Rotating Disk Device for Slit Radiography of the Chest

Sorenson, JA

doi:10.6009/jjrt.kj00003105545

Cited by 7 publications

(10 citation statements)

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“…While prototypes have been built to demonstrate the feasibility of this approach, the construction and need to control and move the heavy and bulky aft-collimator, especially for chest imaging, have turned to be an obstacle in continuing to pursue this approach. [27][28][29] With the advances of digital detector technology, slot-scan imaging systems using slit or slot shaped detector arrays have been developed and investigated. [32][33][34][35][36] This approach has enjoyed the advantage of not having to control and move a heavy and bulky aft-collimator.…”

Section: Introductionmentioning

confidence: 99%

“…With these techniques, one or more collimated narrow fan beams were formed and used to scan across the patient. [25][26][27][28][29][30][31][32][33][34][35][36] A dynamically collimated area detector or a moving detector array is used to record the fan-beam exposure signals only, leaving x-rays scattered from outside the fan beam undetected. The main advantage of the slot-scan imaging technique is its ability to achieve effective scatter rejection without having to attenuate primary x-rays.…”

Section: Introductionmentioning

confidence: 99%

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Scatter rejection and low‐contrast performance of a slot‐scan digital chest radiography system with electronic aft‐collimation: A chest phantom study

et al. 2008

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Anti-scatter grids have been widely used to reject scatter and increase the perceptibility of lowcontrast object in chest radiography; however they also attenuate the primary x-rays, resulting in a substantial degradation of primary information. Compensation for this degradation requires the use of higher exposure technique hence higher dose to the patient. A more efficient approach to reject scatter is the slot-scan imaging technique which employs a narrow scanning x-ray fan beam in conjunction with a slit or slot shaped solid state detector or an area detector used with an aftcollimator. With this approach, scatter can be rejected effectively without the need to attenuate primary x-rays. This paper demonstrates an electronic aft-collimation method, referred to as the alternate line erasure and readout ͑ALER͒ technique, for implementing the slot-scan digital radiography with a modern flat-panel detector. With this technique, instead of first exposing the detector and then reading the image line by line, the image line on the leading edge of the scanning fan beam is reset to erase the scatter accumulated prior to the arrival of the fan beam x-rays, while the image line on the trailing edge of the scanning fan beam is read out to acquire the image signals following the fan-beam exposure. These reset and readout processes are alternated and repeated as the x-ray fan beam scans across the detector. An anthropomorphic chest phantom was imaged to evaluate the scatter rejection ability and the low-contrast performance for the ALER technique and compare them with those for the anti-scatter grid method in full-field chest imaging. With a projected beam width of 16 mm, the slot-scan/ALER technique resulted in an average reduction of the scatter-toprimary ratios by 81%, 84%, 82%, and 86% versus 65%, 73%, 74%, and 73% with the anti-scatter grid method in the lungs, mediastinum, retrocardium, and subdiaphragm, respectively. The average CNR for the slot-scan/ALER technique was found to improve by 135%, 133%, 176%, and 87% versus 15%, 15%, 38%, and −11% with the anti-scatter grid method in the mediastinum, retrocardium, subdiaphragm, and lungs, respectively. These results demonstrated that the slot-scan/ALER technique can be used to achieve equally effective scatter rejection but substantially higher lowcontrast performance than the anti-scatter grid method.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Scatter rejection and low‐contrast performance of a slot‐scan digital chest radiography system with electronic aft‐collimation: A chest phantom study

et al. 2008

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“…A variety of mechanical scanning approaches have been investigated using a stationary x-ray tube and moving slit or aperture assembly to define the beam. [7][8][9][10][11][12][13] Only a small patient volume is irradiated at a time. The active detector area is matched to the beam.…”

Section: Design Principlesmentioning

confidence: 99%

Scanning-beam digital x-ray (SBDX) technology for interventional and diagnostic cardiac angiography

