Management of Patient Radiation Dose

How does good communication affect patient dose?

• encourages reduction in anxiety and emotional stress

• enhances the professional image of the radiographer as a person who cares about the patient’s well-being

• increases the chance for successful completion of the x-ray exam

  • reducing repeats due to poor communication

Poor communication can result in what?

inadequate or misinterpreted instructions may prevent the patient from being able to cooperate as needed, causing repeats

Explain the 2 types of patient motion

Voluntary

• motion that can be controlled

• breathing, discomfort, fear, etc.

• fixed with good communication and immobilization aids

Involuntary

• cannot be controlled

• tremors, chills, heartbeat, peristalsis, etc.

• improved by shortening the length of exposure time and using high speed IRs

What 3 areas should be shielded from the beam?

lens of eye, breasts, thyroid gland

Explain the discontinuation of gonadal shielding

In April 2019, the American Association of Physicists (CARES committee) in Medicine discontinued the use of gonadal shielding and fetal shielding

What was gonadal shielding used for?

used to protect reproductive organs from exposure when within ~5cm of the collimated beam

What is the first step in gonadal protection?

adequate collimation

How much more exposure do female reproductive organs receive than male reproductive organs during a radiograph?

3 times more

Flat contact shield reduces female reproductive organ exposure by ___ and male reproductive organ exposure by ___

female: 50%

male: 90-95%

What are the 4 types of shields?

flat contact, shadow shield, shaped contact shield, clear lead shields

Explain flat contact shields

• made of lead strips or lead impregnated materials 1mm thick

• sited directly over the patient

• most effective for recumbent positioned radiographs

Explain shadow shields

• radiopaque material that is suspended from above the beam-defining system

• cast a shadow in the primary beam over the patient’s reproductive organs

• effective for providing gonadal protection in a sterile field or when incapacitated patients are being examined

Explain shaped contact shields

• 1mm of lead that is contoured to enclose the male reproductive organs

• can be used with disposable or washable athletic supporters

• cup-like shape covers the scrotum and penis whether the patient is recumbent or non-recumbent

Explain clear lead shields

• transparent lead acrylic devices impregnated with 30% lead by weight

• replaces the older style shadow shields and contoured shields

• good for scoliosis exams

• used to protect the patient’s breasts

What is the goal of appropriate technical exposure factors?

minimize patient dose while providing high-quality images, provide sufficient brightness or density, appropriate levels of subject contrast to differentiate among structures, limited quantum noise

Explain the purpose and use of technique charts

• digital image receptors have a wide dynamic range

  • technique charts need to be made for each x-ray unit

• helps prevent overexposure to the patient

• technologists must know if the machine readout is EI# or S#

Higher kVp permits lower mAs settings, which leads to ___

reduced patient entrance dose

___ determines penetration (which is needed to create the differences in x-ray intensities exiting the patient, to produce the desired level of contrast)

kVp

Increasing the kVp by ___ with a 50% decrease in mAs = reduced patient exposure while maintaining a satisfactory image quality

15%

Explain the use of the quality control program

regular monitoring and maintenance of all processing and imaging display equipment in the facility (ensures standardization in the processing of digital images)

How are systematic problems prevented?

acceptance testing of new equipment, regular calibration of existing equipment, and proactive/consistent image review quality control are conducted

Explain air gap technique

• an alternative procedure for reducing scatter

• replaces the use of a grid

• uses an increased OID

  • IR 10-15cm from patient

  • tube 10-12 feet from IR

• equal to an 8:1 ratio grid

What is a repeat image?

any image that must be performed more than once because of human or mechanical error during the production of the initial image

Explain repeats before and after digital imaging

• BEFORE: repeat rates were 10-15%, leading cause was incorrect technical factors

• AFTER: digital images can correct many technical errors, however repeat rates are 5-17% (caused by positioning errors)

Explain the repeat analysis system

• analysis of the department’s repeat rates

  • provides valuable info for process improvement

  • helps minimize patient exposure

  • improves overall performance of the department

• improving performance in the department

  • increases awareness among staff and students of the need to produce quality images

  • staff becoming more careful in producing radiographic images because the techs are aware that images are being reviewed

  • identifies problems that result with in-service education

What are some non-essential examinations?

