Usefulness of diffusion-weighted MR imaging in the evaluation of pulmonary lesions

Purpose

The role of diffusion-weighted MR imaging (DWI) in the differential diagnosis of pulmonary malignant tumours and solid benign lesions was investigated.

Methods

Sixty-two patients with 66 lesions underwent conventional MRI and DWI (diffusion factor of 0 and 500 s/mm²) examinations with 1.5-T MRI. The signal intensity of DWI images was observed and the apparent diffusion coefficient (ADC) values of the lesions were measured. Statistical analyses were performed with the independent samples t test, Pearson’s chi-square test and receiver operating characteristic (ROC) analysis.

Results

The signal intensities of pulmonary malignant tumours and solid benign lesions were not significantly different, but the ADC value of benign lesions was statistically higher than that of malignant tumours (p?=?0.001). By ROC analysis, the optimal threshold of ADC was 1.400?×?10^–3 mm²/s and the sensitivity and specificity were 83.3% and 74.1%, respectively. There were statistical differences between small cell carcinoma (SCLC) and non-small cell carcinoma (NSCLC) as well; the former was lower than the latter (p?=?0.007).

Conclusion

Our data indicate that quantitative analysis of ADC values may help diagnose or distinguish pulmonary lesions, and it also provides a promising method for characterising the pulmonary masses.     

Accuracy of visual analysis vs. apparent diffusion coefficient quantification in differentiating solid benign and malignant focal liver lesions with diffusion-weighted imaging

Purpose

The authors compared the accuracy of diffusion-weighted imaging (DWI) visual analysis (VA) vs. apparent diffusion coefficient quantification (ADC-Q) in assessing malignancy of solid focal liver lesions (FLLs).

Materials and methods

Using a 1.5-T system, two radiologists retrospectively assessed as benign or malignant 50 solid FLLs: (a) by VA of signal intensity on DWI images at b=800 s/mm² and ADC map; (b) by quantifying lesion ADC. Reference standard included histology or follow-up confirmation of diagnosis by a consensus panel. Receiver operating characteristic (ROC) curve analysis was performed.

Results Because of 20 false-negative hepatocellular carcinomas, VA showed lower accuracy than ADC-Q (52.0% vs. 68.0%). However, stratified accuracy for metastases was higher with VA (75.0 vs. 66%). ADC and signal features of malignant and benign FLLs were found to largely overlap

Conclusions

VA performed worse than ADC-Q for hepatocellular carcinoma and better for metastases. Overall, the accuracy of both methods was limited because of the overlap in visual appearance and ADC values between solid benign and malignant FLLs.     

Diffusion-weighted imaging in breast lesion evaluation

Purpose

The purpose of this study was to investigate the ability of diffusion-weighted imaging (DWI) and the apparent diffusion coefficient (ADC) in the detection and characterisation of breast lesions.

Materials and methods

From September 2005 to September 2007, 86 patients with breast lesions who underwent magnetic resonance imaging (MRI) in our department were included in our study. MRI was performed with a 1.5-T unit using a standard protocol including DWI sequence. For each breast lesion, the ADC value was calculated and compared with that of normal breast tissue and to the definitive pathological diagnosis. Mann-Whitney U and Kruskal-Wallis tests were used for statistical analysis.

Results

A total of 126 breast lesions were detected. Pathology results revealed 100 malignant and 26 benign lesions. Mean diameter of lesions was 26.02 mm (range 4–90 mm), including 52 lesions ≤15 mm in size. Mean ADC value of normal glandular tissue was 1.55×10^?3 mm²/s. Mean ADC value of malignant lesions was 0.97×10^?3 mm²/s. Mean ADC value for benign lesions was 1.66×10^?3 mm²/s. Benign lesions showed ADC values significantly higher than malignant lesions (p<0.0001).

Conclusions

DWI provides reliable information to support MRI diagnosis of breast masses. ADC value appears a promising adjunctive parameter in distinguishing malignant from benign breast lesions.     

