Showing papers on "Imaging phantom published in 1976"

Quantitative proton tomography: preliminary experiments.

Abstract: An attempt has been made to see whether energetic protons (158 MeV) could be used instead of X-rays in computerized axial tomography to detect density differences of the order of those at which commercial X-ray tomographs cease to be useful. A circularly symmetrical phantom consisting of Lucite and sugar solutions was used, and density differences of 0.5% were reconstructed with reasonable accuracy from data obtained with very simple equipment. Discontinuities in either density or chemical composition, or both, seem to cause artifacts in the reconstruction. These may be related to the West-Sherwood effect.

Measurement of Radiofrequency Power Absorption in Monkeys, Monkey Phantoms, and Human Phantoms Exposed to 10-50 MHz Fields.

Abstract: : The power absorbed by biological systems and thus the biological insult vary as a function of the frequency of the incident radiofrequency (RF) field. To define the effects of RF radiation on man, it is necessary to quantitate the absorbed power in man and experimental animals over a broad range of frequencies. Prolate spheroid phantoms representing man and monkey were used to determine the absorbed power by differential power measurement techniques, and these data were compared with theoretical results. Power absorption measurements were performed on live monkeys, and these results were compared with the results using phantoms to determine the adequacy of the prolate spheroid model. The results indicate the theory to be excellent for predicting power absorption in the phantom, but the more complex ellipsoid model will be required to predict power absorption in primates.

Ultrasound Transaxial Tomography by Reconstruction

Abstract: The diagnostic potential of transmission imaging with ultrasound has stimulated many attempts to utilize the large differences in ultrasound attenuation between various soft tissues. Most such attempts have met with very limited success due to practical difficulties including scattering and phase distortion by bones, air spaces, and fat. Imaging a transverse plane in the body by transmission scanning of that plane from a large number of angles, and subsequent reconstruction of the transmission image by computer may provide the long desired diagnostic information in many areas of the body. Just as with computerized axial tomography now used successfully for enhanced x-ray imaging, ultrasound transaxial tomography by reconstruction (UTTR) displays those objects causing distortions of the ultrasound and allows, in effect, averaging of data from scans at many angles. Others have investigated UTTR for soft tissue imaging. The present results simulate with phantom measurements the image of soft tissues adjacent to bone-equivalent objects.

Thallium-201: Scintillation Camera Imaging Considerations

Abstract: Modulation transfer functions, line spread functions, and energy spectra were obtained for an Anger scintillation camera using three different collimators and commercially produced $sup 201$Tl. Images of a thyroid phantom were obtained using these collimators. For each of the three collimators, line spread functions and modulation transfer functions were obtained for both the 75-keV x- ray and 167-keV gamma photon of $sup 201$Tl. Although the intrinsic resolution of the scintillation camera is superior when imaging with the 167-keV gamma photon, system performance was superior when the 75-keV x-ray was imaged. Contamination from $sup 202$Tl, which emits abundant 439-keV gamma photons, degraded images taken at 167 keV because of septum penetration. At 75 and 167 keV the converging collimator yielded the best system performance. Imaging time was significantly shorter using the 75-keV x-rays.

Displacement correction factor for fast-neutron dosimetry in a tissue-equivalent phantom.

Abstract: The displacement correction factor to be used for analysis of fast- neutron dosimetric measurements using air-filled EG and G tissue-equivalent ion chambers in a tissue-equivalent phantom has been investigated using the MANTA neutron radiotherapy beam generated by 35-MeV deuterons on a thick Be target. The displacement correction factor inferred from these measurements is 0.970 for the EG and G IC-17 (1.0-cm$sup 3$) ion chamber, and is 0.989 for the EG and G IC- 18 (0.1-cm$sup 3$) ion chamber. This multiplicative displacement correction factor has no significant dependence on depth in the phantom or on neutron beam size. (AIP)

Minicomputer enhancement of scintillation camera images using fast Fourier transform techniques.