• CXR automatically released upon admission

• CXR for pre-employment

• CXR as part of a routine health check up

• CXR for TB screening

• L-spine for pre-employment

• whole body CT screening

The radiation received by a patient can be presented in what 3 ways?

1. entrance skin exposure (ESE)

2. bone marrow dose

3. gonadal dose

What is skin dose?

refers to the dose to the epidermis, the most superficial layers of the skin

What receives the highest dose of radiation?

the skin

What is entrance skin exposure (ESE)?

x-ray exposure to the skin of the patient

ESE can be converted to ___

skin dose (widely used in assessing the amount of radiation received by a patient)

What does GSD stand for?

genetically significant dose

What is genetically significant dose (GSD)?

the Eqd 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 doses received by exposed individual members of the population

("The dose to the reproductive organs that, if given to everyone in a large population, would likely cause the same overall genetic harm to the population as the combined doses that individuals actually received.")

What does bone marrow contain?

stem blood cells that can be depleted or eliminated by exposure to ionizing radiation

What is bone marrow dose (mean marrow dose)?

the average radiation dose to the entire active bone marrow (can only be estimated)

Irradiation of the bone marrow may be responsible for inducing ___

leukemia

Dose area product reflects ___

the patient radiation dose and the amount of tissue irradiated (mGy_a-cm²)

DAP meters are now common on x-ray imaging systems and monitor ___

radiation output from radiographic and fluoroscopic imaging systems

What does FGP stand for?

fluoroscopically guided positioning

What is FGP?

practice of using fluoroscopy to determine the exact location of central ray before taking radiographic exposure

Is FGP suggested?

no; ASRT believes that this is an unethical practice that increases patient dose unnecessarily and should not be used in place of adequate technologist skills

Exposure of patients to medical x-rays is commanding increased attention in our society for 2 reasons:

1. increased frequency of x-ray examinations, including repetitive studies in a short period, is expanding annually (physicians are relying more on radiographic exams to assist them in patient care and diagnosis)

2. concern among public health officials is growing regarding the risk of late effects associated with multiple medical x-ray exposures

What is the ACR?

American College of Radiology

What is the ARC position on abdominal examinations?

• developing embryo-fetus is very radiation sensitive

• non-urgent procedures may be regarded as elective examinations and can be booked at an appropriate time

• perform exams within the first few days after the onset of menses to minimize the possibility of irradiating an embryo

If a patient says they are not pregnant but later finds out they were pregnant for an exam, their MD may request ___

the radiation dose that the embryo-fetus received (info will be calculated by medical physicist, radiologist, or RSO)

If a pregnant patient needs an exam, what precautions should be taken?

• use smallest technical exposure factors

• collimate beam

• lead aprons if possible

Children are much more vulnerable to ___ than adults

late effects of radiation

Children are less likely to hold still during an exposure; what can you do to prevent motion?

• short exposure times

• use appropriate restraint devices

• entertainment and distraction items

What can you do to reduce pediatric gonadal dose?

• adequate shield placement

• manual adjustment of collimation

• set adequate technical factors

• PA instead of AP

• use pediatric protocols (CT)

Explain the Image Gently Campaign

goal is to raise awareness about methods for lowering pediatric dose during medical imaging exams (Dx, fluoro, CT, IR, Nuc Med)

Explain the Image Wisely Campaign

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

What does DEXA stand for?

dual energy x-ray absorptiometry

What is a DEXA scan?

noninvasive x-ray procedure that can quantitatively predict the risk of bone fractures

evaluates osteoporosis

measures bone mineral density