MRI-only lesions: application of diffusion-weighted imaging obviates unnecessary MR-guided breast biopsies

Objective

To assess if the application of diffusion-weighted imaging (DWI) obviates unnecessary MR-guided biopsies in suspicious breast lesions visible only on contrast-enhanced MRI (CE-MRI).

Methods

This institutional review board (IRB)-approved, retrospective, single-centre study included 101 patients (mean age, 49.5; SD 13.9 years) who underwent additional DWI at 1.5 T prior to MRI-guided biopsy of 104 lesions classified as suspicious for malignancy and visible on CE-MRI only. An experienced radiologist, blinded to histopathologic and follow-up results, measured apparent diffusion coefficient (ADC) values obtained from DWI. Diagnostic accuracy was investigated using receiver operating characteristics (ROC) analysis.

Results

Histopathology revealed 20 malignant and 84 benign lesions. Lesions were masses in 61 (15 malignant, 24.6 %) and non-masses in 43 cases (five malignant, 11.6 %). Mean ADC values were 1.53?±?0.38?×?10^?3 mm²/s in benign lesions and 1.06?±?0.27?×?10^?3 mm²/s in malignant lesions. ROC analysis revealed exclusively benign lesions if ADC values were greater than 1.58?×?10^?3 mm²/s. As a consequence, 29 false-positive biopsies (34.5 %) could have been avoided without any false-negative findings. Both in mass and in non-mass lesions, rule-in and rule-out criteria were identified using flexible ADC thresholds based on ROC analysis.

Conclusion

Additional application of DWI in breast lesions visible only on MRI can avoid false-positive, MR-guided biopsies. Thus, DWI should be an integral part of breast MRI protocols.

Key Points

? DWI measurements are a fast and helpful technique for improved breast lesion diagnosis ? DWI application in breast lesions visible only on MRI obviates false-positive, MR-guided biopsies ? Flexible ADC thresholds provide rule-in and rule-out criteria for breast lesion malignancy     

MR diffusion imaging and ADC measurement in solid and cystic mediastinal masses for differentiating benign from malignant lesions

Purpose

The purpose of this study is to evaluate the role of MR diffusion imaging (DWI) and apparent diffusion coefficient (ADC) measurement of solid and cystic mediastinal masses to differentiate benign from malignant 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.     

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.     

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.     

Application of the diffusion kurtosis model for the study of breast lesions

Objectives

To evaluate diffusion-weighted imaging (DWI) and diffusion kurtosis imaging (DKI) in the differentiation and characterisation of breast lesions.

Methods

Thirty-six women underwent breast magnetic resonance imaging (MRI) including a DWI sequence with multiple b-values (50–3,000 s/mm²). Mean values for apparent diffusion coefficient (ADC), mean diffusivity (MD) and mean kurtosis (MK) were calculated by lesion type and histological subtype. Differences and correlation between parameters were determined.

Results

Forty-four lesions were found. There were significant differences between benign and malignant lesions for all parameters (ADC, p?=?0.017; MD, p?=?0.028; MK, p?=?0.017). ADC and MD were higher for benign (1.96?±?0.41?×?10^?3 and 2.17?±?0.42?×?10^?3 mm²/s, respectively) than for malignant lesions (1.33?±?0.18?×?10^?3 and 1.52?±?0.50?×?10^?3 mm²/s). MK was higher for malignant (0.61?±?0.27) than benign lesions (0.37?±?0.18). We found differences between invasive ductal carcinoma (IDC) and fibroadenoma (FA) for all parameters (ADC, MD and MK): p?=?0.016, 0.022 and 0.016, respectively. FA and fibrocystic change (FC) showed differences only in MK (p?=?0.016).

Conclusions

Diffusion in breast lesions follows a non-Gaussian distribution. MK enables differentiation and characterisation of breast lesions, providing new insights into microstructural complexity. To confirm these results, further investigation in a broader sample should be performed.

