Computed tomography with a linear accelerator with radiotherapy applications

Swindell, W.; Simpson, R. G.; Oleson, James R.; Chen, Ching-Tai; Grubbs, Elmer A.

doi:10.1118/1.595391

Cited by 72 publications

(34 citation statements)

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“…The third generation megavoltage CT system previously reported by the authors [20] has been shown to produce better quality images than those reported by Swindell et al [21]. The current image quality of these third generation designs remains much worse than that attained in conventional diagnostic CT scanners.…”

Section: Discussionmentioning

confidence: 93%

“…Such methods are, however, limited to two-dimensional projections for the three-dimensional treatment volume. We have developed and reported a new computed tomographic (CT) scanning technique (megavoltage CT scanning) using a megavoltage X-ray beam emerging from a linear accelerator and have already begun to use it clinically for verification in two ways [19][20][21]. In one way, megavoltage CT scanning is performed after the patient is set on the treatment table.…”

Section: Introductionmentioning

confidence: 99%

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Improvement of image quality in megavoltage computed tomography with second generation scanning mode

Nakagawa

Aoki

Sasaki

1997

Radiat. Oncol. Investig.

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Section: Discussionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Improvement of image quality in megavoltage computed tomography with second generation scanning mode

Nakagawa

Aoki

Sasaki

1997

Radiat. Oncol. Investig.

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“…These high‐Z image artifacts are greatly reduced in MV X‐ray imaging. Past efforts of using the therapeutic MV beams for imaging have proven its feasibility especially in the area of portal imaging while the implementation of megavoltage cone‐beam imaging (MVCB) has also been studied by several different groups 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 and is commercially available (MVision, Siemens Medical Solutions USA, Malvern, PA).…”

Section: Introductionmentioning

confidence: 99%

Low‐dose 2.5 MV cone‐beam computed tomography with thick CsI flat‐panel imager

Tang

Moussot

Morf

et al. 2016

J Applied Clin Med Phys

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Most of the treatment units, both new and old models, are equipped with a megavoltage portal imager but its use for volumetric imaging is limited. This is mainly due to the poor image quality produced by the high‐energy treatment beam (>6 MV). A linac at our center is equipped with a prototype 2.5 MV imaging beam. This study evaluates the feasibility of low‐dose megavoltage cone‐beam imaging with the 2.5 MV beam and a thick cesium iodide detector, which is a high‐efficiency imager. Basic imaging properties such as spatial resolution and modulation transfer function were assessed for the 2.5 MV prototype imaging system. For image quality and imaging dose, a series of megavoltage cone‐beam scans were acquired for the head, thorax, and pelvis of an anthropomorphic phantom and were compared to kilovoltage cone‐beam and 6X megavoltage cone‐beam images. To demonstrate the advantage of MV imaging, a phantom with metallic inserts was scanned and the image quality was compared to CT and kilovoltage cone‐beam scans. With a lower energy beam and higher detector efficiency, the 2.5 MV imaging system generally yields better image quality than does the 6 MV imaging system with the conventional MV imager. In particular, with the anthropomorphic phantom studies, the contrast to noise of bone to tissue is generally improved in the 2.5 MV images compared to 6 MV. With an image quality sufficient for bony alignment, the imaging dose for 2.5 MV cone‐beam images is 2.4−3.4 MU compared to 26 MU in 6 MV cone‐beam scans for the head, thorax, and pelvis regions of the phantom. Unlike kilovoltage cone‐beam, the 2.5 MV imaging system does not suffer from high‐Z image artifacts. This can be very useful for treatment planning in cases where high‐Z prostheses are present.PACS number(s): 87.57.Q‐

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“…[8][9][10] Another CT imaging technique that is also under investigation for soft tissue visualization involves the use of the megavoltage (MV) therapy beam and an electronic portal imaging device (EPID). [5][6][7][8]11,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Although the intrinsic contrast of human anatomical structures is lower at MV energies compared to kV energies, it has been demonstrated that soft tissues can be visualized on MV CBCT images obtained using conventional, as well as investigational, imagers. 8,24,30,33 In addition, MV CBCT can offer some advantages over the kV technique.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo investigations of megavoltage cone‐beam CT using thick, segmented scintillating detectors for soft tissue visualization

et al. 2007

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Megavoltage cone-beam computed tomography (MY CBCT) is a highly promising technique for providing volumetric patient position information in the radiation treatment room. Such information has the potential to greatly assist in registering the patient to the planned treatment position, helping to ensure accurate delivery of the high energy therapy beam to the tumor volume while sparing the surrounding normal tissues. Presently, CBCT systems using conventional MV active matrix flat-panel imagers (AMFPIs), which are commonly used in portal imaging, require a relatively large amount of dose to create images that are clinically useful. This is due to the fact that the phosphor screen detector employed in conventional MV AMFPIs utilizes only ~2% of the incident radiation (for a 6 MV x-ray spectrum). Fortunately, thick, segmented scintillating detectors can overcome this limitation, and the first prototype imager has demonstrated highly promising performance for projection imaging at low doses. It is therefore of definite interest to examine the potential performance of such thick, segmented scintillating detectors for MV CBCT. In this study, Monte Carlo simulations of radiation energy deposition were used to examine reconstructed images of cylindrical CT contrast phantoms, embedded with tissue-equivalent objects. The phantoms were scanned at 6 MV using segmented detectors having various design parameters (i.e., detector thickness, as well as scintillator and septal wall materials). Due to constraints imposed by the nature of this study, the size of the phantoms was limited to ~6 cm. For such phantoms, the simulation results suggest that a 40 mm thick, segmented CsI detector with low density septal walls can delineate electron density differences of ~2.3% and 1.3% at doses of 1.54 and 3.08 cGy, respectively. In addition, it was found that segmented detectors with greater thickness, higher density scintillator material, or lower density septal walls exhibit higher contrastto-noise performance. Finally, the performance of various segmented detectors obtained at a relatively low dose (1.54 cGy) was compared to that of a phosphor screen similar to that employed in conventional MV AMFPIs. This comparison indicates that, for a phosphor screen to achieve the same contrast-to-noise performance as the segmented detectors, ~18 to 59 times more dose is required, depending on the configuration of the segmented detectors.

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Computed tomography with a linear accelerator with radiotherapy applications

Cited by 72 publications

References 0 publications

Improvement of image quality in megavoltage computed tomography with second generation scanning mode

Improvement of image quality in megavoltage computed tomography with second generation scanning mode

Low‐dose 2.5 MV cone‐beam computed tomography with thick CsI flat‐panel imager

Monte Carlo investigations of megavoltage cone‐beam CT using thick, segmented scintillating detectors for soft tissue visualization

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