et al. 2006

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The scanning-beam digital x-ray (SBDX) system is designed for x-ray dose reduction in cardiac angiographic applications. Scatter reduction, efficient detection of primary x-rays, and an inverse beam geometry are the main components of the entrance dose reduction strategy. This paper reports the construction of an SBDX prototype, image reconstruction techniques, and measurements of spatial resolution and x-ray output. The x-ray source has a focal spot that is electronically scanned across a large-area transmission target. A multihole collimator beyond the target defines a series of x-ray beams directed at a distant small-area detector array. The prototype has a 23 cm X 23 cm target, 100 X 100 focal spot positions, and a 5 cm X 5 cm CdTe detector positioned 150 cm from the target. With this nonmechanical method of beam scanning, patient images with low detected scatter are generated at up to 30 frame/s. SBDX data acquisition is tomosynthetic. The prototype simultaneously reconstructs 16 planes spaced throughout the cardiac volume using shift-and-add backprojection. Image frames analogous to conventional projection images are generated with a multiplane compositing algorithm. Single-plane versus multiplane reconstruction of contrast-filled coronary arteries is demonstrated with images of the porcine heart. Phantom and porcine imaging studies show multiplane reconstruction is practicable under clinically realistic levels of patient attenuation and cardiac motion. The modulation transfer function for an in-plane slit at mechanical isocenter measured 0.41-0.56 at 1 cycle/mm, depending on the detector element to image pixel interpolation technique. Modeling indicates that desired gains in spatial resolution are achievable by halving the detector element width. The x-ray exposure rate 15 cm below isocenter, without table or patient in the beam, measured 11.5 R/min at 120 kVp, 24.3 kWp and 3.42 R/min at 70 kVp, 14.2 kWp.

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“…With these techniques, a collimated narrow fan beam was used in conjunction with a dynamically collimated area detector or a tracking detector array to scan across the patient. [24][25][26][27][28][29][30][31][32][33][34][35] The main advantage of the slot-scan technique is its dose efficiency, as primary x-rays do not have to be attenuated. However, it requires accurate and precise alignment of the fan beam collimator with the x-ray tube focal spot.…”

Section: Introductionmentioning

confidence: 99%

Rejection and redistribution of scattered radiation in scan equalization digital radiography (SEDR): Simulation with spot images

Liu¹,

Shaw²

2007

Medical Physics

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The anti-scatter grid has been widely used to reject scatter and increase the perceptibility of a low-contrast object in chest radiography; however, it also attenuated the primary x-rays, resulting in a substantial loss of information and an increased relative noise level in heavily attenuated regions. A more dose efficient approach to scatter rejection is the slot-scan imaging technique. Another problem in chest radiography is the low transmitted x-ray intensity in heavily attenuating regions. It results in a higher relative noise level, thus limiting the contrast sensitivity. A solution to this problem is through the exposure equalization technique, with which the incident x-ray intensity is regionally modulated to compensate for the differences of x-ray attenuation due to the anatomic variation. We are in the process of implementing the scan equalization digital radiography (SEDR) technique, which combines the advantages of slot-scan imaging and exposure equalization. However, associated with the use of exposure equalization is a redistribution of scattered radiation at the detector, which may impact on the benefit of using exposure equalization in conjunction with the slot-scan imaging geometry. In order to understand the scatter properties and their impact in SEDR, we have used spot collimated digital radiographic images to synthesize simulated SEDR images with which scatter components, primary signals, and scatter-to-primary ratios (SPRs) were measured. It was shown that the anti-scatter grid rejected approximately 70% and 80% of scattered radiation in lightly and heavily attenuated regions, respectively, while the slot-scan method can reject as high as 95% (with 1 cm slot width) of scattered radiation without attenuation of the primary x-rays. Using a simple model for scatter effects, we have also estimated and compared the contrast-to-noise ratio degradation factors (CNRDFs, i.e., the fraction by which CNR is reduced). It was found that for quantum limited situations, the slot-scan technique has resulted in a substantial improvement of the image quality, as indicated by higher estimated CNRDFs (less scatter). An estimated improvement of 40%-50% in the lungs, 50%-90% in the mediastinum, and 60%-110% in the subdiaphragm was achieved with the slot-scan over the anti-scatter grid method. Compared to slot-scan imaging, SEDR resulted in higher SPRs in the lungs and lower SPRs in the mediastinum. In the subdiaphragmatic regions, the SPRs remain about the same. This corresponds to lower CNRDFs in the lungs, higher CNRDFs in the mediastinum, and about the same CNRDFs in the subdiaphragmatic regions. It was shown that although SEDR has resulted in minimum improvement over slot-scan imaging in reducing the SPRs, it could improve the contrast sensitivity by raising the primary signal levels in heavily attenuating regions. This advantage needs to be further investigated in our continuing study of the SEDR technique.

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Rotating Disk Device for Slit Radiography of the Chest

Cited by 7 publications

References 0 publications

Scatter rejection and low‐contrast performance of a slot‐scan digital chest radiography system with electronic aft‐collimation: A chest phantom study

Scatter rejection and low‐contrast performance of a slot‐scan digital chest radiography system with electronic aft‐collimation: A chest phantom study

Scanning-beam digital x-ray (SBDX) technology for interventional and diagnostic cardiac angiography

Rejection and redistribution of scattered radiation in scan equalization digital radiography (SEDR): Simulation with spot images

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