Using multiparametric WB-DWI to identify solid tumor metastasis
Multiparametric, whole-body, diffusion-weighted imaging (WB-DWI) is feasible to identify bony and visceral metastatic disease in breast, colorectal, pancreatic, and prostate cancer, according to a study from the Johns Hopkins School of Medicine. Findings reported online in Academic Radiology suggest that WB-DWI combined with positron emission tomography/computed tomography (PET/CT) could improve detection and characterization of tumors. This imaging data could be used as surrogate biomarkers to monitor response to treatment.
If metastatic disease could be identified in its earliest stages, treatment of a patient could potentially be more effective and improve survival. Advanced quantitative MRI, which can provide metrics of the molecular and vascular characteristics of tumors, offers the potential for global tumor assessment and accurate lesion detection without irradiation, according to the authors.
The study focused on 22 patients with Stage IV cancer and 32 healthy volunteers, ranging in age from 27 to 80 years. Axial, sagittal, and coronal fat-suppressed T2-weighted (T2WI), T1-weighted (T1WI), and DWI images were acquired using a dedicated clinical research 3T scanner. A 2D PACE technique was used to decrease respiratory or organ motion. CT and PET scans were also performed.
The Baltimore researchers constructed whole-body apparent diffusion coefficient (ADC) maps, T2-weighted images, and DWI. They divided the WB-MRI and PET/CT scans into six standard anatomic sections and counted the number of suspected lesions within each region from each modality. ADC map values for normal and lesion tissue were calculated.
Ninety-one lesions were detected from PET/CT and 88 from WB-DWI. ADC mapping resulted in a 96% detection rate when combining the T2 and DWI, just 1% lower than the PET/CT images. Lead author Michael A. Jacobs, PhD, professor of radiology and radiological science, and colleagues reported that the DWI and ADC mapping of the different anatomic regions were excellent, and that excellent soft tissue delineation was seen in the thorax and abdomen. Motion-related artifacts decreased and lesion detection were improved by acquiring DWI in the axial plane.
Quantitative WB-ADC map values were significantly different between normal and lesion tissue.
According to the researchers, advantages of improved WB-MRI include the following:
- The use of dedicated phased array coils and continuous table movement permits acquisition of seamless data of multiple anatomic planes within the body. An individualized patient sequence can be developed to fit a patient for a comprehensive imaging evaluation.
- Acquisition of images from the head to the mid-tibia can be performed in 45-60 minutes.
- No irradiation
- Similar or superior tissue delineation and coverage than nuclear imaging methods.
- Ability to image tumors with several different sequences that prove different states of water and provide varying tissue contrasts depending on MRI parameters.
Lmitations of WB-MRI include major motion and ghosting artifacts in coronal imaging of the neck and thoracic areas. The authors recommend that if metastasis is suspected in these areas, WB-DWI should be performed in the axial plane.
The authors also recommend that PET/CT and WB-MRI should both be performed when metastasis is suspected. Data from these combined examinations will enable important biophysical information about both the primary and metastatic tumor environment beyond standardized volumetric data. This will lead to a better characterization of the lesion. They stated that larger studies also need to be performed to gauge the influence of multiparametric WB-MRI in a clinical setting.
REFERENCE
- Jacobs MA, Macura KJ, Zaheer A, et al. Multiparametric Whole-body MRI with diffusion-weighted imaging and ADC mapping for the identification of visceral and osseous metastases from solid tumors. Acad Radiol. Published online April 4, 2018. doi: 10.1016/j.acra.2018.02.010.