Radiation Biology Chapter 10,11,12,15

NCRP reports (The National Council on Radiation Protection and Measurements)

Publications that provide the most recent guidelines on radiation protection for the United States

EfD Limiting System

Set of numeric dose limits that are based on calculations of the various risks of cancer and genetic (hereditary) effects to tissues or organs exposed to radiation

EfD

The sum of both external and internal whole body exposures is considered when establishing this limit

ICRP- The International Commission on Radiological Protection

International authority on the safe use of sources of ionizing radiation. Responsible for providing clear and consistent radiation guidance through its recommendation for occupational dose limits and public dose limits 

RSO

Usually a medical physicist, health physicist, radiologist or other individual qualified through adequate training and experience. This person is designated by a health care facility and approved by the NRC and the state

UNSCEAR- United Nations Scientific Committee on the Effects of Atomic Radiation

A united nations committee that evaluates human and environmental ionizing radiation exposures from a variety of sources, including radioactive materials, radiation producing machines, and radiation accidents

Negligible individual dose (NID)

An annual EfD level that provides a low exposure cut-off level that has been determined to be a dose of negligible risk, meaning that a reduction of individual exposure is unnecessary

Annual occupational EfD limit

An upper boundary limit for radiation workers for yearly whole body exposure (excluding personal medical and natural background exposure) of 50mSv/yr

ALARA concept

Optimization for radiation protection

NARM

Naturally occurring and/or accelerator- produced materials

CFR 35.900 of the Code of Federal Regulations

Document that identify the necessary training and experience for an RSO

Annals of ICRP

Scientific journals published by the ICRP 

Action Limits

Established by health care facilities to trigger an investigation to uncover the reason for any abnormal exposure received by individual staff members

Radiation Control for Health and Safety Act of 1968

Public law passed by congress for establishing and overseeing electronic product radiation control including diagnostic x-ray equipment

OSHA- The Occupational Safety and Health Administration

Agency responsible for regulations concerning an employee’s “right to know” about hazards that may be present in the workplace

BEIR reports 

Publications that list studies of biologic effects and associated risk of groups of people who were either routinely or accidentally exposed to ionizing radiation 

FDA

US regulatory agency that conducts an ongoing product radiation control program, regulating the design and manufacture of electronic products, including diagnostic x ray equipment

EfD limit

Concerns the upper boundary dose of ionizing radiation that results in a negligible risk of body injury or hereditary damage

NRC- nuclear regulatory comission

Regulatory agency that has the power to enforce radiation protection standards in the United States

CumEfD limit

Lifetime EfD limit

Tissue reactions

Biologic somatic effects of ionizing radiation that can be directly related to the dose received

Tissue Weighing Factor (Wt) 

Indicates the ratio of the risk of stochastic effects attributable to irradiation of given organ or tissue (T) to the total risk when the whole body is uniformly irradiated

Radiation- induced malignancy

Cancerous neoplasms caused by exposure to ionizing radiation

Consumer- patient radiation health and safety act of 1981

Federal legislation requiring the establishment of minimal standards for the accreditation of educational programs for persons who perform radiologic procedures and the certification of such persons

Code of standards for diagnostic x-ray equipment

Applies to complete x-ray systems and major components manufactured after august 1, 1974

Occupational exposure

1) annual EDL

2) cumulative EDL

50 mSv

10 mSv x age

Occupational exposure

EqD annual limit

• lens of eye

• localized areas of the skin, hands, and feet

150 mSv

500 mSv

Public exposure (annual) 

1) EDL limit, continuous or frequent exposure 

2) EDL, infrequent exposure

1) 1 mSv

2) 5 mSv

Public exposures (annual)

1) EqD limit lens of eye

2) EqD limit localized areas of the skin, hands, and feet 

1) 15 mSv

2) 50 mSv

Public exposures

1) Remedial action for natural sources

a) EfD (excluding radon)

b) exposure to radon and its decay products 

a) greater than 5 mSv

b) greater than 26 J℠ 

Education and training exposures (annual)

