The efficacy of apparent diffusion coefficient value calculation in differentiation between malignant and benign thyroid nodules

PurposeTo evaluate the efficacy of apparent diffusion coefficient (ADC) calculation in differentiation between malignant and benign thyroid nodules.Methods and materialsA prospective study was conducted in 52 patients. Diffusion-weighted echoplanar imaging was performed and b factors were taken as 0 and 400 s/mm².ResultsThe mean ADC value for malignant thyroid nodules was 0.829±0.179×10^?3 mm²/s and that for benign thyroid nodules was 1.984±0.482×10^?3 mm²/s. The mean ADC value for malignant nodules was significantly lower than that for benign nodules (P=.0001).ConclusionADC value calculation is an effective method in differentiation of malignant thyroid nodules from benign ones.     

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

ObjectiveThe 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 MethodsForty-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/mm² 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.ResultsThe (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.ConclusionWe 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.     

The added value of apparent diffusion coefficient to cerebral blood volume in the preoperative grading of diffuse gliomas

BACKGROUND AND PURPOSE:In cerebral gliomas, rCBV correlates with tumor grade and histologic findings of vascular proliferation. Moreover, ADC assesses water diffusivity and is inversely correlated with tumor grade. In the present work, we have studied whether combined rCBV and ADC values improve the diagnostic accuracy of MR imaging in the preoperative grading of gliomas.MATERIALS AND METHODS:One hundred sixty-two patients with histopathologically confirmed diffuse gliomas underwent DWI and DSC. Mean rCBV and ADC values were compared among the tumor groups with the Student t test or ANOVA. ROC analysis was used to determine rCBV and ADC threshold values for glioma grading.RESULTS:rCBV had significantly different values between grade II and IV gliomas and between grade III and IV tumors, but there were no significant differences between grade II and III gliomas (P > .05). Grade II and III tumors also did not differ when astrocytomas, oligodendrogliomas, and oligoastrocytomas were considered separately. ADC values were significantly different for all 3 grades. The ADC threshold value of 1.185 × 10⁻³ mm²/s and the rCBV cutoff value of 1.74 could be used with high sensitivity in the characterization of high-grade gliomas. The area under the ROC curve for the maximum rCBV and minimum ADC was 0.72 and 0.75, respectively. The combination of rCBV and ADC values increased the area under the ROC curve to 0.83.CONCLUSIONS:ADC measurements are better than rCBV values for distinguishing the grades of gliomas. The combination of minimum ADC and maximum rCBV improves the diagnostic accuracy of glioma grading.

Gliomas are the most common primary neoplasms of the brain in adults,^1,2 ranging in grade from low to high. Glioma grading is based on the histopathologic assessment of the tumor and is critical for planning therapeutic approaches and assessing prognosis and response to therapy.² Advanced MR imaging techniques such as DSC and DWI provide physiologic information that complements the anatomic information obtained from conventional MR imaging.^3–6 DWI quantifies cellularity on the basis of the premise that water diffusivity within the extracellular compartment is inversely related to the content and attenuation of the intracellular space.⁷ The higher the tumor cellularity and grade are, the lower the ADC is because of decreased water diffusivity.^6–8 However, other factors may be complicating this relationship: ADC increases with increased edema and increased edema is seen in high-grade tumors. DSC provides noninvasive assessment of tumor vascularity and angiogenesis^3–6,9 through the examination of the degradation of signal intensity with time associated with the first pass of a bolus of paramagnetic contrast agent.⁹ Because higher vascularity corresponds to a higher tumor grade, as the grade of the astrocytoma increases, the maximum tumor CBV tends to increase.^3,6,7The aim of this study was to evaluate the diagnostic accuracy of combined ADC and CBV values in the preoperative differentiation of diffuse gliomas. Our objectives were the following: 1) to calculate CBV and ADC values for diffuse gliomas included in the study, 2) to establish whether there is any difference in rCBV and ADC values in gliomas classified by tumor grade and histology, 3) to estimate a cutoff CBV and ADC value for differentiation of high- and low-grade gliomas, and 4) to investigate whether combined CBV and ADC values improve the diagnostic accuracy of MR imaging.     

