Optimization of b value in diffusion-weighted MRI for characterization of benign and malignant gynecological lesions

Purpose:

To explore the optimal b value in diffusion‐weighted (DW)‐MRI for differentiation of benign and malignant gynecological lesions.

Materials and Methods:

Consecutive 58 patients (66 lesions) with pathologically confirmed diagnosis of gynecological disease were included in the study. Routine pelvic MRI sequences were used for defining the lesions and reviewed independently for benignity/ malignity. Single‐shot echoplanar imaging (SH‐EPI) DW‐MRI with eight b values and nine apparent diffusion coefficient (ADC) maps were obtained. The lesions were analyzed qualitatively on DW‐MRI for benignity/malignity on a five‐point‐scale and quantitatively by measurement of apparent diffusion coefficient (ADC) values. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic accuracy of ADC values for differentiating between benign and malignant lesions. Pathology results were the reference standard.

Results:

Differentiation between benign and malignant gynecological lesions using visual scoring was found to be successful with b values of 600, 800, or 1000 s/mm². The mean ADC values of malignant lesions were significantly lower than those of benign lesions for all b value (P < 0.005). The ADCs with b = 0 and 600, 0 and 1000 s/mm², 0, 600, 800 and 1000 s/mm², and all b values were more effective for distinguishing malignant from benign gynecological lesions (Az = 0.851, 0.847, 0.848, 0.849, respectively). Using ADC with b = 0, 600, 800, and 1000 s/mm², a threshold value of 1.20 × 10^?3 mm²/s permitted this distinction with a sensitivity of 83%, a specificity of 81%.

Conclusion:

DW‐MRI is an important method, and the optimal b values are between 600 and 1000 s/mm² for differentiation between benign and malignant gynecological lesions. J. Magn. Reson. Imaging 2012;35:650‐659. © 2011 Wiley Periodicals, Inc.

     

The influence of the b‐value combination on apparent diffusion coefficient based differentiation between malignant and benign tissue in cervical cancer

Purpose:

To analyze the influence of different b‐value combinations on apparent diffusion coefficient (ADC)‐based differentiation of known malignant and benign tissue in cervical cancer patients.

Materials and Methods:

A total of 35 patients with stage IB1, IB2, IIA cervical cancer underwent a 3.0T MRI scan prior to radical hysterectomy and pelvic lymph node dissection. Conventional T1‐ and T2‐weighted sequences and a diffusion‐weighted sequence (b = 0, 150, 500, 1000 seconds/mm²) were performed. Regions‐of‐interest (ROI) were drawn on ADC maps derived from five different b‐value combinations (0, 500; 0, 150, 500; 0, 1000; 0, 150, 500, 1000; 150, 500, 1000 seconds/mm²). The influence of the b‐value combination on ADC‐based differentiation of benign and malignant tissue was analyzed using receiver‐operating‐characteristics curves.

Results:

For all b‐value combinations, ADCs were significantly lower (P < 0.001) in cervical malignancies (1.15 ± 0.21·10^?3; 1.10 ± 0.21·10^?3; 0.97 ± 0.18·10^?3; 0.97 ± 0.23·10^?3 and 0.85 ± 0.18·10^?3 mm²/second respectively to the aforementioned b‐value combinations) than in benign cervix (2.08 ± 0.31·10^?3; 2.00 ± 0.29·10^?3; 1.62 ± 0.23·10^?3; 1.54 ± 0.21·10^?3 and 1.42 ± 0.22·10^?3 mm²/second respectively). The diagnostic accuracy was high for all b‐value combinations and without statistical differences between the combinations.

Conclusion:

ADC‐based differentiation of benign from malignant cervical tissue is independent of the tested b‐value combinations. The results support the inclusion and possible pooling of studies using different b‐value combinations in meta‐analyses on ADC‐based tissue differentiation in cervical cancer. J. Magn. Reson. Imaging 2010;32:376–382. © 2010 Wiley‐Liss, Inc.

     

The utility of DW-MRI in the diagnosis of pancreatic focal lesions

Background

Early diagnosis is crucial in management of pancreatic malignancy. DWMRI could be used in differentiating pancreatic lesions and judge about tumor aggressiveness.

