Ultrasound matching procedure. The UStx scan (“current”), daily acquired at treatment stage [axial view (b) and sagittal view (d)], is matched to the reference USSim scan [axial view (a) and sagittal view (c)], which was made during simulation stage. The RPV [white contours in (a) and (c)] on the reference scan is the prostate delineated during the preparation process on the workstation. At treatment stage, this contour is copied to UStx and moved by the operator to correspond to the current position of the prostate [white contours in (b) and (d)]. An automatic adapt function adjusts the reference contour to the gray level boundaries of the prostate in the current scan [black contours in (b) and (d)] to obtain the best volume fit from which the shift is calculated.
Overview of the scanning and matching variability tests. On the days with repeated scans (dark gray), the focus is on the scan variability. On the days with single scans (light gray), the matching procedure is emphasized.
Prostate motion due to probe pressure. The US prostate displacement (the average difference from two measurements normalized to the no pressure level) plotted against the skin displacement for each direction (a)–(c) and for the total displacement vector (d). Each line represents a different patient.
Shifts measured with US localization vs FM MV portal image-based shifts shown in correlation plots (a, d, g), Bland-Altman analysis (b, e, h), and their accompanying histograms (c, f, i). (Abbreviations: UL, upper limit; LL, lower limit).
Graphical overview of the patient specific geometrical characteristics of the prostate CT contour (PCTC), the RPV, and the FMs. The large, light gray spheres have a radius equal to the equivalent radius of the PCTC. Using the radius and relative centroid positions from Table IV , the medium sized and medium gray spheres represent the coverage of the PCTC by the RPV and the small, dark gray spheres represent the PCTC coverage by the FMs.
The user variability for the US localization procedure differentiated for different operator aspects: Inter and intraoperator variability for both the scanning and matching procedures.
Estimate of the SOS distortion of the prostate centroid along the central line of view of the US-probe. Negative values indicate that the true prostate position is shallower than is shown in the US-images.
Overview of the uncertainties (1 SD) of the 3DUS system and (manual) FM positioning on MV EPI.
Overview of the patient specific geometrical characteristics of the prostate CT contour (PCTC), the RPV and the FMs.
Article metrics loading...
Full text loading...