2721 Patient Radiation Dose During Procedures

Limiting Patient Exposure to Ionizing Radiation

• Radiographers must limit the patient’s exposure to ionizing radiation by

  • Employing appropriate radiation reduction techniques

  • Using protective devices that minimize radiation exposure

• Patient exposure can be substantially reduced by using

  • Proper body or part immobilization

  • Motion reduction techniques

  • Appropriate beam limitation devices

  • Adequate filtration of the x ray beam

  • Gonadal or other specific area shielding

  • Suitable technical exposure factor in conjunction with either high speed film screen combinations or computer generated digital images

  • Correct radiographic film processing techniques or appropriate digital image processing

  • The elimination of repeat radiographic exposures can also contribute significantly to limiting patient exposure

Patient Protection

• Effective Communication

  • Provide explanation of procedure in clear precise but simple terms

  • Provide instruction that clearly will avoid motion

  • Inform patient of any discomfort or paint

  • Answer question Re: benefits vs. risk of radiation and dose

• Patient protections during a diagnostic x-ray procedure should begin with clear concise instructions

  • Ability of patient to cooperate

  • Consequences when procedures are not explained for the patient

  • Benefit of explaining procedure to the patient in simple terms

  • Giving the patient the opportunity to ask questions

  • Listening attentively and answering patient questions truthfully in accordance with ethical guidelines

  • Creating a sense of trust between the patient and radiographer

Consequences of Repeat Images

• Additional exposure increases patient dose

• Double dose to patient’s skin and possibly the gonads

• Repeats resulting from carelessness or poor judgement on the part of the radiographer must be eliminated

• Repeat exposure (an additional image) is permissible when recommended by the radiologist for the purpose of obtaining additional diagnostic information

Benefits of a Repeat analysis program

• By determining the number of repeats and the reasons for producing unacceptable radiographic images, existing problems and conditions in an imaging dept will be identified

• Retake analysis is particularly important in CR and DR

  • Readjustment of images by computer

  • Measurement of radiation exposure techniques by a qualified medical physicist

  • Necessity to develop a policy whereby retaken image files can be recovered for analysis

Other Ways to Avoid Repeat Exposures

• Use of immobilization devices

• For use with pediatric, geriatric, or incapacitated patients

• Requirements for restraining patients

  • Use mechanical devices as a first resort

  • Use devices such as: Compression bands, tape, sandbags, sheets, towels, sponges, commercial devices, pigg o stat

  • Holding patients:

    • Use human restraint as a last resort

    • Choose family members friends or other hosp personnel, older individuals are preferred; no one individual should hold routinely

    • RT should never hold pts

    • Provide shielding devices to individual holding

    • Position individual to avoid being exposed to the primary beam

    • Pregnant women or pts < 18 are not allowed to hold

  • Use short exposure times

Protective Shielding

• Purpose: Required when gonads are in or within close proximity (5cm) to the collimated beam; used when shield does not obscure clinical area of interest

• Types

  • Contact shield:

    • Flat contact shield; used for PA or AP proj in recumbent positions, decreases exposure by

    • 1mm lead flat contact shield from the female reduces exposure by about 50%

    • 1mm lead contact shield for the male pt reduces exposure 90-95%

    • Shaped contact shields; Used in recumbent, non recumbent, AP, Oblique, Lateral projections. Decreases exposure by 90-95% Ex: male and female gonads, breast, and lens

  • Shadow shields: Used effectively in a sterile field or when examining an incapacitated pt

  • Clear Lead Shield: Replaces conventional gonadal shields; Ex: gonad and breast, made of transparent lead plastic material impregnated with approx 30% lead by weight

Pt Protection

• Exposure Factors

  • Use high kVp (fixed or optimum) and low mAs

  • Higher energy; more penetrating beam

  • Gives a smaller absorbed dose

  • Use positions that will reduce pt dose

    • Ex: perform skull, facial bones, stenyers projections in prone position to reduce exposure to the eyes by 95%

    • Ex: extremity, forearm - dose increases when pt is seated facing table

  • Position accurately when using AEC device to avoid repeats

Air Gap Technique

• Reduction of scattered radiation

  • An alternative procedure to the use of a radiographic grid for reducing scattered radiation during certain exams

  • Procedure to perform air gap technique

  • Uses for air gap technique

    • Removed scatter raditiaon by using an increased OID, improves image contrast

  • Comparison to grid ration

    • Pt dose higher than non grid technique

    • Pt dose about the same as mid ratio grid

• High kVp radiography

  • Over 90 kVp air gap techniques are for the most part ineffective

  • For chest radiography using 120-140 kVp, air gap techniques may be successful

  • At less than 90 kVp air gap techniques are more efficient

Post Processing and Quality Control Programs

Use the manufacturers recommendation

Report Malfunctions

Quality control program is essential

Includes regular monitoring and maintenance of all processing and imaging display equipment in the facility

