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.     

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.     

Diffusion-weighted magnetic resonance imaging for assessment of lung lesions: repeatability of the apparent diffusion coefficient measurement

Purpose

To establish repeatability of apparent diffusion coefficients (ADCs) acquired from free-breathing diffusion-weighted magnetic resonance imaging (DW-MRI) in malignant lung lesions and investigate effects of lesion size, location and respiratory motion.

Methods

Thirty-six malignant lung lesions (eight patients) were examined twice (1- to 5-h interval) using T1-weighted, T2-weighted and axial single-shot echo-planar DW-MRI (b?=?100, 500, 800 s/mm²) during free-breathing. Regions of interest around target lesions on computed b?=?800 s/mm² images by two independent observers yielded ADC values from maps (pixel-by-pixel fitting using all b values and a mono-exponential decay model). Intra- and inter-observer repeatability was assessed per lesion, per patient and by lesion size (> or <2 cm) or location.

Results

ADCs were similar between observers (mean ± SD, 1.15?±?0.28?×?10^-3 mm²/s, observer 1; 1.15?±?0.29?×?10^-3 mm²/s, observer 2). Intra-observer coefficients of variation of the mean [median] ADC per lesion and per patient were 11 % [11.4 %], 5.7 % [5.7 %] for observer 1 and 9.2 % [9.5 %], 3.9 % [4.7 %] for observer 2 respectively; inter-observer values were 8.9 % [9.3 %] (per lesion) and 3.0 % [3.7 %] (per patient). Inter-observer coefficient of variation (CoV) was greater for lesions <2 cm (n?=?20) compared with >2 cm (n?=?16) (10.8 % vs 6.5 % ADC_mean, 11.3 % vs 6.7 % ADC_median) and for mid (n?=?14) vs apical (n?=?9) or lower zone (n?=?13) lesions (13.9 %, 2.7 %, 3.8 % respectively ADC_mean; 14.2 %, 2.8 %, 4.7 % respectively ADC_median).

Conclusion

Free-breathing DW-MRI of whole lung achieves good intra- and inter-observer repeatability of ADC measurements in malignant lung tumours.

Key Points

? Diffusion-weighted MRI of the lung can be satisfactorily acquired during free-breathing ? DW-MRI demonstrates high contrast between primary and metastatic lesions and normal lung ? Apparent diffusion coefficient (ADC) measurements in lung tumours are repeatable and reliable ? ADC offers potential in assessing response in lung metastases in clinical trials     

Optimising diffusion-weighted imaging in the abdomen and pelvis: comparison of image quality between monopolar and bipolar single-shot spin-echo echo-planar sequences

Objective

To compare geometric distortion, signal-to-noise ratio (SNR), apparent diffusion coefficient (ADC), efficacy of fat suppression and presence of artefact between monopolar (Stejskal and Tanner) and bipolar (twice-refocused, eddy-current-compensating) diffusion-weighted imaging (DWI) sequences in the abdomen and pelvis.

Materials and methods

A semiquantitative distortion index (DI) was derived from the subtraction images with b?=?0 and 1,000 s/mm² in a phantom and compared between the two sequences. Seven subjects were imaged with both sequences using four b values (0, 600, 900 and 1,050 s/mm²) and SNR, ADC for different organs and fat-to-muscle signal ratio (FMR) were compared. Image quality was evaluated by two radiologists on a 5-point scale.

Results

DI was improved in the bipolar sequence, indicating less geometric distortion. SNR was significantly lower for all tissues and b values in the bipolar images compared with the monopolar (p?<?0.05), whereas FMR was not statistically different. ADC in liver, kidney and sacrum was higher in the bipolar scheme compared to the monopolar (p?<?0.03), whereas in muscle it was lower (p?=?0.018). Image quality scores were higher for the bipolar sequence (p?≤?0.025).

Conclusion

Artefact reduction makes the bipolar DWI sequence preferable in abdominopelvic applications, although the trade-off in SNR may compromise ADC measurements in muscle.     

Diffusion-weighted MR imaging in liver metastases of colorectal cancer: reproducibility and biological validation

Objectives

Before diffusion-weighted imaging (DWI) can be implemented in standard clinical practice for response monitoring, data on reproducibility are needed to assess which differences outside the range of normal variation can be detected in an individual patient. In this study we assessed the reproducibility of the apparent diffusion coefficient (ADC) values in colorectal liver metastases. To provide a biological basis for these values, their relation with histopathology was assessed.

