Week 9 C Chapter 40 Radiation Protection, Chapter 31 QC 84

8/11/2019 Week 9 C Chapter 40 Radiation Protection, Chapter 31 QC 84

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Chapter 40 Radiation

Protection Procedures ALARA and Occupational

Exposure


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ALARA

ALARA stands for As Low As Reasonably Achievable. It is the basic principle of radiationprotection procedures.

There is much that we can do to keep exposureto the patient and the operator as low aspossible.

The chiropractor is unique in the fact that youcan perform radiography and refer your patientsfor other types of examinations.


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Occupational Exposures

In radiologic technology, 95% of theoccupational exposure comes fromfluoroscopy and mobile radiography.

Neither would be used in your office so theworst case scenario is that you wouldreceive 5% of the exposure that atechnologist would receive.


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During radiography, the operator should bebehind a protective barrier. These barriers are usually considered as secondary

barriers so protection would be from tube leakage andscatter from the patient. The tube should never bepointed toward this type barrier.

If the barrier can have the tube angled toward the

barrier. It must be a primary barrier. Staying behind the barrier effectively eliminates thesource of occupational exposure if the shielding isadequate.


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Medical Imaging Exposures Fluoroscopy: All personnel will wear protective apron.

If extremities get into the beam lead gloves can beworn.

The radiologist will usually be close to the machine duringfluoroscopy so their exposure will be higher than that thetechnologist. Aprons between the Image intensifier andBucky Slot covers reduce radiologist exposure.

The technologist should stand as far away from the table as

possible during the exam and move closed only whennecessary. The radiologist will use short burst of exposure and keep the

exposure time as short as possible. The 5 minute clock timerwill alarm when 5 minutes of fluoroscopy has been used.


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Medical Imaging Exposures Mobile radiography:

The technologist must wear a lead apron duringmobile plain film or fluoroscopy examinations.

An apron must be assigned to each portablemachine.

The exposure cord for portable radiographicmachines must be 2 meters long to maximizedistance from the tube during exposures.


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Radiology Ancillary Staff Assuming the rooms are adequately shielded,

the receptionist, file room and darkroom staffshould not receive any occupationalexposure.

Radiology ancillary staff should not be used to

hold patients during radiography.


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Occupational Radiation Monitoring

Occupational Radiation Monitoring is required if there isany likelihood that an individual will receive more than1/10 of the recommended dose.

With just plain film radiography, monitoring may not be

required as long as the operator stays in the controlbooth during all exposures. There are some exams such as stress views of the ankle

where the operator would be in the room with the patient.If this is done, monitoring would be necessary.

If the operator ever holds a patient monitoring would benecessary.


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Occupational Radiation Monitoring

Occupational radiation monitoring offersno protection against exposure. It merelyrecords the exposure received.

If needed, find a certified laboratory toprocess the dosimeters.

Types of monitors

Film badges TLD OSL


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Film Badges

Film badges have been used since the 1940sand are still used today.

Exposures below 10 mR are not measured on

the film. Filters along with the window in the badge allowestimation of the energy of the exposure.

The must be worn with the proper side to the

front. They are typically worn on the collar so they

would remain outside the lead apron.


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Film Badges

Advantages Inexpensive Easy to handle and process Reasonably accurate

Disadvantages Can not be reused Sensitive to heat and humidity Must be changes monthly


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TLD

TLD has several advantages over filmbadges. Not sensitive to heat or humidity

Measure exposures to 5mR More sensitiveand accurate.

Can be changed quarterly instead of monthly

Disadvantages Cost but changing badges less frequentlythan monthly eliminates cost problem.


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Optically Stimulated Luminescence

All of the advantages of the TLD over filmbadges plus: Can be re-read to confirm exposure More accurate than TLD


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Where to wear the monitor

The whole body badge is typically worn atcollar level so it can be outside the leadapron.

Fetal monitoring badges used duringpregnancy are worn at waist level underthe apron.

Hand or finger TLDs are worn on theextremity.


