Evaluation of liver diffusion isotropy and characterization of focal hepatic lesions with two single-shot echo-planar MR imaging sequences: prospective study in 66 patients

PURPOSE: To (a) evaluate liver diffusion isotropy, (b) compare two diffusion-weighted magnetic resonance (MR) imaging sequences for the characterization of focal hepatic lesions by using two or four b values, and (c) determine an apparent diffusion coefficient (ADC) threshold value to differentiate benign from malignant lesions. MATERIALS AND METHODS: Sixty-six patients were examined with two single-shot echo-planar diffusion-weighted MR sequences. In the first sequence, liver diffusion isotropy was evaluated by using diffusion gradients in three directions with two b values. In the second sequence, a unidirectional diffusion gradient was used with four b values. ADCs were measured in 43 patients with 52 focal hepatic lesions more than 1 cm in diameter and in 23 patients with 14 normal and nine cirrhotic livers and were compared by using nonparametric tests. RESULTS: Diffusion in the liver parenchyma was isotropic. ADCs of focal hepatic lesions were significantly different between sequences (P <.01). The mean (+/- SD) ADCs in the first sequence were 0.94 x 10(-3) mm(2)/sec +/- 0.60 for metastases, 1.33 x 10(-3) mm(2)/sec +/- 0.13 for HCCs, 1.75 x 10(-3) mm(2)/sec +/- 0.46 for benign hepatocellular lesions, 2.95 x 10(-3) mm(2)/sec +/- 0.67 for hemangiomas, and 3.63 x 10(-3) mm(2)/sec +/- 0.56 for cysts. There was a significant difference between benign (2.45 x 10(-3) mm(2)/sec +/- 0.96, isotropic value) and malignant (1.08 x 10(-3) mm(2)/sec +/- 0.50) lesions (P <.01 for both sequences). CONCLUSION: Diffusion-weighted MR imaging can help differentiate benign from malignant hepatic lesions. The use of two b values in one direction could be sufficient for the design of MR sequences in the liver.     

Diffusion coefficients in abdominal organs and hepatic lesions: evaluation with intravoxel incoherent motion echo-planar MR imaging

PURPOSE: To determine the true diffusion coefficients of abdominal organs and hepatic lesions with intravoxel incoherent motion (IVIM) echo-planar magnetic resonance (MR) imaging. MATERIALS AND METHODS: Seventy-eight patients suspected of having hepatic lesions were examined with IVIM echo-planar MR imaging at 1.5 T. There were 77 hepatic masses (27 hepatocellular carcinomas, 10 metastatic tumors, eight hemangiomas, and 32 cysts) in the 78 patients. The true diffusion coefficient D and the perfusion fraction f were calculated and compared with the apparent diffusion coefficient (ADC). RESULTS: Specific values of D were found for abdominal organs (liver, 0.72 x 10(-3) mm2/sec; spleen, 0.80 x 10(-3) mm2/sec; kidney, 1.38 x 10(-3) mm2/sec; gallbladder, 2.82 x 10(-3) mm2/sec) and for hepatic lesions (hepatocellular carcinoma, 1.02 x 10(-3) mm2/sec; metastasis, 1.16 x 10(-3) mm2/sec; hemangioma, 1.31 x 10(-3) mm2/sec; cysts, 3.03 x 10(-3) mm2/sec). The ADCs of solid organs and solid lesions were significantly higher than their D values, indicating a high contribution of perfusion to the ADCs. CONCLUSION: Perfusion contributes to the ADCs of abdominal organs and hepatic lesions. The D and f values are useful for the characterization of hepatic lesions.     

