Transudative vs exudative pleural effusions: differentiation using Gd-DTPA-enhanced MRI

The aim of this study was to investigate the capability of Gd-DTPA-enhanced MRI to differentiate between exudative and transudative pleural effusions. An MRI examination was performed on 22 patients with different types of pleural effusion (10 transudative and 12 exudative effusions). T1-weighted SE images were obtained before and 20 min after administration of Gd-DTPA (0.1 mmol/kg). The degree of enhancement of pleural effusions was evaluated both by visual assessement and by quantitative analysis of images. None of 10 transudative effusions showed significative enhancement, whereas 10 of 12 exudative effusions showed enhancement (sensitivity 83 %, specificity 100 %, positive predictive value 100 %). The postcontrast signal intensity ratios (SIRs) of exudates were significantly higher than corresponding precontrast ratios (P = 0.0109) and the postcontrast SIRs of exudates were significantly higher than those of transudates (P = 0.0300). Exudative pleural effusions show a significant enhancement following administration of Gd-DTPA. We presume that this may be caused by increased pleural permeability and more rapid passage of a large amount of Gd-DTPA from the blood into the pleural fluid in case of exudative effusions. In our limited group of patients, signal enhancement proved the presence of an exudative effusion. Absence of signal enhancement suggests a transudate, but does not exclude an exudate. Received 9 April 1996; Revision received 12 August 1996; Accepted 4 October 1996     

Diffusion-weighted MR imaging of kidneys in renal artery stenosis

OBJECTIVE: The purpose of our study was to evaluate perfusion and diffusion of kidneys in renal artery stenosis (RAS) and any correlation between stenosis and ADC values and whether this imaging modality may be a noninvasive complementary assessment technique to MR angiography before interventional procedures. MATERIALS AND METHODS: Twenty consecutive patients suspected of having renal artery stenosis were evaluated with renal MR angiography to exclude stenosis and were then included in the study. Transverse DW multisection echo-planar MR imaging was performed. In the transverse ADC map, rectangular regions of interest were placed in the cortex on 3 parts (upper, middle, and lower poles) in each kidney. ADCs of the kidneys were calculated separately for the low, average, and high b-values to enable differentiation of the relative influence of the perfusion fraction and true diffusion. The ADC values of 39 kidneys (13 with renal artery stenosis and 26 normal renal arteries) were compared, and the relationship between stenosis degree and ADC values was calculated. RESULTS: RAS was detected in 11 of 20 (55%) patients with MRA. Thirteen of 39 kidneys demonstrated RAS, and 26 were normal. The ADClow (1.9+/-0.2 versus 2.1+/-0.2; P=.020), ADCaverage (1.7+/-0.2 versus 1.9+/-0.1; P=.006), and ADChigh (1.8+/-0.2 versus 2.0+/-0.1; P=.012) values were significantly lower in patients with kidneys with arterial stenosis than that in patients with kidneys with normal arteries. Statistical analysis revealed that stenosis degree correlated strongly with ADClow (r=-.819; P=.001), ADCaverage (r=-.754; P=.003), and ADChigh (r=-.788; P=.001). The ADClow, ADCaverage, and ADChigh values were significantly lower in patients with kidneys with arterial stenosis than that in patients with kidneys with normal arteries. CONCLUSION: We think that DW MR imaging of kidneys with RAS can help determine the functional status of a renal artery stenosis.     

MR imaging of pleural effusions

To investigate the in vivo magnetic resonance (MR) characteristics of pleural effusions, MR imaging was performed on 22 patients who also underwent thoracentesis. Correlation of the MR scans with results of thoracentesis revealed significant differences among three types of effusions: transudates (T) (n = 4), simple exudates (SE) (n = 9), which did not have malignant cells or infection, and complex exudates (CE) (n = 9), which did have malignant cells or infection. Using normalized MR intensities, CE were more intense than SE, which were brighter than T. The second and third echoes (TE 66 and 99 ms) provided the best differentiation for these three classes of effusions, with p less than 0.06 and p less than 0.006, respectively. Qualitative visual assessment of the increase in signal intensity was also useful in differentiating among the three types of effusions (p less than 0.02). Effective T2 values (normalized to fat) were significantly shorter for exudates than for T (p less than 0.02). Heterogeneity, loculation, and size of effusions were well evaluated on MR. Magnetic resonance is not specific for the etiology of effusions. Nevertheless, with analysis of both quantitative and qualitative parameters, MR may provide an effective noninvasive means for the initial characterization and serial follow-up of pleural effusions.     

