DOI: 10.1186/s40658-017-0188-1Pages: 1-15

Comparison of PET/CT and whole-mount histopathology sections of the human prostate: a new strategy for voxel-wise evaluation

1. University Medical Center Freiburg, Department of Nuclear Medicine

2. University Medical Center Freiburg, Department of Radiation Oncology

3. Claraspital Basel, Department of Nuclear Medicine

4. University Medical Center Freiburg, Department of Urology

5. University Medical Center Freiburg, Department of Pathology

6. German Cancer Consortium (DKTK) Partner Site

Correspondence to:
M. Mix
Email: michael.mix@uniklinik-freiburg.de

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Abstract

Background

Implementation of PET/CT in diagnosis of primary prostate cancer (PCa) requires a profound knowledge about the tracer, preferably from a quantitative evaluation. Direct visual comparison of PET/CT slices to whole prostate sections is hampered by considerable uncertainties from imperfect coregistration and fundamentally different image modalities. In the current study, we present a novel method for advanced voxel-wise comparison of histopathology from excised prostates to pre-surgical PET. Resected prostates from eight patients who underwent PSMA-PET/CT were scanned (ex vivo CT) and thoroughly pathologically prepared. In vivo and ex vivo CT including histopathology were coregistered with three different methods (manual, semi−/automatic). Spatial overlap after CT-based registration was evaluated with dice similarity (DSC). Furthermore, we constructed 3D cancer distribution models from histopathologic information in various slices. Subsequent smoothing reflected the intrinsically limited spatial resolution of PSMA-PET. The resulting histoPET models were used for quantitative analysis of spatial histopathology-PET pattern agreement focusing on p values and coefficients of determination (R2). We examined additional rigid mutual information (MI) coregistration directly based on PSMA-PET and histoPET.

Results

Mean DSC for the three different methods (ManReg, ScalFactReg, and DefReg) were 0.79 ± 0.06, 0.82 ± 0.04, and 0.90 ± 0.02, respectively, while quantification of PET-histopathology pattern agreement after CT-based registration revealed R2 45.7, 43.2, and 41.3% on average with p < 10−5. Subsequent PET-based MI coregistration yielded R2 61.3, 55.9, and 55.6%, respectively, while implying anatomically plausible transformations.

Conclusions

Creating 3D histoPET models based on thorough histopathological preparation allowed sophisticated quantitative analyses showing highly significant correlations between histopathology and (PSMA-)PET. We recommend manual CT-based coregistration followed by a PET-based MI algorithm to overcome limitations of purely CT-based coregistrations for meaningful voxel-wise comparisons between PET and histopathology.

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  • Accepted: Jul 25, 2017
  • Online: Aug 17, 2017

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