Dose and detectability improvements with high energy phase sensitive x-ray imaging in comparison to low energy conventional imaging

Abstract

The objective of this study was to demonstrate the potential benefits of using high energy x-rays for phase sensitive breast imaging through a comparison with conventional mammography imaging. We compared images of a contrast-detail (CD) phantom acquired on a prototype phase sensitive x-ray imaging system with images acquired on a commercial flat panel digital mammography unit. The phase contrast images were acquired using a micro-focus x-ray source with a 50 μm focal spot at 120 kVp and 4.5 mAs, with a magnification factor of 2.46 and a 50 μm pixel pitch. A phase attenuation duality (PAD)-based phase retrieval algorithm that requires only a single phase contrast image was applied. Conventional digital mammography images were acquired at 27 kVp, 131 mAs and 28 kVp, 54 mAs. For the same radiation dose, both the observer study and SNR/FOM comparisons indicated a large improvement by the phase retrieved image as compared to the clinical system for the larger disk sizes, but the improvement was not enough to detect the smallest disks. Compared to the double dose image acquired with the clinical system, the observer study also indicated that the phase retrieved image provided improved detection capabilities for all disk sizes except the smallest disks. Thus the SNR improvement provided by phase contrast imaging is not yet enough to offset the noise reduction provided by the clinical system at the doubled dose level. However, the potential demonstrated by this study for high energy phase sensitive x-ray imaging to improve lesion detection and reduce radiation dose in mammography warrants further investigation of this technique.

Quantitative investigation of the edge enhancement in in-line phase contrast projections and tomosynthesis provided by distributing microbubbles on the interface between two tissues: a phantom study

“…Based on this dose constraint, the corresponding object entrance exposure ( X ESE ) values can be determined by the ratio of the average glandular dose ( D g ) and the normalized average glandular dose coefficient ( D gN ) as follows: $$X_{\mathrm{italicESE}}=\frac{D_g}{D_{gN}}$$ where D g has been selected as the unified dose value of 2.590 mGy, and D gN was determined by experimental and computer simulation methods based on radiation beam quality (x-ray energy or HVL), x-ray tube target material, filter material, breast thickness, and breast tissue composition, which is the same strategy utilized in the literature (Wong et al , 2014; Hendrick, 1994; Suryanarayanan et al , 2002; Wu, 1991; Wu et al , 1991; Wu et al , 1994). For the calculation, we assumed a thickness of 4 cm with a composition of 50% glandular and 50% adipose.…”

“…Several x-ray imaging techniques based on the phase shift have been reported and investigated (Castelli et al , 2011; Tanaka et al , 2013; Zanette et al , 2014), and in-line phase contrast x-ray imaging is one of these methods. The clinical feasibility of in-line phase contrast mammography has been widely reported (Wu et al , 2015b; Wong et al , 2014), and its potential to improve signal-to-noise ratio (SNR) and reduce exposure time as well as radiation dose have been demonstrated in phantom studies (Wong et al , 2014). Recently, the criteria of the type of microbubble used for in-line phase contrast agent has been investigated and discussed by Wu et al (Wu et al , 2017).…”

Detectability comparison between a high energy x-ray phase sensitive and mammography systems in imaging phantoms with varying glandular-adipose ratios

“…This contrast is superimposed onto the attenuation contrast on the image and helps to improve the visibility of the borders of structures and other fine details. As reported previously [24], in-line phase contrast imaging faces two key challenges in clinical implementation. The first challenge is to achieve adequate x-ray transverse coherence while providing sufficient photon flux at short exposure times.…”

“…Micro-focus x-ray sources operating with large source-to-object distances can provide large transverse coherent lengths [20, 21]; however, a very long exposure time is required for imaging due to the limited current of the micro-focus tubes. To address this challenge, a high energy beam of approximately 100–120 kV has been utilized recently to acquire phase sensitive images of soft tissue-equivalent phantoms with shorter exposure time [24, 25]. Secondly, although the interfaces of different tissue areas are greatly accentuated in a phase contrast image, the bulk of the phase contrast in a given tissue area may be lost if the phase shifts vary slowly.…”

Characterization of continuous and pulsed emission modes of a hybrid micro focus x-ray source for medical imaging applications

“…One of the main reason that is limiting the wide use of micro focus x-ray sources in the patient imaging is the long exposure time associated with them to acquire a scan due to their limited output powers. Nevertheless, the technological developments have encouraged the design of new inline PCI set-ups which have permitted to extend the range of applications towards higher x-ray energies [25–27]. Numerous studies have implemented the in-line phase contrast tomosynthesis with micro-focus x-ray sources in preclinical studies with breast tissue samples, fish bone, mouse and rabbit lungs [28–30].…”