1. EDL 

2. EqD limits for organs and tissues

a) lens of the eye

b) localized areas of the skin, hands, and feet

1) 1 mSv

2a) 15 mSv

2b) 50 mSv

Embryo- fetus exposures

1. EqD limit

• monthly

• entire gestation

0.5 mSv

5 mSv

Negligible individual dose (annual)

0.01 mSv

Inherent filtration

the glass envelope encasing the x ray tube, the insulating oil surrounding the tube, and the glass window in the tube housing

Half value layer (HVL)

The thickness of a designated absorber (customarily a metal such as aluminum) required to decrease the intensity of the primary beam by 50% of its initial value

Diagnostic type protective tube housing 

Require to safeguard the patient and imaging personnel from off focus, or leakage radiation by restricting the emission of x rays to the area of the useful, or primary beam 

Spacer bars 

devices that project downward from the x ray tube housing of some collimators to prevent the collimator from being closer than 15cm to the patient 

Added filtration

thin sheets of aluminum of a millimeter r sub- millimeter thickness generally located outside the glass window of the x ray tube housing above the collimator shutters

Control panel or console

Where technical exposure factors such as mA and kVp are selected and seen on indicators by the operator

Scatter radiation 

All the non useful image formation radiation that arises from the interaction of an x ray beam with the atoms of a patient or any other object in the path of the beam 

Positive beam limitation (PBL)

Purpose is to restrict the size and shape of the x ray beam so it does not exceed the size and shape of the selected image receptor

Computed Radiography (CR)

Term used for x ray systems that generate images using the process of photostimulable luminescence (PSL)

Radiographic beam defining system 

consists of two sets of adjustable lead shutters mounted within the collimator at different levels, a light source to illuminate the x ray field and permit it to be centered over the area of clinical interest and mirror to deflect the light beam toward the patient to be imaged 

High level control fluoroscopy (HLCF)

An operating mode for state of the art fluoroscopic equipment in which entrance radiation levels are substantially higher than those normally employed in routine procedure. this higher exposure rate or entrance dose rates allow the examination of smaller and lower contrast objects that are not ordinarily discerned during standard fluoroscopy

carbon fiber

material commonly used in radiographic/fluoroscopic x ray room tabletop that helps reduce patient dose

Nit

a simple term for candelas per square meter 

luminance

brightness of a surface

Amorphous selenium

A photoconductor used to convert x ray energy directly into electrical signals

Mobile (portable) x ray unit 

equipment that should be used to perform radiographic procedures only on patients that cannot be transported to a fixed radiographic installation

Off focus radiation

x rays emitted from parts of the tube other than the focal spot

Last image hold feature for dose reduction

Allows the fluoroscopist to see the most recent image without exposing the patient to another pulse of radiation

DR

The process of recording an electronic image on a flat panel detector in a digital form that may be transferred directly to a computer without further processing or scanning

Source too image receptor distance (SID)

the distance from the anode focal spot to the radiographic IR

Desquamation

sloughing/ shedding off of skin cells

Radiographic grid 

device that improves radiographic contrast and visibility of detail by selectively removing scattered x rays, although increases patient dose 

Useful or primary x ray beam

x rays emitted through the x ray tube window or port

Aluminum

metal most widely selected as a filter material for general purpose radiography

Digital image 

image produced by computer representation of anatomic information and displayed on a monitor 

Body language

nonverbal messages, that if understood as intended will promote effective communication between the radiographer and the patient

Holistic patient care

considering for treatment the whole person rather than just the area of interest (physical emotional, mental health)

Air gap technique

Alternative procedure to the use in place of a radiographic grid for reducing scattered radiation during specific examinations

Flat contact shields 

can be used to protect the reproductive organs when they are not to be included in the area of interest 

Referring physician

individual responsible for ordering a radiologic examination

American association of physicists in medicine (AAPM)

Organization that issued a position statement in April 2019 indicating that patient gonadal shielding and fetal shielding during diagnostic imaging procedures should be discontinued as routine practice

Nonessential radiologic examinations

radiographic examinations performed in the absence of definite medical indications 

