Elsevier

Academic Radiology

Volume 15, Issue 8, August 2008, Pages 1027-1039
Academic Radiology

Original investigation
Registration Methodology for Histological Sections and In Vivo Imaging of Human Prostate1

https://doi.org/10.1016/j.acra.2008.01.022Get rights and content

Rationale and Objectives

Registration enables quantitative spatial correlation of features from different imaging modalities. Our objective is to register in vivo imaging with histologic sections of the human prostate so that histologic truth can be correlated with in vivo imaging features.

Materials and Methods

In vivo imaging of the prostate included T2-weighted anatomic and diffusion weighted 3-T magnetic resonance imaging (MRI) as well as 11C-choline positron emission tomography (PET). In addition, ex vivo 3-T MRI of the prostate specimen, histology, and associated block face photos of the prostate specimen were obtained. A standard registration method based on mutual information (MI) and thin-plate spline (TPS) was applied. Registration among in vivo imaging modalities is well established; however, accurate registration involving histology is difficult. Our approach breaks up the difficult direct registration of histology and in vivo imaging into achievable subregistration tasks involving intermediate ex vivo modalities like block face photography and specimen MRI. Results of subregistration tasks are combined to compute the intended, final registration between in vivo imaging and histology.

Results

The methodology was applied to two patients and found to be clinically feasible. Overall registered anatomic MRI, diffusion MRI, and 11C-choline PET aligned well with histology qualitatively for both patients. There is no ground truth of registration accuracy as the scans are real patient scans. An indirect validation of the registration accuracy has been proposed comparing tumor boundary markings found in diffusion MRI and histologic sections. Registration errors for two patients between diffusion MRI and histology were 3.74 and 2.26 mm.

Conclusion

This proof of concept paper demonstrates a method based on intrinsic image information content for successfully registering in vivo imaging of the human prostate with its post-resection histology, which does not require the use of extrinsic fiducial markers. The methodology successfully mapped histology onto the in vivo imaging space, allowing the observation of how well different in vivo imaging features correspond to histologic truth. The methodology is therefore the basis for a systematic comparison of in vivo imaging for staging of human prostate cancer.

Section snippets

Materials and methods

In this section, we cover general registration framework, scan acquisition details, and overall schematic to register both in vivo and ex vivo imaging modalities. We have obtained informed consents from the patients after fully explaining the nature of data collection protocol and this study.

In this report, we break down the difficult, direct registration of histology and in vivo imaging into more accurate subregistration tasks involving intermediate modalities (i.e., specimen MRI and block

Results

In this section, we show registration results of histology, anatomical MRI, diffusion MRI, and PET for two patients. Intermediate registration between stacked block photographs and ex vivo MRI is covered as well.

Discussion

Patient 1 has a relatively small tumor while patient 2 has a larger tumor. Diffusion MRI is the only in vivo modality that detects a subvolume of the tumor for patient 1, while all in vivo modalities detect the tumor for patient 2. One possible explanation for our results is that bigger tumors are larger than the resolutions of all in vivo modalities, thus the tumors show up in all in vivo modalities. Registered diffusion MRI shows more misalignment in the rectum/peripheral zone, while

Conclusion

We have shown how histology may be registered with in vivo imaging including anatomical MRI, diffusion MRI, and PET for two patients without the use of extrinsic fiducial markers or unsubstantiated assumptions regarding geometric relationships between in vivo and ex vivo image sets. With this registration process we may be able to better quantify which in vivo combination of modalities is better suited to stage prostate cancer.

References (20)

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Supported in part by the U.S. National Institute of Health under grant 1P01CA87634 and P50CA069568.

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