Key Points

? The diffusion kurtosis model provides new information regarding breast lesions ? MD and MK are valid parameters to characterise tissue microstructure ? MK enables improved lesion differentiation ? MK is able to differentiate lesions that display similar ADC values     

Diffusion-weighted magnetic resonance imaging in focal breast lesions: analysis of 78 cases with pathological correlation

Purpose

This study assessed the usefulness of magnetic resonance diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions.

Materials and methods

Gadolinium-enhanced magnetic resonance imaging (MRI) and DWI with determination of the apparent diffusion coefficient (ADC) were performed on 78 women, each with a focal breast lesion at least 7 mm in diameter, which was studied by cytology or histology.

Results

Final diagnoses were obtained by cytology in 29 cases and histology in 49 (11 percutaneous biopsies and 38 surgical specimens). There were 43 benign lesions (13 fibrocystic disease, eight fibroadenoma, seven adenosis, five normal breast tissue, four inflammatory lesions, three intramammary lymph nodes, two scleroelastosis and one fat necrosis) and 35 malignant lesions (30 invasive ductal carcinoma, two invasive lobular carcinoma, one ductal carcinoma in situ, one carcinomatous mastitis and one metastasis from neuroendocrine carcinoma). The mean ADC values were 1.677±0.151 for benign lesions and 1.298±0.129 for malignant lesions (p<0.001). With an ADC cutoff value of 1.48, DWI had 88.6% sensitivity [confidence interval (CI) 78.1%?C99.1%] and 95.3% specificity (CI 88.9%?C100%), with 31 true positives, four false negatives (three invasive ductal carcinoma and one carcinomatous mastitis), 41 true negatives and two false positives (one fat necrosis and one fibroadenoma). With the cutoff value set at 1.52, DWI sensitivity (35 true positive, no false negative) was 100% and specificity was 86% (CI 75.7%?C96.3%) due to 37 true negatives and six false positives (an additional two fibroadenoma and two fibrocystic disease compared with those recorded with the cutoff set at 1.48). The overall accuracy of DWI considering both cutoff values (72 correct evaluations out of 78 cases) was 92.3% (CI 86.4%?C98.2%).

Conclusions

DWI is a reliable tool for characterising focal breast lesions.     

Diffusion-weighted MR imaging for the differentiation of malignant from benign strictures in the periampullary region

Objectives

To investigate the value of DWI for differentiating malignant from benign strictures in the periampullary region.

Methods

We retrospectively analysed data from 78 patients who had undergone magnetic resonance cholangiopanreatography (MRCP) and diffusion-weighted imaging (DWI), in whom biliary strictures in the periampullary region were suspected. Twenty-two malignant and 56 benign lesions were included. One radiologist compared the signal intensity of malignant and benign periampullary lesions on DWI using b?=?500 and 800 s/mm². The signal intensity of bile was also compared, and an optimal b value was determined for periampullary lesions. Two other radiologists reviewed MRCP alone and combined DWI and MRCP for the possibility of malignant periampullary lesions. Diagnostic accuracy was calculated for each reviewer by receiver operating characteristic (ROC) curve analysis.

Results

Malignant periampullary lesions more frequently appeared hyperintense than benign lesions on DWI using the two b values (P?<?0.001). Bile more frequently appeared hyperintense on DWI using b?=?500 s/mm² (87.2 %) than b?=?800 s/mm² (24.4 %). Therefore, b?=?800 s/mm² was determined as the preferred sequence. Diagnostic accuracy for malignant periampullary lesions improved for both reviewers after adding DWI; from 0.714 to 0.924 (P?=?0.006, for reviewer 1) and from 0.714 to 0.919 (P?=?0.007, reviewer 2).

Conclusions

Combined DWI with MRCP can improve the diagnostic accuracy for differentiating malignant from benign strictures in the periampullary region.

Key Points

? Diffusion-weighted magnetic resonance imaging provides yet more information about hepatobiliary structures. ? Diffusion-weighted imaging (DWI) has now been applied to the biliary tree. ? Most periampullary carcinomas appear hyperintense on high b value DWI. ? DWI can help differentiate between malignant and benign periampullary lesions.     