Diffusion-weighted echo-planar MR imaging in differential diagnosis of brain tumors and tumor-like conditions

We assess diffusion-weighted MR images in the differential diagnosis of intracranial brain tumors and tumor-like conditions. Heavily diffusion-weighted (b = 1100 or 1200 s/mm²) axial images were obtained with single-shot echo-planar technique in 93 patients with pathologically confirmed various intracranial tumors and tumor-like conditions with diffusion gradient perpendicular to the images. We compared signal intensity of the lesions with those of gray and white matter, and cerebrospinal fluid (CSF). In 29 cases (31.1 %) the lesions were isointense to gray and/or white matter. However, 5 cases (5.4 %) showed extremely increased signal intensity: two epidermoid cysts; two chordomas; and one brain abscess. The entire portion of a tumor was markedly hyperintense in 10 cases (10.8 %): four malignant lymphomas; four medulloblastomas; one germinoma; and one pineoblastoma. A CSF-like hypointense signal was seen in many cystic tumors, and cystic or necrotic portions of tumors. A neurosarcoid granulation was the only solid lesion showing characteristically a hypointense signal like CSF. The combination of markedly hyperintense and hypointense signals was seen generally in hemorrhagic tumors. Diffusion-weighted echo-planar MR imaging is useful in the differential diagnosis of brain tumors and tumor-like conditions, and suggests specific histological diagnosis in some cases. Received: 30 July 1999; Revised: 2 November 1999; Accepted: 9 December 1999     

1.5T磁共振1H-MRS鉴别良恶性胸腔积液的初步研究

目的：探讨磁共振波谱对良、恶性胸腔积液的鉴别诊断价值。方法收集行胸腔穿刺抽液的胸腔积液标本46例,其中原发病确诊为良性者20例（包括肺结核14例、肺炎6例）,原发病确诊为恶性者26例（包括原发性肺癌18例、乳腺癌5例、肝癌2例、胃癌1例）。对胸腔积液标本进行离心处理,然后利用1.5T磁共振对胸腔积液标本进行波谱采集,分析良恶性胸腔积液的波谱特征。结果胸腔积液的波谱图中主要的代谢峰有乳酸、胆碱、肌酸、肌醇及脂质等。主要代谢物波峰下面积比较：乳酸：结核性（5.19±1.31）、炎性（6.08±1.56）和恶性胸腔积液（2.40±0.43）的乳酸峰下面积差异有统计学意义（F=8.45,P<0.01）;胆碱：结核性（2.75±0.91）、炎性（3.27±1.21）和恶性胸腔积液（6.76±1.73）的胆碱峰下面积差异有统计学意义（F=2.98,P<0.01）;肌醇：结核性（2.71±1.19）、炎性（2.25±0.81）和恶性胸腔积液（5.83±2.08）的肌醇峰下面积差异有统计学意义（F=38.49,P<0.01）。结核性和炎性胸腔积液中乳酸（t=-1.04,P＞0.05）、胆碱（t=-0.58,P＞0.05）和肌醇（t=1.19,P＞0.05）波峰下面积差异无统计学意义。结论良、恶性胸腔积液具有不同的波谱特征,利用磁共振波谱对良、恶性胸腔积液进行鉴别具有一定的临床应用价值。     

Diffusion-weighted MR imaging in leukodystrophies

Leukodystrophies are genetically determined metabolic diseases, in which the underlying biochemical abnormality interferes with the normal build-up and/or maintenance of myelin, which leads to hypo- (or arrested) myelination, or dysmyelination with resultant demyelination. Although conventional magnetic resonance imaging has significantly contributed to recent progress in the diagnostic work-up of these diseases, diffusion-weighted imaging has the potential to further improve our understanding of underlying pathological processes and their dynamics through the assessment of normal and abnormal diffusion properties of cerebral white matter. Evaluation of conventional diffusion-weighted and ADC map images allows the detection of major diffusion abnormalities and the identification of various edema types, of which the so-called myelin edema is particularly relevant to leukodystrophies. Depending on the nature of histopathological changes, stage and progression gradient of diseases, various diffusion-weighted imaging patterns may be seen in leukodystrophies. Absent or low-grade myelin edema is found in mucopolysaccharidoses, GM gangliosidoses, Zellweger disease, adrenomyeloneuropathy, L-2-hydroxyglutaric aciduria, non-ketotic hyperglycinemia, classical phenylketonuria, Van der Knaap disease and the vanishing white matter, medium grade myelin edema in metachromatic leukodystrophy, X-linked adrenoleukodystrophy and HMG coenzyme lyase deficiency and high grade edema in Krabbe disease, Canavan disease, hyperhomocystinemias, maple syrup urine disease and leukodystrophy with brainstem and spinal cord involvement and high lactate.     