Head and neck lesions: characterization with diffusion-weighted echo-planar MR imaging

PURPOSE: To evaluate whether apparent diffusion coefficients (ADCs) calculated from diffusion-weighted echo-planar magnetic resonance (MR) images can be used to characterize head and neck lesions. MATERIALS AND METHODS: Diffusion-weighted echo-planar MR imaging was performed with a 1.5-T MR unit in 97 head and neck lesions in 97 patients. Images were obtained with a diffusion-weighted factor, factor b, of 0, 500, and 1,000 sec/mm(2), and an ADC map was constructed. The ADCs of lesions, cerebrospinal fluid, and spinal cord were calculated. RESULTS: Acceptable images for ADC measurement were obtained in 81 (84%) patients. The mean ADC of malignant lymphomas, (0.66 +/- 0.17[SD]) x 10(-3) mm(2)/sec (n = 13), was significantly smaller (P <.001) than that of carcinomas. The mean ADC of carcinomas, (1.13 +/- 0.43) x 10(-3) mm(2)/sec (n = 36), was significantly smaller (P =.002) than that of benign solid tumors. The mean ADC of benign solid tumors, (1.56 +/- 0.51) x 10(-3) mm(2)/sec (n = 22), was significantly smaller (P =.035) than that of benign cystic lesions, (2.05 +/- 0.62) x 10(-3) mm(2)/sec (n = 10). No significant differences were seen in the mean ADC of cerebrospinal fluid and of spinal cord among four groups of lesions. When an ADC smaller than 1.22 x 10(-3) mm(2)/sec was used for predicting malignancy, the highest accuracy of 86%, with 84% sensitivity and 91% specificity, was obtained. CONCLUSION: Measurement of ADCs may be used to characterize head and neck lesions.     

Differentiation of clinically benign and malignant breast lesions using diffusion-weighted imaging

PURPOSE: To evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions. MATERIALS AND METHODS: Fifty-two female subjects (mean age = 58 years, age range = 25-75 years) with histopathologically proven breast lesions underwent DWI of the breasts with a single-shot echo-planar imaging (EPI) sequence using large b values. The computed mean apparent diffusion coefficients (ADCs) of the breast lesions and cell density were then correlated. RESULTS: The ADCs varied substantially between benign breast lesions ((1.57 +/- 0.23) x 10(-3) mm(2)/second) and malignant breast lesions ((0.97 +/- 0.20) x 10(-3) mm(2)/second). In addition, the mean ADCs of the breast lesions correlated well with tumor cellularity (P < 0.01, r = -0.542). CONCLUSION: The ADC would be an effective parameter in distinguishing between malignant and benign breast lesions. Further, tumor cellularity has a significant influence on the ADCs obtained in both benign and malignant breast tumors.     

Soft-tissue tumors evaluated by line-scan diffusion-weighted imaging: influence of myxoid matrix on the apparent diffusion coefficient

PURPOSE: To compare the apparent diffusion coefficients (ADCs) of myxoid and nonmyxoid soft-tissue tumors using line-scan diffusion-weighted imaging (LSDWI), and to investigate the myxoid matrix influence on ADCs of soft-tissue tumors. MATERIALS AND METHODS: This study enrolled 44 patients with soft tissue tumors. They were divided into two groups: one with myxoid-containing soft-tissue tumors (N = 23) and the other with nonmyxoid soft-tissue tumors (N = 21). The 44 patients were also classified histologically into 26 with malignant soft-tissue tumors and 18 with benign soft-tissue tumors. LSDWI was performed using b values of 5 and 1000 second/mm(2). The ADCs of the tumors were calculated and compared for myxoid and nonmyxoid tumors and for benign and malignant tumors. RESULTS: The ADC (mean +/- SD) was 1.92 +/- 0.41 x 10(-3) mm(2)/second in myxoid containing tumors, whereas the ADC was 0.97 +/- 0.33 x 10(-3) mm(2)/second in nonmyxoid tumors. The ADCs of the myxoid and nonmyxoid tumors were significantly different (P < 0.01). The ADCs were 1.45 +/- 0.59 x 10(-3) mm(2)/second in malignant tumors and 1.50 +/- 0.64 x 10(-3) mm(2)/second in benign tumors. The ADCs of benign and malignant soft-tissue tumors were not significantly different. CONCLUSION: The ADCs of myxoid-containing soft-tissue tumors were significantly higher than those of nonmyxoid soft-tissue tumors. The myxoid matrix influences ADCs of both benign and malignant soft-tissue tumors.     

