Assessment of change in prostate volume and shape following surgical resection through co-registration of in-vivo MRI and fresh specimen ex-vivo MRI

•Preresection prostates to freshly resected prostates were compared for volume and shape.•Volume and shape were quantified using in vivo and ex vivo T2w MRI at 3T.•A −19.5% statistically significant volume decrease was reported after resection.•Significant change in shape is observed on the axial slices.•Findings impact MRI-histology correlation studies and further clinical deductions.

AimTo compare the size and shape of the prostate between in-vivo and fresh ex-vivo magnetic resonance imaging (MRI), in order to quantify alterations in the prostate resulting from surgical resection.Material and methodTen patients who had undergone 3 T prostate MRI using a phased-array coil and who were scheduled for prostatectomy were included in this prospective study. The ex-vivo specimen underwent MRI prior to formalin fixation or any other histopathological processing. Prostate volume in vivo and ex vivo was assessed using planimetry. Prostate shape was assessed by calculating ratios between the diameters of the prostate in all three dimensions.ResultsMean prostate volume was significantly smaller ex vivo than in vivo (39.7 ± 18.6 versus 50.8 ± 26.8 cm3; p = 0.008), with an average change in volume of −19.5%. The right-to-left (RL)/anteroposterior (AP) ratio of the prostate, representing the shape of the prostate within its axial plane, was significantly larger ex vivo than in vivo (1.33 ± 0.14 versus 1.21 ± 0.12; p = 0.015), with an average percent change in RL/AP ratio of the prostate of +12.2%. There was no significant difference between in-vivo and ex-vivo acquisitions in terms of craniocaudal (CC)/AP (p = 0.963, median change = −2.1%) or RL/CC (p = 0.265, median change = +1.3%) ratios.ConclusionThe observed volume and shape change following resection has not previously been assessed by comparison of in-vivo and fresh ex-vivo MRI and likely represents loss of vascularity and of connective tissue attachments in the ex-vivo state. These findings have implications for co-registration platforms under development to facilitate improved understanding of the accuracy of MRI in spatial localization of prostate tumours.