Transcatheter intracavitary fibrinolysis of loculated pleural effusions: Experience in 102 patients

PURPOSE: To assess the efficacy of intrapleural urokinase instillation through small-caliber catheters for the treatment of loculate and/or septate effusions. METHODS: We inserted small-caliber catheters (8.2 Fr) in 102 patients with septate and/or loculate pleural effusions using ultrasonographic guidance. Urokinase (100,000 IU/2 hr, 3 times a day) was instilled through the catheter until the effusion resolved and D-dimer levels were <500 ng/ml. Patients were enrolled regardless of the etiology of the pleural effusion provided there were no contraindications for the use of urokinase. D-dimer levels were determined before and after treatment. Follow-up was performed by chest radiograph and sonography at 1 day, 7 days, and every 30 days thereafter for 6 months. RESULTS: Successful catheter placement was achieved in all cases. The mean time catheters stayed in place was 5.7 days and the mean dose of drug instilled was 690,000 IU. Pleural effusion drainage was complete at the first assessment in all patients. Failure of the treatment, with recurrent effusion at 30 days, occurred in six patients (5.8%). Complete resolution without sequelae was observed in 19 patients (19.6%). In 75 cases (73.5%) resolution was partial, with pleural thickening (>2 mm). Two patients died from unrelated causes within 30 days after catheter placement. Complications were seen in 13 patients (12.74%): hydropneumothorax, nine cases (8.82%); infection of the puncture point, three cases (2.94%); and adverse reaction, one case (0.98%). No further treatment was required. CONCLUSION: The use of intrapleural fibrinolytic agents delivered through small-caliber catheters for the treatment of loculate and/or septate pleural effusion is a simple, effective, minimally invasive and inexpensive procedure that can prevent sequelae and shorten drainage time.     

Diffusion-weighted imaging and proton MR spectroscopy in the characterization of acute disseminated encephalomyelitis

Introduction Acute disseminated encephalomyelitis (ADEM) is usually a monophasic illness characterized by multiple lesions involving gray and white matter. Quantitative MR techniques were used to characterize and stage these lesions. Methods Eight patients (seven males and one female; mean age 19 years, range 5 to 36 years) were studied using conventional MRI (T2- and T1-weighted and FLAIR sequences), diffusion-weighted imaging (DWI) and proton magnetic resonance spectroscopy (MRS). Apparent diffusion coefficient (ADC) values and MRS ratios were calculated for the lesion and for normal-appearing white matter (NAWM). Three patients were imaged in the acute stage (within 7 days of the onset of neurological symptoms) and five in the subacute stage (after 7 days from the onset of symptoms). Results ADC values in NAWM were in the range 0.7–1.24×10⁻³ mm/s² (mean 0.937 ± 0.17 mm/s²). ADC values of ADEM lesions in the acute stage were in the range 0.37–0.68×10⁻³ mm/s² (mean 0.56 ± 0.16 mm/s²) and 1.01–1.31×10⁻³ mm/s² (mean 1.24 ± 0.13 mm/s²) in the subacute stage. MRS ratios were obtained for all patients. NAA/Cho ratios were in the range 1.1–3.5 (mean 1.93 ± 0.86) in the NAWM. NAA/Cho ratios within ADEM lesions in the acute stage were in the range 0.63–1.48 (mean 1.18 ± 0.48) and 0.29–0.84 (mean 0.49 ± 0.22) in the subacute stage. The ADC values, NAA/Cho and Cho/Cr ratios were significantly different between lesions in the acute and subacute stages (P < 0.001, P < 0.027, P < 0.047, respectively). ADC values were significantly different between lesions in the acute (P < 0.009) and subacute stages (P < 0.005) with NAWM. In addition, NAA/Cho and Cho/Cr ratios were significantly different between lesions in the subacute stage and NAWM (P < 0.006, P < 0.007, respectively). Conclusion ADEM lesions were characterized in the acute stage by restricted diffusion and in the subacute stage by free diffusion and a decrease in NAA/Cho ratios. Restricted diffusion and progressive decrease in NAA/Cho ratios may help in staging the disease.     

