Apparent Diffusion Coefficient Ratio Research Articles

Radiation Necrosis in the Brain: Imaging Features and Differentiation from Tumor Recurrence

Radiation necrosis in the brain commonly occurs in three distinct clinical scenarios, namely, radiation therapy for head and neck malignancy or intracranial extraaxial tumor, stereotactic radiation therapy (including radiosurgery) for brain metastasis, and radiation therapy for primary brain tumors. Knowledge of the radiation treatment plan, amount of brain tissue included in the radiation port, type of radiation, location of the primary malignancy, and amount of time elapsed since radiation therapy is extremely important in determining whether the imaging abnormality represents radiation necrosis or recurrent tumor. Conventional magnetic resonance (MR) imaging findings of these two entities overlap considerably, and even at histopathologic analysis, tumor mixed with radiation necrosis is a common finding. Advanced imaging modalities such as diffusion tensor imaging and perfusion MR imaging (with calculation of certain specific parameters such as apparent diffusion coefficient ratios, relative peak height, and percentage of signal recovery), MR spectroscopy, and positron emission tomography can be useful in differentiating between recurrent tumor and radiation necrosis. In everyday practice, the visual assessment of diffusion-weighted and perfusion images may also be helpful by favoring one diagnosis over the other, with restricted diffusion and an elevated relative cerebral blood volume being seen much more frequently in recurrent tumor than in radiation necrosis.

Correlating apparent diffusion coefficients with histopathologic findings on meningiomas

PurposeTo 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 methodsMR 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). ResultsMeningiomas 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±0.21×10−3mm2/s vs 0.85±0.17×10−3mm2/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). ConclusionsMeningioma 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.

Relationship between IDH1 mutation status and magnetic resonance imaging features in WHO grade II and III oligodendroglial tumors.

2082 Background: In gliomas, relationship between radiological characteristics and several biomarkers was the subject of numerous publications. Mutations in the isocitrate dehydrogenase 1 (IDH1) gene have been identified recently to play a key role in these tumors occuring in up to 75% of low-grade diffuse (WHO grade II) and anaplastic (WHO grade III) astrocytic, oligodendroglial and mixed oligodendroglial neoplasms. However, the correlation with magnetic resonance imaging (MRI) features has been little studied. Methods: Patients treated for WHO grade II and III oligodendroglial tumors between 2005 and 2011 were retrospectively identified. Each case has been reviewed by the same neuropathologist. IDH1 and IDH2 mutations were available. Preoperative MRI, including T1 weighted, T2 weighted, T1 contrast enhanced, FLAIR, T2* weighted, diffusion weighted (ADC ratio), perfusion weighted (CBV ratio) and MR spectroscopy, were analyzed by two radiologists blinded from molecular data. Logistic regression analysis and Fisher’s test were used to develop predictive models of genetic profile from imaging. Results: Sixty eight patients, WHO grade II (n= 37) and grade III (n=31) patients were identified. Mean age at diagnosis was 46 years; ratio male/female was 40/28. IDH1 mutations were identified in 42 patients (62 %), IDH2 in 4 patients (6 %). Analysis of tumor location, size, borders, morphological aspect, and signal did not shown any significant difference between IDH1 mutated group and IDH1 non mutated group neither in grade II nor in grade III oligodendroglial tumors. In the same way, MR spectroscopy (Choline/NAA ratio and detection of lipid and lactate) was not relevant to discern the two groups. As well, ADC ratio (1,5 versus 1,4; p=0,35) and CBV ratio (3,4 versus 4,2; p= 0,46) did not reveal any difference between mutated group and non mutated group. Conclusions: In our study, IDH1 mutations were not correlated with MRI features available during routine MRI. Nevertheless, recent studies suggest the ability of MR spectroscopy to detect 2-hydroxyglutarate as an MRI marker of IDH1 mutated tumors, which encourage carrying on research in molecular imaging.

