High resolution stationary digital breast tomosynthesis using distributed carbon nanotube x‐ray source array

Abstract

Purpose: The purpose of this study is to investigate the feasibility of increasing the system spatial resolution and scanning speed of Hologic Selenia Dimensions digital breast tomosynthesis (DBT) scanner by replacing the rotating mammography x-ray tube with a specially designed carbon nanotube (CNT) x-ray source array, which generates all the projection images needed for tomosynthesis reconstruction by electronically activating individual x-ray sources without any mechanical motion. The stationary digital breast tomosynthesis (s-DBT) design aims to (i) increase the system spatial resolution by eliminating image blurring due to x-ray tube motion and (ii) reduce the scanning time. Low spatial resolution and long scanning time are the two main technical limitations of current DBT technology. Methods: A CNT x-ray source array was designed and evaluated against a set of targeted system performance parameters. Simulations were performed to determine the maximum anode heat load at the desired focal spot size and to design the electron focusing optics. Field emission current from CNT cathode was measured for an extended period of time to determine the stable life time of CNT cathode for an expected clinical operation scenario. The source array was manufactured, tested, and integrated with a Selenia scanner. An electronic control unit was developed to interface the source array with the detection system and to scan and regulate x-ray beams. The performance of the s-DBT system was evaluated using physical phantoms. Results: The spatially distributed CNT x-ray source array comprised 31 individually addressable x-ray sources covering a 30 angular span with 1 pitch and an isotropic focal spot size of 0.6 mm at full width at half-maximum. Stable operation at 28 kV(peak) anode voltage and 38 mA tube current was demonstrated with extended lifetime and good source-to-source consistency. For the standard imaging protocol of 15 views over 14, 100 mAs dose, and 2 Â 2 detector binning, the projection resolution along the scanning direction increased of 1.08. The improvement is more pronounced for faster scanning speeds, wider angular coverage, and smaller detector pixel sizes. The scanning speed depends on the detector, the number of views, and the imaging dose. With 240 ms detector readout time, the s-DBT system scanning time is 6.3 s for a 15-view, 100 mAs scan regardless of the angular coverage. The scanning speed can be reduced to less than 4 s when detectors become faster. Initial phantom studies showed good quality reconstructed images. Conclusions: A prototype s-DBT scanner has been developed and evaluated by retrofitting the Selenia rotating gantry DBT scanner with a spatially distributed CNT x-ray source array. Preliminary results show that it improves system spatial resolution substantially by eliminating image blur due to x-ray focal spot motion. The scanner speed of s-DBT system is independent of angular coverage and can be increased with faster detector without image degration. The accelerated lifetime measurement demo...

Radiologists' interpretive efficiency and variability in true- and false-positive detection when screen-reading with tomosynthesis (3D-mammography) relative to standard mammography in population screening

“…Although, this dependency can decrease (as compared to FFDM) because of the clearer DBT view for soft-tissue lesions [32,33] in general, and potentially for calcifications [30,32,34] as well. Furthermore, the radiologist ability to discriminate between abnormal and normal/benign findings typically increases when using DBT [30], which almost exclusively seem to be reflected by improvements in positive predictive values [7,10,11,14,15,25].…”

Enhanced Field Emission from a Carbon Nanotube Array Coated with a Hexagonal Boron Nitride Thin Film

“…The uniformity of the pulse emission current was also greatly improved compared with previous works, which is a crucial metric for some FE devices that operate at high frequencies. [ 42 ] It is obvious from the integrated intensity images (ZnO:Zn phosphor) captured of both the array with a 3 nm thick h -BN coating and the bare CNT array at an emission current of 1 mA (Figure 4 c,d) that the emission of the coated array was much improved compared with that of the bare CNT array. This also indirectly proves the existence of the self-current-limiting mechanism discussed above.…”

Initial clinical evaluation of stationary digital chest tomosynthesis

“…14 A stationary digital breast tomosynthesis (s-DBT) using a CNT x-ray source array has been successfully developed and installed in the University of North Carolina's Women's Hospital for clinical trials. [15][16][17] Using the x-ray source array, the stationary digital chest tomosynthesis (s-DCT) system can achieve full angular coverage in tomosynthesis imaging with no moving parts. 14,[18][19][20] Previous studies on the stability and geometry of the s-DCT system have been published.…”