The value of magnetic resonance imaging in the differentiation between malignant peripheral nerve-sheath tumors and non-neurogenic malignant soft-tissue tumors

Objective To assess the sensitivity and specificity of MRI criteria in the differentiation between malignant peripheral nerve sheath tumors (MPNST) and non-neurogenic malignant soft-tissue tumors (MSTT).Design and patients MRI examinations of 105 patients with pathologically proven malignant soft-tissue lesions (35 MPNST and 70 MSTT) were retrospectively reviewed, the reviewers being unaware of the pathological diagnosis. Using a standardized protocol, the tumors were evaluated for multiple parameters regarding morphology and appearance on different sequences before and after gadolinium contrast administration (location, distribution, delineation, homogeneity, size, shape, relationship to bone and neurovascular bundle, intralesional hemorrhage, necrosis, perilesional edema, lymphangitis and signal intensities). Results were compared using a chi-square or Fisher’s exact test.Results MRI findings suggestive of MPNST (p<0,05) were intermuscular distribution, location on the course of a large nerve, nodular morphology, and overall non-homogeneity on T1-weighted images, T2-weighted images and T1-weighted images after gadolinium contrast injection. MRI findings in favor of MSTT were intramuscular distribution, ill-delineated appearance of more than 20% of the lesion’s circumference, and presence of intralesional blood vessels, perilesional edema and lymphangitis. There is no significant difference for degree and pattern of enhancement after gadolinium contrast injection, nor for presence of bone involvement or cystic or necrotic areas.Conclusion MRI provides several features that contribute to the differentiation between MPNST and non-neurogenic malignant soft-tissue tumors. MRI findings suggestive of MPNST should be helpful to pathologists in the strategy for further examination.     

表观扩散系数值鉴别良恶性骨肿瘤及肿瘤样病变的价值

目的 探讨MR DWI的ADC值鉴别良、恶性骨肿瘤及肿瘤样病变的价值.方法 对18例良性骨肿瘤及肿瘤样病变和26例恶性骨肿瘤行DWI.采用单激发EPI序列,3个扩散敏感梯度,b值分别为0.500、1000 s/nun2.在ADC图上测量每个病变的最低、最高和整体ADC值.结果 良性骨肿瘤及肿瘤样病变的最低ADC值[(1.28±0.49)×10-3mm2/s]高于恶性骨肿瘤[(0.92±0.35)×10-3mm2/s,t=2.839,P<0.01],整体ADC值[(1.62±0.51)×10-3mm2/s]也高于恶性骨肿瘤[(1.21±0.36)×10-3mm2mm/s,t=3.092,P<0.01],但两者都有很大重叠.良性骨肿瘤及肿瘤样病变的最高ADC值[(2.02±0.55)×10-3mm2/s]与恶性骨肿瘤的最高ADC值[(1.71±0.65)×10-3mm2/s]差异无统计学意义(t:1.669,P＞0.05).去掉以囊腔为主的骨囊肿及动脉瘤样骨囊肿病例,则良性骨肿瘤及肿瘤样病变的最低、最高和整体ADC值分别为(1.11±0.31)×10-3mm2/s、(1.88±0.49)×10-3mm2/s和(1.45±0.35)×10-3mm2/s,与恶性骨肿瘤比较差异无统计学意义(t值分别为1.728、0.964、2.012,P值均>0.05).结论 ADC值不能鉴别良、恶性骨肿瘤及肿瘤样病变.     

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.     

Imaging parameter effects in apparent diffusion coefficient determination of magnetic resonance imaging

Purpose

Although an apparent diffusion coefficient (ADC) value is often used for differential diagnosis of tumours, it varies with scanning parameters. The present study was performed to investigate the influence of imaging parameters, i.e., b value, repetition time (TR) and echo time (TE), on ADC value.