Utility of Apparent Diffusion Coefficient Ratios in Distinguishing Common Pediatric Cerebellar Tumors

The aim of this study was to identify clinically useful tumor/normal brain apparent diffusion coefficient (ADC) ratios for distinguishing common pediatric cerebellar tumors. Review of medical records revealed 79 patients with cerebellar tumors who underwent preoperative magnetic resonance imaging, including diffusion-weighted imaging sequences, and surgery. There were 31 pilocytic astrocytomas, 27 medulloblastomas, 14 ependymomas, and seven atypical teratoid/rhabdoid tumors. ADC values were measured by placing regions of interest on the solid tumor and normal brain parenchyma by two reviewers. Tumor/normal brain ADC ratios were calculated. Mean ADC values of the pilocytic astrocytomas were greater than those of ependymomas, whose mean ADC values were greater than those of medulloblastomas and atypical teratoid/rhabdoid tumors. Using a tumor/normal brain ADC ratio threshold of 1.70 to distinguish pilocytic astrocytomas from ependymomas, sensitivity of 92% and specificity of 79% were achieved. A tumor/normal brain ADC ratio threshold of 1.20 enabled the sorting of ependymomas from medulloblastomas with sensitivity of 93% and specificity of 88%. Tumor/normal brain ADC ratios allow the distinguishing of common pediatric cerebellar tumors.

Evaluation of malignant and benign renal lesions using diffusion-weighted MRI with multiple b values

Limited data are available regarding the use of diffusion-weighted (DW) magnetic resonance imaging (MRI) with multiple b values for characterization of renal lesions. To demonstrate and compare the diagnostic performance of DW-MRI with multiple b values for renal lesion characterization. Sixty-three lesions (36 malignant, 27 benign) in 60 consecutive patients (48 men, 12 women; age 60 ± 12.5 years) with solid/cystic renal lesion diagnosed after MRI were included prospectively. Single-shot echo-planar DW abdominal MRI (1.5T) was obtained using seven b values with eight apparent diffusion coefficient (ADC) maps. Contrast-to-noise ratios (CNRs), signal intensities, lesion ADCs, and lesion/normal parenchyma ADC ratios were analyzed. Receiver-operating characteristic analysis was performed. The mean signal intensities of malignant lesions (at b0, 50, and 200s/mm(2)) were significantly lower than those of benign lesions (P < 0.05). The mean ADC values at all b value combinations of malignant lesions were significantly lower than those of benign lesions (P < 0.000), excluding the ADC value at b50 s/mm(2). ADC with all b values could better distinguish between benign and malignant lesions. A 1.35 × 10(-3) mm(2)/s threshold ADC value permitted this distinction with 85.2% sensitivity and 65.6% specificity. The lesion/normal parenchyma ADC ratio was more effective than the lesion ADC. In addition to the ADC value, the signal intensity curve on DW images using multiple b values could be helpful for differentiation of malignant and benign renal lesions.

Abstract 4018: Pretreatment MRI Markers May Predict Hemorrhagic Transformation in Patients Treated with IV tPA

Objectives: Multiple MRI measurements have been investigated as possible markers of post-treatment imaging pathology. The objectives of this study were to understand how well measurements from pre-treatment MRI data including ADC volume, DWI volume, MTT volume, Tmax volume, ADC ratio, and CBV ratio predicted post-treatment hemorrhagic transformation. Methods: Patients were selected from the Lesion Evolution of Stroke and Ischemia On Neuroimaging (LESION) database if they: had an acute ischemic stroke, were treated with IV tPA only, had a pre-treatment MRI with evaluable diffusion (DWI) and perfusion (PWI) weighted imaging, and had measurable lesion volumes on both ADC and Tmax images. All ADC and Tmax maps were calculated in Perfscape™ (Olea Medical). A trained rater applied an ADC threshold of 615 mm 2 /seconds and Tmax threshold of &gt;6 seconds using Neuroscape™ (Olea Medical) to produce the ADC and Tmax volumes that included any voxels across affected slices within the visually confirmed area of ischemia. All CBV maps were calculated from the PWI in PMA™ (ASIST-Japan). The regions of interest (ROIs) from the ADC volumes were used in MIPAV™ (National Institutes of Health) to measure the average voxel intensity (AVI) of the ADC and CBV lesions in both the ischemic (AVII) and contralateral hemispheres (AVIC). Logistic regression with covariates of age, baseline NIHSS, DWI volume, MTT volume, ADC volume, Tmax volume, ADC ratio and CBV ratio was performed. Results: A total of 74 patients met the study criteria with mean age of 67.9 years (range 32-95), median NIHSS of 12 (range 1-40), median DWI volume of 28.21 ml (IQR 11.05-66.52), and median MTT volume of 147.69 ml (IQR 52.9-250). Fifty patients had hemorrhagic transformation status available at 2 and\or 24 hours post-treatment. Fifty-four percent (n=27) had some degree of hemorrhagic transformation at 2 or 24 hours post treatment. The pre-treatment volumes reported as median (IQR 25-75) for the hemorrhagic transformation cohort (n=27) were 55.22 ml (20.32-70.53), 181.75 ml (65.36-252.88), 4.52 ml (1.07-7.39), 51.19 ml (32.67-118.23) for the DWI, MTT, ADC, Tmax and 0.52 (0.5-0.55) for the ADC ratios. The pre-treatment volumes for the non-hemorrhagic transformation cohort (n=23) were 26.07 ml (6.29-66.96), 133.78 ml (58.7-209.09), 5.27 ml (0.74-8.83), 61.33 ml (26.08-85.86) for the DWI, MTT, ADC, Tmax volumes and 0.53 (0.47-0.63) for the ADC ratios. However the CBV ratios using median (IQR 25-75) for the hemorrhagic transformation cohort versus the non-hemorrhagic transformation cohort were 0.27 (0.14-0.42) versus 0.46 (0.17-0.70). The logistic regression analysis demonstrated that patients with lowered CBV ratio on pre-treatment MRI significantly predicted hemorrhagic transformation (p&lt;0.019). Conclusions: Lowered CBV ratio on pre-treatment MRI demonstrates potential as a predictor of hemorrhagic transformation post-treatment.

