Lag correction model and ghosting analysis for an indirect‐conversion flat‐panel imager

Mail, Noor; O’Brien, P.; Pang, G.

doi:10.1120/jacmp.v8i3.2483

Cited by 23 publications

(20 citation statements)

References 23 publications

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“…Both these consequences could be overcome with an adequate image lag correction as has been proposed. 21 In our method, 100 frames where averaged to decrease noise and capture a "snap shot" of the treatment delivery, including that of a dead mouse. In future implementations, this number may be reduced in an effort to capture intrafaction motion of small animals during treatment.…”

Section: Discussionmentioning

confidence: 99%

“…Image lag is often difficult to correct without the equipment necessary to measure the response of the OBI device to an xray impulse. 21 Therefore, to reduce the effects of image lag during irradiations of the OBI device without a complicated correction model, an average image consisting of 100 frames is acquired following the first 300 frames of irradiation so that image intensities would approach a steady-state condition. To access the influence of image lag for this acquisition protocol a falling-edge response step response function was used by rapidly cutting power to the x-ray tube and measuring the residual image signal (i.e., lag).…”

Section: Iic1 Minimizing Obi Perturbations Image: Lag and Scatter-mentioning

confidence: 99%

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A combined dose calculation and verification method for a small animal precision irradiator based on onboard imaging

et al. 2012

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Section: Discussionmentioning

confidence: 99%

Section: Iic1 Minimizing Obi Perturbations Image: Lag and Scatter-mentioning

confidence: 99%

A combined dose calculation and verification method for a small animal precision irradiator based on onboard imaging

et al. 2012

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“…, these types of artifacts are not apparent in the reconstruction, suggesting adequate temporal performance of the scintillator relative to the amount of noise present on the detector. However, in lower noise modes or dose regimes, or higher frame‐rate modes, where lag artifacts may become more apparent in the reconstruction, lag‐mitigation strategies and algorithms may be employed …”

Section: Discussionmentioning

confidence: 99%

Characterizing a novel scintillating glass for application to megavoltage cone‐beam computed tomography

Shedlock

Wang

et al. 2019

Medical Physics

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Purpose The purpose of this study was to evaluate the performance of a prototype electric portal imaging device (EPID) with a high detective quantum efficiency (DQE) scintillator, LKH‐5. Specifically, image quality in context of both planar and megavoltage (MV) cone‐beam computed tomography (CBCT) is analyzed. Methods Planar image quality in terms of modulation transfer function (MTF), noise power spectrum (NPS), and DQE are measured and compared to an existing EPID (AS‐1200) using the 6 MV beamline for a Varian TrueBeam linac. Imager performance is contextualized for three‐dimensional (3D), MV‐CBCT performance by measuring imager lag and analyzing the expected degradation of the DQE as a function of dose. Finally, comparisons between reconstructed images of the Catphan phantom in terms of qualitative quality and signal‐difference‐to‐noise ratio (SDNR) are made for 6 MV images using both conventional and LKH‐5 EPIDs as well as for the kilovoltage (kV) on‐board imager (OBI). Results Analysis of the NPS reveals linearity at all measured doses using the prototype LKH‐5 detector. While the first zero of the MTF is much lower for the LKH‐5 detector than the conventional EPID (0.6 cycles/mm vs 1.6 cycles/mm), the normalized NPS (NNPS) multiplied by total quanta (qNNPS) of the LKH‐5 detector is roughly a factor of seven to eight times lower, yielding a DQE(0) of approximately 8%. First, second, and third frame lag were measured at approximately 23%, 5%, and 1%, respectively, although no noticeable image artifacts were apparent in reconstructed volumes. Analysis of low‐dose performance reveals that DQE(0) remains at 80% of its maximum value at a dose as low as 7.5 × 10−6 MU. For a 400 projection technique, this represents a total scan dose of 0.0030 MU, suggesting that if imaging doses are increased to a value typical of kV‐CBCT scans (~2.7 cGy), the LKH‐5 detector will retain quantum noise limited performance. Finally, comparing Catphan scans, the prototype detector exhibits much lower image noise than the conventional EPID, resulting in improved small object representation. Furthermore, SDNR of H2O and polystyrene cylinders improved from −1.95 and 2.94 to −15 and 18.7, respectively. Conclusions Imaging performance of the prototype LKH‐5 detector was measured and analyzed for both planar and 3D contexts. Improving noise transfer of the detector results in concurrent improvement of DQE(0). For 3D imaging, temporal characteristics were adequate for artifact‐free performance and at relevant doses, the detector retained quantum noise limited performance. Although quantitative MTF measurements suggest poorer resolution, small object representation of the prototype imager is qualitatively improved over the conventional detector due to the measured reduction in noise.