Methods

The phantoms were scanned using diffusion weighted imaging (DWI) with changing b values (b = 0-3000 s/mm²), TR and TE to determine the influence on ADC. Moreover, ADC of the brain in normal volunteers was determined with varying b values (b = 0-1000 s/mm²).

Results

Diffusion decay curves were obtained by biexponential fitting in all phantoms. The points where fast and slow components of the biexponential decay crossed were called turning points. The b values of turning points that crossed from the biexponential curve were different in each phantom. The b values of turning points depended on ADC of fast diffusion component. When ADC is calculated using two b values of front and back for the turning point, the ADC value may be different. Therefore, it was necessary to perform calculations by b value until the turning point to obtain the ADC value of the fast component. In addition, b ≥ 100 was recommended to avoid the influence of perfusion by blood. Furthermore, the choice of long TR and short TE was effective for accurate measurement of ADC.

Conclusion

It is important to determine the turning point for measuring ADC.     

磁共振扩散加权成像在眼眶良恶性肿瘤鉴别中的应用

目的 探讨磁共振扩散加权成像(DWI)及表观扩散系数(ADC)在眼眶良恶性肿瘤鉴别诊断中的价值.方法 回顾性分析40例(良性组∶恶性组=25∶15)眼眶肿瘤病例的DWI及ADC图像,分析其DWI及ADC图像信号特点.逐层勾画肿瘤边界以获得整体感兴趣区(ROD,得到肿瘤平均ADC值(ADCM).眼眶良恶性肿瘤的信号特点比较采用Fisher精确检验,2组间ADCM值比较采用独立样本t检验.炎性假瘤及淋巴瘤的ADCM值比较采用Mann-Whitney U检验.采用受试者工作特征曲线(ROC)法分析AIDCM值对眼眶良恶性肿瘤的鉴别诊断价值.结果 眼眶良恶性肿瘤组间DWI图像信号特点无明显统计学差异(P＞0.05),2组ADC图像信号特点有明显统计学差异(P＜0.05).良性肿瘤的ADCM明显高于恶性肿瘤(P＜0.05),其中炎性假瘤的ADCM明显高于淋巴瘤(P＜0.05).以ADC值≥1.289×10-3 mm2/s判断眼眶肿瘤良恶性,可获得最优的诊断价值[曲线下面积(AUC)0.968;敏感度0.960;特异度0.933].结论 磁共振DWI及ADC值在眼眶肿瘤良恶性鉴别中具有重要价值.     

Segmentation and grading of brain tumors on apparent diffusion coefficient images using self-organizing maps.

An accurate computer-assisted method to perform segmentation of brain tumor on apparent diffusion coefficient (ADC) images and evaluate its grade (malignancy state) has been designed using a mixture of unsupervised artificial neural networks (ANN) and hierarchical multiresolution wavelet. Firstly, the ADC images are decomposed by multiresolution wavelets, which are subsequently selectively reconstructed to form wavelet filtered images. These wavelet filtered images along with FLAIR and T2 weighted images have been utilized as the features to unsupervised neural network - self organizing maps (SOM) - to segment the tumor, edema, necrosis, CSF and normal tissue and grade the malignant state of the tumor. A novel segmentation algorithm based on the number of hits experienced by Best Matching Units (BMU) on SOM maps is proposed. The results shows that the SOM performs well in differentiating the tumor, edema, necrosis, CSF and normal tissue pattern vectors on ADC images. Using the trained SOM and proposed segmentation algorithm, we are able to identify high or low grade tumor, edema, necrosis, CSF and normal tissue. The results are validated against manually segmented images and sensitivity and the specificity are observed to be 0.86 and 0.93, respectively.     