Methods

DWI was performed twice in 1 week in patients scheduled for metastasectomy of colorectal liver metastases. Correlation between ADC values and apoptosis marker p53, anti-apoptotic protein BCL-2, proliferation marker Ki67 and serum vascular endothelial growth factor (VEGF) concentration were assessed.

Results

A good reproducibility coefficient of the mean ADC (coefficient of reproducibility 0.20 × 10^?3?mm²/s) was observed in colorectal liver metastases (n?=?21). The ADC value was related to the proliferation index and BCL-2 expression of the metastases. Furthermore, in metastases recently treated with systemic therapy, the ADC was significantly higher (1.27 × 10^?3?mm²/s vs 1.05 × 10^?3?mm²/s, P?=?0.02).

Conclusions

The good reproducibility, correlation with histopathology and implied sensitivity for systemic treatment-induced anti-tumour effects suggest that DWI might be an excellent tool to monitor response in metastatic colorectal cancer.

Key Points

? ADC values are becoming important oncological biomarkers ? DWI provides reproducibile ADC values in colorectal liver metastases ? The coefficient of reproducibility of the mean ADC is 0.20 × 10 ^?3 ? mm ² /s ? ADC values correlate with proliferation index and are related to BCL-2 expression     

Dynamic characteristics of MR diffusion-weighted imaging in a rabbit liver VX-2 tumor model

Purpose

To investigate prospectively dynamic characteristics of the apparent diffusion coefficient (ADC) on MR diffusion-weighted imaging (DWI) in a rabbit VX-2 tumor model.

Materials and methods

Forty New Zealand rabbits were included in the study, and 47 rabbit VX-2 tumor models were developed by direct and intrahepatic implantation after opening the abdominal cavities. DWI was carried out periodically and respectively on days 7, 14 and 21 after implantation. The VX-2 tumor samples were studied by pathology. The distinction of VX-2 tumors on DWI was assessed by their ADC values by analysis of variance (ANOVA) using SPSS12.0 software.

Results

The ADC values (mean ± SD) × 10^?3 mm²/s of 47 VX-2 tumors in the peripheral and central areas were 2.18 ± 0.29, 1.96 ± 0.33, 1.80 ± 0.35, 2.20 ± 0.29, 2.05 ± 0.30 and 1.96 ± 0.48, respectively, on days 7, 14 and 21 after implantation. ADC values of 47 VX-2 tumors in the area of the tumor periphery, center and normal parenchyma were higher when the b-value was 100 s/mm² than those when the b-value was 300 s/mm² (F = 17.964, p < 0.001; F = 13.986, p < 0.001; F = 128.681, p < 0.001). ADC values in the area of normal liver parenchyma were higher than those in the area of the VX-2 tumor periphery and center when the b-value was 100 or 300 s/mm². ADCs of viable tumor cells in VX-2 tumors were lower on DWI than those in the area of normal liver parenchyma around the tumor, and ADCs of dead tumor cells in VX-2 tumors were unequal, including high, equal and low values, but they were higher than in the area of normal liver parenchyma around tumors after dead tumor cells had been liquefied or had become cystic.

Conclusion

ADC is correlated with the tumor histology and degree of malignancy, and DWI has potential value for dynamically monitoring tumors and evaluating the degree of malignancy and therapeutic effect.     

Characterization of soft tissue masses: can quantitative diffusion weighted imaging reliably distinguish cysts from solid masses?

Objective

To investigate the accuracy of quantitative diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping for characterizing soft tissue masses (STMs) as cysts or solid masses.

Materials and methods

This IRB-approved retrospective study included 36 subjects with 37 STMs imaged by conventional MRI (T1-weighted, T2-weighted, contrast-enhanced T1-weighted sequences) and DWI (b-values 50, 400, 800 s/mm²) with ADC mapping. STMs were defined as non-solid cysts by histology or clinical follow-up, and as solid by histology. For each STM, ADC values (range, mean) were recorded by two observers. Differences between ADC values in cysts and solid STMs were compared using Wilcoxon rank-sum and receiver-operating characteristic (ROC) analysis.

Results

There were higher minimum (1.65 vs 0.68, p?=?0.003) and mean (2.31 vs 1.45, p?=?0.005) ADC values in cysts than solid STMs respectively. Areas under the ROC for minimum and mean ADC values were 0.82 and 0.81 respectively. Using threshold ADC values of 1.8 (minimum) or 2.5 (mean) yielded a sensitivity of 60 % and 80 % respectively, and a specificity of 100 % for classifying a STM as a cyst; for tumors with high fluid–signal intensity, the performance of these threshold values was maintained.

