Multisource inverse-geometry CT. Part II. X-ray source design and prototype

Neculaes, V.B.; Caiafa, Antonio; Cao, Yang; Man, Bruno De; Edic, Peter M.; Frutschy, Kristopher; Gunturi, Satish; Inzinna, Lou; Reynolds, Joseph; Vermilyea, Mark E; Wagner, David K.; Zhang, Xi; Zou, Y.; Pelc, Norbert J.; Lounsberry, Brian

doi:10.1118/1.4954847

Cited by 20 publications

(16 citation statements)

References 16 publications

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“…Neculaes et al. fabricated and tested a high‐power x‐ray source with 32 focal spots, 25 mm spacing between focal spots, and up to 1000 mA power output 18 . Maltz et al.…”

Section: Methodsmentioning

confidence: 99%

A simulated comparison of lung tumor target verification using stereoscopic tomosynthesis or radiography

Hsieh

Cao

et al. 2022

Medical Physics

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Purpose Mobile lung tumors are increasingly being treated with ablative radiotherapy, for which precise motion management is essential. In‐room stereoscopic radiography systems are able to guide ablative radiotherapy for stationary cranial lesions but not optimally for lung tumors unless fiducial markers are inserted. We propose augmenting stereoscopic radiographic systems with multiple small x‐ray sources to provide the capability of imaging with stereoscopic, single frame tomosynthesis. Methods In single frame tomosynthesis, nine x‐ray sources are placed in a 3 × 3 configuration and energized simultaneously. The beams from these sources are collimated so that they converge on the tumor and then diverge to illuminate nine non‐overlapping sectors on the detector. These nine sector images are averaged together and filtered to create the tomosynthesis effect. Single frame tomosynthesis is intended to be an alternative imaging mode for existing stereoscopic systems with a field of view that is three times smaller and a temporal resolution equal to the frame rate of the detector. We simulated stereoscopic tomosynthesis and radiography using Monte Carlo techniques on 60 patients with early‐stage lung cancer from the NSCLC‐Radiomics dataset. Two board‐certified radiation oncologists reviewed these simulated images and rated them on a 4‐point scale (1: tumor not visible; 2: tumor visible but inadequate for motion management; 3: tumor visible and adequate for motion management; 4: tumor visibility excellent). Each tumor was independently presented four times (two viewing angles from radiography and two viewing angles from tomosynthesis) in a blinded fashion over two reading sessions. Results The fraction of tumors that were rated as adequate or excellent for motion management (scores 3 or 4) from at least one viewing angle was 53% using radiography and 90% using tomosynthesis. From both viewing angles, the corresponding fractions were 7% for radiography and 48% for tomosynthesis. Readers agreed exactly on 62% of images and within 1 point on 98% of images. The acquisition technique was estimated to be 75 mAs at 120 kVp per treatment fraction assuming one verification image per breath, approximately one order of magnitude less than a standard dose cone beam CT. Conclusions Stereoscopic tomosynthesis may provide a noninvasive, low dose, intrafraction motion verification technique for lung tumors treated by ablative radiotherapy. The system architecture is compatible with real‐time video capture at 30 frames per second. Simulations suggest that most, but not all, lung tumors can be adequately visualized from at least one viewing angle.

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“…Neculaes et al. fabricated and tested a high‐power x‐ray source with 32 focal spots, 25 mm spacing between focal spots, and up to 1000 mA power output 18 . Maltz et al.…”

Section: Methodsmentioning

confidence: 99%

A simulated comparison of lung tumor target verification using stereoscopic tomosynthesis or radiography

Hsieh

Cao

et al. 2022

Medical Physics

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“…While we have not performed an extensive virtual bowtie system-level study on the IGCT prototype scanner, one virtual bowtie experiment is described in the companion paper. 44…”

Section: C Virtual Bowtiementioning

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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“…In these complex devices, the high voltage anode is held at a fixed kVp and the electron source must be precisely gated in order for each x‐ray source to be operated independently of the others. This has led to the development of a variety of electron sources for x‐ray generation, such as carbon nanotube (CNT)‐based field emitters, 13 tungsten dispenser cathodes, 14 and Spindt type emitters 15 . Recently, spatially distributed x‐ray source array technology with CNT field emitters has been demonstrated for a variety of 3D imaging applications 16–19 .…”

Section: Introductionmentioning

confidence: 99%

Evaluation of carbon nanotube x‐ray source array for stationary head computed tomography

et al. 2021

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Purpose Stationary computed tomography (s‐CT) conceptually offers several advantages over existing rotating gantry‐based CT. Over the last 40 yr, s‐CT has been investigated using different technological approaches. We are developing a s‐CT system specifically for head/brain imaging using carbon nanotube (CNT)‐based field emission x‐ray source array technology. The noncircular geometry requires different assessment approaches as compared to circular geometries. The purpose of the present study is to investigate whether the CNT source array meets the requirements for stationary head CT (s‐HCT). Methods Multiple prototype CNT x‐ray source arrays were manufactured based on the system requirements obtained from simulation. Source characterization was performed using a benchtop setup consisting of an x‐ray source array with 45 distributed focal spots, each operating at 120 kVp, and an electronic control system (ECS) for high speed control of the x‐ray output from individual focal spots. Due to the forward‐angled geometry of the linear anode, the projected focal spot shape is expected to vary at wide angle views. A pinhole method was implemented to determine the effective focal spot size (FSS) in the imaging plane at a range of angular viewpoints with a flat panel detector. The output spectrum and half value layer (HVL) were also evaluated for a range of viewing angles to characterize the beam quality across the fan‐beam. Dosimetry was performed on a simulated scan to evaluate total exposure. Results The prototype CNT x‐ray source array demonstrated adequate specifications for a s‐HCT imaging machine. The source array was operated at 120 kVp with long‐term stability over a full year of regular laboratory use. Multiple cathode current measurements were used to confirm submicrosecond accuracy with regards to exposure time and subsequently dose control. All 45 focal spots were measured with an average value of 1.26 (±0.04) mm × 1.21 (±0.03) mm (equivalent to IEC 1,0). The x‐ray spectrum was found to be appropriately filtered based on sources used in existing rotary CT systems. A stable and reliable output of 0.04 mAs per emitter and a resulting dose of 0.015 mGy per projection were observed over several months of rigorous phantom imaging. Dose per projection was regulated by the ECS and measured with ±0.5% tolerance. Conclusions The CNT x‐ray source array was found to meet the requirements for the proposed stationary head CT scanner, with regard to FSS, beam quality, and dose precision. The remaining challenges are related to the overall system design of a nonrotating CT scanner with distributed sources. The next phase of the project will incorporate multiple CNT source arrays with multirow detectors in a proof‐of‐concept study and analysis of a fully functional s‐HCT system.

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Multisource inverse-geometry CT. Part II. X-ray source design and prototype

Cited by 20 publications

References 16 publications

A simulated comparison of lung tumor target verification using stereoscopic tomosynthesis or radiography

A simulated comparison of lung tumor target verification using stereoscopic tomosynthesis or radiography

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

Evaluation of carbon nanotube x‐ray source array for stationary head computed tomography

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