Use of diffusion-weighted imaging (DWI) in PET/MRI for head and neck cancer evaluation

Objective

The purpose of this study was to analyze whether diffusion-weighted imaging (DWI) adds significant information to positron emission tomography/magnetic resonance imaging (PET/MRI) on lesion detection and characterization in head and neck cancers.

Methods

Seventy patients with different head and neck cancers were enrolled in this prospective study. All patients underwent sequential contrast-enhanced (ce) PET/computed tomography (CT) and cePET/MRI using a tri-modality PET/CT-MR setup either for staging or re-staging. First, the DWI alone was evaluated, followed by the PET/MRI with conventional sequences, and in a third step, the PET/MRI with DWI was evaluated. McNemar’s test was used to evaluate differences in the accuracy of PET/MRI with and without DWI compared to the standard of reference.

Results

One hundred eighty-eight (188) lesions were found, and of those, 118 (62.8 %) were malignant and 70 (37.2 %) were benign. PET/MRI without DWI had a higher accuracy in detecting malignant lesions than DWI alone (86.8 % vs. 60.6 %, p?Conclusion The use of DWI as part of PET/MRI to evaluate head and neck cancers does not provide remarkable information. Thus, the use of DWI might not be needed in clinical PET/MRI protocols for the staging or restaging of head and neck cancers.     

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.

     

Comparison between MRI with spin-echo echo-planar diffusion-weighted sequence (DWI) and histology in the diagnosis of soft-tissue tumours

Purpose

Our aim was to assess the usefulness of magnetic resonance imaging (MRI) with spin-echo echo-planar diffusion-weighted sequences (SE-EPI-DWI) in the study of primary and secondary soft-tissue tumours by correlating the results of imaging and histology.

Material and methods

We retrospectively studied 23 patients (14 men, 9 women; age range 25?C87 years) affected by soft-tissue lesions. The MRI study was performed with baseline and contrast-enhanced SE-T1, proton density/T2-weighted (PD/T2), fat-saturated (FATSAT) DP/T2 and single-shot SE-EPI-DWI (b value 50-400- 800s/mm2) sequences.

Results

We identified 7/23 benign lesions (three myxoid, four nonmyxoid) and 16/23 malignant tumours (four myxoid, 12 nonmyxoid) with a mean diameter between 21 mm and 20 cm. Qualitative analysis of DWI showed persistence of high signal intensity for increasing b-values in all malignant tumours. Quantitative DWI analysis of the apparent diffusion coefficient (ADC) maps showed a statistical difference between benign and malignant lesions.

Conclusions

In our experience, DWI with qualitative and quantitative analysis correlated well with histology.     

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.

The value of diffusion-weighted MRI in the diagnosis of malignant and benign urinary bladder lesions

Objectives

To investigate the role of diffusion-weighted MRI (DWI) in the diagnosis of urinary bladder (UB) tumours by means of measuring apparent diffusion coefficient (ADC) values.

Methods

A total of 83 people aged between 18 and 86 years were included in the study: 63 patients with UB pathology (46 malignant, 17 benign) constituted the case group; 20 individuals without any UB pathology constituted the control group. DWI was applied to all individuals. The ADC values were measured based on the tissue of the UB mass entities and normal UB wall in the control group.

Results

The mean ADC value in the UB carcinoma group was significantly lower than that in the control group: 1.0684 ± 0.26 × 10⁻³ mm² s^–1 and 2.010 ± 0.11 × 10⁻³ mm² s^–1, respectively (p<0.01). There was a significant difference among the mean ADC values of different grades of malignant tumours, corresponding to 0.9185 ± 0.20 mm² s^–1 and 1.281 ± 0.18 mm² s^–1 in high-grade and low-grade malignant UB carcinomas, respectively (p<0.01). The ADC value in the carcinoma group was significantly lower than that in the benign lesion group: 1.0684 ± 0.26 × 10⁻³ mm² s^–1 and 1.803 ± 0.19 × 10⁻³ mm² s^–1, respectively (p<0.01). All 46 malignant lesions displayed a restriction in diffusion; 4 of the 17 benign lesions displayed a mild restriction in diffusion. The sensitivity, specificity and accuracy of DWI in the diagnosis of malignant UB lesions was 100%, 76.5% and 93.65%, respectively.

