Whole‐body diffusion‐weighted imaging: Technical improvement and preliminary results

Abstract

Purpose:To optimize the free-breathing whole-body diffusion-weighted imaging (WB-DWI) protocol by using the short TI inversion-recovery diffusion-weighted echo-planar imaging (STIR-DWEPI) sequence and the built-in body coil. Additionally, to evaluate the feasibility of tumor screening using high-resolution three-dimensional (3D) maximum intensity projection (MIP) images. Materials and Methods:The prescan procedure of STIR-DWEPI was modified using the data from 30 volunteers. During each exam, an optimized center frequency (CF) was used to minimize the slice offsets in consecutive scan stations. Prescan time was reduced from 50 seconds to 20 seconds with improved station profile. Total scan time was 30 minutes for five stations and 1.2 m coverage. A total of 30 patients with histologically-proven malignant disease were scanned under the final protocol using a built-in body coil. The image quality and the degree of background body signal suppression were assessed.Results: Free-breathing WB-DWI was 100% successfully performed in all patients, without slice misregistration, fat contamination, significant distortion, or nonuniformity. The reconstructed 3D-MIP images were adequate to depict malignant lesions in all 30 patients. The results of WB-DWI were found to be comparable to those of single-photon emission computed tomography (SPECT) and positron emission tomography (PET). Conclusion:Stable and high-resolution WB-DWI is feasible using the technical improvements described in this study. WB-DWI might have important clinical value for the detection of primary and metastatic malignancies within the whole body. The potential for diagnosis and therapeutic assessment of tumors should be further assessed in a larger patient cohort.

Fast dixon‐based multisequence and multiplanar MRI for whole‐body detection of cancer metastases

“…The spatial resolution of the T2-and T1-weighted images are in many cases comparable to those used in MRI of limited anatomic regions (see Table 2), though often with larger FOVs. Some very recent WB MRI studies have attempted to include more sequences with conventional image contrast (10,12,24,25). However, these studies cannot accommodate the same number of sequences with WB coverage in a typical time slot of Ϸ1 hour.…”

“…After removing the field inhomogeneity effects in postprocessing, these raw images were then added or subtracted to generate water-only, fat-only, and nonfatsuppressed images for each slice location without any additional data acquisition (15,21). The third sequence in our WB protocol was a STIR-prepared diffusionweighted sequence, which provided diffusion-weighted images with background and fat signal suppression, described by Takahara et al (9) and Li et al (10). For each patient, we started with the subject at the head table position and first acquired axial diffusionweighted images of WB in six or seven stations (depending on the patient height) covering from the vertex of the skull to the upper calves or feet.…”

“…SEVERAL STUDIES have shown that magnetic resonance imaging (MRI) can be used for whole-body (WB) detection of cancer metastases (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). In comparison to other imaging modalities, MRI is potentially more desirable for WB imaging because it does not use ionizing radiation, has excellent soft-tissue contrast, and can provide multisequence and multiplanar imaging capabilities for improved diagnostic accuracy.…”

“…Despite their promising results, most of these WB MRI studies suffer from one or more of the above-mentioned technical limitations and have therefore not fully capitalized on the inherent potentials of MRI that are well established for dedicated imaging of local anatomic regions. Recently, diffusion-weighted (DW) imaging, which provides image contrast that is substantially different from that of traditional T1-or T2-weighted images, has also been used for WB imaging (9,10). Preliminary reports have demonstrated the unique potential of DW images for WB detection of both the primary malignancy and metastases to lymph nodes and other organ systems (9,10,12).…”

“…Recently, diffusion-weighted (DW) imaging, which provides image contrast that is substantially different from that of traditional T1-or T2-weighted images, has also been used for WB imaging (9,10). Preliminary reports have demonstrated the unique potential of DW images for WB detection of both the primary malignancy and metastases to lymph nodes and other organ systems (9,10,12). However, DW images are found to be most useful when they are interpreted in conjunction with conventional T1-and T2-weighted images (13,14).…”