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Occupational Radiation Monitoring Reports

State and federal regulations require that theresults of the occupational radiation monitoringprogram be recorded in a precise fashion andmaintained for review.

Specific information is required to be on thereport including current and cumulativeexposure.

Each site of monitoring must be identified

separately. There will also be a control monitor to measurethe background exposure during transport,handling and storage.


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Occupational Radiation Monitoring Reports

The supplier of the badges must know the typeof radiation for proper calibration of theequipment.

The badges are control are shipped back to thesupplier in a timely manner.

For lost or damaged badges, a health physicistwill estimate the exposure.

The annual exposure is discussed with each

worker and receipt of the information isdocumented. Monthly reports may be posted butcare must be taken with sensitive information.


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Lead apron used for operator or patientprotection must be the equivalent of 0.5mm oflead.

They must be worn when in a room during theexposure or during fluoroscopy.

Half aprons are effective means to providegonad protection during radiography.

0.25 mm of lead aprons should be avoided asthey only attenuate 66% of the beam at 76 kVp.

Protective Apparel


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Aprons used in interventional radiology shouldbe a wrap around type. Thyroid shields may alsobe worn.

Lead gloves can be worn when the hands are inthe beam. Aprons must be stored on specially designed

racks or laid flat on the floor. They are never

folded. Aprons are tested annually for cracks or holes inthe lead, usually by fluoroscopy.

Protective Apparel


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During fluoroscopy radiologic technologistshould stand as far as possible from themachine. Standing behind the radiologist offers added

protection. If you must be in the room, position your body

as far away from the primary beam aspossible.

Position


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Patient holding

Many patients will find the x-ray examination tobe physically demanding. Some may not becapable of staying in position.

This is a particular challenge for weight-bearingradiography. Mechanical supportive devices arelimited for erect studies.

If you have a radiographic table, the patient maybe examined recumbent. Sponges may be usedas supportive devices.


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Patient holding

Radiology or office staff should never hold apatient. Family or friends may be called upon toassist the patient.

The person assisting the patient must wear alead apron and if their hands will be in the beamlead gloves.

Position the person as far away from the primary

beam as possible. Since the person holding the patient may be aparent, make sure they are not pregnant.


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Reducing Unnecessary PatientDose

As a doctor, you have the responsibility todetermine if the radiography is necessary and

justified.

There are more practice guidelines availableevery year to assist in determining if theexamination will yield necessary diagnosticinformation.

There are many examinations that areperformed knowing that they will yield littlehelpful information so they in no way justify thepatient radiation dose.


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Check to see if the patient has previousexaminations that may make the newexamination not necessary.

You may be sued if you dont take filmsand the treatment plan fails because youmissed something the films would show.

The yield of information must be greaterthan the risk of radiation exposure.


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Routine x-ray examinations should not beperformed.

Used the most accurate tests to confirmor rule out your working diagnosis.

Consider using MR instead of CT


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Repeat Examinations

One area of unnecessary patient exposure isrepeated x-ray examinations. Past estimates offrequency has been as high as 10% but theyshould normally not exceed 5%.

Most of the retakes are of the lumbar spine,abdomen and thoracic spine.

Most retake are due to the exposure factors

being incorrect resulting in an over exposed orunder exposed film. Proper measurement areimportant.


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Repeat Examinations

Positioning errors account for about 25% ofretakes. Proper training and practice is importantto fine tune positioning skills.

Motion causes about 11% of retakes so properpatient communication during the exam isimportant.

But do not be afraid to retake a poor quality

film. If you can not see a problem makes itlikely you will miss it. Poor quality exams arenever justified.


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Radiographic Technique

Use as high kVp as possible to getadequate contrast and reduce patientexposure.

Collimate the beam to slightly smaller thanfilm size or the area of interest, whicheveris smaller.

Use the fastest-speed screen-filmcombination consistent with the nature ofthe examination.


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Positioning

When taking films with the patient seated,do not allow the gonad to be in the primarybeam. Position the patient lateral to thebeam.

For female patients turn the patient PA toreduce breast and gonad exposures whenpossible.


