Radiobiology Module 4 Part 2: Patient Protection, CT & Emergencies

Where must radiation caution signs be posted?

In rooms or areas where radioactive materials or radiation sources are used or stored.

What three components commonly appear on a radiation caution sign?

CAUTION wording, the three-blade radiation symbol, and a specific area designation.

What colors are required for the radiation symbol and background?

Magenta, purple, or black symbol on a yellow background.

What dose-rate criterion defines a radiation area?

0.05 mSv in 1 hour at 30 cm.

What dose-rate criterion defines a high radiation area?

1 mSv in 1 hour at 30 cm.

What dose-rate criterion defines a very high radiation area?

5 Gy in 1 hour at 1 m.

What visibility characteristic should radiation warning signs have?

They should be obvious and easy to read.

Why is patient radiation dose important even at low levels?

Stochastic effects are possible even at low doses.

What kind of injury may high-dose interventional fluoroscopy cause?

Tissue reactions, including skin injuries.

What must justify the radiation risk of a medical imaging examination?

Meaningful medical benefit from the examination.

What does entrance skin exposure (ESE) describe?

Dose at the skin where the x-ray beam enters.

What does mean marrow dose (MMD) describe?

Average dose to the entire active bone marrow.

What risk is MMD used to estimate?

Leukemia risk.

What does genetically significant dose (GSD) estimate?

Potential genetic impact across a population based on gonadal exposures.

What is tissue dose?

Radiation dose delivered to a specific organ or tissue.

Why does tissue dose matter when evaluating risk?

Different tissues have different radiosensitivities.

Why is ESE commonly used to compare radiographic techniques?

It is relatively easy to measure or estimate.

Name four ways ESE may be estimated.

Dosimeters, nomograms, known machine output, and technique-based estimates.

Why is ESE not equivalent to whole-body radiation risk?

It measures skin entrance dose, not doses to every organ or their sensitivities.

Name factors that affect ESE.

Technique, distance, filtration, body habitus, and equipment.

Why is ESE harder to estimate in fluoroscopy?

The beam and patient may move during exposure.

Which common radiographic examination usually has relatively low ESE?

Chest radiography.

Which exams can have higher dose and expose more sensitive tissues?

Abdomen, pelvis, and lumbar spine examinations.

Are gonadal dose and marrow dose the same as ESE?

No; they describe different tissues and exposure patterns.

Why does the growth of medical imaging affect population radiation dose?

More imaging can increase average population exposure.

In what clinical areas are fluoroscopic skin injuries particularly documented?

Interventional radiology and cardiac catheterization laboratories.

What approximate fluoroscopy dose rate is cited as potentially substantial?

Upward of 40 mGy/min.

What skin-dose reporting threshold is identified in these lecture notes?

Any skin dose exceeding 15 Gy is described as a sentinel event requiring reporting.

Which FDA-associated organization is named in the skin-injury discussion?

Center for Devices and Radiological Health (CDRH).

Why are risk-benefit decisions especially important in complex interventional cases?

High cumulative doses may cause tissue injury, even when the procedure has substantial medical benefit.

What is the main dose benefit of preventing a repeat exposure?

The patient avoids the radiation from an unnecessary additional image.

How does clear communication contribute to radiation protection?

It improves cooperation and reduces motion and repeats.

How should radiographers describe anticipated discomfort?

Honestly, without overemphasizing it.

Why is motion blur a radiation-protection issue?

It can make images nondiagnostic and lead to repeat exposure.

Which two strategies are especially important for pediatric motion control?

Effective immobilization and very short exposure times.

What is the first step in patient protection before relying on shielding?

Adequate collimation.

When is shielding appropriate according to these notes?

When it protects radiosensitive tissue without compromising the image and follows institutional protocol.

Why are written shielding protocols useful?

They make protection practices consistent.

Why can digital radiography hide technique errors?

Its wide dynamic range may produce viewable images despite inappropriate exposure.

What is the purpose of a radiographic technique chart?

Reduce variation and support consistent dose control.