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Diffusion tensor and dynamic susceptibility contrast MRI in glioblastoma

ObjectiveWe prospectively investigated the correlation between diffusion tensor (DTI), dynamic susceptibility contrast (DSC) perfusion MRI metrics and Ki-67 labelling index in glioblastomas. MethodsWe studied seventeen patients who were operated on for glioblastoma. DTI and DSC MRI were performed within a week prior to surgical excision. Lesion/normal ratios were calculated for the apparent diffusion coefficient (ADC), fractional anisotropy (FA), relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF) and relative mean transit time (rMTT) ratio. In the excised tumour specimens Ki-67 antigen expression was evaluated by the MIB-1 immunostaining method. ResultsA significant correlation was observed between Ki-67 index and ADC ratio (r=−0.528, p=0.029) and FA ratio (r=0.589, p=0.012). rCBV and rMTT presented a trend towards significant correlation with Ki-67 index (r=0.628, p=0.07 and r=0.644, p=0.06 respectively). There was a trend towards better survival for patients with gross total tumour excision and FA values lower than 0.48 (p=0.1 and p=0.09 respectively). No significant correlation was found between ADC ratio, rCBV, rCBF, rMTT and overall survival. ConclusionADC ratio, FA ratio, rCBV and rMTT tumour/normal tissue ratios may represent indicators of glioma proliferation. FA values may hold promise for predicting survival in patients with glioblastoma.

Role of apparent diffusion coefficient values and diffusion-weighted magnetic resonance imaging in differentiation between benign and malignant thyroid nodules

Objective The purpose of the study was to differentiate between benign and malignant thyroid nodules using nodule-spinal cord signal intensity and nodule apparent diffusion coefficient (ADC) ratios on diffusion-weighted magnetic resonance imaging (DW-MRI). Materials and Methods Forty-four patients (27 females, 17 males; mean age, 49 years) with nodules who underwent DW-MRI were included in this study. The images were acquired with 0, 50, 400 and 1000 s/mm 2 b values. ADC maps were calculated afterwards. Fine needle aspiration biopsies (FNAB) were performed at the same day with DW-MRI acquisition. The diagnosis in patients where malignity was detected after FNAB was confirmed by histopathologic analysis of the operation material. The signal intensities of the spinal cord and the nodule were measured additionally, over b-1000 diffusion-weighted images. Nodule/cord signal intensity (SI) ratios were obtained and the digital values were calculated by dividing to ADC values estimated for each nodule. Statistical analysis was performed. Results The (nodule SI-cord SI)/nodule ADC ratio is calculated in the DW images, and a statistically significant relationship was found between this ratio and the histopathology of the nodules ( P<.001). The ratio was determined as 0.27 in benign and 0.86 in malignant lesions. The result of receiver operating characteristic (ROC) analysis was statistically significant, and the area under curve (100%) was considerably high. The threshold value was calculated as 0.56 according to the ROC analysis. According to this threshold value, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy rates for (nodule SI/cord SI)/ADC ratios in differentiating benign from malignant thyroid nodules are calculated as 100%, 97%, 83%, 100%, and 98%, respectively. Conclusion We have found that (nodule/cord SI)/nodule ADC ratio has the highest values for sensitivity and specificity among the tests defined for characterization of nodules.

