Evaluation of Energy Loss and Charge Sharing in Cadmium Telluride Detectors for Photon-Counting Computed Tomography

Cheng, Xu; Danielsson, Mats; Bornefalk, Hans

doi:10.1109/tns.2011.2122267

Cited by 86 publications

(47 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Previous studies based on analytical models or Monte Carlo method usually targeted only one artifact that led to spectral distortions. 17,34,41,45 Therefore, their ability to predict and correct the measured images is limited when the input count rate for a detector is very high. Theoretically, the counting mode of a photon-counting detector can be simulated with either a paralyzable or a nonparalyzable model.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Image‐based spectral distortion correction for photon‐counting x‐ray detectors

Ding

Molloi

2012

Medical Physics

View full text Add to dashboard Cite

Purpose: To investigate the feasibility of using an image-based method to correct for distortions induced by various artifacts in the x-ray spectrum recorded with photon-counting detectors for their application in breast computed tomography (CT). Methods: The polyenergetic incident spectrum was simulated with the tungsten anode spectral model using the interpolating polynomials (TASMIP) code and carefully calibrated to match the x-ray tube in this study. Experiments were performed on a Cadmium-Zinc-Telluride (CZT) photoncounting detector with five energy thresholds. Energy bins were adjusted to evenly distribute the recorded counts above the noise floor. BR12 phantoms of various thicknesses were used for calibration. A nonlinear function was selected to fit the count correlation between the simulated and the measured spectra in the calibration process. To evaluate the proposed spectral distortion correction method, an empirical fitting derived from the calibration process was applied on the raw images recorded for polymethyl methacrylate (PMMA) phantoms of 8.7, 48.8, and 100.0 mm. Both the corrected counts and the effective attenuation coefficient were compared to the simulated values for each of the five energy bins. The feasibility of applying the proposed method to quantitative material decomposition was tested using a dual-energy imaging technique with a three-material phantom that consisted of water, lipid, and protein. The performance of the spectral distortion correction method was quantified using the relative root-mean-square (RMS) error with respect to the expected values from simulations or areal analysis of the decomposition phantom. Results: The implementation of the proposed method reduced the relative RMS error of the output counts in the five energy bins with respect to the simulated incident counts from 23.0%, 33.0%, and 54.0% to 1.2%, 1.8%, and 7.7% for 8.7, 48.8, and 100.0 mm PMMA phantoms, respectively. The accuracy of the effective attenuation coefficient of PMMA estimate was also improved with the proposed spectral distortion correction. Finally, the relative RMS error of water, lipid, and protein decompositions in dual-energy imaging was significantly reduced from 53.4% to 6.8% after correction was applied. Conclusions: The study demonstrated that dramatic distortions in the recorded raw image yielded from a photon-counting detector could be expected, which presents great challenges for applying the quantitative material decomposition method in spectral CT. The proposed semi-empirical correction method can effectively reduce these errors caused by various artifacts, including pulse pileup and charge sharing effects. Furthermore, rather than detector-specific simulation packages, the method requires a relatively simple calibration process and knowledge about the incident spectrum. Therefore, it may be used as a generalized procedure for the spectral distortion correction of different photon-counting detectors in clinical breast CT systems. V C 2012 American Association of Physicists in Medi...

show abstract

Section: Discussionmentioning

confidence: 99%

“…A recent study has suggested that the charge sharing effects should be taken into account when the pixel is smaller than 1 mm 2 . 45 It is thus a major challenge that limits the spatial resolution of a photon-counting detector. Unlike the pulse pileup effect, charge sharing tends to remove counts from the high energy region.…”

Section: Introductionmentioning

confidence: 99%

Image‐based spectral distortion correction for photon‐counting x‐ray detectors

Ding

Molloi

2012

Medical Physics

View full text Add to dashboard Cite

show abstract

“…In all cases, we assume that the site of charge collection is the same as charge liberation, i.e., no charge diffusion. This may be a reasonable assumption for larger adaptively binned elements and higher threshold levels where the number of double-counting events caused by partial energy absorption in neighboring elements is reduced, as discussed by Xu et al 68 and Lundqvist et al, 16 respectively, but represents an optimistic estimate of detector performance for smaller element sizes.…”

Section: B Charge Liberation and Collectionmentioning

confidence: 97%

Detective quantum efficiency of photon‐counting x‐ray detectors

et al. 2015

View full text Add to dashboard Cite

The CSA approach is extended to describe signal and noise propagation through photoelectric and Compton interactions in SPC detectors, including the effects of escape and reabsorption of emission/scatter photons. High-performance SPC systems can be achieved but only for certain combinations of secondary conversion gain, depth-dependent collection efficiency, electronic noise, and reabsorption characteristics.

show abstract

“…Eq. (27). For transition matrices it holds that P i M i;j ¼ 1 since events must be reallocated somewhere.…”

Section: Iiia Basic Assumptionsmentioning

confidence: 99%

Task‐based weights for photon counting spectral x‐ray imaging

Bornefalk

2011

Medical Physics

View full text Add to dashboard Cite

The proposed method makes the spatial frequency dependency of complex correlation structures between bins and their effect on the system detective quantum efficiency easier to analyze and allows optimizing bin weights for given imaging tasks. A potential increase in detectability of double digit percents in silicon detector systems operated at typical CT energies (100 kVp) merits further evaluation on a real system. The method is noted to be of higher relevance for silicon detectors than for cadmium (zink) telluride detectors.

show abstract

Evaluation of Energy Loss and Charge Sharing in Cadmium Telluride Detectors for Photon-Counting Computed Tomography

Cited by 86 publications

References 28 publications

Image‐based spectral distortion correction for photon‐counting x‐ray detectors

Image‐based spectral distortion correction for photon‐counting x‐ray detectors

Detective quantum efficiency of photon‐counting x‐ray detectors

Task‐based weights for photon counting spectral x‐ray imaging

Contact Info

Product

Resources

About