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Patient shielding

Some form of patient shielding should beused on all patients able to reproduce.

All children should have shielding. Pre-menopausal women should be

shielded except when the shield wouldinterfere with the examination.

Men should be shielded beyond 50 years.


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Patient shielding

Shielding must be used when the gonadslie in or near the useful beam and when itdoes not interfere with obtaining the

required diagnostic information. Accurate placement is extremely important.

Repeated examinations can result formimproper placement of the shield.

Proper patient positioning and collimationshould not be relaxed when gonad shieldsare in use.


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Ten Commandments of ALARA

1. Understand and apply the cardinal principles ofradiation control: time, distance and shielding.

2. Do not allow familiarity to result in a false

security.3. Never stand in the primary beam.4. Always wear protective apparel when not

behind a protective barrier.5. Always wear a radiation monitor and position itoutside the protective apron at collar level.


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6. Never hold a patient during radiographicexaminations. Use mechanical restrainingdevices when possible. Otherwise, use

patients or friends to hold the patient.7. The person holding the patient must wear

protective apron and if possible, gloves.8. Use gonadal protective on all people of

childbearing age when it will not interfere withthe examination.


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9. Examinations of the pelvis or lowerabdomen of a pregnant patient should beavoided whenever possible, especiallyduring the first trimester.

10.Always collimate to the smallest field sizeappropriate to the examination.


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Chapter 31 Quality Control

Two areas of activity are designed toensure the best possible image qualitywith the lowest possible exposure andminimum costs. Quality Assurance deals with people Quality Control deals with instrumentation

and equipment.


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Chapter 31 Quality Control

Two areas of activity are designed toensure the best possible image qualitywith the lowest possible exposure andminimum costs. Quality Assurance deals with people Quality Control deals with instrumentation

and equipment.


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Ten Step Approach to Quality Assurance

1. Assign responsibility2. Delineate scope of care

3. Identify aspects of care4. Identify outcomes that effect the aspectsof care.

5. Establish limits of the scope ofassessment.


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Ten Step Approach to Quality Assurance

6. Collect and organize data.7. Evaluate care when outcomes are

reached.8. Take action to improve care9. Assess and document actions

10.Communicate information toorganization-wide QA Program


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QA Projects

Things that QA can evaluate includes Scheduling of patients Instructions given to patients Wait times in the office Interpretation of films Retake analysis Record accuracy


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QA Program

Quality Assurance deals with people andprocesses used to complete tasks.

QA involves training and record keeping.

As the owner of the equipment, you will beresponsible for your radiology services.

The State of California Department of

Radiologic Health established theStandards of Good Practice that is thefoundation of QA and QC in radiography.


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QA and QC Requirements

Degree of requirements vary by state.California and New York have very tightstandards for quality control of theradiographic and processing equipment.

We are required by statue to teach QAand QC in the radiology program. It iscovered in detail in 9 th Quarter. Mytextboook covers QC in detail.


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Quality Control

An acceptable QC program has threesteps:

1. Acceptance Testing2. Routine performance monitoring3. Maintenance


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Acceptance Testing

The x-ray machine, cassettes and filmprocessor or digital system are the largestcapital expense you may experience.

It makes economic sense to make surethat the equipment meets the performancestandards.

It is recommended that a third party suchas a health physicist do the testing.


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Acceptance Testing

Areas that should be tested include on the x-raymachine: Shielding of Room Focal spot size Calibration of mA, timer or mAs Calibration of kVp Linearity of exposure Beam alignment Grid centering Collimation Filtration (HVL)


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Acceptance Testing

Areas that should be tested on the x-raycassettes:

Screen contact Screen speed Light leaks

Light spectrum matching


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Acceptance Testing

Areas that should be tested on the x-rayfilm processor:

Developer temperature Replenishment rates Travel time

Water flow Hypo retention


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Quality Control

After a major repair, the machine should beretested to ensure that it was repaired properly.

When the testing shows that the machine is not

performing properly, service or preventivemaintenance is required.