Abstract: Minicomputer methods were developed to enhance lesions in scintillation camera images. This study was directed towards improving the diagnostic quality of liver images. A PDP-12 digital computer was interfaced to a Pho/Gamma HP III scintillation camera and programmed to carry out two-dimensional frequency-domain analysis and processing as an on-line operation. A two-dimensional frequency spectrum is produced. An interactive program allows the operator to construct graphically a frequency-domain filter and apply it to the data matrix. The filter is optimized using the image of a known phantom and then applied unchanged to the clincial liver image. An inverse Fourier transform produces an enhances image in the spatial domain. Significant enhancement of both phantom and liver images has been obtained.

Development of a Phantom for Evaluation and Assurance of Image Quality In CT Scanning

Abstract: The development and use of a phantom for evaluation, comparison, and quality assurance of CT scanners will be discussed. Examples of measurements on seven CT scanners using early prototypes of the phantom will be presented along with measurements on several scanners using the final phantom configuration. The phantom contains four modular sections which are removable to allow for future fabrication and replacement of individual sections for specialized applications. Section I is used to measure contrast sensitivity and scan slice geometry of the system. Section II is used to measure the sensitometric response of the system. Section III is used to determine the spatial resolution of the system at various contrast levels. Section IV is used to determine the noise, spatial uniformity, alignment, and MTF of the system. In addition, it contains a part with fittings where items may be placed such as in vitro samples, dosimeters, or a motion phantom.© (1976) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A mathematical model of a phantom developed for use in calculations of radiation dose to the body and major internal organs of a Japanese adult.

Abstract: A mathematical model of a phantom simulating the body and major internal organs of a Japanese adult has been developed for use in computer calculations of radiation dose. The total body height of the mathematical phantom is 162 cm, and the total body mass is 55 kg based on densities of 0.3, 1.4, and 1.0 g/cm/sup 3/ for the lung, skeleton, and bulk tissues of the body, respectively.

Change in oxygen enhancement ratio with depth in tissue-equivalent material for a collimated beam of fast neutrons

Abstract: Survival of reproductive capacity of murine leukaemia P-388 cells was assayed in vivo after the cells had been irradiated in vitro under aerobic or hypoxic conditions with collimated beams of X rays or 16 MeV D-Be fast neutrons at various depths in tissue-equivalent phantom material. The response to X-irradiation was the same in the absence of the phantom and at 8·7 cm depth. The response to fast neutrons under aerobic conditions was unchanged from 0 to 23 cm depth within the phantom. However, under hypoxic conditions, the dose-response curve for fast neutrons became significantly steeper with increasing depth in the phantom. The OER decreased from 2·0 in the absence of the phantom to 1·5 at 15 cm deep.

A Collimator for Reduced Radiation Dose with Improved Visualization of Soft Tissues

Abstract: The authors describe a collimator for use in diagnostic radiology. Clinical radiographs show enhanced soft-tissue detail through the use of interchangeable straight and curved wedge filters, and in situ dosimetry using a head phantom shows that the provision for asymmetric beam limitation results in reduction of absorbed dose.

Development and use of a fifteen year-old equivalent mathematical phantom for internal dose calculations. [Radiation dose distributions from /sup 99m/Tc-labeled compounds]

Abstract: The existence of a phantom based on anatomical data for the average fifteen-year-old provides for a proficient means of obtaining estimates of absorbed dose for children of that age. Dimensions representative of an average fifteen-year-old human, obtained from various biological and medical research, were transformed into a mathematical construct of idealized shapes of the exterior, skeletal system, and internal organs of a human. The idealization for an average adult presently in use by the International Commission on Radiological Protection was used as a basis for design. The mathematical equations describing the phantom were developed to be readily adaptable to present-day methods of dose estimation. Typical exposure situations in nuclear medicine have previously been modeled for existing phantoms. With no further development of the exposure model necessary, adaptation to the fifteen-year-old phantom demonstrated the utility of the design. Estimates of absorbed dose were obtained for the administration of two radiopharmaceuticals, /sup 99m/Tc-sulfur colloid and /sup 99m/Tc-DMSA. (auth)

Equally Spaced Parallel-Bar Phantom for Performance Monitoring of Scintillation Cameras

Abstract: A series of transmission phantoms with equally spaced parallel bars has been designed and evaluated as performance monitors of the linearity and resolving power of scintillation cameras. Each phantom in the series has bars of equal width and spacing. The series has a range of bar widths from 3 to 7 mm in 1-mm increments. The concept is to use that one phantom with bar specifications which are best suited to assess the resolving power of a given camera. The results show that improved quality assurance monitoring is accomplished using this technique as compared to using existing phantoms. It is recommended that scintillation cameras be equipped with this type of phantom at time of purchase.