CT评价胸腔积液量准确性的实验研究

目的评价CT测算胸腔积液量的准确性。方法采用GE—sytec 4000i全身CT扫描系统，对注水肺脏模型进行扫描。选取右侧肺脏共作15次测量。由一名熟练的CT操作人员在积液最明显的一层上用轨迹手工圈划出积液的完整轮廓，预设感兴趣区的CT值上下限范围0-20 HU，采用计算机体积测算功能，计算出各层满足上述要求的感兴趣区图像总体积。结果肺脏模型体积CT测值与实际注水量的散点图呈直线趋势，R^2=1.000。回归系数t检验的t值=681、077，P=0．0001（P〈0.001），可认为肺脏模型体积CT测值与实际注水量之间有直线关系；直线回归方程为：Y=-0．238＋0．999X。肺脏模型体积的标准差为893．27504，实际注水量的标准差为894．42719。肺脏模型体积CT测值与实际注水量的相关分析表明，肺脏模型体积CT测值与实际注水量高度相关（P〈0．001）。结论CT能够准确测量胸腔积液量，它有可能替代传统X线的粗略估算。     

HRCT在检出恶性胸腔积液中胸膜病变的价值

目的 探讨HRCT检出恶性胸腔积液中胸膜病变的价值.方法 回顾分析恶性胸腔积液合并胸膜病变患者40例,复习恶性胸腔积液中胸膜病变的HRCT影像学表现.结果 本组40例患者CT平扫显示胸腔大量积液者12例,中等量或少量积液者28例.CT增强扫描,胸膜病变明显强化,主要表现为结节状强化.结论 HRCT主要用于肺部弥漫性病变的检出,通过本组病例发现HRCT对于检出恶性胸腔积液中的胸膜病变亦有较高价值.     

Diffusion-weighted MR imaging of pyogenic intraventricular empyema

Introduction Pyogenic intraventricular empyema (PIE) is a potentially fatal CNS infection. However, it is sometimes difficult to diagnose PIE on the basis of clinical and conventional MRI findings. Diffusion-weighted imaging (DWI) has been accepted as a useful MR sequence for the diagnosis of various intracranial infections. The purpose of this study was to determine the DWI characteristics of PIE and the role of DWI in the diagnosis of PIE. Methods Eight patients with PIE underwent MRI including DWI. We assessed the presence and signal characteristics of PIE. In seven patients, the signal intensities of the PIE and cerebrospinal fluid (CSF) were measured and the contrast-to-noise ratio (CNR) percentage was calculated. ADC values of the PIE, CSF, and white matter were also determined. Results PIE was detected in all patients by DWI, in five (63%) by FLAIR imaging, and in two (25%) by T1- and T2-weighted imaging. The CNR percentages of the PIEs in relation to the CSF were highest for DWI, followed by FLAIR, T1-, and T2-weighted imaging. There were statistically significant differences between the images of each sequence. In all patients, PIE showed hyperintensities on DWI and hypointensities to the CSF and hypo- or isointensities to the white matter on ADC maps. The ADC values (mean±SD) of the PIE, CSF, and white matter were 0.60±0.27, 2.81±0.04, and 0.79±0.08 (×10⁻³ mm²/s). There was a statistically significant difference between PIE and the CSF. Conclusion PIE shows a bright intensity on DWI, and DWI is a sensitive MR sequence for the diagnosis of PIE.     