Initial experience of 3 tesla apparent diffusion coefficient values in differentiating benign and malignant thyroid nodules

Purpose:

To evaluate the role of diffusion‐weighted magnetic resonance imaging (DWMRI) in differentiating benign and malignant thyroid nodules using a 3 Tesla (T) MRI scanner.

Materials and Methods:

Twenty‐eight nodules in 25 patients and 14 healthy control cases were included in the study. DWMRI was acquired with 6 b values with a 3T MRI scanner. The apparent diffusion coefficient (ADC) values of the nodules were calculated from reconstructed ADC map images and were compared with the final histopathological diagnoses.

Results:

The mean ADC value of the benign nodules was 1548 ± 353.4 (×10^?6 mm²/s), and the mean ADC of the malignant nodules was 814 ± 177.12 (×10^?6 mm²/s). The normal thyroid tissue had a mean ADC value of 1323.43 ± 210.35 × 10^?6 mm²/s (958–1689 × 10^?6 mm²/s) in the healthy control group. The ADC values were significantly different among the three groups (P = 0.001). An ADC value of 905 × 10^?6 mm²/s was determined to be the cutoff value for differentiating benign and malignant nodules, with 90% (55.5–98.3) sensitivity and 100% (81.3–100.0) specificity.

Conclusion:

This study suggests that the ADC values of nodules measured with a 3T MRI scanner could help in differentiating benign thyroid nodules from malignant nodules. J. Magn. Reson. Imaging 2013;37:1077–1082. © 2012 Wiley Periodicals, Inc.

     

The role of ADC measurement in differential diagnosis of focal hepatic lesions

Purpose

To evaluate the utility of apparent diffusion coefficient (ADC) measurement in characterization of focal solid hepatic lesions and determine the role of ADC values in differentiation of solid benign and solid malignant hepatic lesions.

Materials and methods

Between June 2006 and December 2010, a total of 95 focal solid hepatic lesions in 95 consecutive patients were evaluated by abdominal MRI. Diffusion weighted MRI was performed with b 100, b 600 and b 1000 gradients with ADC measurements. Comparison of mean ADC values between solid benign (focal nodular hyperplasia and other solid benign lesions) and solid malignant lesion (hepatocellular carcinoma, metastasis, and cholangiocarcinoma) groups and between each benign and malignant lesion was done. The ROC analyses were performed in order to determine cut-off ADC values for differentiation of benign and malignant lesion groups at 3 different gradients.

Results

Twenty-six of 95 lesions were benign and 69 were malignant. Mean ADC values of solid benign lesions at b 100, b 600 and b 1000 gradients were 2.25 ± 0.54 × 10⁻³, 1.97 ± 0.64 × 10⁻³ and 1.52 ± 0.47 × 10⁻³ mm²/s, respectively. Mean ADC values of solid malignant lesions at b 100, b 600 and b 1000 gradients were 1.84 ± 0.57 × 10⁻³, 1.37 ± 0.38 × 10⁻³ and 1.08 ± 0.22 × 10⁻³ mm²/s, respectively. The ADC values of solid benign lesions were significantly higher than solid malignant lesions at all 3 gradients (P < 0.05). Differentiation of benign and malignant subtype lesions from each other in their groups did not yield as significant findings as comparing results between benign and malignant lesions.

Conclusion

Although ADC measurements were not helpful for differentiating subtypes of solid benign or solid malignant lesions, ADC measurements at 3 different gradients may be useful in differential diagnosis of benign lesions from malignant ones.     

Diffusion tensor MRI: Preliminary anisotropy measures and mapping of breast tumors

Purpose:

To investigate whether diffusion tensor imaging (DTI) measures of anisotropy in breast tumors are different from normal breast tissue and can improve the discrimination between benign and malignant lesions.

Materials and Methods:

The study included 81 women with 105 breast lesions (76 malignant, 29 benign). DTI was performed during breast MRI examinations, and fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were measured for breast lesions and normal tissue in each subject. FA and ADC were compared between cancers, benign lesions, and normal tissue by univariate and multivariate analyses.

Results:

The FA of carcinomas (mean ± SD: 0.24 ± 0.07) was significantly lower than normal breast tissue in the same subjects (0.29 ± 0.07; P < 0.0001). Multiple logistic regression showed that FA and ADC were each independent discriminators of malignancy (P < 0.0001), and that FA improved discrimination between cancer and normal tissue over ADC alone. However, there was no difference in FA between malignant and benign lesions (P = 0.98).