Conclusion

Diffusion-weighted imaging with ADC mapping provides a non-contrast MRI alternative for the characterization of STMs as cysts or solid masses. Threshold ADC values exist that provide 100 % specificity for differentiating cysts and solid STMs, even for tumors of high fluid–signal intensity on T2-weighted images.     

Characterization and therapy monitoring of head and neck carcinomas using diffusion-imaging-based intravoxel incoherent motion parameters—preliminary results

Introduction

Using the intravoxel incoherent motion (IVIM) model, diffusion-related coefficient (D) and perfusion-related parameter (f) can be measured. Here, we used IVIM imaging to characterize squamous cell carcinomas of head and neck (HNSCC) and evaluated its application in follow-up after nonsurgical organ preserving therapy.

Methods

Twenty-two patients with locally advanced HNSCC (clinical stage III to IVb) were examined before treatment using eight different b values (b?=?0, 50, 100, 150, 200, 250, 700, 800 s/mm²). All patients were followed for at least 7.5 months after conclusion of therapy. In 16 of these patients, follow-up MRI was available. Using the IVIM approach, f and D were extracted using a bi-exponential fit. For comparison, ADC maps were calculated.

Results

The initial values of f before therapy were located between 5.9 % and 12.9 % (mean: 9.4?±?2.4 %) except for two outliers (f?=?17.9 % and 18.2 %). These two patients exclusively displayed poor initial treatment response. Overall, high initial f (13.1?±?4.1 % vs. 9.1?±?2.4 %) and ADC (1.17?±?0.08?×?10^?3?mm²/s vs. 0.98?±?0.19?×?10^?3?mm²/s) were associated with poor short term outcome (n?=?6) after 7.5 months follow-up. D values before treatment were 0.98?×?10^?3?±?0.18 mm²/s and ADC values were 1.03?×?10^?3?±?0.18 mm²/s. At follow-up, in all primary responders, D (69?±?52 %), f (65?±?46 %), and ADC (68?±?49%) increased.

Conclusions

Our preliminary evaluation indicates that an initial high f may predict poor prognosis in HNSCC. In responders, a significant increase of all IVIM parameters after therapy was demonstrated.     

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.     

Intravoxel incoherent motion model-based liver lesion characterisation from three b-value diffusion-weighted MRI

Objective

To evaluate intravoxel incoherent motion (IVIM) model-based liver lesion characterisation from three b-value diffusion-weighted imaging (DWI).

Methods

The 1.5-T DWI data from a respiratory gated spin-echo echo-planar magnetic resonance imaging sequence (b?=?0, 50, 800 s/mm²) were retrospectively analysed in 38 patients with different liver lesions. Conventional apparent diffusion coefficient ADC?=?ADC(0,800) as well as IVIM-based parameters D′?=?ADC(50,800), ADC_low?=?ADC(0,50), and f′ were calculated voxel-wise. Sixty-one regions of interest in hepatocellular carcinomas (HCCs, n?=?24), haemangiomas (HEMs, n?=?11), focal nodular hyperplasias (FNHs, n?=?11), and healthy liver tissue (REFs, n?=?15) were analysed. Group differences were investigated using Student’s t-test and receiver-operating characteristic (ROC) analysis.

Results

Mean values?±?standard deviations of ADC, D′, ADC_low (in 10^-5 mm²/s), and f′ (in %) for REFs/FNHs/HEMs/HCCs were 130?±?11/143?±?27/168?±?16/113?±?25, 104?±?12/123?±?25/162?±?18/102?±?23, 518?±?66/437?±?97/268?±?69/283?±?120, and 18?±?3/14?±?4/6?±?3/9?±?5, respectively. Differences between lesions and REFs were more significant for IVIM-based parameters than for conventional ADC. ROC analysis showed the best discriminability between HCCs and FNHs for ADC_low and f′ and between HEMs and FNHs or HCCs for D′.

Conclusion

Three instead of two b-value DWI enables a numerically stable and voxel-wise IVIM-based analysis for improved liver lesion characterisation with tolerable acquisition time.

