Journal of Medical Imaging and Radiation Oncology 59 (2015) 141–148

RADIOLO GY—O R I G I N A L A RT I C L E

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The diagnostic value of diffusion-weighted imaging and the apparent diffusion coefficient values in the differentiation of benign and malignant breast lesions Gonca Çabuk,1 Meltem Nass Duce,1 Anıl Özgür,1 Feramuz Demir Apaydın,1 Ays¸e Polat2 and Gülhan Orekici3 1 Department of Radiology, School of Medicine, Mersin University, Mersin, Turkey 2 Department of Pathology, School of Medicine, Mersin University, Mersin, Turkey 3 Department of Biostatistics, School of Medicine, Mersin University, Mersin, Turkey

G Çabuk MD; M Nass Duce MD; A Özgür MD; FD Apaydın MD; A Polat MD; G Orekici PhD. Correspondence Dr Anıl Özgür, Department of Radiology, School of Medicine, Mersin University, 34. Cadde, Çiftlikköy Kampüsü, Mersin 33343, Turkey. Email: [email protected] Conflict of interest: The authors declare that they have no conflicts of interest. Submitted 17 August 2014; accepted 20 November 2014. doi:10.1111/1754-9485.12273

Abstract Introduction: The goal of our study was to evaluate the diagnostic efficacy of diffusion-weighted imaging (DWI) in the differentiation of benign and malignant breast lesions. Methods: Between June 2012 and March 2013, 60 patients with 63 lesions (age range 29–70 years, mean age 48.6 years) were included in our study. All lesions, except complicated cysts and intra-mammary lymph nodes, were confirmed histopathologically. The patients were evaluated with a 1.5 Tesla MR scanner using dedicated bilateral breast coil. DWI images were obtained by echo planar imaging sequence and ‘b’ values were selected as 200, 600 and 1000 s/mm2. Apparent diffusion coefficient (ADC) values of both breast lesions and the normal fibroglandular tissue of the contralateral breast were calculated and statistically compared using Shapiro–Wilk test, Student’s t-test, Mann–Whitney U test, chi-square test and the receiver operating curve. Results: Of 63 lesions, 22 were malignant and 41 were benign. In malignant lesions, the mean ADC values were 1.40 ± 0.41 × 10−3 mm2/s for b = 200, 1.05 ± 0.28 × 10−3 mm2/s for b = 600 and 0.91 ± 0.20 × 10−3 mm2/s for b = 1000 and in benign lesions, the mean ADC values were 2.13 ± 0.85 × 10−3 mm2/s for b = 200, 1.64 ± 0.47 × 10−3 mm2/s for b = 600 and 1.40 ± 0.43 × 10−3 mm2/s for b = 1000. The success of ADC values in differentiation of benign and malignant lesions was statistically significant (P = 0.0001). The threshold values were determined to be 1.50 × 10−3 mm2/s for b = 200, 1.22 × 10−3 mm2/s for b = 600 and 0.98 × 10−3 mm2/s for b = 1000 (P < 0.05). Conclusion: DWI can be an effective radiological method in the differentiation of benign and malignant breast lesions. Key words: apparent diffusion coefficient; breast imaging; diffusion-weighted imaging; magnetic resonance imaging; malignant breast lesion.

Introduction Breast cancer is the most common type of cancer affecting women. Annually, over 1 000 000 new cases are diagnosed worldwide.1 The most effective way of reducing mortality associated with breast cancer is the early diagnosis and treatment. Currently, mammography (MG) is the primary imaging modality for breast cancer screening and diagnosis, with sensitivity rates ranging

© 2015 The Royal Australian and New Zealand College of Radiologists

between 69 and 90%. However, its specificity is relatively low and it has a poor diagnostic value for the assessment of dense breast tissues.2,3 Ultrasonography (US) is the imaging modality of choice in such cases and allows the differentiation between solid and cystic lesions. Furthermore, Doppler US can be used to evaluate the vascularity of the lesion. Magnetic resonance imaging (MRI) is a widely accepted modality as an adjunct to MG and US in the detection of primary or

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recurrent breast cancers.4 While the sensitivity of contrast-enhanced MRI in the diagnosis of breast cancer is approximately 85–99%, its specificity ranges between 40 and 80%.5 Diffusion-weighted imaging (DWI) is one of the techniques that are performed to increase MRI’s specificity.6,7 In this study, with the use of different ‘b’ values, we calculated the mean apparent diffusion coefficient (ADC) values of the normal fibroglandular tissues and histologically proven benign and malignant breast lesions to assess the utility of DWI in the differentiation of benign and malignant breast lesions and to see whether a statistically significant cut-off value exists for this purpose.

