Whole body MRI: improved lesion detection and characterization with diffusion weighted techniques.
Bottom Line: Theory, b-value selection, common artifacts and target to background for optimized viewing will be reviewed for applications in the neck, chest, abdomen, and pelvis.DWI, when used in conjunction with routine imaging, can assist in detecting hemorrhagic degradation products, infection/abscess, and inflammation in colitis, while aiding with discrimination of free fluid and empyema, while limiting the need for intravenous contrast.DWI in conjunction with routine anatomic images provides a platform to improve lesion detection and characterization with findings rivaling other combined anatomic and functional imaging techniques, with the added benefit of no ionizing radiation.
Affiliation: AIM Medical Imaging, Vancouver, BC, Canada. firstname.lastname@example.orgShow MeSH
Related in: MedlinePlus
Mentions: Based on the Stokes-Einstein Eq. , the impact of changes in tissue water motion, and solvent viscosity can be predicted, yielding increased signal for solid tissue, or viscous fluid. A generalization of expected slopes and signal intensity for tissue encountered in body imaging is shown in Figure 6. Due to lack of standardization, the difference between signal intensity of a restricted tissue versus normal tissue at a fixed b-value cannot be adequately quantified; however, the relative difference can be used to increase lesion conspicuity. This fact can aid with discriminating empyema versus simple pleural effusion 19,20 and peritoneal carcinomatosis versus ascites 21,22, which are difficult to distinguish by conventional sequences. The persistence of increased signal with restricted solid tissue corresponds to the lower ADC values described for solid tumor masses. However, the lack of standardization 23 of b-value selection for various organs and lesions limits the reproducibility of ADC values. A generalization of change in ADC values between vascular, cystic, necrotic/viscous, and solid tissue is outlined in Figure 6b. Thus, the low ADC of a solid lesion undergoing therapy can change. Necrotic or edematous tissue will result in an increase in the ADC value. This quantifiable change, if performed at both baseline and following treatment with the same b-values, can be used to monitor response to treatment.
Affiliation: AIM Medical Imaging, Vancouver, BC, Canada. email@example.com