Items tagged “physics”

Helical (a.k.a. spiral) CT image acquisition was a major advance on the earlier stepwise ("stop and shoot") method. With helical CT, the patient is moved through a rotating x-ray beam and detector set. From the perspective of the patient, the x-ray beam from the CT traces a helical path. The he...

Scattering occurs when a sound wave strikes a structure with a different acoustic impedance to the surrounding tissue and which is smaller than the wavelength of the incident sound wave. Such structures are known as “diffuse reflectors,” with examples being red blood cells and non-smooth surface...

Ultrasound machines perform distance measurement to synthesize images from returning echoes. To generate images for an ultrasound scan, machines need to determine the distance of reflective interfaces from the transducer. Simply, the formula used is: distance = (speed x time)/2 Where: distanc...

Side lobe artifacts occur where side lobes reflect sound from a strong reflector that is outside of the central beam, and where the echoes are displayed as if they originated from within the central beam. Ultrasound transducer crystals expand and contract to produce primary ultrasound beams in ...

The physics curriculum is one of our curriculum articles and aims to be a collection of articles that represent core physics and imaging technology knowledge: physics and imaging technology: x-ray physics and imaging technology: ultrasound physics and imaging technology: CT physics and imagi...

X-ray units require a high voltage generator to achieve the necessary power required of an x-ray tube. AC power will supply x-ray units with sinusoidal currents, resulting in 'peaks and troughs', limiting an x-ray tube to produce x-rays only half of the 1/60th of s second cycle.  A single-phase...

Image intensifiers (II) are utilized to convert low energy x-radiation into visible light images. Frequently the detector portion of an x-ray C-arm used in operating theaters, the image intensifier has a low scatter input portion made of low absorption substances such as titanium or aluminum 1,2...

A photon is, in simple terms, an elementary force-carrying particle i.e. a boson 2 (obeys the statistical law of Bose-Einstein). It has a zero mass (rest mass) and travels at, c, the speed of light in vacuo. It is defined as stable with no electric charge and exhibits both wave-like and particle...

Biomolecular radiation damage may result from exposure of biological tissues to ionizing radiation from direct exposure, or via Compton scattering. Mechanism of tissue radiation damage Direct effect if a biological macromolecule (e.g. DNA, RNA, protein) becomes ionized or excited by an ionizi...

The energy difference between spin up and spin down states of hydrogen are important in understanding net magnetization vector of tissue for magnetic resonance imaging. Each hydrogen atom is formed by one proton and one orbiting electron. Because the atomic number is 1, it has a spin quantum nu...