Influence of b value on the measurement of contrast and apparent diffusion coefficient in 3.0 Tesla breast magnetic resonance imaging

Diffusion-weighted imaging (DWI) has been used to characterize not only the brain, but also the breast by implementation of faster imaging techniques and higher magnetic field strengths. However, the optimum b value, which is an important scan parameter for DW images contrast on 3 T breast magnetic resonance imaging (MRI) has not been established. The purpose of this study was to investigate the influence of different b value combinations on the image contrast and apparent diffusion coefficient (ADC) in patients with known invasive carcinoma, ductal carcinoma in situ (DCIS), and normal mammary gland in breast DWI. The analysis procedure consisted of the following methods: 1) T(2) correction of DW images with echo-planar imaging (EPI) T(2)-weighted images; 2) contrast measurement between normal mammary gland and tumor tissues; 3) ADC measurement of normal mammary gland and tumor tissues. In many cases, the highest contrast between normal mammary gland and tumor tissues was obtained using a b value of 1500 s/mm(2). Our results indicated that when only one b value is used, the b value in which signal intensities of normal mammary gland decreases down to noise level, and the contrast between normal mammary gland and tumor tissues is recommended. ADC value decreased with increasing b value. Therefore, when determining the ADC threshold level, it is important to perform the evaluation using ADC values calculated from DW images with the same b value in clinical studies.     

Correlation of the apparent diffusion coefficient value and dynamic magnetic resonance imaging findings with prognostic factors in invasive ductal carcinoma

Purpose

To evaluate the correlation of the mean and minimal apparent diffusion coefficient values (ADC_mean, ADC_minimal) and dynamic magnetic resonance imaging (MRI) findings with prognostic factors in invasive ductal carcinoma.

Materials and Methods

A total of 107 women with invasive ductal cancer underwent breast MRI. The ADC_mean and ADC_minimal of the cancers were computed. MRI findings were retrospectively evaluated according to the Breast Imaging Reporting and Data System (BI‐RADS) lexicon: mass or nonmass type, mass shape, mass margin, nonmass distribution, and enhancement pattern. Histological records were reviewed for tumor size, lymph node metastasis, histologic grade, and expression of estrogen receptors (ER), progesterone receptors (PR), c‐erbB‐2(HER2), Ki‐67, and epidermal growth factor receptors (EGFR). Correlations of ADC values and MR findings with prognostic factors were determined using the Mann–Whitney U‐test and the Kruskal–Wallis test.

Results

The mean ADC_minimal was 0.78 ± 0.24 (×10^?3 mm²/s), and the mean ADC_mean was 1.01 ± 0.23 (×10^?3 mm²/s). There was a significant correlation of the ADC_mean value with ER expression (P = 0.027) and HER2 expression (P = 0.018). There was no significant relationship between ADC_minimal and prognostic factors or between ADC_mean and traditional prognostic factors, PR, Ki‐67 and EGFR. The majority of the mass type lesions were less than 5 cm in size and the majority of nonmass type lesions were more than 2 cm in size (P = 0.022). The margin of mass was significantly associated with lymph node metastasis (P = 0.031), ER expression (P = 0.013), PR expression (P = 0.036), HER2 expression (P = 0.019), and EGRF expression (P = 0.041). The rim internal enhancement was significantly correlated with Ki‐67 expression (P = 0.008).

Conclusion

The low ADC_mean value was related to positive expression of ER and negative expression of HER2. A spiculated margin was related to a good prognosis, but rim enhancement was associated with a poor prognosis. J. Magn. Reson. Imaging 2011;33:102–109. © 2010 Wiley‐Liss, Inc.

     

磁共振扩散加权成像在直肠肿瘤性病变诊断中的价值

目的：通过对不同类型直肠肿瘤病例DWI图像分析和ADC值的测量探讨扩散加权成像对直肠肿瘤性病变的诊断价值。方法比较8例直肠腺瘤,30例中分化腺癌,6例低分化腺癌,7例黏液腺癌,6例淋巴瘤及5例间质瘤的ADC值的差异。结果①直肠淋巴瘤的ADC值明显低于直肠癌、直肠腺瘤,差异有统计学意义（ P＜0．05）,淋巴瘤与间质瘤之间差异无统计学意义（ P ＞0．05）;②直肠腺瘤ADC值低于粘液腺癌（ P ＜0．05）,与间质瘤、腺癌之间差异无统计学意义（ P＞0．05）;③间质瘤 ADC值低于粘液腺癌（ P ＜0．05）,与淋巴瘤、腺癌、腺瘤之间差异无统计学意义（ P ＞0.05）;④粘液腺癌ADC值高于中分化腺癌（ P ＜0．05）,与低分化腺癌之间差异无统计学意义（ P ＞0．05）,中分化、低分化腺癌之间差异无统计学意义（ P ＞0．05）。结论扩散加权成像对不同类型直肠肿瘤、不同类别的直肠腺癌具有一定的鉴别诊断价值,联合MR常规扫描可提高诊断效能。     