CT and radiography of bacterial respiratory infections in AIDS patients

OBJECTIVE: Acute vertebral collapse is common, and it is sometimes difficult to determine whether the cause is benign or malignant. Recently, diffusion-weighted imaging has been reported to be useful for differentiating the two types. The purpose of this study was to evaluate diffusion abnormalities quantitatively in benign and malignant compression fractures using line scan diffusion-weighted imaging. SUBJECTS AND METHODS. Line scan diffusion-weighted imaging was prospectively performed in 17 patients with 20 acute vertebral compression fractures caused by osteoporosis or trauma, in 12 patients with 16 vertebral compression fractures caused by malignant tumors, and in 35 patients with 47 metastatic vertebrae without collapse. Images were obtained at b values of 5 and 1,000 sec/mm(2). The apparent diffusion coefficient (ADC) was measured in vertebral compression fractures and metastatic vertebrae without collapse. RESULTS: The ADC (mean +/- SD) was 1.21 +/- 0.17 x 10(-3) mm(2)/sec in benign compression fractures, 0.92 +/- 0.20 x 10(-3) mm(2)/sec in malignant compression fractures, and 0.83 +/- 0.17 x 10(-3) mm(2)/sec in metastatic vertebral lesions without collapse. The ADC was significantly higher in benign compression fractures than in malignant compression fractures (p < 0.01), although the two types showed considerable overlap. CONCLUSION: Although the quantitative assessment of vertebral diffusion provides additional information concerning compressed vertebrae, the benign and malignant compression fracture ADC values overlap considerably. Therefore, even a quantitative vertebral diffusion assessment may not always permit a clear distinction between benign and malignant compression fractures.     

MR扩散加权成像鉴别乳腺良恶性病变的研究

目的　探讨磁共振扩散加权成像(diffusion weightedMRimaging, DW MRI)的表观扩散系数(apparentdiffusioncoefficient, ADC)在乳腺病变鉴别诊断中的价值。方法　DW- MRI采用单次激发平面回波成像(echo planarimaging, EPI)技术, 扩散敏感系数(b值)分别为0、500、1000s/mm2。计算26个正常乳腺、手术病理证实的24个恶性病灶、30个良性病灶分别在b=1000~0、1000~500、500~0s/mm2 时的ADC值,比较良恶性病变、正常腺体间ADC值差异的统计学意义及b=1000~0、1000~500、500~0s/mm2 间ADC值差异的统计学意义。结果　乳腺良、恶性病变、正常腺体间ADC值差异均有统计学意义(F= 565. 74,P<0 .01),恶性病变ADC值明显低于良性病变和正常腺体组织,良性病变ADC值明显低于正常腺体组织; 3组b值间ADC值差异均有统计学意义(F=21. 30,P<0 .01),b值越低,ADC值越大;把恶性肿瘤ADC值95%可信区间上界( 1. 01×10-3 )mm2 /s定为良恶性病变鉴别的界值,诊断敏感性为64 .0%,特异性为96 .7%。结论　根据ADC值可以对乳腺良恶性病变做出鉴别诊断,其特异性较高,但敏感性较低。     

Characterization of benign and metastatic vertebral compression fractures with quantitative diffusion MR imaging

BACKGROUND AND PURPOSE: Conventional imaging techniques cannot be used to unambiguously and reliably differentiate malignant from benign vertebral compression fractures. Our hypothesis is that these malignant and benign vertebral lesions can be better distinguished on the basis of tissue apparent diffusion coefficients (ADCs). The purpose of this study was to test this hypothesis by using a quantitative diffusion imaging technique. METHODS: Twenty-seven patients with known cancer and suspected metastatic vertebral lesions underwent 1.5-T conventional T1-weighted, T2-weighted, and contrast-enhanced T1-weighted imaging to identify the lesions. Diffusion-weighted images of the areas of interest were acquired by using a fast spin-echo diffusion pulse sequence with b values of 0-250 s/mm(2). The abnormal regions on the diffusion-weighted images were outlined by using the conventional images as guides, and the ADC values were calculated. On the basis of pathologic results and clinical findings, the cases were divided into two categories: benign compression fractures and metastatic lesions. The ADC values for each category were combined and plotted as histograms; this procedure was followed by statistical analysis. RESULTS: The patient group had 12 benign fractures and 15 metastases. The mean ADC values, as obtained from the histograms, were (1.9 +/- 0.3) x 10(-4) mm(2)/s and (3.2 +/- 0.5) x 10(-4) mm(2)/s for metastases and benign fractures, respectively. CONCLUSION: Our results indicate that quantitative ADC mapping, instead of qualitative diffusion-weighted imaging, can provide valuable information in differentiating benign vertebral fractures from metastatic lesions.     