Maximizes the likelihood of producing optimal-quality images

Unnecessary Radiologic Procedures

Nonessential radiologic examinations

Chest x-ray examination on scheduled admission to the hospital

Chest x-ray as part of a pre-employment physical

Lumbar spine examination as part of a pre-employment physical

Chest x-ray or other unjustified examination as part of a routine health checkup

Chest x-ray examination for mass screening for tuberculosis (TB)

Whole-body multi-slice spiral computed tomography (CT) screening

Marked areas in Radiology

Radiation areas are Limited Access Areas:

Unrestricted Area:

Area where radiation level is same as background level

No monitoring, posting or control requirements, no signs

Cannot exceed 2 mrem/hr

These are hallways, waiting rooms, stairwells

Restricted Areas:

Must protect from radiation

Posting Categories:

Radiation Area - radiation warning signs should be posted where radiation level could result in an individuals receiving 5 mrem/hr (or 100 mR in any 5 consecutive days) but 100 mrem in any one hour;

requirement: Controlled Access - “Caution Radiation Area” Sign must be used (3-blade radiation symbol)

High Radiation Area - signs shall be posted at the entrance to any area wherein a person could receive an exposure of 100 mrem or more in one hour

requirement: entrances must have an access control feature such as door interlocks

Very High Radiation Area - where radiation could result in an individual receiving in excess of an absorbed dose of 500 mrem in one hour (applicable to research, not diagnostic radiology)

Radiation Protection - Pregnant Patients

Fetus is most sensitive from the 10th day - 10th week after conception

10-Day Rule – Obsolete by ACR & ICRP (also Bushong recommendation)

Patient Questionnaire/Posting of Signs or Posters/Ask if patient is pregnant

Shield patient when it does not interfere with exam; collimate; use high kVp

Elective Booking - Scheduling of Elective Exams

Considerations for Rad. Exams in Abdominal Region

Limit number of projections

If pregnant patient escapes detection and is irradiated Radiologist/Physicist must:

1st - Calculation/estimation of Fetal Dose by Radiologist

Fetal dose is usually less than 1 rad following a conventional x-ray exam.

2nd - Determine gestational time when exposures occurred

Alternatives - Pregnant Pts

Alternatives:

Continue Pregnancy

Terminate Pregnancy

10-25 rad rule

Below 10 rad a therapeutic abortion is not indicated

Above 25 the risk of latent injury may justify therapeutic abortions

Between 10-25 rad, precise time of irradiation, emotional state of pt and other socio and economic factors contribute to decision

Risk is negligible at 5 rad or less; doses above 15 rad risk of malformations.

Therefore exposure from diagnostic procedures would rarely be the cause for terminating the pregnancy.

Irradiation During an Unknown Pregnancy

If irradiation of an unknown pregnancy occurs, the first step is to list the particulars of the x-ray examination in as much detail as possible.

Irradiating a Pregnant Patient

If the physician feels it is in the best interest of a pregnant or potentially pregnant patient to undergo a radiologic examination, the examination should be performed without delay.

Special effort should be made to minimize the dose of radiation the patient receives to her lower abdomen and pelvic region.

Can be accomplished by

Selecting exposure factors that are appropriate for the examination.

Precisely collimating the radiographic beam to include only the anatomic area of interest.

When the lower abdomen and pelvic region do not need to be included in the area to be irradiated, they should be protected with a lead apron or other suitable protective contact shield so that a developing embryo-fetus does not receive unnecessary radiation exposure.

Pediatric Considerations During Conventional X Ray Imaging

Vulnerability of Children to Radiation Exposure

Children are much more vulnerable to both the late somatic effects and genetic effects of radiation than are adults.

Children require special consideration when undergoing diagnostic x-ray studies.

Appropriate radiation protection methods must be used for each procedure

Children Require Smaller Radiation Doses than Adults Do

Patient Motion and Motion Reduction Methods

Use very short exposure times (select high mA station)

Use effective immobilization

Gaining Cooperation During the Procedure

Use specially designed rooms for pediatric examinations containing suitable entertainment devices and distraction devices

Gonadal Shielding and Gonadal Dose

Concept of internal scatter

Appropriate shielding

When not to shield

Morbid Obesity

Obese patients have an effect on the functionality of imaging equipment

The increased body size have a negative impact on image quality and create technical challenges

Equipment have weight limits

Fluoroscopy towers have a maximum diameter and cannot fit under the tower

Centering on table is important incase you can’t feel land marks. Consider that bony skeleton and most organs are not larger and do not change position.

Larger IR are not always needed for obese patients. Collimator should never be set bigger than IR

Modified exposure techniques need to be used

Need for adequate penetration of the body part

Using a grid can minimize scattering

Keeping repeat images to a minimum