title: Microcalcification detectability using a bench-top prototype photon-counting breast CT based on a Si strip detector.
abstract: OBJECTIVE
  To investigate the feasibility of detecting breast microcalcification (μCa) with a dedicated breast computed tomography (CT) system based on energy-resolved photon-counting silicon (Si) strip detectors.
  
  
  METHODS
  The proposed photon-counting breast CT system and a bench-top prototype photon-counting breast CT system were simulated using a simulation package written in matlab to determine the smallest detectable μCa. A 14 cm diameter cylindrical phantom made of breast tissue with 20% glandularity was used to simulate an average-sized breast. Five different size groups of calcium carbonate grains, from 100 to 180 μm in diameter, were simulated inside of the cylindrical phantom. The images were acquired with a mean glandular dose (MGD) in the range of 0.7-8 mGy. A total of 400 images was used to perform a reader study. Another simulation study was performed using a 1.6 cm diameter cylindrical phantom to validate the experimental results from a bench-top prototype breast CT system. In the experimental study, a bench-top prototype CT system was constructed using a tungsten anode x-ray source and a single line 256-pixels Si strip photon-counting detector with a pixel pitch of 100 μm. Calcium carbonate grains, with diameter in the range of 105-215 μm, were embedded in a cylindrical plastic resin phantom to simulate μCas. The physical phantoms were imaged at 65 kVp with an entrance exposure in the range of 0.6-8 mGy. A total of 500 images was used to perform another reader study. The images were displayed in random order to three blinded observers, who were asked to give a 4-point confidence rating on each image regarding the presence of μCa. The μCa detectability for each image was evaluated by using the average area under the receiver operating characteristic curve (AUC) across the readers.
  
  
  RESULTS
  The simulation results using a 14 cm diameter breast phantom showed that the proposed photon-counting breast CT system can achieve high detection accuracy with an average AUC greater than 0.89 ± 0.07 for μCas larger than 120 μm in diameter at a MGD of 3 mGy. The experimental results using a 1.6 cm diameter breast phantom showed that the prototype system can achieve an average AUC greater than 0.98 ± 0.01 for μCas larger than 140 μm in diameter using an entrance exposure of 1.2 mGy.
  
  
  CONCLUSIONS
  The proposed photon-counting breast CT system based on a Si strip detector can potentially offer superior image quality to detect μCa with a lower dose level than a standard two-view mammography.
authors.affiliation: Department of Radiological Sciences, University of California, Irvine, California 92697.
authors.forename: Hyo-Min
authors.initials: HM
authors.lastname: Cho
authors.affiliation: Department of Radiological Sciences, University of California, Irvine, California 92697.
authors.forename: Huanjun
authors.initials: H
authors.lastname: Ding
authors.affiliation: DxRay Inc., Northridge, California 91324.
authors.forename: William C
authors.initials: WC
authors.lastname: Barber
authors.affiliation: DxRay Inc., Northridge, California 91324.
authors.forename: Jan S
authors.initials: JS
authors.lastname: Iwanczyk
authors.affiliation: Department of Radiological Sciences, University of California, Irvine, California 92697.
authors.forename: Sabee
authors.initials: S
authors.lastname: Molloi
mesh_terms: D019540:Area Under Curve; D001940:Breast; D002114:Calcinosis / Q000000981:diagnostic imaging*; D002119:Calcium Carbonate; D003198:Computer Simulation; D006801:Humans; D008327:Mammography / Q000295:instrumentation* / Q000379:methods*; D008954:Models, Biological; D019047:Phantoms, Imaging; D017785:Photons; D012372:ROC Curve; D011829:Radiation Dosage; D012825:Silicon; D012984:Software; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods*
chemical_list: D002119:Calcium Carbonate; D012825:Silicon