Lung carcinoma: diffusion-weighted mr imaging--preliminary evaluation with apparent diffusion coefficient

PURPOSE: To prospectively evaluate diffusion-weighted (DW) magnetic resonance (MR) imaging with a split acquisition of fast spin-echo signals for diffusion imaging (SPLICE) sequence for tissue characterization of lung carcinomas by using apparent diffusion coefficients (ADCs). Materials and METHODS: An institutional review board approved this study; informed consent was obtained from patients. Thirty patients (nine women, 21 men; mean age, 68.0 years) with lung carcinoma underwent DW MR imaging with the SPLICE sequence. ADC of each lung carcinoma was calculated from DW MR images obtained with low and high b values. ADCs of lung carcinomas were statistically compared among histologic types. Nine surgically excised lung carcinomas were evaluated for correlation between ADCs and tumor cellularities. Analysis of variance was used to determine changes in ADCs and histologic lung carcinoma types. Spearman rank correlation was calculated between ADCs and tumor cellularities. RESULTS: ADCs for lung carcinomas were 1.63 x 10(-3) mm(2)/sec +/- 0.5 (mean +/- standard deviation) for squamous cell carcinoma, 2.12 x 10(-3) mm(2)/sec +/- 0.6 for adenocarcinoma, 1.30 x 10(-3) mm(2)/sec +/- 0.4 for large-cell carcinoma, and 2.09 x 10(-3) mm(2)/sec +/- 0.3 for small-cell carcinoma. ADC of adenocarcinoma was significantly higher than that of squamous cell carcinoma and large-cell carcinoma (P < .05). ADCs were 1.59 x 10(-3) mm(2)/sec +/- 0.5 and 1.70 x 10(-3) mm(2)/sec +/- 0.4 for moderately and poorly differentiated squamous cell carcinoma, respectively. ADCs were 2.52 x 10(-3) mm(2)/sec +/- 0.4 and 1.44 x 10(-3) mm(2)/sec +/- 0.3 for well- and poorly differentiated adenocarcinoma, respectively. ADC of well-differentiated adenocarcinoma was significantly higher than that of moderately and poorly differentiated squamous cell carcinoma and poorly differentiated adenocarcinoma (P < .05). With the Spearman rank test, ADCs of lung carcinomas correlated well with tumor cellularities (Spearman coefficient, -0.75; P < .02). CONCLUSION: ADCs of lung carcinomas overlap, but ADCs of well-differentiated adenocarcinoma appear to be higher than those of other histologic lung carcinoma types.     

Diffusion-weighted imaging of the prostate at 3 T for differentiation of malignant and benign tissue in transition and peripheral zones: preliminary results

OBJECTIVE: To evaluate prospectively the use of apparent diffusion coefficients (ADCs) for the differentiation of malignant and benign tissue in the transition (TZ) and peripheral (PZ) zones of the prostate diffusion-weighted imaging (DWI) at 3 T magnetic resonance imaging (MRI) using a phased-array coil. METHODS: The DWI at 3-T MRI was performed on a total of 35 patients before radical prostatectomy. A single-shot echo-planar imaging DWI technique with b = 0 and b = 1000 s/mm2 was used. The ADC values were measured in both benign and malignant tissues in the PZ and TZ using regions of interest. Differences between PZ and TZ ADC values were estimated using a paired Student t test. Presumed ADC cutoff values in the PZ and TZ for the diagnosis of cancer were assessed by receiver operating characteristic analysis. RESULTS: The ADC values of malignant tissues were significantly lower than those of benign tissues in the PZ and TZ (P < 0.001; 1.32 +/- 0.24 x 10(-3) mm2/s vs 1.97 +/- 0.25 x 10(-3) mm2/s, and 1.37 +/- 0.29 x 10(-3) mm2/s vs 1.79 +/- 0.19 x 10(-3) mm2/s, respectively). For tumor diagnosis, cutoff values of 1.67 x 10(-3) mm2/s (PZ) and 1.61 x 10(-3) mm2/s (TZ) resulted in sensitivities and specificities of 94% and 91% and 90% and 84%, respectively. CONCLUSIONS: The DWI of the prostate at 3T MRI using a phased-array coil was useful for the differentiation of malignant and benign tissues in the TZ and PZ.     

