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J.a. Rowlands - One of the best experts on this subject based on the ideXlab platform.

  • evaluation of the imaging properties of an amorphous selenium based flat panel detector for Digital Fluoroscopy
    Medical Physics, 2004
    Co-Authors: Dylan C. Hunt, Olivier Tousignant, J.a. Rowlands
    Abstract:

    The imaging performance of an amorphous selenium (a‐Se) flat-panel detector for Digital Fluoroscopy was experimentally evaluated using the spatial frequency dependent modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). These parameters were investigated at beam qualities and exposures within the range typical of gastrointestinal fluoroscopic imaging (∼0.1–10 μR, 75 kV). The investigation does not take into consideration the detector cover, which in clinical use will lower the DQE measured here by its percent attenuation. The MTF was found to be less than the expected aperture response and the NPS was not white which together indicate presampling blurring. The cause of this blurring was attributed to charge trapping at the interface between two different layers of the a‐Se. The effect on the DQE was also consistent with presampling blur, which reduces the aliasing in the NPS and thereby reduces the spatial frequency dependence of the DQE. (The DQE was independent of spatial frequency from 0.12 to 0.73 mm−1 due to antialiasing of the NPS.) Moreover, the first zero of the measured MTF and the aperture response appeared at the same spatial frequency (6.66 mm−1 for a pixel of 150 μm). Hence, the geometric fill factor (77%) was increased to an effective fill factor of 99±1%. A large scale (∼32 pixels) correlation in the noise due to the configuration of the readout electronics caused increased noise power in the gate line NPS at low spatial frequency (<0.1 mm−1). The DQE (f=0) was exposure independent over a large range of exposures but became exposure dependent at low exposures due to the electronic noise.

  • amorphous silicon pixel amplifier with spl delta v sub t compensation for low noise Digital Fluoroscopy
    International Electron Devices Meeting, 2002
    Co-Authors: K.s. Karim, A. Nathan, J.a. Rowlands
    Abstract:

    The reported amorphous silicon (a-Si) pixel amplifier offers an improved signal-to-noise ratio compared to its traditional a-Si switch counterpart. Results from this research demonstrate that a-Si on-pixel amplifiers, coupled with a well established X-ray detection technology such as amorphous selenium, meet the minimum requirements for large area, real-time, low noise Digital Fluoroscopy.

  • Amorphous silicon pixel amplifier with /spl Delta/V/sub T/ compensation for low noise Digital Fluoroscopy
    Digest. International Electron Devices Meeting, 2002
    Co-Authors: K.s. Karim, A. Nathan, J.a. Rowlands
    Abstract:

    The reported amorphous silicon (a-Si) pixel amplifier offers an improved signal-to-noise ratio compared to its traditional a-Si switch counterpart. Results from this research demonstrate that a-Si on-pixel amplifiers, coupled with a well established X-ray detection technology such as amorphous selenium, meet the minimum requirements for large area, real-time, low noise Digital Fluoroscopy.

A. Häcker - One of the best experts on this subject based on the ideXlab platform.

  • Influence of endourological devices on 3D reconstruction image quality using the Uro Dyna-CT
    World Journal of Urology, 2013
    Co-Authors: M.-c. Rassweiler, M. Ritter, M.-s. Michel, A. Häcker
    Abstract:

    Purpose The urological Dyna-CT (Uro Dyna-CT) was established in clinical use for classical imaging as well as for interventional surgery. To evaluate whether irradiation artefacts may occur during interventional surgery, we analysed the impact of different instruments on 3D reconstruction in the Uro Dyna-CT. Materials and methods Ten different endourological instruments [ureterorenoscope (URS)-fibrescope, percutaneous nephrolithotomy (PCNL) working sheath] and accessory equipments such as ureteral catheter, guide wires and stents (DJ, MJ) were introduced in a porcine renal pelvis either retrograde via the ureter or transparenchymally. Subsequently, Digital Fluoroscopy, standard X-ray and an Uro Dyna-CT were performed. Three colleagues evaluated the image quality independent from each other. Results There were basically no limitations regarding image quality in Digital Fluoroscopy and standard X-ray. In the Uro Dyna-CT, only with the URS fiberscope and the PCNL working sheath, small artefacts and irradiations were detected, whereas ureteric catheter with and without wire, as well as the hydrophilic guide wire, showed no artefacts at all. The remaining material demonstrated minimal artefacts, which did not affect the image quality. Conclusions The Uro Dyna-CT can be used for all interventional endourological procedures using the common armamentarium and instruments without significant limitation of image quality. There are only minor limitations according a PCNL working sheath and the rigid URS. These instruments should be removed out of the examination field before performing the computed tomography and be replaced afterwards by using a safety wire.