Differentitation between Primary Central Nervous System Lymphoma and Glioblastoma: Added Value of Quantitative Analysis of CT Attenuation and Apparent Diffusion Coefficient

Purpose : Purpose of this study was to determine if quantitative measures of CT attenuation and ADC values in combination with conventional imaging features can differentiate primary central nervous system lymphoma (PCNSL) and glioblastoma (GBM). Materials and Methods: Twenty-six patients with histologically-proven GBM (14 men and 12 women; median age, 50 years; age range, 22 73 years) and 14 patients with PCNSL (11 men and 3 women; median age, 61 years; age range, 41 74 years) were enrolled. Maximum CT attenuation, minimum ADC, and lesion to normal parenchyma minimum ADC ratios were measured in solid tumor regions. Conventional imaging features were evaluated for the following: ill-defined margin, homogeneous enhancement pattern, degree of necrosis, extent of tumor involvement and multiplicity. The Mann-Whitney test was used to compare maximum CT attenuation and minimum ADC values for PCNSL and GBM. Fisher’s exact test was used to evaluate relationships between pathologic diagnoses and imaging features. Results: The CT attenuations were similar for PCNSL and GBM (37.84 ± 6.90 HU versus 37.00 ± 5.54 HU, p = 0.68), but minimum ADC and minimum ADC ratio were significant lower in PCNSL than in GBM (595.01 ± 228.28 10 mm/s versus 736.52 ± 162.05 10 mm/s; p = 0.028, 0.87 ± 0.26 versus 1.14 ± 0.29; p = 0.007). PCNSL showed greater homogeneous enhancement and smaller necrotic areas than GBM (p = 0.003 and p < 0.001, respectively) and was more likely to have multiple tumors than GBM (p = 0.039). When necrotic PCNSL (n = 4) and necrotic GBM (n = 24) were compared, minimum ADC and minimum ADC ratios were also significantly lower in PCNSL, but CT attenuation were not. Conclusion: Although CT attenuation does not provide valuable information, minimum ADC and minimum ADC ratio and some imaging features can aid the differentiation of PCNSL and GBM. Index words : Central Nervous System∙Lymphoma∙Glioblastoma∙Computed tomography (CT) Diffusion weighted imaging (DWI)

High-b-Value Diffusion-weighted MR Imaging of Benign Hepatocellular Lesions: Quantitative and Qualitative Analysis

To analyze the signal intensity (SI) of benign hepatocellular lesions in high-b-value diffusion-weighted (DW) magnetic resonance (MR) images and to compare the apparent diffusion coefficient (ADC) values of focal nodular hyperplasias (FNHs) with those of hepatocellular adenomas (HCAs). This retrospective study was approved by institutional review board, with waiver of informed consent. Inclusion criteria were consecutive patients with diagnosed FNH or HCA who underwent MR imaging with a DW sequence of the liver at three b values, 0, 150, and 600 sec/mm2. The final study population included 67 patients (seven men, 60 women) with 90 hepatocellular lesions (54 FNHs, 36 HCAs). The mean ADC was compared between the lesions and the liver. Receiver operating characteristic analysis was performed to evaluate the diagnostic value of ADC for differentiating HCAs and FNHs. The mean ADC value of all FNHs and HCAs was significantly lower than that of the liver (P=.004). An ADC ratio below 15% was observed in 50 of 54 (93%) FNHs and in 29 of 36 (81%) HCAs. The mean ADC value of FNHs was significantly higher than that of HCAs (P<.001). The area under the receiver operating characteristic curve was 0.760. With a cutoff value of 1.37×10(-3) mm2/sec, the sensitivity and specificity for differentiating HCA from FNH were 70% and 76%, respectively. There was no significant difference in ADC values between HCA subtypes. The SI of most FNHs and HCAs (78 of 90, 87%) increased with increasing b values, whereas none showed a decrease in SI with increasing b values. When the DW MR criteria for benign and malignant liver tumors were applied, 44 of 90 (49%) lesions would have been considered malignant lesions, whereas the other lesions (46 of 90, 51%) would have been considered indeterminate. On DW MR images, benign hepatocellular lesions often show findings that suggest restricted diffusion.

