What’s luminal water imaging, and do we need to care?

Two recent papers by Sabouri et al. have suggested that a new MRI techique known as “luminal water imaging” may be able to improve the ability of MR scans to identify and grade prostate cancer prior to biopsy. However, the current data are preliminary.

The two papers (one in Radiology and the other in the Journal of Magnetic Resonance Imaging) provide data from the use of this new MRI technique in a set of 18 patients who had all, previously, been diagnosed with biopsy-proven prostate cancer.

The estimation of the “luminal water fraction” or LWF was associated with

  • The highest degree of correlation with the patients’ pre-surgical Gleason score (−0.78 ± 0.11, P < .001) and with
  • Very high accuracy for tumor detection, with highest correlations shown by areas under the ROC curve
    • 0.97 in the peripheral zone
    • 0.98 in the transition zone

If results like these can be repeated with larger numbers of patients who have a wider spectrum of Gleason scores, then we are going to be getting closer to the much-touted potential of accurate diagnosis of localized prostate cancer by MRI alone. However, there will be a lot of work necessary before prostate cancer can be diagnosed and effectively treated without the need for a biopsy.

So what is “luminal water imaging”?

Basically it is a way to use MRI to measure the distribution of water in and between the tissues in organs like the prostate.  The “luminal water fraction” or LWF is actual measure of water distribution within such tissues. Higher grades of prostate cancer appears to be correlated with lower amounts of water in and between the relevant tissues.

And one of the great potential benefits of luminal water imaging is that there is no need to use any type of contrast agent to conduct the MRI.

Your sitemaster suspects that we are going to be hearing a good deal more about the evolution of this imaging method over the next 3 to 5 years.

2 Responses

  1. Comparison with the Current Water Diffusion Parameter of mpMRI?

    Having read the abstracts, I am not clear how “luminal water imaging” — a new term for me, differs from the current water diffusion parameter of mpMRI, which is sometimes referred to as the “apparent diffusion coefficient”. It appears that more dimensions of water movement are used in this study, and perhaps they are automated, which could reduce subjectivity in the radiologist’s assessment.

  2. Luminal water imaging is a technique that isolates the signal from water in the luminal spaces. The luminal water contributes to the signal you measure in a diffusion-weighted image but water from elsewhere in the prostate gland contributes too so diffusion imaging isn’t quite as specific.

    Luminal water imaging has generated quite a bit of interest in the MRI community and several other groups have now tested the technique and published papers on their measurements. However, we’re still a little way from seeing the technique become part of a standard mpMRI exam.

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