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Diffusion-Weighted Imaging (MR)
Rebecca Rakow-Penner, MD, PhD; Haydee Ojeda-Fournier, MD; Basak E. Dogan, MD
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KEY FACTS

  • Terminology

    • Imaging

      • Top Differential Diagnoses

        TERMINOLOGY

        • Definitions

          • Diffusion-weighted imaging (DWI)
            • Advanced MR technique that quantifies diffusion of water through tissue, reflecting local cell density and tissue microstructure
              • Application of diffusion-sensitizing gradients to MR pulse sequence allows water molecule displacement to be recognized
              • Diffusion signal is modeled and characterized as anisotropic (planar) or isotropic (equal in all directions)
                • Isotropic diffusion is most relevant for breast cancer cells
              • Allows estimation of cellularity and tissue structure
                • Malignant lesions and metastases usually show limited motion of free water molecules = restricted diffusion
              • DWI provides different information, complementary to dynamic contrast-enhanced MR (DCE-MR)
                • Sensitive to factors affecting microscopic water motion (e.g., cell density, membrane integrity, tissue microstructure)
                • Currently used as adjunct to DCE-MR
              • DWI can be quantitative by calculating apparent diffusion coefficient (ADC)
          • Diffusion restriction
            • Motion of free water molecules is limited (diffusion restriction) directly in proportion to tissue cellularity
              • Typically seen in malignancies, metastases, and cellular neoplasms, which contain higher number of cells per volume than healthy tissue
              • Higher diffusion restriction → hyperintense on DWI
          • Brownian motion
            • Constant, random microscopic motion of free water molecules due to thermal energy
              • Motion of intracellular water molecules impeded by cell microenvironment, extracellular water molecules impeded by cell membranes
          • Echo-planar imaging (EPI) DWI
            • Spin-echo EPI DWI most popular clinical imaging technique for generating diffusion-weighted images
              • 2 diffusion-sensitizing magnetic field gradients applied on either side of 180° radiofrequency refocusing pulse before EPI data collection
          • b-value: Degree of diffusion weighting expressed in s/mm²
            • Multiple sequences, using differing b-values (typically ranging from low b-value of 0-100 to high b-value of 800-1,500 s/mm²) → calculate ADC
            • At very low b-values (< 100 s/mm²), ADC predominantly reflects larger distances of water movement, likely due to faster movement in microvessels
          • ADC value
            • Quantitative measure of diffusion defining area covered by molecule per unit of time and measured in mm²/s
            • Derived logarithmic parameter of signal change with b-value
            • Based on attenuation of signal intensity between at least 2 diffusion-weighted images of lower and higher b-value
              • ↑ number of acquisitions with different b-values generates more accurate ADC values
          • ADC map
            • Parametric image with gray or color scale, representing ADC values of voxels
              • Correlate with DWI for interpretation
              • Usually generated by dedicated software
          • T2 shine-through
            • In tissues with very long transverse relaxation times, hyperintense T2 signal may be mistaken for restricted diffusion
              • Correlation with ADC map is needed to distinguish true restricted diffusion (low ADC values) from T2 shine-through (high ADC values)