  • Influence of endourological devices on 3D reconstruction image quality using the Uro Dyna-CT
    World journal of urology, 2012
    Co-Authors: M.-c. Rassweiler, M. Ritter, M.-s. Michel, A. Häcker
    Abstract:

    The urological Dyna-CT (Uro Dyna-CT) was established in clinical use for classical imaging as well as for interventional surgery. To evaluate whether irradiation artefacts may occur during interventional surgery, we analysed the impact of different instruments on 3D reconstruction in the Uro Dyna-CT. Ten different endourological instruments [ureterorenoscope (URS)-fibrescope, percutaneous nephrolithotomy (PCNL) working sheath] and accessory equipments such as ureteral catheter, guide wires and stents (DJ, MJ) were introduced in a porcine renal pelvis either retrograde via the ureter or transparenchymally. Subsequently, Digital Fluoroscopy, standard X-ray and an Uro Dyna-CT were performed. Three colleagues evaluated the image quality independent from each other. There were basically no limitations regarding image quality in Digital Fluoroscopy and standard X-ray. In the Uro Dyna-CT, only with the URS fiberscope and the PCNL working sheath, small artefacts and irradiations were detected, whereas ureteric catheter with and without wire, as well as the hydrophilic guide wire, showed no artefacts at all. The remaining material demonstrated minimal artefacts, which did not affect the image quality. The Uro Dyna-CT can be used for all interventional endourological procedures using the common armamentarium and instruments without significant limitation of image quality. There are only minor limitations according a PCNL working sheath and the rigid URS. These instruments should be removed out of the examination field before performing the computed tomography and be replaced afterwards by using a safety wire.

M.-c. Rassweiler - One of the best experts on this subject based on the ideXlab platform.

  • Influence of endourological devices on 3D reconstruction image quality using the Uro Dyna-CT
    World Journal of Urology, 2013
    Co-Authors: M.-c. Rassweiler, M. Ritter, M.-s. Michel, A. Häcker
    Abstract:

    Purpose The urological Dyna-CT (Uro Dyna-CT) was established in clinical use for classical imaging as well as for interventional surgery. To evaluate whether irradiation artefacts may occur during interventional surgery, we analysed the impact of different instruments on 3D reconstruction in the Uro Dyna-CT. Materials and methods Ten different endourological instruments [ureterorenoscope (URS)-fibrescope, percutaneous nephrolithotomy (PCNL) working sheath] and accessory equipments such as ureteral catheter, guide wires and stents (DJ, MJ) were introduced in a porcine renal pelvis either retrograde via the ureter or transparenchymally. Subsequently, Digital Fluoroscopy, standard X-ray and an Uro Dyna-CT were performed. Three colleagues evaluated the image quality independent from each other. Results There were basically no limitations regarding image quality in Digital Fluoroscopy and standard X-ray. In the Uro Dyna-CT, only with the URS fiberscope and the PCNL working sheath, small artefacts and irradiations were detected, whereas ureteric catheter with and without wire, as well as the hydrophilic guide wire, showed no artefacts at all. The remaining material demonstrated minimal artefacts, which did not affect the image quality. Conclusions The Uro Dyna-CT can be used for all interventional endourological procedures using the common armamentarium and instruments without significant limitation of image quality. There are only minor limitations according a PCNL working sheath and the rigid URS. These instruments should be removed out of the examination field before performing the computed tomography and be replaced afterwards by using a safety wire.

  • Influence of endourological devices on 3D reconstruction image quality using the Uro Dyna-CT
    World journal of urology, 2012
    Co-Authors: M.-c. Rassweiler, M. Ritter, M.-s. Michel, A. Häcker
    Abstract:

    The urological Dyna-CT (Uro Dyna-CT) was established in clinical use for classical imaging as well as for interventional surgery. To evaluate whether irradiation artefacts may occur during interventional surgery, we analysed the impact of different instruments on 3D reconstruction in the Uro Dyna-CT. Ten different endourological instruments [ureterorenoscope (URS)-fibrescope, percutaneous nephrolithotomy (PCNL) working sheath] and accessory equipments such as ureteral catheter, guide wires and stents (DJ, MJ) were introduced in a porcine renal pelvis either retrograde via the ureter or transparenchymally. Subsequently, Digital Fluoroscopy, standard X-ray and an Uro Dyna-CT were performed. Three colleagues evaluated the image quality independent from each other. There were basically no limitations regarding image quality in Digital Fluoroscopy and standard X-ray. In the Uro Dyna-CT, only with the URS fiberscope and the PCNL working sheath, small artefacts and irradiations were detected, whereas ureteric catheter with and without wire, as well as the hydrophilic guide wire, showed no artefacts at all. The remaining material demonstrated minimal artefacts, which did not affect the image quality. The Uro Dyna-CT can be used for all interventional endourological procedures using the common armamentarium and instruments without significant limitation of image quality. There are only minor limitations according a PCNL working sheath and the rigid URS. These instruments should be removed out of the examination field before performing the computed tomography and be replaced afterwards by using a safety wire.