Key Points

? Quantitative analysis of diffusion-weighted MRI helps liver lesion characterisation. ? Analysis of intravoxel incoherent motion is superior to apparent diffusion coefficient determination. ? Only three b-values enable separation of diffusion and microcirculation effects. ? The method presented is numerically stable, with voxel-wise results and short acquisition times.     

Apparent diffusion coefficient modifications in assessing gastro-oesophageal cancer response to neoadjuvant treatment: comparison with tumour regression grade at histology

Objectives

To assess changes in apparent diffusion coefficient (ΔADC) and volume (ΔV) after neoadjuvant treatment (NT), and tumour regression grade (TRG) in gastro-oesophageal cancers (GEC), and to discriminate responders from non-responders.

Methods

Thirty-two patients with biopsy-proven locally-advanced GEC underwent diffusion weighted magnetic resonance imaging (DWI) pre- and post-NT. Lesion ADC, volume, ΔADC and ΔV were calculated. TRG 1-2-3 patients were classified as R; TRG 4-5 as non-responders. ΔADC-TRG and ΔV-TRG correlations, pre-NT and post-NT ADC, ΔADC and ΔV cut-off values for responders and non-responders were calculated. Two readers measured mean tumour ADCs and interobserver variability was calculated. (Spearman’s and intraclass correlation coefficient [ICC]).

Results

The interobserver reproducibility was very good both for pre-NT (Spearman’s rho?=?0.8160; ICC?=?0.8993) and post-NT (Spearman’s rho?=?0.8357; ICC?=?0.8663). Responders showed lower pre-NT ADC (1.32 versus 1.63?×?10^?3?mm²/s; P?=?0.002) and higher post-NT ADC (2.22 versus 1.51?×?10^?3?mm²/s; P?=?0.001) than non-responders and ADC increased in responders (ΔADC, 85.45 versus ?8.21 %; P?=?0.00005). ΔADC inversely correlated with TRG (r?=??0.71, P?=?0.000004); no difference in ΔV between responders and non-responders (?50.92 % versus ?14.12 %; P?=?0.068) and no correlation ΔV-TRG (r?=?0.02 P?=?0.883) were observed.

Conclusions

The ADC can be used to assess gastro-oesophageal tumour response to neoadjuvant treatment as a reliable expression of tumour regression.

Key Points

? DWI is now being used to assess many cancers. ? Change in ADC measurements offer new information about oesophageal tumours. ? ADC changes are more reliable than dimensional criteria in assessing neoadjuvant treatment. ? Such ADC assessment could optimise management of locally advanced gastro-oesophageal cancers.     

Correlations between diffusion-weighted imaging and breast cancer biomarkers

Objective

We evaluated whether the apparent diffusion coefficient (ADC) provided by diffusion-weighted imaging (DWI) varies according to biological features in breast cancer.

Methods

DWI was performed in 190 patients undergoing dynamic contrast-enhanced magnetic resonance imaging (MRI) for local staging. For each of the 192 index cancers we studied the correlation between ADC and classical histopathological and immunohistochemical breast tumour features (size, histological type, grade, oestrogen receptor [ER] and Ki-67 expression, HER2 status). ADC was compared with immunohistochemical surrogates of the intrinsic subtypes (Luminal A; Luminal B; HER2-enriched; triple-negative). Correlations were analysed using the Mann–Whitney U and Kruskal–Wallis H tests.

Results

A weak, statistically significant correlation was observed between ADC values and the percentage of ER-positive cells (-0.168, P?=?0.020). Median ADC values were significantly higher in ER-negative than in ER-positive tumours (1.110 vs 1.050?×?10^-3?mm²/s, P?=?0.015). HER2-enriched tumours had the highest median ADC value (1.190?×?10^-3?mm²/s, range 0.950–2.090). Multiple comparisons showed that this value was significantly higher than that of Luminal A (1.025?×?10^-3?mm²/s [0.700–1.340], P?=?0.004) and Luminal B/HER2-negative (1.060?×?10^-3?mm²/s [0.470–2.420], P?=?0.008) tumours. A trend towards statistical significance (P?=?0.018) was seen with Luminal B/HER2-positive tumours.

Conclusions

ADC values vary significantly according to biological tumour features, suggesting that cancer heterogeneity influences imaging parameters.

Key Points

? DWI may identify biological heterogeneity of breast neoplasms. ? ADC values vary significantly according to biological features of breast cancer. ? Compared with other types, HER2-enriched tumours show highest median ADC value. ? Knowledge of biological heterogeneity of breast neoplasm may improve imaging interpretation.     