        IMAGING

        • MR Findings

          • Imaging Recommendations

            DIFFERENTIAL DIAGNOSIS

              DIAGNOSTIC CHECKLIST

              • Consider

                • Image Interpretation Pearls

                  • Reporting Tips

                    Selected References

                    1. Amornsiripanitch N et al: Diffusion-weighted MRI characteristics associated with prognostic pathological factors and recurrence risk in invasive ER+/HER2- breast cancers. J Magn Reson Imaging. 48(1):226-36, 2018
                    2. Amornsiripanitch N et al: Visibility of mammographically occult breast cancer on diffusion-weighted MRI versus ultrasound. Clin Imaging. 49:37-43, 2018
                    3. Newitt DC et al: Test-retest repeatability and reproducibility of ADC measures by breast DWI: results from the ACRIN 6698 trial. J Magn Reson Imaging. ePub, 2018
                    4. Partridge SC et al: Diffusion-weighted MRI findings predict pathologic response in neoadjuvant treatment of breast cancer: the ACRIN 6698 Multicenter Trial. Radiology. 180273, 2018
                    5. Surov A et al: Can diffusion-weighted imaging predict tumor grade and expression of Ki-67 in breast cancer? A multicenter analysis. Breast Cancer Res. 20(1):58, 2018
                    6. Partridge SC et al: DWI in the assessment of breast lesions. Top Magn Reson Imaging. 26(5):201-209, 2017
                    7. Partridge SC et al: Diffusion-weighted breast MRI: Clinical applications and emerging techniques. J Magn Reson Imaging. 45(2):337-355, 2017
                    8. Brandão AC et al: Breast magnetic resonance imaging: diffusion-weighted imaging. Magn Reson Imaging Clin N Am. 21(2):321-36, 2013
                    9. Richard R et al: Diffusion-weighted MRI in pretreatment prediction of response to neoadjuvant chemotherapy in patients with breast cancer. Eur Radiol. 23(9):2420-31, 2013
                    10. Martincich L et al: Correlations between diffusion-weighted imaging and breast cancer biomarkers. Eur Radiol. 22(7):1519-28, 2012
                    11. Wu LM et al: Can diffusion-weighted MR imaging and contrast-enhanced MR imaging precisely evaluate and predict pathological response to neoadjuvant chemotherapy in patients with breast cancer? Breast Cancer Res Treat. 135(1):17-28, 2012
                    12. Kul S et al: Contribution of diffusion-weighted imaging to dynamic contrast-enhanced MRI in the characterization of breast tumors. AJR Am J Roentgenol. 196:210-7, 2011
                    13. Malayeri AA et al: Principles and applications of diffusion-weighted imaging in cancer detection, staging, and treatment follow-up. Radiographics. 31(6):1773-91, 2011
                    14. O'Flynn EA et al: Functional magnetic resonance: biomarkers of response in breast cancer. Breast Cancer Res. 13(1):204, 2011
                    15. Woodhams R et al: Diffusion-weighted imaging of the breast: principles and clinical applications. Radiographics. 31(4):1059-84, 2011
                    16. Partridge SC et al: Apparent diffusion coefficient values for discriminating benign and malignant breast MRI lesions: effects of lesion type and size. AJR Am J Roentgenol. 194(6):1664-73, 2010
                    17. Sinha S et al: Recent advances in breast MRI and MRS. NMR Biomed. 22(1):3-16, 2009
                    18. Charles-Edwards EM et al: Diffusion-weighted magnetic resonance imaging and its application to cancer. Cancer Imaging. 6:135-43, 2006
                    Related Anatomy
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                    Related Differential Diagnoses
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                    References
                    Tables

                    Tables

                    KEY FACTS

                    • Terminology

                      • Imaging

                        • Top Differential Diagnoses

                          TERMINOLOGY

                          • Definitions

                            • Diffusion-weighted imaging (DWI)
                              • Advanced MR technique that quantifies diffusion of water through tissue, reflecting local cell density and tissue microstructure
                                • Application of diffusion-sensitizing gradients to MR pulse sequence allows water molecule displacement to be recognized
                                • Diffusion signal is modeled and characterized as anisotropic (planar) or isotropic (equal in all directions)
                                  • Isotropic diffusion is most relevant for breast cancer cells
                                • Allows estimation of cellularity and tissue structure
                                  • Malignant lesions and metastases usually show limited motion of free water molecules = restricted diffusion
                                • DWI provides different information, complementary to dynamic contrast-enhanced MR (DCE-MR)
                                  • Sensitive to factors affecting microscopic water motion (e.g., cell density, membrane integrity, tissue microstructure)
                                  • Currently used as adjunct to DCE-MR
                                • DWI can be quantitative by calculating apparent diffusion coefficient (ADC)
                            • Diffusion restriction
                              • Motion of free water molecules is limited (diffusion restriction) directly in proportion to tissue cellularity
                                • Typically seen in malignancies, metastases, and cellular neoplasms, which contain higher number of cells per volume than healthy tissue
                                • Higher diffusion restriction → hyperintense on DWI
                            • Brownian motion
                              • Constant, random microscopic motion of free water molecules due to thermal energy
                                • Motion of intracellular water molecules impeded by cell microenvironment, extracellular water molecules impeded by cell membranes
                            • Echo-planar imaging (EPI) DWI
                              • Spin-echo EPI DWI most popular clinical imaging technique for generating diffusion-weighted images
                                • 2 diffusion-sensitizing magnetic field gradients applied on either side of 180° radiofrequency refocusing pulse before EPI data collection
                            • b-value: Degree of diffusion weighting expressed in s/mm²
                              • Multiple sequences, using differing b-values (typically ranging from low b-value of 0-100 to high b-value of 800-1,500 s/mm²) → calculate ADC
                              • At very low b-values (< 100 s/mm²), ADC predominantly reflects larger distances of water movement, likely due to faster movement in microvessels
                            • ADC value
                              • Quantitative measure of diffusion defining area covered by molecule per unit of time and measured in mm²/s
                              • Derived logarithmic parameter of signal change with b-value
                              • Based on attenuation of signal intensity between at least 2 diffusion-weighted images of lower and higher b-value
                                • ↑ number of acquisitions with different b-values generates more accurate ADC values
                            • ADC map
                              • Parametric image with gray or color scale, representing ADC values of voxels
                                • Correlate with DWI for interpretation
                                • Usually generated by dedicated software
                            • T2 shine-through
                              • In tissues with very long transverse relaxation times, hyperintense T2 signal may be mistaken for restricted diffusion
                                • Correlation with ADC map is needed to distinguish true restricted diffusion (low ADC values) from T2 shine-through (high ADC values)

