Journal of X-Ray Science and Technology - Volume 17, issue 4

Authors: Benítez, Ricardo Betancourt | Ning, Ruola | Conover, David | Liu, Shaohua

Article Type: Research Article

Abstract: The physical performance of two Flat Panel Detectors has been evaluated. The first Flat Panel Detector is for Fluoroscopic applications, Varian PaxScan 2520, and the second is for Cone Beam Computer Tomography applications, Varian PaxScan 4030CB. First, the spectrum of the X-ray source was measured. Second, the linearity of the detectors was investigated by using an ionization chamber and the average ADU values of the detectors. Third, the temporal resolution was characterized by evaluating their image …lag. Fourth, their spatial resolution was characterized by the pre-sampling Modulation Transfer Function. Fifth, the Normalized Noise Power Spectrum was calculated for various exposures levels. Finally, the Detective Quantum Efficiency was obtained as a function of spatial frequency and entrance exposure. The results illustrate that the physical performance in Detective Quantum Efficiency and Normalized Noise Power Spectrum of the Cone Beam Computer Tomography detector is superior to that of the fluoroscopic detector whereas the latter detector has a higher spatial resolution as demonstrated by larger values of its Modulation Transfer Function at large spatial frequencies. Show more

Keywords: Cone Beam Computer Tomography, Modulation Transfer Function, Edge Spread Function, Normalized Noise Power Spectrum, Detective Quantum Efficiency, Fluoroscopy Flat Panel Detector, Cone Beam Flat Panel Detector

DOI: 10.3233/XST-2009-0234

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 4, pp. 279-293, 2009

Authors: Yu, Hengyong | Cao, Guohua | Burk, Laurel | Lee, Yueh | Lu, Jianping | Santago, Pete | Zhou, Otto | Wang, Ge

Article Type: Research Article

Abstract: In the computed tomography (CT) field, one recent invention is the so-called carbon nanotube (CNT) based field emission x-ray technology. On the other hand, compressive sampling (CS) based interior tomography is a new innovation. Combining the strengths of these two novel subjects, we apply the interior tomography technique to local mouse cardiac imaging using respiration and cardiac gating with a CNT based micro-CT scanner. The major features of our method are: (1) it does …not need exact prior knowledge inside an ROI; and (2) two orthogonal scout projections are employed to regularize the reconstruction. Both numerical simulations and in vivo mouse studies are performed to demonstrate the feasibility of our methodology. Show more

Keywords: Computed tomography (CT), interior tomography, compressive sampling, carbon nanotube, field emission x-ray, respiration gated

DOI: 10.3233/XST-2009-0230

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 4, pp. 295-303, 2009

Authors: Zhang, Jie | Weir, Victor | Fajardo, Liliosa | Lin, Jingying | Hsiung, Hsiang | Ritenour, E. Russell

Article Type: Research Article

Abstract: This study compared patient dose and image quality of a mobile O-arm™ cone beam imaging system in the 3D scan acquisition mode to those of a 64 slice Computed Tomography (CT) imaging system. The investigation included patient dose, scattered radiation, and image quality measurements. The patient dose was measured using a 0.6cc Farmer ion chamber and 30cm long Computed Tomography (CT) head and body polymethylmethacrylate (PMMA) phantoms. The results show that under identical …radiographic techniques (kVp, mAs, etc.) and with the same scan length, the O-arm™ in 3D scan acquisition mode delivers approximately half the radiation dose of a 64 slice CT scanner. Scattered radiation was measured at several locations around the O-arm™, at 1 m, 2 m and 3 m distances in 3D CT scan acquisition mode with a RadCal 10 × 5–180 pancake ion chamber using a 30 cm long CT body phantom as the source of scatter. Similar measurements were made in a 64 slice CT scanner. The data demonstrate that scattered radiation from the O-arm™ to personnel involved in a clinical procedure is comparable to that from a 64 slice CT scanner. Image quality was compared by exposing a CATPHAN phantom to comparable doses in both the O-arm™ and the CT scanner. The resultant images were then evaluated for modulation transfer function (MTF), high-contrast spatial resolution, and low contrast sensitivity for clinical application purpose. The O-arm™ shows comparable high contrast to the CT (7 lp/cm vs. 8 lp/cm). The low contrast in the O-arm™ is not visible due to fixed pattern noise. For image guided surgery applications where the location of a structure is emphasized over a survey of all image details, the O-arm™ has some advantages due to wide radiation beam coverage and lower patient dose. The image quality of the O-arm™ needs significant improvement for other clinical applications where high image quality is desired. Show more

DOI: 10.3233/XST-2009-0231

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 4, pp. 305-317, 2009

Authors: Zhang, Xiaohua | Ning, Ruola | Yang, Dong

Article Type: Research Article

Abstract: In Cone Beam Breast CT (CBBCT) imaging, noise causes degradation of three dimensional breast images, impeding correct diagnosis of breast cancer. Within Feldkamp's cone beam reconstruction framework, applying weighted reconstruction filters to the projection images after pre-processing procedures has long been used to reduce noise and improve image quality. However, CBBCT noise is distributed across frequencies along with the useful signal. Various reconstruction filters working in the frequency domain suppress noise as well …as the edge detail signal. Based on fuzzy c-means clustering and the two-dimensional histogram analysis of a large number of clinical CBBCT data, we managed to discriminate fatty stroma, glandular tissues and the transition areas between these tissues by the local mean and standard deviation values. We also proposed a three-dimensional Gaussian filtering scheme to reduce the noise in 3D reconstructed images adaptively without much blurring of detail signal. Show more