Conclusion

DWI can be beneficial in the differentiation of benign and malignant UB lesions, as well as of high-grade and low-grade UB carcinomas, using quantitative ADC measurements.In recent years, a number of different MRI methods together with conventional ones have been used as part of a routine radiodiagnostic application. Diffusion-weighted MRI (DWI) is considered to be such an imaging method, evaluated within the context of functional MRI and based on the measurement of the accelerated or decelerated microscopic diffusion movements in the protons of the tissues'' water molecules. Images can be obtained in short-period snapshots and do not require any contrast [1-4].The use of DWI had previously been limited to brain examinations because it is sensitive to cardiac, respiratory and peristaltic movements; however, it has been adopted for a much broader use, i.e. for other parts of the body, with the development of fast MRI sequences such as echoplanar imaging (EPI). In early studies, the diffusion-weighted images and the apparent diffusion coefficient (ADC) of tissues and lesions were measured, and the different values obtained were shown to be useful in the differential diagnosis. In later studies, it was reported that ADC vales were related to the cellular intensity of a tumour, and a significant reduction in ADC indicated a malignant tumour [1-4].In DWI studies conducted on patients with head and neck lesions, the mean ADC level was significantly lower in malignant lymphomas, moderately low in patients with carcinomas, moderately high in those with a benign solid masses and markedly higher in those with benign cystic lesions [5].In recent years, DWI has been adopted for widespread use in abdominal examinations. In DWI studies conducted on liver masses, patients with metastatic lesions and hepatocellular carcinoma showed significantly lower ADC levels, those with cavernous haemangiomas showed moderately higher ADC levels, and those with cysts showed markedly higher ADC levels [6].There are also studies reporting that benign renal tumours have much higher ADC values than malignant tumours, and that cystic renal lesions have much higher ADC values than benign solid renal tumours [7].Various researchers in different studies have pointed out that DWI can be an important diagnostic tool in the detection and characterisation of tumours in different regions such as breast, prostate, bladder, cervix, colon, ovary, pancreas and liver. In these studies, it was also indicated that malignant tumours showed much more diffusion restriction and much lower ADC levels than benign tumours owing to their cellularity [8,9].Although DWI studies conducted on bladder masses have not been reported on a broader scale, there has been an increasing tendency to conduct such studies recently. In these studies, the mean ADC levels in bladder tumours have been compared with the surrounding soft tissues and statistically significant results have been obtained. ADC levels in bladder carcinomas were found to be significantly lower than those of the surrounding soft tissues. DWI was also found to have a high sensitivity and specificity in the detection of bladder tumours [10,11].In this study, the mean ADC values obtained from malignant and benign urinary bladder wall pathologies in patients referred to our clinic with a prediagnosis of bladder tumour were compared with the mean ADC values of normal bladder wall in the control group. Also, the ADC levels of the histopathological subgroups of patients with urinary bladder carcinomas were compared among each other. Our aim was to investigate whether DWI could be used in the differentiation of malignant and benign urinary bladder lesions, and whether ADC values found in malignancies could provide any information about the nature of the malignant masses, and thus to research the diagnostic contribution of DWI in standard treatment protocols.     

Diffusion-weighted magnetic resonance imaging of breast lesions: the influence of different fat-suppression techniques on quantitative measurements and their reproducibility

Objective

The aim of this study was to evaluate the influence of different fat-suppression techniques on quantitative measurements and their reproducibility when applied to diffusion-weighted imaging (DWI) of breast lesions.