Acute vertebral body compression fractures: discrimination between benign and malignant causes using apparent diffusion coefficients

Diffusion weighted MRI was performed on patients with acute vertebral body compression. The usefulness of the apparent diffusion coefficient (ADC) in differentiating between benign and malignant fractures was evaluated. A total of 49 acute vertebral body compression fractures were found in 32 patients. 25 fractures in 18 patients were due to osteoporosis, 18 fractures in 12 patients were histologically proven to be due to malignancy, and 6 fractures in 2 patients were due to tuberculosis. Signal intensities on T(1) weighted, short tau inversion recovery (STIR) and diffusion weighted images were compared. ADC values of normal and abnormal vertebral bodies were calculated. Except for two patients with sclerotic metastases, benign acute vertebral fractures were hypointense and malignant acute vertebral fractures were hyperintense with respect to normal bone marrow on diffusion weighted images. Mean combined ADCs (ADC(cmb); average of the combined ADCs in the x, y and z diffusion directions) were 0.23 x 10(-3) mm(2) s(-1) in normal vertebrae, 0.82 x 10(-3) mm(2) s(-1) in malignant acute vertebral fractures and 1.94 x 10(-3) mm(2) s(-1) in benign acute vertebral fractures. The differences between ADC(cmb) values were statistically significant (p<0.001). The ADC is useful in differentiating benign from malignant acute vertebral body compression fractures, but there may be overlapping ADC values between malignant fractures and tuberculous spondylitis.     

Usefulness of the calculated apparent diffusion coefficient value in the differential diagnosis of retroperitoneal masses

PURPOSE: To elucidate whether or not the apparent diffusion coefficient (ADC) values calculated from echo-planar diffusion-weighted (EPDW) MR images are useful in the differential diagnosis of retroperitoneal masses. MATERIALS AND METHODS: In 50 patients with known retroperitoneal masses, EPDW images were performed with b-factors of 0-1100 seconds/mm2. The final histologic diagnoses of these lesions were as follows: 12 malignant lymphomas, four other malignant mesenchymal neoplasms, 25 malignant epithelial neoplasms, seven benign mesenchymal neoplasms, and two nonneoplastic lesions. The ADC values obtained for the solid portion of the lesions were used to represent each lesion, and the values of the histologic groups were compared. RESULTS: The respective value of ADC for 12 malignant lymphomas, four other mesenchymal neoplasms, seven benign mesenchymal neoplasms, and two nonneoplastic lesions were as follows: 0.66 +/- 0.26, 1.26 +/- 0.50, 0.90 +/- 0.20, 1.87 +/- 0.48, 1.32 +/- 0.20 x 10(-3) mm2/second. The ADC value of the malignant lymphoma was significantly lower than that of the other malignant mesenchymal lesions, and was also lower than the ADC of the benign lesions. The ADC value of the malignant epithelial neoplasms was lower than that of the benign mesenchymal tumors. The ADC values of the malignant and benign lesions were 0.94 +/- 0.30 and 1.75 +/- 0.49 x 10(-3) mm2/second, respectively, which also demonstrated a significant difference. CONCLUSION: ADC values calculated from EPDW MR images may provide useful information in the differential diagnosis of retroperitoneal masses.     

