Validation of an Improved Patient-Specific Mold Design for Registration of In-vivo MRI and Histology of the Prostate

Abstract

Fusion of in-vivo magnetic resonance imaging (MRI) with whole mount histology of the prostate is facilitated by the use of a patient-specific mold, that is designed from in-vivo MRI. The mold defines specific sectioning planes with the same orientation and position relative to the prostate as the stack of MRI slices, reducing the registration problem from a 3D to a 2D problem. We present an innovative mold design that specifies the in-and outflow of the urethra as additional landmarks for correct positioning of the prostate in the mold, that allows for the fresh prostate tissue to be fixated inside the mold such that its in-vivo shape is maintained, and that allows for ex-vivo MRI of the prostate in the mold in alignment with in-vivo MRI using the mold as reference frame. Using high-resolution 3D ex-vivo MRI aligned with in-vivo MRI, we demonstrate that our improved mold design results in a more accurate positioning of the prostate inside the mold, significantly reducing out-of-plane rotational offsets. Initial results show that the proposed workflow has the potential to provide detailed histopathological ground truth for the quantitative interpretation of in-vivo and ex-vivo MRI in prostate cancer.

A system using patient‐specific 3D‐printed molds to spatially align in vivo MRI with ex vivo MRI and whole‐mount histopathology for prostate cancer research

“…On the other hand, strategies based on ExV have only been evaluated in relatively small numbers of prostate specimens, often lack standardization of the experimental design (e.g., to achieve consistent positioning of the specimen with respect to InV), or lack integration into the clinical workflow. Recently, there have been initial investigations of alignment strategies that combine the advantages of patient‐specific molds with ExV, but only proof‐of‐concept results have been reported thus far.…”

Apparatus for Histological Validation of In Vivo and Ex Vivo Magnetic Resonance Imaging of the Human Prostate

“…(4, 6). Here, we provide a brief overview of the approaches and problems addressed by the method we describe.…”

“…Rotation errors are more likely around the axes in which the specimen has greatest rotational symmetry. Inclusion of a urethral catheter in the specimen and mold design can decrease rotation errors about the left–right axes of the prostate (6). …”

“…High spatial resolution ex vivo imaging of the prostate specimen has been used as an intermediate “stepping-stone” to improve the accuracy of co-registration of in vivo MRI and histology data, both with (6) and without (16) a patient-specific mold. However, the mold design can be improved to better facilitate comparison between MR and histological images.…”

“…A more basic mold design suitable for a filament printer is described in Ref. (6). The mold features are illustrated in Figure 2 and include

A chamfer at one end of the mold indicates the apex end of the prostate, so that orientation of the prostate during ex vivo imaging is as for in vivo imaging with the patient lying in feet-first supine position.

LP .

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