                          IMAGING

                          • MR Findings

                            • Imaging Recommendations

                              DIFFERENTIAL DIAGNOSIS

                                DIAGNOSTIC CHECKLIST

                                • Consider

                                  • Image Interpretation Pearls

                                    • Reporting Tips

                                      Selected References

                                      1. Amornsiripanitch N et al: Diffusion-weighted MRI characteristics associated with prognostic pathological factors and recurrence risk in invasive ER+/HER2- breast cancers. J Magn Reson Imaging. 48(1):226-36, 2018
                                      2. Amornsiripanitch N et al: Visibility of mammographically occult breast cancer on diffusion-weighted MRI versus ultrasound. Clin Imaging. 49:37-43, 2018
                                      3. Newitt DC et al: Test-retest repeatability and reproducibility of ADC measures by breast DWI: results from the ACRIN 6698 trial. J Magn Reson Imaging. ePub, 2018
                                      4. Partridge SC et al: Diffusion-weighted MRI findings predict pathologic response in neoadjuvant treatment of breast cancer: the ACRIN 6698 Multicenter Trial. Radiology. 180273, 2018
                                      5. Surov A et al: Can diffusion-weighted imaging predict tumor grade and expression of Ki-67 in breast cancer? A multicenter analysis. Breast Cancer Res. 20(1):58, 2018
                                      6. Partridge SC et al: DWI in the assessment of breast lesions. Top Magn Reson Imaging. 26(5):201-209, 2017
                                      7. Partridge SC et al: Diffusion-weighted breast MRI: Clinical applications and emerging techniques. J Magn Reson Imaging. 45(2):337-355, 2017
                                      8. Brandão AC et al: Breast magnetic resonance imaging: diffusion-weighted imaging. Magn Reson Imaging Clin N Am. 21(2):321-36, 2013
                                      9. Richard R et al: Diffusion-weighted MRI in pretreatment prediction of response to neoadjuvant chemotherapy in patients with breast cancer. Eur Radiol. 23(9):2420-31, 2013
                                      10. Martincich L et al: Correlations between diffusion-weighted imaging and breast cancer biomarkers. Eur Radiol. 22(7):1519-28, 2012
                                      11. Wu LM et al: Can diffusion-weighted MR imaging and contrast-enhanced MR imaging precisely evaluate and predict pathological response to neoadjuvant chemotherapy in patients with breast cancer? Breast Cancer Res Treat. 135(1):17-28, 2012
                                      12. Kul S et al: Contribution of diffusion-weighted imaging to dynamic contrast-enhanced MRI in the characterization of breast tumors. AJR Am J Roentgenol. 196:210-7, 2011
                                      13. Malayeri AA et al: Principles and applications of diffusion-weighted imaging in cancer detection, staging, and treatment follow-up. Radiographics. 31(6):1773-91, 2011
                                      14. O'Flynn EA et al: Functional magnetic resonance: biomarkers of response in breast cancer. Breast Cancer Res. 13(1):204, 2011
                                      15. Woodhams R et al: Diffusion-weighted imaging of the breast: principles and clinical applications. Radiographics. 31(4):1059-84, 2011
                                      16. Partridge SC et al: Apparent diffusion coefficient values for discriminating benign and malignant breast MRI lesions: effects of lesion type and size. AJR Am J Roentgenol. 194(6):1664-73, 2010
                                      17. Sinha S et al: Recent advances in breast MRI and MRS. NMR Biomed. 22(1):3-16, 2009
                                      18. Charles-Edwards EM et al: Diffusion-weighted magnetic resonance imaging and its application to cancer. Cancer Imaging. 6:135-43, 2006