Journal of X-Ray Science and Technology - Volume 11, issue 1

Authors: Wang, Ge | Madsen, Mark | Redford, Katherine | Zhao, Shiying | Vannier, Michael W.

Article Type: Research Article

Abstract: The section sensitivity profile (SSP) was well understood in the case of single-row-detector spiral CT. With the introduction of multi-row-detector spiral CT and the transition into cone-beam spiral CT, a revisit to the SSP issue becomes necessary. In this paper, the SSP of multi-row-detector spiral CT is formulated for the half-scan interpolation method at any transverse position. Based on the SSP formula, numerical simulation is performed to quantify the characteristics of the SSP with the …number of detector rows up to 40. It is shown that the SSP varies as a function of the pitch and the number of detector rows. Given an appropriate selection of the pitch and the number of detector rows, the SSP does not change very much over the field of view in terms of the mean, the slice thickness, and the skewness of the SSP. Although in general applications the SSP at the gantry iso-center can be used as the representative of the SSP family, for more accurate analyses the spatial variation of the SSP must be taken into account. Show more

Keywords: multi-row-detector spiral/helical CT, half-scan interpolation, section sensitivity profile (SSP), image quality, pitch effect, moment analysis

Citation: Journal of X-Ray Science and Technology, vol. 11, no. 1, pp. 1-11, 2003

Authors: Jiang, Ming | Wang, Ge

Article Type: Research Article

Abstract: This paper is a supplement and update to the reviews by Kundur and Hatzinakos [7,8] on blind image deconvolution. Most of the methods reviewed in [7,8] require that the PSF and the original image must be irreducible. However, this irreducibility assumption is not true in some important types of applications, such as when the PSF is Gaussian, which is a good model for many imaging systems. After a brief summary of existing blind deconvolution methods, we …report the recent development in this field with an emphasis on Gaussian blind deconvolution and its clinical applications. Show more

Citation: Journal of X-Ray Science and Technology, vol. 11, no. 1, pp. 13-19, 2003

Authors: Mardirossian, George | Urie, Marcia | Fitzgerald, Thomas J. | Mayr, Nina | Montebello, Joseph | Lo, Yuan-Chynan

Article Type: Research Article

Abstract: Commissioning of a Radionics miniature multi-leaf collimator (MMLC) for stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) is reported. With single isocenter and multi static fields, the MMLC can provide better conformity of dose distributions to the target and/or irregularly shaped target volumes than standard arc (circular) field beams with multiple isocenters. Advantages offered by the MMLC over traditional LINAC based SRS and SRT includes greatly improved dose homogeneity to the target, reduced patient …positioning time and reduced treatment time. In this work, the MMLC is attached to a Varian 2300 C/D with Varian 80-leaf multi-leaf collimator. The MMLC has 62 leaves, each measured to a width of 3.53 mm at isocenter, with fields range from 1 × 1 cm to less than 10 × 12 cm. Beam parameters required by the Radionics treatment planning system (XPlan version 2) for evaluating the dose include tissue maximum ratio (TMR), scatter factors (SF), off-axis ratios (OAR), output factors, penumbra function (P) and transmission factors (TF) are performed in this work. Beam data are acquired with a small stereotactic diode, standard ion chambers and radiographic films. Measured profiles of dose distribution are compared to those calculated by the software and absolute dosimetry is performed. Show more

Keywords: dosimetry, stereotactic radiosurgery, miniature multileaf collimator, radiation measurement

Citation: Journal of X-Ray Science and Technology, vol. 11, no. 1, pp. 21-31, 2003

Authors: Wu, Xizeng | Liu, Hong

Article Type: Research Article

Abstract: The in-line phase-contrast imaging has great potential for clinical imaging applications. This work presents a general theoretical formalism for the in-line phase-contrast imaging. The theoretical formalism developed in this work is derived by taking a new strategy to calculate the Fourier transform of image intensity directly. Different from the transport of intensity equation (TIE) formalism for phase-contrast imaging in literature [6], this general formalism covers both the near field regime and the holography regime of …phase-contrast imaging. The image intensity formulas have been derived in both the image space and frequency space. Especially our results show that the Fresnel diffraction image intensity is a sum of convolutions of the cosine- and sine-Fresnel filters with the object attenuation A_0^2(x) and attenuated phase A_0^2(x)φ(x) , respectively. The Pogany-Gao-Wilkins (PGW) formalism is recovered as a special case of our general formalism. In addition, in the low-resolution approximation, the general formula is reduced a spherical wave-generalization of the TIE-based formula for phase-contrast imaging. This spherical wave-generalization will be useful for phase-contrast imaging with a micro-focus x-ray tube. The transition of the formalism from 1-D to 2-D cases has been provided as well. Show more

Citation: Journal of X-Ray Science and Technology, vol. 11, no. 1, pp. 33-42, 2003