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     

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     

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.     

The value of apparent diffusion coefficient in the assessment of cervical cancer

Objectives

To evaluate the potential value of apparent diffusion coefficient (ADC) measurement in the assessment of cervical cancer.

Methods

One hundred twelve patients with cervical cancer and 67 control subjects underwent diffusion-weighted imaging (DWI) in addition to routine MR imaging at 3.0-T MRI before therapy. All ADCs were calculated from b?=?0, 600 s/mm² and b?=?0, 1,000 s/mm².

Results

The ADCs of cervical cancer were significantly lower than those of normal cervix for both ADC maps. There was a statistically significant difference between the ADCs of well-/moderately differentiated (G1/2) tumours and poorly differentiated (G3) tumours, between the ADCs of squamous cell carcinoma and adenocarcinoma, between the pretherapy ADCs of tumour recurrence or metastasis and tumour free patients after radical hysterectomy for both ADC maps. There was no significant difference among the ADCs of cervical cancer when divided by other features (FIGO, lymph node status, tumour size and age groups) for both ADC maps.

Conclusion

ADC values were reliable for differentiating cervical cancer from normal cervix with high diagnostic accuracy. The ADCs can be used to indicate the degree and histological type of cervical cancer, although there is some overlap. G3 tumours and lower ADCs may indicate poor prognosis. The diagnostic accuracy was equal for both ADC maps.

Key Points

? Diffusion-weighted magnetic resonance imaging provides new information about cervical cancer ? Apparent diffusion coefficient values can differentiate cervical cancer from normal cervical tissue ? Pretherapy ADCs can also predict the prognosis for patients who have undergone radical hysterectomy ? ADCs can help indicate the degree and histological type of cervical cancer ? Patients with G3 tumours and lower ADCs may benefit from preoperative chemoradiation     

Diffusion-weighted MRI in pretreatment prediction of response to neoadjuvant chemotherapy in patients with breast cancer

Purpose

To evaluate the accuracy of the apparent diffusion coefficient (ADC) provided by diffusion-weighted imaging (DWI) in predicting the response to neoadjuvant chemotherapy (NACT) at baseline in patients according to their breast tumour phenotypes.

Materials & methods

This retrospective study was approved by our institutional review board. One hundred eighteen consecutive women with locally advanced breast cancer who had undergone NACT followed by breast surgery were included. DWI was performed at 1.5 T less than 2 weeks before NACT. We studied the correlation between pretreatment ADC and response in pathology after surgery according to immunohistochemical features and intrinsic subtypes (luminal A, luminal B, HER2-enriched, and triple-negative tumours).

Results

After surgery, the pathologist recognized 24 complete responders (CRps) and 94 non-complete responders (NCRps). No difference was identified between the pretreatment ADCs of the CRp and NCRp patients. There were differences in pretreatment ADCs among the luminal A (1.001 ± 0.143?×?10^?3 mm²/s), luminal B (0.983 ± 0.150?×?10^?3 mm²/s), HER2-enriched (1.132 ± 0.216?×?10^?3 mm²/s), and triple-negative (1.168 ± 0.245?×?10^?3 mm²/s; P?=?0.0003) tumour subtypes. In triple-negative tumours, the pretreatment ADC was higher in NCRp (1.060 ± 0.143?×?10^?3 mm²/s) than in CRp patients (1.227 ± 0.271?×?10^?3 mm²/s; P?=?0.047).

Conclusion

Pretreatment ADC can predict the response of breast cancer to NACT if tumour subtypes are considered. Key Points ? Apparent diffusion coefficient helps clinicians to assess patients with breast cancer. ? Pretreatment ADC is related to tumour grade and hormone receptor status. ? Pretreatment ADC is lower in luminal A and B than in triple-negative tumours. ? Pretreatment ADC is higher in complete than in non-complete responders to neoadjuvant chemotherapy.     

Apparent diffusion coefficient of the vertebral bone marrow in children with Gaucher's disease type I and III

Purpose

To assess apparent diffusion coefficient (ADC) as a quantitative parameter for detection of vertebral bone marrow infiltration in children with Gaucher’s disease type I and III.

