Tommie J. Morgan

Quality assurance methods and phantoms for magnetic resonance imaging: report of AAPM nuclear magnetic resonance Task Group No. 1.

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Energy dependence of correction factors for two models of Keithley diagnostic ion chambers.

The energy dependence for each of two models of ionization chambers compatible with the Keithley model 35020 Digital Dosimeter, is determined by measurement of the exposure correction factors determined over the diagnostic x-ray range (0.4--4.9 mm AL HVL) for several for several samples of each model. The results of an analysis of variance performed by model on the correction factors are reported as mean correction factors for the x-ray beams evaluated, with a relative standard error of less than 1% for both cases. Energy-dependence curves for the two chamber models are given, and their use is described.

The Commissioning of Computed-Tomography Scanners An Overview

The computed-tomography scanner is a new tool for the medical profession in which a narrow, moving x-ray beam, controlled and measured by a computer, is used to image transverse planes in patients. Because scanners have several unique features, commissioning tests performed during installation can be only partially accomplished by using equipment and procedures designed for conventional x-ray devices. Additional equipment and procedures are required to commission scanners. This paper identifies 21 parameters that should be considered for testing in a scanner commissioning program. Generalized descriptions as to how such tests may be accomplished are outlined and difficulties in testing are cited.

Energy dependence of correction factors for some Victoreen Model 570 Condenser R‐Meter medium‐energy chambers

The energy dependence of each of six models of medium-energy Victoreen 570 Condenser R-Meter chambers was determined by measurement of the exposure correction factors over the diagnostic x-ray beam-quality range (0.4-4.1 mm A1 HVL) for several samples of each model. The results of an analysis of variance performed by model on the correction factors are reported as mean correction factors for the x-ray beams evaluated, with a relative standard error less than 0.8% in all cases. Energy-dependence curves for the six chamber models are given; their use is described.

Energy dependence of correction factors for the Victoreen Model 666 Portable Radiographic Health Survey System.

The energy dependence for each of three models of Victoreen 666 ionization chambers is characterized through an examination of the correction factors determined over the diagnostic x-ray range (0.4-4.9 mm A1 HVL) for many samples of each model. The results of an analysis of variance performed for each chamber model on the correction factors are reported as mean correction factors for the x-ray beams evaluated, with a relative standard error of less than 0.6% in all cases. Energy-dependence curves for the three chamber models are given, and their use is described.

Energy dependence of correction factors for some low-energy direct-reading pocket dosimeters

The energy dependence for each of five models of low-energy direct-reading pocket dosimeters was characterized through an examination of the exposure correction factors determined over the diagnostic x-ray range (0.4-4.1-mm Al HVL) for many samples of each model. The results of an analysis of variance performed by model on the correction factors are reported as mean correction factors for the x-ray beams evaluated, the relative standard error being less than 0.8% in all cases. Energy-dependence curves for the dosimeter models are given, and their use is described.

The Role of CT Scanners in Radiotherapy

The success of radiation therapy depends upon the correct diagnosis of disease and the accurate delivery of radiation dose to that disease. An important part of radiotherapy is treatment planning in which various possibilities for the type, energy, size, and orientation of therapy beams are considered to insure that the intended volume is adequately irradiated. Treatment planning requires that the shape, size and depth of tumors as well as radiation-sensitive tissues be accurately identified. Furthermore, any distortions to radiation dose distributions caused by the presence of tissue inhomogeneities should be corrected. This paper discusses how computed-tomography scanners may be utilized to advantage in radiotherapy. Major benefits of scanners are described and difficulties associated with using scanner images in radiotherapy treatment planning are indicated.

The Commissioning Of Computed-Tomography Scanners: An Overview

The computed-tomography scanner is a new tool for the medical profession in which a narrow, moving x-ray beam, controlled and measured by a computer, is used to image transverse planes in patients. Because scanners have several unique features, commissioning tests performed during installation can only be partially accomplished by using equipment and procedures designed for conventional x-ray devices. Additional equipment and procedures are required to commission scanners. This paper identifies 21 parameters that should be considered for testing in a scanner commissioning program. Generalized descriptions as to how such tests may be accomplished are outlined and difficulties in testing are cited.

Some Sources of Errors in the Performance Testing Of Diagnostic X-Ray Systems

Sources of error associated with the measurement of four performance parameters are discussed in this paper. These are the measurement of half-value layer (HVL), light field edge location, x-ray and light field congruence, and x-ray field size. HVL measurement parameters discussed are field size, the detector energy-dependent response, and x-ray beam filtration. Light field edge location by both visual and photometric methods are compared and differences quantified for one x-ray beam collimator. The impact of the different methods of light field edge location on x-ray and light field congruence are described. X-ray field size measurements for x-ray systems having large focal spots are discussed. The effect of the large focal spot as it impacts on small x-ray field size measurements is described.