CT能谱成像在胸腔渗出液与漏出液定性鉴别中的作用

目的 探讨CT能谱成像定量分析鉴别胸腔积液性质的价值.方法 将20例胸腔积液患者经胸腔穿刺术抽出的胸腔积液放在试管中进行能谱CT扫描,同时抽出的胸腔积液做胸水常规和生化检查.根据实验室检查结果,分为渗出液和漏出液.应用能谱分析软件,分析两组数据的常规混合能量140 kVp图像的CT值差异,以及两组数据的不同keV水平(40～140 keV)的CT值、能谱曲线斜率、有效原子序数、碘-水浓度、钙-水浓度、钙-脂肪浓度等CT能谱成像的定量参数间的差异.对渗出液和漏出液的CT能谱特征参数进行独立样本t检验.结果 根据实验室检查结果,20例中11例渗出液、9例漏出液.渗出液组的常规混合能量140 kVp的图像CT值[(19.56±4.10)HU]高于漏出液组[(13.44±3.46)HU],差异有统计学意义(t=3.002,P=0.010).keV能量越低,其CT值差别越大.在40keV,其CT值差异最大,分别是(47.49±14.60)、(19.76±6.85)HU,差异有统计学意义(t=5.520,P=0.000),渗出液明显高于漏出液;而在140 keV,其CT值差异无统计学意义,平均值分别是(9.76±4.16)和(6.22±3.17)HU(t=2.107,P=0.050).渗出液能谱曲线斜率(0.51±0.23)明显大于漏出液(0.18±0.08),差异有统计学意义(t=4.287,P=0.001).渗出液的有效原子序数、碘(水)浓度、钙(水)浓度、钙(脂肪)浓度明显高于漏出液组,两组的值分别为7.89±0.16和7.67±0.07、(5.74±1.28)和(1.70±0.95)g/L、(7.89±1.78)和(2.53±1.37)g/L、(25.95±1.74)和(20.82±1.40)g/L,差异均有统计学意义(t值分别为4.080、6.998、6.546、6.301,P值均＜0.05).结论 渗出液与漏出液具有不同的能谱曲线和能谱特征物质含量,低能量keV图像在渗出液的鉴别中起重要作用,能谱CT为鉴别胸腔积液的性质提供了一种多参数的方法.     

Non-traumatic thoracic emergencies: imaging and treatment of thoracic fluid collections (including pneumothorax)

Cross-sectional imaging has revolutionised the radiological diagnosis of pleural collections. Not only can the precise location and volume of a pleural effusion be established, but also features specific for the aetiology of the effusion can be demonstrated. Increasingly, radiologists are called upon to perform image-guided biopsies, aspirations and small bore chest drain placement, all of which have been shown to be safe and efficacious. Pneumothoraces occurring due to acute trauma and in an intensive care setting can also benefit from radiological input, both in terms of diagnosis and image-guided treatment.     

Diffusion-weighted MR imaging and ADC measurement in normal prostate,benign prostatic hyperplasia and prostate carcinoma

Purpose

Our aim was to investigate the diffusion-weighted Imaging (DWI) appearance and apparent diffusion coefficient (ADC) values of normal prostatic gland, prostate carcinoma (PCa) and benign prostate hyperplasia (BPH) and to determine the utility of DWI in their characterization.

Materials and methods

During a period of 16 months, 40 consecutive patients, with elevated PSA level and 12 healthy volunteers with no clinical symptoms or history of prostate disease were prospectively evaluated with DWI of the prostate. MRI was performed using a 1.5T MR scanner equipped with a pelvic phased array coil. For anatomical imaging, T2W FSE in the three orthogonal planes, and T1WI in axial plane were obtained. DWI with b values of 0, 300, 500 and 800 s/mm² were performed in axial plane. The results were confirmed by TRUS-guided biopsy or prostatectomy.

Results

Patients ranged in age from 45 to 85 years (mean 66.6 ± 7.9 year). Twenty patients were confirmed to have BPH, whereas 20 patients had PCa. The mean and SD of ADC values for the peripheral zone (PZ), central gland (CG), BPH nodules and PCa were 1.839 ± 0.233, 1.469 ± 0.239, 1.359 ± 0.201 and 0.87 ± 0.13 respectively. The mean ADC value of PCa was significantly lower than that of CG, PZ, and BPH nodule, with p value <0.05.

Conclusion

DW MR imaging characteristics and ADC values can differentiate PCa and BPH. DWI with ADC may be used as a complementary method to conventional MRI in diagnosis of PCa and BPH.     