Conclusion:

Diffusion anisotropy is significantly lower in breast cancers than normal tissue, which may reflect alterations in tissue organization. Our preliminary results suggest that FA adds incremental value over ADC alone for discriminating malignant from normal tissue but does not help with distinguishing benign from malignant lesions. J. Magn. Reson. Imaging 2010; 31: 339–347. © 2010 Wiley‐Liss, Inc.     

Effect of b value and pre-admission of contrast on diagnostic accuracy of 1.5-T breast DWI: a systematic review and meta-analysis

Objectives

To evaluate the effect of the choice of b values and prior use of contrast medium on apparent diffusion coefficients (ADCs) of breast lesions derived from diffusion-weighted imaging (DWI), and on the discrimination between benign and malignant lesions.

Methods

A literature search of relevant DWI studies was performed. The accuracy of DWI to characterize lesions by using b value ≤600 s/mm² and b value >600 s/mm² was presented as pooled sensitivity and specificity, and the ADC was calculated for both groups. Lesions were pooled as pre- or post-contrast DWI.

Results

Of 198 articles, 26 met the inclusion criteria. Median ADCs were significantly higher (13.2–35.1 %, p?b values ≤600 s/mm² compared to >600 s/mm². The sensitivity in both groups was similar (91 % and 89 %, p?=?0.495) as well as the specificity (75 % and 84 %, p?=?0.237). Contrast medium had no significant effects on the ADCs (p?≥?0.08). The differentiation between benign and malignant lesions was optimal (58.4 %) for the combination of b?=?0 and 1,000 s/mm².

Conclusions

The wide variety of b value combinations applied in different studies significantly affects the ADC of breast lesions and confounds quantitative DWI. If only a couple of b values are used, those of b?=?0 and 1,000 s/mm² are recommended for the best improvement of differentiating between benign and malignant lesions.

Key Points

? The choice of b values significantly affects the ADC of breast lesions. ? Sensitivity and specificity are not affected by the choice of b values. ? b values 0 and 1,000 s/mm ² are recommended for optimal differentiation between benign and malignant lesions. ? Contrast medium prior to DWI does not significantly affect the ADC.     

Differential diagnosis of mammographically and clinically occult breast lesions on diffusion‐weighted MRI

Purpose:

To investigate the diagnostic performance of diffusion‐weighted imaging (DWI) for mammographically and clinically occult breast lesions.

Materials and Methods:

The study included 91 women with 118 breast lesions (91 benign, 12 ductal carcinoma in situ [DCIS], 15 invasive carcinoma) initially detected on dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) and assigned BI‐RADS category 3, 4, or 5. DWI was acquired with b = 0 and 600 s/mm². Lesion visibility was assessed on DWI. Apparent diffusion coefficient (ADC) values were compared between malignancies, benign lesions, and normal (no abnormal enhancement on DCE‐MRI) breast tissue, and the diagnostic performance of DWI was assessed based on ADC thresholding.

Results:

Twenty‐four of 27 (89%) malignant and 74/91 (81%) benign lesions were hyperintense on the b = 600 s/mm² diffusion‐weighted images. Both DCIS (1.33 ± 0.19 × 10^?3 mm²/s) and invasive carcinomas (1.30 ± 0.27 × 10^?3mm²/s) were lower in ADC than benign lesions (1.71 ± 0.43 × 10^?3mm²/s; P < 0.001), and each lesion type was lower in ADC than normal tissue (1.90 ± 0.38 × 10^?3mm²/s, P ≤ 0.001). Receiver operating curve (ROC) analysis showed an area under the curve (AUC) of 0.77, and sensitivity = 96%, specificity = 55%, positive predictive value (PPV) = 39%, and negative predictive value (NPV) = 98% for an ADC threshold of 1.60 × 10^?3mm²/s.

Conclusion:

Many mammographically and clinically occult breast carcinomas were visibly hyperintense on diffusion‐weighted images, and ADC enabled differentiation from benign lesions. Further studies evaluating DWI while blinded to DCE‐MRI are necessary to assess the potential of DWI as a noncontrast breast screening technique. J. Magn. Reson. Imaging 2010;1:562–570. © 2010 Wiley‐Liss, Inc.