Diffusion-weighted imaging of the liver: optimizing b value for the detection and characterization of benign and malignant hepatic lesions

PURPOSE: To determine the optimal b values required for diffusion-weighted (DW) imaging of the liver in the detection and characterization of benign and malignant hepatic lesions. MATERIALS AND METHODS: MR images obtained in 76 patients including 28 malignant hepatic lesions (21 hepatocellular carcinomas and 7 metastases) and 27 benign lesions (12 hemangiomas and 15 cysts) were reviewed. DW-echo planner images (EPIs; b values with 100, 200, 400, and 800 s/mm2) were reviewed solely first, and then with T2-weighted EPIs (b=0 s/mm2). RESULTS: Sensitivity for malignant lesions (74%) was highest on DW-EPIs with b value of 100 s/mm2 and T2-weighted EPIs combined (P<0.05), and sensitivity for benign lesions (87%) was highest on DW-EPIs with b value of 800 s/mm2 and T2-weighted EPIs (P<0.05). Specificities were comparably high for all sequences. The Az values for malignant lesions were 0.94, 0.90, 0.87, and 0.89, and those for benign lesions were 0.91, 0.89, 0.87, and 0.94 on DW-EPIs with b values of 100, 200, 400, and 800 and T2-weighted EPIs combined, respectively. Hepatic cysts were clearly distinguished with the cutoff ADC value of 2.5x10(-3) mm2/s using a b value of 400 s/mm2 or greater. CONCLUSION: DW-EPIs with middle b values were not required in the detection and characterization of benign and malignant hepatic lesions.     

Quantitative diffusion imaging in breast cancer: a clinical prospective study

PURPOSE: To study the correlation between apparent diffusion coefficient (ADC) and pathology in patients with undefined breast lesion, to validate how accurately ADC is related to histology, and to define a threshold value of ADC to distinguish malignant from benign lesions. MATERIALS AND METHODS: Seventy-eight patients (110 lesions) were referred for positive or dubious findings. Three-dimensional fast low-angle shot (3D-FLASH) with contrast injection was applied. EPI diffusion-weighted imaging (DWI) with fat saturation was performed, and ROIs were selected on subtraction 3D-FLASH images before and after contrast injection, and copied on an ADC map. Inter- and intraobserver analyses were performed. RESULTS: At pathology 22 lesions were benign, 65 were malignant, and 23 were excluded. The ADCs of malignant and benign lesions were statistically different. In malignant tumors the ADC was (mean +/- SEM) 0.95 +/- 0.027 x 10(-3)mm(2)/second, and in benign tumors it was 1.51 +/- 0.068 x 10(-3)mm(2)/second. According to receiver operating characteristic (ROC) curves, we found a threshold between malignant and benign lesions for highest sensitivity and specificity (both 86%) around 1.13 +/- 0.10 x 10(-3)mm(2)/second. For a threshold of 0.95 +/- 0.10 x 10(-3)mm(2)/second, specificity was 100% but sensitivity was very low. Inter- and intraobserver studies showed good reproducibility. CONCLUSION: The ADC may help to differentiate benign and malignant lesions with good specificity, and may increase the overall specificity of breast MRI.     

Vertebral metastases: assessment with apparent diffusion coefficient

The authors evaluated the apparent diffusion coefficient (ADC) in the assessment of vertebral metastases and acute vertebral compression fractures in 22 patients with known or suspected vertebral metastases. On the basis of significantly (P <.03) different ADCs, vertebral metastases (0.69 x 10(-3) mm2/sec) and pathologic compression fractures (0.65 x 10(-3) mm2/sec) can be safely distinguished from vertebral bodies (1.66 x 10(-3) mm2/sec) and benign compression fractures (1.62 x 10(-3) mm2/sec). Thus, the use of ADCs may increase the specificity of magnetic resonance imaging in these patients.     

Usefulness of diffusion-weighted MRI in differentiating benign from malignant musculoskeletal tumors