Methods Out of 252 dynamic contrast-enhanced (DCE)-MRI of the breast performed for various indications between June 2012 and March 2013, a total of 60 patients (age range 29–70 years; mean age 48.6 years) diagnosed with a benign or malignant breast lesion constituted our study group. The age range was 37–67 years (mean age 53.1 years) for patients with malignant lesions and 29–70 years (mean age 45.9 years) for patients with benign lesions. The diagnosis was histopathologically confirmed for all the malignant and benign lesions except for the complicated cysts and intra-mammary lymph nodes (IMLNs); complicated cysts and IMLNs were diagnosed by the use of US and MRI. IMLNs with a diameter of less than 5mm, simple cysts, lesions that could not be localised on ADC maps, lesions without a confirmed histopathological diagnosis and patients under neoadjuvant chemotherapy were excluded from the study. Normal MRI of the contralateral breasts of the patients constituted the control group. Approval for the study was obtained from the local ethics committee of our centre. All patients were informed about the procedure prior to the examination and signed the corresponding informed consent.

MRI protocol All examinations were performed in the prone position on a 1.5 Tesla MR system (Signa Excite, GE Medical Systems, Milwaukee, WI, USA) using a four-channel bilateral breast coil. After an intravenous injection of gadopentetate dimeglumine (Magnevist; Bayer Schering-Pharma, Berlin, Germany) at 0.2 mmol/kg body weight with a rate of 2 mL/, a 20-mL saline flush was administered with an automatic injector, within a maximum of 40 s. Magnetic resonance examinations of the premenopausal women were performed between days 7 and 14 of their menstrual cycles. All series were obtained in the axial plane. Magnetic resonance imaging protocol consisted of pre- and postcontrast T1-weighted non-fat-suppressed spin-echo

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sequence (repetition time/echo time (TR/TE) 400/11; 320 × 224 matrix; 4-mm slice thickness; 0.6 mm intersection gap; 34–42-cm field of view), T2-weighted shorttime inversion recovery sequence (TR/TE/inversion time 5400/40/150; echo train length 18; 320 × 224 matrix; 4-mm section thickness; 0.6-mm intersection gap; 34–42-cm field of view), T1- weighted 3D spoiled gradient-recalled echo sequence with one unenhanced and multiple contrast-enhanced scans (TR/TE 4.5/1.7; flip angle 10°; 320 × 320 matrix; 2.4-mm slice thickness; 0 intersection gap; 34–42-cm field of view) and a DWI sequence. DWI was performed after DCE-MRI using a multisection spin-echo single-shot echo-planar sequence (echo planar imaging) (TR/TE 4450/87.5; 128 × 128 matrix, 4-mm slice thickness; 0.6-mm intersection gap; 34–42-cm field of view). Sensitising diffusion gradients were applied in three orthogonal planes with b values of 200, 600 and 1000 s/mm2. ADC maps were generated automatically from the diffusionweighted images.

Image interpretation and data collection Magnetic resonance imaging findings were reviewed independently by two radiologists. Inconsistencies were resolved by consensus. With the aid of an image processing software (Advantage Workstation, version 4.2, GE Medical Systems), regions of interest (ROIs) were determined from the areas of greatest lesion enhancement and the time-signal intensity curves were obtained. The morphological and signal intensity characteristics of the lesions along with their contrast enhancement patterns were evaluated and each lesion was assigned into a Breast Imaging Reporting and Data System (BIRADS) category. ADC values of both the lesions and the contralateral healthy breast tissues were obtained from the ADC maps. The size of the ROI was adjusted to the lesion size. The ROI was placed over the lesion, trying to avoid areas of cystic and necrotic components. Three measurements from three different areas from a single lesion were obtained and a mean ADC value was determined for each lesion.

Histopathological evaluation The diagnoses of all malignant and benign lesions, except for the complicated cysts and IMLNs, were histopathologically confirmed by means of core needle biopsy and/or surgery.

Statistics Statistical analysis was performed using SPSS 11.5 (SPSS, Inc., Chicago, IL, USA) and MedCalc®v11.0.1 (MedCalc Software, Ostend, Belgium) softwares. To assess the distribution of the parameters associated with malignant and benign lesions, Shapiro–Wilk test was

© 2015 The Royal Australian and New Zealand College of Radiologists

DWI in the differentiation of breast lesions

used. The descriptive statistics included mean values and the standard deviations for the parameters that were normally distributed. Medians and percentiles were used for the parameters that were not normally distributed and numbers and percentages were used for the categorical parameters. To test the differences between two groups, Student’s t-test was used for normally distributed parameters, Mann–Whitney U test was used for the parameters that have abnormal distribution and chisquare test was used for the categorical data. Receiver operating characteristic analysis was used to assess the power of the ADC value for the discrimination between benign and malignant lesions. A P-value

The diagnostic value of diffusion-weighted imaging and the apparent diffusion coefficient values in the differentiation of benign and malignant breast lesions.

The goal of our study was to evaluate the diagnostic efficacy of diffusion-weighted imaging (DWI) in the differentiation of benign and malignant breas...
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