Observer Performance Studies

Comparison of Digital Stereotactic Breast Biopsy Systems

Two digital radiograph systems for stereotactic mammography, one using a lens to couple a Lanex Regular screen to a back-illuminated charge-coupled device (CCD) and one using a fiber-optic taper to couple a Min-R Regular-type screen to a front-illuminated CCD, were evaluated with respect to observer performance[3].

Methods

Images

The CDMAM phantom (Nuclear Associates, Carle Place, NY) was imaged in a variety of matched conditions using the 2 stereotactic systems. In one condition the phantom was placed between 2 plexiglass plates to simulate low density breasts and in the other it was placed between 4 plexiglass plates to simulate high density breasts.

  Fiber-Optic   Lens  
kV mAs mR mAs mR
  2 plexiglass plates  
27 20 199 24 218
27 50 499 56 509
27 70 700 80 722
30 10 136 14 173
30 30 412 35 428
30 40 549 49 597
  4 plexiglass plates  
27 80 854 88 843
27 190 2050 200 1905
27 280 3010 296 2820
30 40 598 49 628
30 100 1479 112 1437
30 150 2220 168 2170

Display

  • 1024 x 1280 monitor, 65 ft-L

Procedure

6 observers Viewed images from the various imaging conditions in random orders Task = indicate which of the 4 corners for each square in the phantom contained the target disk Window & level were available

Results

Percent Correct Detections Analysis

Figure 1. % correct location detections for fiber-optic and lens-coupled systems with phantom between 2 plexiglass plates (simulating low density breasts). The lens-coupled system resulted in significantly more correct detections at all imaging conditions (p <.05).

Figure 1. % correct location detections for fiber-optic and lens-coupled systems with phantom between 2 plexiglass plates (simulating low density breasts). The lens-coupled system resulted in significantly more correct detections at all imaging conditions (p <.05).

Figure 2. % correct location detections for fiber-optic and lens-coupled systems with phantom between 4 plexiglass plates (simulating high density breasts). The lens-coupled system resulted in significantly more correct detections at all imaging conditions (p <.05).

Figure 2. % correct location detections for fiber-optic and lens-coupled systems with phantom between 4 plexiglass plates (simulating high density breasts). The lens-coupled system resulted in significantly more correct detections at all imaging conditions (p <.05).

Conclusions

  • Detection performance was significantly better using the images from the lens-coupled digital stereotactic breast biopsy system than from the fiber-optic coupled system
  • The difference was greater when 4 plexiglass plates sandwiched the phantom (to simulate more dense breast tissue) than when 2 plexiglass plates were used (to simulate less dense breast tissue)
  • Differences in absorption efficiencies of the phosphors used (95% vs 73%), as well as differences in design of the two digital cameras, can explain the differences in observer performance

Return to Observer Performance Studies page