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Three-dimensional MRI evaluation of the effect of bladder volume on prostate translocation and distortion

Ziga Snoj
Ziga Snoj
, 
Andrew B. Gill
Andrew B. Gill
, 
Leonardo Rundo
Leonardo Rundo
, 
Nikita Sushentsev
Nikita Sushentsev
 und 
Tristan Barrett
Tristan Barrett
   | 14. Jan. 2020
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Article Category: Research Article
Online veröffentlicht: 14. Jan. 2020
Seitenbereich: 48 - 56
Eingereicht: 08. Nov. 2019
Akzeptiert: 19. Dez. 2019
DOI: https://doi.org/10.2478/raon-2020-0001
© 2020 Ziga Snoj, Andrew B. Gill, Leonardo Rundo, Nikita Sushentsev, Tristan Barrett, published by Sciendo
This work is licensed under the Creative Commons Attribution 3.0 Public License.

Figure 1

Overall scheme of the performed MR image analysis tasks. (A) 3D affine co-registration of each pre-void scan (‘moving’ volume) against the post-void scan (‘fixed’ volume). This operation is executed for all the four preparations described in the leftmost box. Subsequent manual delineation of the prostate on the two scans by using the axial reformatting. 3D rigid-body (translation alone t) volume alignment between the centres-of-mass of the two prostate glands under investigation. (B) For each slice, the volume sections are aligned so that their centroids are coincident (information stored in the ‘tree’ of slice centroid translations Ts). (C) Calculation of the RMS of the resultant translocation vector tres. (D) Computation of the resultant distortion vector dres, by considering also the subdivision of the axial plane into the anterior and posterior half-planes.
Overall scheme of the performed MR image analysis tasks. (A) 3D affine co-registration of each pre-void scan (‘moving’ volume) against the post-void scan (‘fixed’ volume). This operation is executed for all the four preparations described in the leftmost box. Subsequent manual delineation of the prostate on the two scans by using the axial reformatting. 3D rigid-body (translation alone t) volume alignment between the centres-of-mass of the two prostate glands under investigation. (B) For each slice, the volume sections are aligned so that their centroids are coincident (information stored in the ‘tree’ of slice centroid translations Ts). (C) Calculation of the RMS of the resultant translocation vector tres. (D) Computation of the resultant distortion vector dres, by considering also the subdivision of the axial plane into the anterior and posterior half-planes.

Figure 2

Example distortion maps of three MRI studies. (A) showing significant prostate translocation with significant base distortion in a study from the rectal group, (B) showing negligible prostate translocation and distortion in a study from the bladder group, and (C) showing significant prostate translocation but negligible prostate distortion in a study from the bladder group. The fixed and moving volumes are depicted in the first and second columns, respectively. In order to show the slice section difference as well as the local translation, the ‘tree’ of slice centroid translations Ts and the distortion surface map (along with the corresponding colour map expressed in mm) are shown in the third and fourth (fifth) columns, respectively.
Example distortion maps of three MRI studies. (A) showing significant prostate translocation with significant base distortion in a study from the rectal group, (B) showing negligible prostate translocation and distortion in a study from the bladder group, and (C) showing significant prostate translocation but negligible prostate distortion in a study from the bladder group. The fixed and moving volumes are depicted in the first and second columns, respectively. In order to show the slice section difference as well as the local translation, the ‘tree’ of slice centroid translations Ts and the distortion surface map (along with the corresponding colour map expressed in mm) are shown in the third and fourth (fifth) columns, respectively.

Figure 3

Prostate translocation plotted with relative bladder volume difference (r = 0.64, p < 0.01) (A). Prostate translocation plotted with bladder volumes (pre-void, post-void, absolute difference) (B).
Prostate translocation plotted with relative bladder volume difference (r = 0.64, p < 0.01) (A). Prostate translocation plotted with bladder volumes (pre-void, post-void, absolute difference) (B).

Figure 4

Translocation in the bladder group according to the prostatic sectors (A) and directions of translocation (B). Translocation in the rectum group according to the prostatic sectors (C) and directions of translocation (D). Each boxplot shows a black solid line and a grey star marker that denote the median and mean values, respectively.
Translocation in the bladder group according to the prostatic sectors (A) and directions of translocation (B). Translocation in the rectum group according to the prostatic sectors (C) and directions of translocation (D). Each boxplot shows a black solid line and a grey star marker that denote the median and mean values, respectively.

Inter-group translocation comparison for whole gland and prostatic sectors

Bladder group Mean ± SD (mm)Rectal group Mean ± SD (mm)p-value
Whole gland2.46 ± 1.734.44 ± 1.74<0.01
Apex1.86 ± 1.393.96 ± 1.92<0.01
Mid-gland2.31 ± 1.834.46 ± 1.88<0.01
Base2.98 ± 2.054.70 ± 1.850.03

Prostate distortion expressed as mean and distortion values of the 90th percentile

Bladder groupRectal group
Mean ± SD (mm)90th percentile ± SD (mm)Mean ± SD (mm)90th percentile ± SD (mm)p-value
Whole gland1.40 ± 0.362.55 ± 0.621.71 ± 0.333.20 ± 0.560.02
Apex1.42 ± 0.532.44 ±0.801.46 ± 0.312.53 ± 0.430.80
Mid-gland1.19 ± 0.272.19 ± 0.501.61 ± 0.412.90 ± 0.67<0.01
Base1.61 ± 0.462.84 ± 0.802.01 ± 0.53.73 ± 0.830.02
Whole gland, anterior1.41 ± 0.352.56 ± 0.601.59 ± 0.302.91 ± 0.500.14
Whole gland, posterior1.40 ± 0.372.54 ± 0.651.82 ± 0.353.36 ± 0.61<0.01
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