Phantom studies of imaging soft tissue through bone with ultrasound transaxial tomography

Abstract: A phantom consisting of a 2.5 cm diameter aluminum rod, a balloon filled with castor oil and a balloon filled with a phenylated silicone fluid were imaged in water with ultrasound transaxial tomography of attenuation by reconstruction (UTTAR). This phantom was chosen to investigate the feasibility of detecting small changes in the ultrasound attenuation coefficient of soft tissues in planes containing bones. Opposed transmitting and receiving transducers were scanned on either side of the phantom just as an x-ray tube and detector are scanned in the EMI x-ray computerized axial tomography system for brain imaging.

The phantom crossroads.

Abstract: My thanks are due to Dr D Oppenheimer of Oxford, Professor I Isherwood of Manchester, and Dr Jean Horton of Cambridge for their help in supplying material; Mr E H Cornelius, librarian to the Royal College of Surgeons, and Mr F M Sutherland, librarian to the British Medical Association, for their help with the bibliography of Sir Victor Horsley; and to Miss Sheila Nicholson for secretarial help. I wish to acknowledge my debt to the successive medical and nursing staffs of the accident services of the Radcliffe Infirmary, Oxford, Addenbrooke's Hospital, Cambridge, and the army neurosurgical unit at Wheatley and Colchester Military Hospitals who over the years helped in the care of the patients on whom this article is based.

An estimate of the 60Co gamma attenuation in the small phantom enployed in the definition of tissue air ratio.

Abstract: Tissue air ratio definition employs a concept of dose at the centre of a small mass of tissues that is suspended in air and is just large enough to give electronic equilibrium at its own centre. When the dose at the centre of the said small mass of tissue is to be derived from a knowledge of exposure in free air at the same point, the attenuation in the small mass of tissue should be taken into account. This attenuation for 1250 keV photons has been evaluated through a theroretical model and the attenuation factor is estimated to be 0.975.

An Evaluation Of Low Light Level Television For Breast Cancer Detection

Abstract: A low light level electronic imaging system is being developed to be used in a mass screening program for breast cancer detection in asymptomatic women. In this technique a mammographic image formed from an x-ray beam collimated by a scanning slit is converted to an intensified visible image which is viewed by a high resolution isocon television camera. The signal which is displayed on a small flat-faced cathode ray tube is photographed onto 70 mm roll film. Some advantages of the system for mass screening are its low cost of operation, ability to eliminate detection of scattered x-rays, short examination time, small format film images, low radiation exposure to the breast and the capability of electronic image processing. The limiting resolution of the system has been measured using lead test patterns and a phantom containing small diameter wires. In these experiments the electronic technique clearly demonstrated a 50u wire and barely detected a 25u wire. Extensive studies of the imaging properties of the system indicate that the image quality is limited chiefly by the television noise. In a clinical study, the ratio of the radiation exposure for the electronic method compared to that for the Lo-Dose film screen technique was measured at 0.17 + 0.06. At this level of exposure, the quality of the images was adequate to demonstrate cancers, calciTications, tumors, skin thickening, and trabecular structure. Calcification can be demonstrated, but at this Stage of development, very fine calcifications are not adequately visualized.

Properties of Masonite as phantom material

Abstract: The radiophysical properties of the material "Masonit" are examined by experimental methods. Indications are given as to atomic composition, density, effective atomic number, concentration of electrons, and linear attenuation coefficient. A comparison with water shows that "Masonit" is a suitable phantom material especially for the purposes of radiotherapy.