MRS and diffusion WI are fast, easy to perform, noninvasive, and provide additional information that can accurately differentiate between necrotic/cystic tumors and cerebral abscesses.     

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.     

MR imaging versus PET/CT for evaluation of pancreatic lesions

Purpose

To retrospectively determine the diagnostic accuracy of magnetic resonance imaging (MRI) and combined positron emission tomography/computed tomography (PET/CT) in the differential diagnosis of benign and malignant pancreatic lesions.

Materials and methods

Twenty-seven patients (15 women/12 men, mean age 56.5 years) with MR imaging and PET/CT studies performed to differentiate benign and malignant pancreatic lesions were identified between October 2008 and October 2010. Both MR and PET/CT data sets were retrospectively and blindly evaluated by two independent readers (4 readers total) with different degrees of experience, using a visual five-point score system. The results were correlated with final diagnosis obtained by histopathology.

Results

17 patients had malignant diseases and 10 patients had benign diseases. Depending on the observer, the sensitivity, specificity, positive predictive value and negative predictive value of MRI varied between 88–94%, 50–80%, 75–89% and 71–89% respectively. Sensitivities, specificities, positive predictive values and negative predictive values of PET/CT were 73%, 56%, 73% and 56% respectively. The diagnostic accuracy of MR for the differential diagnosis of pancreatic lesions was 74–89%, compared with 67% for PET/CT. The weighted Cohen's kappa coefficient was 0.47 at MR and 0.53 at PET/CT.

Conclusion

MRI achieved higher sensitivity and specificity in the differential diagnosis of pancreatic lesions.     

Neurochemical-structural changes evaluation of brain in patients with obstructive sleep apnea syndrome

Purpose

To evaluate neurochemical and structural changes in the patients with newly diagnosed obstructive sleep apnea syndrome (OSAS) by MR spectroscopy (MRS), T2 relaxometry, and diffusion weighted imaging (DWI).

Material and methods

Following the acquisition of routine cranial MR, MRS, T2 relaxometry, and DWI images; spectroscopic metabolite ratios and DWI–T2 relaxometry findings of the thalami, hippocampi, frontal white matter (FWM) and frontal cortex of 24 OSAS patients and 9 controls were statistically compared. The relationship between two groups was evaluated with Mann–Whitney test.

Results

Spectroscopic measurements in the frontal cortex and frontal white matter of the OSAS patients revealed significantly lower NAA/Cr ratios than those of the control group (P = 0.004 and P = 0.006, respectively). The measurements in the frontal white matter of the OSAS patients exhibited significantly lower NAA/Cho ratios compared with those of the control group (P = 0.005). Thalamic Cho/Cr ratios of the patient group were significantly higher than those of the control group (P = 0.002). In terms of the ADC–T2 relaxometry values, there was no significant relationship between the patient and the control groups (P > 0.05).

Conclusion

MRS is a useful and non-invasive modality in showing neurochemical changes in various regions of the brain but our data does not show any change on diffusion weighting or T2 quantification in the OSAS group. DWI and T2 relaxometry appear to be not effective techniques to evaluate the brain structural changes of the patients with newly diagnosed OSAS.     

Quantitative chemical-shift MR imaging cutoff value: Benign versus malignant vertebral compression – Initial experience

Purpose

To evaluate the diagnostic accuracy of in-phase/opposed-phase quantitative chemical shift magnetic resonance (MR) imaging of the spine and to determine the cutoff value that enables differentiation of malignant from benign compression fractures, in patients with known primary malignancy.

Patients and methods

Prospective assessment of thirty-two patients with known primary malignancy who presented with vertebral compression fractures, MR imaging of the spine at 1.5 Tesla with standard conventional MR sequences and additional chemical shift (in-phase/opposed-phase) imaging was done. Quantitative image analysis by drawing regions of interest (ROI) on the abnormal marrow of compressed (study group) and adjacent normal vertebra (control group) was also performed in each patient. The signal intensity ratio (SIR) of the marrow was determined by dividing the mean signal intensity on the opposed-phase to the mean signal intensity on the in-phase images and statistical analysis was performed.

Results

Mean SIR of benign vertebral compression [0.73 ± 0.07 (range 0.12–1.2)] was significantly lower than malignant SIR values [1.72 ± 0.14 (range 0.8–2.96)] (p < 0.0001; area under the ROC curve, 0.97). The optimal SIR cutoff value for separating benign and malignant vertebral compression was found to be 0.91 with a calculated sensitivity of 93%, specificity of 82% and accuracy of 88%.

Conclusion

Quantitative chemical shift MR imaging could be a valuable addition to standard MR imaging techniques and represent a rapid problem solving tool in differentiating benign from malignant vertebral compression, especially in patients with known primary malignancies.