When may high kVp with lower mAs reduce patient dose?

Not specified in the notes.

Why should post-processing not be used as a substitute for correct technique?

It cannot justify unnecessary dose or reliably correct poor image acquisition.

What can happen to skin dose when a projection must be repeated?

It may double for that projection.

Can an additional image ever be justified?

Yes, when necessary to obtain diagnostic information.

Who is responsible for ordering a radiographic examination?

The referring physician.

What is fluoroscopically guided positioning (FGP)?

Using fluoroscopy to position for routine radiography before the radiographic exposure.

Why does the ASRT object to routine FGP?

It unnecessarily increases patient dose and substitutes for competent positioning skills.

What should be asked when pregnancy status is relevant to an examination?

Possibility of pregnancy and last menstrual period, according to policy.

When may a pregnancy test be ordered?

When pregnancy is possible and substantial pelvic irradiation is anticipated.

Does a justified examination automatically need to be postponed during pregnancy?

No; clinical benefit and circumstances should be assessed.

Who should be consulted when uncertainty remains about imaging a pregnant patient?

The radiologist.

Which anatomy should be spared unnecessary exposure during pregnancy?

Abdomen and pelvis.

Who can estimate fetal dose after an inadvertent exposure?

A qualified medical physicist.

How do most diagnostic fetal exposures compare with high-risk thresholds?

Most are below levels associated with high risk.

What communication approach is recommended after possible fetal exposure?

Calm, accurate communication without unnecessary alarm.

What is the ACR position on clinically justified abdominal radiologic exams after pregnancy is considered?

They need not automatically be postponed or selectively scheduled.

Why is CT a major patient-dose concern?

Its increasing use and higher exposure than many individual radiographs.

What determines the dose of a CT examination?

Scanner type and technical factors.

How can CT collimation support radiation protection?

Limit scanning to the intended anatomy.

Is direct patient shielding routinely used in CT according to these notes?

No, it is not typically used.

What two general principles apply to every CT examination?

Justification and dose optimization.

Why are children more vulnerable to radiation than adults?

They are more vulnerable to late somatic and genetic effects.

What technique should be used for pediatric imaging?

Child-sized technique factors rather than adult defaults.

What imaging extent is recommended for children?

Expose or scan only the indicated area.

What is the focus of the Image Gently campaign?

Pediatric radiation dose reduction.

What is the focus of the Image Wisely campaign?

Adult radiation protection.

What type of pediatric CT protocol does Image Gently encourage avoiding when unnecessary?

Multiphase CT protocols.

What takes priority during a radiologic emergency?

Rescue and immediate medical emergencies, followed by radiation and contamination management.

What does RED stand for?

Radiation exposure device.

What does RDD stand for?

Radiologic dispersal device.

What does IND stand for?

Improvised nuclear device.

What two broad pathways of radiation hazard are listed?

External exposure from photons or particles, and internal radioactive contamination.

What outer-boundary dose rate is specified for emergencies?

100 microGy/hr.

What inner-boundary dose rate is specified for emergencies?

100 mGy/hr; conditions inside should be treated as high.

To what maximum dose rate should first-responder detection equipment be capable of measuring?

500 mGy/hr.

What alarm levels are listed for first-responder detection equipment?

100 microGy, 100 mGy, and 500 mGy.

What additional detection equipment may be needed?

Specialized instruments for alpha and beta particles.

Name protective and decontamination supplies listed for emergencies.

Coveralls, shoe covers, respiratory protective devices, and decontamination areas.

What is the RSO role in emergency preparedness?

Oversee readiness and appoint a leader to ensure equipment storage and training.

Which cardinal protection principles remain relevant in radiologic emergencies?

Time, distance, shielding, and ALARA.

What are the three core actions in the final takeaway?

Justify the exam, optimize the technique, and avoid unnecessary dose.

How are staff protected in routine imaging?

Time, distance, shielding, positioning, and monitoring.

How is the public protected in a radiology facility?

Room design, barriers, doors, signage, and safe procedures.