     

Assessment of mediastinal tumors with diffusion‐weighted single‐shot echo‐planar MRI

Purpose

To assess the role of diffusion‐weighted single‐shot echo‐planar magnetic resonance imaging (MRI) in patients with mediastinal tumors.

Methods

Prospective study was conducted on 45 consecutive patients (29 male, 16 female, age 22–66 years, mean 41 years) with mediastinal tumor. They underwent diffusion‐weighted single‐shot echo‐planar MRI of the mediastinum with a b‐factor of 0, 300, and 600 sec/mm². The apparent diffusion coefficient (ADC) value of the mediastinal tumor was correlated with the histopathological findings.

Results

The mean ADC value of malignant mediastinal tumors was 1.09 ± 0.25 × 10^?3 mm²/sec, and of benign tumors was 2.38 ± 0.56 × 10^?3 mm²/sec. There was a significant difference in the mean ADC value between malignant and benign tumors (P = 0.001) and within different grades of malignancy (0.001). When an ADC value of 1.56 × 10^?3 mm²/sec was used as a threshold value for differentiating malignant from benign tumor, the best results were obtained with an accuracy of 95%, sensitivity of 96%, specificity of 94%, positive predictive value of 94%, negative predictive value of 96%, and area under the curve of 0.938.

Conclusion

The ADC value is a noninvasive parameter that can be used for differentiation of malignant from benign mediastinal tumors and grading of mediastinal malignancy. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.

     

Diffusion-weighted MRI in prostatic lesions: Diagnostic performance of normalized ADC using normal peripheral prostatic zone as a reference

Aim of study

Evaluate the potential value of the normal peripheral zone as a reference organ to normalize prostatic lesion apparent diffusion coefficient (ADC) to improve its evaluation of prostatic lesions.

Mediastinal lymph nodes: Assessment with diffusion‐weighted MR imaging

Purpose

To prospectively determine whether the diffusion‐weighted magnetic resonance imaging is useful to distinguish between malignant and benign mediastinal lymph nodes.

Materials and Methods

Thirty‐five patients (14 women, 21 men; mean age 52 years) with 91 lymph nodes in the mediastinum detected by computed tomography underwent 1.5 Tesla (T) diffusion‐weighted MR imaging before mediastinoscopy (n = 29) and mediastinotomy (n = 6). Diffusion‐weighted MR images were acquired with a b factor of 50, and 400 s/mm² using single‐shot echo‐planar sequence.

Results

Of the 35 patients, 18 had diagnosis of malignant tumor. Of the 18 patients with tumor, 8 had nonsmall cell carcinoma, and 10 had small cell carcinoma. Ninety‐one mediastinal lymph nodes were detected in the 35 untreated patients: 19 were pathologically diagnosed as metastatic lymph nodes, and 72 lymph nodes were diagnosed as nonmetastatic lymph nodes, including 50 sarcoidosis, 14 reactive lymphoid hyperplasia, and 8 necrotizing granulamatous lymphadenitis. The apparent diffusion coefficient (ADC) was significantly lower in metastatic lymph nodes (1.012 ± 0.025 × 10^?3 mm²/s; P < 0.0005) than in benign lymph nodes (1.511 ± 0.075 × 10^?3 mm²/s). On the ADC map, malignant nodes showed hyperintense (n = 2, 10.52%), hypointense (n = 14, 73.68%), and mixed intensity (n = 3; 15.78%), whereas benign nodes showed hyperintense (n = 57; 79.16%), hypointense (n = 3; 41.6%), isointense (n = 6; 8.33%), and mixed intensity (n = 6; 8.33%).

Conclusion

Diffusion‐weighted MR with ADC value and signal intensity can be useful in differentiation of malignant and benign mediastinal lymph nodes. J. Magn. Reson. Imaging 2009;30:292–297. © 2009 Wiley‐Liss, Inc.

     

Characterization of malignancy of adnexal lesions using ADC entropy: Comparison with mean ADC and qualitative DWI assessment

Purpose:

To establish the utility of apparent diffusion coefficient (ADC) entropy in discrimination of benign and malignant adnexal lesions, using histopathology as the reference standard, via comparison of the diagnostic performance of ADC entropy with mean ADC and with visual assessments of adnexal lesions on conventional and diffusion‐weighted sequences.