Restricted Diffusion in Spinal Cord Infarction Demonstrated by Magnetic Resonance Line Scan Diffusion Imaging

We report on the use of line scan diffusion magnetic resonance imaging in the evaluation of spinal cord infarctions. Data on 19 patients with clinical findings consistent with spinal cord infarctions and abnormal findings on line scan diffusion imaging were reviewed. The Apparent Diffusion Coefficient (ADC) measurements for the normal spinal cord and for the areas of abnormality were calculated from trace ADC maps. Restricted diffusion was found in all 19 patients. Absolute ADC values in the ischemic area ranged between 395.4 and 575.8 × 10(-6) mm(2)/s, with ADC ratios ranging between 39.4% and 57.4%. Line scan diffusion imaging is technically feasible and appears to be a reliable method to diagnose spinal cord infarction in the acute setting.

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.

Imaging parameters of high grade gliomas in relation to the MGMT promoter methylation status: the CT, diffusion tensor imaging, and perfusion MR imaging

We hypothesized that methyl-guanine methyl transferase (MGMT) promoter methylation status, a predictor of the chemosensitivity for high grade gliomas (HGGs), may be associated with computed tomography (CT)/magnetic resonance (MR) imaging variables. Out of 38 consecutive patients with HGGs, 24 patients whose MGMT promoter methylation status was available [12 men and 12 women; median age, 49years; age range, 22-79years; WHO grade III (n = 7), WHO grade IV (n = 17)] were enrolled retrospectively. CT attenuation, apparent diffusion coefficient (ADC), fractional anisotropy (FA), and relative cerebral blood volume (rCBV) were measured for enhancing tumors. Qualitative imaging features were also analyzed. Mann-Whitney and Fisher's exact tests were used to evaluate relationships between MGMT promoter methylation status and imaging variables. Maximum CT attenuation was significantly lower in the methylated MGMT promoter group than that in the unmethylated MGMT promoter group (30.3 ± 9.5HU versus 39.2 ± 4.7HU, respectively, p = 0.009). While ADC values tended to be higher in the methylated group than in the unmethylated group (p = 0.055), ADC ratio was significantly higher, and the FA and FA ratios were significantly lower in the methylated group than in the unmethylated group (p = 0.032, p = 0.006 and p = 0.007, respectively). In contrast, rCBV ratio did not differ between the two groups (p = 0.380). Regarding imaging features, only ill-defined margin was seen more frequently in the methylated group than in the unmethylated group (45.5% versus 7.7%, respectively, p = 0.048). Preoperative imaging can predict MGMT promoter methylation status, which is of paramount importance for predicting treatment response to chemotherapy with an alkylating agent.

Comparison of imaging features between focal nodular hyperplasia and hepatocellular carcinoma on MR diffusion weighted imaging

Objective To investigate the imaging features of focal nodular hyperplasia and hepatocellular carcinoma on DWI. Methods The data of patients with histopathologically confirmed FNHs and HCCs between August 2008 and November 2010 were collected. A total of 24 patients with 26 FNH lesions and 36 patients with 39 HCC lesions were included in our study. All patients underwent breath-hold DWI with b = 500 s/mm2 and dynamic contrasted-enhanced (DCE) MRI. The imaging findings of FNHs and HCCs were retrospectively analyzed and compared. The signal intensity (SI) of the lesions on DWI were classified as iso-, slightly high, high SI and the distribution of SI between FNHs and HCCs was compared with Fisher exact test. ADC value and lesion-to-liver ADC ratio of FNHs and HCCs were measured and compared by using independent sample t test. ROC was performed to assess the diagnostic value of ADC value and lesion-liver ADC ratio in the characterization FNHs versus HCCs. Results Of 26 FNHs,23 manifested as isointensity or slightly high SI on DWI, but most 25 out of 39 HCCs showed high SI. The distribution of SI between FNHs and HCCs had significant difference ( P = 0. 000). The mean ADC value and lesion-liver ADC ratio for FNHs [ (1.76 ± 0. 62 ) × 10-3 mm2/s and 1.06 ± 0. 18, respectively ] were significantly higher ( P = 0. 001, P = 0. 000, respectively ) than those for HCCs [ ( 1.26 ± 0. 46 ) × 10-3mm2/s and 0. 79 ±0. 12, respectively]. The area (Az) under the ROC for the ADC value and lesionliver ADC ratio for the differentiation of FNHs versus HCCs were 0. 79 ± 0. 05 and 0. 85 ± 0. 05,respectively, with no significant difference (P =0. 270). The specificity of the two measures was 69. 23% and 97.44%, respectively, with significant difference (P = 0. 001 ). Conclusion FNH shows isointensity or slightly high SI with relatively higher ADC value and lesion-liver ADC ratio than those of HCCs on DWI,which is characteristic for its diagnosis and differentiation. Key words: Liver neoplasms; Magnetic resonance imaging; Comparative study