Epidermis

primary function is to protect underlying tissues and structures

DEXA, or DXA scan

test to determine the degree of bone loss by measuring bone mineral density

CARES committee 

group formed by the American association of physicists in medicine (AAPM) whose purpose is for all stakeholders to educate the profession regarding the AAPM gonadal shielding positioning statement  

Bone marrow

of great importance because it contains large numbers of stem, or precursor, blood cells that could be either depleted or, worse, even eliminated by substantial exposure to ionizing radiation

Possibility of pregnancy

something that a radiographer should ask a female patient of childbearing age about before the patient undergoes an x ray examination

Gonadal dose 

radiation exposure received by the male and female reproductive organs

Effective communication

an interaction that produces a satisfying result through an exchange of information

Spatial resolution

the recorded detail in the radiographic image

Quality control program 

Standardization in the processing of digital images, which includes regular monitoring and maintenance of all processing and image display equipment in a facility 

Quantum noise, or mottle 

a blotchy radiographic image that results when an insufficient quantum of x ray photons reaches the IR

Thermoluminescent dosimeters (TLDs)

sensing devices most often used to determine skin dose directly

ESE- entrance skin exposure

may be converted to patient dose by well documented multiplication factors

Image wisely 

campaign that promotes lowering the amount of radiation used in medically necessary imaging procedures and eliminating unnecessary procedure in adult medical imaging  

GSD- genetically significant dose

the equivalent dose to the reproductive organs that, if received by every human in a large population group, would be expected to bring about an identical gross genetic injury to the total population, as does the sum of the actual dose received by exposed individual members of the population

Elective x ray examination

nonurgent x ray procedures that can be booked at an appropriate time to meet the patient needs and safety

Image gently

a campaign to change long established practice by raising awareness about methods for lowering radiation dose during pediatric medical imaging examinations 

Entrance exposure rate

obtained from ionization chamber measurements with the chamber situated just beneath a patient phantom slightly offset from the tabletop as part of routine medical physicist equipment surveys

FGP

the unethical practice of using fluoroscopy to determine the exact location of the central ray before takin fa radiographic exposure

Inverse square law

the intensity of radiation is inversely proportional to the square of the distance from the source

secondary protective barrier 

examples:

Walls of a control booth

X-ray room doors

Structural walls

protects against leakage and scatter radiation not from primary beam

50 mSv

annual occupational effective dose in metric units for whole body exposure during routine operations

Positive beam limition 

restricts the dimensions of the radiographic beam so that its margins do not extend beyond the IR

Primary protective barrier

prevents direct, or unscattered, radiation from reaching personnel or members of the general public on the other side of the barrier

examples:

areas directly in path of beam

concrete walls

shields

lead

0.5 mSv

monthly allowable equivalent dose to the embryo-fetus in metric units from occupational exposure of a pregnant technologist

use factor (U)

(also knowns as a beam direction factor) for primary radiation, the use factor represents the portion of beam on time that the x ray beam is directed at a primary barrier during the week

1 mSv

annual effective dose (EfD) limit set for individual members of the general public

Workload (W)

specified either in units of mAs per week or milliampere- minutes (mA-min) per week

Bucky slot shielding dose 

During a standard fluoroscopic examination, when the bucky tray is positioned at the foot end of the table, this device automatically covers the bucky slot opening in the side of the x ray table. it protects the radiologist and radiographer at the gonadal level 

lead and concrete

most common materials used for structural protective barriers

Occupancy factor (T)

this is used to modify the shielding requirement for a particular barrier by taking into account the fraction of the work week during which the space beyond the barrier is occupied

Remote control fluoroscopic system 

permits the radiologist and assisting radiographer to remain outside the fluoroscopic room at a control console behind a protective barrier while the x ray beam is on 

High level control

mode of operation in which the exposure rate may significantly exceed the rate used in routine fluoroscopy

Protective curtain

during a fluoroscopic examination, this device should be positioned between the fluoroscopist and the patient to intercept scattered radiation above the tabletop

Control booth barrier 

a permanent protective barrier for the radiographer that is located in an x ray room housing stationary radiographic equipment 

CumEfD limit

a radiation workers whole body lifetime effective dose in mSv should not exceed 10 times the persons age in years