Materials and Methods:

In all, 37 adult female patients with an ovarian mass that was resected between June 2006 and January 2011 were included. Volume‐of‐interest was drawn to incorporate all lesion voxels on every slice that included the mass on the ADC map, from which whole‐lesion mean ADC and ADC entropy were calculated. Two independent radiologists also rated each lesion as benign or malignant based on visual assessment of all sequences. The Mann–Whitney test and logistic regression for correlated data were used to compare performance of mean ADC, ADC entropy, and the visual assessments.

Results:

No statistically significant difference was observed in mean ADC between benign and malignant adnexal lesions (P = 0.768). ADC entropy was significantly higher in malignant than in benign lesions (P = 0.009). Accuracy was significantly greater for ADC entropy than for mean ADC (0.018). ADC entropy and visual assessment by the less‐experienced reader showed similar accuracy (P ≥ 0.204). The more experienced reader's accuracy was significantly greater than that of all other assessments (P ≤ 0.039).

Conclusion:

ADC entropy showed significantly greater accuracy than the more traditional metric of mean ADC for distinguishing benign and malignant adnexal lesions. Although whole‐lesion ADC entropy provides a straightforward and objective measurement, its potential benefit decreases with greater reader experience. J. Magn. Reson. Imaging 2013;37:164–171. © 2012 Wiley Periodicals, Inc.     

Diffusion-weighted MR imaging for the diagnosis of abscess complicating fistula-in-ano: preliminary experience

Objective

To investigate the role of diffusion-weighted magnetic resonance imaging (DWMRI) in the diagnosis of abscess-complicating fistula-in-ano.

Methods

This retrospective study was approved by our Institutional Review Board and informed consent was waived. MRI examinations, including fat-suppressed T2-weighted turbo spin-echo (T2-TSE) MRI and DWMRI, of 24 patients with a fistula-in-ano, were reviewed by two independent readers for the presence and number of visible fistulas, conspicuity and apparent diffusion coefficient (ADC) measurement of suspected fistula tracks and pelvic collections. The reference standard was surgical with follow-up findings.

Results

Sensitivity was 91.2 % [95 % CI: 76 %-98 %] for T2-weighted TSE MRI and 100 % [95 % CI: 90 %-100 %] for DWMRI detecting fistulas. ADC values were lower in abscesses than in inflammatory masses (P?=?0.714.10^-6). The area under the ROC curve was 0.971 and the optimal cut-off ADC value was 1.186?×?10^-3 mm²/s, yielding a sensitivity of 100 % [95 % CI: 77 %-100 %], a specificity of 90 % [95 % CI: 66 %-100 %], a positive predictive value of 93 % [95 % CI: 82.8 %-100 %] and a negative predictive value of 90 % [95 % CI: 78 %-100 %] for an abscess diagnosis. Fistula conspicuity was greater with DWMRI than with T2-TSE MRI for the two observers (P?=?0.0034 and P?=?0.0007).

Conclusion

DWMRI shows high sensitivity and specificity for the diagnosis of perianal abscesses and helps discriminate between an abscess and inflammatory mass. Conspicuity of fistulas-in-ano is greater with DWMRI than with T2-weighted TSE MRI.

Key Points

? DWMRI can differentiate between pelvic abscess and inflammatory mass. ? DWMRI helps avoid gadolinium-chelate administration in patients with a suspected fistula-in-ano. ? DWMRI provides high degrees of conspicuity for fistula-in-ano. ? Conspicuity of fistulas is better with DWMRI imaging than with T2-TSE-weighted MRI.     

Diffusion-weighted MRI of fatty liver

Purpose:

To investigate the effect of fat infiltration on the apparent diffusion coefficient (ADC) of liver, and assess the relationship between ADC and hepatic fat fraction (HFF).

Materials and Methods:

MRI scans of 120 consecutive patients were included in this retrospective study. Of these, 42 patients were included in the fatty liver group and 78 in the control group. ADC values were measured from a pair of diffusion‐weighted (DW) images (b = 0 mm²/s and 1000 mm²/s). HFFs were measured using T1W GRE dual‐echo images. The difference between the ADCs of the two groups was assessed with the t‐test. The relationship between HFF and ADC was determined using linear regression analysis and the Pearson correlation coefficient (r).