PURPOSE: To evaluate the usefulness of diffusion-weighted MRI in distinguishing different components and in differentiating benign from malignant musculoskeletal tumors. MATERIALS AND METHODS: Fifty-seven patients with musculoskeletal tumors underwent MR at our institution from October 1999 to April 2002. We evaluated 57 tumors (9 bone tumors and 48 soft tissue tumors). All tumors were classified into 8 groups (myxomatous, fibrous, cystic, cartilaginous, fatty components, hematomas, other benign tumors, and other malignant tumors). MR examinations were performed with a 1.5-Tesla system. Diffusion-weighted single-shot EPI images were obtained in all patients. Apparent diffusion coefficients (ADCs) were calculated by using b factors of 0 and 1,000 sec/mm2. RESULTS: ADC values of myxomatous, cystic, and cartilaginous components were significantly higher than those of other tumors. In cartilaginous tumors, malignant tumor ADC values (2.33 +/- 0.44) were higher than those of benign tumors (2.13 +/- 0.13). However, there was no significant difference between benign and malignant tumors. Except for high-intensity components on T1-weighted imaging and low or homogeneously very high intensity components on T2-weighted imaging, there was a significant difference in ADC between malignant (1.35 +/- 0.40) and benign (1.97 +/- 0.50) tumors. CONCLUSION: Within the limited number of cases, there was a significant difference in ADC between malignant and benign tumors.     

1.5TMR乳腺扩散加权成像b值的优化

目的 通过分析水模、正常乳腺腺体、乳腺良性及恶性病变的ADC值及图像信噪比(SNR)随b值的变化规律,探讨1.5 TMR乳腺DWI合理的b值取值范围.方法 对32例经病理证实的乳腺病变(恶性18例,良性14例)及对侧正常腺体进行乳腺MR检查,采用EPI-DWI序列;b值分别采用0、50、100、200、400、600、800、1000、1200、1400、1600、1800、2000、2200、2400、2600 s/mm2.测量不同b值下水模、正常乳腺腺体、乳腺良性及恶性病变的平均ADC值和图像SNR,采用Pearson相关分析法分析不同b值时的变化规律.结果 DWI的SNR均随b值的增加逐渐下降,二者呈负相关(r=-0.802,P＜0.01),乳腺良、恶性病变的ADC值均随着b值的增加而下降(r=-0.923和-0.855,P＜0.01);当b值取800～1000 s/mm2时,恶性病变与良性病变和正常腺体之间的ADC值差异最大(0.7×10-3mm2/s);当b值＞1400 s/mm2,差异逐渐减小.结论 取b值800～ 1000 s/mm2时,既能取得良好的图像质量,又能有效地鉴别乳腺良、恶性病变,是1.5 TMR乳腺DWI最合理的b值取值范围.     

ADC mapping of benign and malignant breast tumors.

PURPOSE: The purpose of this study was to investigate the utility of diffusion-weighted imaging (DWI) and the apparent diffusion coefficient (ADC) value in differentiating benign and malignant breast lesions and evaluating the detection accuracy of the cancer extension. MATERIALS AND METHODS: We used DWI to obtain images of 191 benign and malignant lesions (24 benign, 167 malignant) before surgical excision. The ADC values of the benign and malignant lesions were compared, as were the values of noninvasive ductal carcinoma (NIDC) and invasive ductal carcinoma (IDC). We also evaluated the ADC map, which represents the distribution of ADC values, and compared it with the cancer extension. RESULTS: The mean ADC value of each type of lesion was as follows: malignant lesions, 1.22+/-0.31 x 10(-3) mm2/s; benign lesions, 1.67+/-0.54 x 10(-3) mm2/s; normal tissues, 2.09+/-0.27 x 10(-3) mm2/s. The mean ADC value of the malignant lesions was statistically lower than that of the benign lesions and normal breast tissues. The ADC value of IDC was statistically lower than that of NIDC. The sensitivity of the ADC value for malignant lesions with a threshold of less than 1.6 x 10(-3) mm2/s was 95% and the specificity was 46%. A full 75% of all malignant cases exhibited a near precise distribution of low ADC values on ADC maps to describe malignant lesions. The main causes of false negative and underestimation of cancer spread were susceptibility artifact because of bleeding and tumor structure. Major histologic types of false-positive lesions were intraductal papilloma and fibrocystic diseases. Fibrocystic diseases also resulted in overestimation of cancer extension. CONCLUSIONS: DWI has the potential in clinical appreciation to detect malignant breast tumors and support the evaluation of tumor extension. However, the benign proliferative change remains to be studied as it mimics the malignant phenomenon on the ADC map.     

