Published in Medical physics
A method of blood flow measurement is described that determines flow through a particular artery in absolute units or as a fraction of the cardiac output. For measuring flow as a percentage of cardiac output, no assumption about the vessel's cross-sectional shape is necessary. If one assumes that the vessel's cross section is circular, then absolut...
Published in Medical physics
A statistical analysis has been made of ionometrically measured parameters related to the central-axis output, the beam symmetry, the beam flatness, and the depth dose for the 6-MV x-ray beam from the Therac-6 linear accelerator. The means and coefficients of variation of the measurements are determined on a monthly basis for each parameter. Mean c...
Published in Medical physics
Instrument AB Scanditronix offers a 6-MV therapeutic photon beam as an option with the 22-MeV medical microtron (MM 22). The method of acceleration, target assembly, and use of two flattening filters produce beams having several characteristics (e.g., field flatness, penetration, and intensity) that are superior to many 6-MV Linac beams. Characteri...
Published in Medical physics
The nuclear magnetic resonance (NMR) spin-lattice relaxation time (T1) of samples taken from human tumors was measured in vitro at Larmor frequencies of 24 and 6.25 MHz. It was found that on the average T1 at 6.25 MHz was linearly related to T1 at 24 MHz. An analogous set of measurements was performed on pieces of normal rat tissue. In this case, t...
Published in Medical physics
Thermal dosimetry is one of the most challenging and necessary aspects of therapeutic hyperthermia. Treatment optimization and assessment of efficacy of the therapy can only be achieved by a quantification of the thermal distributions in normal and malignant tissue induced by specific configurations of heat sources. Radial and axial temperature dis...
Published in Medical physics
Published in Medical physics
Small beams are often applied in radiotherapy, e.g., in shrinking field and high-dose techniques with curative intent. For a given beam, measured field size factors (FSF) may vary with responses of different detectors to nonuniform radiation fluence. Dose rates of small photon and electron beams with diverse profiles were measured in polystyrene wi...
Published in Medical physics
A mobile lung densitometer using conventional x-ray tubes, NaI detectors, and principles of two-source, two-detector Compton scattered densitometry, is described. The device is capable of one to two per second density measurements from a 45-cm3 volume with a precision of 5%. The expected in vivo accuracy (2%-3%) is determined by using an anthropomo...
Published in Medical physics
A system of computer programs has been created to allow the entry of radiotherapy treatment details as defined by the physician, the verification of the machine parameters at every treatment, and the recording of the entire course of treatment. Various utility programs are available to simplify the use and maintenance of the system. The majority of...
Published in Medical physics
For the Clinac 4, open field profiles measured in the principal plane have higher intensity "horns" than those in off-axis planes. The maximum deviation occurs at 1-cm depth, where in the worst case of large field sizes and off-axis distances the deviation can be as high as 16% in the region near the horns. A model is proposed to generate open fiel...
