imperfections, the error in the artificial point represents 
fittihg error, and the error in the anatomic point 
represents fitting and pointing error. 
This process resulted in the boundaries being fitted 
together with four, five, and six parameter transformations, 
using all boundary pixels and a subset of pixels. The 
results are shown in Table 1. 
  
  
  
  
  
  
  
Residuals from Feature Transformations (Pixels at Generated Point) 
Transformation Film Transformed Mean 
No. of Boundary 
Parameters | Pixels 2 —»1 3 -—»1 4 —> 1 
20 0.79 + 0.42 | 0.96 + 0.37 | 1.01 + 0.80 0.92 + 0.12 
4 10 0.77 + 0.37 | 0.93 + 0.41 | 0.98 + 0.48 | 0.89 + 0.11 
6 0.82 + 0.37 | 1.03 + 0,51 | 1.07 + 0.51 | 0.97 + 0.13 
20 0.69 + 0.32 | 0.86 + 0.17 | 0.51 + 0.31 0.69 + 0.24 
5 10 0.74 + 0.44 | 1.00 + 0.26 | 3.31 + 2.82 | 1.68 + 1.42 
6 1.19 + 0.56 | 2.64 + 2.65 | 2.96 + 1.65 | 2.26 + 0.94 
20 0.55 + 0.29 | 0.74 + 0.15 | 0.25 + 0.08 | 0.52 + 0.25 
6 10 0.80 + 0.56 | 0.97 + 0.42 | 0.73 + 0.16 0.83 + 0.12 
6 1.03 + 0.82 | 1.31 + 0.87 | 1.21 + 0.04 1.18 + 0,14 
Mean 0.67 + 0.27 | 1.16 + 0.58 | 1.34 + 1.06 | 1.05 + 0.35 
  
  
  
  
  
  
  
  
Table 1 - Anatomic Feature Boundary Transformations 
4.2 Analysis 
A number of conclusions can be drawn from the boundary 
matching tests, All statements of significance of 
difference made in this analysis were confirmed by t tests 
at the .01 significance level, unless Stated otherwise. The 
data in Table 1 are the mean results obtained from all four 
anatomic points, averaged by type of transformation (reading 
down the table) and by film (reading across the table). 
The best overall results were obtained With six parameter 
matches on all of the boundary points. However, the 
difference between the five and six parameter solutions is 
only significant at the .05 level. This indicates that the 
ability to scale independently in x and Y is a more 
important factor than non-orthogonality of the axes, when a 
single image is rotated and fitted, 
- 178: =~