Material and methods

Prospective study was conducted on 20 infants and children (14 M, 6 F; aged 31–61 months; mean age 46 months) with Gaucher’s disease type I (n?=?13) and III (n?=?7), and 20 age and sex matched controls. They underwent routine and diffusion-weighted MR imaging of the lumbar spine using echo planar imaging with b value of 0, 500 and 1000 sec/mm2. The ADC value of the lumbar vertebral bone marrow was compared in different phenotypes and genotypes; and correlated with bone marrow burden score (BMB), chitotriosidase level, hemoglobin and platelet count.

Results

The mean ADC value of marrow infiltration in patients with Gaucher’s disease (0.39?±?0.06?×?10^?3 mm²/s) was significantly lower (P?=?0.001) than that of vertebral bone marrow in controls (0.54?±?0.05?×?10^?3 mm²/s). The cut-off ADC value used to differentiate patients with Gaucher’s disease from controls was (0.47?×?10^?3 mm²/s); with sensitivity of 95 %; specificity of 95 % and area under the curve of 0.986. The L444P/L444P mutation had significantly lower ADC value compared to other mutations (P?=?0.001). The mean ADC value of the bone marrow negatively correlated with BMB (r?=??0.831; P?=?0.001), and biomarkers of disease activity including chitotriosidase (r?=??0.542; P?=?0.014), hemoglobin (r?=??0.727; P?=?0.001) and platelets (r?=??0.698; P?=?0.001).

Conclusion

We concluded that there is significant difference in the ADC value of vertebral bone marrow between children with Gaucher’s disease and controls, and the ADC value correlated well with genotyping and some biomarkers of disease activity.     

Age-related white matter changes in high b-value q-space diffusion-weighted imaging

Introduction

To assess and compare age-related diffusion changes in the white matter in different cerebral lobes, as quantified by diffusion-weighted imaging (DWI) and high b-value q-space imaging (QSI).

Methods

Seventy-three cases without neurological symptoms or imaging abnormalities were grouped by age as young (<30 years, n?=?20), middle-aged (30–49 years, n?=?19), old (50–69 years, n?=?18), and very old (>70 years, n?=?16) and imaged by a 1.5-T MR scanner for DWI and QSI. Apparent diffusion coefficient (ADC) and mean displacement (MDP) values were calculated in the white matter of frontal, parietal, and temporal lobes and compared using Dunnett’s test, with the young group as a control.

Results

MDP values in frontal and parietal lobes were significantly higher in old and very old age groups than in the young, while those in the temporal lobes were significantly higher only in the very old group. ADC values were significantly higher in all three lobes in the very old group.

Conclusion

QSI is more sensitive than DWI to age-related myelin loss in white matter.     

Diffusion-weighted MRI for distinguishing non-neoplastic cysts from solid masses in the mediastinum: problem-solving in mediastinal masses of indeterminate internal characteristics on CT

Objectives

To evaluate the usefulness of diffusion-weighted (DW) magnetic resonance images for distinguishing non-neoplastic cysts from solid masses of indeterminate internal characteristics on computed tomography (CT) in the mediastinum.

Methods

We enrolled 25 patients with pathologically proved mediastinal masses who underwent both thoracic CT and magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI). MRI was performed in patients with mediastinal masses of indeterminate internal characteristics on CT. Two thoracic radiologists evaluated the morphological features and quantitatively measured the net enhancement of the masses at CT. They also reviewed MR images including unenhanced T1- and T2-weighted images, gadolinium-enhanced images and DW images.

Results

The enrolled patients had 15 solid masses and ten non-neoplastic cysts. Although the morphological features and the extent of enhancement on CT did not differ significantly between solid and cystic masses in the mediastinum (P?>?0.05), non-neoplastic cysts were distinguishable from solid masses by showing signal suppression on high-b-value DW images or high apparent diffusion coefficient (ADC) values of more than 2.5?×?10^-3 mm²/s (P?<?0.001). ADC values of non-neoplastic cysts (3.67?±?0.87?×?10^-3 mm²/s) were significantly higher than that of solid masses (1.46?±?0.50?×?10^-3 mm²/s) (P?<?0.001).

Conclusions

DWI can help differentiate solid and cystic masses in the mediastinum, even when CT findings are questionable.

Key Points

? Non-invasive diagnosis of non-neoplastic cysts can save surgical biopsy or excision. ? Conventional CT or MRI findings cannot always provide a confident diagnosis. ? Mediastinal masses can be well-characterised with DWI. ? Non-neoplastic mediastinal cysts show significantly higher ADC values than cystic tumours. ? DWI is useful to determine treatment strategy.