Combination of high-resolution susceptibility-weighted imaging and the apparent diffusion coefficient: added value to brain tumour imaging and clinical feasibility of non-contrast MRI at 3 T

The purpose of this study was to determine the benefit of high-resolution susceptibility-weighted imaging and the apparent diffusion coefficient for brain tumour imaging, and to assess the clinical feasibility of using a non-contrast MR protocol at 3 T. 73 patients with intra-axial tumours were enrolled into the study. Two experienced neuroradiologists reviewed three MRI sessions: (i) a non-contrast protocol including high-resolution susceptibility-weighted images and apparent diffusion coefficient; (ii) a contrast protocol including MR perfusion images; and (iii) combined contrast and non-contrast protocols. The two observers categorised tumours as glial or non-glial tumours, and then subcategorised the gliomas into low-grade or high-grade tumours. For semi-quantitative analysis, a scoring system based on the degree of intra-tumoral susceptibility signals and the visual apparent diffusion coefficient was used. The two observers diagnosed accurate tumour pathology in 52 (71%) of 73 tumours in the first review, 55 (75%) of 73 tumours in the second review and 61 (84%) of 73 tumours in the third review. The addition of the non-contrast protocol to the contrast protocol significantly differentiated glioblastoma multiforme and metastatic tumours, which was not possible with the contrast protocol alone. The sensitivity, specificity, positive predictive value and negative predictive value for glioma grading with the non-contrast protocol were 83.2%, 100%, 100% and 79.3%, respectively. The addition of both high-resolution susceptibility-weighted imaging and the apparent diffusion coefficient improved the diagnostic performance of the contrast MR protocol for brain tumour imaging and could be feasible in selected patients who cannot tolerate a contrast agent.Contrast-enhanced (CE) conventional MRI, which is commonly used in the evaluation of brain tumours, is usually included as part of the routine brain tumour imaging protocol in most institutions. Although conventional MRI with gadolinium-based contrast agents is useful for the detection and structural characterisation of brain tumours, enhancement after gadolinium reflects disruption of the blood–brain barrier rather than a true assessment of tumour vascularity [1, 2]. Recently, a number of advanced MRI techniques, such as MR perfusion, have been developed to provide biological and physiological information for the assessment of brain tumours [3, 4]. Dynamic susceptibility contrast (DSC) MR perfusion imaging has provided physiological information that allows the evaluation of neovascularity and angiogenesis in brain tumours [5, 6].High-resolution susceptibility-weighted MR imaging (HR-SWI) is a three-dimensional gradient-echo technique that is sensitive to local tissue magnetic susceptibility and is blood oxygen level dependent [7–9]. This new imaging technique has largely been used for the detection of microvenous structures, as well as for the detection of extravascular blood products [10, 11]. The development of 3 T MR scanners and parallel imaging techniques has enabled an increase in the speed, coverage and signal-to-noise ratio of MR images. Therefore, this new technique could be suitable for the examination of patients with various brain disorders in order to obtain high spatial resolution with a reasonable acquisition time.As has been demonstrated in previous reports, HR-SWI has the potential to assess non-invasively the intratumoral microvascularity associated with fast-growing tumours [12, 13]. Diffusion-weighted imaging (DWI) provides information about tumour cellularity and structural integrity by measuring differences in the apparent diffusion coefficient (ADC) [14, 15]. HR-SWI and DWI do not require contrast administration. Although gadolinium-based contrast agents are widely used in the clinical setting for the assessment of brain tumours, HR-SWI and DWI can be integrated easily into a conventional MR examination at any time, as long as no contrast agent is administered. A non-contrast MR protocol can also be applied to patients in whom are contrast agents contraindicated or who cannot tolerate a bolus injection of contrast medium.The purpose of this study was to determine the benefit of HR-SWI and the ADC for brain tumour imaging protocols, including MR perfusion imaging, and to assess the clinical feasibility of the use of non-contrast MR protocols, including HR-SWI and the ADC, at 3 T.     