Manufactures establish recommendedpreventive service schedules. When these arefollowed many repairs become unnecessary.


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Radiographic Quality Control

Areas of concern in x-ray machine Focal Spot Size will impact spatial resolution Filtration will impact patient exposure Collimation will impact patient exposure kVp calibration will impact image quality and

exposure.

Exposure timer accuracy will impact imagequality and exposure


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Focal Spot Testing

When the machine is installed or the tubeis replaced, the focal spot size should bemeasured. Then annually thereafter.

A pin hole camera, star test pattern or linepair test tool.

As the tube ages, the focal spot tends togrow and spatial resolution is lost.


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Filtration

The filtration is measured but determiningthe half value layer of the beam at specificexposure levels. Minimum filtration is

2.5mm aluminum. As a tube ages, tungsten will plate the x-ray port and increase filtration. This cancause technique problems. Inadequatefiltration will significantly increase patientexposure.


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Collimation

If the collimation is misaligned, intendedanatomy can be missed.

It can be tested in many ways from usingpennies to using test patterns.

Misalignment can not exceed 2% of theSID.

It is tested semiannually and after thereplacement of the collimator lamp.


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kVp Calibration

In diagnostic radiology, any change willimpact patient exposure. A variation ofabout 3% will impact contrast and imagedensity.

Can be tested with filtered ion chambers,filtered photodiodes or even a cassette

with calibrated filters. Tested annually.


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Exposure Timer Accuracy

The exposure time is the responsibility ofthe operator. It will impact the density ofthe image and spatial resolution.

Tested with an ion chamber, multi-meterinternally or even a spinning top.

Exposure time must be within 5% forexposure times greater than 10 ms and20% less than 10 ms.


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Exposure Reproducibility

Any exposure using the same factorsshould produce the same level of densityand contrast on the image.

Sequential exposure should bereproducible to within 5%

Can be tested with a rate meter or stepwedge and densitometer.


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Darkroom and Processing

The development of the image isdependent upon the temperature of thedeveloper, its concentration and how long

the film is in the developer. The film is sensitive to variations in theenvironment and processing from the timeit is manufactured until it is processed.

Darkroom and Processor QC is the keyprocess of Quality Control.


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Processing

Processor densitometry is performed dailybefore the first patient is exposed.

A sensitometer is used to produce a step

wedge image on the film that is evaluatedwith a densitometer. The densitometer reads the optical

density of the processed image. A digital thermometer is used to test the

chemical temperatures in the processor.


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Processing

Key densities on the processed film aremeasured and then graphed.

Base plus Fog is measured on an area ofunexposed film to check the darkroomenvironment.

Speed is tested at the level of exposure thatproduces a density of 1.25OD

Contrast is tested at the level that produced adensity of 0.40 OD and one that produced adensity of 2.20.


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Processing

By monitoring these densities, problemswith film processing can be detectedbefore image quality deteriorates.

In 9 th Quarter we will cover how to performprocessor QC and problem solve.


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Waste Records

Since used fixer is classified as ahazardous waste material, it is importantto maintain accurate records of usage and

disposal. The extent of records vary by city, countyand state. You are responsible for theproper disposal of the waste. Someregions include developer as hazardouswaste.


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Silver Recovery

Old radiographic films and repeated filmsare retained for silver recovery. X-rayimages can not be disposed of in normal

trash. They also can not be used to clean theprocessor rollers.

Waste recovery companies will either burnor chemically remove the silver from thefilm.

Performance standards for film


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Performance standards for filmprocessor and darkroom equipmentMeasurement Frequency Tolerance CA Tolerance US

Sensitometry Daily B+F: 0.05MD: 0.10 ODContrast 0.10OD

B+F: 0.08 ODMD 0.15 ODContrast 0.15 OD

Safelight Semiannual < 0.05 OD in 2minutes n/a

Darkroom temp Monthly 70F 5 n/a

Darkroomhumidity

Monthly 50% 10% n/a

Developer temp Daily 0.5F 2-3

Replenishment Daily 5%

Transport Annual 3% 3%


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Accessory QC

The cassettes and screens are the area ofchief concern. Problems with either willresult in artifacts on the images and

increased retakes. The screens need to be properly cleaned

frequently. Mammography screens are

cleaned daily. California recommendsmonthly cleaning.