Results:

Mean HFFs were 0.85 ± 2.86 and 13.67 ± 8.62 in the control and fatty liver groups, respectively. The mean ADC of fatty liver group 1.20 ± 0.22 × 10^?3 mm²/s was significantly lower than that of the control group 1.32 ± 0.23 × 10^?3 mm²/s (P = 0.02). Linear regression analysis revealed an inverse relationship between ADC and HFF (r = ?0.39, P < 0.0001).

Conclusion:

ADC significantly decreases in patients with >5% HFF, and ADC and HFF exhibit an inverse relationship. J. Magn. Reson. Imaging 2012;35:1109‐1111. © 2011 Wiley Periodicals, Inc.

     

The role of MR diffusion in differentiation of malignant and benign hepatic focal lesions

Aim

To determine if focal liver masses could be differentiated as benign or malignant by DWI and ADC maps.

Methods and materials

Sixty focal liver lesions were scanned using 1.5 T MRI. DWI was performed with b 0, b 500 and b 1000 gradients with ADC measurements. Comparison of mean ADC values between each benign and malignant lesion was done. Reference standard of diagnosis was obtained by correlating DWI with histopathologic findings and imaging follow-up. The accuracies of DWI and ADC values were assessed with the Student’s t test, and cut-off values were determined with receiver operating characteristic curve analysis.

Results

When ADC value of 1.0 × 10⁻³ mm²/s was used as a threshold value for differentiation of malignant tumors from benign lesions, sensitivity was 90.3%, specificity 78.57% and accuracy 86.7%. The best result was obtained with the use of ADC cut off value (at b 500) of 1.5 × 10⁻³ mm²/s and ADC cut off value (at b 1000) of 1.0 × 10⁻³ mm²/s, with 90.3% sensitivity, 92.86% specificity, 91.1% accuracy, 96.6% positive predictive value and 81.3% negative predictive value.

Conclusion

DWI and ADC map is a useful tool in differential diagnosis of malignant from benign liver lesions.     

Diffusion-weighted imaging of focal renal lesions: a meta-analysis

Objectives

Contrast-enhanced MRI can only distinguish to a limited extent between malignant and benign focal renal lesions. The aim of this meta-analysis is to review renal diffusion-weighted imaging (DWI) to compare apparent diffusion coefficient (ADC) values for different renal lesions that can be applied in clinical practice.

Methods

A PubMed search was performed to identify relevant articles published 2004–2011 on renal DWI of focal renal lesions. ADC values were extracted by lesion type to determine whether benign or malignant. The data table was finalised in a consensus read. ADC values were evaluated statistically using meta-regression based on a linear mixed model. Two-sided P value <5 % indicated statistical significance.

Results

The meta-analysis is based on 17 studies with 764 patients. Renal cell carcinomas have significant lower ADC values than benign tissue (1.61?±?0.08?×?10^-3 mm²/s vs 2.10?±?0.09?×?10^-3 mm²/s; P?<?0.0001). Uroepithelial malignancies can be differentiated by lowest ADC values (1.30?±?0.11?×?10^-3 mm²/s). There is a significant difference between ADC values of renal cell carcinomas and oncocytomas (1.61?±?0.08?×?10^-3 mm²/s vs 2.00?±?0.08?×?10^-3 mm²/s; P?<?0.0001).

Conclusions

Evaluation of ADC values can help to determine between benign and malignant lesions in general but also seems able to differentiate oncocytomas from malignant tumours, hence potentially reducing the number of unnecessarily performed nephrectomies.

Key Points

? This meta-analysis assesses the role of diffusion-weighted MRI in renal lesions. ? ADC values obtained by DW MRI have been compared for different renal lesions. ? ADC values can help distinguish between benign and malignant tumours. ? Differentiating oncocytomas from malignant tumours can potentially reduce inappropriate nephrectomies.     

Role of diffusion-weighted MR imaging in assessing malignant versus benign skull-base lesions

Purpose

This study was done to assess the role of diffusion-weighted magnetic resonance (MR) imaging in assessing malignant versus benign skull lesions.