扩散系数值在脑星形细胞肿瘤病理学分级中的应用

目的探讨扩散系数值对脑星形细胞肿瘤病理学分级的应用价值。方法对56例脑星形细胞肿瘤进行扩散加权成像（DWI）检查，分别测量肿瘤实质部分、瘤周水肿区、瘤周T1WI正常表现白质区（瘤周白质区）、瘤体镜面对侧正常白质区及瘤周镜面对侧正常白质区的表观扩散系数（ADC）值和指数扩散系数（EDC）值，并计算肿瘤实质部分、瘤周水肿区、瘤周白质区的相对表观扩散系数（rADC）值和相对指数扩散系数（rEDC）值。分析各测量区的扩散系数值与肿瘤病理学分级的关系。结果56例脑星形细胞肿瘤经手术病理证实，低级星形细胞瘤35例（Ⅰ、Ⅱ级），间变性星形细胞瘤8例（Ⅲ级），胶质母细胞瘤13例（Ⅳ级）。低级星形细胞瘤、间变性星形细胞瘤和胶质母细胞瘤肿瘤实质部分的ADC值分别为（1．44±0．26）×10^-3、（0．98±0．22）×10^-3和（0．83±0．15）×10^-3mm^2／s，rADC值分别为（1．91±0．39）％、（1．34±0．33）％和（1．06±0．20）％，EDC值分别为0．26±0．11、0．39±0．09和0．44±0．07，rEDC值分别为（0．55±0．20）％、（0．81±0．19）％和（0．98±0．16）％，各指标间差异均有统计学意义（F值分别为36．189、31．756、19．623和24．760，P值均为0．000）。高级星形细胞瘤（间变性星形细胞瘤和胶质母细胞瘤）的肿瘤实质部分的ADC值和rADC值分别为（0．89±0．19）×10^-3mm^2／s和（1．17±0．28）％，明显低于低级星形细胞瘤（t值分别为8．332和7．620，P值均为0．000），EDC值和rEDC值分别为0．42±0．08和（0．91±0．18）％，明显高于低级星形细胞瘤（t值分别为-6．082和-6．776，P值均为0．000）。以低级星形细胞瘤实质部分的rADC值的下限（1．52％）作为判断低、高级别星形细胞瘤阈值的准确性为89．3％。结论肿瘤实质部分的扩散系数值对脑星形细胞肿瘤的病理学分级准确性较高，尤以rADC值为佳。     

MR扩散加权成像鉴别良恶性骨肿瘤及肿瘤样病变的价值

目的 探讨磁共振扩散加权成像 (DWI)鉴别良、恶性骨肿瘤及肿瘤样病变的价值.方法 选择临床资料完整骨肿瘤及肿瘤样病变患者61例,DWI选用5个不同的弥散敏感系数(b值),分别为0、400、800、1 000、1 500 s/mm2,并得到相应的表观弥散系数(ADC)图,选择感兴趣区计算ADC值,同时选取邻近正常肌肉、骨髓的ADC值作为参照.统计学分析结果以P＜0.05表示差异有统计学意义.结果 (1)良恶性骨肿瘤之间的DWI信号差异无显著性.(2)取b值分别为400、800、1 000 s/mm2和1 500 s/mm2时肿瘤病变实质区ADC值,良性骨肿瘤及肿瘤样病变实质区均高于恶性骨肿瘤实质区,而恶性骨肿瘤实质区又远远大于正常骨髓的ADC值;且良恶性骨肿瘤及肿瘤样病变实质区与正常相邻骨髓的ADC值与b值呈负相关,即随着b值的增高,ADC值降低.结论 磁共振扩散加权成像ADC值有助于鉴别骨肿瘤良恶性病变.     