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

PurposeMeningiomas 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 methodsConventional 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. ResultsThe 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±0.12×10−3mm2/s and 1.22±0.07, respectively. ADC values for atypical and malignant groups were both 0.84±0.1×10−3mm2/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. ConclusionDW MR imaging was not found to have any additional value in determining histological behaviour nor in differentiating histopathological subtypes of meningiomas.

Correlation Analysis of Quantitative Diffusion Parameters in Ipsilateral Cerebral Peduncle during Wallerian Degeneration with Motor Function Outcome after Cerebral Ischemic Stroke

To evaluate the time periods of Wallerian degeneration (WD) in which the diffusion parameters of ipsilateral corticalspinal tract (CST) can be used to predict the motor function outcome after brain infarction. This retrospective study classified 48 diffusion tensor imaging patients with WD along CST into four groups based on the following time points after stroke onset, Group 1: within the first 2 weeks; Group 2: from 3 to 4 weeks; Group 3: from 5 to 14 weeks; Group 4: after 14 weeks. The apparent diffusion coefficient (ADC), fractional anisotropy (FA), and their ratios (=ipsilateral diffusion value/contralateral value) of cerebral peduncle were evaluated. The correlation between imaging parameters in each group and the motor function scores appraised at 8 months after stroke onset were assessed. There was no evident correlation of FA ratio (rFA) in Group 1 with motor function score (P = .05). The rFA and FA correlated with motor function score in other groups (P < .001 in each group). The ADC ratio and ipsilateral ADC value only showed significant correlation of with motor function score in Group 4 (P= .016 and .029, respectively). The rFA and ipsilateral FA values after 2 weeks of stroke onset correlate with the motor function outcome.

Correlation of 18F-FDG Uptake with Apparent Diffusion Coefficient Ratio Measured on Standard and High b Value Diffusion MRI in Head and Neck Cancer

Although the clinical applications of (18)F-FDG PET/CT and diffusion-weighted MRI (DWI) are similar to each other in head and neck cancer, the image acquisition methods in the 2 modalities are significantly different. (18)F-FDG PET/CT traces glucose metabolism, a nonspecific process essential for tumor growth. On the other hand, DWI provides information on Brownian motion of water molecules in tissues, which represents cellularity. The aim of our study was to investigate whether apparent diffusion coefficient (ADC) values at b = 1,000 (ADC(1,000)) and 2,000 (ADC(2,000)) s/mm(2) or whether the change (ADC(ratio)) of ADC values from b = 1,000 to 2,000 s/mm(2) has any significant correlation with the standardized uptake value (SUV) in patients with head and neck squamous cell carcinoma (HNSCC). Our hospital's institutional review board approved this retrospective study. We included 47 patients (32 men and 15 women) with histopathologically proven HNSCC, who underwent both DWI (at both b = 1,000 s/mm(2) and b = 2,000 s/mm(2)) and (18)F-FDG PET/CT in the 2 wk before treatment. ADC(ratio) maps were generated using a pixel-by-pixel computation for which ADC(ratio) is (ADC(2,000)/ADC(1,000)) × 100. The mean ADC(1,000), ADC(2,000), and ADC(ratio) values were evaluated within a manually placed polygonal region of interest within the main tumor on every slice of the ADC(1,000), ADC(2,000), and ADC(ratio) maps, respectively. In addition, the maximal SUV (SUV(max)) and mean SUV (SUV(mean)) were measured for the entire tumor region of interest. Comparisons were made using Pearson correlation analysis, and partial correlation coefficients were derived. No significant correlation was found between the mean ADC(1,000) and SUV(mean) (r = -0.222, P = 0.1325) or the mean ADC(2,000) and SUV(mean) (r = -0.1214, P = 0.4163). However, the ADC(ratio) was significantly and positively correlated to both the SUV(mean) (r = 0.667, P < 0.001) and SUV(max) (r = 0.5855, P < 0.001). The ADC(ratio) and SUV were significantly correlated with each other in primary HNSCC patients, possibly because of a higher-cellularity region as a result of relatively increased tumor proliferation. Further studies are warranted to investigate the possible complementary role of DWI and PET/CT in various clinical settings, including staging and treatment response.