John A. Rowlands - One of the best experts on this subject based on the ideXlab platform.

  • 3-TFT active pixel sensor with correlated double sampling readout circuit for real-time medical x-ray imaging
    2006 IEEE North-East Workshop on Circuits and Systems, 2006
    Co-Authors: N. Safavian, A. Nathan, Gholamreza Chaji, M. Z. Kabir, John A. Rowlands
    Abstract:

    This paper presents a current-programmed, current-output active pixel sensor (APS) suitable for real time x-ray imaging (e.g., Fluoroscopy) using hydrogenated amorphous silicon (a-Si:H) thin film transistor (TFT) technology and an appropriate CMOS readout circuit. The proposed pixel circuit can successfully compensate for characteristic variations such as mobility and threshold voltage shift in a-Si:H TFTs. The proposed readout circuit exploits correlated double sampling (CDS) technique not only for reducing the offset current and low frequency noise, but also to reduce the effect of fixed-pattern noise (FPN) on the array operation. The on-pixel amplification reduces the input referred noise to levels that can satisfy the strict requirements for low noise Digital Fluoroscopy.

  • Active Pixel TFT Arrays for Digital Fluoroscopy in a-Si:H Technology
    MRS Proceedings, 2005
    Co-Authors: Jackson Chi Sun Lai, A. Nathan, N. Safavian, John A. Rowlands
    Abstract:

    Major development challenges in application of hydrogenated amorphous silicon (a-Si:H) technology to large area Digital X-ray imaging and technological attributes such as low temperature deposition and high uniformity over large area evolve around dynamic imaging modalities such as Fluoroscopy, which demands both high speed readout and signal amplification capabilities in addition to long term device stability. This work reports on initial results of a variety of TFT active pixel sensor (APS) structures in a-Si:H technology, each demonstrating unique capabilities such as enhancements in signal gain, TFT threshold voltage immunity, and real-time high speed readout.

  • Evaluation of the imaging properties of an amorphous selenium-based flat panel detector for Digital Fluoroscopy
    Medical physics, 2004
    Co-Authors: Dylan C. Hunt, Olivier Tousignant, John A. Rowlands
    Abstract:

    The imaging performance of an amorphous selenium (a‐Se) flat-panel detector for Digital Fluoroscopy was experimentally evaluated using the spatial frequency dependent modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). These parameters were investigated at beam qualities and exposures within the range typical of gastrointestinal fluoroscopic imaging (∼0.1–10 μR, 75 kV). The investigation does not take into consideration the detector cover, which in clinical use will lower the DQE measured here by its percent attenuation. The MTF was found to be less than the expected aperture response and the NPS was not white which together indicate presampling blurring. The cause of this blurring was attributed to charge trapping at the interface between two different layers of the a‐Se. The effect on the DQE was also consistent with presampling blur, which reduces the aliasing in the NPS and thereby reduces the spatial frequency dependence of the DQE. (The DQE was independent of spatial frequency from 0.12 to 0.73 mm−1 due to antialiasing of the NPS.) Moreover, the first zero of the measured MTF and the aperture response appeared at the same spatial frequency (6.66 mm−1 for a pixel of 150 μm). Hence, the geometric fill factor (77%) was increased to an effective fill factor of 99±1%. A large scale (∼32 pixels) correlation in the noise due to the configuration of the readout electronics caused increased noise power in the gate line NPS at low spatial frequency (

  • Imaging performance of an amorphous selenium flat-panel detector for Digital Fluoroscopy
    Medical Imaging 2003: Physics of Medical Imaging, 2003
    Co-Authors: Dylan C. Hunt, Olivier Tousignant, Yves Demers, Luc Laperriere, John A. Rowlands
    Abstract:

    The imaging performance of a 34.5 x 34.5 cm2 direct conversion flat-panel detector with a 1 mm thick amorphous selenium layer was measured over the fluoroscopic exposure range (0.56 - 10.8 μR/frame). The pixels measured 300 x 300 μm. Measurements of the modulation transfer function (MTF), the noise power spectrum (NPS), and the detective quantum efficiency (DQE) were made. By comparing the MTF to the sinc function the measured effective fill factor of the active matrix was determined to be almost 100%. The electronic noise of the active matrix was measured and found to be 3800 electrons. The DQE(f) was found to be better than the expected sinc2 function. This was due to the presence of a pre-sampling blur identified as charge trapping at an interface in the a-Se layers. At the highest exposure investigated, the DQE(0) was found to be less than the quantum efficiency and the difference was ascribed to a combination of the electronic noise, a small drop in sensitivity due to the charge trapping blur, and incomplete charge collection.

K.s. Karim - One of the best experts on this subject based on the ideXlab platform.