Preoperative grading of presumptive low-grade astrocytomas on MR imaging: diagnostic value of minimum apparent diffusion coefficient

BACKGROUND AND PURPOSE: Histopathologic grade of glial tumors is inversely correlated with the minimum apparent diffusion coefficient (ADC). We assessed the diagnostic values of minimum ADC for preoperative grading of supratentorial astrocytomas that were diagnosed as low-grade astrocytomas on conventional MR imaging.MATERIALS AND METHODS: Among 118 patients with astrocytomas (WHO grades II–IV), 16 who showed typical MR imaging findings of low-grade supratentorial astrocytomas on conventional MR imaging were included. All 16 patients underwent preoperative MR imaging and diffusion-weighted imaging. The minimum ADC value of each tumor was determined from several regions of interest in the tumor on ADC maps. To assess the relationship between the minimum ADC and tumor grade, we performed the Mann-Whitney U test. A receiver operating characteristic (ROC) analysis was used to determine the cutoff value of the minimum ADC that had the best combination of sensitivity and specificity for distinguishing low- and high-grade astrocytomas.RESULTS: Eight of the 16 patients (50%) were confirmed as having high-grade astrocytomas (WHO grades III and IV), and the other 8 patients were confirmed as having low-grade astrocytomas (WHO grade II). The median minimum ADC of the high-grade astrocytoma (1.035 × 10⁻³ mm² · sec⁻¹) group was significantly lower than that of the low-grade astrocytoma group (1.19 × 10⁻³ mm² · sec⁻¹) (P = .021). According to the ROC analysis, the cutoff value of 1.055 × 10⁻³ mm² · sec⁻¹ for the minimum ADC generated the best combination of sensitivity (87.5%) and specificity (79%) (P = .021).CONCLUSION: Measuring minimum ADC can provide valuable diagnostic information for the preoperative grading of presumptive low-grade supratentorial astrocytomas.

Despite aggressive treatments, overall prognosis of high-grade astrocytomas, especially glioblastomas, is still poor, mainly due to their infiltrative nature and high relapse rate compared with those of low-grade astrocytomas.^1–4 Accurate preoperative grading of a brain tumor is thus pivotal in choosing the treatment strategy and in the assessment of prognosis.On conventional MR imaging, malignant gliomas usually show strong contrast enhancement, peritumoral edema, mass effects, heterogeneity, central necrosis, and intratumoral hemorrhage. The typical MR imaging features of low-grade astrocytomas include a relatively well-defined usually homogeneous mass that displays little or no mass effect, with minimal or no vasogenic edema and little or no enhancement after contrast administration.^5–7 Nevertheless, it is not always easy to differentiate low-grade astrocytomas from high-grade ones on the basis of conventional MR imaging findings. It has been reported that high-grade and low-grade astrocytomas can have overlapping features on MR imaging.^2,8–12 Recently, it was shown that the histopathologic grade of glial tumors is inversely correlated with the minimum apparent diffusion coefficient (ADC).^1,3,9,13,14 Thus, we hypothesized that a high-grade astrocytoma may demonstrate a lower minimum ADC value even though it shows the typical MR imaging features of low-grade gliomas.The purpose of this study was to evaluate the diagnostic value of the minimum ADC for preoperative histopathologic grading in supratentorial astrocytomas that showed typical features of low-grade astrocytomas on conventional MR imaging.     

The diagnostic efficacy of apparent diffusion coefficient value and Choline/Creatine ratio in differentiation between parotid gland tumors

Objective

To detect the diagnostic performance of apparent diffusion coefficient (ADC) value and Cho/Cr ratio in distinguishing various pathological subtypes of parotid gland tumors.