SU‐E‐I‐121: MRI Detection of Dominant Intraprostatic Lesions and Correlation with Tumor Microenvironment

Purpose: To determine if MRI is suitable for planning of intratumoral radionuclide therapy of prostatic cancer by correlation of MRI imaging parameters to histologic parameters Methods: All statistical analysis was performed using GraphPad Prism version 5.00 for Windows, GraphPad Software, San Diego California USA, www.graphpad.com. A total of 22 tumors from 10 patients who underwent 3T endorectal MRI and subsequent prostatectomy were investigated retrospectively. Differences in raw T2 signal, T2 signal ratios, apparent diffusion coefficient (ADC), and ADC ratios were tested for significance using one‐way ANOVA for normal tissue, index lesions and secondary lesions as a function of specific pathology parameters (percent stroma, percent glandular area, percent cellularity, glandular area, glandular perimeter, stromal width). Bonferroni multiple comparisons test was performed to test differences in index and secondary tumors as a part of ANOVA analysis. Pearsons correlation was performed for each MRI parameter and pathology parameter based on tissue type as well. Results: Normal tissue MRI parameters were found to be significantly different (p &lt;.05) from index and secondary tumors for all pathologic parameters. Index and secondary lesions showed no significant differences from one another (p&lt;.05). Significant correlations were seen for normal tissue, index and secondary lesions for T2 signal intensity ratios and raw T2 when looking at glandular area and percent luminal space (p &lt;.05, r &gt;.66). Other moderate to strong correlations were seen for ADC and secondary lesions (r &lt; −.58) Conclusions: These results show that MRI has he ability to distinguish between index lesions and secondary lesions as well as informing on the tissue microenvironment. A larger, randomized prospective trial should be performed to further test this hypothesis. MRI will play a central role in successfully planning intratumoral radionuclide therapy of prostatic index lesions in the future.

Diffusion-weighted MRI of focal cystic pancreatic lesions at 3.0-Tesla: preliminary results

To determine the utility of 3.0-Tesla diffusion-weighted (DW) magnetic resonance imaging (MRI) for focal cystic pancreatic lesion (FCPL) characterization. 55 FCPL (34 IPMN, 5 serous cystadenoma, and 16 inflammatory) were evaluated. Two radiologists reviewed in consensus DW-MRI images. Reference standard was obtained from patient history, cytological and histopathology data, FCPL fluid analysis, and follow-up imaging results. Signal intensity (SI) and apparent diffusion coefficient values (ADC) of FCPL and normal pancreas were measured. FCPL-to-pancreas SI and ADC ratios were also calculated. Qualitatively, 11 of 21 non-mucinous vs. 4 of 34 mucinous lesions appeared hyperintense at b value of 1,000 s/mm(2) (P = 0.02). Three FCPL demonstrated restricted diffusion: all inflammatory. Significant differences in mean ADC between neoplastic vs. non-neoplastic (P = 0.009), and mucinous vs. non-mucinous (P = 0.013) lesions were demonstrated. FCPL-to-pancreas ADC and SI ratios demonstrated significant differences between neoplastic vs. non-neoplastic lesions [ADC, (P = 0.019); SI for b values 750 (P = 0.010) and 1,000 s/mm(2) (P = 0.017)] and mucinous vs. non-mucinous lesions [ADC (P = 0.018); SI for b values 750 (P = 0.013) and 1,000 s/mm(2) (P = 0.015)]. Although mean ADC values and FCPL-to-pancreas SI and ADC ratios may be helpful in differentiating FCPL, characterization of individual FCPL by means of 3.0-Tesla DW-MRI appears limited.