The feasibility of an inverse geometry CT system with stationary source arrays

Hsieh, Scott S.; Heanue, Joseph A.; Funk, Tobias; Hinshaw, W. S.; Wilfley, Brian P.; Solomon, Edward G.; Pelc, Norbert J.

doi:10.1118/1.4789918

Cited by 17 publications

(20 citation statements)

References 42 publications

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“…2012, Hsieh et al . 2013, Xu et al 2011, Shan et al 2013), image guided therapy (Maltz et al 2009) and small animal radiation therapy applications (Schreiber et al .…”

Section: Introductionmentioning

confidence: 99%

Studies of a prototype linear stationary x-ray source for tomosynthesis imaging

2014

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A prototype linear X-ray source to implement stationary source – stationary detector tomosynthesis imaging has been studied. Potential applications include human breast and small animal imaging. The source is comprised of ten X-ray source elements each consisting of a field emission cathode, electrostatic lens, and target. The electrostatic lens and target are common to all elements. The source elements form X-ray focal spots with minimum diameters of 0.3 to 0.4 mm at electron beam currents of up to 40 mA with a beam voltage of 40 kV. The X-ray flux versus time was quantified from each source. X-ray bremsstrahlung spectra from tungsten targets were produced using electron beam energies from 35 to 50 keV. The half-value layer was measured to be 0.8 mm, 0.9 mm, and 1.0 mm, respectively, for the 35 kV, 40 kV, and 45 kV tube potentials using the tungsten target. The suppression of voltage breakdown events, particularly during source operation, and the use of a modified form of the standard cold-cathode geometry, enhanced source reliability. The prototype linear source was used to collect tomographic data sets of a mouse phantom using digital tomosynthesis reconstruction methods and demonstrated a slice-sensitivity profile with a full-width-half-maximum of 1.3 mm. Lastly, preliminary studies of tomographic imaging of flow through the mouse phantom were performed.

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“…2012, Hsieh et al . 2013, Xu et al 2011, Shan et al 2013), image guided therapy (Maltz et al 2009) and small animal radiation therapy applications (Schreiber et al .…”

Section: Introductionmentioning

confidence: 99%

Studies of a prototype linear stationary x-ray source for tomosynthesis imaging

2014

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“…Finally, inverse geometry CT system concepts with a stationary source and a rotating detector are being investigated as an alternative to this IGCT architecture. 43…”

Section: Discussionmentioning

confidence: 99%

Multisource inverse-geometry CT. Part I. System concept and development

et al. 2016

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Purpose: This paper presents an overview of multisource inverse-geometry computed tomography (IGCT) as well as the development of a gantry-based research prototype system. The development of the distributed x-ray source is covered in a companion paper [V. B. Neculaes et al., "Multisource inverse-geometry CT. Part II. X-ray source design and prototype," Med. Phys. 43, 4617-4627 (2016)]. While progress updates of this development have been presented at conferences and in journal papers, this paper is the first comprehensive overview of the multisource inverse-geometry CT concept and prototype. The authors also provide a review of all previous IGCT related publications. Methods: The authors designed and implemented a gantry-based 32-source IGCT scanner with 22 cm field-of-view, 16 cm z-coverage, 1 s rotation time, 1.09 × 1.024 mm detector cell size, as low as 0.4 × 0.8 mm focal spot size and 80-140 kVp x-ray source voltage. The system is built using commercially available CT components and a custom made distributed x-ray source. The authors developed dedicated controls, calibrations, and reconstruction algorithms and evaluated the system performance using phantoms and small animals. Results: The authors performed IGCT system experiments and demonstrated tube current up to 125 mA with up to 32 focal spots. The authors measured a spatial resolution of 13 lp/cm at 5% cutoff. The scatter-to-primary ratio is estimated 62% for a 32 cm water phantom at 140 kVp. The authors scanned several phantoms and small animals. The initial images have relatively high noise due to the low x-ray flux levels but minimal artifacts. Conclusions: IGCT has unique benefits in terms of dose-efficiency and cone-beam artifacts, but comes with challenges in terms of scattered radiation and x-ray flux limits. To the authors' knowledge, their prototype is the first gantry-based IGCT scanner. The authors summarized the design and implementation of the scanner and the authors presented results with phantoms and small animals. C 2016 American Association of Physicists in Medicine.[http://dx

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“…The wedge which was translated downwards introduces only a small amount of attenuation, while the wedge that was translated upwards has more attenuation. Reprinted with permission from (Hsieh and Pelc 2013). …”

Section: Figurementioning

confidence: 99%

The piecewise-linear dynamic attenuator reduces the impact of count rate loss with photon-counting detectors

Hsieh

Pelc

2014

Phys. Med. Biol.

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Photon counting x-ray detectors (PCXDs) offer several advantages compared to standard, energy-integrating x-ray detectors but also face significant challenges. One key challenge is the high count rates required in CT. At high count rates, PCXDs exhibit count rate loss and show reduced detective quantum efficiency in signal-rich (or high flux) measurements. In order to reduce count rate requirements, a dynamic beam-shaping filter can be used to redistribute flux incident on the patient. We study the piecewise-linear attenuator in conjunction with PCXDs without energy discrimination capabilities. We examined three detector models: the classic nonparalyzable and paralyzable detector models, and a “hybrid” detector model which is a weighted average of the two which approximates an existing, real detector (Taguchi et al, Med Phys 2011). We derive analytic expressions for the variance of the CT measurements for these detectors. These expressions are used with raw data estimated from DICOM image files of an abdomen and a thorax to estimate variance in reconstructed images for both the dynamic attenuator and a static beam-shaping (“bowtie”) filter. By redistributing flux, the dynamic attenuator reduces dose by 40% without increasing peak variance for the ideal detector. For non-ideal PCXDs, the impact of count rate loss is also reduced. The nonparalyzable detector shows little impact from count rate loss, but with the paralyzable model, count rate loss leads to noise streaks that can be controlled with the dynamic attenuator. With the hybrid model, the characteristic count rates required before noise streaks dominate the reconstruction are reduced by a factor of two to three. We conclude that the piecewise-linear attenuator can reduce the count rate requirements of the PCXD in addition to improving dose efficiency. The magnitude of this reduction depends on the detector, with paralyzable detectors showing much greater benefit than nonparalyzable detectors.

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The feasibility of an inverse geometry CT system with stationary source arrays

Abstract: IGCT with stationary source arrays could be an imaging platform potentially capable of imaging a complete 16-cm thick volume within a tenth of a second.

Cited by 17 publications

References 42 publications

Studies of a prototype linear stationary x-ray source for tomosynthesis imaging

Studies of a prototype linear stationary x-ray source for tomosynthesis imaging

Multisource inverse-geometry CT. Part I. System concept and development

The piecewise-linear dynamic attenuator reduces the impact of count rate loss with photon-counting detectors

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