Methods

Twenty-five patients with different types of breast lesions were examined on a clinical 1.5-T magnetic resonance imaging (MRI) system. Two diffusion-weighted sequences with different fat-suppression methods were applied: one with spectral presaturation by inversion recovery (SPIR), and one with short-TI inversion recovery (STIR). The acquisition of both sequence variants was repeated with modified shim volume. Lesion-to-background contrast (LBC), apparent diffusion coefficients (ADC) ADC(0,1000) and ADC(50,1000), and their coefficients of variation (CV) were determined.

Results

In four patients, the image quality of DWI with SPIR was insufficient. In the other 21 patients, 46 regions of interest (ROI), including 11 malignant and 35 benign lesions, were analysed. The LBC, ADC(0,1000) and ADC(50,1000) values, which did not differ between initial and repeated measurements, were significantly higher for STIR than for SPIR. The mean CV improved from 10.8 % to 4.0 % (P?=?0.0047) for LBC, from 6.3 % to 2.9 % (P?=?0.0041) for ADC(0,1000), and from 6.3 % to 2.6 % (P?=?0.0049) for ADC(50,1000).

Conclusion

For STIR compared to SPIR fat suppression, improved lesion conspicuity, higher ADC values, and better measurement reproducibility were found in breast DWI.

Key Points

? Quality of fat suppression influences quantitative DWI breast lesion measurements. ? In breast DWI, STIR fat suppression worked more reliably than SPIR. ? Lesion-to-background contrast and its reproducibility were significantly higher with STIR fat suppression. ? Lesional ADCs and their reproducibility were significantly higher with STIR fat suppression.     

Diffusion-weighted imaging of solid or predominantly solid gynaecological adnexial masses: is it useful in the differential diagnosis?

Objectives

This study investigated whether diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values provide specific information that allows the diagnosis of solid or predominantly solid gynaecological adnexial lesions, especially whether they can discriminate benign and malignant lesions.

Methods

DWI was performed in 37 patients with histologically proven solid or predominantly solid adnexial lesions (22 malignant and 15 benign neoplasms). The lesions in our data set were divided into two groups, all adnexial lesions or lesions of ovarian origin, for evaluation. The areas of the highest signal intensity on DWI (b = 800 s mm⁻²) and the lowest ADC values within the lesions were evaluated.

Results

On DWI, high signal intensity was observed more often in malignant than in benign lesions (p<0.0001). There was no significant difference between the ADC values of the malignant and benign lesions in either the adnexial (0.88±0.16 vs 0.84±0.42; p = 0.96) or the ovarian (0.85±0.14 vs 1.05±0.2; p = 0.133) lesions. When signal intensities on DWI were compared, however, malignant lesions had higher values than the benign lesions in both the adnexial (0.69±0.21 vs 0.29±0.13; p<0.0001) and the ovarian lesions (0.75±0.14 vs 0.37±0.24; p = 0.003).

Conclusion

On DWI, high signal intensity was observed more frequently with the malignant lesions.MRI plays an important role in the diagnosis of gynaecological adnexial lesions [1-4]. It provides useful information for the characterisation of various ovarian, uterine and tubal masses. Some morphological and signal intensity features of the lesions on MRI are very important for the differential diagnosis [5], but this information may sometimes be non-specific. Many studies have looked at the utility of diffusion-weighted MRI in the differential diagnosis of benign and malignant gynaecological lesions [6]. In particular, the contributions of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values in differentiating between cystic benign lesions and malignant ovarian and uterine lesions have been evaluated [6]. Only one investigation used DWI to assess the solid components of ovarian lesions in a wide study population [11]. To our knowledge, the utility of DWI and ADC values in assessing solid or predominantly solid gynaecological adnexial masses has not been investigated previously.In this study, our goal was to investigate whether DWI and ADC values provide specific information that can diagnose solid or predominantly solid gynaecological adnexial lesions, in particular, whether these parameters can discriminate benign and malignant lesions.     

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.     

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.