EXAM #3 RAD31

Engisch

What is Source to Skin distance requirment?

federal requirement

SSD stationary unit

not less than 38 cm (15 inches)

SSD mobile unit

not less than 12in (30cm)

Filtration

functions to abdorb low energy photons (soft x-ray)

Total filtration

must be at least 2.5mm Al equivalent

What does filtration do?

reduces patient dose

What are x-rays make it through filtration?

high energy (hard x-rays)

Collimation

beam restricting device

How should the boarders be for collimation?

unexposed boarder must be visible at 35cm above tabletop with collimator fully open

Exposure Switch

Dead man type - terminated exposure when pressure is released

How long should the exposure switch be?

cord must be at least 6 feet long

Bucky Slot Cover during fluoro exam

Tray must be moved to the end of the table

What is the minimum lead for Bucky Slot Cover

should be 0.25 mm of lead

Lead Apparel

Should be worn during all fluoro procedures

Protective Curtain should be positioned where?

Should be positioned between the fluoroscopist and patient

Minimum lead for Protective Curtain

should be at least 0.25 mm of lead

Primary purpose for Protective Curtain

reduces scatter from patient

When should the protective curtain be removed?

during a sterile procedure

Cumulative Timer produces?

Produces an audible signal when fluoro time exceeds 5 min

Leakage Radiation

Emitted from tube housing isotropically

What is the limit for leakage radiation?

not to exceed 100mR/hr at 1 meter

who is the main source of Scatter Radiation ?

patient is main source of occupation exposure during fluoroscopy

How is scatter radiation produced?

primarily by compton interaction

What helps to minimize radiation exposure

under table tubes

What are increasing factors that affect scatter?

• high kVp

• large field size 

• thick body part

Primary Barriers

a barrier to attenuate the useful beam

What is most often used with Primary Barriers?

Lead bonded to sheet rock or wood paneling most often used

Primary Barrier: what can be used as alternate to lead

Concrete or steel can be used as alternatives to lead for primary barriers.

height required for primary barrier

must be at least 7 feet tall; rule of thumb - 4in of masonry = 1/16in of lead

Secondary Barrier

A barrier to attenuate leakage and scatter radiation

How much less is Secondary than Primary Barrier?

less thick than primary barriers (1/32in)

What is not required in Secondary barrier?

Lead not required, usually gypsum board, glass or lead acrylic is used

What does Protective Barrier Thickness depend on

Depends on distance (distance adjacent to occupied area, not inside of walls of x-ray room)

Areas in department

1. Controlled Area

2. Uncontrolled Area

Controlled Area 

Occupied by x-ray personnel and patients

What are controlled areas limits based on?

based on proportionate weekly exposure (radiology personnel and patient

What is the exposure rate for controlled area?

exposed rate must be less than 100mrem (1sV/wk)

Uncontrolled Area

Can be occupied by anyone

What are uncontrolled areas limits based on?

can be occupied by anyone (hallway, hospital staff other than radiology)

What is the exposure rate for uncontrolled area?

Exposure rate must be less than 2mrem/wk

What is Workload?

greater number of exams done each week = the thicker the shielding required

use factor (u) = ?

percentage of the x-ray beam is on and directed toward a particular wall

kVp (penetrability) depends on

kVp used in exam room

NCRP recommends Use Factor

¼ use factor - wall

1 use factor - floor

Personnel monitoring devices

1. Thermoluminescence dosimetry monitor radiation exposure

What is dosimeter made of?

crystals are made up of lithium fluoride

What is the process of personnel monitoring dosimeter?

Once exposed to ionizing radiation and then heated, these crystals give off light depending on amount of radiation received. 

NCRP #1 16 recommends (re:dose)

a max annual effective dose limit of 50 mSv recommended to provide for annual exposure

What does OSL stand for?

Optically Stimulated Luminescence dosimetry

Steps for OSL

1. Exposed to ionizing radiation

2. laser illumination

3. measurement of the intensity of the stimulated light emission

What does OSL use?

Uses aluminum oxide as the radiation detector material

What is a pocket dosimeter aka

Pocket ionization chamber

Describe what a pocket dosimeter

Small pocket sized instrument thst discharged a capacitor by ionization of air with in the presence of ionizing radiation.

