X-Rays Vs Ultrasound

X-rays and Ultrasound:
X-rays and ultrasound are two different modalities used for different things, so an ultrasound can do some things an X ray cannot, and vice versa, and so this makes them very difficult to directly compare.
Ultrasound:

Above: An ultrasound machine.

Ultrasound is the use of energy generated by sound waves of 20,000 or more vibrations per second.
Ultrasounds are generated by a device called a transducer. Bearing in mind that sound is a mechanical energy, the transducer uses a crystal driver to concert electrical energy into mechanical energy. The crystal can change shape via electrical stimulation, as the change in shape squeezes the crystal, causing it to generate an electrical signal. The transducer is used to send out a signal and then listen out for the echo, which generates the image seen on ultrasounds. Humans
can hear 20 cycles per second, (cps or Hertz) to 20,000 cps. Most ultrasonic transducers work in an excess of 1,000,000!

Ultrasounds are most commonly used to show different fluid densities and things that are closer to the surface. As the ultrasound images have very low resolution most people have difficulty reading them, and only people with skills in the field can decipher the images. As ultrasound cannot penetrate very deeply thus obese patients and objects with a thick density cannot be viewed easily. As stated in the name, ultrasound makes use of extremely small sound waves to penetrate objects.
Ultrasound was discovered by two researchers, namely Dr. Karl Theodore Dussik of Australia and Prof. Ian Donald of Scotland. Dr. Karl Theodore initially published his first book on the subject (medical ultrasonic’s) in 1942 based on his research which he did on the transmission of ultrasound within the brain. Prof. Ian Donald then developed the practical application of ultrasound in the 1950’s.
Ultrasound is very useful as a medical tool and its uses grow by day, some of these uses include:
- Confirmation of a pregnancy and the assessment of a baby inside the womb.
- Detection of abnormalities of an unborn child within the womb. - The evaluation of blood flow within the blood vessels
- Assessment of glands within and around your neck
- The evaluation and diagnosis of various heart diseases.
- The revealing of certain infections within the body
-To determine abnormal structures or growth within the body (tumors, ect.)

Above: an ultrasound image of a baby inside the womb, as you can see the baby is not clearly visible, but further investigation shows there is a fetus growing.

X-rays:

Above: An X-ray machine

Above: An X-ray of a person’s rib cage, as you can see the X-rays penetrate through less dense objects such as skin (which is not visible in this photograph) and more dense objects are shown in white as you can clearly see in this image.
X-radiation (which is composed of X-rays, hence the name) falls under electromagnetic radiation. X-rays and gamma rays are sometimes confused, but they are different, as X-rays are emitted by electrons outside the nucleus whilst gamma rays are produced inside the nucleus.
X-rays have extremely small wavelengths (10-0.1 nanometers) and so long exposure to them can cause humans harm, but one X-ray here or there is not bad, and this is why medical X-rays are not deadly if used accordingly, but doctors who operate the machinery must wear protective lead aprons as they are often exposed to the radiation.
To generate X-rays you need three things, firstly you need a source of electrons, secondly you need a means of accelerating those electrons to excessively high speeds, and lastly you need a material to receive the impact of the electrons and thus interact with
them.
X-rays are generated when fee electrons give up some of their energy after they have reacted with the orbitals of an atoms electrons or nucleus. The energy that is given off during this reaction appears as electromagnetic energy, which we know as X-rays. There are two types’ atomic processes that can produce the so called X-rays. One of which is called the Bremsstrahlang and the other is known as the K-shell emission. X-rays that are produced via Brensstrahlang are much more useful for medical and industrial purposes.
When a primary x-ray from a source strikes a sample, the X-ray can either be absorbed by the atom or scattered through the material. The process in which an x-ray is absorbed by the atom by transferring all of its energy to an innermost electron is called the "photoelectric effect." During this process, if the primary X-ray had sufficient energy, electrons are ejected from the inner shells, creating vacancies. These vacancies present an unstable condition for the atom. As the atom returns to its stable condition, electrons from the outer shells are transferred to the inner shells and in the process give off a characteristic X-ray whose energy is the difference between the two binding energies of the corresponding shells. Because each element has a unique set of energy levels, each element produces X-rays at a unique set of energies, On the 8th of November 1895, Wilhelm Conrad Rontgen noticed that an image from his cathode ray generator (electron beam) had been projected far beyond its usual range; these rays were generated at the point of contact between the cathode ray beam and the interior of the vacuum tube. These rays where not deflected by magnetic fields, and upon further investigation he discovered that the rays actually penetrated through various forms of matter. He named these rays X-rays, the “X” meaning unknown.
William Coolidge was the inventor of the X-ray tube, which is now called the Coolidge tube. His invention changed the way X-rays where used, as today all medical X-ray machines are largely based on his Coolidge tube.

Above: William Coolidge and his X-ray tube
Differences between the two: | Ultrasound | X-rays | Wave type | Longitudinal mechanical waves | Electromagnetic waves | How is it transferred | Elastic | There is no medium | How is it generated | Stressing the elastic or medium | Accelerating electric charges | What is its velocity | Depending on which medium is used | 299,792,456,2 m/s | Similar waves | Seismic, acoustic | Radio or light |

Above: How an X-ray is formed within an atom.