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Accessory QC

Dirty screens produce white artifacts onthe image.

Multiple white artifacts indicate the need to

replace the screens. Screen contact is tested semiannually. A

problem with screens contact will cause aloss of resolution.

As screens age, they loose speed so thisis also tested.


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Accessory QC

The other important accessory is thegonad protection devices and lead aprons.

Improper care of the apron can result in

cracks and holes in the lead that reducestheir effectiveness. Aprons and shields are tested

semiannually. The easiest was to testthem is with video-fluoroscopy but film canbe used.

Performance Standards for


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Performance Standards for Accessories

Measurement Frequency Tolerance CA Tolerance US

Screen contact Semi annual No problemsdetected

No problemsdetected

Aprons/shields Annually No holes No holes

Screen

matching

Annually 0.05 OD for all

cassettes usedScreen cleaning Monthly Semimonthly


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Record keeping

All electromechanical devices needperiodic service.

There are three types of maintenance. Scheduled maintenance such as processor

monthly or weekly service. It includesobserving moving parts and lubrication.

Preventive maintenance is planned serviceand replacement of parts at regular intervalsbefore they fail at inopportune times.


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Record keeping

Non-scheduled maintenance is the worsttype of service because it impacts patientservice. It may also be very expensive.

With proper scheduled and preventivemaintenance, non-scheduled service can beminimized.

All service schedules should meetmanufacture recommendations.

All service should be documented as partof the quality assurance program.


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Retake Analysis

Required part of a QA program inCalifornia.

Evaluation includes

View repeated Cause of the repeat

Rate of retakes should be less than 5%.

Information can be gathered from the logthat the state mandates for patients beingexposed to radiation.


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Retake Analysis

Done every three months using arelatively large sample of data to seetrends in: Type of examination being repeated. Reasons for the repeated films. Determine if additional training or review is

needed. Determine if equipment service might be

required.


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Repeat Analysis

Your patient log can be designed tocapture both films usage and repeatedfilms.

Data is gathered from log for analysis Repeated films can be put into two main

categories: X-ray Personnel Errors Equipment malfunctions


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X-ray Personnel Errors

Failure to measure patient. Use of improper technical factors (mAs,

kVp or distance) Incorrect positioning Improper Collimation Improper use of accessories such as

cassettes, grids or filters


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X-ray Personnel Errors

Improper handling of exposed orunexposed films.

Failure to clearly communicate to thepatient breathing instructions and toremain still.

Failure to observe patient duringexposure.

X-ray Equipment and Accessory


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X ray Equipment and AccessoryFailure or Malfunctions

Inaccurate calibration of kVp and mA. Inaccurate timer calibration Dirty or damaged cassettes Improperly labeled or damaged grids Malfunctioning collimator

Improper film storage or processorfunction.


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Reasons for Retake Films

Over or under exposure accounts for over50% of retakes nationally.

Errors in positioning (25%) Patient motion 11% Processing errors 6% Wrong view, beam alignment,cassette

screen or grid errors and artifacts.


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Retake Films by Region

Cervical Spine Exams = 7% Thoracic Spine Exams = 17% Lumbar and Abdominal X-rays = 40% Skull, Chest,Lower Extremities = 15% Majority or retake results in

unnecessary exposure to gonads orblood forming organs of the body.


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Daily Log Design

Most regulatory agencieswill require a log ofpatients having radiationexposure.

Columns can be added tocapture film usage,repeats, views repeatedand reason.

This data can begathered and analyzed.


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Retake Analysis

The reason of eachretake is recordedand percentages arecomputed todetermine the overallrate and rate byreason.

Less than 5% is ideal.


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End of Lecture

Return to Lecture Index
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Week 9 C Chapter 40 Radiation Protection, Chapter 31 QC 84

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