When is pocket dosimeter used?

used primarily when working with large amounts of radiation; gives a daily reading of ionizing radiation exposure.

What is pulsed fluoroscopy?

Uses short pulses of x-ray (5 msec or less) instead of constant output

T/F does Pulsed Fluoroscopy reduce patient dose?

TRUE; Reduces patient dose and occupational exposure

General Fluoro

30 pulse/sec

Pulsed Fluoro

15 pulses/sec

What is the max table top dose for High-level fluoro?

Max tabletop dose rate is 20 mrads/min unless recording devices are used

Cardinal Principles of Radiation Protection

Time, Distance, Shielding - collectively known as ALARA (As Low As Reasonably Achievable).

What is patient dose directly related to?

duration of exposure

Operators exposure to scatter is directly related to

patient exposure

What should be kept to a minimum to reduce pt and personnel exposure?

Time of exposure

What is the reset time

5 min

As distance from the source of exposure increase

the radiation exposure decreases

What does ALARA include?

Both occupational dose as well as pt dose

What three recommendations associated with ALARA

1. Radiation exposure must have benefit

2. all exposures must be ALARA

3. individual dose levels must remain below the max allowed

Whole-body dose includes? **

Refers to the cumulative radiation exposure to head, trunk (including gonads and internal organs), arms above the elbow, and legs above the knee.

4 Way(s) to reducing Radiation Dose in Fluoroscopy

Methods include:

1. higher kVp values,

2. more x-ray tube filtration,

3. reducing fluoroscopy times,

4. keeping the image intensifier close to the patient.

What are 3 Radiologic Devices? 

1. A Radiation Exposure Device (RED)

2. A Radiologic Dispersal Device (RDD)

3. An Improvised Nuclear Device (IND)

Radiation Exposure Device (RED)

A sealed source of radioactive material that directly exposes individuals.

EX: a source of radiation sitting in one spot radiating radioactive material 

Radiologic Dispersal Device (RDD)

A bomb that disperses radioactive contamination over a wide area when exploded.

NOT usually life threatening

Improvised Nuclear Device (IND)

Contains nuclear material capable of producing a nuclear explosion.

What is IND considered?

A nuclear weapon

The dose limits established by the NCRP are derived from

biological effects of ionizing radiation and neural stem cell reports

Dose limitse are based on ______ dose-responce relationship to radiation

linear, non-threshold

Patient dose is __________ to the duration of an exposure

directly related

When is it necessary to shield a patient

whenever feasible

What is involved in a whole-body dose?

head, trunk, arms above elbows, legs above the knees

What is ESE stand for?

Entrance Skin Exposure

What is ESE?

The dose of radiation to which the surface of the body is exposed during a radiographic procedure. 

AKA for ESE

Patient Dose

How is ESE estimated?

can be estimated by using a nomogram

How is ESE measured?

Can be measured by Thermoluminescence dosimeters (TLD) and optically stimulated luminescence dosimeters (OSLD)

What is BMD stand for?

Bone Marrow Dose

Why is BMD important?

Why is bone marrow dose important?it is believed to be responsible for radiation induced, lympoma and myeloma (stocastic)

What is BMD also expressed as?

MMD - Mean Marrow Dose

What is the dose of BMD linked to?

The stocastic responses are linked to dose to the stem cells fo the bone marrow

T/F can BMD be measured?

FALSE; can only be estimated

What does GSE stand for?

Genetically Significant Dose

What is GSE?

An estimate fo the genetic significance of gonad radiation dose

is GSE difficult to estimate?

no

What does DRT stand for?

Digital Radiographic Tomosynthesis

What may DRT replace?

may replace a number of CT exams

What is DRT approved for?

Mammography

How does DRT work?

takes 6 to 10 x-ray exposures made at various angled to the IR using a total patient radiation dose approx equal to single DR 

Fluoroscopic Patient Radiation Dose

ESE in Fluoro is must more difficult to estimate than in radiography because x-ray fields move and varies in size

it is difficult to estimate how much each organ is affected