Dental radiology sheet # 1 - Zaid M. Al-Zu’bi

Q: What’s the difference between radiology and radiography?
A: - Radiology: is the branch of medicine that uses radiation for diagnosis, interpreting, and treatment of a disease. 
Radiography:  is the process by which radiographs (x-rays) are made.
Collectively, both radiography and radiology can be named as radiology.

Now we’ll mention some historical events:
Wilhelm C. Roentgen: a German radiologists, he was the 1st who took the Nobel prize in physics because he discovered the X-ray.

Q: How did he discover the X-ray?
A: by experiments using some wires, electricity, some plates, and florescent materials. Suddenly he noticed a Florence emitted from a plate, and then he tried to image his wife’s hand. (Who sadly died because of cancer as a result of the exposure to X-ray for around 15 minutes).

William Coolidge is the one who invented the apparatus that generates the X-ray.

Edmond Kells was the 1st dental X-ray image maker in the U.S, and the one who discovered the most important technique in radiology, the parallel technique.


Note: you shouldn’t put your finger inside the patient’s mouth during taking the radiograph; there is a chance to develop cancer even from one shot of rays.

Radioactive medicine: uses radionuclides and relies on the process of radioactive decay in diagnosis and treatment of diseases.

If there is a cancer, the uptake of the nuclear material will be high, can be detected using the PET/CT scan.
PET/CT: positron emission tomography / computerized tomography.

The radioactive material could be sometimes accompanied with a curative agent that may kill the cancer itself, so this can be considered as therapeutic tool rather than diagnostic.

Methods used in radiography:

CT- scan: is a method employing tomography, used to generate a 3D image of an object from large series of 2D images taken around a single axis of rotation.




Panorama: has the same principle of the CT-scan with the difference that it’s a 2D image for mouth and teeth only.

Some indications for using panorama:
To follow up the growth of the teeth, especially during childhood.
To have a general image for all teeth before performing any surgical process.
For orthodontic treatment.
Any bony problems can be detected by this method.

Exam Q: how many intraoral images are equivalent to one panoramic image?

A: 1 panoramic image = 18 intraoral images.

Mainly the diagnosis using panorama is carried out through comparing between the right and left side of the image.

As we said, panorama gives us a 2D image, so interpreting a trauma extending buccolingualy won’t be seen in panorama, in such cases, the CT scan is mandatory.

The latest generation of the CT scan method is called the multi-detector CT in which it takes many slices within seconds.

Axial section = cross section in radiology.

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MRI:

If the patient has musculature disorder, or in soft tissues in general, then the CT scan or panorama is no more beneficial in diagnosis, so we resort to MRI (magnetic resonance imaging).

MRI technique is free of ionizing radiation.

 A person is inserted inside the powerful magnetic field of the scanner; radio waves being passed through the field, causing spinning of the hydrogen atoms (protons) inside the patient’s body, the frequency at which the protons resonate depends on the strength of the applied magnetic field. After the field is turned off, those protons which absorbed energy revert back to the original lower-energy state. They release the difference in energy as a photon, and the released photons are detected by the scanner as an electromagnetic signal.

 It is this relationship between field-strength and frequency that allows the use of nuclear magnetic resonance for imaging. An image can be constructed because the protons in different tissues return to their equilibrium state at different rates, which is a difference that can be detected.

This is an MRI for a TMJ:





MRI is the best for soft tissues imaging.

It is a 3 dimensional image.


Cone beam CT (CBCT):

During a CBCT scan, the scanner rotates around the patient's head, obtaining up to nearly 600 distinct images. The scanning software collects the data and reconstructs it, producing a 3D image that can then be manipulated and visualized with specialized software.

The best advantage over the normal CT scan is the high reduction in rays’ dose.

Widely used in endo- and ortho- to obtain a clear 3D image to get accurate measurements.

Q: What is the difference between the CBCT and CT?
A: 1- CT:
Conventional CT scanners make use of a fan-beam.
Transmitted radiation takes the form of a helix or spiral.
The data are then interpolated by the scanner into a set of slices making up a volume.
Large anatomical regions of the body can be imaged during a single breath hold, reducing the possibility of artifacts caused by patient movement.
The radiation exposure to a patient from a conventional CT is approximately 100-300 microsieverts (µSv) for the maxilla and 200-500 µSv for the mandible.


2- CBCT:
Cone Beam Computed Tomography (CBCT) or Dental Volume Tomography (DVT) scanners (such as the i-CAT) utilize a cone beam, which radiates from the x-ray source in a cone shape, encompassing a large volume with a single rotation about the patient.
Images are then reconstructed using algorithms to produce 3D images at high resolution.
The radiation exposure (for both mandible and maxilla) is between 34-102 microsieverts (µSv) depending on the time and resolution of the scan.


Notice the different in doses between the two types.
Do not memorize numbers.




Physics:

The atom is composed of nucleus, nucleons (protons and neutrons), and electrons.

In neutral atom, negatives = positives.

Atomic number = number of protons.

Atomic mass number = protons + neutrons.

7 shells as a maximum number around the nucleus in which the electrons spin.

The binding energy and stability increase as the electron gets closer to the nucleus.

Radiation: is the emission or propagation of energy in the form of waves and particles.

X-rays have no mass, but energy.

Types of radiation: 1- corpuscular: there is a mass; the transfer of energy is with velocity.
2- Electromagnetic: it moves as waves in a speed of light (3*10^8 m/s), as a combination between electrical and magnetic fields, which h are perpendicular on each other.

Direct proportion between velocity, frequency, and energy.
An inverse proportion between wave length and energy.
Examples on electromagnetic radiation: visible light, IR, UV, X-rays, gamma rays…
All E.M radiations are measured in nanometers.
X-rays can’t be focused upon one point, nor can be reflected.
Although they travel in straight lines, X-ray beam runs in divergent pattern once it’s shot out from the tube.
The atom called ion when it gains or loses electron or more.

The latent image: it is the image that doesn’t show any feature unless it’s processed.

Q: Why do I need to use a screen (extraoral cassette)?

A: because it aids in converting the excess X-rays into light, so the dose will be less, and so its bad effect.



The End








Zaid M. Al-Zu’bi
Radiology lecture # 1
Dr.Mustafa khader

Best wishes…