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“…The RMS separation of the marker configuration, f k , and the distance between the configuration centroid to the target, d k , is best for the in-FOV, slightly better for out-FOV 45-180 than Cloud, and worst for out-FOV 45- affected by lag. A variety of lag correction techniques 48 are applicable and could reduce the systematic error is x I . An automatic image-to-world registration method has been developed that demonstrates accuracy and reproducibility consistently at or better than that of the conventional manual technique.…”

Section: Discussionmentioning

confidence: 99%

Automatic image‐to‐world registration based on x‐ray projections in cone‐beam CT‐guided interventions

et al. 2009

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Intraoperative imaging offers a means to account for morphological changes occurring during the procedure and resolve geometric uncertainties via integration with a surgical navigation system. Such integration requires registration of the image and world reference frames, conventionally a time consuming, error-prone manual process. This work presents a method of automatic image-toworld registration of intraoperative cone-beam computed tomography ͑CBCT͒ and an optical tracking system. Multimodality ͑MM͒ markers consisting of an infrared ͑IR͒ reflective sphere with a 2 mm tungsten sphere ͑BB͒ placed precisely at the center were designed to permit automatic detection in both the image and tracking ͑world͒ reference frames. Image localization is performed by intensity thresholding and pattern matching directly in 2D projections acquired in each CBCT scan, with 3D image coordinates computed using backprojection and accounting for C-arm geometric calibration. The IR tracking system localized MM markers in the world reference frame, and the image-to-world registration was computed by rigid point matching of image and tracker point sets. The accuracy and reproducibility of the automatic registration technique were compared to conventional ͑manual͒ registration using a variety of marker configurations suitable to neurosurgery ͑markers fixed to cranium͒ and head and neck surgery ͑markers suspended on a subcranial frame͒. The automatic technique exhibited subvoxel marker localization accuracy ͑Ͻ0.8 mm͒ for all marker configurations. The fiducial registration error of the automatic technique was ͑0.35Ϯ 0.01͒ mm, compared to ͑0.64Ϯ 0.07 mm͒ for the manual technique, indicating improved accuracy and reproducibility. The target registration error ͑TRE͒ averaged over all configurations was 1.14 mm for the automatic technique, compared to 1.29 mm for the manual in accuracy, although the difference was not statistically significant ͑p = 0.3͒. A statistically significant improvement in precision was observed-specifically, the standard deviation in TRE was 0.2 mm for the automatic technique versus 0.34 mm for the manual technique ͑p = 0.001͒. The projection-based automatic registration technique demonstrates accuracy and reproducibility equivalent or superior to the conventional manual technique for both neurosurgical and head and neck marker configurations. Use of this method with C-arm CBCT eliminates the burden of manual registration on surgical workflow by providing automatic registration of surgical tracking in 3D images within ϳ20 s of acquisition, with registration automatically updated with each CBCT scan. The automatic registration method is undergoing integration in ongoing clinical trials of intraoperative CBCTguided head and neck surgery.

show abstract

Lag correction model and ghosting analysis for an indirect‐conversion flat‐panel imager

Cited by 23 publications

References 23 publications

A combined dose calculation and verification method for a small animal precision irradiator based on onboard imaging

A combined dose calculation and verification method for a small animal precision irradiator based on onboard imaging

Characterizing a novel scintillating glass for application to megavoltage cone‐beam computed tomography

Automatic image‐to‐world registration based on x‐ray projections in cone‐beam CT‐guided interventions

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