MR扩散加权成像中ADC值对肝脏肿瘤性病变的定性评估

目的评估MR扩散加权成像(DWI)对肝脏肿瘤性病变、特别是影像学表现不典型肿瘤性病变的诊断价值及其良恶性鉴别诊断价值。资料与方法对2010年8月至2011年5月的55例患者(34例为肿瘤患者怀疑有肝脏转移,21例CT、B超等影像学检查拟诊肝脏占位性病变无法进行定性诊断)行MR常规序列及DWI,共发现92个病灶(25个原发性肝癌,27个肝转移瘤,3个肝胆管细胞癌,2个肝硬化结节,2个肝脏局灶性结节增生,7个肝血管瘤,26个肝囊肿)。通过分析肝脏病灶信号强度随b值不同的变化及病灶表观扩散系数(ADC)值的大小(平均数±标准差)等对肝脏肿瘤性病变、特别是不典型肿瘤性病变的良恶性进行诊断及鉴别诊断,以病理结果或随访结果为标准计算其敏感性及特异性。结果 MR DWI上,b=50 s/mm2、500s/mm2及b=50 s/mm2、1000 s/mm2时,良性病变的信号衰减程度高于恶性病变,即b为50 s/mm2、1000 s/mm2时,恶性病变为高信号,而良性病变呈相对等信号或低信号,良恶性病灶信号强度差异明显。恶性病变的ADC值(b值为50 s/mm2、1000 s/mm2时计算)[(0.845±0.0110)×10-3mm2/s,n=55]明显低于良性病变的ADC值(b值为50 s/mm2、1000 s/mm2时计算)[(2.230±0.0497)×10-3mm2/s,n=37],经秩和检验差异具有统计学意义(Z=-7.905,P<0.01),敏感性及特异性分别为96.36%和83.78%。结论 DWI对肝脏肿瘤性病变、特别是影像学表现不典型肿瘤性病变具有较大诊断价值,对肝脏肿瘤性病变的良恶性鉴别诊断是一种简单、实用的影像学检查方法。     

高b值MR扩散加权成像在乳腺良恶性病变诊断中的应用价值

目的 评价高b值MR DWI及ADC值在乳腺良恶性病变诊断中的应用价值.方法 165例患者在行乳腺MR动态增强扫描前行不同b值(分别为500、1500 s/mm2)的DWI扫描,对171个怀疑或高度怀疑恶性病变者行回顾性分析.以正常乳腺组织为参考基准,选择增强图像中异常强化的高信号病变,同时在高b值(b= 1500 s/mm2)DWI中视觉判定是高信号的病变定义为恶性病变阳性结果,否则为良性病变阴性结果.对其中111个DWI视觉判定阳性结果的病变计算ADC值.依据全部病变穿刺活检病理诊断结果,应用Fisher精确检验和Wilcoxon秩和检验对比分析高b值DWI视觉评估中恶性和良性病变的阳性和阴性病灶数,以ADC值=1.13×10-3 mm2/s作为临界值,计算诊断的特异度和敏感度.结果 乳腺病变穿刺活检病理证实的171个乳腺病变中,91个恶性病变,80个良性病变.高b值DWI视觉评估,139个阳性结果中,恶性病变83个,良性病变56个;32个阴性结果中,良性病变24个,恶性病变8个(非肿块性导管原位癌),差异有统计学意义(P＜0.01).所有浸润性癌和肿块样导管原位癌(DCIS)在DWI视觉判定中为阳性,8例非肿块性DCIS判定为假阴性,总体的敏感度为91.2％ (83/91),特异性为30.0％ (24/80).110个肿块样病变和1个局灶性病变DWI视觉评估阳性结果的病变中,63个恶性病变平均ADC值为(0.73±0.24)×10-3 mm2/s,48个良性病变平均ADC值为(1.19±0.42)×10-3mm2/s,差异有统计学意义(Z=5.818,P＜0.01).以ADC值=1.13×10-3mm2/s作为临界值时,61个恶性病变为阳性结果,2个黏液癌为假阴性结果;27个良性病变为阴性结果,21个良性病变为假阳性,诊断敏感度是96.8％(61/63),特异度为56.2％ (27/48).结论 高b值DWI及ADC值对乳腺良恶性病变的鉴别诊断有一定的作用,但在诊断非肿块性乳腺病变时仍需慎重.