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.