Materials and methods

A retrospective analysis was undertaken of 45 patients (26 male, 19 female; age range 14?C68 years, mean age 39 years) with skull-base lesions. Diffusion-weighted MR images were acquired with a bfactor of 500 and 1,000 s/mm² using single-shot echoplanar imaging. Apparent diffusion coefficient (ADC) maps were reconstructed, and the ADC value of the lesion was calculated.

Results

The mean ADC value of malignant tumours was (1.002±0.21)×10^?3 mm²/s and that of benign tumours was (1.63±0.29)×10^?3 mm²/s. There was a statistically significant difference (p=0.001) in the ADC value of malignant skull-base tumours versus benign lesions. Selection of (1.3)×10^?3mm²/s as a threshold value of ADC for differentiating benign from malignant tumours yielded the best result, with an accuracy of 94%, sensitivity of 94%, specificity of 93%, positive predictive value of 93%, negative predictive value of 94% and area under the curve of 0.932.

Conclusions

We conclude that diffusion-weighted MR imaging is a promising, noninvasive approach that can be used to characterise skull-base lesions in that it can help differentiate malignant tumours from benign lesions and evaluate the pathological grading of malignant tumours.     

Role of MR spectroscopy and diffusion-weighted imaging in diagnosis of orbital masses

Purpose

To assess the value of (MRI), (DWI) and (MRS) in the diagnosis of different orbital masses and differentiation between benign and malignant masses.

Assessment of soft tissue tumours of the extremities with diffusion echoplanar MR imaging

Purpose

This study assessed soft tissue tumours of the extremities with diffusion echo-planar magnetic resonance (MR) imaging.

Materials and methods

We carried out a retrospective study of 37 patients (22 male, 15 female; age range 4?C68 years; mean age 41 years) with a soft tissue mass. Diffusion-weighted magnetic resonance (MR) imaging was done using echo-planar imaging (EPI) with b factor of 0.500 and 1,000 mm2/s. The apparent diffusion coefficient (ADC) map was reconstructed with calculation of the ADC values of the mass.

Results

The mean ADC value of the malignant tumours was 1.02±0.03×10^?3mm²/s and that of benign masses 1.54±0.03×10^?3mm²/s. There was a significant difference in the ADC values between malignant soft tissue tumours and benign masses (p<0.001) and within different grades of malignancy (p<0.02). Selection of 1.34×10^?3 mm²/s as a threshold ADC value for differentiating malignant soft tissue tumours from benign masses resulted in an accuracy of 91%, sensitivity of 94%, specificity of 88% and area under the curve of 0.869. There was a significant difference in the ADC value between well- and poorly differentiated malignancies (p=0.001).

Conclusions

Diffusion-weighted echo-planar MR imaging is a promising noninvasive modality that may be helpful in differentiating malignant soft tissue tumours from benign masses as well as in grading malignancy.     

Role of diffusion-weighted MR imaging in chest wall masses

Purpose

To determine the role of diffusion weighted MR imaging and apparent diffusion coefficient (ADC) in chest wall masses.

Materials and methods

This study included 62 patients with chest wall masses. They underwent routine MR imaging and diffusion MR weighted imaging on a 1.5 T MR unit (Symphony-Siemens). Diffusion MR imaging was done with diffusion factor b value of 0, 500, and 1000 s/mm². The apparent diffusion coefficient (ADC) map was reconstructed. The signal intensity was visually assessed on ADC maps and ADC value was measured in chest wall lesions. The mean ADC values correlated with histo-pathological results.

Results

Adequate ADC maps were obtained in 62 patients. The mean ADC values of chest wall lesions were 1.76 ± 0.08 × 10⁻³ mm²/s in inflammatory lesion, 3.21 ± 0.05 × 10⁻³ mm²/s in the cystic lesions, 1.67 ± 0.03 × 10⁻³ mm²/s in neurofibroma, 2.12 ± 0.07 × 10⁻³ in haemangioma, and 0.89 ± 0.06 × 10⁻³ mm²/s in malignant tumors. The mean ADC value of the malignant tumor was significantly different from that of benign chest wall tumors (P < 0.001).

Conclusion

Diffusion weighted MR imaging is a new imaging modality for differentiation malignant from benign chest wall masses. In addition, it has a role in characterization of different malignant and benign tumors.