Diffusion-weighted imaging findings of adnexal torsion: Initial results

Our purpose is to clarify the diffusion-weighted (DW) imaging findings of adnexal torsion. We retrospectively analyzed the DW imaging findings in 11 consecutive patients with surgical confirmation of adnexal torsion. We assessed signal intensity of the adnexal mass and fallopian tube thickening, and the location of abnormal signal intensity within the adnexal mass. On DW imaging, thickening of the fallopian tube was apparent as abnormal signal intensity in 8 of 11 patients. Abnormal signal intensity was inhomogeneous in 7 of 8 patients. Abnormal signal intensity on DW imaging was observed in 10 of 11 adnexal masses, and in the walls of 7 out of 8 adnexal cystic lesions. In adnexal torsion, DW imaging showed abnormal signal intensity in the thickened fallopian tube and in the wall of cystic ovarian lesions. These findings would be feasible to diagnose adnexal torsion.     

Diffusion-weighted MR imaging of the breast: Advantages and pitfalls

The aim of this paper is to review all clinical applications of diffusion weighted MR imaging (DWI) for breast pathology. The challenge of DWI is to obtain the best compromise between lesion detection and characterization. Technical factors affecting lesion characterization and detection are detailed including the effect of contrast administration, the choice of number of b and of b_max, the variation of diagnostic performance according to the type and the size of lesion studied.     

Sonography of malignant pleural effusion

Two hundred and ten patients with exudative pleural effusion were studied by ultrasound for sonographic signs of pleural carcinomatosis. Images were evaluated for echoes within the fluid, septations, sheet-like or nodular pleural masses, and associated lesions of the lung. Our results showed that sonographic findings of echogenic or septated fluid were unspecific for malignancy. Only the evidence of pleural masses was characteristic of malignant effusion. Ultrasound of the chest should therefore be carried out before invasive diagnostic procedures are planned. Received 31 May 1995; Revision received 12 September 1996; Accepted 14 January 1997     

MR扩散加权成像在肾功能评价中的应用

目的探讨MR扩散加权成像在肾功能评价中的价值。方法健康志愿者15例作为对照组,慢性肾病(chron ic k idney d isease,CKD)患者32例(其中肌酐正常组12例,肌酐升高组20例)作为研究组。分别测量各例的表观扩散系数(apparent d iffusion coeffic ient,ADC)并与血清肌酐水平及肌酐清除率对比分析。结果15例志愿者在扩散敏感梯度系数(b值)取50、100、400 s/mm2时平均ADC值分别为(405.366±35.964)×10-5mm2/s、(339.646±23.059)×10-5mm2/s、(254.532±13.676)×10-5mm2/s。CKD组病例中肌酐正常组分别ADC值为(336.622±12.879)×10-5mm2/s、(308.142±20.998)×10-5mm2/s、(211.398±14.604)×10-5mm2/s,肌酐升高组分别为(307.717±84.930)×10-5mm2/s、(265.415±57.754)×10-5mm2/s、(201.672±26.411)×10-5mm2/s,ADC值均低于正常对照组(肌酐正常组与正常对照组比较的t值分别为9.720、5.190、11.093,P值均<0.05;肌酐升高组与正常对照组比较的t值分别为6.533、7.382、10.864,P值均<0.05)。肌酐升高组病例的平均血清肌酐水平为(828.490±699.350)μmol/L,肌酐升高组病例的ADC值与血清肌酐水平负相关,但无统计学意义(b值分别为50、100、400 s/mm2时相关系数分别为-0.272、-0.283、-0.023,P值均>0.05)。肌酐升高组病例的平均肌酐清除率为(15.405±14.541)m l/m in,该组病例的ADC值与肌酐清除率呈弱正相关(b值分别为50、100、400 s/mm2时相关系数分别为0.511、0.430、0.335,P值均<0.05,ADC值与肌酐清楚率呈正相关,但相关关系不密切)。结论对肾脏进行扩散加权成像及ADC值测量是1种有一定潜力且无创的肾功能评价的手段。     