Keywords: Noise reduction, 3D adaptive Gaussian filtering, CBBCT

DOI: 10.3233/XST-2009-0232

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 4, pp. 319-333, 2009

Authors: Khalatbari, Azadeh | Jenab, Kouroush

Article Type: Research Article

Abstract: Today's imaging diagnosis needs to adapt modern techniques of quality engineering to maintain and improve its accuracy and reliability in health care system. One of the main factors that influences diagnostic accuracy of plain film X-ray on detecting pathology is the level of film exposure. If the level of film exposure is not adequate, a normal body structure may be interpretated as pathology and vice versa. This not only influences the patient management but also has …an impact on health care cost and patient's quality of life. Therefore, providing an accurate and high quality image is the first step toward an excellent patient management in any health care system. In this paper, we study these techniques and also present a fuzzy intelligent quality monitoring model, which can be used to keep variables from degrading the image quality. The variables derived from chemical activity, cleaning procedures, maintenance, and monitoring may not be sensed, measured, or calculated precisely due to uncertain situations. Therefore, the γ-level fuzzy Bayesian model for quality monitoring of an image processing is proposed. In order to apply the Bayesian concept, the fuzzy quality characteristics are assumed as fuzzy random variables. Using the fuzzy quality characteristics, the newly developed model calculates the degradation risk for image processing. A numerical example is also presented to demonstrate the application of the model. Show more

Keywords: Imaging quality control, image processor monitoring, Bayesian theory, fuzzy intelligent systems, warning line, control limits

DOI: 10.3233/XST-2009-0228

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 4, pp. 335-346, 2009

Authors: Ahmad, Salahuddin | Vogds, Betty J. | McKenna, Fred | Vlachaki, Maria T.

Article Type: Research Article

Abstract: The objective of this work was to assess the relative impact of radiobiological parameters and radiation dose escalation on Tumor Control Probability for prostate cancer patients treated with radiation. Radiobiological parameters included α/β ratios, cell surviving fraction at 2 Gy (SF_{2} ) and clonogenic cell density (CCD). Using the Niemierko method, TCP was calculated in ten prostate cancer patients as a function of increasing radiation doses (70–140 Gy), α/β ratios (1.5–20), …SF_{2} (0.3–0.7) and CCD (10–20 million cells/cm^{3} ). At 70 Gy and CCD of 10 million/cm^{3} , TCP was above 99% for SF_{2} of 0.3 or 0.4, 97.4%–98.6% for SF_{2} of 0.5 and less than 2% for SF_{2} of 0.6 or 0.7. With dose escalation, TCP values above 99% were demonstrated at 80 Gy for SF_{2} of 0.5 and 100 Gy for SF_{2} of 0.6. For SF_{2} of 0.7, TCP above 99% was demonstrated with 100 Gy and CCD of 10^{4} cells/cm^{3} or 140 Gy and CCD of 10^{7} cells/cm^{3} . TCP decreased with lower α/β of 1.5, but at a much smaller scale compared to SF_{2} changes. TCP modeling predicts that SF_{2} and CCD are dominant predictors of radioresistance in prostate cancer. Radiation doses of 100 Gy or greater may be required for tumors with SF_{2} of 0.6 or above. Relating clinical tumor prognostic indicators such as Gleason score and PSA to radiobiological parameters will allow us to identify subsets of patients in need of higher radiation doses and adjuvant therapy to maximize treatment outcomes. Show more

Keywords: Tumor control probability (TCP), prostate cancer, dose escalation, radiation therapy

DOI: 10.3233/XST-2009-0233

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 4, pp. 347-354, 2009

Authors: Liu, Julian J. | Lutkin, John E.

Article Type: Research Article

Abstract: This study introduces a method to reduce the artefact caused by metal implant, and improve the image quality. The factors affecting the image quality of the existing methods are analysed from a different point of view. The observed projection is decomposed into several components including the correspondence of biological tissues, the correspondence of metal implant, noises, and inconsistencies caused by beam hardening. The correspondence of metal implant is identified by initial reconstruction and forward modelling, …and the noises are detected and isolated from the projection in wavelet domain. The inconsistencies are approximated and compensated. A patient with medial epicondyle of right femur replaced using femoral component made by Biomet Inc was scanned using a GE Lightspeed 16 X-ray CT scanner and the observed projection is processed by this method. The output image shows that all of the streaking caused by metal implant is eliminated, and the darkness areas caused by beam hardening are retrieved. Comparing with the default output of the CT scanner, the image quality has been significantly improved. Show more

Keywords: Computed tomography, metal artefact reduction, noise reduction, reconstruction, forward modelling, accuracy

DOI: 10.3233/XST-2009-0235

Citation: Journal of X-Ray Science and Technology, vol. 17, no. 4, pp. 355-365, 2009