Maxray Cocoon User Manual
Table of Contents
Introduction 3
Background 4
What are X rays? 4
How are X rays Generated? 4
Primary and Scatter Radiation 5
Interactions with Matter 5
Biological Eects of Radiation 6
Linear No-Threshold Risk Model 7
Basic X-ray Safety 7
Safety Rules to Minimize Radiation Dose 7
Worker Radiation Dose Limits 8
Medical Procedure Doses 8
MaxRay Safety 9
Backscatter Shield 9
Geometry of the Backscatter Zone 9
Dosimetry 11
Accidental Exposure Prevention 11
Exposure Time 13
Safe Storage 14
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Introduction
There are many beneficial uses of ionizing radiation; however, of equal importance we note that there
are potential risks associated with its use. Radiation safety training is an important part of any radiation safety program. Receiving appropriate training ensures users are following proper safety practices to maximize the benefits of ionizing radiation while minimizing potential risks and maintaining
a safe work environment.
In this training manual, we discuss basic X-ray safety in addition to specific safety information about
operating the MaxRay Cocoon. The Cocoon is a small, lightweight, handheld X-ray system meant for
dental radiology that is certified by the FDA and is completely safe when used as intended. All operators must read, and become familiar with, the User’s Manual associated with the Cocoon system.
The MaxRay Cocoon mobile X-ray system.
This handheld unit is to be operated only by authorized personnel. DO NOT operate the Cocoon in
any manner other than that specified herein, and in the User’s Manual. And, DO NOT allow anyone
other than trained and certified personnel to operate the Cocoon unit.
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Background
What are X rays?
X rays are a form of ionizing radiation and are a part of the electromagnetic spectrum. X rays are the
same as the light from the sun, except that their energy is much higher. As X rays travel through and
interact with various materials, human tissue for instance, they transfer energy to the atoms of that
material. This process of energy transfer can result in atomic ionization. X rays can penetrate certain
materials, but they can be blocked or shielded with high-density materials.
The electromagnetic spectrum.
When living systems are exposed to ionizing radiation there is a risk for biological damage to occur.
Exposure to X rays in the workplace, however, is highly regulated and current safety standards are
very eective at keeping risks to a minimum.
How are X rays Generated?
X rays are produced in a type of vacuum
tube specifically designed for that function. As power is applied to the tube, X
rays are emitted in a prescribe fashion
from a shielded housing.
Diagram of an X-ray tube.
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Generally, the three parameters that are usually adjusted by the X-ray technician (tube potential
(kVp), tube current (mA), and time (sec)) establish the characteristics of the X-ray beam emanating
from the tube. The tube potential determines the energy range of X rays and the tube current establishes the rate at which X rays are emitted. In the tube, X rays are produced by two means, Bremsstrahlung radiation and characteristic radiation. The two are described below.
Bremsstrahlung Radiation
This is the main type of radiation produced and occurs as the high energy electrons experience a
sudden slowing down, or “breaking”, at the anode target. A spectrum of photon energies is produced.
Bremsstrahlung is also known as “breaking radiation”.
Characteristic Radiation
This type of radiation is produced when an electron interacts with an inner shell electron of a target
atom of the anode. As the inner shell electron is displaced, an electron from an outer shell drops to
fill the vacancy. It is this process that releases characteristic X rays.
All X-ray tubes have some form of filtration, whether it be inherent to the design or added afterward
to adjust the usefulness of the X-ray beam. The X-ray housing will have additional shielding to minimize “leakage radiation” that can cause unwanted exposure to the technician.
Primary and Scatter Radiation
Once X rays leave the tube housing, they are categorized as primary or secondary radiation. Secondary radiation is further characterized into scatter radiation and leakage radiation.
Primary radiation
This type of radiation describes the useful beam of radiation that is produced in the tube and exits the
filtration window as designed. This is the radiation which is fundamental in producing the radiograph.
Continued exposure to the primary beam can result in a significant hazard.
Scatter radiation
This refers to the radiation that is scattered after the primary beam interacts with the patient. The patient is therefore the major source of scatter radiation. Even though the primary beam is much more
intense than scatter radiation, it is this scatter that is of primary concern when protecting the safety
of the worker.
As stated above, leakage radiation refers to radiation from the X-ray tube that penetrates the device
housing. Leakage is usually quite small relative to the primary beam and scatter.
Interactions with Matter
The interaction of X rays with matter is a random process. As tissue is exposed, the X rays may interact with the atoms of the material through which they pass. A small percentage of the X rays will pass
through matter without interacting.
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