腰椎溶骨型转移瘤MR扩散加权成像研究

目的探讨腰椎溶骨型转移瘤的扩散特性、扩散加权成像(DWI)检查技术及其应用价值。方法20例腰椎溶骨型转移瘤患者(病变组)及20例对照者(对照组),分别行矢状面SET1WI,快速SE(FSE)T2WI,脂肪抑制FSET2WI(fatsaturationFSET2WI,FS FSET2WI)及单次激发自旋回波回波平面DWI,比较病变组在各序列的对比噪声比(CNR)。同时评价病变组与对照组的信号衰减率(signalattenuationratio,SAR)和表观扩散系数(apparaentdiffusioncoefficient,ADC)。结果(1)常规MRI表现:20例腰椎溶骨型转移瘤患者,共23个椎体受累。在SET1WI上,病变均呈低信号,在FS FSET2WI和DWI上呈高信号。在FSET2WI上,病变分别呈混杂信号(5例)、等信号(12例)或稍高信号(6例);(2)CNR值:病变组CNR值在FSET2WI上(5.70±3.82)小于SET1WI(25.62±11.73)、FS FSET2WI(23.37±7.48)及DWI(b=600s/mm2)(24.69±9.87)(U值分别为5.393、6.359、5.547,P值均<0.05);(3)SAR值:在DWI上,病变组病变椎体、邻近正常椎体与对照组正常椎体的SAR值分别为:b=165s/mm2时,(33.21±7.76)%、(20.41±5.25)%、(22.09±5.21)%;b=360s/mm2时,(48.28±7.11)%、(27.18±5.04)%、(29.08±5.35)%;b=600s/mm2时,(59.64±7.37)%、(33.82±5.75)%、(34.02±4.50)%。成像条件相同时,病变椎体的SAR值明显高于正常椎体(q值分别为9.844、17.065、20.464、8.246、14.978、19.586,P值均<0.05)。随b值的增高,相同兴趣区(ROI)的SAR值逐渐增高(q值分别为7.344、5.952、4.392、17.084、12.013、10.596、9.739、6.601、6.204,P值均<0.05);(4)ADC值:在DWI上,病变组病变椎体、邻近正常椎体与对照组正常椎体的ADC值分别为:b=165s/mm2时,(2.49±0.70)×10-3mm2/s、(1.36±0.41)×10-3mm2/s、(1.51±0.41)×10-3mm2/s;b=360s/mm2时,(1.87±0.36)×10-3mm2/s、(0.88±0.19)×10-3mm2/s、(0.96±0.21)×10-3mm2/s;b=600s/mm2时,(1.54±0.30)×10-3mm2/s、(0.68±0.16)×10-3mm2/s、(0.70±0.12)×10-3mm2/s。成像条件相同时,病变椎体的ADC值明显高于正常椎体(q值分别为6.683、12.304、12.039、10.422、8.034、8.745,P值均<0.05)。b值越大,相同ROI的ADC值越小(q值分别为8.218、5.686、6.389、10.997、8.512、9.091、8.218、7.037、7.192,P值均<0.05)。结论DWI是以量化的方式,从分子水平对组织病变进行定性,比MR常规序列成像对组织进行定性诊断更加客观。     

MR扩散加权成像在眼眶良恶性肿块鉴别诊断中的应用

目的 分析眶内良恶性肿块的扩散加权成像(DWI)特征,评价表观扩散系数(ADC)值对其诊断价值.方法 对77例眶内肿块进行常规MRI及DWI,其中良性肿块55例,恶性肿块22例.扩散敏感系数(b)值=0、1000 s/mm2,测量病变对侧颞叶脑白质感兴趣区DWI信号,获得相应的肿块区ADC(ADCM)值、病变对侧颞叶脑白质ADC(ADCw)值,计算二者比值(ADCR).以不同ADCM值及ADCR作为临界点区分眶内良恶性肿块绘制出受试者工作特征曲线(ROC).结果 眶内良性肿块ADCM值及ADCR分别为(1.56±0.75)×10-3mm2/s、1.85±0.91;恶性肿块ADCM值及ADCR分别为(1.09±0.42)×10-3mm2/s、1.28±0.53;良性肿块ADCM值及ADCR显著高于恶性肿块(t值分别为2.803、2.735,P值均＜0.01).以不同ADCM值、ADCR作为临界点判断眶内良恶性肿块绘制ROC,曲线下面积均为0.71±0.07.以ADCM值为1.05×10-3mm2/s作为判断眶内良恶性肿块的决定值,灵敏度、特异度和准确率分别为59.1%(13/22)、78.2%(43/55)和72.7%(56/77);以ADCR为1.24作为决定值,灵敏度、特异度和准确率分别为59.1%(13/22)、76.4%(42/55)和71.4%(55/77).结论 DWI可揭示眼眶肿块的扩散特征,ADC值对于良恶性肿块的鉴别诊断具有辅助诊断价值.